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[en] A detailed chemical kinetic mechanism based on the Appel-Bockhorn-Frenklach (ABF) model was established to describe acetylene decomposition, ethylene formation, and soot formation during quenching in coal pyrolysis to acetylene process. The predictions agreed well with the reported acetylene pyrolysis experimental data. Numerical simulations were then performed to deeply understand the reaction behaviors during quenching of coal pyrolysis in thermal plasma, and to optimize the quenching design for better heat recovery. Two key operating parameters of quenching, i.e., the temperature after quenching and the quenching rate, were studied in detail and optimized after the kinetics were validated. The simulation results also proved that hydrogen can promote the formation of ethylene and inhibit the condensation of acetylene during quenching. In particular, in-depth discussion of acetylene decomposition and ethylene formation using this detailed kinetic mechanism combined with thermodynamic method provided a comprehensive understanding of the thermodynamics and kinetics interpreting pilot plant experimental data. - Highlights: • A detailed kinetic model for C_2H_2 decomposition and soot formation is established. • Two key operating parameters of quenching are studied in detail and optimized. • Effects of H_2 on C_2H_4 formation and C_2H_2 condensation during quenching are discussed. • A comprehensive understanding of the pilot plant experimental data is achieved.
[en] Dry reforming is a potential process to convert CO_2 and light alkanes into syngas (H_2 and CO), which can be subsequently transformed to chemicals and fuels. Here in this work, PtNi bimetallic catalysts have been investigated for dry reforming of ethane and butane using both model surfaces and supported powder catalysts. The PtNi bimetallic catalyst shows an improvement in both activity and stability as compared to the corresponding monometallic catalysts. The formation of PtNi alloy and the partial reduction of Ce"4"+ to Ce"3"+ under reaction conditions are demonstrated by in-situ Ambient Pressure X-ray Photoemission Spectroscopy (AP-XPS), X-ray Diffraction (XRD) and X-ray Absorption Fine Structure (XAFS) measurements. A Pt-rich bimetallic surface is revealed by Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) following CO adsorption. Combined in-situ experimental results and Density Functional Theory (DFT) calculations suggest that the Pt-rich PtNi bimetallic surface structure would weaken the binding of surface oxygenates/carbon species and reduce the activation energy for C-C bond scission, leading to an enhanced dry reforming activity.