ARYLSULFONIC ACID - MODIFIED SULFURIC ACID AND USES THEREOF

Abstract

An aqueous composition comprising: sulfuric acid; a modifying agent comprising an arylsulfonic acid; and a peroxide. Said composition being capable of delignifying biomass under milder conditions than conditions under which kraft pulping takes place.

Claims

1. An aqueous acidic composition comprising: sulfuric acid; a modifying agent comprising an arylsulfonic acid; a peroxide; and optionally, a compound comprising an amine group.

2. The composition according to claim 1, wherein the sulfuric acid and said arylsulfonic acid are present in a molar ratio ranging from 28:1 to 2:1.

3. The composition according to claim 1, where said arylsulfonic acid has a molecular weight below 300 g/mol.

4. The composition according to claim 1, where said compound comprising an amine group selected from the group consisting of: imidazole; N-methylimidazole; triazole; monoethanolamine; diethanolamine; triethanolamine; pyrrolidine; and combinations thereof.

5. The composition according to claim 1, where said arylsulfonic acid is selected from the group consisting of: toluenesulfonic acid; benzenesulfonic acid; and combinations thereof.

6. The composition according to claim 1, where said arylsulfonic acid is toluenesulfonic acid.

7. An aqueous composition for use in the delignification of wood, wherein said composition comprises: sulfuric acid; a modifying agent comprising an arylsulfonic acid; and a peroxide. wherein the sulfuric acid and the arylsulfonic acid are present in a mole ratio ranging from 2:1 to 28:1.

8. An aqueous composition for use in the processing and depolymerisation of cellulose from a plant source, wherein said composition comprises: sulfuric acid present in an amount ranging from 20-80 wt % of the total weight of the composition; a modifying agent comprising an arylsulfonic acid; and a peroxide; wherein the sulfuric acid and the arylsulfonic acid are present in a molar ratio ranging from 2:1 to 28:1.

9. The composition according to claim 8, where the peroxide is hydrogen peroxide.

10. 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 comprising an arylsulfonic acid; 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 said lignocellulosic feedstock; optionally, removing a liquid phase comprising dissolved lignin fragments from a solid phase comprising cellulose fibres.

11. The process according to claim 10, wherein said acid is sulfuric acid.

12. The process according to claim 10, wherein said peroxide is hydrogen peroxide.

13. The process according to claim 10, wherein the period of time is sufficient to remove at least 90% of the lignin present on said plant material.

14. The process according to claim 10, wherein the period of time is sufficient to remove at least 95% of the lignin present on said plant material.

15. The process according to claim 10, wherein the temperature of the composition prior to the step of exposing it to the lignocellulosic feedstock is below 50° C.

16. The process according to claim 10, wherein said process is carried out at ambient temperature.

17. The process according to claim 10, wherein said process is carried out at ambient pressure.

18. The process according to claim 10, wherein said arylsulfonic acid is selected from the group consisting of: orthanilic acid; metanilic acid; sulfanilic acid; toluenesulfonic acid; benzenesulfonic acid; and combinations thereof.

19. The process according to claim 10, where said, said arylsulfonic acid is toluenesulfonic acid.

20. The process according to claim 10, wherein sulfuric acid and said arylsulfonic acid are present in a molar ratio ranging from 28:1: to 2:1.

Description

DESCRIPTION OF THE INVENTION

[0061] The experiments carried out using an aqueous acidic composition according to a preferred embodiment of the present invention as shown that wood chips can undergo delignification under controlled reaction conditions and eliminate or at least minimize the degradation of the cellulose. Degradation is understood to mean a darkening of cellulose, which is symbolic of an uncontrolled acid attack on the cellulose and staining thereof.

[0062] The arylsulfonic acid together in the presence of sulfuric acid and the peroxide component, seems to generate a coordination of the compounds which acts as a modified sulfuric acid. In that respect, it is believed that the presence of the arylsulfonic acid forms an adduct with the sulfuric acid to generate a modified sulfuric acid. The strength of the modified acid is dictated by the moles of sulfuric acid to the moles of the arylsulfonic acid. Hence, a composition comprising a molar ratio of 6:1 of sulfuric acid: the arylsulfonic acid would be much less reactive than a composition of the same components in a 28:1 molar ratio.

