[001 ] The present invention relates to a process for the decomposition of methane, and/or the conversion of methane to carbon monoxide and hydrogen, and/or the conversion of methane to hydrogen, and/or the conversion of methane to oxygenated products. These processes may have application in treating engine exhaust gases, syngas generation and hydrogen generation. Also provided are metal-doped apatite catalysts as defined herein and uses thereof.

BACKGROUND OF THE INVENTION

[002] Methane is a major component of natural gas and a widely used fuel source for domestic heating and electricity generation. The process of tracking has allowed previously unrecoverable natural gas reserves to be extracted from shale beds and it is predicted that the USA currently has sufficient natural gas reserves to last at least a century at current usage (U. Izquierdo et al., International Journal of Hydrogen Energy, 38 (2013) 7623-7631 ).

[003] Natural gas is mixed with diesel to produce transportation fuel for dual-fuel engines. The high quantity of methane in the feed mixture produces levels of unburned methane in exhaust gasses that exceed those permitted by current emissions legislation (developed for single fuel engines) and the decomposition of this methane is the focus of much research (Y. Karagoz, et al., Advances in Mechanical Engineering 8(2016) 1 -13; B. Challen, R. Baranescu, Diesel Engine Reference Book, Society of Automotive Engineers, 1999).

[004] Apatites are a group of phosphate minerals, which include hydroxyapatite and fluoroapatite. Calcium hydroxyapatite, Caio(P0 ₄ )6(OH)2, has an elemental composition similar to that found in teeth and bones, and has been used as a substitute material in dental and orthopaedic medical fields (Y.-H. Yang et al., Journal of Materials Chemistry B, 1 (2013) 2447-2450).

[005] Calcium hydroxyapatite possesses a characteristic hexagonal structure of P0 ₄ tetrahedrons, with the P6 ₃ /m space group, whereby charge-balancing Ca ²⁺ and OH ^" ions reside on the c-axis (J.M. Hughes, Structure and Chemistry of the Apatites and Other Calcium Orthophosphates By J. C. Elliot (The London Hospital Medical College). Elsevier: Amsterdam. 1994. xii + 389 pp. ISBN 0-444-81582-1 , Journal of the American Chemical Society, 1 18 (1996) 3072-3072). [006] Their high structural stability, bifunctionality of acidic and basic sites, and the possibility of isomorphous substitution mean that apatites are excellent catalyst supports, as summarised in a recent review (Gruselle, J. Organometallic Chem., 793 (2015) 93-101 ).

[007] The use of metals supported on hydroxyapatite (HAP) has been reported in a range of reactions. In particular, Ni loaded HAP has been reported to be active in dry reforming of methane with about 98% methane conversion at 650 °C (Ziyad et al., Applied Catalysis A: General 317 (2007) 299-309).

[008] Yoon and co-workers studied the effects of adding cerium to Ni/HAP catalysts with a view to reducing the well-established tendency for Ni to generate carbon deposits during reaction. Results showed that temperatures in excess of 650 °C were required for >90% conversion and that cerium doped samples enhanced the catalytic stability due to the oxygen storage capacity of ceria preventing excessive carbon deposition (Yoon et al., Korean J. Chem. Eng., 23(3), 356-361 (2006).

[009] There is a need in the art for alternative catalysts capable of decomposing methane at relatively low temperatures. Such catalysts would be useful for the efficient removal of methane from exhaust systems of dual-fuel engines, e.g. dual-fuel goods vehicles.

[0010] Furthermore, catalytic reforming of methane in the presence of an oxidant (e.g. carbon dioxide, oxygen, water, air) may yield a mixture of carbon monoxide and hydrogen (i.e. syngas), and/or hydrogen and/or oxygenated compounds. Hence the catalytic reforming of methane is a promising technology for reducing greenhouse gases such as carbon dioxide and methane and/or producing a valuable materials and fuels.

[0011] There is a need in the art for an alternative catalyst for converting methane to carbon monoxide and hydrogen/converting methane to hydrogen/converting methane to oxygenated products which allows the conversion to occur efficiently at lower temperature. Furthermore, the catalyst should be stable to carbon deactivation.

[0012] The present invention provides a process for decomposing methane and/or converting methane to hydrogen and carbon monoxide at low temperature using a metal-doped apatite catalyst.

[0013] The present invention also provides a process for converting methane to hydrogen and/or converting methane to oxygenated products at low temperature using a metal-doped apatite catalyst. SUMMARY OF THE INVENTION

[0014] In a first aspect, the present invention provides a process for (a) the decomposition of methane; and/or (b) the conversion of methane to a mixture comprising carbon monoxide and hydrogen; and/or (c) the conversion of methane to hydrogen; and/or (d) the conversion of methane to oxygenated products as defined herein.

[0015] In a second aspect, the present invention provides a process for preparing a metal- doped catalyst as defined herein.

[0016] In a third aspect, the present invention provides a metal-doped catalyst obtainable according to the process of the second aspect.

[0017] In a fourth aspect, the present invention provides a metal-doped apatite as defined herein.

[0018] In a fifth aspect, the present invention provides the use of a metal-doped apatite as defined herein for (a) the decomposition of methane; and/or (b) the conversion of methane to carbon monoxide and hydrogen; and/or (c) the conversion of methane to hydrogen; and/or (d) the conversion of methane to oxygenated products.

[0019] In a sixth aspect, the present invention provides a catalytic converter comprising a metal-doped apatite as defined herein.

[0020] In a seventh aspect, the present invention provides an engine exhaust system comprising a metal-doped apatite as defined herein.

[0021] Preferred, suitable, and optional features of any one particular aspect of the present invention are also preferred, suitable, and optional features of any other aspect.

BRIEF DESCRIPTION OF THE DRA WINGS

[0022] Figure 1 provides a schematic representation of a plug-flow catalyst testing reactor.

[0023] Figure 2 provides the XRPD pattern of Catalyst B (Figure 2b), Catalyst C (Figure 2c) and Catalyst D (Figure 2d).

[0024] Figure 3 provides at top-left, a SEM image; at top right an EDAX spectrum; and at centre and bottom TEM images (200 nm, 50 nm, 20 nm and 10nm) of Catalyst B. [0025] Figure 4a shows methane conversion over Catalysts B, C and D as a function of temperature.

[0026] Figure 4b shows methane conversion over Catalyst B as a function of time at fixed temperature.

[0027] Figure 5 shows TGA profiles of Catalyst B before and after reaction with methane at 297 °C.

DETAILED DESCRIPTION OF THE INVENTION Process for decomposition of methane

[0028] In one aspect, the present invention relates to a process for the decomposition of methane wherein said process comprises contacting a feed mixture comprising methane and an oxidant with a catalytic composition comprising a metal-doped apatite at a low temperature.

[0029] As used herein, "decomposition" refers to the at least partial consumption of methane and its conversion into one or more other materials. Decomposition of methane may be assessed by monitoring the relative concentrations of methane in the input and output of a system (e.g. reactor or engine exhaust system) comprising the catalytic composition of the invention.

[0030] In one embodiment, the process provides complete (i.e. about 100%) methane decomposition at completion in a batch process. In another embodiment, in a batch process, at least about 50% methane decomposition is achieved. Suitably at least about 60% methane decomposition, more suitably at least about 70% methane decomposition, more suitably at least about 80% methane decomposition, more suitably at least about 85% methane decomposition, more suitably at least about 90% methane decomposition, more suitably at least about 95% methane decomposition, more suitably at least about 96% methane decomposition, more suitably at least about 97% methane decomposition, more suitably at least about 98% methane decomposition, more suitably at least about 99% methane decomposition is achieved in a batch process.

[0031] In another embodiment, from about 50% to about 100% methane decomposition is achieved at completion in a batch process. Suitably, about 60% to about 100% methane decomposition; suitably about 70% to about 100% methane decomposition; suitably about 80% to about 100% methane decomposition; suitably about 85% to about 100% methane decomposition; suitably about 90% to about 100% methane decomposition; suitably about 95% to about 100% methane decomposition; suitably about 97% to about 100% methane decomposition; suitably about 98% to about 100% methane decomposition; suitably about 99% to about 100% methane decomposition is achieved in a batch process.

[0032] In another embodiment, in a continuous process, at least about 50% decomposition of methane achieved after about 3 hours of reaction. Suitably at least about 60% decomposition, more suitably at least about 70% decomposition, more suitably at least about 80% decomposition, more suitably at least about 90% decomposition, more suitably at least about 94% decomposition of methane is achieved after about 3 hours of reaction.

[0033] In another embodiment, in a continuous process, from about 50% to about 100% methane decomposition is achieved after 3 hours of reaction. Suitably, about 60% to about 100% methane decomposition; suitably about 70% to about 100% methane decomposition; suitably about 80% to about 100% methane decomposition; suitably about 90% to about 100% is achieved after 3 hours of reaction.

[0034] In another embodiment, in a continuous process, from about 50% to about 94% methane decomposition is achieved after 3 hours of reaction. Suitably, about 60% to about 94% methane decomposition; suitably about 70% to about 94% methane decomposition; suitably about 80% to about 94% methane decomposition; suitably about 90% to about 94% is achieved after 3 hours of reaction.

[0035] In another embodiment, in a continuous process, at least about 50% methane decomposition of methane is achieved after about 8 hours of reaction. Suitably at least about 60% methane decomposition, more suitably at least about 70% methane decomposition, more suitably at least about 80% methane decomposition is achieved after about 8 hours of reaction.

[0036] In another embodiment, in a continuous process, from about 50% to about 80% methane decomposition is achieved after 8 hours of reaction. Suitably, about 60% to about 80% methane decomposition; suitably about 70% to about 80% methane decomposition; suitably about 75% to about 80% methane decomposition is achieved after 8 hours of reaction.

[0037] In another embodiment, in a continuous process, at least about 50% methane decomposition of methane achieved after about 50 hours of reaction. Suitably at least about 60% methane decomposition, more suitably at least about 70% methane decomposition, more suitably at least about 80% methane decomposition is achieved after about 50 hours of reaction. [0038] In another embodiment, in a continuous process, from about 50% to about 80% methane decomposition is achieved after about 50 hours of reaction. Suitably, about 60% to about 80% methane decomposition; suitably about 70% to about 80% methane decomposition; suitably about 75% to about 80% methane decomposition is achieved after about 50 hours of reaction.

