MANUFACTURE OF DISSOLVING PULP GRADE CELLULOSE

Description

FIELD OF THE INVENTION

The present invention is directed to a process for the manufacture of a high purity cellulose, more specifically, to a process to manufacture a dissolving pulp-grade cellulose.

BACKGROUND OF THE INVENTION

The demand for dissolving pulps has been in continuous increase over the years. In particular, dissolving pulps serve as raw material for special fibres (i.e., rayon) as well as other specialized materials such as cellulose-based materials and derivatives (i.e., microcrystalline cellulose, carboxymethyl cellulose, cellulose nitrate, etc.). The supply of competing raw materials (such as cotton) for the production of dissolving is limited and their production is plagued with environmental impacts, such as the vast amounts of land used, large use of water, fertilizers and pesticides used for their growth.

Conventionally, dissolving pulps are produced from biomass materials by using cooking methods which are tailored for generating dissolving pulps. Several approaches have been reported in literature which aim to convert industrial paper pulps into dissolving pulp. Some of these approaches include extraction with alkaline agents followed by enzymatic treatments with hemicellulases to remove hemicelluloses or the use of acid pre-hydrolysis prior to any alkaline pulping process.

Dissolving pulp is a high purity form of cellulose. It has a very high alpha-cellulose content (>90.0%), and a very low hemicellulose content (<5.0%), while lignin and other impurity content are also quite low (<0.5%). Depending on its application, the purity required might be higher and thus, the specifications may be stricter than those mentioned, as it is known, as an example, for cellulose acetate or nitrocellulose. Dissolving pulps can be used as a starting material in a multitude of applications including but not limited to various cellulose-based products, filter paper, various cellulose ether, cellulose esters, microcrystalline cellulose, etc.

Over the years, various enzymes have been employed and studied to improve the cellulose obtained from biomass in the manufacture of dissolving pulps. The two main methods of obtaining cellulose to be treated include the sulfite pulping and kraft pulping. Hemicellulase enzymes such as xylanases have been studied for selectively removing pentosans in pulps obtained from either pulping process in the production of dissolving grade pulp.

U.S. Pat. No. 6,254,722 teaches a method for making dissolving pulp from a cellulosic fiber source consisting essentially of: treating the cellulosic fiber source with a 3-stage sequence of a first alkali extraction stage, a xylanase treatment stage, and a second alkali extraction stage, (a) wherein the cellulosic fiber source is selected from the group consisting of recycled paper products made from hardwood fiber, recycled paper products made from a mixture of hardwood fiber and softwood fiber, and combinations thereof, and wherein the recycled paper products are selected from the group consisting of waste paper from unprinted envelopes, waste paper from de-inked envelopes, waste paper from unprinted ledger paper, waste paper from de-inked ledger paper, and combinations thereof, and (b) wherein each of the first and the second alkali extraction stages is conducted with aqueous sodium hydroxide at a temperature from about 0° C. to about 23° C. and the xylanase stage is conducted at a temperature from about 40° C. to about 70° C., and wherein each of the 3 stages is conducted for a sufficient time and the xylanase stage is conducted with a charge of sufficient unties of activity of xylanase per gram of cellulosic fiber source to obtain dissolving pulp having selected properties of: (i) a resistance of about 97.0% or greater to extraction with 10% sodium hydroxide in water, (ii) a xylan content of about 2.6% or less by weight, (iii) a mannan content of about 1.5% or less by weight, and (iv) a cuene viscosity of about 7.5 or greater centipoise.

PCT patent application WO2014041251A1 discloses a method of producing dissolving pulp from a recycled fibrous feedstock, comprising the steps of: providing a fibrous material comprising cellulose, lignin and hemicellulose, said fibre source further having a lignin content of 0.1 to 7% lignin and an ash content of up to 3%; subjecting the fibrous material to an alkaline extraction at a temperature of about 0 to 25° C., to produce fibres having a reduced content of hemicellulose; subjecting the fibres thus obtained to a bleaching treatment carried out with oxidative chemical reagents in order to reduce the lignin content of the fibres; and recovering the fibres thus obtained.

US patent application US20150107789A1 teaches a method of preparing dissolving pulp, the method comprising the steps of: (i) physically separating a kraft pulp into first and second fractions, the first fraction having a relatively low lignin content and the second fraction having a relatively high lignin content; and (ii) processing the first fraction to produce a dissolving pulp.

US patent application US201502225901A1 discloses a method of producing dissolving pulp from a recycled fibrous feedstock. The method comprises providing a fibrous material comprising cellulose, lignin and hemicellulose, said fibre source further having a lignin content of 0.1 to 7% lignin and an ash content of up to 3%; subjecting the fibrous material to an alkaline extraction at a temperature of about 0 to 25° C., to produce fibres having a reduced content of hemicellulose; subjecting the fibres thus obtained to a bleaching treatment carried out with oxidative chemical reagents in order to reduce the lignin content of the fibres; and recovering the fibres thus obtained. By means of the method, dissolving pulp can be produced from recycled paper and cardboard products.

PCT patent application WO2016079045A1 discloses a method for removal of hemicelluloses from paper-grade alkaline pulp comprising the steps of i) treating the paper-grade alkaline pulp with one or more hemicellulases (X stage); ii) performing hot caustic extraction of the paper-grade alkaline pulp using an alkaline source at a temperature from 70° C. to 160° C. and alkaline conditions of from 0.01 M to 1 M hydroxide ions (HCE stage); iii) optionally bleaching of the pulp obtained in step i) and/or ii) in one or more bleaching steps if ISO brightness of the pulp is below 90%; iv) optionally repeating step i) and/or ii) (one or more times) if the pulp obtained in step i) and/or ii) contains more than 10% hemicelluloses; and thereby generating dissolving pulp having less than 10% hemicelluloses.

U.S. Pat. No. 6,254,722 discloses a method for making dissolving pulp from cellulosic fiber. The fiber is treated with a 3-stage sequence having a first alkali extraction stage, a xylanase treatment stage, and a second alkali extraction stage. Having the xylanase treatment stage sandwiched between 2 alkali extraction stages results in the dissolving pulp exhibiting both a very low xylan content of about 2.6% by weight or less and a very low mannan content of about 1.5% by weight or less. The low contents of these 2 components cannot be achieved with comparison treatments of only an alkali extraction stage, only a xylanase treatment stage, or only 2 stages of a xylanase treatment stage and an alkali extraction stage.

