Study of 1.8 NM Pt nanoparticles anchored on different amorphous silica supports in ethanol decomposition reaction

1.8 nm Pt nanoparticles with narrow size distribution were anchored on mostly identical, amorphous silica supports (SBA-15 [1], MCF-17 [2], Silica Foam [3]) and were tested in ethanol decomposition reactions at < 573 K. The reaction on the Pt/SF (0.117 molecules·site-1 ·s-1 ) was ~2 times faster compared to Pt/MCF-17 (0.055 molecules·site-1 ·s-1 ) and Pt/SBA-15 (0.063 molecules·site-1 ·s-1 ) at 573 K. In the case of Pt/SBA-15, selectivity towards acetaldehyde was ~4 times higher (68%) compared to the Pt/MCF-17 (18%) and Pt/SF (16%) catalysts. In the case of Pt/MCF-17 and Pt/SF, the methane to acetaldehyde ratio was 0.27 and 0.24, respectively, while it was ~ 10 times higher (1.97) for Pt/SBA-15 catalyst. The ethene selectivity was ~2 times higher in the case of Pt/MCF-17 (0.99%) and Pt/SF (0.93%) compared to Pt/SBA-15 (0.41%). Pt/MCF17 and Pt/SBA-15 produces ~ 50% more hydrogen (~27%) compared to Pt/SF catalyst (21 %). Small Angle X-ray Scattering (SAXS) and Transmission Electron Microscopy (TEM) studies showed striking differences in the porosity, pore- and mesostructure, sintering and Pt-SiO2 interface altering effect of the silica supports as well as the Pt nanoparticles decorated catalysts which may have significant effect on the catalytic activity

Optimalization of ceramic-based noble metal-free catalysts for CO oxidation reactions

In this study ceramic supported noble metal-free catalysts promoting the oxidation of CO were examined. In the course of our work several non-noble metal containing catalysts were prepared with different metal content by the well-known wet impreg- nation method and their catalytic activities were analyzed by gas chromatography (GC) experiments in CO oxidation reaction. In addition to GC measurements, X-ray diffraction, scanning electron microscopy, BET and X-ray photoelectron spectros- copy tests were also performed on our samples. During our work we found that cobalt-loaded silica-alumina-based ceramic supported catalyst proved to be the best in CO oxidation due to the high activity and durability with comparable activity with Pt-loaded counterpart

Nitrogen doped carbon aerogel composites with TiO2 and ZnO prepared by atomic layer deposition

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Turning CO2 to CH4 and CO over CeO2 and MCF-17 supported Pt, Ru and Rh nanoclusters – Influence of nanostructure morphology, supporting materials and operating conditions

Efficient conversion of CO2 into CH4 and CO brings an important opportunity to get valuable feedstock for a variety of industrially important reactions as both CH4 and CO are widely used as starting materials for the synthesis of valuable fuels and chemicals. Herein, we synthesized sub-nanometer (<2nm) Platinum (Pt), Ruthenium (Ru) and Rhodium (Rh) nanoclusters (NCs) via colloidal method; successfully decorated over mesoporous CeO2 and high surface area (HSA) siliceous meso-cellular foam (MCF 17) and tested for high-pressure CO2 reduction at lower temperature range (220–340 ◦C). Pt and Ru NCs exhibited typical reverse water gas shift (RWGS) and methanation catalytic performance respectively with minimal influence of the nature of support however, Rh NCs showed drastic variations in the product selectivity which exhibited strong influence of the support over the product distribution. Furthermore, Ru NCs (with a relatively lower metal loading ~ 1 wt %) were found to be highly selective to CH4 (~99 %) and stable (upto 40 hr time on stream) with either CeO2/MCF 17 at 340 ◦C; also Ru NCs exhibited comparatively the highest CO2 conversion (~93 % in case of Ru NCs/CeO2) among the supported metal NCs. HRTEM results showed that metal NCs were homogeneously dispersed with a controlled and uniform particle size (<2nm); no substantial agglomeration of Ru NCs were observed after reaction. Beside the stable dispersion of NCs, Near Ambient Pressure (NAP) in situ XPS of Ru/CeO2 showed that the dynamic Ce3+/Ce4+ ratio of CeO2 can attribute to the high activity and selectivity

Szénhidrogének és alkoholok reakciójának katalitikus és felületkémiai vizsgálata = Catalytic and surface science studies related to the reactions of hydrocarbons and alcohols

