酸性沸石HBeta催化芳基炔烃水合构建芳基酮

Acidic zeolite HBeta catalysis for hydration of aryl alkynes to aryl ketones

将NaOH溶液、Na AlO_(2)、四乙基氢氧化铵按顺序加料后,再加入硅溶胶、季铵盐阳离子聚合物反应得到淡黄色凝胶,将凝胶进行动态晶化和高温煅烧制得Beta沸石。随后,通过水浴进行铵交换得到酸性沸石HBeta。采用XRD、氨气程序升温脱附及N_(2)吸附-脱附对制备的沸石Beta和HBeta进行了表征,考察了酸性沸石HBeta在苯乙炔水合反应中的最优反应条件和底物适用范围,推测了反应机理。结果表明,两种沸石的孔径分布基本一致,均具有介孔结构。酸性沸石HBeta比Beta具有更多的弱酸和中强酸中心,其在催化芳基炔烃水合体系中表现出优异的催化活性和可重复使用性能。HBeta催化的苯乙炔水合反应在相对温和的条件下(120℃,6 h)得到了最优的苯乙酮产率(100%),循环使用4次没有明显的活性损失,产物产率仍可达99%。此外,该催化体系对不同取代基的芳基炔烃展现出良好的兼容性。

Pale yellow gel was prepared by adding NaOH solution,NaAlO_(2) and tetraethyl ammonium hydroxide in order,then adding silica sol and quaternary ammonium salt cationic polymer.Subsequently,Beta zeolite was obtained by dynamical crystallization and high temperature calcination.Then,Beta acidic zeolite(HBeta)was prepared by ammonium exchange.Synthesized zeolite Beta and HBeta,characterized by XRD,temperature programmed desorption of ammonia and N_(2) adsorption desorption,were used to catalyze the hydration of acry alkynes,in which the optimum reaction conditions,substrate range and possible reaction mechanism involved were investigated and discussed.The results showed that,while the two zeolites were both mesoporous with basically the same pore size distributions,zeolite HBeta possessed more weak acid and medium strong acid centers than Beta,which contributed to its excellent catalytic activity and repeatability in hydration of aryl alkynes.The yield of acetophenone reached up to 100% under mild conditions(120℃,6 h),and zeolite HBeta showed no significant activity loss with product yield still up to 99% after recycled four times.Moreover,the catalytic system exhibited good compatibility for alkynes with different aryl substituents.