Study On Calcium Alkoxides Applied To The Guerbet Reaction

In the process of calcium carbide to vinyl ether,there have produced a lot of calcium alkoxides.At present,calcium alkoxides has no way to large-scale industrial applications.Long chain alcohols is a very important chemical product and raw material,widely used in chemical,food,medicine and other industries,Guerbet condensation reaction for the synthesis of long chain alcohols needs to be catalyzed by alkaline catalysts at high temperature.In order to explore the application prospect of calcium alkoxides in the Guerbet reaction,this paper took calcium methoxide and calcium ethoxide as the research objects,focused on the application to their respective mother alcohols(methanol,ethanol)condensation reaction,and preliminarily explored the application of calcium methoxide and calcium ethoxide to other alcohols condensation reaction.This has provided a theoretical basis for large-scale industrial application of calcium alkoxides.In the paper,factors which had an effect on the ethanol condensation and methanol condensation reaction,such as reaction time,reaction temperature and molar ratio of calcium alkoxides/alcohol were investigated.Experiments show that the ethanol condensation reaction catalyzed by calcium ethoxide displayed best result under 8~11h,300~320?,calcium ethoxide / alcohol molar ratio 0.5~1.0,the total selectivity of long chain alcohols was about 57%.The methanol condensation reaction catalyzed by calcium methoxide displayed best result under 8~10h,240~260?,calcium methoxide/methanol molar ratio 0.7~1.0,the total selectivity of long chain alcohols was about 67%.The effects of protective gas species(N2,H2)and their initial pressure on the ethanol condensation catalyzed by calcium ethoxide were discussed.Nitrogen is better than hydrogen;the appropriate initial pressure could improve the selectivity of product.The reaction activity of other alcohols(ethanol,propanol,butanol)condensation catalyzed by calcium methoxide and other alcohols(methanol,n-propanol,n-butanol)condensation catalyzed by calcium ethoxide were studied.With the increase of alcohol molecular weight,the conversion rate increased gradually,the reaction activity increased.Because of the hydrolysis of calcium alkoxides,the small molecule alcohols were introduced.Therefore,in the actual production process,it is more reasonable that calcium alkoxides catalyze the condensation reaction of the corresponding mother alcohols.The catalysis of calcium ethoxide in the reaction system was verified by comparing the product composition of ethanol condensation catalyzed by the basic substance(ethanol calcium,CaO,Ca(OH)2,MgO,Al2O3).The reaction path was in line with Guerbet condensation reaction.Experiments show that,there was not a positive correlation between the reaction activity and the intensity of alkaline catalyst.Therefore,using calcium alkoxides catalyze short chain alcohols to long-chain alcohols was feasible.