Applications of Ru-based single-atom catalysts with high chlorine resistance and high dispersion

Abstract

This invention relates to the application of a Ru-based single-atom catalyst with high chlorine resistance and high dispersion for the oxidative degradation of chlorinated aromatic hydrocarbon pollutants. The preparation process of the Ru-based single-atom catalyst is as follows: a transition metal oxide is dispersed in deionized water to obtain a suspension; a Ru precursor solution is added dropwise to the suspension, stirred until homogeneous, and aged; after filtering off the filtrate, the remaining material is washed and vacuum dried at 50-80°C to obtain a Ru-based single-atom catalyst with the target Ru loading, denoted as Ru SAC. The high dispersion of Ru on the Ru SAC is achieved through the synergistic effect of Ru and the support, and the Ru SAC maintains high low-temperature activity and chlorine resistance even when the actual Ru loading is below 1 wt% and above 0.1 wt%.

Description

Technical Field

[0001] This invention belongs to the field of environmental pollution control, specifically relating to the application of a Ru-based single-atom catalyst with high chlorine resistance and high dispersion for the oxidative degradation of chlorinated aromatic pollutants. Background Technology

[0002] Highly toxic polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in waste incineration flue gas are bioaccumulative and potentially carcinogenic, seriously endangering environmental quality and human health. Their efficient purification has attracted significant public attention. Catalytic oxidation technology can degrade PCAHs into non-toxic products (such as CO2 and H2O) at relatively low temperatures. Commonly used catalytic materials include noble metals (such as Pt, Pd, and Ru) and transition metal oxides (such as MnO). X WO X CeO X However, due to the high electronegativity of chlorine (Cl), chlorine-containing species can easily adsorb onto the electrophilic sites on the catalyst surface (such as oxygen vacancies on noble metal or transition metal surfaces). Accumulated Cl can lead to catalyst chlorination and inhibit the full oxidation of contaminants. Therefore, improving the chlorine resistance of the catalyst is crucial.

[0003] The key to designing chlorine-resistant catalysts lies in the effective removal of chlorine species from the surface. Ruthenium (Ru)-based catalysts can undergo the Deacon reaction (Cl... - The reaction +O2→Cl2+H2O) converts inorganic or free chlorine into chlorine gas, potentially preventing catalyst poisoning by chlorine species. However, currently reported heterogeneous noble metal catalysts generally have high loadings (>1 wt%) and low metal atom utilization (often aggregated into nanoparticles), limiting their widespread application. Single-atom catalysts (SACs) combine the high activity of homogeneous catalysts with the easy recovery advantages of heterogeneous catalysts, making them a research frontier in various catalytic reactions. Therefore, developing highly dispersed Ru-based single-atom catalysts with excellent resistance to chlorine poisoning and catalytic activity for low-cost purification of chlorinated aromatics is of significant research value. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the technical problem to be solved by this invention is to provide an application of a Ru-based single-atom catalyst with high chlorine resistance and high dispersion. This catalyst is obtained by supporting highly dispersed Ru on an oxygen-rich vacancy transition metal oxide and is named Ru SAC. Taking the typical PCAHs model compound, o-dichlorobenzene (o-DCB), as an example, its low-temperature activity and chlorine resistance are tested. The Ru SAC is highly dispersed on Ru by the synergistic effect of Ru and the support. Moreover, Ru SAC can still maintain high low-temperature activity when the actual Ru loading is less than 1 wt% and greater than 0.1 wt%. (1) The reaction temperature T when the initial conversion rate of o-DCB reaches 90% 90 <200℃; (2)Ru SAC has high chlorine resistance: the o-DCB conversion rate is maintained at more than 90% for no less than 500 min at the stability temperature.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] In a first aspect, the present invention provides an application of a Ru-based single-atom catalyst with high chlorine resistance and high dispersion for the degradation of chlorinated aromatic hydrocarbon pollutants. The preparation process of the Ru-based single-atom catalyst is as follows:

[0007] A suspension was obtained by dispersing transition metal oxides in deionized water;

[0008] Add the Ru precursor solution dropwise into the above suspension, stir until homogeneous, and then age.

[0009] After filtering out the filtrate, the remaining material is washed and then dried under vacuum at 50-80℃ to obtain a Ru-based single-atom catalyst with the target Ru loading, denoted as Ru SAC.

