The long-term performance of Co/SiO2 catalysts in CO hydrogenation

The activity in terms of conversion of carbon monoxide was determined for Co/SiO₂ catalysts in CO hydrogenation over a reaction time of 120 h. The catalysts were prepared from nitrate (N) and carbonyl (CO) precursors. The conversion decreased rapidly during the first five hours, and thereafter moderately at a rate related to dispersion, i.e. the higher the dispersion the higher the rate of decrease. The active sites were blocked by wax and coke formed in the reaction, although some agglomeration of particles probably took place on the Co(CO)/SiO₂ catalysts. More carbon was accumulated on Co(CO)/SiO₂ than on Co(N)/SiO₂ during the reaction suggesting a need for frequent regeneration. The reduction-oxidation-reduction treatments indicated, however, that the regenerability of the Co(CO)/SiO₂ in terms of hydrogen uptake is poor, although the amounts adsorbed still remained higher than those for Co(N)/SiO₂.     

Characterization of magnesium promoted Co/SiO2 catalysts

Co/SiO₂, Mg-Co/SiO₂, and Co-Mg/SiO₂ catalysts were prepared from nitrate precursors to get more insight into the effect of magnesium promotion on the cobalt catalyst. The desorption characteristics and reactivity of the catalysts towards synthesis gas were evaluated in a pulse micro reactor connected to an on-line quadrupole mass spectrometer. The presence of MgO both decreased the extent of reduction and increased the dispersion of cobalt. The reactivity results suggested that MgO promotion created new types of active sites, probably at the edge sites of cobalt and magnesium. The highest activity per metallic site available was obtained with a Mg: Co molar ratio of 1/2, i.e. with a high amount of edge sites. In accordance with previous results the formation of CO₂ was clearly suppressed in the presence of MgO, and methanol was formed in trace amounts.     

新型FeCo双金属催化剂催化CO2加氢制低碳烯烃

CO₂加氢制备低碳烯烃是实现C1资源高值化利用的有效途径。为提高低碳烯烃选择性,以Fe-MOF为主体,对苯二甲酸为骨架配体,构建了金属比例可控的铁钴双金属催化剂（FeCo/MC）,阐明了双金属的协同作用及金属比例对加氢性能的影响。发现Co的添加可以增加催化剂表面碱性位而显著地改善CO₂吸附,促进铁的碳化并通过费托反应的CO消耗促进逆水煤气反应。同时,适宜的铁钴比有助于改善金属间亲密度,从而通过合理串联活性位以获取最佳的低碳烯烃选择性和尽可能低的甲烷选择性,铁钴比为6时CO₂转化率为32.72%,低碳烯烃选择性最高达到37.14%。     

Catalytic hydrogenation of CO over the doped perovskite oxide YBa2Cu3O7-x catalysts

Perovskite oxide structured YBa₂Cu₃O₇-x(YBCO) has been first prepared by carbonate precipitation and then modified with palladium or ruthenium by impregnation on the perovskite oxide, while cobalt was co-precipitated simultaneously in the same pH range with perovskite oxide. After characterization the catalysts were used in the temperature range 300–450°C, in the pressure range 1–9 atmospheres and for H₂/CO ratios in the range 1–4 in a differential plug flow reactor for the hydrogenation of carbon monoxide to give hydrocarbons. The perovskite oxide (YBCO) 20% (w/w) and doped 2% (w/w) cobalt oxide catalyst were prepared by the wet chemical method from their nitrate solutions and oxidized at 950°C. Perovskite oxide (Dursun, G. & Winterbottom, J. M., J. Chem. Technol Biotechnol. 63 (1995) 113–16) was also doped with palladium and ruthenium metal by impregnation followed by oxidation at 250°C. The catalysts prepared were characterized by using TemperatureProgrammed Reduction (TPR) to observe the reduction temperature and also to measure total and metal surface area. The modified perovskite oxide on alumina, ruthenium- and cobalt-doped catalysts, has been shown to give a better conversion and also selectivity towards saturated hydrocarbons compared with palladium-doped catalyst. The temperature effect of these catalysts is more consistent, giving a steady increase of conversion with increasing temperature. Although increase of pressure increases the conversion, it causes very little change in product distribution. The activation energy of palladium- and ruthenium-doped, and cobalt co-precipitated catalysts for the reaction has been measured to be 55 kJ mol⁻¹, 75 kJ mol⁻¹ and 50 kJ mol⁻¹ respectively. A general rate equation of the form r=k[H₂]^m[CO]ⁿ has been observed and found to be applicable at the pressures and temperatures used for the catalytic system studied and found to be m≌1·0 for palladium-doped, m≌1·2 for ruthenium-doped and m≌0·95 for cobalt co-precipitated catalysts as n becomes zero or negligibly less than zero. The mechanism of reaction to produce hydrocarbons from syngas has been deduced from the results. It appeared that the carbon monoxide insertion mechanism has been more evident for palladium-doped catalysts whereas the carbide mechanism plays the main role for the ruthenium-doped and cobalt co-precipitated catalysts. © 1998 Society of Chemical Industry     

