A method for recovering and reusing a spent reforming catalyst to prepare a methane dry reforming catalyst, the catalyst and a methane dry reforming method

Abstract

The application discloses a method for preparing a methane dry reforming catalyst from waste reforming catalysts, a catalyst and a methane dry reforming method. The method comprises the following steps: (1) calcining a waste Pt-Re / Al2O3 reforming catalyst, immersing the catalyst in a solution composed of acid, hydrogen peroxide and water to obtain a waste reforming catalyst leaching solution containing Pt, Re and Al ions; (2) co-extracting platinum and rhenium in the leaching solution by using an N235+TBP complex extraction agent to obtain an organic phase containing platinum and rhenium; (3) back-extracting the organic phase containing platinum and rhenium by using NH3H2O to obtain a platinum-rhenium mixed solution; (4) adding a gamma-Al2O3 carrier into the platinum-rhenium mixed solution for impregnation treatment, and sequentially performing drying, grinding and calcination treatment; and (5) calcining under a H2 atmosphere to obtain a methane dry reforming catalyst. The platinum and rhenium are separated and recovered from the waste reforming catalyst by extraction, and the methane dry reforming catalyst is prepared by using an impregnation method, so that the method has the advantages of green pollution-free, low cost, high utilization rate and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of thermal catalytic carbon fixation catalysts, and particularly relates to a method for recycling and reusing waste reforming catalyst (recovery and reuse of noble metals platinum and rhenium) to prepare a methane dry reforming catalyst (Pt-Re / Al2O3 catalyst), a catalyst and a methane dry reforming method. BACKGROUND

[0002] Under the background of economic growth and industrial expansion, the demand for high-octane gasoline produced by the catalytic reforming process of naphtha is rapidly increasing, which also promotes the application and development of reforming catalysts. Petrochemical catalysts are consumables, and the amount of waste is huge every year. The noble metal platinum (Pt) is expensive and scarce in resources, has good high-temperature oxidation resistance and chemical stability, is easy to process into a shape, and has a wide range of applications. Rhenium (Re) is rare in nature and is dispersed, so it is expensive and has a high cost. Platinum-rhenium reforming catalyst is the most widely used reforming catalyst at present. Platinum in the catalyst mainly plays a catalytic role, and the main role of rhenium is to reduce or prevent metal components from condensing, thereby improving the carbon capacity and stability of the catalyst. The catalyst is used in a fixed bed reactor, and the service life of the catalyst is prolonged through regeneration, the generation of waste is reduced, the efficiency and stability of the catalyst are improved, the activity and selectivity of the catalyst are restored, the catalyst can be reused, the demand for new catalysts is reduced, thereby reducing production costs and resource consumption.

[0003] The byproduct hydrogen of the methane dry reforming reaction is also the cheapest hydrogen source for refinery hydrogenation devices. Platinum and rhenium in waste reforming catalysts have great prospect value as secondary resources for recycling and reuse. Methane dry reforming (DRM) is a process in which methane (CH4) and carbon dioxide (CO2), two greenhouse gases, are converted into synthesis gas under the action of a catalyst and react with the catalyst. The carbon fixation catalyst used in methane dry reforming can promote the recycling of clean energy and reduce environmental pollution. At present, the common method for recycling noble metals platinum and rhenium in China is wet recovery, the method for synthesizing the catalyst is impregnation, and the catalytic reforming technology is stable and mature, but there is currently no process for recovering platinum and rhenium from waste reforming catalysts, regenerating them, and synthesizing a catalyst with thermal catalytic carbon fixation performance. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a method for recycling and reusing noble metals in waste reforming catalysts to prepare a methane dry reforming catalyst, a catalyst and a methane dry reforming method. In the present application, noble metals platinum and rhenium are co-extracted from a waste reforming catalyst leaching solution by using N235+TBP extractant through a simple extraction process, and a Pt-Re / Al2O3 catalyst with low cost, high activity and good stability for thermal catalytic carbon fixation is prepared by using an impregnation method. The catalyst has excellent thermal catalytic carbon fixation performance.

