Organosolv

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In industrial paper-making processes, organosolv is a pulping technique that uses an organic solvent to solubilise lignin and hemicellulose. It has been considered in the context of both pulp and paper manufacture and biorefining for subsequent conversion of cellulose to fuel ethanol. The process was invented by Theodor Kleinert in 1968 [1] as an environmentally benign alternative to kraft pulping.

Contents

Organosolv has several advantages when compared to other popular methods such as kraft or sulfite pulping. In particular, the ability to obtain relatively high quality lignin adds value to a process stream otherwise considered as waste. Organosolv solvents are easily recovered by distillation, leading to less water pollution and elimination of the odour usually associated with kraft pulping.

Solvents

Organosolv pulping involves contacting a lignocellulosic feedstock such as chipped wood with an aqueous organic solvent at temperatures ranging from 140 to 220 °C. This causes lignin to break down by hydrolytic cleavage of alpha aryl-ether links into fragments that are soluble in the solvent system. Solvents used include acetone, methanol, ethanol, butanol, ethylene glycol, formic acid, and acetic acid. The concentration of solvent in water ranges from 40 to 80%. Higher boiling solvents have the advantage of a lower process pressure. This is weighed against the more difficult solvent recovery by distillation. [2] Ethanol has been suggested as the preferred solvent due to cost and easy recovery. Although butanol is shown to remove more lignin than other solvents and solvent recovery is simplified due to immiscibility in water, its high cost limits its use.

For pulp production

Numerous authors report that pulping with ethanol-water solutions gives a lignin free pulp yield 4–4.5% higher than that of kraft pulp. [3] [4] [5] [6] [7] The commonly used solvents acetone and ethanol have been examined with respect to pulp properties. The pulping of wheat straw with 40% mixtures of acetone or ethanol with water requires 60 minutes at 180 °C to give good pulp properties. [4] Organic solvents are almost always used as a mixture with water for process considerations such as reducing the vapour pressure and lowering the pH in order to also solubilise hemicellulose.

Only some small organosolv pulp mills are run today for production of pulp from annual renewable non wood fibre sources like straw, bagasse, etc. [8]

For fuel ethanol production

Recently, due to the popularity of second generation biofuels, the organosolv process has been considered in the context of bioethanol production. Cellulose from the organosolv process is susceptible to enzymatic hydrolysis into glucose followed by fermentation to dilute ethanol. The organosolv fractionation of mountain-beetle-killed lodgepole pine has yielded 97% conversion to glucose. Pan et al. [9] recovered 79% of the lignin using conditions of 170 °C, 1.1% w/w H2SO4, 65% v/v ethanol for 60 minutes. Furthermore, ethanol organosolv pretreated rice straw was used to produce biohydrogen using Enterobacter aerogenes . The effect of temperature (120–180 °C), residence time (30–90 min), and ethanol concentration (45–75% v/v) on the hydrogen yield, residual biomass, and lignin recovery was investigated using RSM. The glucose concentration at the optimum conditions was 4.22-fold of untreated straw. [10]

Lignin recovery

The recovery of lignin from ethylene glycol organosolv pulping can be effected by 3 times dilution with acidified water. The lignin precipitates and forms spherical aggregates ranging from 0.5 to 2.5 μm. Filtration, while time-consuming, is then most effective while the mixture is hot (>100 °C). [11] Recovery can be achieved by filtration or centrifugation. Due to the hydrophobic nature of organosolv lignin, flotation of organosolv lignin is effective without the use of the collecting and precipitating agents [12] that are required for flotation of kraft lignin.

Processes

Organocell

Organocell uses two-stage organosolv with roughly 50% methanol solutions. Sodium hydroxide is added in the second stage at a loading of 30% w/w of the dry wood. The lignin from the second stage is isolated by adding phosphoric acid until a pH of 4.0 is reached. [13]

Alcell

The Alcohol Pulping and Recovery (APR) process treats wood in 3 stages, each using increasingly cleaner solvent. The important process parameters are extraction time, temperature, solvent composition and pH. Pilot plant operation has shown that ethanol pulping produces pulp superior to sulphite pulp at a lower cost. Lignin and hemicellulose are recovered in high yields. In 1987 the APR process was renamed the Alcell process. The process uses aqueous ethanol solutions (40–60% v/v) to delignifying wood at temperatures from 180 to 210 °C and 2–3.5 MPa. Solvent is recovered with flash evaporation, vapour condensation and vacuum stripping. [14]

