Dechlorination method of industrial-grade mixed oil

Abstract

The invention provides a dechlorination method of industrial-grade mixed oil, which comprises the following steps: mixing the industrial-grade mixed oil with a photocatalyst, and reacting under an illumination condition, and the preparation method of the photocatalyst comprises the following steps: (1) dipping a porous carrier in a solution containing ferrous ions and ferric ions at the same time, and reacting under the action of inorganic alkali to obtain a porous carrier; generating a magnetic porous carrier loaded with ferroferric oxide; (2) grinding and mixing urea and titanium dioxide, and calcining in an inert atmosphere to obtain composite powder; and (3) loading the composite powder onto a magnetic porous carrier. According to the method, chlorine impurities in the industrial-grade mixed oil are degraded through photocatalysis, the reaction conditions are mild, no secondary pollution is generated in the whole process, and the photocatalyst can be recycled after being regenerated. Furthermore, titanium dioxide, graphite-phase carbon nitride and ferroferric oxide are loaded on a porous carrier, and the titanium dioxide and the graphite-phase carbon nitride can more effectively utilize light energy under the cooperation of the ferroferric oxide, so that the photocatalytic efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of industrial-grade mixed oil, and in particular to a dechlorination method for industrial-grade mixed oil. Background Art

[0002] In today's industrial landscape, industrial-grade blended oil serves as a crucial raw material or energy carrier, enjoying a wide range of applications. It can be derived from food waste, such as through oil extraction and subsequent processing, or through the pyrolysis of waste plastics. After advanced processing, it can be made into biodiesel and biojet fuel for use in industries such as aviation and industrial products, offering new solutions for sustainable energy supply. However, industrial-grade blended oil often contains chlorine impurities. While the concentration of these impurities may be relatively low, their negative impact cannot be underestimated.

[0003] From an industrial production perspective, the presence of chlorine impurities can significantly impact the quality of industrial-grade mixed oil. Firstly, during subsequent processing, such as when using industrial-grade mixed oil for catalytic hydrogenation to produce high-value-added products, chlorine can easily poison the catalyst, altering the structure of its active sites and inhibiting its catalytic activity, significantly reducing its service life and increasing production costs. Secondly, chlorine can exacerbate equipment corrosion. During processing, especially at high temperatures and in the presence of water, chlorides hydrolyze to produce hydrochloric acid, which is highly corrosive to metal equipment. This can cause corrosion and perforation of equipment such as pipelines and reactors, impacting the stable operation of the equipment. Frequent equipment maintenance and replacement is not only time-consuming and labor-intensive, but also causes production interruptions and significant economic losses. Therefore, given the detrimental effects of chlorine impurities on the quality of industrial-grade mixed oils, downstream processing, and environmental protection, research on the dechlorination of industrial-grade mixed oils is of great significance.

[0004] At present, the methods for removing organochlorine from industrial-grade mixed oil mainly include the following: First, physical adsorption method: Commonly used adsorbents include activated carbon, diatomaceous earth, etc. Although this method is simple to operate, its adsorption capacity is limited, and the regeneration process of the adsorbent is difficult and the cost is high. In addition, the selectivity of physical adsorption is poor, which easily leads to the loss of effective components in the oil, affecting the quality and economic value of the oil. Second, chemical dechlorination method: (1) Alkali treatment: dechlorination is achieved by chemical reaction between alkaline substances and organochlorine compounds. However, this method consumes a large amount of oil, resulting in a 20% to 40% decrease in yield. At the same time, other impurities may be introduced during the alkaline treatment process, affecting the purity of the oil. (2) Reduction / oxidation method: Although reduction dechlorination can effectively remove organochlorine, it is easy to leave residual metal contamination, such as iron and zinc content can be as high as 100 to 500 ppm; although the oxidation method can remove organochlorine, it may generate highly toxic byproducts such as dioxins, which cause serious harm to the environment and human health. Third, high-temperature treatment method: (1) Incineration: It needs to be carried out at a high temperature of more than 1100°C, which consumes extremely high energy and causes serious equipment corrosion. A large amount of harmful gases, such as HCl, may also be produced during the high-temperature treatment process, further exacerbating the corrosion of the equipment. (2) Pyrolysis: Although it can be carried out at a lower temperature, there are also problems of equipment corrosion and deterioration of oil quality. The HCl generated during the pyrolysis process not only corrodes the reactor, but also affects the quality of the oil. Fourth, biodegradation method: The metabolism of microorganisms is used to degrade organochlorine compounds. Although this method is environmentally friendly and has no secondary pollution, the degradation rate is slow and the effect on specific types of organochlorine compounds is limited, making it difficult to meet the high-efficiency requirements of industrial production.

