Recent advances in multifunctional capsule catalysts in heterogeneous catalysis

Abstract

Capsule catalysts composed of pre-shaped core catalysts and layer zeolites have been widely used in the tandem reactions where multiple continuous reactions are combined into one process. They show excellent catalytic performance in heterogeneous catalysis, including the direct synthesis of middle isoparaffins or dimethyl ether from syngas, as compared to the conventional hybrid catalysts. The present review highlights the recent development in the design of capsule catalysts and their catalytic applications in heterogeneous catalysis. The capsule catalyst preparation methods are introduced in detail, such as hydrothermal synthesis method, dual-layer method, physically adhesive method and single crystal crystallization method. Furthermore, several new applications of capsule catalysts in heterogeneous catalytic processes are presented such as in the direct synthesis of liquefied petroleum gas from syngas, the direct synthesis of para-xylene from syngas and methane dehydroaromatization. In addition, the development in the design of multifunctional capsule catalysts is discussed, which makes the capsule catalyst not just a simple combination of two different catalysts, but has some special functions such as changing the surface hydrophobic or acid properties of the core catalysts. Finally, the future perspectives of the design and applications of capsule catalysts in heterogeneous catalysis are provided.

Current status of research on the synthesis of hydrogen, hydrocarbons and conversion of carbon dioxide in the framework of reducing anthropogenic pressure on the environment and switching to environmentally friendly energy sources

“…When using bifunctional or tandem catalysts for the implementation of subsequent heterogeneous catalytic processes of CO 2 conversion, the presence of hydrogen is necessary, the source of which is paid little attention in the studies. The authors discuss the potential to produce H 2 through electrolysis from renewable energy sources and water, or through the use of photocatalytic hydrogen production processes [1][2][3][4][5][6][7].…”

Direct Synthesis of Dimethyl Ether from CO2: Recent Advances in Bifunctional/Hybrid Catalytic Systems

“…In this sense, the catalyst selectivity can be more controlled by assembling the metal and acid functions of the hybrid catalyst into the nanostructures such as the core-shell-structured capsule catalyst. The space-confined reaction environment associated with the structured capsule catalyst could favor the control of the selectivity to DME in the direct hydrogenation of CO 2 [145,146]. In addition, the bifunctional nanostructured capsule catalysts enhance the synergetic effect between metal and acid sites and allow some changes in their surface properties (hydrophobicity).…”

“…Recent developments in the design of multifunctional capsule catalysts and their use in heterogeneous catalytic reactions were recently reviewed by Bao and Tsubaki [147], and Gao et al [146].…”

A Review on the Conversion of Synthetic Gas to LPG over Hybrid Nanostructure Zeolites Catalysts

“…There are several proposed mechanisms attributed to the direct approach. [78,79] Typically, methanol is synthesized in the first step on the metal oxide catalyst. Then, the methanol is dehydrated easily into DME over the acid sites of the zeolite catalysts, then on the same surface the intermediates are converted into propane and butane products.…”

“…In the direct method, LPG is produced directly from syngas. There are several proposed mechanisms attributed to the direct approach [78,79] . Typically, methanol is synthesized in the first step on the metal oxide catalyst.…”