Synthesis Of Dimethyl Carbonate From Oxidative Carbonylation Of Methanol Catalyzed By Supported Copper Complex

Dimethyl carbonate?DMC?,as a green chemical product,is an important intermediate.The synthesis methods include phosgene,ester exchange,direct synthesis of CO₂,urea alcoholysis and oxidative carbonylation of methanol.The oxidative carbonylation of methanol has the advantages of cheap raw materials,simple process and few by-products,and is the most valuable industrialized method at present.It is found that the copper complex catalyst exhibits the low corrosion and the high activity in the oxidative carbonylation of methanol,while it is difficult to separate from the solution after the reaction.Therefore,the heterogenization of the copper complex catalyst is an effective method to solve the separation problem.In the thesis,six catalysts,[Cu?phen?I]₂/H-ZSM-5,[Cu?phen?I]₂/HY,[Cu?phen?I]₂/H?,[Cu?phen?I]₂/Na-ZSM-5,[Cu?phen?I]₂/Na Y and[Cu?phen?I]₂/Na?,were prepared by impregnation method with 1,0-phenanthroline?phen?as ligand,Cu I as copper meterial and different types of molecular sieves as the carriers.[Cu?phen?I]₂/Na-ZSM-5 was also prepared through the step method with Cu SO₄or Cu Cl₂seelected as copper meterials.Carbon supported[Cu?phen?I]₂was prepared by using glucose carbon,activated carbon and nitrogenous carbon as the carriers.These solid catalysts were characterized by infrared spectrum,BET,solid UV-Vis,X-ray powder diffraction,thermogravimetry and X-ray photoelectron energy spectrum,and the factors influencing their activity in the oxidative carbonylation of methanol to DMC were studied in detail.1.Among[Cu?phen?I]₂/H-ZSM-5,[Cu?phen?I]₂/HY and[Cu?phen?I]₂/H?,there were no strong acid centers,and the lowest total acid number on the surface of H-ZSM-5,all of which resulted in the hydrolysis rate of DMC being the lowst and[Cu?phen?I]₂/H-ZSM-5showing the highest activity.The turnover?TON?and the selectivity of DMC were 52.5mol _DMC/mol _Cuand 75.9%,respectively.Among[Cu?phen?I]₂/Na-ZSM-5,[Cu?phen?I]₂/Na Y and[Cu?phen?I]₂/Na?,Na-ZSM-5 had the strongest base centers on its surface,which made[Cu?phen?I]₂/Na-ZSM-5 exhibit the highest activity.The TON and the selecivity of DMC were 88.4 mol _DMC/mol _Cuand 99.9%,respectively.In addition,the thermal stability of sodium zeolite supported catalysts was higher than that of hydrogen zeolite supported catalysts,which led to the formers showing the higher activity.Among six catalysts,the activity of[Cu?phen?I]₂/Na-ZSM-5 was the highest.2.The optimum conditions for the preparation of[Cu?phen?I]₂/Na-ZSM-5 were the impregnation temperature of 10?,impregnation time of 12 h and spin steaming temperature of 35?.When[Cu?phen?I]₂/Na-ZSM-5 prepared under above optimum conditions was used,the TON and the selectivity of DMC were up to 104.9 mol _DMC/mol _Cuand 99.9%at 130?for 5 h.3.[Cu?phen?I]₂/Na-ZSM-5-Cu Cl₂and[Cu?phen?I]₂/Na-ZSM-5-Cu SO₄were prepared through a stepwise method,which included the synthesis of Cu I from different copper sources in the moleculer sieve and then[Cu?phen?I]₂from the reaction of phen and Cu I,and exhibited the highly activity,but the DMC selectivity on them was lower than that on[Cu?phen?I]₂/Na-ZSM-5.[Cu?phen?I]₂/Na-ZSM-5 was modified by phenyl trimethoxysilane and 3-aminopropyl triethoxysilane to obtain[Cu?phen?I]₂/Na-ZSM-5-Ph and[Cu?phen?I]₂/Na-ZSM-5-Apts.The TON on[Cu?phen?I]₂/Na-ZSM-5-Ph was 91.2mol _DMC/mol _Cu,while that on[Cu?phen?I]₂/Na-ZSM-5-Apts was only 55.9 mol _DMC/mol _Cu.The repeatability of[Cu?phen?I]₂/Na-ZSM-5-Ph was better than that of the unmodified catalyst,indicating that the modification could reduce the loss of active components.4.Three carbon carriers,C1,C2 and C3,were prepared by different carbon sources,and were used to syhtesize[Cu?phen?I]₂/C1,[Cu?phen?I]₂/C2 and[Cu?phen?I]₂/C3 by the impregnation method.Among them,the activity[Cu?phen?I]₂/C2 was the highest,and the TON and the selectivity of DMC were 39.8 mol _DMC/mol _Cuand 99.9%,respectively.5.After C2 with above 200 mesh was treated in 0.4 mol/L Na OH solution,then was used to load[Cu?phen?I]₂by the impregnation method.[Cu?phen?I]₂/C2 exhibited the TON of 109.5 mol _DMC/mol _Cuand the DMC selectivity of 80.6%,and could be reuse for at least 3 times.