Synthesis Of SUZ-4 Zeolite And Its Catalytic Application

Dimethyl ether(DME)as an important downstream product of coal chemical industry,can replace liquefied petroleum gas or diesel and have environmentally friendly characteristics,so that it becomes the current concern of green chemicals.Aluminosilicate zeolite is an effective catalyst for the vapor phase dehydration of methanol to synthesize dimethyl ether.Many studies have shown that the silicoaluminite zeolite with strong Bronsted acid is a better catalyst for the gas phase dehydration of methanol to produce dimethyl ether.At present,many dimethyl ether production process has been using silica alumina zeolite as the main reaction catalyst.The synthesis of molecular sieves is generally carried out under conditions of organic templating agents.Organic templating agents are the main source of molecular sieve synthesis and the main source of pollution.SUZ-4 zeolite is a new kind of microporous silica-alumina zeolite with strong Bronsted acid sites.In this paper,we used beer silica gel as silicon source in the low template(dynamic composition:10KOH:1.0Al2O3:0.4TEAOH:21.2SiO2:498.6H2O)to synthesize the SUZ-4 zeolite,compared with the traditional program greatly reduces the use of organic templating agents.It was found that OH-/SiO2 in the initial gel affected the synthesis of molecular sieves,the results showed that the optimum conditions for the synthesis of SUZ-4 were 0.519?0.333.The SUZ-4 zeolite with relative crystallinity of 100%were successfully prepared by cheap TEAB.The hydrogenation of SUZ-4 zeolite was studied.Ammonium exchange was carried out using ammonium nitrate solution.The effects of solid-liquid ratio,exchange conditions and calcination were studied.It was found that the exchange concentration in the first exchange was the main controlling factor;the effect of exchange concentration was weakened in the second exchange and it worked with exchange temperature.The calcination after each exchange is favorable for hydrogenation,and K ion exchange degree after treatment with two rounds of baking can reach 73%.The use of organic weak acid(HAc)can effectively improve the hydrogenation degree of zeolite;but the role of ultrasonic assisted is very limited.SUZ-4 zeolite after different ion modification,Cu can enter the molecular sieve internal pore,but Fe load on the outer surface of the molecular sieve.Compared with H2SZ-4 zeolite,Cu/SUZ-4 acid strength weakened,the total acid content was almost unchanged;Fe/SUZ-4 acid strength increased,the total amount of acid is reduced.The modification of the three catalysts showed that Fe modification was beneficial to methanol conversion,and Cu modification was not conducive to methanol conversion.Within a certain range,the main factor affecting the gas phase dehydration of methanol is the acid strength of the catalyst,independent of the amount of acid of catalyst.