[0005] To achieve the above object, the present application adopts the following technical solutions:

[0006] In a first aspect, the present application provides a method for recycling waste reforming catalyst to prepare a methane dry reforming catalyst, comprising the following steps:

[0007] (1) calcining the waste Pt-Re / Al2O3 reforming catalyst, and then placing it in a solution composed of acid, hydrogen peroxide and water to leach, obtaining a waste reforming catalyst leaching solution containing Pt ions, Re ions and Al ions;

[0008] (2) co-extracting platinum and rhenium in the waste reforming catalyst leaching solution with an N235+TBP complexing extractant, obtaining an organic phase containing platinum and rhenium;

[0009] (3) back-extracting the organic phase containing platinum and rhenium with NH3·H2O, obtaining a platinum-rhenium mixed solution;

[0010] (4) adding a γ-Al2O3 carrier to the platinum-rhenium mixed solution to stir and perform impregnation treatment, and then sequentially performing drying, grinding and calcination treatment;

[0011] (5) calcining the product obtained by the calcination treatment in a H2 atmosphere, obtaining the methane dry reforming catalyst Pt-Re / Al2O3.

[0012] In the above method for recycling waste reforming catalyst to prepare a methane dry reforming catalyst, in step (1), the temperature in the calcination step is 400℃, and the time is 4h;

[0013] In the solution composed of acid, hydrogen peroxide and water, the concentration of the acid is 2.0M, and the mass concentration of H2O2 is 5%; wherein the acid includes hydrochloric acid;

[0014] In the leaching step, the liquid-solid ratio is 5g:1mL, the leaching temperature is 120℃, and the leaching time is 3h;

[0015] As an example, in the waste reforming catalyst leaching solution, the concentration of Pt ions is 100ppm, the concentration of Re ions is 200ppm, and the concentration of Al ions is 900ppm.

[0016] In the above method for recycling waste reforming catalyst to prepare a methane dry reforming catalyst, the N235+TBP complexing extractant is composed of N235, TBP and a diluent, and the diluent is preferably petroleum ether;

[0017] The concentration of N235 extractant in the N235+TBP compound extractant is 10% to 30% by mass percentage, the concentration of TBP is 5% to 20% by mass percentage, and the concentration of diluent is 50% to 85% by mass percentage; as an example, the compound extractant is selected from any one of 10% N235+5% TBP, 10% N235+10% TBP, 20% N235+5% TBP, 20% N235+10% TBP, 30% N235+5% TBP, and 30% N235+10% TBP; in the present application, the term N235 refers to the abbreviation of trioctyl tertiary amine, and the term TBP refers to the abbreviation of tributyl phosphate. In the co-extraction step, the co-extraction phase ratio A / O is 1:(1-1.5), such as 1:1 or 1:1.5; the co-extraction time is 5-20 min, specifically 5 min, 10 min, 15 min, or 20 min.

[0018] The method further comprises, before co-extraction, adjusting the pH of the co-extraction system to 1-7, specifically, pH=1, 2, 3, 4, 5, 6, or 7.

[0019] In the above method for recycling waste reforming catalyst to prepare a methane dry reforming catalyst, the concentration of NH3·H2O is 10%-20% by mass percentage, specifically 10%, 15%, or 20%.

[0020] In the back-extraction step, the back-extraction phase ratio A / O is 1:(1-1.5), specifically 1:1 or 1:1.5; the back-extraction time is 5-20 min, specifically 5 min, 10 min, 15 min, or 20 min.

[0021] The method further comprises, after back-extraction, adjusting the pH of the system after back-extraction to the pH value of the co-extraction step, and then separating the aqueous phase and the organic phase. Specifically, the pH is 1, 2, 3, 4, 5, 6, or 7.

