Continuous production of an adsorption product of a nitrooxy-functional organic compound

Abstract

The invention relates to a 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 process comprising the steps of: continuously feeding particulate adsorbent material into an elongated cavity; continuously conveying the material within the cavity in a downstream direction; continuously spraying a liquid adsorbate onto the particulate adsorbent material, wherein the liquid adsorbate comprises the nitrooxy-functional organic compound; continuously agitating the mixture thus obtained to form the adsorption product; and continuously removing the adsorption product from the cavity. The invention further relates to an adsorption product obtained by such process and the use of such adsorption product in ruminant nutrition.

Claims

1. A process for the continuous production of an adsorption product of a nitrooxy-functional organic compound adsorbed on the surface of a particulate adsorbent material, comprising the steps of: providing a mixing drum comprising an elongated cavity; continuously feeding particulate adsorbent material into the elongated cavity; continuously conveying the material within the elongated cavity in a downstream direction; continuously spraying a liquid adsorbate onto the particulate adsorbent material, wherein the liquid adsorbate comprises the nitrooxy-functional organic compound; continuously agitating the mixture thus obtained to form the adsorption product; and continuously removing the adsorption product from the cavity, wherein the elongated cavity comprises an initial transport zone where the particulate adsorbent material is conveyed in the downstream direction, and a mixing zone where the liquid adsorbate is sprayed onto the particulate adsorbent material and the mixture thus obtained is continuously agitated by mixing instruments to form the adsorption product, the liquid adsorbate is continuously sprayed onto the particulate adsorbent material as the adsorbent material is conveyed along the elongated cavity in the downstream direction, and the particulate adsorbent material is conveyed in the downstream direction by a screw conveyor in a continuous manner, and the mixing instruments are mixing paddles mounted on a shaft, said shaft extending through the elongated cavity in a longitudinal direction.

2. The process of claim 1, wherein the particulate adsorbent material is granular silica, charcoal or zeolite material having average grain size between 10-1000 μm.

3. The process of claim 1, wherein the particulate adsorbent material is a porous material having a specific surface area of at least 100 m.sup.2/g and/or an oil adsorption capacity of between 100 and 300 ml/100 g.

4. The process of claim 1, wherein the nitrooxy-functional organic compound is a compound of formula (I) below ##STR00033## wherein n is an integer from 1 to 10; R1 is H, C1-6-alkyl, phenyl, —OH, —NH2, —CN, —COOH, —COO-M+, —O(C═O)R2, —NH(C═O)R3, SO2(NH)R4 or —ONO2; R2, R3 and R4 are independently from each other either C1-6-alkyl, phenyl or pyridyl, with the proviso that when n is >3 the hydrocarbon chain may be interrupted by —O— or —NH—; and M+ is a metal cation or an ammonium.

5. The process of claim 4, wherein the nitrooxy-functional organic compound is one selected from 3-nitrooxypropanol, 9-nitrooxynonanol, 5-nitrooxy pentanoic acid, 6-nitrooxy hexanoic acid, bis(2-hydroxyethyl)amine dinitrate, 1,3-bis-nitrooxypropane, 1,4-bis-nitrooxybutane, 1,5-bis-nitrooxypentane and mixtures thereof.

6. The process of claim 4, wherein the nitrooxy-functional organic compound is a mixture of two or more nitrooxy-functional compounds of formula (I).

7. The process of claim 1, wherein the liquid adsorbate comprises the nitrooxy-functional organic compound in liquid solution.

8. The process of claim 1, wherein average residence time of the particulate material in the cavity is between 2 and 15 minutes and/or ratio of introduction rate of liquid adsorbate to introduction rate of particulate adsorbent material is between 60 and 140 ml of liquid adsorbate per 100 g particulate adsorbent material.

9. The process of claim 1, wherein the sprayed liquid adsorbent has a temperature of between 10 and 40° C., and/or the liquid adsorbent is sprayed through one or more nozzles, and/or spray pressure of the liquid adsorbent is between 3 and 9 bar, and/or the cavity has a tubular shape, and/or L/D (length/diameter) ratio of the cavity is between 2 and 10.

10. The process of claim 1, wherein 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.

11. The process of claim 1, wherein the cavity is inclined in downstream direction, and/or the cavity is partially filled with material.

12. The process of claim 2, wherein the particulate adsorbent material is granular silica material with average grain size between 50-500 μm.

13. The process of claim 12, wherein the average grain size is between 200-400 μm.

14. The process of claim 3, wherein the particulate adsorbent material has a specific surface area of at least 200 m.sup.2/g.

15. The process of claim 4, wherein M+ is sodium (Na+), potassium (K+), lithium (Li+), magnesium (Mg2+), calcium (Ca2+), barium (Ba2+), strontium (Sr2+), or ammonium (NH4+).

