Method for enriching palladium from palladium-containing waste liquid by using chelate resin and preparing nitrogen-doped graphitized carbon-loaded nano-palladium catalyst and application of nitrogen-doped graphitized carbon-loaded nano-palladium catalyst

Abstract

The invention discloses a method for enriching palladium from palladium-containing waste liquid by using chelate resin and preparing a nitrogen-doped graphitized carbon-loaded nano-palladium catalyst and application. The problems of loss of metal palladium, environmental pollution and the like in a palladium catalyst recovery and reutilization process are solved. The method for preparing the nitrogen-doped graphitized carbon-loaded nano-palladium catalyst comprises the following steps: 1, adding chelating resin into an aqueous solution containing PdCl4 < 2->, stirring and adsorbing, centrifuging, and drying to obtain PdCl4 < 2->-loaded chelating resin; and 2, putting the chelate resin loaded with the PdCl4 < 2-> into a tubular furnace, and carrying out a carbon thermal reduction reaction at the temperature of 500-1000 DEG C in a nitrogen atmosphere. According to the preparation method of the nitrogen-doped graphitized carbon loaded nano-palladium catalyst, nitrogen-doped graphitized carbon is formed under the action of metal ions, so that the conductivity and the electron transmission capability of a carrier are enhanced, and the activity and the stability of a Pd / NGC catalyst in a 12H-NEC dehydrogenation reaction process are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of nano palladium catalysts, and particularly relates to a method for enriching palladium from palladium-containing waste liquid by using chelating resin and preparing a nitrogen-doped graphitized carbon-loaded nano palladium catalyst. Background Art

[0002] Hydrogen energy is a secondary energy source with many advantages such as high combustion heat release, abundant sources, and green environmental protection. However, hydrogen storage is a bottleneck problem in the development of hydrogen economy. Liquid organic hydrogen carrier (LOHC) uses the reversible hydrogenation and dehydrogenation of liquid organic matter to achieve hydrogen storage and transportation. Existing oil and gas facilities can realize long-distance transportation and storage of hydrogen, solving the problems of high-pressure hydrogen storage and natural gas pipeline transportation. It is one of the most promising low-cost hydrogen storage and transportation technologies. N-ethylcarbazole (NEC) belongs to N-heterocyclic LOHC. Its fully hydrogenated product dodecahydro-N-ethylcarbazole (12H-NEC) has a mass hydrogen storage capacity of 5.8wt.%, and the complete dehydrogenation temperature is less than 200℃, which is a relatively ideal LOHC. In order to realize the commercial application of N-heterocyclic LOHC, the development of dehydrogenation catalysts with high catalytic activity, high selectivity, low cost and good catalytic stability has become the key to the commercial application of N-heterocyclic LOHC.

[0003] Precious metal supported catalysts show high catalytic activity for the dehydrogenation of N-heterocyclic LOHC, among which Pd catalyst has the best catalytic performance. Supported Pd catalyst is a commonly used catalyst in chemical production. However, during the production process, due to factors such as metal or carrier burnout and loss of effective components, the catalyst performance is reduced until it becomes ineffective and cannot be used. In addition, metallic Pd belongs to the platinum group metal and is expensive. Therefore, it is of great significance to recover metallic palladium from the ineffective palladium-containing waste catalyst and to re-prepare the Pd nanocatalyst supported by nitrogen-doped graphitized carbon by carbon thermal reduction in the absence of a reducing agent and a stabilizer. Summary of the invention

[0004] In order to solve the problems of loss of metal palladium and environmental pollution during the recovery and reuse of palladium catalysts, poor catalytic performance of existing dehydrogenation catalysts, etc., the present invention provides a method and application of enriching palladium from palladium-containing waste liquid using chelating resin and preparing a nano palladium catalyst supported by nitrogen-doped graphitized carbon.

