The hydrogenation of levulinic acid to γ-valerolactone over Cu–ZrO2 catalysts prepared by a pH-gradient methodology

A novel pH gradient methodology was used to synthesise a series of Cu–ZrO2 catalysts containing different quantities of Cu and Zr.All of the catalysts were highly selective to the desired product,γ-valerolactone, and are considerably more stable than Cu–ZrO2 catalysts prepared by other co-precipitation methods for this reaction.Characterisation and further investigation of these catalysts by XRD, BET, SEM and XPS provided insight into the nature of the catalytic active site and the physicochemical properties that lead to catalyst stability.We consider the active site to be the interface between Cu/CuOxand ZrOx and that lattice Cu species assist with the dispersion of surface Cu through the promotion of a strong metal support interaction.This enhanced understanding of the active site and roles of lattice and surface Cu will assist with future catalyst design.As such, we conclude that the activity of Cu–ZrO2 catalysts in this reaction is dictated by the quantity of Cu–Zr interface sites.

Zero-oxidation state precursor assisted fabrication of highly dispersed and stable Pt catalyst for chemoselective hydrogenation ofα,β-unsaturated aldehydes

The chemoselective hydrogenation ofα,β-unsaturated aldehydes is a key strategy for the synthesis of fine chemicals.Herein,we developed an efficient method of depositing Pt particles on FeO_(x)/SBA-15.This strategy is dependent on using a platinumdivinyltetramethyldisiloxane complex(Pt^(0)-DVTMS)as the precursor,which we demonstrate can be removed through a H_(2)-treatment under mild conditions.This,in turn,allowed for the synthesis of catalysts with well dispersed Pt particles.The presence of FeO_(x) species also aided Pt dispersion;when coated onto SBA-15,FeO_(x) strongly interacted with dissociated Pt species,inhibiting both Pt aggregation and metal leaching.Using cinnamaldehyde as a modelα,β-unsaturated aldehyde,it was demonstrated that this catalyst was highly selective towards the unsaturated alcohol and no obvious loss in activity was observed over five recycles.This catalyst was determined to be significantly more effective than an analogous catalyst prepared using chloroplatinic acid as a precursor,evidencing the importance of using the Pt0-DVTMS precursor.We corroborate the excellent catalytic performance to highly dispersed Pt-species,whereby Pt0 and Pt^(2+) play a critical role in activating H_(2) and the C=O bond.This research demonstrates that the Pt precursor can have a significant impact on the physicochemical properties and thus,the performance of the final catalyst.It also evidences how metal support interactions can dramatically influence selectivity in such hydrogenation reactions.This novel catalyst preparation protocol,using a DVTMS ligand for Pt impregnation,offers a facile approach to the design of multi-component heterogeneous catalysts.

Multiporous Carbon Encapsulated Ni Nanoparticles Promoting Glycerol Valorisation towards Hydrogenation against Rearrangement

A dual-templating method was used to synthesize a series of hierarchical carbon supports containing different proportions of spherical macropores(ca.200 nm in diameter)and mesoporous channels(ca.4 nm in diameter).These and some other conventional carbon materials were subsequently impregnated with Ni and tested for the conversion of glycerol.The hierarchical catalysts exhibited a significantly higher conversion(96%)and selectivity(77%)to 1,2-propanediol,and the specificity selectivity coefficient(6.1)towards 1,2-propanediol against lactic acid was three times higher than that observed over a conventional Ni/Cmnicro catalyst(2.1).The enhanced performance of these materials,compared with the Ni nanoparticles supported on conventional carbon supports,was attributed to their high surface areas(>1110 m^2·g^-1)and large pore volumes(ca.0.4 cm^3·g^-1)permitting greater accessibility of substrate and/or intermediates to Ni active sites.Given that the concentration of accessible Ni sites in these materials is higher,a competitive benzilic-acid-rearrangement reaction to produce lactic acid was suppressed,leading to an enhanced hydrogenation selectivity to 1,2-propanediol.This study evidences the potential benefits,which can be established from utilizing hierarchical support materials in the valorization of biomass.

Adjacent Pt Nanoparticles and Sub-nanometer WO_(x)Clusters Determine Catalytic Isomerization of C_(7)H_(16)

Processes for the isomerization of light alkanes have been commercialized;however,the isomerization of paraffins(C_(n)H_(2n+2),n≥7)remains a challenge.On mesoporous tungsten-zirconia catalyst supported Pt catalysts(Pt/WZrOx),initial isomerization productivity of 5249 moli-C7/molPt/h was obtained for n-heptane reforming at 275°C and 5 bar of hydrogen.