共查询到19条相似文献,搜索用时 140 毫秒
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四氢萘是多环芳烃加氢转化的产物或者中间体,其加氢裂解行为和规律的研究在重芳烃转化和脱除领域有着重要的意义。采用等体积浸渍法制备得到了氧化铝负载贵金属(Pt,Ir和Pd)催化剂和酸性分子筛(MOR和ZSM-5)负载铂双功能催化剂,考察了它们催化四氢萘加氢裂解的反应行为。氧化铝为载体时金属催化剂表面主要发生加氢及脱氢反应,其中金属Pt表现出最高的加氢和脱氢活性。双功能催化剂上四氢萘发生加氢裂化、异构化、氢转移及烷基化等复杂反应,金属Pt通过氢溢流作用提高了分子筛Br?nsted酸活性从而提高催化剂加氢裂解活性和选择性,但过量金属Pt会加剧苯环加氢而不利于单环芳烃的生成。分子筛孔道的限域作用对四氢萘的反应活性及产物分布有重要影响,相比Pt/ZSM-5催化剂,Pt/MOR表现出更高的裂解活性及异构化选择性。Pt/MOR催化剂上四氢萘加氢裂解主要通过异构-裂解路径进行,异构化活性及异构体构型决定了裂解活性及产物的分布。 相似文献
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采用H_2-TPD表征加氢改质催化剂上氢溢流效应,并考察氢溢流效应与柴油加氢改质催化剂性能的关联性,研究分子筛含量对加氢改质催化剂性能的影响和加氢改质催化剂的吸附-脱附氢性能,结果表明,分子筛不仅是催化剂的酸中心,而且对催化剂的加氢-脱氢性能有影响,催化剂的吸附氢量与柴油十六烷值提高值有良好的对应关系,说明催化剂的吸附氢量越高,其加氢性能越好,表明加氢功能与酸功能的良好匹配能够有效改善催化剂的加氢性能,金属组分能够决定加氢性能,加氢性能也会受分子筛的影响。 相似文献
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提升双电层超级电容器(EDLCs)能量密度的关键在于提高多孔炭电极材料的耐电压特性。然而目前提高多孔炭耐电压特性的难点是既脱除多孔炭的含氧基团、又不破坏多孔炭的层次孔结构。对此,选择镍基催化剂、利用催化剂表面发生的氢溢流现象,实现低温条件下脱除多孔炭的含氧基团,得到低氧含量的多孔炭。与H2气氛下的热还原脱氧过程相比,基于氢溢流现象的脱氧过程除了热解反应和加氢反应,还包括高活性氢原子参与的剧烈加氢反应。此外,考察了基于一级氢溢流和二级氢溢流现象的多孔炭脱氧过程的作用机制。由于镍纳米颗粒和多孔炭之间存在Ni-O-C键和Ni-C键,一级氢溢流抑制了多孔炭含氧基团的脱除。二级氢溢流避免了Ni-C键和Ni-O-C键的形成,解离的高活性氢原子可在厘米级别的长距离范围内扩散,能更有效脱除多孔炭表面的C-O、CO等含氧基团。此外,二级氢溢流脱氧后得到的多孔炭(PC-Ni-655)的碳层结构的有序度提高且孔道结构没有被破坏。当PC-Ni-655应用于EDLCs时,在3.3 V的高电压窗口下表现出较小的自放电现象和良好的循环稳定性(在1 A·g-1循环5 000圈后,容量保持率为87.9%)。 相似文献
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2015年8月镇海炼化120×10~4 t/a焦化汽油与非芳汽油混合油加氢装置增上C_5加氢预加氢单元,对预加氢单元工艺特点进行了简单介绍。预加氢单元增加后,多次出现催化剂活性下降现象,通过比较分析,指出循环氢中硫化氢含量高是导致催化剂活性下降的主要原因,通过优化工况,实现了C_5加氢单元长周期运行。 相似文献
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为提高镍基催化剂对萘系化合物的加氢活性和单环芳烃的收率,本研究以Al_2O_3为载体采用浸渍法制备了不同金属助剂修饰的系列Ni-M/Al_2O_3加氢催化剂,对催化剂的物性结构和形貌进行了表征,并考察了其在重整重芳烃中萘系化合物的加氢反应性能。结果表明,含Cu助剂的催化剂具有较佳的织构性能,金属活性组分高度分散,在C_(10)~+重芳烃加氢中具有良好的反应选择性和活性。在反应温度为140℃,压力为1.5 MPa,氢油体积比为300,新鲜油体积空速为1.0 h~(-1)的条件下,萘的转化率和四氢萘的选择性分别达到98%和99%,反应1 000 h稳定性良好。 相似文献
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探讨反应温度、压力、停留时间、氢烃比等工艺操作参数对Prime G+工艺选择性加氢和加氢脱硫的影响.在压力一定条件下,该工艺应尽可能在低温下操作.选择性加氢部分可提高氢烃比,满足适宜二烯烃加氢限制烯烃加氢并保持催化剂的稳定性.加氢脱硫部分提高氢/烃比增加了加氢脱硫的活性和选择性.在加氢脱硫的过程中要注意循环气中硫化氢的... 相似文献
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制氢原料加氢净化催化剂使用技术 总被引:3,自引:0,他引:3
介绍了制氢原料加氢精制催化剂的化学组成、物理结构与活性特点;阐述了氢解反应的影响因素和加氢催化剂选用原则;论述了加氢催化剂在装填、预硫化、投料、停工过程的生产操作要领和相关注意事项. 相似文献
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近年来,硫酸氢钠(NaHSO4)作为一种稳定的、廉价的试剂,被广泛的应用在有机合成中。其可在不同的温和条件下高产率的催化氧化反应,C—O的形成与断裂等反应类型,根据硫酸氢钠的不同形式综述了其在有机合成中的其它新应用。 相似文献
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Highly effective conversion of carbon dioxide to valuable compounds on composite catalysts 总被引:5,自引:0,他引:5
T. Inui 《Catalysis Today》1996,29(1-4):329-337
