Method for synchronously converting residual sludge oil and polysaccharide to obtain high-value liquid fuel

Abstract

The present application relates to the technical field of high-value liquid fuel preparation from residual sludge, and provides a method for synchronously converting oil and fat and polysaccharide in residual sludge to prepare high-value liquid fuel, which takes residual sludge as a substrate, adds a double-layer acid-base catalyst and methanol, and performs high-temperature catalytic reaction to realize the synchronous conversion of oil and fat in residual sludge to FAMEs and polysaccharide to ML. In view of the characteristics of the sludge, such as more free fatty acids, and the need for acid-base double-site synergistic catalysis for polysaccharide conversion, the method uses a double-layer acid-base catalyst with a layered structure similar to that of artichoke, which ensures that the acid-base double sites can efficiently play a role, and the polysaccharide in the sludge is subjected to acid-base synergistic catalytic conversion to ML; at the same time, the outer acid site reacts with free fatty acids first to avoid catalyst poisoning caused by excessive content of free fatty acids, and the inner alkali site synergistically catalyzes the conversion of oil and fat in the sludge to FAMEs. Through synchronous conversion, high-value fine products are obtained, providing a more valuable way for the treatment of residual sludge.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high-value conversion of residual sludge, in particular to a method for synchronously converting oil and fat and polysaccharide in residual sludge to obtain high-value liquid fuel, and more particularly to a method for synchronously converting oil and fat and polysaccharide in residual sludge to obtain high-value liquid fuel, which uses an external acid and internal alkali bifunctional catalyst as a catalyst and takes residual sludge in a sewage plant as a substrate, catalyzes the conversion of oil and fat in the residual sludge into FAMEs, and the conversion of polysaccharide in the residual sludge into ML to realize the co-production of high-value liquid fuel. BACKGROUND

[0002] At present, the amount of sewage produced in the world is huge every year, and the amount of sludge, as the "twin brother" of sewage, is also huge. The sludge has a large water content, occupies a large area for landfill disposal, and improper disposal can cause secondary pollution problems such as landfill leachate. The sludge has a complex composition, mainly including various types of organic matter, microorganisms, inorganic particles, colloids and other substances, and is easy to breed bacteria and emit odor. In the prior art, the sludge can be resourcefully utilized by composting fermentation and building material utilization, but the composting treatment is not thorough and is easy to cause secondary pollution, and the building material utilization may have environmental and human risks, and the existing resourceful treatment and disposal cannot achieve fine conversion of potential substrates in the sludge into high-value products. Therefore, how to properly dispose of the sludge is still a big problem in the treatment of municipal solid waste.

[0003] The residual sludge contains a large amount of free fatty acids (FFAs) and has a water content of up to 99%. In addition, the residual sludge also contains polysaccharides and cellulose and other components with resource conversion potential. The oil and fat and polysaccharides in the residual sludge can be catalytically converted to obtain biodiesel and methyl levulinate (ML), respectively. The existing resource conversion method for the treatment and disposal of residual sludge obtains relatively rough products, ignores the fine utilization of the sludge, does not achieve valuable material recovery, and fails to utilize the functional molecules in the sludge. Some studies on the catalytic conversion of cheap sludge to obtain high-value and expensive products are also limited to the utilization of a single component such as oil and fat, and the resource conversion and utilization of the sludge is not complete, and the recovery amount of high-value products is not high. Therefore, it is of great significance to synchronously convert the FFAs, oil and fat and polysaccharides and other components with resource conversion potential in the residual sludge for utilization, which is of great significance for the treatment of sludge.

[0004] Biodiesel is a clean and efficient new energy, and large-scale application can effectively alleviate the energy crisis, reduce people's dependence on fossil fuels, and gradually attract widespread attention. The main component of biodiesel is fatty acid methyl ester (FAMEs), which is usually obtained by esterification or transesterification of fatty acids and oil and fat as substrates with methanol under the action of an acid or alkali catalyst. However, the presence of a large amount of FFAs in the catalytic system will cause poisoning of the alkali catalyst, thereby reducing the catalytic efficiency and affecting the separation of the product.

[0005] Methyl levulinate (ML) is an important platform compound, which is a short-chain ester containing fatty acids. It has potential applications, such as being used as a fuel additive to improve the performance of diesel and petroleum, and has the advantages of good low-temperature fluidity, high lubricity, stable flash point, non-toxicity and non-corrosion. ML is mainly synthesized by using hexose as a substrate, methanol as a solvent, and acid-base catalysts for synergistic catalysis.

