Catalytic Cracking Of Lignin By Micro-Mesoporous Molecular Sieve To Prepare Aromatic Compounds

Catalyzed cracking reactions commonly used zeolite molecular sieves,ionic liquids and other catalysts due to their own problems,leading to the cracking products more impurity and contents were low,and catalytic cracking lignin to get better product distributions and higher product contents,the preparation of larger pore size and acidic zeolite catalyst were the key.In this dissertation,micro-mesoporous molecular sieves with long-range order,good crystallinity,and uniform pore distribution were designed and synthesized.With N-methylimidazole and tetramethylethylenediamine as precursors,triblock copolymers F₁₂₇?Mn=12600?,P₁₂₃?Mn=5800?,L₆₄?Mn=2900?were introduced into the structure as side chains.Six types of novel ionic liquids with both ionic and nonionic structural properties were designed and synthesized,such as[F₁₂₇mim]Cl,[P₁₂₃mim]Cl,[L₆₄mim]Cl,[N₂-F₁₂₇]Cl,[N₂-P₁₂₃]Cl and[N₂-L₆₄]Cl.And using the six new ionic liquids created the micro-mesoporous molecular sieves FNS-7,PNS-7,LNS-7,FGS-7,PGS-7,LGS-7.The characterization results showed that the synthesized molecular sieves had highly ordered pore structure,large specific surface area,better mesoporous ordering and strong acid sites.In addition,the PNS-7 series molecular sieves had better structural properties than the PGS-7series molecular sieves.Compared with the traditional molecular sieve MAS-7,the PNS-7 and PGS-7molecular sieves had better catalytic performance.The reaction conditions were optimized to obtain better reaction conditions:catalyst molecular sieves 0.1 g,solvent ethylene glycol 12.5 mL,temperature 180°C,and time 3 h.The selectivity of vanillic acid and vanillin,the major products of the PNS-7 molecular sieve catalytic cracking lignin reaction,were 28.2%and 29.6%,and the residue rate was27.6%.The selectivity of vanillic acid and vanillin,the major products of the PGS-7molecular sieves for catalytic cracking of lignin,were 26.6%and 28%,and the residue rate was 29.7%.Under these conditions,the selectivity to the products of the FNS-7,LNS-7,FGS-7,and LGS-7 molecular sieves were lower than the PNS-7 and PGS-7 molecular sieves.Selecting Sn,Co,Cu and Zr four metals and acidic group SO₄^2-loaded on the PNS-7 and PGS-7 series molecular sieves to study the influence of the addition of metal active components and acid group on the performance of molecular sieve catalysts?specific surface area,pore volume,pore size,and acidity?.In turn,the effects of catalytic cracking of lignin on the preparation of aromatic compounds.The selectivity of the vanillin and vanillic acid improved 20%⁴0%,but the SO₄^2-/Sn-PNS-7?vanillic acid 39%and vanillin 40.2%?and SO₄^2-/Sn-PGS-7?vanillic acid 37.6%and vanillin 39.2%?molecular sieves had the highest selectivity.The results showed that the Sn was successfully loaded on the molecular sieves,but the long-range order,crystallinity of the pores,BET surface area,BJH pore volume and pore size of the modified zeolites were decreased.The NH₃-TPD characterization showed that the amounts of weak acid were significantly increased.In conclusion,this study successfully created novel ionic liquids with both cationic and non-ionic structural properties as template agents and synthesized highly ordered pore structure,large specific surface area,better mesoporous order and strongly acidic centers of micro-mesoporous molecular sieves.Selecting Sn,Co,Cu,Zr four kinds of metals and acid group SO₄^2-loaded on the molecular sieves,the long-range order,crystallinity of the pores,BET surface,BJH hole volume and aperture were reduced,but the amounts of weak acids increased significantly and the catalytic performance was improved.