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.

A highly active catalyst derived from CuO particles for selective hydrogenation of acetylene in large excess ethylene.

The removal of acetylene impurities is indispensable in the production of ethylene. An Ag-promoted Pd catalyst is industrially used to remove acetylene impurities by selective hydrogenation. It is highly desirable to replace Pd with non-precious metals. In the present investigation, CuO particles, which are most frequently used as the precursors for Cu-based catalysts, were prepared through the solution-based chemical precipitation method and used to prepare high-performance catalysts for selective hydrogenation of acetylene in large excess ethylene. The non-precious metal catalyst was prepared by treating CuO particles with acetylene-containing gas (0.5 vol% C2H2/Ar) at 120 °C and subsequent hydrogen reduction at 150 °C. The obtained catalyst was tested in selective hydrogenation of acetylene in a large excess of ethylene (0.72 vol% CH4 as the internal standard, 0.45 vol% C2H2, 88.83 vol% C2H4, 10.00 vol% H2). It exhibited significantly higher activity than the counterpart of Cu metals, achieving 100% conversion of acetylene without ethylene loss at 110 °C and atmospheric pressure. The characterization by means of XRD, XPS, TEM, H2-TPR, CO-FTIR, and EPR verified the formation of an interstitial copper carbide (CuxC), which was responsible for the enhanced hydrogenation activity.

An efficient NiCu@C/Al2O3 catalyst for selective hydrogenation of acetylene.

The development of non-noble metal catalysts for selective hydrogenation still remains a challenge. Herein, NiCu@carbon core-shell nanoparticles supported on Al2O3 (NiCu@C/Al2O3) were prepared, which showed enhanced catalytic performance of acetylene-selective hydrogenation in comparison with NiCu/Al2O3 without carbon encapsulation. In detail, NiCu@C/Al2O3 displayed high ethylene selectivity (>86%) even at an acetylene conversion of 100% and excellent stability (>90 h). Thus, NiCu@C/Al2O3 exhibited great potential as an alternative to Pd-based catalysts for acetylene-selective hydrogenation.

Copper-Based Catalysts for Selective Hydrogenation of Acetylene Derived from Cu(OH)2.

Replacing precious metals with cheap metals in catalysts is a topic of interest in both industry and academia but challenging. Here, a selective hydrogenation catalyst was prepared by thermal treatment of Cu(OH)2 nanowires with acetylene-containing gas at 120 °C followed by hydrogen reduction at 150 °C. The characterization by means of transmission electron microscopy observation, X-ray diffraction, and X-ray photoelectron spectroscopy revealed that two crystallites were present in the resultant catalyst. One of the crystal phases was metal Cu, whereas the other crystal phase was ascribed to an interstitial copper carbide (Cu x C) phase. The reduction of freshly prepared copper (II) acetylide (CuC2) at 150 °C also afforded the formation of Cu and Cu x C crystallites, indicating that CuC2 was the precursor or an intermediate in the formation of Cu x C. The prepared catalysts consisting of Cu and Cu x C exhibited a considerably high hydrogenation activity at low temperatures in the selective hydrogenation of acetylene in the ethylene stream. In the presence of a large excess of ethylene, acetylene was completely converted at 110 °C and atmospheric pressure with an ethane selectivity of <15%, and the conversion and selectivity were constant in a 260 h run.