Effect of calcination temperature on structure and performance of Ni/TiO_2-SiO_2 catalyst for CO_2 reforming of methane

The influence of calcination temperature on the structure and catalytic behavior of Ni/TiO2-SiO2 catalyst, for CO2 reforming of methane to synthesis gas under atmospheric pressure, was investigated. The results showed that the Ni/TiO2-SiO2 catalyst calcined at 700 ℃ had high and stable activity while the catalysts calcined at 550 and 850 ℃ had low and unstable activity. Depending on the calcination temperature, one, two, or three of the following Ni-containing species, NiO, Ni2.44Ti0.72Si0.07O4, and NiTiO3 were identified by combining the temperature programmed reduction （TPR） and X-ray diffraction （XRD） results. Their reducibility decreased in the sequence： NiO〉Ni2.44Ti0.72Si0.07O4〉NiTiO3. It suggests that high and stable activities observed over the Ni/TiO2-SiO2 catalyst calcined at 700 ~C were induced by the formation of Ni2.44Ti0.72Si0.07O4 and smaller NiO species crystallite size.

Coke-Resistant Ni-based Catayst for Partial Oxidation and CO_2-Reforming of Methane to Syngas

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Comparative study on the reaction of methane over a ZnO bed in the absence and presence of CO_2

The reaction of zinc oxide with methane in the absence and presence of CO2 were theoretically and experimentally investigated using HSC Chemistry 5.1 software and a fixed bed reactor, respectively. In the absence of CO2 at 1193 K, the reduction of ZnO was accompanied with methane cracking, and metallic zinc, CO, and H2 were the main reaction products. This system could be utilized for the co-production of metallic zinc and synthesis gas, in which ZnO was a donor of oxygen. In the presence of CO2, ZnO plays as a catalyst in the CO2 reforming of methane and produces syngas with the average H2/CO ratio of 0.88 at 1193 K, which was close to the total reaction theoretic value of 1. It was also found that higher temperature favored high CH4 and CO2 conversions. XRD technique was used to characterize the ZnO species. The result showed that there were no differences in the peak profiles of the XRD patterns of the ZnO powder obtained before and after passing the CH4/CO2 mixed gases for 6 h at 1193 K. It is suggested that ZnO functions as a catalyst according to the redox cycle and metallic zinc plays the role of intermediate product in this process.

Methane reforming with CO_2 to syngas over CeO_2-promoted Ni/Al_2O_3-ZrO_2 catalysts prepared via a direct sol-gel process

CeO2-promoted Ni/Al2O3-ZrO2 （Ni/Al2O3-ZrO2-CeO2） catalysts were prepared by a direct sol-gel process with citric acid as gelling agent. The catalysts used for the methane reforming with CO2 was studied by infrared spectroscopy （IR）, thermal gravimetric analysis （TGA）, microscopic analysis, X-ray diffraction （XRD） and temperature-programmed reduction （TPR）. The catalytic performance for CO2 reforming of methane to synthesis gas was investigated in a continuous-flow micro-reactor under atmospheric pressure. TGA, IR, XRD and microscopic analysis show that the catalysts prepared by the direct sol-gel process consist of Ni particles with a nanostructure of around 5 nm and an amorphous-phase composite oxide support. There exists a chemical interaction between metallic Ni particles and supports, which makes metallic Ni well dispersed, highly active and stable. The addition of CeO2 effectively improves the dispersion and the stability of Ni particles of the prepared catalysts, and enhances the adsorption of CO2 on the surface of catalysts. The catalytic tests for methane reforming with CO2 to synthesis gas show that the Ni/Al2O3-ZrO2-CeO2 catalysts show excellent activity and stability compared with the Ni/Al2O3 catalyst. The excellent catalytic activity and stability of the Ni/Al2O3-ZrO2-CeO2 are attributed to the highly, uniformly and stably dispersed small metallic Ni particles, the high reducibility of the Ni oxides and the interaction between metallic Ni particles and the composite oxide supports.

CO_2 reforming of glycerol over La-Ni/Al_2O_3 catalyst:A longevity evaluative study

This paper reports on the longevity of glycerol-dry（CO2） reforming over the lanthanum（La） promoted Ni/Al2O3 catalysts.The XRD results showed that the Ni particle was well-dispersed in the presence of La promoter.In addition,via the NH3-TPD analysis,it was found that the La promoter has reduced the acidity of Ni catalyst which may have explained the mitigation of carbon laydown.It was determined that the 3.0 wt% La-promoted Ni/Al2O3 catalyst possessed the largest BET specific surface area of 97 m2 g-1.Consequently,it yielded the best catalytic longevity performance with conversion attained more than 90%,even after 72 h of reaction duration.Significantly,it can be confirmed that the presence of CO2 during the glycerol dry reforming was essential in reducing carbon deposition,most likely via gasification pathway.This has ensured a stability of catalytic activity for a long reaction period（72 h）.

