镍基催化剂上乙醇水蒸气重整反应的研究

考察了载体对Ni催化剂乙醇水蒸气重整制氢反应性能的影响。结果表明,Ni/CeO2催化剂具有较好的低温活性和氢气选择性。对Ni担载量和焙烧温度考察发现,400℃焙烧的15%NiCeO2催化剂具有较好的催化性能;继续升高焙烧温度引起NiO和CeO2粒子的显著增大,导致对氢气选择性的降低。较小的Ni和CeO2粒子有利于乙醇水汽重整反应的进行,而大的粒子倾向于乙醇的分解反应。 350℃时,在反应过程中分别添加CO、CO2和CH4的结果表明没有发生CO和CO2甲烷化反应,而发生了一定程度的CH4水汽重整反应。     

Ethanol steam reforming over Ni-Cu/Al2O3-MyOz （M = Si, La, Mg, and Zn） catalysts

Ni-based catalysts doped with copper additives were studied on their role in ethanol steam reforming reaction.The effects of Ca content,support species involving Al2O3-SiO2,Al2O3-MgO,Al2O3-ZnO,and Al2O3-La2O3,on the catalytic performance were studied.Characterizations by TPR,XRD,NH3-TPD,XPS,and TGA indicated that catalysts 30Ni5Cu/Al2O3-MgO and 30NiSCu/Al2O3-ZnO have much higher H2 selectivity than 30NiSCu/Al2O3-SiO2,as well as good coke resistance.H2 selectivity for 30Ni5Cu/Al2O3-MgO catalyst was 73.3% at 450℃ and increased to 94.0% at 600 ℃,whereas for 30NiSCu/Al2O3-ZnO catalyst,the H2 selectivity was 63.6% at 450 ℃ and 95.2% at 600 ℃.These Al2O3-MgO and Al2O3-ZnO supported Ni-Cu bimetallic catalysts may have important applications in the production of hydrogen by ethanol steam reforming reactions.     

Sorption-enhanced steam methane reforming over Ni/Al2O3/KNaTiO3 bifunctional material

The performance of a new lab-made bifunctional material Ni/Al₂O₃/KNaTiO₃ for producing high purity H₂ via sorption-enhanced steam methane reforming (SESMR) was investigated. A series of bifunctional materials with 10 wt% Ni loading but different wt% ratios of KNaTiO₃ and Al₂O₃ was prepared by wetness impregnation method. All the materials were calcined at 700 °C for 3 hours and screened for their catalytic activity in a continuous flow fixed-bed reactor. The material containing 50 wt% each of KNaTiO₃ and Al₂O₃ (designated as HM) was found to be the best choice. The optimum process parameters for the production of high purity H₂ were determined: temperature = 700 °C, steam to carbon (S/C) molar ratio = 6 and gas-hourly space velocity (GHSV) = 2000 cm³ g^-1 h^-1. The values of CH₄ conversion, H₂ yield and H₂ purity were 87, 87 and 90%, respectively, at the optimum reaction conditions. The adsorption capacity of HM was found to be 14.7 wt%. With a breakthrough time of 10 min, the material was stable for 8 adsorption-desorption cycles. The regeneration of HM was achieved with N₂ gas at the same reaction temperature. Overall, the activity of this material for SESMR was very promising.     

Carbon dioxide reforming of methane on monolithic Ni/Al2O3-based catalysts

Nickel-alumina catalysts supported on cordierite monoliths of honeycomb structure surpass essentially the conventional granulated ones with respect to the output in carbon dioxide reforming of methane. Adjusting the surface acid-base properties of catalysts by introduction of alkali metal (Na, K) oxides inhibits the carbonization and as a result, improves the operational stability of these catalysts. An effect of promotion of nickel-alumina based composite doped by lanthanum oxide is found. This effect, caused by an additional route for the CO2 activation on Ni-La2O3/Al2O3/cordierite catalyst, is displayed in increase of methane conversion under conditions of an oxidant excess.     

A unique microwave effect on the microstructural modification of Cu/ZnO/Al2O3 catalysts for steam reforming of methanol

A short time (3-10 min) of microwave irradiation on the CuO/ZnO/Al2O3 oxide precursor can result in a unique tailored microstructural modification on the catalyst, leading to a significantly enhanced performance for H2 production from steam reforming of methanol.     