[0005] In summary, existing industrial-grade mixed oil dechlorination technologies generally face challenges such as low dechlorination efficiency, high processing costs, secondary pollution, and compromised oil quality. Therefore, developing an efficient, low-cost, and secondary pollution-free method for removing organic chlorine while maintaining oil quality is a pressing technical challenge in industrial production. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for dechlorinating industrial-grade mixed oil with high efficiency, low cost, no secondary pollution and the ability to maintain oil quality.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] The invention provides a dechlorination method for industrial-grade mixed oil, which comprises mixing the industrial-grade mixed oil with a photocatalyst and reacting the mixture under light conditions.

[0009] The industrial-grade mixed oil (UCO) of the present invention is a mixed oil refined from waste oil and fat as raw materials. Its chemical name is fatty acid triglyceride. It is mainly refined and purified from restaurant waste oil and brine oil, and its main components include triglycerides and fatty acids.

[0010] This invention utilizes photocatalytic degradation of organochlorine in industrial-grade mixed oils. The reaction conditions are relatively mild, unlike other high-temperature, high-pressure reactions. This prevents changes in the composition of the industrial-grade mixed oil during the reaction, which could lead to substandard performance in other indicators. The invention also improves photocatalytic efficiency by optimizing the photocatalyst and other factors. Furthermore, the photocatalyst is easy to separate and can be reused after regeneration, resulting in low cost and no secondary pollution.

[0011] In some embodiments, the method for preparing the photocatalyst comprises the following steps:

[0012] (1) immersing the porous carrier in a solution containing both divalent iron ions and trivalent iron ions, and reacting the solution under the action of an inorganic base to generate a magnetic porous carrier loaded with ferrosoferric oxide;

[0013] (2) grinding and mixing urea and titanium dioxide, and calcining them under an inert atmosphere to obtain a composite powder;

[0014] (3) Loading the composite powder onto the magnetic porous carrier.

[0015] The present invention constructs a stable composite structure by in-situ generating ferroferric oxide (Fe3O4) on a porous carrier. By calcining urea and titanium dioxide at high temperature simultaneously, the graphite phase carbon nitride (g-C3N4) generated by the decomposition of urea can be evenly dispersed on the titanium dioxide (TiO2) surface. This evenly dispersed structure helps to improve the separation efficiency of photogenerated carriers and enhance the photocatalytic performance of the catalyst. At the same time, the two can work together to significantly improve the photocatalytic efficiency, expand the light absorption range, and achieve more efficient organic chlorine degradation. Further, titanium dioxide and graphite phase carbon nitride are loaded onto the above-mentioned composite structure. Titanium dioxide and graphite phase carbon nitride can more effectively utilize light energy and improve photocatalytic efficiency under the coordination of ferroferric oxide. In addition, the photocatalyst can be easily separated and recovered by an external magnetic field, simplifying the separation process and reducing the loss of catalyst, thereby significantly reducing production costs.

[0016] In some embodiments, the mass ratio of the urea to the titanium dioxide is 1:(2.5-4), such as 1:2.5, 1:3, 1:3.5, or 1:4. Excessively large or small mass ratios of urea to titanium dioxide will reduce the photocatalytic effect, so it is preferably within the above range.

[0017] In some embodiments, the calcination temperature in step (2) is 500-650°C, such as 500°C, 530°C, 550°C, 580°C, 600°C, 630°C, or 650°C.

[0018] Furthermore, the calcination time in step (2) is 1 to 3 hours, such as 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours.

[0019] In some embodiments, the titanium dioxide is mixed crystal titanium dioxide, and its average particle size is 20 to 30 nm.

[0020] In some specific embodiments, the titanium dioxide is P25 nano titanium dioxide.

