Field of the disclosure

The present disclosure relates to a process for petrochemicals synthesis from liquefied natural gas (LNG) as well as to an installation for performing such a process. In particular, the present disclosure relates to the production of oxygenated hydrocarbons, such as methanol, from liquefied natural gas.

Background

The huge reserves of natural gas have driven research for exploiting this resource either as fuel and/or as feedstock for chemical production processes. The very high chemical stability of methane, natural gas major component, however, renders its transformation very difficult. Nowadays, the industrially implemented processes are of the indirect type, i.e. natural gas is first converted into synthesis gas or “syngas”, a mixture of carbon monoxide and hydrogen, which is then further converted into valuable products like hydrocarbons, alcohols and many others.

The conversion of natural gas into syngas requires a lot of energy. For this reason, more energy-efficient routes have been investigated. The direct conversion of natural gas into chemicals, without going through the intermediate synthesis gas, could be more energy efficient. These direct routes, however, are not yet competitive with the indirect route due to too low thermal efficiencies and too important heat and momentum transfer duties, as stated in the study of Lange J.-P. et al. (Chem. Eng. Sci., 1996, 51, 2379-2387).

Indeed, direct routes for natural gas conversion still need a relatively high energy input in order to activate the very stable methane, and are generally quite exothermic and have a poor selectivity. The conversion of natural gas is therefore kept low and/or the natural gas is processed in dilution with an inert gas. Recycling the unconverted (diluted) gas is then essential in order to obtain an economically viable process. This recycling, in turn, requires energy for the recycling compressors, which more than annihilates the energy savings obtained by skipping the syngas production stage.

Methods aiming at enhancing the conversion of natural gas per pass have been reported in the art. These methods focus on the design of the reactor for enhancing the selectivity of the conversion reactions. For example, patent US 4,618,732 discloses a process for converting natural gas containing methane into methanol, which intimately mixes the natural gas feed with the oxidant (gaseous air or oxygen-enriched air or (pure) oxygen) before introduction into an inert reactor. The use of an inert reactor would reduce side reactions leading to poor selectivity. As much as 90% by volume of the methane consumed can be converted into methanol and as much as 10 to 20% by volume of the methane can be reacted in each pass through the reactor. The selectivity for methanol is improved by careful premixing of methane and oxygen and by eliminating reactor wall effects by the use of glass-lined reactors.

Another method for avoiding side reactions and for reducing reaction time while ensuring thorough radial mixing, is the use of inert reactor packing material as described in patent US 4,982,023. Although inert surfaces do reduce deep oxidation of methane to carbon monoxide and carbon dioxide compared to metal surfaces, their effect is not significant enough to allow reaching sufficiently high methanol yields per pass at reasonable selectivities.

The use of engine-type reactors is disclosed in patent US 2,922,809. The process described allows controlling very short reaction times together with very fast temperature quenching rates to avoid secondary reactions and thus improves selectivity towards methanol. The conversion rates are however extremely low, which thus requires very high recycling rates.

Fuel pipes (combustion reactors) have also been used to keep the reaction times very short, as described in patent GB 2 159 153. In this type of reactor, natural gas and the oxidant react in the form of a flame. However, the conversion into methanol remains very low.

Non-thermal plasma reactors are described as quite effective in reaching high selectivity towards methanol in direct partial oxidation of methane. For example, patent IT 1391370 describes the use of a gliding arc in a tornado (GAT) reactor for converting methane into methanol. Nozaki T. et al. (Stud. Surf. Sci. Catal., 2004, 147, 505-510) describe having reached one-pass yields of methanol up to 17% using a flow-type, non-equilibrium, microplasma reactor. The energy efficiencies of this type of reactor at an industrial scale, however, are still to be determined.

W02008/041076 describes systems and methods for regasifying liquefied natural gas (LNG). The LNG is regasified by transferring heat from a steam methane reforming reaction to the LNG. In one embodiment, heat is transferred to the LNG from a synthesis gas produced in a steam methane reforming reaction. In another embodiment, heat is transferred to the LNG from a flue gas provided from a furnace heating a steam methane reforming reactor. By using excess heat from the steam methane reforming process, less energy may be consumed to regasify LNG. WO2014/145398 describes a method for preparing oxygenated hydrocarbons that includes steps of reacting a first heated hydrocarbon-containing gas stream with an oxygen-containing gas stream in a reactor to form a first product blend, recovering the energy generated in the reactor to preheat incoming hydrocarbon feed to the reactor and/or to drive endothermic reactions that generate synthesis gas, separating and condensing one or more liquid oxygenated hydrocarbons from the product stream, separating a reject stream from a recycle stream, mixing remaining gaseous hydrocarbon product from the recycle stream with the first hydrocarbon-containing gas stream after one reaction cycle, converting the first reject stream to a synthesis gas mixture, and converting the synthesis gas mixture to light alkanes to be blended with one or with oxygenates in an output stream to optionally form higher molecular weight oxygenates.

