Dachuan Shi

Kinetics and Mechanism of Ketonization of Acetic Acid on Ru/TiO2 Catalyst

Ru/TiO2 shows great promise as a catalyst in ketonization of carboxylic acids, an effective reaction for upgrading pyrolysis vapors that contain significant amounts of acetic acid. In this study, we have investigated the kinetics of acetic acid ketonization over Ru/TiO2 catalysts from different pre-treatments. The observed reaction order (>1.5) with respect to acetic acid lends support to a bimolecular pathway of adsorbed carboxylates that produces a β-ketoacid intermediate. The negative reaction orders with respect to CO2, water, and acetone reflect the inhibition by competitive adsorption on the active sites. The observed rate enhancement by reduction in H2 and inhibition by the presence of O2 indicate that the active sites for this reaction include coordinatively unsaturated cation sites.

Single-Walled Carbon Nanotubes Do Not Pierce Aqueous Phospholipid Bilayers at Low Salt Concentration

Because of their unique physical, chemical, and electrical properties, carbon nanotubes are an attractive material for many potential applications. Their interactions with biological entities are, however, not yet completely understood. To fill this knowledge gap, we present experimental results for aqueous systems containing single-walled carbon nanotubes and phospholipid membranes, prepared in the form of liposomes. Our results suggest that dispersed single-walled carbon nanotubes, instead of piercing the liposome membranes, adsorb on them at low ionic strength. Transmission electron microscopy and dye-leakage experiments show that the liposomes remain for the most part intact in the presence of the nanotubes. Further, the liposomes are found to stabilize carbon nanotube dispersions when the surfactant sodium dodecylbenezenesulfonate is present at low concentrations. Quantifying the interactions between carbon nanotubes and phospholipid membranes could not only shed light on potential nanotubes cytotoxicity but also open up new research venues for their use in controlled drug delivery and/or gene and cancer therapy.

Fine-Tuning the Acid–Base Properties of Boron-Doped Magnesium Oxide Catalyst for the Selective Aldol Condensation

Controlled incorporation of dopants into the structure of metal oxide catalysts can be used to fine‐tune their topological, chemical, and electronic properties. Conventional preparation methods (coprecipitation and impregnation) tend to produce materials with a limited extent of chemical interaction between metal oxide and dopant, small pore volume, and disconnected pore structure. Herein, we describe a combustion method to optimize both the porous structure of metal oxides and the chemical interaction with dopants. By exploiting the differences in melting points between metal oxide (MgO) and dopant (B), it is possible to create hierarchical mixed oxides with tailored chemical structure. As a model reaction, we employed the aldol condensation of acetaldehyde to crotyl alcohol, a key intermediate step in the conversion of bioethanol to 1,3‐butadiene, to show the unique characteristics of these materials. The B–Mg mixed oxide prepared by combustion exhibits an order of magnitude higher productivity of C4 products than conventional MgO and B–MgO. We anticipate that our approach could be extended to the development of other dual oxides with open structure for unrestricted diffusion and enhanced chemical interaction of acid and basic metal oxides.