镍钼杂多酸簇的组装及加氢催化剂的研究

发布时间：2018-01-14 21:09

本文关键词：镍钼杂多酸簇的组装及加氢催化剂的研究　出处：《中国石油大学(华东)》2015年博士论文　论文类型：学位论文

【摘要】：近年来,我国中东部地区雾霾严重,空气出现大范围污染。研究表明,汽车尾气是引起雾霾的主要原因之一。同时,汽车尾气中的SO2也会带来更大的环境污染。因此,降低汽车油品的硫含量意义重大。当前,工业上加氢脱硫(hydrodesulfurization,HDS)催化剂制备过程用到的浸渍液体系含有多种镍钼杂多酸簇小分子。这一体系组分复杂,很难确定其具体组成,不利于研究HDS催化剂的活性相结构和构效关系。因此,制备具有确定组成和分子结构、金属原子结合紧密的镍钼杂多酸簇,并以此为加氢催化剂活性相前驱体研究,对于深入理解常规加氢催化剂的活性相组成及反应本质具有重要意义。本论文针对清洁油品生产的高性能HDS催化剂研制,采用自组装、溶液生长等方法合成得到特定结构钼镍双金属杂多酸簇,对其结构进行解析和表征;同时以这些镍钼杂多酸簇为前驱体制备HDS催化剂,采用现代分析手段系统表征催化剂结构与性能之间关系,研究催化剂活性相的形成过程,揭示镍钼杂多酸簇为前驱体制备HDS催化剂活性高的原因。首先,采用4,4?-联吡啶配体,利用其配位作用和弱相互作用力诱导常规浸渍液中的镍钼杂多酸簇小分子自组装得到了两种层状结构的镍钼杂多酸簇(Mo2Ni和PMo11Ni)。考察了钼源、镍源、浓度、含氮有机配体、反应体系的pH值及反应温度等因素的影响,实验发现pH值是影响产物结构的重要因素。PMo11Ni的合成pH为4.3,在这一酸度下,反应体系容易解离得到[HPMo11O39]6-单缺位结构,Ni原子进而占据空缺位形成单取代的Keggin型镍钼杂多酸簇。pH升高至5.4,反应体系中的[HPMo11O39]6-单缺位结构不稳定,发生分解,最终形成Mo2Ni。由晶体结构的新颖性看,PMo11Ni是首例合成的单取代Keggin型镍钼杂多酸簇,其一维结构为独特的常青藤状;同时首次发现PMo11Ni中存在独特的杂多酸基超分子合成子结构,这一结构对于研究有机-无机杂化材料的组装具有重要意义。Mo2Ni分子结构内镍钼原子配位后交错相连,四配位钼原子与五配位钼原子稳定共存,并且五配位钼原子呈现较完美的三角双锥配位结构。其次,合成得到了Waugh结构镍钼杂多酸簇并采用离子交换法将其Ni/Mo原子比提高至0.44,为高Ni/Mo原子比的HDS催化剂前驱体合成创新了实验方法。以合成的Waugh结构镍钼杂多酸簇制备得到了HDS催化剂,避免了常规催化剂出现的焙烧后生成大的MoO3颗粒团聚、催化剂堵孔严重的缺点;基于Waugh结构镍钼杂多酸簇前驱体的HDS催化剂镍钼组分颗粒小,分散性好;同时该催化剂还原温度低,载体氧化铝与Ni、Mo金属组分的相互作用弱,高活性II型Ni-Mo-S活性相易于形成。再次,合成得到了不同Ni/Mo原子比的Strandberg结构镍钼杂多酸簇并将其制备得到HDS催化剂。常规催化剂制备过程中产生较大的(NH4)4[Ni(OH)6Mo6O18]颗粒易团聚,催化剂堵孔严重;而采用Strandberg结构镍钼杂多酸簇可以避免上述副反应,制备的催化剂镍钼组分颗粒小,分散性好。HRTEM和DRIFT结果表明,该催化剂中高活性的II型Ni-Mo-S活性相的数量多,催化剂活性高。实验详细考察了Strandberg结构镍钼杂多酸簇的硫化过程。Strandberg结构镍钼杂多酸簇易硫化,先形成NiMoO4。Ni原子先硫化形成NiS,250℃时生成MoS2,其后,NiS会在MoS2上二次分散形成Ni-Mo-S活性相。最后,详细考察了两种层状镍钼杂多酸簇PMo11Ni及Mo2Ni的硫化过程。结果表明,Mo2Ni和PMo11Ni都易于硫化,Mo2Ni在硫化温度为200℃时出现MoS2,而PMo11Ni的硫化温度为300℃。推测原因可能是由于PMo11Ni中存在大量的氢键以及较强的π···π作用使其硫化温度相对较高。XRD及XPS表明,PMo11Ni硫化后仅得到MoS2,而Mo2Ni硫化产物除了MoS2还有NixSy,原因可能是Mo2Ni中Ni含量高;Mo2Ni和PMo11Ni硫化产物中Ni-Mo-S活性相结构含量较高。此外,Mo2Ni和PMo11Ni硫化产物比表面积分别可达58.9 m2/g和49.7 m2/g。
[Abstract]:In recent years, China's eastern region severe haze, air pollution appear in the area. The study shows that the automobile exhaust is one of the main causes of haze. At the same time, in the automobile exhaust SO2 will bring greater environmental pollution. Therefore, to reduce the sulfur content of oil major automobile industry. At present, hydrodesulfurization (hydrodesulfurization, HDS) catalysts prepared by impregnation process system used contains a variety of nickel molybdenum heteropoly acid cluster small molecules. This system component is complex, it is difficult to determine the specific composition, is not conducive to the study of HDS catalyst active phase structure and structure-activity relationship. Therefore, the preparation has determined the composition and molecular structure of metal atom binding nickel molybdenum heteropoly acid cluster closely, and as hydrogenation precursor research, has important significance for understanding the normal hydrogenation activity of the catalyst composition and reaction essence. This thesis. The development of high performance HDS catalyst for the production of clean oil, using the self-assembly method solution growth synthesized specific structure of nickel molybdenum bimetallic cluster analysis and characterization of heteropoly acid and its structure; at the same time in the preparation of nickel molybdenum heteropoly acid cluster HDS catalyst precursor, the relationship between the modern analysis methods of system structure and performance characterization of catalyst the formation process, activity of catalyst, nickel molybdenum heteropoly acid revealed clusters as precursor for the preparation of HDS catalyst with high activity. First, using 4,4? - bipyridine ligand, the coordination interaction and weak interaction induced by nickel molybdenum heteropoly acid cluster small molecular self-assembly in conventional impregnation by nickel molybdenum heteropoly acid cluster two layered structure (Mo2Ni and PMo11Ni). The effects of Mo Ni source, source, concentration, nitrogen containing