[0021] In some embodiments, the step (3) specifically comprises: dispersing the composite powder in an organic solvent to form a suspension, then adding the magnetic porous carrier to the suspension, and ultrasonically treating the suspension.

[0022] Furthermore, the organic solvent is an alcohol solvent, such as ethanol, methanol, etc.

[0023] In some embodiments, the concentration of the suspension is 1 to 5 mg / mL.

[0024] In some embodiments, the mass ratio of the composite powder in step (3) to the magnetic porous carrier is 1:(1-5.5), such as 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, and 1:5.5.

[0025] In some embodiments, the ultrasonic treatment time is 1.5 to 3.5 hours.

[0026] In some embodiments, the method for preparing the photocatalyst further comprises calcining the magnetic porous carrier loaded with the composite powder under an inert atmosphere after step (3). The calcination yields a stable and enhanced photocatalyst, which is convenient for reuse and avoids secondary pollution.

[0027] Furthermore, the calcination after step (3) is performed by stepwise temperature increase.

[0028] Furthermore, the staged temperature-raising calcination includes first calcining at 300-350° C. for 2-4.5 hours, and then heating to 450-550° C. and calcining for 1-1.5 hours.

[0029] In some embodiments, the step (3) further comprises centrifuging the system after the ultrasonic treatment to remove unloaded composite powder.

[0030] Furthermore, the centrifugal speed is 3000-5000 rpm, and the time is 6-13 minutes.

[0031] In some embodiments, the step (3) further comprises washing the magnetic porous carrier of the composite powder before the calcination, and then vacuum drying.

[0032] In some specific embodiments, the vacuum drying comprises vacuum drying at 60-80° C. for 5-12 hours.

[0033] In some specific embodiments, ethanol is used to wash the magnetic porous carrier of the composite powder.

[0034] Furthermore, the number of times of washing with ethanol is 2 to 5 times.

[0035] In some embodiments, the method for preparing the photocatalyst further comprises, before step (1), pre-treating the porous support. The pre-treatment comprises immersing the porous support in an acid solution for reflux treatment, then washing with water until neutral, and drying. The pre-treatment can remove ash and surface impurities from the porous support, facilitating subsequent loading.

[0036] In some specific embodiments, the acid solution is an aqueous nitric acid solution.

[0037] Furthermore, the mass concentration of the acid solution is 7.5% to 12%.

[0038] In some specific embodiments, the reflux treatment is performed at a temperature of 75 to 85° C. and for a time of 4 to 8 hours.

[0039] In some embodiments, the porous support is activated carbon.

[0040] Furthermore, the particle size of the porous carrier is 100-200 mesh.

[0041] In some embodiments, the molar ratio of ferrous ions to ferric ions in the solution containing both ferrous ions and ferric ions is 1:(1.5-3), and the total molar concentration of ferrous ions and ferric ions is 0.25-0.8 mol / L.

[0042] In some embodiments, the volume ratio of the porous carrier to the solution containing both divalent iron ions and trivalent iron ions is 1: (1.5-2.5)

[0043] In some embodiments, the inorganic base in step (1) is selected from one or more of sodium hydroxide and potassium hydroxide.

[0044] Furthermore, the pH of the reaction system in step (1) is controlled to be 10-11, and the temperature is controlled to be 45-70°C.

[0045] In some embodiments, the reaction under light conditions is an intermittent light reaction.

[0046] Furthermore, the intermittent illumination reaction includes the steps of performing a light-shielding reaction and an illumination reaction multiple times or in a single cycle, wherein the light-shielding reaction time accounts for 1 / 3 to 2 / 3 of the total time of the light-shielding reaction and the illumination reaction, and is more preferably 0.4 to 0.6, such as 0.5. Intermittent illumination facilitates the photocatalyst to adsorb organic chlorine in oils and fats, forming a high-concentration organic chlorine environment locally, effectively promoting the efficiency of photocatalytic degradation of organic chlorine. At the same time, after the organic chlorine substances adsorbed on the photocatalyst are degraded, it facilitates the continued adsorption of the photocatalyst.

[0047] In some specific embodiments, the intermittent light reaction includes a first light avoidance reaction, a first light exposure reaction, a second light avoidance reaction, and a second light exposure reaction in sequence, wherein the time of the first light avoidance reaction is 1 to 3 times that of the first light exposure reaction, and the time of the second light avoidance reaction is 1 / 4 to 1 / 2 of that of the second light exposure reaction.

