Abstract
A novel, solvent-deficient precipitation (SDP) method for catalyst preparation in general and for preparation of iron FT catalysts in particular is reported. Eight catalysts using a 23 factorial design of experiments to identify the key preparation variables were prepared. The catalysts were characterized by electron microprobe, N2 adsorption, TEM, XRD, and ICP. Results show that the morphology of the catalysts, i.e., surface area, pore volume, pore size distribution, crystallite sizes, and promoter distribution are significantly influenced by (1) whether or not the precursor catalyst is washed, (2) the promoter addition step, and (3) the drying condition (temperature). Consequently, the activity, selectivity, and stability of the catalysts determined from fixed-bed testing are also affected by these three variables. Unwashed catalysts prepared by a one-step method and dried at 100 °C produced the most active catalysts for FT synthesis. The catalysts of this study prepared by SDP compared favorably in activity, productivity, and stability with Fe FT catalysts reported in the literature. It is believed that this facile SDP approach has promise for development of future FT catalysts, and also offers a potential alternate route for the preparation of other catalysts for various other applications.
Highlights
Demand for liquid fuel sources combined with political unrest in some of the world’s regions most abundant in oil and natural gas, in addition to the recent natural gas boom from hydraulic fracturing have pushed global and domestic energy policies to focus on domestic production and sustainability
We report the preparation of eight iron FT catalysts and the use of a 23 factorial design of experiments to identify the key preparation variables
Levels for timing of promoter addition were “1 Step” in which potassium and silica promoters were added to the salts of iron and copper before precipitation, and the catalyst was created in a single step, and “2 Step”
Summary
Demand for liquid fuel sources combined with political unrest in some of the world’s regions most abundant in oil and natural gas, in addition to the recent natural gas boom from hydraulic fracturing have pushed global and domestic energy policies to focus on domestic production and sustainability. Catalyst preparation is a complex process intended to produce desirable chemical, physical, and catalytic properties in the final catalyst through choice of materials (i.e., metal, precursor, promoter, and support) and by manipulation of preparation variables and conditions (e.g., precipitation pH and temperature, washing, drying and calcination temperatures, and reduction environment and temperature) [2]. Supporting a catalyst on an oxide matrix (e.g., alumina, silica, ceria, or titania) requires extra preparation time and steps, but is desirable when the precursor is expensive (as is the case for cobalt or precious metal catalysts) or when structural enhancements (e.g., surface area, pore volume, or pore diameter) increase the dispersion, selectivity, or stability of the catalyst. Replacing water in precursor pores with low surface tension alcohols resulted in larger surface areas Catalysts prepared by this method were of comparable activity to a low activity Co catalyst and had lower selectivities to CH4. This facile SDP approach seems to have potential for the development of FT catalysts, and for preparing heterogeneous catalysts for other applications as well
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
