Use of a 2 liquid phase system in biomass delignification

Abstract

Method for controlled delignification of lignocellulosic feedstock, said method comprising the steps of: providing a reactive phase of pH less than 1, said reactive phase comprising: water; sulfuric acid; a source of peroxide; a modifying agent, said modifying agent adapted to control the reactivity of the sulfuric acid; providing a holding phase, said holding phase comprising an organic solvent which does not react with the aqueous acidic composition; combining said reactive phase and holding phase to form a reaction mixture; exposing a lignocellulosic material to said reaction mixture for a period of time sufficient to allow delignification of the lignocellulosic material.

Claims

1. A method for controlled delignification of lignocellulosic feedstock, said method comprising the steps of: providing a reactive phase of pH less than 1, said reactive phase comprising: water; sulfuric acid; a source of peroxide; a modifying agent, said modifying agent adapted to control the reactivity of the sulfuric acid; providing a holding phase, said holding phase comprising an organic solvent which does not react with the aqueous acidic composition; combining said reactive phase and holding phase to form a reaction mixture; exposing a lignocellulosic material to said reaction mixture for a period of time sufficient to allow delignification of the lignocellulosic material.

2. The method according to claim 1 where the reactive phase and the holding phase are present in a weight ratio ranging from 2:1 to 1:2.

3. The method according to claim 1 where the reactive phase and the holding phase are present in a weight ratio ranging from 1.5:1 to 1:1.5.

4. The method according to claim 1 where the holding phase comprises a solvent selected from the group consisting of: ethyl acetate; propyl acetate; butyl acetate; and combinations thereof.

5. The method according to claim 1 where the sulfuric acid and the source of peroxide are present in a molar ratio ranging from 3:1 to 1:3.

6. The method according to claim 1 where the sulfuric acid and the modifying agent are present in a molar ratio ranging from 10:1 to 1:10.

7. The method according to claim 1 where the sulfuric acid and the modifying agent are present in a molar ratio ranging from 3:1 to 1:3.

8. The method according to claim 1 where the modifying agent is selected from the group consisting of: imidazole; n-alkylimidazole; taurine; a taurine derivative; a taurine-related compound; alkylsulfonic acid; aryl sulfonic acid; triethanolamine; and combinations thereof.

9. The method according to claim 8 where the taurine derivative or taurine-related compound is selected from the group consisting of: sulfamic acid; taurolidine; taurocholic acid; tauroselcholic acid; tauromustine; 5-taurinomethyluridine and 5-taurinomethyl-2-thiouridine; homotaurine (tramiprosate); acamprosate; and taurates.

10. The method according to claim 1 where the period of time sufficient to remove at least 80% of the lignin present on said plant material.

11. The method according to claim 1, wherein the amount of lignin removed is more than 90%.

12. A one-pot process to separate lignin from a lignocellulosic feedstock, said process comprising the steps of: providing a vessel; providing said lignocellulosic feedstock; providing a composition comprising; an acid; a modifying agent; and a peroxide; exposing said lignocellulosic feedstock to said composition in said vessel for a period of time sufficient to remove at least 80% of the lignin present in said lignocellulosic feedstock; optionally, removing a liquid phase comprising dissolved lignin fragments from a solid phase comprising cellulose fibres.

13. The process according to claim 12, wherein the modifying agent selected from the group consisting of: sulfamic acid; imidazole; n-alkylimidazole; taurine; a taurine derivative; a taurine-related compound; alkylsulfonic acid; aryl sulfonic acid; triethanolamine; and combinations thereof.

14. The process according to claim 13, wherein the alkylsulfonic acid is selected from the group consisting of: methanesulfonic acid; ethanesulfonic acid; propanesulfonic acid and combinations thereof.

15. The process according to claim 13, wherein the aryl sulfonic acid is selected from the group consisting of: toluenesulfonic acid; benzenesulfonic acid; and combinations thereof.

16. The process according to claim 12, wherein the initial temperature of the composition prior to the step of exposing it to the lignocellulosic feedstock is below 50° C.

17. The method according to claim 12, wherein the period of time is sufficient to remove at least 90% of the lignin present on said plant material.

18. A one-pot process to separate lignin from a lignocellulosic feedstock, said process comprising the steps of: providing a vessel; providing said lignocellulosic feedstock; providing a composition comprising; an acid; a modifying agent; a peroxide; exposing said lignocellulosic feedstock to said composition in said vessel creating a reaction mixture, wherein the exposure is done for a period of time sufficient to remove at least 80% of the lignin present said lignocellulosic feedstock; exposing the reaction mixture to a water immiscible solvent; separating a liquid phase comprising: said water immiscible solvent; and dissolved lignin fragments; from a solid phase comprising cellulose fibres.

