Direct Synthesis of Hydrogen Peroxide from Hydrogen and Oxygen over Mesoporous Silica-Shell-Coated, Palladium-Nanocrystal-Grafted SiO₂ Nanobeads

Abstract

Many studies have been conducted on core–shell structured nanocatalysts thanks to their high thermal and physical stability. However, for a typical core–shell structure, shell thickness and pore size that affect mass transfer through the shell are difficult to control. Herein, we synthesized a different type of core–shell catalyst, in which a mesoporous silica shell encapsulates the Pd-nanocrystals-grafted-SiO2 nanobeads. With the preparation method introduced, we successfully controlled the thickness of the shell layer and generated a mesoporous texture over the shell layer. In activity tests, the production rate of hydrogen peroxide significantly increased when using the mesoporous shell catalyst over the microporous shell catalyst of similar shell thickness. The thickening of the mesoporous shell layer reduced the production rate of hydrogen peroxide. Thus, the thinner the thickness of a mesoporous shell, the more favorable in terms of pore-diffusion rate. However, the shell thickness should be adequately adjusted, because an extremely thin shell layer cannot protect the core Pd crystals from thermal agglomeration in a calcination and reduction process.

The Direct Synthesis of H2O2 Using TS‐1 Supported Catalysts

“…The shortcomings of the anthraquinone process can be overcome via the direct synthesis of H 2 O 2 from H 2 and O 2 , outlined in Figure , which provides a greener, more atom efficient process for H 2 O 2 generation and has the potential to be adopted at point of use. In particular, Pd‐based catalysts have been demonstrated to offer high activity towards the direct synthesis of H 2 O 2 . However, catalytic selectivity is often a concern and requires the use of halide and strong acid additives to inhibit H 2 O 2 degradation and the production of H 2 O via decomposition and hydrogenation pathways, both of which are more thermodynamically favourable than the formation of H 2 O 2 .…”

Experimental Evaluation of a Membrane Micro Channel Reactor for Liquid Phase Direct Synthesis of Hydrogen Peroxide in Continuous Flow Using Nafion® Membranes for Safe Utilization of Undiluted Reactants

“…The passivation procedure was applied and the setup was thoroughly cleaned once it had been found that catalyst traces were present after the coating experiments (Table 1, Exp.-Nr. : [29][30][31][32][33][34][35][36][37]. Experiments affected by catalyst traces are obviously not shown in this work and are neither part of the experimental discussion.…”

“…Lastly, structural modifications of the support material are known to influence catalyst performance as well. Pd/TiO 2 modified with heterogeneous carbon [34] and core-shell structured Pd/SiO 2 with a microporous Si shell on silica beads [35] showed an increased catalytic performance with decreased adsorption of H 2 O 2 .…”

Solar‐Driven Production of Hydrogen Peroxide from Water and Dioxygen

“…[60][61][62] Thus, extensive efforts have been devoted to achieve direct synthesis of H 2 O 2 from H 2 and O 2 using variousc atalysts, enabling efficient and on-site H 2 O 2 production, which not only significantly reduces the cost for H 2 O 2 synthesis, transport, storage, and handling, but also facilitates the subsequento xidationr eactions. [60][61][62][63][64][65][66][67][68][69][70] However,agas mixture of H 2 andO 2 has potentiale xplosion risk. It is highly desired to produce H 2 O 2 from H 2 Oa nd O 2 without using H 2 .…”