[0006] In view of the problems of difficult recovery of liquid catalysts, limited catalytic performance of solid acid or base catalysts, and the like, researchers have developed a solid acid-base bifunctional catalyst to solve the above problems. However, the solid catalyst with coexisting organic acid sites and organic base sites is less common, and the organic acid sites and organic base sites of the conventional solid catalyst are spatially separated and disordered, and there is a problem of poor synergistic effect.

[0007] Therefore, it is of great significance to use a new method to simultaneously convert residual sludge oil and polysaccharides to obtain high-value liquid fuel. SUMMARY

[0008] In view of the problem that the prior art has not realized efficient co-production of biodiesel and ML from residual sludge, the present application provides a method for simultaneously converting residual sludge oil and polysaccharides to obtain high-value liquid fuel.

[0009] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0010] The present application provides a method for simultaneously converting residual sludge oil and polysaccharides to obtain high-value liquid fuel, comprising the following steps:

[0011] Using residual sludge as a substrate, mixing a double-layer acid-base catalyst and methanol with the residual sludge to obtain a residual sludge co-production mixture;

[0012] Performing high-temperature catalytic reaction on the residual sludge co-production mixture to simultaneously convert oil in the sludge to obtain FAMEs and convert polysaccharides to obtain ML, so as to realize the simultaneous conversion of residual sludge oil and polysaccharides to obtain high-value liquid fuel.

[0013] Further, the mass ratio of methanol to residual sludge is 27-157, and the amount of the double-layer acid-base catalyst is 25%-100% of the mass of the residual sludge.

[0014] Further, the temperature of the high-temperature catalytic reaction is 170-190 DEG C, and the reaction time is 16-24 h.

[0015] Preferably, the double-layer acid-base catalyst is a double-layer acid-base catalyst with an outside-acid-inside-base Thistle structure, in which acid sites exist in the outer layer and base sites exist in the inner layer.

[0016] Further, the preparation method of the double-layer acid-base catalyst is as follows:

[0017] Preparation of opal structure by using SiO2 ball as template;

[0018] Synthesis of photolysis amino protecting group;

[0019] Outer layer etching of opal structure and occupation of outer layer etching space by aminoethanethiol to obtain single layer ball;

[0020] Inner layer etching of single layer ball and occupation of inner layer etching space by photolysis amino protecting group to obtain double layer ball with structure of chrysanthemum;

[0021] Ultraviolet irradiation of double layer ball with structure of chrysanthemum to make photolysis amino protecting group in double layer ball with structure of chrysanthemum deprotection to provide alkaline site-NH2;

[0022] Oxidation of aminoethanethiol on outer layer of double layer ball with structure of chrysanthemum after ultraviolet irradiation to expose acidic site-SO3H of double layer ball with structure of chrysanthemum to obtain double layer acid-base catalyst.

[0023] Further, the method for preparing opal structure is as follows:

[0024] Preparation of SiO2 nanoball by using tetraethyl orthosilicate, anhydrous ethanol, ammonia water and water, specifically, adding tetraethyl orthosilicate into anhydrous ethanol to mix uniformly to obtain mixed liquid a; wherein the volume ratio of tetraethyl orthosilicate and anhydrous ethanol in the mixed liquid a is 1:5;

[0025] Adding ammonia water and water into anhydrous ethanol to mix uniformly to obtain mixed liquid b; wherein the volume ratio of ammonia water, water and anhydrous ethanol in the mixed liquid b is 1:3:10;

[0026] Heating the mixed liquid b to 35-45℃, adding the mixed liquid a into the heated mixed liquid b to stir to obtain milky white suspension;

[0027] Centrifuging and precipitating the milky white suspension, drying and calcining under the condition of 550-650℃ to obtain SiO2 nanoball;

[0028] Adding the SiO2 nanoball into mixed liquid containing methyl methacrylate solution, N-propyleneoxysuccinimide, ethylene glycol dimethacrylate solution, dimethyl sulfoxide and 2-hydroxy-2-methylpropiophenone and irradiating by ultraviolet light to obtain opal structure.

[0029] Further, the method for synthesizing photolysis amino protecting group is as follows:

[0030] Adding 6-nitroacetaldehyde and sodium borohydride into anhydrous ethanol to mix uniformly, removing anhydrous ethanol to obtain solid product I;

[0031] The solid product I and 1,1'-carbonyl diimidazole are added into CH2Cl2, and the reaction is completed to obtain product II;

[0032] Ethylene diamine is added into product II, and the reaction is completed, washed, and rotary evaporated to obtain the photolytic amino protecting group.

[0033] Further, the opal structure is etched by using a 10v% HF solution to etch the outer layer and the single layer sphere.

[0034] Further, the aminoethyl mercaptan of the outer layer of the chenopodium structure double-layer sphere is oxidized to expose the acid site-SO3H of the chenopodium structure double-layer sphere.

