α al2o3

Ni-Based catalysts supported on CeO₂ (Sigma Aldrich Co.), α-Al₂O₃ (Alfa Aesar Co.), Y₂O₃ (Sigma Aldrich Co., St. Louis, MO, USA) and TiO₂ (G-5, Cristal Global Co.) were prepared by a wet impregnation method. Nickel nitrate hexahydrate (Ni(NO₃)₂·6H₂O; Sigma Aldrich Co.) was dissolved in distilled water at 80 °C. After impregnation, the moisture was removed at 80 °C using a rotary vacuum evaporator and then dried at 103 °C oven for 12 h. The samples were calcined at 400 °C for 2 h and then samples were reduced at 420 °C for 2 h with a 30% H₂/N₂. The obtained samples were grounded and sieved using a 40–50 mesh. Ni loading was fixed at 10 wt%.

Diphenylacetylene (Sigma-Aldrich, St. Louis, MO, USA, >98%) and n-hexane (Merck KGaA, Darmstadt, Germany, 98%) were used without further purification. Gases and gaseous mixtures used for catalyst reduction and catalytic tests were supplied by Linde Gas Rus (Balashikha, Russia): 5%H₂/Ar, H₂ (99.9999% grade) and He (99.999% grade). For the catalyst preparation α-Al₂O₃ (Alfa Aesar, Haverhill, MA, USA, S_sp = 8 m²/g) was used as a carrier.

All catalysts comprising Fe as active metal, Mn as first promoter and either of Cu, Ni or K as second/third promoter were synthesized using coimpregnation method. Active metal and promoters were coimpregnated on α-Al₂O₃ (Alfa Aesar, 99.9%) support. Support, Fe(NO₃)₃.9H₂O (Merck, ACS), Mn(NO₃)₂.4H₂O (Merck, >98.5%) and either of Cu(NO₃)₂.3H₂O (Merck, >99.5%), Ni(NO₃)₂.6H₂O (Merck, ACS) or KNO₃ (Merck, ISO) were first taken into an Erlenmeyer flask. Then, this powder mixture was slurried either in deionized water or n-pentane (Sigma-Aldrich, reagent grade, 98%). Aqueous mixture was mixed in an ultrasonic bath, whereas n-pentane comprising solution was stirred overnight. Prepared catalysts were dried at 110 °C and calcined at 430 °C under dry air atmosphere for 3 h. Catalyst were named according to the type and amount of metal used, and the type of solvent as follows: xFeyMnzAkB-s where x, y, z and k are the weight percentage of the metal used, A and B represent the second and third promoter (Cu, Ni or K), s indicates the type of solvent used (w-water, p-pentane). In this study, the weight percentage of Fe (x) and Mn (y) in the catalysts were determined to be 15 and 0.3, respectively; z and k were used as 0.5, 1, 1.5, 2, and 2.5. A representative notation for a catalyst comprising 0.3 wt.% Mn, 0.5 wt%Cu prepared by n-pentane is: 15Fe0.3Mn0.5Cu-p.