TITLE

SEPARATION METHOD

TECHNICAL FIELD THIS INVENTION relates to methods for separating a polyol and optionally a sugar, more particularly glycerol and optionally xylose, from a liquids fraction produced following treatment of a lignocellulosic material with a pretreatment solution.

BACKGROUND

Lignocellulosic material can be used, amongst other things, to produce biofuels (e.g., bioethanol) and biochemicals, and thus is an alternative to fossil fuels. For efficient biofuel production from lignocellulosic materials, the cellulose and/or hemicellulose components of lignocellulosic material need to be converted to monosaccharides (i.e., monosugars) that are capable of being fermented into ethanol or butanol. Prior work in this area has proposed processes to produce fermentable sugars from lignocellulosic material that involve a chemical and/or physical pretreatment to disrupt the natural structure of the lignocellulosic material, followed by enzymatic hydrolysis of the cellulose and hemicellulose components into monosugars. In this regard, the chemical pretreatment may include the use of, for example, polyols such as glycerol. However, these processes currently have not been commercialized owing to the high cost, low efficiency, adverse reaction conditions, and other issues associated with the pretreatment process.

Accordingly, improved methods for producing partially hydrolysed lignocellulosic material, inclusive of recovery and recycling of the chemical pretreatment agents such as polyols, are required.

SUMMARY

The present invention is predicated in part on a surprising discovery that the fast-moving components of aqueous biomass pretreatment liquid fractions are pH sensitive and prone to precipitate during separation. Overcoming this problem required the use of an otherwise not obvious, alternative separation strategy. Following the alternative strategy described herein, glycerol and xylose can be successfully separated from a liquids fraction or hydrolysate produced following pretreatment of lignocellulosic material by way of a two-stage separation process using simulated moving bed (SMB) chromatography. This invention thus makes it possible to recycle a substantial portion of the glycerol previously used in the pretreatment of lignocellulosic material, whilst also obtaining fermentable sugars obtained as a co-product of the pretreatment process.

In a first aspect, the invention provides a method of separating a polyol from a liquids fraction obtained from treating a lignocellulosic material with an agent comprising the polyol, the method including the step of:

(i) contacting the liquids fraction obtained from treating the lignocellulosic material with the agent comprising the polyol with a first separation unit to facilitate production of a first fraction comprising the polyol and a second fraction comprising an acid soluble component.

In one embodiment, the acid soluble component is or comprises lignin.

Suitably, the first fraction further comprises a sugar. In particular embodiments, the sugar is at least partly derived from hydrolysis of a hemicellulose component of the lignocellulosic material. More particularly, the sugar may be selected from the group consisting of xylose, glucose, mannose, arabinose and any combination thereof. Even more particularly, the sugar can be xylose.

In certain embodiments, the present method further includes the step of contacting the first fraction with a second separation unit to facilitate production of a third fraction comprising the polyol and a fourth fraction comprising the sugar.

In some embodiments, the present method further includes the initial step of adding an acid to the liquids fraction of step (i) in an amount effective to lower the pH thereof to about 4 or less.

In one embodiment, the liquids fraction has a pH of about 4 or less.

Suitably, step (i) of the present method is substantially performed at a pH of about 4 or less. More particularly, step (i) can be substantially performed at a pH of between about 2 and about 3.5.

In particular embodiments, one or both of the first and second separation units are or comprise a chromatographic separation unit, such as an adsorption chromatographic separation unit, an ion exchange chromatographic separation unit and/or an ion exclusion chromatographic separation unit. In one preferred embodiment, the chromatographic separation unit is or comprises a simulated moving bed chromatographic separation unit.

Suitably, step (i) comprises contacting the first separation unit with an eluent to at least partly produce the first and second fractions. In one embodiment, the eluent is substantially deionized or demineralized.

In some embodiments, the first fraction, the third fraction and/or the fourth fraction are substantially deionized.

In one embodiment, the present method further includes the initial step of separating the liquids fraction from the lignocellulosic material treated with the agent. In this regard, the present method suitably further includes the initial step of treating the lignocellulosic material with the agent.

In some embodiments, the method of the present aspect results in the separation or recovery of about 70% to about 100% of the polyol from the liquids fraction.

In other embodiments, the method of the present aspect results in the separation or recovery of about 70% to about 100% of the sugar from the liquids fraction.

Suitably, the polyol is or comprises glycerol.

In a second aspect, the invention provides a polyol produced by the method according to the first aspect.

In a third aspect, the invention provides a sugar produced by the method according to the first aspect.

In a fourth aspect, the invention provides a system for separating a polyol from a liquids fraction obtained from treating a lignocellulosic material with an agent comprising the polyol, the system comprising:

a first separation unit configured to produce a first fraction comprising the polyol and a second fraction comprising an acid soluble component when contacted with the liquids fraction obtained from treating the lignocellulosic material with the agent comprising the polyol; and optionally

a second separation unit configured to produce a third fraction comprising the polyol and a fourth fraction comprising a sugar when contacted with the first fraction.

Suitably, the system of the present aspect is for use in the method of the first aspect.

Throughout this specification, unless otherwise indicated, “ comprise”,

“ comprises” and“ comprising” are used inclusively rather than exclusively, so that a stated integer or group of integers may include one or more other non-stated integers or groups of integers. Conversely, the terms“ consist”,“ consists” and“ consisting” are used exclusively, such that a stated integer or group of integers are required or mandatory, and no other integers may be present. The phrase“ consisting essentially of indicates that a stated integer or group of integers are required or mandatory, but that other elements that do not interfere with or contribute to the activity or action of the stated integer or group of integers are optional.

It will also be appreciated that the indefinite articles“a” and“un” are not to be read as singular indefinite articles or as otherwise excluding more than one or more than a single subject to which the indefinite article refers. For example,“a” sugar includes one sugar, one or more sugars or a plurality of sugars.

BRIEF DESCRIPTION OF THE DRAWINGS

By way of example only, an embodiment of the invention is described more fully hereinafter with reference to the accompanying drawings, in which:-

Figure 1 shows a typical schematic arrangement of an eight-cell SMB separator system.

Figure 2 demonstrates a hypothetical example of a four-column simulated moving bed chromatography system.

Figure 3 demonstrates a schematic of an embodiment of a system of the invention.

Figure 4 demonstrates the SMBC of Example 1 and the formation of a dark precipitate in the raffinate line.

Figure 5: Buckets #1- #4 from left to right, represent the colour and precipitate removed from the resin during an in-place backwash procedure. As backwash continued, the colour decreased but in bucket # 4 precipitate is still noticeable.

Figure 6 demonstrates pH testing of the liquids fraction of Example 1.

Figure 7 demonstrates standard addition results for glycerol in the dilute extract of Example 1.

Figure 8 shows results of a pulse test of a sample for xylose/glycerol separation.

Figure 9 shows an FTIR of the unknown precipitate obtained in Example 1 upon raising feedstock to ~ 4 pH and above.

Figure 10 demonstrates progressive clean-up of concentrated loop two glycerol product.

Figure 11 demonstrates separation of two components using an imaginary true moving bed chromatography system.

Figure 12 demonstrates a typical internal concentration profile of a separator, with feed and product locations shown.

Figure 13 shows a valve sequencing schematic for first loop separator time period 1.1.

Figure 14 shows a valve sequencing schematic for first loop separator time period 2.1.

Figure 15 demonstrates a valve sequencing schematic for first loop separator time period 3.1.

Figure 16 shows a valve sequencing schematic for first loop separator time period 4.1.

Figure 17 demonstrates a valve sequencing schematic for first loop separator time periods 1.2, 2.2, 3.2 and 4.2.

Figure 18 shows a valve sequencing schematic for second loop separator step

1

Figure 19 demonstrates a valve sequencing schematic for second loop separator step 2.

Figure 20 shows a valve sequencing schematic for second loop separator step

3.

Figure 21 shows a valve sequencing schematic for second loop separator step

4.

Figure 22 demonstrates a valve sequencing schematic for second loop separator step 5.