[0035] Further, the mass yield of the FAMEs can reach 96.5%, and the mass yield of the ML can reach 12.4%. Compared with the prior art, the present application has the following beneficial effects:

[0036] The method uses residual sludge as a substrate, mixes a double-layer acid-base catalyst and methanol with the residual sludge to obtain a residual sludge co-production mixture, and performs high-temperature catalytic reaction on the residual sludge co-production mixture to obtain FAMEs and ML, thereby realizing the synchronous conversion of residual sludge oil and polysaccharide to obtain high-value liquid fuel. In view of the high content of free fatty acids in the sludge, the method uses a double-layer acid-base catalyst to ensure that the acid-base double sites can independently and efficiently play a role in the preparation of FAMEs, thereby avoiding poisoning of the alkali catalytic site, and the acid-base synergistic catalysis can accelerate the conversion of polysaccharide to ML. The method realizes the catalytic conversion and utilization of sludge in the form of high-value liquid fuel. The method is simple and easy to operate, and uses residual sludge from a sewage plant as a substrate to co-produce high-value liquid fuel, thereby improving the value of the resource conversion of the residual sludge, providing a new way for the rationalization of the treatment and disposal of urban solid waste sludge, and having important significance for the resource utilization of residual sludge.

[0037] The double-layer acid-base catalyst in the method is prepared by taking SiO2 ball as a template to prepare a protein structure, and performing inner and outer etching on the protein structure; a photo-cleavage amino protecting group (NVOC) is synthesized, aminoethyl mercaptan is used to occupy the outer etching space, and the photo-cleavage amino protecting group is used to occupy the inner etching space, so as to obtain a double-layer ball with a chrysanthemum-like structure; finally, ultraviolet irradiation is performed to remove the photo-cleavage amino protecting group in the inner part of the double-layer ball with the chrysanthemum-like structure, to provide an alkaline site -NH2, and the aminoethyl mercaptan on the outer part of the double-layer ball with the chrysanthemum-like structure is oxidized, to expose an acid site -SO3H. The method is simple, and the reaction condition is mild. The double-layer acid-base catalyst prepared by the method has a layered structure similar to a chrysanthemum, so that organic acid sites and organic base sites exist in the same space and are arranged in an orderly manner inside and outside. Therefore, neutralization reaction does not occur, so that the organic acid and base sites can play a high-efficiency catalytic role respectively. The outer part is designed to have a water-resistant sulfonic acid group as an acid site, which helps to prolong the service life of the catalyst. Meanwhile, the spatial separation of the organic acid and base sites can avoid poisoning caused by the reaction of a large amount of FFAs with the base catalytic site. The acid site in the outer part can ensure that the FFAs in the sludge are first subjected to esterification reaction to convert the FFAs into biodiesel, and can convert the triglyceride in the sludge into biodiesel through transesterification reaction. The base site in the inner part can efficiently catalyze the conversion of the triglyceride into FAMEs when the amount of FFAs is greatly reduced, so as to improve the mass yield. The synergistic effect of the acid site and the base site can also efficiently catalyze the conversion of polysaccharide in the sludge into ML, so as to realize the spatial separation and orderly arrangement of the organic acid and base sites, ensure that the acid and base sites can synergistically play a high-efficiency role, and realize the value-added utilization of the co-production of liquid fuel from the residual sludge. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 A process flow chart for a method for simultaneously converting oil and polysaccharide in residual sludge to prepare high-value liquid fuel. DETAILED DESCRIPTION

[0039] To make the objectives, 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 in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0040] The following detailed description of embodiments of the application in the drawings provided is not intended to limit the scope of the application claimed, but merely represents selected embodiments of the application. Based upon the embodiments in the application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of the application.

[0041] It should be noted that similar reference numbers and letters represent similar items in the following drawings, and therefore, once an item is defined in one drawing, it need not be further defined and explained in subsequent drawings.

[0042] In the description of the embodiments of the application, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the product of the application is usually placed, and are only for the convenience of describing the application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the application. In addition, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0043] 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.

[0044] In the description of the embodiments of the application, it should also 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 detachably connected, or integrally connected; can be mechanically connected, or electrically connected; can be directly connected, or indirectly connected through an intermediate medium, or the internal communication of two elements. For those of ordinary skill in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0045] The application will be further described in detail below in conjunction with specific embodiments, which are an explanation of the application rather than a limitation.

