Fred Shafizadeh

Pyrolysis of cellulose

Pyrolysis of cellulose under vacuum and atmospheric pressure gave a tar containing various amounts of 1,6-anhydro-β-D-glucopyranose, 1,6-anhydro-β-D-glucofuranose, α- and β-D-glucose, 3-deoxy-D-erythro-hexosulose, oligo- and polysaccharides, and some dehydration products. The polysaccharide fraction had no reducing end-group, was randomly linked, contained some furanoid rings, and was very similar to the polysaccharide condensation-product of 1,6-anhydro-β-D-glucose. These results are consistent with a series of inter- and intra-molecular transglycosylation and dehydration and rehydration reactions.

Some reactions of levoglucosenone

Abstract The role of the major variables in the pyrolytic production of levoglucosenone from acid-treated cellulose and paper has been established. Reduction, oxidation, acid- and base-catalyzed addition, acetolysis, and rearrangement reactions of this product have been investigated. These reactions proceed with considerable stereo-selectivity to give a variety of novel compounds. Nucleophilic addition to the double bond provides a facile method for the synthesis of 4-thio and other 4-substituted sugar derivatives.

Chemical composition and thermal analysis of cottonwood

Abstract Analysis of extracted cottonwood shows the presence of lignin and 76.1% of cell-wall polysaccharides. The polysaccharides consist of cellulose (44.1%), 4- O -methylglucuronoxylan (20.8%), and glucomannan (9.7%). Differential thermal analysis and thermogravimetric analysis data show the relationship between the pyrolytic properties of the selected wood and its components.

Sesquiterpene lactones and systematics of the genus Artemisia

Abstract The sesquiterpene lactones isolated from species in the genus Artemisia have been reviewed in an attempt to better understand the phylogeny and systematics of the four sections (subgenera), Abrotanum, Absinthium, Dracunculus and Seriphidium, proposed by Besser in 1829. The absence of hair on the receptacle is the only morphological characteristic separating species of Abrotanum from the species of Absinthium. There are no chemical characteristics segregating the species in these two subgenera since both produce eudesmanolides and guaianolides that are identical or biosynthetically similar. This suggests that the two subgenera could be combined into one (Artemisia) as proposed by Poljakov. The subgenus Seriphidium is composed of two geographical groups, one in the Old World and the other in the New World. The Old World species almost exclusively produce sesquiterpene lactones in the eudesmanolide class whereas the New World species (section Tridentatae) produce eudesmanolides and guaianolides, many of the latter being identical or structurally related to the sesquiterpene lactones in New World Abrotanum species. The chemical data in conjunction with geographic distributions suggest that the subgenus Seriphidium is polyphyletic and that the section Tridentatae originated from Abrotanum. Consequently, the Tridentate should be recognized as a subgenus separate and distinct from the Old World Seriphidium. There was insufficient information from the subgenus Dracunculus for interpretation.

Pyrolytic Reactions and Products of Biomass

The biomass or commonly available lignocellulosic materials could be converted to different types of fuel and chemical feedstock by a variety of thermochemical processes. Each of these processes involves two highly significant and inter-related general aspects: first, material and energy transformations that could be explored and understood through the discipline of chemistry; second, material transport and heat transfer that could be investigated and designed through the disciplines of process engineering. Variations of the reaction conditions and the processing design, which are closely related, are often investigated in a sporadic or empirical manner in order to define the optimum conditions that provide high yields of operational efficiency.

The influence of exchangeable cations on the carbonization of biomass

Abstract Cations of calcium and potassium added to wood through ion exchange have unique effects on the thermal decomposition of the wood. Addition of calcium ions increases the decomposition temperature of the wood and affects the char yield only slightly, while addition of potassium ions reduces the decomposition temperature and significantly increases the char yield. These effects are distinct from the effects of salts of the same elements added to the same or similar materials through absorption of a solution of the salt. For instance, potassium carbonate absorbed on cellulose significantly increases its decomposition temperature, although it has the opposite effect when added to wood through ion exchange. The primary sites for ion exchange are believed to be glucuronic acids in the hemicellulose fraction, and it is therefore likely that the effects of exchanged cations are due primarily to their influence on the decomposition of this component. When naturally occuring inorganic species are removed from wood by acid washing, the char yield is reduced and the cellular structure of the wood can be lost during carbonization, particularly at high heating rates.

Thermal degradation of xylan and related model compounds

Pyrolysis of O-acetyl-4-O-methylglucuronoxylan, 4-O-methylglucuronoxylan, and β-D-xylopyranosides involves thermal cleavage of the glycosidic groups. The resulting glycosyl units partly form random condensation products and are partly degraded to a variety of volatile products and char. Composition of the pyrolysis products changes with the introduction of additive or substituent groups. Addition of sodium hydroxide produces increased amounts of products of low molecular weight arising from carbonyl fragmentation and disproportionation, and zinc chloride promotes the formation of 2-furaldehyde, water, and char.

1,5-Anhydro-4-deoxy-d-glycero-hex-1-en-3-ulose and other pyrolysis products of cellulose

Abstract Uncatalyzed pyrolysis of cellulose provides a tar containing mainly 1,6-anhydro- d -glucose derivatives and some unsaturated products. The latter include a new enone that has been isolated by preparative column chromatography in 1.4% yield and identified as 1,5-anhydro-4-deoxy- d - glycero -hex-l-en-3-ulose. This compound is also formed by pyrolysis of other carbohydrate polymers. A mechanism for its production from internal units has been deduced from the experimental data. The pyrolysis products of cellulose also contain 3,5-dihydroxy-2-methyl-4 H -pyran-4-one, which appears to be an oxidation product.

Kinetics of gasification of Douglas Fir and Cottonwood chars by carbon dioxide

Abstract Arrhenius kinetic parameters have been determined for the CO 2 gasification of chars (heat treatment at 1000 °C) prepared from well-characterized samples of a hardwood, a softwood and a Montana lignite. The effects of pre-pyrolysis addition of inorganic salts of the alkali, alkaline earth and transition metal groups to the wood samples have also been determined. The reactivities of the chars of the cottonwood and lignite samples exceeded that of Douglas fir char by a factor of four to seven between 700 and 900 °C. The reactivity of the wood char was related to the inorganic content of the sample. There was very little difference in the reactivity of chars prepared from the hardwood and the softwood after treatment with similar quantities of inorganic salts. The inorganic content of the lignite char was more than five times greater than that of cottonwood char, but its reactivity was similar. The carbonates of sodium and potassium were equally effective gasification catalysts. The transition metal salts were the most effective catalysts initially, but they lost their activity well before the gasification was complete. The data indicate that treatment of wood with aqueous salts results in replacement of some of the natural minerals by ion exchange, and that these exchangeable ions play a major role in controlling reactivity of the chars.

Preparation of 1,6-anhydro-3,4-dideoxy-β-D-glycero-hex-3-enopyranos-2-ulose (levoglucosenone) and some derivatives thereof

Abstract 1,6-Anhydro-3,4-dideoxy-β- D - glycero -hex-3-enopyranos-2-ulose (levoglucosenone) was prepared on a laboratory scale by pyrolysis of H 3 PO 4 -treated, Kraft waste-paper. The aldehyde components of the pyrolyzate were removed by reaction with 5,5-dimethyl-1,3-cyclohexanedione (dimedone), and levoglucosenone was obtained in 3.3% yield by distillation of the remaining material. A variety of deoxy, keto, and branched-chain sugars was obtained by reduction of levoglucosenone, and by its reaction with Grignard reagents under different conditions.