19. The one-pot process according to claim 18, wherein the water immiscible solvent is selected from the group consisting of: ethyl acetate; propyl acetate; butyl acetate; and combinations thereof.

20. The one-pot process according to claim 18, wherein the water immiscible solvent is selected from the group consisting of: xylene; hexane; toluene and combinations thereof.

Description

DESCRIPTION OF THE INVENTION

(1) The experiments carried out using an aqueous acidic composition according to a preferred embodiment of the present invention have shown that various lignocellulosic biomass components (such as wood chips, straw, alfalfa, etc.) can undergo delignification under controlled reaction conditions and eliminate or at least minimize the degradation and/or depolymerization of the cellulose as well as provide lignin depolymerization products which are soluble (i.e. separated from cellulose). Degradation is understood to mean a darkening of cellulose, which is symbolic of an uncontrolled acid attack on the cellulose and staining thereof.

(2) In the disclosed methods and compositions, biomass is used and/or fractioned. The term “biomass,” or “lignocellulosic biomass” as used herein, refers to living or dead biological material that can be used in one or more of the disclosed processes. Biomass can comprise any cellulosic or lignocellulosic material and includes materials comprising cellulose, and optionally further comprising hemicellulose, lignin, starch, oligosaccharides and/or monosaccharides, biopolymers, natural derivatives of biopolymers, their mixtures, and breakdown products (e.g., metabolites). Biomass can also comprise additional components, such as protein and/or lipids. Biomass can be derived from a single source, or biomass can comprise a mixture derived from more than one source. Some specific examples of biomass include, but are not limited to, bioenergy crops, agricultural residues, municipal solid waste, industrial solid waste, sludge from paper manufacture, yard waste, wood and forestry waste. Additional examples of biomass include, but are not limited to, corn grain, corn cobs, crop residues such as corn husks, alfalfa, corn stover, grasses, wheat, wheat straw, hay, rice straw, switchgrass, waste paper, sugar cane bagasse, sorghum, soy, components obtained from milling of grains, trees (e.g., pine), branches, roots, leaves, wood chips, wood pulp, sawdust, shrubs and bushes, vegetables, fruits, flowers, animal manure, multi-component feed, and crustacean biomass (i.e., chitinous biomass).

EXAMPLES

(3) The composition according to a preferred embodiment of the present invention used in the delignification test was prepared by preparing a modified acid comprising taurine and sulfuric acid. This modified acid was prepared by dissolving 1 molar equivalent of taurine into sulfuric acid and subsequently adding hydrogen peroxide.

(4) Carrying out delignification of lignocellulosic biomass using a method according to a preferred embodiment of the present invention provides for several advantages, including but not limited to: increase in the rates of reaction by shifting the equilibrium chemical reaction towards the product side; reducing the overall process time; and allow “on-the-fly” separation of potential products which are not water-soluble but which are soluble in an organic solvent. Additional advantages of the present invention will be set forth in part in the description that follows, and in part will be obvious from the description, or can be learned by practice of the aspects described below. The advantages described below will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive.

(5) According to a preferred embodiment of the method of the present invention, a composition comprising sulfuric acid:taurine:hydrogen peroxide in a 5.0:1.0:1.0 molar ratio is used. The resulting pH of the composition is less than 1. Preferably, the resulting pH of the composition was less than 0.5. A range of compositions with the same components were prepared and the delignification testing carried out on those compositions are reported in Tables 1-8.

(6) The compositions were clear and odorless with densities ranging between 1.1 and 1.8 g/cm.sup.3.

(7) When performing delignification of wood using a composition according to a preferred embodiment of the present invention, the process can be carried out at substantially lower temperatures than temperatures used in the conventional kraft pulping process. The advantages are substantial, here are a few: the kraft pulping process requires temperatures in the vicinity of 176-180° C. in order to perform the delignification process, a preferred embodiment of the process according to the present invention can delignify wood at far lower temperatures, even as low as 20° C. According to a preferred embodiment of the present invention, the delignification of wood can be performed at temperatures as low as 30° C. According to another preferred embodiment of the present invention, the delignification of wood can be performed at temperatures as low as 40° C. According to yet another preferred embodiment of the present invention, the delignification of wood can be performed at temperatures as low as 50° C. According to yet another preferred embodiment of the present invention, the delignification of wood can be performed at temperatures as low as 60° C. Other advantages include: a lower input of energy; reduction of emissions and reduced capital expenditures; reduced maintenance; lower shut down/turn around costs; also, there are HSE advantages compared to conventional kraft pulping compositions.

