Cheng H.N.,U.S. Department of Agriculture |
Wartelle L.H.,U.S. Department of Agriculture |
Klasson K.T.,U.S. Department of Agriculture |
Edwards J.C.,Process NMR Associates LLC
Carbon | Year: 2010
A large number of solid-state NMR and ESR experiments were explored as potential tools to study chemical structure, mobility, and pore volume of activated carbon. We used a model system where pecan shells were activated with phosphoric acid, and carbonized at 450 °C for 4 h with varying amounts of air flow. Through the use of different NMR experiments (e.g., CP-MAS, SPE-MAS, and DD-MAS) several structural parameters were calculated such as mole fraction of bridgehead aromatic carbons, number of carbons per aromatic ring system, and number of phenolic carbons per aromatic ring system. The relaxation time measurements (T1, TCH, and T1ρ H) were indicative of the relative mobility of different structural units. ESR spectra showed the presence of π-type aromatic free radicals in the carbonized samples with a slight shift in g value with increasing oxidation. The combined NMR and ESR data give a consistent picture of the carbon structure and the carbonization process, which is not easily available otherwise. In addition, the 1H NMR data on adsorbed water are shown to be consistent with the trends in the amount of pore volumes for different samples of activated carbons. © 2010 Elsevier Ltd. All rights reserved.
White J.,Active Spectrum, Inc. |
White J.,Process NMR Associates LLC |
Giammatteo P.,Active Spectrum, Inc. |
Giammatteo P.,Process NMR Associates LLC
ACS National Meeting Book of Abstracts | Year: 2010
Asphaltenes can pose serious problems for crude oil producers and pipelines, by increasing viscosity of the crude and potentially fouling pipelines and equipment. Here we present a new advance in relatively low-cost on-line electron spin resonance sensor technology which enables continuous, on-line measurement of asphaltene and vanadium concentration in crude oil. Detection limits of 0.1% asphaltene and 5 ppm vanadium are demonstrated in a broad range of crude oils.