Figure 23 shows a valve sequencing schematic for second loop separator step

6

DETAILED DESCRIPTION

The present invention arises, in part, from the identification of novel methods of separating or recovering a polyol and optionally a sugar from a liquids fraction or hydrolysate produced or derived from treatment of a lignocellulosic material with a pretreatment agent that includes the polyol. The method of the invention also produces a fraction or stream that contains an acid soluble by-product of the pretreatment process that is separate from that fraction or stream that contains the polyol. As such, the present invention advantageously reduces or prevents accumulation of a precipitate of the acid soluble by-product, and in particular precipitated lignin, in a separation unit utilised for recovery of the polyol. This thereby allows for substantially uninterrupted or continuous operation of the separation unit, without the need for, or reducing the frequency of, cleaning thereof. Additionally, the present method obviates the requirement for an initial precipitation and/or filtration step so as to remove the acid soluble by-product prior to introduction of the liquids fraction to the separation unit. Such methods typically add impurities, are capital intensive and can result in reduced recovery of the polyol and/or sugar.

Accordingly, the methods described herein typically have fewer effluent or waste treatment issues, lower capital and operational costs and/or are more efficient than those previously described in the art. Additionally, initial removal of the precipitable acid soluble by-product or component produces a polyol-containing fraction that is suitable for further processing, such as by further chromatographic separation, without the risk of the aforementioned precipitation effects.

Accordingly, in one aspect, the invention provides a method of separating a polyol from a liquids fraction obtained from treating a lignocellulosic material with an agent comprising the polyol, the method including the step of:

(i) contacting the liquids fraction obtained from treating the lignocellulosic material with the agent comprising the polyol with a first separation unit to facilitate production of a first fraction comprising the polyol and a second fraction comprising an acid soluble component.

The term“ polyol” as used herein refers to an alcohol containing multiple hydroxyl groups. Examples of polyols of the present invention include, but are not limited to, 1,2-propanediol, 1,3 -propanediol, glycerol, 2,3-butanediol, 1,3-butanediol, 2-methyl-l, 3 -propanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5- pentanedial, 2, 2-dimethyl- 1,3 -propanediol, 2-m ethyl- 1,4-butanediol, 2-methyl-l, 3- butanediol, 1,1,1-trimethylol ethane, 3-methyl-l,5-pentanediol, 1 , 1 , 1 - trimethyl ol propane, 1,7-heptanediol, 2-ethyl-l,6-hexanediol, 1,9-nonanediol, 1,11- undecanediol, diethylene glycol, triethylene glycol, oligoethylene glycol, 2,2'- thiodiglycol, diglycols or polyglycols prepared from 1,2-propylene oxide, propylene glycol, ethylene glycol, sorbitol, dibutylene glycol, tributylene glycol, tetrabutylene glycol, dihexylene ether glycol, trihexylene ether glycol, tetrahexylene ether glycol, 1,4-cyclohexanediol, 1,3-cyclohexanediol, or any combination thereof. The polyol can be present in the agent in pure (e.g., refined or technical grade) or impure (e.g., crude or purified crude) form.

Suitably, the polyol is selected from the group consisting of glycerol, ethylene glycol and any combinations thereof.

In one particular embodiment, the polyol is glycerol.

In certain embodiments of the present invention, a polyol in the first fraction and/or the third fraction has a purity of about 40% to about 99.9% or any range therein, such as, but not limited to, about 60% to about 99.9%, or about 70% to about 97%. In particular embodiments of the present invention, the polyol content or purity of the first fraction is about 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%,

64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%,

78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%,

92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%,

99.6%, 99.7%, 99.8%, 99.9%, or any range therein.

In some embodiments of the present invention, the method results in the removal and/or recovery of about 20% or more (e.g., about 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100% etc.) or any range therein of the polyol in the first fraction compared to the amount of the polyol present in the liquid fraction prior to treatment with or application of the method of the present aspect.

As used herein, “ treating” or “ treatment” may refer to, for example, contacting, soaking, steam impregnating, spraying, suspending, immersing, saturating, dipping, wetting, rinsing, washing, submerging, percolating and/or any variation and/or combination thereof.

The terms " lignocellulosic " or "lignocellulose" , as used herein, refer to material comprising lignin and/or cellulose. Lignocellulosic material can also comprise hemicellulose, xylan, proteins, lipids, carbohydrates, such as starches and/or sugars, or any combination thereof. Lignocellulosic material can be derived from living or previously living plant material (e.g., lignocellulosic biomass). " Biomass ," as used herein, refers to any lignocellulosic material and can be used as an energy source.

Lignocellulosic material (e.g., lignocellulosic biomass) can be derived from a single material or a combination of materials and/or can be non-modified and/or modified. Lignocellulosic material can be transgenic (i.e., genetically modified). Lignocellulose is generally found, for example, in the fibers, pulp, stems, leaves, hulls, canes, husks, and/or cobs of plants or fibers, leaves, branches, bark, and/or wood of trees and/or bushes. Examples of lignocellulosic materials include, but are not limited to, agricultural biomass, e.g., farming and/or forestry material and/or residues, branches, bushes, canes, forests, grains, grasses, short rotation woody crops, herbaceous crops, and/or leaves; oil palm fibre waste such as empty fruit bunch and palm trunk; energy crops, e.g., corn, millet, and/or soybeans; energy crop residues; paper mill residues; sawmill residues; municipal paper waste; orchard prunings; Willow coppice and Mallee coppice; wood waste; wood chip, logging waste; forest thinning; short-rotation woody crops; bagasse, such as sugar cane bagasse and/or sorghum bagasse, duckweed; wheat straw; oat straw; rice straw; barley straw; rye straw; flax straw; soy hulls; rice hulls; rice straw; tobacco; corn gluten feed; oat hulls; com kernel; fiber from kernels; com stover; corn stalks; com cobs; com husks; canola; miscanthus; energy cane; prairie grass; gamagrass; foxtail; sugar beet pulp; citrus fruit pulp; seed hulls; lawn clippings; cotton, seaweed; trees; shrubs; wheat; wheat straw; products and/or by-products from wet or dry milling of grains; yard waste; plant and/or tree waste products; herbaceous material and/or crops; forests; fruits; flowers; needles; logs; roots; saplings; shrubs; switch grasses; vegetables; fruit peels; vines; wheat middlings; oat hulls; hard and soft woods; or any combination thereof.

It would be appreciated that lignocellulosic material can be used, amongst other things, to produce biofuels (e.g., bioethanol) and biochemicals. For efficient biofuel production from lignocellulosic materials, the cellulose and/or hemicellulose components of lignocellulosic material need to be converted to monosaccharides (i.e., monosugars) that are capable of being fermented into ethanol, butanol or other fermentation products as are known in the art. Generally, the production of fermentable sugars from lignocellulosic material involves an initial chemical and/or physical pretreatment or hydrolysis step to disrupt the natural structure of the lignocellulosic material. In this regard, the treated lignocellulosic material described herein may be suitable for and/or may have undergone during the pretreatment step, at least partial hydrolysis thereof by any such means or method known in the art.

As would be readily understood by the skilled artisan, the method described herein may remove the acid-soluble component, such as a salt and/or lignin, present in the liquids fraction. Accordingly, in some embodiments of the present invention, the method results in the removal and/or recovery of about 20% or more (e.g., about 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100% etc.) or any range therein of the acid soluble component, such as a salt and/or lignin, in the second fraction compared to the amount of the acid soluble component present in the liquid fraction prior to treatment with or application of the method of the present aspect.

In one embodiment, the acid soluble component is or comprises lignin. In this regard, it would be appreciated that the term“ lignin”, refers to a complex polymer that is generally the principle non-carbohydrate constituent of plant material. The lignin in plant material is typically bound to cellulose fibres and functions to harden and/or strengthen plant cell walls. The term encompasses all available forms of lignin, either naturally occurring or formed from conventional processes (e.g., non-naturally occurring), such as pulping processes. To this end, it will be appreciated that lignin may be removed from the lignocellulosic material during treatment with the agent comprising the polyol by hydrolysis of the chemical bonds that hold the lignocellulosic material together.

In other embodiments, the acid soluble component is or comprises a salt, inclusive of inorganic and organic salts as are known in the art. Examples of salts include but are not limited to sulphates, phosphates, chlorides, acetates and urinates of sodium, potassium, calcium, magnesium and iron.