(8) In each one of the above preferred embodiments, the temperature at which the processes are carried out are substantially lower than the current energy-intensive kraft process.

(9) Moreover, the kraft process uses high pressures to perform the delignification of wood which is initially capital intensive, dangerous, expensive to maintain and has high associated turn-around costs. According to a preferred embodiment of the present invention, the delignification of wood can be performed at atmospheric pressure. This, in turn, circumvents the need for highly specialized and expensive industrial equipment such as pressure vessels/digestors. It also allows the implementation of delignification units in many of parts of the world where the implementation of a kraft plant would previously be impracticable due to a variety of reasons.

(10) Some of the advantages of a process according to a preferred embodiment of the present invention, over a conventional kraft process are substantial as the heat/energy requirement for the latter is not only a great source of pollution but is, in large part, the reason the resulting pulp product is so expensive and has high initial capital requirements. The energy savings in the implementation of a process according to a preferred embodiment of the present invention would be reflected in a lower priced pulp and environmental benefits which would have both an immediate impact and a long-lasting multi-generational benefit for all.

(11) Further cost savings in the full or partial implementation of a process according to a preferred embodiment of the present invention, can be found in the absence or minimization of restrictive regulations for the operation of a high temperature and high-pressure pulp digestors.

(12) A 2 immiscible liquids phase system can increase reaction rates when compounds are exposed to two non-miscible solvents that retain the feed material and reaction products differentially. For these biomass reactions, an aqueous “reaction phase” is used to hold all of the initial components and the feedstock, which in this case pertains to the plant biomass and the acid/peroxide mixture.

(13) Once the degradation reaction has started, the products are gradually transferred into the non-reactive “holding phase”. Preferably, vigorous agitation is used to increase contact between the two phases and so to maximize transfer of reaction products that are soluble in the holding phase. Removing reaction products “on the fly” during the reaction can reduce the overall processing time as potential equilibrium reactions are pushed towards the product side. The plant biomass is not soluble in either of the liquid phases and residuals can be filtered off at the end of the reaction process.

Experiments

(14) Experiments were carried out using various organic solvents to determine whether the delignification reaction could be improved by having a 2-phase system which would allow dissolved lignin fragments to migrate into an organic (holding) phase and allow to push the reaction in the aqueous phase towards increased delignification or faster delignification.

(15) Several solvents were selected to provide a holding phase for dissolved lignin fragments. Among the solvents analyzed, there was toluene, ethyl acetate, octanoic acid; iso-octane, hexanoic acid and nitrobenzene. Experiments involving the latter two solvents could not be completed as there was a reaction occurring between the acidic composition and the organic solvent which contaminated the reaction medium.

(16) The experiments with the remaining solvents were carried out at room temperature under atmospheric pressure. The duration of the experiments was scheduled to be around 3 hours. The goal of the experiments was to assess the viability of each solvent to be part of a 2-phase system with an aqueous acid medium.

(17) The first set of experiments carried out was a control where there was no organic phase present in the reaction vessel. Hence, this control would allow to determine the increase in efficiency (if any) by using an approach according to the present invention. Each composition was exposed to a wood sample, a lignin control and a cellulose control.

(18) Commercially available lignin (Sigma-Aldrich; Lignin, kraft; Prod #471003) was also used as a control in the testing.

(19) Commercially available cellulose (Sigma-Aldrich; Cellulose, fibres (medium); Prod #C6288) was also used as a control in the testing.

(20) The use of lignin and cellulose controls allow the determination of the extent of reaction of the composition when exposed to a lignocellulosic material, in this case, wood shavings. This allows one to assess whether the composition tested is too reactive against cellulose or not sufficiently reactive enough to dissolve all of the pure lignin control.

(21) Table 1 displays the results of a series of 3 control experiments where there are varying ratios of sulfuric acid, hydrogen peroxide and modifying agent (taurine).

(22) TABLE-US-00001 TABLE 1 Control Experiments of delignification of lignocellulosic feedstock using sulfuric acid, hydrogen peroxide and a modifying agent in various ratios at room temperature and atmospheric pressure No organic solvent Blend recovery [mass %] H.sub.2SO.sub.4 H.sub.2O.sub.2 Taurine (moles) wood lignin cellulose 1 3 0 1:3:0 78.07% 48.12% 89.47% 2 6 1 2:6:1 84.12% 51.17% 94.87% 3 9 1 3:9:1 83.76% 53.75% 92.82%

(23) Table 2 displays the results of a series of 3 experiments where there are varying ratios of sulfuric acid, hydrogen peroxide and modifying agent (taurine) and where there is toluene present as a holding phase (organic solvent).

