Process for the Preparation of Aromatic Compounds

Abstract

Aromatic compounds are prepared from a feed stream comprising biomass or a mixture of biomass and synthetic polymer in a process, comprising: a) subjecting the feed stream to a pyrolysis treatment in the presence of a cracking catalyst to yield a vaporous fraction comprising hydrocarbons with olefinic unsaturation and oxygen containing organic compounds and coke-laden cracking catalyst; b) separating the vaporous fraction from the coke-laden cracking catalyst; c) contacting the vaporous fraction with a second, aromatization catalyst in a conversion treatment to yield a conversion product comprising aromatic compounds; and d) recovering aromatic compounds from the conversion product, wherein the cracking catalyst is a naturally occurring material, selected from the group consisting of inorganic salts, refractory oxides, minerals, industrial rock and mixtures thereof.

Claims

1. Process for the conversion of a feed stream comprising biomass, the process comprising: a) subjecting the feed stream to a pyrolysis treatment in the presence of a cracking catalyst to yield a vaporous fraction comprising hydrocarbons with olefinic unsaturation and oxygen containing organic compounds and coke-laden cracking catalyst; b) separating the vaporous fraction from the coke-laden cracking catalyst; c) contacting the vaporous fraction with a catalyst in a conversion treatment to yield a conversion product; and d) recovering the conversion product, wherein (i) the process concerns the preparation of aromatic compounds; (ii) the process concerns a two-step catalytic process, making use of different catalysts in different steps; (iii) the cracking catalyst in step (a) is a naturally occurring material, selected from the group consisting of inorganic salts, refractory oxides, minerals, industrial rock and mixtures thereof; (iv) the catalyst in step (c) is an aromatization catalyst selected from the group consisting of ZSM-5, ZSM-11, ZSM-35, ZSM-23, ferrierite, zeolite beta, zeolite Y, zeolite X, mordenite, zeolite, A. IM-5, SSZ-20, SSZ-55, MCM-22, TNU-9 and combinations thereof; and (v) aromatic compounds are recovered from the conversion product, by subjecting the conversion product to fractionation, yielding aromatic compounds as separate fraction or fractions and a residue, or by contacting the conversion product with a liquid hydrocarbon to obtain a hydrocarbon phase containing aromatic compounds, and an oxygen-containing compound phase, and separating the hydrocarbon phase from the oxygen-containing compound phase.

2. Process according to claim 1, wherein the cracking catalyst is an amorphous silica alumina.

3. Process according to claim 1, wherein the cracking catalyst is bentonite.

4. Process according to claim 1, wherein the pyrolysis treatment in step a) is carried out at a temperature of 450 to 1000° C. and a pressure of 1 to 6 bar.

5. Process according to claim 1, wherein the pyrolysis treatment in step a) takes place in a fluidized bed or an auger reactor.

6. Process according to claim 1, wherein the coke-laden cracking catalyst is regenerated by contacting the coke-laden cracking catalyst with oxygen to yield a regenerated cracking catalyst.

7. Process according to claim 6, wherein the regenerated cracking catalyst is recycled to the pyrolysis treatment of step a).

8. Process according to claim 1, wherein the feed stream comprises biomass selected from the group consisting of agricultural waste, plants, wood and combinations thereof.

9. Process according to claim 1, wherein the feed stream comprises biomass selected from the group consisting of glucose, maltose, starch, cellobiose, cellulose, hemi-cellulose, other polysaccharides, lignin, sugar cane bagasse, lignocellulosic materials, food waste, animal waste, manure and corn stover.

10. Process according to claim 1, wherein the conversion treatment in step c) is carried out at a temperature in the range of 300 to 1000° C. and a pressure in the range of 1 to 4 bar.

11. Process according to claim 1, wherein the second, aromatization catalyst is a zeolitic catalyst, suitably selected from aluminosilicates, SAPOs, silicalites and combinations thereof.

12. Process according to claim 1, wherein the second, aromatization catalyst is acidic.

13. Process according to claim 12, wherein the second, aromatization catalyst is made acidic by ion exchange with ammonium salts and subsequent calcination.

14. Process according to claim 1, wherein the second, aromatization catalyst has been selected from the group consisting of ZSM-5, ZSM-11, ZSM-35, ZSM-23, ferrierite, zeolite beta, zeolite Y, zeolite X, mordenite, zeolite A, IM-5, SSZ-20, SSZ-55, MCM-22, TNU-9 and combinations thereof.

15. Process according to claim 1, wherein the second, aromatization catalyst comprises an amorphous binder in addition to a zeolite.

16. Process according to claim 15, wherein the amorphous binder has been selected from inorganic refractory oxides, in particular alumina, silica, silica-alumina, titania, zirconia or mixtures thereof, preferably silica-alumina.

17. Process according to claim 16, wherein the amount of amorphous binder in the second, aromatization catalyst is in the range of 0 to 80% wt, based on the weight of the zeolite and the amorphous binder.

18. Process according to claim 1, wherein the conversion treatment is carried out in a fixed bed, a moving bed or a fluidized bed.

19. (canceled)

20. Process according to claim 1, wherein the residue is combusted to yield energy.

21. Process according to claim 1, wherein the conversion product is subjected to fractionation yielding an olefin fraction.

22. Process according to claim 21, wherein at least part of the olefin fraction is recycled to the conversion treatment or to the pyrolysis treatment or to both.

23. (canceled)

Description

[0047] The invention is further illustrated by means of the attached drawings and Examples. In the drawing:

[0048] FIG. 1 is a flow diagram of an embodiment of the method according to the invention;

[0049] FIG. 2 displays the influence of the cracking catalysts on vapor composition; and

[0050] FIG. 3 displays the results of catalytic pyrolysis and H-ZSM-5 (23) upgrading of pinewood.

