Active site tuning based on pseudo-binary alloys for low-temperature acetylene semihydrogenation.

The development of an efficient catalytic system for low-temperature acetylene semihydrogenation using nonnoble metals is important for the cost-effective production of polymer-grade pure ethylene. However, it remains challenging owing to the intrinsic low activity. Herein, we report a flexibly tunable catalyst design concept based on a pseudo-binary alloy, which enabled a remarkable enhancement in the catalytic activity, selectivity, and durability of a Ni-based material. A series of (Ni1-xCux)3Ga/TiO2 catalysts exhibiting L12-type pseudo-binary alloy structures with various Cu contents (x = 0.2, 0.25, 0.33, 0.5, 0.6, and 0.75) were prepared for active site tuning. The optimal catalyst, (Ni0.8Cu0.2)3Ga/TiO2, exhibited outstandingly high catalytic activity among reported 3d transition metal-based systems and excellent ethylene selectivity (96%) and long-term stability (100 h) with near full conversion even at 150 °C. A mechanistic study revealed that Ni2Cu hollow sites on the (111) surface weakened the strong adsorption of acetylene and vinyl adsorbate, which significantly accelerated the hydrogenation process and inhibited undesired ethane formation.

Metallic Catalysts for Oxidative Dehydrogenation of Propane Using CO2.

The oxidative dehydrogenation of propane using CO2 (CO2 -ODP) is a promising technique for realizing high-yield propylene production and CO2 usage. Developing a highly efficient catalyst for CO2 -ODP is essential and beneficial to the chemical industry and for realizing net-zero emissions. Many studies have investigated metal oxide-based catalysts, revealing that rapid deactivation and low selectivity remain limiting factors for their industrial applications. In recent years, metallic nanoparticle catalysts have become increasingly attractive due to their unique properties. Therefore, we summarize the performance of metal-based catalysts in CO2 -ODP reactions by considering catalyst design concepts, different mechanisms in the reaction process, and the role of CO2 .

High-entropy intermetallics on ceria as efficient catalysts for the oxidative dehydrogenation of propane using CO2.

The oxidative dehydrogenation of propane using CO2 (CO2-ODP) is a promising technique for high-yield propylene production and CO2 utilization. The development of a highly efficient catalyst for CO2-ODP is of great interest and benefit to the chemical industry as well as net zero emissions. Here, we report a unique catalyst material and design concept based on high-entropy intermetallics for this challenging chemistry. A senary (PtCoNi)(SnInGa) catalyst supported on CeO2 with a PtSn intermetallic structure exhibits a considerably higher catalytic activity, C3H6 selectivity, long-term stability, and CO2 utilization efficiency at 600 °C than previously reported. Multi-metallization of the Pt and Sn sites by Co/Ni and In/Ga, respectively, greatly enhances propylene selectivity, CO2 activation ability, thermal stability, and regenerable ability. The results obtained in this study can promote carbon-neutralization of industrial processes for light alkane conversion.

Nickel-Based High-Entropy Intermetallic as a Highly Active and Selective Catalyst for Acetylene Semihydrogenation.

Acetylene semihydrogenation is a key technology for producing polymer-grade ethylene from crude ethylene. Ni-based catalysts are promising alternatives to noble-metals for this process. However, achieving high catalytic activity and selectivity remains a big challenge. We report a novel catalyst design based on high-entropy intermetallics (HEI), which provide thermally stable isolated Ni without excess counterpart metals and achieve exceptionally high performance. Intermetallic NiGa was multi-metalized to a (NiFeCu)(GaGe), where the Ni and Ga sites were partially substituted with Fe/Cu and Ge, respectively, without altering the parent CsCl-type structure. The NiFeCuGaGe/SiO2 HEI catalyst completely inhibited ethylene overhydrogenation even at complete acetylene conversion, and exhibited five-times higher activity than other 3d-transition-metal-based catalysts. The DFT study showed that the surface energy decreased by multi-metallization, which drastically weakened ethylene adsorption.

Doubly Decorated Platinum-Gallium Intermetallics as Stable Catalysts for Propane Dehydrogenation.

Propane dehydrogenation (PDH) is a promising chemical process that can satisfy the increasing global demand for propylene. However, the Pt-based catalysts that have been reported thus far are typically deactivated at ≥600 °C by side reactions and coke formation. Thus, such catalysts possess an insufficient life. Herein, we report a novel catalyst design concept, namely, the double decoration of PtGa intermetallics by Pb and Ca, which synergize the geometric and electronic promotion effects on the catalyst stability, respectively. Pb is deposited on the three-fold Pt3 sites of the PtGa nanoparticles to block them, whereas Ca, which affords an electron-enriched single-atom-like Pt1 site, is placed around the nanoparticles. Thus, PtGa-Ca-Pb/SiO2 exhibits an outstandingly high catalytic stability, even at 600 °C (kd =0.00033 h-1 , τ=3067 h), and almost no deactivation of the catalyst was observed for up to 1 month for the first time.

A Cu-Pd single-atom alloy catalyst for highly efficient NO reduction.

A series of Cu-Pd alloy nanoparticles supported on Al2O3 were prepared and tested as catalysts for deNO x reactions. XRD, HAADF-STEM, XAFS, and FT-IR analyses revealed that a single-atom alloy structure was formed when the Cu/Pd ratio was 5, where Pd atoms were well isolated by Cu atoms. Compared with Pd/Al2O3, Cu5Pd/Al2O3 exhibited outstanding catalytic activity and N2 selectivity in the reduction of NO by CO: for the first time, the complete conversion of NO to N2 was achieved even at 175 °C, with long-term stability for at least 30 h. High catalytic performance was also obtained in the presence of O2 and C3H6 (model exhaust gas), where a 90% decrease in Pd use was achieved with minimum evolution of N2O. Kinetic and DFT studies demonstrated that N-O bond breaking of the (NO)2 dimer was the rate-determining step and was kinetically promoted by the isolated Pd.