Synergistic catalytic oxidation method for VOCs (volatile organic compounds) and conventional pollutants based on hierarchical pores and multi-physical field

Abstract

The invention discloses a collaborative catalytic oxidation method for VOCs and conventional pollutants based on hierarchical pores and a multi-physical field, and belongs to the technical field of catalytic oxidation of pollutants. The method comprises the following steps: constructing a carbon material with graded pores, wherein the graded pores of the carbon material comprise micro pores and medium and large pores; a catalytic oxidation catalyst of VOCs is directionally loaded in middle and large pores; the method comprises the following steps: putting a hierarchical porous carbon material into a fixed bed reactor, introducing simulated flue gas containing VOCs and conventional pollutants, and introducing a multi-physical field for heating in the concerted catalytic oxidation process of the VOCs and the conventional pollutants. By constructing the hierarchical porous carbon material, hierarchical occurrence of pollutants is realized, competition of VOCs and conventional pollutants on adsorption catalytic sites is slowed down, the synergistic removal efficiency is improved, the temperature required by catalytic oxidation of VOCs is reduced through a multi-physical field heating mode and the energy absorption effect of metal sites in middle and large pores, and the catalytic oxidation efficiency of VOCs is improved. And the VOCs are matched with the catalytic oxidation temperature interval of the conventional pollutants.

Description

Technical Field

[0001] The invention relates to a method for cooperative catalytic oxidation of VOCs and conventional pollutants based on hierarchical pores and multi-physical fields, belonging to the technical field of catalytic oxidation of pollutants. Background Art

[0002] SO2 and NO are produced during coal combustion. x The catalytic oxidation technology based on carbon-based porous materials is regarded as a potential technology for removing pollutants from coal-fired flue gas. This technology can not only remove conventional pollutants such as SO2 and NO x It can be converted into high-value chemicals H2SO4 and HNO3 to achieve resource recycling (Appl.Surf.Sci.2015,357,1895-1901; J.Clean.Prod.2022,335,130360; Carbon 2023,201,37-48), and can also directly degrade VOCs into harmless CO2 and H2O. Therefore, if VOCs and conventional pollutants can be catalytically oxidized in a coordinated manner, it is expected to achieve economical and efficient synergistic removal of VOCs and conventional pollutants in coal-fired flue gas. However, the synergistic catalytic oxidation of VOCs and conventional pollutants currently faces two bottlenecks:

[0003] 1. VOCs and conventional pollutants will compete for the adsorption and catalytic oxidation sites of porous carbon during the catalytic oxidation process, resulting in low removal efficiency.

[0004] 2. The temperature range for catalytic oxidation of VOCs and conventional pollutants does not match.

[0005] Specifically, VOCs are highly inert and require higher temperatures (usually over 200°C) to be oxidized and degraded, while the optimal catalytic oxidation temperature range for conventional pollutants SO2 and NOx is relatively low (usually less than 100°C). This mismatch in temperature range makes it difficult to simultaneously take into account the removal efficiency of VOCs and conventional pollutants during the synergistic removal process. Summary of the invention

[0006] In order to solve the problems existing in the background technology, the present invention provides a method for the coordinated catalytic oxidation of VOCs and conventional pollutants based on hierarchical pores and multi-physical fields.

[0007] To achieve the above object, the present invention adopts the following technical solution: a method for synergistic catalytic oxidation of VOCs and conventional pollutants based on hierarchical pores and multi-physical fields, the method comprising the following steps:

[0008] S1: constructing a carbon material with hierarchical pores, wherein the hierarchical pores of the carbon material include micropores and mesopores and macropores; the mesopores and macropores serve as storage sites for large-sized VOCs, and the micropores serve as storage sites for small-sized conventional pollutants;

[0009] The pore diameter of the micropores in S1 is less than 0.7 nm, and the pore volume of the micropores is not less than 40%.

[0010] The pore diameter of the mesopores and macropores in S1 is greater than 2 nm, and the pore volume of the mesopores and macropores accounts for 40-60%.

[0011] S2: a catalytic oxidation catalyst for directionally loading VOCs in the mesopores;

[0012] S2 The catalyst includes one or more combinations of cobalt-based, nickel-based, titanium-based, manganese-based, copper-based, chromium-based, cerium-based metals and their oxides.

[0013] S2 The catalyst loading is not less than 10wt%.

[0014] S2 The real part of the relative complex dielectric constant of the catalyst is not less than 5, and the imaginary part is not less than 0.5.

[0015] S3: The hierarchical porous carbon material is placed in a fixed bed reactor and a simulated flue gas containing VOCs and conventional pollutants is introduced. Multi-physical fields are introduced for heating during the synergistic catalytic oxidation of VOCs and conventional pollutants.

