Preparation Of WO_X/MCM-41 Catalyst And Performance Of Solketal Synthesis

Biodiesel technology is one of the important ways to solve the current oil crisis.High value-added conversion and utilization of the by-product glycerin is the key issue to reduce cost.Accordinglly,development more efficient solid acid catalyst and more reasonable catalytic conversion process becomes the key point in the high value-added conversion and utilization of glycerin.This paper designed and prepared a high-performance and stable WO_X/MCM-41 solid acid catalyst based on the characteristics of acetalization of glycerol to produce solketal.The catalytic performances in batch reactor and continuous flow microchannel reactor were also studied.The main research contents and results are as follows:（1）A series of supported WO_X/MCM-41 solid acid catalysts were designed and prepared.The mesoporous MCM-41 molecular sieve with high specific surface area was prepared by the traditional hydrothermal synthesis method and the WO_Xspecies was loaded by wet impregnation.The parameters of the loading amount of ammonium tungstate,impregnation temperature,calcination temperature and other conditions were investigated.XRD/UV-Vis/TPR/XPS/TPD/N₂adsorption-desorption/TEM and other cha-racterization results showed that the loading amount of ammonium tungstate could significantly change the loading amounts of WO_Xspecies on MCM-41 substrate.In addition,the calcination temperature could also affect the dispersion of the WO_Xspecies on the MCM-41 support.The loading amount of ammonium tungstate and calcination temperature synergistically affected the acid strength of the WO_X/MCM-41 solid acid catalyst.（2）The synthesis performance of solketal was tested and the catalyst was screened both in a batch tank reactor.The WO_X/MCM-41 solid acid catalyst with 10wt%ammonium tungstate loading amount and calcined at 550°C was firstly used as the catalyst to investigate and optimize the effect of reaction conditions on the performance of acetone glycidol synthesis,including catalyst dosage,reactant feed ratio,reaction temperature and reaction time were investigated and optimized.The results showed that the solketal yield increased significantly with the increase of catalyst dosage and reactant acetone/glycerol feeding ratio.However,the solketal yield increased unconspicuously with reaction temperature and reaction time.Then through the catalyst screening,the results showed that the WO_X/MCM-41 solid acid catalyst with 20wt%ammonium tungstate loading amount and calcined at 350°C showed the highest solketal yield.Under the optimized conditions of 10wt%catalyst dosage,acetone/glycerin molar ratio of 6,reaction temperature of 50°C and reaction time of 2 h,the highest solketal yield was87.77%.Both of the leaching experiment and the recycling test showed that these solid acid catalysts exhibited excellent catalytic stability.（3）The synthesis performance of solketal in a continuous flow capillary microchannel was tested.The coating microchannel reactor was firstly prepared by continuous flow feeding method.The effect paratmeters of the feed suspension ratio and concentration,residence time,coating time,coating times and other conditions were investigated.The results showed that the coating catalytic performance and coating thickness increased with the increase of the feed suspension ratio and concentration,residence time,coating time and coating times.Based on the above-mentioned coated microchannel reactor,the effect parameters of the feed molar ratio and residence time on the synthesis performance of solketal were investigated and optimized.The results showed that the solketal yields increased with the increase of the acetone/glycerol feed molar ratio and residence time.Under the optimized acetone/glycerol feed molar ratio of5 and residence time of 2.6 min,the highest solketal yield was 41.12%.In addition,the long-term continuous operation test of 50 h showed that the coated microchannel reactor exhibited excellent catalytic stability.