[0005] The method of the present invention for enriching palladium from palladium-containing waste liquid by using chelating resin and preparing a nitrogen-doped graphitized carbon-supported nano-palladium catalyst is achieved by the following steps:

[0006] Step 1: Using chelating resin to remove PdCl4 2- Enriching palladium in solution:

[0007] To the PdCl42- Add chelating resin to the aqueous solution (waste liquid containing palladium) and stir to obtain adsorbed PdCl4 2- The chelating resin is then centrifuged and dried to obtain the loaded PdCl4 2- Chelating resin;

[0008] Step 2: Preparation of nitrogen-doped graphitized carbon-supported nano-palladium catalyst (Pd / NGC):

[0009] Load PdCl4 2- The chelating resin is placed in a tube furnace, and a carbon thermal reduction reaction is carried out at a temperature of 500-1000° C. for 2-4 hours under a nitrogen atmosphere, and then cooled to room temperature under a nitrogen atmosphere, and then ground to obtain a nitrogen-doped graphitized carbon-supported nano-palladium catalyst (Pd / NGC);

[0010] The chelating resin has an amino functional group, and the amino functional group is one or more of a tertiary amino group, an amino group, an iminodiacetic acid group, and a quaternary ammonium group.

[0011] The application of the nitrogen-doped graphitized carbon-supported nano-palladium catalyst of the present invention is to use the nitrogen-doped graphitized carbon-supported nano-palladium catalyst as a dehydrogenation catalyst of dodecahydro-N-ethylcarbazole (12H-NEC).

[0012] The invention discloses a method for preparing a nano-palladium catalyst supported by nitrogen-doped graphitized carbon by enriching palladium from palladium-containing waste liquid using a chelating resin, wherein the low-concentration PdCl4 generated after the waste palladium catalyst is recovered is treated with different types of chelating resins having amino functional groups such as tertiary amino groups, amino groups, iminodiacetic acid groups, quaternary ammonium groups, or having amino groups and carboxylic acid groups, phosphoric acid groups, sulfate groups, etc. 2- The leaching solution is adsorbed and enriched to form adsorbed PdCl4 2- After the chelating resin is separated and dried, it is calcined at high temperature in a N2 atmosphere to directly obtain a nano palladium catalyst (Pd / NGC) supported by nitrogen-doped graphitized carbon in one step. The invention has simple operation and low preparation cost.

[0013] The method for preparing a nano-palladium catalyst supported by nitrogen-doped graphitized carbon by enriching palladium from palladium-containing waste liquid using a chelating resin is disclosed. During the carbonization process of the chelating resin, the carbon acts as a carrier and a reducing agent at the same time. 0 The invention is embedded on the surface of NGC to improve its catalytic stability. The raw material cost of the invention is low, the source is wide and pollution-free, and it is an environmentally friendly preparation process.

[0014] The method for preparing a nano-palladium catalyst supported by nitrogen-doped graphitized carbon by enriching palladium from palladium-containing waste liquid using a chelating resin of the present invention forms nitrogen-doped graphitized carbon (NGC) under the action of metal ions, thereby enhancing the conductivity and electron transport capacity of the carrier, and improving the activity and stability of the Pd / NGC catalyst in the 12H-NEC dehydrogenation reaction process. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 TEM photo of the first embodiment of the invention for enriching palladium from palladium-containing waste liquid using chelating resin and preparing a nano-palladium catalyst supported by nitrogen-doped graphitized carbon;

[0016] Figure 2 The XPS spectrum of Pd 3d of the nano-palladium catalyst supported by nitrogen-doped graphitized carbon is prepared by enriching palladium from palladium-containing waste liquid using chelating resin in the specific embodiment 1;

[0017] Figure 3 The XPS spectrum of N1s of the nano-palladium catalyst supported on nitrogen-doped graphitized carbon is prepared by enriching palladium from palladium-containing waste liquid using chelating resin in the specific embodiment 1;

[0018] Figure 4 The XPS spectrum of C1s of the nano-palladium catalyst supported on nitrogen-doped graphitized carbon is prepared by enriching palladium from palladium-containing waste liquid using chelating resin in the specific embodiment 1;

[0019] Figure 5 The Raman spectra of the specific embodiments 1, 2, 3 and 4 for enriching palladium from palladium-containing waste liquid using chelating resin and preparing nitrogen-doped graphitized carbon-supported nano-palladium catalyst;

[0020] Figure 6 The performance curves of the commercial Pd / C in catalyzing 12H-NEC dehydrogenation reaction in the first, second, third and fourth embodiments of the present invention are as follows:

