AU2012202602B2 - Depolymerization of Lignin Using Solid Acid Catalysts - Google Patents
Depolymerization of Lignin Using Solid Acid Catalysts Download PDFInfo
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- AU2012202602B2 AU2012202602B2 AU2012202602A AU2012202602A AU2012202602B2 AU 2012202602 B2 AU2012202602 B2 AU 2012202602B2 AU 2012202602 A AU2012202602 A AU 2012202602A AU 2012202602 A AU2012202602 A AU 2012202602A AU 2012202602 B2 AU2012202602 B2 AU 2012202602B2
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- Prior art keywords
- lignin
- och
- catalyst
- depolymerization
- reaction
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- 229920005610 lignin Polymers 0.000 title claims abstract description 123
- 239000003054 catalyst Substances 0.000 title claims abstract description 58
- 239000011973 solid acid Substances 0.000 title claims abstract description 14
- 238000000034 method Methods 0.000 claims abstract description 55
- 238000006243 chemical reaction Methods 0.000 claims description 34
- 239000002904 solvent Substances 0.000 claims description 17
- 229910052739 hydrogen Inorganic materials 0.000 claims description 16
- 239000003960 organic solvent Substances 0.000 claims description 16
- 150000002989 phenols Chemical class 0.000 claims description 16
- 239000001257 hydrogen Substances 0.000 claims description 15
- 239000000203 mixture Substances 0.000 claims description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 14
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 claims description 13
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 12
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims description 12
- 239000002253 acid Substances 0.000 claims description 10
- 238000003756 stirring Methods 0.000 claims description 10
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- 229910044991 metal oxide Inorganic materials 0.000 claims description 6
- 150000004706 metal oxides Chemical class 0.000 claims description 6
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 claims description 6
- 150000007513 acids Chemical class 0.000 claims description 5
- 150000001298 alcohols Chemical class 0.000 claims description 5
- 150000002148 esters Chemical class 0.000 claims description 5
- 238000011010 flushing procedure Methods 0.000 claims description 5
- 229910052757 nitrogen Inorganic materials 0.000 claims description 5
- 229910021536 Zeolite Inorganic materials 0.000 claims description 4
- -1 clays Inorganic materials 0.000 claims description 4
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 claims description 4
- 239000010457 zeolite Substances 0.000 claims description 4
- 229910052786 argon Inorganic materials 0.000 claims description 3
- 229910052734 helium Inorganic materials 0.000 claims description 3
- 239000001307 helium Substances 0.000 claims description 3
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 3
- 230000000087 stabilizing effect Effects 0.000 claims description 3
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 claims description 2
- 239000003570 air Substances 0.000 claims description 2
- 238000010438 heat treatment Methods 0.000 claims description 2
- 229910003455 mixed metal oxide Inorganic materials 0.000 claims description 2
- 239000008096 xylene Substances 0.000 claims description 2
- 125000004108 n-butyl group Chemical group [H]C([H])([H])C([H])([H])C([H])([H])C([H])([H])* 0.000 claims 2
- 125000004435 hydrogen atom Chemical class [H]* 0.000 claims 1
- 125000000896 monocarboxylic acid group Chemical group 0.000 claims 1
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N phenol group Chemical group C1(=CC=CC=C1)O ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 abstract description 12
- 150000001875 compounds Chemical class 0.000 abstract description 11
- 239000012298 atmosphere Substances 0.000 abstract description 9
- 239000000178 monomer Substances 0.000 abstract description 8
- 239000000047 product Substances 0.000 description 28
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 24
- 230000000694 effects Effects 0.000 description 16
- 238000012691 depolymerization reaction Methods 0.000 description 15
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 12
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 9
- 229930195733 hydrocarbon Natural products 0.000 description 8
- 150000002430 hydrocarbons Chemical class 0.000 description 8
- 239000000463 material Substances 0.000 description 8
- 125000002485 formyl group Chemical class [H]C(*)=O 0.000 description 7
- 102220043690 rs1049562 Human genes 0.000 description 6
- 229910004298 SiO 2 Inorganic materials 0.000 description 5
- 229920002678 cellulose Polymers 0.000 description 5
- 239000001913 cellulose Substances 0.000 description 5
- 238000002474 experimental method Methods 0.000 description 5
- 239000007789 gas Substances 0.000 description 5
- 239000011541 reaction mixture Substances 0.000 description 5
- 241000196324 Embryophyta Species 0.000 description 4
- 229920002488 Hemicellulose Polymers 0.000 description 4
- 239000002585 base Substances 0.000 description 4
- 239000000470 constituent Substances 0.000 description 4
- 239000002816 fuel additive Substances 0.000 description 4
- 238000002290 gas chromatography-mass spectrometry Methods 0.000 description 4
- 238000005984 hydrogenation reaction Methods 0.000 description 4
- 150000002576 ketones Chemical class 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 230000002378 acidificating effect Effects 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 3
- 150000001491 aromatic compounds Chemical class 0.000 description 3
- 210000002421 cell wall Anatomy 0.000 description 3
- 238000006356 dehydrogenation reaction Methods 0.000 description 3
- 150000002170 ethers Chemical class 0.000 description 3
- 239000000446 fuel Substances 0.000 description 3
- 239000012978 lignocellulosic material Substances 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 230000035484 reaction time Effects 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 125000001424 substituent group Chemical group 0.000 description 3