[0016] S3: The multi-physical field heating method is microwave irradiation and Joule electric heating. The microwave power of the microwave irradiation is 50-150W. The voltage of the Joule electric heating is 0.5-3V.

[0017] The temperature of the multi-physical field heating in S3 is 50-100°C.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention realizes the hierarchical storage of pollutants by constructing hierarchical porous carbon materials, which reduces the competition between VOCs and conventional pollutants for adsorption catalytic sites and improves the synergistic removal efficiency. At the same time, the coupling of multi-physical field heating methods such as microwave heating and Joule electric heating and the energy absorption of metal sites in medium and large pores reduces the temperature required for catalytic oxidation of VOCs, so that the catalytic oxidation temperature range of VOCs and conventional pollutants is matched. The present invention has fewer steps and a short process, and only requires cheap carbon-based catalysts, which reduces the complexity and investment cost of pollutant control and has significant economic advantages. DETAILED DESCRIPTION

[0020] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0021] A method for synergistic catalytic oxidation of VOCs and conventional pollutants based on hierarchical pores and multi-physical fields, the method comprising the following steps:

[0022] S1: Construct a carbon material with hierarchical pores, wherein the hierarchical pores of the carbon material include micropores and mesopores; the mesopores serve as storage sites for large-sized VOCs (including one or more of toluene, halogenated aromatic hydrocarbons, xylene, and condensed aromatic hydrocarbons), and the micropores serve as storage sites for small-sized conventional pollutants (including SO2, NO x , mercury or other substances) are stored;

[0023] The hierarchical porous carbon material is prepared by a trace alkali metal salt catalytic activation method, and the directional regulation of pore grouping and size is achieved by regulating the type and content of the alkali metal salt;

[0024] The pore diameter of the micropores in S1 is less than 0.7 nm, and the pore volume of the micropores is not less than 40%.

[0025] The pore diameter of the mesopores and macropores in S1 is greater than 2 nm, and the pore volume of the mesopores and macropores accounts for 40-60%.

[0026] S2: The catalytic oxidation catalyst of VOCs is directionally loaded in the mesoporous and macroporous materials; the catalyst is loaded in a directionally loaded manner into the mesoporous and macroporous materials by impregnation and in-situ thermal deposition methods.

[0027] S2 The catalyst includes one or more combinations of cobalt-based, nickel-based, titanium-based, manganese-based, copper-based, chromium-based, cerium-based metals and their oxides.

[0028] S2 The catalyst loading is not less than 10wt%.

[0029] S2 The real part of the relative complex dielectric constant of the catalyst is not less than 5, and the imaginary part is not less than 0.5.

[0030] S3: Place the hierarchical porous carbon material into a fixed bed reactor and introduce simulated flue gas containing VOCs and conventional pollutants. During the synergistic catalytic oxidation of VOCs and conventional pollutants (the concentration of VOCs in the synergistic catalytic oxidation process is 50-300 ppm, the concentration of conventional pollutants is 200-1000 ppm, and the O2 concentration is not less than 5 vol%), a multi-physical field is introduced for heating at a temperature of 50-100°C.

[0031] S3: The multi-physical field heating method is microwave irradiation and Joule electric heating. The microwave power of the microwave irradiation is 50-150W. The voltage of the Joule electric heating is 0.5-3V.

[0032] The temperature of the multi-physical field heating in S3 is 50-100°C.

[0033] Embodiment 1:

[0034] S1: Using coal as raw material, a hierarchical porous carbon material with micropore volume accounting for 55% and medium and macropore volume accounting for 45% was prepared by catalytic activation method of trace alkali metal salt;

[0035] S2: 10wt% CoO3 was impregnated into the hierarchical porous carbon material, so that the real part of the dielectric constant of the material reached 8 and the imaginary part was 0.7;

[0036] S3: The prepared hierarchical pore carbon-based catalyst was placed in a fixed bed reactor and introduced with 200 ppm of toluene, 500 ppm of SO2 and NO, 5 vol% of O2, 8 vol% of H2O, and the rest being N2 simulated flue gas, and a multi-pollutant synergistic catalytic oxidation experiment was carried out under microwave irradiation with a power of 80 W.

[0037] Experimental results:

[0038] It was measured that the removal efficiency of SO2, NO and toluene reached 95% within 1 hour.

