Method and system for producing liquid fuel from mixed polysaccharides catalyzed by temperature-sensitive phase change acid

Abstract

The application relates to the technical field of residual sludge resource utilization, and discloses a method and system for preparing liquid fuel from mixed polysaccharides in residual sludge by using temperature-sensitive phase change acid as a catalyst. The system comprises a raw material receiving unit, a water content adjusting unit, a catalytic reaction unit, a methanol storage, injection and recovery unit, a product separation unit and a catalyst storage, injection and recovery unit. The residual sludge is used as a substrate, and a temperature-sensitive phase change acid catalyst and methanol are added to realize the conversion of mixed polysaccharides in the residual sludge into biofuel and fuel additives through high-temperature catalytic reaction. The temperature-sensitive phase change characteristic of the catalyst enables it to dissolve in methanol in a high-temperature reaction environment to form a homogeneous reaction environment; and after the reaction is completed, the catalyst changes into a heterogeneous phase and floats above the reaction liquid to be quickly separated and recovered. The method realizes the combination of the advantages of homogeneous and heterogeneous acid catalysis, and breaks through the bottleneck that the existing method cannot simultaneously consider high reaction efficiency, simple catalyst recovery and low equipment corrosion.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of resource utilization of excess sludge, and particularly relates to a method and system for preparing liquid fuel and fuel additive from excess sludge mixed polysaccharides by using temperature-sensitive phase change acid catalysis. BACKGROUND

[0002] With the acceleration of industrialization, the importance of wastewater treatment in environmental management is increasingly prominent. However, the continuous increase in the production of excess sludge not only intensifies the pressure on treatment facilities and land resources, but also may cause secondary environmental pollution. Therefore, how to efficiently treat excess sludge and realize its resource utilization has become a hot research issue.

[0003] The polysaccharides rich in excess sludge can theoretically be used as a raw material for the synthesis of clean liquid biofuels. However, due to the complex composition of mixed polysaccharides (such as glucose, fructose, rhamnose, cellulose, etc.), and the interweaving of protein, lipid, mineral and other components in the sludge, forming a stable composite structure, resulting in great challenges in its resource utilization. Currently, research on the conversion of sugars to clean liquid biofuels mainly focuses on the conversion of pure sugars, while the utilization of mixed polysaccharides in excess sludge has not been fully developed. Methyl levulinate (ML) as a fuel additive can be blended with petrochemical diesel and biodiesel. The carbonyl and ester groups in the ML molecule can isomerize to enol structures, participate in substitution, hydrolysis, addition, condensation, oxidation and reduction reactions, and derive a variety of high-value chemicals with industrial value, while effectively improving the cleanliness of combustion. In addition, during the conversion of excess sludge mixed polysaccharides to ML, furan aldehydes (such as HMF and MMF) can be simultaneously prepared, which also have important industrial value. The aldehyde group, hydroxymethyl group and furan functional group in the HMF molecule can be prepared into a variety of high-quality clean liquid biofuels and chemical products through oxidation, reduction, etherification and other reactions; while MMF becomes an ideal fuel additive due to its excellent blending performance.

[0004] However, existing researches mostly use homogeneous catalysts to prepare ML, HMF and MMF from complex polysaccharide raw materials, which has problems such as difficult catalyst separation, poor recycling performance, equipment corrosion, etc. In addition, most of the heterogeneous acid catalysts have low contact efficiency of raw materials and catalysts in "solid-solid" reactions, resulting in poor reaction effect. The conventional heterogeneous acid catalysis strategy for sludge solubilization relies on external conditions such as heating and pressurization to dissolve or step-by-step liquefy solid excess sludge, gradually realizing the contact of raw material molecules and "heterogeneous non-uniform" acid catalytic sites. SUMMARY

