Method and system for preparing liquid fuel by catalyzing residual sludge mixed polysaccharide through temperature-sensitive phase change acid

Abstract

The invention relates to the technical field of residual sludge resource utilization, and discloses a method and system for preparing liquid fuel by catalyzing residual sludge mixed polysaccharide through temperature-sensitive phase change acid. 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, a temperature-sensitive phase change acid catalyst and methanol are added, and a high-temperature catalytic reaction is carried out, so that the mixed polysaccharide in the residual sludge is converted into the biofuel and the fuel additive. Due to the temperature-sensitive phase change characteristic of the catalyst, the catalyst is dissolved in methanol in a high-temperature reaction environment to form a homogeneous reaction environment; and after the reaction is finished, the catalyst is converted into a heterogeneous phase and floats above the reaction liquid, so that the catalyst can be quickly separated and recycled. According to the method, the advantages of homogeneous / heterogeneous acid catalysis are combined, and the bottleneck that the existing method cannot give consideration to high reaction efficiency, simple and convenient catalyst recovery and low equipment corrosion is broken through.

Description

Technical Field

[0001] The invention belongs to the technical field of excess sludge resource utilization, and specifically relates to a method and a system for preparing liquid fuel and fuel additive by using excess sludge mixed with polysaccharides catalyzed by temperature-sensitive phase change acid. Background Art

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

[0003] The polysaccharides rich in excess sludge can theoretically be used as raw materials 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 components such as proteins, lipids, and minerals in the sludge to form a stable composite structure, its resource utilization faces great challenges. At present, research on the conversion of sugars into clean liquid biofuels mainly focuses on the conversion of pure sugars, while the utilization of mixed polysaccharide resources in excess sludge has not been fully developed. Methyl levulinate (ML) is a fuel additive that can be blended with petrochemical diesel and biodiesel. The carbonyl and ester functional groups in the ML molecule can be isomerized into enol structures, participate in substitution, hydrolysis, addition, condensation, oxidation-reduction and other reactions, and derive a variety of high-value-added chemicals with industrial value, while effectively improving the cleanliness of combustion. In addition, in the process of converting excess sludge mixed polysaccharides into ML, furan aldehydes (such as HMF and MMF) can be simultaneously produced, and these compounds also have important industrial value. The aldehyde, hydroxymethyl and furan functional groups in the HMF molecule can be used to prepare a variety of high-quality clean liquid biofuels and chemical products through oxidation, reduction, etherification and other reactions; and MMF has become an ideal fuel additive due to its excellent blending properties.

[0004] However, existing studies have mostly used homogeneous catalysts to produce ML, HMF and MMF from complex polysaccharide raw materials, which have problems such as difficult catalyst separation, poor recyclability, and equipment corrosion. In addition, most heterogeneous acid catalysts have poor reaction effects in "solid-solid" reactions due to low contact efficiency between the raw materials and the catalyst. Conventional heterogeneous acid-catalyzed residual sludge solvent hydrolysis strategies rely on external conditions such as heating and pressurization. By dissolving or gradually liquefying the solid residual sludge, the raw material molecules are gradually brought into contact with the "heterogeneous and non-uniform" acid catalytic sites. Summary of the invention

[0005] The purpose of the present invention is to strengthen the directional alcoholysis of mixed polysaccharides in excess sludge, realize the conversion of polysaccharides in excess sludge into high value-added clean oxygen-containing biofuels, and provide a method and system for preparing liquid fuel from mixed polysaccharides in excess sludge by temperature-sensitive phase change acid catalysis.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing liquid fuel by mixing excess sludge with polysaccharides using a temperature-sensitive phase change acid catalyst, comprising the following steps: Using residual sludge as substrate, adding thermosensitive phase change acid catalyst and methanol, a high-temperature catalytic reaction is carried out to convert the mixed polysaccharides in the residual sludge into liquid fuel and fuel additives. The main products are HMF, MMF and ML, realizing the high-value and refined utilization of mixed polysaccharides in the residual sludge.

[0007] A further improvement of the present invention is that the preparation method of the thermosensitive phase change acid catalyst is: [Bmim]Cl and phosphotungstic acid aqueous solution were stirred at room temperature to form 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.

[0008] A further improvement of the present invention is that the molar ratio of [Bmim]Cl to phosphotungstic acid is 1-3, and the stirring time of [Bmim]Cl and the phosphotungstic acid aqueous solution is 8-10 h.

[0009] A further improvement of the present invention is that the acetonitrile is recrystallized 2-3 times, the temperature is 60-80°C, and the drying time is 10-12 h.

[0010] A further improvement of the present invention is that the excess sludge comprises dry solids and water, and the mass ratio of the methanol to the dry solids is 27-79.

[0011] A further improvement of the present invention is that the dosage of the temperature-sensitive phase change acid catalyst is 25%-100% of the dry weight of the residual sludge.

[0012] A further improvement of the present invention is that the temperature of the high temperature catalytic reaction is 140°C-200°C and the reaction time is 4-16 h.

[0013] In a second aspect, the present invention also provides a system for preparing liquid fuel by using temperature-sensitive phase change acid-catalyzed excess sludge mixed with polysaccharides, including a raw material receiving unit, a moisture content regulating 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, the moisture content adjusting unit is provided with a dehydrator, the outlet of the receiving hopper is connected to the inlet of the dehydrator, and the outlet of the dehydrator is connected to the catalytic reaction unit; The catalytic reaction unit is provided with a main reactor, which is connected to the outlet of the dehydrator, the methanol storage, injection and recovery unit is provided with a methanol storage tank, the catalyst storage, injection and recovery unit is provided with a catalyst storage tank, the main reactor is connected to the methanol storage tank through a pipeline, and the main reactor is connected to the catalyst storage tank through a conveyor; The product separation unit comprises a distillation tower group, and the distillation tower group is connected to the main reactor.

[0014] A further improvement of the present invention is that the receiving hopper and the dehydrator, the dehydrator and the main reactor are connected by a screw conveyor, and the main reactor and the distillation tower group are connected by a pipeline.

[0015] A further improvement of the present invention is that a pump and a control valve are provided on the pipeline.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for preparing liquid fuel from mixed polysaccharides of excess sludge by using a thermosensitive phase change acid catalyzed by excess sludge. The method uses excess sludge as a substrate, mixes a thermosensitive phase change acid catalyst and methanol with the excess sludge, and performs a 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. At the same time, the novel thermosensitive phase change acid catalyst used in the method has both homogeneous acid catalytic characteristics and the characteristics of being easy to recycle and reuse, realizing the combination of the advantages of homogeneous acid catalysis and heterogeneous acid catalysis and avoiding the disadvantages, and converting the heterogeneous acid catalyst into a homogeneous phase during the reaction process, realizing effective contact between the raw material molecules and the acidic catalytic sites, creating a milder reaction environment, improving the catalytic reaction efficiency, and improving the atomic utilization rate. After the reaction is completed, the catalyst is restored to a heterogeneous state through phase transition, thereby realizing convenient catalyst circulation.

[0017] The present invention also provides a system for preparing liquid fuel from mixed polysaccharides from waste sludge by temperature-sensitive phase change acid catalysis, which enables the mixed polysaccharides in sewage sludge to be directional liquefied into aldehydes / esters for value-added utilization, provides a new method and technical approach for the value-added utilization of mixed polysaccharides from waste sludge, and realizes the directional conversion of mixed polysaccharides in waste sludge to produce high-value-added biofuel. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings described herein are only for explanation purposes and are not intended to limit the scope of the present invention in any way. In addition, the shapes and proportional dimensions of the various components in the drawings are only schematic, used to help understand the present invention, and are not intended to specifically limit the shapes and proportional dimensions of the various components of the present invention.

[0019] Figure 1 This is a flow chart of a method for preparing liquid fuel by mixing excess sludge with polysaccharides using a temperature-sensitive phase change acid catalyst according to the present invention; Figure 2 This is a schematic diagram of the system structure of preparing liquid fuel by mixing excess sludge with polysaccharides using a temperature-sensitive phase change acid catalyzed method according to the present invention; Figure 3 The present invention is a system flow chart for preparing liquid fuel by using temperature-sensitive phase change acid to catalyze excess sludge mixed with polysaccharides.

[0020] Among them: 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 tower group. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0022] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0024] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0025] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0026] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] The present invention is further described in detail below in conjunction with the accompanying drawings: like Figure 1 As shown, the present invention provides a method for preparing liquid fuel by mixing excess sludge with polysaccharides using temperature-sensitive phase change acid catalysis, comprising the following steps: S1, taking the excess sludge as a substrate, mixing the thermosensitive phase change acid catalyst, methanol and the excess sludge to obtain a mixture; Specifically, after adjusting the moisture content of the residual sludge, methanol is used as a solvent, and a thermosensitive phase change acid catalyst is added and mixed evenly, wherein the residual sludge includes dry solids and water, and the mass ratio of methanol to dry solids is 27-79; the dosage of the thermosensitive phase change acid catalyst is 25%-100% of the dry weight of the residual sludge.

[0028] S2, subjecting the mixture in S1 to a high-temperature catalytic reaction to convert the mixed polysaccharides in the residual sludge into HMF, MMF and ML, thereby realizing high-value refined utilization of the mixed polysaccharides in the residual sludge.

[0029] Specifically, the mixture is subjected to a high temperature catalytic reaction at 140°C-200°C for 4-16 hours to obtain HMF, MMF and ML.

[0030] It should be noted that during the reaction, the reaction environment is in a high temperature state, and the thermosensitive phase change acid catalyst used is a homogeneous phase; after the reaction is completed, the system is cooled, and the thermosensitive phase change acid catalyst is transformed into a heterogeneous phase and floats above the reaction liquid, which is conveniently separated from the product, thereby realizing the recycling of the thermosensitive phase change acid catalyst.

[0031] Wherein, the preparation method of the thermosensitive phase change acid catalyst is: Mix [Bmim]Cl and phosphotungstic acid in a molar ratio of 1-3 and stir at room temperature for 8-10 h to form a white precipitate; The white precipitate was filtered and washed with ultrapure water several times. The white precipitate was recrystallized from acetonitrile 2-3 times and dried at 60-80 °C for 10-12 h to obtain [Bmim] n H 3-n PW 12 O 40 Thermosensitive phase change acid catalyst.

[0032] Preferably, the recrystallization is repeated twice and dried at 80 °C for 12 h to obtain [Bmim] n H 3-n PW 12 O 40 Thermosensitive phase change acid catalyst.

[0033] like Figure 2 and Figure 3 As shown, the present invention also provides a system for preparing liquid fuel by using temperature-sensitive phase change acid-catalyzed excess sludge mixed with polysaccharides, including a raw material receiving unit, a moisture content regulating 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, which is a storage container for excess sludge and is set to a conical structure, which is conducive to material flow and prevents bridging blockage; the moisture content regulating unit is provided with a dehydrator 3, the outlet of the receiving hopper 1 is connected to the inlet of the dehydrator 3 through a screw conveyor 2, the screw conveyor 2 realizes the closed transportation of excess sludge from the receiving hopper 1 to the dehydrator 3, and the progressive push of the screw conveyor 2 can effectively treat high-viscosity sludge, and the mechanical matching with the outlet of the receiving hopper 1 is good, ensuring continuous and stable feeding. The outlet of the dehydrator 3 is connected to the catalytic reaction unit; the catalytic reaction unit is provided with a main reactor 5, and the main reactor 5 is connected to the outlet of the dehydrator 3. The methanol storage, injection and recovery unit is provided with a methanol storage tank 4, and the catalyst storage, injection and recovery unit is provided with a catalyst storage tank 6, the pipeline is connected to the methanol storage tank 4, and a pump and a control valve are arranged on the pipeline; the main reactor 5 is connected to the catalyst storage tank 6 through a conveyor; the main reactor 5 is used to provide a high-temperature and high-pressure reaction environment, and the integrated stirring device ensures sufficient contact between the excess sludge, methanol and the catalyst. The product separation unit includes a distillation tower group 7, which separates methanol, HMF, MMF, ML and other components with different boiling points through multi-stage distillation, and the methanol is recycled. After the reaction is completed, the temperature is lowered, and the catalyst is restored to a heterogeneous phase and returned to the catalyst storage tank 6 to realize the recycling of the catalyst; the distillation tower group 7 is connected to the main reactor 5.

[0034] Example 1 The excess sludge in this example was derived from the Fourth Sludge Treatment Plant in Xi'an. The content of polysaccharides in the sludge was determined to be 5.84 wt %, the content of protein was 43.80 wt %, and the content of lipid was 6.02 wt %.

[0035] The excess sludge is continuously conveyed to the dehydrator 3 by the screw conveyor 2 for moisture adjustment, so that the moisture content of the excess sludge is 0%. The excess sludge after dehydration is mixed with the methanol injected from the methanol storage tank 4 and the [Bmim]H provided by the catalyst storage tank 6. 2 PW 12 O 40 The thermosensitive phase change acid catalyst is mixed and then enters the main reactor 5 for high-temperature catalytic reaction at 200 °C for 8 hours, wherein the mass ratio of sludge, methanol and catalyst is 1:52.67:0.67. The reaction products enter the distillation tower group 7 and are separated to obtain HMF, MMF and ML, with yields of 152.40 mg / g dry polysaccharides, 100.46 mg / g dry polysaccharides and 73.63 mg / g dry polysaccharides, respectively.

[0036] Example 2 The difference from Example 1 is: In this embodiment, the temperature of the high temperature catalytic reaction is 160°C, and the yields of HMF, MMF and ML obtained by separation of the reaction products by distillation tower group 7 are 94.75 mg / g dry polysaccharide, 55.37 mg / g dry polysaccharide and 39.38 mg / g dry polysaccharide, respectively.

[0037] Example 3 The difference from Example 1 is: In this embodiment, the temperature of the high temperature catalytic reaction is 180°C, and the yields of HMF, MMF and ML obtained by separation of the reaction products by distillation tower group 7 are 129.00 mg / g dry polysaccharide, 84.48 mg / g dry polysaccharide and 41.67 mg / g dry polysaccharide, respectively.

[0038] Example 4 The difference from Example 1 is: In this embodiment, the mass ratio of sludge, methanol and catalyst is 1:79:1, and the yields of HMF, MMF and ML obtained by separation of the reaction products by distillation tower group 7 are 69.68 mg / g dry polysaccharide, 62.71 mg / g dry polysaccharide and 56.44 mg / g dry polysaccharide, respectively.

[0039] Example 5 The difference from Example 1 is: In this embodiment, the mass ratio of sludge, methanol and catalyst is 1:39.5:0.5, and the yields of HMF, MMF and ML obtained by separation of the reaction products by distillation tower group 7 are 124.95 mg / g dry polysaccharide, 112.45 mg / g dry polysaccharide and 101.21 mg / g dry polysaccharide, respectively.

[0040] Example 6 The difference from Example 1 is: In this embodiment, the mass ratio of sludge, methanol and catalyst is 1:31.6:0.4, and the yields of HMF, MMF and ML obtained by separation of the reaction products by distillation tower group 7 are 112.78 mg / g dry polysaccharide, 101.50 mg / g dry polysaccharide and 91.35 mg / g dry polysaccharide, respectively.