[0046] Referring to Figure 1 The application discloses a method for synchronously converting residual sludge oil and polysaccharide to obtain high-value liquid fuel, comprising the following steps:

[0047] S1: taking the excess sludge as a substrate, mixing the double-layer acid-base catalyst and methanol with the excess sludge to obtain an excess sludge co-production mixture, the specific operation being: after the concentration treatment of the excess sludge, adding the double-layer acid-base catalyst into the methanol as a solvent, mixing uniformly to obtain the excess sludge co-production mixture; wherein the mass ratio of the methanol to the excess sludge is 27-157, and the amount of the double-layer acid-base catalyst is 25%-100% of the mass of the excess sludge.

[0048] S2: carrying out high-temperature catalytic reaction on the excess sludge co-production mixture to simultaneously convert the oil and fat in the sludge to obtain FAMEs and convert the polysaccharide to obtain ML, so as to realize the simultaneous conversion of the oil and fat and the polysaccharide in the excess sludge to obtain high-value liquid fuel, the specific operation being: carrying out high-temperature catalytic reaction on the excess sludge co-production mixture at 170-190°C for 16-24h to obtain FAMEs and ML, so as to realize the simultaneous conversion of the oil and fat and the polysaccharide in the excess sludge to obtain high-value liquid fuel.

[0049] The double-layer acid-base catalyst is an external-acid and internal-base double-layer acid-base catalyst with an external-acid and internal-base thistle structure, and the preparation method is:

[0050] The opal structure is prepared by taking SiO2 balls as a template, namely:

[0051] SiO2 nanoballs are prepared by using tetraethyl orthosilicate, anhydrous ethanol, ammonia water and water, namely: adding the tetraethyl orthosilicate into the anhydrous ethanol, mixing uniformly to obtain a mixed solution a; wherein the volume ratio of the tetraethyl orthosilicate to the anhydrous ethanol in the mixed solution a is 1:5;

[0052] Ammonia water and water are added into the anhydrous ethanol, mixed uniformly to obtain a mixed solution b; wherein the volume ratio of the ammonia water to the water to the anhydrous ethanol in the mixed solution b is 1:3:10;

[0053] The mixed solution b is heated to 35-45°C, the mixed solution a is added dropwise into the heated mixed solution b, and stirring is carried out to obtain a milky white suspension;

[0054] The milky white suspension is centrifuged and precipitated, dried at 60-70°C, and calcined at 550-650°C for 3-4h to obtain SiO2 nanoballs;

[0055] The SiO2 nanospheres are added into a mixed solution containing methyl methacrylate, N-acryloxy succinimide, ethylene glycol dimethacrylate, dimethyl sulfoxide and 2-hydroxy-2-methylpropiophenone, and then ultraviolet light is irradiated to obtain the opal structure; wherein the ratio of methyl methacrylate, N-acryloxy succinimide, ethylene glycol dimethacrylate, dimethyl sulfoxide, 2-hydroxy-2-methylpropiophenone and SiO2 nanospheres is 0.6g:0.6g:0.12g:200μL:10μL:0.8g; the ultraviolet light irradiation time is 5min-8min.

[0056] Then, the photolysis amino protecting group is synthesized, that is:

[0057] The 6-nitroethanal and sodium borohydride are added into anhydrous ethanol, mixed uniformly, the solution is clear and turns into brown yellow, and the stirring is continued for 5-6h, wherein the ratio of 6-nitroethanal, sodium borohydride and anhydrous ethanol is 2.5g:0.45g:50mL; the anhydrous ethanol is removed by rotary evaporation under vacuum condition, and the solid product I is prepared;

[0058] The solid product I and 1,1'-carbonyldiimidazole are added into CH2Cl2, mixed and reacted completely to obtain the product II;

[0059] The ethylenediamine is added into the product II, stirred and reacted for 12-13h, then diluted with CH2Cl2, washed with saturated NaCl solution, and rotary evaporated under vacuum condition to obtain the photolysis amino protecting group; wherein the ratio of the solid product I, 1,1'-carbonyldiimidazole and ethylenediamine is 1.2g:1.37g:6.26mL.

[0060] The opal structure is subjected to outer layer etching, and the aminoethanethiol is used to occupy the outer layer etching space to obtain the single-layered sphere, that is:

[0061] The opal structure is etched in 10v% hydrofluoric acid for 4-5min, and then washed with ultrapure water to obtain the outer layer etched opal structure; the outer layer etched opal structure is immersed in a 0.1mol / L 2-aminoethanethiol methanol solution for 1-1.5h, taken out and washed with methanol to obtain the single-layered sphere.

[0062] The single-layered sphere is subjected to inner layer etching, and the photolysis amino protecting group is used to occupy the inner layer etching space to obtain the double-layered sphere with chrysanthemum-like structure, that is:

[0063] The obtained single-layered sphere is again placed in 10% hydrofluoric acid for etching for 4-5 min, and after etching, it is washed with ultrapure water to obtain an opal structure with inner-layer etching; the opal structure with inner-layer etching is immersed in a photolyzed amino protecting group solution with a solvent of CH2Cl2 and MeOH at a mass ratio of 1:1 at a concentration of 0.1 mol / L for 1-1.5 h; and then the opal structure is washed with a CH2Cl2 and MeOH solution at a mass ratio of 1:1 to obtain a chenopodium-type double-layered sphere.

[0064] The chenopodium-type double-layered sphere is subjected to ultraviolet irradiation to remove the photolyzed amino protecting group inside the chenopodium-type double-layered sphere to provide an alkaline site -NH2, that is:

[0065] The chenopodium-type double-layered sphere with exposed acidic site -SO3H is subjected to ultraviolet irradiation for 2-3 h to remove the photolyzed amino protecting group inside the chenopodium-type double-layered sphere to provide an alkaline site -NH2.

[0066] Finally, after the ultraviolet irradiation is completed, the aminoethyl mercaptan on the outer layer of the chenopodium-type double-layered sphere is subjected to oxidation to expose the acidic site -SO3H of the chenopodium-type double-layered sphere to obtain a double-layered acid-base catalyst, that is:

[0067] After the ultraviolet irradiation is completed, the chenopodium-type double-layered sphere is placed in a 35wt% H2O2 solution, and is reacted at 40-45°C under a nitrogen atmosphere for 6-8 h to expose the acidic site -SO3H of the chenopodium-type double-layered sphere to obtain a double-layered acid-base catalyst.

[0068] Example 1

[0069] First, a double-layered acid-base catalyst is prepared:

[0070] 10 mL of tetraethyl orthosilicate was added to a 50 mL solution of anhydrous ethanol, stirred to obtain a mixture a; 10 mL of ammonia water, 30 mL of ultrapure water was added to 100 mL of anhydrous ethanol, stirred to obtain a mixture b; the mixture b was placed in a 40°C water bath, the a liquid was slowly added to the b liquid, stirred at 100 r / min for 3.5 h to obtain a milky white suspension; the milky white suspension was placed in a centrifuge tube, centrifuged at 4000 r / min for 3 h, the supernatant was poured, and the precipitate was dried in a 60°C oven for 12 h, then placed in a muffle furnace and calcined at 600°C for 3 h to obtain SiO2 nanospheres. 0.60 g of methyl methacrylate, 0.60 g of N-acryloxy succinimide, 0.12 g of ethylene glycol dimethacrylate, 200 μL of dimethyl sulfoxide and 10 μL of 2-hydroxy-2-methylbenzophenone were placed in a container and stirred to form a clear solution, then 0.8 g of SiO2 nanospheres was added to the solution, stirred uniformly and irradiated with ultraviolet light for 5 min, then the solution filled the voids of the SiO2 spheres and solidified to form a skeleton, and a opal structure was obtained. In a 50 mL solution of anhydrous ethanol, 2.5 g of 6-nitroacetaldehyde and 0.45 g of sodium borohydride were added and stirred for 30 s, then the solution was clear and turned brown yellow, and the stirring was continued at room temperature for 5 h, then the anhydrous ethanol was removed by rotary evaporation under vacuum to obtain a solid product I; 1.2 g of solid product I and 1.37 g of 1,1'-carbonyl diimidazole were mixed and added to 20 mL of CH2Cl2, stirred at room temperature for 12 h, then 15 mL of CH2Cl2 was added and stirred, 6.26 mL of ethylenediamine was added dropwise and stirred for another 12 h, then diluted with CH2Cl2 to 100 mL; washed twice with saturated NaCl solution, and vacuum rotary evaporated to obtain a photolyzed amino protecting group.The opal structure is put into 10v% hydrofluoric acid for 5 min for the first etching, i.e. etching the outer layer of the opal structure, and after the etching is completed, the opal structure is washed with ultrapure water for three times to obtain the opal structure with outer layer etching; then, the opal structure with outer layer etching is immersed into a 0.1 mol / L 2-aminoethanethiol methanol solution for 1 h, washed with methanol for three times to obtain a single-layer sphere; the single-layer sphere is put into 10v% hydrofluoric acid again until the internal etching process is completed, and then washed with ultrapure water for three times to obtain the opal structure with inner layer etching; the opal structure with inner layer etching is immersed into a 0.1 mol / L photolyzed amino protecting group solution for 1 h, the solvent of the photolyzed amino protecting group solution is CH2Cl2 and MeOH with a mass ratio of 1:1, and then washed with a CH2Cl2 and MeOH solution with a mass ratio of 1:1 for three times to obtain a chrysanthemum-like structure double-layer sphere; then, the chrysanthemum-like structure double-layer sphere is irradiated with ultraviolet light for 2 h to deprotect and expose -NH2, to provide basic sites -NH2, and finally, the chrysanthemum-like structure double-layer sphere is immersed into a 35wt% H2O2 solution, and reacted at 40℃ under N2 atmosphere for 6 h to oxidize and expose acidic sites -SO3H to obtain a double-layer level acid-base catalyst, denoted as -NH2 / -SO3H PMCS.

