The incorporation of copper nanoparticles on the graphite surface leads to the development of catalytic materials capable of selectively hydrogenating acetylene into ethylene and promoting the dimerization reaction to produce butenes. The catalytic properties can be modulated depending on the metal precursor employed. Based on our experimental data, it can be inferred that ethylene, the primary product, serves as an intermediate in the dimerization reaction.

Abstract

Dimerization of acetylene to C4 olefins was investigated using copper-based nanoparticles supported on graphite. Catalysts, prepared from various precursors and modified with Ag or Ni in some cases, were evaluated in a continuous flow reactor under atmospheric pressure at temperatures in the range 100–200 °C. Notably, all catalysts, except for the Cu─Ni bimetallic sample, showed high selectivity for partial hydrogenation, with ethylene as the main product. Selectivity toward butenes (1-butene, 2-butenes and butadiene) increased with a temperature rise from 100 to 150 °C; however, it remained stable between 150 and 200 °C. Comparison of the catalytic performance among the different catalysts at 150 °C revealed that the catalyst with 10% of Cu (10Cu/G (copper supported graphite)) provided the highest selectivity toward butenes, albeit at the expense of a reduction in the carbon balance (C.B.). The formation of C4 compounds appeared to involve secondary reactions of ethylene. To correlate the catalytic performance with surface characteristics, the catalysts were characterized before reaction (BR) and after reaction (AR) using a combination of structural, morphological, and spectroscopic techniques. These analyses, together with thermogravimetric measurements, were used to investigate the nature of carbon deposits. Interestingly, coke formation did not significantly alter catalytic behavior.