钌炭催化剂的制备及其在芳环加氢反应中的应用

芳环加氢反应是最重要的合成反应之一,钌炭催化剂在芳环加氢反应中具有优异的催化性能。综述钌炭催化剂的制备方法和载体性质对钌炭催化剂的影响以及钌炭催化剂在苯、苯甲酸和对苯二甲酸二甲酯等芳环加氢反应中的应用进展。负载型钌炭催化剂的制备方法主要有浸渍法、沉淀法和升华法,超声辅助浸渍法可将大部分钌纳米粒子引入到炭载体的孔道内部,得到限域型负载钌炭催化剂。而镶嵌式钌炭催化剂主要是指通过原位炭化的方法将钌粒子部分镶嵌在炭的孔壁上,一步得到钌炭催化剂,其制备方法主要有软模板剂法和硬模板剂法。除制备方法外,炭的骨架结构、表面性质及氮掺杂对钌炭催化剂的性能影响也较大。镶嵌式钌炭催化剂具有钌纳米粒子和炭载体之间的相互作用强、催化剂抗流失及烧结性能好,在芳环加氢反应中表现出卓越的催化性能和稳定性。随着新制备技术的出现,新型镶嵌式钌炭催化剂将可能实现产业化。     

Effect of metal dispersion on CO hydrogenation over Pd/HZSM-5 catalysts

Pd/HZSM-5 catalysts prepared by ion-exchange method using Pd(NH₃) ₄ ²⁺ were calcined and reduced at different temperatures to provide different metal dispersions. The effect of Pd dispersion on CO adsorption characteristics and acidity were observed through FT-IR study. Methanol and dimethyl ether were the main products in CO hydrogénation over Pd/HZSM-5 catalyst with small Pd particles on which CO was weakly adsorbed, while the selectivity to methane increased with metal sizes.     

CO加氢合成低碳醇用CuCo/SiO2催化剂的反应性能研究

采用共浸渍法制备了CuCo/SiO₂双金属催化剂,以CO加氢合成低碳醇为模型反应考察了不同反应温度、压力和空速下催化剂的反应性能,并采用X射线（XRD）、热重分析(TG)和程序升温还原(TPR)技术对催化剂进行了表征。结果表明,（533～563） K,随反应温度升高,CO 转化率从14.9%增加到40.4%,醇类的时空收率呈现先增大再减小的趋势, 553 K取得最优值;升高反应压力能显著提高醇类的选择性;（1 200 ~4 800） h^-1,随空速增加,CO 加氢活性降低,醇类产物的选择性显著增加, 使时空收率提高。〖JP2〗XRD结果表明,反应前催化剂主要成分为CuO、Co₃O₄和CuCo尖晶石物相,反应后则为Cu⁰和Co²⁺。TG和TPR结果表明,前驱体的适宜焙烧温度为623 K,催化剂的原位还原温度为593 K。     

核壳纳米材料制备及其在CO/CO2热催化加氢中的应用

采用多种包覆方法制备的核壳纳米材料具有许多优于单一材料的性能,其独特的核壳结构可产生出色的协同作用和新特性,现在已经广泛用于催化、吸附、储能与转化、药物传递和光学等领域。在CO/CO₂热催化加氢反应过程中,壳层包覆可对核体粒子表面进行修饰,如改变核体的表面电荷、官能团和反应特性等,从而提高核体的稳定性与分散性。核壳催化剂可形成封闭的内部微环境以富集反应物,提高反应速率和催化活性。部分核壳催化剂甚至还能实现接力催化,并提高体系内的能量利用率。主要介绍了核壳纳米材料的常用制备方法,不同类型壳层包覆的核壳催化剂在CO/CO₂热催化加氢中的应用进展,并对该领域的未来发展进行了展望。     

Promoting effects of thoria and molybdena on cobalt catalysts in the hydrogenation of CO

Thoria- or molybdena-promoted Co/silica (alumina) catalysts were prepared by co-impregnation. The catalysts were characterized with temperature programmed reduction and temperature programmed surface reaction techniques and hydrogenation of carbon monoxide. Thoria enhanced not only the activity but also the selectivity of olefins and long-chain hydrocarbons. Molybdena effectively promoted only the activity, but did not alter the product distribution pattern. Thoria and molybdena exhibited a tendency to spread onto and to interact intimately with alumina; the promoting effects on alumina were much less pronounced than on silica.     