A demonstration organosolv pulp mill operated in Miramichi, New Brunswick, Canada from 1989 to 1996 using the Alcell process. Repap owned the IP to the process when taken over by hedge funds in 1997. The pilot plant boasted superior environmental performance, excellent bleached pulp, an economically attractive scale of 300 tons/day and commercially attractive by-products. It is said that the technology can be used to exploit small regions of hardwood resource that could not support a modern sized kraft mill. [7]

CIMV process

Compagnie Industrielle de la Materière Végétale in France have developed a process where wheat straw is treated with acetic acid / formic acid / water (30/55/15 v/v/v) for 3.5 h at 105 °C under atmospheric pressure. The obtained fibres are screened and bleached. At this conditions the lignin is dissolved and hemicelluloses are hydrolysed to oligo and monosaccharides. Organic acids are collected by concentration of the cooking liquor and then lignin is precipitated by adding water and high pressure filtration. [8]

Chempolis process

Chempolis Ltd in Oulu, Finland has developed, since 1995, a process concept where any lignocellulosic fibrous biomass sources are delignified with formic acid (biosolvent) in a compact process. The so-called "formico" technology incorporates full biosolvent recovery by evaporation and distillation in order to have a closed-loop process with minimal water need and effluent discharge. The delignification selectively fractionates lignocellulose components into cellulosic fibre, hemicellulose and lignin. Part of the hemicelluloses react to furfural and acetic acid, which are recovered in the distillation process to high-grade commercial products. The clean cellulosic fibre is used in various high-end packaging and textile purposes (bleached easily with hydrogen peroxide), or hydrolysed into high-purity glucose readily converted into biochemicals, or the glucose is easily fermented to bioethanol. The dissolved hemicelluloses and lignin after delignification are concentrated in evaporation and separated to produce hemicellulose fraction suitable for fermentation into ethanol or conversion to biochemicals. The separated lignin is sulfur-free and used in high-end applications replacing fossil aromatics. [8]

American Science and Technology (AST) process

American Science and Technology (AST) based out of Chicago, Illinois, USA, has developed a process which uses a patented second generation Organosolv process to convert any kind of biomass to more than 10 industrial fine chemicals, organic intermediates and solvents. With a 2 ton/day production facility located in Wausau, Wisconsin, AST can also make high quality pulp, glucose, fructose and lignin. With the AST process, lignocellulosic biomass is treated with sulfuric acid, water, butanol and other organic solvents, water, an organic or inorganic acid, and catalyst for one to three hours at 150 to 200 °C. The results produce fibers that are screened and bleached for paper products. At these conditions, the lignin is dissolved in organic solvent and hemicelluloses are used to produce more organic solvent. Organic solvents are collected by separating water from the cooking liquor and then the lignin is precipitated by adding water, heat, and filtration.

Aldehyde assisted fractionation (AAF) process

The Bloom process was developed at EPFL in Lausanne [15] and is commercialised by Bloom Biorenewables Sàrl. [16] This method is based on a protection chemistry that prevents lignin and C5 sugars condensation. [17]

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Cellulose is an organic compound with the formula (C
6H
10O
5)
n, a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell wall of green plants, many forms of algae and the oomycetes. Some species of bacteria secrete it to form biofilms. Cellulose is the most abundant organic polymer on Earth. The cellulose content of cotton fiber is 90%, that of wood is 40–50%, and that of dried hemp is approximately 57%.

<span class="mw-page-title-main">Lignin</span> Structural phenolic polymer in plant cell walls

Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity and do not rot easily. Chemically, lignins are polymers made by cross-linking phenolic precursors.

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Pulp is a fibrous lignocellulosic material prepared by chemically, semi-chemically or mechanically producing cellulosic fibers from wood, fiber crops, waste paper, or rags. Mixed with water and other chemicals or plant-based additives, pulp is the major raw material used in papermaking and the industrial production of other paper products.