Suitably, the first fraction further comprises a sugar. As used herein, the term “sugar” refers to mono-, di-, and oligo-saccharides, also known in the art as non- hydrogenated carbohydrates of empirical formula (CH2O) ¹¹ . Examples of sugars include but are not limited to, xylose, glucose, mannose, galactose, rhamnose, and arabinose. In one embodiment, the sugar is at least partly derived from hydrolysis of a hemicellulose component of the lignocellulosic material. More particularly, the sugar can be xylose.

Suitably, the sugar is or comprises a fermentable sugar. "Fermentable sugar " as used herein, refers to oligosaccharides and/or monosaccharides that may be used as a carbon source by a microorganism in a fermentation process. Examples of fermentable sugars include glucose, xylose, arabinose, galactose, mannose, rhamnose, sucrose, fructose, or any combination thereof.

As such, the present method may result in the separation or recovery of greater than about 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% (such as about 100%) or any range therein of the sugar in the first fraction compared to the amount of the sugar present in the liquid fraction prior to treatment with or application of the method of the present aspect.

In certain embodiments, the present method further includes the step of:

(ii) contacting the first fraction with a second separation unit to facilitate production of a third fraction comprising the polyol and a fourth fraction comprising the sugar.

Suitably, the present method results in the removal and/or recovery of about 20% or more (e.g., about 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100% etc.) or any range therein of the polyol in the third fraction compared to the amount of the polyol present in the first fraction and/or the liquids fraction prior to treatment with or application of the method of the present aspect. In some embodiments, the method of the present aspect results in the separation or recovery of about 70% to about 100% (e.g., 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, 100% and any range therein) of the polyol from the liquids fraction and/or the first fraction.

In particular embodiments of the present invention, the polyol content or purity of the third fraction is about 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%,

62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%,

76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%,

90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%,

99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or any range therein.

Additionally, the present method may result in the separation or recovery of greater than about 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% (such as about 100%) or any range therein of the sugar in the fourth fraction compared to the amount of the sugar present in the first fraction and/or the liquids fraction prior to treatment with or application of the method of the present aspect. In some embodiments, the method of the present aspect results in the separation or recovery of about 70% to about 100% (e.g., 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, 100% or any range therein) of the sugar from the liquids fraction and/or the first fraction.

In particular embodiments of the present invention, the sugar content or purity of the fourth fraction is about 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%,

53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%,

67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%,

81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%,

95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or any range therein.

Suitably, the liquids fraction, the first fraction, the second fraction, the third fraction and/or the fourth fraction contain or comprise a level of dissolved solids of about 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%,

43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%,

57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%,

71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%,

85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%,

99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or any range therein.

In some embodiments, the present method further includes the initial step of adding an acid to the liquids fraction of step (i) in an amount effective to lower the pH thereof to about 4 or less.

The skilled person would readily understand that the term " acid ", as used herein, refers to various water-soluble compounds with a pH of less than 7 that can be reacted with an alkali to form a salt. Examples of acids can be monoprotic or polyprotic and can comprise one, two, three, or more acid functional groups. Examples of acids include, but are not limited to, mineral acids, Lewis acids, acidic metal salts, organic acids, solid acids, inorganic acids, or any combination thereof. Specific acids include, but are not limited to hydrochloric acid, sulfuric acid, phosphoric acid, hydrofluoric acid, hydrobromic acid, hydroiodic acid, nitric acid, formic acid, acetic acid, methanesulfonic acid, toluenesulfonic acid, boron trifluoride diethyl etherate, scandium (III) trifluoromethanesulfonate, titanium (IV) isopropoxide, tin (IV) chloride, zinc (II) bromide, iron (II) chloride, iron (III) chloride, zinc (II) chloride, copper (I) chloride, copper (I) bromide, copper (II) chloride, copper (II) bromide, aluminum chloride, chromium (II) chloride, chromium (III) chloride, vanadium (III) chloride, molybdenum (III) chloride, palladium (II) chloride, platinum (II) chloride, platinum (IV) chloride, ruthenium (III) chloride, rhodium (III) chloride, zeolites, activated zeolites, or any combination thereof.

In one embodiment, the acid is selected from the group consisting of sulphuric acid, hydrochloric acid, phosphoric acid, hydrofluoric acid, hydrobromic acid, nitric acid, acid metal salts and any combination thereof. Even more particularly, the acid can be sulphuric acid.

In one embodiment, the liquids fraction has a pH of about 4 (e.g., about 4, 3.9,

3.8, 3.7, 3.6, 3.5, 3.4, 3.3, 3.2, 3.1, 3.0, 2.9, 2.8, 2.7, 2.6, 2.5, 2.4, 2.3, 2.2, 2.1, 2.0,

1.9, 1.8, 1.7, 1.6, 1.5 or any range therein) or less.

Suitably, step (i) of the present method is substantially performed at a pH of about 4 (e.g., about 4, 3.9, 3.8, 3.7, 3.6, 3.5, 3.4, 3.3, 3.2, 3.1, 3.0, 2.9, 2.8, 2.7, 2.6, 2.5, 2.4, 2.3, 2.2, 2.1, 2.0, 1.9, 1.8, 1.7, 1.6, 1.5 or any range therein) or less. More particularly, step (i) can be substantially performed at a pH of between about 2 and about 3.5.

Suitably, steps (i) and/or (ii) are carried out at a temperature from about 20 to 99°C, or any range therein, such as, but not limited to, about 20°C to about 90°C or about 25°C to about 80°C. In particular embodiments, step (i) is carried out at a temperature of about 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, 41°C, 42°C, 43°C,

44°C, 45°C, 46°C, 47°C, 48°C, 49°C, 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C,

57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C,

70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, 81°C, 82°C,

83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C, 90°C, 91°C, 92°C, 93°C, 94°C, 95°C,

96°C, 97°C, 98°C and 99°C. Preferably, step (i) is carried out at a temperature from about 65°C to about 75°C. As would be well understood by the skilled artisan, steps (i) and (ii) of the present method may be performed at different temperatures.

In particular embodiments, one or both of the first and second separation units are or comprise a chromatographic separation unit, such as an adsorption chromatographic separation unit, an ion exchange chromatographic separation unit and/or an ion exclusion chromatographic separation unit. In one preferred embodiment, the chromatographic separation unit is or comprises a simulated moving bed chromatographic separation unit.

The term“ chromatographic separation” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and refers without limitation to rate-based separation of one or more chemical species over a stationary solid phase by differential partitioning of the species between the stationary phase and a mobile phase. Differential partitioning can occur during the contacting of a process feed stream with a stationary phase, upon contacting a stationary phase having adsorbed species, or both.

As used herein, the term“ adsorption chromatography’ is broadly directed to a type of separation method involving the use of a stationary phase to selectively adsorb and thereby take up and concentrate the desired solutes from a mobile phase.

As generally used herein,“ion- exchange chromatography’ is broadly directed to a type of separation method involving the use a substrate or structure, such as an ion-exchange membrane or ion-exchange resin, that participates in an ion-exchange reaction. Ion-exchangers typically include a high molecular compound or polymer having an acidic group (cation exchange group), such as a sulfonic acid or phosphonic acid group or a basic group (anion exchange group), such as an amino group or imidazole group.

It will be understood, that an ion-exchange reaction is generally an adsorption phenomenon where the mechanism of adsorption is electrostatic. In this regard, electrostatic forces act to hold ions to charged functional groups on the surface of the ion-exchanger. The adsorbed ions normally replace ions that are on the resin surface on a 1 : 1 charge basis. In some cases, there may also be more than electrostatic forces holding the ion to the functional group of the ion-exchanger. For example, for weakly acid functional groups, such as carboxylic groups, hydrogen bonding is partially responsible for attracting H ⁺ ions. Another example is the strong bonding between Ca and PO4 when PO4 is used for a functional group. A detailed discussion of ion exchange can be found in ION EXCHANGE by F. G. Helfferich (McGraw-Hill, New York, 1962), which is incorporated by reference herein.

The ion-exchanger of the present invention may be any of the various types known in the art, including natural (e.g., proteins, soils, lignin, coal, metal oxides, aluminosilicates (zeolites) (Na0A1203.4Si02)) and synthetic (e.g., zeolite gels, polymeric resins (macroreticular, large pores)) ion-exchangers, albeit without limitation thereto. Suitably, the ion-exchanger is a low cross-linked strong acid ion- exchanger.

