Preparation of Pd/SiO2 catalysts for methanol synthesis I. Ion exchange of 6Pd(NH3)4)(AcO)2

FTIR Study of the Adsorption of Methanol on Clean and Ca-Promoted Pd/SiO2 Catalysts

“…The catalysts were made by ion-exchanging palladium acetate (Engelhard, 99.5% w/w) in aqueous ammonia (pH 11) onto the prepurified, calcined support. The support, a mesoporous silica (Davison G59: BET surface area = 254 m 2 /g, modal radius = 83 Å), was purified by organic and inorganic washing (7). After air drying, the anchored Pd tetraammine complex was decomposed to the diammine one at 423 K. Part of the stock was used as such, to prepare a first type of Ca-promoted catalysts (S code), where maximum Ca-Pd interaction was expected, while a second part was H 2 prereduced instead (723 K, 2 h, heating rate: 2 K/min), to minimize said interaction (R code).…”

Exploring Pd adsorption, diffusion, permeation, and nucleation on bilayer SiO2/Ru as a function of hydroxylation and precursor environment: From UHV to catalyst preparation

“…For TPD measurements, the sample was positioned directly in front of the skimmer cone encapsulating the differentially pumped mass spectrometer and heated at a rate of 9 K/sec. Within UHV, Pd was deposited over the various samples at  100 K using an electron beam evaporator (Omicron, EMT3), and fluxes were established with the aid of quartz micro-balance (Inficon, SQM [19][20][21][22][23][24]. Following liquid exposure, samples were blown dry in a flow of helium before reintroduction to the UHV system following placement within and subsequent evacuation of the transfer-chamber.…”

“…Highly dispersed Pd particles find widespread use in a number of silica-supported reaction systems [19][20][21][22][23][24][34][35][36][37][38][39][40][41][42][43], with many of those prepared via impregnation of silicas with Pd salts (chloride, nitrate) or adsorption of Pd complexes (acetate, ammine). For the latter, several studies have been conducted to characterize the adsorption, decomposition, nucleation, and activation of ligand-coordinated Pd precursor species brought into contact with high surface-area silicas within aqueous environments [21,22,24].…”

“…For the latter, several studies have been conducted to characterize the adsorption, decomposition, nucleation, and activation of ligand-coordinated Pd precursor species brought into contact with high surface-area silicas within aqueous environments [21,22,24]. While an ion-exchange mechanism has previously been suggested to dominate the interaction of ammine-complexes with the silica support, more recent work favors an interpretation based upon strong electrostatic adsorption [24].…”

“…To track the condition-dependent evolution of Pd remaining on the surface following our solution-based deposition, we have generated Figure 6, which shows the Pd 3d (Figure 6a centers [46]. Notably, we see no evidence of Pd film penetration, which we ascribe to the presence of the large ligand-spheres surrounding the Pd-centers that are also noted to result in high dispersion over higher surface-area silicates [19][20][21][22][23][34][35][36][37][38].…”