[0063] 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 0° C. According to a preferred embodiment of the present invention, the delignification of wood can be performed at temperatures as low as 10° 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 health, safety and environment (“HSE”) advantages compared to conventional kraft pulping compositions.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

Experiment #1—Preparation of a Stable Sulfuric Acid-Peroxide-TSA Composition

[0068] Experiments were carried out to mix sulfuric acid with TSA and hydrogen peroxide. The inventors have surprisingly discovered that the order of the addition of the components is important since, if the components are not mixed in the proper order, the resulting composition will not be stable as there will be a spontaneous decomposition reaction which will occur upon the addition of peroxide to the acidic mixture.

[0069] To prepare a stable modified acid composition comprising sulfuric acid and an arylsulfonic acid, such as TSA, and peroxide, one must first combine the sulfuric acid with the peroxide source and thoroughly mix them together. Once that is completed, one can then add an arylsulfonic acid, such as TSA to the mixture and thus generate a TSA-modified sulfuric acid and peroxide composition.

[0070] The person skilled in the art will understand that the term ‘stability’ or ‘stable’ when associated with a composition comprising sulfuric acid, a peroxide and an arylsulfonic acid means that the composition does not readily degrade upon the addition of the arylsulfonic acid compound to a mixture comprising sulfuric acid and a peroxide. Preferably, the term stable or stability when associated with such a preferred composition means that the composition will retain a substantial part of its acidic character without degrading for a period of at least 24 hours. More preferably, the term stable or stability when associated with such a preferred composition means that the composition will retain a substantial part of its acidic character without degrading for a period of at least 48 hours. Even more preferably, the term stable or stability when associated with such a preferred composition means that the composition will retain a substantial part of its acidic character without degrading for a period of at least 72 hours.

[0071] For the H.sub.2SO.sub.4:H.sub.2O.sub.2:TSA blend with a 5:5:1 molar ratio, 54.0 g of a hydrogen peroxide solution in water (29%) was slowly added to 48.5 g of concentrated sulfuric acid (93%). As the mixing releases a large amount of heat the beaker was placed in an ice bath. Then, 17.5 g TSA was added to the mixture.

[0072] When TSA is added to the sulfuric acid before the addition of the peroxide solution, the mixture turns brown and starts to boil rapidly. TSA is not stable in concentrated sulfuric acid. The acid therefore needs to be “diluted” with hydrogen peroxide solution before adding TSA. The pH of the resulting composition was less than 1.

Delignification Experiments

[0073] After mixing, the resulting composition is split into 4 equal parts. One part was exposed to 1.5 g of wood shavings, another part was exposed to commercially available lignin and another part was exposed to commercially available cellulose respectively and stirred at ambient conditions for 3 hours. The fourth part of the blend is kept as a blend reference sample.

[0074] Control tests were run for the respective mixtures with just kraft lignin or just cellulose added instead of biomass. Commercially available lignin (Sigma-Aldrich; Lignin, kraft; Prod#471003) was used as a control in the testing. Commercially available cellulose (Sigma-Aldrich; Cellulose, fibers (medium); Prod#C6288) was also used as a control in the testing.

[0075] The solid phase of each blend was filtered off after 3 h of reaction time, rinsed with water and dried in an oven at 45° C. to constant weight. An effective blend should dissolve all lignin and leave the cellulose as intact as possible. The results of the experiments are reported in Table 1 below.

TABLE-US-00001 TABLE 1 Recovery of solids (% of initial mass) after 3 h reaction time Molar Wood Lignin Cellulose Ratio Chemical Yield (%) Yield (%) Yield (%) 5:5:1 H.sub.2SO.sub.4:H.sub.2O.sub.2:TSA 37.65% 0.00% 91.69% 10:10:1 H.sub.2SO.sub.4:H.sub.2O.sub.2:TSA 37.55% 0.00% 90.35% 20:20:1 H.sub.2SO.sub.4:H.sub.2O.sub.2:TSA 41.58% 0.00% 92.46% 10:10:1:1 H.sub.2SO.sub.4:H.sub.2O.sub.2: 42.61% 0.00% 88.68% imidazole:TSA 10:10:1:1 H.sub.2SO.sub.4:H.sub.2O.sub.2: 55.33% 0.00% 86.11% triethanolamine:TSA 10:10:1 H.sub.2SO.sub.4:H.sub.2O.sub.2: 41.69% 0.00% 94.10% benzenesulfonic acid

