Gary D. McGinnis

Rapid steam hydrolysis/extraction of mixed hardwoods as a biomass pretreatment.

Abstract Rapid steam hydrolysis of wood chips with continuous condensate/product removal was investigated as a biomass pretreatment similar to steam explosion. Steam was introduced at the top of a pressurized reactor containing mixed southern hardwood chips while steam condensate and partible products were removed at the bottom of the reactor. A reaction time of one minute was employed for isothermal steaming runs from 160-280°C. Fractionation of wood occurred at temperatures above 200°C as hemicellulose and lignin began to appear in the steam condensate fraction, leaving a cellulose-rich fraction in the steaming reactor. At high temperatures cellulose was not degraded as much as it was in steam explosion at the same temperature, presumably due to the removal of acetic acid as it is formed. Lignin extracted from the solid residue appeared particularly reactive as determined by nitrobenzene oxidation and pyrolysis/gas chromatography. Lignin collected in the steam condensate was also very reactive, presumab...

The Pyrolytic Behavior of Selected Lignin Preparations

Abstract A pyrolytic study of a variety of lignins prepared from hardwood and softwood species, and of selected commercial lignins, was performed using isothermal and dynamic thermogravimetric analysis and pyrolysis-gas chromatography. The lignins were evaluated according to weight loss, rate of weight loss, and products formed during the pyrolysis in an inert atmosphere. These data were then compared to nitrobenzene oxidation data. Infrared spectroscopy was used to determine structural changes of lignin during initial weight loss in the temperature range of 250° to 320°C. Structural changes appear to occur without any appreciable weight loss. Lignins thermal behavior during pyrolysis depends upon the degree of condensation present in the initial lignin. Thermogravimetric analysis is shown to be a simple and accurate method to determine the extent of lignin condensation. The yield of monomeric phenols is also dependent on the degree of lignin condensation.

Wet oxidation of model carbohydrate compounds

Abstract The major product formed by wet oxidation of a series of model compounds: d -xylose, d -glucose, d -glucitol, cellulose, and dextran, was formic acid. Its yield varied according to the structure of the carbohydrate, oxygen pressure, temperature, and the presence or absence of ferric sulfate. Acetic acid was also formed; its yield was much less dependent on the structure of the carbohydrate. Other products formed include methanol, acetaldehyde, acetone, and a series of hydroxylated acids.

Estimation of Cellulose Crystallinity Using Fourier Transform-Infrared Spectroscopy and Dynamic Thermogravimetry

Abstract Dynamic thermogravimetry (tga), differential thermogravimetry (dtg), and Fourier Transform-Infrared Spectroscopy (FT-IR) were performed on a variety of celluloses with different cyr3tallinities. The data were compared to the crystallinlty indices (C.I.) determined by X-ray diffraction. Highly significant correlations (99.9%) included: a positive linear correlation of the maximum dtg value; a logarithmic relation of the temperature at which the initial 10% weight loss occurred; and a linear relationship of three FT-IR absorbance ratios (1108/1091 cm−1), (1430/1403 cm−1), and (1459/1403 cm−1). A significant logarithmic correlation was also found for the temperature at maximum dtg for cotton linter samples. These relationships are discussed.

The use of reverse phase columns for separation of unsubstituted carbohydrates

Abstract Reverse-phase chromatography can be used to separate unsubstituted oligosaccharides using water as the eluent. The retention time of the individual oligosaccharides was found to be dependent on the molecular weight of the oligosaccharide and the type and the anomeric configuration of the linkage. This technique can be used for characterizing polysaccharides based on identification of the oligosaccharide fractions obtained by partial acid hydrolysis or for the isolation and purification of oligosaccharides.

The separation of substituted carbohydrates by high-performance liquid chromatography

Separation of a wide variety of partially and completely substituted carbohydrates was achieved by using two types of gel permeation columns. The relative retention time was dependent on two factors: the relative polarity of the carbohydrate and its molecular weight.

High-pressure liquid chromatography of carbohydrates

Abstract A procedure is described for the separation of water-soluble wood polysaccharides on Bio-Glas (granular porous glass) and Bio-Gel P (polyacrylamide) packed columns using high-pressure liquid chromatography (HPLC). An example of HPLC employing non-aqueous solvent systems and EM Gel OR-PVA (vinyl acetate copolymer) type packing materials is also discussed.

Comparison of the Reaction Rates of the Alkali-Catalyzed Addition of Formaldehyde to Phenol and Selected Lignins

Abstract A comparison of the reaction rates of the alkali-catalyzed addition of formaldehyde to phenol, Kraft lignin, and steam-exploded lignin was studied by monitoring the disappearance of formaldehyde at four temperatures to determine the Arrhenius parameters. 1H-NMR spectra of acetylated lignins and their hydroxymethylated derivatives and the disappearance of formaldehyde during lignin-formaldehyde reactions were used to quantify the degree of formaldehyde substitution. The rate of the addition of formaldehyde to phenol was faster than the addition of formaldehyde to lignin, although the lignin-formaldehyde reactions were essentially complete under the reaction conditions examined. Both lignin-formaldehyde reactions had lower activation energies than the phenol-formaldehyde reaction. Kraft lignin has a faster rate of reaction with formaldehyde than steam-exploded lignin and the rate of formaldehyde addition to lignin is dependent on the reactive site availability on the lignin molecules.

High-performance liquid chromatography of sugar oximes

Preparation des O-(p-nitrobenzyl), O-benzyl et O-methyl oximes et separation par chromatographie liquide. Detection UV au-dessus de 200 nm

Thermal decomposition of methyl α-d-glycopyranosides

Abstract Thermal analysis, coupled with chemical studies, indicates that methyl α- d -glycopyranosides undergo thermal decomposition in two overlapping stages. At lower temperatures, the major reaction is loss of the methoxyl group as methanol, and intra- or inter-molecular condensation of the glycosyl portion of the molecule. At higher temperatures, the predominant reaction is fragmentation of the transglycosylation products. Both reactions were found to be dependent on the configuration of the starting methyl α- d -glycopyranoside.