[Show abstract][Hide abstract] ABSTRACT: A bioadhesive composition for bonding together adjacent surfaces of wood comprises a microbially-produced fermentation residue containing adherent microbial cells and glycocalyx. This residue finds particular application as a replacement for a significant amount of phenol-formaldehyde (PF) or other conventional adhesive component commonly used in the production of plywood and other wood products.
[Show abstract][Hide abstract] ABSTRACT: Residues from the fermentation of cellulose by the anaerobic bacteria Ruminococcus albus (strain 7) or Ruminococcus flavefaciens (strains FD-1 or B34b) containing residual cellulose, bacterial cells and their associated adhesins, were examined for their ability to serve as components of adhesives for plywood fabrication. The residues contained differing amounts of protein (0.4-4.2% of dry weight), but the ratios of monosaccharides recovered following two-stage treatment of the residue with detergent (pH 7) and TFA were similar for all three strains (0.71 glucose:0.18 xylose:0.08 mannose:0.02 galactose), suggesting similarities in exopolysaccharide composition. Three-ply aspen panels prepared with fermentation residues (FR) displayed better shear strength and wood failure under dry conditions than following a vacuum/pressure/soak/dry treatment, but adhesive properties were inferior to those prepared with conventional phenol-formaldehyde (PF) adhesives. However, panels prepared by incorporating the R. albus 7 FR into PF formulation, at 73% by weight of the total adhesive, exhibited shear strength and wood failure similar to that obtained with PF adhesive alone. Use of residues from fermentations by these bacteria as components of adhesives may add value to biomass fermentations aimed primarily at producing ethanol and other chemical products.
Applied Microbiology and Biotechnology 12/2003; 63(1):29-34. · 3.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The effect of precipitation on the molecular weight distributions of cellulose tricarbanilate (CTC) samples prepared from α-pulp, hydrolyzed α-pulp, and Avicel was determined using size exclusion chromatography (SEC). Precipitation of the CTC samples in methanol resulted in the loss of a low molecular weight fraction accounting for 26% of the weight of the hydrolyzed α-pulp, 20% of the Avicel, and 5% of the α-pulp. Precipitation in a methanol/water mixture resulted in less fractionation; in this case, however, the reaction byproducts were also precipitated. These results indicate that the molecular weight distribution of precipitated CTC may not accurately reflect the molecular weight distribution of the original cellulose. SEC analysis of the nonvolatile products from the carbanilation reaction offers a simple method for determining the complete molecular weight distribution of this cellulose derivative.
[Show abstract][Hide abstract] ABSTRACT: The rates (k) of hydroxymethylation of phenol, resorcinol, phloroglucinol, and several methylphenols in diluted 10% dimethylformamide aqueous
alkaline solution were calculated based on the consumption of phenols and formaldehyde. Thek values of phloroglucinol and resorcinol relative to that of phenol were about 62000 and 1200 times, respectively. The phenols
that have methyl or hydroxyl groups at the C-3 or C-5 position (or both) have larger rate constants than phenols with substituents
at other positions. Several kinds of atomic charge of the carbons on the aromatic ring of phenols were calculated using the
semiempirical orab initio method. The correlations between the averagek (Ave.k) and average electrostatic charges (Ave.q) at the carbons were fairly good. Highest occupied molecular orbitals (HOMO) were observed. The best correlation between
Ave.k and Ave.q was obtained when diphenols and triphenols were assumed to exist in solution as their respective di-anion.