In one particular embodiment, the ion-exchanger is or comprises an ion- exchange resin. Ion-exchange resins typically include an insoluble matrix (or support structure) in the form of small beads fabricated from an organic polymer substrate. The material generally has a structure of pores on the surface that, upon chemical activation, can comprise exchange sites that trap and release ions.

The term“ ion exclusion chromatography’ refers to a separation technique that separates ionic species in solution from non-ionic species, or weakly ionic species from strongly ionic species, by employing a resin having a structure that allows the non-ionic species or weakly ionic species to diffuse into it while preventing more ionic species from entering the resin. The species with less ionic character then elutes after the more ionic species.

The term“ simulated moving bed chromatography” as used herein is a broad term, and is to be given its ordinary and customary meaning to a person of ordinary skill in the art (and is not to be limited to a special or customized meaning), and refers without limitation to forms of chromatographic separation or other adsorptive processes where, for example, through a valving arrangement, movement of solid phase in a direction opposite of the mobile phase is simulated or accomplished. Generally, such systems allow for continuous feed streams to be used with resulting continuous outlet streams. The adsorption that takes place in this form of chromatography frequently is a partitioning of adsorbed species from the process feed between a stationary phase and a mobile phase, with adsorbed species being shifted to create portions of the mobile phase having higher and lower concentrations.

Suitably, step (i) comprises contacting the first separation unit with an eluent to at least partly produce the first and/or second fractions. In one embodiment, the eluent is substantially deionized or demineralized.

In particular embodiments, it is also preferred that the first fraction, the third fraction and/or the fourth fraction are substantially deionized.

By“ substantially deionizeF is meant an eluent, such as reverse osmosis (RO) or distilled water, or fraction, with no ions, or with a low concentration of ions (e.g., less than about 50 milli-Osmoles, or less than about 10 milli-Osmoles).

It will be appreciated that the method of the present aspect may further include the step of contacting the second separation unit with a further eluent to at least partly produce the third and/or fourth fractions. In one embodiment, the present method further includes the initial step of separating the liquids fraction from the lignocellulosic material treated with the agent. By way of example, the liquids fraction can be separated from lignocellulosic material via methods such as, but not limited to, vacuum filtration, membrane filtration, sieve filtration, partial or coarse separation, microcentrifugation, high-speed centrifugation, ultracentrifugation, or any combination thereof, prior to being contacted with the first separation unit as per the method described herein.

The present method suitably may further include the initial step of treating the lignocellulosic material with the agent. In this regard, the treatment step may be performed by any method as is known in the prior art. By way of example, a method of treating lignocellulosic material sequentially with an acid and/or an alkali and a polyol to produce a partially hydrolysed lignocellulosic material is described in PCT/AU2015/050390, which is incorporated by reference herein. Suitably, the method of the present invention at least partially hydrolyses the lignocellulosic material. " Partial hydrolysis" or " partially hydrolyses " and any grammatical variants thereof, as used herein, refer to the hydrolysis reaction cleaving or breaking less than 100% of the chemical bonds that hold the lignocellulosic material together. An alternative method of treating lignocellulosic material with an agent comprising a polyol is disclosed in US2014/0093918, which is also incorporated in its entirety herein.

As would be readily understood by the skilled artisan, " alkali ", as used herein, refers to various water-soluble compounds with a pH of greater than 7 that can be reacted with an acid to form a salt. By way of example, an alkali can include, but is not limited to, sodium hydroxide, potassium hydroxide, ammonium hydroxide, magnesium hydroxide and alkali metal salts such as, but not limited to, sodium carbonate and potassium carbonate.

In some embodiments, the method of the present aspect further includes the step of filtering the liquids fraction and/or the first fraction prior to contacting the first and/or second separation units respectively, such as by way of a filtration unit as described herein.

In particular embodiments, the method further includes the step of concentrating the first, third and/or fourth fractions. To this end, the first, third and fourth fractions may be concentrated by any method known in the art, inclusive of evaporation and reverse osmosis. Evaporation may not only remove water, but also other evaporable liquids, such as methanol and other solvents. Reverse osmosis may be used initially to concentrate a low concentration glycerol- and/or sugar-containing fraction (i.e., first and/or third fractions) by removing at least some of, for example, the water from the fraction. Evaporation can be performed, for example, by a vacuum evaporator, suitably at a temperature and pressure that avoid possible decomposition of the polyol and/or the sugar during the evaporation process.

In some embodiments, the polyol recovered or recycled in the first and/or third fractions may undergo or be subjected to one or more subsequent steps of purification or refining. In this regard, the recovered or recycled polyol may be in a partially purified or refined form. Methods of purification of the recovered or recycled polyol may include, but are not limited to, filtration, chromatographic separation, distillation, evaporation, demineralization, adsorption processes that remove contaminants, for example, percolation through columns containing activated carbon or diatomaceous earth or some other adsorptive material, and any combination thereof.

In another aspect, the invention provides a system for separating a polyol from a liquids fraction obtained from treating a lignocellulosic material with an agent comprising the polyol, the system comprising:

a first separation unit configured to produce a first fraction comprising the polyol and a second fraction comprising an acid soluble component when contacted with the liquids fraction obtained from treating the lignocellulosic material with the agent comprising the polyol; and optionally

a second separation unit configured to produce a third fraction comprising the polyol and a fourth fraction comprising a sugar when contacted with the first fraction.

Suitably, the first and/or second separation units are that hereinbefore described.

In certain embodiments, the system further comprises a filtration unit which is capable of filtering the liquids fraction prior to contacting the first and/or second separation units.

In some embodiments, the system further comprises one or more concentration units, such as evaporation units, for concentrating the first, third and/or fourth fractions.

In particular embodiments, the system further comprises a purification unit capable of at least partly purifying the third and/or fourth fractions so as to facilitate at least partial removal of one or more contaminants or impurities therefrom. Preferably, the purification unit comprises a mixed bed chromatographic module and/or an activated carbon module.

Suitably, the system is for use in the method hereinbefore described.

A preferred embodiment of the system is shown in Figure 3. In referring to Figure 3, the system 10 comprises a filtration unit 11 for initially filtering the liquids fraction 5 derived from pretreatment of a lignocellulosic material with an agent comprising a polyol. From the filtration unit 11, the liquids fraction 5 enters a first simulated moving bed separation unit 12, which is configured to separate the liquids fraction 5 into a first fraction 1 containing the polyol and a sugar and a second fraction 2 containing acid soluble components, such as salts, lignin and other by products or contaminants of the previous pretreatment reaction.

The first fraction 1 is then transferred to a first evaporation unit 13 to apply a low level of heat and pressure and thereby concentrate the first fraction 1 to a desired percentage of dissolved solids. From the first evaporation unit 13, the first fraction 1 enters a second simulated moving bed separation unit 14, wherein the first fraction 1 is subsequently separated into a third fraction 3 containing the polyol and a fourth fraction 4 containing the sugar.

The system 10 further comprises second and third evaporation units 15,16 for concentrating the respective third and fourth fractions 3,4 to a desired level of dissolved solids and/or purity. Optionally, the fourth fraction 4 may further be treated with a purification unit 17, which is designed to remove one or more impurities or contaminants therefrom. For the system 10, the purification unit 17 comprises a mixed bed chromatographic module and an activated carbon module.

In a related aspect, the invention provides a polyol, such as glycerol, produced by the method or system hereinbefore described.

In a further aspect, the invention provides a sugar, such as xylose, produced by the method or system hereinbefore described.

All computer programs, algorithms, patent and scientific literature referred to herein is incorporated herein by reference.

In order that the invention may be readily understood and put into practical effect, particularly preferred embodiments will now be described by way of the following non-limiting examples. EXAMPLE 1

One possible method of recovering chemical pretreatment agents is chromatography. For example, when an aqueous biomass pretreatment liquid fractions containing a polyol and an acid (chemical agents) and hemicellulose sugars (a co product) is passed through a column packed with a strong acid cation exchange resin, the first components to exit are those that are completely excluded from the resin beads and therefore move the fastest - namely the charged inorganic salts, colorant molecules and other high molecular weight compounds. These excluded components are followed by the sugars. Last to elute from the column are the smallest and most adsorbed components - in this case, primarily the polyol.

