Written by: Tamás Ollár. Supervisor: Dr. Pál Tétényi. Theses of the PhD dissertation

Transcription

1 Theses of the PhD dissertation The effect of the sulfur mobility over sulfide catalysts in thiophene desulphurisation process Doctoral School of Chemical Engineering and Material Science, University of Pannonia Written by: Tamás Ollár Supervisor: Dr. Pál Tétényi Centre for Energy Research Hungarian Academy of Science Budapest 2013

2 1. INTRODUCTION AND OBJECTIVES Catalytic hydrogenation techniques have been used in the refining of crude oil for more than 80 years. Currently, the production of petroleum industry aims at improved quality and environmentally friendly motor fuels. More detailed knowledge of the active site is essential for developing catalytic desulfurization process and catalyst properties. Thiophene hydrodesulfurization (HDS) reaction over MoS 2 containing catalysts produced H 2 S and hydrocarbons. Well-known correlation exists between the sulfur exchange capacity and the thiophene HDS activity of the catalysts. HDS activity is generally attributed to vacancies at the edge sites, Vogelaar et al., however, pointed out that the main reason for deactivation during thiophene HDS is the loss of sulfur from the active phase. Therefore the mobility of the catalytic sulfur plays an important part in HDS. A number of studies of HDS catalysts have descovered some kind of correlation between the exchangeable sulfur species on sulfide catalysts and hydrodesulfurization activity. Massoth et al. observed a linear correlation between the total sulfur exchange capacity and thiophene hydrodesulfurization activity of different metal-promoted molybdenum- and tungsten-oxide based catalysts. The general objectives of my research and development work was to answer, how general is the linear correlation between S exchange and HDS activity (whether there is any correlation in the case of new generation catalysts?), what is the reason of this correlation, and what is the role of the surface sulfur in the HDS process. Examinations were carried out on alumina supported sulfided Mo catalysts prepared by impregnation in our laboratory and newly developed, industrially used catalysts, produced by well-known firms.

3 2. EXPERIMENTAL The amounts of sulfur uptake and exchange were determined by radioisotope tracer method in a gas circulation apparatus using 35 S labelled hydrogen sulfide (H 2 35 S). H 2 35 S were prepared in our laboratory from H 2 35 SO 4 by reducing it over fine iron powder. For this study it was necessary to develop the methodology for measuring the isotopic tracer, for accurate detection of small quantities. To this end, samples from the gas phase were absorbed in NaOH solution and shaked with special scintillation mixture and the radioactivity were determined by liquid scintillation spectrometer. Experiments of catalytic reactions have been performed in a gas circulation apparatus as well as in pulse reactor. The thiophene conversion products were analysed by on-line joined gas chromatograph and liquid scintillation spectrometer.

