Yufei He

Low‐pressure ammonia synthesis technology holds revolutionary significance in ensuring food security, promoting energy transition, and addressing climate change. However, the hydrogen poisoning of catalysts has long restricted the development of low‐pressure ammonia synthesis processes. Focusing on the regulation of support surface properties, this study successfully prepared a Ru/Al ₂ O ₃ ‐La‐C catalyst. By regulating the transfer and desorption pathways of hydrogen on the catalyst surface, the hydrogen poisoning phenomenon under low‐pressure conditions was effectively alleviated. Under the reaction conditions of 400°C and 3 MPa, the ammonia synthesis yield of the Ru/Al ₂ O ₃ ‐La‐C catalyst reached 4.74 mmol NH ₃ ·g _cat ⁻¹ ·h ⁻¹ , which was 10 times higher than that of the unmodified Ru/Al ₂ O ₃ catalyst. Meanwhile, the reaction order of hydrogen changed from −0.43 to 0.58, and the reaction order of nitrogen changed from 0.98 to 0.44, further confirming that the hydrogen poisoning issue of the catalyst was significantly improved and the activation of nitrogen was promoted. Characterization results from H ₂ ‐TPD and H‐D exchange experiments showed that La doping constructed La‐O sites, which facilitated the transfer of active hydrogen from the active component Ru to the support. In contrast, the introduction of carbon regulated the recombination and desorption mode of hydrogen on the surface of metallic Ru, prompting hydrogen to desorb in the form of H ₂ instead of forming H ₂ O. This study provides a new insight for the design and development of catalysts for low‐pressure ammonia synthesis.

Achieving acceptable propane conversion in the endothermic propane dehydrogenation (PDH) reaction demands high temperatures, which exacerbate the activity‐stability trade‐off through low propylene selectivity and accelerated coking deactivation. Addressing this, we leverage the essence of Le Chatelier's principle—shifting reaction equilibrium through rapid in situ H ₂ removal—a strategy conventionally deemed unattainable on Al ₂ O ₃ supports due to hydrogen spillover limitations. The synergistic sites between the La _1– SnO _x promoter and Pt enable the redistribution of surface H species away from the Pt active centers. Consequently, the La ₁ ‐Pt _n /SnO _x /Al ₂ O ₃ catalyst achieves propane conversions approaching the thermodynamic equilibrium conversion over 300–600 °C. Moreover, modulation of hydrogen surface diffusion behavior influences unselective C–C(H) scission of propylene and modifies coke structure and secondary cracking propensity, which is associated with the substantially improved durability observed for La ₁ ‐Pt _n /SnO _x /Al ₂ O ₃ compared to the Pt _n /SnO _x /Al ₂ O ₃ (commercial mimic) catalyst. This superior performance demonstrates that, the introduction of La ₁ –SnO _x not only overcomes the inert hydrogen‐trapping nature of Al ₂ O ₃ , but also alleviates the conventional activity–stability trade‐off in PDH catalysis, illustrating how atomically dispersed promoters can circumvent intrinsic support limitations and thereby expand the performance boundaries of Al ₂ O ₃ ‐based dehydrogenation catalysts.

Achieving acceptable propane conversion in the endothermic propane dehydrogenation (PDH) reaction demands high temperatures, which exacerbate the activity‐stability trade‐off through low propylene selectivity and accelerated coking deactivation. Addressing this, we leverage the essence of Le Chatelier's principle—shifting reaction equilibrium through rapid in situ H ₂ removal—a strategy conventionally deemed unattainable on Al ₂ O ₃ supports due to hydrogen spillover limitations. The synergistic sites between the La _1– SnO _x promoter and Pt enable the redistribution of surface H species away from the Pt active centers. Consequently, the La ₁ ‐Pt _n /SnO _x /Al ₂ O ₃ catalyst achieves propane conversions approaching the thermodynamic equilibrium conversion over 300–600 °C. Moreover, modulation of hydrogen surface diffusion behavior influences unselective C–C(H) scission of propylene and modifies coke structure and secondary cracking propensity, which is associated with the substantially improved durability observed for La ₁ ‐Pt _n /SnO _x /Al ₂ O ₃ compared to the Pt _n /SnO _x /Al ₂ O ₃ (commercial mimic) catalyst. This superior performance demonstrates that, the introduction of La ₁ –SnO _x not only overcomes the inert hydrogen‐trapping nature of Al ₂ O ₃ , but also alleviates the conventional activity–stability trade‐off in PDH catalysis, illustrating how atomically dispersed promoters can circumvent intrinsic support limitations and thereby expand the performance boundaries of Al ₂ O ₃ ‐based dehydrogenation catalysts.

Micro‐fluidized beds significantly enhance mass and heat transfer efficiency in gas–liquid–solid catalytic reaction systems due to their high specific surface area characteristics. However, scale effects often induce bubble coalescence and promote slugging tendencies. To address these limitations, this study utilizes a microporous distributor with apertures smaller than the particle size to compartmentalize conventional miniaturized fluidized beds, accordingly constructing a novel miniaturized confined fluidized bed. Furthermore, by employing a triple analysis framework integrating power spectral density, wavelet decomposition, and K ‐means clustering, the bubble dynamics within the confined gas–liquid–solid micro‐fluidized bed are quantitatively characterized. Based on the extracted bubble dynamics characteristics, thresholds for classing bubble motion states in the confined micro‐fluidized bed are summarized. Additionally, K ‐means clustering is utilized to objectively analyze geometric and operational parameters on bubble dynamics features, enabling the partitioning of operating gas‐velocity regimes corresponding to different bubble motion states without subjective human influence.

Nano‐catalysts demonstrate exceptional performance in heterogeneous reactions, yet their potential is often underutilized due to a lack of attention to engineering design. In this study, an innovative encapsulated structure is presented for nano‐catalysts and a corresponding catalytic system. Using an oil‐in‐water droplet strategy, millimeter‐sized hollow spherical alumina (Al ₂ O ₃ ‐HS) is fabricated with an average diameter of ≈3 mm and a hollow void size of ≈1 mm. This approach enables the one‐step encapsulation of nanoscale Pd/Al ₂ O ₃ within the Al ₂ O ₃ ‐HS. The resulting assembly is immobilized within a tubular reactor for the hydrogenation of 2‐ethylanthraquinone, with hydrogen introduced from the bottom of the reactor. Remarkably, the encapsulated catalyst achieved twice the H ₂ O ₂ productivity of conventional supported catalysts. This enhancement is attributed to the cavity‐constrained fluidization behavior of Pd/Al ₂ O ₃ within the hollow alumina spheres. The design introduces a novel catalytic system that combines shell‐immobilization with the fluidization of encapsulated nano‐catalysts. As the gas velocity exceeds the minimum fluidization velocity, the Pd/Al ₂ O ₃ particles remain highly accessible while allowing efficient gas and product flow. This hybrid approach integrates the advantages of fixed‐bed and fluidized‐bed systems, offering a promising solution to the technical challenges limiting the industrial application of nano‐catalysts.