Journal of Wood Science 03/2002; 48(2):153-158. · 0.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Phenolic resins are important adhesives used by the forest products industry. The phenolic compounds in these resins are derived primarily from petrochemical sources. Alternate sources of phenolic compounds in- clude tannins, lignins, biomass pyrolysis products, and coal gasification products. Because of variations in their chemical structures, the reactivities of these phenolic compounds with formaldehyde vary in quite subtle ways. A method is needed for predicting the reactivity of phenolic compounds with formaldehyde in order to al- low researchers to efficiently choose those compounds that might make the best candidates for new adhesive systems prior to conducting extensive laboratory trials. Computational chemistry has been used to study the relationship between the reactivity of a number of phe- nolic compounds with formaldehyde in an aqueous, al- kaline system, and charges calculated for reactive sites on the aromatic ring of the phenolic compound. Atomic-charges for each phenolic compound were cal- culated by ab initio methods at the RHF/6-31 +G level of theory using the ChelpG method. Reaction rate con- stants were determined from measurements of the con- centrations of the phenolic compounds and formalde- hyde as functions of time. The reaction rate constants varied over a wide range (approx. 10 -2 to 10 4 L mol -1 hr. -1 ). An estimate of the reactivity per reactive site on the phenolic ring was determined by dividing the rate constant by the number of reactive sites. The charge per reactive site was estimated by summing the charges at all the reactive sites on the phenolic ring and dividing by the number of reactive sites. A strong correlation was observed between the reactivity per reactive site and the average charge per reactive site.
[Show abstract][Hide abstract] ABSTRACT: The effects of temperature, acid concentration, and reactant concentration on the rate of formation of difurfuryldiamines from the reactions of furfurylamine with formaldehyde and acetaldehyde were experimentally investigated. On the basis of the data from these experiments, a semimechanistic reaction model network was proposed and a mathematical model which describes the observed kinetic behavior was derived. Rate constants for the model reactions were found to depend exponentially both on the reciprocal of the absolute temperature and on the acid concentration. The mathematical model predicts concentration versus time profiles for reactants, intermediate, and product for the reaction of furfurylamine and acetaldehyde under the following conditions: 20 °C < temperature < 50 °C, 3 M < nominal acid concentration < 6 M, 1.17 M < [furfurylamine] < 1.2 M, and 0.303 M < [acetaldehyde] < 1.17 M. For the reaction of furfurylamine with formaldehyde the model is applicable for 30 °C < temperature < 50 °C, 3 M < nominal acid concentration < 6 M, [furfurylamine] = 1.17 M, and [formaldehyde] = 0.58 M.
[Show abstract][Hide abstract] ABSTRACT: A protocol which employs a methyl silicone gum capillary column for gas chromatographic analysis of the products of the acid- catalyzed reaction of furfurylamine with aldehydes is presented, and its efficacy is demonstrated.
Journal of Chromatography A 08/1993; 644(2):383–387. · 4.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Thirteen prehydrolyzed samples of cellulose, including native, mercerized, and regenerated materials were hydrolyzed in 1% and 1.5% sulfuric acid at 160, 170, and 180°C. Pseudo first-order rate constants and weight average degrees of polymerization were determined for each sample. For all cellulose samples, data from several experiments were used to determine the dependence of the rate of hydrolysis on sulfuric acid concentration. The results obtained in this study indicate that Sharples' end-attack model is consistent with kinetic data for the hydrolysis of cellulose II samples, but is not applicable to the hydrolysis of cellulose I samples. X-ray diffraction analyses indicated that, for native and mercerized cellulose samples, structural changes during dilute acid hydrolysis are not significant. However, data for rayon indicated that such changes may need to be taken into account in analysis of the reaction kinetics.
[Show abstract][Hide abstract] ABSTRACT: Nine prehydrolyzed cellulose samples, including native, mercerized, and regenerated celluloses were hydrolyzed in 2% sulfuric acid at 150, 160, and 170°C. The first-order rate constants and the weight average degrees of polymerization (by size exclusion chromatography) were determined for each sample. The results indicate that Sharples' end-attack model [Trans. Faraday Soc., 53, 1003 (1957)] is consistent with kinetic data for cellulose II samples, but is not appropriate for characterizing the reactions of cellulose I samples.
[Show abstract][Hide abstract] ABSTRACT: The end-attack model proposed by Sharples [Trans. Faraday Soc., 53, 1003 (1957)] for the dilute acid hydrolysis of crystalline cellulose was tested using the results from the size-exclusion chromatographic analysis of samples of crystalline cellulose I and cellulose II hydrolyzed in 6.1N HCl at 107°C. The differential number distribution of the molecular weight of hydrolyzed cellulose was found to be approximately exponential, a result which is consistent with the end-attack model. Differences in the rates of hydrolysis of cellulosic materials appear to arise from differences in both the degree of polymerization and the microstructure of hydrolyzed cellulose. Evidence is also presented which suggests that the recrystallization upon hydrolysis results in part from the lateral accretion of chains which are cleaved during the hydrolysis of amorphous regions in the cellulose microfibrils.