[0005] The present application aims to strengthen the directional alcoholysis of mixed polysaccharides in residual sludge, realize the conversion of polysaccharides in residual sludge into high-value clean oxygen-containing biofuels, and provide a method and system for preparing liquid fuel from mixed polysaccharides in residual sludge by using a temperature-sensitive phase change acid catalyst.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] In the first aspect, the present application provides a method for preparing liquid fuel from mixed polysaccharides in residual sludge by using a temperature-sensitive phase change acid catalyst, which comprises the following steps:

[0008] The residual sludge is used as a substrate, a temperature-sensitive phase change acid catalyst and methanol are added, and a high-temperature catalytic reaction is carried out, so that the mixed polysaccharides in the residual sludge are converted into liquid fuel and fuel additives, the main products are HMF, MMF and ML, and the high-value fine utilization of the mixed polysaccharides in the residual sludge is realized.

[0009] Further improvement of the present application is that the preparation method of the temperature-sensitive phase change acid catalyst is:

[0010] [Bmim]Cl and phosphotungstic acid aqueous solution are stirred at room temperature to form a white precipitate;

[0011] The white precipitate is filtered and washed with ultrapure water, and then dried after recrystallization with acetonitrile to obtain [Bmim] n H 3-n PW 12 O 40 Temperature-sensitive phase change acid catalyst.

[0012] Further improvement of the present application is that the molar ratio of [Bmim]Cl to phosphotungstic acid is 1-3, and the stirring time of [Bmim]Cl and phosphotungstic acid aqueous solution is 8-10 h.

[0013] Further improvement of the present application is that the recrystallization of acetonitrile is 2-3 times, the temperature is 60-80 DEG C, and the drying time is 10-12 h.

[0014] Further improvement of the present application is that the residual sludge includes dry base solid and water, and the mass ratio of methanol to dry base solid is 27-79.

[0015] Further improvement of the present application is that the amount of the temperature-sensitive phase change acid catalyst is 25%-100% of the dry weight of the residual sludge.

[0016] Further improvement of the present application is that the temperature of the high-temperature catalytic reaction is 140 DEG C-200 DEG C, and the reaction time is 4-16 h.

[0017] In a second aspect, the present application further provides a system for preparing liquid fuel from mixed polysaccharides in excess sludge by using temperature-sensitive phase-change acid catalysis, which comprises a raw material receiving unit, a water content adjusting unit, a catalytic reaction unit, a methanol storage, injection and recovery unit, a product separation unit and a catalyst storage, injection and recovery unit.

[0018] The raw material receiving unit is provided with a receiving hopper, and the water content adjusting unit is provided with a dewatering machine, wherein the outlet of the receiving hopper is connected to the inlet of the dewatering machine, and the outlet of the dewatering machine is connected to the catalytic reaction unit.

[0019] The catalytic reaction unit is provided with a main reactor, which is connected to the outlet of the dewatering machine, the methanol storage, injection and recovery unit is provided with a methanol storage tank, and the catalyst storage, injection and recovery unit is provided with a catalyst storage tank, wherein the main reactor is in communication with the methanol storage tank through a pipeline, and the main reactor is in communication with the catalyst storage tank through a conveyor.

[0020] The product separation unit comprises a distillation column group, which is connected to the main reactor.

[0021] Further improvement of the present application is that the receiving hopper and the dewatering machine, and the dewatering machine and the main reactor are connected through screw conveyors, and the main reactor and the distillation column group are connected through a pipeline.

[0022] Further improvement of the present application is that the pipeline is provided with a pump and a control valve.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] The present application provides a method for preparing liquid fuel from mixed polysaccharides in excess sludge by using temperature-sensitive phase-change acid catalysis, which uses excess sludge as a substrate, mixes a temperature-sensitive phase-change acid catalyst and methanol with the excess sludge, and performs high-temperature catalytic reaction on the mixture to convert the mixed polysaccharides in the excess sludge to obtain HMF, MMF and ML, thereby realizing high-value and high-quality utilization of the mixed polysaccharides in the excess sludge. Meanwhile, the new type of temperature-sensitive phase-change acid catalyst used in the method has the characteristics of both homogeneous acid catalysis and easy recycling, realizes the combination of the advantages of homogeneous acid catalysis and heterogeneous acid catalysis and avoids the disadvantages, changes the heterogeneous acid catalyst to homogeneous in the reaction process, realizes effective contact between the raw material molecules and the acid catalytic sites, creates a relatively mild reaction environment, improves the catalytic reaction efficiency, improves the atomic utilization rate, and restores the catalyst to a heterogeneous state after the reaction, thereby realizing convenient recycling of the catalyst.

[0025] The application also provides a system for preparing liquid fuel by using temperature-sensitive phase change acid to catalyze mixed polysaccharide in residual sludge, and provides a new method and technical approach for directional liquefaction and value-added utilization of mixed polysaccharide in sludge, and realizes directional conversion of mixed polysaccharide in residual sludge to prepare high-value-added biofuel. BRIEF DESCRIPTION OF DRAWINGS

[0026] The drawings described herein are for purposes of illustration only and are not intended to limit the scope of the present disclosure in any way. Additionally, one skilled in the art will recognize that the drawings in general are not to scale and that actual dimensions can be larger or smaller than as shown.

[0027] Figure 1 A flow chart of a method for preparing liquid fuel by using temperature-sensitive phase change acid to catalyze mixed polysaccharide in residual sludge according to the application;

[0028] Figure 2 A schematic diagram of a system for preparing liquid fuel by using temperature-sensitive phase change acid to catalyze mixed polysaccharide in residual sludge according to the application;

[0029] Figure 3 A flow chart of a system for preparing liquid fuel by using temperature-sensitive phase change acid to catalyze mixed polysaccharide in residual sludge according to the application.

[0030] Wherein: 1-receiving hopper, 2-screw conveyor, 3-dehydrator, 4-methanol storage tank (storage tank and recovery tank), 5-main reactor, 6-catalyst storage tank (storage tank and recovery tank), 7-distillation column group. DETAILED DESCRIPTION

[0031] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described below in connection with the drawings of the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0032] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed application, but only represents selected embodiments of the application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present application.

[0033] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0034] In the description of the embodiments of the present application, it should be noted that if the terms "upper", "lower", "horizontal", "inner" and the like indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, or the orientation or position relationship when the product of the present application is usually placed, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0035] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly inclined. For example, "horizontal" only means that its direction is relatively more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0036] In the description of the embodiments of the present application, it should be noted that unless otherwise explicitly specified and limited, if the terms "arrangement", "installation", "connection", "connection" appear, they should be understood in a broad sense, for example, they can be fixedly connected, or can be detachably connected, or integrally connected; can be mechanically connected, or can be electrically connected; can be directly connected, or can be indirectly connected through an intermediate medium; can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0037] The present application will be described in further detail below in conjunction with the drawings:

[0038] As shown in the accompanying drawings, Figure 1 The present application provides a method for preparing liquid fuel by catalyzing mixed polysaccharides in residual sludge with temperature-sensitive phase change acid, comprising the following steps:

[0039] S1, using residual sludge as a substrate, mixing temperature-sensitive phase change acid catalyst, methanol and residual sludge to obtain a mixture;

[0040] Specifically, after adjusting the moisture content of the residual sludge, methanol is used as a solvent, and a temperature-sensitive phase change acid catalyst is added and mixed uniformly, wherein the residual sludge includes dry base solid and water, the mass ratio of methanol to dry base solid is 27-79; the amount of temperature-sensitive phase change acid catalyst is 25%-100% of the dry weight of residual sludge.

[0041] S2, the mixture in S1 is subjected to high-temperature catalytic reaction to convert mixed polysaccharides in residual sludge to obtain HMF, MMF and ML, realizing high-value and fine utilization of mixed polysaccharides in residual sludge.

[0042] Specifically, the mixture is subjected to high-temperature catalytic reaction at 140-200 DEG C for 4-16 h to obtain HMF, MMF and ML.

[0043] It should be noted that during the reaction, the reaction environment is at high temperature, and the temperature-sensitive phase change acid catalyst is homogeneous; after the reaction is completed, the system is subjected to cooling treatment, the temperature-sensitive phase change acid catalyst is converted into heterogeneous phase, and is floated above the reaction liquid, which is convenient to separate from the product, and realizes the recycling of the temperature-sensitive phase change acid catalyst.

[0044] The preparation method of the temperature-sensitive phase change acid catalyst is as follows:

[0045] The [Bmim]Cl with a molar ratio of 1-3 is mixed with phosphotungstic acid, and stirred at room temperature for 8-10 h to form a white precipitate;

[0046] The white precipitate is filtered and washed with ultrapure water for several times, the white precipitate is recrystallized with acetonitrile for 2-3 times, and is dried at 60-80 DEG C for 10-12 h to obtain [Bmim]Cl-PW12O40. n H 3-n PW 12 O 40 Temperature-sensitive phase change acid catalyst.

[0047] Preferably, the recrystallization times are 2 times, and the drying is carried out at 80 DEG C for 12 h to obtain [Bmim]Cl-PW12O40. n H 3-n PW 12 O 40 Temperature-sensitive phase change acid catalyst.

[0048] As shown in Figure 2 and Figure 3 The present application also provides a temperature-sensitive phase change acid catalytic residual sludge mixed polysaccharide system for preparing liquid fuel, which comprises a raw material receiving unit, a water content adjusting unit, a catalytic reaction unit, a methanol storage, injection and recovery unit, a product separation unit and a catalyst storage, injection and recovery unit.

[0049] The raw material receiving unit is equipped with a receiving hopper 1, which serves as a storage container for residual sludge. The hopper is designed with a conical structure to facilitate material flow and prevent bridging and blockage. The moisture content adjustment unit is equipped with a dewatering machine 3. The outlet of the receiving hopper 1 is connected to the inlet of the dewatering machine 3 via a screw conveyor 2. The screw conveyor 2 enables the closed-loop transport of residual sludge from the receiving hopper 1 to the dewatering machine 3, and its progressive pushing action effectively handles high-viscosity sludge. It also exhibits good mechanical compatibility with the outlet of the receiving hopper 1, ensuring continuous and stable feeding. The outlet of the dewatering machine 3 is connected to a catalytic reaction unit. The catalytic reaction unit is equipped with a main reactor 5, which is connected to the outlet of the dewatering machine 3. The methanol storage, injection, and recovery unit is equipped with a methanol storage tank 4, and the catalyst storage, injection, and recovery unit is equipped with a catalyst storage tank 6. Pipelines connect the catalyst storage tank 4 to the methanol storage tank 4, and pumps and control valves are installed on these pipelines. The main reactor 5 is connected to the catalyst storage tank 6 via a conveyor. The main reactor 5 provides a high-temperature, high-pressure reaction environment, and an integrated stirring device ensures sufficient contact between the residual sludge, methanol, and catalyst. The product separation unit includes a distillation column group 7, which separates methanol, HMF, MMF, and ML, among other components with different boiling points, through multi-stage distillation. The methanol is recycled. After the reaction is completed, the catalyst is cooled down, and the catalyst is restored to a heterogeneous phase and returned to the catalyst storage tank 6, thus realizing the recovery and recycling of the catalyst. The distillation column group 7 is connected to the main reactor 5.

[0050] Example 1

[0051] In this embodiment, the remaining sludge came from the Xi'an Fourth Sludge Treatment Plant. The content of polysaccharides in the sludge was measured to be 5.84 wt%, the content of protein was 43.80 wt%, and the content of lipids was 6.02 wt%.

[0052] The remaining sludge is continuously conveyed to the dewatering machine 3 via screw conveyor 2 for moisture content adjustment, bringing the moisture content of the remaining sludge to 0%. The dewatered remaining sludge is then mixed with methanol injected into the methanol storage tank 4 and [Bmim]H2PW supplied by the catalyst storage tank 6. 12 O 40 The thermosensitive phase change acid catalyst was mixed and then fed into the main reactor 5, where a high-temperature catalytic reaction was carried out at 200 °C for 8 h. The mass ratio of sludge, methanol and catalyst was 1:52.67:0.67. The reaction products were fed into distillation column group 7 and separated to obtain HMF, MMF and ML with yields of 152.40 mg / g dry polysaccharide, 100.46 mg / g dry polysaccharide and 73.63 mg / g dry polysaccharide, respectively.

[0053] Example 2

[0054] The difference from Example 1 is:

[0055] The temperature of the high-temperature catalytic reaction in this embodiment is 160 ℃, and the yields of HMF, MMF and ML obtained by separating the reaction product through distillation column group 7 are 94.75 mg / g of dry polysaccharide, 55.37 mg / g of dry polysaccharide and 39.38 mg / g of dry polysaccharide, respectively.

[0056] Example 3

[0057] Different from Example 1 is that:

[0058] The temperature of the high-temperature catalytic reaction in this embodiment is 180 ℃, and the yields of HMF, MMF and ML obtained by separating the reaction product through distillation column group 7 are 129.00 mg / g of dry polysaccharide, 84.48 mg / g of dry polysaccharide and 41.67 mg / g of dry polysaccharide, respectively.

[0059] Example 4

[0060] Different from Example 1 is that:

[0061] The mass ratio of sludge, methanol and catalyst in this embodiment is 1:79:1, and the yields of HMF, MMF and ML obtained by separating the reaction product through distillation column group 7 are 69.68 mg / g of dry polysaccharide, 62.71 mg / g of dry polysaccharide and 56.44 mg / g of dry polysaccharide, respectively.

[0062] Example 5

[0063] Different from Example 1 is that:

[0064] The mass ratio of sludge, methanol and catalyst in this embodiment is 1:39.5:0.5, and the yields of HMF, MMF and ML obtained by separating the reaction product through distillation column group 7 are 124.95 mg / g of dry polysaccharide, 112.45 mg / g of dry polysaccharide and 101.21 mg / g of dry polysaccharide, respectively.

[0065] Example 6

[0066] Different from Example 1 is that:

[0067] The mass ratio of sludge, methanol and catalyst in this embodiment is 1:31.6:0.4, and the yields of HMF, MMF and ML obtained by separating the reaction product through distillation column group 7 are 112.78 mg / g of dry polysaccharide, 101.50 mg / g of dry polysaccharide and 91.35 mg / g of dry polysaccharide, respectively.

[0068] Example 7

[0069] Different from Example 1 is that:

[0070] The mass ratio of sludge, methanol and catalyst in this example was 1:26.33:0.33, and the yield of HMF, MMF and ML obtained by separating the reaction product through distillation column group 7 was 122.05 mg / g dry polysaccharide, 109.84 mg / g dry polysaccharide and 98.86 mg / g dry polysaccharide, respectively.

[0071] Example 8

[0072] Different from Example 1 was that:

[0073] In this example, the residual sludge had a moisture content of 30%, and the yield of HMF, MMF and ML obtained by separating the reaction product through distillation column group 7 was 154.00 mg / g dry polysaccharide, 77.78 mg / g dry polysaccharide and 93.36 mg / g dry polysaccharide, respectively.

[0074] Example 9

[0075] Different from Example 1 was that:

[0076] In this example, the residual sludge had a moisture content of 50%, and the yield of HMF, MMF and ML obtained by separating the reaction product through distillation column group 7 was 158.90 mg / g dry polysaccharide, 80.11 mg / g dry polysaccharide and 96.52 mg / g dry polysaccharide, respectively.

