| As an environmental benign green-chemical, dimethyl carbonate (DMC) regarded as"new elementary-block"has wide application prospects. At present, catalysts for vapor phase oxidative carbonylation of methanol to synthesize DMC are mainly three types:CuCl2 supported catalysts, Wacker catalysts and Cu-exchanged zeolite catalysts. Chloride loss existed in the former two catalysts resulted in catalyst deactivation and equipment corrosion problems. The activity and selectivity of DMC in Cu-exchanged zeolite catalysts prepared by CuCl, in which chloride left still existed, were unfortunately low when compared to activated carbon (AC)-based catalysts.In order to solve the stability and corrosion problems initiated by Cl loss in catalysts, researchers prepared series of supported copper catalysts from chloride-free copper sources. Cu2O/HY exhibited good initial activity in catalytic synthesis of DMC, while CuO dispersed in zeolites was not active for oxidative carbonylation. The Cu+ generated from the auto-reduction of Cu2+ through high temperature activation was the active center. Our team prepared Cu2O/AC and Cu0/AC catalysts through pyrolysis of copper acetate and Cu2(NO3)(OH)3 at different temperature, respectively. Other researchers suggested that the catalytic activity of copper-based catalyst resulted from the synergy of CuO and Cu2O. It can be seen that copper in three valence states were active for catalytic synthesis of DMC. In this thesis, AC supported CuO, Cu2O and Cu0 catalysts were prepared by different methods from chloride-free copper sources. The relationship between catalytic activity, structure and surface characterization was studied. The conclusions are listed as follows.(1) Cu/AC catalysts were prepared by hydrazine hydrate reduction of Cu(NO3)2-3H2O/AC. Catalyst prepared by moderate reduction exhibited good catalytic activity, while over-reduction decreased the activity. CuO was the only copper species when there was no reductant. Cu2+was gradually reduced to Cu2O and/or Cu0 with increasing molar ratio of hydrazine hydrate to copper nitrate. The unreduced Cu(OH)2 decomposed to CuO and highly dispersed on the surface of AC during drying process of the catalysts. When the molar ratio of hydrazine hydrate to copper nitrate was 0.75, the catalytic activity for oxidative carbonylation of methanol was the highest. Cu2O and dispersed CuO were proved as main copper species, and Cu2O as main catalytic active centre. The higher catalytic activity of Cu/AC-0.75 catalyst resulted from the high dispersed, regular shaped, mean sized Cu2O.(2) Microwave-assisted polyol process was utilized to prepare Cu/AC catalysts. Catalyst prepared by heating AC-glycol-copper acetate precursor to 160。C and cooling to room temperature immediately exhibited the best activity. Characterization analysis results indicated that the highly dispersed CuO was the reason for good catalytic performance. Increasing the heat treatment time, the valence of Cu species decreased as well as the catalytic activity. The introduction of Zn, Ni additives into the catalyst decreased the catalytic activity.(3) Cu2O/AC catalyst prepared by pyrolysis of copper acetate supported on active carbon was pretreated under oxidative (O2/N2) and reductive (H2/N2 & CO/N2) atmospheres. The oxidation/reduction of Cu2O was incomplete by pretreatment for 1 h at 300。C. Increasing the pretreatment temperature to 350。C and prolonging the pretreatment time to 4 h, Cu2O in catalyst could be completely oxidized to CuO, while unique metallic copper existed in catalyst pretreated by reductive atmosphere. The surface O content of the catalyst pretreated by O2 increased. As the reaction atmosphere for DMC synthesis was weak oxidative, O1s/C1s molar ratio on the surface of catalysts increased and copper species were oxidized to certain degrees after reaction. The catalyst pretreated by CO at 350。C exhibited high activity. After 58 h reaction, the activity of CU2O/AC and catalysts pretreated by reductive atmospheres tended to be similar. Comparing the catalytic performance of each catalyst, the valence between fresh catalyst and catalyst after reaction, we figured out that metallic copper exhibited a high initial activity while Cu2O exhibited a stable activity and valence. Cu2+/Cu+/Cu formed easily in catalysts with copper in a lower valence state were catalytic for the reaction.(4) Comparing the catalytic properties of catalysts prepared from different copper sources, it was found that each kind of Cu2+ was active for DMC synthesis. Copper ammonia solution and copper nitrate exhibited good catalytic activity.(5) The effect of preparation method on catalytic performance of CuO/AC was studied. Despite the low copper loading on catalyst CuO/AC-CH prepared by chemical adsorption, the catalytic performance was excellent. During 9 h running time, the average value of STYDMC, SDMC and CMeOH were 120.48mg·(g·h)-1,77.43% and 3.63%, respectively.
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