[0076] A blend with a ratio of 10:10:1 of sulfuric acid (93% conc. used) to peroxide (as 29% solution) to TSA resulted in a mass recovery of a little over 37% from wood and roughly 90% for the cellulose control. A blend with a ratio of 10:10:1:1 of sulfuric acid (93% conc. used) to peroxide (as 29% solution) to imidazole to TSA resulted in a mass recovery of a little over 42% from wood and roughly 89% for the cellulose control. This shows that the acid/peroxide mixture is well controlled with either TSA alone or TSA in combination with a compound containing an amine group. In all cases, the lignin control indicated a complete destruction of lignin, which is the desired result.

[0077] The above experiment is a clear indication that a preferred composition according to the present invention not only provides an adequate dissolving acid to delignify plant material but is also valuable in controlling the ultimate degradation of cellulosic material into carbon black residue resulting in higher yields potentially for the operators thus increasing profitability while reducing emissions and the risk to the employees, contractors and public.

[0078] Additional testing was carried out to confirm the above initial results and to explore the feasibility of using other ratios or other compounds with similar chemical features or characteristics as modifying agent or as combination of compounds acting as modifying agent according to a preferred embodiment of the present invention. The results of the experiments are set out below in Tables 2 to 14.

TABLE-US-00002 TABLE 2 Recovery of solids (% of initial mass) after 3 h reaction time using benzenesulfonic acid (BSA) as modifying agent Molar Wood Lignin Cellulose Ratio Chemical Yield (%) Yield (%) Yield (%) 10:10:1 H.sub.2SO.sub.4:H.sub.2O.sub.2: 41.7% 0% 94.1% benzensulfonic acid

TABLE-US-00003 TABLE 3 Recovery of solids (% of initial mass) after 3 h reaction time using toluenesulfonic acid as modifying agent Molar Wood Lignin Cellulose Ratio Chemicals Yield (%) Yield (%) Yield (%) 5:5:1 H.sub.2SO.sub.4:H.sub.2O.sub.2: 37.7 0% 91.7% toluenesulfonic acid 10:10:1 H.sub.2SO.sub.4:H.sub.2O.sub.2:    37.5% 0% 90.3% toluenesulfonic acid 20:20:1 H.sub.2SO.sub.4:H.sub.2O.sub.2: 41.6 0% 92.5% toluenesulfonic acid

TABLE-US-00004 TABLE 4 Recovery of solids (% of initial mass) after 3 h reaction time using imidazole-TSA acid as modifying agent Molar Wood Lignin Cellulose Ratio Chemicals Yield (%) Yield (%) Yield (%) 10:10:1:1 H.sub.2SO.sub.4:H.sub.2O.sub.2: 42.6% 0% 88.1% imidazole-TSA

TABLE-US-00005 TABLE 5 Recovery of solids (% of initial mass) after 3 h reaction time using TEOA-TSA acid as modifying agent Molar Wood Lignin Cellulose Ratio Chemicals Yield (%) Yield (%) Yield (%) 10:10:1:1 H.sub.2SO.sub.4:H.sub.2O.sub.2:TEOA-TSA 55.3% 0% 86.1%

TABLE-US-00006 TABLE 6 Recovery of solids (% of initial mass) after 3 h reaction time using MEOA-TSA acidas modifying agent Molar Wood Lignin Cellulose Ratio Chemicals Yield (%) Yield (%) Yield (%) 10:10:1:1 H.sub.2SO.sub.4:H.sub.2O.sub.2:MEOA-TSA 39.4% 0% 97.8%

TABLE-US-00007 TABLE 7 Recovery of solids (% of initial mass) after 3 h reaction time using DEOA-TSA acid as modifying agent Molar Wood Lignin Cellulose Ratio Chemicals Yield (%) Yield (%) Yield (%) 10:10:1:1 H.sub.2SO.sub.4:H.sub.2O.sub.2:DEOA-TSA 42.7% 0% 98.2%

TABLE-US-00008 TABLE 8 Recovery of solids (% of initial mass) after 3 h reaction time using N-Methylimidazole-TSA acid as modifying agent Molar Wood Lignin Cellulose Ratio Chemicals Yield (%) Yield (%) Yield (%) 10:10:1:1 H.sub.2SO.sub.4:H.sub.2O.sub.2: 47.6% 0% 100% N-methylimidazole:TSA