PCT patent application WO 2010/104458 is directed to a process for the manufacturing of shaped cellulose material from lignocellulose by a sequence of separation, dissolving and cellulose shaping steps, characterized in that the process comprises the steps of: a) providing a feed of comminuted lignocellulosic material comprising cellulose, hemicelluloses and lignin; b) separating lignin from lignocellulosic feed material by cooking the material at a temperature between about 110 and 200 C.° during a time period of about 1 hour to 6 hours in an aqueous solution comprising soluble alkali, alkali earth metal or phosphorous compounds thereby forming a first stream of solid material enriched in cellulose and a second stream rich in dissolved lignin; c) treating said first stream of cellulose from step b) by at least one of oxygen delignification, bleaching and alkali extraction to form a cellulose pulp with a lignin content below about 2% preferably a lignin content below about 1%; d) treating spent liquor streams comprising dissolved lignin, alkali, alkali earth, phosphorous or sulfur compounds in a chemicals recovery system comprising a spent liquor concentration unit, optionally a causticising unit, and a gas generator or recovery boiler unit wherein fresh alkali, alkali earth metal, phosphorous or sulfur compounds are recovered and reformed; e) dissolving cellulose having a lignin content below about 2% by weight in a solution comprising alkali, alkali earth, phosphorous or sulfur compounds or dissolving cellulose in a molten salt, said solution optionally comprising one or more additives, thereby forming a substantially homogeneous solution comprising dissolved cellulose and thereafter shaping dissolved cellulose into fibers, films or cellulose derivatives in an one or more cellulose shaping steps; f) directly or indirectly recycling spent cellulose dissolving or cellulose shaping chemicals comprising one or more of alkali, alkali earth metal, phosphorous and sulfur compounds to one or more of the chemical recovery units of step d) said spent chemicals discharged from at least one of: f1) a cellulose dissolving step; f2) a cellulose shaping or cellulose coagulation step; f3) a shaped cellulose washing step; g) charging fresh cellulose dissolving or cellulose shaping chemicals comprising alkali, alkali earth metal, phosphorous or sulfur compounds reclaimed directly or indirectly from a chemicals recovery unit in step d) to a cellulose dissolving or cellulose shaping step in e).

In light of the prior art, there still exists a need for a better method to manufacture dissolving pulp grade cellulose. Many of the present methods employ reaction systems which require alkali or acid reactions at temperatures above 100° C. and pressures above atmospheric. This heat and pressure requirement must be generated and therefore adds to the ultimate cost of the final product. Avoiding high temperature processes inherently leads to lower manufacturing costs and generally safer working environments for operators and their crews. In other instances, methods to manufacture dissolving grade pulp require multiple steps which are time consuming and therefore lead to higher production costs. Lastly, when these manufacturing processes rely on hemicellulases and other enzymes, the costs of those are, in most cases, prohibitive not allowing the overall manufacturing process to be financially feasible.

SUMMARY OF THE INVENTION

Accordingly, there is provided herein a process which can be used to manufacture dissolving pulp grade cellulose where each step of the process is carried out at a temperature below 50° C. The economic savings by the implementation of such a process are substantial. In addition to that, the carbon footprint savings associated with a lower energy input is significant, allowing this process to having a considerably lower carbon intensity. Moreover, by employing a modified Caro's acid in the delignification step of the process, the resulting cellulose is more easily converted to a dissolving pulp grade cellulose and does not require multiple subsequent reaction steps to yield such grade of cellulose.

According to a first aspect of the present invention, there is provided a process to manufacture dissolving pulp grade cellulose said process comprising the steps of:

• • providing a lignocellulosic material, wherein the lignin content is >2%;
  • optionally, comminuting said lignocellulosic material into chips of a particle size no greater than 5 cm;
  • providing a modified Caro's acid, wherein said modified Caro's acid selected from the group consisting of:
    • composition A; composition B; composition C; composition D; composition E;
    • composition F; composition G; composition H; composition I; and composition J;
      wherein said composition A comprises:
  • sulfuric acid;
  • a compound comprising an amine moiety and a sulfonic acid moiety; and
  • a peroxide; and wherein sulfuric acid, said compound comprising an amine moiety and a sulfonic acid moiety and said peroxide are present in a molar ratio of no less than 1:1:1;
    wherein said composition B comprises:
  • sulfuric acid;
  • a compound comprising an amine moiety;
  • a compound comprising a sulfonic acid moiety; and
  • a peroxide; wherein sulfuric acid and said a compound comprising an amine moiety and said compound comprising a sulfonic acid moiety are present in a molar ratio of no less than 1:1:1;
    wherein said composition C comprises:
  • an alkylsulfonic acid; and
  • a peroxide; wherein said alkylsulfonic acid and said peroxide are present in a molar ratio of no less than 1:1;
    wherein said composition D comprises:
  • sulfuric acid;
  • a heterocyclic compound; and
  • a peroxide; and wherein sulfuric acid and said a heterocyclic compound; are present in a molar ratio of no less than 1:1;
    wherein said composition E comprises:
  • sulfuric acid;
  • a modifying agent comprising a compound containing an amine group; and
  • a peroxide; and wherein sulfuric acid and said compound containing an amine group;
  • are present in a molar ratio of no less than 1:1;
    wherein said composition F comprises:
  • sulfuric acid;
  • a modifying agent comprising an alkanesulfonic acid and
  • a peroxide; and wherein sulfuric acid and said alkanesulfonic acid are present in a molar ratio of no less than 1:1;
    wherein said composition G comprises:
  • sulfuric acid;
  • a substituted aromatic compound; and
  • a peroxide; and wherein sulfuric acid and said substituted aromatic compound; are present in a molar ratio of no less than 1:1;
    wherein said composition H comprises:
  • sulfuric acid;
  • a modifying agent comprising an arylsulfonic acid;
  • a peroxide; and
  • optionally, a compound containing an amine group; wherein sulfuric acid and said a arylsulfonic acid; are present in a molar ratio of no less than 1:1;
    wherein said composition I comprises:
  • sulfuric acid;
  • a heterocyclic compound;
  • an alkanesulfonic acid and
  • a peroxide; and wherein sulfuric acid and said a heterocyclic compound; are present in a molar ratio of no less than 1:1;
    wherein said composition J comprises:
  • sulfuric acid;
  • a carbonyl-containing nitrogenous base compound; and
  • a peroxide; and wherein sulfuric acid and said a carbonyl-containing nitrogenous base compound; are present in a molar ratio of no less than 1:1;
  • exposing said lignocellulosic material to said modified Caro's acid at a temperature of less than or equal to 45° C. for a period of time sufficient to allow the modified Caro's acid to delignify said lignocellulosic material and yield a solid cellulosic portion and a liquid portion with a high dissolved lignin content;
  • separating said solid cellulosic portion from said liquid portion;
    wherein said solid cellulosic portion has the following characteristics:
  • lignin content below 1%;
  • hemicellulose content below 15%; and
  • cellulose content of at least 75%;
  • exposing said solid cellulosic portion to a caustic solution yielding causticized solids;
  • filtering said causticized solids;
  • re-slurrying said causticized solids and neutralizing such to yield a dissolving pulp cellulose; and
  • washing said dissolving pulp cellulose with water to remove the neutralized salts to obtain a high purity dissolving pulp cellulose having the following characteristics:
  • over 90% cellulose content;
  • less than 1% lignin content;
  • less than 5% hemicellulose content; and
  • an intrinsic viscosity ranging between 100-800 mL/g.

