Process for producing BTX by catalytic pyrolysis from biomass without recycling oxygenated compounds

Abstract

A process for producing BTX and alcohols from biomass, comprising at least a) catalytic pyrolysis of said biomass in a fluidized-bed reactor producing a gaseous pyrolysis effluent; b) separation of said gaseous pyrolysis effluent into at least one BTX fraction and a gaseous effluent comprising at least carbon monoxide and carbon dioxide, c) recycling at least part of said gaseous effluent comprising at least carbon monoxide and carbon dioxide into the reactor of said step a), d) purging said gaseous effluent recycled according to step c) to produce a purge effluent, e) sending at least part of said purge effluent from step d) into a fermentation step producing a liquid fermentation stream comprising at least one stream comprising at least one oxygenated compound chosen from alcohols, diols, acid alcohols, carboxylic acids, aldehydes, ketones and esters, alone or as a mixture.

Claims

1. Process for producing benzene, toluene, o- and p-xylene (BTX) and alcohols from biomass, comprising at least the following steps: a) conducting catalytic pyrolysis of said biomass in a fluidized-bed reactor producing a gaseous pyrolysis effluent, b) separating said gaseous pyrolysis effluent into at least one BTX fraction and a gaseous effluent comprising at least carbon monoxide and carbon dioxide, c) recycling at least part of said gaseous effluent comprising at least carbon monoxide and carbon dioxide into the reactor of said step a), d) purging said gaseous effluent recycled according to step c) to produce a purge effluent, e) sending at least part of said purge effluent from step d) into a fermentation step producing a liquid fermentation stream comprising at least one stream comprising at least one oxygenated compound selected from the group consisting of an alcohol containing 2 to 6 carbon atoms, a diol containing 2 to 4 carbon atoms, an acid alcohol containing 2 to 4 carbon atoms, a carboxylic acid containing 2 to 6 carbon atoms, an aldehyde containing 2 to 12 carbon atoms, a ketone containing 3 to 12 carbon atoms, an ester containing 2 to 12 carbon atoms, and mixtures thereof, and wherein the stream comprises at least one oxygenated compound selected from the group consisting of ethanol, n-propanol, isopropanol, butanol, isobutanol, hexanol, butyric acid, hexanoic acid, lactic acid, acetone, butanone and 2,3-butylene glycol (2,3-butanediol), alone or as a mixture.

2. Process according to claim 1, in which the catalytic pyrolysis step a) takes place in the presence of a zeolite catalyst comprising at least one zeolite selected from the group consisting of Zeolite Socony Mobil (ZSM)-5, ferrierite, zeolite beta, zeolite Y, mordenite, ZSM-23, ZSM-57, EU-1 and ZSM-11, whether or not doped with a metal selected from the group consisting of iron, gallium, zinc and lanthanum.

3. Process according to claim 1, in which the catalytic pyrolysis step a) is performed at a temperature of between 400 and 1000 C., at an absolute pressure of between 0.1 and 0.5 MPa and at a weight hourly space velocity (WHSV) of between 0.01 and 10 h.sup.1.

4. Process according to claim 1, in which said fermentation step e) is performed in the presence of at least one microorganism chosen from the following microorganism selected from the group consisting of Acetogenium kivui, Acetoanaerobium noterae, Acetobacterium woodii, Alkalibaculum bacchi CP11 (ATCC BAA-1772), Blautia producta, Butyribacterium methylotrophicum, Caldanaerobacter subterraneous, Caldanaerobacter pacificus subterraneous, 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 O-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 mixtures thereof.

5. Process according to claim 4, in which the microorganisms are chosen from Clostridium autoethanogenum, Clostridium ljungdahlii, Clostridium aceticum, Morella thermoacetica, Acetobacterium woodii and Alkalibaculum bacchi for producing ethanol and/or acetate, Clostridium autoethanogenum, Clostridium ljungdahlii and C. ragdalei for producing 2,3-butanediol and Clostridium carboxidivorans, Clostridium drakei, Clostridium scatologenes or Butyribacterium methylotrophicum for producing butyrate and butanol; cultures comprising a mixture of two or more microorganisms may also be used.

6. Process according to claim 1, in which said fermentation step e) is performed at a growth temperature of between 20 and 80 C., at an absolute pressure of between 0.1 and 0.4 MPa and at a pH of between 3 and 9.

7. Process according to claim 1, further comprising introducing a hydrogen supplement into said fermentation of step e).

8. Process according to claim 1, further comprising f) separating said fermentation stream obtained after step e) into at least stream comprising at least one oxygenated compound, an aqueous fraction and an unreacted gaseous effluent.

9. Process according to claim 8, in which said separation step f) is performed using the steam originating from the catalytic pyrolysis step a).

10. Process according to claim 8, in which said stream of oxygenated compounds separated out on conclusion of step e) is not recycled into catalytic pyrolysis step a).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates the process according to the invention in the preferred embodiment in which the stream of oxygenated compounds produced in the fermentation step is not recycled into the catalytic pyrolysis step.

(2) In FIG. 1, the biomass is fed via pipe 1 into a fluidized-bed catalytic pyrolysis reactor A. The gaseous effluent from catalytic pyrolysis is then sent via pipe 2 into a fractionation section B so as to recover an uncondensable gaseous effluent, comprising at least carbon monoxide (CO) and carbon dioxide (CO.sub.2) via pipe 6, a liquid cut known as 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.

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

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

(5) A purge of said gaseous recycle effluent is produced via pipe 7 upstream of the compressor C.

