The invention relates to process for the continuous production of an adsorption product of a nitrooxy-functional organic compound adsorbed on the surface of a particulate adsorbent material. The invention further relates to an adsorption prod- uct obtained by such process and its use in ruminant nutrition

Nitrooxy-functional organic compounds are widely used in animal nutrition to dimin- ish methane production in ruminants. For example, the drug 3-Nitrooxypropanol, abbreviated 3NOP, is an organic compound with the formula HO-CH2-CH2-CH2-O- NO2. It is the mononitrate ester of 1 ,3-propanediol. The compound is an inhibitor of the enzyme methyl coenzyme M reductase (MCR). MCR catalyzes the final step in methanogenesis. When it is fed to ruminants such as cows, their methane produc- tion is diminished and they gain weight. Ruminants are some of the greatest con- tributors of methane, a significant greenhouse gas. Accordingly, 3NOP is used in agriculture in large quantities. Ruminant nutrition products have been developed that contain 3NOP in the form of an adsorption product of 3NOP adsorbed on the surface of a particulate adsorbent material. These products were discontinuously produced in batch processes to be able to guarantee homogenous filler loadings and generally high quality. From the viewpoint of production efficiency, however, continuous process settings would be preferable.

The invention aims to provide a process for the continuous production of a high quality adsorption product of a nitrooxy-functional organic compound adsorbed on the surface of a particulate adsorbent material.

Against this background, the invention relates to a process for the continuous pro- duction of an adsorption product of a nitrooxy-functional organic compounds ad- sorbed on the surface of a particulate adsorbent material, the process comprising the steps of: continuously feeding particulate adsorbent material into an elongated cavity; continuously conveying the material within the cavity in a downstream direc- tion; continuously spraying a liquid adsorbate onto the particulate adsorbent materi- al, wherein the liquid adsorbate comprises a nitrooxy-functional organic compound; continuously agitating the mixture thus obtained to form the adsorption product; and continuously removing the adsorption product from the cavity. Such continuous set- ting has been found out to yield a high quality adsorption product at increased pro- duction efficiency as compared to state of the art methods.

In one embodiment, the particulate adsorbent material is granular silica, charcoal or zeolite material. Granular silica material is preferred in some embodiments. The average grain size of the granular material may be between 10-1000 pm, preferably 50-500 pm and more preferably between 200-400 pm as determined with laser dif fraction system dry measurement (Malvern MasterSizer 3000). The inclusive graph- ic standard deviation of the granular material diameter as expressed in phi units may be smaller 1. The particulate adsorbent material is preferably a porous materi- al. Specifically, it is preferred that the adsorbent material has a specific surface area of at least 100 m ² /g and preferably at least 200 m ² /g as determined using the BET method according to DIN ISO 9277. In one embodiment, the particulate adsorbent material is a porous material having an oil adsorption capacity of between 100 and 300 ml/100g, as determined according to DIN ISO 19246.

In one embodiment, the nitrooxy-functional organic compound is a compound of formula (I) below

wherein n is an integer from 1 to 10; R ¹ is H, Ci _-6 -alkyl, phenyl, -OH, -NH ₂ , -CN, - COOH, -COO M ⁺ , -0(C=0)R ² , -NH(C=0)R ³ , S0 ₂ (NH)R ⁴ or -ON0 ₂ ; R ² , R ³ and R ⁴ are independently from each other either Ci _-6 -alkyl, phenyl or pyridyl, with the pro- viso that when n is >3 the hydrocarbon chain may be interrupted by -O- or -NH-; and M ⁺ is a metal cation or an ammonium, preferably M ⁺ is sodium (Na ⁺ ), potassium (K ⁺ ), lithium (Li ⁺ ), magnesium (Mg ²⁺ ), calcium (Ca ²⁺ ), barium (Ba ²⁺ ), strontium (Sr ²⁺ ), and ammonium (NH ₄ ⁺ ).