According to a preferred embodiment of the present invention, said step of exposing said lignocellulosic material to said modified Caro's acid is carried out at a temperature ranging from 25° C. to 45° C. Preferably, said step of exposing said lignocellulosic material to said modified Caro's acid is carried out at a temperature ranging from 30° C. to 40° C. More preferably, said step of exposing said lignocellulosic material to said modified Caro's acid is carried out at a temperature ranging from 30° C. to 35° C.

According to a preferred embodiment of the present invention, said caustic solution has a concentration of NaOH ranging from 2 to 20% wt. Preferably, said caustic solution has a concentration of NaOH ranging from 5 to 10% wt.

According to a preferred embodiment of the present invention, said step of exposing said solid cellulosic portion to a caustic solution can last for a duration ranging between 1 minute and 24 hours. Preferably, said step of exposing said cellulosic portion to a caustic solution can last for a duration ranging between 10 minutes to 6 hours.

According to a preferred embodiment of the present invention, said step of filtering said causticized solids uses a filter ranging from 1 to 1000 μm. Preferably, said step of filtering said causticized solids uses a filter ranging from 10 to 200 μm.

According to a preferred embodiment of the present invention, said step of re-slurrying said causticized solids and neutralizing such is carried out to obtain a final pH ranging between 5 and 8.

According to a preferred embodiment of the present invention, said step of performing at least one wash one said dissolving pulp cellulose removes salts and thus yields a high purity dissolving pulp.

Preferably, said lignocellulosic material is in a reactor in a concentration of up to 10% wt. of the total weight of a reaction mass created by said material and said modified Caro's acid.

According to a preferred embodiment of the present invention, said high purity dissolving pulp cellulose has a cellulose content of over 92%. More preferably, said high purity dissolving pulp cellulose has a cellulose content of over 95%. Even more preferably, said high purity dissolving pulp cellulose has a cellulose content of over 97%.

According to a preferred embodiment of the present invention, said high purity dissolving pulp cellulose has a lignin content of less than 0.8%. More preferably, said high purity dissolving pulp cellulose has a cellulose content of less than 0.6%. Even more preferably, said high purity dissolving pulp cellulose has a cellulose content of less than 0.4%.

According to a preferred embodiment of the present invention, said high purity dissolving pulp cellulose has a hemicellulose content of less than 4%. More preferably, said high purity dissolving pulp cellulose has a hemicellulose content of less than 3%. Even more preferably, said high purity dissolving pulp cellulose has a hemicellulose content of less than 2%.

According to a preferred embodiment of the present invention, said high purity dissolving pulp cellulose has an intrinsic viscosity between 200 and 700 mL/g. More preferably, said high purity dissolving pulp cellulose has an intrinsic viscosity between 400 and 600 mL/g.

According to another aspect of the present invention, there is provided a use of cellulose for the manufacture of dissolving pulp grade cellulose, wherein said dissolving pulp grade cellulose is prepared according to the following process steps:

• • providing a lignocellulosic material comprising a lignin content over 2% wt;
  • optionally, comminuting said lignocellulosic material into chips having a particle size no greater than 5 cm;
  • providing a modified Caro's acid, wherein said modified Caro's acid selected from the group consisting of:
    • composition A; composition B; composition C; composition D; composition E;
    • composition F; composition G; composition H; composition I; and composition J;
      wherein said composition A comprises:
  • sulfuric acid;
  • a compound comprising an amine moiety and a sulfonic acid moiety; and
  • a peroxide; and wherein sulfuric acid, said compound comprising an amine moiety and a sulfonic acid moiety and said peroxide are present in a molar ratio of no less than 1:1:1;
    wherein said composition B comprises:
  • sulfuric acid;
  • a compound comprising an amine moiety;
  • a compound comprising a sulfonic acid moiety; and
  • a peroxide; wherein sulfuric acid and said a compound comprising an amine moiety and said compound comprising a sulfonic acid moiety are present in a molar ratio of no less than 1:1:1;
    wherein said composition C comprises:
  • an alkylsulfonic acid; and
  • a peroxide; wherein said alkylsulfonic acid and said peroxide are present in a molar ratio of no less than 1:1;
    wherein said composition D comprises:
  • sulfuric acid;
  • a heterocyclic compound; and
  • a peroxide; and wherein sulfuric acid and said a heterocyclic compound; are present in a molar ratio of no less than 1:1;
    wherein said composition E comprises:
  • sulfuric acid;
  • a modifying agent comprising a compound containing an amine group; and
  • a peroxide; and wherein sulfuric acid and said compound containing an amine group; are present in a molar ratio of no less than 1:1;
    wherein said composition F comprises:
  • sulfuric acid;
  • a modifying agent comprising an alkanesulfonic acid and
  • a peroxide; and wherein sulfuric acid and said alkanesulfonic acid are present in a molar ratio of no less than 1:1;
    wherein said composition G comprises:
  • sulfuric acid;
  • a substituted aromatic compound; and
  • a peroxide; and wherein sulfuric acid and said substituted aromatic compound; are present in a molar ratio of no less than 1:1;
    wherein said composition H comprises:
  • sulfuric acid;
  • a modifying agent comprising an arylsulfonic acid;
  • a peroxide; and
  • optionally, a compound containing an amine group; wherein sulfuric acid and said a arylsulfonic acid; are present in a molar ratio of no less than 1:1;
    wherein said composition I comprises:
  • sulfuric acid;
  • a heterocyclic compound;
  • an alkanesulfonic acid and
  • a peroxide; and wherein sulfuric acid and said a heterocyclic compound; are present in a molar ratio of no less than 1:1;
    wherein said composition J comprises:
  • sulfuric acid;
  • a carbonyl-containing nitrogenous base compound; and
  • a peroxide; and wherein sulfuric acid and said a carbonyl-containing nitrogenous base compound; are present in a molar ratio of no less than 1:1;
  • exposing said chips to said modified Caro's acid at a temperature of less than or equal to 45° C. for a period of time sufficient to allow the modified Caro's acid to delignify said chips and yield a solid cellulosic portion;
    wherein said solid cellulosic portion has the following characteristics: lignin content below 1%; hemicellulose content below 15%; and cellulose content of at least 75%.

