Из истории гидроархеологических исследований на озере Иссык-Куль

Статья посвящена истории археологических исследований на озере Иссык-Куль. На основе архивных данных реконструируются первые попытки изучения дна озера русскими путешественниками и учеными в середине ХIХ века; описывается проект Г.А.Колпаковского по доставке на озеро водолазного оборудования (1871); оцениваются результаты работ экспедиций Д.Ф.Винника и современное состояние дел по изучению подводных памятников озера.Стаття присвячена історії археологічних досліджень на озері Іссик-куль. На основі архівних даних реконструюються перші спроби вивчення дна озера російськими мандрівниками і ученими в середині ХIХ століття; описується проект Г.А.Колпаковського з доставки на озеро водолазного обладнання (1871); оцінюються результати робіт експедицій Д.Ф.Вінника і сучасний стан справ по вивченню підводних пам'ятників озера.The article is devoted to the history of archaeological researches at lake Issik Kul. On the basis of the archived documents the first attempts to investigate the lake bottom by Russian travelers and scientists in the middle of ХIХ age are reconstructed; the G.A.Kolpakovskiy’s project concerning the delivery of diving equipment (1871) to the lake is described; the work results of D.F.Vinnik’s expeditions and modern researches of archaeological artefacts of the lake are assessed

Partial oxidation of methane using Pt/CeZrO 2 /Al 2 O 3 catalysts -effect of preparation methods

Abstract The effect of the preparation method of Pt/CeZrO2/Al2O3 catalysts on the dispersions of the metal and of the ceria-zirconia on the surface of the alumina and on the catalytic performance of methane partial oxidation reaction was evaluated. The ceria-zirconia materials were supported on the alumina surface by precipitation and impregnation and all the samples contained 1.5 wt.% of Pt. The dispersion of the ceriazirconia was evaluated by adsorbed CO2 infrared spectroscopy and the dispersion of the metal was determined by the dehydrogenation of cyclohexane. The reducibility of the catalysts was measured by oxygen storage capacity and temperature programmed reduction. The samples prepared by impregnation present higher activity, stability and selectivity to form CO and H2 than the ones prepared by precipitation. The characterization results show that all the samples had practically the same platinum dispersion but the dispersion of the ceria-zirconia material on the alumina was more effective when the impregnation method was used. The impregnation favors a high coverage degree of the alumina by the ceria-based oxides. This means that a larger fraction of platinum particles is in contact with ceria or ceria-zirconia oxide. The metalsupport interface is a key factor to avoid the carbon deposits that are responsible for the deactivation of some samples

Study of the performance of Rh/La2O3eSiO2 and Rh/CeO2 catalysts for SR of ethanol in a conventional fixed-bed reactor and a membrane reactor

The performance of Rh/La2O3–SiO2 and Rh/CeO2 catalysts for steam reforming of ethanol was investigated in a conventional fixed-bed reactor and a membrane reactor. This reactor was built with a self-supported Pd–Ag membrane, and its performance was compared to that the conventional reactor employing the same residence time and temperature. The effect of steam to ethanol molar ratio, ethanol concentration, temperature and contact time over hydrogen permeation and hydrogen recovery was investigated. In all cases, the ethanol conversion was kept at 100%, and the products formed were only H2, CO2, CO and CH4. In the membrane reactor, the overall ethanol reforming reaction was favored without the formation of carbon deposits. The highest permeated and H2 recovery was obtained for low ethanol content in the feed (high H2O/Ethanol ratio) and the methane formation was unfavored, in agreement with the high production of hydrogen. A slight difference in the hydrogen permeated/feed ethanol ratio was observed at higher sweep gas flow rates being higher for Rh supported on CeO2 in comparison with the Rh/La2O3–SiO2 catalyst. The best results were obtained with a H2O/Ethanol molar ratio equal to 10 and the highest membrane permeation area. Under these conditions, the H2 recovery reached values of about 70% and the hydrogen produced for each mole of ethanol exhibited the highest value close to 2.8.Fil: da Silva, Adriana M.. Instituto Nacional de Tecnologia; BrasilFil: Mattos, Lisiane V.. Universidade Federal Fluminense; BrasilFil: Múnera Agudelo, John Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Lombardo, Eduardo Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Noronha, Fabio B.. Instituto Nacional de Tecnologia; BrasilFil: Cornaglia, Laura Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; Argentin

Controlling carbon formation over Ni/CeO2 catalyst for dry reforming of CH4 by tuning Ni crystallite size and oxygen vacancies of the support

International audienceThis work investigates the effect of Ni crystallite size and oxygen vacancies of the support on the formation of carbon over Ni/CeO2 catalysts for dry reforming of methane at 1073 K. A large crystallite size variation is achieved by using different Ni loading (5 and 10 wt%) and calcination temperatures (673, 873, 1073 and 1473 K). In situ XRD and XANES experiments reveal that the increase in calcination temperature increases the Ni crystallite size, whereas the amount of oxygen vacancies decreases. The amount of carbon formed during DRM increases as Ni crystallite size increases, achieving a maximum at around 20−30 nm and then, it continuously decreases. However, carbon deposition is negligeable below 10 nm and above 100 nm. For the catalysts with very large Ni crystallite sizes, the CH4 dissociation rate is likely so low that carbon species formed reacts and carbon accumulation does not take place. However, the oxygen vacancies of ceria do not contribute to the carbon removal from the Ni surface due to the low metal-support interface on these large Ni particles

Long-term stability of Pt/Ce0.8Me0.2O2-γ/Al2O3 (Me = Gd, Nb, Pr, and Zr) catalysts for steam reforming of methane

International audienceThis study investigated the influence of dopants (Gd, Nb, Pr, and Zr) on the performance of Pt/CexMe1-xO2-γ/Al2O3 catalysts for the methane steam reforming (SRM) at 1073 K and at different space velocities. In-situ XRD, in-situ XANES, and Raman spectroscopy revealed the formation of a solid solution on the supports with Gd, Pr and Zr and an improvement in reducibility. No evidence of complete niobium inclusion into the ceria framework was observed and AlNbO4 and CeNbO4 phases were detected. All catalysts exhibited a severe initial deactivation, however, with Pt/CeNb/Al being most stable. Analyses of all spent catalysts revealed a negligible carbon deposition during the catalytic tests. TEM, XRD and N2 physisorption showed a collapse of the alumina structure and sintering of Pt particles as causing the early deactivation. The formation of segregated phases for Nb-doped ceria improved the thermal resistance of alumina and provided a closer contact with Pt crystallites, resulting in better stability