Methacrolein Homogeneous Hydrogenation Synthesis Of Methyl Allyl Research

α,β-unsaturated alcohols are commercially achieved by using metal hydride such as NaBH4 or AlLiH4 as reductant,but this process involves a violent quench step and a troublesome extraction step.Development of green and safe processes for the synthesis of α,β-unsaturated alcohols has attracted great attentions.The selective hydrogenation of α,β-unsaturated aldehyde will get different hydrogenation products.However,it is very difficult to control the selectivity of the hydrogenation of α,β-unsaturated aldehyde,as it is thermodynamically more favored to produce saturated aldehyde or saturated alcohol than the unsaturated alcohols.Therefore,it is a challenge to researchers that how to enhance the selectivity of unsaturated alcohols.Methacrolein homogenous hydrogenation synthesis of methallyl alcohol was studied in this paper.Firstly,MAL was synthesized as an intermediate by propionaldehyde condensing with formaldehyde in the presence of catalyst in liquid phase.Effects of reactant ratio,reaction temperature and reaction time on the conversion and yield were investigated.The proper reaction conditions were ascertained as follows: the mole ratio of formaldehyde/propionaldehyde = 1.1/1;reaction time = 50min;reaction temperature= 48℃.Under the above condition,propionaldehyde conversion and MAL yield reached up to 99.2% and 89.7% respectively.Secondly,MAL was reduced homogeneously to methallyl alcohol over aluminum isopropoxide with isopropanol as the hydrogen transfer agent.It was found that the conversion and the selectivity to methallyl alcohol could reached to 95% and87% respectively,when the reaction was carried out for 12 h at 55℃.Finally,methallyl alcohol was synthesized in the presence of homogeneous hydrogenation catalytic RuHCl(dppp)(dpen).The proper reaction conditions were ascertained as follows: the mole ratio of MAL/catalyst = 2000;reaction time = 8h;reaction temperature = 80℃.Under the above condition,MAL conversion and the selectivity of methallyl alcohol reached up to 99.4% and 86.8% respectively.The study shows that the above two methods can be selectively hydrogenated to produce methallyl alcohol.But the research group synthesized the methacrolein homogeneous catalysts of RuHCl(dppp)(dpen)for selective hydrogenation,which has important academic significance and economic value.