According to yet another aspect of the present invention, there is provided a method to manufacture a dissolving pulp cellulose at low temperature, wherein said method comprises the following steps:

• • a first step which delignifies a lignocellulosic biomass to a high purity cellulose, wherein said first delignification step comprises exposing chips of a lignocellulosic material to a modified Caro's acid at a temperature of less than or equal to 45° C. for a period of time sufficient to allow the modified Caro's acid to delignify said chips and yield a solid cellulosic portion; and wherein said high purity cellulose having the following characteristics:
    • lignin content below 1%;
    • hemicellulose content below 15%; and
    • cellulose content of at least 75%; and
  • a second step which exposes said high purity cellulose to a caustic solution to yield a dissolving pulp cellulose;
    wherein said dissolving pulp cellulose having the following characteristics:
  • over 90% cellulose content;
  • less than 1% lignin content;
  • less than 5% hemicellulose content; and
  • an intrinsic viscosity ranging between 100-800 mL/g.

Preferably, the method further comprises a step of re-slurrying said causticized solids and neutralizing such to yield a dissolving pulp cellulose.

Preferably, the method further comprises at least one wash step of said dissolving pulp cellulose removes salts and thus yields a high purity dissolving pulp cellulose.

One of the advantages of the method of the present invention is that the delignification comprises a main single lignin and hemicellulose removal step while the remaining steps are substantially directed to the removal of any remaining hemicellulose.

Employing such an approach will minimize the number of steps necessary to achieve a material which can then be converted to dissolving pulp.

Conventional approaches to make dissolving pulp include the delignification step by kraft pulping, followed by a series of bleaching steps and washing steps in between each one of the bleaching steps. Considering the fact that Kraft pulping is already an energy intensive method to delignify biomass, any additional steps (such as bleaching) only compound the problem further and make such approach to prepare dissolving pulp highly energy intensive and pricey.

DETAILED DESCRIPTION OF THE INVENTION

According to a preferred embodiment of the present invention, there is provided a method to manufacture a dissolving pulp cellulose at low temperature, wherein said method comprises the following steps:

• • a first step which delignifies a lignocellulosic biomass comprising over 2% lignin content to a high purity cellulose,
    wherein said first delignification step comprises exposing chips of a lignocellulosic material to a modified Caro's acid at a temperature of less than or equal to 45° C. for a period of time sufficient to allow the modified Caro's acid to delignify said chips and yield a solid cellulosic portion; and wherein said high purity cellulose having the following characteristics:
  • lignin content below 1%;
  • hemicellulose content below 15%; and
  • cellulose content of at least 75%;
  • a second causticizing step which exposes said high purity cellulose to a caustic solution to yield a dissolving pulp cellulose;
    wherein said dissolving pulp cellulose having the following characteristics:
  • over 90% cellulose content;
  • less than 1% lignin content;
  • less than 5% hemicellulose content; and
  • an intrinsic viscosity ranging between 100-800 mL/g.

According to a preferred embodiment of the present invention, the step of delignification of lignocellulosic biomass material which yields a modified Caro's acid delignified cellulose comprises:

• • providing said lignocellulosic biomass material comprising cellulose fibers and lignin;
  • exposing said lignocellulosic biomass material requiring delignification to a modified Caro's acid composition having a pH of less than 1, said modified Caro's acid composition selected from the group consisting of: composition A; composition B; composition C; composition D; composition E; composition F; composition G; composition H; composition I; and composition J;
    wherein said composition A comprises:
  • sulfuric acid;
  • a compound comprising an amine moiety and a sulfonic acid moiety; and
  • a peroxide; and wherein sulfuric acid, said compound comprising an amine moiety and a sulfonic acid moiety and said peroxide are present in a molar ratio of no less than 1:1:1;
    wherein said composition B comprises:
  • sulfuric acid;
  • a compound comprising an amine moiety;
  • a compound comprising a sulfonic acid moiety; and
  • a peroxide; wherein sulfuric acid and said a compound comprising an amine moiety and said compound comprising a sulfonic acid moiety are present in a molar ratio of no less than 1:1:1;
    wherein said composition C comprises:
  • an alkylsulfonic acid; and
  • a peroxide; wherein said alkylsulfonic acid and said peroxide are present in a molar ratio of no less than 1:1;
    wherein said composition D comprises:
  • sulfuric acid;
  • a heterocyclic compound; and
  • a peroxide; and wherein sulfuric acid and said a heterocyclic compound; are present in a molar ratio of no less than 1:1;
    wherein said composition E comprises:
  • sulfuric acid;
  • a modifying agent comprising a compound containing an amine group; and
  • a peroxide; and wherein sulfuric acid and said compound containing an amine group; are present in a molar ratio of no less than 1:1;
    wherein said composition F comprises:
  • sulfuric acid;
  • a modifying agent comprising an alkanesulfonic acid and
  • a peroxide; and wherein sulfuric acid and said alkanesulfonic acid are present in a molar ratio of no less than 1:1;
    wherein said composition G comprises:
  • sulfuric acid;
  • a substituted aromatic compound; and
  • a peroxide; and wherein sulfuric acid and said substituted aromatic compound; are present in a molar ratio of no less than 1:1;
    wherein said composition H comprises:
  • sulfuric acid;
  • a modifying agent comprising an arylsulfonic acid;
  • a peroxide; and
  • optionally, a compound containing an amine group; wherein sulfuric acid and said a arylsulfonic acid; are present in a molar ratio of no less than 1:1;
    wherein said composition I comprises:
  • sulfuric acid;
  • a heterocyclic compound;
  • an alkanesulfonic acid and
  • a peroxide; and wherein sulfuric acid and said a heterocyclic compound; are present in a molar ratio of no less than 1:1;
    wherein said composition J comprises:
  • sulfuric acid;
  • a carbonyl-containing nitrogenous base compound; and
  • a peroxide; and wherein sulfuric acid and said a carbonyl-containing nitrogenous base compound; are present in a molar ratio of no less than 1:1;
    for a period of time sufficient to remove substantially all of the lignin and most of the hemicellulose present on said biomass material to yield a high purity cellulose (i.e. wherein said cellulose has the following characteristics: lignin content below 1%; hemicellulose content below 15%; and cellulose content of at least 75%). The process can be carried out for a varying duration of time depending on the particle size of the biomass being fed into the process. Preferably, the delignification step of the process can last from 2 to 20 hours depending partly on that characteristic. Moreover, the temperature of the resulting mixture also has an impact on the duration of the process as the reaction is highly exothermic, precautions are taken to prevent a runaway degradation of the cellulose. This would result in a carbon black resulting product with no value. The process is preferably run at temperatures below 50° C., more preferably at temperatures below 40° C. Even more preferably at temperatures below 35° C. Preferably, the delignification step can be performed with a cooling means adapted to control the heat generated by the chemical reaction of delignification and maintain the temperature to avoid an undesirable ‘runaway’ reaction.