There is still a need for a process of transforming natural gas into one or more liquid petrochemicals selected from oxygenated hydrocarbons {e.g, methanol) with improved thermal efficiency and, with preference, for improved heat and/or momentum transfer duties.

Summary

According to a first aspect, the disclosure provides a process for transforming liquefied natural gas into one or more liquid petrochemicals selected from oxygenated hydrocarbons, the process comprising the following steps: a) providing a liquefied natural gas stream, b) providing heat to said liquefied natural gas stream to regazifying it so as to produce a regasified natural gas stream, c) converting at least one portion of the said regasified natural gas stream into a stream of petrochemicals compounds selected from oxygenated hydrocarbons by contacting at least one portion of regasified natural gas stream with at least one reactant being a stream of gaseous air enriched with oxygen; wherein the conversion reaction is exothermic so that the stream of petrochemicals compounds shows a temperature higher than the temperature of the said regasified natural gas stream; wherein said process is remarkable in that at least a part of the heat requested for the regasifying step (b) is provided by heat transfer from the stream of petrochemicals compounds obtained in step (c) to the said liquefied natural gas stream, and in that the process further comprises the steps of: i. providing a gaseous air stream, and ii. removing at least a part of the gaseous nitrogen contained in the said gaseous air stream, to produce a stream of gaseous nitrogen showing a temperature T1 , and a stream of liquid air enriched with oxygen showing a temperature T3; iii. increasing the temperature T1 of the stream of gaseous nitrogen to a temperature T2, T2 being higher than T1 , by heat transfer from the gaseous air stream provided in step (i) to the stream of gaseous nitrogen, iv. increasing the temperature of the liquefied natural gas stream before the regasifying step (b) by heat transfer from the stream of gaseous nitrogen showing the temperature T2 to said liquefied natural gas stream, and v. increasing the temperature T3 of the stream of liquid air enriched with oxygen to a temperature T4, T4 being higher than T3, by heat transfer from the gaseous air stream provided in step (i) to the stream of liquid air enriched with oxygen.

As it is understood from the above definition, the integrated process of the disclosure allows not only reusing the heat of the stream of petrochemicals compounds selected from oxygenated hydrocarbons as a source of energy for the regasification unit, but also the heat recovered from the air separation unit. Such thermal integration involving several heat transfers allows the production of petrochemicals compounds comprising oxygenated hydrocarbons, such as methanol and/or formaldehyde, directly from LNG and with a single pass. The integrated process shows an improved the thermal efficiency by comparison of known processes. This integrated process has also the ecological advantage to allow avoiding the waste of the heat generated by the partial oxidation of the NG and of the air separation.

With preference, the petrochemicals compounds selected from oxygenated hydrocarbons comprise at least one alcohol and/or at least one aldehyde; preferably at least one alcohol. For example, the petrochemicals compounds selected from oxygenated hydrocarbons comprise one or more selected from methanol, ethanol, propanol, butanol, pentanol, formaldehyde, acetaldehyde, propionaldehyde and any combinations thereof.

For example, the petrochemicals compounds selected from oxygenated hydrocarbons comprise one or more alcohols selected from the group consisting of methanol, ethanol, propanol, butanol, pentanol and combinations; with preference, one or more alcohols selected from methanol and/or ethanol; more preferably the petrochemicals compounds selected from oxygenated hydrocarbons are or comprise methanol.

For example, the petrochemicals compounds selected from oxygenated hydrocarbons comprise one or more aldehydes selected from the group consisting of formaldehyde, acetaldehyde, propionaldehyde and any combinations thereof; with preference, one or more aldehydes selected from formaldehyde and/or acetaldehyde; more preferably the petrochemicals compounds selected from oxygenated hydrocarbons comprise formaldehyde. For example, the petrochemicals compounds selected from oxygenated hydrocarbons are or comprise methanol and/or formaldehyde; with preference the petrochemicals compounds selected from oxygenated hydrocarbons are or comprise methanol.

With preference, the process for transforming liquefied natural gas into one or more liquid petrochemicals comprises a step of pressurization of said liquefied natural gas before the regasifying step (b) to obtain a pressurized liquefied natural gas stream; with preference, said step of pressurization provides a pressurized liquefied natural gas stream having a pressure comprised between 7 MPa and 10 MPa, preferably between 8 MPa and 9 MPa.

Pressurizing the liquefied natural gas further allows reducing the momentum transfer duty since the need for a gas-compressing power needed to feed the pressurized regasified natural gas stream to the conversion reactor is considerably lowered or even suppressed.

For example, the flow of the pressurized regasified natural gas stream converted in step (c) is obtained by a liquid pump used in step (a).