As understood above, Ci_ ₆ -alkyl encompasses straight-chain Ci- ₆ -alkyl, as well as branched C _3-6 -alkyl and cyclic C _5-6 -alkyl. Preferred examples of pyridyl are 2-pyridyl and 3-pyridyl.

In one embodiment, n is an integer from 1 to 7; and/or R ¹ is -OH, -CN, -ON0 ₂ , phenyl, -0(C=0)R ² , -NH(C=0)R ³ , S0 ₂ (NH)R ⁴ ; and/or R ² , R ³ and R ⁴ are inde- pendently from each other either Ci _-6 -alkyl, phenyl or pyridyl, with the proviso that when n is >3 the hydrocarbon chain may be interrupted by -O- or -NH-.

In one embodiment, n is an integer from 1 to 5; and/or R ¹ is -OH, -CN, -ON0 ₂ , phenyl, -0(C=0)R ² , -NH(C=0)R ³ , S0 ₂ (NH)R ⁴ ; and/or R ² is phenyl or Ci _-6 -alkyl; and/or wherein R ³ is pyridyl; and/or R ⁴ is Ci _-6 -alkyl, with the proviso that when n is >3 the hydrocarbon chain may be interrupted by -O- or -NH-. In one embodiment, n is an integer between 3 and 9 and R ¹ is OH, COOH or - 0N0 ₂ , with the proviso that when n is > 3 the hydrocarbon chain may be interrupted by -O- or -NH-.

Exemplary compounds of formula (I) are 3-nitrooxypropanol (3NOP, CAS-No: 100502-66-7), 9-nitrooxynonanol, 5-nitrooxy pentanoic acid (CAS 74754-56-6), 6- nitrooxy hexanoic acid (CAS 74754-55-5), bis(2-hydroxyethyl)amine dinitrate (CAS 20830-49-3), 1 ,3-bis-nitrooxypropane, 1 ,4-bis-nitrooxybutane (CAS 3457-91 -8), 1 ,5- bis-nitrooxypentane (CAS 3457-92-9) and mixtures thereof.

A preferred compound in the context of the present invention is 3-nitrooxypropanol (3NOP; n = 3; R ¹ = OH). The compounds of formula (I) according to the present invention are, in principle, known and either commercially available or can be prepared in analogy to the pro- cesses as e.g. disclosed in WO 2012/084629.

In one embodiment, compounds of formula (I) are selected from the list of com- pounds, and salts thereof comprising: 3-Nitrooxypropanol, racemate-4- Phenylbutane-1 ,2-diyl dinitrate, 2-(Hydroxymethyl)-2-(nitrooxymethyl)-1 ,3- propanediol, N-Ethyl-3-nitrooxy-propionic sulfonyl amide, 5-Nitrooxy-pentanenitrile, 5-Nitrooxy-pentane, 3-Nitrooxy-propyl propionate, 1 ,3-bis-Nitrooxypropane, 1 ,4-bis- Nitrooxybutane, 1 ,5-bis-Nitrooxypentane, 3-Nitrooxy-propyl benzoate, 3-Nitrooxy- propyl hexanoate, 3-Nitrooxy-propyl 5-nitrooxy-hexanoate, Benzylnitrate, isosorbid- dinitrate, and N-[2-(Nitrooxy)ethyl]-3-pyridinecarboxamide, 2-Nitro-5-nitrooxymethyl- furan, and Bis-(2-nitrooxyethyl) ether as listed in Table 1 :

Table 1 : Exemplary compounds of formula (I)

