Promotion of Mg(OH)₂ in Cu-Based Catalysts for Selective Hydrogenation of Acetylene

The selective hydrogenation of acetylene is of industrially indispensable in the production of polymer-grade ethylene. The design of non-precious metal catalysts with outstanding performance is of pivotal importance in order to replace the supported Pd–Ag catalysts. Our previous work showed that a copper carbide (Cu_xC)-containing catalyst exhibited high hydrogenation activity and selectivity under mild conditions. In the present work, Mg(OH)₂ was used to modify the Cu_xC-containing catalyst in order to improve its catalytic performance. Mg(OH)₂-modified Cu_xC-containing catalyst was prepared from a coprecipitate of Cu(OH)₂ and Mg(OH)₂, which was obtained by precipitation of Cu(NO₃)₂ and Mg(NO₃)₂ solution with dropwise addition of NaOH solution, by thermal treatment in C₂H₂/Ar (0.5%) at 120 ℃ followed by H₂ reduction at 150 ℃. The introduction of Mg(OH)₂ led to reduced Cu_xC crystalline size and to increased amount of Cu_xC crystallites. In addition, the basic nature of Mg(OH)₂ is favorable to suppress the undesired oligomerization. The prepared catalyst showed excellent catalytic performance with complete acetylene conversion, low selectivity to unwanted ethane (24%), and high stability at 100 °C and atmospheric pressure in the presence of large excess ethylene in 100 h.