For example, the conversion reaction of step (c) is performed by partial oxidation of at least one portion of the regasified natural gas stream to produce a stream of methanol and/or into a stream of formaldehyde; preferably, into a stream of methanol.

For example, the conversion reaction of step (c) is performed by contacting at least one portion of the regasified natural gas stream with at least one reactant; with preference, said at least one reactant is a stream of gaseous air enriched with oxygen.

For example, the conversion reaction of step (c) is performed with a residence time ranging from 0.1 to 100 seconds; preferably ranging from 0.5 to 30 seconds; more preferably ranging from 1 to 10 seconds, and most preferably ranging from 3 to 8 seconds. It as been found that the use of short residence time favours the selectivity to methanol and/or formaldehyde.

For example, the conversion reaction of step (c) is performed at a pressure from 7 to 10 MPa, a temperature ranging from 300°C to 600°C and a methane to oxygen molar ratio ranging from 1 :1 to 50:1. With preference, the conversion reaction of step (c) is performed at a pressure from 7 to 10 MPa, a temperature ranging from 300°C to 600°C, a methane to oxygen molar ratio ranging from 1 :1 to 50:1 , and a residence time ranging from 1 to 10 seconds.

In an embodiment, the conversion reaction of step (c) is performed using one or more transition metal ion loaded zeolite catalysts and/or metal ion loaded mesoporous silica catalysts. With preference, the one or more transition metal ion loaded zeolite catalysts are selected from a rhodium zeolite catalyst, a copper zeolite catalyst, an iron zeolite catalyst, a nickel zeolite catalyst, an iridium zeolite catalyst or a combination thereof. In another embodiment, the conversion reaction of step (c) is performed in the absence of catalyst; with preference, the conversion reaction of step (c) is performed in a conversion reactor comprising an internal surface made of silica or coated with silica.

In an embodiment, the process comprises a step of mixing the at least one portion of the regasified natural gas stream and the stream of gaseous air enriched with oxygen that is performed before the step (c). It has been found that such a mixing step favours the selectivity to methanol.

For example, step (ii) of removing at least a part of the nitrogen is conducted to remove at least 50 mol% of the gaseous nitrogen contained in the gaseous air stream; for example; at least 60 mol%; for example, at least 80 mol%; for example, at least 90 mol%.

For example, step (ii) of removing at least a part of the nitrogen is conducted to remove at most 95 mol% of the gaseous nitrogen contained in the gaseous air stream.

In an embodiment, the process further comprises a step (d) of separating one or more liquid petrochemicals comprising oxygenated hydrocarbons from the said stream of petrochemicals compounds.

For example, the separation step (d) is performed, and the separation step (d) further comprises separating unconverted regasified natural gas from the stream of petrochemicals compounds. With preference, said unconverted regasified natural gas is recombined with the regasified natural gas stream obtained in the regasifying step (b).

In an embodiment, the process comprises a step of preheating the at least one portion of said regasified natural gas stream before step (c). With preference, the step of preheating the at least one portion of said regasified natural gas stream before step (c) is performed by heat exchange between the stream of petrochemicals compounds and the at least one portion of said regasified natural gas stream.

According to a second aspect, the disclosure provides an installation to transform liquefied natural gas into one or more liquid petrochemicals comprising oxygenated hydrocarbons according to the first aspect of the disclosure; wherein said installation is remarkable in that it comprises: a tank suitable to be loaded with liquefied natural gas, a regasification unit downstream to the tank, a conversion reactor downstream to the regasification unit, a gas/liquid separation system downstream to the conversion reactor, wherein said conversion reactor and said gas/liquid separation system are in fluidic connection by a line conveying a stream of petrochemicals compounds exiting the conversion reactor, where a portion of the said line is coupled with the regasification unit to transfer heat from the stream of petrochemicals compounds to the liquefied natural gas stream by indirect contact through a heat exchanger; and in that the installation further comprises an air separation unit, wherein:

- the air separation unit comprising a gaseous air stream input line and one or more output lines, wherein one output line is a liquid air enriched with oxygen stream output line in fluidic connection with said conversion reactor and being upstream of said conversion reactor; wherein at least one heat exchanger is arranged between the gaseous air stream input line and the liquid air enriched with oxygen output line exiting the separator to increase the temperature of the liquid air enriched with oxygen stream by heat transfer from the gaseous air stream to the liquid air enriched with oxygen stream;

- the air separation unit comprising a separator, wherein one output line is a gaseous nitrogen stream output line, and wherein at least two heat exchangers are arranged successively on the said gaseous nitrogen stream output line; namely: a first heat exchanger arranged between the gaseous air stream input line and the gaseous nitrogen stream output line to increase the temperature of the gaseous nitrogen stream exiting the separator by heat transfer from the gaseous air stream (29) to the gaseous nitrogen stream, and a second heat exchanger, placed downstream of the first heat exchanger, that is arranged between the gaseous nitrogen stream output line exiting the first heat exchanger and a line that connects the tank to the regasification unit to increase the temperature of a liquefied natural gas stream circulating within said line by heat transfer from the gaseous nitrogen stream to the said liquefied natural gas stream.