In principle, by using enough elution water and a resin column of enough length, it would be possible to obtain complete separation of all of the individual feed components in pure form. However, this would require a system with uneconomic capital and operating costs.

In practice, the disadvantages of batch column chromatography can be overcome by continuous simulated moving bed (SMB) chromatography. A SMB chromatographic separator includes several fixed-bed resin columns (or cells) connected in an endless loop, with the outlet of each cell being connected to the inlet of the next cell. Recirculation pumps between the cells provide a continuous flow of material around the loop and downward through each resin column. Arrangements consisting of either four or eight resin columns are typical, and Figure 1 below shows the basic schematic configuration of an eight cell SMB system.

By periodically switching valves in the direction of the internal recirculation flow, it is possible to simulate a true moving bed of resin (hence this technology is known as simulated moving bed chromatography). For example, consider a hypothetical four-column SMB system as shown in Figure 2 below, with a continuous flow of eluent circulating through the loop in a clockwise direction. By periodically rotating the positions of the feed, eluent water and product valves (every few minutes) in the clockwise direction, the“backwards” flow of resin in a counter-clockwise direction can be simulated. If one considers a frame of reference that moves along with the changing feed inlet position as shown in the figure, then the resin columns appear to be rotating in a counter-clockwise direction, in a step-by-step periodic way. This is the same as in a true moving bed, although the resin in the SMB system moves intermittently, rather than continuously. The switching of valve locations around the loop takes place to simulate an internal flow of resin. As for a true moving bed, the effective path length for the separation can be increased by faster internal recirculation of the resin and elution water. This is achieved in a simulated moving bed system by reducing the step time (making the column-wise backward movement of the resin more frequent) and increasing the internal fluid flows, but with a resulting increase in pressure drop.

During SMB operation, a separated concentration profile is maintained within the system, containing a distribution of all components originally present in the feed stream. This concentration profile circulates continuously around the loop of resin columns, and is similar in nature (and in order of component elution) to that obtained with a batch chromatographic column. Feed material and eluent water are added into the circulating profile, while extract (target product) and raffinate (waste) streams are withdrawn from the profile at appropriate points between the individual cells, depending on the location of the moving profile at any point in time.

While some cross-contamination between neighbouring components is often inevitable, it should be possible to separate a polyol as an extract from an aqueous biomass pretreatment liquid in a single SMB loop and to further separate hemicellulose sugars from the fastest moving components, viz. charged inorganic salts, colorant molecules and other high molecular weight compounds is a subsequent SMB loop. Such a system is known as coupled loop SMB chromatography, and is the basis of the method described below.

The present Example was designed to test the recovery of glycerol from an agent used to pretreat lignocellulosic material by treatment through a 1st loop only SMB (Simulated Moving Bed) chromatography system. This SMB configuration was designed to separate glycerol (extract) from sugars and salts (raffinate) in a first loop, with the intention separating xylose and salts in a second loop. In this experiment only the first loop was investigated.

Prior to this study, a short-term pilot test was run on a liquid fraction from mixed southern hardwood treated with aqueous glycerol and a catalytic amount of sulphuric acid (referred to hear as the pretreatment process). This filtrate consisted of 27% mass solutes and 74% of solutes as glycerol (referred to here as purity). The short-term test established separator operating parameters. The present study was run using a liquid fraction from the same pretreatment process, but at a much higher solutes content, viz. 49% mass solutes and 82% glycerol purity. The higher concentrations in the present study required a significant change of separator operating parameters, particularly, determination of proper [water/feed] and [extract/raffinate] ratios.

A major objective of the present Example was to attempt an increase in solids loading. Separator size is inversely proportional to loading, so a significant increase in loading results in a significant reduction in full-scale capital expense. While a Lanxess 375 micron resin was used in the short-term test, a decision was made to use a smaller, more kinetically efficient Mitsubishi 220 micron resin for the present evaluation.

Improved kinetics will generally allow a higher system loading to be used. The pilot tests were, typically, operated at about twice the loading of the earlier test. The purpose was to demonstrate that the system size could be reduced by half. Another major decision concerned the resin cation form. It was decided to proceed with sodium form while realizing that the resin would equilibrate at some ratio of H+ and other cations.

Results

Pilot test Leaf-2 with sodium form resin

Pilot SMB operating parameters:

Resin used: Mitsubishi 530 Na+

Cell dimensions: 2” X 5’— 8 cell configuration

Void: .55

Solutes loading: approximately 85 Lbs solutes/ft ³ resin/day

Steptime: 10 minutes

Temperature: 70 Celsius

Feed concentration: 49% mass solutes

Feed glycerol purity: 81%

Water/Feed: 4.0

Extract/Raffmate: 1.0

Feed rate: 40 ml/min

Control method: Conventional Results obtained from cycles 129 to 1329:

Operating parameters were held constant for the first 10 days of operation to evaluate equilibration and performance. Subsequent adjustment of the void setting demonstrated improved separation efficiency. It was possible to obtain an approximate 88 glycerol purity extract from 80 purity feed with close to 100% recovery. On the negative side, sugars were poorly recovered in the raffinate. Because the glycerol purity increased without eliminating the sugars, there was a significant amount of non-glycerol, non-sugars being passed to the raffinate. The composition of these materials in the raffinate was not determined.

An important and unexpected observation during the tests was that the feed exhibited a very great sensitivity to pH. Although the feed was initially processed through membrane microfiltration and was crystal clear, over time a precipitate began to form in the SMB. The summation of system pressure drop increased from day to day and eventually prevented the separator from operating normally.

Softened water (pH = 7) was used as eluent and appeared to have an impact on the pH of the discharge streams. The reason was that the sodium in the softened water exchanged with the hydrogen ion in the resin and, together with the water pH, raised the internal system pH. The feed pH was ~ 2.1, and once the pH of the raffinate stream approached 4, noticeable precipitation in the recycle lines occurred (See Figure 4). As the tests continued with the same water source, the precipitation began to show up in the extract stream. All indications were that the resin beds were becoming saturated with an unknown solid material.

A simple caustic rinse was used to dissolve the precipitate in the resin beds and dislodge a dark colour precipitate which had formed on the translucent PFA recycle lines. The water source was switched from softened water to RO water (5 pH and free of exchangeable sodium ions) to try to avoid future precipitation.

Before precipitation occurred, both discharge streams were very clear with a light golden tint. Prior to caustic rinse, the resin beds were backwashed to determine the severity of the precipitate accumulation. See Figure 5.

Bench Top Precipitation Tests

Benchtop tests were run wherein microfiltered feed was adjusted with sodium hydroxide to pH 3, 4, 5, 6, 7 and 10. It was determined that as pH approached 4, the colour of the original solution began to darken and centrifugation of the liquid revealed the presence of a precipitate. At pH levels of 5 and 6, large amounts of precipitate formed.

As the pH of the material was increased past 7, much of the precipitate resolubilized, especially in the 10 - 11 pH range. Although centrifuged samples of feed at the higher pH levels showed less solids, the material remained quite dark since not all of the fine precipitate went back into solution. Interestingly, once acid was added to the high pH solutions, all solids went into solution and the colour of the feed sample returned to its original tint. The precipitation therefore appears to be reversible.

A more detailed bench test was subsequently run (See Figure 6).

From these tests, it became apparent that most of the precipitation occurred between pH = 5 - 6. A sample of the precipitate was subjected to FTIR (Figure 7). No clear match could be made with a library of compounds, but there were some similarities to spectra of lignin. Without being bound by any theory, it is believed that the precipitate is derived at least in part from an acid soluble lignin. Other possible contaminants includes salts and soaps from the lignocellulosic material.

A pilot pretreatment test was then run to evaluate the possibility of removing the precipitate prior to feeding the separator. The pH of 200 litres of feed material was raised to 6 and then membrane microfiltered. Even after microfiltration, which displayed no evident solids in the permeate, the feed colour was much darker than the original feedstock. The dark colour generated uncertainty whether this would be a worthwhile approach, and this precipitation and filtration strategy was abandoned.

