Microwave In The Preparation Of The Catalyst And The Promotion Of The Rosin Esterification Reaction

Microwave, as one of the green chemical methods, is applied to preparation of solid acid catalysts, rosin and glycerol's esterification reactions. This paper aims at decreasing reaction time, advancing energy's utilization efficiency, improving the quality of product, and investigating the optimal technics of catalyst preparation and microwave-assisting rosin esterification reaction.Microwave-assisting method and conventional way are employed respectively in preparation of SO₄^2-/TiO₂-SiO₂, S₂O_82-/TiO₂-SiO₂ solid superacid catalysts and ZnO solid acid catalysts. The prepared catalysts are applied in microwave-assisting rosin and glycerol's esterification reaction. The prepared catalysts with better capability is ZnO(M2) catalyst acquiring by microwave solid phase method. The best conditions for preparing ZnO(M2) catalyst under single factor experimentation are: microwave power P3; microwave solid phase reaction time tM2; desiccation temperature TD3; desiccation time tD1; calcination temperature TC3; calcination time tC3.The best conditions of microwave-assisting rosin and glycerol's esterification reaction obtaining by single factor experimentation and orthogonal experimentation are: microwave power P4; reaction temperature T4; mole proportion of rosin and glycerol 2:1; ZnO(M2) catalyst percentage 0.2% (comparing with rosin's mass); reaction time 55min. Under the optimally technical condition the indexes of esterification products are: acid value 8.5mgKOH/g; chroma (Fe-Co method) 7; softening point 87.5℃; solubility in benzene(1:1) clear; specific gravity (25℃/25℃) 1.086; ash percentage 0.04%.The corresponding indexes accord with national standards GB10287-88.The prepared ZnO(M2) catalyst is examined by XRD, TEM, IR and other tests.The result shows that ZnO(M2) possesses fine crystalline character , high purity,average particle diameter 25nm and diameter uniformity. The IR test reveals thatZnO(M2) solid acid catalyst is with a bio-activity center of L acid and B acid.Esterification reaction results show that L acid is the main catalytic activity center.Experiments indicate that the higher the ZnO's purity and the smaller its particlediameter are, the better its catalytic abilities are. Comparing with conventional esterification reactions and technics of 136 rosin glyceride used in industry, microwave-assisting rosin esterification reaction and nitrogen blowing technics in this paper take an obvious predominance which reduce reaction time, improve chroma, and enhance the softening points of products.Discussion about the mechanism of preparing ZnO(M2) catalyst by microwave solid phase method is elementarily made. It is considered that polarity reactant firstly produce a great deal of tiny liquid drops just like many micro reactors on surface of solid particulate with microwave's assistance, then part of reactant dissolve in the micro reactors. With the function of microwave, just like many micro mixers, the reactions are rapidly promoted. Discussion of microwave's assistance mechanism in rosin esterification reaction is elementarily made too. It is considered that microwave doesn't change the process and mechanism of the reaction. However, microwave with proper intensity drives polarity reactant molecules and intermediates to move in order on the basis of thermal motion, and enhance the effective colliding odds, therefore, the reaction is promoted.