Propane formation by aqueous-phase reforming of glycerol over Pt/H-ZSM5 catalysts

Solid acid supports such as H-ZSM5, H-Mordenite, γ-Al₂O₃, USY and Beta catalysts were modified with Pt. These Pt/oxide catalysts were found to be active for propane formation through aqueous reforming of glycerol in the presence of hydrogen. The reforming reactions, possibly, proceeded through reaction cycles of dehydration on acid sites and hydrogenation on Pt sites over the catalysts.     

On the Preparation of Ni–La Supported on Silica by Sol-gel Process via Propionates

Ni–La/SiO₂ catalysts were prepared by using a new metal organic precursor M(OC₃H₇)_n, dissolved in organic solvent, hydrolysed and finally condensed to form inorganic polymers containing M–O–M or M–(μOH)–M linkages. An optimal distribution of both the active phase ‘Ni’ and the promoter ‘La₂O₃’ was ensured by addition of their corresponding salts, previously dissolved in propionic acid, to a silica solution prior to gelation. After drying under vacuum the precursor was submitted to thermal treatment in air at 600°C with a heating rate of 1°C min^–1. The precursors and the corresponding catalysts were characterised by various techniques (TG-DTA, XRD, FTIR, TEM, BET and porosimetry) and tested for methane dry reforming. This revised version was published online in August 2006 with corrections to the Cover Date.     

Low CO content hydrogen production from oxidative steam reforming of ethanol over CuO-CeO2 catalysts at low-temperature

CuO-CeO₂ catalysts were prepared by a urea precipitation method for the oxidative steam reforming of ethanol at low-temperature. The catalytic performance was evaluated and the catalysts were characterized by inductively coupled plasma atomic emission spectroscopy, X-ray diffraction, temperature-programmed reduction, field emission scanning electron microscopy and thermo-gravimetric analysis. Over CuO-CeO₂ catalysts, H₂ with low CO content was produced in the whole tested temperature range of 250–450 °C. The non-noble metal catalyst 20CuCe showed higher H₂ production rate than 1%/oRh/CeO₂ catalyst at 300–400 °C and the advantage was more obvious after 20 h testing at 400 °C. These results further confirmed that CuO-CeO₂ catalysts may be suitable candidates for low temperature hydrogen production from ethanol.     

镍基催化剂上稻草水蒸气重整制富氢合成气

采用浸渍法制备了SiO₂, γ-Al₂O₃, CaO和TiO₂负载的Ni催化剂, 以及不同MgO含量的MgO-7.5%Ni/γ-Al₂O₃催化剂,利用X射线衍射和N₂吸附-脱附技术表征了催化剂的结构,在固定床反应器上评价了它们在稻草水蒸气催化重整制合成气反应中的催化性能,考察了反应条件对催化剂性能的影响.结果表明, 以γ-Al₂O₃为载体时Ni催化剂活性最高,其中7.5%Ni/γ-Al₂O₃催化剂的H₂收率可达1071.3ml/g,H₂:CO的体积比为1.4:1;同时,MgO的添加进一步提高了该催化剂的性能,当MgO含量为1.0%时,H₂收率可达1194.6ml/g,H₂:CO体积比可达3.9:1.可见MgO的加入促进了Ni基催化剂上稻草水蒸气催化重整制合成气反应的进行,同时使得合成气中CO发生水-汽转换反应,从而大大提高了合成气中H₂含量.     

n-Octane reforming over modified catalysts: effect of regeneration on the catalyst performance

The effect of multiple oxidation-reduction cycles on the catalyst performance was studied. Pt-Sn-Sn, Pt-Sn-Ir, Pt-Sn-Au and Pt-Sn-Pd supported on g-Al₂O₃ were compared with the reference Pt-Sn/-Al₂O₃ catalyst in n-octane test reactions. The carbonaceous deposits were burned off from the catalysts after each reaction. The regeneration procedure consisted only two steps: the burn off in air and the reduction in hydrogen. No significant change, as a consequence of the regeneration, was observed in the conversion, the liquid yield and the product distribution, except at the Pt-Sn-Pd and Pt-Sn-Au catalysts. These catalysts lost part of their activity. With the palladium modified catalyst the rupture reactions became more dominant with the number of regeneration cycles. The aromatic part of the product decreased, the isoparaffin part increased in the case of both modified catalysts. The reference, the tin and iridium modified catalysts had stable catalytic performance: the activity and selectivity of the catalysts remained constant after a few oxidation cycles.     