[0039] In another embodiment, in a continuous process, at least about 50% methane decomposition of methane achieved after about 90 hours of reaction. Suitably at least about 60% methane decomposition, more suitably at least about 70% methane decomposition, more suitably at least about 75% methane decomposition is achieved after about 90 hours of reaction.

[0040] In another embodiment, in a continuous process, from about 50% to about 80% methane decomposition is achieved after about 90 hours of reaction. Suitably, about 60% to about 80% methane decomposition; suitably about 70% to about 80% methane decomposition; suitably about 75% to about 80% methane decomposition is achieved after about 90 hours of reaction.

[0041 ] In another embodiment, in a continuous process, from about 50% to about 77% methane decomposition is achieved after about 97 hours of reaction. Suitably, about 60% to about 77% methane decomposition; suitably about 70% to about 77% methane decomposition; suitably about 75% to about 77% methane decomposition is achieved after about 97 hours of reaction.

[0042] In one embodiment, the process comprises contacting the feed mixture with the catalytic composition at ambient pressure or above ambient pressure. For instance, the process may comprise contacting the feed mixture with the catalytic composition at a pressure of about 1 atmosphere (atm) or about 101 KPa. In another embodiment, the process may comprise contacting the feed mixture with the catalytic composition at a pressure of greater than about 1 atmosphere (atm) or about 101 KPa.

[0043] In one embodiment, the process comprises contacting the feed mixture with the catalytic composition at a pressure of equal to or greater than about 125 KPa, for example greater than about 150 KPa, for example greater than about 175 KPa, for example greater than about 200 KPa, for example greater than about 225 KPa, for example greater than about 250 KPa, for example greater than about 275 KPa.

[0044] In one embodiment, the process comprises contacting the feed mixture with the catalytic composition at a pressure of from about 101 KPa to about 1000 KPa. For example, a pressure of from about 101 KPa to about 500 KPa. For example, a pressure of from about 101 KPa to about 475 KPa. For example, a pressure of from about 101 KPa to about 450 KPa. For example, a pressure of from about 101 KPa to about 425 KPa. For example, a pressure of from about 101 KPa to about 400 KPa. For example, a pressure of from about 101 KPa to about 375 KPa. For example, a pressure of from about 101 KPa to about 350 KPa.

[0045] In another embodiment, the process comprises contacting the feed mixture with the catalytic composition at a pressure of from about 150 KPa to about 1000 KPa. For example, the process comprises contacting the feed mixture with the catalytic composition at a pressure of from about 150 KPa to about 500 KPa. For example, a pressure of from about 150 KPa to about 475 KPa. For example, a pressure of from about 150 KPa to about 450 KPa. For example, a pressure of from about 150 KPa to about 425 KPa. For example, a pressure of from about 150 KPa to about 400 KPa. For example, a pressure of from about 150 KPa to about 375 KPa. For example, a pressure of from about 150 KPa to about 350 KPa.

[0046] Any suitable space velocity may be employed for contacting the feed mixture with the catalytic composition. For instance, the feed mixture may be fed over the catalytic composition at a weight hour space velocity (WHSV) of equal to or greater than about 0.1 hr ¹ . For instance, the feed mixture may be fed over the catalytic composition at a weight hour space velocity (WHSV) of equal to or greater than about 0.5 hr ¹ . Suitably, the weight hour space velocity is equal to or greater than about 1 .0 hr ¹ , for instance equal to or greater than about 1 .5 hr ¹ , or for example equal to or greater than about 2.0 hr ¹ .

[0047] In one embodiment WHSV is from about 0.1 hr ¹ to about 10 hr ¹ . For example, a WHSV of from about 0.1 hr ¹ to about 5 hr ¹ . For example, a WHSV of from about 0.1 hr ¹ to about 4.5 hr ¹ . For example, a WHSV of from about 0.1 hr ¹ to about 4.0 hr ¹ . For example, a WHSV of from about 0.1 hr ¹ to about 3.5 hr ¹ . For example, a WHSV of from about 0.1 hr ¹ to about 3.0 hr ¹ . For example, a WHSV of from about 0.1 hr ¹ to about 2.5 hr ¹ .

[0048] In one embodiment WHSV is from about 0.5 hr ¹ to about 5 hr ¹ . For example, a WHSV of from about 0.5 hr ¹ to about 4.5 hr ¹ . For example, a WHSV of from about 0.5 hr ¹ to about 4.0 hr ¹ . For example, a WHSV of from about 0.5 hr ¹ to about 3.5 hr ¹ . For example, a WHSV of from about 0.5 hr ¹ to about 3.0 hr ¹ . For example, a WHSV of from about 0.5 hr ¹ to about 2.5 hr ¹ .

[0049] In another embodiment, the WHSV is from about 1 .0 hr ¹ to about 5 hr ¹ . For example, a WHSV of from about 1 .0 hr ¹ to about 4.5 hr ¹ . For example, a WHSV of from about 1 .0 hr ¹ to about 4.0 hr ¹ . For example, a WHSV of from about 1 .0 hr ¹ to about 3.5 hr ¹ . For example, a WHSV of from about 1 .0 hr ¹ to about 3.0 hr ¹ . For example, a WHSV of from about 1 .0 hr ¹ to about 2.5 hr ¹ .

[0050] In another embodiment, the WHSV is from about 1 .5 hr ¹ to about 2.5 hr ¹ , for instance, about 2.0 hr ¹ .

[0051] In one embodiment, the rate at which the feed mixture is contacted with the catalytic composition is about 10ml/min or greater. For example, a rate of about 20ml/min or greater. For example, a rate of about 30ml/min or greater. For example, a rate of about 40ml/min or greater. For example, a rate of about 50ml/min or greater. For example, a rate of about 60ml/min or greater. For example, a rate of about 70ml/min or greater. For example, a rate of about 80ml/min or greater. For example, a rate of about 90ml/min or greater. For example, a rate of about 100ml/min or greater.

[0052] In one embodiment, the rate at which the feed mixture is contacted with the catalytic composition is about 10ml/min to about 500ml/min. For example, a rate of about 10ml/min to about 400ml/min. For example, a rate of about 10ml/min to about 300ml/min. For example, a rate of about 10ml/min to about 250ml/min. For example, a rate of about 10ml/min to about 200ml/min. For example, a rate of about 10ml/min to about 150ml/min. For example, a rate of about 10ml/min to about 100ml/min.

[0053] In one embodiment, the rate at which the feed mixture is contacted with the catalytic composition is about 50ml/min to about 500ml/min. For example, a rate of about 50ml/min to about 400ml/min. For example, a rate of about 10ml/min to about 300ml/min. For example, a rate of about 50ml/min to about 250ml/min. For example, a rate of about 50ml/min to about 200ml/min. For example, a rate of about 50ml/min to about 150ml/min. For example, a rate of about 50ml/min to about 100ml/min.

[0054] In one embodiment, the rate at which the feed mixture is contacted with the catalytic composition is about 10Oml/min to about 500ml/min. For example, a rate of about 10Oml/min to about 400ml/min. For example, a rate of about 100ml/min to about 300ml/min. For example, a rate of about 100ml/min to about 250ml/min. For example, a rate of about 100ml/min to about 200ml/min. For example, a rate of about 10ml/min to about 150ml/min. For example, a rate of about 100ml/min.

[0055] The process of contacting the feed mixture with the catalytic composition is typically performed at low temperature. As used herein, low temperature refers to a temperature which is relatively lower than temperatures used in the art (see Ziyad et al., Applied Catalysis A: General 317 (2007) 299-309 for instance). In one embodiment, low temperature refers to a temperature of about 600 °C or lower. For example, a temperature of about 550 °C or lower. For example, a temperature of about 500 °C or lower. For example, a temperature of about 450 °C or lower. For example, a temperature of about 400 °C or lower. For example, a temperature of about 350 °C or lower. For example, a temperature of about 300 °C or lower. For example, a temperature of about 275 °C or lower. For example, a temperature of about 250 °C or lower. For example, a temperature of about 225 °C or lower. For example, a temperature of about 200 °C or lower.

[0056] In a one embodiment, the process comprises contacting the feed mixture with the catalytic composition at a temperature of from about 100 ^e C to about 650 ^e C, for example from about 100 ^e C to about 600 ^e C, for example from about 100 ^e C to about 550 ^e C, for example from about 100 ^e C to about 500 ^e C, for example from about 100 ^e C to about 450 ^e C, for example from about 100 ^e C to about 400 ^e C, for example from about 100 ^e C to about 350 ^e C, for example from about 100 ^e C to about 300 ^e C, for example from about 100 ^e C to about 275 ^e C, for example from about 100 ^e C to about 250 ^e C, for example from about 100 ^e C to about 225 ^e C, for example from about 100 ^e C to about 200 ^e C.

[0057] In a one embodiment, the process comprises contacting the feed mixture with the catalytic composition at a temperature of from about 150 ^e C to about 650 ^e C, for example from about 150 ^e C to about 600 ^e C, for example from about 150 ^e C to about 550 ^e C, for example from about 150 ^e C to about 500 ^e C, for example from about 150 ^e C to about 450 ^e C, for example from about 150 ^e C to about 400 ^e C, for example from about 150 ^e C to about 350 ^e C, for example from about 150 ^e C to about 300 ^e C, for example from about 150 ^e C to about 275 ^e C, for example from about 150 ^e C to about 250 ^e C, for example from about 150 ^e C to about 225 ^e C, for example from about 150 ^e C to about 200 ^e C.

[0058] In a one embodiment, the process comprises contacting the feed mixture with the catalytic composition at a temperature of from about 175 ^e C to about 650 ^e C, for example from about 175 ^e C to about 600 ^e C, for example from about 175 ^e C to about 550 ^e C, for example from about 175 ^e C to about 500 ^e C, for example from about 175 ^e C to about 450 ^e C, for example from about 175 ^e C to about 400 ^e C, for example from about 175 ^e C to about 350 ^e C, for example from about 175 ^e C to about 300 ^e C, for example from about 175 ^e C to about 275 ^e C, for example from about 175 ^e C to about 250 ^e C, for example from about 175 ^e C to about 225 ^e C, for example from about 175 ^e C to about 200 ^e C.

