Gasification of black liquor could drastically increase the flexibility and improve the profit potential of a mature industry. The continuous efforts made in the area of black liquor gasification (BLG) are bringing this technology closer to commercial realization and potential wide-spread implementation. Research exploring the integration of BLG into the kraft process and the potential of BLG enabled modified pulping technologies on modern pulping operations is important to support this effort. The following effort is focused on such research, utilizing laboratory pulping experiments and process simulation. The separation of sodium and sulfur achieved through gasification of recovered black liquor can be utilized in processes like modified continuous cooking, split sulfidity and green liquor pretreatment pulping, and polysulfide-anthraquinone pulping to improve pulp yield and properties. Laboratory pulping protocols have been developed for these modified pulping technologies and different process options evaluated. The process simulation work around BLG has led to the development of a WinGEMS module for the low temperature MTCI steam reforming process, and case studies comparing a simulated conventional kraft process to different process options built around the implementation of a BLG unit operation into the kraft recovery cycle. The implementation of gasification, functioning as the core of wood pulping recovery operations in a biorefinery, would enable the application of modified pulping technologies while creating a synthetic product gas that could be utilized in the production of value added products in addition to wood pulp. The evaluated modified pulping technologies have indicated the potential of yield increases of 1-3% points with improved product quality, and the potential for capital and operating cost savings relative to the conventional kraft process. Process simulation work has shown that the net variable operating cost for a pulping process using BLGCC is highly dependent on the cost of lime kiln fuel and the selling price of green power to the grid. Under the initial assumptions taken in the performed case study, the BLGCC process combined with split sulfidity or PSAQ pulping operations had net variable operating cost 2-4% greater than the kraft reference. When comparing the BLG cases to the MCC reference, the net variable operating cost break even point based on lime kiln fuel cost is about $47/barrel for the split sulfidity and lower charge polysulfide processes, and about $38/barrel for the higher polysulfide charge process. This is significantly lower than assumed kiln fuel price of $60/barrel used in this work. If the sales price for power to the grid could be increased through green power credits from 3.5 to 6 ¢/KWh cost savings of about $40/ODtP could be realized in the investigated BLG processes. Other alternatives to improve the process economics around BLG would be to modify or eliminate the lime kiln unit operations, utilizing high sulfidity green liquor pretreatment, PSAQ with auto-causticization, or converting the process to mini-sulfide sulfite-AQ.

The objective of this research is to understand the interfacial behavior of cellulase enzymes and its effect on cellulose hydrolysis. This research began with an in-situ monitoring of cellulose hydrolysis using a piezoelectric based quartz crystal microbalance. The time-course kinetics was modeled using a dose response model. The adsorption indicated by the frequency drop followed a Langmuir model as cellulase enzyme increased. Another important part of this research is the development of a new cellulase activity assay based on the piezoelectric technique. This assay provides an easier and more user friendly method for cellulase enzyme activity measurement. It also helps to clarify an element of the interpretation of frequency drops after the injection of cellulase solutions in the hydrolysis of cellulose film, which has been neglected in previous research. Interfacial adsorption of cellulase protein was also investigated using the depletion method. The effects of substrate properties, primarily the crystallinity, which was characterized using X-ray diffraction, were investigated. The effect of surface area, which was measured using both laser light scattering and BET adsorption, on cellulase adsorption were also investigated. It was found that crystallinity played a more important role in cellulase adsorption than surface areas of cellulosic substrate. In characterization of cellulosic substrates, the water retention value (WRV) was also investigated. The results indicated that lower crystallintiy substrates have higher water retention ability. The cellulase adsorption, as well as desorption, was also studied by using sodium dodecyle sulphate polyacrylamide gel electrophoresis (SDS-PAGE). The adsorption results followed the same trend as indicated by the depletion methods. The various isozymes demonstrated a uniform adsorption in proportion to their concentrations. Desorption appeared uniform. Higher pH was found to create higher desorption for a particular cellulase from a particular substrates. It was also found that cellulase from Trichoderma reesei had higher affinity to cellulosic substrates used in this work than the one from Aspergillus niger.