[0021] Figure 7 The performance curve of the 12H-NEC dehydrogenation reaction of the nano-palladium catalyst supported on nitrogen-doped graphitized carbon for enriching palladium from palladium-containing waste liquid using chelating resin in specific embodiments one, five and six;

[0022] Figure 8 The performance curve of the 12H-NEC dehydrogenation reaction of the nano-palladium catalyst supported on nitrogen-doped graphitized carbon for enriching palladium from palladium-containing waste liquid using chelating resin in specific embodiments one, seven, eight and nine;

[0023] Fig. 9A bar chart showing a specific embodiment 1 of enriching palladium from palladium-containing waste liquid using a chelating resin and preparing a nitrogen-doped graphitized carbon-supported nano-palladium catalyst and a comparative example 1 of a 12H-NEC dehydrogenation reaction cycle test. DETAILED DESCRIPTION

[0024] Specific embodiment 1: In this embodiment, the method of enriching palladium from palladium-containing waste liquid using chelating resin and preparing nitrogen-doped graphitized carbon-supported nano-palladium catalyst is implemented according to the following steps:

[0025] Step 1: Using chelating resin to remove PdCl4 2- Enriching palladium in solution:

[0026] To the PdCl4 2- Add chelating resin to the aqueous solution (waste liquid containing palladium) and stir to obtain adsorbed PdCl4 2- The chelating resin is then centrifuged and dried to obtain the loaded PdCl4 2- Chelating resin;

[0027] Step 2: Preparation of nitrogen-doped graphitized carbon-supported nano-palladium catalyst (Pd / NGC):

[0028] Load PdCl4 2- The chelating resin is placed in a tube furnace, and a carbon thermal reduction reaction is carried out at a temperature of 500-1000° C. for 2-4 hours under a nitrogen atmosphere, and then cooled to room temperature under a nitrogen atmosphere, and then ground to obtain a nitrogen-doped graphitized carbon-supported nano-palladium catalyst (Pd / NGC);

[0029] The chelating resin has an amino functional group, and the amino functional group is one or more of a tertiary amino group, an amino group, an iminodiacetic acid group, and a quaternary ammonium group.

[0030] This embodiment uses a chelating ion exchange resin to recover the low-concentration PdCl4 produced by the waste palladium catalyst. 2- The leaching solution is adsorbed and enriched to form adsorbed PdCl4 2- The chelating resin is separated and dried, and then calcined at high temperature in a N2 atmosphere to directly obtain the nitrogen-doped graphitized carbon-supported nano-palladium catalyst (Pd / NGC) in one step. During the carbonization process, the chelating resin will form nitrogen-doped graphitized carbon (NGC) under the action of metal ions, and PdCl4 2- Generation of Pd by carbothermal reduction 0 Carbon acts as both a carrier and a reducing agent, and the loaded Pd 0 Embedded on the surface of NGC, it improves its catalytic stability. The present invention omits the adsorption of PdCl4 2-The chelating resin requires elution, purification, dissolution, loading, reduction and other steps to recover palladium and circulate the many operations to prepare the supported palladium catalyst. It is not only simple to operate, environmentally friendly, and low in preparation cost, but also has high efficiency in catalyzing the release of hydrogen from liquid organic hydrogen carriers (LOHCs).

[0031] Specific embodiment 2: This embodiment is different from specific embodiment 1 in that the chelating resin also has carboxylic acid, phosphoric acid or sulfate functional groups.

[0032] Specific embodiment 3: This embodiment is different from specific embodiment 1 or 2 in that step 1 contains PdCl4 2- PdCl4 in aqueous solution 2- The concentration is 0.001~0.01mol / L.

[0033] Specific embodiment 4: This embodiment is different from the specific embodiments 1 to 3 in that the PdCl4 is contained in step 1. 2- The liquid-to-solid ratio of the aqueous solution to the chelating resin is 5-60 mL / g.

[0034] This experimental method contains PdCl4 2- The liquid-to-solid ratio of aqueous solution to chelating resin refers to 5-60 mL of PdCl4 2- Add 1g of chelating resin into the aqueous solution.