[0022] In the above method for recycling waste reforming catalyst to prepare a methane dry reforming catalyst, in the platinum-rhenium mixed solution, the mass fraction ratio of platinum to rhenium is 1:(0.5-2), specifically 1:1, 1:2, or 2:1.

[0023] The mass fraction of the γ-Al2O3 carrier in the methane dry reforming catalyst is 80%-99.97%, preferably 99.94%-99.97%, such as 99.94%, 99.96 wt%, or 99.97%.

[0024] In the method for preparing the methane dry reforming catalyst from the waste reforming catalyst, in the impregnation treatment step, the solid-liquid ratio is 1:20, the temperature is 80℃, and the stirring time is 9h-12h. It can be understood that the solid-liquid ratio of 1:20 means that 1g of γ-Al2O3 carrier corresponds to 20mL of platinum-rhenium mixed solution. As an example, the stirring time is specifically 9h, 10h or 12h.

[0025] In the drying step, the drying is vacuum drying, the drying temperature is 50℃-80℃, such as 50℃, 60℃, 80℃, and the drying time is 12h. Further, the method further comprises a grinding step of 30min after the drying.

[0026] In the calcination treatment step, the calcination time is 3-5h, specifically 3h, 4h, 5h, the calcination temperature is 400℃-600℃, specifically 400℃, 500℃, 600℃, and the heating rate is 5℃ / min as an example. The calcination treatment is specifically performed in a muffle furnace.

[0027] In the method for preparing the methane dry reforming catalyst from the waste reforming catalyst, in the calcination step, the H2 flow rate is 30sccm.

[0028] In the calcination step, the calcination temperature is 400℃-600℃, specifically 400℃, 500℃, 600℃, and the calcination time is 3-5h, specifically 3h, 4h, 5h. As an example, the heating rate is 5℃ / min. The calcination treatment is specifically performed in a tube furnace. Further, the method further comprises a grinding step of 30min after the calcination.

[0029] In a second aspect, the application further provides the methane dry reforming catalyst Pt-Re / Al2O3 prepared by the method.

[0030] In a third aspect, the application provides a methane dry reforming method, comprising the following steps: using the methane dry reforming catalyst Pt-Re / Al2O3 as a catalyst, and reacting a mixed gas containing methane and carbon dioxide with the catalyst in a fixed bed reactor.

[0031] In the methane dry reforming method, in the mixed gas, the volume ratio of methane to carbon dioxide is 1:(1-2), such as 1:1 or 1:2.

[0032] The flow rate of methane and carbon dioxide corresponding to 0.2g of the catalyst is (2-4)ml / min, such as 2ml / min or 4ml / min.

[0033] The temperature of the reaction is 400-850 DEG C, and can be 400 DEG C, 500 DEG C, 600 DEG C, 700 DEG C, 800 DEG C or 850 DEG C.

[0034] The mixed gas is balanced by nitrogen or argon, and the volume fraction of methane and carbon dioxide in the mixed gas is 10-20%, such as 10% or 20%.

[0035] The present application has the following beneficial effects:

[0036] (1) A simple process for recycling precious metals in waste reforming catalysts to prepare carbon sequestration catalysts is developed, and the simplest extraction separation is used to recover precious metals platinum and rhenium, and the impregnation method is used to recycle and prepare low-cost high-activity thermal catalysts, which is overall green and pollution-free, low in raw material cost, high in utilization rate, low in energy consumption, good in effect, and suitable for large-scale preparation.

[0037] (2) The combination of precious metals platinum and rhenium and the gamma-Al2O3 carrier improves the conversion rate of CH4 and CO2 in the thermal catalytic CH4 / CO2 dry reforming reaction, and almost reaches 100% conversion, and the yield of CO and H2 is as high as 98.99%, which has strong carbon sequestration ability and cleaning ability.

