Process for producing BTX by catalytic pyrolysis from biomass with injection of oxygenated compounds

Abstract

A process is described for producing a BTX cut from biomass comprising at least one step of catalytic pyrolysis of said biomass in a fluidized-bed reactor in which a stream comprising at least one oxygenated compound selected from alcohols having 2 to 12 carbon atoms, alcohol acids having 2 to 12 carbon atoms, diols having 2 to 12 carbon atoms, carboxylic acids having 2 to 12 carbon atoms, ethers having 2 to 12 carbon atoms, aldehydes having 2 to 12 carbon atoms, esters having 2 to 12 carbon atoms and glycerol, alone or mixed, is fed into the catalytic pyrolysis reactor.

Claims

1. A process producing a BTX cut from biomass comprising at least one catalytic pyrolysis of said biomass in a fluidized-bed catalytic pyrolysis reactor in which a stream comprising at least one oxygenated compound that is alcohols having 2 to 12 carbon atoms, alcohol acids having 2 to 12 carbon atoms, diols having 2 to 12 carbon atoms, carboxylic acids having 2 to 12 carbon atoms, ethers having 2 to 12 carbon atoms, aldehydes having 2 to 12 carbon atoms, esters having 2 to 12 carbon atoms or glycerol, alone or mixed, is fed into the catalytic pyrolysis reactor.

2. The process according to claim 1, wherein the catalytic pyrolysis operates in the presence of a zeolite catalyst comprising at least one zeolite that is ZSM-5, ferrierite, zeolite Beta, zeolite Y, mordenite, ZSM-23, ZSM-57, EU-1, or ZSM-11, optionally doped with iron, gallium, zinc or lanthanum.

3. The process according to claim 1, wherein the catalytic pyrolysis produces a gaseous effluent, which is then sent to a fractionation section so as to separate at least one gaseous effluent comprising at least carbon monoxide and carbon dioxide, a liquid cut called BTX and a liquid cut comprising at least 50 wt % of compounds having a number of carbon atoms greater than 9.

4. The process according to claim 3, wherein at least a proportion of said gaseous effluent comprising carbon monoxide (CO) and carbon dioxide (CO.sub.2) is recycled via a compressor to the reactor of the catalytic pyrolysis and said gaseous recycle effluent is purged, either upstream, or downstream of said compressor.

5. The process according to claim 1, wherein said stream of oxygenated compounds fed into the catalytic pyrolysis reactor comprises at least one oxygenated compound that is alcohols having 2 to 6 carbon atoms, alcohol acids having 2 to 6 carbon atoms, diols having 2 to 6 carbon atoms, carboxylic acids having 2 to 6 carbon atoms, ethers having 2 to 6 carbon atoms, aldehydes having 2 to 6 carbon atoms, esters having 2 to 6 carbon atoms or glycerol, alone or mixed.

6. The process according to claim 5, wherein the alcohols having 2 to 6 carbon atoms of said stream of oxygenated compounds are ethanol, n-propanol and isopropanol, butanol, isobutanol, 2,3-butanediol, isononanol, 2-ethylhexanol or hexanol, alone or mixed, the alcohol acids having 2 to 6 carbon atoms are lactic acid, tartaric acid, glycolic acid or citric acid, alone or mixed, the carboxylic acids having 2 to 6 carbon atoms are acetic acid, butyric acid, pyruvic acid or hexanoic acid, alone or mixed, the diols having 2 to 6 carbon atoms are ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, trimethylene glycol, butylene glycol, n-butylene glycol or 2,3-butylene glycol, alone or mixed, the ethers having 2 to 6 carbon atoms are dimethyl ether, methyl ethyl ether, diethyl ether, methyl propyl ether, methyl tert-butyl ether, ethyl tert-butyl ether, or tetrahydrofuran, alone or mixed, the aldehydes having 2 to 6 carbon atoms are ethanal, propanal, butanal, pentanal, 3-methylbutanal, hexanal, furfural or glyoxal alone or mixed, and the esters having 2 to 6 carbon atoms are methyl formate, methyl acetate, methyl propionate, methyl butanoate, methyl pentanoate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, or butyl butyrate, alone or mixed.

7. The process according to claim 1, wherein said stream fed into the catalytic pyrolysis reactor is a stream comprising at least one oxygenated compound that is ethanol, butanol, isobutanol, isopropanol, n-propanol, hexanol, acetic acid, butyric acid, hexanoic acid, lactic acid or 2,3-butylene glycol (butane-2,3-diol), alone or mixed.

8. The process according to claim 7, wherein said stream comprising at least one oxygenated compound is produced in fermentation of a purge of the gaseous recycle effluent comprising CO and CO.sub.2 produced by catalytic pyrolysis.