CO/CO2加氢制芳烃的研究进展

将CO/CO₂直接转化为芳烃是一种极具挑战性的非石油路线合成途径。本文主要对CO/CO₂通过不同反应途径制取芳烃过程中复合催化剂的开发和反应机理的研究进展进行了综述。阐述了利用反应耦合思想,构筑的复合催化剂在CO/CO₂的高效转化和产物调控等方面取得了突破性的进展。重点介绍了复合催化剂用于CO加氢制芳烃主要的两种反应途径,活性金属的类别、分子筛的结构与酸性和活性组分的组装方式与接触度对CO₂加氢制芳烃催化性能的影响。指出协同加氢与芳构化反应活性的匹配是影响催化剂性能的关键。提出开发高效稳定的催化剂用于提高CO/CO₂的转化率和芳烃产物的产率以及反应机理的探索仍然是未来研究的重点。     

硅藻土负载Co-Fe肉桂醛选择加氢催化剂的制备与表征

以肉桂醛选择性加氢制肉桂醇为探针反应,通过制备不同Fe含量的Co-Fe/硅藻土催化剂并进行催化性能评价。结合XRD、SEM和正电子寿命谱等进行表征,结果表明,Fe对Co₃O₄晶体的完整程度产生影响,导致晶体缺陷数增加。Fe引入使活性助分在载体硅藻土表面分散性更好,分散的单层性明显,负载在硅藻土上催化剂的晶粒粒径也有变小趋势。     

Co/TiO2-SiO2催化剂上肉桂醛选择性加氢制备肉桂醇

采用等体积浸渍法制备了系列Co/TiO₂-SiO₂催化剂,用于肉桂醛选择性加氢制备肉桂醇反应体系。系统考察了钴含量、焙烧温度、还原温度、稀土助剂等参数变化对钴催化剂选择性加氢性能的影响。结果表明,钴催化剂的活性和选择性与其表面钴的晶粒度有一定关系,较大尺寸的钴物种对肉桂醛加氢有利。当Co含量为15%、焙烧温度和还原温度均为823 K时,催化剂表现出良好的加氢性能。稀土助剂La和Ce的引入能改善Co /TiO₂-SiO₂催化剂表面活性组分钴的分散度,提高了钴催化剂的加氢性能。     

Co/SiO2 catalysts prepared from Co2(CO)8 for CO hydrogenation into alcohols and hydrocarbons: characterization by magnetic methods and temperature-programmed hydrogenation

The hydrogenation of carbon monoxide over Co/SiO₂ catalysts obtained by reduction of precursors prepared by the reaction of dicobaltoctacarbonyl with silica gives rise to a mixture of alcohols and hydrocarbons. The chain growth probability for hydrocarbon synthesis is similar to that observed over conventional catalysts prepared by the ammonia method (=0.74) with a comparable metal dispersion (metal particle size 4 nm). Alcohol formation yields a smaller chain growth probability (=0.42). Magnetic measurements have shown that in the latter catalyst, small cobalt clusters (1 nm) are likely to be present together with the cobalt particles (4 nm), this observation reconciles apparently conflicting results from the literature. It has been speculated that alcohol formation might be related to the presence of these clusters according to a concerted mechanism. Furthermore, the observation of large amounts of acetates by temperature-programmed hydrogenation, not detected in hydrocarbon selective catalysts, suggests that they may play a role in ethanol synthesis.     

Co/TiO2-SiO2催化剂上肉桂醛选择性加氢制备肉桂醇

采用等体积浸渍法制备了系列Co/TiO₂-SiO₂催化剂,用于肉桂醛选择性加氢制备肉桂醇反应体系。系统考察了钴含量、焙烧温度、还原温度、稀土助剂等参数变化对钴催化剂选择性加氢性能的影响。结果表明,钴催化剂的活性和选择性与其表面钴的晶粒度有一定关系,较大尺寸的钴物种对肉桂醛加氢有利。当Co含量为15%、焙烧温度和还原温度均为823 K时,催化剂表现出良好的加氢性能。稀土助剂La和Ce的引入能改善Co /TiO₂-SiO₂催化剂表面活性组分钴的分散度,提高了钴催化剂的加氢性能。     

以大孔二氧化硅为载体的Cs／SiO2催化剂的制备及表征

提出一种以大孔SiO2为载体,负载碱金属的催化材料的制备方法。用无乳化剂乳液聚合法合成聚苯乙烯（PS）微球为模板剂,对SiO2进行扩孔,制备大孔SiO2载体,用微波负载法负载碱金属Cs,并对催化剂进行相关表征。结果表明,粒径为200～250nm左右的PS为较佳模板剂,扩孔后负载碱金属Cs量为13．28％,制得的Cs／SiO2催化剂孔径约为250nm,比表面积为2．965×10^2m^2·g^-1,总孔容积为1．806cc·g^-1,且在催化合成丙烯酸甲酯的反应中有较高的活性,酯收率在50％以上。     