Tanulmányoztuk a benzol, metanol, dimetil és dietil éter aromatizációját és a metilezését a ZSM-5 zeolitra rávitt Mo2C, Ga2O3 és ZnO-on. Mindhárom anyag hatásosan katalizálta a metanol aromatizációját, és a Mo2C/ZSM-5 elősegítette a benzol metilezését is. Spektroszkópiai módszerekkel feltártuk a zeolit és a Mo2C szerepét. Kísérleteink másik részében a hidrogén előállítására koncentráltunk. Elsődleges célunk a drága platina fémeket helyettesítő olcsó és stabilis katalizátor szintézise volt. Erre a célra legmegfelelőbbnek ismét a Mo2C bizonyult. Amennyiben a Mo2C-t nagy felületű többfalú szén nanocsőre vagy Norit szénre vittük rá, az alkoholok átalakításának iránya megváltozott: az etanol és metanol aromatizációja helyett a hidrogén képződése került előtérbe. A hidrogén előállításával kapcsolatos kutatási programunk talán egyik legfontosabb eredménye, hogy a Mo2C/carbon katalizátoron a HCOOH bomlásának katalízisével sikerült tiszta, CO mentes hidrogént előállítanunk alacsony hőmérsékleten. Párhuzamosan folyó elektron-spektroszkópiai módszerekkel feltártuk a reakciók primér lépéseit és a felületen képződő gyökök átalakulásának irányát. Elektron- foton- és ion spektroszkópiával (AES, XPS, LEIS, RAIRS), valamint STM-el tanulmányoztuk a kétfémes nanoszerkezetek képződését és fizikai-kémiai sajátságait egykristály titán-dioxid felületen. Eredményeinket 20 nemzetközi folyóiratban megjelent dolgozatban közöltük és azokról különböző nemzetközi konferenciákon 35 előadást tartottunk. | The adsorption and reaction pathways of methanol, dimethyl and diethyl ethers have been investigated on pure and Mo2C containing ZSM-5. ZSM-5 effectively catalyzed the reaction of all the three compounds above 473 K to yield various olefins and aromatics. Adding Mo2C to the zeolites greatly promoted the formation of aromatics very likely by catalyzing the aromatization of olefins formed in the reaction. Addition of benzene to dimethyl ether markedly increased the formation of toluene, xylene and C9 aromatics on ZSM-5. The enhancement was further increased by ZnO and Mo2C promoters. Extensive research has been carried out recently to develop a procedure for the production of clean hydrogen for fuel cells. Efforts were also made to replace the expensive Pt metals with more effective, stable, and less expensive catalysts. We found that Mo2C when it is prepared on different carbon supports is an effective catalyst for the decomposition of alcohols and ether to give hydrogen. In the case of reforming of HCOOH we achieved to produce H2 free of CO. The adsorption and reaction pathways of above compounds on Mo2C/Mo(100) have been studied by several electron spectroscopic methods. The results helped to establish the mechanism of the catalytic reactions. Detailed spectroscopic experiments were performed concerning the interaction of Au with Rh on TiO2(100). We gave account on our results in 20 papers published in international journals, and presented 35 lectures at various Conferences

In-situ DRIFTS and NAP-XPS Exploration of the Complexity of CO2 Hydrogenation over Size Controlled Pt Nanoparticles Supported on Mesoporous NiO

4.8 nm Pt nanoparticles were anchored onto the surface of mesoporous nickel-oxide supports (NiO). Pt/NiO samples were compared to pristine NiO and Pt/SBA-15 silica catalysts in CO2 hydrogenation to form carbon-monoxide, methane and ethane at 473-673 K. 1 % Pt/NiO were ~20 times and ~1.5 times more active at 493 K compared to Pt/SBA-15 and NiO catalysts, respectively. However, the Pt-free NiO support has an activity of 120% compared to Pt/NiO catalysts at 673 K. In the case of 1% Pt/SBA-15 catalyst, selectivity towards methane was 13 %, while it was 90% and 98% for NiO and 1% Pt/NiO at 673 K, respectively. Exploration of the results of the reactions was performed by Near Ambient Pressure X-ray Photoelectron Spectroscopy (NAP-XPS) as well as in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). In the case of pure NiO, we found that the surface of the support was mainly covered by elemental Ni under reaction condition, where the Ni/NiOx system is responsible for the high activity of Pt-free catalyst. In the case of Pt/NiO, Pt improves the reduction of NiOx towards metallic Ni. In the case of the 1 % Pt/NiO catalysts, the presence of limited amount of Pt resulted in an optimal quantity of oxidized Pt fraction at 673 K showing the presence of a Pt/PtOx/Ni/NiOx mixed phase where the different interfaces may be responsible for the high activity and selectivity towards methane. In the case of pure NiO under reaction condition, small amounts of formaldehyde as well as hydrogen perturbed CO [HnCO (n=1,2)] were detected. However, in the case of 1 % Pt/NiO catalysts, besides the absence of formaldehyde a significant amount of HnCO (n=2-3) was present on the surface responsible for the high activity and methane selectivity