- CXWXQJXEFPUFDZ-UHFFFAOYSA-N tetralin Chemical compound C1=CC=C2CCCCC2=C1 CXWXQJXEFPUFDZ-UHFFFAOYSA-N 0.000 description 3
- HIXDQWDOVZUNNA-UHFFFAOYSA-N 2-(3,4-dimethoxyphenyl)-5-hydroxy-7-methoxychromen-4-one Chemical compound C=1C(OC)=CC(O)=C(C(C=2)=O)C=1OC=2C1=CC=C(OC)C(OC)=C1 HIXDQWDOVZUNNA-UHFFFAOYSA-N 0.000 description 2
- 239000002028 Biomass Substances 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 150000004996 alkyl benzenes Chemical class 0.000 description 2
- 125000000217 alkyl group Chemical group 0.000 description 2
- 125000003118 aryl group Chemical group 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 239000002551 biofuel Substances 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 238000004517 catalytic hydrocracking Methods 0.000 description 2
- 239000007809 chemical reaction catalyst Substances 0.000 description 2
- JMFRWRFFLBVWSI-NSCUHMNNSA-N coniferol Chemical compound COC1=CC(\C=C\CO)=CC=C1O JMFRWRFFLBVWSI-NSCUHMNNSA-N 0.000 description 2
- 239000000539 dimer Substances 0.000 description 2
- 229910001873 dinitrogen Inorganic materials 0.000 description 2
- RTZKZFJDLAIYFH-UHFFFAOYSA-N ether Substances CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 2
- 239000012634 fragment Substances 0.000 description 2
- 150000002431 hydrogen Chemical class 0.000 description 2
- 239000000852 hydrogen donor Substances 0.000 description 2
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 2
- 239000011261 inert gas Substances 0.000 description 2
- 239000013067 intermediate product Substances 0.000 description 2
- 239000002029 lignocellulosic biomass Substances 0.000 description 2
- 239000012263 liquid product Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 239000012429 reaction media Substances 0.000 description 2
- 239000011949 solid catalyst Substances 0.000 description 2
- LZFOPEXOUVTGJS-ONEGZZNKSA-N trans-sinapyl alcohol Chemical compound COC1=CC(\C=C\CO)=CC(OC)=C1O LZFOPEXOUVTGJS-ONEGZZNKSA-N 0.000 description 2
- 239000003039 volatile agent Substances 0.000 description 2
- YHEWWEXPVKCVFY-UHFFFAOYSA-N 2,6-Dimethoxy-4-propylphenol Chemical compound CCCC1=CC(OC)=C(O)C(OC)=C1 YHEWWEXPVKCVFY-UHFFFAOYSA-N 0.000 description 1
- KLSLBUSXWBJMEC-UHFFFAOYSA-N 4-Propylphenol Chemical compound CCCC1=CC=C(O)C=C1 KLSLBUSXWBJMEC-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- PXIKRTCSSLJURC-UHFFFAOYSA-N Dihydroeugenol Chemical compound CCCC1=CC=C(O)C(OC)=C1 PXIKRTCSSLJURC-UHFFFAOYSA-N 0.000 description 1
- 208000033962 Fontaine progeroid syndrome Diseases 0.000 description 1
- 241000209504 Poaceae Species 0.000 description 1
- 241000592342 Tracheophyta Species 0.000 description 1
- 150000001242 acetic acid derivatives Chemical class 0.000 description 1
- 239000003377 acid catalyst Substances 0.000 description 1
- 150000001335 aliphatic alkanes Chemical class 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 229910000288 alkali metal carbonate Inorganic materials 0.000 description 1
- 150000008041 alkali metal carbonates Chemical class 0.000 description 1
- 150000008044 alkali metal hydroxides Chemical class 0.000 description 1
- 229910001860 alkaline earth metal hydroxide Inorganic materials 0.000 description 1
- 229910000287 alkaline earth metal oxide Inorganic materials 0.000 description 1
- 125000003545 alkoxy group Chemical group 0.000 description 1
- 229940100198 alkylating agent Drugs 0.000 description 1
- 239000002168 alkylating agent Substances 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 229920006125 amorphous polymer Polymers 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 125000001797 benzyl group Chemical group [H]C1=C([H])C([H])=C(C([H])=C1[H])C([H])([H])* 0.000 description 1
- 229920001222 biopolymer Polymers 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000011203 carbon fibre reinforced carbon Substances 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 150000001732 carboxylic acid derivatives Chemical class 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- LZFOPEXOUVTGJS-UHFFFAOYSA-N cis-sinapyl alcohol Natural products COC1=CC(C=CCO)=CC(OC)=C1O LZFOPEXOUVTGJS-UHFFFAOYSA-N 0.000 description 1
- 239000004927 clay Substances 0.000 description 1
- 229910000428 cobalt oxide Inorganic materials 0.000 description 1
- IVMYJDGYRUAWML-UHFFFAOYSA-N cobalt(ii) oxide Chemical compound [Co]=O IVMYJDGYRUAWML-UHFFFAOYSA-N 0.000 description 1
- 229940119526 coniferyl alcohol Drugs 0.000 description 1
- 239000012084 conversion product Substances 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 150000001924 cycloalkanes Chemical class 0.000 description 1
- 125000004981 cycloalkylmethyl group Chemical group 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000006392 deoxygenation reaction Methods 0.000 description 1
- GUJOJGAPFQRJSV-UHFFFAOYSA-N dialuminum;dioxosilane;oxygen(2-);hydrate Chemical compound O.[O-2].[O-2].[O-2].[Al+3].[Al+3].O=[Si]=O.O=[Si]=O.O=[Si]=O.O=[Si]=O GUJOJGAPFQRJSV-UHFFFAOYSA-N 0.000 description 1
- 238000006266 etherification reaction Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 230000002209 hydrophobic effect Effects 0.000 description 1
- 229910017053 inorganic salt Inorganic materials 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 239000002655 kraft paper Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229920002521 macromolecule Polymers 0.000 description 1
- GBMDVOWEEQVZKZ-UHFFFAOYSA-N methanol;hydrate Chemical compound O.OC GBMDVOWEEQVZKZ-UHFFFAOYSA-N 0.000 description 1
- 229910000476 molybdenum oxide Inorganic materials 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 229910000480 nickel oxide Inorganic materials 0.000 description 1
- 238000005580 one pot reaction Methods 0.000 description 1
- 229920000620 organic polymer Polymers 0.000 description 1
- PQQKPALAQIIWST-UHFFFAOYSA-N oxomolybdenum Chemical compound [Mo]=O PQQKPALAQIIWST-UHFFFAOYSA-N 0.000 description 1
- GNRSAWUEBMWBQH-UHFFFAOYSA-N oxonickel Chemical compound [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 description 1