Propane oxidation with chemically bound oxygen on Pt/TiO2/Al2O3 and Pt/CeO2/Al2O3 catalysts

Possible mechanisms are suggested for propane oxidation on Pt/TiO₂/Al₂O₃ and Pt/CeO₂/Al₂O₃ catalysts in the cyclic reactant supply mode. As compared to the steady-state process, the process conducted as catalyst oxidation-reduction cycles results in a very different product composition: it is more selective toward partial oxidation products and yields much smaller amounts of complete oxidation products. It is established by isothermal and temperature-programmed oxygen desorption that, under the reaction conditions examined, the oxygen desorbed from the catalyst surface into the gas phase makes a negligible contribution to propane oxidation. It is proved by XPS that propane oxidation is due to the chemically bound oxygen of the catalyst. The hypothetical mechanism of the process includes propane activation on Pt followed by the transfer of the activated species to the oxygen-storing component (TiO₂ or CeO₂), where the intermediates are oxidized by chemically bound oxygen.     

Characterization of La-promoted Ni/Al2O3 catalysts for hydrogen production from glycerol dry reforming

In the current paper, dry (CO₂)-reforming of glycerol, a new reforming route, was carried out over alumina (Al₂O₃)-supported, non-promoted and lanthanum-promoted nickel (Ni) catalysts. Both sets of catalysts were synthesized via a wet co-impregnation procedure. Physicochemical characterization of the catalysts showed that the promoted catalyst possessed smaller metal crystallite size, hence higher metal dispersion compared to the virgin Ni/Al₂O₃ catalyst. This was also corroborated by the surface images captured by the FESEM analysis. From temperature-programmed calcination analysis, the derivative weight profiles revealed two peaks, which represent a water elimination peak at a temperature range of 373 to 473 K followed by nickel nitrate decomposition from 473 to 573 K. In addition, BET surface area measurements gave 85.0 m²·g⁻¹ for the non-promoted Ni catalyst, whilst the promoted catalysts showed an average of 1% to 6% improvement depending on the La loadings. Significantly, reaction studies at 873 K showed that glycerol dry reforming successfully produced H₂. The 2%La-Ni/Al₂O₃ catalyst, which possessed the largest BET surface area, gave an optimum H₂ generation (9.70%) at a glycerol conversion of 24.5%.     

一种新型结构的CO2重整CH4催化剂的制备与催化性能研究

研制高效、稳定的Ni基催化剂一直是CO2重整CH4反应过程的重点之一。本文采用微波技术和真空浸渍法制备了ZrO2单层分布的负载型ZrO2／Al2O3复合载体和活性物种单层分布的Ni／ZrO2／Al2O3催化剂,并利用XRO、FT-IR、TPR、TPD、BET等技术研究了新型结构催化剂的分散状态、体相结构、表面性能、催化活性及稳定性。结果表明,催化剂在CO2重整CH4反应体系中具有良好的催化活性和稳定性。     

Ni/Al2O3和Fe/Al2O3催化剂催化乙醇水蒸气重整制氢的对比研究

甲醇、乙醇等低碳醇催化重整制氢是燃料电池氢源的重要技术之一.乙醇和甲醇相比,更容易存储,低毒且可以从生物质经发酵获得[1,2].乙醇可以通过裂解、部分氧化、水蒸气重整和氧化重整等途径制氢[3~6].已有的文献表明,Pt、Ru、Rh、Pd等贵金属可有效地催化乙醇重整反应,载体多选用     

