Removal of nitrogen-containing impurities form alcohol compositions

Abstract

Process for the treatment of an alcohol composition containing nitrogen-containing contaminants by contacting the alcohol composition in the vapor phase with an adsorbent in an adsorption zone.

Claims

1. A process for the treatment of an alcohol composition comprising nitrogen-containing contaminants, the process comprising contacting the alcohol composition in the vapour phase with an adsorbent in an adsorption zone.

2. A process according to claim 1, wherein the alcohol composition comprises one or more alcohols selected from C.sub.1 to C.sub.6 saturated monohydric alcohols.

3. A process according to claim 2, wherein the alcohol composition comprises one or more alcohols selected from ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol and isobutanol (2-methyl-propan-1-ol).

4. A process according to claim 3, wherein the alcohol composition comprises one or more alcohols produced from a biological source.

5. A process according to claim 4, wherein the alcohol composition comprises bio-ethanol.

6. A process according to claim 1, wherein the nitrogen-containing contaminants comprise one or more nitrogen-containing compounds from the group consisting of nitriles, amines, ammonium cations, amides, imides and mixtures thereof.

7. A process according to claim 1, wherein the treated alcohol composition has a nitrogen content of less than 2 ppmw.

8. A process according to claim 1, wherein the adsorbent is a microporous aluminosilicate, a mesoporous aluminosilicate or a silica-alumina.

9. A process according to claim 1, wherein the adsorbent is a zeolite.

10. A process according to claim 9, wherein the zeolite has at least one channel defined by a 10-membered or 12-membered ring.

11. A process according to claim 10, wherein the zeolite is in the acidic (H) form.

12. A process according to claim 1, wherein the alcohol compositions is contacted with the adsorbent at a pressure of from 0.1 to 25 bara, or from 0.5 to 20 bara, or from 0.75 to 15 bara, or from 1 to 15 bara.

13. A process according to claim 8, wherein the alcohol compositions is contacted with the adsorbent at a pressure of from 0.1 to 25 bara, or from 0.5 to 20 bara, or from 0.75 to 15 bara, or from 1 to 15 bara.

14. A process according to claim 9, wherein the alcohol compositions is contacted with the adsorbent at a pressure of from 0.1 to 25 bara, or from 0.5 to 20 bara, or from 0.75 to 15 bara, or from 1 to 15 bara.

15. A process for the preparation of olefins from an alcohol composition comprising a dehydratable alcohol and nitrogen-containing contaminants, the process comprising: (i) contacting the alcohol composition in the vapour phase with an adsorbent in an adsorption zone to form a treated alcohol composition; and (ii) contacting the treated alcohol composition with an alcohol dehydration catalyst in an alcohol dehydration zone under conditions effective to dehydrate the alcohol to the corresponding olefin.

16. A process according to claim 15, wherein the treated alcohol composition is contacted with the alcohol dehydration catalyst in the vapour phase.

17. A process according to claim 16, wherein the alcohol dehydration catalyst is selected from crystalline silicates, dealuminated crystalline silicates, phosphorus modified zeolites and supported heteropolyacids.

18. A process according to claim 1, wherein the alcohol composition comprises one or more alcohols selected from C.sub.2 to C.sub.6 saturated monohydric alcohols.

19. A process according to claim 1, wherein the alcohol composition comprises one or more alcohols selected from C.sub.2 to C.sub.4 saturated monohydric alcohols.

20. A process according to claim 2, wherein the alcohol composition comprises one or more alcohols selected from ethanol, 1-propanol and isobutanol.

21. A process according to claim 2, wherein the alcohol composition comprises ethanol.

22. A process according to claim 1, wherein the treated alcohol composition has a nitrogen content of less than 1 ppmw.

23. A process according to claim 1, wherein the treated alcohol composition has a nitrogen content of less than 0.5 ppmw.

