TY - JOUR

T1 - Δ-Alumina supported cobalt catalysts promoted by ruthenium for Fischer-Tropsch synthesis

AU - Kungurova, Olga A.

AU - Khassin, Alexander A.

AU - Cherepanova, Svetlana V.

AU - Saraev, Andrey A.

AU - Kaichev, Vasily V.

AU - Shtertser, Natalya V.

AU - Chermashentseva, Galina K.

AU - Gerasimov, Еvgeny Yu

AU - Paukshtis, Еvgeny A.

AU - Vodyankina, Оlga V.

AU - Minyukova, Tatyana P.

AU - Abou-Jaoudé, Georges

PY - 2017/6/5

Y1 - 2017/6/5

N2 - The paper presents the low-temperature nitrogen adsorption, TG, XRD, IR spectroscopy, XPS, TEM and SEM data for ruthenium promoted (0.2–1 wt.%) Сo-δAl2O3 catalysts and characteristics of the catalysts in Fischer-Tropsch synthesis after their activation under the conditions ensuring the reduction of comparable fractions of metallic cobalt. It was shown that cobalt in oxide precursors is a component of the spinel-like Со3-xAlxO4 phase containing the impurity anions СО3 2−, NO3 −, ОН−, and NO in promoted samples, which belong to the thermolysis product of the Ru precursor. Average sizes of Со3-xAlxO4 crystallites are in a range of 5–10 nm. As ruthenium content in the catalyst increases upon reduction, the temperature of metallic phase formation decreases substantially (by more than 150 °C). After the reduction, selectivity of promoted catalysts for α-olefins and high-molecular hydrocarbons was higher in comparison with unpromoted catalysts, without a noticeable decrease in catalytic activity. Therewith, in 0.5–1.0 wt.% catalysts, a part of ruthenium forms individual ultradispersed metallic particles ca. 1 nm in size that are located on the surface of oxide support and are not active in Fischer-Tropsch synthesis. The oxide layer decorating the surface of metallic cobalt particles is also strongly enriched with ruthenium. In the 0.2 wt.% catalyst, the major part of ruthenium resides in metallic cobalt particles. Although the ruthenium-cobalt alloy segregates with enrichment of the surface with cobalt, the presence of ruthenium in the metallic particles and probably in the decorating oxide layer exerts a considerable effect on selectivity of the catalysts.

AB - The paper presents the low-temperature nitrogen adsorption, TG, XRD, IR spectroscopy, XPS, TEM and SEM data for ruthenium promoted (0.2–1 wt.%) Сo-δAl2O3 catalysts and characteristics of the catalysts in Fischer-Tropsch synthesis after their activation under the conditions ensuring the reduction of comparable fractions of metallic cobalt. It was shown that cobalt in oxide precursors is a component of the spinel-like Со3-xAlxO4 phase containing the impurity anions СО3 2−, NO3 −, ОН−, and NO in promoted samples, which belong to the thermolysis product of the Ru precursor. Average sizes of Со3-xAlxO4 crystallites are in a range of 5–10 nm. As ruthenium content in the catalyst increases upon reduction, the temperature of metallic phase formation decreases substantially (by more than 150 °C). After the reduction, selectivity of promoted catalysts for α-olefins and high-molecular hydrocarbons was higher in comparison with unpromoted catalysts, without a noticeable decrease in catalytic activity. Therewith, in 0.5–1.0 wt.% catalysts, a part of ruthenium forms individual ultradispersed metallic particles ca. 1 nm in size that are located on the surface of oxide support and are not active in Fischer-Tropsch synthesis. The oxide layer decorating the surface of metallic cobalt particles is also strongly enriched with ruthenium. In the 0.2 wt.% catalyst, the major part of ruthenium resides in metallic cobalt particles. Although the ruthenium-cobalt alloy segregates with enrichment of the surface with cobalt, the presence of ruthenium in the metallic particles and probably in the decorating oxide layer exerts a considerable effect on selectivity of the catalysts.

KW - Cobalt-alumina catalysts

KW - Cobalt-ruthenium alloy

KW - Fischer-Tropsch synthesis

KW - Promotion

KW - Ruthenium

KW - CO-PRECIPITATED CATALYSTS

KW - CHEMICAL-STATE

KW - OXIDE

KW - RU

KW - ACID

KW - SEGREGATION

KW - X-RAY PHOTOELECTRON

KW - REDUCTION

KW - TEMPERATURE

KW - DIFFRACTION

UR - http://www.scopus.com/inward/record.url?scp=85017446133&partnerID=8YFLogxK

U2 - 10.1016/j.apcata.2017.04.003

DO - 10.1016/j.apcata.2017.04.003

M3 - Article

AN - SCOPUS:85017446133

VL - 539

SP - 48

EP - 58

JO - Applied Catalysis A: General

JF - Applied Catalysis A: General

SN - 0926-860X

ER -