Direct Methyl Formate Formation from Methanol over Supported Palladium Nanoparticles at Low Temperature

Abstract

Palladium nanoparticles of different sizes and supported on TiO2 (2 wt. %) were synthesized by using the water‐in‐oil microemulsion method. The control of palladium nanoparticles was investigated in terms of the nature of organic surfactant and solvent. Attention was paid to the reduction of palladium ions in solution during synthesis. Materials were characterized by N2‐BET at low temperature, XRD, XPS, H2 chemisorption, and TEM and were tested in the gas phase oxidation of methanol. The results confirmed the effect of microemulsion composition on the size of palladium nanoparticles. The direct formation of methyl formate from methanol was observed. Supported palladium catalysts produced methyl formate at low temperature (<150 °C) with a very high selectivity, and, in some cases, a selectivity of approximately 100 %. At higher temperature, methyl formate is not formed at all and the total oxidation to CO2 occurs. A linear correlation between palladium particle size and methanol conversion was observed. Conversion and selectivity were correlated with the acidity of the catalysts. Very small particles were more active but less selective. A mechanism was proposed to explain the formation of methyl formate from methanol.

Synergetic Behavior of TiO2‐Supported Pd(z)Pt(1−z) Catalysts in the Green Synthesis of Methyl Formate

“…For the TiO 2 support, the typical diffraction pattern (Figure S1) of a mixture of anatase and rutile was found, which was in agreement with a previous report . Concerning Pd(1.0)‐IWI, the fresh catalyst, that is, only calcined, exhibited a diffraction peak at 2 θ =33.85° that corresponds to PdO(1 0 1).…”

“…It is important to notice that despite the weak synergetic effects in MeOH conversion displayed by Pd( z )Pt(1− z )‐MicE, these catalysts were more active in the reaction than Pd( z )Pt(1−z)‐IWI and that synergetic effects for the production of MF were indeed present for both series of catalysts. The literature also indicates that one of the characteristics that make Pd nanoparticles very active and selective in the reaction is a narrow particle size distribution . This characteristic is present for Pd( z )Pt(1− z )‐MicE.…”

“…Except for noble‐metal‐based catalysts, the aforementioned oxides perform modestly in the reaction . The performance of noble metals has been related to their reducibility . Lichtenberger et al .…”

“…This bimetallic system was selected to benefit from the probable synergetic effects coming from the individual properties of each metal in oxidation. On the one hand, platinum is known to be a very efficient catalyst in oxidation reactions, and, on the other hand, palladium has shown a high selectivity to MF . Several papers report on the synergy between Pd and Pt for diverse reactions such as the hydrogenation of aromatics and oxygenates, and the combustion of hydrocarbons .…”

Reconstruction of Rh nanoparticles in methanol oxidation reaction

“…10 Recently, various noble metal catalysts including Au, 11 Pd, 12 Ag, 13 and Au-Pd alloy 14 nanoparticles show good catalytic activities for the selective oxidation of methanol to methyl formate. 10 Recently, various noble metal catalysts including Au, 11 Pd, 12 Ag, 13 and Au-Pd alloy 14 nanoparticles show good catalytic activities for the selective oxidation of methanol to methyl formate.…”