[0048] In some specific embodiments, the total time of the intermittent illumination reaction is 3 to 5 hours.

[0049] In some embodiments, the reaction under light conditions is a continuous light reaction.

[0050] Furthermore, the duration of the continuous illumination reaction is 3 to 5 hours.

[0051] In some embodiments, the wavelength of the light is 450-470 nm and the light intensity is 80-120 mW / cm 2 By optimizing the wavelength and light intensity, it is possible to effectively balance efficiency and thermal effect, while matching the absorption peak of g-C3N4 and improving photocatalytic efficiency.

[0052] In some embodiments, the dechlorination method further comprises mixing the industrial-grade mixed oil with a diluent to form a low-viscosity grease before mixing the industrial-grade mixed oil with the photocatalyst. The low-viscosity grease facilitates dispersion of the photocatalyst and prevents aggregation of photocatalyst particles, thereby increasing the effective surface area and light absorption efficiency of the photocatalyst. Furthermore, it facilitates rapid mass transfer between reactants and products, improving reaction rate and efficiency.

[0053] In some embodiments, the diluent is n-hexane.

[0054] In some embodiments, the volume ratio of the diluent to the industrial-grade mixed oil is (3.5-5):1, such as 3.5:1, 4:1, 4.5:1, or 5:1.

[0055] In some embodiments, the photocatalyst accounts for 1.5% to 5% of the mass of the industrial-grade mixed oil.

[0056] In some embodiments, the dechlorination method further comprises washing the industrial-grade mixed oil with water before reacting under the light conditions.

[0057] In some embodiments, after the reaction under the light irradiation conditions, the reaction system is washed with water to remove inorganic chlorine in the industrial-grade mixed oil.

[0058] In some specific embodiments, the water washing reagent is a sodium hydroxide aqueous solution or water.

[0059] Furthermore, the mass concentration of the sodium hydroxide aqueous solution is 10% to 20%.

[0060] In some specific embodiments, the water washing reagent accounts for 5% to 20% of the mass of the industrial-grade mixed oil.

[0061] In some embodiments, the dechlorination method further includes, after the reaction under the illumination conditions, using a permanent magnet to absorb and separate the photocatalyst in the reaction system to obtain a recovered photocatalyst, then revitalizing the recovered photocatalyst to restore its activity, and then mixing the revitalized photocatalyst with the industrial-grade mixed oil and reacting under illumination conditions. The reaction under illumination conditions is specifically described above and will not be repeated here.

[0062] Furthermore, the resurrection treatment includes washing the recovered photocatalyst, drying it and then irradiating it under an ultraviolet lamp.

[0063] Furthermore, the wavelength of the ultraviolet lamp is 254nm.

[0064] A second aspect of the present invention is to provide a photocatalyst comprising a porous support and ferrosoferric oxide, titanium dioxide and graphite-phase carbon nitride supported on the porous support.

[0065] The third aspect of the present invention is to provide a method for preparing a photocatalyst. The preparation method is as described above and will not be described in detail here.

[0066] The fourth aspect of the present invention is to provide an application of the above-mentioned photocatalyst, wherein the application includes using the photocatalyst to degrade organic chlorine in industrial-grade mixed oil, as described above.

[0067] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0068] The present invention utilizes photocatalytic degradation of chlorine impurities in industrial-grade mixed oil, and the reaction conditions are relatively mild, which can avoid the change of components of industrial-grade mixed oil during the reaction, thereby causing other indicators to be unqualified. The present invention is also by in-situ generation of ferroferric oxide on a porous carrier, thereby constructing a stable composite structure, by high-temperature calcination of urea and titanium dioxide, so that the graphite phase carbon nitride generated by the decomposition of urea can be evenly dispersed on the surface of titanium dioxide, further by loading titanium dioxide and graphite phase carbon nitride onto the above-mentioned composite structure, titanium dioxide and graphite phase carbon nitride are in the collaboration of ferroferric oxide. It is possible to more effectively utilize light energy and improve photocatalytic efficiency. In addition, the photocatalyst of the present invention can be easily separated and recovered by an external magnetic field, with low separation difficulty, low cost, and no secondary pollution throughout the process. DETAILED DESCRIPTION

[0069] The present invention is further described below with reference to the following examples. However, the present invention is not limited to the following examples. The implementation conditions used in the examples may be further adjusted according to the specific requirements of the application. Unspecified implementation conditions are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention may be combined with each other as long as they do not conflict with each other.

