Catalytic Performance Of Chlorine-free Cu/AC Catalysts For The Methanol Liquid-phase Oxidative Carbonylation

As an environmental benign green-chemical,Dimethyl carbonate(DMC)has wide industrial application prospects and has been used as an important intermediate in organic synthesis.Especially in recent years,the gradually industrialization of the use of DMC as gasoline additive and green solvent,making the increasing demand of the DMC market,and DMC synthesis is of much attention.At present,the traditional catalysts for oxidation carbonylation of methanol to synthesize DMC awalys load chlorinated precursors,and the Cl in the catalyst easly lost to form HCl during the catalytic process,which cause the equipment corrosion and decrement of the activity.Studies have shown that Cl is not the necessary element for the oxidative carbonylation of methanol to synthesize DMC.King prepared chloride-free Cu20/Y catalyst,which prepared excellent performance for DMC synthesis but started to deactivate rapidly after 1.5 h on stream.Romano U found the effect of water in the slurry reactor system is extremely complex,too high or too low are both not conducive to the reaction.Study of the chlorine-free catalyst with good activity and stability has become one of the important research directions in recent years.In this thesis,we used AC as the support,selected Cu(CH3COO)2·H2O as the copper source,and acquired chlorine-free Cu/AC catalyst exhibited high activity by the process of pyrolysis in metal copper organic salts and then activated by high temperature calcination.The stability,microstructure and performance of the catalyst in methanol oxidation carbonylation were investigated.And the effect of water on the catalytic activity and microscopic structure of catalyst was aslo investigated.Also XRD,XPS,TPR,TG-DTG and AAS were used to characterize these catalysts.After the analysis of evaluation and characterization,the following conclusions were obtained:(1)The chlorine-free catalyst expressed good activity in the oxidative carbonylation of methanol when the mesh of activated carbon 140-160,dipping time 12 h.(2)The fresh catalyst expressed high activity in the synthesis of dimethyl carbonate,and activity for recycled catalyst became a little lower with the increased of recycling number,indicating that the chlorine-free catalyst expressed good stability.(3)The losing of Cu element was accompanied in the reaction by the characteristics of the elemental analysis.When the cooper lost to a certain extent,the phenomenon became not obvious,that is the reason why the catalyst keeping good stability.(4)There were Cu and Cu2O species in fresh catalyst and the catalyst was instability.With the cycling times increased,the low valence Cu species was oxidized,and some was lost.The copper species in catalyst was identified as Cu20 and the decentralized of CuO.(5)The presence of H2O accelerated the inactivation rate of catalyst Cu/AC for DMC synthesis.(6)XRD,H2-TPR and element analysis of characterization results of the catalysts showed that:the presence of H2O accelerated the rate of Cu element.With the amount of H2O increasing,the water and Cu component formed to Cu2(OH)2CO3 which expressed no activity for DMC synthesis,and accelerated the catalyst deactive rapidly.