9. The process according to claim 8, wherein said stream comprising at least one oxygenated compound is separated from a fermentation stream produced by the fermentation in a separation using steam derived from the catalytic pyrolysis.

10. The process according to claim 8, wherein said fermentation step is carried out in the presence of at least one microorganism that is: Acetogenium kivui, Acetoanaerobium noterae, Acetobacterium woodii, Alkalibaculum bacchi CP11 (ATCC BAA-1772), Blautia producta, Butyribacterium methylotrophicum, Coldanaerobacter subterraneus, Coldanaerobacter pacificus subterraneus, Hydrogenoformans carboxydothermus, Clostridium aceticum, Clostridium acetobutylicum, Clostridium acetobutylicum P262 (DSM 19630 from DSMZ Germany), Clostridium autoethanogenum (DSM 19630 from DSMZ Germany), Clostridium autoethanogenum (DSM 10061 from DSMZ Germany), Clostridium autoethanogenum (DSM 23693 from DSMZ Germany), Clostridium autoethanogenum (DSM 24138 from DSMZ Germany), Clostridium carboxidivorans P7 (ATCC PTA-7827), Clostridium coskatii (ATCC PTA-10522), Clostridium drakei, Clostridium ljungdahlii PETC (ATCC 49587), Clostridium ERI2 ljungdahlii (ATCC 55380), Clostridium ljungdahlii C-01 (ATCC 55988), Clostridium ljungdahlii 0-52 (ATCC 55889), Clostridium magnum, Clostridium pasteurianum (DSM 525 from DSMZ Germany), Clostridium ragsdali P11 (ATCC BAA-622), Clostridium scatologenes, Clostridium thermoaceticum, Clostridium ultunense, Desulfotomaculum kuznetsovii, Eubacterium limosum, Sulfurreducens geobacter, Methanosarcina acetivorans, Methanosarcina barken, Morrella thermoacetica, Morrella thermoautotrophica, Oxobacter pfennigii, Peptostreptococcus productus, Ruminococcus productus, Thermoanaerobacter kivui, and or mixtures thereof.

11. The process according to claim 10, wherein the microorganisms are Clostridium autoethanogenum, Clostridium ljungdahlii, Clostridium aceticum, Morella thermoacetica, Acetobacterium woodiia or Alkalibaculum bacchi for producing ethanol and/or acetate, Clostridium autoethanogenum, Clostridium ljungdahlii or C. ragdalei for producing 2,3-butanediol or Clostridium carboxidivorans, Clostridium drakei, Clostridium scatologenes or Butyribacterium methylotrophicum for producing butyrate and butanol, or cultures comprising a mixture of two or more of said microorganisms.

12. The process according to claim 8, wherein part of the purge of the gaseous recycle effluent comprising at least carbon monoxide and carbon dioxide, used as feed for the fermentation step in the form of gaseous substrate, has a weight ratio H.sub.2/CO of 0 to 1.2 or H.sub.2CO.sub.2 of 0 to 1.7.

13. The process according to claim 8, wherein said fermentation is carried out at a growing temperature of 20 to 80° C., at an absolute pressure of 0.1 to 0.4 MPa and at a pH of 3 to 9.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 illustrates the process according to the invention comprising a step of catalytic pyrolysis of biomass in which a stream of oxygenated compounds is added and

(2) FIG. 2 illustrates the preferred embodiment of the invention in which the stream of oxygenated compounds is produced in a step of fermentation of a residual effluent from the catalytic pyrolysis step of the process according to the invention.

(3) In FIG. 1, the biomass is fed via pipe 1 into a fluidized-bed catalytic pyrolysis reactor A. A stream comprising at least one oxygenated compound is also fed via pipe 10 into the catalytic pyrolysis reactor. The gaseous effluent from catalytic pyrolysis is then sent via pipe 2 into a fractionation section B so as to recover a non-condensable gaseous effluent, comprising at least carbon monoxide (CO) and carbon dioxide (CO.sub.2) via pipe 6, a liquid cut called BTX via pipe 3, a heavy liquid cut predominantly comprising compounds having a number of carbon atoms greater than 9, via pipe 4 and water via pipe 5.

(4) Flue gases are also withdrawn from the pyrolysis reactor via pipe 9.

(5) At least a proportion of said gaseous effluent comprising carbon monoxide (CO) and carbon dioxide (CO.sub.2) is recycled via a compressor C, to the reactor of the catalytic pyrolysis step via pipe 8.

(6) Purge of said gaseous recycle effluent is carried out via pipe 7 upstream of the compressor C.

