Study On The Preparation Of Mn-SAPO-34 And Its Catalytic Reaction Of ?-pinene Epoxidation

Turpentine was a kind of natural renewable resources,and most of its products were high value-added green products,such as camphor,borneol,terpineol,aromatic alcohol,sandalwood,terpene resin etc..It is mainly composed by?-pinene and?-pinene,which were a pair of isomers with the similar properties.Owing to its unique molecular structure,?-pinene had an extremely active chemical property which can participate in many chemical reactions,such as hydrogenation,epoxidation,pyrolysis and polymerization reaction.There was a rich resource of turpentine in our country and its production ranks first in the world,however,the deep processing utilization,was low.Therefore,research and development of high-performance and environmentally-friendly?-pinene epoxidation catalysts are of great significance to the field of deep processing of turpentine in China.SAPO-34 was a kind of chabazite zeolite with of eight members ring ellipsoidal cage molecular framework structure.Its molecular skeleton was negatively charged with ability to cation exchange.A large number of B acid centers were existed on the surface of SAPO-34 molecular sieve,and its acidity and pore size can be adjusted.In addition,SAPO-34 molecular sieve had higher thermal and mechanical stability.Therefore,this kind of molecular sieve was always used as excellent catalyst carrier and attracting more attention.In this study,Mn-SAPO-34 supported catalyst was prepared by ion-exchange method,with SAPO-34 molecular sieve as a carrier and manganous acetate as active constituent.And then the carrier and catalyst were characterized.The specific research aspects are as follows:?1?SAPO-34 molecular sieve was prepared by hydrothermal method.And the surface area of the material was used as probes to determine the optimal conditions:the molar ratio of TEA/Al₂O₃/P₂O₅/Si O₂/H₂O was 3:1:1:0.6:50,the crystallization temperature was 200?,and the crystallization time was 48h.Under this preparation condition,SAPO-34 molecular sieve was characterized by XRD,TG,BET,SEM,TEM and NH₃-TPD.the results showed that the material that silicoaluminophosphate molecular sieve SAPO-34 with CHA was successfully synthesized.It had high crystallinity,smooth surface,no amorphous structure,higher thermal stability,surface area at 562.60m²·g^-1,and the crystal size was almost identical.?2?Mn-SAPO-34 catalyst was prepared by ion exchange method and investigated optimal catalyst preparation conditions by single factor test and BBD response surface method,and the optimal preparation conditions are as follows:m(Mn²⁺)/m?SAPO-34?at 0.2,system p H at 5,preparation temperature at 61.5?,preparation time at 6h.After that,the process conditions of?-pinene epoxidation reaction were investigated to determine the optimal conditions for the reaction temperature at 17?,the acetonitrile dosage at 25g,the catalyst dosage at 100mg,the cocatalyst dosage at 1g.Under this conditions,the conversion of?-pinene was99.92%,2,3-epoxypinane selectivity was 94.62%,2,3-epoxypinane yield was 94.54%,and the reproducibility was well.?3?The age of the catalyst was studied,and the characteristics of catalyst subsequently were characterized by XRD,ICP,SEM,TEM and SEM-EDS.The experimental results showed that Mn-SAPO-34 catalyst can be the most efficiently used 5 times and more effectively used 6 times.when the catalyst used at 7th times,it began to be inactive,and the reason are as follow:1)The loss of active components;2)Some active components are oxidized;3)Because of the skeleton structure of the carrier partially collapsed and its specific surface area decreased,the agglomerate phenomenon of active components were aggravated until the catalyst was inactivated;4)Loss of Si elements.In that the content of silicon can directly affect the catalytic activity of the catalyst when SAPO-34 molecular sieves were treated as carriers.