Preferably, said sulfuric acid, said compound comprising an amine moiety and a sulfonic acid moiety and said peroxide are present in a molar ratio of no more than 15:1:1. Preferably, for a modified Caro's acid comprising sulfuric acid, peroxide and taurine (as the modifier component), the molar composition is as follows: H₂O:H₂O₂:H₂SO₄:Taurine in a molar ratio of 56:10:10:1. Preferably, for a modified Caro's acid comprising TEOA/MSA, the molar composition is as follows: H₂O:H₂O₂:H₂SO₄:TEOA:MSA in a molar ratio of 56:10:10:1:1.

According to a preferred embodiment of the approach to obtain low lignin cellulose, said sulfuric acid and said compound comprising an amine moiety and a sulfonic acid moiety are present in a molar ratio of no less than 3:1.

Preferably, said compound comprising an amine moiety and a sulfonic acid moiety is selected from the group consisting of: taurine; taurine derivatives; and taurine-related compounds.

According to a preferred embodiment of the approach to obtain low lignin cellulose, 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; as well as aminoalkylsulfonic acids where the alkyl is selected from the group consisting of C₁-C₅ linear alkyl and C₃-C₅ branched alkyl.

Preferably, said linear alkylaminosulfonic acid is selected form the group consisting of: methyl; ethyl (taurine); propyl; and butyl.

Preferably, branched aminoalkylsulfonic acid is selected from the group consisting of: isopropyl; isobutyl; and isopentyl.

According to a preferred embodiment of the approach to obtain low lignin cellulose, said compound comprising an amine moiety and a sulfonic acid moiety is taurine.

According to a preferred embodiment of the approach to obtain low lignin cellulose, said sulfuric acid and compound comprising an amine moiety and a sulfonic acid moiety are present in a molar ratio of no less than 3:1.

According to a preferred embodiment of the approach to obtain low lignin cellulose, said compound comprising an amine moiety is an alkanolamine is selected from the group consisting of: monoethanolamine; diethanolamine; triethanolamine; and combinations thereof.

According to a preferred embodiment of the approach to obtain low lignin cellulose, said compound comprising a sulfonic acid moiety is selected from the group consisting of: alkylsulfonic acids; arylsulfonic acids; and combinations thereof.

Preferably, said alkylsulfonic acid is selected from the group consisting of: alkylsulfonic acids where the alkyl groups range from C₁-C₆ and are linear or branched; and combinations thereof. More preferably, said alkylsulfonic acid is selected from the group consisting of: methanesulfonic acid; ethanesulfonic acid; propanesulfonic acid; 2-propanesulfonic acid; isobutylsulfonic acid; t-butylsulfonic acid; butanesulfonic acid; iso-pentylsulfonic acid; t-pentylsulfonic acid; pentanesulfonic acid; t-butylhexanesulfonic acid; and combinations thereof.

Preferably, said arylsulfonic acid is selected from the group consisting of: toluenesulfonic acid; benzesulfonic acid; and combinations thereof.

According to a preferred embodiment of the approach to obtain low lignin cellulose, said alkylsulfonic acid; and said peroxide are present in a molar ratio of no less than 1:1.

Preferably, said compound comprising a sulfonic acid moiety is methanesulfonic acid.

According to a preferred embodiment of the approach to obtain a high purity cellulose, said Composition C may further comprise a compound comprising an amine moiety. Preferably, the compound comprising an amine moiety has a molecular weight below 300 g/mol. Preferably also, the compound comprising an amine moiety is a primary amine. More preferably, the compound comprising an amine moiety is an alkanolamine. Preferably, the compound comprising an amine moiety is a tertiary amine. According to a preferred embodiment of the approach to obtain low lignin cellulose, the alkanolamine is selected from the group consisting of: monoethanolamine; diethanolamine; triethanolamine; and combinations thereof. Preferably, the alkanolamine is triethanolamine.

According to a preferred embodiment of the approach to obtain low lignin cellulose, said in Composition C, said sulfuric acid and said a compound comprising an amine moiety and said compound comprising a sulfonic acid moiety are present in a molar ratio of no less than 1:1:1.

Preferably, in Composition C, said sulfuric acid, said compound comprising an amine moiety and said compound comprising a sulfonic acid moiety are present in a molar ratio ranging from 28:1:1 to 2:1:1.

Preferably, in Composition C, said compound comprising an amine moiety is triethanolamine and said compound comprising a sulfonic acid moiety is methanesulfonic acid.

According to preferred embodiment of the present invention, the modified Caro's acid used (as disclosed in Canadian patent application 3,128,678) comprises: sulfuric acid; a heterocyclic compound and a peroxide; and wherein sulfuric acid and said a heterocyclic compound; are present in a molar ratio of no less than 1:1. Preferably, the sulfuric acid and said heterocyclic compound are present in a molar ratio ranging from 28:1 to 2:1 More preferably, the sulfuric acid and heterocyclic compound are present in a molar ratio ranging from 24:1 to 3:1. Preferably, the sulfuric acid and heterocyclic compound are present in a molar ratio ranging from 20:1 to 4:1. More preferably, the sulfuric acid and heterocyclic compound are present in a molar ratio ranging from 16:1 to 5:1. Preferably, the sulfuric acid and heterocyclic compound are present in a molar ratio ranging from 12:1 to 6:1. Also preferably, said heterocyclic compound has a molecular weight below 300 g/mol. Also preferably, said heterocyclic compound has a molecular weight below 150 g/mol. More preferably, said heterocyclic compound is a secondary amine. According to a preferred embodiment of the present invention, said heterocyclic compound is selected from the group consisting of: imidazole; triazole; and N-methylimidazole.