[0035] Specific embodiment 5: This embodiment is different from the specific embodiments 1 to 4 in that in step 1, the PdCl4 2- Add chelating resin to the aqueous solution and stir for 2 to 6 hours.

[0036] Specific implementation method 6: This implementation method is different from specific implementation methods 1 to 5 in that step 1 is to stir the reaction at a temperature of 20 to 50°C.

[0037] Specific embodiment 7: This embodiment is different from the specific embodiments 1 to 6 in that in step 2, PdCl4 is loaded 2- The chelating resin is placed in a tubular furnace, and the flow rate of nitrogen is controlled to be 10-50 mL / min.

[0038] Specific implementation eight: This implementation differs from specific implementations one to seven in that in step two, the temperature is raised to 500-1000° C. at a heating rate of 1-10° C. / min under a nitrogen atmosphere.

[0039] Specific embodiment 9: This embodiment is different from specific embodiments 1 to 8 in that in step 2, the carbon thermal reduction reaction is carried out at a temperature of 700 to 800° C. for 3 to 4 hours.

[0040] Embodiment 1: The method of enriching palladium from palladium-containing waste liquid using chelating resin and preparing nitrogen-doped graphitized carbon-supported nano-palladium catalyst in this embodiment is implemented according to the following steps:

[0041] Step 1: Using chelating resin to remove PdCl4 2- Enriching palladium in solution:

[0042] Add 10.1 mL of 0.004 mol / L PdCl4 2- Add 1g of chelating resin to the aqueous solution and stir at 30℃ for 3h to obtain adsorbed PdCl4 2- The chelating resin is then centrifuged and dried to obtain the loaded PdCl4 2- Chelating resin;

[0043] Step 2: Preparation of nitrogen-doped graphitized carbon-supported nano-palladium catalyst (Pd / NGC):

[0044] Load PdCl4 2- The chelating resin was placed in a tube furnace, heated to 750°C at a heating rate of 2°C / min under a nitrogen atmosphere, and subjected to a carbon thermal reduction reaction for 3 hours. Then, the catalyst was cooled to room temperature under a nitrogen atmosphere, and then ground to obtain a nitrogen-doped graphitized carbon-supported nano-palladium catalyst (Pd / NGC).

[0045] The chelating resin is aminophosphonic acid chelating resin.

[0046] Embodiment 2: The method of enriching palladium from palladium-containing waste liquid using chelating resin and preparing nitrogen-doped graphitized carbon-supported nano-palladium catalyst in this embodiment is implemented according to the following steps:

[0047] Step 1: Using chelating resin to remove PdCl4 2- Enriching palladium in solution:

[0048] Add 10.1 mL of 0.004 mol / L PdCl4 2- Add 1g of chelating resin to the aqueous solution and stir at 30℃ for 3h to obtain adsorbed PdCl4 2- The chelating resin is then centrifuged and dried to obtain the loaded PdCl4 2- Chelating resin;

[0049] Step 2: Preparation of nitrogen-doped graphitized carbon-supported nano-palladium catalyst (Pd / NGC):

[0050] Load PdCl4 2-The chelating resin was placed in a tube furnace, heated to 700°C at a heating rate of 2°C / min under a nitrogen atmosphere, and subjected to a carbon thermal reduction reaction for 3 hours. Then, the catalyst was cooled to room temperature under a nitrogen atmosphere, and ground to obtain a nitrogen-doped graphitized carbon-supported nano-palladium catalyst (Pd / NGC).

[0051] The chelating resin is aminophosphonic acid chelating resin.

[0052] Embodiment 3: The method of enriching palladium from palladium-containing waste liquid using chelating resin and preparing nitrogen-doped graphitized carbon-supported nano-palladium catalyst in this embodiment is implemented according to the following steps:

[0053] Step 1: Using chelating resin to remove PdCl4 2- Enriching palladium in solution:

[0054] Add 10.1 mL of 0.004 mol / L PdCl4 2- Add 1g of chelating resin to the aqueous solution and stir at 30℃ for 3h to obtain adsorbed PdCl4 2- The chelating resin is then centrifuged and dried to obtain the loaded PdCl4 2- Chelating resin;

[0055] Step 2: Preparation of nitrogen-doped graphitized carbon-supported nano-palladium catalyst (Pd / NGC):

[0056] Load PdCl4 2- The chelating resin was placed in a tubular furnace, heated to 800°C at a heating rate of 2°C / min in a nitrogen atmosphere, and subjected to a carbon thermal reduction reaction for 3 hours. Then, the catalyst was cooled to room temperature in a nitrogen atmosphere, and ground to obtain a nitrogen-doped graphitized carbon-supported nano-palladium catalyst (Pd / NGC).