[0010] Furthermore, the solid content in the suspension is 2-10 g / 100 mL.

[0011] Furthermore, the target Ru loading is 0.1wt%-1.0wt%, preferably 0.15wt%-0.6wt%.

[0012] Furthermore, the concentration of the Ru precursor solution is 1-10 wt%, preferably 3-5 wt%.

[0013] Further, the Ru precursor is one or more of RuCl3, ruthenium acetylacetonate, and ruthenium acetate, preferably RuCl3 or ruthenium acetate; the Ru precursor solution is added at a rate of 0.1-2 mL / min, preferably 0.8-1.2 mL / min.

[0014] Furthermore, the transition metal oxide is oxygen-vacancy-rich MnO.X CeO X TiO X One or more of the transition metal oxides, preferably MnO X .

[0015] Furthermore, the chlorinated aromatic hydrocarbon pollutant is at least one of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, chlorobenzene, o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, dichlorotoluene, etc., wherein the process of degrading o-dichlorobenzene (o-DCB) is as follows:

[0016] Oxidation activity test: o-DCB concentration was 100 ppm, catalyst dosage was 100 mg, total reaction gas flow rate was 60 mL / min, and equilibrium gas was 10% O2 / N2 mixture. The conversion rate of o-DCB of the catalyst was evaluated at 120-300℃.

[0017] Chlorine resistance stability evaluation: The temperature at which the initial o-DCB conversion rate reaches 90% is denoted as T. 90 The stability test measures the time during which the o-DCB conversion rate remains above 90% at a continuous testing temperature. The stability temperature refers to the time during which the o-DCB conversion rate remains above 90%. 90 Temperatures within the range of 20-60℃.

[0018] Secondly, the present invention provides a Ru-based single-atom catalyst with high chlorine resistance and high dispersion. The Ru-based single-atom catalyst is obtained by dripping a Ru precursor solution into a support suspension, filtration and drying. The Ru in the Ru-based single-atom catalyst is highly dispersed at no less than 80%, and the target Ru loading is no more than 1.0 wt%.

[0019] Compared with the prior art, the beneficial effects of the present invention include, but are not limited to:

[0020] (1) This invention combines oxygen-vacancy-rich transition metal oxides with highly dispersed Ru for the degradation of chloroaromatic pollutants. On the one hand, the introduction of Ru increases the surface active oxygen content, oxygen vacancy concentration, and redox capacity of the catalyst; on the other hand, the in-situ generation of low-valence Ru(III) during the catalytic process can promote the deep oxidation of o-DCB. Compared with other reported catalytic systems, the highly dispersed, low-loading Ru SAC catalyst prepared in this invention exhibits excellent low-temperature activity and stability. At a theoretical Ru loading of 0.2 wt%, the T0 value is significantly higher than that of other catalysts. 90 The stability temperature is 180.5℃, and it also exhibits excellent stability. The o-DCB conversion rate is maintained at over 90% for 700 min at the stability temperature.

[0021] (2) The Ru SAC of the present invention has excellent high chlorine resistance stability. This is partly due to the fact that high-valence Ru(Ⅳ) can remove inorganic chlorine from the catalyst surface through the Deacon reaction (Cl-+O2→Cl2+H2O) during the reaction process. More importantly, the introduction of Ru inhibits the growth of support grain size during the reaction process, ensuring the structural stability and oxidation activity of the catalyst.

[0022] (3) In the Ru SAC of the present invention, Ru is in a monodisperse state, with only oxygen on the support coordinating with Ru, thus avoiding the formation of Ru nanoclusters and exhibiting high dispersion. Attached Figure Description

[0023] Figure 1 Fresh MnO X XRD patterns of the support and the catalytic degradation of o-DCB at 230℃;

[0024] Figure 2 Fresh 0.2Ru SAC / MnO X XRD patterns of the support and the catalytic degradation of o-DCB at 230℃. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to embodiments, but this is not intended to limit the scope of protection of this application.

[0026] This invention prepares a highly dispersed Ru single-atom catalyst using an oxygen-rich vacancy transition metal oxide as a support, and evaluates the catalyst performance (oxidation activity and stability) under ambient pressure using o-DCB as a model pollutant for chlorinated aromatic hydrocarbons.