Pt/Co3O4/3DOM Al2O3：甲苯燃烧的高效催化剂

与硫氧化物、氮氧化物、一氧化碳以及悬浮颗粒一样,大部分挥发性有机物(VOCs)污染大气环境.控制 VOCs排放有多种方法,其中催化氧化法是一种有效技术,关键在于获得高效催化剂.
　　近年来,负载过渡金属和贵金属催化剂因具有比单纯负载贵金属和单纯负载过渡金属氧化物更好的催化性能而备受关注.在负载贵金属催化剂中,高比表面积载体负载 Pt, Pd或 Rh催化剂得到广泛而深入的研究,尽管这些催化剂成本较高,但是其对 VOCs氧化反应显示了很高的低温催化活性.众所周知,催化活性取决于贵金属和 VOCs的种类,不同负载贵金属催化剂对特定反应会表现出不同的催化活性.负载 Pt催化剂对长链碳氢化合物和芳香族化合物氧化反应表现出更高的活性.相对于负载贵金属催化剂,负载过渡金属氧化物催化剂不仅具有良好的氧化活性,而且价格低廉.迄今已发现许多过渡金属氧化物(如 Co3O4, Cr2O3和 MnO2等)对典型 VOCs氧化反应具有催化活性,其中 Co3O4的催化活性尤为突出.研究表明, Co3O4的性质和分散度是决定其性能的关键因素,制备方法、载体性质和过渡金属氧化物负载量对 Co3O4的物化性质具有重要影响,而且在负载 Pt催化剂中添加金属氧化物能改善其催化性能.尽管多孔氧化铝是一种常用的载体材料,但目前尚无文献报道三维有序大孔-介孔氧化铝负载 Co3O4和 Pt纳米粒子催化剂的制备及其对甲苯氧化反应的催化性能.
　　本文采用聚甲基丙烯酸甲酯微球胶晶模板法、等体积浸渍法和聚乙烯醇保护的硼氢化钠还原法制备了三维有序大孔-介孔(3DOM Al2O3)负载 Co3O4和 Pt (xPt/yCo3O4/3DOM Al2O3, Pt的质量分数(x%)为0-1.4%, Co3O4的质量分数(y%)为0-9.2%)纳米催化剂.通过电感耦合等离子体原子发射光谱、X射线衍射、氮气吸附-脱附、扫描电子显微镜、透射电子显微镜、选区电子衍射、X射线光电子能谱及氢气程序升温还原等技术表征了催化剂的物化性质,利用固定床微型石英反应器评价了催化剂对甲苯氧化反应的催化活性.结果表明,xPt/yCo3O4/3DOMAl2O3催化剂具有多级孔结构(大孔孔径为180–200 nm,介孔孔径为4–6 nm),比表面积为94?102 m2/g.粒径为18.3 nm的 Co3O4纳米粒子和粒径为2.3?2.5 nm的 Pt纳米粒子均匀分散在3DOM Al2O3表面.在xPt/yCo3O4/3DOM Al2O3催化剂中,1.3Pt/8.9Co3O4/3DOM Al2O3拥有最高的 Oads浓度、最好的低温还原性和最高的甲苯氧化反应催化活性(当空速为20000mL g–1 h–1时,甲苯转化率达90%的反应温度为160oC).基于催化剂的活性数据和结构表征,我们认为,1.3Pt/8.9Co3O4/3DOM Al2O3优异的催化性能与其高分散的 Pt纳米粒子、高的 Oads浓度、好的低温还原性、Pt和 Co3O4纳米粒子间的强相互作用以及多级孔结构相关.     

Methane steam reforming over rhodium promoted Ni/Al2O3 catalysts

The effect of Rh addition upon catalyst characteristics and performance in methane steam reforming was investigated using Rh-promoted Ni/Al₂O₃ catalysts. The number of reduced metal atoms exposed on the surface increased for the Rh-promoted catalysts. Rh-promoted catalysts showed an increase in CH₄ reforming activity; however, constant turnover frequencies for promoted and unpromoted catalysts suggest that the increase in the number of metal surface atoms caused the activity enhancement. Rh also facilitated reduction of Ni/Al₂O₃.     

Ni/Al2O3 catalysts for CO methanation: Effect of Al2O3 supports calcined at different temperatures

The correlation between phase structures and surface acidity of Al₂O₃ supports calcined at different temperatures and the catalytic performance of Ni/Al₂O₃ catalysts in the production of synthetic natural gas (SNG) via CO methanation was systematically investigated. A series of 10 wt% NiO/Al₂O₃ catalysts were prepared by the conventional impregnation method, and the phase structures and surface acidity of Al₂O₃ supports were adjusted by calcining the commercial γ-Al₂O₃ at different temperatures (600–1200 °C). CO methanation reaction was carried out in the temperature range of 300–600 °C at different weight hourly space velocities (WHSV = 30000 and 120000 mL·g^?1·h^?1) and pressures (0.1 and 3.0 MPa). It was found that high calcination temperature not only led to the growth in Ni particle size, but also weakened the interaction between Ni nanoparticles and Al₂O₃ supports due to the rapid decrease of the specific surface area and acidity of Al₂O₃ supports. Interestingly, Ni catalysts supported on Al₂O₃ calcined at 1200 °C (Ni/Al₂O₃-1200) exhibited the best catalytic activity for CO methanation under different reaction conditions. Lifetime reaction tests also indicated that Ni/Al₂O₃-1200 was the most active and stable catalyst compared with the other three catalysts, whose supports were calcined at lower temperatures (600, 800 and 1000 °C). These findings would therefore be helpful to develop Ni/Al₂O₃ methanation catalyst for SNG production.     

Syngas production from methane dry reforming over Ni/Al2O3 catalyst

Research on Chemical Intermediates - We evaluated dry reforming of methane in a tubular fixed-bed reactor at various reaction temperatures from 923 to 973 K using different reactant...     