[0077] Example 10

[0078] Different from Example 1 was that:

[0079] In this example, the residual sludge had a moisture content of 60%, and the yield of HMF, MMF and ML obtained by separating the reaction product through distillation column group 7 was 134.40 mg / g dry polysaccharide, 67.67 mg / g dry polysaccharide and 81.62 mg / g dry polysaccharide, respectively.

[0080] Example 11

[0081] Different from Example 1 was that:

[0082] In this example, the residual sludge had a moisture content of 80%, and the yield of HMF, MMF and ML obtained by separating the reaction product through distillation column group 7 was 117.60 mg / g dry polysaccharide, 59.11 mg / g dry polysaccharide and 71.50 mg / g dry polysaccharide, respectively.

[0083] Example 12

[0084] Different from Example 1 was that:

[0085] In this embodiment, the residual sludge has a moisture content of 99%, and the yields of HMF, MMF and ML obtained by separating the reaction product through distillation column group 7 are 99.40 mg / g dry polysaccharide, 49.78 mg / g dry polysaccharide and 60.46 mg / g dry polysaccharide, respectively.

[0086] Example 13

[0087] Different from Example 1 is that:

[0088] In this embodiment, the residual sludge is from the Fourth Sludge Treatment Plant in Xi'an, and the polysaccharide content in the sludge is 6.92 wt%, the protein content is 39.77 wt%, and the lipid content is 7.14 wt%. The yields of HMF, MMF and ML obtained by separating the reaction product through distillation column group 7 are 148.02 mg / g dry polysaccharide, 96.93 mg / g dry polysaccharide and 69.13 mg / g dry polysaccharide, respectively.

[0089] Example 14

[0090] Different from Example 1 is that:

[0091] In this embodiment, the residual sludge is from the Fourth Sludge Treatment Plant in Xi'an, and the polysaccharide content in the sludge is 7.51 wt%, the protein content is 41.35 wt%, and the lipid content is 6.93 wt%. The yields of HMF, MMF and ML obtained by separating the reaction product through distillation column group 7 are 146.05 mg / g dry polysaccharide, 93.41 mg / g dry polysaccharide and 60.33 mg / g dry polysaccharide, respectively.

[0092] The above examples show that the temperature-sensitive phase change acid catalyst [Bmim]H2PW 12 O 40 The residual sludge mixed polysaccharide can be efficiently converted into liquid biofuels, the market price of the obtained product is high, and the conversion of low-value residual sludge into high-value chemical products is realized. The temperature-sensitive phase change property of the catalyst can ensure that the catalyst is homogeneous during the reaction process, improve the utilization rate of the active sites of the catalyst, and after the reaction, the catalyst can be conveniently recovered through "homogeneous-heterogeneous" reversible transformation and recycled multiple times.

[0093] Many embodiments and many applications other than those described herein will be apparent to those skilled in the art from consideration of the specification and practice of the teachings herein. Therefore, the scope of the present teachings should be determined by the appended claims and equivalents thereof, rather than by the description alone. All articles and references, including patent applications and publications, are incorporated herein by reference for all that they contain. Any aspect of the subject matter disclosed herein that is not recited in the claims is hereby abandoned. The summary of the application is not intended to limit the scope of the application.

[0094] The above description is further detailed of the present application, and cannot be considered as limiting the specific embodiments of the present application to the above, and for those skilled in the art, without departing from the concept of the present application, a number of simple deductions or replacements can also be made, which should be considered as belonging to the present application determined by the submitted claims.