[0039] Embodiment 2:

[0040] The difference between this embodiment and embodiment 1 is that:

[0041] S3: The prepared hierarchical pore carbon-based catalyst was placed in a fixed bed reactor and introduced with 200 ppm of toluene, 500 ppm of SO2 and NO, 5 vol% of O2, 8 vol% of H2O, and the rest of N2 simulated flue gas, and a multi-pollutant synergistic catalytic oxidation experiment was carried out using Joule electric heating with an input voltage of 1.5 V.

[0042] Experimental results:

[0043] It was measured that the removal efficiency of SO2, NO and toluene could reach 97% within 1 hour.

[0044] Comparative experiment 1:

[0045] The difference between this comparative experiment and Example 1 is:

[0046] S1: Using coal as raw material, a hierarchical porous carbon material with micropore volume accounting for 90% and medium and macropore volume accounting for 45% was prepared by catalytic activation method of trace alkali metal salt;

[0047] Experimental results:

[0048] It was measured that the SO2 removal efficiency within 1 hour was 80%, the toluene removal efficiency was 70%, and the NO removal efficiency was only 50%.

[0049] Comparative experiment 2:

[0050] The difference between this comparative experiment and Example 1 is:

[0051] S3: The prepared hierarchical pore carbon-based catalyst was placed in a fixed bed reactor and introduced with 200 ppm of toluene, 500 ppm of SO2 and NO, 5 vol% of O2, 8 vol% of H2O, and the rest being N2 simulated flue gas, and heated at 250°C to carry out a multi-pollutant synergistic catalytic oxidation experiment.

[0052] Experimental results:

[0053] It was measured that the SO2 removal efficiency within 1 hour was 35%, the NO removal efficiency was 10%, and the toluene removal efficiency was 45%.

[0054] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalents of the claims be included in the present invention.

[0055] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for synergistic catalytic oxidation of VOCs and conventional pollutants based on hierarchical pores and multi-physical fields, characterized in that: The method comprises the following steps: S1: constructing a carbon material with hierarchical pores, wherein the hierarchical pores of the carbon material include micropores and mesopores and macropores; the mesopores and macropores serve as storage sites for large-sized VOCs, and the micropores serve as storage sites for small-sized conventional pollutants; S2: a catalytic oxidation catalyst for directionally loading VOCs in the mesopores; S3: The hierarchical porous carbon material is placed in a fixed bed reactor and a simulated flue gas containing VOCs and conventional pollutants is introduced. Multi-physical fields are introduced for heating during the synergistic catalytic oxidation of VOCs and conventional pollutants.

2. The method for synergistic catalytic oxidation of VOCs and conventional pollutants based on hierarchical pores and multi-physical fields according to claim 1, characterized in that: The pore diameter of the micropores in S1 is less than 0.7 nm, and the pore volume of the micropores is not less than 40%.

3. A method for synergistic catalytic oxidation of VOCs and conventional pollutants based on hierarchical pores and multi-physical fields according to claim 1 or 2, characterized in that: The pore diameter of the mesopores and macropores in S1 is greater than 2 nm, and the pore volume of the mesopores and macropores accounts for 40-60%.

4. The method for synergistic catalytic oxidation of VOCs and conventional pollutants based on hierarchical pores and multi-physical fields according to claim 1, characterized in that: S2 The catalyst includes one or more combinations of cobalt-based, nickel-based, titanium-based, manganese-based, copper-based, chromium-based, cerium-based metals and their oxides.

5. The method for synergistic catalytic oxidation of VOCs and conventional pollutants based on hierarchical pores and multi-physical fields according to claim 1, characterized in that: S2 The catalyst loading is not less than 10wt%.

6. The method for synergistic catalytic oxidation of VOCs and conventional pollutants based on hierarchical pores and multi-physical fields according to claim 1, characterized in that: S2 The real part of the relative complex dielectric constant of the catalyst is not less than 5, and the imaginary part is not less than 0.

5.

7. The method for synergistic catalytic oxidation of VOCs and conventional pollutants based on hierarchical pores and multi-physical fields according to claim 1, characterized in that: The multi-physical field heating method described in S3 is microwave irradiation and Joule electric heating.

8. The method for synergistic catalytic oxidation of VOCs and conventional pollutants based on hierarchical pores and multi-physical fields according to claim 7, characterized in that: The microwave power of the microwave irradiation is 50-150W.

9. The method for synergistic catalytic oxidation of VOCs and conventional pollutants based on hierarchical pores and multi-physical fields according to claim 7, characterized in that: The voltage of the Joule electric heating is 0.5-3V.

10. A method for synergistic catalytic oxidation of VOCs and conventional pollutants based on hierarchical pores and multi-physical fields according to claim 8 or 9, characterized in that: The temperature of the multi-physical field heating in S3 is 50-100°C.