The Pd-Pb catalyst supported on Al2O3 was prepared by the two-step impregnation method.The oxidative esterification of methacrolein （MAL） to methyl methacrylate （MMA） was carried out in a stainless bubble autoclave over the catalyst.The influences of the reaction conditions on catalytic activity were investigated in detail.The optimal reaction conditions were as follows: T=80℃, P=0.3 MPa, methanol∶MAL=8∶1 （ molar ratio ）, catalyst mass concentration in the reaction system 3.84%, pH of the reaction system 7—8, oxygen flux rate 30 ml·min -1 .Under the above conditions,MAL conversion and MMA selectivity reached 91% and 84%, respectively.The catalyst was recycled for seven times and still kept good selectivity.
Supported multi-metal catalyst was prepared by impregnation.A variety of factors such as reaction temperature, feedstock ratio, alkali concentration, catalyst concentration and antipolymerizer concentration were systematically investigated in terms of their effects on the oxidative esterification reaction for methyl methacrylate production from methacrolein.The experimental results showed that under the condition of temperature 333 K,methanol/methacrolein ratio 97∶1(molar ratio),NaOH concentration 0.001 g·ml^-1 and catalyst concentration 0.02 g·ml^-1, methacrolein conversion and methyl methacrylate selectivity were about 100% and 71.4% respectively, after 30 min reaction.
