Synthesis, Characterization, and Catalytic Properties of Pd and Pd–Ag Catalysts Supported on Nanocrystalline TiO2 Prepared by the Solvothermal Method

Abstract

Nanocrystalline titania have been prepared by thermal decomposition of titanium (IV) n-butoxide in two different solvents (toluene and 1,4-butanediol) at 320°C and employed as supports for Pd and Pd-Ag catalysts for selective acetylene hydrogenation for the first time. The titania products obtained from both solvents were pure anatase phase with relatively the same crystallite sizes and BET surface areas. However, due to different crystallization pathways, the number of Ti 3+ defective sites as shown by ESR results of the titania prepared in toluene was much higher than the ones prepared in 1,4-butanediol. It was found that the use of anatase titania with higher defective sites as a support for Pd catalysts resulted in lower activity and selectivity in selective acetylene hydrogenation. However, this effect was suppressed by Ag promotion.

Unusual Catalytic Performance for Selective Acetylene Hydrogenation over Pd Nanoparticles Fabricated on N,O-containing Organic Groups Modified Silica

“…3a), and the S E decreases dramatically with the increase of reaction temperature (curve a of Fig. 3b), which is in agreement with the literature results [7,[33][34][35][36]. However, for I-Pd/MSiO 2 catalyst, it is striking that both the ethylene selectivity (from 24 to 68%, curve b of Fig.…”

“…3a) increase with the rising reaction temperature, which is drastically different from that of Pd/C-SiO 2 (curve a of Fig. 3b) and the results shown in literatures [7,[33][34][35][36]. Numerous previous work [2,3,6] have demontrated that the coke deposition can lead to the increase of ethylene selectivity.…”

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

“…For example, Kang et al [5] showed that high ethylene selectivity (> 90%) can be obtained over Pd/TiO 2 and Pd/Si-modified TiO 2 when they were reduced at 500 o C due to the strong metal-support interaction (SMSI) effect at about 50% conversion of acetylene. In our previous studies, the solvothermal-derived TiO 2 supported Pd catalysts exhibited 40% selectivity of ethylene at complete conversion of acetylene [6]. Ethylene selectivity ≥ 80% has been reported over Pd catalysts supported on the mixed phase TiO 2 containing 44% rutile phase [7] and the sol-gelderived TiO 2 at acetylene conversion < 50% [8].…”

“…Despite its long-term application in industry, Pdbased catalysts still suffer from poor selectivity of acetylene conversion to ethylene which leads to the production of a large amount of ethane and the waste of ethylene [2,3] According to a recent review by Kim et al [4], to achieve high selectivity and activity of Pdbased catalysts, recent trend has been (i) to add a second metal to form alloy with Pd or to suppress the number of multicoordination sites of the Pd surface and (ii) to induce the strong metal-support interaction (SMSI) effect so that the adsorption strength of ethylene is weakened [5]. A number of previous studies show that the presence of Ti 3+ species that was in contact with Pd promotes the SMSI on Pd/TiO 2 catalysts, resulting in an improved catalyst performance in the selective acetylene hydrogenation [6][7][8][9][10].…”

Effect of Support Crystallite Size on Catalytic Activity and Deactivation of Nanocrystalline ZnAl2O4-Supported Pd Catalysts in Liquid-Phase Hydrogenation

“…The products obtained by solvothermal synthesis usually show uniform morphology, well-controlled chemical composition, and narrow particle size distribution. As catalyst supports, solvothermal-derived nanocrystalline oxides have been shown to provide better catalytic properties of the corresponding supported metal catalysts compared to commercially available supports [19][20][21]. In this study, nanocrystalline ZnAl 2 O 4 spinels were prepared by the solvothermal method using toluene as the solvent and were employed as Pd catalyst supports.…”