[0070] Unless otherwise specified, the raw materials and equipment used in the following examples and comparative examples are all commercially available products.

[0071] Example 1: This example provides a method for dechlorinating an industrial-grade mixed oil, comprising the following steps:

[0072] Step 1: Soak activated carbon (coconut shell activated carbon, particle size 100-200 mesh, purchased from Tanernuo New Materials) in a 10% HNO3 aqueous solution. Reflux the activated carbon at 80°C for 6 hours to remove ash and surface impurities. Then, wash with deionized water until neutral, dry at 120°C for 12 hours, and set aside.

[0073] Step 2: Immerse the activated carbon pretreated in Step 1 in a FeCl3 / FeSO4 aqueous solution (the mass concentration of the FeCl3 / FeSO4 aqueous solution is 0.4 mol / L, wherein the molar ratio of FeCl3 to FeSO4 is 1.65:1) and ultrasonically disperse for 30 minutes. The volume ratio of the pretreated activated carbon to the FeCl3 / FeSO4 aqueous solution is 1:2.5. Add a 10.5% NaOH aqueous solution dropwise to adjust the pH of the system to 10-11. Stir at 65°C for 2 hours to generate Fe3O4 nanoparticles. Separate with a magnet and dry to obtain magnetic activated carbon for later use.

[0074] Step 3: Mix urea and P25 TiO2 (purchased from Xi'an Qiyue Biology) in a mass ratio of 1:3.2 and grind them, then calcine them at 585°C for 2 hours under a nitrogen environment to obtain a TiO2 / g-C3N4 composite photocatalyst for later use.

[0075] Step 4: Disperse the composite photocatalyst powder in ethanol and magnetically stir to form a uniform suspension at a concentration of 3 mg / mL. The magnetic activated carbon prepared in Step 2 (mass ratio of composite photocatalyst to magnetic activated carbon: 1:4) is added to the suspension. The mixture is sonicated for 2.5 hours to ensure that the composite photocatalyst fully penetrates the pores of the magnetic activated carbon. The sonicated mixture is then centrifuged at 4000 rpm for 10 minutes to remove unloaded composite photocatalyst particles. The mixture is then washed 2-5 times with ethanol and vacuum-dried at 70°C for 3 hours to obtain a composite material. The dried composite material is then calcined in a tube furnace under an inert atmosphere (nitrogen) at 320°C for 3-3.5 hours and then at 500°C for 1-1.5 hours to obtain a stably enhanced magnetic photocatalytic activated carbon.

[0076] Step 5: The industrial-grade mixed oil (chlorine content is 43.62ppm) is washed with a sodium hydroxide aqueous solution with a mass concentration of 15% (the sodium hydroxide aqueous solution accounts for 15% of the mass content of the industrial-grade mixed oil). After sufficient stirring, the lower water layer is allowed to stand and separate. The upper layer is the industrial-grade mixed oil from which inorganic chlorine has been removed (chlorine: 36.77ppm). After removing water from it, 4 times its mass of food-grade n-hexane is added to obtain a low-viscosity grease.

[0077] Step 6: Take 100g of the above low viscosity oil and 3.5g of the above magnetic photocatalytic activated carbon and add them into a transparent quartz glass reaction tank (the bottom of the transparent quartz glass reaction tank is equipped with a blue LED array, λ = 460nm, light intensity 80-120mW / cm 2 ), react in the dark for 1 hour, turn on the LED light source, react under light for 0.5 hour, then react in the dark for 1 hour, turn on the LED light source again, react under light for 1.5 hours, and control the reaction temperature to be 50°C. After the reaction, a permanent magnet (0.5T) was used to adsorb the magnetic photocatalytic activated carbon in the reaction solution. The separation time was 5 minutes, and the recovery rate was >98%. The treated industrial-grade mixed oil was washed twice with deionized water, and the amount of deionized water was 8% of the mass of the industrial-grade mixed oil. After washing, centrifugation was performed, and the upper layer of oil was taken. The chlorine content of the sample was detected by a microcoulomb chlorine analyzer, which was 4.62ppm.

