Preparation method and application of oil shale semicoke catalyst

Abstract

The invention belongs to the field of waste resource utilization and the field of wastewater treatment, and particularly relates to a preparation method and application of an oil shale semi-coke catalyst, and the preparation method comprises the following steps: crushing, grinding and sieving oil shale semi-coke to obtain oil shale semi-coke powder; dispersing the obtained oil shale semi-coke powder into an activator solution, stirring and reacting at room temperature to activate the oil shale semi-coke powder, and finally centrifuging, washing and drying to obtain the target product oil shale semi-coke catalyst. The oil shale semicoke is a solid residue obtained by destructive distillation of oil shale at 450-600 DEG C under an anaerobic condition. The activating agent solution is one of nitric acid, oxalic acid or phosphoric acid, and the mass concentration of the activating agent solution is 4-32%. According to the invention, the lattice structure and surface element composition of the oil shale semicoke can be adjusted, the specific surface area of the oil shale semicoke is increased, the catalytic activity of the oil shale semicoke is improved, and the removal effect of persulfate on organic matters is improved in a pH range of 4-10.

Description

Technical Field

[0001] The invention belongs to the field of waste resource utilization and wastewater treatment, and in particular relates to a preparation method of an oil shale semi-coke catalyst and application thereof. Background Art

[0002] Oil shale is an unconventional oil and gas resource with abundant resources, and is listed as a very important alternative energy source in the 21st century. Oil shale is oxygen-free distilled at 450-600°C to obtain shale oil and solid waste oil shale coke. More than 80% of oil shale coke is disposed of by backfilling or stockpiling, which occupies land resources and pollutes the environment. The development of new high-value-added products and new uses of oil shale coke has become a focus of attention.

[0003] Oil shale coke is mainly composed of inorganic minerals and organic compounds, and has a rich pore structure. The inorganic phase is mainly quartz, kaolinite and hematite, and the organic compounds mainly include carboxylic acids, pyridines, amides and imidazoles. The organic matter content of oil shale coke in Fushun, Liaoning is about 4-6%. The various metal oxides inside the oil shale coke and the organic compounds outside constitute the structural characteristics of metal-organic framework compound materials. This structural feature gives shale coke unique properties. For example, the current research on oil shale coke is to improve its adsorption capacity. For example, Chinese patent CN106423113B uses microwave high-pressure hydrothermal method, ultrasonic mixed acid activation method, and ultrasonic mixed alkali activation method to modify oil shale coke in two steps or three steps to prepare modified oil shale coke adsorbent. Chinese patent CN110523373B washes, dries and crushes agricultural and forestry biomass waste, mixes it with oil shale coke powder, adds the mixture to an activator for activation, then calcines and carbonizes it under nitrogen protection, and finally pickles, washes, dries and crushes it to obtain an oil shale coke adsorbent product. The unique structural characteristics of shale coke give it good catalytic performance, but so far, there has been no research report on the activation of oil shale coke to prepare high-efficiency catalysts.

[0004] In the field of sewage treatment, the Fenton process is a relatively mature advanced oxidation technology, which is favored for its simple operation, fast reaction speed, simple equipment and other characteristics. However, this method has the following disadvantages, such as the optimal pH value of the reaction system is 2-3; the reaction generates a large amount of iron-containing sludge, which increases the difficulty of subsequent treatment. Persulfate advanced oxidation technology, as an alternative to traditional advanced oxidation technology, is based on SO4 -It is the main active oxide with high oxidizing property. Theoretically, it can degrade most organic matter. It has broad application prospects in the treatment of wastewater containing toxic, harmful and difficult-to-degrade organic matter. At present, the research on persulfate heterogeneous catalysts is still mainly focused on active ingredients, which requires complex preparation processes and greatly increases the cost of the catalyst. The development of persulfate heterogeneous catalysts with a wide pH range, simple preparation process, and easy separation and recovery is crucial for the practical application of persulfate advanced oxidation technology. Summary of the invention

[0005] The present invention aims to overcome the shortcomings of the prior art and provide a method for preparing an oil shale semi-coke catalyst which has a simple preparation process, low cost, is easy to recycle, has a wide pH adaptability range, and improves the removal effect of persulfate on organic matter.

[0006] The present invention also provides the use of the oil shale semi-coke catalyst prepared by the method in the persulfate catalytic degradation of industrial organic wastewater.

[0007] To solve the above technical problems, the present invention is achieved as follows: A method for preparing an oil shale semi-coke catalyst comprises the following steps: (1) crushing, grinding, and sieving the oil shale coke to obtain oil shale coke powder; (2) The oil shale coke powder obtained in step (1) is dispersed in an activator solution, and mechanically stirred at room temperature to activate the oil shale coke powder. Finally, the target product, oil shale coke catalyst, is obtained by centrifugation, washing, and drying.

