摘要: Chemical-looping steam methane reforming (CL-SMR) is a novel method proposed on the base of chemical looping combustion (CLC) technology. In the CL-SMR scheme, methane is partially oxidized to syngas (H2/CO(molar ratio)=2.0) by the lattice oxygen in reformer reactor in the absence of gaseous oxidant, and then the reduced oxygen carrier is oxidized by steam to produce hydrogen in steam reactor. The use of perovskite type oxide LaFeO3 as an oxygen carrier in CL-SMR was studied. While the basicity of CaO/MgO modified oxygen carriers, LaFeO3-CaO and LaFeO3-MgO, were also synthesized aiming to increase specific surface area, thermostability, and resistance to coke formation. The synthesized oxides were characterized by X-ray diffraction (XRD), H2-temperature-programmed reduction (H2-TPR), Brunauer-Emmett-Teller (BET) surface area and X-ray photoelectron spectroscopy (XPS). Three oxygen carriers exhibited high active and selective for syngas production from methane, and maintained perovskite type over cyclic redox operations. The LF-CaO sample is the best candidate for the CL-SMR of the three samples judging from the reactivity, selectivity, and resistance to carbon formation. It showed good regenerability during 5 redox reactions.
摘要: Nickel immobilized on organically modified montmorillonite (Ni/OMt) was prepared by impregnation method and used as the catalyst for hydrogen production from ethanol steam-reforming; the Ni/OMt catalyst was characterized by XRD, FT-IR, H2-TPR, SEM, XPS and N2 adsorption-desorption. The results indicate that in comparison with the catalyst of nickel supported on unmodified montmorillonite (Ni/MMT), the Ni/OMt catalyst exhibits higher surface area and pore volume as well as higher nickel dispersion with smaller metallic particle size. For the ethanol steam-reforming over Ni/OMt, the conversion of ethanol keeps at 100%, with a selectivity of 70% to hydrogen during the 30h reaction test at 773K;however, over the unmodified Ni/MMT catalyst, severe carbon deposition is observed after reaction for only 10h, accompanying with catalyst deactivation and the formation of byproducts such as acetaldehyde and ethylene. The modification of MMT with cetyltrimethylammonium bromide (CTAB) can significantly improve the stability of the Ni/OMt catalyst in ethanol steam-reforming and reduce the carbon deposition rate by immobilizing highly dispersed nanoparticle Ni on the interlayers of OMt; the selectivity to ethylene and acetaldehyde is also greatly depressed.
摘要: Hollow tungsten carbide and cobalt spheres (HTCCS) with cobalt concentration of 6% were prepared by spray conversion and reduction carbonization methods. The HTCCS with diameters of about 8-18μm were covered with 0.3-1.0μm microporous. The Pd/WC catalyst was prepared through the replacement reaction between Co nanoparticles on the surface of HTCCS and PdCl4. The electro-catalytic performances for formic acid electro-oxidation were investigated by cyclic voltammetry and chronoamperometry. It exhibited the low onset potential, excellent catalytic activity and stability compared with Pd/C due to the larger electrochemical surface area (ECSA) and the synergistic effect between Pd and WC.