[0078] Example 2: This example is substantially the same as Example 1, except that the reaction conditions in step 6 are different.

[0079] In this embodiment, after adding the reaction raw materials in step 6, the reaction is first carried out in the dark for 2 hours, and then the LED light source is turned on and the reaction is carried out under light for 2 hours. The rest is the same as in embodiment 1.

[0080] In this embodiment, the chlorine content of the sample tested using a microcoulometric analyzer is 10.88 ppm.

[0081] Example 3: This example is basically the same as Example 1, except that the reaction conditions in step 6 are different.

[0082] In this embodiment, in step 6, after adding the reaction raw materials, the LED light source is turned on and the illumination reaction is continued for 4 hours. The rest is the same as in embodiment 1.

[0083] In this embodiment, the chlorine content of the sample tested using a microcoulometric analyzer is 12.47 ppm.

[0084] Example 4: The magnetic photocatalytic activated carbon recovered in Example 1 was washed with n-hexane three times, dried at 60° C., and irradiated under an ultraviolet lamp (254 nm) for 1 hour to degrade residual organic matter and restore activity to obtain recovered magnetic photocatalytic activated carbon.

[0085] Then, a low-viscosity grease was prepared according to the method of Example 1. 100 g of the low-viscosity grease and 3.5 g of recovered magnetic photocatalytic activated carbon were added to a transparent quartz glass reaction tank (same as in Example 1). The LED light source was turned on and the reaction was continued for 4 hours. The remaining steps were the same as in Step 6 of Example 1. The magnetic photocatalytic activated carbon in the reaction solution was adsorbed using a permanent magnet (0.5 T). The separation time was 5 minutes, and the recovery rate was >98%.

[0086] In this embodiment, the chlorine content of the sample detected by a microcoulomb chlorine analyzer is 12.65 ppm.

[0087] Example 5: The magnetic photocatalytic activated carbon recovered in Example 1 was washed with n-hexane three times, dried at 60° C., and irradiated under an ultraviolet lamp (254 nm) for 1 hour to degrade residual organic matter and restore activity to obtain recovered magnetic photocatalytic activated carbon.

[0088] Next, a low-viscosity grease was prepared according to the method of Example 1. 100 g of the low-viscosity grease and 3.5 g of recovered magnetic photocatalytic activated carbon were added to a transparent quartz glass reaction tank (same as in Example 1). The reaction conditions and post-processing were the same as in Step 6 of Example 1. The magnetic photocatalytic activated carbon in the reaction solution was adsorbed using a permanent magnet (0.5 T). The separation time was 5 minutes, and the recovery rate was >98%.

[0089] In this embodiment, the chlorine content of the sample detected by a microcoulomb chlorine analyzer is 4.42 ppm.

[0090] Comparative Example 1: This comparative example provides a method for dechlorinating an industrial-grade mixed oil, comprising the following steps:

[0091] Step 1: Soak the activated carbon (same as in Example 1) in a 10% HNO3 aqueous solution and reflux at 80°C for 6 hours to remove ash and surface impurities. Then, wash with deionized water until neutral, dry at 120°C for 12 hours, and set aside.

[0092] Step 2: Prepare low-viscosity grease according to step 5 of Example 1.

[0093] Step 3: Add 3.5 g of the activated carbon treated in Step 1 to 100 g of low-viscosity grease, following the same reaction conditions as in Step 6 of Example 1. A microcoulometric analyzer was used to measure the chlorine content of the washed sample, which was 26.33 ppm. The activated carbon was separated by negative pressure filtration in 23 minutes, with a recovery rate of >95.5%.

[0094] Comparative Example 2: This comparative example is basically the same as Comparative Example 1, except that magnetic activated carbon is used instead of activated carbon in step 3. The magnetic activated carbon is prepared according to the preparation method of magnetic activated carbon in Example 1.

[0095] The chlorine content of the sample was tested using a microcoulometric analyzer and was found to be 28.46 ppm. The magnetic activated carbon in the reaction solution was adsorbed using a permanent magnet (0.5 T) with a separation time of 5 minutes and a recovery rate of >98%.

