Characterization of Mixtures of Linear and Branched Hydrocarbons Confined within Porous Media Using 2D DQF-COSY NMR Spectroscopy.

The analysis of 1D anti-diagonal spectra from the projections of 2D double-quantum filtered correlation spectroscopy NMR spectra is presented for the determination of the compositions of liquid mixtures of linear and branched alkanes confined within porous media. These projected spectra do not include the effects of line broadening and therefore retain high-resolution information even in the presence of inhomogeneous magnetic fields as are commonly found in porous media. A partial least-square regression analysis is used to characterize the mixture compositions.

Experimental Determination of H and CO Diffusion Coefficients in a Wax Mixture Confined in a Porous Titania Catalyst Support.

The ability to measure and predict molecular diffusion coefficients in multicomponent mixtures is not only of fundamental scientific interest but also of significant relevance in understanding how catalytic processes proceed. In the present work, the direct measurement of the molecular diffusion of H and CO gas-phase species diffusing in -alkane mixtures using pulsed-field gradient (PFG) nuclear magnetic resonance (NMR) methods is reported. The work is of direct relevance to Fischer-Tropsch (FT) catalysis, with the measurements being made of the gas-wax system with the wax in both the bulk liquid state and when confined within a titania catalyst support, at temperatures and pressures typical of low-temperature FT synthesis.

Determination of Carbon Number Distributions of Mixtures of Linear Hydrocarbons Confined within Porous Media Using Pulsed Field Gradient NMR.

Pulsed field gradient (PFG) NMR measurements, combined with a novel optimization method, are used to determine the composition of hydrocarbon mixtures of linear alkanes (C7-C16) in both the bulk liquid state and when imbibed within a porous medium of mean pore diameter 28.6 nm. The method predicts the average carbon number of a given mixture to an accuracy of ±1 carbon number and the mole fraction of a mixture component to within an average root-mean-square error of ±0.

Cross-conjugation and quantum interference: a general correlation?

We discuss the relationship between the π-conjugation pattern, molecular length, and charge transport properties of molecular wires, both from an experimental and a theoretical viewpoint. Specifically, we focus on the role of quantum interference in the conductance properties of cross-conjugated molecules. For this, we compare experiments on two series of dithiolated wires.

Effect of molecular weight, crystallinity, and hydrophobicity on the acoustic activation of polymer-shelled ultrasound contrast agents.

Polymer-shelled microbubbles are applied as ultrasound contrast agents. To investigate the effect of the polymer on microbubble preparation and acoustic properties, polylactides with systematic variations in molecular weight, crystallinity, and end-group hydrophobicity were used. Polymer-shelled cyclodecane filled capsules were prepared by emulsification, and the cyclodecane was removed by lyophilization to obtain hollow capsules.