A DFT Study on the Catalytic CO Oxidative Coupling to Dimethyl Oxalate on Al-Doped Core–Shell Pd Clusters

A series of core–shell catalysts aiming at CO oxidative coupling to dimethyl oxalate (DMO) were constructed, and effects of the second metal doping and surface structures on the reaction activity and favorable reaction path were investigated by using the density functional theory (DFT) method. Pd₁₃, Al@Pd₁₂, and Ag@Pd₁₂ were first studied to find the proper doping metal. Our results showed that the activity of CO oxidative coupling to DMO follows the order of Al@Pd₁₂ > Pd₁₃ > Ag@Pd₁₂, and the same result was also obtained via the electronic analysis. In addition, Al₆@Pd₃₂ and Al₁₃@Pd₄₂ catalysts with higher doping ratio and lower cost than that of Al@Pd₁₂ were selected to examine the influence of surface structure on the reaction activity. It showed that CO + CH₃O → COOCH₃ + CO → OCCOOCH₃ + CH₃O → DMO is the favorable pathway on the (100) surface of Al₆@Pd₃₂ catalyst, while CO + CH₃O → CO + CH₃O (COOCH₃) → COOCH₃ + COOCH₃ → DMO is the optimal pathway on the (111) surface of Al@Pd₁₂ and Al₁₃@Pd₄₂, which indicated that the surface structure of catalysts affected the preferable pathway of DMO formation. Moreover, activities of CO oxidative coupling to DMO on AlPd core–shell catalysts followed the order of Al@Pd₁₂ > Al₁₃@Pd₄₂ > Al₆@Pd₃₂. In addition, Al₁₃@Pd₄₂ also exhibited a good selectivity between DMO and DMC. Thus, Al₁₃@Pd₄₂ is a proper catalyst with high activity, high selectivity, and low cost because of high Al:Pd ratio

A Highly Stable and Active CaO/Al2O3 Base Catalyst in the Form of Calcium Aluminate Phase for Oxidation of Cyclohexanone to epsilon-Caprolactone

National Natural Science Foundation of China [20973140, 201106118, 21303140]A series of CaO/Al2O3 base catalysts with different crystal phases is prepared via thermal treatment. The as-prepared base catalysts are tested through Baeyer-Villiger oxidation of cyclohexanone to epsilon-caprolactone in liquid-phase using a mixture of aqueous hydrogen peroxide and benzonitrile as oxidant. The corresponding results show that the CaO/Al2O3 catalysts with high thermal treatment temperature (e.g. 900 A degrees C) exhibit excellent activity as well as stability. Upon these, the catalysts are characterized by TG-DTG, XRD, N-2-physisorption, SEM and CO2-TPD techniques. The characterization results clearly suggest that such a stable and efficient catalytic performance is beneficial from the formation of calcium aluminate phase, thus overcoming one of base catalyst application barriers, that Ca or CaO species loss (leach) from CaO-based catalysts during reactions. Correspondingly, it can be inferred that the treatment of the catalysts at different temperatures results in the diverse distribution of basic strength. Furthermore, it is also demonstrated that the suitable base strength (medium strength is good for the reaction selected in the work) plays a critically role in the improvement of catalytic performance. Finally, the effects of operation conditions on catalytic activity and product selectivity are also determined and discussed

A highly stable and active CaO/Al2O3 base catalyst in the form of calcium aluminate phase for oxidation of cyclohexanone to Ε-caprolactone

A series of CaO/Al2O3 base catalysts with different crystal phases is prepared via thermal treatment. The as-prepared base catalysts are tested through Baeyer-Villiger oxidation of cyclohexanone to Ε-caprolactone in liquid-phase using a mixture of aqueous hydrogen peroxide and benzonitrile as oxidant. The corresponding results show that the CaO/Al2O3 catalysts with high thermal treatment temperature (e.g. 900 °C) exhibit excellent activity as well as stability. Upon these, the catalysts are characterized by TG-DTG, XRD, N 2-physisorption, SEM and CO2-TPD techniques. The characterization results clearly suggest that such a stable and efficient catalytic performance is beneficial from the formation of calcium aluminate phase, thus overcoming one of base catalyst application barriers, that Ca or CaO species loss (leach) from CaO-based catalysts during reactions. Correspondingly, it can be inferred that the treatment of the catalysts at different temperatures results in the diverse distribution of basic strength. Furthermore, it is also demonstrated that the suitable base strength (medium strength is good for the reaction selected in the work) plays a critically role in the improvement of catalytic performance. Finally, the effects of operation conditions on catalytic activity and product selectivity are also determined and discussed. ? 2014 Springer Science+Business Media New York

Synthesis of different ruthenium nickel bimetallic nanostructures and an investigation of the structure-activity relationship for benzene hydrogenation to cyclohexane

The catalytic properties of catalysts are generally highly dependent on their nanostructures in most heterogeneous catalytic reactions. Therefore, to acquire targeted catalytic activity, selectivity, and stability, catalysts with a specific nanostructure should be designed and synthesized. Herein, Ru-Ni bimetallic nanoparticles with different nanostructures, Ru-Ni alloy, Ru@Ni, and Ru clusters-on-Ni on carbon, have been synthesized by annealing Ru-Ni/C in flowing N2+10% H2 at different temperatures. The various nanostructures of the Ru-Ni bimetallic nanoparticles have been characterized and their catalytic behaviors were evaluated using benzene hydrogenation to cyclohexane. The relationship between the Ru-Ni bimetallic nanostructures and their catalytic performance is presented. It was found that Ru-Ni alloy/C and Ru clusters-on-Ni/C are much more active than Ru@Ni/C. This study also provides a simple method to design and control the nanostructures of the Ru-Ni bimetallic nanoparticles. ? 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim