A method for preparing a cellulose membrane by extracting cellulose from wood sugar residue

Abstract

The application provides a method for preparing a cellulose membrane from cellulose extracted from xylose residues, and belongs to the technical field of recycling of xylose residues. The xylose residues are mixed with an ionic liquid-co-solvent system, a cellulose solution obtained through centrifugal separation is vacuum defoamed, and a regenerated cellulose membrane is prepared through a flow casting method; the co-solvent and the ionic liquid in the coagulation bath after regeneration of the cellulose membrane can be recycled and utilized, the method is simple in process, mild in reaction condition and friendly to the environment, the prepared cellulose membrane is high in transparency and high in mechanical strength, the effective conversion and utilization of solid residues in the current xylose production process are solved, and a new way is provided for value-added utilization of agricultural and forestry waste biomass residues.

Description

Technical Field

[0001] This invention relates to the field of xylose residue recycling technology, and in particular to a method for extracting cellulose from xylose residue to prepare cellulose membranes. Background Technology

[0002] Cellulose-based polymeric materials, such as regenerated cellulose fibers and films, have attracted widespread attention due to their biodegradability, low toxicity, good biocompatibility, and renewability. Xylose residue is the solid waste remaining after extracting xylose from corn cobs using dilute acid hydrolysis in industry. During the extraction process, the hemicellulose component of the corn cob is largely hydrolyzed by the dilute acid; therefore, the remaining solid residue contains a large amount of cellulose and lignin, representing a rich renewable woody biomass resource. However, in actual production and daily life, the vast majority of xylose residue is directly burned or discarded in the open air, causing serious resource waste and environmental pollution. Traditional alkaline cooking methods for cellulose extraction from xylose residue suffer from problems such as demanding preparation conditions, difficulty in recycling, equipment corrosion, and environmental hazards.

[0003] Ionic liquids have attracted widespread attention in the field of lignocellulosic resource utilization due to their high thermal stability, negligible vapor pressure, excellent cellulose solubility, and ease of recycling and reuse. Patent CN103147331A uses a mixture of four imidazole ionic liquids to extract cellulose from lignocellulosic biomass such as straw, peanut shells, and wheat bran, achieving a purity of over 99% for the regenerated cellulose. However, the mixing of multiple ionic liquids leads to significant cellulose degradation during extraction, and the high viscosity and cost of the mixed ionic liquids limit the subsequent use of the regenerated cellulose. Furthermore, patent US20200239508A1 discloses the extraction of lignin from lignocellulosic waste using pyridine ionic liquids, achieving an extraction rate of up to 90%. However, the use of an acidic proton solvent containing bisulfate during extraction results in high synthesis costs, complex operation, and potential equipment corrosion.

[0004] Therefore, there is an urgent need to design a simple, mild, and environmentally friendly method for extracting cellulose from xylose residue to prepare cellulose membranes. Summary of the Invention

[0005] The purpose of this invention is to provide a method for extracting cellulose from xylose residue to prepare cellulose membranes. This method is simple, has mild conditions, is environmentally friendly, and produces cellulose membranes with high transparency and high mechanical strength.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for extracting cellulose from xylose residue to prepare a cellulose membrane, comprising the following steps:

[0008] The pretreated xylose residue was mixed with an ionic liquid-cosolvent, and the resulting mixture was separated to obtain a cellulose solution.

[0009] After vacuum degassing the cellulose solution, a cellulose film is formed by casting.

[0010] The xylose residue is the solid residue remaining after extracting xylose from corn cobs by dilute acid hydrolysis.

[0011] The ionic liquid is one or more of 1-R2-3-R1-imidazolium dimethyl phosphate, 1-R2-3-R1-imidazolium diethyl phosphate, 1-R2-3-R1-imidazolium dibutyl phosphate, and 1-R2-3-R1-imidazolium chloride; wherein R1 and R2 are independently -C m H 2n+1 m and n take values ​​from 1 to 10, and both m and n are positive integers.

[0012] Preferably, the ionic liquid is any one or a combination of at least two of the following: 1-ethyl-3-methylimidazolium phosphate, 1-ethyl-3-methylimidazolium phosphate, 1-allyl-3-methylimidazolium phosphate, 1-butyl-3-methylimidazolium phosphate, 1-butyl-3-ethylimidazolium phosphate, and 1-ethyl-3-methylimidazolium chloride.

[0013] Preferably, the xylose residue comprises 55.4–64.9 wt% cellulose and 19.6–26.8 wt% lignin.

[0014] Preferably, the co-solvent is one or more of DMSO, DMF, and DMAc.

[0015] Preferably, the mass ratio of the xylose residue, ionic liquid, and co-solvent is 0.02–0.10:1:0.5–3.

[0016] Preferably, the mixing temperature is 60–100°C, and the mixing time is 0.5–3 hours.

[0017] Preferably, the mixing is carried out under stirring conditions, and the stirring speed is 100-150 rpm.

[0018] Preferably, the vacuum degassing treatment time is 6h to 18h, and the vacuum degassing treatment temperature is 50 to 80℃.

[0019] Preferably, the coagulation bath used in the casting method is water and / or ethanol.

[0020] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0021] 1) The synthesis methods of phosphate ester ionic liquids and halogen ionic liquids used in this invention are simple, low-cost, have low viscosity, and high thermal stability.

[0022] 2) This invention utilizes the high polarity of the co-solvent to interact with the hydrogen bonds and van der Waals forces in the cellulose molecules, thereby disrupting the interaction forces between cellulose molecules, thus swelling the cellulose in the xylose residue, significantly reducing the viscosity of the ionic liquid, accelerating the mass transfer between the ionic liquid and cellulose, and further effectively reducing the cost of the solvent while improving the solubility of the ionic liquid.

[0023] 3) The method described in this invention treats xylose residue using an ionic liquid compound system to obtain a high-purity cellulose solution for casting. Both the co-solvent and the ionic liquid in the coagulation bath can be recycled and reused, and their solubility remains essentially unchanged. This method is simple, has mild reaction conditions, and is environmentally friendly. The prepared cellulose membrane has high transparency and high mechanical strength, solving the problem of effective conversion and utilization of solid residues in the current xylose production process and providing a new way for the value-added utilization of industrial and agricultural waste biomass residues.

[0024] 4) The mixed system of phosphate ester ionic liquid, halogen ionic liquid and co-solvent used in this invention can efficiently dissolve cellulose in xylose residue under normal pressure, and cellulose film is prepared by casting method. Compared with the traditional alkaline cooking method, the method provided by this invention has milder reaction conditions, is simpler to operate and more environmentally friendly. The ionic liquid and co-solvent used can be recycled. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the operation process of the method for extracting and separating cellulose from xylose residue to prepare cellulose membrane according to the present invention;

[0026] Figure 2 This is a photograph of the xylose residue raw material used in this invention.

[0027] Figure 3 This is a picture of the xylose residue obtained after pretreatment such as washing, drying, crushing, and degreasing in this invention. Detailed Implementation

[0028] like Figure 1 As shown, the present invention provides a method for preparing cellulose membranes by extracting cellulose from xylose residue, comprising the following steps:

[0029] The pretreated xylose residue was mixed with an ionic liquid-cosolvent, and the resulting mixture was separated to obtain a cellulose solution.

[0030] After vacuum degassing the cellulose solution, a cellulose film is formed by casting.

[0031] The xylose residue is the solid residue remaining after extracting xylose from corn cobs by dilute acid hydrolysis.

[0032] The ionic liquid is one or more of 1-R2-3-R1-imidazolium dimethyl phosphate, 1-R2-3-R1-imidazolium diethyl phosphate, 1-R2-3-R1-imidazolium dibutyl phosphate, and 1-R2-3-R1-imidazolium chloride; wherein R1 and R2 are independently -C m H 2n+1 m and n take values ​​from 1 to 10, and both m and n are positive integers.

[0033] In this invention, unless otherwise specified, all raw materials required for preparation are commercially available products well known to those skilled in the art.

[0034] This invention involves mixing pretreated xylose residue with an ionic liquid-cosolvent, separating the resulting mixture, and obtaining a cellulose solution.

[0035] In this invention, the xylose residue is the remaining solid residue after extracting xylose from corn cobs using dilute acid hydrolysis, such as... Figure 2 As shown; the present invention does not have a special limitation on the source of the xylose residue, which can be obtained in a manner known in the art.

[0036] In this invention, the pretreatment is preferably to wash, dry, pulverize, and defatted the xylose residue in sequence; the washing is preferably to wash the xylose residue until neutral; the drying is preferably to dry it at 60°C with forced air until constant weight; the pulverization is preferably to pulverize the xylose residue to 50-70 mesh; the defatting is preferably to place the xylose residue in a Soxhlet extractor, add a mixture of benzene and ethanol in a volume ratio of 2:1 until it exceeds its overflow equilibrium, and then heat and maintain the benzene-ethanol mixture in the bottom flask to boil vigorously for extraction, with the extraction number reaching 36 times.

[0037] In this invention, the xylose residue preferably comprises 55.4–64.9 wt% cellulose and 19.6–26.8 wt% lignin.

[0038] In this invention, the co-solvent is preferably one or more of DMSO, DMF and DMAc; when the co-solvent is two or more of the above, this invention does not have a special limitation on the ratio of different types of co-solvents, and any ratio is acceptable.

[0039] The co-solvent used in this invention, due to its high polarity, can interact with the hydrogen bonds and van der Waals forces in cellulose molecules, thereby disrupting the intermolecular forces of cellulose molecules, thus swelling the cellulose in the xylose residue, significantly reducing the viscosity of the ionic liquid, accelerating the mass transfer between the ionic liquid and cellulose, and further effectively reducing the cost of the solvent while improving the solubility of the ionic liquid.

[0040] In this invention, the ionic liquid is one or more of 1-R2-3-R1-imidazolium dimethyl phosphate, 1-R2-3-R1-imidazolium diethyl phosphate, 1-R2-3-R1-imidazolium dibutyl phosphate, and 1-R2-3-R1-imidazolium chloride; wherein R1 and R2 are independently -C. m H 2n+1 The values ​​of m and n are 1 to 10, and both m and n are positive integers; preferably, it is any one or a combination of at least two of 1-ethyl-3-methylimidazolium phosphate, 1-ethyl-3-methylimidazolium phosphate, 1-allyl-3-methylimidazolium phosphate, 1-butyl-3-methylimidazolium phosphate, 1-butyl-3-ethylimidazolium phosphate and 1-ethyl-3-methylimidazolium chloride; when the ionic liquid is two or more of the above, the present invention does not have a special limitation on the ratio of different types of ionic liquids, and any ratio is acceptable.

[0041] The synthesis methods for phosphate ester ionic liquids and halogen ionic liquids described in this invention are simple, have low viscosity, and high thermal stability.

[0042] In this invention, the mass ratio of the xylose residue, ionic liquid, and co-solvent is preferably 0.02-0.10:1:0.5-3; more preferably 0.035-0.07:1:0.5-2; and even more preferably 0.04-0.06:1:0.5-1.

[0043] In this invention, the mixing temperature is preferably 60-100°C, more preferably 70-90°C, and even more preferably 80-90°C; the mixing time is preferably 0.5-3h, more preferably 0.5-2h, and even more preferably 1.5-2h.

[0044] In this invention, the mixing is preferably carried out under stirring conditions, and the stirring speed is preferably 100-150 rpm, more preferably 100-140 rpm, and even more preferably 120-140 rpm.

[0045] During the mixing process, the cellulose in the pretreated xylose residue dissolves, resulting in a mixture containing cellulose.

[0046] After the mixing is completed, centrifugation is performed to obtain a cellulose solution.

[0047] In this invention, the cellulose solution is subjected to vacuum degassing treatment, and then film is formed by casting to obtain a cellulose film.

[0048] In this invention, the vacuum degassing treatment is preferably carried out in a vacuum drying oven to remove air bubbles from the cellulose solution.

[0049] In this invention, the vacuum degassing treatment time is preferably 6 to 18 hours, more preferably 6 to 10 hours, and even more preferably 8 to 10 hours; the vacuum degassing treatment temperature is preferably 50 to 80°C, more preferably 60 to 70°C, and even more preferably 60 to 65°C.

[0050] In this invention, the preferred casting method is to uniformly coat a film onto a glass plate using a film scraper, then obtain a cellulose wet film in a coagulation bath. After changing the coagulation bath multiple times, the cellulose wet film is fixed with a clamp and naturally dried at room temperature for 48 hours to obtain a cellulose membrane.

[0051] In this invention, the coagulation bath is preferably water and / or ethanol; when the coagulation bath is a mixture of the above two, this invention does not have a special limitation on the ratio of different types of coagulation baths, and any ratio is acceptable.

[0052] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0053] Example 1

[0054] (1) Remove xylitol residue (such as...) Figure 2 (As shown) Wash until neutral, dry it to constant weight by blowing air at 60℃, pulverize and sieve, take 50-70 mesh xylose residue, wrap it in filter paper and extract it, place it in a Soxhlet extractor, add a benzene and ethanol mixture with a volume ratio of 2:1 until it exceeds its overflow equilibrium, heat and keep the benzene-ethanol mixture in the bottom flask boiling vigorously, extract and cycle 36 times, then take out the paper package and air dry it naturally;

[0055] (2) Take 0.35g of pretreated xylose residue (e.g.) Figure 3 As shown, defatted xylose residue powder (50-70 mesh), 10g DMSO, and 10g 1-ethyl-3-methylimidazolium diethyl phosphate were dissolved at a dissolution temperature of 80℃ and a mechanical stirring speed of 100rpm for 2 hours. After the dissolution, the cellulose solution was obtained by centrifugation.

[0056] (3) The cellulose solution was placed in a vacuum drying oven and kept at 60°C for 6 hours. After degassing, the film was uniformly coated onto a glass plate using a film coating machine. The cellulose wet film was then obtained in deionized water. The cellulose wet film was fixed with a clamp after changing the coagulation bath 3 times and then dried naturally at room temperature for 48 hours to obtain the cellulose membrane.

[0057] Example 2

[0058] The only difference from Example 1 is that the pretreated xylose residue used was 0.40g, the ionic liquids 1-ethyl-3-methylimidazolium phosphate diethyl ester and 1-ethyl-3-methylimidazolium phosphate dimethyl ester were 5g each, the dissolution temperature was 70℃, the mechanical stirring speed was 120rpm, the dissolution time was 1.5h, and other conditions remained unchanged.

[0059] Example 3

[0060] The only difference from Example 2 is that the pretreated xylose residue used is 0.70g, the ionic liquid 1-ethyl-3-methylimidazolium dimethyl phosphate is 10g, the mechanical stirring speed is 150rpm, and other reaction conditions remain unchanged.

[0061] Example 4

[0062] The only difference from Example 1 is that the pretreated xylose residue used was 0.60g, DMSO and DMF were 15g each, 10g of ionic liquid 1-allyl-3-methylimidazolium phosphate was used, the dissolution time was 2.0h, and other reaction conditions remained unchanged.

[0063] Example 5

[0064] The only difference from Example 2 is that the pretreated xylose residue used was 0.45g, the ionic liquid 1-butyl-3-methylimidazolium dimethyl phosphate was 10g, the dissolution temperature was 90℃, and other reaction conditions remained unchanged.

[0065] Example 6

[0066] The only difference from Example 1 is that the pretreated xylose residue used is 0.65g, DMSO and DMAc are 15g each, ionic liquids 1-butyl-3-ethylimidazolium phosphate and 1-butyl-3-methylimidazolium phosphate are 5g each, the mechanical stirring speed is 150rpm, and other reaction conditions remain unchanged.

[0067] Example 7

[0068] The other operations are the same as in Example 1, except that the pretreated xylose residue powder used is 0.50g, DMSO and DMF are 10g each, 1-ethyl-3-methylimidazolium chloride is 10g, the mechanical stirring speed for dissolution is 140rpm, and other reaction conditions remain unchanged.

[0069] Performance testing

[0070] 1) In accordance with GB / T 10004-2008 Plastic Composite Films and Bags for Packaging - Dry Lamination and Extrusion Lamination, the cellulose films obtained in Examples 1-8 were subjected to transverse / longitudinal tensile strength tests. The light transmittance, degree of polymerization, and cellulose purity of the cellulose films were tested using methods well-known to those in the art. The results are as follows:

[0071] The cellulose membrane obtained in Example 1 has a longitudinal tensile strength of 24.3 N / mm, a transverse tensile strength of 14.7 N / mm, a light transmittance of 90.3%, a degree of polymerization of 459, and a cellulose purity of 99.5%.

[0072] The cellulose membrane obtained in Example 2 has a longitudinal tensile strength of 23.7 N / mm, a transverse tensile strength of 14.4 N / mm, a light transmittance of 88.6%, a degree of polymerization of 455, and a cellulose purity of 97.5%.

[0073] The cellulose membrane obtained in Example 3 has a longitudinal tensile strength of 22.3 N / mm, a transverse tensile strength of 12.7 N / mm, a light transmittance of 88.1%, a degree of polymerization of 441, and a cellulose purity of 96.6%.

[0074] The cellulose membrane obtained in Example 4 has a longitudinal tensile strength of 23.7 N / mm, a transverse tensile strength of 13.7 N / mm, a light transmittance of 86.5%, a degree of polymerization of 458, and a cellulose purity of 95.4%.

[0075] The cellulose membrane obtained in Example 5 has a longitudinal tensile strength of 23.1 N / mm, a transverse tensile strength of 12.9 N / mm, a light transmittance of 83.6%, a degree of polymerization of 446, and a cellulose purity of 94.8%.

[0076] The cellulose membrane obtained in Example 6 has a longitudinal tensile strength of 23.5 N / mm, a transverse tensile strength of 13.8 N / mm, a light transmittance of 84.5%, a degree of polymerization of 454, and a cellulose purity of 95.8%.

[0077] The cellulose film obtained in Example 7 has a longitudinal tensile strength of 22.7 N / mm, a transverse tensile strength of 12.9 N / mm, a light transmittance of 87.8%, a degree of polymerization of 443, and a cellulose purity of 96.3%.

[0078] 2) The ionic liquid and co-solvent in the coagulation baths of Examples 1-7 were recovered by rotary evaporation under negative pressure at 80°C. The resulting mixture was then dried under vacuum at 80°C to remove residual trace amounts of water and / or ethanol. The results are as follows:

[0079] The recovery rate of the ionic liquid obtained in Example 1 was 97.4%;

[0080] The recovery rate of the ionic liquid obtained in Example 2 was 97.8%;

[0081] The recovery rate of the ionic liquid obtained in Example 3 was 96.3%;

[0082] The recovery rate of the ionic liquid obtained in Example 4 was 97.5%;

[0083] The recovery rate of the ionic liquid obtained in Example 5 was 97.8%;

[0084] The recovery rate of the ionic liquid obtained in Example 6 was 97.2%;

[0085] The recovery rate of the ionic liquid obtained in Example 7 was 97.2%.

[0086] 3) Repeat steps (2) and (3) of Example 1 with the ionic liquids recovered from Examples 1 to 7 to prepare a regenerated cellulose membrane. The longitudinal tensile strength and transverse tensile strength of the cellulose membrane were determined according to GB / T 10004-2008 Plastic Composite Films and Bags for Packaging (Dry Lamination and Extrusion Lamination). The transmittance, degree of polymerization, and cellulose purity of the cellulose film were determined using methods well-known to those in the art. The results are as follows:

[0087] The regenerated cellulose membrane obtained from the recovered ionic liquid in Example 1 has a longitudinal tensile strength of 24.2 N / mm, a transverse tensile strength of 14.8 N / mm, a light transmittance of 90.1%, a degree of polymerization of 457, and a cellulose purity of 99.4%.

[0088] The regenerated cellulose membrane of the recovered ionic liquid in Example 2 has a longitudinal tensile strength of 23.5 N / mm, a transverse tensile strength of 14.3 N / mm, a light transmittance of 88.5%, a degree of polymerization of 456, and a cellulose purity of 97.3%.

[0089] The regenerated cellulose membrane obtained from the recovered ionic liquid in Example 3 has a longitudinal tensile strength of 22.5 N / mm, a transverse tensile strength of 12.3 N / mm, a light transmittance of 87.9%, a degree of polymerization of 443, and a cellulose purity of 96.5%.

[0090] The regenerated cellulose membrane obtained from the recovered ionic liquid in Example 4 has a longitudinal tensile strength of 23.5 N / mm, a transverse tensile strength of 13.4 N / mm, a light transmittance of 86.4%, a degree of polymerization of 455, and a cellulose purity of 95.1%.

[0091] The regenerated cellulose membrane of the recovered ionic liquid in Example 5 has a longitudinal tensile strength of 23.1 N / mm, a transverse tensile strength of 12.8 N / mm, a light transmittance of 83.3%, a degree of polymerization of 444, and a cellulose purity of 94.7%.

[0092] The regenerated cellulose membrane of the recovered ionic liquid in Example 6 has a longitudinal tensile strength of 23.3 N / mm, a transverse tensile strength of 13.8 N / mm, a light transmittance of 84.3%, a degree of polymerization of 455, and a cellulose purity of 95.7%.

[0093] The regenerated cellulose membrane of the recovered ionic liquid in Example 7 has a longitudinal tensile strength of 22.6 N / mm, a transverse tensile strength of 12.9 N / mm, a light transmittance of 87.7%, a degree of polymerization of 442, and a cellulose purity of 96.1%.

[0094] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing cellulose membranes by extracting cellulose from xylose residue, characterized in that, Includes the following steps: The pretreated xylose residue was mixed with an ionic liquid-cosolvent, and the resulting mixture was separated to obtain a cellulose solution. After vacuum degassing the cellulose solution, a cellulose film is formed by casting. The xylose residue is the solid residue remaining after extracting xylose from corn cobs by dilute acid hydrolysis; the xylose residue includes 55.4–64.9 wt% cellulose and 19.6–26.8 wt% lignin; The ionic liquid is one or more of 1-R2-3-R1-imidazolium dimethyl phosphate, 1-R2-3-R1-imidazolium diethyl phosphate, 1-R2-3-R1-imidazolium dibutyl phosphate, and 1-R2-3-R1-imidazolium chloride; wherein R1 and R2 are independently -C m H 2n+1 m and n take values ​​from 1 to 10, and both m and n are positive integers; The co-solvent is one or more of DMSO, DMF, and DMAc; The mass ratio of the xylose residue, ionic liquid, and co-solvent is 0.02–0.10:1:0.5–3.

2. The method for preparing cellulose membranes from xylose residue according to claim 1, characterized in that, The ionic liquid is any one or at least two of the following: 1-ethyl-3-methylimidazolium phosphate, 1-ethyl-3-methylimidazolium phosphate, 1-allyl-3-methylimidazolium phosphate, 1-butyl-3-methylimidazolium phosphate, 1-butyl-3-ethylimidazolium phosphate, and 1-ethyl-3-methylimidazolium chloride.

3. The method for preparing cellulose membranes from xylose residue according to claim 1, characterized in that, The mixing temperature is 60–100°C, and the mixing time is 0.5–3 hours.

4. The method for preparing cellulose membranes from xylose residue according to claim 1 or 3, characterized in that, The mixing is carried out under stirring conditions, and the stirring speed is 100-150 rpm.

5. The method for preparing cellulose membranes from xylose residue according to claim 1, characterized in that, The vacuum degassing treatment lasts for 6 to 18 hours, and the vacuum degassing treatment temperature is 50 to 80°C.

6. The method for preparing cellulose membranes from xylose residue according to claim 1, characterized in that, The coagulation bath used in the casting method is water and / or ethanol.

Images