[0008] Furthermore, in step (1), the oil shale semi-coke is a solid residue obtained by dry distillation of oil shale at 450°C to 600°C under anaerobic conditions.

[0009] Furthermore, in step (1), the protective gas used in the dry distillation process is nitrogen or coal gas.

[0010] Furthermore, in step (2), the activator solution is one of nitric acid, oxalic acid or phosphoric acid, and the mass concentration of the activator solution is 4 to 32%.

[0011] Furthermore, in step (2), the oil shale semi-coke powder is added to the activator solution at a solid-liquid mass ratio of 1:1 to 5.

[0012] Furthermore, in step (2), the stirring speed of the stirring reaction is 500 to 1000 rpm, and the stirring time is 2 to 6 hours.

[0013] Furthermore, in step (2), the centrifugal speed is 1500-2000 rpm, the centrifugal time is 6-10 min; the drying temperature is 105° C., and the drying time is 5-8 h.

[0014] The oil shale semi-coke catalyst prepared by the above-mentioned oil shale semi-coke catalyst preparation method is used in the persulfate catalytic degradation of industrial organic wastewater.

[0015] Furthermore, the application of the oil shale semi-coke catalyst of the present invention in the persulfate catalytic degradation of industrial organic wastewater comprises the following steps: preparing 100 mL of a solution with a pollutant concentration of 100 mg / L, adjusting the pH value to a range of 4 to 10, adding 0.1 to 1 g of persulfate, and then adding 0.3 to 1.5 g of the oil shale semi-coke catalyst, and reacting at 25 to 55° C. for 0 to 40 min.

[0016] Furthermore, the pollutant of the present invention is phenol.

[0017] Furthermore, the persulfate described in the present invention is potassium persulfate or sodium persulfate.

[0018] Compared with the prior art, the present invention has the following technical effects: (1) The present invention introduces acid sites and functional groups into the oil shale coke through an acid activation method, thereby adjusting the lattice structure of the oil shale coke and increasing the specific surface area, thereby effectively improving the catalytic activity of the oil shale coke.

[0019] (2) The oil shale semi-coke catalyst prepared by the present invention has a porous structure. The transition metal Fe and oxygen-containing functional groups composed of C, N and O on its surface serve as active sites, which activate persulfate by free radical or non-free radical means, thereby promoting the generation of sulfate radicals, hydroxyl radicals, superoxide radicals and singlet oxygen active species, and significantly improving the removal effect of persulfate on organic matter in the pH range of 4 to 10.

[0020] (3) The method of the present invention uses oil shale semi-coke as the main raw material to prepare a heterogeneous catalyst, which realizes the resource utilization of solid waste after oil shale distillation. The preparation method is simple and easy, with low cost. After the reaction is completed, it can be separated by magnetic separation and reused without causing secondary pollution. It has great application prospects in the removal of difficult-to-degrade organic pollutants in industrial wastewater.

[0021] The pollutants that can be degraded by persulfate oxidation activated by the oil shale semi-coke catalyst prepared by the present invention are not limited to phenol. All pollutants that can be degraded by persulfate oxidation activated can be degraded by this method, which has certain universality. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 Figure 1 is a diagram of N2 adsorption desorption of the oil shale semi-coke catalyst prepared in Example 1 of the present invention; Figure 2 This is an X-ray photoelectron spectroscopy (XPS) diagram of the oil shale semi-coke catalyst prepared in Example 1 of the present invention; Figure 3 This is a diagram showing the effect of the oil shale semi-coke catalyst prepared in Example 1 of the present invention on the activation of persulfate oxidation and degradation of phenol under different pH conditions; Figure 4 This is an X-ray photoelectron spectroscopy (XPS) diagram of the oil shale semi-coke catalyst prepared in Example 1 of the present invention before and after persulfate activation; Figure 5 This is a diagram showing the effect of reusing the oil shale semi-coke catalyst prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0024] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0025] Example 1 The preparation method of the oil shale semi-coke catalyst comprises the following steps: the oil shale semi-coke is a solid residue obtained by dry distillation of oil shale at 450°C to 600°C under coal gas protection. The oil shale semi-coke is crushed, ground, and passed through a 120-mesh sieve to obtain oil shale semi-coke powder. The oil shale semi-coke powder is dispersed in an 8% nitric acid solution, and the solid-liquid mass ratio of the oil shale semi-coke powder to the 8% nitric acid solution is 1:3. The reaction is stirred at room temperature for 6 hours at a stirring speed of 1000 rpm. Finally, the reaction is centrifuged at a centrifugal speed of 1800 rpm and a centrifugal time of 8 minutes. The solid powder is washed with deionized water and dried at 105°C for 6 hours.