[0071] The residual sludge of a sewage treatment plant is obtained, and after concentration treatment, dry sludge is obtained. It is determined that the oil content in the sludge is 6.0%, and the polysaccharide content is 10.0%. In a typical one-pot method, the sludge is the reaction substrate, and the above-prepared double-layer level acid-base catalyst is used as the catalyst, and methanol is used as the solvent; the weight ratio of alcohol to sludge is 53:1, the catalyst dosage is 67% of the mass of the sludge, the catalytic reaction time is 20 h, and the reaction temperature is 170℃. The results show that the mass yield of FAMEs can reach 96.50%, and the mass yield of ML can reach 12.40%.

[0072] Example 2

[0073] Different from example 1 is that:

[0074] The residual sludge of a sewage treatment plant is obtained, and after concentration treatment, dry sludge is obtained. It is determined that the oil content in the sludge is 6.0%, and the polysaccharide content is 10.0%. In a typical one-pot method, the sludge is the reaction substrate, and the above-prepared double-layer level acid-base catalyst is used as the catalyst, and methanol is used as the solvent; the weight ratio of alcohol to sludge is 53:1, the catalyst dosage is 67% of the mass of the sludge, the catalytic reaction time is 20 h, and the reaction temperature is 170℃. The results show that the mass yield of FAMEs can reach 62.4%, and the mass yield of ML can reach 10.92%.

[0075] Example 3

[0076] Different from example 1 is that:

[0077] Obtaining a sewage treatment plant sludge, concentrated after getting dry sludge, measured, sludge oil content of 8.5%, polysaccharide content of 5%. Typical one pot method, sludge as the reaction substrate, the above preparation of double layer acid-base catalyst as catalyst, methanol as solvent; alcohol sludge weight ratio of 53:1, the amount of catalyst for the sludge quality of 67%, catalytic reaction time 20h, reaction temperature of 190℃. The results for FAMEs mass yield can reach 63.26%, ML mass yield can reach 10.16%.

[0078] Example 4

[0079] Different from example 1 is:

[0080] Obtaining a sewage treatment plant sludge, concentrated after getting dry sludge, measured, sludge oil content of 7%, polysaccharide content of 5.7%. Typical one pot method, sludge as the reaction substrate, the above preparation of double layer acid-base catalyst as catalyst, methanol as solvent; alcohol sludge weight ratio of 53:1, the amount of catalyst for the sludge quality of 67%, catalytic reaction time 20h, reaction temperature of 190℃. The results for FAMEs mass yield can reach 67.76%, ML mass yield can reach 7.78%.

[0081] Example 5

[0082] Different from example 1 is:

[0083] Obtaining a sewage treatment plant sludge, concentrated after getting dry sludge, measured, sludge oil content of 6%, polysaccharide content of 10%. Typical one pot method, sludge as the reaction substrate, the above preparation of double layer acid-base catalyst as catalyst, methanol as solvent; alcohol sludge weight ratio of 53:1, the amount of catalyst for the sludge quality of 67%, catalytic reaction time 24h, reaction temperature of 170℃. The results for FAMEs mass yield can reach 53.18%, ML mass yield can reach 10.16%.

[0084] Example 6

[0085] Different from example 1 is:

[0086] Obtaining a sewage treatment plant sludge, concentrated after getting dry sludge, measured, sludge oil content of 6%, polysaccharide content of 10%. Typical one pot method, sludge as the reaction substrate, the above preparation of double layer acid-base catalyst as catalyst, methanol as solvent; alcohol sludge weight ratio of 53:1, the amount of catalyst for the sludge quality of 67%, catalytic reaction time 16h, reaction temperature of 190℃. The results for FAMEs mass yield can reach 78.11%, ML mass yield can reach 11.8%.

[0087] Example 7

[0088] Different from example 1 is that:

[0089] Obtain the residual sludge from a sewage treatment plant, and get dry sludge after concentration treatment. The oil content in the sludge is 8%, and the polysaccharide content is 7%. In a typical one-pot method, the sludge is the reaction substrate, the above prepared double-layer acid-base catalyst is used as the catalyst, and methanol is used as the solvent; the weight ratio of alcohol to sludge is 27:1, the catalyst dosage is 50% of the mass of the sludge, the catalytic reaction time is 20h, and the reaction temperature is 190℃. The results are that the mass yield of FAMEs can reach 64.5%, and the mass yield of ML can reach 10.25%.