According to preferred embodiment of the present invention, the modified Caro's acid used (as disclosed in Canadian patent application 3,128,677) comprises: sulfuric acid; a modifying agent comprising a compound containing an amine group and a peroxide; and wherein sulfuric acid and said compound containing an amine group; are present in a molar ratio of no less than 1:1. Preferably, the sulfuric acid and said compound containing an amine group are present in a molar ratio ranging from 28:1 to 2:1. More preferably, the sulfuric acid and compound containing an amine group are present in a molar ratio ranging from 24:1 to 3:1. Preferably, the sulfuric acid and compound containing an amine group are present in a molar ratio ranging from 20:1 to 4:1. More preferably, the sulfuric acid and compound containing an amine group are present in a molar ratio ranging from 16:1 to 5:1. Preferably, the sulfuric acid and compound containing an amine group are present in a molar ratio ranging from 12:1 to 6:1. According to a preferred embodiment of the present invention, the modifying agent is selected in the group consisting of: TEOA; MEOA; pyrrolidine; DEOA; ethylenediamine; diethylamine; triethylamine; morpholine; MEA-triazine; and combinations thereof. According to a more preferred embodiment of the present invention, the modifying agent is TEOA; MEOA; pyrrolidine; DEOA; ethylenediamine; triethylamine.

According to preferred embodiment of the present invention, the modified Caro's acid used (as disclosed in Canadian patent application 3,128,676) comprises: sulfuric acid; a modifying agent comprising an alkanesulfonic acid and a peroxide; and wherein sulfuric acid and said alkanesulfonic acid are present in a molar ratio of no less than 1:1. Preferably, said alkanesulfonic acid is selected from the group consisting of: alkanesulfonic acids where the alkyl groups range from C₁-C₆ and are linear or branched; and combinations thereof. Preferably, said alkanesulfonic acid is selected from the group consisting of: methanesulfonic acid; ethanesulfonic acid; propanesulfonic acid; 2-propanesulfonic acid; isobutylsulfonic acid; t-butylsulfonic acid; butanesulfonic acid; iso-pentylsulfonic acid; t-pentylsulfonic acid; pentanesulfonic acid; t-butylhexanesulfonic acid; and combinations thereof. More preferably, said alkanesulfonic acid is methanesulfonic acid. Also preferably, said alkanesulfonic acid has a molecular weight below 300 g/mol. Also preferably, said alkanesulfonic acid has a molecular weight below 150 g/mol. Preferably, the sulfuric acid and said alkanesulfonic acid and are present in a molar ratio ranging from 28:1 to 2:1. More preferably, the sulfuric acid and alkanesulfonic acid are present in a molar ratio ranging from 24:1 to 3:1. Preferably, the sulfuric acid and alkanesulfonic acid are present in a molar ratio ranging from 20:1 to 4:1. More preferably, the sulfuric acid and alkanesulfonic acid are present in a molar ratio ranging from 16:1 to 5:1. According to a preferred embodiment of the present invention, the sulfuric acid and alkanesulfonic acid are present in a molar ratio ranging from 12:1 to 6:1.

According to preferred embodiment of the present invention, the modified Caro's acid used (as disclosed in Canadian patent application 3,128,675) comprises: sulfuric acid; a substituted aromatic compound and a peroxide; and wherein sulfuric acid and said substituted aromatic compound; are present in a molar ratio of no less than 1:1. Preferably, the substituted aromatic compound comprises at least two substituents. More preferably, at least one substituent is an amine group and at least one of the other substituents is a sulfonic acid moiety. According to a preferred embodiment, the substituted aromatic compound comprises three or more substituent. According to a preferred embodiment of the present invention, the substituted aromatic compound comprises at least a sulfonic acid moiety. According to another preferred embodiment of the present invention, the substituted aromatic compound comprises an aromatic compound having a sulfonamide substituent, where the compound can be selected from the group consisting of: benzenesulfonamides; toluenesulfonamides; substituted benzenesulfonamides; and substituted toluenesulfonamides. Preferably, the sulfuric acid and said substituted aromatic compound and are present in a molar ratio ranging from 28:1 to 2:1. More preferably, the sulfuric acid and substituted aromatic compound are present in a molar ratio ranging from 24:1 to 3:1. Preferably, the sulfuric acid and substituted aromatic compound are present in a molar ratio ranging from 20:1 to 4:1. More preferably, the sulfuric acid and substituted aromatic compound are present in a molar ratio ranging from 16:1 to 5:1. Preferably, the sulfuric acid and substituted aromatic compound are present in a molar ratio ranging from 12:1 to 6:1.

According to preferred embodiment of the present invention, the modified Caro's acid used (as disclosed in Canadian patent application 3,128,674) comprises: sulfuric acid; a modifying agent comprising an arylsulfonic acid; a peroxide; and optionally, a compound containing an amine group; wherein sulfuric acid and said a arylsulfonic acid; are present in a molar ratio of no less than 1:1. Preferably, the compound containing an amine group is selected from the group consisting of: imidazole; N-methylimidazole; triazole; monoethanolamine (MEOA); diethanolamine (DEOA); triethanolamine (TEOA); pyrrolidine and combinations thereof. According to a preferred embodiment of the present invention, sulfuric acid and the peroxide are present in a molar ratio of approximately 1:1. Preferably, the sulfuric acid and said arylsulfonic acid and are present in a molar ratio ranging from 28:1 to 2:1. More preferably, the sulfuric acid and arylsulfonic acid are present in a molar ratio ranging from 24:1 to 3:1. Preferably, the sulfuric acid and arylsulfonic acid are present in a molar ratio ranging from 20:1 to 4:1. More preferably, the sulfuric acid and arylsulfonic acid are present in a molar ratio ranging from 16:1 to 5:1. According to a preferred embodiment of the present invention, the sulfuric acid and arylsulfonic acid are present in a molar ratio ranging from 12:1 to 6:1. Also preferably, said arylsulfonic acid has a molecular weight below 300 g/mol. Also preferably, said arylsulfonic acid has a molecular weight below 150 g/mol. Even more preferably, said arylsulfonic acid is selected from the group consisting of: orthanilic acid; metanilic acid; sulfanilic acid; toluenesulfonic acid; benzenesulfonic acid; and combinations thereof.

