Study On Ethanol Synthesis Over Cu-Based Catalysts Prepared By Complete Liquid Phase Technology

Ethanol has been widely used in medicine, paintings,cosmetics and so on. It is also a raw material which can be applied for preparing chemicals such as acetaldehyde, acetic acid, chloroethane and intermediates for detergents, pesticides, perfumes, paintings and so on. Adding ethanol into gasoline increases the contents of oxygen in gasoline which can burn completely. The development of ethanol-gasoline will ease the shortage of liquid fuels in our country.Because of the wide range of raw materials, the synthesis of ethanol from syngas is corresponding to the energy structure and has a bright future. However, by-products like hydrocarbons, methanol, dimethyl ether are generated in the process of ethanol synthesis from syngas. The improvement of selectivity of ethanol hinders the development of the synthesis of ethanol from syngas currently. Rh-based catalysts are most highly selective of ethanol synthesis from syngas, whereas the high price of Rh makes the mass production unrealistic.Aiming at specialties of slurry bed reactor, our research group has put forward a new catalysts preparing method named complete liquid phase technology. We found a high selectivity of ethanol in the process of catalytic activity test of Cu-based catalyst for methanol synthesis. Thus, on the basis of these experimental results and catalysts of methanol synthesis prepared by complete liquid phase technology, we prepared lots of modified catalysts to improve ethanol selectivity.In order to obtain good ethanol selectivity, we design adding different amount of Cs to catalysts and preparing a series of catalysts by different sources of Cu and Zn more over the impact of storage time on catalysts after heat treatment is also investigated. These catalysts are characterized by H2-TPR> XRD、NH3-TPD-MS、N2-adsorption. Combining with the results of catalytic performances, the main conclusions are as follows:1. The amount of Cs has a significant influence on CO conversion and ethanol selectivity of catalysts. The ethanol selectivity reaches the highest point at 18.3% when the molar ratio of Cs and Cu is 3%. The addition of Cs also leads to higher surface area and change in average pore size of catalysts. When the molar ratio of Cs and Cu is 3%, the average pore size reaches to its highest point.2. When Cu(NO3)2 is replaced by (CH3COO)2Cu, the ethanol selectivity reaches the highest point at 13.6%. Comparing with the catalyst without replacing of source of Cu before reaction, there is existence of CU2O without other copperish phase. The phase composition of catalyst has significantly changed.3. When catalyst is kept at room temperature for 5 days after heat treatment, the ethanol selectivity reaches 24.9%; while catalyst used for reaction is reacted immediately after heat treatment, the ethanol selectivity reduces to 5% and lasts for only one day. There are CuO and CU2O with no existence of Cu0 in the catalyst which is stored for 5 days. However, only Cu0 is existed in the immediately used catalyst.