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14H
8O
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<span class="mw-page-title-main">Kraft process</span> Process of converting wood into wood pulp

The kraft process (also known as kraft pulping or sulfate process) is a process for conversion of wood into wood pulp, which consists of almost pure cellulose fibres, the main component of paper. The kraft process involves treatment of wood chips with a hot mixture of water, sodium hydroxide (NaOH), and sodium sulfide (Na2S), known as white liquor, that breaks the bonds that link lignin, hemicellulose, and cellulose. The technology entails several steps, both mechanical and chemical. It is the dominant method for producing paper. In some situations, the process has been controversial because kraft plants can release odorous products and in some situations produce substantial liquid wastes.

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<span class="mw-page-title-main">Pulp mill</span> Facility which pulps wood or plant fibre

A pulp mill is a manufacturing facility that converts wood chips or other plant fiber sources into a thick fiber board which can be shipped to a paper mill for further processing. Pulp can be manufactured using mechanical, semi-chemical, or fully chemical methods. The finished product may be either bleached or non-bleached, depending on the customer requirements.

<span class="mw-page-title-main">Black liquor</span> Industrial by-product

In industrial chemistry, black liquor is the by-product from the kraft process when digesting pulpwood into paper pulp removing lignin, hemicelluloses and other extractives from the wood to free the cellulose fibers.

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Lignocellulose refers to plant dry matter (biomass), so called lignocellulosic biomass. It is the most abundantly available raw material on the Earth for the production of biofuels. It is composed of two kinds of carbohydrate polymers, cellulose and hemicellulose, and an aromatic-rich polymer called lignin. Any biomass rich in cellulose, hemicelluloses, and lignin are commonly referred to as lignocellulosic biomass. Each component has a distinct chemical behavior. Being a composite of three very different components makes the processing of lignocellulose challenging. The evolved resistance to degradation or even separation is referred to as recalcitrance. Overcoming this recalcitrance to produce useful, high value products requires a combination of heat, chemicals, enzymes, and microorganisms. These carbohydrate-containing polymers contain different sugar monomers and they are covalently bound to lignin.

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Abengoa, S.A. was a Spanish multinational company in the green infrastructure, energy and water sectors. The company was founded in 1941 by Javier Benjumea Puigcerver and José Manuel Abaurre Fernández-Pasalagua, and was based in Seville, Spain. Its current chairman is Gonzalo Urquijo Fernández de Araoz. After repeated bankruptcies and rescues, it declared insolvency in February 2021 amid various regulatory and financial charges against the board and management, the second-largest corporate collapse in Spanish history.

<span class="mw-page-title-main">Acetone–butanol–ethanol fermentation</span> Chemical process

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Cellulose fibers are fibers made with ethers or esters of cellulose, which can be obtained from the bark, wood or leaves of plants, or from other plant-based material. In addition to cellulose, the fibers may also contain hemicellulose and lignin, with different percentages of these components altering the mechanical properties of the fibers.

White liquor is a strongly alkaline solution mainly of sodium hydroxide and sodium sulfide. It is used in the first stage of the Kraft process in which lignin and hemicellulose are separated from cellulose fiber for the production of pulp. The white liquor breaks the bonds between lignin and cellulose. It is called white liquor due to its white opaque colour.

Inbicon is a Danish company that produces cellulosic ethanol.

Cellulosic sugars are derived from non-food biomass (e.g. wood, agricultural residues, municipal solid waste). The biomass is primarily composed of carbohydrate polymers cellulose, hemicellulose, and an aromatic polymer (lignin). The hemicellulose is a polymer of mainly five-carbon sugars C5H10O5 (xylose). and the cellulose is a polymer of six-carbon sugar C6H12O6 (glucose). Cellulose fibers are considered to be a plant’s structural building blocks and are tightly bound to lignin, but the biomass can be deconstructed using Acid hydrolysis, enzymatic hydrolysis, organosolv dissolution, autohydrolysis or supercritical hydrolysis. A more recent mechanical method offers hope that at last, a more economic and waste free method has been found although it is still to scale and is not yet commercial.