[0090] Example 8

[0091] Different from example 1 is that:

[0092] Obtain the residual sludge from a sewage treatment plant, and get dry sludge after concentration treatment. The oil content in the sludge is 6.4%, and the polysaccharide content is 5.0%. In a typical one-pot method, the sludge is the reaction substrate, the above prepared double-layer acid-base catalyst is used as the catalyst, and methanol is used as the solvent; the weight ratio of alcohol to sludge is 100:1, the catalyst dosage is 25% of the mass of the sludge, the catalytic reaction time is 24h, and the reaction temperature is 190℃. The results are that the mass yield of FAMEs can reach 53.6%, and the mass yield of ML can reach 10.1%.

[0093] Example 9

[0094] Different from example 1 is that:

[0095] Obtain the residual sludge from a sewage treatment plant, and get dry sludge after concentration treatment. The oil content in the sludge is 10.6%, and the polysaccharide content is 7%. In a typical one-pot method, the sludge is the reaction substrate, the above prepared double-layer acid-base catalyst is used as the catalyst, and methanol is used as the solvent; the weight ratio of alcohol to sludge is 157:1, the catalyst dosage is 100% of the mass of the sludge, the catalytic reaction time is 24h, and the reaction temperature is 190℃. The results are that the mass yield of FAMEs can reach 90.6%, and the mass yield of ML can reach 12.2%.

[0096] Example 10

[0097] Different from example 1 is that:

[0098] The residual sludge of a sewage treatment plant is obtained, and dry sludge is obtained after concentration treatment. It is determined that the oil content in the sludge is 11%, and the polysaccharide content is 5%. In a typical one-pot method, the sludge is the reaction substrate, the above-prepared double-layer acid-base catalyst is used as the catalyst, and methanol is used as the solvent; the weight ratio of alcohol to sludge is 124:1, the catalyst dosage is 85% of the mass of the sludge, the catalytic reaction time is 24 h, and the reaction temperature is 180°C. The results show that the mass yield of FAMEs can reach 85.56%, and the mass yield of ML can reach 11.2%.

[0099] Example 11

[0100] Different from example 1 is:

[0101] The residual sludge of a sewage treatment plant is obtained, and dry sludge is obtained after concentration treatment. It is determined that the oil content in the sludge is 9%, and the polysaccharide content is 6.3%. In a typical one-pot method, the sludge is the reaction substrate, the above-prepared double-layer acid-base catalyst is used as the catalyst, and methanol is used as the solvent; the weight ratio of alcohol to sludge is 80:1, the catalyst dosage is 60% of the mass of the sludge, the catalytic reaction time is 22 h, and the reaction temperature is 185°C. The results show that the mass yield of FAMEs can reach 83.56%, and the mass yield of ML can reach 10.82%.

[0102] In summary, a method for synchronously converting residual sludge oil and polysaccharide to produce high-value liquid fuel is provided. The method uses residual sludge of a sewage plant as a substrate, methanol as a solvent, and a double-layer acid-base catalyst as a catalyst for a typical high-temperature catalytic reaction. The acid-base double-site synergistic effect of the double-layer acid-base catalyst catalyzes the conversion of polysaccharide in the sludge to methyl levulinate, improves the catalytic rate, and increases the yield. The method realizes the catalytic conversion of residual sludge to high-value liquid fuel, and truly realizes the co-production of biodiesel and ML from residual sludge, thereby improving the utilization rate of sludge resources.

[0103] The above only describes the preferred embodiments of the present application, and is not intended to limit the technical solutions of the present application in any way. Those skilled in the art should understand that the technical solutions can be easily modified and replaced without departing from the spirit and principles of the present application, and these modifications and replacements also fall within the scope of protection of the claims.

