高分散Ru/Si_(3)N_(4)催化剂的制备及其在CO_(2)加氢中的应用

氮化硅是一种良好的载体,具有较高的水热稳定性和机械稳定性,其表面的氨基基团能够较好地锚定金属,显著提高金属分散度。但是,商品氮化硅比表面积较低,对金属分散作用仍然有限。因此,以自制的高比表面积氮化硅(Si_(3)N_(4))为载体,通过浸渍法制备了不同Ru负载量(质量分数分别为0.5%、1.0%和2.0%)的催化剂(分别为0.5%Ru/Si_(3)N_(4)、1.0%Ru/Si_(3)N_(4)和2.0%Ru/Si_(3)N_(4)),并以商品氮化硅(Si_(3)N_(4)-C)为载体制备了2.0%Ru/Si_(3)N_(4)-C催化剂作为对照组。表征了催化剂的理化性质,测试了其在300℃、0.1 MPa下的CO_(2)加氢反应活性。结果显示,与Si_(3)N_(4)-C相比,Si_(3)N_(4)的比表面积较高(502 m^(2)/g),Si_(3)N_(4)作为载体显著提高了金属分散度,降低了金属粒径,催化剂暴露出更多的活性位点。0.5%Ru/Si_(3)N_(4)的金属粒径较小,展现出强的H_(2)吸附能力,H难以解吸,抑制了中间物种CO加氢生成CH_(4)。随着Ru负载量增加,金属粒径增大,催化剂的CH_(4)选择性更好。Ru/Si_(3)N_(4)系列催化剂中,2.0%Ru/Si_(3)N_(4)的CH_(4)选择性较高(98.8%)。空速为10000 m L/(g·h)时,0.5%Ru/Si_(3)N_(4)的CO选择性为88.2%。与2.0%Ru/Si_(3)N_(4)相比,2.0%Ru/Si_(3)N_(4)-C的金属粒径更大,活性位点较少,活性更低。2.0%Ru/Si_(3)N_(4)和2.0%Ru/Si_(3)N_(4)-C的CO_(2)转化率分别为53.1%和9.2%。Si_(3)N_(4)有效提高了金属分散度,提高了催化剂的CO_(2)加氢反应活性;通过调控Ru负载量控制催化剂金属粒径,可实现对产物CO或CH_(4)选择性的调控。

Ru@Al_(x)-mSiO_(2)中空介孔核壳型催化剂苯酚加氢脱氧制苯性能研究

为解决负载型Ru催化剂在酚类化合物加氢脱氧反应中稳定性差的问题,以含Ru的二氧化硅微球(Ru@SiO_(2))为前驱体、偏铝酸钠(NaAlO_(2))为铝源,在碱性条件下通过选择性蚀刻制备了一系列不同Al负载量(质量分数)的中空介孔核壳型催化剂Ru@Al_(x)-mSiO_(2)(x=0.5、1.0、1.5或2.0)。采用TEM、HAADF-STEM、XRD、N_(2)吸/脱附、NH_(3)-TPD和H_(2)-TPD等对催化剂的微观结构和理化性质进行了表征。以苯酚加氢脱氧制备苯为模型反应,考察了Ru@Al_(x)-mSiO_(2)催化剂的催化性能。结果表明,在60℃、2.0 MPa的反应条件下,向Ru@mSiO_(2)中引入Al能显著提高苯选择性,这是因为Al的负载提供了丰富的酸性位点,其不仅可以辅助金属Ru解离H_(2)增加苯酚加氢活性,还能够增强苯酚的脱氧性能进而提高苯选择性。在所有催化剂中,Ru@Al1.0-mSiO_(2)展现出了最高的苯酚转化率(80.5%)和苯选择性(96.5%),这归因于金属Ru与硅铝酸盐壳层间的协同效应。此外,由于中空介孔硅铝酸盐壳层的限域保护作用,Ru@Al1.0-mSiO_(2)催化剂在多次催化循环加氢脱氧实验后,仍展现出了优异的稳定性。

