Abstract
Steam reforming of light hydrocarbons provides a promising method for hydrogen production. Ni-based catalysts are so far the best and the most commonly used catalysts for steam reforming because of their acceptably high activity and significantly lower cost in comparison with alternative precious metal-based catalysts. However, nickel catalysts are susceptible to deactivation from the deposition of carbon, even when operating at steam-to-carbon ratios predicted to be thermodynamically outside of the carbon-forming regime. Reactivity and deactivation by carbon formation can be tuned by modifying Ni surfaces with a second metal, such as Au through alloy formation. In the present review, we summarize the very recent progress in the design, synthesis, and characterization of supported bimetallic Ni-based catalysts for steam reforming. The progress in the modification of Ni with noble metals (such as Au and Ag) is discussed in terms of preparation, characterization and pretreatment methods. Moreover, the comparison with the effects of other metals (such as Sn, Cu, Co, Mo, Fe, Gd and B) is addressed. The differences of catalytic activity, thermal stability and carbon species between bimetallic and monometallic Ni-based catalysts are also briefly shown.
Highlights
Production of synthesis gas from natural gas and Fisher-Tropsch synthesis from the synthesis gas have become very important in the chemical industry for reasons related to the soaring petroleum price, depletion of oil reserves, and environmental problems with exhaust gases [1,2,3]
The middle-step sites acted as the nucleation center for the growth of filamentous carbon and had the potential to prevent catalyst nanoparticles from being destroyed. These findings provided a rational interpretation of the experimental observations that Ag/Ni surface alloy exhibited lower catalytic activity towards steam reforming of methane but high resistance to coke formation
The addition of a small amount of second metals such as Au, Ag, Sn, Cu, Co, et al to Ni catalysts significantly modifies the properties of metallic Ni particles by the formation of Ni-M bimetallic surface alloys
Summary
Production of synthesis gas from natural gas and Fisher-Tropsch synthesis from the synthesis gas have become very important in the chemical industry for reasons related to the soaring petroleum price, depletion of oil reserves, and environmental problems with exhaust gases [1,2,3]. The reaction rate is limited by the heat transfer and the scale merit of the syngas production by this method is low Other combined technologies such as autothermal reforming, oxidative reforming, and so on, are used to realize the large-scale synthesis gas production. Is introduced to the catalyst bed together with methane and steam, is a promising method for syngas production because the reaction conditions can be adjusted by balancing exothermic combustion and endothermic reforming to an autothermal system. The resistance to coke formation in the steam reforming of methane, as well as the relationship between the catalytic performance and the structure of bimetallic catalysts, are discussed. M/Ni, sequential impregnation; M-Ni, co-impregnation; Cp, co-precipitation; Dp, deposition-precipitation; Cs, combustion synthesis; SR, steam reforming; PO, partial oxidation; DR, dry reforming; ATR, autothermal reforming; A, activity; C, coke resistant; S, selectivity
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