【作者】 王耀东；

【导师】 姜浩锡； 柳巨澜；

【作者基本信息】 天津大学 ， 化学工程， 2019， 硕士

【摘要】 负载型贵金属催化剂具有广泛的应用领域。高分散的贵金属催化剂可提升金属原子利用率,提高催化效能,已经成为近年来学者的研究热点。超临界流体沉积法（SFD）是一种绿色的微粒化方法,利用超临界流体具有的特殊溶解和传递性质,可制备出金属颗粒更小、尺寸更均匀的高分散催化剂。本论文采用超临界流体沉积方法制备高分散Pt/Al₂O₃催化剂并用于催化重整反应,课题具有重要的理论意义和实用价值。论文首先通过考察不同的金属前驱盐、共溶剂和载体预处理方式对超临界流体沉积法中的溶解过程进行了研究。发现使用Na₂PtCl₆作为前驱盐、乙醇作为共溶剂时,制备的Pt/Al₂O₃的Pt颗粒粒径最小、金属分散度最高。对载体进行乙醇预处理后与未经预处理的载体所制备的催化剂在Pt颗粒、金属分散度、负载量等方面并无明显区别,但经过脱羟基处理的巯基改性的载体所制备的催化剂在各方面都有所下降。论文对影响SFD法中的沉积过程的温度、压力、时间、负载量及还原条件进行了系统考察,并根据Pt颗粒的分散情况筛选出适宜的Pt/Al₂O₃催化剂制备工艺条件:沉积温度40℃、压力11 MPa、时间3 h,理论负载量0.5 wt.%,并采用N₂气氛热分解的方法进行还原。采用环己烷脱氢生成苯的反应为催化重整反应模型,对上述研究所优选出的分散较好的催化剂进行了活性评价。可以发现,采用SFD法制备的0.12 wt.%、0.24 wt.%、0.37 wt.%三种催化剂的活性均表现出优良的催化活性,Pt负载量越高,催化剂的活性越高;相比传统的普通浸渍法,SFD方法体现了明显的尺寸效应和贵金属降量效应:0.12 wt.%催化剂已优于普通浸渍法制备的0.4 wt.%的催化剂。更多还原

【Abstract】 Supported noble metal catalysts have a wide range of applications.Highly dispersed noble metal catalysts can improve the utilization of metal atoms and catalytic efficiency,which has become a research hotspot of scholars in recent years.Supercritical Fluid Deposition（SFD）is a green micronization method.By utilizing the special dissolution and transport properties of supercritical fluids,highly dispersed catalysts with smaller metal particles and more uniform size can be prepared.In this paper,highly dispersed Pt/Al₂O₃ catalysts were prepared by supercritical fluid deposition method and used in catalytic reforming reaction.This topic has important theoretical significance and practical value.Firstly,the dissolution process in supercritical fluid deposition was studied by investigating different metal precursor salts,co-solvents and carrier pretreatment methods.It was found that when Na₂PtCl₆ was used as precursor salt and ethanol as co-solvent,the particle size of Pt/Al₂O₃ prepared was the smallest and the metal dispersion was the highest.The catalyst prepared by ethanol pretreatment is not significantly different from the catalyst prepared by untreated carrier in terms of Pt particles,metal dispersion and loading,but the catalyst prepared by thiol modified carrier after dehydroxylation has decreased in all aspects.In this paper,the temperature,pressure,time,load and reduction conditions affecting the deposition process in SFD method were systematically investigated.According to the dispersion of Pt particles,the optimum preparation conditions of Pt/Al₂O₃ catalyst were selected:deposition temperature as 40℃,pressure as 11 MPa,time as 3 h,nominal load 0.5 wt.%,and reduction was carried out by N₂ atmosphere thermal decomposition.The catalytic reforming reaction model of benzene from cyclohexane dehydrogenation was used to evaluate the activity of the catalyst with better dispersion.It can be found that the catalysts prepared by SFD with 0.12 wt.%,0.24 wt.%and 0.37wt.%exhibit excellent catalytic activity.The higher the Pt loading,the higher the catalytic activity.Compared with the traditional impregnation method,SFD method shows obvious size effect and effect of reducing the quantity of precious metal:0.12wt.%catalyst is better than the catalyst prepared by ordinary impregnation method with 0.4 wt.% catalyst.更多还原