[0026] Example 2 The preparation method of the oil shale semi-coke catalyst comprises the following steps: the oil shale semi-coke is a solid residue obtained by dry distillation of oil shale at 450°C to 600°C under coal gas protection. The oil shale semi-coke is crushed, ground, and passed through a 120-mesh sieve to obtain oil shale semi-coke powder. The oil shale semi-coke powder is dispersed in a 16% oxalic acid solution, and the solid-liquid mass ratio of the oil shale semi-coke powder to the 16% oxalic acid solution is 1:3. The reaction is stirred at room temperature for 6 hours at a stirring speed of 1000 rpm. Finally, the reaction is centrifuged at a centrifugal speed of 1800 rpm and a centrifugal time of 8 minutes. The solid powder is washed with deionized water and dried at 105°C for 6 hours.

[0027] Example 3 The preparation method of the oil shale semi-coke catalyst comprises the following steps: the oil shale semi-coke is a solid residue obtained by dry distillation of oil shale at 450°C to 600°C under coal gas protection. The oil shale semi-coke is crushed, ground, and passed through a 120-mesh sieve to obtain oil shale semi-coke powder. The oil shale semi-coke powder is dispersed in an 8% phosphoric acid solution, and the solid-liquid mass ratio of the oil shale semi-coke powder to the 8% phosphoric acid solution is 1:1. The reaction is stirred at room temperature for 6 hours, and the stirring speed is 1000 rpm. Finally, it is centrifuged at a centrifugal speed of 1800 rpm and a centrifugal time of 8 minutes. The solid powder is washed with deionized water and dried at 105°C for 6 hours.

[0028] Example 4 1.5 g of the oil shale semi-coke catalyst prepared in Example 1 of the present invention was added to 100 mL of phenol wastewater (phenol concentration was 100 mg / L), the pH was adjusted to 4-10, 0.3 g of potassium persulfate was added, and the reaction was carried out at 55° C. for 30 minutes with a mechanical stirring speed of 1000 rpm. After the reaction was completed, the solution was filtered through a 0.45 μm filter membrane, and the degradation effect of potassium persulfate and oil shale semi-coke catalyst on phenol was measured at 510 nm under different pH conditions using an ultraviolet spectrophotometer.

[0029] Effect Example 1 The oil shale semi-coke catalyst prepared in Example 1 of the present invention was tested for N2 adsorption-desorption performance. The results are as follows: Figure 1 As shown. The oil shale semi-coke catalyst prepared in Example 1 of the present invention has obvious mesoporous characteristics, and the pore shape is parallel plate pores. The specific surface area is increased by 22% compared with the original oil shale semi-coke sample. The pore volume is increased by 29.4% compared with the original oil shale semi-coke sample.

[0030] Effect Example 2 The oil shale semi-coke catalyst prepared in Example 1 of the present invention was subjected to XPS performance test, and the results are as follows: Figure 2The oil shale semi-coke catalyst prepared in Example 1 of the present invention has a more significant element C concentration, accounting for 24.38% of the total amount, the proportion of CO and C=O functional groups increased by 4.35% and 2.07% respectively compared with before acidification, and the proportion of pyrrole nitrogen increased by 2.15% compared with before acidification, which provides a certain basis for improving the activity of the prepared oil shale semi-coke catalyst.

[0031] Effect Example 3 The test results of Example 4 of the present invention are as follows Figure 3 shown.

[0032] from Figure 3 It can be seen that the removal rate of phenol in the range of pH = 4 to 10 by using the oil shale semi-coke catalyst and potassium persulfate at the same time reaches more than 88%, and more than 99% when the pH is 10. This shows that the oil shale semi-coke catalyst prepared in Example 1 of the present invention can stimulate persulfate to degrade phenol in a wider pH range. The removal effect of phenol is better in a neutral and alkaline environment.

