Process for the production of cellulose, lignocellulosic sugars, lignosulfonate, and ethanol

A process for producing lignocellulosic sugars, lignosulfonate, and ethanol, from lignocellulosic biomass comprising:

• (a) contacting lignocellulosic biomass in a first container with steam, wherein the lignocellulosic biomass absorbs water from the steam, thereby removing air from the lignocellulosic biomass;
• (b) contacting the steamed lignocellulosic biomass in a second container with a pretreatment composition comprising sulfur dioxide and water at a temperature between 125° C. and 133° C. under pressure for 20-90 minutes to generate pretreated material;
• wherein the pretreatment composition comprises about 40 wt. % sulfur dioxide and about 60 wt. % water based on the combined weight of sulfur dioxide and water (including water from the steamed lignocellulosic biomass), and the ratio of pretreatment composition to lignocellulosic biomass dry weight is from about 1 to 8 kg/kg (including water from the steamed lignocellulosic biomass in the mass of the pretreatment composition);
• thereby releasing and/or dissolving lignin and hemicellulose from the lignocellulosic biomass into the pretreatment composition and leaving a solid fraction comprising cellulose, wherein the lignin content in the solid fraction comprising cellulose is less than 14 wt. %, the cellulose yield is about 87 wt. % to about 97 wt. % based on the amount of cellulose in the lignocellulosic biomass, and a total saccharide recovery from the lignocellulosic biomass after steps (a) and (b) is greater than 91%;
• wherein 75-100% of the lignin from the lignocellulosic biomass is sulfonated to produce lignosulfonic acid (LS), and at least about 85% of the sugar moieties of the released hemicellulose from the lignocellulosic biomass are hydrolyzed to monosaccharide form;
• and
• wherein the pretreated material comprises 0.1 wt. % furfural or less;
• 0.2 wt. % levulinic acid or less, and less than 0.1 wt. % hydroxymethylfurfural, with respect to dry weight of the pretreated material;
• (c) releasing pressure from the pretreated material and recovering sulfur dioxide from gas released from the pretreated material as a result of releasing pressure, producing a first mixture;
• (d) neutralizing the first mixture to an appropriate pH level for enzymatic hydrolysis;
• (e) contacting the neutralized first mixture with a cellulase, a glucosidase, a hemicellulase, or a combination thereof, to provide a second mixture comprising glucose derived from cellulose and monosaccharides derived from hemicellulose as well as lignosulfonate (salt of lignosulfonic acid), lignin, and oligosaccharides;
• and
• (f) adjusting pH of the second mixture and subjecting the second mixture to fermentation to produce ethanol.

A process for producing cellulose, lignocellulosic sugars, lignosulfonate, and ethanol, from wood sawdust comprising:

