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The reduction reaction of carbon dioxide (RR -CO 2) to CH 3 OH using metal catalysts can reduce the energy required by this process. In this study, we investigated the RR -CO 2 mechanisms with Cu-, Ni-, and Mn-doped carbon nanotubes (CNTs). The substitutional (doping with carbon atom) positions in CNTs are suitable sites for adsorbing Cu, Ni, and Mn metals. The reaction paths to the RR -CO 2 were investigated in the gas and solvent phases. The results demonstrated that the overpotential values with Cu-, Ni-, and Mn-doped CNT(8, 0) and CNT(6, 6) catalysts in the gas and solvent phases were lower than that obtained with metal catalysts in previous studies (−1.116 V). Thus, metal-doped CNT(8, 0) and CNT(6, 6) catalysts with low overpotentials could be applied in the RR -CO 2. • Potential of nano-structures to RR- CO 2 is examined. • Possible reaction mechanisms for CO 2 reduction to CH 3 OH are investigated. • Over potential of RR- CO 2 on nano-structures are lower than metal catalysts. • Nano-structures are proposed as efficient catalysts for RR- CO 2. [ABSTRACT FROM AUTHOR]

Ni 10 La x /MAO catalysts with high Ni dispersion was prepared by wet impregnation method. Characterization results showed that metal dispersion of Ni obviously improved on catalyst surface after La doping. Under the long-term reaction conditions (800 °C, 10 h), Ni 10 La 5 /MAO catalyst could exhibit the highest catalytic performance (93% of CH 4 conversion, 71% of CO 2 conversion and less than 3% activity loss) with lower Ni particle size (12.6 nm) and carbon deposition (8.9 %). [Display omitted] • La doping significantly increased the content of active species Ni0. • High dispersion of Ni species efficiently inhibited the growth of carbon. • Ni 10 La 5 /MgAl 2 O 4 catalyst owned the highest catalytic activity and stability in methane bi-reforming system. Ni-based catalysts were widely studied for methane reforming system in the past decades, while catalytic deactivation by carbon deposition and metal sintering limited its industrial application life. In this work, La-promoted Ni/MgAl 2 O 4 catalysts were investigated over methane bi-reforming reaction, and significantly improved the activity and stability of catalysts. Multiple characterizations showed that the introduction of La increased the content and dispersion of active species (Ni0), providing sufficient sites for methane adsorption and dissociation. Besides, smaller particle size of active metal (12.6 nm) was proved to inhibiting carbon accumulation on catalyst surface. Ni 10 La 5 /MgAl 2 O 4 catalyst was found to exhibit the highest catalytic performance (93% of CH 4 conversion, 71% of CO 2 conversion and less than 3% activity loss) under long-term reaction conditions (800 °C, 10 h). This work will provide important guiding significance for the design of high-efficiency methane reforming catalysts. [ABSTRACT FROM AUTHOR]

We successfully realized the highly selective aromatization of n-hexane by the assistance of CO 2 over Zn modified HZSM-5 catalyst. The in situ H originated from the C-H activation of n-hexane and cyclohexane could be timely removed through the dynamic evolution between CO 2 and Lewis acid site, thus inhibiting the hydrogen transfer side reaction and promoting the desorption of BTEX. Therefore, the Zn/ZSM-5-CO 2 catalyst exhibits as high as 49.7% BTEX yield, which is nearly 10% higher than that of the Zn/ZSM-5-N 2 catalyst (40.3%). [Display omitted] • The introduction of CO 2 could timely remove the in situ H. • Hydrogen transfer between olefins and aromatics is effectively inhibited. • The binding of hydrogen proton to π electrons is weakened. • The loss of medium strength Lewis acid is significantly reduced. • The Zn/ZSM-5-CO 2 catalyst exhibits as high as 49.7% BTEX yield and superior catalytic stability. Controlling the evolution of H species in CO 2 -assisted alkane activation represents an opportunity for simultaneously upgrading light alkanes and greenhouse gas CO 2. Herein, we successfully realized the highly selective aromatization of n -hexane by the assistance of CO 2 over Zn modified HZSM-5 catalyst. Multi-characterizations demonstrated that the introduction of CO 2 could timely remove the in situ H originated from the C-H activation of n -hexane and cyclohexane through the dynamic evolution of the pentagonal coordination Zn-OH+-(CO)-O-Zn structure. On this basis, hydrogen transfer between olefins and aromatics is effectively inhibited, and the binding between π electrons of benzene ring and hydrogen proton is weakened, accelerating the generation and desorption of BTEX. Therefore, the Zn/ZSM-5-CO 2 displays a record high 49.7% BTEX yield, which is nearly 10% higher than that of the Zn/ZSM-5-N 2 (40.3%). In addition, the loss of medium strength Lewis acid caused by in situ H reduction of Si(Al)-O-Zn structure is significantly reduced, ensuring its superior catalytic stability under long-term conditions. These results may provide some insights for the profitable utilization of petrochemical resources to aromatics over zeolites. [ABSTRACT FROM AUTHOR]