Preferred compounds of formula (I) based on the strength of their effect in reducing methane are selected from the list of compounds, and salts thereof comprising: 3- Nitrooxy propanol, 5-Nitrooxy-pentanenitrile, 5-Nitrooxy-pentane, 3-Nitrooxy-propyl propionate, 1 ,3-bis-Nitrooxypropane, 1 ,4-bis-Nitrooxybutane, 1 ,5-bis- Nitrooxypentane, 3-Nitrooxy-propyl benzoate, 3-Nitrooxy-propyl hexanoate, 3- Nitrooxy-propyl 5-nitrooxy-hexanoate, isosorbid-dinitrate, and N-[2-(Nitrooxy)ethyl]- 3-pyridinecarboxamide, and Bis-(2-nitrooxyethyl) ether as listed in Table 2: Table 2: Preferred compounds of formula (I)

ln one embodiment, the nitrooxy-fu notional compound as used in the process of the invention can be a mixture of two or more nitrooxy-fu notional compounds, prefera- bly a mixture of two or more nitrooxy-fu notional compounds of formula (I) as defined above.

A suitable combination is a mixture of 3-nitrooxy propanol and 1 ,3-bis- nitrooxypropane. Preferably the ratio 3-nitrooxy propanol / 1 ,3-bis-nitrooxypropane is comprised between 1/10 and 1000/1 , more preferably, between 1/5 and 100/1 , most preferably, between 1/1 and 10/1.

In one embodiment, the liquid adsorbate comprises the nitrooxy-fu nctional organic compound in liquid solution, wherein preferably the solvent comprises water, i.e., is pure water, an aqueous solution or a mixture of water with a polar organic solvent, like an alcohol, ketone or the like.

In another embodiment, the solvent can also be an organic solvent, preferably an organic solvent comprising one or more alcoholic groups. Suitable solvents corn- prise polyols like diols or triols. Diols and especially aliphatic diols like propylene glycol can be particularly preferred. Mixtures of water and such organic solvents can also be suitable in this context.

In one embodiment, the concentration of the nitrooxy-functional organic compound in the solution is between 10-40 wt.%. In some embodiments, concentrations of 15- 30 wt% are preferred.

In another embodiment, the liquid adsorbate comprises the nitrooxy-functional or- ganic compound in its pure form, i.e., as an essentially solvent-free liquid corn- pound. For example, the substance 3-Nitrooxypropanol (3NOP, a drug given to ru- minants to reduce methane emission) is a liquid at room temperature and could hence also be atomized in its pure form. It may be that these pure compounds comprise some residual solvent, e.g., less than 10 wt% or less than 5 wt% or less than two wt% of solvents, e.g., solvents as described above.

In one embodiment, the average residence time of the particulate material in the cavity is adjusted to be between 2 and 15 minutes and preferably between 5 and 10 minutes. At a given cavity layout, the residence time can be adjusted by varying the particulate adsorbent material feed rate and, in the case of active conveying, the conveying speed. Depending on cavity volume, exemplary particulate adsorbent material feed rates can exceed 100, 500, 1.000 or even 5.000 kg/h.

In one embodiment, the ratio of the introduction rate of liquid adsorbate to the intro- duction rate of particulate adsorbent material is between 60 and 140 ml, preferably between 80 and 120 ml of liquid adsorbate per 100 g particulate adsorbent material. These ratios may be employed in the process of the invention to obtain a product of sufficiently high and homogenous load. Generally, the ratio should be balanced and consider the adsorption capacity of the material pair.

In one embodiment, the sprayed liquid adsorbent has a temperature of between 10 and 40°C and/or wherein the liquid adsorbent is sprayed through one or more noz- zles and/or wherein the spray pressure of the liquid adsorbent is between 3 and 9 bar. The temperature can be room temperature or the liquid can be preheated or precooled. The temperature has an influence on viscosity and hence spraying be- havior. In some applications, viscosities between 10 and 500 mPa-s and preferably between 50 and 200 mPa-s may be considered ideal.

In one embodiment, the cavity has a tubular shape and/or wherein the L/D (length/diameter) ratio of the cavity is between 2 and 10, preferably between 3 and 7. The total volume of the cavity can, in one example, be between 0,1 and 2 m ³ , but smaller or larger volumes are also possible. Such layouts may be used to obtain a product of sufficiently high and homogenous load. A too small ratio or too large vol- ume may deteriorate product quality. A too large ratio or too small volume may de- crease process efficiency.