[0096] Comparative Example 3: This comparative example is basically the same as Example 1, except that the reaction conditions in step 6 are different.

[0097] In this comparative example, after adding the reaction raw materials in step 6, stirring was carried out at 50° C. in the dark for 4 h, and the rest was the same as step 6 of Example 1.

[0098] In this comparative example, the chlorine content of the sample tested using a microcoulomb analyzer was 27.68 ppm.

[0099] Comparative Example 4: This comparative example provides a method for dechlorinating an industrial-grade mixed oil, which is basically the same as Example 1, except that the magnetic photocatalytic activated carbon used in steps 3 and 6 is different.

[0100] In this comparative example, in step 3, only the P25 TiO2 was ground and then calcined under nitrogen, using the same calcination conditions as in Example 1, to obtain a TiO2 photocatalyst. Magnetic photocatalytic activated carbon was then prepared by referring to step 4 of Example 1, and the magnetic photocatalytic activated carbon was reacted with a low-viscosity grease, referring to step 6 of Example 1.

[0101] In this comparative example, the chlorine content of the sample detected by microcoulomb chlorine analyzer was 10.12 ppm.

[0102] Comparative Example 5: This comparative example provides a method for dechlorination of industrial-grade mixed oil, which is basically the same as Example 1, except that the magnetic photocatalytic activated carbon used in steps 3 and 6 is different.

[0103] In this comparative example, in step 3, only urea was ground and then calcined under nitrogen, with the calcination conditions referring to Example 1, to obtain a g-C3N4 photocatalyst. Then, magnetic photocatalytic activated carbon was prepared according to step 4 of Example 1, and the magnetic photocatalytic activated carbon was reacted with a low-viscosity grease according to step 6 of Example 1.

[0104] After the reaction was completed, a sample was taken for testing. The chlorine content of the sample was 24.72 ppm using a microcoulomb chlorine analyzer.

[0105] Comparative Examples 1 and 2 show that using only activated carbon or magnetic activated carbon to treat chlorine impurities in oil and fat is limited in its removal effect. Compared with conventional activated carbon (such as the activated carbon in Comparative Example 1), the use of magnetic materials combined with activated carbon reduces the separation difficulty and improves the efficiency.

[0106] By comparing Example 1 with Comparative Examples 4 and 5, it was found that loading only TiO2 or g-C3N4 on the magnetic activated carbon had limited chlorine removal effect. Unexpectedly, loading both TiO2 and g-C3N4 on the magnetic activated carbon significantly improved the removal of organic chlorine from oils and fats.

[0107] The magnetic photocatalytic activated carbon of the present application is difficult to exert its chlorine removal effect under light-proof conditions (see Comparative Example 3). It can effectively degrade the organic chlorine in grease under light conditions. The present application further optimizes the lighting conditions and adopts intermittently turned on LED light sources during the photocatalytic reaction (such as Examples 1 and 2). This method is not only conducive to the magnetic photocatalytic activated carbon to adsorb organic chlorine in grease, but also can form a high-concentration organic chlorine environment locally, thereby effectively improving the efficiency of photocatalytic degradation of organic chlorine. At the same time, after being degraded, the organic chlorine adsorbed on the magnetic photocatalytic activated carbon can prompt the activated carbon to continue to adsorb more organic chlorine, forming a virtuous circle, and further improving the efficiency and effect of the entire degradation process.

[0108] The above detailed description of the present invention is intended to enable persons familiar with the art to understand the contents of the present invention and implement them. It does not limit the scope of protection of the present invention. Any equivalent changes or modifications made based on the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for dechlorinating industrial-grade mixed oil, characterized in that: The dechlorination method comprises mixing an industrial-grade mixed oil with a photocatalyst and reacting the mixture under light conditions. The preparation method of the photocatalyst comprises the following steps: (1) immersing the porous carrier in a solution containing both divalent iron ions and trivalent iron ions, and reacting the solution under the action of an inorganic base to generate a magnetic porous carrier loaded with ferrosoferric oxide; (2) grinding and mixing urea and titanium dioxide, and calcining them under an inert atmosphere to obtain a composite powder; (3) Loading the composite powder onto the magnetic porous carrier.