[Show abstract][Hide abstract] ABSTRACT: For adhesive self-sufficiency, the wood industry needs new adhesive systems in which all or part of the petroleum-derived phenolic component is replaced by a renewable material without sacrificing high durability or ease of bonding. We tested the bonding of wood veneers, using phenolic resins in which part of the phenol-formaldehyde was replaced with carbohydrates. Our experiments show that the addition of non-reducing carbohydrates and various polyols to phenol-formaldehyde resol-resins does not adversely affect the dry- or wet-shear strength of 2-ply Douglas-fir panels bonded with the modified resins. Reducing carbohydrates, however, cannot be used as the modifier. In general, addition of about 0.6–1.0 mole of modifier per mole of phenol is optimal in the formulation of carbohydrate-or polyol-modified resin. Preliminary results show that part but not all of the modifier is chemically bound into the resin, apparently through an ether linkage. The water prehydrolysate of southern red oak wood, when reduced with sodium borohydride to convert the reducing sugars to alditols, can be used to modify phenol-formaldehyde resins. This use of wood prehydrolysates can be economically beneficial to processes producing alcohol and chemicals from wood as well as to the wood industry and consumers of bonded wood products.
Journal of Wood Chemistry and Technology 01/1986; 6(4):591-613. · 1.18 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Despite continuing interest in various processes for producing ethanol or other chemicals from agricultural and wood residues, little attention has been given to improving the kinetic modeling of dilute acid saccharification of cellulosics, a key step in many of these processes. A new model for cellulose saccharification is proposed. It incorporates the effect of the neutralizing capacity of the substrate, the presence of readily hydrolyzable cellulose, and the reversion reactions of glucose. Although general in nature, the model was developed specifically for application to the dilute sulfuric acid saccharification of prehydrolyzed wood lignocellulose. A computer program to simulate the new model under various reaction conditions was prepared. This program reasonably predicts yields of fermentable (monomeric) sugar, reducing sugar, reversion material, remaining cellulose, as well as glucose lost by dehydration, all as a function of acid concentration, temperature, and reaction time.
Journal of Wood Chemistry and Technology 01/1985; 5(4):461-489. · 1.18 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Various solvent systems capable of dissolving cellulose have been reported in the literature. Cuene (cupriethylene diamine hydroxide) and FeTNa (ferric sodium tartrate) are well known examples. Preliminary experiments were conducted with Cuene and FeTNa to determine if the cellulose dissolving ability of these systems could be used to bond yellow birch veneers. The results indicate that relatively high dry shear strengths, and low wet shear strengths are obtained.
Journal of Wood Chemistry and Technology 01/1984; 4(4):533-540. · 1.18 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Most processes for utilizing wood as a source of chemicals and liquid fuels include a prehydrolysis step to remove the hemicellulose prior to the main hydrolysis of the cellulose to glucose. Two promising prehydrolysis methods, the Iotech steam explosion process and the Stake process, are based on water prehydrolysis (autohydrolysis). The kinetics of water and of dilute (5%) acetic acid prehydrolysis of southern red oak wood over the temperature range of 170 to 240 C were investigated. Kinetic parameters were determined that permitted modeling not only of xylan removal from the wood but also of the occurrence of xylan oligosaccharides, free xylose, furfural, and further degradation products in the prehydrolyzate. At lower temperatures (approximately 170 to 200 C), xylan removal could be modeled as the sum of two parallel reactions (one for an easily hydrolyzed portion and one for a more resistant portion of xylan) using the equation derived in Part I. At the highest temperature studied (236.9 C), the removal of xylan from the wood was best modeled as a single reaction with a small fraction of the xylan being essentially nonreactive. The occurrence of xylan oligosaccharides, xylose, furfural, and further degradation products in the prehydrolyzate was modeled as consecutive, irreversible pseudo first-order reactions. A timelag associated with the depolymerization of the xylan oligosaccharides to xylose was accounted for in the model by allowing the apparent rate constant for the formation of xylose to increase exponentially with time to a maximum value.