Pd/Al2O3 catalysts prepared from Pd nitrate dissolved in water (Pd-water) and toluene (Pd-toluene) were investigated in the gas-phase selective hydrogenation of 1,3-butadiene under various reaction conditions. As revealed by TEM and CO chemisorption results, smaller Pd particle sizes with more uniform particle size distribution were obtained on Pd-toluene catalysts. Reduction at 500 °C resulted in sintering of Pd particles with Pd-water showing higher degree of metal sintering than Pd-toluene. Sintering of Pd particles may result in low-index surfaces which promoted butane formation and lowered 1-butene selectivity. While Pd dispersion and/or Pd particle size strongly affected 1,3-butadiene hydrogenation rate and 1-butene selectivity, the selectivity to 2-butenes was quite similar at 47–55% for all the catalysts under various reaction conditions.
Lee, DC, Kim, JH, Kim, WJ, Kang, JH, Moon, SH (2003) Appl Catal A. 244:83.