Regulation Of Submicron ZSM-5 Zeolite With Silicon Precursor Under Acid Hydrolysis And Its Catalytic Pyrolysis Of Bagasse Lignin

Under strong acid condition,the hydrolyzed synthesis of SiO₂obtained by co-hydrolysis of ethyl orthosilicate and ethanol as the silicon source,the preparation of nano-scale ZSM-5zeolite,the synthesis process is controlled,and The catalytic performance of its catalytic pyrolysis of lignin to produce high value-added compounds was investigated.The specific research results are as follows:（1）When sulfuric acid is used as the acidic medium,the degree of aggregation and the connection mode of the product obtained by hydrolyzing TEOS vary with the hydrolysis time,By changing the hydrolysis time and adjusting the aggregation degree and structure of the SiO₂precursor,when the hydrolysis p H=2 and the hydrolysis time was 20 h,a linear chain structure with Q₃structure and a trimer（-Si-O-Si-）n and a trace amount of silicon source precursor with Q₄structure tetramer Si（OH）₄can be prepared.（2）The Addition of ethanol,as a co-solvent in the precursor acid hydrolysis system could regulate the particle size,pore volume,and average pore size of ZSM-5 zeolite.When n（C₂H₅OH）:n（TEOS）=12,the effect was the best.The particle size of the zeolite was 180-210nm.Compared with the condition without ethanol hydrolysis,the particle size was reduced by about 48%,and the specific surface area and pore volume have also been increased by 52%and 29%,respectively.（3）Under the condition of static crystallization,the optimization results of synthesis system of ZSM-5 zeolite by hydrolysis of TEOS with sulfuric acid as catalyst were as follows:TPAOH as template,TEOS as silicon source,Al（OH）₃as aluminum source,n（SiO₂）:n（Al（OH）₃）:n（TPAOH）:n（H₂O）=1:0.025:0.3:60 and crystallizing at 180^oC for 30 h,ZSM-5zeolite with particle size of 200-410 nm,specific surface area of 446.579 m²/g and total pore volume of 0.55 cm³/g could be prepared.（4）The type of aluminum source affected the crystallinity,morphology,and specific surface area of ZSM-5 zeolite.Using TEOS as the silicon source,TPAOH as the template agent,and crystallizing at 180^oC for 30 h.ZSM-5 synthesized with Al₂（SO₄）₃·18H₂O as the aluminum source was a rod-shaped stacked microscopic spherical aggregates.ZSM-5 zeolite synthesized with Al（OH）₃as aluminum source was in the shape of nanometer square tablets with uniform particle size;ZSM-5 zeolite synthesized by Al（NO₃）₃·9H₂O as aluminum source was a micron scale"coffin"crystal.ZSM-5 zeolite with the highest relative crystallinity of100%,the largest specific surface area of 446.58 m²/g and the smallest particle size of 200 nm could be synthesized by using Al（OH）₃as the aluminum source.（5）The yield and selectivity of gas-liquid solid products obtained from the catalytic pyrolysis of lignin were different with the addition of ZSM-5 zeollite.When the amount of ZSM-5 zeolite and lignin was 2:1,the yield of liquid pyrolysis products was the highest,42.5%,and the selectivity of phenols in liquid products was 78.1%,which was 16.1%higher than that of pure lignin without catalyst.The liquid products were mainly phenols,guaiacols,syringyls,esters,benzene,furan,and carboxylic acid.（6）The crystallinity,liquid yield of catalytic pyrolysis lignin,and acidity of the regenerated ZSM-5 zeolite after reaction were lower than that of fresh ZSM-5 zeolite,indicating that the acid sites and catalytic activity consumed by the reaction could not be recovered fully by calcinationto remove the deposited carbon.