【作者】 南军；

【导师】 刘晨光；

【作者基本信息】 中国石油大学 ， 化学工程与技术， 2007， 博士

【摘要】 石脑油馏分的催化重整生成油富含芳烃和溶剂油馏分,同时也含有少量的烯烃,要生产出合格的芳烃和溶剂油产品,就必须脱除其中的烯烃。采用选择性加氢深度脱烯烃是一种有效的手段,制备活性高、选择性好的催化剂是关键所在。本论文对选择性深度加氢脱烯烃用贵金属Pd基催化剂的制备规律及其影响因素进行了研究,开发出一种具有良好的加氢活性和选择性以及稳定性的Pd基双金属催化剂,该催化剂具有加氢性能好、成本低、原料适应性广等特点,尤其可用于重整汽油全馏分的选择性加氢。本论文首先对单金属Pd催化剂进行制备及使用研究。采用饱和浸渍法制备了一系列蛋壳型Pd催化剂,在高压微反装置上分别以模拟油和重整汽油全馏分为原料,对催化剂的活性、选择性进行评价。单金属Pd负载在氧化铝催化剂的制备研究结果表明:载体前驱物拟薄水铝石的最佳焙烧温度为700°C;少量碱性金属助剂对载体的改性会降低载体的表面酸性;活性组分的浸渍溶液在pH值>4的条件下可以制成蛋壳型分布的单金属Pd催化剂;Pd含量以不大于0.2m%为宜。该单金属Pd/Al2O3催化剂在重整汽油BTX馏分选择性加氢脱烯烃的反应中表现出好的加氢活性和选择性。单使用Pd作活性组分的贵金属催化剂用于连续重整生成油全馏分选择性加氢脱烯烃反应时,会发生可逆性失活。通过微反实验及对失活前后催化剂的分析表征,结果表明其失活原因是:催化重整汽油选择性加氢脱烯烃的工艺条件相对比较缓和,由于连续重整操作条件较为苛刻,导致重整过程中生成的高沸点馏分等其它热敏类物质在此反应温度下会强吸附或部分聚合在催化剂表面,造成催化剂失活。采用添加助剂改性的方法对单Pd催化剂进行改性研究,结果发现加入第二金属Pt制成的双金属催化剂中,Pt的引入使催化剂具有较好的稳定性,对重整汽油的加氢效果能满足工业要求。此新型助剂改性双金属Pd基催化剂优化的制备条件为:1)拟薄水铝石粉为原料,载体焙烧温度700°C,可对载体进行碱性助剂改性;2)采用共浸渍法按等体积浸渍的方式浸以氯化钯和氯铂酸的水溶液,浸渍时间为30min;3)Pd、Pt原子比为2:1的为最佳配比催化剂,适宜的金属负载总量为0.2m%。在活性组分的非均匀分布研究中综合催化剂的活性和选择性来考虑,以Pd和Pt在载体中均呈蛋壳型分布较适宜,壳层厚度～150μm左右最为适宜。对双金属催化剂的加氢作用机理的深入研究发现第二金属Pt添加后与主活性组分Pd间发生相互作用,助剂的存在显著提高了金属的分散度,使得(Pd+Pt)/Al2O3双金属催化剂具有更高的加氢活性,容易使催化剂表面吸附的重组分被加氢成危害较小的相对轻组分而除去,从而提高催化剂的稳定性。脉冲微反和原位红外的结果表明双金属催化剂上烯烃的C=C双键加氢和芳烃的苯环加氢发生在相同的活性中心上,存在有竞争吸附作用,彼此间有较强的相互影响。本论文中最终确定的双金属催化剂UDO-01能够满足重整汽油苯馏分、BTX馏分和全馏分的选择性加氢要求。此外得到一种优化的开工方案,即Pd基催化剂开工过程中采用预还原后先降低温度,再阶段式升温,可以不采用预硫化过程而避免芳烃的过量转化。100ml的小试装置上对重整汽油全馏分的实验结果表明双金属催化剂UDO-01具有很高的活性稳定性、选择性和较大的提温区间,加氢过程中产品油的溴值小于200mgBr/100g oil,同时芳烃损失小于0.5m%。更多还原