- 229930015763 p-coumaryl alcohol Natural products 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000008188 pellet Substances 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 150000002978 peroxides Chemical class 0.000 description 1
- 229930015704 phenylpropanoid Natural products 0.000 description 1
- 150000002995 phenylpropanoid derivatives Chemical class 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000002203 pretreatment Methods 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000000638 solvent extraction Methods 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 239000003930 superacid Substances 0.000 description 1
- PTNLHDGQWUGONS-UHFFFAOYSA-N trans-p-coumaric alcohol Natural products OCC=CC1=CC=C(O)C=C1 PTNLHDGQWUGONS-UHFFFAOYSA-N 0.000 description 1
- PTNLHDGQWUGONS-OWOJBTEDSA-N trans-p-coumaryl alcohol Chemical compound OC\C=C\C1=CC=C(O)C=C1 PTNLHDGQWUGONS-OWOJBTEDSA-N 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- GPPXJZIENCGNKB-UHFFFAOYSA-N vanadium Chemical compound [V]#[V] GPPXJZIENCGNKB-UHFFFAOYSA-N 0.000 description 1
- 239000002023 wood Substances 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/584—Recycling of catalysts
Landscapes
- Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Catalysts (AREA)
Abstract
The invention provides for a process for the depolymerization of lignin in an inert atmosphere to result in substituted phenolic monomer compounds. The process is catalysed by heterogeneous solid acid catalysts and is carried out in batch or continuous mode.
Description
DEPOLYMERIZATION OF LIGNIN USING SOLID ACID CATALYSTS FIELD OF THE INVENTION The present invention relates to an improved process for depolymerization of lignin using solid acid 5 catalyst in the absence of hydrogen and in an inert atmosphere to yield substituted phenolic monomer compounds. BACKGROUND AND PRIOR ART OF THE INVENTION Lignin is a complex chemical compound most commonly derived from wood and one of the most .0 abundant organic polymers on Earth. Lignin is typically deposited in nearly all vascular plants and provides rigidity and strength to their cell walls. As a biopolymer, lignin is unusual because of its heterogeneity and lack of a defined primary structure. Lignin refers to a biomass material which is a cross-linked racemic macromolecule with molecular masses in excess of 10,000 u. It is relatively hydrophobic and aromatic in nature. The degree of 15 polymerisation in nature is difficult to measure, since it is fragmented during extraction and the molecule consists of various types of substructures which appear to repeat in a haphazard manner. The lignin polymeric structure is composed primarily of three phenylpropanoid building units: p hydroxyphenylpropane, guaiacylpropane, and syringylpropane interconnected by etheric and carbon to-carbon linkages. Generally, in unprocessed lignins, two thirds or more of these linkages are ether 20 bonds, while the remaining linkages are carbon-carbon bonds. Different types of lignin differ significantly in the ratio between these monomers. Numerous efforts on lignin conversion to high-value fuels and fuel additives have included a number of single stage processing methods including hydrocracking, cracking, hydrogenation, hydrotreating, liquefaction in hydrogen-donor solvents, and the like. However, to date, these approaches have 25 achieved limited success for a variety of reasons. During the past few years several studies have been initiated to develop two-stage processes for making liquid fuels and fuel additives from lignin. Further, there is ample literature available on depolymerization of lignin. The vast majority of lignin research in terms of transportation fuel production is done that utilize gaseous hydrogen and different catalysts to remove the covalently bound oxygen as water. 30 References may be made to US6214976, wherein inventor discloses a process for depolymerizing and/or chemically modifying lignin or lignin-like compounds using a solution of copper and peroxide at a temperature of less than 100 0 C. References may be made to US5959167, wherein inventor describes a process for converting lignin into reformulated hydrocarbon gasoline, comprising subjecting the lignin material to a base-catalyzed 2 depolymerization to produce a depolymerized lignin product consisting of alkylated phenols, alkylated alkoxyphenols, hydrocarbons, and mixtures thereof; Further, the depolymerized lignin product is subjected to a sequential two-step hydroprocessing reaction (HPR) to produce a reformulated hydrocarbon gasoline product. 5 References may be made to US6172272, wherein inventor discloses a process for converting lignin into reformulated partially oxygenated gasoline comprising subjecting the lignin material to a base catalyzed depolymerization reaction in the presence of a supercritical alcohol at 2404C-270 0 C; followed by selective hydrocracking reaction at 340 0 C-375 0 C, which utilizes superacid catalyst (platinum modified catalyst) to produce a high oxygen-content depolymerized lignin product mainly composed of i0 alkylated phenols, alkylated alkoxyphenols, and alkylbenzenes. In the second stage of the process, the depolymerized lignin product is subjected to an exhaustive etherification reaction with MeOH in presence of a catalyst; optionally followed by a partial ring hydrogenation reaction to produce a reformulated, partially oxygenated/etherified gasoline product, which includes a mixture of substituted phenyl/methyl ethers, cycloalkyl methyl ethers, C7-C1O alkylbenzenes, C6-C1O branched L5 and multibranched paraffins, and alkylated and polyalkylated cycloalkanes. References may be made to US6100385, wherein inventor discloses a method of producing lignin phenol from lignin, which comprises placing lignin in contact with a hydrogen donor organic solvent such as tetralin, lignin phenol or biomass oil; converting the lignin into low molecular weight-lignin phenol by reducing the lignin in the presence of a reducing agent (such as CO, H2, H2S and mixture 20 thereof) and a catalyst at a temperature preferably about 3000C to about 