With preference, said installation further comprises a liquid pump, said liquid pump being disposed between said tank and said regasification unit.

With preference, said installation further comprises a pump arranged on said liquid air enriched with oxygen stream output line.

For example, the air separation unit comprises a gaseous air stream input line and one or more output lines, wherein one output line is a gaseous nitrogen stream output line.

With preference said gaseous nitrogen stream output line is arranged to form a loop to recycle the gaseous nitrogen stream exiting the second heat exchanger into the separator. For example, the installation comprises an air separation unit, the air separation unit comprising a separator, a gaseous air stream input line and one or more output lines, wherein one output line is a liquid air enriched with oxygen stream output line and wherein at least one heat exchanger is arranged between the gaseous air stream input line and the liquid air enriched with oxygen output line exiting the separator to increase the temperature of the liquid air enriched with oxygen stream by heat transfer from the gaseous air stream to the liquid air enriched with oxygen stream.

For example, the installation further comprises a transportation unit downstream of the regasification unit, for example, said installation comprises at least one line to redirect at least a part of the gas stream exiting said gas/liquid separation system to the said transportation unit.

For example, the conversion reactor is a cold plasma reactor.

For example, the installation further comprises downstream to the gas/liquid separation system a methanol-to-olefins unit and/or a methanol-to-gasoline unit and/or a methanol-to- formaldehyde unit and/or a methanol-to-dimethyl ether unit.

For example, the installation further comprises a pre-mixing chamber arranged to mix the regasified natural gas stream and the stream of gaseous air enriched with oxygen before they enter the conversion reactor.

For example, the installation further comprises a heat exchanger arranged between the line conveying a stream of petrochemicals compounds exiting the conversion reactor and the line of regasified natural gas stream to pre-heat the regasified natural gas stream before entering the conversion reactor.

Description of the figure

Figure 1 illustrates an embodiment of an installation to conduct the process according to the disclosure.

Detailed description

For the disclosure, the following definitions are given:

The term “alkali metal” refers to an element classified as an element from group 1 of the periodic table of elements, excluding hydrogen. According to this definition, the alkali metals are Li, Na, K, Rb, Cs and Fr. The term “alkaline earth metal” refers to an element classified as an element from group 2 of the periodic table of elements. According to this definition, the alkaline earth metals are Be, Mg, Ca, Sr, Ba and Ra.

The term “transition metal” refers to an element whose atom has a partially filled d sub-shell, or which can give rise to cations with an incomplete d sub-shell (IIIPAC definition). According to this definition, the transition metals are Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, La, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Ac, Rf, Db, Sg, Bh, Hs, Mt, Ds, Rg, and Cn.

Zeolite codes (e.g., CHA...) are defined according to the “Atlas of Zeolite Framework Types", 6 ^th revised edition, 2007, Elsevier, to which the present application also refers.

The terms "comprising", "comprises" and "comprised of" as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. The terms "comprising”, "comprises" and "comprised of" also include the term “consisting of”.

The yield to particular chemical compounds is determined as the mathematical product between the selectivity to said particular chemical compounds and the conversion rate of the chemical reaction. The mathematical product is expressed as a percentage.

The recitation of numerical ranges by endpoints includes all integer numbers and, where appropriate, fractions subsumed within that range (e.g. 1 to 5 can include 1 , 2, 3, 4, 5 when referring to, for example, a number of elements, and can also include 1 .5, 2, 2.75 and 3.80, when referring to, for example, measurements). The recitation of endpoints also includes the recited endpoint values themselves (e.g. from 1.0 to 5.0 includes both 1.0 and 5.0). Any numerical range recited herein is intended to include all sub-ranges subsumed therein.

The particular features, structures, characteristics or embodiments may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments.

Integrating a regasification unit with a conversion reactor

As it can be seen in figure 1 , the liguefied natural gas 3 from storage tank 1 is directed into a regasification unit 11 .

The liguefied natural gas 3 can be pressurized through a liguid pump 5 before being directed to the regasification unit 11. With preference, the liguid pump 5 allows obtaining pressurized liquefied natural gas 7 which can have a pressure ranging between 7 MPa and 10 MPa, preferably between 7.5 MPa and 9.5 MPa. In that case, the stream of regasified natural gas 13 exiting the regasification unit 11 is pressurized and the flow of said stream of regasified natural gas 13 can be achieved by the liquid pump 5.

