The selective oxidation of n-butanol to butyraldehyde by oxygen using stable Pt-based nanoparticulate catalysts: an efficient route for upgrading aqueous biobutanol

Supported Pt nanoparticles are shown to be active and selective towards butyraldehyde in the base-free oxidation of n-butanol by O2 in an aqueous phase. The formation of butyric acid as a by-product promoted the leaching of Pt and consequently the activity of the catalysts decreased upon reuse. Characterisation showed that the degree to which Pt leached from the catalysts was related to both the metal–support interaction and metal particle size. A catalyst active and stable (<1% metal leaching) in the aqueous reaction medium was obtained when Pt nanoparticles were supported on activated carbon and prepared by a chemical vapour impregnation method. The presence of n-butanol in the aqueous medium is required to inhibit the over oxidation of butyraldehyde to butyric acid. Consequently, high selectivities towards butyraldehyde can only be obtained at intermediate n-butanol conversion

The role of tungsten oxide in the selective hydrogenolysis of glycerol to 1,3-propanediol over Pt/WO x /Al 2 O 3

Bi-functional heterogeneous catalysts combining a noble metal with an oxophilic metal (mainly W or Re) were reported to be selective for the CO hydrogenolysis of glycerol to the high added-value 1,3-propanediol. Despite intensive research work carried out, there is a great deal of controversy about the role of the oxophilic metal. In this work, the hydrogenolysis of glycerol over Pt/WOx/Al2O3 catalysts was studied in real time by in-situ attenuated total reflection infrared (ATR-IR) spectroscopy. Moreover, ex-situ ATR-IR spectroscopic studies were also used to study the interactions between glycerol and the different catalytic surfaces. The results obtained indicate a stronger adsorption of glycerol through the primary hydroxy group/s when tungsten oxides are grafted onto the γ-Al2O3 support. The competitive adsorption between the reactant and the main reaction products for the same active sites, and the effect of the hydrogen availability were also studied. The evidences found in this work point out a triple role of tungsten oxide in the reaction, acting as: (i) a strong anchoring site for the primary hydroxy group/s of glycerol, (ii) a supplier of protons, and (iii) a stabilizer of the secondary carbocation. Under the best conditions, a remarkable high yield of 1,3-propanediol of 38.5% was obtained after only 4 h of reaction time

The role of tungsten oxide in the selective hydrogenolysis of glycerol to 1,3-propanediol over Pt/WO x /Al 2 O 3

Bi-functional heterogeneous catalysts combining a noble metal with an oxophilic metal (mainly W or Re) were reported to be selective for the CO hydrogenolysis of glycerol to the high added-value 1,3-propanediol. Despite intensive research work carried out, there is a great deal of controversy about the role of the oxophilic metal. In this work, the hydrogenolysis of glycerol over Pt/WOx/Al2O3 catalysts was studied in real time by in-situ attenuated total reflection infrared (ATR-IR) spectroscopy. Moreover, ex-situ ATR-IR spectroscopic studies were also used to study the interactions between glycerol and the different catalytic surfaces. The results obtained indicate a stronger adsorption of glycerol through the primary hydroxy group/s when tungsten oxides are grafted onto the γ-Al2O3 support. The competitive adsorption between the reactant and the main reaction products for the same active sites, and the effect of the hydrogen availability were also studied. The evidences found in this work point out a triple role of tungsten oxide in the reaction, acting as: (i) a strong anchoring site for the primary hydroxy group/s of glycerol, (ii) a supplier of protons, and (iii) a stabilizer of the secondary carbocation. Under the best conditions, a remarkable high yield of 1,3-propanediol of 38.5% was obtained after only 4 h of reaction time

Selective oxidation of n-butanol using gold-palladium supported nanoparticles under base-free conditions

The base-free selective catalytic oxidation of n-butanol by O2 in an aqueous phase has been studied using Au-Pd bimetallic nanoparticles supported on titania. Au-Pd/TiO2 catalysts were prepared by different methods: wet impregnation, physical mixing, deposition–precipitation and sol immobilisation. The sol immobilisation technique, which used polyvinyl alcohol (PVA) as the stabilizing agent, gave the catalyst with the smallest average particle size and the highest stable activity and selectivity towards butyric acid. Increasing the amount of PVA resulted in a decrease in the size of the nanoparticles. However, it also reduced activity by limiting the accessibility of reactants to the active sites. Heating the catalyst to reflux with water at 90 °C for 1 h was the best method to enhance the surface exposure of the nanoparticles without affecting their size, as determined by TEM, X-ray photoelectron spectroscopy and CO chemisorption analysis. This catalyst was not only active and selective towards butyric acid but was also stable under the operating conditions