(6) The purge of said gaseous recycle effluent is then sent via pipe 7 into a fermentation step D producing a liquid fermentation stream comprising at least one stream comprising at least one oxygenated compound that is withdrawn via pipe 10. The fermentation step D also comprises separation of the liquid fermentation stream obtained into a stream comprising at least one oxygenated compound that is withdrawn via pipe 10, water withdrawn via pipe 12 and an uncondensable gaseous stream comprising unreacted CO and CO.sub.2, withdrawn via pipe 11.

(7) The invention is illustrated by the following examples, which are not in any way limiting.

EXAMPLE 1: COMPARATIVE: CATALYTIC PYROLYSIS WITHOUT INTRODUCING 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 portion of the uncondensable 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 ZSMS with a crystal content of 40%. The reactor is operated at a temperature of 580 C., at a pressure of 0.2 MPa abs. and at a catalytic WHSV of 0.3 h.sup.1.

(10) Under these conditions, the yield of BTX is 15% by weight relative to the ash-free dry feed.

EXAMPLE 2: ACCORDING TO THE INVENTION

(11) Example 2 corresponds to the case of a catalytic pyrolysis conducted under the same operating conditions as those of Example 1, but for which the uncondensable gaseous effluent purge comprising at least CO and CO.sub.2 is sent to a fermentation unit.

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

(13) TABLE-US-00001 TABLE 1 Composition of the purge constituting the feed of the fermentation unit Composition of the recycled gas wt % Hydrogen 0.5% CO 50.0% CO.sub.2 35.4% Methane 7.3% Ethane 0.5% Ethylene 4.8% Propane 0.1% Propylene 1.3%

(14) The fermentation step is performed using a strain of Clostridium ljungdahlii specifically allowing the conversion of CO to ethanol under the following operating conditions: The percentage of CO contained in the gaseous substrate that is supplied to the fermentation process is 50% by weight and the growth medium of the microorganism is the PETC medium (American Type Culture Collection (ATCC) medium 1754).

(15) The fermentation step is fed with the stream of gaseous substrate described above and is conducted at atmospheric pressure, with stirring at 300 rpm, at a temperature of 39 C., at a pH regulated between 5.5 and 6.0, and at a redox potential of 250 mV. 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.

(16) The production process results in the generation of a liquid fermentation stream separated from the strain extracted from the reactor, said fermentation liquid comprising 94% by weight of water, 5% by weight of ethanol and 1% by weight 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.

(17) Thus, a total production of 8.5 tonnes of ethanol per hour is generated which corresponds to a yield of about 8% by weight relative to the ash-free dry biomass.

(18) According to this embodiment of the invention, a high-value-added product is generated in addition to the BTX cut, starting from CO ultimately intended to be burnt, which very significantly improves the overall viability of the system.

EXAMPLE 3: ACCORDING TO THE INVENTION

(19) Example 3 corresponds to the case of a catalytic pyrolysis conducted under the same operating conditions as those of Example 1, but for which the uncondensable gaseous effluent purge comprising at least CO and CO.sub.2 is sent to a specific fermentation unit allowing conversion of the CO into ethanol and 2,3-butanediol.

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

(21) Relative to Example 3, the fermentation step is conducted with the aid of a strain of Clostridium autoethanogeum DSMZ 10061 specifically allowing the conversion of CO into ethanol and 2,3-butanediol under the following operating conditions: The percentage of CO contained in the gaseous substrate arriving into the fermentation process is 50%, and the percentage of hydrogen is 0.5%. The growth medium is defined as follows:

(22) Growth and alcohol production medium: per litre of medium

(23) Solution 1 (MgCl.sub.2.6H.sub.2O 10 g/L, CaCl.sub.2.2H.sub.2O 15 g/L): 8.33 mL

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

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

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

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

(28) Metal solution 1: 1 mL

(29) Metal solution 2: 1 mL

(30) Sodium tungstate solution (2.94 g/L): 0.1 mL

(31) Vitamin solution: 10.00 mL

(32) Composition of the metal and vitamin solutions

(33) Metal solution 1 (per litre)

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

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

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

(37) HCl (38%): 30 mL

(38) Metal solution 2 (per litre)

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

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

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

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

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

(44) HCl (38%): 5 mL

(45) Vitamin solution (per litre)

(46) Biotin: 20 mg

(47) Folic acid: 20 mg

(48) Pyridoxine: 10 mg

(49) Thiamine: 50 mg

(50) Riboflavin: 50 mg

(51) Vitamin B3: 50 mg

(52) Pantothenic acid: 50 mg

(53) Vitamin B12: 50 mg

(54) Para-Aminobenzoate: 50 mg

(55) Lipoic acid: 50 mg

(56) The fermentation step is fed with the stream of gaseous substrate described above and is conducted 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 introduction of sulfur supplied by additions of Na.sub.2S. It comprises a first phase of production of the microorganism by means of a propagation chain resulting in a sufficient amount of microorganisms for inoculating the production reactors.

(57) The production process results in the generation of a liquid fermentation stream separated from the strain extracted from the reactor, said fermentation liquid comprising 95% by weight of water, 4.2% by weight of ethanol and 0.8% by weight of 2,3-butanediol. These alcohols are optionally recovered by distillation resulting in an azeotropic cut comprising 95% of alcohols.

(58) Thus, a total production of 6.9 tonnes of ethanol and 1.4 tonnes of 2,3-butanediol per hour is generated, which corresponds to a yield of about 6.6% and 1.3% by weight relative to the ash-free dry biomass for ethanol and 2,3-butanediol, respectively. As for Example 2, the production of additional value-added products from CO intended for combustion very significantly improves the overall viability of the system.

(59) According to this other embodiment of the invention, the production of alcohols may be different as a function of the embodiment of the fermentation process making it possible to be more flexible and to be as close as possible to the economic optimum.