Ru/AC和Ru-NPs/AC催化剂对乙炔氢氯化反应催化活性的比较

针对乙炔氢氯化反应无汞催化剂的开发,Ru基催化剂是最具工业潜力的催化剂之一。结合表面积分析仪(BET)、程序升温还原(TPR)、透射电镜(TEM)和程序升温脱附(TPD),以及动力学实验探究了导致Ru/AC(AC为活性炭)和高温H_(2)处理后Ru-NPs/AC催化性能差异的原因。在排除内、外扩散的条件下,通过动力学实验判断了反应级数,初步推测了基元反应步骤和决速步骤。结果表明,Ru-NPs/AC相对于Ru/AC总反应速率更低,表观活化能更高,这是由于高温H_(2)处理后活性组分的分散度降低、Ru物种被还原,并且导致活性中心对C_(2)H_(2)的吸附性能降低。

制备方法对Ru/CeO_(2)催化氨分解性能的影响

采用共沉淀法、沉积沉淀法和浸渍法制备了Ru/CeO_(2)催化剂,利用XRD、N_(2)吸附-脱附、SEM、CO_(2)-TPD、H_(2)-TPD、H_(2)-TPR、XPS、N_(2)-TPD等方法对催化剂进行表征,并考察了催化剂的氨分解性能。实验结果表明,共沉淀法制备的Ru/CeO_(2)-CP催化剂在450℃、气时空速15000 h-1条件下,氨转化率可达80.7%,是沉积沉淀法和浸渍法制备Ru/CeO_(2)催化剂的1.3,2.7倍。共沉淀法制备的催化剂表面疏松,具有最大的比表面积,为催化剂提供了更为丰富的碱性位点。CeO_(2)载体与Ru金属间的强相互作用有利于电子从CeO_(2)向Ru的转移,提高了Ru粒子表面的电子密度,促进了N物种在催化剂表面的结合脱附。

氧化物载体对Ru基催化剂催化乙醇水蒸气重整制氢反应性能的影响

分别以ZrO_(2)、Al_(2)O_(3)、La_(2)O_(3)为载体构建Ru基催化剂,借助XRD、SEM、H_(2)-TPR、XPS、乙醇水蒸气重整制氢实验及in situ-DRIFTS等对所制催化剂进行了相关测试。结果表明,Ru/ZrO_(2)催化剂的催化性能相比Ru/Al_(2)O_(3)和Ru/La_(2)O_(3)催化剂有显著提升,使用Ru/ZrO_(2)催化剂在450℃下催化乙醇水蒸气重整制氢的乙醇转化率和氢气选择性分别达到90.0%和78.4%,Ru/ZrO_(2)催化剂具有优异的稳定性、分散性、更强的C—C键裂解能力和催化乙醇氧化脱氢性能。

Selective CO Methanation over Ru Catalysts Supported on Nanostructured TiO2 with Different Crystalline Phases and Morphology

Nanostructured titanium dioxides were synthesized via various post-treatments of titanate nanofibers obtained from titanium precursors by hydrothermal reactions. The microstructures of TiO2 and supported Ru/TiO2 catalysts were characterized with X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray analysis, and nitrogen adsorption isotherms. The phase structure, particle size, morphology, and specific surface area were determined. The supported Ru catalysts were applied for the selective methanation of CO in a hydrogen-rich stream. The results indicated that the Ru catalyst supported on rutile and TiO2-B exhibited higher catalytic performance than the counterpart supported on anatase, which suggested the distinct interaction between Ru nanoparticles and TiO2 resulting from different crystalline phases and morphology.

沉淀剂对Ru-Zn催化剂催化苯选择加氢性能的影响

采用共沉淀法制备Ru-Zn催化剂,考察了沉淀剂种类、沉淀pH值对其催化苯选择性加氢性能的影响,并采用N_(2)物理吸附、XRD、SEM、H_(2)-TPR对催化剂进行了表征。结果表明,以NaOH为沉淀剂,沉淀pH=7时制备的Ru-Zn-f催化剂性能较好,苯转化率为40%时,环己烯选择性为82.70%,且该催化剂重复使用5次后,环己烯选择性仍维持在81%以上,稳定性好,具有较好的工业应用前景。