550 0 C, wherein said catalyst contains molybdenum oxide and a second component selected from the group consisting of nickel oxide or cobalt oxide supported on alumina (neutral, acidic or basic). References may be made to US2008050792, wherein inventor discloses a process for conversion of a lignin material to a bio-fuel, comprising subjecting the lignin material to a base catalyzed 25 depolymerization reaction at a temperature of 230 0 C-350 0 C to produce a partially depolymerized lignin, which is a mixture of monomeric and oligomeric alkylated phenols, biphenols, alkoxyphenols and some hydrocarbons; subjecting the partially depolymerized lignin to a stabilization/partial hydrodeoxygenation reaction in the presence of a solid metal catalyst containing one or more metals selected from the group consisting of Group VI and Group VIII metals of the Periodic Table and 30 vanadium and combinations thereof on a solid support at a temperature of about 2000C to 300 0 C to form a partially hydrodeoxygenated product; followed by hydroprocessing step to yield bio fuel. References may be made to W02009021733, wherein inventor discloses a method of converting a lignin material into a liquid product, wherein lignin material is subjected to a treatment in a reaction medium of at least one C1-C2 carboxylic acid, and/or salts and/or esters thereof; optionally at least 3 one alcohol and/or water; optionally an alkylating agent, and optionally an inorganic salt under elevated pressure to yield a liquid product. The said method is carried out in the absence of added gaseous H 2 and/or in the absence of any added catalyst at reaction temperature from 320 0 C-420 0 C. References may be made to US2010137663, wherein inventor relates to a process for producing 5 chemicals from lignin comprising: combining lignin with a hydrogenation catalyst under hydrogen atmosphere along with base selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides, alkaline earth metal oxides, alkali metal carbonates, and mixtures thereof; reacting the mixture in lignin hydrolysis process conditions at a temperature between 250 0 C and 450 0 C to form an intermediate product stream having a reduced oxygen content; and contacting the 10 intermediate product stream with a deoxygenation and a dehydrogenation catalyst at dehydrogenation reaction conditions including a temperature of between 400 0 C and 900 0 C thereby generating a product stream comprising aromatic compounds. These methods are not environmentally benign and are energy consuming. Hence, it is required to develop a process which will not use soluble base, will operate at milder reaction conditions, and will 15 be environmentally benign. References may be made to US2010137665, wherein inventor discloses a process for the production of hydrocarbons and hydrogen from lignin wherein the first step comprises combining lignin with water and an acidic or basic catalyst in the presence or absence of hydrogen atmosphere to form a mixture of hydrocarbons and light oxygenates with some undecomposed lignin. For acidic depolymerization, it is 20 preferred to have a hydrogen atmosphere. The second step involves decomposing light oxygenates to hydrogen and carbon dioxide in presence of a decomposition catalyst to form a second intermediate stream comprising hydrogen; followed by a third step of combining second intermediate stream with a hydrogenation catalyst to form decomposed lignin, hydrogenated or partially hydrogenated compounds; further contacting the third stream with a dehydrogenation catalyst to form a stream 25 comprising aromatic compounds. It is a process to produce hydrocarbons from lignin, without the addition of an external source of hydrogen, the process itself generates hydrogen that is used in the process. However, there is still a need in the art for an improved and environment friendly process for depolymerization of lignin which will ameliorate the drawbacks of existing prior processes. 30 OBJECTIVE OF THE INVENTION Main objective of the present invention is to provide an improved process for depolymerization of lignin using solid acid catalyst.
4 Another objective of the invention is to carried out the depolymerization process in the absence of hydrogen and in an inert atmosphere to yield substituted phenolic monomer compounds. SUMMARY OF THE INVENTION 5 Accordingly, present invention provides an one pot and single step process for the conversion of lignin to substituted phenolic compounds using heterogeneous solid acid catalyst and the said process comprising the steps of: i. charging lignin and catalyst in the ratio ranging between 0.1:1 to 1:0.1 in a reactor followed by charging a solvent; [0 ii. optionally flushing the reactor with inert gas or air; iii. adjusting the pressure to 1 to 70 bar and temperature in the range of 50 to 300*C of the reactor, under stirring; iv. raising the stirring speed to 10 to 2000 rpm after stabilizing the required temperature; v. carrying the above said reaction for period in the range of 0.1 to 96 hrs to obtain 15 substituted phenolic compounds. In an embodiment of the present invention, heterogeneous solid acid catalyst used is selected from the group consisting of zeolite, clays, metal oxides, mixed metal oxides, supported metal oxides, acid treated oxides. In another embodiment of the present invention, inert gas used in step (b) is selected from the group 20 consisting of nitrogen, argon, helium and hydrogen. In yet another embodiment of the present invention, solvent used is selected from the group consisting of organic solvent or a mixture of water and organic solvent in a ratio of 1:99 to 99:1 and said organic solvent is selected from the group consisting of alcohols, esters, hexane, acids, toluene and xylene. 25 In yet another embodiment of the present invention, said catalyst is recyclable and reusable. In yet another embodiment of the present invention, substituted phenolic monomer compounds are representated by general formula 1 R3 R4 R1 R2 wherein, 30 R1 = -H, -OH, -OCH 3 , -OCH 2
-CH
3 , -CH=CH 2 , -CH=CH-CH 3
.