[0038] (3) The Pt-Re / Al2O3 catalyst prepared by the present application has guiding significance for maximizing resource utilization of waste materials, and provides new insights for alleviating the environmental pollution challenge caused by current fossil fuel consumption. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 It is a process flow chart for recycling waste reforming catalysts to prepare methane dry reforming catalysts (carbon sequestration catalysts) in the embodiments of the present application.

[0040] Figure 2 It is an XRD graph of the Pt-Re / Al2O3 catalyst prepared in Example 1.

[0041] Figure 3 It is a thermal performance graph of the methane conversion rate in the methane dry reforming reaction of the Pt-Re / Al2O3 catalyst prepared in Example 1.

[0042] Figure 4 It is a curve of the ratio of H2 / CO in the methane dry reforming reaction of the Pt-Re / Al2O3 catalyst prepared in Example 1 with temperature. DETAILED DESCRIPTION

[0043] The present application will be further described in conjunction with the specific embodiments. The examples given are only to illustrate the present application, and are not intended to limit the scope of the present application. The examples provided below can serve as a guide for further improvement by those of ordinary skill in the art, and do not in any way constitute a limitation on the present application.

[0044] The methods used in the following examples are conventional methods, and are performed according to the techniques or conditions described in the literature in the art or according to the product instructions, unless otherwise specified. The materials, reagents, etc. used in the following examples are commercially available, unless otherwise specified.

[0045] The spent Pt-Re / Al2O3 reforming catalyst used in the following examples has the following main components: Al2O3, 95.52%; PtO2, 0.25%; ReO4, 0.46%; Cl, 1.61%; SO3, 0.71%; Fe2O3, 0.42%; TiO2, 0.17%; GaO3, 0.08%. -

[0046] The calculation formula of the extraction efficiency of each metal in the following examples is as follows:

[0047]

[0048] In this formula, M represents the metal (Pt, Re, Al), E represents the extraction efficiency, C0 is the initial concentration of the metal in the leaching solution, C1 is the concentration of the metal in the extraction solution, V0 is the volume of the original solution, and V represents the volume of the extraction solution.

[0049] Example 1

[0050] The platinum and rhenium are recovered and the Pt-Re / Al2O3 catalyst is prepared according to the flow chart as shown in Figure 1 The specific steps are as follows:

[0051] ​(1) The waste Pt-Re / Al2O3 reforming catalyst was calcined at 400°C for 4h, then 2.0M HCl+5% H2O2 solution was added to the calcined sample at a liquid-solid ratio of 5g:1ml, and leached at 120°C for 3h, and the leaching solution was collected. 1000ml of waste reforming catalyst leaching solution was measured, in which the concentration of Pt ion was 100ppm, the concentration of Re ion was 200ppm, and the concentration of Al ion was 900ppm. A 30% N235+5% TBP extractant was prepared, and the pH was adjusted to 1, 2, 3, 5, and 7 using 2mol / L HCl solution and 4mol / L NaOH solution, and extracted at O:A=1:1, and the extraction time was controlled at 5min to obtain an organic phase containing platinum and rhenium. At pH=2, the extraction rate of platinum and rhenium was the highest, and the specific data is shown in Table 1.

[0052] (2) A 20% ammonia solution was prepared to strip the extracted organic phase, the stripping time was 5min, O:A=1.5:1, and the platinum-rhenium mixed solution was obtained by separating funnel at pH=2, and the mass ratio of platinum to rhenium in the mixed solution was Pt:Re=1:2.

[0053] (3) 100ml of platinum-rhenium mixed solution was measured, 5g of γ-Al2O3 carrier was weighed into a beaker, and the temperature was set to 80°C on a constant temperature stirrer, and stirred for 9h. The stirred product was placed in a constant temperature drying oven for drying for 12h, and the temperature was set to 80°C, and the dried product was ground in a mortar for 30min. It was placed in a muffle furnace for calcination, the temperature was set to 400°C, the holding time was 3h, and the heating rate was 5°C / min.

