Improved catalytic performance of Pd/TiO2 in the selective hydrogenation of acetylene by using H2-treated sol–gel TiO2

Abstract

The anatase nanocrystalline TiO 2 samples were synthesized by a sol-gel method with a thermal treatment under air and H 2 atmospheres at 350°C and employed as the supports for preparation of Pd/TiO 2 catalysts by impregnation and electroless deposition methods. The surface Ti 3+ defects on the TiO 2 significantly increased when treated under H 2 , compared to air, with no changes in the average crystallite size, specific surface area, and pore structure.The CO chemisorption and IR of adsorbed CO results showed that the use of H 2 -treated TiO 2 resulted in higher Pd dispersion and the formation of more isolated adsorption sites, hence improving the catalytic performance in terms of both acetylene conversion and ethylene selectivity.

Recent advances in selective acetylene hydrogenation using palladium containing catalysts

“…However, a marked effect on the number of defect sites, as accessed by EPR measurements was observed for samples pre-treated in N 2 or H 2 . Materials with more Ti 3+ defects then resulted in higher Pd dispersion and improved acetylene conversion during catalyst testing [37,38]. On the basis of data presented it is not clear if the enhanced activity is purely as a result of more Pd surface atoms, a particle size effect or whether turnover frequency also increased.…”

“…It is therefore thought that acetylene will be more readily find the active Pd sites compared with ethylene which allows for less overhydrogenation. Riyapan created by various thermal pre-treatments to TiO 2 prior to addition of Pd by either impregnation or electroless deposition (metal deposition in the absence of an external current) [37,38]. TiO 2 was prepared by a sol-gel methodology and then treated in hydrogen, nitrogen, oxygen or air at 623 K. In general, the thermal pretreatment appeared to have relatively little effect on physicochemical properties such as surface area and pore diameter.…”

“…Regardless, samples on H 2 or N 2 pre-treated TiO 2 exhibited marked improvement in ethylene selectivity. Most notably, pre-treatment in H 2 resulted in 85%-90% ethylene selectivity at 100% conversion [37]. The authors postulated that higher defect site concentrations resulted in more strong metal support interactions which increased selectivity.…”

Flame-made Pt/TiO2 catalysts for the liquid-phase selective hydrogenation of 3-nitrostyrene

“…For comparison purposes, Pt/TiO 2 catalysts were also prepared by impregnation method using a sol-gel TiO 2 support [24] and an aqueous solution of H 2 PtCl 6 ·6H 2 O. The catalysts were dried in an oven at 100 • C for 24 h. The prepared catalysts were calcined in oxygen at 500 • C for 2 h, and reduced in H 2 at 200-700 • C.…”

Kinetic Parameters for the Selective Hydrogenation of Acetylene on GaPd2 and GaPd

“…[4] As this reaction is also of high interest for basic research, other support materials such as carbon or different oxidess uch as SiO 2 and TiO 2 have been investigated. [5][6][7][8] The activity of elemental Pd catalysts is somewhat high but the selectivity for ethylene is limited to 20 %a t2 00 8C, which is determined by the electronic and geometrics tructure of the catalyst. [9] In such elemental Pd or Pd alloy catalysts, each atom is surrounded by 12 other (Pd) atomsi nt he first coordination shell.…”