Claims

1. A method for simultaneous conversion of excess sludge oil and fat and polysaccharide to produce high-value liquid fuel, characterized in that, The method comprises the following steps: The double-layer acid-base catalyst and methanol are mixed with the excess sludge to obtain a mixed mixture of the excess sludge; The mixed mixture of the excess sludge is subjected to high-temperature catalytic reaction to simultaneously convert oil and fat in the sludge to obtain FAMEs and convert polysaccharides to obtain ML, so that the high-value liquid fuel is obtained by simultaneously converting the oil and fat and the polysaccharides in the excess sludge; The preparation method of the double-layer acid-base catalyst comprises the following steps: The opal structure is prepared by using SiO2 balls as a template; A photolysis amino protecting group is synthesized; The opal structure is subjected to outer layer etching, and aminoethyl mercaptan is used to occupy the outer layer etching space to obtain a single-layer ball; The single-layer ball is subjected to inner layer etching, and the photolysis amino protecting group is used to occupy the inner layer etching space to obtain a double-layer ball with a chrysanthemum-like structure; The double-layer ball with the chrysanthemum-like structure is subjected to ultraviolet irradiation, so that the photolysis amino protecting group in the double-layer ball is deprotected to provide an alkaline site -NH2; After the ultraviolet irradiation is completed, the aminoethyl mercaptan on the outer layer of the double-layer ball with the chrysanthemum-like structure is subjected to oxidation to expose an acid site -SO3H of the double-layer ball with the chrysanthemum-like structure, so that the double-layer acid-base catalyst is obtained.

2. The process for simultaneous conversion of excess sludge oil and polysaccharide to high value liquid fuel as claimed in claim 1 wherein, The mass ratio of the methanol to the excess sludge is 27-157, and the amount of the double-layer acid-base catalyst is 25%-100% of the mass of the excess sludge.

3. The process for simultaneous conversion of excess sludge oil and polysaccharide to high value liquid fuel as claimed in claim 1 wherein, The temperature of the high-temperature catalytic reaction is 170-190 DEG C, and the reaction time is 16-24 h.

4. The method of simultaneous conversion of excess sludge oil and polysaccharide to produce high value liquid fuel as claimed in claim 1 wherein, The double-layer acid-base catalyst is an outer-acid and inner-alkali double-layer acid-base catalyst with a chrysanthemum-like structure.

5. The process for simultaneous conversion of excess sludge oil and fat and polysaccharide into high value liquid fuel as claimed in claim 1 wherein, The method for preparing the opal structure comprises the following steps: SiO2 nanoballs are prepared by using tetraethyl orthosilicate, anhydrous ethanol, ammonia water and water, specifically, the tetraethyl orthosilicate is added into the anhydrous ethanol to obtain a mixed solution a; the volume ratio of the tetraethyl orthosilicate to the anhydrous ethanol in the mixed solution a is 1:5; The ammonia water, the water and the anhydrous ethanol are added into the anhydrous ethanol to obtain a mixed solution b; the volume ratio of the ammonia water, the water and the anhydrous ethanol in the mixed solution b is 1:3:10; The mixed solution b is heated to 35-45 DEG C, and the mixed solution a is added into the heated mixed solution b to obtain a milky white suspension; The milky white suspension is centrifuged, precipitated, dried and calcined at 550-650 DEG C to obtain the SiO2 nanoballs; The SiO2 nanoballs are added into a mixed solution containing a methyl methacrylate solution, N-propylene succinimidyl, an ethylene glycol dimethyl acrylate solution, dimethyl sulfoxide and 2-hydroxy-2-methylpropiophenone, and ultraviolet light is irradiated to obtain the opal structure.

6. The process for simultaneous conversion of excess sludge oil and fat and polysaccharide into high value liquid fuel as claimed in claim 1 wherein, The method for synthesizing the photolysis amino protecting group comprises the following steps: The 6-nitroacetaldehyde and sodium borohydride are added into anhydrous ethanol, mixed uniformly, and the anhydrous ethanol is removed to obtain a solid product I; The solid product I and 1,1'-carbonyl diimidazole are added into CH2Cl2, mixed and reacted completely to obtain a product II; The ethylenediamine is added into the product II, mixed and reacted completely, washed, and rotary evaporated to obtain the photolysis amino protecting group.

7. The process for simultaneous conversion of excess sludge oil and polysaccharide to high value liquid fuel as claimed in claim 1 wherein, Both the outer layer and the single layer sphere of the opal structure are etched by using a 10 v% HF solution.

8. The process for simultaneous conversion of excess sludge oil and polysaccharide to high value liquid fuel as claimed in claim 1 wherein, The method for exposing the acid site -SO3H of the chrysanthemum-like structure double-layer sphere by oxidizing the aminoethyl mercaptan on the outer layer of the chrysanthemum-like structure double-layer sphere is as follows: the chrysanthemum-like structure double-layer sphere is placed in a 35 wt% H2O2 solution to react, so that the acid site -SO3H of the chrysanthemum-like structure double-layer sphere is exposed.

9. The process for simultaneous conversion of excess sludge oil and polysaccharide to high value liquid fuel as claimed in any one of claims 1 to 8, wherein, The mass yield of the FAMEs can reach 96.5%, and the mass yield of the ML can reach 12.4%.

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