Synthesis, Characterization And Catalytic Activity Of Molded Titanium Silicate-1 For Ammoximation Of Cyclohexanone

Cyclohexanone oxime,as a key intermediate,is primarily used in the production ofε-caprolactam.Almost all of the present commercial processes for oxime synthesis are the cyclohexanone-hydroxylamine route,which is environment-unfriendly because of its complex process and the production of lower value by-product of ammonium sulphate.In 1990, Enichem of Italy developed and built an industrial equipment of liquid phase ammoximation catalyzed by titanium silicate-1,which opened a new period of industrial production of cyclohexanone oxime.Using titanium silicate-1（TS-1） as catalyst,cyclohexanone oxime can be prepared from cyclohexanone,ammonia and hydrogen peroxide,which is called liquid phase ammoximation process.It can not only proceed in mild reaction condition,reach high selectivity,but also can avoid byproducts.Finally,it is regard as a "Zero Omission" process. However,TS-1 is very expensive and with small-granularited catalyst,which causes difficulties in industrial production,for example separation and recycle.So,how to separate and reuse the titanium silicate-1 zeolite is becoming the most urgent problem to be resolved in the research and development of ammoximation of cyclohexanone.The molding of TS-1 is one of the most important methods to resolve the problem of catalyst separation in the process of ammoximation in industry.In this thesis,molded TS-1 are prepared using different methods such as extruding or spraying.The molded catalyst are also characterised by FTIR,XRD,BET et al.It shows that the physical properties of molded TS-1 are different from that of TS-1 powder,such as the reducing of specific surface area and pore volume,which may owe to the bonding of TS-1 and SiO₂ under high temperature. Moreover,the change of the phyical property may effect the catalytic properties of the molded catalyst.Major factors in molding process,which includes the calcined temperature,the time under calcined temperature,the atmosphere used and the content of TS-1,are studied detailedly.Preliminary experiments on molded catalyst are done by the method of single factor test,using crush strength and yield as the estimated index.Futhermore,detailed study are carried out by the method of orthogonal test,using the same estimated index as above.The study shows difference between the molding of extruding and spraying.The consequence of the four major factors is also discussed.The results illustrate that the optimized molding conditions of extruding are a calcined temperature of 800℃,a time of 4 h,an atmosphere of O₂ and 80%（wt%） TS-1 in molded catlyst.Similarily,the appropriate molding conditions of spraying are of a calcined temperature of 800℃,a time of 4 h,an atmosphere of O₂ and more than 80%（wt%） TS-1 in molded catalyst.Whatever the method of molding used,the calcined temperature is the most important factor and the the content of TS-1 is least.However,the contradiction between strength and catalytic properties is the major barrier for the molding of TS-1.Compared to interval test,continual test can better evaluate the property of catalyst.The molded catalyst,which show excellent catalytic performance in interval test,are selected to be evaluated in continual test.The deactived catalyst are characterised by FTIR,XRD,BET and ICP et al.The results show that the pore blocking by reaction byproducts,the titanium leaching as well as the silica dissolution are the main reasons for the deactivation.Moreover, it also show that the particle distibution of the deactivated molded catalyst is close to that of the TS-1 powder,which means the futher rearch should focus on the enhancement of the strengh on the basis of good catalytic properties...