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An electrochemical synthesis of various 3‐selenylated chromones via selenylation of alkynyl aryl ketones without the employment of catalyst and chemical‐oxidant is described here. This method features mild conditions, high efficiency, and wide substrate scope. Furthermore, the scale‐up reaction runs smoothly which indicates the practicability of this electrosynthesis strategy. [ABSTRACT FROM AUTHOR]

Co and Ni are widely used to prepare bimetallic catalysts for dry reforming of methane (DRM) due to their comparable electronic configurations. In this study, a series of NixCoy-HAP catalysts were prepared, and by combining the characterization with XRD, H 2 -TPR, XPS, and TEM, the influence of Co incorporation on the redox properties, catalytic activity, catalytic stability, carbon deposition resistance and side reactions of the catalysts was evaluated. The results showed that both Ni and Co are homogeneously dispersed in the HAP structure by ion-exchange. The addition of Co enhances the reducibility of NixCoy-HAP and significantly improves the catalytic activity in the initial stage. Ni5Co1-HAP exhibits best catalytic stability in a 100-h long-term reaction accompanied by the deactivation of CH 4 and CO 2 with only 0.09% h−1 and 0.10% h−1, respectively. Characterization of the spent catalysts demonstrates that the decrease in activity of high Co content catalysts (Ni1Co5-HAP and Ni1Co10-HAP) is not due to carbon deposition, but rather that the addition of Co facilitates the RWGS side reaction. Process characterization of the catalysts in the CH 4 one-component reaction indicates that an increase in the concentrates of one promotes a faster reduction of the other metal due to the strong electronic coupling of Ni and Co. These insights revealed here can pave the way for the preparation of Ni–Co bimetallic catalysts with high catalytic activity, robust resistance to carbon deposition and inhibition of a RWGS side reaction. [Display omitted] • Ni and Co with strong electronic coupling improved the reducibility of metal oxides. • Ni5Co1-HAP catalysts exhibited excellent catalytic stability (during 100 h DRM reaction). • NixCoy-HAP catalysts with high Co/Ni ratio provide enhanced carbon deposition resistance, but promoted RWGS reaction. • Partial oxidation of CH 4 induced by lattice oxygen was essential for catalyst "self-activation". [ABSTRACT FROM AUTHOR]

The doping of the second metal Mo is expected to further enhance the carbon deposition resistance of Ni-based catalysts for syngas production via dry reforming of methane (DRM). In this study, the hydroxyapatite (HAP) was used as the support and a small Mo dosage was doped in the Ni-based catalysts to investigate the effect of intrinsic hydroxyl and Mo doping on the catalytic activity and carbon deposition resistance in DRM reaction. The catalyst characterization results show that both Ni and Mo are doped into the HAP structure with relatively uniform dispersion. The basic site strength of Ni4Mo0.2-HAP catalyst containing Mo is significantly higher than that of without Mo. The Mo dopant significantly improves the initial catalytic activity, but has minimal effect on the stability enhancement. Whether the catalyst is pre-reduced or not is crucial to the initial activity of the DRM reaction, the non-pre-reduced catalysts will go through a "self-activation" stage at the beginning of the reaction, where the "hydroxyl group" are proved to play as an "oxygen supply" for the partial oxidation of CH 4 or the oxidation of the carbon deposition in the initial stage. Only trace amount of carbon deposition is found after 100 h of DRM reaction on Ni3Mo0.2-HAP catalyst. The NiMo-HAP catalysts exhibit excellent initial activity and resistance to carbon deposition due to the synergistic effect of Ni–Mo alloy and hydroxyl groups in the hydroxyapatite support. [Display omitted] • The doping of Mo improved the initial activity of the NiMo-HAP catalyst. • NiMo-HAP catalysts exhibited enhanced carbon deposition resistance (during 100 h DRM reaction). • Hydroxyl groups and NiMo alloys synergistically contributed to the DRM catalytic activity and stability. • NiMo-HAP maintained structural stability after 100 h DRM reaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ce doping improved oxygen species mobility and reduced carbon deposition. • The intervening of Ce followed by Ni facilitated the formation of oxygen vacancies. • Optimized parameters for plasma-catalytic benzene steam reforming were obtained. • Preventing deep benzene cracking to form graphitic carbon was critical. Non-thermal plasma (NTP) coupled Ni-based catalysts show significant potential in reforming of biomass tar for syngas production. Carbon deposition on catalysts remains a troubling problem. Ce doping can contribute to the improvement of oxygen vacancies and oxygen activity, which is expected to solve this challenge. In this study, Ce-doped Ni-based catalysts with HAP as support have been prepared. Benzene was selected as a tar model and the effects of Ni/Ce, steam to carbon ratio (S/C), reaction temperature, discharge power, Ni/Ce intervention order and catalysts preparation method on catalytic activity and stability were investigated in NTP-catalytic system. The results show that Ni3/Ce5-HAP-C exhibits