In one embodiment, the cavity comprises an initial transport zone where the particu- late adsorbent material is actively conveyed in a downstream direction, preferably by a screw conveyor, and wherein the cavity comprises a mixing zone where the liquid adsorbate is sprayed onto the particulate adsorbent material and the mixture thus obtained is agitated by mixing instruments to form the adsorption product, preferably by mixing instruments such as mixing paddles that are mounted on a shaft that extends through the cavity in a longitudinal direction.

The process may be carried out in an apparatus that includes a mixing drum corn- prising the elongated and preferably tubular cavity with an upstream adsorbent in- let, a downstream product outlet and one or more injection nozzles for spraying the liquid adsorbate. A rotating member may extend through the cavity in its longitudi- nal direction. It may comprise at least one helical conveying blade to form a screw conveyor in one longitudinal zone of the cavity and mixing instruments in another longitudinal zone of the cavity.

The mixing instruments such as mixing paddles are preferably distributed over the length of the mixing zone. The distribution can be regular or irregular. In one em- bodiment, the operative surfaces of the paddles are slanted backwards. In other words, the operative surfaces of the paddles are not parallel to the longitudinal di- rection cavity but are slanted to effect reverse movement of the particulate material. Such reverse mixing can beneficially influence adsorption quality and homogeneity. Other suitable mixing instruments that may be used alternatively to or in conjunction with mixing paddles comprise screw fragments.

In one embodiment, the cavity comprises an intermediate transport zone within the mixing zone, where premixed material is actively conveyed in a downstream direc- tion from a primary to a secondary mixing zone, preferably by another screw con- veyor. In this embodiment, the liquid adsorbate is sprayed onto the particulate ad- sorbent material in the primary mixing zone prior intermediate transport.

In an alternative embodiment, the secondary mixing zone can be replaced by a resting zone without mixing paddles.

In one embodiment, the cavity comprises a terminal transport zone where product material is actively conveyed in a downstream direction from the mixing zone to the outlet, preferably by another screw conveyor.

Indications as made above regarding the cavity altogether, such as average resi- dence times, L/D ratio, cavity volume, or the like may in one embodiment more specifically apply to the mixing zone or mixing zones of the cavity.

In one embodiment, the screw conveyor and/or shaft-mounted mixing elements are operated at a rotational speed such that the peripheral speed of the screw conveyor and/or shaft-mounted mixing elements is 1 m/s or less. These low peripheral speeds can be preferred to avoid excessive frictional heat that may negatively af- fect potentially heat-sensitive nitrooxy-functional organic compound and unwanted dust formation due to grinding of the particulate materials. The risk of smoldering, fires and dust explosions can thereby be minimized. The peripheral speed as de- fined above relates to the point of highest radial extension. Depending on the radius of the cavity, such can correspond to rotational speeds of, e.g., less than 50 rpm. In one embodiment, the cavity is inclined in downstream direction, wherein the in- cline angle is preferably between 15 and 45° and/or wherein the cavity is partially filled with material, wherein preferably the mixing zone comprises a subsection that is fully filled with material and a subsection that is partially filled with material. It can be provided that the incline angle and the length and diameter of the mixing zone are such that there are longitudinal positions within the mixing zone whose entire cross-section remains below the level of product removal, and preferably such that longitudinal positions whose entire cross-section remains below the level of product removal account for at least 30% of all longitudinal positions within the mixing zone.

In one embodiment, the liquid adsorbate is sprayed onto the particulate adsorbent material at a longitudinal position of the cavity where it is fully filled with particulate adsorbent material and/or wherein the cavity volume unoccupied by the particulate material is filled with ambient air. In other words, no inert gas blanket is introduced to the cavity. Dust formation and flammable vapor may largely be avoided by the continuous process where the liquid adsorbate is directly sprayed onto the adsor- bent material and the mixture is conveyed through an elongated cavity. Inert gas may hence not be needed to avoid any explosion risk, even when using flammable materials.

