Anderson series of polyoxometalates assembly of mesoporous silica spheres as catalysts for propane dehydrogenation by carbon dioxide oxidation

Propane dehydrogenation using CO₂ as a mild oxidizer (CO₂-ODP) is a promising technology for high propylene production and CO₂ reduction utilization. Among them, the reverse water gas shift reaction (RWGS) can change the reaction equilibrium to increase the propylene yield, and the Boudouard reaction can assist in the carbon accumulation elimination. However, the efficiency of the catalysts developed so far is limited, we introduced the Cr active component during the synthesis of porous silica spheres to form a CO₂-ODP catalyst, with a uniform distribution of active sites via (NH₄)₃[CrMo₆O₂₄H₆]·7H₂O produce a derivative. As an α-type Anderson series of polyoxometalates (POMs), this six octahedral structure formed by Mo participation surrounds the central atom Cr, which is more stable in structure by electrostatic effect, its derivatives generated after calcination are stably bound to the silica-based carrier, which reduces the formation of inert α-Cr₂O₃ by CrO_x aggregation during the catalytic process. Meanwhile, the oxygen atoms rich in polyoxometalates are more likely to form Si–O bonds with the carrier, which makes the active sites evenly and stably branched in the inner wall of the pores of mesoporous silica spheres, reduces the influence of carbon accumulation, and facilitates the activation and regeneration. The CO₂ conversion of the catalyst CrMoO_x@ mesoporous silica spheres (MSS) is typically greater than 20% under selected ideal conditions. This synthesis method of assembling POMs with mesoporous materials opens a new pathway for developing propane dehydrogenation catalysts. Compared to traditional impregnation synthesis, this catalyst contains a lower Cr content while achieving higher CO₂ consumption efficiency.