Preparation Of Ethyl Levulinate From Wheat Stalk Over Solid Acids

With the development of economics,non-renewable resources such as coal,petroleum and natural gas are gradually depleted,therefore,there is an urgent need to exploit renewable resources.As a renewable resource,biomass has received great attention due to its abundance and cheapness.At present,the preparation of high value-added platform compounds from biomass is very popular.In this study,solid acid catalysts ware prepared using SO₄^2-and Zr（SO₄）₂ as active components and SiO₂as carrier,and a series of characterizations ware performed.Then the catalytical activity was explored using glucose as a model compound.Finally,using straw treated by alkaline hydrogen peroxide solution of ethanol as raw material,ethyl levulinate（EL）was prepared over the solid acid catalysts.The reaction conditions ware optimized,and the product was separated by vacuum distillation.Firstly,wheat straw was pretreated in ethanolic solution containing alkaline hydrogen peroxide.Under these conditions,the removal rate of lignin reach 72.7%.Secondly,the catalytical activity was explored by the reaction of converting model compound glucose to EL.The effects of reaction temperature,reaction time,catalyst dosage and loading amount on the catalytic conversion of glucose to EL ware studied.Under suitable conditions,the yield of EL is 32.05%when SO₄^-2/SiO₂ was used as catalyst,and the yield of EL is 30.38%when Zr（SO₄）₂/SiO₂ was used as catalyst,indicating that these two catalysts have good catalytic activity.Finally,using the treated straw as raw material,the influence of different factors on the yield of EL over SO₄^2-/SiO₂ and Zr（SO₄）₂/SiO₂ ware investigated by single factor test,and then orthogonal experiments ware carried out to optimize the reaction conditions.The optimum conditions for the straw conversion over SO₄^2-/SiO₂ are 40min reaction time,190 ^oC reaction temperature,0.6 g catalyst dosage,2.5 g raw material dosage.Under these conditions,yield of EL is 16.52%.The optimum conditions for the catalytical conversion of straw over Zr（SO₄）₂/SiO₂ are reaction time50 min,reaction temperature 190 ^oC,catalyst dosage 0.5 g,the loading 30%.Under these conditions,the yield of EL is 17.14%.The reaction mixture was purified by vacuum distillation,and the relative content of EL is up to approximately 90%after these three steps of vacuum distillation.