(24) TABLE-US-00002 TABLE 2 Experiments of delignification of lignocellulosic feedstock using an aqueous composition of sulfuric acid, hydrogen peroxide and a modifying agent in various ratios in a 2-phase system comprising toluene as holding phase solvent at room temperature and atmospheric pressure 1:1 wt:wt Aq:toluene Blend recovery [mass %] H.sub.2SO.sub.4 H.sub.2O.sub.2 Taurine (moles) wood lignin cellulose 1 3 0 1:3:0 78.06% 52.31% 90.41% 2 6 1 2:6:1 87.16% 57.5% 90.65% 3 9 1 3:9:1 76.32% 50.83% 91.4% 10 10 1 10:10:1 51.51% 16.47% 93.7%

(25) When toluene was utilized as the holding phase, the reaction rate increases markedly, potentially due to the formation of toluenesulfonic acid. The toluene does not indicate a discernable change in color, however the bleaching effect of the system is rapid. It takes less than 24 hours to fully bleach a wood shavings sample. In the above instances, the experiments were terminated after less than 3 hours.

(26) Table 3 displays the results of a series of 3 experiments where there are varying ratios of sulfuric acid, hydrogen peroxide and modifying agent (taurine) and where there is ethyl acetate present as a holding phase (organic solvent).

(27) TABLE-US-00003 TABLE 3 Experiments of delignification of lignocellulosic feedstock using an aqueous composition of sulfuric acid, hydrogen peroxide and a modifying agent in various ratios in a 2-phase system comprising Ethyl acetate as holding phase solvent at room temperature and atmospheric pressure 1:1 wt:wt Aq:EtOAc Blend recovery [mass %] H.sub.2SO.sub.4 H.sub.2O.sub.2 Taurine (moles) wood lignin cellulose 1 3 0 1:3:0 81.71% 0.00% 86.44% 2 6 1 2:6:1 87.17% 0.00% 93.33% 3 9 1 3:9:1 83.89% 0.00% 93.02%

(28) Table 4 displays the results of a series of 3 experiments where there are varying ratios of sulfuric acid, hydrogen peroxide and modifying agent (taurine) and where octanoic acid is present as a holding phase (organic solvent).

(29) TABLE-US-00004 TABLE 4 Experiments of delignification of lignocellulosic feedstock using an aqueous composition of sulfuric acid, hydrogen peroxide and a modifying agent in various ratios in a 2-phase system comprising octanoic acid as holding phase solvent at room temperature and atmospheric pressure 1:1 wt:wt Aq:Octanoic acid Blend recovery [mass %] H.sub.2SO.sub.4 H.sub.2O.sub.2 Taurine (moles) Wood lignin cellulose 1 3 0 1:3:0 81% 81% 136% 2 6 1 2:6:1 95% 66% 112% 3 9 1 3:9:1 87% 39%  88%

(30) Table 5 displays the results of a series of 4 experiments where there are varying ratios of sulfuric acid, hydrogen peroxide and modifying agent (taurine) and where iso-octane is present as a holding phase (organic solvent). It is to be noted that i-Octane has almost the same boiling point as water (99.3° C.) but is not miscible with it (easy decanting separation). It is a good organic, inert solvent and is widely used in GCMS analysis. It is also readily available.

(31) TABLE-US-00005 TABLE 5 Experiments of delignification of lignocellulosic feedstock using an aqueous composition of sulfuric acid, hydrogen peroxide and a modifying agent in various ratios in a 2-phase system comprising iso-octane as holding phase solvent at room temperature and atmospheric pressure 1:1 wt:wt Aq:Iso-octane Blend recovery [mass %] H.sub.2SO.sub.4 H.sub.2O.sub.2 Taurine (moles) wood lignin cellulose 1 3 0 1:3:0 70% 51% 92% 2 6 1 2:6:1 92% 63% 112%  3 9 1 3:9:1 70% 41% 93% 10 10 1 10:10:1 47.69%   31.73%   99.02%  

(32) When ethyl acetate is used as the holding phase the reaction rate does not increase as much, but the holding phase seems to take up more colored products than other hydrocarbons tested.

(33) Table 6 displays the results of a series of 3 experiments where there are varying ratios of sulfuric acid, hydrogen peroxide and modifying agent (taurine) and where xylene is present as a holding phase (organic solvent).

