New insight was gained into the acidity-reactivity relationships of sulfated zirconia (SZ) catalysts prepared via (NH 4 ) 2 SO 4 impregnation of Zr(OH) 4 for propanoic acid esterification with methanol. A family of systematically related SZs was characterized by bulk and surface analyses including XRD, XPS, TGA-MS, N 2 porosimetry, temperature-programmed propylamine decomposition, and FTIR of adsorbed pyridine, as well as methylbutynol (MBOH) as a reactive probe molecule. Increasing surface sulfation induces a transition from amphoteric character for the parent zirconia and low S loadings <1.7 wt %, evidenced by MBOH conversion to 3-hydroxy-3-methyl-2-butanone, methylbutyne and acetone, with higher S loadings resulting in strong Brønsted-Lewis acid pairs upon completion of the sulfate monolayer, which favored MBOH conversion to prenal. Catalytic activity for propanoic acid esterification directly correlated with acid strength determined from propylamine decomposition, coincident with the formation of Brønsted-Lewis acid pairs identified by MBOH reactive titration. Monodispersed bisulfate species are likely responsible for superacidity at intermediate sulfur loadings.

A series with gold supported on monoclinic (m-), tetragonal (t-) ZrO2, and Mg-modified zirconia were prepared and used for the catalytic oxidation of biomass-derived 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid (FDCA). The Au stabilized on Mg-modified zirconia calcined at 600 °C (denoted as Au/MZ-600) exhibited a superior catalytic performance with 95% of FDCA yield after 4 h by adapting a two-temperature step reaction. The structure–activity relationship was investigated by using X-ray diffraction, temperature-programmed reduction by H2, X-ray absorption spectroscopy, temperature-programmed desorption of CO2, and N2 adsorption–desorption methods. The results clearly demonstrate that the addition of Mg ions in/on the zirconia support at appropriate calcination temperature plays an important role in optimizing the interaction between gold nanoparticles and the support by fine-tuning the surface base properties of the zirconia supports and creation of oxygen vacancies. Accordingly, tuning these gold–support interactions is essential to achieve high dispersion of small-sized gold nanoparticles with enhanced metallic character, which plays a significant role in enhancing the catalytic activity of the final catalyst.

Isosorbide is a widely touted intermediate for the production of biorenewable polymers and plastics, accessible through the aqueous phase cascade conversion of D-sorbitol to isosorbide via 1,4-sorbitan. However, existing routes to isosorbide typically employ mineral acids under forcing conditions, and hence alternative heterogeneously catalyzed processes are highly desirable. Aqueous phase D-sorbitol conversion was therefore investigated over families of sulfated zirconia (SZ) solid acid catalysts, with the effect of employing monoclinic, tetragonal ZrO2, or Zr­(OH)4 as the parent support compared. The cascade proceeds via a stepwise dehydration to 1,4-sorbitan and subsequently isosorbide, with the latter favored over stronger acid sites. Monoclinic SZ exhibits superior activity to tetragonal SZ, reflecting a higher acid site density and pyrosulfate formation at lower SO4 2– loadings than over the other supports. Isosorbide selectivity at iso-conversion was proportional to acid site density, but independent of zirconia phase.

MgO-ZrO 2 mixed oxides prepared with different Mg/Zr atomic ratios (denoted as xMZ:w here x is the atomic ratio of Mg/Zr)are investigated for the glucose isomerization to fructose in water at 95 8C. The highest fructose yield of 33 %i so btained over 0.76MZ with % 74 %s electivity after 3h.T og ain insighti nto the structure-activity relationships, the prepared catalysts are characterizedb yN 2 physisorption, XRD, FTIR and CO 2 -TPD. The results indicate that the addition of MgO drastically changed the textual property of ZrO 2 and increased the number of basic sites. The kinetic studies revealed that the Lewis basic sites (cus-O 2À )g enerated from the highly dispersed MgO are the active sites responsible for the enhanced isomerization activity.N otably, MZ is reusable for four runs without as ignificant decrease in catalysta ctivity.A ccordingly,t his study provides an easily prepared, cheap,a nd recyclable catalystt hat may hold great potential for fructose production.[a] Dr.A .I.M.R abee, S.

No abstract

No abstract

No abstract

Mixed metal oxides are promising heterogeneous catalysts for biofuel production from lipids via alcoholysis, however, the impact of solid acidity and/or basicity on reactivity is comparatively poorly understood. Two systematically related families of MgO-ZrO 2 mixed oxide catalysts were therefore prepared by different synthetic routes to elucidate the impact of surface acid-base properties on catalytic performance in the transesterification of tributyrin with methanol. The resulting materials were characterized by TGA-MS, ICP-OES, N 2 porosimetry, XRD, TEM, XPS, DRIFTS, and CO 2 -temperature-programmed desorption (TPD). MgO-ZrO 2 catalysts prepared by both non-aqueous impregnation and citric acid-mediated sol-gel routes exhibit excellent activity and stability. The citrate routes favor highly dispersed MgO and concomitant Lewis acid-base pair formation at the interface with zirconia. However, for both the citrate and impregnation routes, tributyrin transesterification occurs over a common, strongly basic MgO active site.