【作者】 李彦鹏；

【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】 邻苯基苯酚(OPP)是一种重要的有机化工产品,目前多采取环己酮缩合-脱氢法合成。本论文针对该工艺的两个步骤即环己酮自缩合反应以及环己酮二聚物脱氢反应中所使用的催化剂进行了研究,开发出了具有较高转化率和理想选择性的适用于环己酮缩合反应的固体催化剂,以及具有较高二聚物转化率和OPP选择性且稳定性优良的脱氢催化剂。对于环己酮缩合反应的研究结果表明,使用传统浓H2SO4催化剂虽然转化率较高但是选择性较低且无法再生,而使用γ-Al2O3类固体酸催化剂则具有理想的催化活性和极佳的可再生性能。对γ-Al2O3催化环己酮缩合反应的机理研究表明,不同固体催化剂材料的孔结构性质等物理性质对其催化活性具有一定影响,但对于γ-Al2O3系列催化剂而言其催化活性与其孔道以及晶相之间没有必然联系,而与其表面的L酸量之间存在密切联系。本文首次以原位IR手段研究了环己酮在γ-Al2O3表面的缩合反应,结果表明环己酮的确可以在γ-Al2O3催化下发生反应。而且通过不同物种在γ-Al2O3表面吸附的IR研究证实,其催化环己酮缩合极有可能是通过其L酸中心进行。通过对二聚物脱氢催化剂的研究表明,单Pt催化剂性能最好,而双金属复配催化剂如Pt-Pd、Pt-Sn、Pt-Re等效果均不理想,未改性载体中以γ-Al2O3载体的效果最好、稳定性最佳。对脱氢催化剂的助剂改性结果表明,碱金属K盐具有优秀的改性效果,其中以K2CO3的效果最佳。而助剂改性机理研究表明,K助剂的改性作用体现在两方面:一是K物种对Pt组分的电性促进作用,二是其对Al2O3载体的酸性调变作用。而且研究结果表明K对Pt组分促进作用的贡献高于其对载体的酸性调变作用。但研究同时发现K改性的Pt/Al2O3催化剂容易失活,进一步的研究结果表明积炭并不是其失活的主要原因,而很可能是由于K物种在催化剂表面发生迁移而对Pt中心的过度覆盖造成的。本文重点对脱氢催化剂的载体改性进行了研究,发现Li2O、SrO和BaO的改性效果较好,而使用CeO2则有利于提高脱氢催化剂的稳定性,此外以由原位晶化法制备的MgAl水滑石焙烧得到的Mg(Al)O复合氧化物作为脱氢催化剂载体也具有很好的OPP选择性和理想的活性稳定性。本文以CeO2改性为基础,使用K助剂-Ce复合改性工艺和碱性金属氧化物-Ce载体复合改性工艺制得的脱氢催化剂均具有理想的活性稳定性,其中以Sr-Ce复合载体改性催化剂的稳定性最好。寿命测试结果表明0.5%Pt/5%SrO-5%CeO2-Al2O3催化剂在300h运转时间内其转化率和选择性可以分别稳定在95%和91%以上,具有理想的工业应用价值。更多还原

【Abstract】 O-phenylphenol (OPP) was an important organic chemical which was widely used in many fields. Nowadays OPP was mostly catalytically synthesized through a two-step process, that was, cyclohexanon’s self-condensation and dimers’dehydrogenation. In this thesis, catalysts applied to the two-step reactions had been studied. A seiries of solid catalysts with high conversion and excellent selectivity for the self-condensation reaction of cyclohexanone, and dehydrogenation catalysts with high dimer conversion rate and OPP selectivity as well as the ideal stability had also been developed.Results indicated that as to the self-condensation reaction of cyclohexanone, conventional H2SO4 catalyst had relatively higher conversion rate but it showed lower selectivity and could not be recovered and regenerated, whileγ-Al2O3 catalyst had ideal catalytic activity and much higher selectivity than the former and could be regenerated for over eight times. Mechanism study ofγ-Al2O3-catalyzed condensation reaction indicated that its catalytic performance was not so necessarily connected with its pore properties and crystalling phase but had close relations to its surface Lewis acidity. In-situ IR analysis was firstly adopted in this paper to study the condensation reaction of cyclohexanone on the surface ofγ-Al2O3 catalyst and results confirmed that cyclohexanone indeed could be condensated under catalysis effect ofγ-Al2O3 and IR results from different species’adsorption behaviors on Al2O3 surface also reflected that cyclohexanone’s self-condensationi reaction most likely underwent under catalysis effect with the Lewis acid sites on the surface ofγ-Al2O3 material.Results from the research of the dehyogenation catalysts showed that Pt/Al2O3 was the best mono-component catalyst and bi-component catalysts such as Pt-Pd, Pt-Sn and Pt-Re showed poor dehydrogenation activities.γ-Al2O3 was the ideal support which showed relatively the best performance as well as the stability. Additve-modification research works indicated that K additives had better modification effect than other modifiers and K2CO3 was the best among them. Results reflected that K additives had modification effect at two aspects, that were, firstly the electrical promotion effect as to the Pt component and secondly the suppressing of the surface acidity onγ-Al2O3 support, and the former was relatively the more important that the latter. However, stability tests indicated that K-modified catalysts were relatively easier gotten deactivated and mechanism study reflected that carbon deposition was not the main reason for the deactivation and the most probable reason was the migration of K species on the surface of catalyst which led to the excessive loss of Pt active surface by their covering effect. Support-modification studies were focused on in this paper and Li2O, SrO and BaO were found to be prospective modifiers and CeO2 was surprisingly found to have positive effect on the stability of the modified dehydrogenation catalysts. Catalysts with calcined in-situly generated MgAl hydrotalcites as supports also showed good OPP selectivity as well as prospective stability. On the basis of CeO2-modification, combined modification processes such as K-Ce and basic metal oxides-Ce modification methods were adopted to promote catalysts’hydrogenation activity, and more importantly, their stabilities. Several optimistic results had been earned and SrO-CeO2 combined modification catalyst showed the best stability. Life test indicated that 0.5%Pt/5%SrO-5%CeO2-Al2O3 catalyst had excellent performance during a 300h run, whose conversion rate and selectivity could be maintained over 95% and 91% respectively thus made it very promising for industrial use.更多还原