【Abstract】 To produce qualified aromatics and solvent products, a small amount olefins must be removed which are contained in reformate processed from catalytic reform. It was a valid means to take selective hydrogenation to remove olefins deeply; accordingly, it was key method to develop a new hydrogenation catalyst with high activity and selectivity. In this paper, preparation rules and influencing factors of noble Pd-based catalysts used to deeply removed olefin were researched and a Pd-based double metal catalyst with high activity, selectivity and stabilization was developed. This catalyst possesses some characteristics of good hydrogenation performance, low cost and wide feeds adaptability, which especially can be used for hydrogenation of whole fraction.At the first, study on preparation and application of single Pd catalysts was performed. A series of Pd-based catalysts which were supported on Al2O3 with egg-shell distribution of Pd in the catalyst had been prepared by dry impregnation and the catalytic performances of these catalysts had been studied on a high-pressure microreactor utilizing model oil and reformate oil as reactants. The research results of catalyst preparation showed that the optimal calcination temperature of pseudo-boehmite should be 700°C; the addition of alkali-metal could decrease the surface acidity of support; the egg-shell distribution single Pd catalyst could be obtained under pH value bigger than 4 of impregnation resolution; the content of Pd should be lower than 0.2m%.This Pd/Al2O3 catalyst exhibited good activity and selectivity in the selective hydrogenation reaction of BTX fraction.It was found that the catalysts were temporarily deactived when the single Pd catalysts were used to process whole fraction of reformate oil. By means of micro-reaction tests and analysis of catalysts before and after using, the results indicated that due to thermo sensitive high-boiling heavy component which was produced from catalytic reform process adsorbed or partially polymerized to the catalyst surface under relatively severe operation condition.The method of adding promoter to modify the single Pd catalyst was applied and with the function of the second metal Pt the double metal catalyst can be used to hold good stabilization to selective hydrogenation of refomate at the aim that the result products can meet the industrial requirement. The best preparation conditions of this modified double metal were shown as follow: the pseudo-boehmite can be taken as the material, the optimal calcination temperature of support should be 700°C, and alkali promoter can be used to modify the support; the solution of PdCl2 and H4PtCl6 was used to co-impregnate the support by dry impregnation, the impregnate time was 30min; the best atomic ratio of Pd/Pt was 2 and total metal content was 0.2m%.Considering the activity and selectivity of catalyst, it was suitable that the distribution of Pd and Pt in support existed in egg-shell state and the thickness of egg-shell was about 150μm in the research of heterogeneous distribution of active component .In the discussion of hydrogenation mechanism to double metal catalysts, it was found that the interactions of two metals led to the increase the degree of metal dispersion. As a result, due to the (Pd+Pt)/Al2O3 catalysts had higher hydrogenation activity; it was easy that the heavy component adsorbed changed to relatively light component which had minor endangering and the stabilization of catalyst was increased greatly. The results of pulse micro-reactor and in-situ IR showed that hydrogenation of C=C double bond and hydrogenation of benzene cycle occurred on the same active site of double metal catalyst. The competitive adsorption existed between two reactions and relatively strong interaction took place in each other.The double metal catalyst UDO-01 could fulfill the requirement of selective hydrogenation of benzene fraction, BTX fraction and whole fraction. It was concluded that the in the running process, feeding in low temperature and temperature-programmed procedure were employed to avoid the excess conversion of aromatics after the catalysts were reduced without presulfurization process. The results of hydrogenation tests to whole fraction of reformate on a 100ml-scale pilot unit indicated that the double metal had higher stabilization, selectivity and major temperature interval. In the hydrogenation process, the bromine number of products was less than 200mgBr/100g oil and aromatics loss was lower than 0.5m%.更多还原