Research progress in regulation of lignin catalytic pyrolysis products
As an important renewable organic carbon source,lignin's unique three-dimensional cross-linked structure brings rich chemical potential,but also brings problems for its efficient conversion and utilization.Catalytic pyrolysis is an effective means to realize green,low carbon and high value utilization of lignin.In the research field of catalytic pyrolysis of lignin,methane,syngas,light aromatic hydrocarbons and high-performance porous carbon materials have become the high value of the target products.In view of this,the key regulatory roles of various catalysts in the catalytic pyrolysis of lignin were deeply and systematically discussed,focusing on the application of high-value products in the catalytic pyrolysis of lignin.Among them,AAEMs catalysts can be divided into alkali metal salt and alkaline earth metal salt.Although alkali metal salt reduces the liquid phase yield,it increases the yield of phenol and other monophenols,while alkaline earth metal salt increases the liquid phase yield,and has a significant selectivity effect on enhancing phenol.Alkali metal salts contribute to the formation of gaseous products and can improve the selectivity of H2.Although alkali earth metal salts inhibit the formation of gaseous products,they play an important role in the water-gas conversion reaction.In terms of solid phase products,alkali metal salts are more conducive to improving the yield of biochar than alkaline earth metal salts,and can further optimize its structure and enhance its reactivity.Metal oxide catalysts are mainly divided into acidic and alkaline categories.In the catalytic pyrolysis process of lignin,acid metal oxides can significantly improve the yield of liquid products,show high selectivity to phenol and MAHs,contribute to the generation of CO and CH4,and inhibit the generation of biomass carbon.Although alkaline metal oxides can inhibit the production of liquid phase products,they can effectively promote the formation of phenol,and play an outstanding role in promoting the formation of gas phase products and optimizing the structure of biochar.The perovskite catalyst has the advantage of cubic equal structure and excellent redox performance.Metal ion doping significantly increased the oxygen vacancy content,improved the selectivity of liquid phase yield with phenol and MAHs,inhibited the decarboxylation and decarbonylation reactions,increased the selectivity of CH4,and reduced the biochar yield,and the cyclic catalytic pyrolysis stability was good.The catalytic performance of molecular sieve catalyst is related to its acid-base and surface structure.Lignin with high acidity and suitable pore size can promote lignin pyrolysis and recombination,and affect the yield and selectivity of three-phase products.The catalytic performance can be optimized by metal loading or acidizing pretreatment,and the selectivity of the target product can be improved.Low-cost catalysts such as bentonite are also important,whose acidic sites and pore structure affect product selectivity.Combined with molecular sieve,MAHs selectivity can be greatly improved,and it also has unique regulatory effects on gas and solid phase products.On the basis of this,the optimization strategy of catalysts to achieve high value regulation of lignin catalytic pyrolysis products was further proposed.The future development trend was prospected,and it was emphasized that the exploration of new catalysts with synergistic catalysis and their catalytic mechanism should be strengthened to build technical support for the efficient utilization of lignin catalytic pyrolysis products and promote the continuous development of this field.
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维普