According to preferred embodiment of the present invention, the modified Caro's acid used (as disclosed in Canadian patent application 3,128,673) comprises: sulfuric acid; a heterocyclic compound; an alkanesulfonic acid and a peroxide; and wherein sulfuric acid and said a heterocyclic compound; are present in a molar ratio of no less than 1:1. Preferably, said aqueous acidic composition comprising: sulfuric acid; a heterocyclic compound; an arylsulfonic acid; and wherein sulfuric acid and said a heterocyclic compound; are present in a molar ratio of no less than 1:1. Preferably, the arylsulfonic acid is toluenesulfonic acid.

Preferably, the sulfuric acid, the heterocyclic compound and the alkanesulfonic acid are present in a molar ratio ranging from 28:1:1 to 2:1:1. More preferably, the sulfuric acid the heterocyclic compound and the alkanesulfonic acid are present in a molar ratio ranging from 24:1:1 to 3:1:1. Preferably, the sulfuric acid, the heterocyclic compound and the alkanesulfonic acid are present in a molar ratio ranging from 20:1:1 to 4:1:1. More preferably, the sulfuric acid, the heterocyclic compound and the alkanesulfonic acid are present in a molar ratio ranging from 16:1:1 to 5:1:1. According to a preferred embodiment of the present invention, the sulfuric acid and heterocyclic compound are present in a molar ratio ranging from 12:1:1 to 6:1:1. Also preferably, said heterocyclic compound has a molecular weight below 300 g/mol. Also preferably, said heterocyclic compound has a molecular weight below 150 g/mol. Even more preferably, said heterocyclic compound is selected from the group consisting of: imidazole; triazole; n-methylimidazole; and combinations thereof. Preferably, the alkanesulfonic acid is selected from the group consisting of: alkylsulfonic acids where the alkyl groups range from C₁-C₆ and are linear or branched; and combinations thereof. Preferably, said alkylsulfonic acid is selected from the group consisting of: methanesulfonic acid; ethanesulfonic acid; propanesulfonic acid; 2-propanesulfonic acid; isobutylsulfonic acid; t-butylsulfonic acid; butanesulfonic acid; iso-pentylsulfonic acid; t-pentylsulfonic acid; pentanesulfonic acid; t-butylhexanesulfonic acid; and combinations thereof. More preferably, said alkylsulfonic acid is methanesulfonic acid.

According to preferred embodiment of the present invention, the modified Caro's acid used (as disclosed in Canadian patent application 3,128,672) comprises: sulfuric acid; a carbonyl-containing nitrogenous base compound and a peroxide; and wherein sulfuric acid and said a carbonyl-containing nitrogenous base compound; are present in a molar ratio of no less than 1:1. According to a preferred embodiment of the present invention, the carbonyl-containing nitrogenous base compound is selected from the group consisting of: caffeine; lysine; creatine; glutamine; creatinine; 4-aminobenzoic acid; glycine; NMP (N-methyl-2-pyrrolidinone); histidine; DMA (N,N-dimethylacetamide); arginine; 2,3-pyridinedicarboxylic acid; hydantoin; and combinations thereof. Preferably, the sulfuric acid and said carbonyl-containing nitrogenous base compound and are present in a molar ratio ranging from 28:1 to 2:1. More preferably, the sulfuric acid and carbonyl-containing nitrogenous base compound are present in a molar ratio ranging from 24:1 to 3:1. Preferably, the sulfuric acid and carbonyl-containing nitrogenous base compound are present in a molar ratio ranging from 20:1 to 4:1. More preferably, the sulfuric acid and carbonyl-containing nitrogenous base compound are present in a molar ratio ranging from 16:1 to 5:1. According to a preferred embodiment of the present invention, the sulfuric acid and carbonyl-containing nitrogenous base compound are present in a molar ratio ranging from 12:1 to 6:1.

Experiment #1

The following experimentation was conducted using sugarcane bagasse as the biomass feedstock. The sugarcane bagasse was characterized to determine the content of acid-insoluble lignin (also known as Klason lignin) as well as carbohydrate composition. The carbohydrate composition gives an indication of cellulose and hemicellulose distribution within the biomass. Results of the characterization of the sugarcane bagasse are shown in Table 1.

TABLE 1
Results of the characterization of the sugarcane
bagasse used in the experiments.

	Parameter	Units	Result

	Klason lignin	%, OD basis	19.7%
	Arabinan	%, extracted OD basis	1.6%
	Xylan	%, extracted OD basis	26.2%
	Mannan	%, extracted OD basis	<0.1%
	Galactan	%, extracted OD basis	0.4%
	Glucan	%, extracted OD basis	39.4%

The bagasse was exposed to a delignification reaction according to the method described herein using a modified Caro's acid composition comprising of a 10:10:1:18 molar ratio between the acid, peroxide, modifier, and water. The reaction was left stirring at 35° C. for 18 hours, after which the solids were extracted from the liquid and a yield of the solids was obtained. The cellulose solids were characterized post-delignification to determine composition of the solids (see Table 2) as well as quality of the fibers (Table 3).

TABLE 2
Results of the characterization of the cellulose
solids from the delignification.

	Parameter	Result

	Kappa number	1.2
	Lignin content (%)	0.16%
	Ash content (%)	8.14%
	Cellulose + hemicellulose content (%)	91.70%
	Cellulose content (%)	96.9%
	Hemicellulose content (%)	3.1%

TABLE 3
Results of the characterization of the
sugarcane bagasse cellulosic solids.

