Pt-O4 Moiety Induced Electron Localization toward In2O-Triggered Acetylene Semi-Hydrogenation

Zr(OH)4-Catalyzed Semi-Hydrogenation of Phenylacetylene with Terminal Zr-O-H as Active Site: Inactive for Free Styrene

In the field of industrial semi-hydrogenation of trace alkynes amidst alkene feedstocks, the pivotal challenge lies in circumventing the hydrogenation of alkenes. Herein, we present Zr(OH)4 as an innovative catalyst for the semi-hydrogenation of phenylacetylene, demonstrating remarkable selectivity towards styrene (>96 %), while exhibiting inactivity towards free styrene. Notably, Zr(OH)4 achieves a 95 % conversion of quasi-industry 1 mol % phenylacetylene within styrene, with a mere 0.44 % styrene loss. Experimental and theoretical results confirm both terminal Zr-O-H and bridge Zr-O-H can dissociate H2, while the terminal Zr-O-H plays a crucial role on activating phenylacetylene through the sequential hydrogenation process of C6H5C≡CH→C6H5C=CH2→C6H5CH=CH2. The high rate of phenylacetylene removal is attributed to its strong adsorption capacity, while Zr(OH)4 has a significantly weaker adsorption capacity for styrene.

Bi-modified Cu-Based Catalysts for Acetylene Hydrogenation: Leveraging Dispersion and Hydrogen Spillover

Removing trace acetylene from the ethylene stream through selective hydrogenation is a crucial process in the production of polymer-grade ethylene. However, achieving high selectivity while maintaining high activity remains a significant challenge, especially for nonprecious metal catalysts. Herein, the trade-off between activity and selectivity is solved by synergizing enhanced dispersion and hydrogen spillover. Specifically, a bubbling method is proposed for preparing SiO2-supported copper and/or bismuth carbonate with high dispersion, which is then employed to synthesize highly dispersed Bi-modified CuxC-Cu catalyst. The catalyst displays outstanding catalytic performance for acetylene selective hydrogenation, achieving acetylene conversion of 100% and ethylene selectivity of 91.1% at 100 °C. The high activity originates from the enhanced dispersion, and the exceptional selectivity is due to the enhanced spillover capacity of active hydrogen from CuxC to Cu, which is promoted by the Bi addition. The results offer an avenue to design efficient catalysts for selective hydrogenation from nonprecious metals.

Finding Natural, Dense, and Stable Frustrated Lewis Pairs on Wurtzite Crystal Surfaces for Small-Molecule Activation

The surface frustrated Lewis pairs (SFLPs) open up new opportunities for substituting noble metals in the activation and conversion of stable molecules. However, the applications of SFLPs on a larger scale are impeded by the complex construction process, low surface density, and sensitivity to the reaction environment. Herein, wurtzite-structured crystals such as GaN, ZnO, and AlP are found for developing natural, dense, and stable SFLPs. It is revealed that the SFLPs can naturally exist on the (100) and (110) surfaces of wurtzite-structured crystals. All the surface cations and anions serve as the Lewis acid and Lewis base in SFLPs, respectively, contributing to the surface density of SFLPs as high as 7.26×1014 cm-2. Ab initio molecular dynamics simulations indicate that the SFLPs can keep stable under high temperatures and the reaction atmospheres of CO and H2O. Moreover, outstanding performance for activating the given small molecules is achieved on these natural SFLPs, which originates from the optimal orbital overlap between SFLPs and small molecules. Overall, these findings not only provide a simple method to obtain dense and stable SFLPs but also unfold the nature of SFLPs toward the facile activation of small molecules.

Atomic Design of Alkyne Semihydrogenation Catalysts via Active Learning

Alkyne hydrogenation on palladium-based catalysts modified with silver is currently used in industry to eliminate trace amounts of alkynes in alkenes produced from steam cracking and alkane dehydrogenation processes. Intensive efforts have been devoted to designing an alternative catalyst for improvement, especially in terms of selectivity and catalyst cost, which is still far away from that as expected. Here, we describe an atomic design of a high-performance Ni-based intermetallic catalyst aided by active machine learning combined with density functional theory calculations. The engineered NiIn catalyst exhibits >97% selectivity to ethylene and propylene at the full conversion of acetylene and propyne at mild temperature, outperforming the reported Ni-based catalysts and even noble Pd-based ones. Detailed mechanistic studies using theoretical calculations and advanced characterizations elucidate that the atomic-level defined coordination environment of Ni sites and well-designed hybridization of Ni 3d with In 5p orbital determine the semihydrogenation pathway.