the best catalytic activity at a reaction temperature of 450 °C, an S/C of 1.6, and a discharge power of 86 W with benzene conversion of 94.99 %, total gas yield of 3501.20 mL/g benzene and energy efficiency of 8.75 g/kWh. An increase in Ce proportion significantly enhances the reducibility of the metal oxides and the mobility of the oxygen species, and effectively reduces the catalyst carbon deposition. The increase in temperature significantly enhances the catalyst reactivity and selectivity. The order of metal intervention of Ce followed by Ni proves to be favorable for the Ni-Ce bimetallic catalysts, and the first intervening Ce is able to enhance the lattice oxygen activity and the dispersion of Ni metal. Characterization of the spent catalysts indicates that graphitic carbon is the main type of carbon deposition, and reducing the conversion of benzene and its intermediates into graphitic carbon is crucial to enhance the stability of the catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • High initial benzene concentration (70–190 g/Nm3) experiments are performed in NTP-catalytic system. • Performance of NTP alone and NTP-catalytic system are compared. • The catalysts facilitate the intermediates convert to gaseous products. • The Ni3-HAP catalyst exhibits the maximum benzene conversion (92.13 %) and energy efficiency (8.49 g/kWh). • Catalyst deactivation in NTP-catalytic systems is due to carbon deposition rather than metal sintering. Non-thermal plasma (NTP) coupled Ni-based catalysts are a promising method for tar steam reforming to syngas. In this work, Ni-based catalysts supported on hydroxyapatite (Ni-HAP) and γAl 2 O 3 (Ni-γAl 2 O 3) coupled with a coaxial dielectric barrier discharge (DBD) plasma were used to degrade biomass tar, and benzene was selected as a typical unbranched benzene ring structured tar model compound. In the NTP alone system, an increase in discharge power leads to benzene deep cracking to carbon deposition. In the NTP-catalytic system, the reaction temperature is a critical factor for catalysis, and the catalyst leads to a significant increase in benzene conversion and total gas yield, prompting the conversion of more cracking intermediates to gaseous products. Steam in the system has both positive and negative effects: a certain amount of steam can increase the amount of H· and ·OH, promoting benzene decomposition and carbon deposit elimination; excessive steam will compete for energetic electrons or oxidize the active metal in the catalyst, inhibiting benzene conversion. The Ni3-HAP catalyst exhibits the maximum benzene conversion (92.13 %) and energy efficiency (8.49 g/kWh), thanks to the formed Ni2+[I] and Ni2+[II] in the lattice due to the flexible ion exchange properties of the HAP support. The main reason for the catalyst activity degradation is carbon deposition rather than catalyst sintering. A good match among tar conversion rate, degree of decomposition, steam content and steam decomposition rate is critical for efficient and stable operation of the NTP-catalytic system. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ca-deficient hydroxyapatite (HAP-D) were used as support to stabilize Ni nanoparticles. • Defects were favorable for Ni and the support to form strong metal-support interaction (SMSI). • The Ni2+[I], Ni2+[II] and OH– in the catalyst structure cooperatively minimized the carbon deposition during the DRM process. • The Ni 0.5 /HAP-D catalyst was stable for 200 h without obvious deactivation and carbon deposition. Excellent carbon resistance and stable operations are essential for the industrialization of catalytic dry reforming of methane (DRM). In this study, a series of Ni/HAP and Ni/HAP-D catalysts are used to investigate their DRM reaction performance, including activity, durability, and resistance to carbon deposition. Combined with H 2 -TPR and XPS results, Ni in the Ni/HAP prefers to replace the external Ca atoms in hydroxyapatite. The inherently "Ca-deficient" HAP-D support facilitates a more robust anchor positioning for the Ni metal, and a significant fraction of the Ni atoms will be embedded in the inner structure of hydroxyapatite in the form of Ni2+[I] and Ni2+[II]. The catalytic activity of the Ni/HAP-D series of catalysts for CH 4 and CO 2 is significantly higher than that of the Ni/HAP series of catalysts, demonstrating that the Ni morphology, the combined form between Ni and support plays a crucial role in the DRM reaction. The deactivation rate of the Ni 0.5 /HAP-D catalyst is only 0.008% h−1 and 0.007% h−1 for CH 4 and CO 2 , respectively, in a 200-h durability test. In the spent Ni 0.5 /HAP catalyst after 118-h reaction, the presence of NiO crystalline phase is detected, indicating that partial Ni is oxidized by CO 2 during the reaction, and amorphous carbon and graphitic carbon are also detected. In contrast, no NiO crystalline phase is detected in the spent Ni/HAP-D catalyst after 200-h reaction, and only trace amounts of graphitic carbon are observed, indicating that the Ni presence pattern of Ni 0.5 /HAP-D contributes to its stability and resistance to carbon deposition. This work provides insights into the design of supported nickel-based catalysts with both excellent stability and surprisingly resistant to carbon deposits for DRM applications. [ABSTRACT FROM AUTHOR]