Promoting effect of Pt in Ni-based catalysts for CH4 reforming

The effect of Pt/Ni ratio on the surface properties and catalytic behavior of bimetallic PtNi catalysts for reforming of methane with CO₂ was studied. The TPR, FTIR of adsorbed CO and XPS data showed that introduction of a small amount of Pt (0.3 – 0.5 wt.%) into the Ni catalyst leads to a decrease of the NiO size, its easy reduction and a uniform distribution of the nickel metal particles.     

Effect of Calcined Temperature on Coke Deposition for Autothermal Reforming of Methane with Ni-Cu Catalyst

Ni/CuO-ZrO₂-CeO₂-Al₂O₃ catalysts were prepared by co-precipitation method at pH=9 and using Na₂CO₃ as the precipitant. The Ni loading (mass fraction) of the catalysts was 10%. The catalysts were characterized by X-ray diffraction, temperature-programmed oxidation (TPO), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS). The effects of calcined temperature of support on coke deposition were studied. TPO, SEM and XPS results indicated there was no peak of higher temperature oxygen consumption on Ni/CuO-ZrO₂-CeO₂-Al₂O₃catalyst (support was calcined at 800 ^oC), which could lead to the deactivation of the catalyst. The carbon species were carbonate and inactive carbon (filamentous carbon species) on the surface of catalyst reacting for 40 h which perhaps led to the deactivation of the catalyst.     

低贵金属Pt-Rh型三效催化剂空燃比性能的研究

研究了以浸渍法制备的低贵金属Pt-Rh型三效催化剂对C₃H₈, CO, NO的催化活性. 主要考察了CeO₂-ZrO₂和BaO的添加对催化剂空燃比性能的影响, 通过氧化反应、水气变换和蒸汽重整的性能研究, 探讨了催化剂三效工作窗口扩大的原因. 结果表明, 催化剂中只添加CeO₂-ZrO₂时即具有优异的水气变换性能, 蒸汽重整在250 ℃左右发生, 并且在450 ℃以下时C₃H₈的转化率一直保持在20%左右; BaO添加到含有CeO₂-ZrO₂的催化剂中对水气变换和蒸汽重整则有明显的促进作用, 能进一步扩大催化剂的三效工作窗口; 催化剂中只添加CeO₂-ZrO₂时, 能明显提高催化剂对CO的氧化反应活性, 但对C₃H₈的氧化反应的影响则不明显; BaO和CeO₂-ZrO₂同时存在于催化剂中时, 能进一步提高CO的氧化反应活性, 对C₃H₈的氧化反应则没有明显的促进作用.     

Hydrogen Production by Catalytic Reforming of Gaseous Hydrocarbons (Methane &; LPG)

Hydrogen has been attracting great interest as a major energy source in near future. The lack of an infrastructure has led to a research effort to develop fuel processing technology for production of hydrogen. In this review, we are reporting the catalytic reforming of gaseous hydrocarbons carried out in our research group, covering dry-reforming of CH₄, tri-reforming of CH₄, the electrocatalytic reforming of CH₄ by CO₂ in the SOFC (solid oxide fuel cell) system and steam reforming of LPG. Especially, we have focused on our work, though the related work from other researchers is also discussed wherever necessary. It was found that tri-reforming of CH₄ over NiO–YSZ–CeO₂ catalyst was more desirable than dry-reforming of CH₄ due to higher reforming activity and less carbon formation. The synthesis gas produced by tri-reforming of CH₄ can be used for the production of dimethyl ether, Fischer–Tropsch synthesis fuels and high valued chemicals. To improve the problem of deactivation of catalyst due to carbon formation in the dry reforming of CH_4, the internal reforming of CH₄ by CO₂ in SOFC system with NiO–YSZ–CeO₂ anode catalyst was suggested for cogeneration of a syngas and electricity. It was found that Rh-spc-Ni/MgAl catalyst showed long term stability for 1,100 h in the steam reforming of LPG under the tested conditions. The addition of Rh to spc-Ni/MgAl catalyst restricted the deactivation of catalyst due to carbon formation in the steam reforming of LPG and diesel under the tested conditions. The result suggested that the developed reforming catalysts can be used in the reforming process of CH₄, LNG and LPG for application to hydrogen station and fuel processor system.     

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%.     

Carbon Dioxide Reforming of Methane to Synthesis Gas Over Ni/MgO-Al2O3-AlPO4 Catalysts

Carbon dioxide reforming of methane to synthesis gas was studied over Ni/MgO-Al₂O₃-AlPO₄ catalysts. The conventional Ni/Al₂O₃ and Ni/MgO-Al₂O₃ catalysts were included for comparison. These catalysts were characterized by nitrogen adsorption and hydrogen chemisorption. The results show that Ni/MgO-Al₂O₃-AlPO₄ was more active than the other two catalysts especially at high reaction temperatures. MgO-Al₂O₃-AlPO₄ has a large pore diameter with a very uniform pore size distribution. It can overcome the pore diffusion effect under high temperature reaction conditions.     