The invention further relates to an adsorption product of a nitrooxy-functional organ- ic compound adsorbed on the surface of a particulate adsorbent obtained by the process of the invention and the use of such adsorption product in ruminant nutri- tion.

Further details and advantages of the invention will be explained in the following with reference to the figures and working examples. The figures show:

Figure 1 : a longitudinal section of a mixing drum that may be used to carry out a process of the invention;

Figure 2: a flow diagram illustrating the process of the invention; and Figure 3: an assay showing the surface loading of 3NOP over process time at different residence times.

In Figure 1 a mixing drum that may be used to carry out a process of the invention is schematically illustrated. The mixing drum 11 is generally tubular in shape and has an elongated tubular cavity 12 of essentially circular cross-section for receiving the particulate granular adsorbent material. On the upstream end of the cavity 12, an adsorbent inlet opening 13 is provided on the upper side of the cavity wall. On the downstream end of the cavity 12, a product outlet opening 14 is provided on the lower side of the cavity wall. The mixing drum 11 is made of stainless steel and consists of two halves, a base 11a and a lid 11 b. The inlet opening 13 is arranged at the lid 11 b. The outlet opening 14 is arranged at the base 11 a. The overall length L of the cavity 12 is 140 cm and the diameter D is 20 cm, accounting for an L/D ra- tio of 7,0 and a total chamber volume of 0,044 m ³ .

The inlet opening 13 may be connected to a feeding apparatus for continuously in- troducing a controlled amount of granular adsorbent material to the cavity 12, such as a suitable gravimetric loss-on-weight type powder feeder. Such is apparent from the flow diagram of Figure 2, where the mixing step 101 that is carried out in the apparatus 10 is preceded, on the one hand, by a step 201 of charging a feeder from a granular adsorbent material reservoir and a step 202 of feeding the granular ad- sorbent material to the inlet 13.

A rotating shaft 15 extends through the cavity in longitudinal direction. The shaft 15 is arranged in the center of the circle defined by the cross-section of the cavity 12 and is operably connected to an electric motor for driving the shaft 15 at a desired rotation speed. The regular rotation direction of the shaft 15 is counterclockwise, when looking in the direction of the product flow that is symbolized in Figure 1 by the arrow. The rotating shaft 15 comprises two types of rotating annexes that are distributed over the length of the cavity 12, namely helical conveying blades 17a, 17c and 17e as well as mixing instruments 18-1 and 18-2b. The helical conveying blade 17a is arranged around the shaft 15 in the initial transport section 12a of the cavity 12 that is adjacent to the inlet opening 13. The mixing instruments 18-1 and 18-2 are dis- tributed within primary and secondary mixing zones 12b and 12d that follow the ini tial transport section 12a. The primary and secondary mixing zones 12b and 12d are separated by an intermediate transport zone 12c, where the helical conveying blade 17c is arranged around the shaft 15. The intermediate transport zone 12c is rather short and the number of full rotations of the helical conveying blade 17c around the shaft 15 is less than two. The mixing zones 12b and 12d are followed by a terminal transport zone 12e, where the helical conveying blade 17e is arranged around the shaft 15.

The mixing instruments comprise a number of pairs of mixing paddles 18-1 , where- in the individual paddles 18-1 of the pairs are slightly offset in longitudinal direction. Specifically, in the primary mixing zone 12b, two helical mixing blade fragments 18- 2 are arranged between the pairs. In contrast to the helical conveying blades 17a, 17c or 17e, the blade fragments 18-2 do not comprise a closed surface but rather an open construction such as to limit the feeding forward action. The secondary mixing zone 12d only comprises mixing paddles 18-1 .

In an alternative embodiment, the secondary mixing zone 12d can be replaced by a resting zone without mixing paddles 18-1 or blade fragments 18-2.