[0051] Referring to FIG. 1, a feed stream containing biomass, or a mixture of biomass and synthetic polymer is passed into a pyrolysis reactor A via a line 1. To the reactor A also a stream of cracking catalyst is passed via a line 2. In the pyrolysis reactor A the cracking catalyst and feed stream are contacted with each other at pyrolysis conditions to yield a vaporous phase and a solid phase which consists of the cracking catalyst with coke residues deposited thereon. After the reaction the vaporous fraction and the coke-laden cracking catalyst are passed via a line 3 to a separator B. In B the vaporous fraction is withdrawn via a line 5 whereas the coke-laden catalyst by gravity drops to the bottom of separator B and is then withdrawn via a line 4. The coke-laden cracking catalyst may be recycled to the reactor A. It may also be subjected to regeneration by burning off of the coke from the cracking catalyst. It may also be used as landfill, e.g. after removal of the coke.

[0052] The vaporous fraction in the line 5 is passed to a second reactor C, where it is passed over a bed of aromatization catalyst 6 to be converted into aromatic compounds. The conversion product leaves the reactor C as a vapor via a line 7. Although reactor C has been depicted as a fixed-bed reactor it is emphasized that also a fluid bed reactor is feasible. In either case zeolitic aromatization catalyst may be removed from the reactor C. The conversion product is subsequently passed into an extraction column D where it is contacted with a liquid hydrocarbon stream that is sprayed into the column D via a line 8 that is provided with a nozzle or manifold. Due to the contact with the liquid hydrocarbon, the aromatic compounds in the conversion product condense and are withdrawn, together with other liquids, e.g. liquid oxygen-containing compounds, via a line 10. Any residual gases are discharged via a line 9 for further treatment and disposal (not shown). The liquid aromatic products, liquid hydrocarbon and liquid oxygen-containing compounds in the line 10 are separated from each other, e.g. by phase extraction and/or fractionation (not shown).

[0053] The invention will be further elucidated by means of the following examples.

EXAMPLE 1

[0054] In a series of experiments mixtures of pinewood (<200 micron) and catalysts (ratio 1:5, 2-5 mg of a homogeneous mixture) were subjected to catalytic pyrolysis with a cracking catalyst (inert atmosphere (He), T=540° C.) in a tandem micro-reactor and the vapors obtained were subsequently (ex situ) up-graded in a second reactor containing H-ZSM-5(23) (80 mg, particle size 212-425 micrometers, T=550° C.). The products obtained were analyzed by GC-MS and the amount of aromatics formed (benzene, toluene, xylenes) was calculated afterwards.

[0055] FIG. 2 displays the influence of the cracking catalysts on vapor composition. It shows that the use of different cracking catalysts can significantly influence the composition of the vapor phase formed.

[0056] FIG. 3 displays the results of catalytic pyrolysis and H-ZSM-5 (23) upgrading of pinewood. The amounts of BTX formed are relative to a blanc reaction (non-catalytic pyrolysis and H-ZSM-5 (23) up-grading). The figure clearly shows that the catalytic pyrolysis and the subsequent up-grading of vapors obtained with H-ZSM-5 (23) clearly distinguishes from the non-catalytic pyrolysis and up-grading (=blanc). Under identical conditions, depending on the catalyst used, approximately 20-25% higher yields of BTX were obtained.

EXAMPLE 2

[0057] In a series of experiments plywood sawdust with a particle size of 0.1 to 1.0 cm was subjected to pyrolysis in a pyrolysis reactor based upon auger reactor technology. The composition of the sawdust was 44.4% wt cellulose, 19.0% wt hemicellulose; lignin 29.7% wt, balance being water and inorganic salts. The catalytic pyrolysis was conducted with different catalysts; Catalyst 1 being an amorphous silica-alumina (Saint-Gobain NorPro catalyst SS61138) and Catalyst 2 being H-ZSM-5 with a silica to alumina ratio of about 23. Catalyst 2 consisted of the zeolite (70% wt) and an alumina (pseudoboehmite) binder (30% wt). Before use the catalysts were ground to a particle size of 160 to 650 micrometers, and mixed with quartz sand in a weight ratio of catalyst to sand of 1:3. The catalysts were used in a catalyst to sawdust weight ratio (C/S) of 2.5 or 5.0.

[0058] The catalytic pyrolysis steps were conducted at different temperatures and different catalysts/feed ratios for a period of up to 12 hr at atmospheric pressure. For comparison purposes, the amount of aromatic compounds for some experiments was determined after the pyrolysis step. In two-step processes the vaporous fraction that was obtained in the pyrolysis reaction was passed over a packed bed of Catalyst 2. The amounts of benzene, toluene and xylenes (BTX) were determined and calculated on the basis of the feed.

[0059] For clarity's sake the results of BTX are normalized, the BTX yield of experiment 3 being equal to 100% and the BTX yield of Catalyst 1 being zero %.

[0060] Reaction conditions and results are shown in Table 1.

TABLE-US-00001 TABLE 1 Conversion Relative Exp. Pyrolysis Duration, BTX, No. Catal. C/S T, ° C. Catal. T, ° C. hr % 1 1 5.0 600 — — —  1 2 2 2.5 500 — — —  32 3 1 2.5 500 2 500 0.10 100

[0061] The results show that amorphous silica-alumina does not lead to any amount of aromatic compounds. However, H-ZSM-5 does yield some aromatic compounds in a catalytic pyrolysis process, but the yield is further increased in the process according to the present invention.