The highly effective catalytic conversion of CO2 into valuable compounds was investigated by multi-functional catalysts composed of base-metal oxides as the main components promoted by a low concentration of precious metals and gallium oxide. The desired reduced state of catalyst metal oxides for exhibiting the optimum catalytic performance could be controlled by both the hydrogen spillover on the precious metal parts and the inverse-spillover from the Ga parts. By applying those principal concepts in the catalyst structure-design, the rapid CO2 reforming of methane, the rapid CO2 methanation, the effective synthesis of methanol and/or ethanol from CO2 and H2, and selective syntheses of high quality gasoline and/or light olefins by means of one-pass conversion of CO2-H2 mixture via methanol as the intermediate product, were respectively realized. Those novel catalytic reactions would have a high potential to moderate the accumulation of CO2 come from fossil fuel combustion, while compensating the cost of hydrogen as the reducing reagent. 相似文献
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This paper is an extensive review of the literature dealing with the class of catalytic membrane reactors which involves hydrogen permeable membranes made of palladium and palladium alloys. The fundamental factors which affect hydrogen permeability are first discussed. A classification of the many reactions which have been conducted in such reactors at both laboratory and commercial scales is then presented. The various techniques for the preparation of palladium- based membranes are described and the literature on modeling and design of these reactors is also reviewed. 相似文献
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Water denitrification over catalytic membranes: hydrogen spillover and catalytic activity of macroporous membranes loaded with Pd and Cu 总被引:3,自引:0,他引:3
Mono- and bimetallic catalytic membranes were prepared via deposition of Pd and Cu onto macroporous polymeric membrane. The membranes were employed to catalyze the reaction of nitrate ions reduction by hydrogen in water. Monometallic Pd- and Cu-loaded membranes were poorly active in the reaction, while bimetallic (Pd+Cu)-loaded membranes exhibited high catalytic activity. Combination of monometallic Pd- and Cu-loaded membranes in one stack resulted in high catalytic activity, similar to that of bimetallic (Pd+Cu)-loaded membranes. The results of this study provide experimental support for a hypothesis on hydrogen spillover as a part of the molecular mechanism of nitrate ions reduction by hydrogen in water over palladium–copper catalytic system. 相似文献