Cellulose Acetate Production Research Articles

Thermal behavior of cellulose acetate produced from homogeneous acetylation of bacterial cellulose

Cellulose acetate (CA) is one of the most important cellulose derivatives and its main applications are its use in membranes, films, fibers, plastics and filters. CAs are produced from cellulose sources such as: cotton, sugar cane bagasse, wood and others. One promissory source of cellulose is bacterial cellulose (BC). In this work, CA was produced from the homogeneous acetylation reaction of bacterial cellulose. Degree of substitution (DS) values can be controlled by the acetylation time. The characterization of CA samples showed the formation of a heterogeneous structure for CA samples submitted to a short acetylation time. A more homogeneous structure was produced for samples prepared with a long acetylation time. This fact changes the thermal behavior of the CA samples. Thermal characterization revealed that samples submitted to longer acetylation times display higher crystallinity and thermal stability than samples submitted to a short acetylation time. The observation of these characteristics is important for the production of cellulose acetate from this alternative source.

Process for obtaining cellulose acetate from agricultural by-products

Agricultural residues such as corn fiber, rice hulls and wheat straw can be used as abundant low-cost feedstock for production of fuel ethanol. However, the cost of cellulase enzymes to saccharify cellulose to glucose is a major hindrance. As an alternative, a novel process to obtain industrially important cellulose acetate from these by-products after removing hemicellulosic sugars was developed. Rice-straw, wheat hull and corn fiber were treated with dilute acid at a moderate temperature to hydrolyze the hemicellulose to monomeric sugars that can be fermented to ethanol. The cellulose was then treated with acetic anhydride and catalytic amount of sulfuric acid to make cellulose acetate. The production of cellulose acetate was confirmed by NMR analysis. The pretreatment used to hydrolyze the hemicellulose was also useful for cellulose acetate production. Without the pretreatment cellulose acetate conversions from wheat straw, corn fiber, and rice hulls were 0.5, 1.8 and 13.5, respectively. After pretreatment the conversion rate increased to about 25 wt% for all three agricultural residues used.

2.2 Cotton fibers as natural raw materials for cellulose acetate production

AbstractThe commercially available cotton species are only three botanical species. For these species, the cotton fibers were described to consist of two different types of fibers termed “lint” and “linter”. The structure and chemical constituents of these cotton fibers were compared, so as to use them judiciously as natural raw materials for cellulose acetate production.

2. The raw materials of CA 2.1 Wood as natural raw materials for cellulose acetate production

AbstractThe molecular arrangement of wood cell wall is described in relation to the physical and mechanical properties of wood. The chemical composition of wood is also summarized to illustrate the heterogeneity in distribution of cell wall constituents to use wood plup fibers judiciously as natural raw materials for cellulose acetate production.

2.3 Wood pulp manufacturing and quality characteristics

AbstractCellulose acetate being important in the fiber and textile industries is usually prepared from high quality cellulose such as cotton linters and wood pulps with an alpha cellulose content of more than 95%. In this section, therefore, wood pulps and cotton linters appropriate for cellulose acetate production were discussed in their chemical and physical properties so as to use them judiciously as natural raw materials for cellulose acetate production.

Electrochemical approaches to environmental problems in the process industry

Electrochemical processes can provide valuable contributions to the protection of the environment through implementation of effluent treatment and production-integrated processes for the minimisation of waste and toxic compounds. As examples of effluent treatment, electrochemical reactors for removal of metal ions from waste water, anodic destruction of organic pollutants and new electrochemical abatement techniques for the purification of flue gases will be described. Further examples consider salt splitting by membrane techniques. As examples for production-integrated industrial processes fluidised bed electrolysis for metal recovery in the cellulose acetate production, the membrane process for industrial chlor-alkali electrolysis, and the electroreduction of dichloracetic acid are considered.

Effects of solvent addition to acetylation medium on cellulose triacetate prepared from low-grade hardwood dissolving pulp

As cellulose triacetate was prepared from low-grade hardwood-dissolving pulp, a considerable amount of the insoluble residue was present in the acetylation medium of the acetic acid/acetic anhydride/sulfuric acid system, and it consisted mainly of cellulose triacetate (CTA) and xylan diacetate (XDA). As one of the remedies for reducing the insoluble residue, a solvent was added to the acetylation medium and the effects of the solvent addition on the amount of insoluble residue formed were studied. To do so, 17 different solvents were selected so as to cover a wide range of solubility parameters. The obtained results clearly indicated that the addition of the solvent affects the amount of insoluble residue and that, excluding dichloroacetic acid, nitromethane was effective for its reduction, but that neither methylene chloride nor nitroethane were in spite of their effectiveness for softwood-dissolving pulp, which would be due to the intrinsic properties of XDA on the solubility in the acetylation medium. A new acetylation system with such an appropriate solvent would, therefore, provide a clue as to an industrial usage of the low-grade hardwood-dissolving pulps for cellulose acetate production. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1445–1449, 1998