2. The method for dechlorinating industrial grade mixed oil according to claim 1, wherein: The mass ratio of the urea to the titanium dioxide is 1:(2.5-4); and / or, The calcination temperature in step (2) is 500-650° C. and the calcination time is 1-3 hours; and / or, The titanium dioxide is mixed crystal titanium dioxide, and its average particle size is 20 to 30 nm.

3. The method for dechlorinating industrial-grade mixed oil according to claim 1, wherein: The step (3) specifically comprises: dispersing the composite powder in an organic solvent to form a suspension, then adding the magnetic porous carrier to the suspension, and ultrasonically treating the suspension; and / or, The mass ratio of the composite powder to the magnetic porous carrier in step (3) is 1:(1-5.5).

4. The method for dechlorinating industrial-grade mixed oil according to claim 1, wherein: The method for preparing the photocatalyst further comprises, after step (3), calcining the magnetic porous carrier loaded with the composite powder under an inert atmosphere; and / or, The method for preparing the photocatalyst further comprises, before step (1), pre-treating the porous carrier, wherein the pre-treatment comprises immersing the porous carrier in an acid solution for reflux treatment, then washing with water until neutral, and drying.

5. The method for dechlorinating industrial-grade mixed oil according to claim 1, wherein: The porous carrier is activated carbon; and / or, The particle size of the porous carrier is 100 to 200 meshes; and / or, The molar ratio of the ferrous ions to the ferric ions in the solution containing both ferrous ions and ferric ions is 1:(1.5-3), and the total molar concentration of the ferrous ions and the ferric ions is 0.25-0.8 mol / L; and / or, The volume ratio of the porous carrier to the solution containing both divalent iron ions and trivalent iron ions is 1:(1.5-2.5); and / or, The inorganic base is selected from one or more of sodium hydroxide and potassium hydroxide.

6. The method for dechlorinating industrial-grade mixed oil according to claim 1, wherein: The reaction under light conditions is an intermittent light reaction.

7. The method for dechlorinating industrial-grade mixed oil according to claim 6, characterized in that: The intermittent illumination reaction includes the steps of performing light-avoidance reaction and illumination reaction multiple times or once, wherein the time of the light-avoidance reaction accounts for 1 / 3 to 2 / 3 of the total time of the light-avoidance reaction and the illumination reaction.

8. The method for dechlorinating industrial-grade mixed oil according to claim 1, wherein: The reaction under light conditions is a continuous light reaction.

9. The method for dechlorinating an industrial-grade mixed oil according to any one of claims 1, 6, 7, and 8, characterized in that: The wavelength of the light is 450-470 nm and the light intensity is 80-120 mW / cm 2 .

10. The method for dechlorinating industrial-grade mixed oil according to claim 1, characterized in that: The dechlorination method further comprises mixing the industrial-grade mixed oil with a diluent to form a low-viscosity grease before mixing the industrial-grade mixed oil with the photocatalyst.

11. The method for dechlorinating industrial-grade mixed oil according to claim 10, characterized in that: The diluent is n-hexane; and / or, The volume ratio of the diluent to the industrial-grade mixed oil is (3.5-5):

1.

12. The method for dechlorinating industrial-grade mixed oil according to claim 1, wherein: The photocatalyst accounts for 1.5% to 5% of the mass of the industrial-grade mixed oil.

13. The method for dechlorinating industrial-grade mixed oil according to claim 1, characterized in that: The dechlorination method further comprises washing the industrial-grade mixed oil with water before reacting under the light conditions; and / or washing the reaction system with water after reacting under the light conditions.

14. The method for dechlorinating industrial-grade mixed oil according to claim 1, wherein: The dechlorination method further includes, after the reaction under the light conditions, using a permanent magnet to absorb and separate the photocatalyst in the reaction system to obtain a recovered photocatalyst, then resurrecting the recovered photocatalyst to restore its activity, and then mixing the resurrected photocatalyst with the industrial-grade mixed oil to react under light conditions.

15. The method for dechlorinating industrial-grade mixed oil according to claim 14, characterized in that: The resurrection treatment includes washing the recovered photocatalyst, drying it and then irradiating it under an ultraviolet lamp.