[0041] Example 7 The difference from Example 1 is: In this embodiment, the mass ratio of sludge, methanol and catalyst is 1:26.33:0.33, and the yields of HMF, MMF and ML obtained by separation of the reaction products by distillation tower group 7 are 122.05 mg / g dry polysaccharide, 109.84 mg / g dry polysaccharide and 98.86 mg / g dry polysaccharide, respectively.

[0042] Example 8 The difference from Example 1 is: In this embodiment, the moisture content of the excess sludge was set to 30%, and the yields of HMF, MMF and ML obtained by separation of the reaction products by distillation tower group 7 were 154.00 mg / g dry polysaccharide, 77.78 mg / g dry polysaccharide and 93.36 mg / g dry polysaccharide, respectively.

[0043] Example 9 The difference from Example 1 is: In this embodiment, the moisture content of the excess sludge was set to 50%, and the yields of HMF, MMF and ML obtained by separation of the reaction products by distillation tower group 7 were 158.90 mg / g dry polysaccharide, 80.11 mg / g dry polysaccharide and 96.52 mg / g dry polysaccharide, respectively.

[0044] Example 10 The difference from Example 1 is: In this embodiment, the moisture content of the residual sludge is set to 60%, and the yields of HMF, MMF and ML obtained by separation of the reaction products by distillation tower group 7 are 134.40 mg / g dry polysaccharide, 67.67 mg / g dry polysaccharide and 81.62 mg / g dry polysaccharide, respectively.

[0045] Embodiment 11 The difference from Example 1 is: In this embodiment, the moisture content of the excess sludge is 80%, and the yields of HMF, MMF and ML obtained by separation of the reaction products by distillation tower group 7 are 117.60 mg / g dry polysaccharide, 59.11 mg / g dry polysaccharide and 71.50 mg / g dry polysaccharide, respectively.

[0046] Example 12 The difference from Example 1 is: In this embodiment, the moisture content of the excess sludge is 99%, and the yields of HMF, MMF and ML obtained by separation of the reaction products by distillation tower group 7 are 99.40 mg / g dry polysaccharide, 49.78 mg / g dry polysaccharide and 60.46 mg / g dry polysaccharide, respectively.

[0047] Embodiment 13 The difference from Example 1 is: In this embodiment, the excess sludge is derived from the Fourth Sludge Treatment Plant in Xi'an. The content of polysaccharides in the sludge is determined to be 6.92 wt%, the content of protein is 39.77 wt%, and the content of lipids is 7.14 wt%. The yields of HMF, MMF and ML obtained by separation of the reaction products by distillation tower group 7 are 148.02 mg / g dry polysaccharides, 96.93 mg / g dry polysaccharides and 69.13 mg / g dry polysaccharides, respectively.

[0048] Embodiment 14 The difference from Example 1 is: In this embodiment, the excess sludge is derived from the Fourth Sludge Treatment Plant in Xi'an. The content of polysaccharides in the sludge is determined to be 7.51 wt%, the content of protein is 41.35 wt%, and the content of lipids is 6.93 wt%. The yields of HMF, MMF and ML obtained by separating the reaction products by distillation tower group 7 are 146.05 mg / g dry polysaccharides, 93.41 mg / g dry polysaccharides and 60.33 mg / g dry polysaccharides, respectively.

[0049] The above examples show that the thermosensitive phase change acid catalyst [Bmim]H 2 PW 12 O 40 It can efficiently convert residual sludge mixed with polysaccharides to obtain liquid biofuels. The market price of the obtained products is high, realizing the transformation of low-value residual sludge into high-value chemical products. The temperature-sensitive phase change characteristics of the catalyst can ensure that the catalyst is homogeneous during the reaction process, improve the utilization rate of catalytic active sites, and after the reaction, the catalyst can be easily recovered through the "homogeneous-heterogeneous" reversible transformation and reused multiple times.

