Xinmei Liu

This review systematically summarizes recent advances in propane-selective porous materials, highlights mechanisms inverting olefin preference, and proposes future directions for application-oriented development.

Catalyst deactivation caused by carbon deposition remains a major obstacle to the large-scale application of dry reforming of methane (DRM). Previous studies have primarily focused on controlling particle size and electronic properties of the metal component to improve coke resistance, while the role of the metal crystal plane has always been overlooked. Herein, metallic Ni with various proportions of Ni(111) and Ni(220) crystal planes was fabricated on the Ni/NaY catalyst by modulating nickel precursors. The reduction of NiO tends to form Ni(111), whereas the reduction of nickel silicate generated during the in situ solid grinding synthesis favors the formation of Ni(220). Therefore, the in situ-synthesized Ni/NaY catalyst exhibits a higher Ni(220) content than the impregnation-prepared counterpart. The rate-limiting step for CH4 activation shifts from CH4→ CH3* on Ni(111) to CH3*→ CH2* on Ni(220), preserving more saturated CHx* active intermediates and suppressing excessive CH4 cracking. Besides, the CO2 activation on Ni(220) primarily follows the pathway of CO2→ HCOO*, which is distinct from that of CO2→ HCO3*→ HCOO* on Ni(111). This direct conversion of CO2 increases the concentration of OH* generated from HCOO* decomposition. The resulting OH* promotes oxidization of the CHx* into CO, thereby inhibiting excessive CH4 cracking and carbon deposition. Therefore, an efficient dynamic equilibrium between CH4 activation and the timely oxidation of CHx* intermediates is achieved by engineering the Ni crystal plane, enhancing both activity and coke resistance. The Ni(220)-enriched catalyst exhibits negligible carbon deposition compared with the Ni(111)-enriched counterpart after 12 h of reaction while maintaining CH4 and CO2 conversions of 83.7% and 86.5%, respectively. This work provides a strategy to boost coke resistance of Ni-based DRM catalysts through crystal plane engineering.

Furfural is a key platform chemical in biorefining, accessible through the direct conversion of xylose. However, its production is notably influenced by the synergistic effect between the density and spatial distribution of Brønsted acid (BA) and Lewis acid (LA) sites in solid acid catalysts. In this work, a novel fluoride-free quasi-solid-phase synthesis method was developed to fabricate (Sn, Al)-H-Beta catalysts featuring adjacent framework Sn-O-Al active sites. The ratio and amount of BA and LA sites can be effectively controlled by varying the framework Sn content in the catalysts. Meanwhile, the adjacent Sn-O-Al active sites achieve the spatial proximity of BA and LA sites, reducing the side reactions along the diffusion path of intermediates. In situ FTIR and DFT calculation results demonstrated that the Sn-O-Al active sites promote the adsorption and isomerization of xylose by activating the C=O bonds in its aldehyde groups and the adjacent C-O/C-H bonds. The optimal QSP-Beta-1.6Sn catalyst could achieve 76.7% furfural yield with a 99% conversion at 190 °C for 2 h in the water/GVL system. This study provides a rational design strategy for solid acid catalysts with synergistic acid sites in cascade biorefining.

The direct catalytic cracking of long-chain alkyl aromatics into light olefins is a key strategy for efficient oil-to-chemicals conversion. While current research has primarily focused on solid acid catalysts, investigations of solid bases, particularly rare-earth metal oxides, remain scarce, and their mechanistic roles are poorly understood. Here, density functional theory (DFT) calculations followed by experimental validation were conducted to elucidate the cracking mechanism of n-butylbenzene on the CeO₂(111) surface. The CeO₂(111) facet provides bifunctional active sites: Lewis-basic surface oxygen (O^2-) and redox-active Ce⁴⁺/Ce³⁺ centers cooperatively mediate hydrogen-atom and electron transfer processes to drive radical-based C-H and C-C bond activation. Compared with the carbanion pathway, C-H activation preferentially proceeds via a hydrogen atom transfer (HAT) mechanism, forming carbon-centered radicals that undergo β-scission to yield light olefins. Among the competing routes, C3-H activation followed by C1-C2 bond cleavage exhibits a relatively low energy barrier (1.75 eV), preferentially yielding propylene. In contrast, the ethylene-forming route is kinetically hindered by a higher barrier (2.25 eV), resulting from the dehydrogenation of surface-bound C₂H₅* species and surface electronic reorganization. The synergistic interplay between Ce 4f redox flexibility and surface basicity thus governs selective C-H/C-C bond activation and product distribution. This study provides fundamental insight into radical-mediated, nonacidic hydrocarbon cracking on rare-earth oxides and a mechanistic basis for designing a selective base-type oil-to-chemicals catalysts.

A facile design strategy to enhance Au–Ti synergy in Au/TS-1 catalysts through precise control of TPAOH/Si ratios is demonstrated, and the exceptional propylene oxide selectivity (∼95%) with stable activity is exhibited.

CO ₂ hydrogenation to ethanol is an attractive strategy for mitigating CO ₂ emissions. In this work, CoCeO _x complex oxide catalysts with different Co/Ce ratios were used for CO ₂ hydrogenation to ethanol. It was found that a decrease in Co/Ce ratio contributed to oxygen vacancy formation, which facilitated the adsorption and activation of CO ₂ . However, the decrease in Co/Ce ratio hampered H ₂ adsorption and activation due to the decreased Co sites. Therefore, moderate Co/Ce ratio maintained a balance between H ₂ and CO ₂ activation, resulting in the best catalytic activity and STY. CoCeO _x catalyst with Co/Ce ratio of 1 exhibited the highest space‐time yield of 1.40 mmol _EtOH ·g _cat ⁻¹ ·h ⁻¹ with ethanol selectivity of 12.3% and CO ₂ conversion of 51.4% under 235 °C and 2 MPa. In situ DRIFTS analysis further proved the synergistic effect between oxygen vacancies and cobalt species. On one hand, oxygen vacancies provide cobalt species with more HCOO ^* species, promoting the formation of ethanol. One the other hand, cobalt species make the oxygen vacancies from nonrenewable to recyclable by dissociating hydrogen. Our work provides valuable guidance for the design of catalysts and insights into the synergistic effect between oxygen vacancies and cobalt species in CO ₂ hydrogenation.