The stream of regasified natural gas 13 exiting the regasification unit 11 is partly or entirely directed to a conversion reactor 17. The stream of regasified natural gas 13 is thus converted into a stream of petrochemicals compounds 19. The integrated process is remarkable in that the regasifying step (b) includes providing heat to the liquefied natural gas stream (3; 7) and in that at least a part of the heat requested for the regasifying step (b) is provided by heat transfer from the stream of petrochemicals compounds 19 obtained in step (c) to the said liquefied natural gas stream. Thus, the heat of the stream of petrochemicals compounds 19 is not wasted and is reused as a source of energy for the regasification unit 11.

Additionally, in the presence of the liquid pump 5, namely when the stream of regasified natural gas 13 is pressurized, the same liquid pump 5 can also control the flow of the stream of regasified natural gas which is fed into the conversion reactor 17. In this case, the momentum transfer duty is reduced by reducing the need for a gas-compressing power needed to feed the pressurized regasified natural gas stream 13 to the conversion reactor 17.

It is further advantageous that the stream of regasified natural gas 13 (pressurized or not, but preferably pressurized) is directed into a heat exchanger 53 before entering into the conversion reactor 17, said heat exchanger 53 is coupled to the stream of petrochemical compounds 19. This allows further recovery of the heat carried by the stream of petrochemical compounds 19 by transferring the heat of said stream to the stream of regasified natural gas 13, improving thus the energy efficiency of the integrated process.

Thus, the process can comprise a step of preheating the at least one portion of said regasified natural gas stream before step (c). With preference, the step of preheating the at least one portion of said regasified natural gas stream before step (c) is performed by heat exchange between the stream of petrochemicals compounds and the at least one portion of said regasified natural gas stream. Alternatively, or in a complementary manner, the step of preheating can be performed with a furnace (not illustrated).

Optionally, the stream of petrochemicals compounds 19 is directed into a gas/liquid separation system 21. Said gas/liquid separation system 21 is used to separate the unconverted regasified natural gas 27 from one or more liquid petrochemicals 23. Ideally, the one or more liquid petrochemicals 23, preferably oxygenated chemical compounds, are recovered in a recovery unit 25 and/or directed to a methanol-to-olefins (MTO) unit (not represented) and/or a methanol-to-gasoline (MTG) unit (not represented) and/or a methanol-to-formaldehyde unit (not represented) and/or a methanol-to-dimethyl ether unit (not represented).

Optionally, as shown in figure 1 , the unconverted regasified natural gas 27 is entirely recombined with the stream of regasified natural gas 13 exiting the regasification unit 11. Said stream of regasified natural gas 13 can be transported to a transportation unit 15. Upon the needs, gas compressor or gas regulator (not illustrated) can be placed on the lines exiting the gas/liquid separation system 21.

Instead of recombining the unconverted regasified natural gas 27 with the stream of regasified natural gas 13 exiting the regasification unit 11 , the unconverted regasified natural gas can also be partly or entirely recycled into a conversion reactor 17 (not shown). The portion which is not recycled can then be recombined with the stream of regasified natural gas exiting the regasification unit.

Integrating a liquefied natural gas regasification unit 11 with a conversion reactor 17 that allows direct partial oxidation of methane to methanol unit allows using the heat released by the direct partial oxidation of methane for the regasification of the liquefied natural gas and allows using the high-pressure natural gas produced by the regasification unit 11 efficiently as feedstock for the direct partial oxidation of methane. By comparison, in classical stand-alone direct partial oxidation of methane to methanol unit, the energy efficiency is poor due to the necessity for evacuating the reaction heat from the unit, and also due to the need for compressors to pressurize and recycle the (unconverted) natural gas. The process has the double advantage of reusing the heat that is released from the conversion reactor and of preventing the need for compressors to convey the pressurized natural gas.

Production of methanol by partial oxidation of the reqasified natural gas

As schematized in figure 1 , it is particularly preferred that the conversion reactor 17 is a partial oxidation unit coupled to an air separation unit. The air separation unit comprises a separator 31 useful to treat an incoming stream of gaseous air 29 to separate the two major components of the air, namely nitrogen and oxygen, into a stream of liquid air enriched with oxygen, preferably a stream of liquid oxygen 33 and a gaseous nitrogen stream 41. The gaseous nitrogen stream 41 can further comprise noble gas.

The process therefore further comprises the steps of: i. providing a gaseous air stream, and ii. removing at least a part of the gaseous nitrogen contained in the said gaseous air stream, to produce a stream of gaseous nitrogen and a stream of liquid air enriched with oxygen. For example, step (ii) of removing at least a part of the nitrogen is conducted to remove at least 50 mol% of the gaseous nitrogen contained in the gaseous air stream; for example; at least 60 mol%; for example, at least 80 mol%; for example, at least 90 mol%. For example, step (ii) of removing at least a part of the nitrogen is conducted to remove at most 95 mol.% of the of the gaseous nitrogen contained in the gaseous air stream.