[0057] The chelating resin is aminophosphonic acid chelating resin.

[0058] Embodiment 4: The method of enriching palladium from palladium-containing waste liquid using chelating resin and preparing nitrogen-doped graphitized carbon-supported nano-palladium catalyst in this embodiment is implemented according to the following steps:

[0059] Step 1: Using chelating resin to remove PdCl4 2- Enriching palladium in solution:

[0060] Add 10.1 mL of 0.004 mol / L PdCl4 2- Add 1g of chelating resin to the aqueous solution and stir at 30℃ for 3h to obtain adsorbed PdCl4 2- The chelating resin is then centrifuged and dried to obtain the loaded PdCl4 2- Chelating resin;

[0061] Step 2: Preparation of nitrogen-doped graphitized carbon-supported nano-palladium catalyst (Pd / NGC):

[0062] Load PdCl4 2- The chelating resin was placed in a tube furnace, heated to 850°C at a heating rate of 2°C / min under a nitrogen atmosphere, and subjected to a carbon thermal reduction reaction for 3 hours. After cooling to room temperature under a nitrogen atmosphere, the nano-palladium catalyst supported on nitrogen-doped graphitized carbon (Pd / NGC) was obtained after grinding.

[0063] The chelating resin is aminophosphonic acid chelating resin.

[0064] Embodiment 5: The method of enriching palladium from palladium-containing waste liquid using chelating resin and preparing nitrogen-doped graphitized carbon-supported nano-palladium catalyst in this embodiment is implemented according to the following steps:

[0065] Step 1: Using chelating resin to remove PdCl4 2- Enriching palladium in solution:

[0066] Add 10.1 mL of 0.004 mol / L PdCl4 2- Add 1g of chelating resin to the aqueous solution and stir at 30℃ for 3h to obtain adsorbed PdCl4 2- The chelating resin is then centrifuged and dried to obtain the loaded PdCl4 2- Chelating resin;

[0067] Step 2: Preparation of nitrogen-doped graphitized carbon-supported nano-palladium catalyst (Pd / NGC):

[0068] Load PdCl4 2- The chelating resin was placed in a tubular furnace, heated to 750°C at a heating rate of 2°C / min under a nitrogen atmosphere, and subjected to a carbon thermal reduction reaction for 2 hours. After cooling to room temperature under a nitrogen atmosphere, the nano-palladium catalyst supported on nitrogen-doped graphitized carbon (Pd / NGC) was obtained after grinding.

[0069] The chelating resin is aminophosphonic acid chelating resin.

[0070] Embodiment 6: The method of enriching palladium from palladium-containing waste liquid using chelating resin and preparing nitrogen-doped graphitized carbon-supported nano-palladium catalyst in this embodiment is implemented according to the following steps:

[0071] Step 1: Using chelating resin to remove PdCl4 2- Enriching palladium in solution:

[0072] Add 10.1 mL of 0.004 mol / L PdCl4 2-Add 1g of chelating resin to the aqueous solution and stir at 30℃ for 3h to obtain adsorbed PdCl4 2- The chelating resin is then centrifuged and dried to obtain the loaded PdCl4 2- Chelating resin;

[0073] Step 2: Preparation of nitrogen-doped graphitized carbon-supported nano-palladium catalyst (Pd / NGC):

[0074] Load PdCl4 2- The chelating resin was placed in a tubular furnace, heated to 750°C at a heating rate of 2°C / min under a nitrogen atmosphere, and subjected to a carbon thermal reduction reaction for 4 hours. Then, the catalyst was cooled to room temperature under a nitrogen atmosphere, and then ground to obtain a nitrogen-doped graphitized carbon-supported nano-palladium catalyst (Pd / NGC).