4 3. NEW SCIENTIFIC RESULTS 1. A linear correlation was observed between the sulfur exchange capacity and HDS activity of new generation catalysts containing phosphorus. The amount of phosphorus has no influence on this correlation. 2. I have shown in this work that during thiophene HDS conversion also thiophene recyclization occurs. The conversion of thiophene over H 2 35 S sulfided catalyst resulted thiophene containing labelled sulfur. 3. Over sulfided HDS catalysts butadiene can produce thiophene and hydrogen in presence of H 2 S: Bu 2= + H 2 S thiophene + 2H 2. This fact can be one of the reason why H 2 S inhibits strongly the HDS reactions. 4. Butadiene can remove sulfur from the surface of sulfided catalysts, as opposed to exposure to H 2. Butadiene can produce thiophene by reacting with surface sulfur of the catalysts. This phenomenon can be one of the reasons of surface sulfur decreasing during HDS. 5. Molybdenum based sulfide catalysts show higher hydrogenation activity in the presence of H 2 S. This increased hydrogenation activity of HDS catalysts in presence of H 2 S can serve as an explanation why the amount of HYD products does not decrease to the same extent as the amount of DDS products drops during HDS process inhibited by H 2 S. Based on these results it is clear, that the change in product distribution as a function of the partial pressure of H 2 S, would not offer an evidence that the two separate pathways (HYD and DDS) requires different active sites. [5] Ollár T., Szabó B., Rédey Á. (poster) IR spectroscopic Study Adsorted CO and H 2 on Ga 2 O 3 /Al 2 O 3 catalyst surface, Europacat-VI, Innsbruck, Austria, August 31 September 4, [6] Z. Bacsik, T. Ollár, J. Mink (poster) Open path FTIR Study of Atmospheric Pollutants in Industrial Environment 5 th International Austro-Tunisian Meeting on Analytical Chemistry of the Environment, March 23-24, 2000, Graz, Austria [7] Bacsik Z., Herczeg A., Ollár T., Mink J. (oral presentation) Légköri szennyezők nagyérzékenységű FT-IR spektroszkópiája MTA Spektrokémiai Munkabizottságának Ülése, március ,Veszprém, Magyarország [8] J. Mink, Z. Bacsik, A. Herczeg, V. Komlósi, T. Ollár (oral peresentation) New Developments in FTIR Study of Atmospheric Pollutants Euroanalysis XI, September 3-5, 2000, Lisbon, Portugal [9] J. Mink, Z. Bacsik, T. Ollár, V. Komlósi (poster) Field FTIR Monitoring of Atmospheric Pollutants in Industrial Environment Euroanalysis XI, September 3-5, 2000, Lisbon, Portugal [10] Z. Bacsik, J. Mink, T. Ollar, V. Komlosi (poster) FTIR Monitoring of Atmospheric Pollutants in Industrial Environment 4 th Euroconference on Environmental Analytical Chemistry, September 14-19, 2000, Visegrád, Hungary [11] J. Mink, Z. Bacsik, A. Herczeg, V. Komlósi, T Ollár (oral peresentation) Advanced Methods in FTIR study of Atmospheric Pollutants 4 th Euroconference on Environmental Analytical Chemistry, September 14-19, 2000, Visegrád, Hungary [12] Bacsik, Z., Mink, J., Komlósi, V. and Ollár, T. (poster) Extractive and Open Path FTIR Detection of Atmospheric Pollutants in Industrial Environment EUROANALYSIS-12, September 8-13, 2002, Dortmund, Germany

5 4.3. Other publications Published articles [1] Nasser H, Redey A, Yuzhakova T, Toth ZN, Ollar T. FTIR study of CO adsorption on molybdena-alumina catalysts for surface characterization REACTION KINETICS AND CATALYSIS LETTERS, 92(2) [2] Bacsik Z, Komlosi V, Ollar T, Mink J. Comparison of open path and extractive long-path FTIR techniques in detection of air pollutants APPLIED SPECTROSCOPY REVIEWS 41 (1) [3] Szabó B., Ollár T., Rédey Á. Reaction Mechanism of Cumene Cracking over MoO 3 /γ-al 2 O 3 Catalyst, PROCEEDING OF MICROCAD 2004 INTERNATIONAL SCIENTIFIC CONFERENCE, pp , Miskolc, March 18-19, Oral and poster presentations [1] Ollar T., Szabó B., Rédey Á. (poster) Investigation of H 2 Pretreatment of Ga 2 O 3 Containing Catalysts by FTIR Spectroscopy, 13 th International Congress on Catalysis, Paris, July 11-16, [2] Ollár T., Szabó B., Rédey Á. (oral presentation) Selective Reduction of NO over Ga 2 O 3 /Al 2 O 3 Catalysts in the Presence of Methane, 9 th FECS Conference on Chemistry and Environment, Bordeaux, France, August 29-September 1, [3] Szabó B., Ollár T., Rédey Á. (poster) Cumene Cracking over Reduced MoO 3 /-Al 2 O 3 Catalysts, 9 th FECS Conference on Chemistry and Environment, Bordeaux, France, August 29-September 1, [4] Szabó B., Ollár, T., Rédey, Á. (poster) Investigation of Surface Chemistry Properties of Ga 2 O 3 /Al 2 O 3 Catalysts by FT-IR Spectroscopy, Sixth International Symposium & Exhibition on Environmental Contamination, Prague, Czech Republic, September 1-4, Thiophene recyclization takes also place under inert conditions over sulfided molybdenum based catalysts. Thiophene adsorption over labeled sulfur sulfided Mo 35 S 2 catalyst produced H 2 35 S in the presence and in the absence of hydrogen too, while HDS reaction does not occur. 7. The fact that hydrogen sulfide leaves the catalyst surface during the adsorption of thiophene, points to the absence of inhibitory effect of hydrogen sulfide, unlike previous claims that hydrogen sulfide may block active sites. The inhibitory effect on the one hand between the butadiene and hydrogen sulfide (or other diolefins) - the formation of thiophene (or thiophene derivatives) indicates an interaction, namely that hydrogen sulfide can displace thiophene already adsorbed on the active sites, but not reacted yet. 8. Based on the findings and results of investigations of other researchers, I developed further the thiophene desulfurization process known mechanism. According to my proposed reaction mechanism thiophene desulfurization takes place via the exchange of surface sulfur.

