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Abstract: Supported gold nanoparticles have been proven to be active in the hydrogenation of the acetylene. In this work, we applied gold nanoparticles supported on silica for the selective hydrogenation of acetylene in excess ethylene that was close to current industrial practices. Amine group surface-functionalized silica was used to absorb the gold precursor , and small size-controlled gold nanoparticles are formed after chemical reduction. For the first time, O2 plasma was employed to remove the APTES grafted on the surface of silica for preparing the highly dispersed gold nanoparticles (∼3nm). The results of IR, TGA, XRD, and TEM showed that O2 plasma working under mild conditions (room temperature and low pressure) can efficiently remove the organic compounds without causing the aggregation of the gold nanoparticles. The plasma-treated catalyst Au/SiO2 gave excellent low-temperature selective catalytic activity in the hydrogenation of acetylene. The effects of the reduction temperatures on the catalytic performances of the Au/SiO2 were investigated. The enhanced performance of gold nanoparticles supported on silica as pretreated by O2 plasma was ascribed to two effects: (1) the small size of the gold nanoparticles supported on silica, (2) the nearly neutral charge on the Au nanoparticle, which is favorable to the activation of hydrogen. [Copyright &y& Elsevier]

Abstract: Au–Cu bimetallic nanoparticles supported on SBA-15 have been reported to be much more active in CO oxidation than the corresponding monometallic counterparts in our previous work. In this work, in situ techniques including XRD, EPR, XANES, and FT-IR were employed to reveal the structural changes of the Au–Cu bimetallic particles during different pretreatment and reaction conditions, and to clarify the essence of the synergistic effect between gold and copper. The results showed that gold remained as Au0 in any treatment conditions, while copper was very sensitive to the treatment temperature and atmosphere. The freshly reduced catalyst was a mixture of Au3Cu1 intermetallic phase and Cu2O amorphous phase. In CO oxidation, the Au3Cu1 intermetallic phase was segregated into a gold core decorated with tiny CuO x patches, and CO adsorbed on Au0 reacted with active oxygen provided by the neighboring CuO x , thus enhancing greatly the activity for CO oxidation. [Copyright &y& Elsevier]

A Ru-Mo bimetallic catalyst was developed by decorating Ru NPs with mononuclear Mo5+Ox for the selective hydrodeoxygenation (HDO) of amides to amines, where the C O bond of amide is selectively activated on the low-coordinated mononuclear Mo5+Ox sites and the HDO reaction proceeds at the interface of Ru and Mo5+Ox. [Display omitted] • A highly active, selective and stable RuMo/SiO 2 catalyst with Ru nanoparticles of ∼ 2 nm decorated with mononuclear Mo5+Ox has been developed for the HDO of primary amides to amines. • The catalytic performance relies critically on the Mo/Ru ratio, and high activity and selectivity are only achieved when Mo/Ru ratio is smaller than 0.12 where mononuclear Mo5+Ox dominates. • The characterizations and reaction kinetics show that the C O bond of the amide is activated on the low-coordinated mononuclear Mo5+Ox species and the reaction proceeds at the MoRu interface. The selective hydrodeoxygenation (HDO) of amides is a key methodology to producing amines, yet it remains a great challenge due to the highly stable amide molecular structure. In this study a series of 2Ru x Mo/SiO 2 (x = 0 ∼ 3) catalysts were prepared with sequential impregnation method followed by reduction. The reaction tests showed that the target amine yield presented a volcano-shape dependence on the Mo content, and reached the highest value at the Mo content of 0.2 wt% which corresponded to a Mo/Ru atomic ratio of 0.11 and a Mo surface density of 0.08. By contrast, a higher Mo content resulted in dramatic decrease in both activity and selectivity. By using HAADF-STEM, X-ray absorption spectroscopy (XAS), H 2 -TPR and CO-chemisorption, the structure of the best-performance 2Ru0.2Mo/SiO 2 catalyst was identified as Ru NPs of ∼ 2 nm decorated with mononuclear Mo5+O x species, which was in contrast with the polymeric MoO 2 -like species partially covering the Ru surface for the 2Ru3Mo/SiO 2. Kinetic studies revealed that the reaction order with respect to CyCONH 2 was 1.2, −0.1 and −0.5 over the 2Ru/SiO 2 , 2Ru0.2Mo/SiO 2 and 2Ru3Mo/SiO 2 , respectively, which indicated amide was selectively activated on the low-coordinated Mo5+O x sites while H 2 was activated on the Ru sites and the reaction proceeded at the Mo-Ru interface. The turnover frequency based on interfacial Ru-Mo sites reached 407.8 h−1, which was more than twofold higher than that of Ru-W system (175.6 h−1) we previously reported. [ABSTRACT FROM AUTHOR]

Catalytic hydrogenation of CO 2 to methane was investigated over Ru/rutile TiO 2 , focusing on the influence of the pretreatment temperature on the activity. Rutile TiO 2 stabilized Ru nanoparticles even after pretreatment at 800 °C; therefore it was possible to establish the structure–activity relationship without considering the particle size effect. The CO 2 turnover frequency initially increased with increasing pretreatment temperature from 300 to 800 °C, and reached a maximum value of 1.59 s −1 on Ru/rutile TiO 2 pretreated at 600 °C; it decreased to 1.16 s −1 for the sample pretreated at 800 °C. The characterization results indicated that the activity depended on both the extent of encapsulation of Ru particles by TiO x layers and the number of hydroxyl groups on the TiO x surface. The mechanism of CO 2 methanation was discussed based on in situ diffuse-reflectance infrared Fourier-transform spectroscopy results. [ABSTRACT FROM AUTHOR]

Abstract: Hydrous hydrazine, such as hydrazine monohydrate (N2H4·H2O), is a promising hydrogen carrier material due to its high content of hydrogen (8.0wt%). The decomposition of hydrous hydrazine to H2 with a high selectivity and a high activity under mild conditions is the key to its potential usage as a hydrogen carrier material. Platinum-modified Ni/Al2O3 catalysts (NiPt x /Al2O3) were prepared starting from Ni–Al hydrotalcite and tested in the decomposition of hydrous hydrazine. Compared with Ni/Al2O3, the TOF was enhanced sevenfold over NiPt0.057/Al2O3; meanwhile, the selectivity to H2 was increased to 98%. Characterization results by means of HAADF-STEM, XRD, and EXAFS revealed the presence of surface Pt–Ni alloy in this Pt-promoted catalyst. The formation of Pt–Ni alloy could significantly weaken the interaction between adspecies produced (including H2 and NH x ) and surface Ni atoms, which is confirmed by microcalorimetry and TPD results. The weakening effect could account for the greatly enhanced reaction rate, as well as H2 selectivity on NiPt x /Al2O3 catalysts. [Copyright &y& Elsevier]