[0059] In a one embodiment, the process comprises contacting the feed mixture with the catalytic composition at a temperature of from about 200 ^e C to about 650 ^e C, for example from about 200 ^e C to about 600 ^e C, for example from about 200 ^e C to about 550 ^e C, for example from about 200 ^e C to about 500 ^e C, for example from about 200 ^e C to about 450 ^e C, for example from about 200 ^e C to about 400 ^e C, for example from about 200 ^e C to about 350 ^e C, for example from about 200 ^e C to about 300 ^e C, for example from about 200 ^e C to about 275 ^e C, for example from about 200 ^e C to about 250 ^e C, for example from about 200 ^e C to about 225 ^e C, for example about 200 ^e C.

[0060] In a one embodiment, the process comprises contacting the feed mixture with the catalytic composition at a temperature of from about 225 ^e C to about 650 ^e C, for example from about 225 ^e C to about 600 ^e C, for example from about 225 ^e C to about 550 ^e C, for example from about 225 ^e C to about 500 ^e C, for example from about 225 ^e C to about 450 ^e C, for example from about 225 ^e C to about 400 ^e C, for example from about 225 ^e C to about 350 ^e C, for example from about 225 ^e C to about 300 ^e C, for example from about 225 ^e C to about 275 ^e C, for example from about 225 ^e C to about 250 ^e C, for example about 225 ^e C

[0061] In a one embodiment, the process comprises contacting the feed mixture with the catalytic composition at a temperature of from about 250 ^e C to about 650 ^e C, for example from about 250 ^e C to about 600 ^e C, for example from about 250 ^e C to about 550 ^e C, for example from about 250 ^e C to about 500 ^e C, for example from about 250 ^e C to about 450 ^e C, for example from about 250 ^e C to about 400 ^e C, for example from about 250 ^e C to about 350 ^e C, for example from about 250 ^e C to about 300 ^e C, for example from about 250 ^e C to about 275 ^e C, for example from about 250 ^e C.

[0062] In a one embodiment, the process comprises contacting the feed mixture with the catalytic composition at a temperature of from about 275 ^e C to about 650 ^e C, for example from about 275 ^e C to about 600 ^e C, for example from about 275 ^e C to about 550 ^e C, for example from about 275 ^e C to about 500 ^e C, for example from about 275 ^e C to about 450 ^e C, for example from about 275 ^e C to about 400 ^e C, for example from about 275 ^e C to about 350 ^e C, for example from about 275 ^e C to about 300 ^e C, for example from about 275 ^e C.

[0063] In a one embodiment, the process comprises contacting the feed mixture with the catalytic composition at a temperature of from about 300 ^e C to about 650 ^e C, for example from about 300 ^e C to about 600 ^e C, for example from about 300 ^e C to about 550 ^e C, for example from about 300 ^e C to about 500 ^e C, for example from about 300 ^e C to about 450 ^e C, for example from about 300 ^e C to about 400 ^e C, for example from about 300 ^e C to about 350 ^e C, for example from about 300 ^e C to about 325 ^e C, for example from about 300 ^e C. [0064] In a one embodiment, the process comprises contacting the feed mixture with the catalytic composition at a temperature of from about 325 ^e C to about 650 ^e C, for example from about 325 ^e C to about 600 ^e C, for example from about 325 ^e C to about 550 ^e C, for example from about 325 ^e C to about 500 ^e C, for example from about 325 ^e C to about 450 ^e C, for example from about 325 ^e C to about 400 ^e C, for example from about 325 ^e C to about 350 ^e C, for example from about 325 ^e C.

[0065] In one embodiment, the process comprises contacting the feed mixture with the catalytic composition at a temperature of greater than about 200 °C and a pressure of greater than about 101 KPa.

[0066] In another embodiment, the process comprises contacting the feed mixture with a catalytic composition at a temperature of from about 200 ^e C to about 600 ^e C and a pressure of about 101 KPa.

[0067] In another embodiment, the process comprises contacting the feed mixture with a catalytic composition at a temperature of from about 200 ^e C to about 500 ^e C and a pressure of from about 101 KPa.

[0068] In another embodiment, the process comprises contacting the feed mixture with a catalytic composition at a temperature of from about 200 ^e C to about 400 ^e C and a pressure of from about 101 KPa.

[0069] In another embodiment, the process comprises contacting the feed mixture with a catalytic composition at a temperature of from about 200 ^e C to about 350 ^e C and a pressure of from about 101 KPa.

[0070] In another embodiment, the process comprises contacting the feed mixture with a catalytic composition at a temperature of from about 200 ^e C to about 400 ^e C and a pressure of from about 101 KPa to about 200 KPa.

[0071 ] In another embodiment, the process comprises contacting the feed mixture with a catalytic composition at a temperature of from about 250 °C to about 350 °C and a pressure of from about 101 KPa to about 200 KPa.

[0072] In another embodiment, the process comprises contacting the feed mixture with a catalytic composition at a temperature of about 250 °C to about 350 °C and a pressure of about 101 KPa and a feed rate of about 50 to about 200 ml/min. [0073] In one embodiment, at least about 50% methane decomposition is achieved at a temperature of about 250 °C. Suitably at least about 60% methane decomposition is achieved at a temperature of about 250 °C, more suitably at least about 70% methane decomposition, more suitably at least about 80% methane decomposition, more suitably at least about 90% methane decomposition, more suitably at least about 95% methane decomposition is achieved at a temperature of about 250 °C.

[0074] In another embodiment, at least about 20% methane decomposition is achieved at a temperature of about 225 °C. Suitably at least about 30% methane decomposition is achieved at a temperature of about 225 °C, more suitably at least about 40% methane decomposition, more suitably at least about 50% methane decomposition, more suitably at least about 60% methane decomposition, more suitably at least about 70% methane decomposition, more suitably at least about 80% methane decomposition is achieved at a temperature of about 225 °C.

[0075] In another embodiment, at least about 20% methane decomposition is achieved at a temperature of about 250 °C. Suitably at least about 30% methane decomposition is achieved at a temperature of about 250 °C., more suitably at least about 40% methane decomposition, more suitably at least about 50% methane decomposition, more suitably at least about 60% methane decomposition, more suitably at least about 70% methane decomposition is achieved at a temperature of about 250 °C.

[0076] In one embodiment, about 90% to about 100% methane decomposition is achieved at a temperature of about 450 °C or less, suitably a temperature of about 400 °C or less, suitably a temperature of about 350 °C or less, suitably a temperature of about 300 °C or less, suitably a temperature of about 250 °C or less, suitably a temperature of about 200 °C or less.

[0077] In one embodiment, about 90% to about 100% methane decomposition is achieved at a temperature of between about 200 °C and about 450 °C, suitably a temperature of between about 200 °C and about 400 °C, suitably a temperature of between about 200 °C and about 350 °C, suitably a temperature of between about 200 °C and about 300 °C, suitably a temperature of between about 200 °C and about 250 °C, suitably a temperature of about 200 °C.

[0078] In one embodiment, about 80% to about 100% methane decomposition is achieved at a temperature of about 450 °C or less, suitably a temperature of about 400 °C or less, suitably a temperature of about 350 °C or less, suitably a temperature of about 300 °C or less, suitably a temperature of about 250 °C or less, suitably a temperature of about 200 °C or less. [0079] In one embodiment, about 80% to about 100% methane decomposition is achieved at a temperature of between about 200 °C and about 450 °C, suitably a temperature of between about 200 °C and about 400 °C, suitably a temperature of between about 200 °C and about 350 °C, suitably a temperature of between about 200 °C and about 300 °C, suitably a temperature of between about 200 °C and about 250 °C, suitably a temperature of about 200 °C.

[0080] In one embodiment, about 70% to about 100% methane decomposition is achieved at a temperature of about 450 °C or less, suitably a temperature of about 400 °C or less, suitably a temperature of about 350 °C or less, suitably a temperature of about 300 °C or less, suitably a temperature of about 250 °C or less, suitably a temperature of about 200 °C or less.

[0081] In one embodiment, about 70% to about 100% methane decomposition is achieved at a temperature of between about 200 °C and about 450 °C, suitably a temperature of between about 200 °C and about 400 °C, suitably a temperature of between about 200 °C and about 350 °C, suitably a temperature of between about 200 °C and about 300 °C, suitably a temperature of between about 200 °C and about 250 °C, suitably a temperature of about 200 °C.

[0082] In one embodiment, about 60% to about 100% methane decomposition is achieved at a temperature of about 450 °C or less, suitably a temperature of about 400 °C or less, suitably a temperature of about 350 °C or less, suitably a temperature of about 300 °C or less, suitably a temperature of about 250 °C or less, suitably a temperature of about 200 °C or less.

[0083] In one embodiment, about 60% to about 100% methane decomposition is achieved at a temperature of between about 200 °C and about 450 °C, suitably a temperature of between about 200 °C and about 400 °C, suitably a temperature of between about 200 °C and about 350 °C, suitably a temperature of between about 200 °C and about 300 °C, suitably a temperature of between about 200 °C and about 250 °C, suitably a temperature of about 200 °C.

[0084] In one embodiment, about 50% to about 100% methane decomposition is achieved at a temperature of about 450 °C or less, suitably a temperature of about 400 °C or less, suitably a temperature of about 350 °C or less, suitably a temperature of about 300 °C or less, suitably a temperature of about 250 °C or less, suitably a temperature of about 200 °C or less.

[0085] In one embodiment, about 50% to about 100% methane decomposition is achieved at a temperature of between about 200 °C and about 450 °C, suitably a temperature of between about 200 °C and about 400 °C, suitably a temperature of between about 200 °C and about 350 °C, suitably a temperature of between about 200 °C and about 300 °C, suitably a temperature of between about 200 °C and about 250 °C, suitably a temperature of about 200 °C. [0086] In one embodiment, the process is carried out in an engine exhaust system. For example, in the exhaust system of an internal combustion engine. For example, a dual-fuel internal combustion engine fuelled by a combination of diesel and methane.

[0087] In one embodiment, the oxidant is selected from one or more of air, carbon dioxide, oxygen, nitrogen oxides and water, suitably the oxidant is selected from air and carbon dioxide.

[0088] In one embodiment, the feed mixture comprises methane and carbon dioxide.

[0089] In one embodiment, the feed mixture comprises about 1 % or more of methane. For example, about 2% or more of methane. For example, about 3% or more of methane. For example, about 4% or more of methane. For example, about 5% or more of methane. For example, about 6% or more of methane. For example, about 7% or more of methane. For example, about 8% or more of methane. For example, about 9% or more of methane. For example, about 10% or more of methane.

