Lignin production

Advances in technology have increased the importance of lignin products in various industrial appHcations. They are derived from an abundant, renewable resource, and they are nontoxic and versatile in performance. 

Applications of Kraft Lignins. Because of the high fuel value of black Hquor, kraft lignin products are generaUy used in high value... 

Programs containing lignins as the primary polymeric dispersant are generally formulated to provide 30 to 50 ppm of active lignin product in the BW. 

Set-up for Ethylene Glycol Lignin Production. A process development unit (PDU), previously described by Chornet and co-workers (11), was used for the experiments. A typical preparation consists of initially mixing 1-1.2 kg of wood meal with 10 1 of ethylene glycol. The mixture is allowed to stand overnight for imbibition to take place. To enhance solvent to substrate penetration, the slurry is homogenized at 200°C in the pretreatment section of the PDU. It is then pumped through the treatment section which consists of a tubular reactor at 220°C. The product slurry is collected in a receiver. The detailed procedure and choice of conditions above have been published elsewhere (11,12). 

Daishowais the largest, most diversified producer of lignin products in the world, with two plants located in Wisconsin and a third located in Quebec. Research and Development effort is carried out in major laboratories located in Rothschild, Wisconsin, and Quebec City, Quebec. 

The sulfonated lignin products function primarily as dispersants in aqueous systems and help to form stable dispersions of a number of insoluble materials. For example, lignin dispersants find use in pigments, carbon black, gypsum, ceramics, coal slurry and water treatment systems to mention some of the more prominent applications. 

In addition to these defined functions, lignin products are also known for their ability to reduce the size of particles, reduce slurry viscosities, inhibit crystal growth, sequester and complex metals, and function as interactive carriers. 

Although in many of the reports lignin products of either a cyclohexyl or phenyl nucleus with one, two, or no carbon side chains attached have been reported, the greater abundance (under nonalkaline conditions) of the propyl side chain must be regarded as evidence for the essentially C6-C-C-C nature of a unit of the lignin substance. 

In this chapter I will focus on biochemical and molecular aspects leading to lignin production. We have studied in detail phenylalanine ammonia lyase (PAL EC 4.3.1.5), the first enzyme of the general phenylpropanoid pathway, and cinnamyl alcohol dehydrogenase (CAD EC 1.1.1.195), an enzyme specific to the branch pathway leading to lignin formation. 

Figure 1. Major low molecular weight lignin products isolated and identified...

Figure 2. HPLC analysis of low molecular weight lignin products after acid hydrolysis of spruce wood (detector responses at 280 nm, positive curve, and at 350 nm, negative curve). (Two diastereoisomers of compound 13 are present as separate peaks.)...

Most of the research on the macromolecular chemistry of lignin has been concentrated on iignosulfonates and kraft lignin because of the insolubility of lignin in its native state. The polymer properties are of importance for the evaluation of the technical applicability of lignin products. For theoretical considerations, see Sections 3.2.2 and 3.2.3. 

Essentially all of the lignin commercially available is isolated as byproducts from either the sulphite or the kraft process. Table II gives a very conservative idea of annual lignin production in the United States (2) and worldwide 36). 

Figure 9. Partial spectra illustrating vinyl ether formation in lignin a. acety-lated / -guaiacyl vinyl ether III b.140 °C control c. DEPT spectrum of 140 °C control d. guaiacyl model/lignin product prior to chromatographic separation e. DEPT spectrum of 50 °C control.

Figure 10. Spectra of lignin product from 140 °C/1 hour treatment a. conventional broadband (BB) decoupled b. DEPT c. QUAT.

Lignocellulosic research today is poised on the threshold of a new era of research breakthroughs. It has enabled the use of a wide variety of lignocellulosic materials, low-quality wood species and sawdust, and low-value lignin products. Lignocellulosic and cellulosic research efforts are under way to produce novel products for construction, transportation, plastics, fiber, packaging, and medical applications. Some of the major activities in chemical modifications of wood, cellulose, and lignins are the main features of this book. 

In addition to the analyses of lignin products by PGCMS as discussed here, one sample of estuarine sediment, comparable to sample S-15, was analyzed for lignin oxidation products by the CuO oxidation method (22). The distribution of various types of phenolic compounds In the sediment Is compared to that of Spartlna... 

In 1974 a major Norwegian manufacturer of lignin products started regular production of UF-lignosulfonates. The plant has been expanded several times and today the production is some thousand tons per year of product. 

An extensive development program in Finland, conducted by Dr. Kaj Forss, has shown that UF is a simple, efficient and inexpensive method for tailoring a lignin product for this purpose. 

K Lundquist, B losefsson, and G Nyquist. Analysis of Lignin Products by Fluorescence Spectroscopy. Holrforschung 32 27-32, 1978. 

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