Research On The Catalyst And Reaction Process For Methanol Synthesis At Low Temperature In Slurry Phase

Liquid phase synthesis of methanol (LPSM) at lower temperature can effectively raise the conversion degree and selectivity of the methanol synthesis. The reaction performance of this reaction is greatly relied on the catalyst used. In this work, the catalytic effects, reaction mechanism, reaction process and parameters, kinetics and deactivation of the catalysts were systematically discussed. A Cu/Cr catalyst for LPSM was prepared with a complex precipitation technique. Based on the activity measurement, the optimal parameters for the catalyst preparation and reaction operation were well investigated. A principle process for LPSM was proposed.The catalyst prepared by the complex precipitation method has a higher surface area (92 m2/g). The precipitate possesses a uniform and smaller crystal size, about 40-50 nm. The activity measurement showed that this catalyst had a higher activity than the catalyst obtained from a traditional precipitation method. The preparation condition of the catalyst showed great influence on the performance of the catalyst. The atomic ratio of Cu/Cr in catalyst significantly affects the activity and selectivity. The Optimal ratio was found in the range of 0.9-1.0. The PH value of the precipitation solution influenced on the activity, but it did not influence on the selectivity. In our experimental condition, the effects of aging time and aging temperature on both activity and selectivity were negligible. The results also showed that calcining the catalyst in a nitrogen atmosphere brought about a better performance than in an air atmosphere. The preferred temperature for calcinations is 340-350.Solvent effects on the reaction were examined. The results show that the dielectric constant of the solvent has a significant influence on the reaction rate. Nonpolar solvents with lower dielectric constant or non-protonic polar solvents, suchas xylene, acetone and tetrhydric furan, can enhance the synthesis reaction. The optimal operation parameters for the LPSM are suggested to be 110-120 , 4.5-5.0 MPa, 2.5-3.0%(wt) of initial methanol concentration and 4%(wt) of sodium methoxide concentration.The deactivation of the catalytic system was tested. The deactivation of this catalytic system is due to the deactivation of sodium methoxide catalyst. The hydrogenolysis process is the rate-limiting step of the synthesis. The deactivation of sodium methoxide can be lowered and the reaction rate increased by improving the hydrogenolysis process.