Analyzing Structural and Physicochemical Characteristics of Bismuth-Promoted Fe-Containing Catalysts of CO Hydrogenation
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ICAL KINETICS AND CATALYSIS
Analyzing Structural and Physicochemical Characteristics of Bismuth-Promoted Fe-Containing Catalysts of CO Hydrogenation G. V. Pankinaa,*, A. N. Kharlanova, A. V. Shumyantseva, and V. V. Lunina a
Department of Chemistry, Moscow State University, Moscow, 119991 Russia *e-mail: [email protected]
Received January 27, 2020; revised January 27, 2020; accepted February 11, 2020
Abstract—Carbon material (СAm), prepared on the basis of shadbush (Amelanchier) wood is used as a support of bismuth-promoted (0.6 wt %) Fe-containing catalyst of CO hydrogenation. Structural, morphological, and physicochemical characteristics of the systems are studied. It is established via IR spectroscopy that subcarbonyl and bridge forms of absorption are observed when bismuth is present on a surface of Fe/СAm during calcination in a stream of CO. At the same time, only iron oxide particles form, substantially facilitating the process of catalyst reduction afterward. Keywords: carbon material, iron-containing catalyst, IR spectral method, sub-carbonyl and bridge absorption forms DOI: 10.1134/S0036024420100234
INTRODUCTION A great many works have in recent decades been devoted to the synthesis and use of carbon materials (CMs) produced from such renewable sources of plant origin as wood from different forest trees, paddy husk, coffee waste, or biomass [1–3]. The use of CMs as supports for catalysts containing metals (specifically Fe and Co) is particularly required in CO hydrogenation or Fischer–Tropsch synthesis (FTS), for which Н2/СО synthesis gas can be obtained from coal biomass and natural or shale gas. It is well known that producing CMs from renewable natural sources eliminates the use of fairly valuable reactants and solves the environmentally relevant problem of utilizing wood waste. The costs of producing CMs and their subsequent prices are in this case relatively low. Depending on the variety of wood and the type of soil, the elemental composition of coals can vary in both quality and quantity. The composition of charcoal can include small amounts of metal impurities (1–3 wt %) that are used as promoters of catalytic CO hydrogenation (e.g., potassium, copper, and cadmium). In [4], we showed that CM prepared from shadbush wood had an initial potassium content of around 2 wt %. It is known that as a promoter of iron-supported catalyst, potassium has a strong effect on activity and selectivity of FTS catalysts by raising the rate of iron carbide formation [5, 6]. In selecting a support for metal-containing catalysts, it is important to remember that there is no oxide–oxide interaction between a porous substrate
and an active component. At the stage of preparing a catalyst, this results in the formation of intermediate compounds that are hard to reduce (e.g., spinel structures, which are virtually nonreducible at the indicated temperatures) [7]. Such supports therefore include magnesium aluminum spinels of different stoichiometric composition, and CMs that do not interact with the active component. Iron
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