The step (ii) of removing at least a part of the gaseous nitrogen contained in the said gaseous airstream produces a stream of gaseous nitrogen showing a temperature T 1 , and the process further comprises the following steps: iii. increasing the temperature T1 of the stream of gaseous nitrogen to a temperature T2, T2 being higher than T1 ; with preference, by heat transfer from the gaseous air stream provided in step (i) to the stream of gaseous nitrogen showing the temperature T 1 , and iv. increasing the temperature of the liquefied natural gas stream before the regasifying step (b) by heat transfer from the stream of gaseous nitrogen showing the temperature T2 to the said liquefied natural gas stream.

The step (ii) of removing at least a part of the gaseous nitrogen contained in the said gaseous airstream produces a stream of liquid air enriched with oxygen showing a temperature T3, and the process further comprises the step of v. increasing the temperature T3 of the stream of liquid air enriched with oxygen to a temperature T4, T4 being higher than T3; with preference, by heat transfer from the gaseous air stream provided in step (i) to the stream of liquid air enriched with oxygen showing the temperature T3.The stream of liquid air enriched with oxygen, preferably the stream of liquid oxygen 33, can be advantageously pressurized in a pump 35 after exiting the air separation unit.

The stream of liquid air enriched with oxygen has preferably a pressure ranging from 0.1 to 6 MPa; preferably, from 1 to 5 MPa; more preferably ranging from 6 to 10 MPa; preferably from 7 to 10 MPa; more preferably from 7.5 to 9.5 MPa; even more preferably from 8 to 9 MPa. Advantageously the stream of liquid air enriched with oxygen, preferably the stream of liquid oxygen 33 has a pressure equal to or similar to the pressure of the regasified natural gas stream 13. The liquid oxygen stream 33, or the pressurized liquid oxygen stream 37, is directed to heat exchanger 43 where it is regasified by heat exchange with the incoming stream of gaseous air 29 into a stream of gaseous oxygen 39. The gaseous oxygen stream 39 is directed to the conversion reactor 17 and is used as a source of reactant in the conversion of the regasified natural gas stream 13 into a stream of petrochemicals compounds 19. Thus, preferably, the regasified natural gas stream 13 is partially oxidized into a stream of methanol and/or a stream of formaldehyde into the conversion reactor 17. The stream of methanol and/or the stream of formaldehyde can be separated from the unconverted regasified natural gas 27 in the gas/liquid separation system 21 . Advantageously, one or more of a methanol-to-olefin (MTO) unit, a methanol-to-gasoline (MTG) unit, a methanol-to- formaldehyde unit, a methanol-to-dimethyl ether unit (not represented) are coupled to the installation to directly transform the methanol into more valuable olefins.

To obtain a high yield of methanol thanks to a good selectivity favouring the formation of methanol over formaldehyde, the reactant gases, i.e. the regasified natural gas stream 13 and the gaseous oxygen stream 39, can be intimately mixed before entering the conversion reactor 17 as shown by the lines upstream to the conversion reactor 17 on figure 1. The mixing of gases preferably takes place in a pre-mixing chamber (not represented).

The pre-mixing chamber may comprise a static mixer (helical, wafer type, fin type, high shear type or any other type). Precise gas flow regulation can be obtained by using mass flowmeters (thermal, multi-variable differential pressure, vortex, or any other type), turbine flowmeters or any other type of gas flowmeter.

When implementing thermal partial oxidation of methane to methanol, perfect homogeneous mixing of the reactant gases, for example in the pre-mixing chamber, is necessary to reduce the formation of higher oxidation products, such as formaldehyde.

When implementing plasma-assisted partial oxidation of methane, it may be preferred to feed the oxygen gas stream separately to the plasma irradiation zone which is within the conversion reactor 17 and introduce the natural gas stream downstream of the plasma irradiation zone.

Pre-heatinq of the li natural before its

The line between the tank 1 and the regasification unit 11 advantageously comprises at least one heat exchanging device 49 to increase the temperature of the liquefied natural gas (3; 7) before this one is fed to the regasification unit 11. As the liquefied natural gas 3 or the pressurized liquefied natural gas 7 can thus be pre-heated in the one or more heating devices 49 into a pre-heated stream 9 of liquefied natural gas, the regasification process occurring in the regasification unit 11 has a reduced heat transfer duty.