References

  1. ↑ US 3585104,Kleinert, Theodor N.,"Organosolv pulping and recovery process",published 1971-06-15
  2. ↑ Sarkanen, KV, Acid-catalysed delignification of lignocellulosics in organic solvents, in Progress in Biomass Conversion, K V Sarkanen and D A Tillman, Editors. (1980), Academic Press. p. 127-144.
  3. ↑ Botello, J. I.; Gilarranz, M. A.; Rodríguez, F.; Oliet, M. (February 1999). "Preliminary study on products distribution in alcohol pulping of Eucalyptus globulus". Journal of Chemical Technology and Biotechnology. 74 (2): 141–148. doi:10.1002/(SICI)1097-4660(199902)74:2<141::AID-JCTB1>3.0.CO;2-0.
  4. 1 2 Alcaide, LJ, Dominguez, JCG, Ot, IP, Influence of cooking variables in the organosolv pulping of wheat straw using mixtures of ethanol, acetone, and water. TAPPI, (2003). 2(1): p. 27-31.
  5. ↑ Garrote, G, Eugenio, ME, Diaz, MJ, Ariza, J, Lopez, F, Hydrothermal and pulp processing of Eucalyptus. Bioresource Technology, (2003). 88(1): p. 61-68.
  6. ↑ Kleinert, TN, Organosolvent pulping with aqueous alcohol. TAPPI, (1974). 57(8): p. 99-102.
  7. 1 2 Pye, EK, Lora, JH, The Alcell process. A proven alternative to kraft pulping. TAPPI, (1991). 74(3): p. 113-118.
  8. 1 2 3 Popa, Valetin I. (2013). "2.7". Pulp Production and Processing: From Papermaking to High-Tech Products. Shawsbury, Shrewsbury, Shropshire, UK: Smithers Rapra Technology Ltd. pp. 59–60. ISBN   978-1-84735-634-5.
  9. ↑ Pan, Xuejun; Xie, Dan; Yu, Richard W.; Lam, Dexter; Saddler, Jack N. (2007). "Pretreatment of lodgepole pine killed by mountain pine beetle using the ethanol organosolv process: Fractionation and process optimization". Industrial & Engineering Chemistry Research. 46 (8): 2609–2617. doi:10.1021/ie061576l.
  10. ↑ Asadi, Nooshin; Zilouei, Hamid (March 2017). "Optimization of organosolv pretreatment of rice straw for enhanced biohydrogen production using Enterobacter aerogenes". Bioresource Technology. 227: 335–344. doi:10.1016/j.biortech.2016.12.073. PMID   28042989.
  11. ↑ Thring, RW, Chornet, E, Overend, RP, Recovery of a solvolytic lignin - effects of spent liquor acid volume ratio, acid concentration and temperature. Biomass, (1990). 23(4): p. 289-305.
  12. ↑ Macfarlane, AL, Prestidge, R, Farid, MM, Chen, JJJ, Dissolved air flotation: A novel approach to recovery of organosolv lignin. Chemical Engineering Journal, (2009). 148(1): p. 15-19.
  13. ↑ Lindner, A, Wegener, G, Characterization of lignins from organosolv pulping according to the organocell process. 1. Elemental analysis, nonlignin portions and functional-groups. Journal of Wood Chemistry and Technology, (1988). 8(3): p. 323-340.
  14. ↑ US 4100016,Diebold, Vincent B.; Cowan, Wavell F.& Walsh, John K.,"Solvent pulping process",published 1978-07-11, assigned to C.P. Associates Ltd.
  15. ↑ US 10906856,Luterbacher, Jeremy Scott&Shuai, Li,"Production of monomers from lignin during depolymerisation of lignocellulose-containing composition",published 2021-02-02, assigned to Ecole Polytechnique Federale de Lausanne
  16. ↑ "Bloom". www.bloombiorenewables.com. Retrieved 2019-08-28.
  17. ↑ Shuai, Li; Amiri, Masoud Talebi; Questell-Santiago, Ydna M.; Héroguel, Florent; Li, Yanding; Kim, Hoon; Meilan, Richard; Chapple, Clint; Ralph, John (21 October 2016). "Formaldehyde stabilization facilitates lignin monomer production during biomass depolymerization". Science. 354 (6310): 329–333. Bibcode:2016Sci...354..329S. doi: 10.1126/science.aaf7810 . ISSN   1095-9203. PMID   27846566.
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