Effect of Ni loadings on the activity and coke formation of MgO-modified Ni/Al2O3 nanocatalyst in dry reforming of methane

MgO-modified Ni/Al₂O₃ catalysts with different Ni loadings were prepared and employed in dry reforming of methane (DRM). The effect of Ni loadings on the activity and coke formation of Ni/MgO-Al₂O₃ catalysts were investigated. The synthesized catalysts were characterized by XRD, N₂ adsorption-desorption, SEM, TPO and TPR techniques. The obtained results showed that increasing nickel loading decreased the BET surface area and increased the catalytic activity and amount of deposited carbon. In addition, the effect of gas hourly space velocity (GHSV) and feed ratio were studied.     

Structure and Catalytic Properties of Ceria-based Nickel Catalysts for CO<Subscript>2</Subscript> Reforming of Methane

Carbon dioxide reforming (CDR) of methane to synthesis gas over supported nickel catalysts has been reviewed. The present review mainly focuses on the advantage of ceria based nickel catalysts for the CDR of methane. Nickel catalysts supported on ceria–zirconia showed the highest activity for CDR than nickel supported on other oxides such as zirconia, ceria and alumina. The addition of zirconia to ceria enhances the catalytic activity as well as the catalyst stability. The catalytic performance also depends on the crystal structure of Ni–Ce–ZrO₂. For example, nickel catalysts co-precipitated with Ce_0.8Zr_0.2O₂ having cubic phase gave synthesis gas with CH₄ conversion more than 97% at 800 °C and the activity was maintained for 100 h during the reaction. On the contrary, Ni–Ce–ZrO₂ having tetragonal phase (Ce_0.8Zr_0.2O₂) or mixed oxide phase (Ce_0.5Zr_0.5O₂) deactivated during the reaction due to carbon formation. The enhanced catalytic performance of co-precipitated catalyst is attributed to a combination effect of nano-crystalline nature of cubic Ce_0.8Zr_0.2O₂ support and the finely dispersed nano size NiO _x crystallites, resulting in the intimate contact between Ni and Ce_0.8Zr_0.2O₂ particles. The Ni/Ce–ZrO₂/θ–Al₂O₃ also exhibited high catalytic activity during CDR with a synthesis gas conversion more than 97% at 800 °C without significant deactivation for more than 40 h. The high stability of the catalyst is mainly ascribed to the beneficial pre-coating of Ce–ZrO₂ resulting in the existence of stable NiO _x species, a strong interaction between Ni and the support, and an abundance of mobile oxygen species in itself. TPR results further confirmed that NiO _x formation was more favorable than NiO or NiAl₂O₄ formation and further results suggested the existence of strong metal-support interaction (SMSI) between Ni and the support. Some of the important factors to optimize the CDR of methane such as reaction temperature, space velocity, feed CO₂/CH₄ ratio and H₂O and/or O₂ addition were also examined.     

Selective CO oxidation in presence of H2 over Cu/Cr/Ba catalysts

Cu/Cr/Ba based catalysts were found to be nonprecious metal catalysts that can selectively oxidize CO in a H₂-containing stream. The CO concentration in the methanol reformer effluent can be reduced from 1–2 mol% to about 0.3 mol% with only a very small extent of H₂ oxidation.     

碱金属和碱土金属促进的Ni/SiO2催化剂上甲烷的二氧化碳重整制合成气

Ni/SiO2 catalysts promoted by alkali metals K and Cs or alkaline earth metals Mg, Ca, Sr and Ba were prepared, characterized by H2-TPR and XRD, and used for the production of synthesis gas via methane reforming with CO2. Though K and Cs promoted Ni catalysts could eliminate coke deposition, the reforming activity of these promoted catalysts was decreased heavily. Mg and Ca promoted Ni/SiO2 catalysts exhibited excellent coke resistance ability with minor loss of the reforming activity of Ni/SiO2. Ba showed poor coke resistance ability and small amount of Sr increased the formation of coke. The possible mechanism of these promoters was discussed.     