24. A process according to claim 1, wherein the treated alcohol composition has a nitrogen content of less than 0.25 ppmw.

25. A process according to claim 1, wherein the treated alcohol composition has a nitrogen content of less than 0.1 ppmw.

26. A process according to claim 1, wherein the treated alcohol composition has a nitrogen content of less than 0.05 ppmw.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will now be illustrated, without limiting the scope thereof, with reference to the following Examples and the accompanying Figures, in which:

(2) FIG. 1 shows a schematic of an experimental apparatus for testing the removal of nitrogen compounds from alcohol compositions in the vapour phase.

(3) FIG. 2 shows a GC-NPD chromatogram for Bioethanol A prior to treatment for the removal of nitrogen containing compounds. The portion of the chromatogram from ca. 0 to 5 min is shown enlarged in the inset.

(4) FIG. 3 shows a GC-NPD chromatogram for Bioethanol B prior to treatment for the removal of nitrogen containing compounds.

(5) FIG. 4 shows a GC-NPD chromatogram for Bioethanol A following contacting with zeolite HY (SAR=5.2) at 25 C. in the liquid phase.

(6) FIG. 5 shows a GC-NPD chromatogram for Bioethanol A following contacting with zeolite HY (SAR=5.2) at 130 C. in the liquid phase. The portion of the chromatogram from ca. 1 to 3 min is shown enlarged in the inset.

(7) FIG. 6 shows a GC-NPD chromatogram for Bioethanol A following contacting with zeolite HY (SAR=5.2) at 200 C. in the vapour phase.

(8) FIG. 7 shows a GC-NPD chromatogram for Bioethanol A following contacting with zeolite HY (SAR=5.2) at 150 C. in the vapour phase. The portion of the chromatogram from ca. 1 to 3 min is shown enlarged in the inset.

(9) FIG. 8 shows a GC-NPD chromatogram for Bioethanol A following contacting with zeolite HY (SAR=5.2) at 130 C. in the vapour phase. The portion of the chromatogram from ca. 1 to 3 min is shown enlarged in the inset.

(10) FIG. 9 shows a GC-NPD chromatogram for Bioethanol B following contacting with zeolite Hy (SAR=5.2) at 150 C. in the vapour phase. The portion of the chromatogram from ca. 1 to 3 min is shown enlarged in the inset.

(11) FIG. 10 shows a GC-NPD chromatogram for Bioethanol B following contacting with zeolite H-Mordenite (SAR=20) at 25 C. in the liquid phase. The portion of the chromatogram from ca. 1 to 3 min is shown enlarged in the inset.

(12) FIG. 11 shows a GC-NPD chromatogram for Bioethanol B following contacting with zeolite H-Mordenite (SAR=20) at 100 C. in the liquid phase. The portion of the chromatogram from ca. 1 to 3 min is shown enlarged in the inset.

(13) FIG. 12 shows a GC-NPD chromatogram for Bioethanol B following contacting with zeolite H-Mordenite (SAR=20) at 150 C. in the vapour phase. The portion of the chromatogram from ca. 1 to 3 min is shown enlarged in the inset.

EXAMPLES

(14) In the following Examples, the removal of nitrogen containing contaminants using zeolite adsorbents was examined in the liquid and vapour phases.

(15) Liquid phase experiments were carried out using a Vapourtec reactor unit. The apparatus comprises a feed reservoir, an HPLC pump, a pre-heater, a reactor tube, a cool-down section and a product reservoir. In each experiment the reactor tube was loaded with 20 mL of adsorbent. The adsorbent bed was flushed with approximately 150 mL of pure synthetic ethanol using flow rates up to 7.5 mL/min. This process removed trapped air bubbles from the adsorbent bed thus preventing channelling. Reactions were all carried out with a LHSV of 1 h.sup.1 relative to the volume of adsorbent (0.333 mL/min). The process was carried out over four consecutive days and stopped overnight (24 hours total run time). The first day of each new experiment used a pure synthetic ethanol feed to ensure a reliable baseline. Bio-ethanol was fed on the subsequent 3 days. When restarting the process each day, the adsorbent bed was washed with 40 mL of the bio-ethanol feed prior to sample collection to avoid results being distorted by possible leaching of nitrogen-containing contaminants from the adsorbent bed into the stationary liquid alcohol phase overnight. Samples collected on each of the four consecutive days were analysed by chemiluminescence, ion-chromatography, GC and GC-NPD techniques.