Claims

1. A method for producing liquid fuel from waste sludge mixed with polysaccharides using a temperature-sensitive phase change acid catalyst, characterized in that, Includes the following steps: Using waste sludge as a substrate, a temperature-sensitive phase change acid catalyst and methanol are added to carry out a high-temperature catalytic reaction, which converts the mixed polysaccharides in the waste sludge into liquid fuel and fuel additives. The main products are hydroxymethylfurfural, MMF and methyl levulinate, realizing the high-value and refined utilization of the mixed polysaccharides in the waste sludge. The preparation method of the thermosensitive phase change acid catalyst is as follows: [Bmim]Cl was stirred with an aqueous solution of phosphotungstic acid at room temperature, resulting in a white precipitate. The white precipitate was filtered and washed with ultrapure water, recrystallized from acetonitrile, and dried to obtain [Bmim]. n H 3-n PW 12 O 40 Thermosensitive phase change acid catalyst.

2. The method for producing liquid fuel from residual sludge mixed with polysaccharides using a temperature-sensitive phase change acid catalysis according to claim 1, characterized in that, The molar ratio of [Bmim]Cl to phosphotungstic acid is 1-3, and the stirring time of the [Bmim]Cl and phosphotungstic acid aqueous solution is 8-10 h.

3. The method for producing liquid fuel from residual sludge mixed with polysaccharides using a temperature-sensitive phase change acid catalysis according to claim 1, characterized in that, The acetonitrile is recrystallized 2-3 times at a temperature of 60-80 ℃ and dried for 10-12 h.

4. The method for producing liquid fuel from residual sludge mixed with polysaccharides using a temperature-sensitive phase change acid catalysis according to claim 1, characterized in that, The remaining sludge comprises dry-based solids and water, wherein the mass ratio of methanol to dry-based solids is 27-79.

5. The method for producing liquid fuel from waste sludge mixed with polysaccharides using a temperature-sensitive phase change acid catalysis according to claim 1, characterized in that, The amount of the thermosensitive phase change acid catalyst used is 25%-100% of the dry weight of the remaining sludge.

6. The method for producing liquid fuel from residual sludge mixed with polysaccharides using a temperature-sensitive phase change acid catalysis according to claim 1, characterized in that, The high-temperature catalytic reaction is carried out at a temperature of 140 ℃-200 ℃ and a reaction time of 4-16 h.

7. A system for producing liquid fuel from waste sludge mixed with polysaccharides using a temperature-sensitive phase change acid catalyst, characterized in that, It includes a raw material receiving unit, a moisture content adjustment unit, a catalytic reaction unit, a methanol storage, injection and recovery unit, a product separation unit, and a catalyst storage, injection and recovery unit; The raw material receiving unit is provided with a receiving hopper (1), and the moisture content adjustment unit is provided with a dehydrator (3). The outlet of the receiving hopper (1) is connected to the inlet of the dehydrator (3), and the outlet of the dehydrator (3) is connected to the catalytic reaction unit. The catalytic reaction unit is equipped with a main reactor (5), which is connected to the outlet of the dehydrator (3). The methanol storage, injection and recovery unit is equipped with a methanol storage tank (4), and the catalyst storage, injection and recovery unit is equipped with a catalyst storage tank (6). The main reactor (5) is connected to the methanol storage tank (4) through a pipeline, and the main reactor (5) is connected to the catalyst storage tank (6) through a conveyor. The product separation unit includes a distillation column group (7), which is connected to the main reactor (5). The catalyst storage tank (6) contains the thermosensitive phase change acid catalyst according to any one of claims 1 to 6.

8. The system for producing liquid fuel from residual sludge mixed with polysaccharides using a temperature-sensitive phase change acid catalysis according to claim 7, characterized in that, The receiving hopper (1) is connected to the dewatering machine (3), and the dewatering machine (3) is connected to the main reactor (5) via a screw conveyor (2). The main reactor (5) is connected to the distillation tower group (7) via a pipeline.

9. The system for producing liquid fuel from residual sludge mixed with polysaccharides using a temperature-sensitive phase change acid catalysis according to claim 7, characterized in that, The pipeline is equipped with a pump and control valves.

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