Prepared Of Methyl Acetate By Carbonylation Of Dimethyl Ether Over HSUZ-4 Zeolite

Methyl acetate（MA）is prepared by carbonylation of dimethyl ether（DME）,and MA is further hydrogenated to ethanol.It is a new ethanol preparation process,that has the advantages of high atomic economy,good product selectivity,and mild reaction conditions.It has broad industrial prospects.As the core of this route,it is the key to develop efficient and stable DME carbonylation catalysts.HSUZ-4 zeolite is a new high durability zeolite for the carbonylation of dimethyl ether.However,its industrial application is still hindered due to its low activity.Therefore,in order to effectively improve the catalytic performance of HSUZ-4 zeolite,this article uses HSUZ-4 zeolite as the basic catalyst and modifies it through post-processing methods such as etching with ammonium fluoride solution,alkali treatment with sodium hydroxide solution,and ion exchange with zirconium nitrate solution.The reaction performance of the modified catalyst was evaluated under reaction conditions of 493 K,2.0 MPa,and a space velocity of 1200 m L/（g·h）.At the same time,XRD,BET,ICP-OES,SEM,TEM,NH₃-TPD,FTIR,NH₃-IR,²⁷Al MAS NMR,²⁹Si MAS NMR and XPS techniques were used to systematically characterize the catalysts,establishing a basic structure-activity relationship.The specific contents are as follows:Ammonium type SUZ-4 zeolite（NH₄-SUZ-4）was etched with ammonium fluoride solution of the same concentration.The effects of treatment temperature and time on the etching process were investigated,respectively.It was found that ammonium fluoride etching resulted in the formation of a large number of mesopores in the zeolite,but at the same time caused damage to the zeolite skeleton structure.With the increase of etching intensity,a large amount of aluminum in the zeolite skeleton fell off,and the active Br（?）nsted acid sites were largely removed,resulting in a rapid decline in the catalytic performance.The DME conversion and MA selectivity of the sample without ammonium fluoride solution treatment were 17%and 91%,respectively.When the sample was treated with 40 wt.%ammonium fluoride solution at 50℃for 60 minutes,the two data decreased to 10%and 80%,respectively.Sodium hydroxide solution was used to treat SUZ-4 zeolite containing a template.The effect of treatment temperature on the catalytic performance of zeolite under the same treatment time was investigated.It was found that after treatment with sodium hydroxide solution,the K⁺originally located in the zeolite cage can be exchanged out of the zeolite,increasing the Br（?）nsted acid sites of the catalyst,thereby improving the reaction performance of the catalyst.At the same time,the number of mesopores in the zeolite increases after alkali treatment,which helps to improve the mass transfer efficiency in the catalyst reaction process.When 0.4 mol/L sodium hydroxide solution was used and treated at 50℃for 60 minutes,the obtained samples exhibited the best catalytic activity,with DME conversion and MA selectivity reaching 24%and 92%,respectively.A series of Zr-HSUZ-4 catalysts were prepared by ion exchange of HSUZ-4 with zirconium nitrate solution.It was found that Zr atoms can replace aluminum in the zeolite framework and enter the zeolite framework in a tetrahedral coordination form.At the same time,the exchange process promotes more K⁺to escape from the zeolite,increasing the active Br（?）nsted acid sites in the 8-MR pores of the zeolite,effectively improving the catalytic activity of the catalyst.Among the three different concentrations of zirconium nitrate solution used,the zeolite catalyst obtained by treating with 0.01 mol/L zirconium nitrate solution showed the best catalytic performance.The maximum values of DME conversion and product MA selectivity reached 30%and 95%,respectively,which were much higher than those of HSUZ-4 zeolite catalyst.