TABLE-US-00009 TABLE 9 Recovery of solids (% of initial mass) after 3 h reaction time using pyrrolidine-TSA acid as modifying agent Molar Wood Lignin Cellulose Ratio Chemicals Yield (%) Yield (%) Yield (%) 10:10:1:1 H.sub.2SO.sub.4:H.sub.2O.sub.2:pyrrolidineTSA 38.0% 0% 98.6%

TABLE-US-00010 TABLE 10 Recovery of solids (% of initial mass) after 3 h reaction time using MEOA-BSA acid as modifying agent Molar Wood Lignin Cellulose Ratio Chemicals Yield (%) Yield (%) Yield (%) 10:10:1:1 H.sub.2SO.sub.4:H.sub.2O.sub.2:MEOA-BSA 44.7% 0% 99.6%

TABLE-US-00011 TABLE 11 Recovery of solids (% of initial mass) after 3 h reaction time using DEOA-BSA acid as modifying agent Molar Wood Lignin Cellulose Ratio Chemicals Yield (%) Yield (%) Yield (%) 10:10:1:1 H.sub.2SO.sub.4:H.sub.2O.sub.2:DEOA-BSA 45.72% 0% 95.18%

TABLE-US-00012 TABLE 12 Recovery of solids (% of initial mass) after 3 h reaction time using imidazole-BSA acid as modifying agent Molar Wood Lignin Cellulose Ratio Chemicals Yield (%) Yield (%) Yield (%) 10:10:1:1 H.sub.2SO.sub.4:H.sub.2O.sub.2:imidazole-BSA 42.5% 0% 96.5%

TABLE-US-00013 TABLE 13 Recovery of solids (% of initial mass) after 3 h reaction time using N-Methylimidazole-BSA acid as modifying agent Molar Wood Lignin Cellulose Ratio Chemicals Yield (%) Yield (%) Yield (%) 10:10:1:1 H.sub.2SO.sub.4:H.sub.2O.sub.2: 45.6% 0% 96.8% N-methylimidazole-BSA

TABLE-US-00014 TABLE 14 Recovery of solids (% of initial mass) after 3 h reaction time using pyrrolidine-BSA acid as modifying agent Molar Wood Lignin Cellulose Ratio Chemicals Yield (%) Yield (%) Yield (%) 10:10:1:1 H.sub.2SO.sub.4:H.sub.2O.sub.2: 45.8% 0% 96.6% pyrrolidine-BSA

[0079] A method to yield glucose from wood pulp would represent a significant advancement to the current process where the conversion of such is chemical and energy intensive, costly, emissions intensive and dangerous all while not resulting in highly efficient results, especially in large-scale operations. It is desirable to employ a composition which may delignify wood but also allows the operator some control in order to preserve the cellulose rather than degrading it to carbon black resulting in higher efficiencies and yields along with increased safety and reduced overall costs.

[0080] According to a preferred embodiment of the method of the present invention, the separation of lignin can be effected and the resulting cellulose fibers can be further processed to yield glucose monomers. Glucose chemistry has a multitude of uses including as a starting block in the preparation of widely used chemicals including but not limited to diacetonide, dithioacetal, glucoside, glucal and hydroxyglucal to name but a few.

[0081] According to another preferred embodiment of the present invention, the composition can be used to decompose organic material by oxidation such as those used in water treatment, water purification and/or water desalination. An example of this is the removal (i.e. destruction) of algae on filtration membranes. As such membranes can be quite expensive, it is imperative that they be used for as long as possible. However, given the difficulty to remove organic matter which accumulates on it over time, new approaches are necessary to do so efficiently and with as little damage to the membrane as possible. Mineral acids are too strong and, while they will remove the organic matter, will damage the filtration membranes. A preferred composition of the present invention remedies this issue as it is less aggressive than the mineral acids and, as such, will remove the organic contaminants in a much milder approach, therefore sparing the membrane.

[0082] While the foregoing invention has been described in some detail for purposes of clarity and understanding, it will be appreciated by those skilled in the relevant arts, once they have been made familiar with this disclosure that various changes in form and detail can be made without departing from the true scope of the invention in the appended claims.