The apparatus 10 further comprises injection nozzles 19 for injecting a liquid ad- sorbate to the cavity 12, and more specifically to an early position within the primary mixing zone 12b. Specifically, the nozzles 19 are arranged at a longitudinal position corresponding to the upstream pair of mixing paddles 18. The injection nozzles 19 are connected to a suitable liquid supply that includes a tank, a heating, a liquid pump and a volume flow meter whose signal is used to regulate pump operation. Such, again, is apparent from the flow diagram of Figure 2, where the mixing step 101 is also preceded by a step 301 of suctioning liquid adsorbate from a liquid ad- sorbate tank and, optionally, preheating the liquid adsorbate to a desired tempera- ture, a step 302 of pumping the liquid adsorbate to the nozzles 19 and a step 303 of measuring the volume flow towards the nozzles 19.

The rotating shaft 15 and the rotating annexes 17a, 17c, 17e, 18-1 and 18-2 are all made of stainless steel. The injection nozzles 19 are arranged at the lid 11 b. The rotating shaft 15 and motor are arranged at the base 11a.

The outlet opening 14 can be connected to a suitable packaging apparatus for weighting and packaging the product. Also this is apparent from the flow diagram of Figure 2, where the mixing step 101 is followed by a packaging step 401.

A lifting means including, for example, suitable swivel joints and a hydraulic cylinder may be used to lift the end section of the tubular mixing drum 11 to adjust a certain incline of the tubular cavity 12. In consideration of such incline, the primary and secondary mixing zones 12b and 12d can further be subdivided in fully filled sec- tions and partially filled sections. Specifically, owing to the essentially fluid behavior of suitable granular adsorbent materials, the materials will form an essentially pla- nar surface within the cavity 12. The surface level corresponds essentially to the level of the lowest points of action of the helical conveying blades 17c and 17e, re- spectively, as any fluidly behaving material that reaches these levels will be trans- ported further by the blade 17c or 17e. The longitudinal position of the boundary between the fully filled and partially filled sections hence depends on the ratio of length to diameter of the mixing zones 12b and 12d as well as on the incline angle of the cavity 12. In this regard, the incline angle is preferably set such that the injec- tion nozzles 19 are arranged at an early position within the primary mixing zone 12b that is fully filled in operation.

In an experimental setup, the mixing drum as shown in Figure 1 was loaded with a particulate silica material with a nominal median particle size of between 45-50 pm and a solution of 23% of 3-Nitrooxypropanol (3NOP, a drug given to ruminants to reduce methane emission) dissolved in 77% propylene glycol solvent as liquid ad- sorbent material. The weight ratio of the granular silica material and the liquid ad- sorbent material was 50/50. The inclination of the cavity 12 was set to 33°. The ro- tation speed of the shaft was set to 45 rpm, which led to a peripheral speed of the rotating annexes 17a, 17c, 17e, 18-1 and 18-2 of around 0,5 m/s. Nozzle pressure was 6 bar. Silica temperature was 27°C.

Using these settings, the filled chamber volume was determined at 0,017 m ³ , corre- sponding to approx. 38% of the total chamber volume. The feed rates (granular ma- terial) necessary to attain certain average residence times (standard deviation is about 40%) as determined in this experiment are outlined in Table 1 below.

Table 1 :

In Figure 3 an assay is shown that illustrates the surface loading of 3NOP over pro- cess time at different residence times. While it would be expected that lowering the residence times have a negative impact on the adsorption homogeneity, the assay shows indeed very good adsorption homogeneity even at an average residence time of only 2 min 30 sec. Accordingly, scaling calculations would suggest that an output of several tons of product per hour would be attainable with bigger mixers having a chamber volume of, for example, between 0,1 and 2 m ³ . Such scaling cal- culations for commercially available mixers are shown in Table 2 below.

Table 2

Similar assays have demonstrated no difference in loading and homogeneity be- tween adsorbate temperatures of 15°C, 25°C and 35°C.