Oxidative Hydrolysis Of Methyl Oleate Over Tungsten-based Mesoporous Material MCM-41 For The Production Of Methyl 9,10-dihydroxystearate

Currently,the development of renewable bio-based products based on biomass has attracted much attention.Among them,bio-based polyols produced with vegetable oils as raw materials through appropriate modification are an important chemical intermediate.Its production cost is stable,environmentally friendly,degradable,and excellent in physical and chemical properties.It can partially replace raw materials produced from traditional fossil resources and reduce environmental pollution.In this paper,methyl oleate is used as the raw material to hydroxylate the carbon-carbon double bond under the catalysis of the tungsten-based mesoporous material MCM-41to prepare the bio-based polyol methyl 9,10-dihydroxystearate,which provided a new comprehensive development and utilization path for vegetable oil.In this paper,the structural design and modification of the catalyst were first carried out.The supported WO₃/MCM-41 catalysts with different W loading and the doped W-MCM-41 catalysts with different W doping were prepared by the impregnation method and the hydrothermal method,respectively.The experimental results suggested that the doped W-MCM-41 catalysts have the higher reactivity than the supported WO₃/MCM-41 catalysts,and the conversion of methyl oleate was 96%within the reaction time of 2 h,and the yield of methyl 9,10-dihydroxystearate was72%.At the same time,the stability of the catalyst was investigated,and it was found that the doped W-MCM-41 catalyst still had high activity after being reused 8 times.On the basis of obtaining a suitable catalyst,the reaction conditions of oxidative hydrolysis was further optimized and the reaction path was explored.The effects of reaction temperature,reaction time,amount of oxidant,amount of catalyst and amount of solvent on the conversion of methyl oleate and the yield of methyl 9,10-dihydroxystearate were investigated.Appropriate reaction temperature,reaction time,H₂O₂/feedstock?molar ratio?,catalyst/feedstock?weight ratio?and t-Bu OH/feedstock?weight ratio?were 80?,1.5 h,2.5,0.03 and 2,respectively.Under this condition,the conversion rate of methyl oleate reached 99%,and the yield of methyl 9,10-dihydroxystearate reached 79%.Finally,the solvent-freezing crystallization method was used to separate and purify the target product methyl 9,10-dihydroxystearate.The influence of the freezing temperature,freezing time,the amount of solvent and the type of solvent on the product yield and purity was inspected.Finally,it was concluded that when ethyl acetate was used as the solvent and frozen at 5?for 8 h,and the solvent/mixed product volume ratio was 3:1,the product yield of more than 70%can be obtained,and the highest purity can reach more than 99%.