6 4. PUBLICATIONS IN THE TOPIC OF THE PHD DISSERTATION Published articles [1] T. Ollár, T. Szarvas and P. Tétényi On the Role of Butadiene Conversion in Thiophene Hydrodesulfurization TOPICS IN CATALYSIS, AUGUST 2012, VOLUME 55, ISSUE 11-13, [2] Pál Tétényi, Tamás Ollár, Tibor Szarvas Sulfur exchange capacity and thiophene hydrodesulfurization activity of sulfided molybdena-alumina catalysts promoted by nickel CATALYSIS TODAY 181 (2012) corresponding author [3] Tetenyi P., Ollar T., Schay Z., Schnörch P, Szarvas T. Sulfur uptake determination on Ni containing molybdena-alumina samples by radioisotope tracer technique APPLIED RADIATION AND ISOTOPES 66 (9) [4] Tétényi Pál, Ollár Tamás, Schay Zoltán, Szarvas Tibor és Tellinger Olga Nikkel-molibdén-oxid katalizátorok kénfelvétele és hidrodeszulfuráló aktivitásuk Magyar Kémiai Folyóirat, 115 évfolyam, 3-4. szám, ORAL AND POSTER PRESENTATION [1] Tamás Ollár, Tibor Szarvas, Pál Tétényi (poster) Transiton metal sulfides for cleaner energy 3 rd European Energy Conference E2C 2013, October Budapest, Hungary [2] Tamás Ollár, Tibor Szarvas, Pál Tétényi (flash oral presentation) A probable mechanism of thiophene HDS: as calculated from the correlation between sulfur exchange capacity and thiophene HDS activity VI. International Symposium on Molecular Aspects of Catalysis by Sulfides (MACS), May Satillieau, France [3] Tamás Ollár, Tibor Szarvas, Pál Tétényi (poster) Butadiene interactions on the HDS catalysts surface VI. International Symposium on Molecular Aspects of Catalysis by Sulfides (MACS), May Satillieau, France [4] Tamás Ollár, Tibor Szarvas, Pál Tétényi (poster) Mechanism of Butadiene heterocyclization over sulfided HDS catalysts IX International Conference Mechanisms of Catalytic Reactions, october, St.Petersburg, Russia [5] Tamás Ollár, Tibor Szarvas, Pál Tétényi (poster) Consequence of the reverse reaction in HDS 15 th International Congress on Catalysis, July 1 6, 2012, München, Germany [6] Tamás Ollár, Tibor Szarvas, Pál Tétényi (poster) Behavior of catalytic sulfur EuropaCat X 28 August - 2 September Glasgow, Scotland [7] Ollár Tamás, Szarvas Tibor, Tétényi Pál (oral presentation) Katalizátor kén kölcsönhatás különböző aktivitású hidrodeszulfuráló katalizátorokon MTA Katalízis Munkabizottság, 2010 március 17. Budapest, Magyarország [8] Tamás Ollár, Tibor Szarvas, Pál Tétényi (poster) New effect in the reaction of the thiophene HDS monitored by radioisotope tracer technique 10 th Pannonian International Congress on Catalysis, August 29 september , Kraków, Polska [9] Ollár Tamás, Szarvas Tibor, Tétényi Pál (oral presentation) Hidrogénező kéntelenítési (HDS) reakció és katalizátorainak vizsgálata radioizotópos nyomjelzéssel) MKE 1. Nemzeti Konferencia május Sopron [10] Ollár Tamás, Schay Zoltán, Schnörch Péter, Szarvas Tibor és Tétényi Pál (oral presentation) Kénfelvétel meghatározása 35 S izotóp nyomjelzéssel Őszi Radiokémiai Napok október Sopron