(34) TABLE-US-00006 TABLE 6 Experiments of delignification of lignocellulosic feedstock using an aqueous composition of sulfuric acid, hydrogen peroxide and a modifying agent in various ratios in a 2-phase system comprising xylene as holding phase solvent at room temperature and atmospheric pressure 1:1 wt:wt Aq:xylene Blend recovery [mass %] H.sub.2SO.sub.4 H.sub.2O.sub.2 Taurine (moles) wood lignin cellulose 2 6 1 2:6:1 85.0% 57.7% 99.2% 3 9 1 3:9:1 65.2% 59.7% 99.9% 10 10 1 10:10:1 52.17% 10.79% 93.7%

(35) Table 7 displays the results of a series of 3 experiments where there are varying ratios of sulfuric acid, hydrogen peroxide and modifying agent (taurine) and where hexane is present as a holding phase (organic solvent).

(36) TABLE-US-00007 TABLE 7 Experiments of delignification of lignocellulosic feedstock using an aqueous composition of sulfuric acid, hydrogen peroxide and a modifying agent in various ratios in a 2-phase system comprising hexane as holding phase solvent at room temperature and atmospheric pressure 1:1 wt:wt Aq:hexane Blend recovery [mass %] H.sub.2SO.sub.4 H.sub.2O.sub.2 Taurine (moles) wood lignin cellulose 2 6 1 2:6:1 79.8% 60.8% 99.2% 3 9 1 3:9:1 .sup. 71% 58.9% 99.6% 10 10 1 10:10:1 50.01%  7.36% 96.37%

(37) Table 8 displays the results of an experiment where sulfuric acid, hydrogen peroxide and a modifying agent (taurine) are used in the presence of HT-40 (holding phase—organic solvent).

(38) TABLE-US-00008 TABLE 8 Experiments of delignification of lignocellulosic feedstock using an aqueous composition of sulfuric acid, hydrogen peroxide and a modifying agent in various ratios in a 2-phase system comprising HT-40 as holding phase solvent at room temperature and atmospheric pressure 1:1 wt:wt Aq:HT-40 Blend recovery [mass %] H.sub.2SO.sub.4 H.sub.2O.sub.2 Taurine (moles) wood lignin cellulose 10 10 1 10:10:1 63.1% 51.3% 97.4%

(39) Preferably, the second phase should be large enough to hold as much as possible reaction product. According to a preferred embodiment, the holding phase, made up of a hydrophobic fluid, should have a volume having of at least half the volume of the reaction phase and up to a maximum of twice volume of the reaction phase.

(40) According to a preferred embodiment, the reaction phase comprises a mineral acid and a source of peroxide.

(41) According to another preferred embodiment, the reaction phase comprises a modified mineral acid and a source of peroxide. The modified acid is created by combining a mineral acid such as sulfuric acid with a compound comprising an amine moiety and a sulfonic acid moiety selected from the group consisting of: taurine and derivatives thereof such as taurine-related compounds; wherein the sulfuric acid and said amine-containing compound are present in a mole ratio ranging from 3:1 to 100:1. More preferably, the sulfuric acid and said amine-containing compound are present in a mole ratio ranging from 5:1 to 50:1. Even more preferably, the sulfuric acid and said amine-containing compound are present in a mole ratio ranging from 5:1 to 10:1.

(42) Preferably, the modifying agent selected from the group consisting of: imidazole; n-alkylimidazole; taurine; a taurine derivative; a taurine-related compound; alkylsulfonic acid; aryl sulfonic acid; triethanolamine; and combinations thereof. Preferably, the alkylsulfonic acid is selected from the group consisting of: methanesulfonic acid; ethanesulfonic acid; sulfamic acid and combinations thereof. Preferably, the aryl sulfonic acid is selected from the group consisting of: toluenesulfonic acid; benzenesulfonic acid; and combinations thereof. Preferably, said taurine derivative or taurine-related compound is selected from the group consisting of: taurolidine; taurocholic acid; tauroselcholic acid; tauromustine; 5-taurinomethyluridine and 5-taurinomethyl-2-thiouridine; homotaurine (tramiprosate); acamprosate; and taurates.

(43) Dermal Corrosiveness Testing

(44) The modified acid+peroxide composition was compared to a conventional acid+peroxide composition to assess the immediate dermal corrosiveness. The modified acid composition (with peroxide) provided substantial protection to dermal tissue when compared to the conventional acid composition (with peroxide). This substantiates the additional safety of this type of modified acid in combination with a peroxide compared to an acid without a modifier present.

(45) The embodiments described herein are to be understood to be exemplary and numerous modification and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the claims appended hereto, the invention may be practiced otherwise than as specifically disclosed herein.