5 R2 = -H, -OH, -OCH 3 , -OCH 2
-CH
3 , -CH=CH 2 , -CH=CH-CH 3 , -CO-CH 3 , -CO-CH=CH 2 , -CH 2
-CH
3 ,
-CH
2
-CH
2
-CH
3 , -CHO, -CHOH-CHOH-CH 3 , -CHOH-CO-CH 2 0H, -C(CH 3
)
3 ,; R3 = -H, -OH, -OCH 3 , -OCH 2
-CH
3 , -CH=CH 2 , -CH=CH-CH 3 , -CO-CH 3 , -CO-CH=CH 2 , -CH 2
-CH
3 ,
-CH
2
-CH
2
-CH
3 , -CHO, -CH 2
-CO-CH
3 , -CH 2 OH, -CH 2
-CH
2 OH, -CO-OCH 3
-CH
2 -COOH, -CH=CH-CHO, 5 -CH=CH-COOH, -CH 2
-CH
2
-CH
2
-CH
3 , -Ph/Ar, -0-Ph/Ar; R4 = -H, -OH, -OCH 3 , -OCH 2
-CH
3 , -CH=CH 2 , -CH=CH-CH 3 , -CO-CH 3 , -CH 2
-CH
3 , -CHO, CH 2
-CH
2
-CH
3 , -CH 2
-CH
2 OH, -CH 2 OH, -CH=CH-OH, -CH=CH-CH 2 OH, CH 2
-CO-CH
3 , -COOH,
-CH
2 -COOH, -CH=CH-CHO, -CH=CH-COOH, -CH 2
-CH
2
-CH
2
-CH
3 , -OCH 2 R1, -Ph/Ar, -0-Ph/Ar. In yet another embodiment of the present invention, said process is conducted in batch mode. 0 In yet another embodiment of the present invention, said process is conducted in continuous mode. In yet another embodiment of the present invention, products are soluble in any of the following category of solvents in pure form or in mixture (with varying ratios) of thereof such as Polar, non polar, polar protic, polar aprotic, aromatics, substituted aromatics, hydrocarbons, halogenated, aldehydes, ketones, alcohols, ethers, acetates, volatiles and non-volatiles. 5 In yet another embodiment of the present invention, depending up on the reaction conditions employed after the reaction and evaporating reaction media, final mass may be obtained as solid or as viscous oil. In yet another embodiment of the present invention, products may have molecular weight in the range of 100-400 having varying substituent groups. .0 A definition of the specific embodiment of the invention claimed herein follows. In a broad format, the invention provides process for the conversion of lignin to substituted phenolic compounds, said process comprising the steps of: i. charging lignin and a catalyst in a ratio ranging between 0.1:1 to 1:0.1 into a reactor followed by charging a solvent, wherein the catalyst is a heterogeneous solid acid 25 catalyst; ii. optionally flushing the reactor with nitrogen, argon, helium, hydrogen, or air; iii. adjusting the reactor to operate at atmospheric pressure and heating the reactor to a temperature in the range of 50 to 300'C with under stirring; iv. raising the stirring speed to 10 to 2000 rpm after stabilizing at the temperature; and 30 carrying out a reaction for a period in the range of 0.1 to 96 hours to obtain substituted phenolic compounds.
5a BRIEF DESCRIPTION OF THE DRAWING Scheme 1 represents depolymerization of lignin (a component of lignocellulosic material) using solid acid catalysts. Figure 1 depicts the monomer compounds (a to p) derived by the process according to the present 5 invention. Figure 2 represents the GCMS of phenolic compounds (a to p and q to a') of general formula 1. m/z values for q to a' compounds are Nq ] 0 [Text continues on page 6.] 6 DETAILED DESCRIPTION OF THE INVENTION Lignin is one of the main constituent among the 3 major constituents of the lignocellulosic biomass. The other two constituents are cellulose and hemicelluloses. The main role of lignin in plant cell walls is to stick together cellulose and hemicelllulose. Normally, 10-30 wt% (dry) of lignin is present in 5 lignocellulosic biomass. Lignin is a 3-D amorphous polymer made up of several units of aromatic compounds joined together. The aromatic rings may have varying substituent groups such as hydroxyl, alkoxy, ether, alkyl, aldehyde, ketone, etc. The composition, and molecular weight of lignin differ from plant to plant. The percentage of lignin in the cell wall varies with the type of plant whether it is a tree, bush, hurb, grasses etc. The 3 major building blocks of lignin are as follows, HO HO HO oH H H P-coumaryl Conifreyl Sinapyl alcohol alcohol alcohol L0 The molecular weight of lignin generally ranges from 300 to 20,000. However, it is also possible to have lignins with higher molecular weights such as, 70,000 and more. There are several kind of linkages in lignin like 0-0-4, 0-5, 5-5, 4-0-5 etc. which depicts C-C & C-0 linkages, among them D-0-4 linkage is dominant, consisting of more than half of the linkage structures of lignin. Following is a typical 15 structure of lignin, though confirm structure of lignin is yet to be derived.
