Water Gas Shift Reaction Over Co-Mo-K/Al₂O₃-MgO-n Catalysts

The characteristics of fossil energy resources in China are short of oil, less gas and relatively abundant coal. Coal is treated as the main energy of China and this situation will not change for a long time, which is the core reason of the environment pollution by burning directly, however, is not accepted. Using coal cleanly and efficiently will be the development direction in the future. As the core technology for coal qualitative transformation, pyrolysis is getting more and more attention, but it is hard to deal with the waste water generated during processing. To solve the problem, the water gas shift reaction is introduced into pyrolysis process, which will reduce or even remove the waste water generation during pyrolysis, and finally realize zero waste water discharge during pyrolysis. The research of suitable catalysts for waste gas shift reaction during pyrolysis has become a key question.Magnesium aluminum composite oxides supporter were prepared by coprecipitation in this thesis. The effect of magnesium aluminum mol ratio、hydrolysis temperature、PH value, aging time and calcination temperature to the physical and chemical properties of magnesium aluminum composite oxides were studied. The results showed that the optimum condition were the hydrolysis temperature was70℃, PH was9.5, aging time was5h and calcination temperature was650℃, while the magnesium aluminum composite oxide had a more completely polymorph and better pore structure and better surface area.Water gas shift reaction on catalysts was studied in a continuous fixed bed reaction, and only hydrogen and carbon dioxide were found among the products. Five kinds of water gas shift activity were discussed, and the results showed that the shift activity was Co-Mo-K/Al2O3-MgO-0.8> Co-Mo-K/Al2O3>Co-Mo-K/MgO>Co-Mo-K/Al2O3-MgO-0.5>Co-Mo-K/Al2O3-MgO-0.2.The effect of different reaction conditions of the water gas shift reaction was studied, and the results showed that, the best temperature for water gas shift reaction on Co-Mo-K/Al2O3-MgO-n catalysts was300℃, and the best gas liquid ratio was900ml/ml, best temperature was0.5MPa.The effect of benzene on the water gas shift reaction was also studied and the result showed that, the addition of benzene lowered the conversion of Carbon monoxide on CMMA-0.8catalyst, and restrained the shift reaction clearly. According to the calculation of reaction thermodynamic and experimental study showed that benzene occurred hydrogenation reaction during200-400℃. Due to the competitive adsorption of benzene and water gas on the catalysts activity sites and the effect of chemical reaction balance, the shift reaction of water gas and the hydrogenation of benzene was antagonism in some degree.The effect of thiophene on the water gas shift reaction was also studied, and the results showed that, the addition of thiophene lowered the conversion of water gas on CMMA-n catalyst, and inhibited the water gas shift reaction. When the solution changed back to the none thiophene solution, the CO conversion was rebounded in some degree within a certain time, which revealed the prepared CMMA-n catalyst had sulfur resistance. The sulfur resistance of prepared CMMA-n catalyst was lowered than the industrial QCS-4catalyst.