Abstract
Catalysts for the sulfuric acid (SA) decomposition, one of three reactions in Sulfur–Iodine (SI) cycle to produce hydrogen, should be active and stable in wide temperature ranges of 650–850 °C. Pt based catalysts are explored for SA decomposition, but they suffered from the severe Pt loss at the high temperature of 850 °C. Uniform platinum nanoparticles (NPs) are physically trapped within mesopores of the mesoporous SBA-15 prepared in a “one pot” method (Ptx.x-NTS, x.x: loaded Pt wt%). Other Pt catalysts are prepared to stabilize Pt particles using 3-mercaptopropyletrimethoxysilane (MPTMS) as a stabilizing agent (Ptx.x-TS, x.x: loaded Pt wt%). The co-assembly method in the one pot is based on the I+M–S+ scheme in which S+ (Protonated block copolymer) and I+ (Cationic inorganic precursor) are assembled together through the M– (PtCl6-) mediator. The MPTMS containing thiol group is used to modify the cationic precursors (I+) in order to hold the Pt nanoparticles in meso-channels as the reduced platinum metal is easy to bond with thiol groups. The prepared samples are characterized by XRD, TEM, CO Chemisorption, N2 adsorption desorption, and ICP-OES techniques. The TEM images show that the small Pt NPs of an average size of 7.0 (±0.84 nm) are uniformly dispersed within the mesopores on the mesoporous SBA-15. The thiol stabilized Pt-TS catalysts display the exceptional catalytic stability for sulfuric acid decomposition at the high temperature of 850 °C for 50 h. The overall average metal loss is 67% for the Pt2.0-NTS for 50 h at 76,000 mL.gcat−1.h−1, while it is 16% for the Pt2.0-TS. The metal loss of Pt/SBA-15 is significantly suppressed by the surface functionalization using MPTMS in the catalyst preparation step.
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•Pt catalyst supported on SBA-15 support for sulfuric acid decomposition.•Pt sintering, aggregation and dissolution are main reasons for deactivation due to low affinity of silica.•Pt NPs embedded and stabilized by MPTMS on SBA-15 walls was more active and stable.•High activity and stability at 850 °C achieved in corrosive environment up to 50 h.