Study of catalytic hydrogenation performance for the Pd/CeO2 catalysts

Pd/CeO2 catalysts with different metallic Pd loading were synthesized by impregnation method. The physicochemical properties of prepared Pd/CeO2 catalysts and corresponding precursors were studied by XRD, XPS, H2-TPD and H2-TPR. Moreover, the catalytic performance of the Pd/CeO2 catalysts was investigated via gas phase benzene hydrogenation reaction at the temperature of 100–200 °C under atmosphere pressure. Results show that the catalytic performance of prepared Pd/CeO2 catalysts is directly related to the metallic Pd content. The amounts of active metallic Pd and adsorbed-desorbed hydrogen species on Pd/CeO2 catalysts increase with the increasing metallic Pd loading from 1.0 to 3.0%, while the numbers of them are slightly reduced on Pd/CeO2(3.5) catalyst. Furthermore, metallic Pd is highly dispersed on the nano-CeO2 supports, therefore, the prepared Pd/CeO2 catalysts present good gas phase benzene catalytic hydrogenation performance. At 200 °C, the benzene conversion over the Pd/CeO2 catalysts with different metallic Pd loading follows the rule: Pd/CeO2(3.0) > Pd/CeO2(3.5) > Pd/CeO2(2.5) > Pd/CeO2(2.0) > Pd/CeO2(1.5) > Pd/CeO2(1.0), corresponding values are 94.3, 96.4, 89.9, 82.8, 72.7, 42.6 and 94.3%. And the cyclohexane selectivity is 100% on all prepared Pd/CeO2 catalysts.

Hydrogenation of benzene and toluene over supported rhodium and rhodium-gold catalysts

Rhodium and rhodium-gold catalysts supported on amorphous aluminosilicates (ASA), titanium dioxide (rutile, TiO2) was prepared in two different ways: absorption and colloidal method. The catalysts were characterized by an inductively coupled plasma optical emission spectrometer (ICP-OES), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The activity and selectivity of the prepared catalysts were tested by the hydrogenation of benzene and toluene. Hydrogenation was conducted at a pressure of 4 MPa and a temperature 80 °C. The bimetallic Rh-Au/ASA catalyst prepared by the absorption method showed higher activity and selectivity in benzene hydrogenation reaction, the same catalyst prepared by the colloidal method demonstrated lower selectivity.

Formation of ruthenium nanoparticles inside aluminosilicate nanotubes and their catalytic activity in aromatics hydrogenation: the impact of complexing agents and reduction procedure

Ruthenium particles with size from 1 to 7 nm were formed by reduction of ruthenium complexes with urea, ethylenediaminetetraacetic acid, acetone azine, 1,2-Bis(2-furylmethylene)hydrazine) inside halloysite nanotubes. Catalysts of different morphology with Ru content from 0.75 to 0.93 %wt. were obtained using NaBH4 or H2 as reducing agents and tested in benzene hydrogenation as a model reaction. NaBH4 reduced catalysts showed similar catalytic activity with 100 % benzene conversion after 1.5 h. Reduction with H2 resulted in a decrease of catalytic activity for all samples. High benzene conversion was achieved only in the case of 1,2-Bis(2-furylmethylene)hydrazine and ethylenediaminetetraacetic acid. It was concluded that the thermal stability of complexing agents plays a key role in activity of catalysts reduced with H2.

Ruthenium Catalysts Templated on Mesoporous MCM-41 Type Silica and Natural Clay Nanotubes for Hydrogenation of Benzene to Cyclohexane

Mesoporous ruthenium catalysts (0.74–3.06 wt%) based on ordered Mobil Composition of Matter No. 41 (MCM-41) silica arrays on aluminosilicate halloysite nanotubes (HNTs), as well as HNT-based counterparts, were synthesized and tested in benzene hydrogenation. The structure of HNT core-shell silica composite-supported Ru catalysts were investigated by transmission electron microscopy (TEM), X-ray fluorescence (XRF) and temperature-programmed reduction (TPR-H2). The textural characteristics were specified by low-temperature nitrogen adsorption/desorption. The catalytic evaluation of Ru nanoparticles supported on both the pristine HNTs and MCM-41/HNT composite in benzene hydrogenation was carried out in a Parr multiple reactor system with batch stirred reactors (autoclaves) at 80 °C, a hydrogen pressure of 3.0 MPa and a hydrogen/benzene molar ratio of 3.3. Due to its hierarchical structure and high specific surface area, the MCM-41/HNT composite provided the uniform distribution and stabilization of Ru nanoparticles (NPs) resulted in the higher specific activity and stability as compared with the HNT-based counterpart. The highest specific activity (5594 h−1) along with deep benzene hydrogenation to cyclohexane was achieved for the Ru/MCM-41/HNT catalyst with a low metal content.