Binder-free TS-1 coating on SiC foam with in-situ H2O2 regeneration for enhanced phenol hydroxylation

Developing highly efficient and durable catalysts for phenol hydroxylation remains a long-standing challenge in heterogeneous catalysis. Herein, a binder-free titanium silicalite-1 (TS-1) coating supported on silicon carbide (SiC) foam was fabricated via a tetra-n-butylammonium hydroxide (TPAOH)-assisted dissolution–recrystallization route. The effect of TPAOH concentration on coating structure evolution and catalytic performance was systematically investigated. The optimized treatment (0.03 M TPAOH) transformed the amorphous silica binder into crystalline TS-1, creating abundant inter-crystalline and intracrystalline mesopores while strengthening the interfacial bonding between the TS-1 coating and the SiC support. These structural features significantly enhanced active-site accessibility and mechanical robustness, resulting in substantially improved catalytic activity and long-term stability in fixed-bed phenol hydroxylation. Comparative studies between structured TS-1/SiC foam catalysts and granular TS-1 catalysts revealed that, even with similar micro- and mesoporosity, the macroscopic geometry of the structured catalyst provided 15 times greater external contact area than that of the granular catalyst and more efficient active-site accessibility, leading to superior overall performance. Furthermore, an innovative in-situ H 2 O 2 regeneration strategy was developed to remove coke deposits directly within the fixed bed under operating conditions. This mild oxidative treatment effectively restored over 93.4 % of the initial catalytic activity after multiple regeneration cycles without structural degradation, demonstrating the catalyst's outstanding stability and reusability. Overall, this work highlights how cooperative optimization of pore architecture and geometric configuration can substantially improve both catalytic efficiency and durability, offering a sustainable and industrially viable pathway for continuous phenol hydroxylation in fixed-bed reactors. This approach bridges the gap between laboratory-scale catalyst design and industrial continuous operation. • Binder-free TS-1 coating was made by TPAOH-assisted dissolution-recrystallization. • Binder-free coating enhances active-site accessibility and mechanical robustness. • SiC foam support increases the exposure of TS-1 active sites. • In-situ H 2 O 2 regeneration strategy recovers over 93.4 % catalytic activity. • Catalyst retains structural and catalytic integrity after 4 regeneration cycles.