电镀法制备Ru/Ni-foam催化剂及其催化硼氢化钠水解产氢性能研究

氢能作为一种高效、环保的可再生能源,具有广阔的应用前景,通过催化剂使硼氢化钠(Na BH4)水解产氢是一种安全、高效和实用性强的化学产氢技术。以电化学沉积方法制备的Ru/Ni-foam(Ru/NF)作为硼氢化钠水解制氢的催化剂,研究了不同的反应温度、不同的硼氢化钠浓度、不同的反应p H以及催化剂稳定性4种因素对该催化反应的影响规律。结果表明:用电镀方法得到的Ru/NF催化剂在10%(质量分数)Na OH、15%Na BH4、室温条件下,可以达到1894 m L/(min·g)的产氢速率,具有很好的实际应用前景。

Effect of the graphitic degree of carbon supports on the catalytic performance of ammonia synthesis over Ba-Ru-K/HSGC catalyst

A series of high surface area graphitic carbon materials （HSGCs） were prepared by ball-milling method. Effect of the graphitic degree of HSGCs on the catalytic performance of Ba-Ru-K/HSGC-x （x is the ball-milling time in hour） catalysts was studied using ammonia synthesis as a probe reaction. The graphitic degree and pore structure of HSGC-x supports could be successfully tuned via the variation of ball-milling time. Ru nanoparticles of different Ba-Ru-K/HSGC-x catalysts are homogeneously distributed on the supports with the particle sizes ranging from 1.6 to 2.0 nm. The graphitic degree of the support is closely related to its facile electron transfer capability and so plays an important role in improving the intrinsic catalytic performance of Ba-Ru-K/HSGC-x catalyst.

Inhibiting effect of tungstic compounds on glucose hydrogenation over Ru/C catalyst

The effect of acid component including various conventional acids and tungstic compounds on glucose hydrogenation over a series of binary catalyst system containing Ru/C catalyst was investigated. The results showed that HC1, H2SO4, H3BO3, H3PO4, and HNO3 had negligible effect, while all the tungstic compounds imposed inhibiting effects on the hydrogenation of glucose over Ru/C catalyst, and the suppressing effect followed the order of H2WO4〉HPW〉WO3〉AMT〉HSiW. This order is the same as the order of ethylene glycol （EG） yields in the one-pot conversion of glucose to EG, suggesting the important role of competition between glucose hydrogenation and retro-aldol condensation in controlling the selectivity of EG.

A highly stable and active mesoporous ruthenium catalyst for ammonia synthesis prepared by a RuCl_3/SiO_2-templated approach

Molecular nitrogen is relatively inert and the activation of its triple bond is full of challenges and of significance.Hence,searching for an efficiently heterogeneous catalyst with high stability and dispersion is one of the important targets of chemical technology.Here,we report a Ba‐K/Ru‐MC catalyst with Ru particle size of 1.5–2.5 nm semi‐embedded in a mesoporous C matrix and with dual promoters of Ba and K that exhibits a higher activity than the supported Ba‐Ru‐K/MC catalyst,although both have similar metal particle sizes for ammonia synthesis.Further,the Ba‐K/Ru‐MC catalyst is more active than commercial fused Fe catalysts and supported Ru catalysts.Characterization techniques such as high‐resolution transmission electron microscopy,N2 physisorption,CO chemisorption,and temperature‐programmed reduction suggest that the Ru nanoparticles have strong interactions with the C matrix in Ba‐K/Ru‐MC,which may facilitate electron transport better than supported nanoparticles.

Effects of Reaction Conditions on Performance of Ru Catalyst and Iron Catalyst for Ammonia Synthesis

Activated carbon-supported Ru-based catalyst and A301 iron catalyst were prepared,and the influences of reaction temperature,space velocity,pressure,and H2/N2 ratio on performance of iron catalyst coupled with Ru catalyst in series for ammonia synthesis were investigated.The activity tests were also performed on the single Ru and Fe catalysts as comparison.Results showed that the activity of the Ru catalyst for ammonia synthesis was higher than that of the iron catalyst by 33.5%-37.6% under the reaction conditions：375-400 °C,10 MPa,10000 h-1,H2︰N2 3,and the Ru catalyst also had better thermal stability when treated at 475 °C for 20 h.The outlet ammonia concentration using Fe-Ru catalyst was increased by 45.6%-63.5% than that of the single-iron catalyst at low tem-perature （375-400 °C）,and the outlet ammonia concentration increased with increasing Ru catalyst loading.

