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Revealing the reaction mechanism to guide the industrial production of targeted products still remains a grand challenge for catalytic cracking of light alkanes to olefins over metal‐acid bifunctional catalyst. Herein, we systematically investigated the reaction mechanism of n‐pentane cracking on the Ag/ZSM‐5 bifunctional catalyst featuring both dehydrogenation and cracking capabilities. Specifically, overall cracking network of n‐pentane was comprehensively constructed to show the roles of metal dehydrogenation sites and acid sites respectively, in which metal Ag could substitute the H of the Brønsted acid site to form the Al–O–Ag linkage with enhanced adsorption and activation of n‐pentane, while Brønsted acid site with weak acid strength relay to promote cracking reaction. Thanks to this synergy of the two active sites, the apparent activation energy of n‐pentane cracking to light olefins was decreased from 82.77 KJ/mol to 68.26 KJ/mol and the proportion of specific path (C5H12 → H2 + C5H10) in n‐pentane monomolecular cracking reaction increased from 14.62% to 69.24%. In addition, 0.57Ag/ZSM‐5 catalyst exhibited the conversion of n‐pentane up to 67.55 wt%, which improved the performance of the parent ZSM‐5 by 13.42 wt%. These analysis results of reaction mechanism may provide some insights for the rational design of catalysts and the full utilization of petrochemical resources. [ABSTRACT FROM AUTHOR]

Engineering acid site spatial location of zeolite catalyst harbors tremendous potential to boost catalytic performance but still remains a grand challenge for aromatization reaction. Herein, we successfully manipulate acid site spatial location inside the ZSM‐5 channels to promote the hexane aromatization via the simple SiO2 coating treatment. Multi‐techniques demonstrated that the medium strong L acid in the channel originated from the Si(Al)OZn structure is mainly retained in the Zn/ZSM‐5‐Si catalyst by covering the acid sites outside the channel. Surprisingly, there is a good linear relationship between BTEX yield and this medium strong L acid content. Based on the reaction kinetics, in situ FT‐IR and theoretical calculations, it is found that the L acid with confinement effect served as the main active site could prominently enhance the cyclization of propene intermediate and the dehydrogenation of cycloalkane due to the strong affinity between the C/H and ZnOx, and control the desorption of BTEX (mainly benzene, toluene, ethylbenzene, and p‐xylene) by weakening the binding of hydrogen proton to π electrons. Compared with the ordinary Zn/ZSM‐5 catalyst, the yield of BTEX is increased by nearly 10%, and the Zn/ZSM‐5‐Si catalyst exhibits excellent anti coking deactivation ability. This strategy together with mechanistic results may pave the rational design of efficient Zn/ZSM‐5 catalysts for aromatization reaction. [ABSTRACT FROM AUTHOR]

Achieving efficient catalytic conversion over a heterogeneous catalyst with excellent resistance against leaching is still a grand challenge for sustainable chemical synthesis in aqueous solution. Herein, we devised a single‐atom Pt1/hydroxyapatite (HAP) catalyst via a simple hydrothermal strategy. Gratifyingly, this robust Pt1/HAP catalyst exhibits remarkable catalytic selectivity and catalyst stability for the selective oxidation of C2–C4 polyols to corresponding primary hydroxy acids. It is found that the Pt−(O−P) linkages with strong electron‐withdrawing function of PO43− (Pt1−OPO43− pair active site) not only realize the activation of the C−H bond, but also destabilize the transition state from adsorbed hydroxy acids toward the C−C cleavage, resulting in the sharply increased selectivity of hydroxy acids. Moreover, the strong PO43−‐coordination effect provides electrostatic stabilization for single‐atom Pt, ensuring the highly efficient catalysis of Pt1/HAP for over 160 hours with superior leaching resistance. [ABSTRACT FROM AUTHOR]

A systematic study of Au‐promoted and unpromoted Pt/MgO/SBA‐15 catalyst is developed to separate the promoter effect from electron transfer effect between Au and Pt. Multi‐characterizations revealed that Au and Pt metals in these bimetallic catalysts mainly exist in the form of alloy, and the main role of Au is to reduce the size of AuPt alloy nanoparticles, thus enhancing the adsorption and activation of intermediate products. Through the optimization of various factors (including MgO content, Au/Pt molar ratio, reaction temperature and time), the Au1Pt2/MgO/SBA‐15 (0.05) catalyst exhibits excellent catalytic activity and glyceric acid selectivity for the selective oxidation of glycerol. Density functional theory calculation confirmed that the synergistic effect between Pt and Au active sites could facilitate the oxidation of primary hydroxyl group by promoting the activation of CH bond and the oxidation of aldehyde group. The results may give insights on designing effective Pt based bimetallic catalyst for selective oxidation of glycerol. [ABSTRACT FROM AUTHOR]