		Before
Analysis	Unit	treatment

C. S. Freeness	mL	99
Basis weight, conditioned	g/m2	66.52
Bulk	cc/g	1.49
Burst index	kPa · m2/g	1.58
Tear index	mN · m2/g	1.74
Tensile index	N · m/g	43.2
Tensile	km	4.40
Stretch	%	1.27
Tensile Energy Absorption	J/m2	23.8

Fiber Quality Analyzer: HiRes

Population	fibers/mg	36,620
AFL, arithmetic	mm	0.32
LWAFL	mm	0.592
WWAFL	mm	0.929
Width	μm	21.4
Coarseness	mg/m	0.084
Curl, length weighted		0.139
Kink index	l/mm	1.86
Percent fines, <0.2 mm, arithmetic	%	47.9
Percent fines, <0.2 mm, length weighted	%	17.6

The wet solids were exposed to a solution of NaOH with a final concentration of 8% wt. NaOH at room temperature for 2 hours. The solids were filtered through a 60 μm filter. The resulting cellulose was reslurried and neutralized to pH 6.5. Several washes were conducted to remove salts and obtain a high purity dissolving pulp sample. The sample thus obtained was characterized for composition (Table 4) as well as fiber analysis (see Table 5). For clarity, in Table 4, R₁₀ is the portion of the pulp that resists a 10% NaOH concentration, which includes undegraded cellulose or alpha cellulose and R₁₈ is the portion of the pulp that resists 18% NaOH, consisting of the cellulose portion (both degraded and undegraded, alpha and beta). Alongside in Table 4 are shown typical specifications observed for dissolving pulps.

As observed in Table 4, the results of the characterization of the sugarcane bagasse dissolving pulp post-caustic treatment meet the specifications in said Table. This highlights that the method described herein allows the production of a high purity dissolving pulp from any biomass using a low-energy process (i.e., ambient temperature, ambient pressure) that brings significant environmental and financial benefits compared to other processes which have substantially higher energy requirements.

TABLE 4
Results of the characterization of the
sugarcane bagasse dissolving pulp.

			Typical Dissolving
	Parameter	Result	Pulp Specification

	Kappa number	0.7	<1-5
	Lignin content (% wt.)	0.09%	<0.1-1%
	R10 (% wt.)	92.9%	>90%
	R18 (% wt.)	96.9%	>95%
	Brightness	79.2%	N/A
	Intrinsic viscosity (mL/g)	350	300-600

TABLE 5
Results of the characterization of the sugarcane
bagasse cellulosic solids post-caustic treatment

		After
Analysis	Unit	treatment

C. S. Freeness	mL	427
Basis weight, conditioned	g/m2	67.07
Bulk	cc/g	1.66
Burst index	kPa · m2/g	0.61
Tear index	mN · m2/g	1.69
Tensile index	N · m/g	18.2
Tensile	km	1.86
Stretch	%	0.95
Tensile Energy Absorption	J/m2	7.7

Fiber Quality Analyzer: HiRes

Population	fibers/mg	36,270
AFL, arithmetic	mm	0.30
LWAFL	mm	0.545
WWAFL	mm	0.885
Width	μm	21.0
Coarseness	mg/m	0.092
Curl, length weighted		0.217
Kink index	l/mm	2.51
Percent fines, <0.2 mm, arithmetic	%	48.9
Percent fines, <0.2 mm, length weighted	%	19.4

Experiment #2

The following experimentation was conducted using hardwood waste as the biomass feedstock. The hardwood waste was characterized to determine the content of acid-insoluble lignin (also known as Klason lignin) as well as carbohydrate composition. The carbohydrate composition gives an indication of cellulose and hemicellulose distribution within the biomass. Results of the characterization of the hardwood are shown in Table 6.

TABLE 6
Results of the characterization of the
hardwood waste used in the experiments.

	Parameter	Units	Result

	Klason lignin	%, OD basis	19.8%
	Arabinan	%, extracted OD basis	0.2%
	Xylan	%, extracted OD basis	17.9%
	Mannan	%, extracted OD basis	1.3%
	Galactan	%, extracted OD basis	0.3%
	Glucan	%, extracted OD basis	43.6%

The hardwood waste was exposed to a delignification reaction according to the method described herein using a modified Caro's acid composition comprising of a 10:10:1:18 molar ratio between the acid, peroxide, modifier, and water. The reaction was left stirring at 35° C. for 18 hours, after which the solids were extracted from the liquid and a yield of the solids was obtained. The wet solids were exposed to a solution of NaOH with a final concentration of 8% wt. NaOH at room temperature for 2 hours. The solids were filtered through a 60 μm filter. The resulting cellulose was reslurried and neutralized. Several washes were conducted to remove salts and obtain a high purity dissolving pulp sample. The sample thus obtained was characterized for composition (Table 7). For clarity, in Table 4, R₁₀ is the portion of the pulp that resists a 10% NaOH concentration, which includes undegraded cellulose or alpha cellulose and R₁₈ is the portion of the pulp that resists 18% NaOH, consisting of the cellulose portion (both degraded and undegraded, alpha and beta).

TABLE 7
Results of the characterization of
the hardwood waste dissolving pulp.

	Parameter	Result

	Kappa number	0.4
	Lignin content (% wt.)	0.06%
	R10 (% wt.)	90.0%
	R18 (% wt.)	99.2%
	Ash content	<0.5%

As observed in Table 7, the results of the characterization of the sugarcane bagasse dissolving pulp post-caustic treatment meet the specifications in Table 4. This highlights that the method described herein allows the production of a high purity dissolving pulp from any biomass using a low-energy process (i.e., ambient temperature, ambient pressure) that brings significant environmental and financial benefits compared to other processes which have substantially higher energy requirements.

It should be known to those skilled in the art that not all lignocellulosic biomass types are desirable in the preparation of dissolving pulp grade cellulose production, as the intrinsic inorganic content of the biomass may be trapped in the fibers, and thus difficult to remove. By way of example, rice hulls and rice straw contain around 15 and 25% wt. of non-volatile inorganic material (ash), respectively. In the case of these biomasses, more than 80% (from rice hulls) and more than 40% (from rice straws) of the ash is comprised of silicon dioxide and silicate salts of calcium, sodium, aluminum and combinations thereof. These types of salts are non-water soluble, and their removal is complex typically employing non-commodity chemicals and specialized equipment, which increases production costs or renders the biomass inviable for this process as the inorganic content is to be removed to avoid interference with the equipment (i.e., plugging of nozzles).

According to a preferred embodiment of the present invention, the lignocellulosic material comprising a lignin content over 2% may be selected from the group consisting of: virgin biomass; waste lignocellulosic biomass; and recycled lignocellulosic biomass. More preferably, the lignocellulosic material is selected from the group consisting of: waste products from forestry operations; waste products from agricultural sources; and waste materials from municipal waste. Preferably, the material comprising a lignin content over 2% is selected from the group consisting of: hardwoods; softwoods; barks; agricultural wastes; herbaceous materials and grasses; fruit pulps; waste from the paper industry; newspaper and cardboard wastes; and combinations thereof.

When used in this specification and claims, the terms “comprises” and “comprising” and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components. The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilized for realizing the invention in diverse forms thereof.