In one embodiment, it is preferred that the heat exchanging device 49 is a heat exchanger functioning in cooperation with the air separation unit. Indeed, the gaseous nitrogen stream 41 exiting the separator 31 can be recycled to heat exchanger 49 to transfer its heat to the liquefied natural gas (3; 7) to generate the pre-heated stream 9 of liquefied natural gas. To perform this transfer, the gaseous nitrogen stream 41 exiting the separator 31 and having a temperature T1 is conveyed into an additional heat exchanger 43 to be heated into a gaseous nitrogen stream 45 having a temperature T2, T2 being superior to T1. The gaseous nitrogen stream 45 having a temperature T2, or at least a portion of it, can, therefore, be used to transfer its excess of temperature to the liquefied natural gas 3 or to the pressurized liquefied natural gas 7, to pre-heat this liquefied natural gas before its regasification. The gaseous nitrogen stream 45 is preferably having a pressure of at most 4 MPa; more preferably of at most 2 MPa; even more preferably of at most 1 MPa.

The gaseous stream of nitrogen 51 exiting the heat exchanger after having transferred its heat to the liquefied natural gas (3; 7) has a temperature inferior to the temperature T2 and can be recycled into the separator 31 .

Similarly, the separator 31 provides a liquid oxygen stream (33; 37) with a temperature T3. The additional heat exchanger 43 can be advantageously disposed on the line of the liquid oxygen stream (33; 37) to produce a gaseous oxygen stream 39 having a temperature T4, T4 being superior to T3, before feeding the conversion reactor 17 with the gaseous oxygen stream.

The additional heat exchanger 43 also allows decreasing the temperature of the incoming stream of gaseous air 29 before its passage through the air separation unit 31.

Any excess of gaseous nitrogen stream 45 can be advantageously purged from the gaseous nitrogen loop via line 47.

Features of the conversion reactor and of the step (c)

The step (c) is preferably a direct partial oxidation step. The conversion reactor 17 allows the conversion of a stream of regasified natural gas 13 into petrochemicals compounds by partial oxidation in step (c). The reaction of conversion of step (c) is exothermic and the heat released from the conversion reactor 17 with the stream of petrochemicals compounds is reused in the installation to support the regasification unit 11. The conversion reactor 17 can be a fired heated tubular reactor, a photoreactor, an electromagnetic reactor, a plasma reactor or a cold plasma reactor.

Preferably, the conversion reactor 17 is a cold plasma reactor. Such a non-thermal plasma reactor allows the partial oxidation of methane reactions to take place at room temperature, and thus enhances the selectivity towards methanol. The heat generated by the partial oxidation of methane is removed by transferring it to the regasification unit 11 according to the principle of the present disclosure. This transfer of heat thus further avoids the ”over-oxidation” of methane.

When a plasma is not employed, then it is preferred that the conversion reactor 17 is operated at a temperature from 300°C to 800°C, more preferably from 400°C to 700°C. Thus, the conversion reaction of step (c) is performed at a temperature from 300°C to 800°C, more preferably from 400°C to 700°C. The conversion reaction of step (c) is exothermic.

These relatively low temperatures allow for avoiding the formation of highly oxidised products such as carbon monoxide or carbon dioxide. As stated above, when plasma is not employed, it is preferred that the installation comprises a pre-mixing chamber (not shown) upstream to the conversion reactor 17.

With preference, the conversion reactor 17 is operated under a pressure ranging from 0.1 to 10 MPa; preferably from 1 to 10 MPa. Thus, the step (c) is performed at a pressure ranging from 0.1 to 10 MPa; preferably from 1 to 10 MPa.

In an embodiment, the conversion reaction of step (c) is performed at a pressure ranging from 0.1 to 6 MPa; preferably, from 1 to 5 MPa; more preferably from 2 to 4 MPa. In another embodiment, the step (c) is performed at a pressure ranging from 6 to 10 MPa; preferably from 7 to 10 MPa; more preferably from 7.5 to 9.5 MPa; even more preferably from 8 to 9 MPa.

Upon the needs, gas compressor or gas regulator (not illustrated) can be placed on the line that fluidically connect the regasification unit 11 and the conversion reactor 17.

The conversion reactor 17 is also preferably operated at a residence time ranging from 0.1 to 100 seconds, more preferably from 1 to 10 seconds, even more preferably is 5 seconds. Thus, the conversion reaction of step (c) is performed with a residence time ranging from 0.1 to 100 seconds; preferably ranging from 0.5 to 30 seconds; more preferably ranging from 1 to 10 seconds, and most preferably ranging from 3 to 8 seconds.

For example, the conversion reaction of step (c) is performed with a residence time of at most 100 seconds; preferably, of at most 80 seconds or at most 60 seconds; more preferably, of at most 40 seconds or at most 30 seconds; even more preferably, of at most 20 seconds or at most 15 seconds; most preferably of at most 10 seconds or at most 8 seconds. For example, the conversion reaction of step (c) is performed with a residence time of at least 0.1 seconds; preferably of at least 0.5 seconds; more preferably of at least 1 second; even more preferably of at least 2 seconds and most preferably of at least 3 seconds.