载体对Ni基催化剂催化蒽醌加氢活性的影响

研究了载体对Ni基催化剂用于蒽醌法制备H₂O₂加氢活性的影响,同时对比了骨架镍的催化活性,考察Ni负载量对催化剂活性的影响。结果表明,负载在SiO₂上的催化剂比负载在γ-Al₂O₃上的催化活性高,对于Ni/SiO₂催化剂,Ni负载质量分数28.57%～50%时,加氢活性较高,按单位质量纯Ni上H₂O₂产量计算,Ni/SiO₂优于骨架镍催化剂,Ni负载量过高时,加氢活性降低。2-乙基蒽醌在Ni/SiO₂催化剂上的加氢为结构敏感型反应,当Ni在SiO₂的分散度达到约18%时,催化活性较佳。     

Si掺杂对Cu/ZrO2催化CO2加氢制甲醇性能的影响

为了提高Cu/ZrO₂催化剂在二氧化碳加氢制甲醇中的催化活性,制备了一系列不同Si/Zr的Si-ZrO₂载体并负载5%（质量分数）Cu得到了Cu/Si-ZrO₂催化剂。对所制备的催化剂进行了X射线衍射（XRD）、N₂物理吸脱附（BET）、X射线光电子能谱（XPS）、氢气程序升温还原（H₂-TPR）、二氧化碳程序升温脱附（CO₂-TPD）及高分辨透射电子显微镜 （HRTEM） 的表征。结果表明,Si的掺杂使得Cu/ZrO₂体系获得了稳定的晶相,大的比表面积和更多的碱性位点,尤其是中强碱性位点,同时产生了更多的氧空位,促进了CO₂的吸附和转化,因此得到了更高活性的催化剂。当Si与Zr的摩尔比为0.2时,在质量空速为6000 ml·g^-1·h^-1,温度为220℃、压力为3.0 MPa,V（H₂）∶V（CO₂）=3∶1（体积比）条件下,催化剂的CO₂转化率为4.6%,CH₃OH选择性为85%。     

Si掺杂对Cu/ZrO2催化CO2加氢制甲醇性能的影响

为了提高Cu/ZrO₂催化剂在二氧化碳加氢制甲醇中的催化活性,制备了一系列不同Si/Zr的Si-ZrO₂载体并负载5%（质量分数）Cu得到了Cu/Si-ZrO₂催化剂。对所制备的催化剂进行了X射线衍射（XRD）、N₂物理吸脱附（BET）、X射线光电子能谱（XPS）、氢气程序升温还原（H₂-TPR）、二氧化碳程序升温脱附（CO₂-TPD）及高分辨透射电子显微镜 （HRTEM） 的表征。结果表明,Si的掺杂使得Cu/ZrO₂体系获得了稳定的晶相,大的比表面积和更多的碱性位点,尤其是中强碱性位点,同时产生了更多的氧空位,促进了CO₂的吸附和转化,因此得到了更高活性的催化剂。当Si与Zr的摩尔比为0.2时,在质量空速为6000 ml·g^-1·h^-1,温度为220℃、压力为3.0 MPa,V（H₂）∶V（CO₂）=3∶1（体积比）条件下,催化剂的CO₂转化率为4.6%,CH₃OH选择性为85%。     

Carbon monoxide hydrogenation over cobalt catalyst in a tube-wall reactor: Part 1. Experimental studies

Effects of temperature (250?275°C), pressure (0.1-1.03 MPa) and feed gas exposure velocity (139-722 μm/s) were studied on carbon monoxide hydrogenation in a tube-wall reactor using plasma-sprayed cobalt catalyst. The specific catalytic activity and hydrocarbon selectivity increased with an increase in pressure and temperature and a decrease in the exposure velocity. The results showed that the formation of olefins especially ethylene and propylene was favored at low pressures, low temperatures and high exposure velocities. This catalyst was found to be selective for C₅⁺ hydrocarbons (27-34 wt.%) at increased pressures (0.69-1.03 MPa).     

碳包裹非贵金属催化剂的制备及其在催化加氢中的应用

实现非贵金属催化剂在加氢反应中的广泛应用对工业催化领域具有重要意义,新型碳包裹非贵金属催化剂因其优异的结构稳定性和催化加氢性能而备受关注。本文综述了近年来碳包裹非贵金属催化剂及其制备方法的研究进展,归纳总结了不同制备方法对碳包裹结构的影响以及其优缺点,并介绍了碳包裹非贵金属催化剂在硝基类芳烃、羰基类芳烃、苯酚、喹啉加氢以及费托合成等加氢反应中的催化性能以及稳定性表现。文中提出：目前该催化剂亟需解决的问题是实现金属粒子尺寸以及碳壳结构的可控调变,今后的一个研究方向是进一步探索能够简便调节催化剂结构并且经济可行的制备方法。