Highly selective CO methanation over amorphous Ni-Ru-B/ZrO_2 catalyst

Amorphous Ni-Ru-B/ZrO2 catalyst was prepared by the means of chemical reduction, and selective CO methanation as a strategy for CO removal in fuel processing applications was investigated over the amorphous Ni-Ru-B/ZrO2 catalyst. The result showed that, at the temperature of 210-230 ℃, the catalyst was shown to be capable of reducing CO in a hydrogen-rich reformate to less than 10 ppm, while keeping the CO2 conversion below 1.55% and the hydrogen consumption below 6.50%. ？2009 Xin Fa Dong. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Study on the Nanosized Amorphous Ru-Fe-B/ZrO_2 Alloy Catalyst for Benzene Selective Hydrogenation to Cyclohexene

A novel nanosized amorphous Ru-Fe-B/ZrO2 alloy catalyst for benzene selective hydrogenation to cyclohexene was investigated. The superior properties of this catalyst were attributed to the combination of the nanosize and the amorphous character as well as to its textural character. In addition, the concentration of zinc ions, the content of ZrO2 in the slurry, and the pretreatment of the catalyst were found to be effective in improving the activity and the selectivity of the catalyst.

Ru surface density effect on ammonia synthesis activity and hydrogen poisoning of ceria-supported Ru catalysts

Evaluating the effect of metal surface density on catalytic performance is critical for designing high-activity metal-based catalysts.In this study,a series of ceria(CeCO_(2))-supported Ru catalysts(Ru/CeCO_(2))were prepared to analyze the effect of Ru surface density on the catalytic performance of Ru/CeCO_(2) for ammonia synthesis.For the Ru/CeCO_(2) catalysts with Ru surface densities lower than 0.68 Ru nm^(-2),the Ru layers were in close contact with CeCO_(2),and electrons were transferred directly from the CeCO_(2) defect sites to the Ru species.In such cases,the adsorption of hydrogen species on the Ru sites in the vicinity of 0 atoms was high,leading to a high ammonia synthesis activity and strong hydrogen poisoning.In contrast,the preferential aggregation of Ru species into large particles on top of the Ru overlayer resulted in the coexistence of Ru clusters and particles,for catalysts with a Ru surface density higher than 1.4 Ru nm^(-2),for which Ru particles were isolated from the direct electronic influence of CeCO_(2).Consequently,the Ru-Ceth interactions were weak,and hydrogen poisoning can be significantly alleviated.Overall,electron transfer and hydrogen adsorption synergistically affected the synthesis of ammonia over Ru/CeCO_(2) catalysts,and catalyst samples with a Ru surface density lower than 0.31 Ru nm^(-2) or exactly 2.1 Ru nm^(-2) exhibited high catalytic activity for ammonia synthesis.

Ru/FeO_x catalyst performance design: Highly dispersed Ru species for selective carbon dioxide hydrogenation

A series of Ru/FeOx catalysts were synthesized for the selective hydrogenation of CO2to CO.Detailed characterizations of the catalysts through X‐ray diffraction,X‐ray photoelectron spectroscopy,transmission electron microscopy,and temperature‐programmed techniques were performed to directly monitor the surface chemical properties and the catalytic performance to elucidate the reaction mechanism.Highly dispersed Ru species were observed on the surface of FeOx regardless of the initial Ru loading.Varying the Ru loading resulted in changes to the Ru coverage over the FeOx surface,which had a significant impact on the interaction between Ru and adsorbed H,and concomitantly,the H2activation capacity via the ability for H2dissociation.FeOx having0.01%of Ru loading exhibited100%selectivity toward CO resulting from the very strong interaction between Ru and adsorbed H,which limits the desorption of the activated H species and hinders over‐reduction of CO to CH4.Further increasing the Ru loading of the catalysts to above0.01%resulted in the adsorbed H to be easily dissociated,as a result of a weaker interaction with Ru,which allowed excessive CO reduction to produce CH4.Understanding how to selectively design the catalyst by tuning the initial loading of the active phase has broader implications on the design of supported metal catalysts toward preparing liquid fuels from CO2.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences toward preparing liquid fuels from CO2.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved.