[0027] The preparation process of Ru SAC is as follows: 0.5 g of transition metal oxide is placed in 20 mL of deionized water and stirred at room temperature to obtain a suspension. Then, a certain amount of Ru precursor solution is added dropwise to the above suspension at a certain rate and stirred for 3 h, followed by aging for 1 h. The filtrate is then filtered off to remove the Ru ligand. The remaining material is washed and dried overnight in a vacuum oven at 60 °C to obtain Ru-based single-atom catalysts with different loadings, which are Ru SACs.

[0028] The control group prepared Ru catalysts, denoted as RuNPs, using an impregnation method. The specific preparation process was as follows: First, 0.5 g of transition metal oxide and a certain amount of RuCl3 precursor solution were stirred until homogeneous. Then, the mixture was placed in a fume hood for at least 3 hours and dried overnight in an oven at 60°C. Finally, the mixture was placed in a tube furnace under a 5% H2 / Ar mixed gas and reduced at 300°C for 1 hour to obtain RuNPs.

[0029] The Ru precursor may be one or more of RuCl3, ruthenium acetylacetonate, ruthenium acetate, etc., preferably RuCl3 or ruthenium acetate.

[0030] The Ru precursor solution concentration is 1-10 wt%, preferably 3-5 wt%.

[0031] The Ru precursor solution is added at a rate of 0.1-2 mL / min, preferably at a rate of 1 mL / min.

[0032] The Ru loading is 0.1wt%-1.0wt%, preferably 0.15wt%-0.6wt%.

[0033] The transition metal oxide is oxygen-vacancy-rich MnO. X CeO X TiO X One or more of the following, preferably, the transition metal oxide is MnO X , of which 1 <x<2。

[0034] The process of evaluating catalyst performance (oxidation activity, stability) under normal pressure conditions is as follows:

[0035] 1. Oxidation activity test: o-DCB concentration was 100 ppm, catalyst dosage was 100 mg, total reaction gas flow rate was 60 mL / min, and equilibrium gas was a 10% O2 / N2 mixture, where 10% refers to the volume percentage of oxygen in the mixture. The conversion rate of o-DCB by the catalyst was evaluated at 120-300℃.

[0036] 2. Chlorine resistance stability evaluation: The temperature at which the initial o-DCB conversion rate reaches 90% is denoted as T. 90 The stability test measures the time during which the o-DCB conversion rate remains above 90% at a continuous testing temperature. The stability temperature refers to the time during which the o-DCB conversion rate remains above 90%. 90 Temperatures within the range of 20-60℃.

[0037] Example 1

[0038] (1) Preparation of Ru SAC / MnOx: Take 0.5g MnO X The sample was placed in 20 mL of deionized water and stirred vigorously at room temperature to obtain a suspension. Then, RuCl3 solution was added dropwise to the suspension at a rate of 1 mL / min while stirring. After stirring for 3 h, the sample was aged for 1 h. The washed sample was dried overnight in a vacuum oven at 60 °C to obtain RuSAC / MnO with a theoretical loading of 0.2 wt%. X catalyst.

[0039] (2) Preparation of RuNPs / MnOx: First, 0.5 g of MnOx and a certain amount of RuCl3 solution were stirred and mixed evenly. Then, the mixture was placed in a fume hood for more than 3 hours and dried overnight in an oven at 60°C. Finally, it was placed in a tube furnace under a 5% H2 / Ar mixed gas and reduced at 300°C for 1 hour to obtain RuNPs / MnOx.

[0040] Table 1. Activity and stability of MnOx-supported Ru-based catalysts for the oxidative degradation of o-DCB

[0041]

[0042] [1] Dispersion: Measured by the ratio of CO pulse adsorption to actual loading, and the actual loading was obtained by inductively coupled plasma (ICP) testing;

[0043] [2] T 90 The reaction temperature at which the initial conversion rate of o-DCB reaches 90%;

[0044] [3] Stability: The o-DCB conversion rate can be maintained at 90% for a duration of time at 240℃.

[0045] Table 1 shows that the dispersion of Ru NPs (45%) is much lower than that of Ru SAC (95%), confirming that the present invention can successfully prepare highly dispersed Ru-based catalysts. In particular, the highly dispersed 0.2Ru SAC exhibits higher catalytic activity and stability. 90 At 180.5℃, and 240℃, the o-DCB conversion rate can be maintained at no less than 90% for 700 min. However, 0.2Ru NPs exhibit poor activity and stability: T 90 At temperatures above 200℃, the o-DCB conversion rate is 90% at 240℃, but the effect lasts for less than 100 minutes.

