Study On Conversion Of Methanol To Isoparaffin By FER And Beta Coupling Catalysis

The initial purpose of the paper is to synthesize the isomeric alkane from methanol,it is reported by the literatures that the reaction can be realized by the mechanism ofolefins recycle isomeric reaction of methanol by the catalysis of Beta molecular sieve.However,the catalyst is easy to be blocked and cause inactivation.It's also reported that DME feeding could achieve longer lifetime catalyzed by SAPO-11,ZSM-5.In order to solve the problem of fast inactivation of Beta molecular sieve,this paper studied the catalysis performance from methanol as raw material,by coupling of Beta molecular sieve with FER molecular sieve,which showed high activity and high selectivity during the catalysis of MTD.The result was concluded as below:The approach was to convert Beta molecular sieve catalyze MTH.reaction to DTH reaction by MTD reaction mechanism of FER molecular sieve catalysis.Because of the small two-dimensional channel structure of FER molecular sieve,the formation of hydrocarbon pool intermediates was inhibited,the conversion of methanol was above 93%and the selectivity of DME was above 98%by adjustment of process parameter and acidity of molecular sieve,which provided an effective DME feeding environment for Beta molecular sieve catalyzed DTH reactions.The DTH reaction from DME can achieve longer Beta molecular sieve lifetime than MTH reaction from methanol.Besides low temperature had greater advantage,the mechanism was related to the accumulation rate of the methylbenzene in the molecular sieve.So low temperature was chosen for Beta molecular sieve catalyzed DTH reaction.The synthesis of isobutane by Beta molecular sieve catalyzed DTH reaction was closely related to the homologous reaction,including methylation reaction,?-cracking reaction and hydrogen transfer reaction.The results showed that the acidity need to be controlled between 0.70 mmol/g and 1.12 mmlo/g.Following experiments were designed to reduce the acidity of Beta molecular sieve to 1.05 mmol/g by the SCS modification method,and the acid strength was between 0.64 and 1.08 to study the acidity effect on reaction selectivity.The results showed that strong acidity increased the hydrogen transfer rate and was negative to generation of C8+ species,and caused low selectivity of isobutane,so appropriate weak strong acid center proper of Beta molecular sieve was needed.