Study On The Preparation Of New Zeolite Catalyst And Its Catalytic Isomerization Of Dichlorobenzene

M-Dichlorobenzene is an important intermediate in fine chemicals,which was mainly used in the synthesis of the intermediate of pesticides,pharmaceuticals,dyes and pigments.The synthesis of m-dichlorobenzene is generally based on nitrobenzene as a raw material or through isomerization of o-dichlorobenzene/p-dichlorobenzene.Strong environmental pollution and hard to recycle of catalysis if nitrobenzene and Al Cl₃-type catalysts was used as raw material and catalysis to synthesis m-dichlorobenzene.In order to overcome these disadvantages,it's essensial to choose environmentally friendly and recyclable catalysts.Solid acid catalysts such as molecular sieves is an option.The solid acid catalyst loaded with different types of metals can increase the density and strength of the acidic sites,thereby improving the catalytic isomerization of dichlorobenzene.This paper studied the performance of zeolite molecular sieve loaded with different metals to catalyze the isomerization of dichlorobenzene.The prepared molecular sieve was characterized by X-ray diffraction,N₂-adsorption/desorption,scanning electron microscopy(SEM),transmission electron microscopy(TEM)and other means to confirm the structure.The isomerization reaction of dichlorobenzene was carried out in the reactor to investigate its effect.In addition,the application of the prepared molecular sieve was extended and applied to the synthesis process of phoxim to investigate its effect.A new structure direct agent was used to synthesize the VPI-5 molecular sieve zeolite.This method used N₃N₃(C₁₈H₃₇-N(CH₃)-C₆H₁₂-N(CH₃)₂)as a structure directing agent for the first time.After characterization,the results showed that VPI-5 molecular sieve was indeed formed,but there was a slight structural change after calcination,the height of characteristic peak was reduced slightly at low angles.Using VPI-5,ZSM-5,?,mordenite and USY molecular sieves to catalyze the isomerization of o-dichlorobenzene,results showed that ZSM-5 molecular sieve has the best catalytic isomerization effect while other molecular sieves have relatively poor catalytic effects.The mesoporous ZSM-5 molecular sieve was synthesized by the hydrothermal synthesis method and the dry glue conversion method,after characterization,the effect of the mesoporous ZSM-5 molecular sieve on the catalytic isomerization of dichlorobenzene isomerization was investigated.The results showed that,compared with ordinary ZSM-5 molecular sieve,mesoporous ZSM-5 molecular sieve increases the conversion rate of o-dichlorobenzene from 11.0%to 25.7%when catalyzing the isomerization of dichlorobenzene,but the selectivity of m-dichlorobenzene was reduced from78.0%to 60.8%.In order to ensure the selectivity of m-dichlorobenzene,we selected ordinary ZSM-5 molecular sieve for modification.The ZSM-5molecular sieve was hydrophobically modified and modified with different metals(Fe,Cu,Cr,Gd)loading,and the influence on the isomerization of dichlorobenzene was investigated.The results showed that,compared with ordinary ZSM-5 molecular sieves,1 wt.%Gd/ZSM-5 molecular sieve loaded with metal Gd has the best effect catalytic of isomerization of o-dichlorobenzene.Under the premise of ensuring the selectivity of m-dichlorobenzene,the conversion rate of o-dichlorobenzene has also been improved.Furthermore,Gd/ZSM-5 molecular sieves with different contents were prepared,and their effects on the isomerization reaction of o-dichlorobenzene were tested after characterization.The results showed that1 wt.%Gd/ZSM-5 molecular sieve has the best effect,the conversion rate of o-dichlorobenzene and the selectivity of m-dichlorobenzene are both the highest.The prepared molecular sieve was extended and applied to the synthesis of phoxim,and the synthesis conditions of phoxim were optimized.The results showed that the molecular sieve prepared by metal-supported modification has a better catalytic effect on the production of oxime.Among them,the Gd/ZSM-5 prepared by metal Gd support has the best effect on the preparation of phoxim.The oxime yield reaches 30%,and the selectivity of cis-oxime reaches 80%,the reason may be that the metal activity promotes the reaction.In addition,the synthesis of phoxim from benzyl alcohol is safer and greener,and there is less?-cyanobenzoxime catalyzed by prepared molecular sieve.Using a strong base as the reactant to generate?-cyanoben-zoxime sodium and further generate phoxim is the best route.