(16) The experimental set-up for vapour phase reactions is shown in FIG. 1. The apparatus comprises a quartz reactor tube (5) fitted with a porosity 1 quartz frit (not shown) and connected to a syringe pump (10) to supply the alcohol composition and to a source of nitrogen carrier gas (15). The reactor tube was loaded with 12 mL carborundum (20), 5 mL of the active zeolite material (25) and a further 12 mL of carborundum (30) to act as a vaporiser. In order to ensure effective gas flow through the zeolite bed all zeolites were pressed (12 tonnes, 32 mm die set) and sieved (250-500 m) prior to use. The reactor tube was secured in a Carbolite tube furnace (35) and heated to the desired temperature. A cooled liquid trap (40) was provided to collect the treated alcohol and a gas collection vessel (45) was supplied to collect non-condensable components.

(17) In each vapour phase experiment, the N.sub.2 flow rate was 50 mL/min and the liquid flow rate was 5 mL/hour (LHSV=1). Vapour phase reactions were conducted at ambient pressure unless stated otherwise. Liquid and gaseous samples were analysed by GC and GC-NPD.

(18) Alcohol Compositions

(19) In the following Examples, the clean up of two bioethanol compositions from two different sources is examined. Details of the amounts of contaminants present in the two bioethanol compositions are provided in Table 1.

(20) TABLE-US-00001 TABLE 1 Contaminant Bioethanol A Bioethanol B Other alcohols 720 ppmw 425 ppmw Non-alcohol oxygenates 431 ppmw 1245 ppmw Water 0.54 wt % 0.15 wt % Total nitrogen 1.0 ppmw 6.1 ppmw Nitrogen as acetonitrile 60 ppbw 240 ppbw Total acetonitrile 180 ppbw 700 ppbw

(21) GC-NPD chromatograms for Bioethanol A and Bioethanol B prior to treatment to remove nitrogen-containing contaminants are shown in FIGS. 2 and 3, respectively. The peak at ca. 2.4 min is ethanol, and the remaining peaks are attributed to nitrogen-containing compounds.

Comparative Examples A and B

Liquid Phase Testing

(22) In these Examples, the removal of nitrogen-containing contaminants from Bioethanol A was examined in the liquid phase using zeolite HY (SAR=5.2) as the adsorbent at 25 C. (Example A) and at 130 C. (Example B).

(23) The GC-NPD chromatogram for the test at 25 C. is shown in FIG. 4, with the bottom trace on the chromatograph corresponds to a synthetic ethanol composition which contained no discernable amounts of nitrogen-containing contaminants; the remaining three traces on the chromatographs correspond, from bottom to top, to the first, second and third day. The GC-NPD chromatogram of the liquid collected from the 25 C. test showed a number of signals consistent with the presence of nitrogen-containing contaminants from the bio-ethanol. The residual nitrogen content was found to be 0.4 ppm by chemiluminescence.

(24) The GC-NPD chromatogram for the test at 130 C. is shown in FIG. 5, with results from the 1.sup.st to 4.sup.th days shown in order from bottom to top. The chromatogram showed a reduced number of signals that are consistent with the presence of nitrogen-containing compounds. The residual nitrogen content was found to be 0.3 ppm by chemiluminescence.

