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Oxidative Dehydrogenation of Isobutane on CrOx/Oxide Support Catalysts: Effect of Potassium on Physicochemical and Catalytic Properties

Samson K., Grzybowska B., Grabowski R., Banares M. A., Lozano Diz E.

Polish Journal of Chemistry

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2009

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Vol. 83, nr 11

1977-1992

EN

A series of catalysts containing CrOx (equivalent to 1 theoretical monolayer of Cr2O3) on Al2O3, TiO2, SiO2 and MgO supports, with and with out the potassium additive, have been prepared, characterized by different methods and tested in oxidative dehydrogenation, ODH, of isobutane. Addition of potassium did not affect the structure of the catalysts. It led to a slight decrease in the total activity for all the catalysts and anincrease in the selectivity to isobutene only for the CrOx/TiO2 system. A decrease for CrOx/Al2O3 and Cr/SiO2, on the potassium doping and practically no change in selectivity for CrOx/MgO catalysts, were observed. For all the studied catalysts the K additive decreased the acidity, increased the basicity and decreased the reducibility. No clear correlations between the selectivty and the acid-base properties or reducibility were found. The total activity decreases with the increasing electronegativity of the support cation, except for CrMgO catalyst.

2

Au/Fe3O4 and Au/Fe2O3 Catalysts: Physicochemical Properties and Oxidation of CO and Propane

Grzybowska B., Ruszel M., Samson K., Grabowski R., Spiridis N., Freindl K., Korecki J.

Polish Journal of Chemistry

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2009

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Vol. 83, nr 12

2129-2136

EN

Catalysts containing Au deposited on Fe3O4 (commercial Cerac) and on Fe2O3 were synthesized, characterized by XPS, XRD, Mössbauer spectroscopy, H2TPR, isopropanol decomposition – a probe reaction of acid-base properties, and tested in oxidation of CO and C3H8. Au//Fe3O4 cat a lyst, containing a mixture of magnetite and maghemite (gamma-Fe2O3) phases, was found to be more acidic containing more surface OH groups and less reducible than Au/alfa-Fe2O3 (hematite). The activity in oxidation of CO and propane was higher for Au/alfa-Fe2O3 catalyst as compared with Au/Fe3O4.

3

Oxidative Dehydrogenation of Isobutane on VOx/Oxide Support Catalysts: Effect of the Potassium Additive

Samson K., Grzybowska-Świerkosz B.

Polish Journal of Chemistry

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2007

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Vol. 81, nr 7

1345-1354

EN

Effect of the potassium additive on physicochemical and catalytic properties in oxidative dehydrogenation (ODH) of isobutane has been studied for a series of vanadia-based catalysts supported on different oxides (SiO2, Al2O3, TiO2, MgO). The catalysts (denoted as VS where S is a cation of a support), containing 1 or 1.5 monolayer (mnl) of V2O5 were prepared by impregnation method, characterized by BET, XPS, isopropanol decomposition (probe reaction for acido-basic properties) and tested in isobutane ODH in the temperature range 250-450_C. For all the catalysts the K additive decreased the acidity and increased the basicity, decreased the total acitivity, and increased (with the exception of VMg catalyst) the selectivity to isobutene. The increase in the selectivity was attributed to the decrease in acidity and increase in basicity of the catalysts. For VMg, different distribution of carbon oxides and different kinetic scheme were observed (dominance of CO2 formed by a consecutive path over CO formed by a parallel route) as compared with other catalysts (dominance of CO over CO2). These facts suggest, that the decrease in the selectivity to isobutene by the K additive observed for VMg catalyst is due to modification by K of other than acido-basic properties (most probably interaction of the catalysts with oxygen), which control the selectivity in this case.

4

Badania podatności na korozję naprężeniową spawanych złączy ze stali austenitycznej oraz duplex

Łabanowski J., Krzysztofowicz K., Samson K.

Przegląd Spawalnictwa

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2006

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R. 78, nr 5-6

46-49

PL

Przedstawiono wyniki badań spawanych złączy różnoimiennych wykonanych ze stali austenitycznej gatunku AISI 316L oraz duplex 2205. Wykonano 3 płyty próbne za pomocą spawania automatycznego łukiem krytym pod topnikiem. Złącza różniły się sposobem przygotowania krawędzi oraz zastosowaną energią liniową spawania. Badania właściwości mechanicznych złączy wykazały zadowalające wyniki, spełniające wymagania okrętowych towarzystw klasyfikacyjnych, pomimo zastosowania dużych energii liniowych spawania. Badania podatności na korozję naprężeniową złączy wykonano metodą odkształcania z małą prędkością. Próby przeprowadzono w środowisku obojętnym oraz agresywnym (MgCI2]. Próbki badane w środowisku obojętnym pękały w materiale o niższych właściwościach mechanicznych w stali austenitycznej. Badania w środowisku MgCI2 wykazały pękanie złączy po stronie stali duplex w obszarze strefy wpływu ciepła (SWC).

