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

Ethane steam reforming over a platinum/alumina catalyst: effect of sulphur poisoning

In this study we have examined the adsorption of hydrogen sulfide and methanethiol over platinum catalysts and examined the effect of these poisons on the steam reforming of ethane. Adsorption of hydrogen sulfide was measured at 293 and 873 K. At 873 K the adsorbed state of hydrogen sulfide in the presence of hydrogen was SH rather than S, even though the Pt:S ratio was unity. The effect of 11.2 ppm hydrogen sulfide or methanethiol on the steam reforming of ethane was studied at 873 K and 20 barg. Both poisons deactivated the catalyst over a number of hours, but methanethiol was found to be more deleterious, reducing the conversion by almost an order of magnitude, possibly due to the co-deposition of sulfur and carbon. Changes in the selectivity revealed that the effect of sulfur was not uniform on the reactions occurring, with the production of methane reduced proportionally more than the other products, due to the surface sensitivity of the hydrogenolysis and methanation reactions. The water-gas shift reaction was affected to a lesser extent. No regeneration was observed when hydrogen sulfide was removed from the feedstream in agreement with adsorption studies. A slight regeneration was observed when methanethiol was removed from the feed, but this was believed to be due to the removal of carbon rather than sulfur. The overall effect of sulfur poisoning was to reduce activity and enhance hydrogen selectivity

Impact of the morphology and reactivity of nanoscale zero-valent iron (NZVI) on dechlorinating bacteria

Abstract Nanoscale zero-valent iron (NZVI) is increasingly used for reducing chlorinated organic contaminants in soil or groundwater. However, little is known about what impact the particles will have on the biochemical processes and the indigenous microbial communities. Nanoiron reactivity is affected by the structure and morphology of nanoparticles that complicates the applicability in bioremediation. In this study, the effect of precursors (ferrous sulfate and ferric chloride) and reducing agents (sodium dithionite and sodium borohydride) on the morphology and the reactivity of NZVIs was investigated. We also studied the impact of differently synthesized NZVIs on microbial community, which take part in reductive dechlorination. We demonstrated that both the applied iron precursor and the reducing agent had influence on the structure of the nanoparticles. Spherical nanoparticles with higher Fe0 content (>90%) was observed by using sodium borohydride as reducing agent, while application of sodium dithionite as reducing agent resulted nanostructures with lower Fe0 content (between 68,7 and 85,5%). To determine the influence of differently synthesized NZVIs on cell viability anaerobic enriched microcosm were used. NVZI was used in 0.1 g/L concentration in all batch experiments. Relative amount of Dehalococcoides, sulfate reducers (SRBs) and methanogens were measured by quantitative PCR. We found that the relative amount of Dehalococcoides slowly decreased in all experiments independently from the precursor and reducing agent, whereas the total amount of microbes increased. The only clear distinction was in relative amount of sulfate reducers which were higher in the presence of NZVIs synthesized from sodium dithionite