Examples 1 to 3

Vapour Phase Testing

(25) In these Examples, the removal of nitrogen-containing contaminants from Bioethanol A was examined in the vapour phase using zeolite HY (SAR=5.2) as the adsorbent at 200 C. (Example 1), 150 C. (Example 2) and 130 C. (Example 3) and at ambient pressure.

(26) Nitrogen-containing contaminants were completely removed from Bioethanol B at 200 C. However, this temperature also resulted in the ethanol undergoing both etherification and dehydration reactions to give a mixture of water and the following carbon containing products; ethanol (11.9%), diethylether (38.3%), ethylene (49.1%) and ethane (0.15%).

(27) Reducing the reaction temperature to 150 C. resulted in lower conversion of the ethanol to diethyl ether (18.9%) and almost no conversion to ethylene (0.05%). No ethane was observed at 150 C. The GC-NPD chromatogram of the liquid fraction shows that almost all nitrogen compounds were effectively removed, the only exception was acetonitrile which was observed at 130 ppbw (40 ppbw of nitrogen).

(28) At 130 C. conversion of ethanol to diethyl ether was lower still (3.6%) with no observable formation of ethylene or ethane.

(29) It can clearly be seen from the comparison of the GC-NPD results of comparative Examples A and B and Examples 1 to 3, presented in FIGS. 4-5 and 6-8 respectively, that contacting the alcohol composition with the adsorbent in the vapour phase leads to an unexpected improvement in the removal of nitrogen containing impurities from the alcohol composition compared to when the alcohol composition is contacted with the adsorbent in the liquid phase.

Example 4

Vapour Phase Testing

(30) In this Example, the removal of nitrogen-containing contaminants from Bioethanol B was examined in the vapour phase using zeolite HY (SAR=5.2) as the adsorbent at 150 C. and at ambient pressure. The GC-NPD chromatogram is shown in FIG. 9.

(31) Nitrogen-containing contaminants were almost completely removed at 150 C., with the only exception being a small amount of acetonitrile (290 ppbw, corresponding to 100 ppbw of nitrogen). This result shows that, although the acetonitrile was not fully removed, the concentration is significantly reduced and the large amounts of other nitrogen-containing contaminants in Bioethanol B were completely removed.

Comparative Examples C and D

Liquid Phase Testing

(32) In these Examples, the removal of nitrogen-containing contaminants from Bioethanol B was examined in the liquid phase using H-Mordenite (H-MOR; SAR=20) as the adsorbent at 25 C. (comparative example C) and at 100 C. (comparative example D); the GC-NPD chromatograms are shown in FIGS. 10 and 11 respectively. In each of FIGS. 10 and 11, the bottom trace on the chromatograph corresponds to a synthetic ethanol composition which contained no discernable amounts of nitrogen-containing contaminants; the remaining three traces on the chromatographs correspond, from bottom to top, to the first, second and third day.

(33) The experiment using H-MOR (SAR 20) at 25 C. with Bioethanol B showed an unusual result in that less than 100 ppbw acetonitrile was detected. However, the concentrations of significant number of other organic nitrogen compounds remained unchanged.

(34) At 100 C. the H-MOR (SAR 20) showed enhanced removal of organic nitrogen compounds (compared to the 25 C. experiment) but significant levels remained (see FIG. 11). Acetonitrile was initially removed to below 100 ppbw (see 2nd chromatogram in FIG. 11), but at this temperature the effect was short lived with breakthrough observed on only the second day of the test (see the 3.sup.rd and 4.sup.th chromatograms in FIG. 11).

Example 5

Vapour Phase Testing

(35) In this Example, the removal of nitrogen-containing contaminants from Bioethanol B was examined in the vapour phase using H-MOR (SAR=20) as the adsorbent at 150 C. The GC-NPD chromatogram for this test is shown in FIG. 12.

(36) Nitrogen-containing contaminants were almost completely removed at 150 C., with the only exception being a small amount of MeCN (250 ppbw, corresponding to 85 ppbw of nitrogen).