Synthesis Of Dimethyl Carbonate From The Oxidative Carbonylation Of Methanol Catalyzed By Cu-5-substituted-1,10-phenanthroline Complexes

Dimethyl carbonate(DMC), which is a kind of green chemical product, has been received great focus recently. The mainly synthesized methods for DMC contain the phosgene, the ester exchange and the oxidative carbonylation of methanol. The oxidative carbonylation of methanol to DMC is highly promising for industrial application due to the inexpensive materials, simple process and low pollution. Cu Cl is widely used in the liquid phase carbonylation of methanol. However, the application of Cu Cl is hindered because of the shortcomings of low stability, strong corrosiveness of chlorine and inactivation from the loss of chlorine. The literaturs have reported that 1,10-phenanthroline(phen) added can reduce the corrosion rate of chlorine, and improve the selectivity of DMC and the conversion of methanol. However the effect of the catalytic properties of 1,10-phenanthroline copper complex on the carbonylation synthesis of DMC in the literatures is limited to 1,10- phenanthroline itself, while the influence of the substituents on phen is rarely repored.In this thesis, four penanthrolines(5-NO2-phen, 5-NH2-phen, 5-CH3-phen, 5-Cl-phenn) were synthesised. Among them, the synthesis conditions of 5-CH3-phen were discussed in detail. Cu(5-R-phen)X2(R = NH2、CH3、H、Cl、NO2,X= Cl、Br、SCN)were prepared with 5-R-phen as the ligand and characterized by IR and TGA. In the oxidative carbonylation of methanol, the effect of the substituents on phen on the catalytic activity and technological conditions were investigated, and the reaction mechanism was suggested.(1) In the synthesis of 6-methyl-8-nitro–quinoline by the Skraup reaction, which is an intermediate to prepare 5-methyl-phenanthroline, KI/concentrated sulfuric acid as an oxidant was used to replace iodine. By means of a strong oxidizing of concentrated sulfuric acid to achieve the cycle of I-�'I2�'I-, the amount of iodine was greatly reduced. The yield of 6-methyl-8-nitroquinoline was up to 73% on the conditions of the molar ratio of 4-methyl-2-nitroaniline, glycerin, concentrated sulfuric acid and KI of 1:3:3:0.1, reaction time of 3h and reaction temperature of 140℃.(2) 6-methyl-8-aminoquinoline were synthesized with 6-methyl-8-nitro-quinoline and hydrazine hydrate as material and Pd/C as the catalyst. When the molar ratio of 6-methyl-8-nitro-quinoline to hydrazine hydrate was 1:2 with the 10% amount of catalyst based on the weight of 6-methyl-8-nitro-quinoline andthe reflux time 9h, the yield was 73.5%.(3) In the oxidative carbonylation of methanol to DMC catalyzed by Cu(5-R-phen)Cl2(R = NO2、NH2、H、Cl、CH3), if positive or negative inductive effect of substituents was too strong, resulting in the too strong or weak coordination effect between the copper complexes and CO, the activation of CO and the insertion of CO in the Cu-O bond were difficult, and the catalytic activity was reduced. When the substituent was the methyl group with the weak electron donating effect, the catalytic activity was the highest. TON reached to 52.3molDMC·molCu-1 with DMC selectivity of 96% on the conditions of reaction pressure of 4MPa, part pressure ratio of CO to O2 of 19:1(below the explosion limit of CO), reaction tempareter of 120℃, reaction time of 4h and molar concentration of copper ion of 0.0125mol/L.(4) When the anion of Cl in Cu(5-R-phen)Cl2 was replaced by Br, the influence of electron effect of substituents on the activity of Cu(5-R-phen)Br2 are in agreement with that of Cu(5-R-phen)Cl2. Among of Cu(5-R-phen)Br2, Cu(5-CH3-phen)Br2 exhibited the highest performance, and TON arrived to 53.8molDMC·molCu-1 with the 95% selectivity.(5) Non-halogen catalysts Cu(5-R-phen)(NCS)2(R = NH2, CH3, H, Cl, NO2) were prepared with Cl- replaced with SCN-. When they were used as the catalysts in the oxidative carbonylation of methanol, the electronic effect of substituents was the same as that of Cu(5-R-phen)Cl2. Because of soft base S atom coordinated with soft acid Cu(I) and hard base N coordinated with borderline Cu(II), it was easy for the bridged intermediate(CO)Cu(I)-SCN-Cu(II)(OCH3) to be formed, which was of benefit to producing the key substance Cu(II)(COOCH3) by the inset of CO in the Cu-O bond, therefore the catalyst had the high catalytic activity. Among them, Cu(5-CH3-phen)(NCS)2 showed the highest performance. TON reached to 52.7 molDMC·molCu-1 on the conditions of reaction pressure of 4MPa, part pressure ratio of CO to O2 of 19:1, reaction temperation of 120℃, reaction time of 4h and molar concentration of copper ion remained at 0.0125mol/L.