The Catalytic Study On Direct Synthesis Of Dimethyl Carbonate

CO2 is one of the main greenhouse gases, which is a widely available resource. The problem of retrieve and reuse of CO2 can be solved effectively by means of synthetizing dimethyl carbonate (DMC) with it. At present, the preparation reaction path of DMC with CO2 and methanol is receiving extensive attention. However, low conversion rate, together with lack of efficient catalyst and reliable processing system are problems to be solved. Due to the special three dimensional channel structure, MCM-48 has advantage in the catalyst of macromolecule. Whereas, there is no catalyst active center in MCM-48, and the hydrothermal stability of which is also low. In the present paper, copper and nickel are mixed into the modified MCM-48 which has good hydrothermal stability, and catalyst with excellent performance is prepared by such approach. Numerical simulation of temperature and density distribution in the synthesis of DMC with CO2 and methanol in the fixed bed reactor is implemented using gPROMS.MCM-48 is synthesized by the directly hydrothermal method under the condition of fluorine ion. The copper or/and nickel is doped in MCM-48.And the structural performance of these samples is characterized by XRD, SEM, TEM, FTIR, ICP-AES. The results show that (1) when n(KF)/n(Si)=0.10, the structural performance of MCM-48 is the best, and it has uniform size and spherical particles, besides, that F" can make MCM-48 skeleton more perfect can improve hydrothermal stability of MCM-48.(2) when the molar ration of n(M)/n(Si) (M=Cu or Ni) is in 0-0.03, MCM-48 doped Cu or Ni can be prepared, which has the cubic structure of MCM-48 and has the higher content of copper and nickel. These results indicate that when copper or nickel can replace part of the silicion, MCM-48 containing active center can also be synthesized. Besides, when n(Cu)/n(Si)=0.015, structural performance of the sample is considered the best. At the same time, when n(Cu+Ni)/n(Si)=0.01-0.02, MCM-48 doped Cu and Ni have also been synthesised.(3) The cubic structure of Cu-MCM-48 can be effected by F" and the molar ratio of n(CTAB)/n(Si).MCM-48/ZSM-5 mesoporous/microporous composite molecule, whose cell wall has MFI structure, is synthesized by the two-crystallization method, and the structural performance of the samples is characterized by XRD, SEM, FTIR, TEM. The results show that (1) when n(NaOH)/n(Si)=0.3,the reaction t=4h and the mole ratio of n(Na2SO4)/n(Si)=0.005-0.015 in the first step crystallization process, the excellent structural performance of MCM-48/ZSM-5 composite molecular can be synthesized and the samples have uniform size and spherical particles.(2) On the basis of the above conditions, when n(M2+)/n(Si)=0.005-0.015, Cu(Ni)-MCM-48/ZSM-5 can be synthesized successfully, and when n(M2+)/n(Si)=0.01, Cu(Ni)-ZM-3-0.01 has the excellent structure performance.The two-dimensional model for the reactor is constructed considering mass transfer, heat transfer, fluid flow and reaction dynamics simultaneously. Meanwhile, the temperature and density distribution at axial and radial directions are expressed using partial differential equations. Based on this model, the synthesis reaction of DMC using CO2 and methanol is simulated, and elementary conditions such as the density and temperature distribution in the reactor are obtained. Simulation results are similar to the results in the related literature. With the help of simulation on the reactor optimization, we can make a better solution on reactor design.