[0075] The chelating resin is aminophosphonic acid chelating resin.

[0076] Embodiment 7: The method of enriching palladium from palladium-containing waste liquid using chelating resin and preparing nitrogen-doped graphitized carbon-supported nano-palladium catalyst in this embodiment is implemented according to the following steps:

[0077] Step 1: Using chelating resin to remove PdCl4 2- Enriching palladium in solution:

[0078] Add 5.05 mL of 0.004 mol / L PdCl4 2- Add 1g of chelating resin to the aqueous solution and stir at 30℃ for 3h to obtain adsorbed PdCl4 2- The chelating resin is then centrifuged and dried to obtain the loaded PdCl4 2- Chelating resin;

[0079] Step 2: Preparation of nitrogen-doped graphitized carbon-supported nano-palladium catalyst (Pd / NGC):

[0080] Load PdCl4 2- The chelating resin was placed in a tube furnace, heated to 750°C at a heating rate of 2°C / min under a nitrogen atmosphere, and subjected to a carbon thermal reduction reaction for 3 hours. Then, the catalyst was cooled to room temperature under a nitrogen atmosphere, and then ground to obtain a nitrogen-doped graphitized carbon-supported nano-palladium catalyst (Pd / NGC).

[0081] The chelating resin is aminophosphonic acid chelating resin.

[0082] Embodiment 8: The method of enriching palladium from palladium-containing waste liquid using chelating resin and preparing nitrogen-doped graphitized carbon-supported nano-palladium catalyst in this embodiment is implemented according to the following steps:

[0083] Step 1: Using chelating resin to remove PdCl42- Enriching palladium in solution:

[0084] Add 30.3 mL of 0.004 mol / L PdCl4 2- Add 1g of chelating resin to the aqueous solution and stir at 30℃ for 3h to obtain adsorbed PdCl4 2- The chelating resin is then centrifuged and dried to obtain the loaded PdCl4 2- Chelating resin;

[0085] Step 2: Preparation of nitrogen-doped graphitized carbon-supported nano-palladium catalyst (Pd / NGC):

[0086] Load PdCl4 2- The chelating resin was placed in a tube furnace, heated to 750°C at a heating rate of 2°C / min under a nitrogen atmosphere, and subjected to a carbon thermal reduction reaction for 3 hours. Then, the catalyst was cooled to room temperature under a nitrogen atmosphere, and then ground to obtain a nitrogen-doped graphitized carbon-supported nano-palladium catalyst (Pd / NGC).

[0087] The chelating resin is aminophosphonic acid chelating resin.

[0088] Embodiment 9: The method of enriching palladium from palladium-containing waste liquid using chelating resin and preparing nitrogen-doped graphitized carbon-supported nano-palladium catalyst in this embodiment is implemented according to the following steps:

[0089] Step 1: Using chelating resin to remove PdCl4 2- Enriching palladium in solution:

[0090] Add 50.5 mL of 0.004 mol / L PdCl4 2- Add 1g of chelating resin to the aqueous solution and stir at 30℃ for 3h to obtain adsorbed PdCl4 2- The chelating resin is then centrifuged and dried to obtain the loaded PdCl4 2- Chelating resin;

[0091] Step 2: Preparation of nitrogen-doped graphitized carbon-supported nano-palladium catalyst (Pd / NGC):

[0092] Load PdCl4 2- The chelating resin was placed in a tube furnace, heated to 750°C at a heating rate of 2°C / min under a nitrogen atmosphere, and subjected to a carbon thermal reduction reaction for 3 hours. Then, the catalyst was cooled to room temperature under a nitrogen atmosphere, and then ground to obtain a nitrogen-doped graphitized carbon-supported nano-palladium catalyst (Pd / NGC).

[0093] The chelating resin is aminophosphonic acid chelating resin.

[0094] Comparative Example:

[0095] The catalyst Pd / NGC prepared in this example and commercial Pd / C with a Pd loading of 5 wt.% were used to catalyze the dehydrogenation reaction of 12H-NEC. The catalyst and 12H-NEC were mixed at a molar ratio of Pd to 12H-NEC in the catalyst of 0.3:100, and the reaction temperature was 180°C.