7 - 0 Ho / OH HO C o0 HO ~~0 Or0Spirodienone \. /OH HO oo \- / OH p-Coumaryl alcohol o OH fragment 0 o' 5-5' HO O HO o OH 0HO o o o 0 H 0 H HO OH H0O -- I OH HO 0O OH P.O OH H HH HO OH HO OHI\H OH OH f Ho __. 0 Coniferyl alcohol H 0 fragment HO 0 - / HO 0 Branching caused by Phenylcoumaran dibenzodioxocin linkage It is possible to isolate the lignin from other constituents such as cellulose and hemicellulose by various pre-treatment or isolation techniques. Depending on the technique by which lignin is isolated the 5 names for lignin are given. For e.g. if lignin is extracted using organic solvent (solvent extraction) then it is called as, Organosolv. If lignin is extracted using alkali treatment then it is called as, Kraft or alkaline lignin. There are many other types of lignin such as, Klason Willstaetter, Pyrolytic, dealkaline lignin etc. Present invention provides an improved process of depolymerization of lignin using solid acid catalyst in the absence of hydrogen and in an inert atmosphere to yield substituted phenolic monomer 10 compounds and gases (CO, H 2 , CH 4 , alkanes etc.). The catalyst used in the depolymerization reaction is selected from zeolite, clays, metal oxides, acid treated oxides etc. These catalysts work at milder reaction conditions and are also easy to separate from reaction mixture and are recyclable. The reaction is carried out at a temperature below 3000C, preferably in the temperature range of 215 0 C to 300 0 C. 15 The catalyst used in the depolymerization reaction is selected from zeolite, clays, metal oxides, acid treated oxides etc. These catalysts work at milder reaction conditions below 2700C and the said reaction resulted into 65% yield with almost more than 85% mass balance. Lignin derived from organosolv process, solid acid catalyst, mixture of water and organic solvent are charged in an autoclave. According to the invention, ratio of organic solvent to water varies between 20 0.15:0.85 to 0.85:0.15. The organic solvent is selected from alcohols, ethers, esters, acids, aldehydes, ketones, halogenated and non-halogenated having different polarities and dielectric constants, alone 8 or in combinations thereof, preferably, Toluene, methanol, ethanol, phenol and water preferably water. The reaction is typically carried out in the temperature range of 215*C to 300*C for a time period of 5 minutes to 2 hours. 5 Lignin, HUSY (Si/AI=15) and mixture of water and organic solvent (30 g) were charged in an autoclave (batch reactor). After flushing the reactor with nitrogen gas, nitrogen of at least 2 bar was charged. Reactor was heated up to 230*C under the stirring (100 rpm). After attaining the desired temperature of 230 0 C stirring was increased up to 500 rpm. Reaction was stopped after 30 minutes. Analysis of reaction mixture was done by GC, GC-MS. o Solid catalyst having acid functionality of the present invention depolymerizes lignin into phenolic compounds with >25% yield with almost more than 85% mass balance. High mass balance obtained in the process is due to low loss in the form of gas. The earlier known processes end up with low mass balance due to degradation of products or formation of gaseous products. From the GC-MS analysis it is found that the phenolic compounds (m/z ranges from 124 to 220) are obtained and accordingly .5 probable structures are derived which are in accordance with the reported structures obtained under different reaction systems. Depolymerization of lignin (a component of lignocellulosic material) using solid acid catalysts is reported in Scheme 1. Phenolic compounds derived from the process of the invention comprise compound of general formula R3 R4 R1 R2 wherein, 25 R1 = -H, -OH, -OCH 3 , -OCH 2
-CH
3 , -CH=CH 2 , -CH=CH-CH 3 R2 = -H, -OH, -OCH 3 , -OCH 2
-CH
3 , -CH=CH 2 , -CH=CH-CH 3 , -CO-CH 3 , -CO-CH=CH 2 , -CH 2
-CH
3 , -CH 2
-CH
2
-CH
3 , CHO, -CHOH-CHOH-CH 3 , -CHOH-CO-CH 2 0H, -C(CH 3
)
3 , . R3 = -H, -OH, -OCH 3 , -OCH 2
-CH
3 , -CH=CH 2 , -CH=CH-CH 3 , -CO-CH 3 , -CO-CH=CH 2 , -CH 2
-CH
3 , -CH 2
-CH
2
-CH
3 , CHO, -CH 2
-CO-CH
3 , -CH 2 OH, -CH 2
-CH
2 OH, -CO-OCH 3
-CH
2 -COOH, -CH=CH-CHO, -CH=CH-COOH, -CH 2
-CH
2 30 CH 2
-CH
3 , -Ph/Ar, -O-Ph/Ar. R4 = -H, -OH, -OCH 3 , -OCH 2
-CH
3 , -CH=CH 2 , -CH=CH-CH 3 , -CO-CH 3 , -CH 2
-CH
3
,
9 -CHO, CH 2
-CH
2
-CH
3 , -CH 2
-CH
2 OH, -CH 2 OH, -CH=CH-OH, -CH=CH-CH 2 OH, CH2-CO-CH 3 , -COOH, -CH2 COOH, -CH=CH-CHO, -CH=CH-COOH, -CH 2
-CH
2
-CH
2
-CH
3 , -OCH 2 R1, -Ph/Ar, -0-Ph/Ar. The alkyl chains, aldehydes, acids, hydroxyl groups are attached to ring or to substituent's in different combinations. The preferred embodiments of the phenolic products by the process of the invention 5 are as depicted in figure 1. The process of the invention is carried out in batch mode. The process is carried out in continuous mode in fixed bed reactor. The lignin solubilised in water or organic solvents from the group of alcohols, ethers, esters, acids, aldehydes, ketones, halogenated and non-halogenated having different polarities and dielectric constants is used as a feed. The solvents .0 used can be in the pure form or mixture of different solvents with changing ratio. The concenteration of feed may be from 0.5 to 50%. The catalyst can be loaded in any of the form like powder, beads, pellets, meshed particles, extrudates etc. either in the pure form or mixed with inert material. The contact time of the feed can be varied from 0.1 second to few minutes (<10 min). The temperatures used in this study can be >50 0 C and <500'C. The reactions can be carried out either at atmosphere 15 pressure or in the pressure range of 1-200 bar. The analysis of the reaction mixture can be done either online or offline. Phenolic compounds obtained after lignin depolymerization could be used as such or as a starting material to synthesize other chemicals or can be further converted into chemicals which can be used as a fuel additive. 20 Further, the knowledge of conversion of hemicellulose and cellulose using solid catalysts already available, addition of knowledge on lignin depolymerization is beneficial in developing a process wherein total lignocellulosic materials (cellulose, hemicellulose and lignin) could be converted into chemicals. 25 Examples The following examples are given by way of illustration therefore should not construed to limit the scope of the invention. Example 1 30 General Example In an autoclave (batch reactor) lignin (0.5 g), HUSY (Si/AI=15) (0.5 g) and mixture of water and organic solvent (30 g) were charged. After flushing the reactor with nitrogen gas for 3 times, nitrogen (7 bar) was charged. Reactor was heated up to 230 0 C under the stirring (100 rpm). After attaining the desired temperature of 230*C stirring was increased up to 500 rpm. Reaction was stopped after 30 minutes.