[0090] In another embodiment, the feed mixture comprises about 1 % to about 10% of methane. For example, about 2% to about 10% of methane. For example, about 3% to about 10% of methane. For example, about 4% to about 10% of methane. For example, about 5% to about 10% of methane. For example, about 6% to about 10% of methane. For example, about 7% to about 10% of methane. For example, about 8% to about 10% of methane. For example, about 9% to about 10% of methane. For example, about 10% of methane.

[0091 ] In another embodiment, the feed mixture comprises about 1 % to about 7% of methane. For example, about 2% to about 7% of methane. For example, about 3% to about 7% of methane. For example, about 4% to about 7% of methane. For example, about 5% to about 7% of methane. For example, about 6% to about 7% of methane. For example, about 7of methane.

[0092] In another embodiment, the feed mixture comprises about 1 % to about 5% of methane. For example, about 2% to about 5% of methane. For example, about 3% to about 5% of methane. For example, about 4% to about 5% of methane. For example, about 5% methane.

[0093] In one embodiment, the feed mixture comprises methane and oxidant is a ratio of about 2:1 to about 1 :2. For example, in a ratio of about 3:2 to about 2:3. For example in a ratio of about 4:3 to about 3:4. For example, in a ratio of about 5:4 to about 4:5. For example in a ratio of about 1 :1 . [0094] In one embodiment, the feed mixture is the exhaust gas of an engine fuelled at least partially by methane. For example, in one embodiment the feed mixture is the exhaust gas a methane/diesel fuelled engine.

[0095] In one embodiment, the feed mixture is the exhaust gas of an internal combustion engine fuelled at least partially by methane. For example, in one embodiment the feed mixture is the exhaust gas a methane/diesel fuelled engine.

[0096] In another embodiment, the feed mixture is the exhaust gas of a methane/gasoline fuelled engine.

[0097] In one embodiment, the feed mixture is the exhaust gas of a vehicle powered by at least partially by methane.

[0098] In another embodiment, the feed mixture is the exhaust gas of a vehicle powered by a methane/diesel fuelled engine. In another embodiment, the feed mixture is the exhaust gas of a vehicle powered by a methane/gasoline fuelled engine.

Process for conversion of methane

[0099] In one aspect, the present invention relates to a process for the conversion of methane to carbon monoxide and hydrogen wherein said process comprises contacting a feed mixture comprising methane and an oxidant with a catalytic composition comprising a metal-doped apatite at a low temperature.

[00100] As used herein "conversion of methane to carbon monoxide and hydrogen" refers to a chemical reaction process in which methane is at least partially consumed and carbon monoxide and hydrogen are generated.

[00101 ] In one embodiment, the process provides complete (i.e. >99%) methane conversion to carbon monoxide and hydrogen in a batch process. In another embodiment, in a batch process, at least about 50% methane conversion is achieved at completion. Suitably at least about 60% methane conversion, more suitably at least about 70% methane conversion, more suitably at least about 80% methane conversion, more suitably at least about 90% methane conversion, more suitably at least about 95% methane conversion is achieved in a batch process at completion.

[00102] In another embodiment, from about 50% to about 100% methane conversion to carbon monoxide and hydrogen is achieved in a batch process at completion. Suitably, about 60% to about 100% methane conversion; suitably about 70% to about 100% methane conversion; suitably about 80% to about 100% methane conversion; suitably about 90% to about 100% methane conversion; suitably about 95% to about 100% methane conversion; suitably about 97% to about 100% methane conversion is achieved in a batch process at completion.

[00103] In another embodiment, in a continuous process, at least about 50% conversion of methane to carbon monoxide and hydrogen is achieved after about 3 hours of reaction. Suitably at least about 60% conversion, more suitably at least about 70% conversion, more suitably at least about 80% conversion, more suitably at least about 90% conversion, more suitably at least about 94% conversion of methane is achieved after about 3 hours of reaction.

[00104] In another embodiment, in a continuous process, from about 50% to about 100% methane conversion to carbon monoxide and hydrogen is achieved after 3 hours of reaction. Suitably, about 60% to about 100% methane conversion; suitably about 70% to about 100% methane conversion; suitably about 80% to about 100% methane conversion; suitably about 90% to about 100% methane conversion after 3 hours of reaction.

[00105] In another embodiment, in a continuous process, from about 50% to about 94% methane conversion to carbon monoxide and hydrogen is achieved after 3 hours of reaction. Suitably, about 60% to about 94% methane conversion; suitably about 70% to about 94% methane conversion; suitably about 80% to about 94% methane conversion; suitably about 90% to about 94% methane conversion after 3 hours of reaction.

[00106] In another embodiment, in a continuous process, at least about 50% methane conversion to carbon monoxide and hydrogen is achieved after about 8 hours of reaction. Suitably at least about 60% methane conversion, more suitably at least about 70% methane decomposition, more suitably at least about 80% methane conversion is achieved after about 8 hours of reaction.

[00107] In another embodiment, in a continuous process, from about 50% to about 80% methane conversion is achieved after 8 hours of reaction. Suitably, about 60% to about 80% methane conversion; suitably about 70% to about 80% methane conversion; suitably about 75% to about 80% methane conversion is achieved after 8 hours of reaction.

[00108] In another embodiment, in a continuous process, at least about 50% methane conversion to carbon monoxide and hydrogen is achieved after about 50 hours of reaction. Suitably at least about 60% methane conversion, more suitably at least about 70% methane conversion, more suitably at least about 80% methane conversion is achieved after about 50 hours of reaction.

[00109] In another embodiment, in a continuous process, from about 50% to about 80% methane conversion to carbon monoxide and hydrogen is achieved after about 50 hours of reaction. Suitably, about 60% to about 80% methane conversion; suitably about 70% to about 80% methane conversion; suitably about 75% to about 80% methane conversion is achieved after about 50 hours of reaction.

[00110] In another embodiment, in a continuous process, at least about 50% methane conversion to carbon monoxide and hydrogen is achieved after about 90 hours of reaction. Suitably at least about 60% methane conversion, more suitably at least about 70% methane conversion, more suitably at least about 75% methane conversion is achieved after about 90 hours of reaction.

[00111 ] In another embodiment, in a continuous process, from about 50% to about 80% methane conversion to carbon monoxide and hydrogen is achieved after about 90 hours of reaction. Suitably, about 60% to about 80% methane conversion; suitably about 70% to about 80% methane conversion; suitably about 75% to about 80% methane conversion is achieved after about 90 hours of reaction.

[00112] In another embodiment, in a continuous process, from about 50% to about 77% methane conversion to carbon monoxide and hydrogen is achieved after about 97 hours of reaction. Suitably, about 60% to about 77% methane conversion; suitably about 70% to about 77% methane conversion; suitably about 75% to about 77% methane conversion is achieved after about 97 hours of reaction.

[00113] In one embodiment, at least about 50% methane conversion to carbon monoxide and hydrogen is achieved at a temperature of about 250 °C. Suitably at least about 60% methane conversion to carbon monoxide and hydrogen is achieved at a temperature of about 250 °C, more suitably at least about 70% methane conversion to carbon monoxide and hydrogen, more suitably at least about 80% methane conversion to carbon monoxide and hydrogen, more suitably at least about 90% methane conversion to carbon monoxide and hydrogen, more suitably at least about 95% methane conversion to carbon monoxide and hydrogen is achieved at a temperature of about 250 °C.

[00114] In another embodiment, at least about 20% methane conversion to carbon monoxide and hydrogen is achieved at a temperature of about 225°C. Suitably at least about 30% methane conversion to carbon monoxide and hydrogen is achieved at a temperature of about 225 °C, more suitably at least about 40% methane conversion to carbon monoxide and hydrogen, more suitably at least about 50% methane conversion to carbon monoxide and hydrogen, more suitably at least about 60% methane conversion to carbon monoxide and hydrogen, more suitably at least about 70% methane conversion to carbon monoxide and hydrogen, more suitably at least about 80% methane conversion to carbon monoxide and hydrogen is achieved at a temperature of about 225 °C.

[00115] In another embodiment, at least about 20% methane conversion to carbon monoxide and hydrogen is achieved at a temperature of about 200 °C. Suitably at least about 30% methane conversion to carbon monoxide and hydrogen is achieved at a temperature of about 250 °C, more suitably at least about 40% methane conversion to carbon monoxide and hydrogen, more suitably at least about 50% methane conversion to carbon monoxide and hydrogen, more suitably at least about 60% methane conversion to carbon monoxide and hydrogen, more suitably at least about 70% methane conversion to carbon monoxide and hydrogen is achieved at a temperature of about 250 °C.

[00116] In one embodiment, about 90% to about 100% methane conversion is achieved at a temperature of about 450 °C or less, suitably a temperature of about 400 °C or less, suitably a temperature of about 350 °C or less, suitably a temperature of about 300 °C or less, suitably a temperature of about 250 °C or less, suitably a temperature of about 200 °C or less.

[00117] In one embodiment, about 90% to about 100% methane conversion is achieved at a temperature of between about 200 °C and about 450 °C, suitably a temperature of between about 200 °C and about 400 °C, suitably a temperature of between about 200 °C and about 350 °C, suitably a temperature of between about 200 °C and about 300 °C, suitably a temperature of between about 200 °C and about 250 °C, suitably a temperature of about 200 °C.

[00118] In one embodiment, about 80% to about 100% methane conversion is achieved at a temperature of about 450 °C or less, suitably a temperature of about 400 °C or less, suitably a temperature of about 350 °C or less, suitably a temperature of about 300 °C or less, suitably a temperature of about 250 °C or less, suitably a temperature of about 200 °C or less.

[00119] In one embodiment, about 80% to about 100% methane conversion is achieved at a temperature of about 450 °C or less, suitably a temperature of about 400 °C or less, suitably a temperature of about 350 °C or less, suitably a temperature of about 300 °C or less, suitably a temperature of about 250 °C or less, suitably a temperature of about 200 °C or less.

[00120] In one embodiment, about 80% to about 100% methane conversion is achieved at a temperature of between about 200 °C and about 450 °C, suitably a temperature of between about 200 °C and about 400 °C, suitably a temperature of between about 200 °C and about 350 °C, suitably a temperature of between about 200 °C and about 300 °C, suitably a temperature of between about 200 °C and about 250 °C, suitably a temperature of about 200 °C.