Selective CO methanation over amorphous Ni-Ru-B/ZrO_2 catalyst for hydrogen-rich gas purification

Amorphous Ni-Ru-B/ZrO2 catalysts were prepared by chemical reduction method. The effects of Ni-Ru-B loading and Ru/Ni mole ratio on the catalytic performance for selective CO methanation from reformed fuel were studied, and the catalysts were characterized by BET, ICP, XRD and TPD. The results showed that Ru strongly affected the catalytic activity and selectivity by increasing the thermal stability of amorphous structure, promoting the dispersion of the catalyst particle, and intensifying the CO adsorption. For the catalysts with Ru/Ni mole ratio under 0.15, the CO methanation conversion and selectivity increased significantly with the increasing Ru/Ni mole ratio. Among all the catalysts investigated, the 30 wt% Ni-Ru-B loading amorphous Ni61Ru9B30/ZrO2 catalyst with 0.15 Ru/Ni mole ratio presented the best catalytic performance, over which higher than 99.9% of CO conversion was obtained in the temperature range of 230℃-250℃, and the CO2 conversion was kept under the level of 0.9%.

A Novel Ultrafine Ru-B Amorphous Alloy Catalyst for Glucose Hydrogenation to Sorbitol

An ultrafine Ru-B amorphous alloy catalyst was prepared by chemical reduction with KBH4 in aqueous solution, which exhibited perfect selectivity to sorbitol (~100%) and very high activity during the liquid phase glucose hydrogenation, much higher than the corresponding crystallized Ru-B, the pure Ru powder, and Raney Ni catalysts. The correlation of the catalytic activity to both the structural and surface electronic characteristics was discussed briefly.

Tuned selectivity and enhanced activity of CO_(2) methanation over Ru catalysts by modified metal-carbonate interfaces

Carbonate-modified metal-support interfaces allow Ru/MnCO_(3) catalyst to exhibit over 99% selectivity,great specific activity and long-term anti-CO poisoning stability in atmospheric CO_(2) methanation.As a contrast,Ru/MnO catalyst with metal-oxide interfaces prefers reverse water-gas shift rather than methanation route,along with a remarkably lower activity and a less than 15% CH_(4) selectivity.The carbonatemodified interfaces are found to stabilize the Ru species and activate CO_(2) and H_(2) molecules.Ru-CO^(4) species are identified as the reaction intermediates steadily formed from CO_(2) dissociation,which show moderate adsorption strength and high reactivity in further hydrogenation to CH_(4),Furthermore,carbonates of Ru/MnCO_(3) are found to be consumed by hydrogenation to form CH_(4) and replenished by exchange with CO_(2),which are in a dynamic equilibrium during the reaction.Modification with surface carbonates is proved as an efficient strategy to endow metal-support interfaces of Ru-based catalysts with unique catalytic functions for selective CO_(2) hydrogenation.

CO_2 methanation over TiO_2–Al_2O_3 binary oxides supported Ru catalysts

TiO_2 modified Al_2O_3 binary oxide was prepared by a wet-impregnation method and used as the support for ruthenium catalyst. The catalytic performance of Ru/TiO_2–Al_2O_3catalyst in CO_2 methanation reaction was investigated. Compared with Ru/Al_2O_3 catalyst, the Ru/TiO_2–Al_2O_3catalytic system exhibited a much higher activity in CO_2 methanation reaction. The reaction rate over Ru/TiO_2–Al_2O_3 was 0.59 mol CO_2·(g Ru)1·h-1, 3.1 times higher than that on Ru/Al_2O_3[0.19 mol CO_2·(gRu)-1·h-1]. The effect of TiO_2 content and TiO_2–Al_2O_3calcination temperature on catalytic performance was addressed. The corresponding structures of each catalyst were characterized by means of H_2-TPR, XRD, and TEM. Results indicated that the averaged particle size of the Ru on TiO_2–Al_2O_3support is 2.8 nm, smaller than that on Al_2O_3 support of 4.3 nm. Therefore, we conclude that the improved activity over Ru/TiO_2–Al_2O_3catalyst is originated from the smaller particle size of ruthenium resulting from a strong interaction between Ru and the rutile-TiO_2 support, which hindered the aggregation of Ru nanoparticles.