Catalytic Oxidative Carbonylation Of Methanol And Modification About Metal Cations In The CuY Catalyst

Dimethyl carbonate (DMC) is a new kind of non-toxic organic products and wildly used in the chemical industry, which has unique chemical structure and excellent activity in different reactions. There are many kinds of process routes of the DMC synthesis, and oxidative carbonylation of methanol has many advantages such as the larger thermodynamics equilibrium constant, abundant raw materials,and low cost. Due to these advantages, this reaction has been a focus in recent years. At present, the main catalyst for the reaction is the copper based activated carbon catalyst, Wacker catalyst with chloride, and the copper based zeolite catalyst. In the above catalyst products, catalyst with chlorine has higher catalytic activity, but the loss of Cl" could cause some problems such as equipment corrosion and catalyst deactivation. In the chloride-free catalyst, the CuY catalyst completely avoided chloride ions loss during the preparation program, so it solved all the problems caused by the chloride catalyst, and the performance of CuY catalyst had been improved in further study.Understanding the exact role of copper ions in the reaction is the key to prepare the CuY catalyst. Previous research has found when copper ions are in the different cages structure of Y zeolite, the catalytic activity of CuY catalyst has a clear difference. Further, in the case of cationic additives introduced, the distribution of copper ions in Y type molecular sieve will change obviously.The introduce of cerium and lanthanum ions in the process of preparing CuY zeolite will lead more Cu2+move the supercages of Y zeolite, which is significantly beneficial to activity improvement in the reaction. And it can be found that after the introduction of the alkaline earth metal such as cesium into the Y zeolite, although the content of the copper species in the supercages decreased, the desorption performance of CO as well as the preservation capacity of crystal stracture had been certainly improved. Thus, the introduction of cesium ions can also achieve the goal to improve the reactivity. On this basis, in this thesis, used NaY zeolite as the support, we discussed the CuY catalyst reaction activity in the vapor oxidative carbonylation of methanol and the relationship betwee Cu ions location and space time yield, catalyst selectivity and methanol conversion, according to two sides of catalyst preparation method and cationian modification.The micro-structure, active species and reaction activity of catalyst were analyzed by XRD, TPD, TPR, BET technics. The main conclusions are listed as follows:(1)Pretreatment of Y zeolite significantly changed the aperture and pore volume.which has. In the experiment, surface properties of the Y zeolite are influenced by the impurities and moisture due to long-time storage. Therefore, the catalyst made by pretreatment has the higher reaction activity than the catalyst made by the traditional way. In this way, the pretreatment ensures the carrier performance in subsequent trials.(2)The copper species distribution in zeolite super cages was changed by different contents of lanthanum ions. When the lanthanum introduced content is3wt%of catalyst, the catalyst showed the best reaction activity. The form of copper ions distribution in the zeolite proved the filling effect when earth metal lanthanum was introduced into the Y zeolite.(3)Using the method of introducing additives, Cu ions were introduced to prepare the CuCuY zeolite, in which Cu ion would use its filling effect to control the copper species content in the Y zeolite in the subsequent process of exchanging with copper ammonia solution. In the same copper content condition, the CuCuY calalyst has higher reaction activity than CuY catalyst prepared by traditional methods.