[00121 ] In one embodiment, about 70% to about 100% methane conversion is achieved at a temperature of about 450 °C or less, suitably a temperature of about 400 °C or less, suitably a temperature of about 350 °C or less, suitably a temperature of about 300 °C or less, suitably a temperature of about 250 °C or less, suitably a temperature of about 200 °C or less.

[00122] In one embodiment, about 70% to about 100% methane conversion is achieved at a temperature of between about 200 °C and about 450 °C, suitably a temperature of between about 200 °C and about 400 °C, suitably a temperature of between about 200 °C and about 350 °C, suitably a temperature of between about 200 °C and about 300 °C, suitably a temperature of between about 200 °C and about 250 °C, suitably a temperature of about 200 °C.

[00123] In one embodiment, about 60% to about 100% methane conversion is achieved at a temperature of about 450 °C or less, suitably a temperature of about 400 °C or less, suitably a temperature of about 350 °C or less, suitably a temperature of about 300 °C or less, suitably a temperature of about 250 °C or less, suitably a temperature of about 200 °C or less.

[00124] In one embodiment, about 60% to about 100% methane conversion is achieved at a temperature of between about 200 °C and about 450 °C, suitably a temperature of between about 200 °C and about 400 °C, suitably a temperature of between about 200 °C and about 350 °C, suitably a temperature of between about 200 °C and about 300 °C, suitably a temperature of between about 200 °C and about 250 °C, suitably a temperature of about 200 °C.

[00125] In one embodiment, about 50% to about 100% methane conversion is achieved at a temperature of about 450 °C or less, suitably a temperature of about 400 °C or less, suitably a temperature of about 350 °C or less, suitably a temperature of about 300 °C or less, suitably a temperature of about 250 °C or less, suitably a temperature of about 200 °C or less.

[00126] In one embodiment, about 50% to about 100% methane conversion is achieved at a temperature of between about 200 °C and about 450 °C, suitably a temperature of between about 200 °C and about 400 °C, suitably a temperature of between about 200 °C and about 350 °C, suitably a temperature of between about 200 °C and about 300 °C, suitably a temperature of between about 200 °C and about 250 °C, suitably a temperature of about 200 °C. [00127] Suitable temperatures, pressures, WHSVs and feed rates are provided above. Each of the relevant embodiments above are equally applicable to the present aspect of the invention.

[00128] Although the process may be performed batch-wise, a continuous mode may be employed. Thus, the process typically comprises continuously feeding said feed mixture over the catalytic composition. In one embodiment, the process is performed using a suitable reactor, such as a reformer.

[00129] In one embodiment, the feed mixture comprises methane and an oxidant selected from carbon dioxide, air and water, suitably carbon dioxide or water, suitably carbon dioxide.

[00130] In one embodiment, the feed mixture essentially consists of methane and an oxidant. In one embodiment, the oxidant is selected from carbon dioxide, air, nitrogen oxides and water, suitably carbon dioxide or water, suitably carbon dioxide.

[00131 ] In one embodiment, the feed mixture consists of methane and an oxidant. In one embodiment, the oxidant is selected from carbon dioxide, air, nitrogen oxides, oxygen and water, suitably air, carbon dioxide and water. In another embodiment, the oxidant is selected from carbon dioxide and air.

[00132] In one embodiment, the feed mixture comprises about 5% or more of methane For example, about 10% or more of methane. For example, about 20% or more of methane. For example, about 30% or more of methane. For example, about 40% or more of methane. For example, about 50% or more of methane. For example, about 60% or more of methane. For example, about 70% or more of methane. For example, about 80% or more of methane. For example, about 90% or more of methane. For example, about 95% or more of methane.

[00133] In another embodiment, the feed mixture comprises about 10% to about 95% of methane. For example, about 20% to about 95% of methane. For example, about 30% to about 95% of methane. For example, about 40% to about 95% of methane. For example, about 50% to about 95% of methane. For example, about 60% to about 95% of methane. For example, about 70% to about 95% of methane. For example, about 80% to about 95% of methane. For example, about 90% to about 95% of methane.

[00134] In another embodiment, the feed mixture comprises about 10% to about 70% of methane. For example, about 20% to about 70% of methane. For example, about 30% to about 70% of methane. For example, about 40% to about 70% of methane. For example, about 50% to about 70% of methane. For example, about 60% to about 70% of methane. For example, about 70% of methane.

[00135] In another embodiment, the feed mixture comprises about 10% to about 50% of methane. For example, about 20% to about 50% of methane. For example, about 30% to about 50% of methane. For example, about 40% to about 50% of methane. For example, about 50% methane.

[00136] In one embodiment, the feed mixture comprises methane and oxidant in a ratio of about 2:1 to about 1 :2. For example, in a ratio of about 3:2 to about 2:3. For example in a ratio of about 4:3 to about 3:4. For example, in a ratio of about 5:4 to about 4:5. For example in a ratio of about 1 :1 .

[00137] In one embodiment, the feed mixture comprises natural gas and an oxidant. In one embodiment, the oxidant is selected from one or more of air, carbon dioxide, nitrogen oxides water and oxygen, suitably the oxidant is carbon dioxide or air.

[00138] In one embodiment, the feed mixture essentially consists of natural gas and carbon dioxide. In one embodiment the ratio of natural gas to oxidant is about 1 :1 .

[00139] In one embodiment, the feed mixture consists of natural gas and carbon dioxide. In one embodiment the ratio of natural gas to oxidant is about 1 :1 .

[00140] In another aspect, the invention relates to a process for the conversion of methane to hydrogen wherein said process comprises contacting a feed mixture comprising methane and an oxidant with a catalytic composition comprising a metal-doped apatite at a low temperature.

[00141 ] In another aspect, the invention relates to a process for the conversion of methane to oxygenated products wherein said process comprises contacting a feed mixture comprising methane and an oxidant with a catalytic composition comprising a metal-doped apatite at a low temperature.

[00142] In one embodiment, the oxygenated products are selected from formaldehyde, methanol, formic acid and ethanoic acid.

[00143] For each of these aspects, suitable temperatures, conversion rates, pressures, WHSVs, feed rates and combinations thereof are provided above in respect of the conversion of methane to carbon monoxide and hydrogen. [00144] Preferred, suitable, and optional features of any one particular aspect of the present invention are also preferred, suitable, and optional features of any other aspect.

Catalytic Composition

[00145] The processes of the invention comprise contacting the feed mixture with a catalytic composition comprising a metal-doped apatite.

[00146] The metal of the metal-doped apatite, may be selected from the metal, its oxides and mixtures thereof.

[00147] In one embodiment, the metal is a transition metal. The transition metal may be a group 3, group 4, group 5, group 6, group 7, group 8, group 9, group 10, group 1 1 or group 12. For example, the transition metal may be a group 3, group 4, group 5, group 6, group 10, group 1 1 or group 12 transition metal.

[00148] In one embodiment, the transition metal is selected from scandium (Sc), yttrium (Y), lutetium (Lu), lawrencium (Lr), titanium (Ti), zirconium (Zr), hafnium (Hf ), rutherfordium (Rf), vanadium (V), niobium (Nb), tantalum (Ta), dubnium (Db), chromium (Cr), molybdenum (Mo), tungsten (W), seaborgium (Sg), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd) or mercury (Hg).

[00149] In one embodiment, the metal is an oxide of a transition metal. The oxide of a transition metal may be an oxide of a group 3, group 4, group 5, group 6, group 10, group 1 1 or group 12 transition metal.

[00150] The oxide of a transition metal may be an oxide of scandium (Sc) , yttrium(Y), lutetium (Lu), lawrencium (Lr), titanium (Ti), zirconium (Zr), hafnium (Hf), rutherfordium (Rf), vanadium (V), niobium (Nb), tantalum (Ta), dubnium (Db), chromium (Cr), molybdenum (Mo), tungsten (W) , seaborgium (Sg), nickel (Ni), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd) or mercury (Hg).

[00151 ] In one embodiment, the metal or metal oxide is selected from a group 8, group 9, group 10, group 1 1 or group 12 transition metal. In one embodiment, the metal is selected from iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, zinc cadium, and mercury. In one embodiment, the metal oxide is selected from an oxide of iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, zinc, cadmium, and mercury. [00152] In one embodiment, the metal or metal oxide is selected from a group 9, group 10, group 1 1 or group 12 transition metal. In one embodiment, the metal may be selected from cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, zinc, cadmium, and mercury. In one embodiment, the metal oxide is selected from an oxide of cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver, gold, zinc, cadmium, and mercury.

[00153] In one embodiment, the metal or metal oxide is selected from a group 9, group 10 or group 1 1 transition metal. In one embodiment, the metal is selected from cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver and gold. In one embodiment, the metal oxide is selected from an oxide of cobalt, rhodium, iridium, nickel, palladium, platinum, copper, silver and gold.

[00154] In one embodiment, the metal or metal oxide is selected from a group 10 or group 1 1 transition metal. In one embodiment, the metal may be selected from nickel, palladium, platinum, copper, silver and gold. In one embodiment, the metal oxide is selected from an oxide of nickel, palladium, platinum, copper, silver and gold.

[00155] In one embodiment, the metal or metal oxide is selected from a group 1 1 transition metal. In one embodiment, the metal may be selected from nickel, palladium and platinum. In one embodiment, the metal is selected from an oxide of nickel, palladium and platinum.

[00156] In one embodiment, the metal is selected from nickel and palladium, suitably palladium. In one embodiment, the metal oxide is selected from an oxide of nickel, and palladium, suitably palladium.

[00157] In one embodiment, the metal is selected from cobalt, iron, platinum, rhodium, ruthenium, gold, nickel and palladium. In one embodiment, the metal oxide is selected from an oxide of cobalt, iron, platinum, rhodium, ruthenium, gold, nickel and palladium.

[00158] In one embodiment, the particle size of the metal may be in the nanoscale. For instance, the particle size diameter may be in the nanoscale.

[00159] As used herein, a particle size diameter in the nanoscale refers to populations of metal nanoparticles having d(0.5) values of 100 nm or less. For example, d(0.5) values of 90 nm or less. For example, d(0.5) values of 80 nm or less. For example, d(0.5) values of 70 nm or less. For example, d(0.5) values of 60 nm or less. For example, d(0.5) values of 50 nm or less. For example, d(0.5) values of 40 nm or less. For example, d(0.5) values of 30 nm or less. For example, d(0.5) values of 20 nm or less. For example, d(0.5) values of 10 nm or less.