[0050] Many embodiments and many applications beyond the examples provided will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of the present teachings should not be determined with reference to the above description, but rather with reference to the preceding claims and the full scope of equivalents to which such claims are entitled. For the purpose of comprehensiveness, all articles and references, including disclosures of patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the preceding claims is not intended to be a disclaimer of such subject matter, nor should it be considered that the applicants did not consider such subject matter to be part of the disclosed inventive subject matter.

[0051] The above content is a further detailed description of the present invention. It cannot be determined that the specific implementation methods of the present invention are limited to these. For ordinary technicians in the technical field to which the present invention belongs, without departing from the concept of the present invention, they can also make several simple deductions or substitutions, which should be regarded as belonging to the protection scope of the present invention determined by the submitted claims.

Claims

1. A method for preparing liquid fuel by mixing excess sludge with polysaccharides using a thermosensitive phase change acid catalyst, characterized in that: The following steps are involved: Using residual sludge as substrate, adding thermosensitive phase change acid catalyst and methanol, a high-temperature catalytic reaction is carried out to convert the mixed polysaccharides in the residual sludge into liquid fuel and fuel additives. The main products are HMF, MMF and ML, realizing the high-value and refined utilization of mixed polysaccharides in the residual sludge.

2. The method for preparing liquid fuel by using excess sludge mixed with polysaccharides catalyzed by temperature-sensitive phase change acid according to claim 1, characterized in that: The preparation method of the temperature-sensitive phase change acid catalyst is: [Bmim]Cl and phosphotungstic acid aqueous solution were stirred at room temperature to form 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.

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

4. The method for preparing liquid fuel by using excess sludge mixed with polysaccharides catalyzed by temperature-sensitive phase change acid according to claim 2, characterized in that: The acetonitrile is recrystallized 2-3 times at a temperature of 60-80° C. and a drying time of 10-12 h.

5. The method for preparing liquid fuel by using excess sludge mixed with polysaccharides catalyzed by temperature-sensitive phase change acid according to claim 1, characterized in that: The residual sludge comprises dry solid and water, and the mass ratio of the methanol to the dry solid is 27-79.

6. The method for preparing liquid fuel by using excess sludge mixed with polysaccharides catalyzed by temperature-sensitive phase change acid according to claim 1, characterized in that: The dosage of the thermosensitive phase change acid catalyst is 25%-100% of the dry weight of the residual sludge.

7. The method for preparing liquid fuel by using excess sludge mixed with polysaccharides catalyzed by temperature-sensitive phase change acid according to claim 1, characterized in that: The temperature of the high temperature catalytic reaction is 140°C-200°C, and the reaction time is 4-16 h.

8. A system for preparing liquid fuel by mixing excess sludge with polysaccharides using temperature-sensitive phase change acid catalysis, characterized in that: It includes a raw material receiving unit, a moisture content regulating 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 regulating 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 provided with a main reactor (5), the main reactor (5) is connected to the outlet of the dehydrator (3), the methanol storage, injection and recovery unit is provided with a methanol storage tank (4), the catalyst storage, injection and recovery unit is provided 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 comprises a distillation tower group (7), and the distillation tower group (7) is connected to the main reactor (5).

9. The system for preparing liquid fuel by using excess sludge mixed with polysaccharides catalyzed by temperature-sensitive phase change acid according to claim 8, characterized in that: The receiving hopper (1) and the dehydrator (3), and the dehydrator (3) and the main reactor (5) are connected via a screw conveyor (2), and the main reactor (5) and the distillation tower group (7) are connected via a pipeline.

10. The system for preparing liquid fuel by using excess sludge mixed with polysaccharides catalyzed by temperature-sensitive phase change acid according to claim 8, characterized in that: A pump and a control valve are arranged on the pipeline.

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