Benzyl alcohol oxidation with Pd-Zn/TiO₂: computational and experimental studies

Abstract

Pd–Zn/TiO 2 catalysts containing 1 wt% total metal loading, but with different Pd to Zn ratios, were prepared using a modified impregnation method and tested in the solvent-free aerobic oxidation of benzyl alcohol. The catalyst with the higher Pd content exhibited an enhanced activity for benzyl alcohol oxidation. However, the selectivity to benzaldehyde was significantly improved with increasing presence of Zn. The effect of reduction temperature on catalyst activity was investigated for the catalyst having a Pd to Zn metal molar ratio of 9:1. It was found that lower reduction temperature leads to the formation of PdZn nanoparticles with a wide particle size distribution. In contrast, smaller PdZn particles were formed upon catalyst reduction at higher temperatures. Computational studies were performed to compare the adsorption energies of benzyl alcohol and the reaction products (benzaldehyde and toluene) on PdZn surfaces to understand the oxidation mechanism and further explain the correlation between the catalyst composition and its activity.

Controlling the Production of Acid Catalyzed Products of Furfural Hydrogenation by Pd/TiO2

“…To understand the influence the colloidal solvent has on the accessibility of TiO 2 Brønsted acid sites, we utilised hydrogen temperature programmed reduction (H 2 ‐TPR) to measure the uptake of H 2 for the PdWPA and PdMeP catalysts (Figure 8). The H 2 ‐TPR data for both catalyst exhibits three features below 350 °C: (I) a negative peak at ∼50 °C, which is assigned to the decomposition of Pd hydride, [76–80] (II) an additional negative peak between 100–150 °C that is indicative of dehydration, [81] and (III) a positive feature between 200–350 °C that has been reported as the reduction of Ti 4+ to Ti 3+ in the vicinity of Pd, i. e ., hydrogen spillover from Pd to the support [82,83] …”

Role of defects in carbon materials during metal-free formic acid dehydrogenation

“…49 All the calculations include the long-range dispersion correction approach by Grimme, 50,51 which is an improvement on pure DFT to evaluate molecular interactions. [52][53][54][55] We included also the implicit solvation model as implemented in VASPsol describing the bulk water effect of electrostatics, cavitation, and dispersion on the FA interaction with the C-materials. 56,57 The optimization thresholds were 10 −5 eV and 0.01 eV/Å for electronic and ionic forces relaxation, respectively.…”

Selective Catalytic Oxidation of Benzyl Alcohol by MoO2 Nanoparticles

“…The catalytic performance demonstrated by the two different catalysts was relevant and their performances in the oxidation of BzOH to BzCHO using TBHP or H2O2 with or without solvent are compared in Table 4. As shown in entries 14-16, the overall catalytic performance of the MoO2-Fe2O3 and MoO2 calcined nanomaterials was comparable or better than other catalytic nanomaterials reported in the literature [6,[23][24][25][26][27][28][29][30][31][32][33][34]. The catalysts shown in Table 4 cover a wide selection of The catalytic performance demonstrated by the two different catalysts was relevant and their performances in the oxidation of BzOH to BzCHO using TBHP or H 2 O 2 with or without solvent are compared in Table 4.…”

“…Numerous methods have been developed to achieve the desired transformation with the use of a stoichiometric amount of oxidant. The oxidation of benzyl alcohol to benzaldehyde continues to be studied, since this reaction has a high reactivity, but presents selectivity issues yielding some by-products, which are well-known [6]. In this context, both homogeneous and heterogeneous transition metal-based catalysts have been developed for aerobic alcohol oxidations [7].…”