organic ligands, the influence factors of pH value of reaction system and reaction temperature, we found that pH Values are important factors affecting the synthesis of pH.PMo11Ni structure of the product was 4.3, the acidity, the reaction system is easy to dissociate monovacant [HPMo11O39]6- structure, and Ni atoms occupy the empty absence form Keggin type nickel molybdenum heteropoly acid mono substituted cluster.PH increased to 5.4, [HPMo11O39]6- monovacant structure in the reaction system is not stable, happen decomposition of Mo2Ni. was formed by the novelty of the crystal structure, PMo11Ni is the first synthesis of mono substituted Keggin type heteropoly acid nickel molybdenum cluster, the one-dimensional structure for the unique evergreen vines; at the same time, first discovered the existence of a unique Hybrid Polyoxometalate based supramolecular synthon PMo11Ni structure, the structure of.Mo2Ni has an important significance in molecular structure nickel molybdenum atoms after interwoven for assembly of organic inorganic hybrid materials, four coordination atoms of molybdenum and molybdenum atoms are five coordinated and stable coexistence, five coordination atoms showed a mo The perfect trigonal bipyramidal coordination structure. Secondly, synthesized Waugh structure of nickel molybdenum heteropoly acid and ion exchange method was used to cluster the Ni/Mo atomic ratio increased to 0.44, the innovation of experimental methods for high Ni/Mo atomic ratio of HDS catalyst precursor synthesis. Waugh structure heteropoly acid synthesis of nickel molybdenum clusters were prepared the HDS catalyst, avoiding the conventional catalyst calcination after the formation of large MoO3 particles agglomeration, catalyst pore blocking defects; HDS catalyst Ni Mo group Waugh structure of nickel molybdenum heteropoly acid cluster precursor particles based on small, well dispersed; and the catalyst reduction temperature is low, alumina and Ni interaction Mo metal component is weak, high activity of II type Ni-Mo-S active phase is easily formed. Thirdly, synthesized with different atomic ratios of Ni/Mo Strandberg structure of nickel molybdenum heteropoly acid and its cluster was prepared by HDS catalyst. The conventional catalyst preparation. Greatly in the process of (NH4) 4[Ni (OH) 6Mo6O18] catalyst particles agglomerate, plugging hole is serious; while using Strandberg structure of nickel molybdenum heteropoly acid clusters can avoid these side effects, the catalyst composition of the prepared nickel molybdenum particles are small, well dispersed.HRTEM and DRIFT results showed that the catalyst of high activity number the II type Ni-Mo-S active phase, high catalytic activity. The experiment investigated Strandberg structure of nickel molybdenum heteropoly acid curing process of.Strandberg cluster structure of nickel molybdenum heteropoly acid sulfide cluster easy to form a NiMoO4.Ni atom, first sulfide to form NiS, form MoS2, 250 degrees NiS later, two dispersed in the MoS2 form of Ni-Mo-S activity finally, the effects of vulcanization process with two layered nickel molybdenum heteropoly acid cluster PMo11Ni and Mo2Ni. The results showed that Mo2Ni and PMo11Ni are easy to cure, Mo2Ni in the curing temperature of MoS2 200 DEG C, and the curing temperature of PMo11Ni is 300 C. Presumably due to the presence of a large number of hydrogen bonds and strong PMo11Ni in the curing temperature is relatively high.XRD and XPS showed that PMo11Ni and MoS2 are only after curing, Mo2Ni curing product except MoS2 and NixSy, may be due to high content of Ni in Mo2Ni; Ni-Mo-S active phase structure with high Mo2Ni content and PMo11Ni sulfide in the product. In addition, Mo2Ni and PMo11Ni curing product specific surface area up to 58.9 m2/g and 49.7 m2/g. respectively.

【学位授予单位】：中国石油大学(华东)
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TE624.9

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