16. The process of claim 5, wherein the nitrooxy-functional organic compound is 3-nitrooxypropanol (3NOP; n=3; R1=OH).

17. The process of claim 6, wherein the nitrooxy-functional organic compound is a mixture of 3-nitrooxy propanol and 1,3-bis-nitrooxypropane.

18. The process of claim 7, wherein solvent in the liquid solution comprises water, and/or concentration of the nitrooxy-functional organic compound in the solution is between 10-40 wt. %.

19. The process of claim 8, wherein the average residence time of the particulate material in the cavity is between 5 and 10 minutes and/or the ratio of the introduction rate of liquid adsorbate to the introduction rate of particulate adsorbent material is between 80 and 120 ml of liquid adsorbate per 100 g particulate adsorbent material.

20. The process of claim 9, wherein the L/D (length/diameter) ratio of the cavity is between 3 and 7.

21. The process of claim 11, wherein the incline angle is between 15 and 45°, and/or the mixing zone comprises a subsection that is fully filled with material and a subsection that is partially filled with material.

22. The process of claim 21, wherein the liquid adsorbate is only sprayed onto the particulate adsorbent material at a longitudinal position of the cavity where it is fully filled with particulate adsorbent material, and cavity volume unoccupied by the particulate material is filled with only ambient air, preventing an inert gas blanket from being introduced into the cavity.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

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

(2) FIG. 1: a longitudinal section of a mixing drum that may be used to carry out a process of the invention;

(3) FIG. 2: a flow diagram illustrating the process of the invention; and

(4) FIG. 3: an assay showing the surface loading of 3NOP over process time at different residence times.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(5) In FIG. 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 11b. The inlet opening 13 is arranged at the lid 11b. The outlet opening 14 is arranged at the base 11a. The overall length L of the cavity 12 is 140 cm and the diameter D is 20 cm, accounting for an L/D ratio of 7.0 and a total chamber volume of 0.044 m.sup.3.

(6) The inlet opening 13 may be connected to a feeding apparatus for continuously introducing 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 FIG. 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 adsorbent material to the inlet 13.

(7) 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 FIG. 1 by the arrow.

(8) 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 distributed within primary and secondary mixing zones 12b and 12d that follow the initial 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.

(9) The mixing instruments comprise a number of pairs of mixing paddles 18-1, wherein 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.

(10) 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.

(11) The apparatus 10 further comprises injection nozzles 19 for injecting a liquid adsorbate 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 FIG. 2, where the mixing step 101 is also preceded by a step 301 of suctioning liquid adsorbate from a liquid adsorbate tank and, optionally, preheating the liquid adsorbate to a desired temperature, 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.

(12) 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 11b. The rotating shaft 15 and motor are arranged at the base 11a.

(13) 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 FIG. 2, where the mixing step 101 is followed by a packaging step 401.

(14) 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 sections and partially filled sections. Specifically, owing to the essentially fluid behavior of suitable granular adsorbent materials, the materials will form an essentially planar 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, respectively, as any fluidly behaving material that reaches these levels will be transported 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 injection nozzles 19 are arranged at an early position within the primary mixing zone 12b that is fully filled in operation.

(15) In an experimental setup, the mixing drum as shown in FIG. 1 was loaded with a particulate silica material with a nominal median particle size of between 45-50 μm 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 adsorbent material. The weight ratio of the granular silica material and the liquid adsorbent material was 50/50. The inclination of the cavity 12 was set to 33°. The rotation 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.

(16) Using these settings, the filled chamber volume was determined at 0.017 m.sup.3, corresponding to approx. 38% of the total chamber volume. The feed rates (granular material) necessary to attain certain average residence times (standard deviation is about 40%) as determined in this experiment are outlined in Table 1 below.

(17) TABLE-US-00003 TABLE 1 Residence time Feed rate  2 min 30 sec 249 kg/h  5 min 124 kg/h  7 min  89 kg/h 10 min  62 kg/h

(18) In FIG. 3 an assay is shown that illustrates the surface loading of 3NOP over process 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.sup.3. Such scaling calculations for commercially available mixers are shown in Table 2 below.

(19) TABLE-US-00004 TABLE 2 Pilot Mixer Ruberg DLM 350-1500 Ruberg DLM 800-3000 L[m] 1.4 1.5 3.0 D[m] 0.2 0.35 0.8 L/D 7.0 4.3 3.8 chamber [m.sup.3] volume 0.0044 0.144 1.507 filled [%] chamber 38 38 50 75 38% 50% 75% [m.sup.3] volume 0.017 0.055 0.072 0.108 0.573 0.754 1.130 feed rate at residence time [kg/h] 2.5 min 249 816 1.073 1.610 8.522 11.214 16.820 5 min 124 408 537 805 4.261 5.607 8.410 7 min 89 291 383 575 3.044 4.005 6.007 10 min 62 204 268 402 2.131 2.803 4.205

(20) Similar assays have demonstrated no difference in loading and homogeneity between adsorbate temperatures of 15° C., 25° C. and 35° C.