10 Analysis of reaction mixture was done by GC, GC-MS. The lignin used in these examples were organosolv or dealkaline. Yield: >25% Mass balance: >90%. 5 Example 2 Effect of temperature and reaction time on depolymerization reaction Catalyst HUSY (Si/AI=15) as described in example 1 was employed for lignin depolymerization reaction. The effect of reaction temperature and reaction time on depolymerization reaction is demonstrated by .0 the results presented in Table 1. Table 1: Results on depolymerization of lignin Expt. Catalyst Temp, 0 C Time, min Lignin Product Mass No. conv., % yield, % balance, % 1 HUSY (Si/Al=15) 215 30 22 24 95 2 HUSY (Si/AI=15) 230 30 35 25 94 3 -- 230 30 21 8 86 4 HUSY (Si/AI=15) 230 70 43 31 94 5 HUSY (Si/AI=15) 250 30 34 35 95 6 -- 250 30 22 10 85 7 HUSY (Si/AI=15) 250 70 47 27 89 Lignin, 0.5 g; HUSY (Si/AI=15), 0.5 g; MeOH+H 2 0=25+5 (wt basis); N2, 7 bar@ 25"C Example 3 15 Effect of Catalyst on depolymerization of lignin Table 2 represents different catalysts used in the depolymerization reaction according to the invention. The reaction temperature and time of reaction was same, 250*C and 70 minutes respectively, for all experiments carried out. Table 2: Effect of Catalyst on depolymerization of lignin Expt. No. Catalyst Lignin conv., Product Mass balance, % yield, % % 1 HUSY 47 27 89 (Si/AI=15) 2 Clay, K1O 40 16 88 3 S0 4 /ZrO 2 52 22 85 4 Nb 2 0 5 38 23 93 20 Lignin, 0.5 g; Catalyst, 0.5 g; MeOH+H20=25+5 (wt basis); N2 pressure, 7 bar@ 25 0
C
l1 Example 4 Effect of pressure on depolymerization of lignin Catalyst HUSY (Si/AI=15) as described in example 1 was employed for lignin depolymerization reaction for 30 minutes to see the effect of pressure on depolymerization reaction of lignin. Results observed 5 are presented in Table3. Table 3: Effect of pressure on depolymerization of lignin Expt. No. Pressure, Lignin Product Mass bar conv., % yield, % balance, % 1 7 30 22 96 2 1 44 37 96 Lignin, 0.5 g; HUSY (Si/AI=15), 0.5 g; MeOH+H20=15+15 (wt basis); Temperature, 250 0 C Example 5 10 Effect of different gases on depolymerization of lignin Table 4 represents the results of experiments carried out employing different gases such as N2 and H2 in the lignin depolymerization reaction for 70 minutes employing HUSY (Si/AI=15) as catalyst. Table 4: Effect of different gases on depolymerization of lignin Expt. No. Pressure, Lignin Product Mass bar conv., % yield, % balance, % 1 N2,7 47 27 90 2 H2,7 52 17 82 Lignin, 0.5 g; HUSY (Si/AI=15), 0.5 g; MeOH+H20=25+5 (wt basis); Temperature, 250*C 15 Example 6 Effect of different solvent ratio on depolymerization of lignin The Catalyst HUSY (Si/AI=15) as described in example 1 with varying solvent ratios of the same solvent was employed in depolymerization reaction of lignin for 30 minutes. Results of the experiments are 20 represented in Table 5. Table 5: Effect of solvent ratio on depolymerization of lignin Expt. MeOH+H20 Lignin Product Mass No. (wt+wt) conv., % yield, % balance, % 1 25+5 34 35 96 2 15+15 30 32 96 3 5+25 Sticky mass was observed 12 Lignin, 0.5 g; HUSY (Si/AI=15), 0.5 g; N2 Pressure, 7 bar @RT; Temperature, 250 0 C Example 7 Effect of different solvents on depolymerization of lignin 5 Table 6 represents different experiments carried out in presence of different solvents in the lignin depolymerization reaction according to the invention, employing HUSY (Si/AI=15) as catalyst. Table 6: Effect of different solvents on depolymerization of lignin Expt. Solvent Time, Lignin Product Mass No. Wt basis min conv., % yield, % balance, % 1 MeOH+H20=25+5 30 34 35 91 2 Phenol+H20=7+30 Shows products forming. 3 H20 (100%) Shows products forming. 4 EtOH+H20=25+5 30 25 20 85 5 Toluene 30 23 10 87 Lignin, 0.5 g; HUSY (Si/AI=15), 0.5 g; N2 Pressure, 7 bar @RT; Temperature, 250 0 C 10 Example 8: The effect of catalyst on depolymerization of dealkaline lignin Table 7 represents different experiments carried out in presence of different catalyst in the lignin (dealkaline)* depolymerization reaction Exp. No Catalyst Lignin conversion, % Product yield, % Mass balance, % 1. HZSM-5 84 50 91 2. Si0 2
-AI
2 0 3 85 26 81 3. MoO 3 /SiO 2 90 28 91 4. Ga 2
O
3 /SiO 2 45 15 92 5 W0 3 /SiO 2 90 55 85 6 SO 4 /ZrO 2 76 15 87 7 Nb 2 0 5 68 18 89 8 K10 (clay) 56 09 84 * Lignin, 0.5 g; HUSY (Si/AI=15), 0.5 g; N2 Pressure, 7 bar @RT; Temperature, 250 0 C. "Monomer and dimer products soluble in water/organic solvents. 15 EXAMPLE 9: The effect of time on depolymerisation of dealkaline lignin Table 8 The effect of reaction temperature and reaction time on depolymerization reaction is demonstrated by the results presented in Table 8 using SiO 2
-AI
2 0 3 as catalyst*.