[0033] Effect Example 4 The oil shale semi-coke catalyst prepared in Example 1 of the present invention was subjected to XPS performance test after the catalytic reaction in Example 4. The results are as follows: Figure 4 The C1s XPS spectrum of the oil shale semi-coke catalyst prepared in Example 1 of the present invention after reaction ( Figure 4 b), which is convoluted into four peaks at 284.8, 285.6, 288.54 and 293.1 eV, corresponding to CC, CO, C=O and satellite peaks (π-π), respectively. The main peak of the C1s spectrum remains unchanged after the reaction, while the ratio of graphitic N to pyrrolic N shows a significant change before and after the reaction ( Figure 4 c). The proportion of pyrrolic N decreased by 1.22% after catalysis, while the proportion of graphitic N increased by 0.91%, from which it can be inferred that CN has a significant contribution to the electron transfer process. Fe 2p spectrum, in which the main peak with a binding energy of 719.6 eV indicates that iron exists in a zero-valent state. Corresponding to Fe 2p 3 / 2 and Fe 2p 1 / 2 The peaks at 710 and 725 eV represent oxidized Fe 3+ cation, while the peaks at 713.1 eV and 727.7 eV are Fe 2+ After the reaction, the presence of Fe(II) at the 710.8 and 727.7 eV energy levels increased significantly. This indicates that Fe(III) can continuously accept electrons and convert them back to Fe(II), thus establishing the iron cycle.

[0034] Effect Example 5 After the degradation reaction was completed, the oil shale semi-coke catalyst was recovered by a strong magnetic magnet, washed with deionized water, dried at 105°C, and used in the second round of phenol degradation experiment using activated potassium persulfate. The experimental steps were the same as in Example 4. The oil shale semi-coke catalyst prepared in Example 1 and persulfate were added to the phenol wastewater at the same time. This cycle experiment was repeated 3 times to measure the reuse effect of the oil shale semi-coke catalyst prepared in Example 1 of the present invention. The results are shown in FIG. Figure 5 .

[0035] from Figure 5 It can be seen that the phenol removal rates in the first, second, third and fourth rounds of experiments were 98.5%, 92.25%, 86.4% and 83.6% respectively. In the four rounds of experiments, the phenol removal rate was higher than that of the single potassium persulfate and single acidified oil shale semi-coke in Example 1, indicating that the four-time reuse of acidified oil shale semi-coke had a better effect.

[0036] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing an oil shale semi-coke catalyst, characterized in that: The following steps are involved: (1) crushing, grinding, and sieving the oil shale coke to obtain oil shale coke powder; (2) The oil shale coke powder obtained in step (1) is dispersed in an activator solution, and mechanically stirred at room temperature to activate the oil shale coke powder. Finally, the target product, oil shale coke catalyst, is obtained by centrifugation, washing, and drying.

2. The method for preparing the oil shale semi-coke catalyst according to claim 1, characterized in that: In step (1), the oil shale semi-coke is a solid residue obtained by dry distillation of oil shale at 450°C to 600°C under anaerobic conditions.

3. The method for preparing the oil shale semi-coke catalyst according to claim 2, characterized in that: In step (1), the protective gas used in the dry distillation process is nitrogen or coal gas.

4. The method for preparing the oil shale semi-coke catalyst according to claim 3, characterized in that: In step (2), the activator solution is one of nitric acid, oxalic acid or phosphoric acid, and the mass concentration of the activator solution is 4 to 32%.

5. The method for preparing the oil shale semi-coke catalyst according to claim 4, characterized in that: In step (2), the oil shale semi-coke powder is added to the activator solution at a solid-liquid mass ratio of 1:1 to 5.

6. The method for preparing the oil shale semi-coke catalyst according to claim 5, characterized in that: In step (2), the stirring speed of the stirring reaction is 500 to 1000 rpm, and the mechanical stirring time is 2 to 6 hours.

7. The method for preparing the oil shale semi-coke catalyst according to claim 6, characterized in that: In step (2), the centrifugal speed is 1500-2000 rpm, the centrifugal time is 6-10 min; the drying temperature is 105° C., and the drying time is 5-8 h.

8. Use of the oil shale semi-coke catalyst prepared by the method for preparing the oil shale semi-coke catalyst according to any one of claims 1 to 7 in the persulfate catalytic degradation of industrial organic wastewater.

9. The use of the oil shale semi-coke catalyst prepared by the method for preparing the oil shale semi-coke catalyst according to claim 8 in the persulfate catalytic degradation of industrial organic wastewater, characterized in that: The method comprises the following steps: preparing 100 mL of a solution with a pollutant concentration of 100 mg / L, adjusting the pH value to a range of 4 to 10, adding 0.1 to 1 g of persulfate, and then adding 0.3 to 1.5 g of the oil shale semi-coke catalyst, and reacting at 25 to 55° C. for 0 to 40 minutes.

10. The use of the oil shale semi-coke catalyst prepared by the method for preparing the oil shale semi-coke catalyst according to claim 9 in the persulfate catalytic degradation of industrial organic wastewater, characterized in that: The pollutant is phenol.

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