[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.
[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.
[Show abstract][Hide abstract] ABSTRACT: Computational chemistry methods can be used to explore the theoretical chemistry behind reactive sys- tems, to compare the relative chemical reactivity of dif- ferent systems, and, by extension, to predict the reactiv- ity of new systems. Ongoing research has focused on the reactivity of a wide variety of phenolic compounds with formaldehyde using semi-empirical and ab initio computational chemistry methods. This research has been expanded to study theoretical transition states formed on reacting phenol with formaldehyde. Accord- ing to transition state theory, the energy of a transition state is related to the reaction rate. Transition states for reaction of formaldehyde at the ortho- and para-posi- tions of phenol were determined by computational means. These theoretical calculations predict that formaldehyde reacts faster at the para-position of phe- nol than at the ortho-position, in agreement with ex- perimental data.
[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: The liquid phase hydrogenation reactions of both furfurylamine and 5,5'-ethylidenedifurfurylamine to the corresponding tetrahydrofuran compounds have been investigated over a rhodium on alumina catalyst suspended in a methanol solution. The reactions were studied at temperatures from 42.5 to 80.1 degrees C and hydrogen pressures from 231 to 1380 kPa (33.5 to 200 psi). The effects of the amount of catalyst and the concentrations of both reactants and products on the rates of these reactions were also investigated. Analysis of the data from these investigations using the method of initial rates indicates that the rates of hydrogenation of both furfurylamine and 5,5'-ethylidenedifurfurylamine are consistent with Hougen-Watson-Langmuir-Hinshelwood reaction mechanisms. The overall activation energies for the hydrogenation of furfurylamine and 5,5'-ethylidenedifurfurylamine are 49.4 +/- 2.5 and 63 +/- 4 kJ/mol, respectively.
[Show abstract][Hide abstract] ABSTRACT: Difurfuryl diamino compounds can be obtained via single-step reactions of furfurylamine with formaldehyde and other aldehydes in 2.5-5.2 M hydrochloric acid at 20-50 degrees C. Yields for the single step reaction (30-50%) are comparable to those for three-step procedures involving protection and deprotection of the amino group.
The Journal of Organic Chemistry 03/1995; 60(6). DOI:10.1021/jo00111a017 · 4.64 Impact Factor
[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. DOI:10.1016/0021-9673(93)80723-L · 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: Epoxy resin adhesives are widely used because of their strength, versatility, and ability to bond a variety of substrates. Furfurylamines represent a potential, new class of epoxy curing agents. Furfuryl amine (FA), tetrahydrofurfuryl amine (THFA), and 5,5′-methylenebis-2-furanmethanamine (DFA) were studied as possible epoxy curing agents. The utility of FA and THFA are limited by their volatility at the temperatures needed to effect cure of diglycidyl-ether of bisphenol A (DGEBA) based epoxy resins. DFA is a very effective epoxy curing agent with the ability to cure DGEBA at rates similar to that of standard epoxy curing agents such as liethylenetriamine.
Journal of Polymer Science Part A Polymer Chemistry 01/1992; 30(4). DOI:10.1002/pola.1992.080300403 · 3.54 Impact Factor
[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: New adhesive systems are needed in which part or all of the petroleum-derived phenolic component is replaced by a readily available, renewable material without sacrificing durability or bonding ease. In this study, up to about 50% of the phenol-formaldehyde was replaced with carbohydrates and the modified resins used to bond wood veneer panels. The carbohydrate modified resins were formulated and cured under neutral conditions. The resins bond wood with acceptable dry- and wet-shear strengths, and wood failures. Reducing as well as nonreducing carbohydrates can be used as modifiers. The carbohydrate modifiers are being incorporated into the resin via ether linkages between the hydroxyls of the carbohydrate and methylol groups in the phenol-formaldehyde resin. The resins formulated under neutral conditions are very light in color.
[Show abstract][Hide abstract] ABSTRACT: Adhesives derived from natural resources and the possibilites for their industrial utilization, particularly in the forest products industry, have been a focus of considerable attention in recent times. While such adhesives have been used for most of mankind's history, substantial progress has been made in the last 15 years in producing durable adhesives from renewable resources that come close to meeting today's exacting industry standards. A number of important opportunities exist for further refinement of promising adhesive systems and for the development of new ones. Recent advances demonstrate the breadth of available possibilities for using nature's own storehouse for adhesive production and offer an excellent starting point for future research effort needed for its optimum exploitation.
[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: The reversion products formed during the acid hydrolysis of Avicel to d-glucose, under conditions envisaged for the industrial conversion of woody biomass into monomeric sugars, have been determined by using gas-liquid chromatography. Avicel was hydrolyzed in dilute sulfuric acid (0.26–1.27 wt.%) between 160 and 250° in small (3 mm, i.d.) glass tubes at a 3:1 liquid-to-solid ratio. The anhydro sugars, levoglucosan and 1,6-anhydro-β-d-glucofuranose, were produced in the ratio of 7:3 and ocnstituted > 50% of the total yield of reversion products. The yield of anhydro sugar followed equilibrium kinetics, and reached 6% at maximum yields (50%) of d-glucose. Isomaltose and gentiobiose were the most preponderant disaccharides found among the reversion products, constituting together ∼25% of the reversion products. The (1→2)- and (1→3)-linked α-disaccharides preponderated over their β counterparts. The total yields of reversion products approached 10% on the basis of the d-glucose theoretically available.
Carbohydrate Research 02/1989; 185(2-185):249-260. DOI:10.1016/0008-6215(89)80040-0 · 1.92 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A reduction/permethylation technique has been developed for the quantitative gas Chromatographie analysis of anhydrosugars, monosaccharides, and disaccharides. All derivatizations are carried out in the same vial, and transfers are not necessary until recovery of the permethylated derivatives. The reaction scheme is extremely simple and offers improved accuracy over standard GC carbohydrate analysis protocols. Emphasis is placed on quantitative compound recovery, and relative response factors are presented for several carbohydrates. The sodium hydroxide/methyl iodide permethylation reaction has also been shown to be a viable replacement for standard dimsyl anion procedures utilized for methylation analysis of polysaccharides. Application of the reduction/permethylation sequence to the analysis of the hydrolyzate resulting from the dilute sulfuric acid hydrolysis of cellulose demonstrates that reversion products account for a considerable amount of the glucose losses, with levoglucosan, 1, 6-anhydro-β-D-glucofuranose, isomaltose, and gentiobiose predominating.