[0046] Figure 1 and Figure 2 As shown, this is the MnO carrier in this embodiment. X and 0.2Ru SAC / MnO X The comparison of XRD patterns before and after catalytic degradation (degradation temperature 230℃) shows that 0.2Ru SAC / MnO X The grain size of MnO did not change significantly before and after the reaction (grain size was approximately 15.9 nm-16.9 nm), while... X (310) The grain size at the crystal plane increased from 15.0 nm fresh to 42.6 nm after use, indicating that the Ru SAC of the present invention can suppress MnO XThe phase transition of the support maintains its high activity. The turning point for the decline in the catalytic activity of pure MnOx is around 230℃. For pure MnOx, further increases in temperature cannot further improve its activity, and its stable activity is not high. However, the activity of 0.2Ru SAC / MnOX can still be improved at around 230℃ and remain highly stable.

[0047] Example 2

[0048] Except for replacing the carrier with CeO X and TiO X In addition, Ru SAC / CeO X Ru NPs / CeO X and Ru SAC / TiO X Ru NPs / TiO X The preparation process is similar to that of Ru SAC / MnOx and Ru NPs / MnOx in Example 1.

[0049] Table 2. Activity and stability of Ru-based catalysts supported on different supports for the oxidative degradation of o-DCB

[0050]

[0051] [1] Stability when MnOx is used as a support: The o-DCB conversion rate of over 90% can be maintained for a sustained period of time at 240℃.

[0052] [2] Stability when CeOx is used as a support: The o-DCB conversion rate of over 90% can be maintained for a sustained period of time at 330℃.

[0053] [3] Stability when TiOx is used as a support: The o-DCB conversion rate of over 90% can be maintained for a sustained period of time at 290℃.

[0054] Table 2 shows that highly dispersed Ru-based catalysts can still be prepared using different transition metal oxides as supports according to this invention. For example, when CeOx and TiOx are used as supports, the dispersion of Ru SAC is not less than 90%, which is much higher than that of the corresponding Ru NPs catalysts (the dispersion is about 30%). At the same time, the low-temperature activity and stability of Ru SACs supported on different supports are better than those of the corresponding Ru NPs. For example, all Ru SACs can maintain an o-DCB conversion rate of not less than 90% for more than 700 min at the corresponding stability temperature, while the stability of Ru NPs is less than 100 min.

[0055] It is worth noting that when MnOx is used as the support, the low-temperature activity (T) of Ru SAC is... 90=180.5℃) is superior to CeOx, and the low-temperature activity of Ru SAC when TiOx is used as the support is better than that of CeOx. 90 The temperatures are 300℃ and 240℃, respectively. Therefore, the following examples use MnOx as the optimal support for illustration.

[0056] Example 3

[0057] Except for the different mass of RuCl3 solution added during the preparation process, the preparation processes of 0.05Ru SAC, 0.1Ru SAC, 0.5Ru SAC, and 1.0Ru SAC are similar to those of 0.2Ru SAC / MnOx in Example 1.

[0058] Table 3. Activity and stability of Ru SAC / MnOx catalysts with different theoretical loadings for the oxidative degradation of o-DCB

[0059]

[0060] As shown in Table 3, from the perspective of dispersibility, when the theoretical Ru loading is less than 1.0 wt%, highly dispersed Ru SAC (dispersibility greater than 70%) can be prepared. However, when the theoretical Ru loading is 1.0 wt%, the dispersibility decreases to 65% due to the tendency of Ru to agglomerate.

[0061] From the perspective of activity and stability, when the theoretical loading is 0.05 wt%, both activity and stability decrease: T 90 Above 200°C, the stability is less than 50 min. Therefore, considering the optimal dispersibility, activity, and stability, the Ru loading is preferably 0.1-0.8 wt%, more preferably 0.15-0.6 wt%.

[0062] Example 4

[0063] Except for replacing the precursor solutions with PdCl2 and PtCl4 solutions, the preparation processes of Pt SAC / MnOx and Pd SAC / MnOx are similar to those of Ru SAC / MnOx in Example 1(1).