The objective of this research is to understand the drying behavior of cellulose fibers characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). A parameter termed ?hard-to-remove (HR) water content? was defined as the ratio of water mass to fiber mass at the transition between the constant and falling rate drying zones of an isothermal TGA experiment. The HR water content showed a linear relationship with water retention value. TGA and DSC were used to explain the linear relationship. During drying, free water was observed to evaporate first, followed by trapped water, freezing bound water and then non-freezing bound water, with some overlap. Trapped water can be described as water bound to the fibers, but difficult to evaporate. For pilot papermachine samples, all the water in the wet web entering the dryer section was HR water, with no free water detected. Based on the results, a qualitative drying model of cellulose fibers was proposed with regard to decreasing moisture ratio. Changes in the pore size distribution during drying were determined using DSC measurements and the Gibbs-Thomson equation. Larger pores collapsed first followed by the sequential collapse of smaller pores, indicating that pore wall collapse resistance is critical. The average pore size for bleached softwood was calculated to be about 80 nm and decreased with drying. A constant pore size of about 20 nm was observed at moisture ratios below 0.3 g/g, which corresponds to one-to-two layers of non-freezing bound water. The heat of vaporization of water associated with cellulose fibers was determined using modulated DSC and showed a steep increase at moisture ratios below 0.3 g/g, indicating that a higher energy is required to evaporate non-freezing bound water.

Lignin, the glue that keeps fibers together, is a complex three dimensional network polymer which has shown association phenomena in solution. Following the molecular weight of the biopolymer in solution as a function of time allow us to explore their observable de-association phenomena. These measurements were carried out using multiple angle light scattering (MALS) photometry in the static mode. EMAL (Enzymatic Mild Acidolysis Lignin) from hardwood and softwood were isolated and an additional method for the complete dissolution of such biopolymers in THF was further developed. Once the challenge of the measurement procedures were worked out, some rather accurate dn/dC values for lignin solutions were obtained as a function of time. This effort when coupled to additional work using static light scattering measurements (Zimm plots) for the same solutions offered an insight into the self-assembly processes operating within the lignin biopolymer.

Polyampholytes are polymers that have both positively and negatively charged groups in the same chain. In recent years polyampholytes have started to be used in papermaking applications, as well as in sludge treatment processes. Benefits, in the case of papermaking, have included increased dry-strength and faster removal of water. But the molecular mechanisms by which such benefits are achieved have not been fully understood. This thesis project focused on effects related to polyampholyte charge density. A series of polyampholytes with a fixed charge ratio but different charge density was used for the experiments. Analysis methods included pH titrations, streaming current titrations, and adsorption isotherms. From pH titrations the charge density of cationic and anionic groups under different pH were calculated. From streaming current tests the net apparent charge density under different pH was calculated. And from adsorption tests it was found that the highest adsorbed amounts were achieved in certain cases corresponding to the highest content of ionic groups on the polyampholytes. Adsorption depended strongly on pH. Substantial differences were observed when comparing results obtained with polyampholyte samples versus ordinary polyelectrolyte samples with same charge density of cationic or anionic groups.

This study aims at elucidating a variety of salient features that dictate the kinetics and chain length effects governing the formation and antimicrobial activity of sugar esters of fatty acids. To do this, anomerically pure glucose, sucrose and cellobiose sugars were transesterified with the methyl esters of fatty acids of variable chain lengths C4, C8, C12, C18, and C20. The methyl esters of butyric, caprylic, lauric, stearic and arachidic acids were reacted with the above carbohydrates to give the respective penta and octaesters. The kinetics of these transesterification reactions were followed by quantitative 31P NMR after phosphitylation of the labile OH groups with 1,3,2- dioxaphospholanyl chloride. This approach proved to be a facile and quantitative means to follow the specific substitutions occurring at the various OH positions within the sugars as a function of degree of conversion, and incoming chain length. As anticipated, a variety of steric and hydrophobic effects were shown to play a key role in determining the reactivity of these systems. The various sugar esters were then adsorbed onto cellulose disks and their microbial activity was examined. Finally, cellulose esters of butyric acid were synthesized using the acyl chloride process.