Advantageously, the conversion reactor 17 is operated at a methane to oxygen molar ratio ranging from 1 :1 to 80:1 ; preferably from 1 :1 to 50:1 and more preferably ranging from 1 :1 to 30:1. Thus, the conversion reaction of step (c) is performed with a methane to oxygen molar ratio ranging from 1 :1 to 80:1 ; preferably from 1 :1 to 50:1 and more preferably ranging from 1 :1 to 30:1.

Advantageously, the conversion reactor 17 is operated under a pressure from 1 to 10 MPa, a temperature from 300°C to 600°C, a residence time from 0.1 to 100 s. and a methane to oxygen molar ratio from 1 :1 to 50:1.

For example, the conversion reaction of step (c) is performed at a pressure from 7 to 10 MPa, a temperature ranging from 300°C to 600°C and a methane to oxygen molar ratio ranging from 1 :1 to 50:1. With preference, the conversion reaction of step (c) is performed at a pressure from 7 to 10 MPa, a temperature ranging from 300°C to 600°C, a methane to oxygen molar ratio ranging from 1 :1 to 50:1 , and a residence time ranging from 1 to 10 seconds.

The conversion in the conversion reactor 17 can be achieved either in the heterogeneous phase or in the homogeneous phase, as detailed below.

Heterogeneous phase

In this first alternative, the processing of the regasified natural gas stream 13 implies the use of a heterogeneous (solid) catalyst in the conversion reactor 17.

The catalyst is typically a transition metal ion loaded zeolite catalyst, for example, a rhodium zeolite catalyst, a copper zeolite catalyst, an iron zeolite catalyst, a nickel zeolite catalyst, an iridium zeolite catalyst or a combination thereof.

Instead of zeolite, mesoporous silica can be used, for example, MCM-41.

The catalyst has generally a transition metal loading of 0.05 to 10 wt.%, preferentially between 0.10 and 5 wt.%, for example, 0.50 wt.%.

The transition metal ion loaded zeolite catalyst can comprise one or more transition metals, for example, two transition metals or three transition metals. The transition metal ion loaded zeolite catalyst can further comprise a non-transition metal, such as one or more alkali metals and/or one or more alkaline earth metals.

The transition metal ion loaded zeolite catalyst can be made on one hand, from one or more transition metal salts, one or more alkali metal salts and/or one or more alkaline earth metal salts and on the other hand, from zeolite and/or mesoporous silica.

The zeolite can have a Si/AI molar ratio ranging between 5 and 1000, for instance, 15 or 100.

The zeolites are selected from the group of AEI, AFX, ANA, BEA, BPH, CHA, EON, FAU, FER, GIS, HEU, LAU, LTL, MAZ, MEI, MFI, MOR, PAU, PHI, STI or SZR families.

The zeolites are selected from the list comprising ZSM-5, ferrierite, SSZ-13, TS-1 , amicite, zeolite X, zeolite Y, barrerite, clinoptilolite, harmotome, laumontite, mordenite, paulingite, or pollucite.

The catalyst can be prepared by incipient wetness impregnation of nitrate salts of the one or more transition metals into the ammonium salts of the zeolite followed by reduction with hydrogen or a mixture of hydrogen and inert gas, at a temperature comprised between 400°C and 700°C during a time comprised between 1 and 5 hours.

Specific examples of the transition metal ion loaded zeolite catalyst include, but are not limited to, Fe-ZSM-5, Cu-ZSM-5, Rh-ZSM-5, RhNa-ZSM-5, lrCu-ZSM-5, lrCuPd-ZSM-5 or Rh-MOR.

In this second alternative, the processing of the regasified natural gas stream 13 does not imply the use of a catalyst. One example of the conversion reactor 17 that is configured to perform the partial oxidation of the natural gas is described in the patent EP 2 170 792 B1. The reactor comprises an internal surface made of silica or coated with silica, surrounding a reaction zone in which the gases, i.e. the regasified natural gas stream 13 and the gaseous oxygen stream 33, react. Silica means a composition consisting essentially of silica and comprising no component harming the conversion of methane to methanol. Advantageously, this is pure silica under the usual meaning of the man skilled in the art. Silica can be amorphous, crystalline or of any structure or can be quartz. The internal surface of the conversion reactor 17 can be made partly with a type of silica and partly with another type of silica. The internal surface can be coated partly with a type of silica and partly with another type of silica. The internal surface can be a combination of a part made with a type of silica and a part coated with another or the same type of silica. Advantageously, the internal surface is made of quartz or coated with quartz.

Advantageously, the internal surface, made of silica, preferably quartz, or coated with silica, preferably quartz, is treated with HF before the conversion of regasified natural gas stream 13 into methanol.