Characterization of Alumina and Silica Sol-Gel Encapsulated Fe/Co/Ru Nanocatalysts in Microchannel Reactors for F-T Synthesis of Higher Alkanes

Abstract

We have been investigating conversion of syngas (CO: H 2 ) to higher alkanes [Fischer-Tropsch (F-T) Process] in 5 µm and 25 µm channel microreactors coated with sol-gel encapsulated Fe/Co-nanocatalysts. These nano-metal-catalysts were incorporated into the sol-gel matrix by two methods: 1) metal nitrate solutions; 2) metal oxide nanoparticles. Characterization of these catalysts containing Co and Fe in alumina and silica sol-gel has been carried out by several techniques. The surface area measurements by BET method show an average specific surface area of 285 m 2 /g for alumina and 300 m 2 /g for silica sol-gel encapsulated catalysts. In order to optimize the sol-gel preparation and deposition in the microchannels, the elemental composition of sol-gel encapsulated catalyst was examined by EDX. The SEM and AFM images of the reactors before and after deposition of the catalysts have also been studied. Hydrogenation-reduction efficiency of the activated Fe-Co catalysts and the level of poisoning after the reaction were estimated using a vibrating sample magnetometer (VSM). The result suggests more efficient reduction in the case of the nano-particle metal oxides compared to that derived from metal nitrate solutions. In overall, 85% of the catalyst is poisoned after 25 hrs of catalytic reaction. The surface area and the syngas conversion results indicate that silica sol-gel matrix may be a better catalyst support. For alumina sol-gel support, higher conversion of syn-gas is observed with 25 µm microreactor channels. For silica sol-gel, syngas conversion as high as 73% has been achieved by adding Ru as a promoter to the Fe/Co catalyst mixture.

Microreactors for Syngas Conversion to Higher Alkanes: Characterization of Sol−Gel-Encapsulated Nanoscale Fe−Co Catalysts in the Microchannels

“…However, the EDX analysis shows only 5−7% of Fe−Co catalyst in the hydrogenated reactor. To have a better understanding of the nanocatalyst, we have separately synthesized CoO nanoparticles (15−30 nm) and used commercially available Fe 2 O 3 nanoparticles (10−40 nm) as catalyst precursors in the sol−gel matrix. , The EDX analysis of these systems is included in Table . The data suggest that the metal oxide nanoparticle method yields much higher metal loading compared to that obtained by the metal nitrate procedure.…”

NiFe2O4@SiO2 Nanoparticles Stabilized by Porous Silica Shells

“…Alloy nanoparticles can be more effective catalysts or have better magnetic properties than pure component nanoparticles [1,7,8]. Performance of alloy nanoparticles in applications such as FT depends on control of both composition and particle size [9][10][11][12][13]. However, one disadvantage of subjecting small metallic nanoparticles to the high temperatures required in catalytic reactors is that they tend to sinter or aggregate into larger particles.…”