Gyula Halasi

Production of hydrogen from dimethyl ether over supported rhodium catalysts

Infrared (IR) spectroscopy revealed that dimethyl ether (DME) undergoes partial dissociation on pure and rhodium‐containing CeO2 at 300 K to yield methoxy and methyl species. This process is promoted by the presence of rhodium. By means of thermal desorption measurements (TPD), the adsorption of DME on Rh/CeO2 at 300 K and subsequent decomposition of DME (Tp≈370 K), releasing H2, CO, CO2, and CH4, with Tp between 420 and 673 K, were ascertained. Rh/CeO2 is an effective catalyst for the decomposition of DME to give H2 (29–35 %), CO (27–30 %) and CH4 (32–38 %) as major products with complete conversion at 673–723 K. Adding water to DME changed the product distribution and increased the selectivity of H2 formation from 30–35 % to 58 % at 723 K. In situ IR spectroscopy showed absorption bands of CO at 2034 and 1893 cm−1 during the reaction at 673–773 K. Deactivation of the catalyst did not occur at 773 K during the time measured (approximately 10 h). Rh deposited on carbon Norit also exhibited a high activity towards the decomposition of DME, but the selectivity towards hydrogen was lower.

Outstanding Activity and Selectivity of Controlled Size Pt Nanoparticles Over WO3 Nanowires in Ethanol Decomposition Reaction

Pt nanoparticles with controlled size of 1.5 and 6.5 nm were anchored onto the surface of WO₃ nanowires (WO₃NW) as well as on MCF-17 silica. In the case of WO₃NW and MCF-17 supported nanoparticles, 1.5 nm Pt nanoparticles were more active in ethanol decomposition reaction at 533 K. 6.5 nm Pt/WO₃NW catalyst showed ~6 times higher activity compared to MCF-17 supported 6.5 nm Pt nanoparticles. While MCF-17 supported catalysts produced hydrogen, methane, carbon-monoxide and acetaldehyde, the tungsten-oxide supported Pt nanoparticles produced a huge amount of acetone as well as ethene with a high acetaldehyde selectivity besides H₂, CH₄ and CO. The hydrogen formation was significantly higher when the Pt size was 1.5 nm. The metallic nanoparticles, the acid sites and the oxidized centers of support play important role in the formation of decomposition products of ethanol.

Designed Pt Promoted 3D Mesoporous Co3O4 Catalyst in CO2 Hydrogenation

Controlled size Pt nanoparticles were anchored onto the surface of 3D mesoporous cobalt-oxide support and was tested in CO₂ hydrogenation reactions compared to commercial cobalt-oxide supported Pt nanoparticles prepared by the wet impregnation method as well as SBA-15 silica supported nanoparticles. Designed Pt/mesoporous cobalt-oxide catalysts showed the highest activity as well as the highest methane selectivity. Such catalyst was active at 573 K, while other catalysts showed activity >673 K.

Development and Application of Carbon-Layer-Stabilized, Nitrogen-Doped, Bamboo-Like Carbon Nanotube Catalysts in CO2 Hydrogenation

Abstract Nitrogen‐doped, bamboo‐like carbon nanotubes (BCNTs) were synthesized from butylamine by catalytic chemical vapor deposition (CCVD method). The nanotubes were oxidized by H2SO4/HNO3 treatment and used to prepare calcium alginate gelled BCNT spheres. These beads were first carbonized and then Pd, Rh and Ni nanoparticles were anchored on the surface of the spheres. These systems were then applied as catalysts in CO2 hydrogenation. The BCNT support was examined by Raman spectroscopy, dynamic light scattering (DLS) and X‐ray photoelectron spectroscopy (XPS). The prepared catalysts were characterized by HRTEM and SEM. The oxidation pretreatment of BCNTs was successful, with the electrokinetic potential of the water‐based dispersion of BCNTs measuring −59.9 mV, meaning the nanotube dispersion is stable. Pyridinic and graphitic types of incorporated nitrogen centers were identified in the structure of the nanotubes, according to the XPS measurements. The Pd‐containing BCNT sphere catalyst was the most efficient in the catalytic studies. The highest conversion was reached on the Pd catalyst at 723 K, as well as at 873 K. The difference in the formation rate of CO was much less at 873 K between the Pd and Rh compared to the 723 K values. Accordingly, the application of Pd‐containing BCNT/carbon‐supported catalyst favored the generation of CO. However, the Ni‐BCNT/carbon catalyst leads to the formation of CH4 as the major product.

Exploring Pd/Al2O3 Catalysed Redox Isomerisation of Allyl Alcohol as a Platform to Create Structural Diversity

We report our results on exploiting the different reactivities present in the catalytic cycle of the Pd/Al2O3 catalyzed redox isomerization of allyl alcohol. We show that the reactivity of allyl alcohol derived acrolein and enol can be involved in further cascade reactions leading to a diverse set of products. While the oxidation product acrolein can react via Michael and oxa-Michael reactions, the isomerization product enol can be readily involved in aldol condensation processes. Salicylaldehydes, that are able to react on their electrophilic carbonyl and nucleophilic OH-groups with allyl alcohol derived enol and acrolein, respectively, are used to explore conditions where the structure of the product heterocycles can be controlled.Graphical Abstract