[0096] Figure 1 This is a TEM photo of the method of enriching palladium from palladium-containing waste liquid using chelating resin and preparing a nitrogen-doped graphitized carbon-supported nano-palladium catalyst in Example 1. Figure 1 It can be seen that the Pd nanoparticles are evenly dispersed on the surface of the NGC carrier without agglomeration.

[0097] Figure 2 The XPS spectrum of Pd 3d of the nano-palladium catalyst supported on nitrogen-doped graphitized carbon prepared by enriching palladium from palladium-containing waste liquid using chelating resin in Example 1. Figure 2 It can be seen that PdCl4 in the Pd / NGC catalyst prepared by carbothermal reduction 2- Reduced to Pd 0 .

[0098] Figure 3 This is the XPS spectrum of N1s of the nano-palladium catalyst supported on nitrogen-doped graphitized carbon prepared by enriching palladium from palladium-containing waste liquid using chelating resin in Example 1. Figure 3 It can be seen that nitrogen-doped carbon supports were successfully prepared by carbothermal reduction.

[0099] Figure 4 This is the XPS spectrum of C1s of the nano-palladium catalyst supported on nitrogen-doped graphitized carbon prepared by enriching palladium from palladium-containing waste liquid using chelating resin in Example 1. Figure 4 It can be seen that the carbon support was graphitized at a carbothermal temperature of 750 °C.

[0100] Figure 5 The Raman spectra of the nano-palladium catalyst supported by nitrogen-doped graphitized carbon are prepared by enriching palladium from palladium-containing waste liquid using chelating resin in Examples 1, 2, 3, and 4. Figure 5 It can be seen that the graphitization degree of NGC carrier in the Pd / NGC catalyst prepared by carbothermal treatment at 750 °C for 3 h is the highest (I D / I G minimum value).

[0101] Figure 6 The graphs show the relationship between the amount of hydrogen released and the reaction time in the 12H-NEC dehydrogenation reaction catalyzed by commercial Pd / C in Example 1, 2, 3 and 4 using chelating resin to enrich palladium from palladium-containing waste liquid and prepare nitrogen-doped graphitized carbon-supported nano-palladium catalysts and in Example 1. Figure 6It can be seen that Pd / NGC prepared with a carbothermal temperature of 750°C and a carbothermal time of 3 h showed the highest activity in catalyzing the dehydrogenation reaction of 12H-NEC, and the dehydrogenation efficiency was 100% after 4 h of reaction, which was much higher than that of commercial Pd / C.

[0102] Figure 7 The graph is a curve showing the relationship between the amount of hydrogen released and the reaction time in the dehydrogenation reaction of 12H-NEC catalyzed by the nano-palladium supported on nitrogen-doped graphitized carbon in the preparation of palladium enrichment from palladium-containing waste liquid using chelating resin in Examples 1, 5 and 6. Figure 7 It can be seen that the Pd / NGC catalyst prepared when the carbon heating temperature is 750℃ and the carbon heating time is 3h has the largest hydrogen release in the 12H-NEC dehydrogenation reaction.

[0103] Figure 8 The graphs are the relationship between the amount of hydrogen released and the reaction time of the nano-palladium catalyst supported by nitrogen-doped graphitized carbon in the 12H-NEC dehydrogenation reaction in which palladium is enriched from palladium-containing waste liquid using chelating resin in Examples 1, 7, 8 and 9. Figure 8 It can be seen that the Pd / NGC catalyst with a Pd loading of 1 wt.% has the largest hydrogen release amount in the 12H-NEC dehydrogenation reaction.

[0104] Fig. 9 The graph is a bar chart showing the cycle test of enriching palladium from palladium-containing wastewater using chelating resin to prepare nitrogen-doped graphitized carbon-supported nano-palladium catalyst in Example 1 and Comparative Example 1 in the 12H-NEC dehydrogenation reaction. Fig. 9 It can be seen that compared with commercial Pd / C, Pd / NGC prepared by carbothermal reduction showed higher stability in catalyzing the 12H-NEC dehydrogenation reaction, and its dehydrogenation efficiency after the seventh cycle decreased from 100% to 95.1%, while the dehydrogenation efficiency of commercial Pd / C after the seventh cycle decreased from 96.3% to 73.9%.