(7) In FIG. 2, pipes 1 to 9 and the elements A, B and C are identical to those described for FIG. 1. The purge of said gaseous recycle effluent is then sent via pipe 7 to a fermentation step D that produces a liquid fermentation stream comprising at least one stream comprising at least one oxygenated compound withdrawn via pipe 10. The fermentation step D also comprises separation of the stream of fermentation liquid obtained in a stream comprising at least one oxygenated compound withdrawn via pipe 10, water withdrawn via pipe 13 and a gaseous stream of non-condensables comprising unreacted CO and CO.sub.2, withdrawn via pipe 12. A portion of said liquid fermentation stream comprising at least one stream comprising at least one oxygenated compound is then recycled to the catalytic pyrolysis reactor A via pipe 11.

EXAMPLES

Example 1: Comparative: Catalytic Pyrolysis without Introduction of a Stream of Oxygenated Compounds

(8) Example 1 presents the case of catalytic pyrolysis of a variety of pine with a capacity of 2500 tonnes per day with a non-condensable portion of the gaseous effluent comprising at least CO and CO.sub.2 separated from the gaseous effluent from pyrolysis being recycled to the catalytic pyrolysis reactor. The biomass is fed into the catalytic pyrolysis reactor at a rate of 104 tonnes per hour. The recycle/biomass weight ratio is 1.5 so as to be in the desired hydrodynamic conditions.

(9) In this example the catalyst used is a commercial ZSM5 having a content of crystals of 40%. The reactor is operated at a temperature of 580° C., at a pressure of 0.2 MPa abs. and at a catalytic LHSV of 0.3 h-1.

(10) In these conditions the yield of BTX is 15 wt % relative to the ash-free dry feed.

Example 2: According to the Invention

(11) Example 2 corresponds to the case of catalytic pyrolysis carried out in the same operating conditions as in example 1 but for which a stream of ethanol from a process for hydrogenation of sugars is added. The case considered corresponds to an ethanol stream of 2.2 tonnes per hour.

(12) In these conditions, the yield of BTX is improved very significantly by 4% relative to the reference case (Example 1).

Example 3: According to the Invention

(13) Example 3 corresponds to the case of catalytic pyrolysis carried out in the same operating conditions as those in example 1 but for which the non-condensable purge of the gaseous effluent comprising at least CO and CO.sub.2 is sent to a fermentation unit.

(14) The purge in question constitutes the feed of the fermentation step and corresponds to a stream of gaseous substrate of 33 tonnes per hour having the composition presented in Table 1.

(15) TABLE-US-00001 TABLE 1 Composition of the purge constituting the feed of the fermentation unit Composition of the purge wt % Hydrogen 0.5% CO 50.0% CO.sub.2 35.4% Methane 7.3% Ethane 0.5% Ethylene 6.0% Propane 0.1%

(16) The fermentation step is carried out using a strain of Clostridium ljungdahlii specifically allowing conversion of CO to ethanol in the following operating conditions:

(17) The percentage of CO contained in the gaseous substrate that is supplied to the fermentation process is 50 wt % and the growth medium of the microorganism is the PETC medium (American Type Culture Collection (ATCC) medium 1754).

(18) The fermentation step is supplied with the stream of gaseous substrate described above and is carried out at atmospheric pressure, with stirring at 300 rpm, at a temperature of 39° C., at a pH regulated between 5.5 and 6, and at a redox potential of 250 mV (Ag/AgCl electrode). It comprises a first phase of production of the microorganism through a chain of propagation leading to a sufficient quantity of microorganisms for inoculating the production reactors.

(19) The production process generates a liquid fermentation stream separated from the strain extracted from the reactor, said fermentation liquid comprising 95 wt % of water, 5 wt % of ethanol and 1 wt % of residual acetic acid. The alcohols, mainly ethanol, contained in this stream are recovered by distillation leading to an azeotropic cut comprising 95% of alcohols.

(20) Thus, a total output of 8.5 tonnes of ethanol per hour is generated. 26% of this output is recycled to the catalytic pyrolysis reactor, i.e. 2.2 tonnes per hour. The proportion of ethanol recycled to the catalytic pyrolysis reactor represents 2 wt % of the biomass fed into said catalytic pyrolysis reactor.

(21) As in example 2, the output of BTX is improved by 4% relative to the reference case (example 1) but in addition an output of 6 wt % of ethanol relative to the ash-free dry feed is generated, which greatly improves the profitability of the process relative to example 2 and demonstrates the advantage of combining pyrolysis with a fermentation step. This combination makes it possible to upgrade the pyrolysis purge, which is generally intended to be flared into products with high added value, namely BTX and ethanol.