[00160] As used herein, "d(0.5)" (which may also be written as "d(v, 0.5)" or volume median diameter) represents the particle size (diameter) for which the cumulative volume of all particles smaller than the d(0.5) value in a population is equal to 50% of the total volume of all particles within that population.

[00161 ] A particle size distribution as described herein (e.g. d(0.5)) can be determined by various conventional methods of analysis, such as Laser light scattering, laser diffraction, sedimentation methods, pulse methods, electrical zone sensing, sieve analysis and optical microscopy (usually combined with image analysis).

[00162] In one embodiment, populations of metal nanoparticles have d(0.5) values of about 1 nm to about 100 nm. For example, d(0.5) values of about 1 nm to about 90 nm. For example, d(0.5) values of about 1 nm to about 80 nm. For example, d(0.5) values of about 1 nm to about 70 nm. For example, d(0.5) values of about 1 nm to about 60 nm. For example, d(0.5) values of about 1 nm to about 50 nm. For example, d(0.5) values of about 1 nm to about 40 nm. For example, d(0.5) values of about 1 nm to about 30 nm. For example, d(0.5) values of about 1 nm to about 20 nm. For example, d(0.5) values of about 1 nm to about 10 nm.

[00163] In another embodiment, populations of metal nanoparticles have d(0.5) values of about 10 nm to about 100 nm. For example, d(0.5) values of about 10 nm to about 90 nm. For example, d(0.5) values of about 10 nm to about 80 nm. For example, d(0.5) values of about 10 nm to about 70 nm. For example, d(0.5) values of about 10 nm to about 60 nm. For example, d(0.5) values of about 10 nm to about 50 nm. For example, d(0.5) values of about 10 nm to about 40 nm. For example, d(0.5) values of about 10 nm to about 30 nm. For example, d(0.5) values of about 10 nm to about 20 nm. For example, d(0.5) values of about 10 nm.

[00164] In another embodiment, populations of metal nanoparticles have d(0.5) values of about 20 nm to about 100 nm. For example, d(0.5) values of about 20 nm to about 90 nm. For example, d(0.5) values of about 20 nm to about 80 nm. For example, d(0.5) values of about 20 nm to about 70 nm. For example, d(0.5) values of about 20 nm to about 60 nm. For example, d(0.5) values of about 20 nm to about 50 nm. For example, d(0.5) values of about 20 nm to about 40 nm. For example, d(0.5) values of about 20 nm to about 30 nm. For example, d(0.5) values of about 20 nm. [00165] In another embodiment, populations of metal nanoparticles have d(0.5) values of about 30 nm to about 100 nm. For example, d(0.5) values of about 30 nm to about 90 nm. For example, d(0.5) values of about 30 nm to about 80 nm. For example, d(0.5) values of about 30 nm to about 70 nm. For example, d(0.5) values of about 30 nm to about 60 nm. For example, d(0.5) values of about 30 nm to about 50 nm. For example, d(0.5) values of about 30 nm to about 40 nm. For example, d(0.5) values of about 30 nm.

[00166] In another embodiment, populations of metal nanoparticles have d(0.5) values of about 20 nm to about 100 nm. For example, d(0.5) values of about 40 nm to about 90 nm. For example, d(0.5) values of about 40 nm to about 80 nm. For example, d(0.5) values of about 40 nm to about 70 nm. For example, d(0.5) values of about 40 nm to about 60 nm. For example, d(0.5) values of about 40 nm to about 50 nm. For example, d(0.5) values of about 40 nm.

[00167] In another embodiment, populations of metal nanoparticles have d(0.5) values of about 50 nm to about 100 nm. For example, d(0.5) values of about 50 nm to about 90 nm. For example, d(0.5) values of about 50 nm to about 80 nm. For example, d(0.5) values of about 50 nm to about 70 nm. For example, d(0.5) values of about 50 nm to about 60 nm. For example, d(0.5) values of about 50 nm.

[00168] The metal or metal oxide, in one embodiment, comprises 25 % or less of the total weight of the catalytic composition. In another embodiment, the metal or metal oxide comprises 20% or less of the total weight of the catalytic composition. For example, 15 wt.% or less of the catalytic composition. For example, 10 wt.% or less of the catalytic composition. For example, 5 wt.% or less of the catalytic composition. For example, 4 wt.% or less of the catalytic composition. For example, 3 wt.% or less of the catalytic composition. For example, 2 wt.% or less of the catalytic composition. For example, 1 wt.% or less of the catalytic composition. For example, 0.5 wt.% or less of the catalytic composition. For example, 0.1 wt.% or less of the catalytic composition.

[00169] In another embodiment, the metal or metal oxide comprises about 0.01 % to about 25% of the total weight of the catalytic composition. For example, about 0.01 wt. % to about 20 wt. % of the catalytic composition. For example, about 0.01 wt. % to about 15 wt. % of the catalytic composition. For example, about 0.01 wt. % to about 10 wt. % of the catalytic composition. For example, about 0.01 wt. % to about 5 wt. % of the catalytic composition. For example, about 0.01 wt. % to about 4 wt. % of the catalytic composition. For example, about 0.01 wt. % to about 3 wt. % of the catalytic composition. For example, about 0.01 wt. % to about 2 wt. % of the catalytic composition. For example, about 0.01 wt. % to about 1 wt. % of the catalytic composition. For example, about 0.01 wt. % to about 0.5 wt. % of the catalytic composition. For example, about 0.01 wt. % to about 0.1 wt. % of the catalytic composition.

[00170] In another embodiment, the metal or metal oxide comprises about 0.1 % to about 25% of the total weight of the catalytic composition. For example, about 0.1 wt. % to about 20 wt. % of the catalytic composition. For example, about 0.1 wt. % to about 15 wt. % of the catalytic composition. For example, about 0.1 wt. % to about 10 wt. % of the catalytic composition. For example, about 0.1 wt. % to about 5 wt. % of the catalytic composition. For example, about 0.1 wt. % to about 4 wt. % of the catalytic composition. For example, about 0.1 wt. % to about 3 wt. % of the catalytic composition. For example, about 0.1 wt. % to about 2 wt. % of the catalytic composition. For example, about 0.1 wt. % to about 1 wt. % of the catalytic composition. For example, about 0.1 wt. % to about 0.5 wt. % of the catalytic composition. For example, about 0.1 wt. % of the catalytic composition.

[00171 ] In another embodiment, the metal or metal oxide comprises about 0.5 % to about 25% of the total weight of the catalytic composition. For example, about 0.5 wt. % to about 20 wt. % of the catalytic composition. For example, about 0.5 wt. % to about 15 wt. % of the catalytic composition. For example, about 0.5 wt. % to about 10 wt. % of the catalytic composition. For example, about 0.5 wt. % to about 5 wt. % of the catalytic composition. For example, about 0.5 wt. % to about 4 wt. % of the catalytic composition. For example, about 0.5 wt. % to about 3 wt. % of the catalytic composition. For example, about 0.5 wt. % to about 2 wt. % of the catalytic composition. For example, about 0.5 wt. % to about 1 wt. % of the catalytic composition. For example, about 0 0.5 wt. % of the catalytic composition.

[00172] In another embodiment, the metal or metal oxide comprises about 1 % to about 25% of the total weight of the catalytic composition. For example, about 1 wt. % to about 20 wt. % of the catalytic composition. For example, about 1 wt. % to about 15 wt. % of the catalytic composition. For example, about 1 wt. % to about 10 wt. % of the catalytic composition. For example, about 1 wt. % to about 5 wt. % of the catalytic composition. For example, about 1 wt. % to about 4 wt. % of the catalytic composition. For example, about 1 wt. % to about 3 wt. % of the catalytic composition. For example, about 1 wt. % to about 2 wt. % of the catalytic composition. For example, about 1 wt. % of the catalytic composition.

[00173] In another embodiment, the metal or metal oxide comprises about 2 % to about 25% of the total weight of the catalytic composition. For example, about 2 wt. % to about 20 wt. % of the catalytic composition. For example, about 2 wt. % to about 15 wt. % of the catalytic composition. For example, about 2 wt. % to about 10 wt. % of the catalytic composition. For example, about 2 wt. % to about 5 wt. % of the catalytic composition. For example, about 2 wt. % to about 4 wt. % of the catalytic composition. For example, about 2 wt. % to about 3 wt. % of the catalytic composition. For example, about 2 wt. % of the catalytic composition.

[00174] In another embodiment, the metal or metal oxide comprises about 3 % to about 25% of the total weight of the catalytic composition. For example, about 3 wt. % to about 20 wt. % of the catalytic composition. For example, about 3 wt. % to about 15 wt. % of the catalytic composition. For example, about 3 wt. % to about 10 wt. % of the catalytic composition. For example, about 3 wt. % to about 5 wt. % of the catalytic composition. For example, about 3 wt. % to about 4 wt. % of the catalytic composition. For example, about 3 wt. % of the catalytic composition.

[00175] In another embodiment, the metal or metal oxide comprises about 4 % to about 25% of the total weight of the catalytic composition. For example, about 4 wt. % to about 20 wt. % of the catalytic composition. For example, about 4 wt. % to about 15 wt. % of the catalytic composition. For example, about 4 wt. % to about 10 wt. % of the catalytic composition. For example, about 4 wt. % to about 5 wt. % of the catalytic composition. For example, about 4 wt. % of the catalytic composition.

[00176] In one embodiment, the apatite is selected from hydroxyapatite, fluorapatite, chlorapatite and bromoapatite. In one embodiment, the apatite is hydroxyapatite.

[00177] In one embodiment, the apatite is of general formula Cai ₀ (PO ₄ )6(X)2, wherein X is selected from OH, F, CI and Br. In one embodiment, X is selected from OH and F.

[00178] In one embodiment, the apatite is calcium hydroxyapatite of formula

[00179] In one embodiment, the apatite is obtainable by a soft templating method. Suitable soft templating methods would be known to the skilled person.

[00180] In one embodiment, the apatite is obtainable by a hard templating method. Suitable hard templating methods would be known to the skilled person.

