Study On The Hydrophobic Catalysts For One-step Preparation Of Methyl Methacrylate

Methyl methacrylate (MMA) is an important organic chemical material, mainly used for the production of PMMA and other resins.MMA was mainly produced by the old method of Acetone-Cyanohydrin(ACH) process in the world.It is very necessary to develop new production processes for the environmental and economic benefits. The process of one-step conversion of methacrolein(MAL) to MMA is a green process with great potential.The catalysts used for one-step conversion of MAL to MMA were studied.A new series of hydrophobic palladium catalyst was prepared, its catalytic performance was greatly improved compared with the conventional catalysts.Firstly,the hydrophobic sole-palladium catalysts were prepared by impregnation. The SDB-4 Styrene-Divinylbenzene copolymer(SDB) with great surface area and aperture was chosen as the carrier,the appropriate loading of Pd was 3%,reduction temperature is 180~220℃, reduction time is 8~12 hours.Pd3%/SDB-4 was prepared in the hydrogen with flow rate of 30ml/min under 200℃for 10 hours,MMA yield was 55.7%.Secondly,hydrophobic multi-metal catalysts were prepared by the addition of bismuth, lead and other metals in the sole-palladium catalysts.Their catalytic activities were compared and the influence of each metal on the catalysts was briefly analyzed. The effects of reaction time, temperature, amounts of catalyst,mole ratio of reactants on MAL conversion rate and reaction selectivity were studied. The optimal reaction conditions were:mole ratio of methanol to MAL was 40/1,catalyst added 4.5%, reaction temperature was 50℃,flow rate of oxygen was 0.53m/h,reaction time was 6 hours.Under the above conditions, the MAL conversion rate reached 86.9%,the reaction selectivity was 90.3%. Life of the catalyst was also studied, MMA yield remains above 75% after the catalyst was used for five time.The catalysts were tested by BET,XRD and ESEM at last.Finally, the heterogeneous catalytic reaction process was discussed as well as the possible catalytic mechanism.The appropriate explanation of reaction phenomenon and the way to improve catalytic properties were proposed.