13 Exp. No. Time Lignin conversion Product yield,%# Mass balance, (min.) % % 1. 30 85 26 80 2. 60 85 41 86 3. 90 92 50 84 4 120 95 70 85 Lignin, 0.5 g; HUSY (Si/Al=15), 0.5 g; N2 Pressure, 7 bar @RT; Temperature, 250 0 C. 4Monomer and dimer products soluble in water/organic solvents. EXAMPLE 10: Catalyst recyclability 5 Catalyst recyclability was tested and it has been found out that with SiO 2 -A1 2 0 3 catalyst in presence of methanol-water system at 250 0 C and within 30 min. in first reaction 26% products yield was obtained. After reaction catalyst was recovered and used for the next reaction and under similar reaction conditions 24% products yield is observed. LO ADVANTAGES OF THE INVENTION 1. The products obtained are value added products, useful as such or as a fuel additives 2. The process can be carried out in batch as well as continuous modes. 3. The heterogeneous acid catalysts used as corrosion-free. 4. The catalysts are easily separable from reaction mixture. L5 5. A safer process conducted in inert atmosphere. The term "comprise" and variants of the term such as "comprises" or "comprising" are used herein to denote the inclusion of a stated integer or stated integers but not to exclude any other integer or any other integers, unless in the context or usage an exclusive interpretation of the term is required. 20 Any reference to publications cited in this specification is not an admission that the disclosures constitute common general knowledge in Australia.
Claims (8)
1. A process for the conversion of lignin to substituted phenolic compounds, said process comprising the steps of: i. charging lignin and a catalyst in a ratio ranging between 0.1:1 to 1:0.1 into a reactor followed by charging a solvent, wherein the catalyst is a heterogeneous solid acid catalyst; ii. optionally flushing the reactor with nitrogen, argon, helium, hydrogen, or air; iii. adjusting the reactor to operate at atmospheric pressure and heating the reactor to a temperature in the range of 50 to 300'C with under stirring; iv. raising the stirring speed to 10 to 2000 rpm after stabilizing at the temperature; and v. carrying out a reaction for a period in the range of 0.1 to 96 hours to obtain substituted phenolic compounds.
2. The process as claimed in claim 1, wherein the heterogeneous solid acid catalyst is selected from the group consisting of zeolite, clays, metal oxides, mixed metal oxides, supported metal oxides, and acid treated oxides.
3. The process as claimed in claim 1 or claim 2, wherein the solvent is selected from the group consisting of organic solvent or a mixture of water and organic solvent in a ratio of 1:99 to 99:1 and said organic solvent is selected from the group consisting of alcohols, esters, hexane, acids, toluene, and xylene.
4. The process as claimed in claim 1, wherein said catalyst is recyclable and reusable.
5. The process as claimed in any one of claims 1 to 4, wherein the substituted phenolic compounds are represented by general formula 1 R3 R4 RI R2 wherein, RI= -H, -OH, -OCH 3 , -OCH 2 -CH 3 , -CH=CH 2 , -CH=CH-CH 3 ; R2 = -H, -OH, -OCH 3 , -OCH 2 -CH 3 , -CH=CH 2 , -CH=CH-CH 3 , -CO-CH 3 , -CO-CH=CH 2 , -CH 2 -CH 3 , -CH 2 -CH 2 CH 3 , -CHO, -CHOH-CHOH-CH 3 , -CHOH-CO-CH 2 OH, -C(CH 3 ) 3 , 15 R3 = -H, -OH, -OCH 3 , -OCH 2 -CH 3 , -CH=CH 2 , -CH=CH-CH 3 , -CO-CH 3 , -CO-CH=CH 2 , -CH 2 -CH 3 , -CH 2 -CH 2 CH 3 , -CHO, -CH 2 -CO-CH 3 , -CH 2 OH, -CH 2 -CH 2 OH, -CO-OCH 3 -CH 2 -COOH, -CH=CH-CHO, -CH=CH COOH, -CH 2 -CH 2 -CH 2 -CH 3 , -Ph/Ar, -0-Ph/Ar; R4 = -H, -OH, -OCH 3 , -OCH 2 -CH 3 , -CH=CH 2 , -CH=CH-CH 3 , -CO-CH 3 , -CH 2 -CH 3 , -CHO, CH 2 -CH 2 -CH 3 , -CH 2 -CH 2 OH, -CH 2 OH, -CH=CH-OH, -CH=CH-CH 2 OH, CH 2 -CO-CH 3 , -COOH, -CH 2 -COOH, -CH=CH-CHO, -CH=CH-COOH, -CH 2 -CH 2 -CH 2 -CH 3 , -OCH 2 R1, -Ph/Ar, -0-Ph/Ar.
6. The process as claimed in any one of claims 1 to 5, wherein said process is conducted in batch mode.
7. The process as claimed in any one of claims 1 to 5, wherein said process is conducted in continuous mode.
8. A process for the conversion of lignin to substituted phenolic compounds as defined in claim 1, and substantially as hereinbefore described with reference to one or more of the accompanying examples. Date: 18 August 2015
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