[00181 ] The metal-doped apatite suitably has a BET surface area of at least about 50 m ² /g. BET surface area can be measured according to techniques known in the art. For example, BET surface area may be determined by equilibrium adsorption and desorption isoftherms of nitrogen at -196°C for instance. [00182] In embodiment, the BET surface area of the metal-doped apatite is at least about 60 m ² /g. For example, the metal-doped apatite may have a BET surface area of at least about 70 m ² /g. For example, the metal-doped apatite may have a BET surface area of at least about 80 m ² /g. For example, the metal-doped apatite may have a BET surface area of at least about 90 m ² /g. For example, the metal-doped apatite may have a BET surface area of at least 100 m ² /g. For example, the metal-doped apatite may have a BET surface area of at least about 1 10 m ² /g. For example, the metal-doped apatite may have a BET surface area of at least about 120 m ² /g. For example, the metal-doped apatite may have a BET surface area of at least about 130 m ² /g. For example, the metal-doped apatite may have a BET surface area of at least about 140 m ² /g. For example, the metal-doped apatite may have a BET surface area of at least about 150 m ² /g.

[00183] The metal-doped apatite suitably has a BET surface area of from about 50 m ² /g to about 1000 m ² /g. For example, the metal-doped apatite may have a BET surface area of from about 50 m ² /g to about 900 m ² /g. For example, the metal-doped apatite may have a BET surface area of from about 50 m ² /g to about 800 m ² /g. For example, the metal-doped apatite may have a BET surface area of from about 50 m ² /g to about 700 m ² /g. For example, the metal-doped apatite may have a BET surface area of from about 50 m ² /g to about 600 m ² /g. For example, the metal-doped apatite may have a BET surface area of from about 50 m ² /g to about 500 m ² /g. For example, the metal-doped apatite may have a BET surface area of from about 50 m ² /g to about 400 m ² /g. For example, the metal-doped apatite may have a BET surface area of from about 50 m ² /g to about 300 m ² /g. For example, the metal-doped apatite may have a BET surface area of from about 50 m ² /g to about 200 m ² /g.

[00184] The metal-doped apatite suitably has a BET surface area of from about 100 m ² /g to about 1000 m ² /g. For example, the metal-doped apatite may have a BET surface area of from about 100 m ² /g to about 900 m ² /g. For example, the metal-doped apatite may have a BET surface area of from about 100 m ² /g to about 800 m ² /g. For example, the metal- doped apatite may have a BET surface area of from about 100 m ² /g to about 700 m ² /g. For example, the metal-doped apatite may have a BET surface area of from about 100 m ² /g to about 600 m ² /g. For example, the metal-doped apatite may have a BET surface area of from about 100 m ² /g to about 500 m ² /g. For example, the metal-doped apatite may have a BET surface area of from about 100 m ² /g to about 400 m ² /g. For example, the metal-doped apatite may have a BET surface area of from about 100 m ² /g to about 300 m ² /g. For example, the metal-doped apatite may have a BET surface area of from about 100 m ² /g to about 200 m ² /g. For example, the metal-doped apatite may have a BET surface area of from about 150 m ² /g to about 200 m ² /g. [00185] In one embodiment, the metal or metal oxide is selected from group 10 transition metal, the apatite is hydroxyapatite and the BET surface area of the metal-doped apatite is greater than about 100 m ² /g, suitably greater than about 150 m ² /g.

[00186] In one embodiment, the metal or metal oxide is selected from group 10 transition metal, the apatite is hydroxyapatite and the metal or oxide comprises about 1 % to about 10% of the total weight of the catalytic composition, suitably about 1 % to about 5%.

[00187] In one embodiment, the metal or metal oxide is selected from group 10 transition metal, the apatite is hydroxyapatite, the BET surface area of the metal-doped apatite is about 100 m ² /g to about 200 m ² /g, and the metal or oxide comprises about 1 % to about 5%.

[00188] In one embodiment, the metal or metal oxide is selected from nickel and palladium or oxides thereof, the apatite is hydroxyapatite and the BET surface area of the metal-doped apatite is greater than about 100 m ² /g, suitably greater than about 150 m ² /g.

[00189] In one embodiment, the metal or metal oxide is selected from nickel and palladium or oxides thereof, the apatite is hydroxyapatite and the metal or oxide comprises about 1 % to about 10% of the total weight of the catalytic composition, suitably about 1 % to about 5%.

[00190] In one embodiment, the metal or metal oxide is selected from nickel and palladium or oxides thereof, the apatite is hydroxyapatite, the BET surface area of the metal- doped apatite is about 100 m ² /g to about 200 m ² /g, and the metal or oxide comprises about 1 % to about 5%.

[00191 ] In one embodiment, the metal or metal oxide is a transition metal, suitably selected from groups 9, 10 and 1 1 , and the metal has a d(0.5) value of 100nm or less. For example, d(0.5) values of 90 nm or less. For example, d(0.5) values of 80 nm or less. For example, d(0.5) values of 70 nm or less. For example, d(0.5) values of 60 nm or less. For example, d(0.5) values of 50 nm or less. For example, d(0.5) values of 40 nm or less. For example, d(0.5) values of 30 nm or less. For example, d(0.5) values of 20 nm or less. For example, d(0.5) values of 10 nm or less.

[00192] In another embodiment, the metal or metal oxide is a transition metal selected from group 10, and the metal has a d(0.5) value of 10Onm or less. For example, d(0.5) values of 90 nm or less. For example, d(0.5) values of 80 nm or less. For example, d(0.5) values of 70 nm or less. For example, d(0.5) values of 60 nm or less. For example, d(0.5) values of 50 nm or less. For example, d(0.5) values of 40 nm or less. For example, d(0.5) values of 30 nm or less. For example, d(0.5) values of 20 nm or less. For example, d(0.5) values of 10 nm or less.

[00193] In another embodiment, the metal or metal oxide is a transition metal selected from nickel or palladium, and the metal has a d(0.5) value of 100nm or less. For example, d(0.5) values of 90 nm or less. For example, d(0.5) values of 80 nm or less. For example, d(0.5) values of 70 nm or less. For example, d(0.5) values of 60 nm or less. For example, d(0.5) values of 50 nm or less. For example, d(0.5) values of 40 nm or less. For example, d(0.5) values of 30 nm or less. For example, d(0.5) values of 20 nm or less. For example, d(0.5) values of 10 nm or less.

[00194] In another embodiment, the metal or metal oxide is a transition metal selected from nickel or palladium, the apatite is hydroxyapatite and the metal has a d(0.5) value of 100nm or less. For example, d(0.5) values of 90 nm or less. For example, d(0.5) values of 80 nm or less. For example, d(0.5) values of 70 nm or less. For example, d(0.5) values of 60 nm or less. For example, d(0.5) values of 50 nm or less. For example, d(0.5) values of 40 nm or less. For example, d(0.5) values of 30 nm or less. For example, d(0.5) values of 20 nm or less. For example, d(0.5) values of 10 nm or less.

[00195] In one embodiment, the metal-doped apatite has an XRPD pattern substantially as depicted in any one of Figures 2b, 2c and 2d.

[00196] In one embodiment, the metal-doped apatite has an XRPD pattern substantially as depicted in any one of Figures 2b and 2d.

[00197] In one embodiment, the metal-doped apatite has an XRPD pattern substantially as depicted in Figure 2b.

[00198] In one embodiment, the metal-doped apatite has an XRPD pattern substantially as depicted in Figure 2d.

[00199] In one embodiment, the catalytic composition comprises one or more further components. In one embodiment, the catalytic composition further comprises one or more of cerium, sodium, potassium and magnesium.

[00200] In one embodiment, the catalytic composition essentially consists/consists of a metal-doped apatite.

[00201 ] In one aspect, the present invention relates to a metal-doped apatite as described in any one of the above mentioned embodiments. Process for preparation of catalytic composition

[00202] In another aspect, the present invention relates to a process for the preparation of a metal-doped apatite wherein the metal and apatite are complexed by an ion-exchange process.

[00203] In another aspect, the present invention relates to a metal-doped apatite obtainable by the above described process.

Uses

[00204] In another aspect, the present invention provides the use of a metal-doped apatite as defined herein for the decomposition of methane.

[00205] In one embodiment, there is provided the use of a metal-doped apatite as defined herein for the decomposition of methane at low temperature.

[00206] Suitably, a temperature of about 550 °C or lower. For example, a temperature of about 500 °C or lower. For example, a temperature of about 450 °C or lower. For example, a temperature of about 400 °C or lower. For example, a temperature of about 350 °C or lower. For example, a temperature of about 300 °C or lower. For example, a temperature of about 275 °C or lower. For example, a temperature of about 250 °C or lower. For example, a temperature of about 225 °C or lower. For example, a temperature of about 200 °C or lower.

[00207] Suitably at a temperature of from about 200 ^e C to about 650 ^e C, for example from about 200 ^e C to about 600 ^e C, for example from about 200 ^e C to about 550 ^e C, for example from about 200 ^e C to about 500 ^e C, for example from about 200 ^e C to about 450 ^e C, for example from about 200 ^e C to about 400 ^e C, for example from about 200 ^e C to about 350 ^e C, for example from about 200 ^e C to about 300 ^e C, for example from about 200 ^e C to about 275 ^e C, for example from about 200 ^e C to about 250 ^e C, for example from about 200 ^e C to about 225 ^e C, for example about 200 ^e C.

[00208] Suitably the decomposition of methane is in situ in an engine exhaust system.

[00209] Suitably, the engine exhaust system is the exhaust system of an internal combustion engine.

[00210] In one embodiment, the exhaust system is that of an engine fuelled at least partially by methane. For example, the exhaust gas a methane/diesel fuelled engine. [00211 ] In another embodiment, the exhaust system is that of a methane/gasoline fuelled engine.

[00212] In one embodiment, the exhaust system is of a vehicle powered by at least partially by methane.

[00213] In another embodiment, the exhaust system is of a vehicle powered by a methane/diesel fuelled engine or a methane/gasoline fuelled engine.

[00214] In another aspect, the present invention provides a catalytic converter comprising a metal-doped apatite as defined herein. Suitably, the catalytic converter is a catalytic converter in the exhaust system of a vehicle. Suitably, the catalytic converter is a catalytic converter in the exhaust system of a vehicle powered by at least partially by methane. Suitably, the catalytic converter is a catalytic converter in the exhaust system of a vehicle powered by a methane/diesel fuelled engine or a methane/gasoline fuelled engine.

