Abstract
Nanosized catalyst dispersions have significant potential for improving hydrocarbon production from carbon monoxide and hydrogen via Fischer–Tropsch synthesis, an essential alternative to the use of petroleum as a raw material. New dispersed cobalt catalysts and dispersed-phase cobalt-based catalysts with Pd, Al2O3, or ZrO2 additives for the Fischer–Tropsch synthesis were synthesized in the present work. A dispersed cobalt phase was prepared in a heavy paraffin medium using ex situ and in situ approaches through thermal decomposition of a nitrate precursor at various temperatures. Analyses showed that an increase in the temperature for catalytic suspension formation from 215 to 260°C enlarged the particles in the dispersed phase from 190 to 264 nm, which was probably due to increased agglomeration at elevated temperatures. The rheological properties of the obtained catalytic suspensions can be described by the Bingham equation. Furthermore, the concentration of the dispersed phase had a direct impact on the structure of the entire catalytic system. Ultrafine suspensions of palladium-promoted catalytic systems were tested for the Fischer–Tropsch synthesis. The overall yield of C5+ hydrocarbons was as high as 50 g/m3, and the productivity of the Pd-promoted catalytic systems reached 270–290 g/(kgCo · h).
Highlights
The production of liquid fuel is a priority for processing alternative raw materials (Dry, 2002; Neste Corporation, 2016; Douvartzides et al, 2019)
We studied the effect of cobalt precursor decomposition conditions on the particle size of the dispersed phase in the final catalyst dispersions at temperatures over that of cobalt nitrate decomposition 208◦
This study applied two approaches to generate cobalt-based dispersions ex situ: direct decomposition of cobalt nitrate in the dispersion medium and slow introduction of an aqueous solution of cobalt nitrate into paraffin pre-heated to the desired temperature
Summary
The production of liquid fuel is a priority for processing alternative raw materials (Dry, 2002; Neste Corporation, 2016; Douvartzides et al, 2019). The most unified technology for generating synthetic fuels is a two-stage method based on the partial oxidation of any carbon-containing feedstock to produce synthesis gas, or syngas (a mixture of carbon monoxide and hydrogen), followed by conversion to liquid hydrocarbons. The second stage of this process is referred to as the Fischer–Tropsch synthesis (FTS) (Mahmoudi et al, 2018), a catalytic process in which the catalyst precisely determines the yield and composition of the products and sets the requirements for the syngas properties. The FTS catalyst governs the concept of the entire method for producing synthetic petroleum products. The synthesis of hydrocarbons from CO and H2 (FTS) is one of very few heterogeneous catalytic radical polymerization reactions (Henrici-Olivé and Olivé, 1984; Davis, 2001; Kollár et al, 2010)
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