EN

The paper presents investigation results of dissimilar welds of duplex and austenitic 316L stainless steels. Three test plates were performed with the use of submerged arc welding with various edge preparations. Mechanical examinations showed that joints properties meet the requirements of ship classification societies, despite of application rather high welding heat inputs. The susceptibility of welded joints to stress corrosion cracking was investigated with the use of Slow Strain Rate. Test technique in the inert and 35% MgCI2 solution environments. It was revealed that samples tested in inert environment crack at austenitic steel zone, and crack at heat affected zones of duplex steel when tested in MgCI2 environment.

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Potassium Effects on Kinetics of Propane Oxydehydrogenation on Vanadia-Titania Catalyst

Grabowski R., Samson K.

Polish Journal of Chemistry

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2003

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Vol. 77 / nr 4

459-470

EN

Oxidative dehydrogenation of propane (ODH) over V2O5/TiO2 and V2O5/TiO2 doped with K was carried out by measuring conversions and selectivities for various feed compositions, contact times and temperatures. The results obtained for both catalysts were interpreted on the basis of the mechanism, in which propene is formed through Eley-Rideal sequence of steps, i.e. without participation of the adsorbed propane species. Kinetic constants (activation energies, pre-exponential factors) for the model ofODHreaction of propane on these catalysts, obtained on the basis of steady-state results, are given. Addition of K to vanadia-titania catalysts leads to the decrease of total combustion of propane and consecutive combustion of propene. It has been found that the direct propane total oxidation is 5_9 times lower than that of the consecutive propene oxidation and is almost temperature independent for potassium doped catalyst, whereas it quickly decreases with temperature for a non-doped catalyst. Secondly, the addition of K to a vanadia-titania catalyst decreases the activation energies for propene formation (k1), parallel formation of COx (k3) and reoxidation of the catalyst (kOS). Potassium exhibits a stronger inhibitory effect on the secondary propene combustion, what reflects the lower acidity of V+5 cations modified by the strongly basic alkali oxide species.

6

Oxidative Dehydrogenation of Propane on Supported Mlybdena Catalysts: Effect of the Support Nature and Additives

Klisińska A., Samson K., Grzybowska B.

Polish Journal of Chemistry

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2003

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Vol. 77 / nr 12

1867-1874

EN

Oxidative dehydrogenation of propane has been studied on molybdena deposited on SiO2, Al2O3, TiO2, and MgO. The catalytic performance depended on the support nature, the selectivity to propene at iso-conversion decreasing in the sequence: MoOx/SiO2 >MoOx/Al2O3 ~ MoOx/TiO2 > MoOx/MgO. Introduction of the K, Cr , Ni and V additives to MoOx/SiO2 and Cr to MoOx/MgO catalysts led to the increase of the total activity. The increase of the selectivity to propene was observed for the Cr and Ni additives, whereas the K and V in the MoOx/SiO2 catalysts decreased the selectivity (K and higher amounts of V), or did not affect it (lower amounts of vanadium).

7

Effect of Thermal Treatment of the Al3O3 and TiO2 supports on Properties of Dispersed Chromium Oxide in Oxidative Dehydrogenation of Isobutane

Grzybowska B., Samson K., Keromnes L., Wcisło K., Duła R., Serwicka E. M.

Polish Journal of Chemistry

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2001

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Vol. 75, nr 2

283-292

EN

Chromium oxide has been dispersed on Al2O3 and TiO2 supports, heated between 500-1200 C, and the catalysts obtained have been tested in oxidative dehydrogenation of isobutane at 280 C. For the CrOx/Al2O3 system the thermal treatment of alumina, which leads to the decrease in the specific surface area and polymorphic transformations of the initial -Al2O3 into , and modifications, does not affect the catalytic performance of the catalysts in the reaction under study. On the other hand, the transformation of anatase-TiO2 into rutile-TiO2, occurring on heating at 1000 C, leads to catalysts of a higher activity and selectivity to isobutene. Amelioration of the catalytic properties for CrOx/rutile-TiO2, as compared with CrOx/anatase-TiO2 catalysts, has been ascribed to changes in the structure of the CrOx active centres, evidenced by ESR.