【作者】 邓凯；

【导师】 周春晖； 俞卫华；

【作者基本信息】 浙江工业大学 ， 物理化学， 2017， 硕士

【摘要】 在众多的甘油催化脱水制备丙烯醛的催化剂中,氧化钨催化剂由于它强而可调变性的酸性位受到了广泛的关注。但是,研究氧化钨的物种和它表面酸性之间的关系以及对甘油催化制备丙烯醛活性之间的影响的研究很少。本文将氧化钨负载在酸化的蒙脱土上然后分别在350,450,550度煅烧。研究了氧化钨的物种种类和煅烧温度之间的关系,以及氧化钨的物种和其表面酸性之间的关系。氧化钨的物种和表面酸性用X射线衍射、BET、氨-程序升温脱附,紫外可见光谱,吡啶-红外吸附、热重等手段表征。在350度煅烧温度下,负载在酸化蒙脱石上的氧化钨物种是孤立的WO6物种;在450度煅烧温度下,负载在酸化蒙脱石的氧化钨物种是孤立的WO6物种和结晶的WO3粒子;在550度煅烧温度下,负载在酸化蒙脱石上的氧化钨物种是结晶的WO3粒子。在350和450度煅烧条件下制备的WOx/H+-mt催化剂上面的氧化钨呈现无定型的形态。在550度煅烧的条件下制备的WOx/H+-mt催化剂上面的氧化钨呈现结晶形态。相比于结晶形态的氧化钨物种,无定型形态的氧化钨的物种表现出更高的酸性。随着煅烧温度的增加,催化剂的总酸量和中等酸性位都呈现减少的趋势。中等强度的酸性位和B酸位对甘油催化脱水生成丙烯醛是至关重要的。WOx/H+-mt-350呈现最好的催化活性,甘油的转化率达到100%,丙烯醛的选择性达到60.74%。更多还原

【Abstract】 Among several types of catalysts for glycerol conversion to glycerol,tungsten oxide catalysts have attracted much attention due to their strong uniform acidic sites.However,not many researches have been devoted toward understanding the relationships of different tungsten oxide species and their surface acidic characteristics for its effect on the catalytic performance during glycerol conversion to acrolein.In this work,the WOx /H+-mt catalyst calcined at 350,450,550 °C to study the variation of the WOx species with calcination temperature.The evolution of catalyst acidity and WOx species are carefully resolved and analyzed by using surface area and pore size distribution measurements,X-ray diffraction,NH3-TPD,X-ray photoelectron spectra,UV–vis spectroscopy,pyridine adsorbed FT-IR spectroscopy.The tungsten oxide species on H+-mt support are determined to be isolated WO6,a mixture of two surface WOx and crystalline WO3 nanoparticles with various calcination temperature.The WOx/H+-mt catalysts prepared by calcination at 350 and 450°C are shown amorphous WOx species.Therefore,calcination at 550°C are shown crystallized WOx species.The amorphous WOx species showed significantly higher acidity compared with the crystallized WOx species.The fraction of total acidity and medium acid sites are found to decrease with calcination temperature increasing.The mediun acid sites and Br?nsted acidic sites are essential for high glycerol conversion and acrolein selectivity.The WOx/ H+-mt-350 catalyst is found to be highly active during the dehydration reaction and exhibited 60.74% acrolein selectivity with 100% conversion of glycerol.更多还原