Studies On Liquid-phase Selective Hydrogenation Of Cinnamaldehyde With Pt Or Pt-FeO_x Catalysts Supported On The Composite Oxide Materials

Chemo-selective hydrogenation of?,?-unsaturated aldehydes at carbonyl?C=O?group to produce the?,?-unsaturated alcohol is an important reaction for the chemical industries.It was found that the promotion of Fe can greatly improve the catalytic performance of Pt-based catalyst when used in the selective hydrogenation of cinnamaldehyde?CAL?.In this thesis,we study the liquid-phase selective hydrogenation of CAL with Pt or Pt-FeO_x catalysts supported on the composite oxide materials.This thesis is mainly focused on the two aspects as follows:In the preliminary research of this group,we found that the Pt/TiO₂@SBA-15?Pt/15TS?catalysts was more selective for the liquid-phase hydrogenation of benzaldehyde in water owing to proper interaction of Pt nanoparticles with the TiO₂@SBA-15 composites,which prompted us to expand its catalytic application to the liquid-phase hydrogenation of CAL.Furthermore,we found that Pt/Fe molar ratio of 4/1 was the optimal value for the Pt-Fe/Al₂O₃@SBA-15 catalysts.Therefore,we prepared the Pt-FeO_x/TiO₂@SBA-15 catalyst?the Pt/Fe molar ratio of 4:1?via an impregnation method,through optimizing the preparation conditions to regulate the interaction of Pt-FeO_x and Pt-15TS.We found that Pt-FeO_x/15TS-500 catalyst furnished the best catalytic activity,with the highest TOF value reaching 3.06 s^-11 and the selectivity to cinnamyl alcohol of 86.4%at the same time.In addition,the Pt-FeO_x/15TS-500 catalyst can be recycled for eight times at least.In the second part,perovskite materials has electronic-mixed ion conductivity,then often be used as the cathode of solid oxide fuel cell,the sensor,high temperature heating material,and the substitute of some redox catalysts of precious metal.Perovskite composite oxides also have wide application in catalytic field,but rarely as catalyst for the hydrogenation of?,?-unsaturated aldehyde.So we attempt to prepare the Pt catalyst using the perovskite composite oxides of YCo_xFe_1-xO₃ as support.The Fe/Co molar ratio in the YCo_xFe_1-xO₃ is adjustable,and the FeO_x and CoO_x can be isolated by the Y₂O₃,so that the state or form of FeOx is quite different from the conventional Pt-Fe catalysts.Nevertheless,due to the intrinsic low specific surface area of the perovskite material,the dispersion of metal particles will be limited on its surface.Hence,we used the SBA-15 as a hard template to expand its specific surface area,meanwhile,we adjusted the proportion of the perovskite composite oxides.Finally we found that with the Fe/Co ratio of 0.5/0.5 or 0.7/0.3 the catalyst had the best catalytic performance.The Pt/YCo_0.3Fe_0.7O₃ catalyst can afford up to 98.9%conversion of CAL,with 94.9%selectivity to cinnamic alcohol.We also investigated the kinetics behaviors of the selective hydrogenation of CAL using the Pt/YCo_0.3Fe_0.7O₃ catalyst.At 90 ^oC,the CAL conversion could reach about 57.0%within 5 minutes,obtaining above 95%selectivity to cinnamyl alcohol.Until CAL was fully converted,theselectivity to cinnamic alcohol decreased and the saturated alcohol was increased meanwhile.The Pt/YCo_0.3Fe_0.7O₃ catalyst can be recycled about four times.Nevertheless.Since the fifth recycling,the activity declined obviously.With characterization of the used catalyst,coke are deposited on the catalyst surface,and the structure of perovskite was partially changed.