Study On CuZnAl Catalyst Prepared By Complete Liquid Phase Method For CO Hydrogenation In A Fixed Bed Reactor

Along with our country’s rapid economic growth, the demand for energy was more and more urgent. In the special situation of shortage of oil resources, rich in coal resources and the public’s growing awareness of environmental protection conditions, the conversion of coal into clean energy has attracted extensive attention. Therefore, using gas or coal as the basis of the liquid fuel production as the complement of clean oil resources, has the extremely important strategic significance to the future development of our country. Methanol, ethanol and dimethyl ether are not only important feedstock for the production of many chemicals, but also potentially cleaner alternative fuel for the future.Medicine, farminsecticide, spice, dope, dyestuff and composite material all need methanol and ethanol for dissolvent and raw stuff.The CuZnAl catalyst was prepared by a improved complete liquid-phase method which glycerol instead of liquid paraffin as heat medium in the process of preparation.The catalyst reducibility, bulk phase, crystal size, surface acid and surface state were characterized by Fourier Transform Infrared Spectrometer (FTIR), X-ray diffraction (XRD), N2adsorption-desorption experiment and X-ray photo electron spectroscopy (XPS), temperature programmed reduction (TPR), NH3-TPD-MS, the catalytic activity of catalysts for direct synthesis of CO hydrogenation from syngas were evaluated in a micro fixed-bed-reactor. The effect of different heat-treatment medium,atomic ratio of Cu-Zn-Al, different heat treatment temperature and concentration of surfactant on structure of catalysts and catalytic performance was investigated. The experimental results come to following conclusions:1) The catalytic activity of using glycerol as heat-treatment medium preparation is better than paraffin as that of catalyst in a fixed bed, and Cu is mainly exists in the form of Cu2O crystal phase in the catalyst.2) Using glycerol as heat medium preparation of Cu-Zn-Al catalyst can improve the Cu content in the catalyst surface and reduce the carbon content, the carbon of catalyst surface is the important factor that affect to improve completely liquid catalyst activity.3) Under the condition of nitrate decomposition, the lower heat treatment temperature, the more content of Cu2O crystallinity and the better of catalyst activity, conducive to promoting the production of dimethyl ether, and less by-products.4) Higher heat treatment temperature can lead to glycerol polymerization occurred and oxidation reaction during heat treatment process, which resulted in the catalyst activity center are covered and the decrease of catalytic activity. 5) Adding surfactant can improve the activity of catalyst in the process of preparing catalyst, which conducive to generate methanol and reduce the produce of alkane and CO2, but not conducive to the formation of dimethyl ether.6) Surfactant is not easily to remove in the process of preparation, may destabilize the activity of catalyst in the later and the catalytic activity is gradually reduced.7) Under the condition of the mole ratio of2:1:0.8, the Cu-Zn-Al catalyst of different aluminum content of CO conversion is highest, the more active center of methanol dehydration, the more beneficial to produce dimethyl ether.8) Due to the catalyst R140-0.8is largest of the specific surface,resulted in the relatively highest of catalytic activity and the highest selectivity of dimethyl ether. The increase of specific surface can improve the surface of the catalyst activity center and is conducive to produce dimethyl ether reaction of methanol dehydration...