Study On Catalytic Synthesis Of Solketal By Carbon-Based Solid Acid Catalyst

Solketal is a high-quality solvent,plasticizer and important chemical intermediate with favorable market prospect.It is mainly synthesized from glycerol and acetone with acid catalysts.However,there will appear some problems such as environment pollution,difficulty in product separation and the corrosion of equipment when it is catalyzed by the conventional liquid acid.Solid acid catalyst,as an eco-friendly catalyst with high catalytic activity for various reactions,convenience for separation and recycle,can be a better solution to solve the above problems.And it has caught a broad attention among the scholars of catalytic field.A series of carbon-based solid acid catalysts were prepared with bamboo powder as raw material and p-toluenesulfonic acid monohydrate as sulfonating agent.The catalytic reaction of acetone and glycerol was carried out using the prepared carbon-based solid acid catalysts.After screening out a suitable catalyst,the catalytic reaction of acetone and glycerol by the catalyst were studied systematically.The research contents are as follows:?1?Using bamboo powder as raw material and p-toluenesulfonic acid monohydrate as sulfonating agent,carbon-based solid acid catalysts were made by one-pot simultaneous carbonization and sulfonation method,and then nitrogen heat treatment,air heat treatment,ZnCl₂ pretreatment,H₂O₂ pretreatment respectively.Meanwhile,a porous carbon-based solid acid was prepared by first preparing activated carbon and then sulfonating with sulfuric acid.Then the catalysts prepared above was compared with a commercial resin catalyst.The surface acidity of carbon-based solid acid treated with nitrogen was the highest,while the surface sulfur content and acidity of solid acid prepared by activated carbon method were the lowest.The prepared solid acid catalysts were characterized and evaluated in the catalytic synthesis of solketal under the same conditions.The experimental results show that,under the same conditions,the yield of solketal was highest when using the carbon-based solid acid catalyst dealt with nitrogen heat treatment.?2?In order to further investigate the catalytic performance of the carbon-based solid acid catalyst dealt with nitrogen heat treatment,the effects of reaction temperature,reaction time,molar ratio of acetone to glycerol and catalyst dosage on the synthesis of solketal were studied,and then the suitable reaction conditions were determined:reaction temperature at 60 ?,reaction time of 20 min,n?acetone?:n?glycerol?=5:1,catalyst dosage of 0.4%by the mass of glycerol.Under this optimized conditions,conversion of glycerol reached 86.65%and yield of solketal reached 84.72%.?3?The 2^nd kinetic model was developed for the reaction of acetone and glycerol to solketal using the carbon-based solid acid catalyst dealt with nitrogen heat treatment.When eliminating the effects of internal and external diffusion,the kinetics of solketal synthesis was studied in optimized catalyst dosage?0.4%by the mass of glycerol?and reaction temperature range?313.2?333.2 K?and the kinetic model parameters were obtained.The value of pre-exponential factor k0 is 1.01×10⁶ L·mol^-1·s^-1,and activation energy E_a is 61.13kJ·mol^-1.