Enhancement of the Hydrogenation and Dehydrogenation Characteristics of Mg by Adding Small Amounts of Nickel and Titanium

We compared the hydrogenation and dehydrogenation properties of Mg-based alloys to which small amounts of transition elements (Ni and Ti), halides (TaF5 and VCl3), and complex hydrides (LiBH4 and NaAlH4) were added through grinding in a hydrogen atmosphere (reactive milling). Mg-1.25Ni-1.25Ti is one of the samples compared, having a composition of 97.5 wt.% Mg + 1.25 wt.% Ni and 1.25 wt.% Ti. Even though Mg-1.25Ni-1.25Ti did not have the highest initial hydrogenation rate, it had the largest quantities of hydrogen absorbed and released for 60 min and the highest initial dehydrogenation rate. In addition, Mg-1.25Ni-1.25Ti did not show the incubation period in the dehydrogenation. We thus investigated the hydrogenation and dehydrogenation properties of Mg-1.25Ni-1.25Ti in more detail. Activated Mg-1.25Ni-1.25Ti absorbed 5.91 wt.% H in 12 bar H2 and released 5.80 wt.% H in 1.0 bar H2 at 593 K for 60 min at n = 3. For 5 wt.% hydrogen absorption by Mg-1.25Ni-1.25Ti, 18.7 min was required at 593 K in 12 bar H2 at n = 3. Although only small amounts of Ni and Ti were added, the hydrogenation and dehydrogenation properties of Mg were greatly improved. Ni and Ti-added Mg had a higher initial dehydrogenation rate and a larger Hd (60 min) than only Ni-added Mg, suggesting that the TiH1.924 and NiTi formed in Mg-1.25Ni-1.25Ti play roles in the increases in the initial dehydrogenation rate and Hd (60 min), probably acting as active sites for the nucleation of the Mg-H solid solution phase.

Hydrogenation of Para-Nitrotoluene on Catalytic Systems Containing Oxides of Rare Earth Elements

This work is devoted to the study of the activity of 1% platinum catalysts containing rare earth element oxides (OREE) - Gd2O3, Ce2O3 and aluminum oxide as a carrier in the hydrogenation reactions of nitro compounds on the example of n-nitrotoluene. These catalytic systems in the conditions of liquid-phase hydrogenation provide high selectivity of the process and practically quantitative yield. The process was controlled by the potentiometric method, the reaction rate was judged by the amount of hydrogen absorbed per unit time. It is found that 20% and higher aqueous alcohol solutions can be used as a solvent during hydrogenation. It was found that the initial hydrogenation rate for 1% Pt/Gd2O3 is 3.2 times higher, and for 1% Pt/Ce2O3 Cerium it is 1.6 times higher relative to the 1% Pt/Al2O3 comparison catalyst.

Hydrogenation of Nitro Compounds over Catalytic Systems Containing Rare-Earth Oxides

The paper studies the activity of 1 % palladium catalysts containing rare earth oxides (REOs) and alumina as a carrier in the hydrogenation of nitro compounds exemplified by nitrobenzene and o-nitro anisole. Under the liquid-phase hydrogenation conditions, these catalytic systems provide high selectivity of the process and a quantitative yield. It has been found that the partial replacement of Al2O3 with REO allows increasing the hydrogenation rate by 5–6 times, as compared with the reference catalyst and by 1.2–1.7 times as compared with the individual carrier. The oxide mixtures (REO and Al2O3) containing 20–40 % REO allow reaching the same hydrogenation rate with that over an REO-containing 1 % Pd catalyst.

A synergetic effect between a single Cu site and S vacancy on an MoS2 basal plane for methanol synthesis from syngas

Compared to MoS2(001), the synergetic effect between the single Cu site and S vacancy on Cu/MoS2(001) destabilizes O, which not only increases the CO hydrogenation rate by 5 orders of magnitude, but leads to the selectivity switch from CH4 to CH3OH.

Number and intrinsic activity of cobalt surface sites in platinum promoted zeolite catalysts for carbon monoxide hydrogenation

A larger number and a more uniform distribution of cobalt sites with almost the same intrinsic activity results in higher carbon monoxide hydrogenation rate in the mordenite compared to ZSM-5 zeolite.

Carbon Nanotubes-Supported Well-Dispersed Pd Nanoparticles for the Efficiently Selective Hydrogenation of Benzoic Acid to Synthesize Cyclohexane Carboxylic Acid

Pd and carbon nanotube (CNT) composites were prepared by well-dispersed deposition of Pd nanoparticles on commercial CNT, and applied to the selective hydrogenation of benzoic acid (BA) to synthesize cyclohexane carboxylic acid (CCA). The catalysts and the hydrogenation products were analyzed by XRD, TEM, TG, FTIR, UV-Vis absorption, GC and GC-MS, respectively. Hydrogenation process was also optimized through varying the reaction parameters. The results demonstrate that Pd/CNT catalysts possess the highest hydrogenation efficiency, give the full conversion of BA and 100.0% selectivity towards CCA at the optimal hydrogenation conditions, by comparing with some commercial hydrogenation catalysts and Pd/C catalysts with commercial carbonaceous supports. The excellent hydrogenation performance of Pd/CNT is attributed to the stable crystalline CNT support and the high dispersion of Pd nanoparticles. In addition, the protic solvent is also beneficial to lower the activation energy barrier of BA hydrogenation, and further to improve the hydrogenation rate. This work implies that CNT can be potentially chosen as an effective carbonaceous support to prepare Pd/C catalyst with an outstanding performance of BA selective hydrogenation.

A New Concept of Stirred Multiphase Reactor Using a Stationary Catalytic Foam

Developing new stirred gas–liquid–solid reactors with high mass transfer capabilities is still a challenge. In this publication, we present a new concept of multiphase reactor using a stationary catalytic foam and a gas-inducing impeller. The gas–liquid (GL) and liquid–solid (LS) mass transfer rates in this reactor were compared to a stirred reactor with basket filled with beads. Batch absorption of hydrogen and measurement of α-methylstyrene hydrogenation rate on Pd/Al2O3 catalyst were used to evaluate kGLaGL coefficients and kLS coefficients, respectively. With similar LS transfer rates to the basket-reactor and much higher GL transfer rates, the new reactor reveals a very promising tool for intrinsic kinetics investigations.

ACETONE HYDRATION KINETICS AND EVALUATION OF INPUT OF 2-PROPANOL DEHYDRATION REACTION ON RANEY NICKEL UNDER HYDROGENATION CONDITIONS

The problem of kinetics of skeletal nickel samples saturation with hydrogen in an aqueous solution of 2-propanol of azeotropic composition was discussed. 2-propanol dehydrogenation and acetone hydrogenation rate constants were calculated. Kinetic model of processes under study was offered.

Enhancement of catalytic activity of Pd-PVP colloid for direct H2O2 synthesis from H2 and O2 in water with addition of 0.5 atom% Pt or Ir

Atomically dispersed Pt or Ir atoms enhance H2O2 and H2O formation on Pd nano-particles leaving the H2O2 hydrogenation rate unchanged, while Ru, Rh, or Au atoms show little effect.

Hollow mesoporous silica supported PtIr bimetal catalysts for selective hydrogenation of phenol: significant promotion effect of iridium

Ir promoted Pt catalyst is prepared using hollow mesoporous silica as support. It shows high hydrogenation rate of 4255 mmol h−1 gPt−1 at mild conditions (50 °C and 0.5 MPa of pH2). The promotion effect of Ir contributes to the enhanced activity.