Example 4

(22) Example 4 corresponds to the case of catalytic pyrolysis carried out in the same operating conditions as those in example 1 but for which the non-condensable purge of the gaseous effluent comprising at least CO and CO.sub.2 is sent to a special fermentation unit for conversion of CO to ethanol and 2,3-butanediol.

(23) The purge in question corresponds to a stream of gaseous substrate of 33 tonnes per hour having the same composition as in example 3 and presented in Table 1.

(24) Relative to example 3, the fermentation step is carried out using a strain of Clostridium autoethanogenum DSMZ 10061 specifically for conversion of CO to ethanol and 2,3-butanediol in the following operating conditions:

(25) The percentage of CO contained in the gaseous substrate that is supplied to the fermentation process is 50%, and the percentage of hydrogen is 0.5%. The growth medium is defined as follows:

(26) Medium for growth and production of alcohols: Per litre of medium

(27) Solution 1 (MgCl.sub.2.6H.sub.2O 10 g/L, CaCl.sub.2. 2H.sub.2O 15 g/L): 8.33 mL

(28) Solution 2 (NaCl 12 g/L, KCl 15 g/L): 8.33 mL

(29) CH.sub.3COONH.sub.4 3.00 g

(30) Resazurine solution (1 g/L): 1.00 mL

(31) H.sub.3PO.sub.4 (85%): 0.37 mL

(32) Metals solution 1:1 mL

(33) Metals solution 2:1 mL

(34) Solution of sodium tungstate (2.94 g/L): 0.1 mL

(35) Solution of vitamins: 10.00 mL

(36) Composition of the solutions of metals and vitamins

(37) Metals solution 1 (per litre)

(38) FeSO.sub.4.7H.sub.2O: 0.10 g

(39) ZnSO.sub.4.7H.sub.2O: 0.20 g

(40) NiCl.sub.2.6H.sub.2O: 0.02 g

(41) HCl (38%): 30 mL

(42) Metals solution 2 (per litre)

(43) MnSO.sub.4.H.sub.2O: 0.5 g

(44) CoCl.sub.2.6H.sub.2O: 0.5 g

(45) H.sub.3BO.sub.3: 0.3 g

(46) NaMoO.sub.4.2H.sub.2O: 0.03 g

(47) Na.sub.2SeO.sub.3: 0.02 g

(48) HCl (38%): 5 mL

(49) Solution of vitamins (per litre)

(50) Biotin: 20 mg

(51) Folic acid: 20 mg

(52) Pyridoxine: 10 mg

(53) Thiamine: 50 mg

(54) Riboflavin: 50 mg

(55) Vitamin B3: 50 mg

(56) Pantothenic acid: 50 mg

(57) Vitamin B12: 50 mg

(58) Para-aminobenzoate: 50 mg

(59) Lipoic acid: 50 mg

(60) The fermentation step is supplied with the stream of gaseous substrate described above and is carried out at atmospheric pressure, at a temperature of 37° C., a pH regulated at 5.3 with NH.sub.4OH, a redox potential maintained at 250 mV and supply of sulphur supplied by adding Na.sub.2S. It comprises a first phase of production of the microorganism through a chain of propagation leading to a sufficient quantity of microorganisms for inoculating the production reactors.

(61) The production process generates a liquid fermentation stream separated from the strain extracted from the reactor, said fermentation liquid comprising 95 wt % of water, 4.2 wt % of ethanol and 0.8 wt % of 2,3-butanediol. These alcohols are optionally recovered by distillation leading to an azeotropic cut comprising 95% of alcohols.

(62) Thus, a total output of 6.9 tonnes of ethanol and 1.4 tonnes of 2,3-butanediol per hour is generated. 27% of this output is recycled to the catalytic pyrolysis reactor, i.e. 2.2 tonnes per hour or the same recycle flow rate as in example 3.

(63) The proportion of ethanol and of 2,3-butanediol recycled to the catalytic pyrolysis reactor represents 2 wt % of the biomass fed into said catalytic pyrolysis reactor.

(64) With this new operating mode of the fermentation process, production of BTX is improved by 4.5% relative to the reference case (example 1) and is therefore increased relative to example 3 (regarding the large capacity of the unit, an increase of several tenths of a point has a strong impact on the profitability of the unit) and an output of 5.8 wt % of the mixture of ethanol and 2,3-butanediol relative to the ash-free dry feed is generated, which greatly improves the profitability of the process relative to example 2. As in example 3, the combination of catalytic pyrolysis and fermentation makes it possible to upgrade the pyrolysis purge intended to be flared into products of high added value, namely BTX and alcohols with, for example 4, better selectivity for BTX relative to example 3.