Preparation Of Multistage Pore SAPO-11 Molecular Sieve And Its Catalytic Performance For Alkylation Of Naphthalene

In this paper,silicoaluminophosphate SAPO-11 molecule sieves and hierarchical SAPO-11 molecule sieves were synthesized by traditional hydrothermal method,then the structure and acidity were investigated by XRD,SEM,N2 physical adsorption and Py-IR.SAPO-11 molecule sieves synthesized by different method were used as catalysts in probe reaction of alkylation of naphthalene with methanol to evaluation their catalytic performance.SAPO-11 molecule sieves were modified by dealumination treatment using citric acid and tartaric acid,respectively.The effect of acid concentration and treatment time on the structure,acidity,and catalytic performance in the alkylation of naphthalene was investigated.It showed that the catalytic performance of SAPO-11 molecule sieves reduced after treatment using high concentration of acid at long treatment time resulting in break the skeleton structure of molecular sieves.SAPO-11 molecule sieves with 0.4mol/L of tartaric acid and treatment time of 1h possessed the best catalytic performance in reaction of alkylation of naphthalene with methanol.The CoSAPO-11 molecule sieves were synthesized using the X zeolites ion exchanged with Co2+ as the cobalt source and silica source.The catalyst showed excellent high catalytic activity and stability,when the conversion of naphthalene equals to 72.7%,the selectivity for 2,6-DMN and the 2,6-DMN/2,7-DMN ratio reached 30.6%and 1.61,respectively.SAPO-11 molecule sieves with smaller particles were synthesized uing Cetyltrimethylammonium Bromide(CTAB)as structure directing agent,polyethyleneglycol(PEG)as growth inhibitors.The structure and acidity of samples were adjusted by changing the feeding order,quantity of CTAB or PEG with different polymerization degree.It exhibited that the more mesopore volume and weak acid sites and best catalytic performance were obtained on the catalyst,which were synthesized with the CTAB/DPA ratio of 0.02,by the feeding order CTAB following DPA in the initial gel as well.While the PEG(4000)/DPA ratio was 0.33 in the initial gel for SAPO-11 molecule sieves,the sample possesseed the largest weak B acid sites and minimum of strong acid sites.When the conversion of naphthalene equals to 66.2%,the selectivity for 2,6-DMN and the 2,6-DMN/2,7-DMN ratio reached 30.6%and 1.52,respectively.A series of hierarchical SAPO-11 molecule sieves were synthesized by types and content of mesoporous templates such as glucose,nanosized carbon materials and[3-(trimethoxysilyl)propyl]hexadecyldimethylammonium chloride(TPHAC).Compared to the samples synthesized with the template of TPHAC and glucose,the hierarchical SAPO-11 molecule sieves synthesized by carbon nanotubes possessed larger mesoporous volume with keeping the acid sites of microporous molecule sieves,resulting in better catalytic activity and selectivity of 2,6-DMN.When the conversion of naphthalene equaled to 61.0%,the selectivity for 2,6-DMN and the of 2,6-DMN/2,7-DMN ratio reached 28.4%and 1.51,respectively.