• (a) contacting wood sawdust in a first container with steam, wherein the wood sawdust absorbs water from the steam, thereby removing air from the wood sawdust;
• (b) contacting the steamed wood sawdust in a second container with a pretreatment composition comprising sulfur dioxide and water at a temperature of about 130° C. under pressure for about 60-90 minutes to generate pretreated material;
• wherein the pretreatment composition comprises about 40 wt. % sulfur dioxide and about 60 wt. % water based on the combined weight of sulfur dioxide and water (including water from the steamed wood sawdust), and the ratio of pretreatment composition to wood sawdust dry weight is from about 2 kg/kg to 8 kg/kg (including water from the steamed wood sawdust in the mass of the pretreatment composition);
• thereby releasing and/or dissolving lignin and hemicellulose from the wood sawdust into the pretreatment composition and leaving a solid fraction comprising cellulose, wherein the lignin content in the solid fraction comprising cellulose is less than 14 wt. %, the cellulose yield is about 87 wt. % to about 97 wt. % based on the amount of cellulose in the wood sawdust, and a total saccharide recovery from the wood sawdust after steps (a) and (b) is greater than 91%;
• wherein at least about 85% of the lignin from the wood sawdust is sulfonated to produce lignosulfonic acid (LS), and at least about 85% of the sugar moieties of the released hemicellulose from the wood sawdust are hydrolyzed to monosaccharide form;
• and
• wherein the pretreated material comprises less than 0.1 wt. % furfural;
• less than 0.1 wt. % hydroxymethylfurfural, and about 0.1 wt. % levulinic acid or less, with respect to dry weight of the pretreated material;
• (c) releasing pressure from the pretreated material, and recovering sulfur dioxide from gas released from the pretreated material as a result of releasing pressure;
• (d) removing dissolved material from the cellulose by washing with water or by applying pressure to the cellulose to drain off the dissolved material, to provide washed cellulose or pressed cellulose, referred to as a washed cellulose stream, wherein the dissolved material comprises lignosulfonic acid (LS), lignin, hemicellulose oligomers, and monosaccharides;
• (e) adjusting the pH of the washed cellulose stream from step (d) and contacting it with a cellulase, a glucosidase, a hemicellulase, or a combination thereof, to produce glucose and to release small amounts of insoluble lignin and hemicellulose-derived monosaccharides;
• and
• (f) neutralizing the glucose and the dissolved material to an appropriate pH level and subjecting the glucose, the dissolved material, or a combination thereof to fermentation to produce ethanol, wherein when the glucose and dissolved material are subjected to fermentation, at least about 275 kg ethanol per bone dry tonne of wood sawdust is produced.

A process for producing ethanol and lignosulfonate from wood sawdust comprising:

• (a) contacting wood sawdust in a first container with steam, wherein the wood sawdust absorbs water from the steam, thereby removing air from the wood sawdust;
• (b) contacting the steamed wood sawdust in a second container with a pretreatment composition comprising sulfur dioxide and water at a temperature of about 130° C. under pressure for about 60-90 minutes to generate pretreated material;
• wherein the pretreatment composition comprises about 40 wt. % sulfur dioxide and 60 wt. % water based on the combined weight of sulfur dioxide and water (including water from the steamed wood sawdust), and the ratio of pretreatment composition to wood sawdust dry weight is from about 2 kg/kg to 8 kg/kg (including water from the steamed wood sawdust in the mass of the pretreatment composition);
• thereby releasing and/or dissolving lignin and hemicellulose from the wood sawdust into the pretreatment composition and leaving a solid fraction comprising cellulose, wherein the lignin content in the solid fraction comprising cellulose is less than 14 wt. %, the cellulose yield is about 87 wt. % to about 97 wt. % based on the amount of cellulose in the wood sawdust, and a total saccharide recovery from the wood sawdust after steps (a) and (b) is greater than 91%;
• and
• wherein the pretreated material comprises 0.1 wt. % furfural or less;
• 0.2 wt. % levulinic acid or less, and less than 0.1 wt. % hydroxymethylfurfural, with respect to dry weight of the pretreated material;
• wherein at least 85% of the lignin from the wood sawdust is sulfonated to produce lignosulfonic acid (LS), and at least about 85% of the sugar moieties of the released hemicellulose from the wood sawdust are hydrolyzed to monosaccharide form;
• (c) releasing pressure from the pretreated material and recovering sulfur dioxide from gas released from the pretreated material as a result of releasing pressure, producing a first mixture;
• (d) neutralizing the first mixture to an appropriate pH level for enzymatic hydrolysis;
• (e) contacting the neutralized first mixture with a cellulase, a glucosidase, a hemicellulase, or a combination thereof, to provide a second mixture comprising glucose derived from cellulose and monosaccharides derived from hemicellulose as well as lignosulfonate (salt of lignosulfonic acid), lignin, and oligosaccharides;
• and
• (f) adjusting pH of the second mixture and subjecting the second mixture to fermentation to produce at least about 275 kg of ethanol per bone dry tonne of wood sawdust.