Claims

1. A method for enriching palladium from palladium-containing waste liquid using a chelating resin and preparing a nano-palladium catalyst supported by nitrogen-doped graphitized carbon, characterized in that The method for preparing the nitrogen-doped graphitized carbon-supported nano-palladium catalyst is achieved by the following steps: Step 1: Using chelating resin to remove PdCl4 2- Enriching palladium in solution: To the PdCl4 2- Add chelating resin to the aqueous solution and stir to obtain adsorbed PdCl4 2- The chelating resin is then centrifuged and dried to obtain the loaded PdCl4 2- Chelating resin; Step 2: Preparation of nitrogen-doped graphitized carbon-supported nano-palladium catalyst: Load PdCl4 2- The chelating resin is placed in a tubular furnace, and a carbon thermal reduction reaction is carried out at a temperature of 500 to 1000° C. for 2 to 4 hours under a nitrogen atmosphere, and then cooled to room temperature under a nitrogen atmosphere, and then ground to obtain a nitrogen-doped graphitized carbon-supported nano-palladium catalyst; The chelating resin has an amino functional group, and the amino functional group is one or more of a tertiary amino group, an amino group, an iminodiacetic acid group, and a quaternary ammonium group.

2. The method of utilizing chelated resin to enrich palladium from palladium-containing waste liquid and prepare a nano-palladium catalyst supported by nitrogen-doped graphitized carbon according to claim 1, characterized in that The chelating resin also has carboxylic acid, phosphoric acid or sulfate functional groups.

3. The method of utilizing chelated resin to enrich palladium from palladium-containing waste liquid and prepare a nano palladium catalyst supported by nitrogen-doped graphitized carbon according to claim 1, characterized in that Step 1 contains PdCl4 2- PdCl4 in aqueous solution 2- The concentration is 0.001~0.01mol / L.

4. The method of utilizing chelated resin to enrich palladium from palladium-containing waste liquid and prepare a nano palladium catalyst supported by nitrogen-doped graphitized carbon according to claim 1, characterized in that Control the presence of PdCl4 in step 1 2- The liquid-to-solid ratio of the aqueous solution to the chelating resin is 5-60 mL / g.

5. The method of utilizing chelated resin to enrich palladium from palladium-containing waste liquid and prepare a nano palladium catalyst supported by nitrogen-doped graphitized carbon according to claim 1, characterized in that In step 1, add PdCl4 2- Add chelating resin to the aqueous solution and stir for 2 to 6 hours.

6. The method of utilizing chelated resin to enrich palladium from palladium-containing waste liquid and prepare a nano palladium catalyst supported by nitrogen-doped graphitized carbon according to claim 1, characterized in that Step 1: Stir the reaction at a temperature of 20-50°C.

7. The method of utilizing chelated resin to enrich palladium from palladium-containing waste liquid and prepare a nano palladium catalyst supported by nitrogen-doped graphitized carbon according to claim 1, characterized in that In step 2, PdCl4 is loaded 2- The chelating resin is placed in a tubular furnace, and the flow rate of nitrogen is controlled to be 10-50 mL / min.

8. The method of utilizing chelated resin to enrich palladium from palladium-containing waste liquid and prepare a nano palladium catalyst supported by nitrogen-doped graphitized carbon according to claim 1, characterized in that In step 2, the temperature is increased to 500-1000° C. at a heating rate of 1-10° C. / min under a nitrogen atmosphere.

9. The method of utilizing chelated resin to enrich palladium from palladium-containing waste liquid and prepare a nano palladium catalyst supported by nitrogen-doped graphitized carbon according to claim 1, characterized in that In step 2, the carbon thermal reduction reaction is carried out at a temperature of 700-800° C. for 3-4 hours.

10. The use of the nitrogen-doped graphitized carbon-supported nano-palladium catalyst prepared as claimed in claim 1, characterized in that The nitrogen-doped graphitized carbon-supported nano-palladium catalyst is used as a dehydrogenation catalyst for dodecahydro-N-ethylcarbazole.

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