It was decided to proceed with a hydrogen form resin rather than the sodium form used in the first set of tests. The reasoning was that while the resin would still approach a hydrogen/sodium equilibrium, starting with a low pH environment and controlling input materials may prevent long term precipitation. One negative of this approach was that the unknown component would still be fed to the separator and be distributed in some manner to products. The hope was that the component would primarily pass into the raffinate.

Pilot test Leaf-2 with hydrogen form resin

In addition to using a resin in the hydrogen form, the specific resin was changed for these tests. Finex CS 11GC, which has a 325 micron bead size, was used. The reason for this change was the immediate availability of the hydrogen form Finex resin. Although there was some risk in using a larger bead resin with respect to the high loading target, a decision was made to try the material. Results demonstrated that the high loading (reducing the separator size by ½ compared with the earlier tests) was still possible with this larger resin.

Pilot SMB operating parameters:

Resin used: Finex CS 11GC H+ Cell dimensions: 2” X 5’— 8 cell configuration

Void: .61

Solutes loading: approximately 85 Lbs solutes/ft ³ resin/day

Steptime: 10 minutes

Temperature: 70 Celsius

Feed concentration: 49% mass solutes

Feed glycerol purity: 81%

Water/Feed: 4.0

Extract/Raffmate: 1.0

Feed rate: 40 ml/min

Control method: Conventional

The following tables compare results using the hydrogen and sodium resins using similar operating parameters (including softened water for eluent).

After equilibration, very little difference was observed between tests with the two different cation form resins. Performance equilibrated to a similar state in either case. The slight variations may be due to the different feedstock totes used for each set of tests.

During the hydrogen form resin tests it became clear that the eluent water was the main cause of the precipitation problem. This conclusion was made following a switch from RO eluent water to softened water eluent. The separator products soon began to darken and a darkening of separator tubing was observed. A return to RO water for eluent reversed the darkening problem and removed the colour from the tubing. Note that the softened water condition was used for the samples compared in Table 8 - and therefore responsible for the higher pHs. While it was expected that the hydrogen form resin would help avoid the precipitation problem, this was demonstrated to be incorrect. The eluent water was the main driver of the pH rise.

In comparison with the softened water eluent results, pH values from subsequent tests using RO eluent water showed that the raffinate fraction will equilibrate at about 3.7 pH and the extract will equilibrate at about 2.6 pH.

Following the return to RO water eluent, parameters were changed to address the goal of obtaining higher glycerol purity and a higher recovery of sugars. To increase extract purity (for most feedstocks), the extract to raffinate ratio is typically lowered. This leads to a trade-off wherein the higher product purity is accompanied by a lower recovery. The following set of tables list the results of progressive E/R reduction.

Surprisingly, significantly lowering the E/R ratio resulted in only a slight increase in glycerol purity and recovery remained very high. With respect to sugars, recovery remained very poor. The explanation for these results would appear to be that the sugars (primarily xylose) exhibit separation characteristics very similar to the glycerol. As E/R was reduced, the sugars remained with the glycerol and therefore prevented both an increase in glycerol purity in the extract and an increase in sugars recovery in the raffinate.

In an attempt to magnify the glycerol/sugars separation, an increase in steptime was evaluated. It had been found previously that a longer steptime than ordinarily expected could improve performance. The steptime was therefore increased from 10 to 12 minutes.

The change in steptime did not cause a significant change in results. In the current configuration, SMB glycerol/sugars separation was demonstrated to be poor.

The last pilot test involved a reduction in eluent use. For the higher concentration feed, at over twice the solutes content of the first short-term test, the water/feed ratio was doubled (so that the amount of water on DS was about equal in both tests). However, because water use is such a primary factor in full-scale operating costs, we began reducing this ratio. The final test involved dropping W/F by 25% (from 4.0 to 3.0).

Reducing the water to feed ratio did not result in a negative effect. Sugars recovery was a little higher than at the higher W/F. Glycerol purity was about the same and recovery was still very high. These results suggested reducing W/F to a still lower value (e.g., 2.0).

Glycerol Fraction Evaporation

For this task, the pilot SMB separator was operated at what was considered the best set of parameters for producing the highest glycerol purity. Approximately 300 litres of dilute extract with a solids concentration of 35% was collected over 5 days. The glycerol fraction was concentrated to about 68% solids under partial vacuum and at a temperature of 70 °C (to reduce the likelihood of colour formation). The table below lists results.

Colour and glycerol purity before and after evaporation matched well. There was a significant pH rise through evaporation. As discussed, it is best to maintain a pH less than 4 to assure that precipitation will not become an issue. However, since extract contains much less non-glycerol material than the feed, the pH rise did not appear to be a problem.

Conclusions The higher solutes liquid fraction contained an unknown material which precipitates upon a pH rise to about 4 and above. The precipitation can occur in the SMB separator when water containing significant cations (such as soft water) exchanges with the hydrogen cations attached to the resin. If the material is not pre-precipitated and filtered prior to the SMB, it appears necessary to use a de-ionized eluent - such as RO water or perhaps condensate (if the pH is not high).

Irrespective of the choice of resin i.e. hydrogen or sodium form, the resin will equilibrate to a stable condition determined by the cations in the feed (and water).

At least for the resins tested here the primary sugar in the liquid fraction, xylose, was poorly separated from glycerol with cation resin in the equilibrated sodium/hydrogen form. Most of the final glycerol product contamination was xylose (as much as 68% of the extract non-glycerol was xylose). However, an earlier pulse test using Lanxess GF-303, a strong cation resin in hydrogen form showed good separation of xylose and glycerol (see result in Figure 8). Lanxess GF-303 resin appears to be a very good medium for effective glycerol and sugars separation. From previous experience with glycerol solutions, salts and high molecular weight compounds will be located on the chromatogram prior to the sugars. An application of SMB can be expected to have a good probability of successful separation of glycerol from this type of mixture.

EXAMPLE 2

Previous testing in Example 1 demonstrated that it is difficult to separate glycerol from xylose and salts. Therefore, in Example 2, an alternative separation strategy was assessed, viz. glycerol and xylose eluted together and separated from the salts/non-glycerol in a first SMB loop followed by a second loop focused only on the glycerol/xylose separation.

The primary objective was to collect a high purity glycerol extract and a lower purity xylose raffinate from SMB loop 2.

A second objective is to determine the upper bound on loading (system size is inversely proportional to loading) and the lower bound on water/feed ratios on both loops.

A third objective is to determine the feasibility of taking a thin cut of extract with minimal sugars contamination that can more easily be upgraded to a high-grade glycerol, and a separate, larger recycle cut at minimum 85% purity.

Feed precipitation during separator operation

An important and unexpected observation during the prior Phase 1 tests was that the liquid fraction feed was sensitive to pH. Although the feed was initially processed through membrane microfiltration and was crystal clear, over time a precipitate began to form in the SMB. When softened water (pH = 7) was used as eluent. As a result, R.O. water was used for all further testing, and in this example. During start-up of this test the system pH did rise for the first few days of operation (due to resin cation form equilibration) and then returned to a stable low pH. Although the initial pH rise was accompanied by a temporary rise in colour, precipitation did not occur and the system operated for the approximately 4 month duration without any precipitation or colour increase. This is an important observation since it suggests that long term operation of the Glycell SMB process can be maintained with respect to precipitation problems.

It is also noted that the raffinate obtained from the first loop of the Phase 2 configuration was precipitate-able with upward pH adjustment (indicating the presence of perhaps soluble lignin or soaps). The extract fraction from the first loop (primarily glycerol + xylose) was not precipitate-able suggesting that the second loop SMB should be quite stable in this regard.

Pilot test flow scheme

Figure 1 illustrates the general flow scheme for the pilot test.

Process steps:

1. Digester filtrate was passed through microfiltration to eliminate suspended solids and microbiological contamination.

2. Membrane filtrate was fed to SMB loop 1 to recover a glycerol/xylose fraction and a non-glycerol/xylose fraction.

3. The glycerol/xylose fraction was concentrated to about 43% DS.

4. The concentrated glycerol/xylose fraction was fed to SMB loop 2 to recover a glycerol fraction and a xylose fraction.

5. The xylose fraction was concentrated to 50% DS.

6. The glycerol fraction was concentrated to 80% DS and then passed through a demineralization/carbon clean-up process.

Testing comprised runs over a range of conditions with progressive adjustment of operating parameters in

each test to bring the system to the reported performance.