Pt/Al2O3和Pt/CeO2/Al2O3催化甲烷部分氧化制合成气反应

研究了Pt/Al₂O₃和Pt/CeO₂/Al₂O₃对甲烷部分氧化制合成气反应的催化活性,发现Pt/CeO₂/Al₂O₃显示了更高的甲烷转化率和合成气选择性.用H₂-TPR、H₂-TPD、SEM-EDX和XRD等技术对催化剂进行了表征.CeO₂和Pt相互作用促进Pt在催化剂表面的分散,抑制Pt在催化剂表面的迁移;降低了催化剂的燃烧活性,提高了催化剂的部分氧化活性和选择性,可避免因催化剂床层局部温度过高而导致催化剂活性下降或失活,提高了催化剂的稳定性.同时,CeO₂通过促进水汽变换反应使反应体系迅速达到平衡,提高了催化剂对H₂的选择性.     

流化床反应器中不同Ni/Al2O3催化剂上CH4-CO2重整反应性能的比较研究

采用浸渍法、溶胶 凝胶过程与普通干燥、超临界干燥过程相结合的方法制备了三种20%的NiO-Al2O3体系催化剂，利用BET、XRD、H2 TPR、H2-TPD等方法对各催化剂样品物化性质进行了表征，并考察了催化剂在流化床反应器中CH4-CO2重整反应的催化性能。研究结果表明，经923K焙烧后气凝胶催化剂中镍与载体间作用力最强，主要为固定NiO和尖晶石NiAl2O4结构，而浸渍型催化剂和干凝胶催化剂中镍与载体间作用力较弱。三种催化剂中，气凝胶催化剂具有比表面积较大、堆密度较低、Ni还原度及分散度较高的特点。它在流化床反应器中所形成的聚团流态化状态具有较高的床层膨胀率，大量多孔疏松状的纳米颗粒聚团在床内的循环运动有效地提高了传质效率，能使得生成的沉积炭快速得到气化，从而抑制了催化剂失活；对于浸渍型催化剂和干凝胶催化剂，流化床反应器中床层膨胀率较低、颗粒循环量较少、传质效率较低，易于造成催化剂表面积炭失活。经用TG和XRD等方法对反应后催化剂分析表征，证明催化剂表面石墨碳的沉积是导致浸渍型催化剂和干凝胶催化剂失活的主要原因。     

Ni/Al2O3和Ni/La2O3催化剂上低温乙醇水蒸气重整制氢

 采用浸渍、热分解和氢还原等步骤制备了两种纳米晶载体催化剂Ni/Al2O3和Ni/La2O3,应用X射线衍射、X射线光电子能谱、N2吸附和扫描电镜对催化剂的体相和表面结构进行了测定,采用固定床反应器考察了催化剂对乙醇水蒸气重整制氢反应的催化性能. 实验结果表明, 15.3%Ni/La2O3催化剂对乙醇的低温水蒸气重整反应表现出较高的催化活性和稳定性. 250 ℃时乙醇的转化率已达到80.7%,氢气的选择性为49.5%; 330 ℃时乙醇的转化率达到100%,氢气的选择性可达54.3%. 16.1%Ni/Al2O3催化剂对低温乙醇水蒸气重整反应的催化活性较低.     

Highly active copper catalysts for steam reforming of methanol. Catalysts derived from Cu/Zn/Al alloys

-Hydrogen transfer from -phenylethyl hydroperoxide (HROOH) to excited anthraquinone, acetophenone and benzophenone occurs only in the polar aprotic acetonitrile. At the same time, the triplet of duroquinone abstracts -hydrogen both in polar and non-polar solvents. The rate constant of the latter reaction decreases with increasing solvent polarity.     

催化剂Ni/Y2O3上低温乙醇水蒸气重整制氢研究——氢气预还原对催化剂性能的影响

用浸渍－热分解－氢还原法(IHDHR)和浸渍－热分解法(IHD)分别制备了两种纳米尺寸的Ni/Y2O3催化剂，并应用X-光电子能谱、X-射线衍射、BET比表面测试等分析技术对两种催化剂的结构进行了表征和比较。采用固定床反应器对两种催化剂的催化性能进行实验测试。结果表明，氢气预还原与否对该纳米Ni/Y2O3催化剂的催化性能有一定的影响，经过氢气预还原的催化剂对低温乙醇水蒸气重整反应表现出较高的活性和稳定性，250?℃时，乙醇的转化率达到81.9%；320 ℃时，乙醇的转化率达到95.3%，对氢气的选择性为53.6%。对经过氢预还原的Ni/Y2O3催化剂进行了60 h的稳定性测试。