Exploring the morphological effect of Ni_xMg_(1-x)O catalysts on CO_2 reforming of methane

To gain deep insight into the Morphological effect of NixMg1-xO catalysts on the reaction of CO2reforming with methane, we designed and fabricated three different spatial structural NixMg1-xO catalysts.These NixMg1-xO catalysts with specific models such as rod, sheet and sphere, exhibited various activity and stability in CO2reforming reaction. Herein NixMg1-xO nanorods displayed higher catalytic activity, in which methane conversion was up to 72% and CO2conversion was 64% at 670°C with a space velocity of 79,200 mL/(gcath), compared with nanosheet and nanosphere counterparts. Furthermore, both catalysts of NixMg1-xO nanorod and nanosheet showed a high resistance toward coke deposition and sintering of active sites in the process of CO2reforming of methane.

A Novel Catalyst for CO_(2) Reforming of CH_4

A novel Ni-Co/SiO2 catalyst which exhibits high activity and excellent anti-carbon deposition property for CO2 reforming of CH4 to synthesis gas is developed.

Enhanced near-zero-CO2-emission chemicals-oriented oil production from coal with inherent CO2 recycling: Part I—PRB coal fast pyrolysis coupled with CO2/CH4 reforming

In this study,the Powder River Basin(PRB)coal fast pyrolysis was conducted at 700°C in the atmosphere of syngas produced by CH4-CO2 reforming in two different patterns,including the double reactors pattern(the first reactor is for syngas production and the second is for coal pyrolysis)and double layers pattern(catalyst was at upper layer and coal was at lower layer).Besides,pure gases atmosphere including N2,H2,CO,H2-CO were also tested to investigate the mechanism of the coal pyrolysis under different atmospheres.The pyrolysis products including gas,liquid and char were characterized,the result showed that,compared with the inert atmosphere,the tar yield is improved with the reducing atmospheres,as well as the tar quality.The hydrogen partial pressure is the key point for that improvement.In the atmosphere of H2,the tar yield was increased by 31.3%and the contained BTX(benzene,toluene and xylene)and naphthalene were increased by 27.1%and 133.4%.The double reactors pattern also performed outstandingly,with 25.4%increment of tar yield and 25.0%and 79.4%for the BTX and naphthalene.The double layers pattern is not effective enough due to the low temperature(700°C)in which the Ni-based catalyst was not fully activated.

Thermodynamic analysis of mixed and dry reforming of methane for solar thermal applications

Thermodynamic analysis of the reforming of methane with carbon dioxide alone （＂dry reforming＂） and with carbon dioxide and steam together （＂mixed reforming＂） is performed as part of a project which investigates the suitability of these endothermic reactions for the storage of solar thermal energy. The Gibbs free energy minimization method was employed to identify thermodynamically optimal operating conditions for dry reforming as well as mixed reforming with a desired H2/CO molar ratio of 2. The non-stoichiometric equilibrium model was developed using FactSage software to conduct the thermodynamic calculations for carbon formation, H2/CO ratio, CH4 conversion and H2 yield as a function of reaction temperature, pressure and reactant molar ratios. Thermodynamic calculations demonstrate that in the mixed reforming process, optimal operating conditions in a carbon-free zone are under H2O/CH4 /CO2 =1.0/1.0/0.5, p = 1 to 10 bar and T = 800 to 850℃ for the production of syngas with a H2 /CO molar ratio of 2. Under the optimal conditions, the maximum H2 yield of 88.0% is achieved at 1 bar and 850℃ with a maximum CH4 conversion of 99.3%. In the dry reforming process, a carbon formation regime is always present at a CO2/CH4 molar ratio of 1 for T = 700 1000℃ and p = 1-30 bar, whereas a carbon-free regime can be obtained at a CO2/CH4 molar ratio greater than 1.5 and T≥800℃.

Synthesis Gas Production from Natural Gas on Supported Pt Catalysts

Auto-thermal reforming of methane, combining partial oxidation and reforming of methane with CO2 or steam, was carried out with Pt/Al2O3, Pt/ZrO2 and Pt/CeO2 catalysts, in a temperature range of 300-900℃. The auto-thermal reforming occurs in two simultaneous stages, namely, total combustion of methane and reforming of the unconverted methane with steam and CO2, with the O2 conversion of 100% starting from 450℃. For combination with CO2 reforming, the Pt/CeO2 catalyst showed the lowest initial activity at 800℃, and the highest stability over 40 h on-stream. This catalyst also presented the best performance for the reaction with steam at 800℃. The higher resistance to coke formation of the catalyst supported on ceria is due to the metal-support interactions and the higher mobility of oxygen in the oxide lattice.

Ni/MgO catalyst prepared via dielectric-barrier discharge plasma with improved catalytic performance for carbon dioxide reforming of methane

A Ni/MgO catalyst was prepared via novel dielectric-barrier discharge （DBD） plasma decomposition method. The combined characterization of Bmnauer- Emmett-Teller measurement, X-ray diffraction, hydrogen temperature-programmed reduction and transmission electron microscopy shows that DBD plasma treatment enhances the support-metal interaction of Ni/MgO catalyst and facilitates the formation of smaller Ni particles. Sphere-like Ni particles form on plasma treated Ni/MgO catalysts. The plasma treated Ni/MgO catalyst shows a significantly improved low temperature activity and good stability for CO2 reforming of methane to syngas.