The research investigated the interactions between paperboard and the gypsum core during the manufacturing process of gypsum wallboard. The goal of this research was to understand the paper properties that can affect the quality of the adhesive bond under simulated test conditions. The categories of paper properties tested include strength properties, surface properties, and paper additives. This research showed that the current test methods in use did not provide enough sensitive and reproducibility data to gain crucial insight into the paper/core adhesive interaction. A new evaluation method must be secured. However, with the results obtained, it was believed that the three types of failure could be described. First, the adhesive bond may fail resulting in a clean peel during bond quality testing. Second, the paper bond network may fail resulting in complete paper coverage of the gypsum core. Third, a mixed failure of adhesive and paper bond resulted in incomplete and varied paper coverage of the gypsum core.

The research described here provides the technology and theory to quantify surface quality for a variety of wood and wood-based products. This technology provides a means of monitoring trends in surface quality which can be used to discriminate between Agood@ products and Abad@ products (the methods described in this research are not intended to provide ?grading? of individual workpieces) as well as provide information to the machine operator as to the source of poor quality machined surfaces. The analysis can be done either on-line at industrial speeds or off-line as a periodic quality control tool. Although the surface quality can be quantifiably measured, the determination of the best feature from the surface profile (root mean square, peak amplitude, average wavelength, frequency content, Joint Time and Frequency Analysis (JTFA) and Wavelet Analysis results, etc.) for the quantification of surface Adefects@ is highly dependent on the application. This research consisted of three broad areas: (1) determination of an optimal hardware configuration for both laboratory and industrial surface scans of wood products, (2) determination of the optimal set of surface descriptors as well as the development of advanced signal processing techniques such as the wavelet transform to accurately describe the quality of a surface as well as provide information to the machine operator on the cause of the loss of surface quality, and (3) development of a software interface to distill the advanced signal processing techniques into a readily obtainable and readable format for the machine operator as well as provide assistance for process decisions.

In an effort to comprehensively study the wood property variation in juvenile wood, compression wood, and mature wood, and also to provide a rapid and cost-effective assessment tool to screening the wood chemical property variation, several loblolly pines (Pinus tadea), and transmittance near infrared spectroscopy were utilized in this study. The method development results show that a successful screening of wood chemical property variation, such as lignin and á-cellulose contents, could be adapted using stacked wood wafers microtomed from increment cores and combining with transmittance near infrared spectroscopy. The morphological, chemical, and metabolic analyses of juvenile wood and compression wood show that although compression wood and juvenile wood share some properties, they are actually distinct in their chemistry during development and in final wood chemistry and anatomy. The within tree variation analyses also show that juvenile wood from the top of the tree and that from the base of the tree are more different in morphological structures than in chemical structures. A similar pattern was found between juvenile wood and mature wood. The results obtained suggest that the within tree compression wood percentage and the fiber quality differences inherent in juvenile wood appear to have a greater influence on the final wood products.

Structure-property relationships of cellulose-based materials including paper, micro- and nano-fiber composites are often strongly influenced by environmental variables. The interaction of polymeric and crystalline structure in cellulose bio-based materials is of high technological importance. Therefore, understanding the underlying mechanism of environmental/material interactions is crucial for engineering products from bio-based materials. This study was undertaken in an effort to develop a technique for the assessment of dimensional stability of cellulose microfibrils as a function of different relative humidity. Analysis of atomic force microscopy images showed that the local dimensional properties of cellulose microfibrils are highly responsive to variable relative humidity, and their hygro-expansive behavior depends on the relative humidity history, and their method of preparation. The results obtained suggested that dimensional and hygro-expansive behaviors of cellulose microfibrils are related to their ultra-structural arrangements and their origin, either directly or indirectly. These findings, hopefully, will prompt an open discussion regarding the dynamic interactions between cellulose and water molecules at a nano-scale.