Iron Fischer-Tropsch Catalysts Prepared by Solvent-Deficient Precipitation (SDP): Effects of Washing, Promoter Addition Step, and Drying Temperature

Abstract

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 2 3 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.

Dehydrogenation of 2-[(n-Methylcyclohexyl)Methyl]Piperidine over Mesoporous Pd-Al2O3 Catalysts Prepared by Solvent Deficient Precipitation: Influence of Calcination Conditions

“…In the present study, all MPdA catalysts were synthesized in a single step by mixing their precursors; hence the distribution and particle sizes of Pd may also depend on the synthesis procedure as well as on the properties of the Al 2 O 3 . Therefore, the reality of smaller-size Pd particles in all the MPdA catalysts, irrespective of the calcination temperature, may result from the solvent deficient environment generated in the synthesis procedure, which inhibits the migration of reagent materials that would subsequently terminate the nucleation of nanoparticles [27,28]. It was established in our previous study that PdO and γ-Al 2 O 3 were the final phases of their precursors (i.e., boehmite (AlOOH) for Al and PdO, Pd(NH 3 ) 2 (NO 2 ) 2 , and (Pd(NO 2 )(NH 3 ) 3 ) 2 (Pd(NH 3 ) 4 (NO 3 ) 4 ) for Pd) in the MPdA catalyst after calcination [9].…”

“…In the SDP method, when the metal nitrate reacts with ammonium bicarbonate, they form a solvent deficient environment which then yields an intermediate hydroxide product (e.g. metal hydroxide or metal oxide hydroxide) and an ammonium nitrate (NH 4 NO 3 ) byproduct [27,28]. During aggregation in the solvent deficient environment, the spectator ions or molecules (NH 4…”

A simple coupled ANNs‐RSM approach in modeling product distribution of Fischer‐Tropsch synthesis using a microchannel reactor with Ru‐promoted Co/Al 2 O 3 catalyst

“…4 The Langmuir-Hinshelwood-Hougen-Watson (LHHW) type approach has been found successfully in describing many different heterogeneous catalytic reactions such as methylcyclohexane dehydrogenation over Pt/Al 2 O 3 catalyst, the oxidation of nitric oxide over carbon catalysts, esterification of acetic acid with ethanol over ion exchange resins etc. 10 Although the efforts of using complex LHHW mechanistic approach with the aid of genetic algorithm (GA) for data regression provide the robust solutions, [11][12][13][14][15] the limitations pertaining to the debatable mechanistic elementary reactions, difficulties of being both physical and statistical relevance, tedious computational times, and complexity of the established kinetic system based upon proposed mechanistic elementary reactions, all pose persistent challenges on designing and sizing the catalytic process involving the complex kinetics in the realistic scenario. 10 Although the efforts of using complex LHHW mechanistic approach with the aid of genetic algorithm (GA) for data regression provide the robust solutions, [11][12][13][14][15] the limitations pertaining to the debatable mechanistic elementary reactions, difficulties of being both physical and statistical relevance, tedious computational times, and complexity of the established kinetic system based upon proposed mechanistic elementary reactions, all pose persistent challenges on designing and sizing the catalytic process involving the complex kinetics in the realistic scenario.…”

“…[6][7][8][9] Among them, Fischer-Tropsch (FT) synthesis is one of the extensively investigated area using the LHHW approach. 10 Although the efforts of using complex LHHW mechanistic approach with the aid of genetic algorithm (GA) for data regression provide the robust solutions, [11][12][13][14][15] the limitations pertaining to the debatable mechanistic elementary reactions, difficulties of being both physical and statistical relevance, tedious computational times, and complexity of the established kinetic system based upon proposed mechanistic elementary reactions, all pose persistent challenges on designing and sizing the catalytic process involving the complex kinetics in the realistic scenario. [16][17][18][19][20][21][22][23][24][25] Due to its inherent features of fast converge, less computational time together with equipped statistical analysis, the hybrid ANNs-RSM has been successfully implemented into many practical applications such as investigation of the flexible mechanism considering friction dynamics in lubricating industry, 26 structural reliabilities studies, 27 and optimization of biohydrogen productions etc.…”

Feature Papers to Celebrate the Landmarks of Catalysts

“…3. Brunner and coworkers prepared iron Fischer-Tropsch catalysts by using solvent-deficient precipitation, focusing on the impacts of different catalyst preparation steps [3]. They found that the key steps in catalyst synthesis were whether the precursor catalyst was washed, how the promoted was added, and the drying condition.…”