[00215] In another aspect, the present invention provides an engine exhaust system comprising a metal-doped apatite as defined herein. Suitably, the engine exhaust system is an engine exhaust system of a vehicle. Suitably, the engine exhaust system is an engine exhaust system of a vehicle powered by at least partially by methane. Suitably, the engine exhaust system is an engine exhaust system of a vehicle powered by a methane/diesel fuelled engine or a methane/gasoline fuelled engine.

[00216] In another aspect, the present invention provides the use of a metal-doped apatite as defined herein for the conversion of methane to carbon monoxide and hydrogen, and/or the conversion of methane to hydrogen and/or the conversion of methane to oxygenated products.

[00217] The invention will now be further described by the following non-limiting examples.

EXAMPLES

Materials and chemicals

[00218] All chemicals were obtained from Sigma-Aldrich and used as received without any further purification. All solutions were made using deionised water with resistivity not less than 18.2 ΜΩ cm. Catalyst synthesis

[00219] Ca(N0 ₃ ) ₂ (7.88 g) was mixed with KH ₂ P0 ₄ (2.72 g), dissolved in deionised water (26.6 mL) and acidified by cone. HN0 ₃ (13.6 mL) to avoid precipitation of Ca ₃ (P0 ₄ )2. This acidic solution was then added to a mixture of Tween60 and nonaoxyethylene dodecyl ether (C12EO9, 26 g and 10.66 g, respectively) and heated to 60 °C with stirring until a clear solution was formed. The solution was cooled to room temperature and treated with NH ₃ (44 mL) added dropwise to precipitate HAP. The suspension was stirred overnight, filtered, washed with ethanol and water, dried and calcined in air for 5 hours at 550 °C.

[00220] Catalyst B was prepared by ion exchange: 50 mg of PdCI ₂ was dissolved in 100 ml deionised water, added to 1 g HAP and the resulting mixture was stirred for three days at room temperature, filtered, vacuum dried and calcined at 550 °C for 3 hours.

[00221 ] Catalyst C and Catalyst D prepared using a hard-templating route: SBA-15 (1 g) was impregnated with aqueous solution containing sucrose (1 .25 g), concentrated H ₂ S0 ₄ (78.87 μΐ) and deionised water (5 mL). The mixture was dried in an oven for 6 hours at 100 °C and a further 6 hours at 160 °C. The sample was impregnated again with the solution of sucrose (0.8 g), concentrated H ₂ S0 ₄ (50.7 μΐ) and deionised water (5 mL) and dried in the oven in the same manner as before. The carbonisation was completed by pyrolysis in 50 mL min ¹ He at 800 °C. The obtained powder was washed twice with NaOH (0.1 M, 50:50 ethanol :water) at 100 °C to remove silica template, then filtered and dried at 120 °C to give carbon nanorods. Carbon nanorods (0.3g) were suspended in deionised water (6 mL) using sonication, added to a solution of (NH ₄ ) ₂ HP0 (0.4 M, 100 mL) and stirred at room temperature in a 2 L beaker. Ca(N0 ₃ ) ₂ (0.6 M, 100 mL) was added dropwise over one hour, resulting in a 'milky' suspension of HAP. The Ca/P molar ratio was kept at 1 .67 corresponding to the stoichiometry of HAP. The pH was maintained through the addition of NaOH (0.1 M) within the range 9.4-9.5. This 'milky' suspension was stirred overnight at room temperature. The obtained precipitate was filtered, washed alternately with water and ethanol three times, oven dried at 65 °C for six hours, and calcined at 600 °C in air for 2 hours.

[00222] Pd was added in the form of Pd(N0 ₃ ) ₂ to Catalyst C and as PdCI ₂ to Catalyst D, each in an identical manner to the ion exchange method described for Catalyst B.

[00223] A reference catalytic material was prepared by adding Pd(N0 ₃ ) ₂ to zeolite Y (Zeolyst, 780 m ² g ^~1 , Si/AI 30) in an identical manner to the ion exchange method described for Catalyst B. Characterisation

[00224] X-Ray diffraction (XRD) was conducted in powder spinning mode at ambient conditions using a Panalytical X'Pert Powder diffractometer with Cu K _a radiation (λ = 1 .5406 A). All powder diffraction patterns were recorded with step size 0.052 and step time 200 s, using an X-ray tube operated at 40 kV and 30 mA with fixed 1/2 ° anti-scatter slit.

[00225] Nitrogen adsorption/desorption measurements were carried out using a Micromeritics ASAP 2020 Surface Analyser at -196 °C. Samples were degassed under vacuum (p < 10 ^~5 mbar) for 3 h at 300 °C prior to analysis. BET surface areas of the samples were calculated in the relative pressure range 0.05-0.30.

[00226] Microscopic images were recorded using a Supra 40VP (Carl Zeiss Ltd, UK) scanning electron microscope (SEM) or JEOL JEM 210 transmission electron microscopy (TEM).

[00227] Semi-quantitative chemical analysis was performed by energy-dispersive X-ray spectroscopy (EDAX) using an Apollo 40 SDD instrument.

[00228] Thermogravimetric analysis (TGA) measurements were recorded using a Perkin Elmer 4000 instrument heated at 10 °C min ¹ from 25-820 °C in 40.0 ml min ¹ flowing air.

Catalytic tests

[00229] The catalyst activity was studied in a quartz fixed bed reactor, Figure 1 , placed inside a temperature controlled furnace (Carbolite type 3216, Tempatron, PID500/1 10/330). The catalyst (0.2 g) was placed in a quartz tube (10 mm diameter, 1 mm thickness) between quartz wool plugs. A feed mixture of 100 ml min ^-1 comprising CH ₄ :CC>2:He equal to 5:5:90 was used in all catalytic tests. Gases were supplied from lecture bottles (CKGAS filled to 200 Bar at 15 °C) and regulated using single stage CONCOA 302 series gas regulators. The flow of each gas was maintained using Bronkhorst UK model F-201 CV mass flow controllers. Prior to reaction the catalyst was reduced in 30 ml min ¹ H ₂ for 1 hour at 300 °C. The reaction products were monitored by a Hewlett Packard 5890 series II gas chromatograph equipped with a GS- GASPRO column (60 m x 0.32 mm) connected via a 6-way gas sampling valve to a thermal conductivity detector. Measurements were recorded at 50 °C intervals (after holding at that temperature for 5 mins) between 205 and 650 °C using a heating rate of 10 °C min ¹ . A stability study was then conducted at 297 °C (on the same sample after testing from 205-650 °C without any treatment) whereby hourly measurements were recorded, after which the reactor cooled to ambient temperature overnight in He. The next morning the reactor was heated from RT to 297 °C at 10 °C min ¹ in He and the stability study procedure was repeated for a further 9 days giving a total of 97 hours testing.

Results and Discussion

[00230] The XRD patterns, Figure 2, confirm the characteristic P6 ₃ /m hexagonal atom arrangement of HAP in all catalysts.

[00231 ] Nitrogen adsorption showed the following BET surface areas; Catalyst B - 1 15 m ² g- ¹ ; Catalyst C - 59.5 m ² g ¹ ; and Catalyst D - 67.4 m ² g ¹ .

[00232] The SEM (top left, Figure 3) images of Catalyst B, reveals the agglomerated and crystalline structure of the catalyst and EDAX (top right, Figure 3) shows the presence of elements Ca, P, O, and Pd, as expected. TEM shows that the Pd nanoparticles are highly dispersed on the support surface (centre and bottom, Figure 3) and confirms the presence of sub-micron sized catalyst particles (centre and bottom, Figure 3).

[00233] The catalytic properties were evaluated in the continuous conversion of methane, first as a function of temperature. Figure 4a shows that the catalytic activity varied considerably over the range of catalysts used.

[00234] The methane conversion for Pd-zeolite Y was 0-20% over the range 200-450 °C and increased thereafter reaching 93% at 650 °C. In contrast, the results for Catalyst B showed that the methane feed was 23% decomposed at 205 °C and fully decomposed over the temperature range 255-650 °C. These results confirm that Catalyst B is active at (relatively) low operating temperatures in methane decomposition.

[00235] The stability of Catalyst B was determined by recording the conversion of methane as a function of reaction time at fixed temperature 297 °C (Figure 4b). The methane conversion, initially >99%, dropped to 94% after 3 hours on stream, 80% after 8 hours, and retained practically constant activity at 77±2% conversion thereafter for a total of 97 hours testing.

[00236] The conversion for Catalyst C increased from 78% at 205 °C to 91 % at 650 °C (Figure 4a), while Catalyst D removed >99% of methane over the full temperature range.

[00237] The amount of carbon deposited on Catalyst B was analysed by comparing TGA signals for catalysts tested before and after the methane reforming reactions (Figure 5). The weight loss before reaction between 1 10-200 °C is due to physisorbed water and at higher temperatures is assigned to chemisorbed water and possibly carbon dioxide (both resulting partially from exposure to the atmosphere before reaction). The sample tested after reaction shows a much lower weight loss between room temperature and 530 °C due to its previous use as a catalyst up to a maximum temperature of 650 °C, which is expected to remove residual water and carbon dioxide. The weight loss between 530 and 720 °C, 1 .89 wt%, is attributed to the oxidation of carbon deposited during the methane reforming reaction. This low value for weight loss supports the consistently high levels of methane conversion observed over the entire duration of stability testing.

Conclusion

[00238] Novel metal-doped apatite catalysts has been developed that successfully decompose over 99% of methane at low temperature and retain catalytic activity at 77±2% conversion for a total of 97 hours testing.

[00239] These catalysts are expected to useful in catalytic converters, in particular, catalytic convertors for use in engine exhaust systems.

[00240] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference in their entirety and to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein (to the maximum extent permitted by law).

[00241 ] All headings and sub-headings are used herein for convenience only and should not be construed as limiting the invention in any way.

[00242] The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise paragraphed. No language in the specification should be construed as indicating any non-paragraphed element as essential to the practice of the invention.

[00243] The citation and incorporation of patent documents herein is done for convenience only and does not reflect any view of the validity, patentability, and/or enforceability of such patent documents.

[00244] This invention includes all modifications and equivalents of the subject matter recited in the paragraphs appended hereto as permitted by applicable law.