摘要: The interaction between coal and biomass has been widely investigated. However, the mechanism is always proposed based on physicochemical structure and reactivity of char mixture. In this work, char mixture after co-pyrolysis of anthracite and biomass was separated based on different shape and size, and then structure and reactivity of the coal char were analyzed to reveal mechanism of coal-biomass interaction. Anthracite char samples with different corn straw (CS) blending ratios were prepared by pyrolysis in a fixed bed reactor at 600 and 900℃. The AAEM concentration and microcrystalline structures of coal char were examined by inductively coupled plasma-optical emission spectrometry (ICP-OES) system and X-ray diffraction (XRD). The gasification reactivity of char sample after separation was analyzed by TGA under CO2. The results show that concentration of active K and Mg in coal char samples gradually increased and more disordered carbon structure formed as the CS proportion in the blending increased from 0 to 80%. The coal char in the blending captured more AAEM species by volatile-char interactions instead of escaping with volatile from biomass during co-pyrolysis process. Meanwhile, higher pyrolysis temperature led to volatilization and inactivation of K and Na, and also decrease in graphitization degree. Moreover, both addition of CS and low pyrolysis temperature could promote gasification reactivity of coal char sample. Furthermore, a satisfactory linear correlation (R2=0.9009) between alkali index AI and R0.5 of the char samples was established. This indicated that AAEMs performed the dominate effect to enhance gasification reactivity of coal char during co-gasification of coal and biomass.
摘要: The dimethyl ether (DME) carbonylation reaction over mordenite is greatly affected by the mass transfer process. In this research, hierarchical mordenite catalysts were synthesized and characterized to investigate the influence of mesopores on the structure, mass transfer and catalytic performance. The results show that the medium-strong acid sites decrease while strong acid sites increase over the hierarchical samples. The introduced mesopores can significantly improve the mass transfer efficiency and the carbonylation performances are markedly improved on the hierarchical samples. In addition, the polymerization degree of coke deposition on the deactivated samples decreases although the coke amount increases. Excessive usage of mesopore templates can damage the structure of the MOR catalysts, thus leading to the loss of acid sites and the decrease in catalytic performance.
摘要: Platinum-silver alloy nanoparticles (PtxAgy NPs) were synthesized in a molten salt system without using any organic surfactants or solvents; the catalytic role of Ag in the methanol electrooxidation reaction (MOR) in alkaline electrolyte over PtxAgy NPs was investigated. The TEM images suggest that Pt52Ag48 nanotubes (NTs) can be obtained when the Pt/Ag ratio in the molten salt precursor reaches 1. The methanol electrooxidation reaction test results indicate that the Pt52Ag48 NTs with a clean surface exhibits a much better catalytic performance than the conventional Pt black in MOR. Meanwhile, the catalytic activity of the Pt52Ag48 NTs is greatly related to the positive potential limit; the peak current of MOR reaches 1.61 mA/μgPt with a positive potential limit from -1.0 to 0.5 V (vs. SCE), which is 1.92 times higher than that with a positive potential limit from -1.0 to 0.1 V (vs. SCE). The Ag element in the surface layer of PtxAgy alloy may promote the MOR through a redox process during the electrochemical cycle. The insight shown in work should be beneficial to the application of PtxAgy alloy in the direct methanol fuel cells (DMFCs).