Dry reforming of methane for syngas production: A review and assessment of catalyst development and efficacy

Dry reforming of methane (DRM) involves catalytic reaction of CO₂ and CH₄ to produce syngas. Although the process is environmentally beneficial, it has not been implemented on industrial level due to multiple challenges, particularly with regard to catalyst deactivation because of use of very high temperature. A majority of research has been carried out with catalysts based on nickel. However, recently many new varieties catalysts using noble metals, structured silica-foams, zeolites, etc. have been investigated for DRM. The present review paper deals with understanding the process of DRM, importance of catalysts, supports and promoters, various methods of synthesis of catalysts, design of catalyst, catalytic performance and ways to enhance it, constraining elements like poisoning of the catalyst, in addition to physicochemical properties of catalysts. Various properties of supports and promoters like reduction/oxidation potential, acidity/basicity, reducibility, oxygen storage capacity, etc. are responsible for catalyst activity and stability. It identifies critical gaps and provides future directions.     

预处理方法对Ni-Co双金属催化剂性能与结构的影响

浸渍法制备了Ni-Co/La₂O₃-γ-Al₂O₃双金属催化剂, 经氢气还原预处理后, 再分别由一氧化碳、甲烷和二氧化碳进行再次预处理, 考察了预处理方法对该催化剂上沼气重整制氢性能的影响, 并运用X射线衍射(XRD)、热重-差示扫描量热(TG-DSC)、透射电子显微镜(TEM)等手段对催化剂进行了表征. 结果表明, 与传统氢气还原预处理相比, 经氢气与一氧化碳预处理后, 催化剂性能无明显变化; 经氢气与甲烷预处理后, 催化剂性能明显变差; 而经氢气和二氧化碳预处理后, 催化剂性能明显变优, 且能基本消除该催化剂上沼气重整反应的诱导期. 分析结果表明, 经氢气和二氧化碳预处理后, 催化剂中金属颗粒较小, 分布较均匀, 粒径分布范围较窄, 从而减少了催化剂表面碳的沉积, 增强了催化剂的抗积炭性能, 可延长催化剂的使用寿命.     

Comparison of two preparation methods of supported Li?Ni catalyst on alumina for selective oxidation of methane

Lithium-added nickel catalysts on alumina were prepared for CO₂ reforming of methane by two methods, precipitation and impregnation. Performances of the catalysts were investigated by TG, CO-adsorption and SEM analysis. The catalyst with ratio of Li/Ni=1.0 prepared by precipitation method has high nickel dispersion, catalytic activity and stability for CO₂ reforming of methane.     

Design of coke-free methane dry reforming catalysts by molecular tuning of nitrogen-rich combustion precursors

The valorization of methane and carbon dioxide is a promising solution for mitigating global warming. The dry reforming of methane (DRM) is capable of concomitant conversion of these greenhouse gases into starting materials for production of synthetic fuels, promoting a carbon neutral avenue for fuel production. The development of efficient, stable, and economic catalysts presents a challenge owing to the comparatively rapid deactivation of DRM catalysts under reaction conditions. Here, Ni/La₂O₃ DRM catalysts are prepared by combustion synthesis of Ni and La complexes of nitrogen-rich precursors. We expound the relationship between structures of the combustion precursors, the thermochemistry of their combustion, the structures of the resultant Ni/La₂O₃ catalysts, and their performance under DRM conditions. We show that the best catalyst is derived from energetic precursor which has the sharpest exotherm and rapidly releases the largest amounts of nitrogen gas. These properties give rise to the crystallization of the Ni/La₂O₃ catalyst with high Ni dispersion and strong metal-support interactions. This work can act as starting point to expand the link between the chemistry of combustion precursors and the resulting catalyst properties, eventually realizing the rational design of high-performance catalysts prepared by combustion synthesis through tailoring the chemistry and structure of the nitrogen-rich precursors.     

Low-Temperature Direct Electrochemical Methanol Reforming Enabled by CO-Immune Mo-Based Hydrogen Evolution Catalysts

Hydrogen storage in the form of intermediate artificial fuels such as methanol is important for future chemical and energy applications, and the electrochemical regeneration of hydrogen from methanol is thermodynamically favorable compared to direct water splitting. However, CO produced from methanol oxidation can adsorb to H₂-evolution catalysts and drastically reduce activity. In this study, we explore the origins of CO immunity in Mo-containing H₂-evolution catalysts. Unlike conventional catalysts such as Pt or Ni, Mo-based catalysts display remarkable immunity to CO poisoning. The origin of this behavior in NiMo appears to arise from the apparent inability of CO to bind Mo under electrocatalytic conditions, with mechanistic consequences for the H₂-evolution reaction (HER) in these systems. This specific property of Mo-based HER catalysts makes them ideal in environments where poisons might be present.