Effects of solvent addition to acetylation medium on cellulose triacetate prepared from low‐grade hardwood dissolving pulp

As cellulose triacetate was prepared from low-grade hardwood-dissolving pulp, a considerable amount of the insoluble residue was present in the acetylation medium of the acetic acid/acetic anhydride/sulfuric acid system, and it consisted mainly of cellulose triacetate (CTA) and xylan diacetate (XDA). As one of the remedies for reducing the insoluble residue, a solvent was added to the acetylation medium and the effects of the solvent addition on the amount of insoluble residue formed were studied. To do so, 17 different solvents were selected so as to cover a wide range of solubility parameters. The obtained results clearly indicated that the addition of the solvent affects the amount of insoluble residue and that, excluding dichloroacetic acid, nitromethane was effective for its reduction, but that neither methylene chloride nor nitroethane were in spite of their effectiveness for softwood-dissolving pulp, which would be due to the intrinsic properties of XDA on the solubility in the acetylation medium. A new acetylation system with such an appropriate solvent would, therefore, provide a clue as to an industrial usage of the low-grade hardwood-dissolving pulps for cellulose acetate production. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1445–1449, 1998

The Eastern and Western branches of the Wood/Ljungdahl pathway: how the East and West were won

Figure 1 is a transmission electron micrograph of Clostridium ljungdahlii [1]. It, like Acetobacterium woodii [2], was named after someone who made great contributions to the understanding of how anaerobes fix carbon dioxide. C. ljungdahlii was named after Lars Ljungdahl; A. woodii after Harland Wood. I had the good fortune to train under both Lars and Harland and have continued research in this area for approximately fifteen years, learning and gaining greater and greater appreciation for the art of anaerobes. This review introduces the concept of the Eastern and Western branches of the Wood/Ljungdahl pathway. The Eastern branch is important in one-carbon metabolism of all organisms; the Western branch is unique to anaerobic microorganisms that use the Wood/Ljungdahl pathway for fixing carbon dioxide or carbon monoxide to generate cell carbon or for synthesizing acetate (acetogens) or methane (aceticlastic methanogens) to generate energy. In focusing on the biochemistry and enzymology of this pathway, I, unfortunately, must risk leaving the important ecology and physiology of these organisms in the lurch. They are responsible for the turnover of a trillion tons of acetic acid per year. They convert a variety of compounds including sugars, aromatic compounds, and inorganic compounds like CO and H2 and CO2 into acetic acid which is then used by methane producing bacteria to make natural gas. They are important in soil microbiology and, in the biology of organisms that house them in their digestive system, like humans, termites and ruminants like cows and sheep [3–5]. The story of acetogens can be traced back to the ancient times when someone discovered that apple or grape juice could be fermented, first to alcohol and then to acetic acid, producing cider vinegar, which contains 3–6% acetic acid. The word acetum is the Latin word for vinegar. Acetic acid was isolated in pure form by Stahl in 1700. Over the years, it has been found to be an excellent solvent for many organic compounds and some inorganic compounds. It also is essential in the production of cellulose acetate and is used widely in the textile and rubber industries.

Innovation of Cellulose Acetate Production by the Vacuum Acetylation

Innovation of Cellulose Acetate Production by the Vacuum Acetylation

A new approach for the production of cellulose acetate: Acetylation of mechanical pulp with subsequent isolation of cellulose acetate by differential solubility

AbstractA heretofore uninvestigated approach to the production of cellulose acetate, the acetylation of whole wood pulp with subsequent isolation of the cellulose derivative by differential solubility, is described. The mechanical pulp used was produced by refining aspen wood chips with a disc refiner. Two conventional acetylation techniques, the fibrous and solution process, were employed to acetylato all components of the pulp. The cellulose acetate was isolated from the acetylated lignin and hemicellulose by dissolving in dichloromethane/methanol (9:1, v/v). The advantage of this new approach is that the high cost involved in using an extensively purified dissolving pulp are avoided. Both acetylation techniques yielded a product that was about 84% cellulose acetate. The remaining acetylated components were lignin and hemicellulose. The yield of cellulose acetate, based on the cellulose content of the original pulp and the product, was 75–80%.

Highly reactive wood pulps for cellulose acetate production

AbstractWood pulps highly reactive in both high‐ and low‐catalyst cellulose acetate processes can be prepared by mercerization and then treatment with alkylene oxides; only trace levels of substitution are required. The fiber inactivating effects of mercerization after drying are overcome, and several acetate properties are improved by this process. The reactivity characteristics cannot be duplicated by similar modifications of nonmercerized fibers; in low catalyst processes such pulps actually show reduced reactivity.

Optimum choice of materials for fabrication of process equipment for cellulose acetate production

Optimum choice of materials for fabrication of process equipment for cellulose acetate production

Preparation of cellulose from wood pulp by continuous acetylation

Abstract