Pilot test4 cell loop 1

The high solutes liquid fraction from Example 1 viz. 49% mass solutes and 82% glycerol purity was used for an initial rough evaluation of the proposed separation. This first test involved operation of the first loop of the proposed separation configuration (separation of the glycerol and xylose from the salts/lignin).

In addition to using 8 cells, the loading was decreased by half compared to the 4 cell test. The reason was to determine a possible“best case” result (but not best-case economics) as a frame of reference.

Operating parameters:

Resin: Mitsubishi 530 (sodium form prior to equilibration)

Separator configuration: 4 cells

Solutes loading: 85 lbs/ft ³ resin/day

1397 cycles were run on the pilot system. Representative results are listed in Table 1 with %DS by both Karl Fisher and glycerol by refractive index.

Results were favourable for this first test of the proposed alternative separation strategy. The combined glycerol + xylose was recovered at 99% at a combined purity of 93.4 (Note: It was found useful to refer, at times, to the combined glycerol + xylose purities and recoveries in this work, as this was the combination passed on to the second loop separation). With respect to individual components, glycerol recovery was 99.7% and xylose recovery was 90.2%.

Conductivity measurement indicated a very good separation of charged species (inorganic salts and other conductive compounds):

Pilot test 8 cell loop 1 A second preliminary test using leftover Example 1 feedstock was run in order to determine if an 8 cell configuration (instead of 4) would provide an improvement in results for loop 1 operation. Operating parameters:

Resin: Mitsubishi 530 (sodium form prior to equilibration)

Separator configuration: 8 cells

Solutes loading: 40 lbs/ft ³ resin/day

Steptime: 12 minutes

Temperature: 70 C

Feed %DS: 49%

Feed glycerol purity: 81%

W/F: 4.5

E/R: 1.2

Results are listed in Table 2.

1328 cycles were run on the pilot systemGlycerol was recovered at 99.5% and xylose at 98.5.

The glycerol + xylose purity and recovery were somewhat higher than with 4 cell operation due to the 2.5 point higher feed purity. The conclusion of these preliminary tests was that using a 4 cell operation (less equipment) and high loading (smaller equipment size) would be sufficient for the first loop operation.

Having demonstrated that the proposed separation of glycerol/xylose from nonglycerol/xylose on the first loop was successful, the tests proceeded to the combination of both loop 1 and 2 and the use of the new secondary filtrate.

Pilot test coupled loop (loop 1)

This test used a high solutes liquid fraction similar to that used in from Example 1 viz. 47% mass solutes and 84% glycerol purity. In addition to optimizing operating parameters, the extract from this test was concentrated for use as feed for the second loop of the SMB configuration.

Operating parameters (loop 1):

Resin: Mitsubishi 530 (sodium form prior to equilibration)

Separator configuration: 4 cells

Solute loading: 80 lbs/ft ³ resin/day

Steptime: 11 minutes

Temperature: 70 C

Feed %DS: 47%

Feed glycerol purity: 87-91%

W/F: 4.5

E/R: 1.2

Note: In the following tables,“others” refers to non-glycerol/xylose components.

1792 cycles were run on the pilot system. Glycerol was recovered at 99.3% and xylose at 93.6%.

Glycerol was recovered at 99.2% and xylose at 95.9%. Overall, the first loop operation was considered successful. Extract was concentrated to about 43% DS and sent to loop 2.

Pilot test coupled loop (loop 2)

This pilot test was the first attempt at separating the glycerol and xylose from one another on a second loop. Resin: Mitsubishi 530 (sodium form prior to equilibration)

Separator configuration: 8 cells

Solutes loading: 30-35 lbs/ft ³ resin/day

Steptime: 12 minutes

Temperature: 70 C

Feed %DS: 43%

Feed glycerol purity: 85-91%

W/F: 3.5

E/R: 0.4

1171 cycles were run on the pilot system. With glycerol recovery at 97.7% and purity of 97.0, the results of the second loop testing demonstrated that the proposed separator strategy will successfully separate glycerol and separately sugars from biomass pretreatment liquid fractions.

Pilot test at higher xylose concentrations in feed

In final testing, we evaluated the consequences of operating with higher xylose concentrations, ~ 7% on weight. 105 cycles were run on the loop 1 pilot system.

Results continued to be favourable for loop 1.

108 cycles were run on the loop 2 pilot system.

Overall operation using the higher xylose concentration was very good. Considering both loop 1 and loop 2, the overall glycerol recovery from initial SMB feed to product was 96.2 and the overall xylose recovery was 88.3. Final glycerol purity was 97.4 and final xylose purity was 60.9. Loop 2 xylose profile

A five point sample collection of a raffinate profile was evaluated during test 7-b in order to determine if a thin cut could be collected which would provide a very high purity xylose product The results are listed on table 9 (this table also contains a glycerol profile).

The xylose exhibits a more complicated profile than glycerol, and there are some opportunities for taking a cut of this profile - although not necessarily for an extremely high xylose fraction. It appears that the xylose profile could be split into two fractions, one containing about the first 6 minutes and the second containing the last 6 minutes. This may result in a final xylose fraction with about 5 points higher purity. This would also eliminate some leading front contaminants such as colour and salts and some crossover glycerol (note the high glycerol purity at raffinate 0 and 3 minutes. This is due to extract glycerol passing through the water phase to the raffinate).

Summary

A coupled loop SMB system can be configured to separate biomass pretreatment liquid fractions containing glycerol and sugars into high purity products with high recoveries, viz. 97.4% purity, 96.2% recovery glycerol and a 60.9 purity, 88.3 recovery xylose (along with a third non-glycerol/xylose fraction).

If SMB eluent water composition is controlled, for example by using demineralized water, condensate or other cation free water, then the separator can operate long term without the occurrence of pH dependent precipitation.

A 4 cell (rather than 8 cell) separator can be used for loop 1 and this will result in reduced scale-up capital costs. The first loop can be operated at relatively high solutes loading (about 85 lbs solids/ft ³ resin/day). This will result in a smaller, less costly scaled up system.

Profile analysis demonstrated that it may be worthwhile to cut the xylose profile into two fractions in order to raise the xylose purity by about 5 points.

Engineering data collected during this trial is sufficient to design a scaled-up demonstration SMB system based on the alternate separation strategy.

EXAMPLE 3

The present Example describes an exemplary system of the invention. The chromatographic separator is designed to separate biomass pretreatment liquid fractions containing glycerol and sugars into glycerol, xylose and a salt-rich non glycerol / non-xylose waste stream using coupled loop chromatography. This chromatography process is divided into two separation stages (making up the coupled loop). In the first loop, an output stream containing salts and the other non-glycerol / non-xylose components of the feed material is separated from the valuable glycerol and xylose, which are contained in a stream known as upgrade. In the second loop, this upgrade (after concentration by evaporation) is separated into a glycerol-rich extract stream and a xylose-rich raffinate stream.

The coupled loop chromatographic separator described in this Example is designed to process 1.6 metric tons per day of Glycell digester filtrate at a dissolved solids concentration of 50%, with additional quality parameters as specified below. The resin employed to carry out the separation is Mitsubishi UBK 530 chromatography resin, and the total resin inventory of the system is 60 ft ³ .

The first loop separator consists of four resin cells, each one being 13½ inches in diameter, 5 ft high and containing 5 ft ³ of resin. The second loop separator consists of eight resin cells, each one being 13½ inches in diameter, 5 ft high and containing 5 ft ³ of resin.

Coupled Loop Chromatography

Coupled loop chromatography is carried out using two separate but linked SMB chromatographic systems that separate glycerol, xylose and a salt-rich non glycerol / non-xylose waste stream from the Glycell digester filtrate feed material. To achieve this separation, the resin columns are filled with a strong cation exchange resin that is initially in the sodium form.

