Ethanol Hydrogenation Of Methyl Acetate

Ethanol is an important chemical raw material. It is widely used in foodmanufacture, chemical industry, medicine and other fields, especially been used asvehicle fuel. At present, the mainly process in the production for ethanol isfermentation of biomass. The food fermentation has an obvious drawback in China,because the primary materials compete with people for food and contest with foodfor the fields. The pretreatment of the cellulose fermentation is difficult and maybring pollution. Another process in the production for ethanol is Ethylene hydration,but it has been eliminated gradually as its high cost. So the technology of gas-basedethanol production has caused widespread concern.Nowadays, the technology of both methanol carbonylation to acetic acid andacetic acid esterification to ester is extremely marture. Furthermore, theoverproduction of acetic acid brings the raw material price down. The process ofacetic ester-acetic acid hydrogenation for ethanol has a distinct advantage, which isthe hotspot of synthesis gas-based, the ethanol technology. Considering theapproach of direct hydrogenation of acetic acid needs harsh process conditions.Comparing with this, hydrogenation of acetic acid via ester is better for application.The core technology of indirect hydrogenation is the catalyst of hydrogenation ofacetate ester. This paper studies the impact of catalysts and reaction conditions forthe hydrogenation of methyl acetate-ethanol reaction. We select appropriateprimary catalyst, carrier, additives to study catalyst preparation method andconditions on catalyst performance. On the basis of the optimum catalyst, we furtherstudy the impact of process conditions on the catalyst performance, the stability ofthe catalyst and catalyst deactivation reasons.This thesis is divided into three parts:Firstly, we studied the thermodynamics of the reaction of methyl acetatehydrogenation of ethanol. When the reaction temperature is increased, theequilibrium conversion of the methyl acetate is gradually reduced to hydrogen theester ratio increases, increase in the conversion rate of methyl acetate. Suitable reaction temperature and higher esters of hydrogen ratio is conducive to the increasein the conversion of methyl acetate. The transesterification reaction is the main sidereaction under the reaction conditions in the near equilibrium state, to improve thehydrogenation activity of the catalyst can effectively reduce the selectivity of theethyl acetate byproduct. And increasing the reaction pressure is conducive to inhibitthe formation of other byproducts, such as acetaldehyde, ethylene and ethane.We investigated the effects of different preparation methods of Cu/SiO₂catalyst precipitation, including: impregnation method, ion-exchange method andsol-gel method. We then studied the catalysts prepared by different methods,different catalyst, by physical adsorption, H2-TPR, elemental analysis and XRD; andcompared the activity performance of different catalysts for methyl acetatehydrogenation reaction to produce ethanol. Catalyst Cu+species may be the activesite of the methyl acetate hydrogenation reaction to produce ethanol. Suitable porestructure is conducive to the diffusion of methyl acetate molecules of reactant andproduct ethanol molecules on the catalyst. The catalysts prepared by thehomogeneous precipitation of ammonia method are more active than the catalystprepared by other methods, which may be related to it has a suitable pore structure.We prepared of a series of Cu/SiO₂catalysts with different the coppercontent by ammonia method, and investigated the activity performance of differentcatalysts for methyl acetate hydrogenation reaction to produce ethanol in a fixed-bedmicroreactor. And we studied the effect of the copper content, calcinationtemperature and additives on the Catalyst Performance for the activity performance.Based on the optimized catalyst, we investigated the effect of Reaction pressure,hydrogen ester ratio and liquid hourly space velocity of reaction conditions for theactivity performance, to determine the optimal reaction conditions. Based on theanalysis of reason of deactivation, the carbon deposition, and hence the change ofthe pore structure of the catalyst, is the main reason leading to the deactivation ofthe catalyst. The catalyst stability improved, after adding the promoters.