Catalytic Depolymerization Of Lignin Using The Transition Metal(Co, Ni, Mo) Catalysts

As the only natural resource contains the aromatic rings,lignin is regarded to be a promising substitution to replace the fossil resources to obtaine the aromatic chemicals.Recently,the catalytic cleavage of?-O-4 bonds in lignin becomes one of the most important stratage for the valorization of lignin,since the large amount of?-O-4 bonds in lignin molecules.However,there are still challenges in lignin valorization,such as the low selectivity and costly separated operation.Thus,this work aimed on the present situation of lignin depolymerization processes,developed novel catalysts and catalytic system to realize the selectivity depolymerization of lignin and its model compounds.Further more,the dynamic model of cellulose depolymerization was carried out and the kenitic parameters obtained through the experimental data were used in the simulative continous operation process to investigate the effects of the operation conditions.The details are as follows.1 The use of a highly dispersed Co catalyst for the oxidative cleavage of the?-O-4 bonds of lignin model compounds at a low oxygen pressure.Under the optimized reaction conditions conversion of 2-?2-methoxyphenoxy?-1-phenylethanol?MPP-ol?up to 95%with high selectivities were achieved with a variety of substrates investigated.The reusability of the Co catalyst with the high catalytic efficiency indicates its potential application in the oxidative cleavage of C-O bonds.2 A series of lignolsulfonate derived carbon supported sulfide metal catalysts?MS/C,M=Co,Ni,Mo?were developed and successfully used in the lignin and its model compound hydrogenolysis.The BET and NH₃-TPD characterizations shown the catalysts have big surface areas and weak acid sites.By analyzing the XRD data and the TEM images,all of the catalysts shown homogeneous distribution of the surfur and metal sepices,except to the NiS/C and NiMoS/C.More intresting,the hydrogenolysis reaction occurred in aqueous phase and the model compound achieved to more than 95%conversion at 180^oC and 1 Mpa H₂ under the catalysis of CoS/C,NiS/C and CoMoS/C.The catalysts also have high activity and selectivity to real lignin,the yield of 4-propylguaiacol attained to 23.7 mg/g lignosulfonate and the selectivity was 84%.More over,the catalysts showed wonderful reusability for the hydrogenolysis in aqueous phase,which maintained similar activity and selectivity after 7 cycles.3 An efficient emulsion microreactor was constructed for selective conversion of lignosulfonate to useful chemicals via hydrogen transfer reaction based on the self-surfactivity of this natural aromatic polymer.Industrial Raney Ni and isopropanol were used as catalyst and hydrogen donor,respectively.The results showed that the emulsion microreactor has a remarkable process intensification effect on the lignosulfonate depolymerization.Under mild condition of 200 ^oC for 2.0 h,116.1 mg g^-1 of volatile phenolic monomer can be obtained,which is twice of that from other investigated process without emulsion.In particular,39.3 mg g^-1 of which is composed of 4-ethyl guaiacol,an important and versatile chemical currently from petrochemical industry.Furthermore,the solvent separates to two phases automatically after reaction due to the consumption of lignosulfonate,which makes handy products enrichment and separation.4 A kinetic model for the batch reactor was described for catalytic cellulose degradation in cooperative ionic liquid pairs based on an intensive analysis of the experimental parameters.Our fitting results show that the proposed model agrees well with the experimental data.The kinetic parameters obtained from the above model were subsequently applied to the continuous stirred tank reactor?CSTR?by constructing a mathematical process model for the continuous operation of cellulose degradation combined with product separation.The effects of reaction temperature,retention time,extract flow rate and distribution coefficients were intensively investigated.The findings presented in this work will serve as a beneficial reference for further biomass transformation of industrial purpose.