[0064] Table 4. Activity and stability of different active metal SAC / MnOx catalysts for the oxidative degradation of o-DCB

[0065]

[0066] Table 4 shows that highly dispersed catalysts can be prepared using different noble metals as active species according to this invention. For example, when Pt and Pd are selected as active metals, the dispersion of the prepared catalysts is higher than 90%. From the perspective of activity and stability, only Ru SAC exhibits high activity and stability, while Pt SAC and Pd SAC show relatively high activity and stability under the same test conditions.90 All values ​​exceeded 200℃, which is greater than the Ru SAC values ​​under the same testing conditions, and the stability of Pt SAC and Pd SAC was less than 10 min. These results confirm that Ru has a unique advantage in efficiently removing chlorine species from the catalyst surface during o-DCB oxidation, ensuring its chlorine resistance, while Pd or Pt do not possess this advantage. Therefore, Ru is preferred as the active metal in this invention.

[0067] Example 5

[0068] This embodiment uses a 0.2Ru SAC / MnOx catalyst to catalyze polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, chlorobenzene, p-dichlorobenzene, or dichlorotoluene, respectively.

[0069] With a chlorinated aromatic hydrocarbon contaminant concentration of 100 ppm, a catalyst dosage of 100 mg, a total reaction gas flow rate of 60 mL / min, and a balance gas of 10% O2 / N2 mixture, calculate the catalyst conversion rate at 120-300℃ and determine T. 90 The temperature point was determined, and the conversion rate was continuously tested at 240℃ for a period of time at which the stability temperature was maintained above 90%.

[0070] Tests have shown that all catalysts of this invention exhibit high chlorine resistance.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0072] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. An application of a Ru-based single-atom catalyst with high chlorine resistance and high dispersion, characterized in that, The preparation process of the Ru-based single-atom catalyst for the oxidative degradation of chlorinated aromatic hydrocarbon pollutants is as follows: A suspension was obtained by dispersing transition metal oxides in deionized water; Add the Ru precursor solution dropwise into the above suspension, stir until homogeneous, and then age. After filtering out the filtrate, the remaining material was washed and then dried under vacuum at 50-80 °C to obtain a Ru-based single-atom catalyst with the target Ru loading, denoted as Ru SAC. The target Ru loading is 0.1 wt%-1.0 wt%; the transition metal oxide is MnO. X ; Ru SAC still exhibits high low-temperature activity and high chlorine resistance when the target Ru loading is less than 1 wt% and greater than 0.1 wt%: (1) o -Reaction temperature T under DCB conversion rate of 90% 90 < 200 ℃; (2) Stability temperature o - The DCB conversion rate is maintained above 90% for no less than 500 minutes; the stability temperature index is T. 90 Temperatures within the range of 20-60 ℃.

2. The application according to claim 1, characterized in that, The solid content in the suspension is 2-10 g / 100mL.

3. The application according to claim 1, characterized in that, The target load for Ru is 0.15 wt% - 0.6 wt%.

4. The application according to claim 1, characterized in that, The concentration of the Ru precursor solution is 1-10 wt%.

5. The application according to claim 4, characterized in that, The concentration of the Ru precursor solution is 3-5 wt%.

6. The application according to claim 1, characterized in that, The Ru precursor is one or more of RuCl3, ruthenium acetylacetonate, and ruthenium acetate; the Ru precursor solution is added at a rate of 0.1-2 mL / min.

7. The application according to claim 6, characterized in that, The Ru precursor solution was added at a rate of 0.8-1.2 mL / min.

8. The application according to claim 6, characterized in that, The Ru precursor is RuCl3 or ruthenium acetate.

9. The application according to claim 1, characterized in that, Degradation of o-dichlorobenzene o The DCB process is as follows: Oxidative activity test: o The DCB concentration was 100 ppm, the catalyst dosage was 100 mg, the total flow rate of the reaction gas was 60 mL / min, and the equilibrium gas was a 10% O2 / N2 mixture. The catalyst was evaluated at 120-300 °C. o -DCB conversion rate; Chlorine resistance stability evaluation: o The temperature at which the DCB conversion rate initially reaches 90% is denoted as T. 90 Continuous testing of stability under temperature o - DCB conversion rate remains above 90% for a period of time.

10. The application according to claim 1, characterized in that, The Ru-based single-atom catalyst contains highly dispersed Ru with a dispersion of not less than 80%.

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