Alumina-based catalyst support Fischer-Tropsch catalysts

Enache, D.I., Roy-Auberger, M., and Revel, R. Differences in the characteristics and catalytic properties of cobalt-based Fischer-Tropsch catalysts supported on zirconia and alumina. Applied Catalysis. A, General, 2004, 268, 51. 

Supported cobalt is considered to be the most favourable catalytic material for the synthesis of long-chain hydrocarbons from natural gas-based synthesis gas because of its high activity, high selectivity for linear paraffins, low water-gas shift activity, and low price compared to noble metals. Common supports for Fischer-Tropsch catalysts include alumina, silica, and titania. 

Catalysts of commercial significance are either iron-based or cobalt-based. Iron-based catalysts are typically not supported, whereas cobalt-based catalysts are usually supported on alumina, silica, or a similar material. The three-phase low-temperature Fischer-Tropsch (LTFT) technology can be operated in either... 

Support modification has been reported earlier in the open literature [5,6,7,8,9]. Zirconia modification of silica supports was used to prevent the formation of unreducible cobalt-silicates [5]. Zr, Ce, Hf, or U modification of titania supports was reported to prevent the formation of cobalt-titanates during regeneration [6]. To increase the porosity of titania supports, they were modified with small amounts of binders, e.g. silica, alumina or zirconia [7]. Lanthanum oxide promotion of alumina was reported to be beneficial for improved production of products with higher boiling points [8], and zirconia modification of alumina supports was carried out to decrease the interaction of cobalt with alumina [9]. All these modified supports were either used for fixed bed cobalt based Fischer-Tropsch synthesis catalysts or they were used for slurry phase cobalt catalysts, but not tested under realistic Fischer-Tropsch synthesis conditions in large scale slurry bed reactors. 

It is well known that alumina, titania [10,11,12] and magnesium oxide [13,14] dissolve in acidic aqueous solutions and even at pH values close to the isoelectric point [15,16], In this study, it will be shown that these support surfaces were modified with promoters to increase the inertness thereof to acidic/aqueous environments, and not to stabilise the support against sintering and loss in surface area at high temperatures [17,18], This paper will deal with the modification of alumina and titania supports for cobalt based slurry phase Fischer-Tropsch catalysts to ensure the successful operation of slurry phase bubble column reactors on commercial scale,... 

The support geometry is important with respect to Fischer-Tropsch synthesis performance (i.e. activity and selectivity) of the resultant catalyst based thereon. The modified alumina support after silica modification did indeed produce a catalyst with the desired Fischer-Tropsch synthesis characteristics [4]. 

De Haan, R., Joorst, G., Mokoena, E., Nicolaides, C.P., 2007. Non-sullided nickel supported on sihcated alumina as catalyst for the hydrocracking of n-hexadecane and of iron-based Fischer—Tropsch wax. Apphed Catalysis A 327, 247—254. 

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