First Loop

In the first SMB loop, comprising four resin columns, Glycell digester filtrate (feed) is separated into a salt rich non-glycerol / non-xylose waste stream and an “upgrade” stream containing primarily glycerol and xylose. This separation removes the least strongly-adsorbed components from the feed material (namely the inorganic salts, colorants and other large molecules), leaving the separation of the two most- valuable components to be carried out in the second loop.

Operation of the first loop is divided into four equal time steps, with the valve configuration within the system changing sequentially at the start of each time step as shown in Figures 9 to 12.

Second Loop

In the second SMB loop, consisting of eight resin columns, the upgrade stream from the first loop is separated into a glycerol-rich extract stream and a xylose-rich raffinate stream. Operation of the second loop is divided into eight equal time steps, with the valve configuration within the system changing sequentially at the start of each time step. During each time step, the feed and product valves are open at appropriate locations to match the internal concentration profile, as shown in Figure 13 through Figure 20 below for steps 1 through 8, respectively. The first time step refers to the step during which the upgrade feed material entering the system enters the top of the first physical resin column in the series. Subsequent steps are similarly numbered according to the resin column receiving feed of upgrade material from the first loop.

Each second loop step has a typical duration of 12 minutes.

Internal Concentration Profiles

For reference purposes, a typical repeated internal concentration profile for the first loop of the Glycell digester filtrate chromatographic separator is shown in Figure 21. A typical repeated internal concentration profile for the second loop of the separator is shown in Figure 22 and detailed composition data of the glycerol and sugars products are shown in Figure 23.

Feed Materials

Glycell Digester Filtrate

The feed material to the first loop of the chromatographic separator preferably complies with the quality parameters specified in Table 1 below.

Some of the components of the Glycell digester filtrate may change their chromatographic behaviour as a function of pH, depending on factors such as their ionization or dissociation in solution. Changes in pH may also result in the precipitation of some components of the feed, which would contaminate the system with suspended solids. In previous pilot testing, precipitation of suspended solids was observed within the chromatographic system whenever any of the product streams approached or exceeded a pH value of 4. It is thus preferable for efficient operation that the feed material has a relatively stable pH in the range given in Table 1 in order that these components remain in solution. It is important to note that large shifts in feed composition or concentration will cause changes in product quality and difficulty with maintaining effective steady state operation of the separator. To maximize performance and to keep the need for operating parameter changes to a minimum, the dissolved solids concentration and composition of the feed material should be controlled at near-constant conditions.

Concentrated Upgrade

The upgrade stream from the first loop of the separator is concentrated by evaporation and then fed into the second loop of the separator. This upgrade feed material to the second loop should comply with the quality parameters specified in Table 2 below. Material not meeting these minimum requirements should not be accepted for processing in the second loop, as this can have severe consequences in terms of separator operation and performance.

Water

The elution water used in the chromatographic separator preferably complies with the quality parameters specified in Table 3 below.

It should be free of oxidizing agents, foam, oil and microbiological contamination with bacteria, yeasts or moulds. Iron and other heavy metals are resin de-crosslinking catalysts and their presence in the elution water should be avoided. The cation exchange resin in the chromatographic separator is originally supplied in the sodium form and will equilibrate during operation with the various cations present in the feed material, resulting in the resin having a mixed cationic form. However, the presence of significant concentrations of divalent cations (particularly calcium and magnesium) in the eluent water may result in a change in the ionic form of the resin to the divalent form, which is likely to be less effective for the chromatographic separation of the feed material. It is therefore preferable that the water used for chromatographic elution be essentially free of divalent ionic compounds.

The eluent water used in the chromatographic system is typically obtained by recycling the process condensate obtained when concentrating the product fractions from the separator by multiple effect evaporation, and from various heat exchanger condensates. Only softened water (or a factory condensate stream containing no hardness) should be used as make-up for any minor water losses in the system, or to provide replacement water when one of the resin cells is being backwashed.

Products

Based on the design of the Glycell digester filtrate chromatographic separator, the product qualities as described below are expected.

Non-Glycerol / Non-Xylose Waste Stream

The non-glycerol / non-xylose raffinate fraction from the first loop separator is expected to have a typical dissolved solids concentration of 1.2%, with a combined “glycerol + xylose” purity of approximately 17. lg/lOOg DS.

Glycerol-Rich Extract

The extract from the second loop separator is expected to have a dissolved solids content of approximately 30.9%, depending on the separator operating parameters used (particularly the water-to feed ratio and the extract-to-raffmate ratio). The extract glycerol purity is expected to be 97.4g/100g DS, at an overall glycerol recovery across the chromatography system of 98.7%.

Xylose-Rich Raffinate

The dissolved solids content of the raffinate from the second loop separator is expected to be approximately 2.1%, depending on the separator operating parameters used (particularly the water-to feed ratio and the extract-to-raffmate ratio).

Filtration

Filtration of the feed material for the chromatographic separator is necessary to eliminate suspended solids that would plug the resin bed and restrict flow. Depending on the application, suspended solids removal may be carried out by microfiltration, or perhaps by a membrane filter press, along with associated ancillary equipment, such as tanks, filter aid and body feed preparation equipment. Filtration should ensure a maximum suspended content in the filtered liquor of 5 ppm or less, with a maximum particle size of 5 pm. Operation of the filtration system should be carried out according to the instructions of the manufacturer. This filtration step is one of the most critical operations in the entire chromatographic separation plant.

Feed Dilution

After filtration, the Glycell digester filtrate may be diluted using condensate (and sweet water obtained during the sludge dewatering portion of the filtration cycle of the feed filters) to a controlled and uniform dissolved solids concentration of 50% ± 0.5%. Similarly, the concentrated upgrade stream entering the second loop should be controlled to a dissolved solids concentration of 42% ± 0.5%. The accurate control of concentration at this point in the process is preferable in order to ensure the efficient operation of the chromatographic separator. Changing the concentration of the feed to the separator would require different separator operating conditions to achieve efficient operation. Frequent variations in feed concentration outside of the target range will make it difficult to optimize the operation of the separator and lead to sub-standard performance.

The conditioned feed and condensate streams are blended together using a static mixer and the resulting dissolved solids concentration is measured using an inline refractometer, which controls the rate of condensate addition by means of a variable frequency drive on the condensate pump motor. The flow rate of diluted feed to degassing is measured by means of a flow meter.

Water Pretreatment

The water used as an eluent in the chromatographic separator should meet certain quality standards. The primary source of this water is usually recycled condensate from the evaporator stations used to concentrate the chromatographic separator products, from any non-contact final effect condensers in these evaporator stations and from various heat exchangers. However, during normal operation an additional supply of clean process water will be required, to make up for losses (for example, in non-condensable gas venting from the evaporators) and to allow for a continuous purge stream to prevent contamination build-up. This make-up water should be free of suspended solids and hardness (for example, good quality process condensate or water obtained by softening, deionization or reverse osmosis). On start up of the system, an initial supply of condensate from the evaporator stations may not be available. Under these conditions, the elution water supply tank should be filled using a suitable source of make-up water before start-up.

On shutdown, once no further process operations require a source of water, the eluent tank can be emptied. Due to the high quality of this water, it is often possible to divert any excess eluent water into other process water circuits.

Xylose Cut

The second chromatographic loop carries out the separation of the glycerol and xylose originally present in the Glycell digester filtrate feed stream. Although the glycerol product fraction can be obtained at a relatively high level of purity and recovery, the xylose product fraction (due to the low concentration of xylose originally present in the feed) is significantly contaminated with glycerol. Should a slightly higher- purity xylose product be desired, then this could potentially be achieved using a“xylose cut”.

To do this, the final 50% of the dilute xylose product stream leaving the chromatographic separator in each step (on a time-proportional basis) would be separated from the rest of the raffinate stream as the xylose cut. This latter 50% of the raffinate flow would contain material with a xylose purity up to 5% points higher than the average value for the raffinate stream. The initial 50% of the raffinate stream flow (with lower purity) could be recycled for reprocessing through the chromatography system or discarded along with the non-glycerol / non-xylose waste stream from the first loop separator.

It should be noted that the separator (as delivered) does not currently have the discrete control valves installed that would be necessary to separate a xylose cut. These would need to be installed by the customer, after the raffinate flow control valve on Loop 2.