【作者】 傅武俊；

【导师】 郑晓玲；

【作者基本信息】 福州大学 ， 无机化学， 2003， 硕士

【摘要】 本文分别以多种活性炭、氧化铝为载体，采用浸渍法制备一系列氨合成钌催化剂，利用物理吸附、化学吸附、元素分析和扫描电镜等表征手段，结合氨合成活性评价，探索了载体、助剂、制备过程及使用条件对钌催化剂氨合成催化活性的影响。结果表明，具有高纯度、高比表面、大孔容及合理孔分布的活性炭载体有利于活性组分有效均匀的分散，制备出高活性的氨合成钌催化剂。对于Ru/AC催化剂，碱土金属类助剂的促进作用要优于碱金属类助剂，而且二者的最佳用量不同。与单助剂钌催化剂相比，双助剂钌催化体系的催化活性更高，采用分步浸渍法比共浸渍法更为有效。钌金属为贵金属，从性价比方面考虑，钌负载量以4 wt%为佳。RuCl3/AC在较低温度下就能进行脱氯还原，为避免高温下炭载体的流失和钌粒子的烧结，脱氯还原温度不宜过高。模拟工业氨合成条件，考察温度、压力、空速对Ru/AC催化剂的影响。结果表明，钌催化剂在低温、低压下使用显示出了良好的催化活性。在反应压力较高时，升高温度有助于克服钌催化剂在高压下的氢吸附现象。以氧化铝为载体的氨合成钌催化剂，活性相的分散并不完全取决于氧化铝载体的比表面，较大的比孔容、合理的孔径分布是决定金属分散度的主要因素。CsNO3和Ba(NO3)2均是Ru/Al2O3催化剂的有效助剂；稀土硝酸盐Sm(NO3)3的促进效果较差，但若用其对氧化铝载体进行改性处理，可有效的抑制钌催化剂高压下的强氢吸附，显著提高钌催化剂的活性。更多还原

【Abstract】 Many kinds of activated carbon and alumina were used as the supports to prepare a series of ruthenium catalysts. Physical adsorption, chemical adsorption, elemental analysis, scanning electron microscope were carried out to characterize the properties of supports and ruthenium catalysts. The ammonia synthesis activities were also measured. It has attracted much attention to study the effect of supports, promoter, and preparation process and reaction condition on the catalytic properties of ruthenium catalyst for ammonia synthesis.When activated carbon was used as support to prepare the ruthenium catalyst, it was found that the ammonia synthesis activity of Ru/AC catalyst was directly related to the properties of activated carbon. The ruthenium catalyst supported by the special activated carbon, which had high purity, high surface area, large pore volume and proper pore structure, usually had high catalytic properties for ammonia synthesis. A series of alkaline and alkaline-earth metal were used as promoter to prepare the single-promoted or double-promoted. For the single-promoted Ru/AC catalyst, it was confirmed that alkaline-earth metal are more effective in ammonia synthesis than alkaline metal promoter. For the double-promoted catalyst, it was more active when the promoters were impregnated step by step than that the promoters were co-impregnated. For Ru/AC catalyst, Ru loading affected the catalytic activity obviously. With the Ru loading increased, the activity of catalyst also increased, but the dispersion of the Ru decreased reversely. The optimal Ru loading was 4 wt%. In order to avoid sintering of the Ru particle and the methanation of the carbon<WP=5>support, the ruthenium catalyst should be reduced at a relative low temperature.Under the reaction condition similar with the industrial application, the effects of the reaction temperature, pressure and GHSV on the ruthenium catalyst were also investigated. The result showed that the Ru catalyst had relatively high catalytic properties at a low temperature and under a middle pressure. The enhancement of reaction temperature could weaken a strong adsorption of hydrogen in high pressure and would be beneficial to improve the activity of the ruthenium catalyst for ammonia synthesis.Ruthenium catalyst supported on alumina was also studied. The result showed that Ru dispersion of catalyst was not completely determined by surface area of the support, the large pore volume and fitting pore size were the main factors of affecting the Ru dispersion. Barium and cesium nitrate were proved to be effective promoter for Ru/Al2O3 catalyst. If used to modify the Al2O3 support, Sm(NO3)3 would be more effective than being the promoter singly.更多还原