[0054] (4) The calcined product was placed in a tube furnace and calcined in a H2 atmosphere, the H2 flow rate was 30sccm, the temperature was set to 400°C, the holding time was 3h, and the heating rate was 5°C / min. The calcined product was ground for 30min to obtain a Pt-Re / Al2O3 catalyst (0.2wt% Pt, 0.4wt% Re, 99.94wt% γ-Al2O3 carrier).

[0055] This example uses a 30% N235+5% TBP complex extractant to extract platinum and rhenium at different pH (1, 2, 3, 5, 7), at pH=2, O:A=1:1, and extraction time of 5min, the co-extraction rate of platinum and rhenium is as high as 99.99%, and the co-extraction is the highest. Using 20% ammonia water for stripping, O:A=1.5:1, and stripping time of 5min, the stripping rate is as high as 99.99%, the mass ratio of Pt to Re in the platinum-rhenium mixed solution is 1:2, and it is found that different extraction pH does not affect the ratio of Pt to Re in the platinum-rhenium mixed solution.

[0056] The XRD pattern of the prepared Pt-Re / Al2O3 catalyst is shown inFigure 2 ,from Figure 2 It can be seen that the Pt-Re / Al2O3 catalyst still exhibits the face-centered cubic crystal structure of platinum. With rhenium supported on porous Al2O3, the doping of rhenium did not affect the crystal structure. The main role of rhenium is to reduce or prevent the "agglomeration" of metal components, thereby improving the catalyst's carbon tolerance and stability. The platinum and rhenium contents were determined by inductively coupled plasma optical emission spectrometry (ICP-OES), and the total mass fraction ratio of platinum to rhenium was 1:2. These tests indicate that the Pt-Re / Al2O3 catalyst was successfully prepared.

[0057] Example 2

[0058] According to such Figure 1 The flowchart shown illustrates the recovery of platinum and rhenium and the preparation of a Pt-Re / Al2O3 catalyst. The specific steps are as follows:

[0059] (1) The spent Pt-Re / Al2O3 reforming catalyst was calcined at 400℃ for 4 h. Then, a 2.0 M HCl + 5% H2O2 solution was added to the calcined sample at a liquid-to-solid ratio of 5 g: 1 mL. The sample was leached at 120℃ for 3 h, and the leachate was collected. 1000 mL of the spent reforming catalyst leachate was taken, containing 100 ppm Pt ions, 200 ppm Re ions, and 900 ppm Al ions. A 30% N235 + 10% TBP extractant was prepared. The pH was adjusted using 2 mol / L HCl solution and 4 mol / L NaOH solution to achieve pH values ​​of 1, 2, 3, 5, and 7. Extraction was performed at an O:A ratio of 1:1, with an extraction time controlled at 5 min, yielding an organic phase containing platinum and rhenium. The highest extraction rate of platinum and rhenium was observed at pH = 2, as shown in Table 1.

[0060] (2) Prepare a 20% ammonia solution to back-extract the extracted organic phase for 5 min, with O:A = 1.5:1. Under pH = 2 conditions, obtain a platinum-rhenium mixture through a separatory funnel. The mass ratio of platinum to rhenium in the mixture is Pt:Re = 1:2.

[0061] (3) Measure 100 ml of platinum-rhenium mixture, weigh 5 g of γ-Al2O3 support and place it in a beaker. Set the temperature to 80 °C on a constant temperature stirrer and stir for 9 h. Place the stirred product in a constant temperature drying oven and dry for 12 h at 80 °C. Grind the dried product in a mortar for 30 min. Place it in a muffle furnace for calcination at 400 °C for 3 h at a heating rate of 5 °C / min.

[0062] (4) Put the calcined product into a tube furnace and perform calcination under H2 atmosphere, with H2 flow rate of 30 sccm, temperature setting of 400°C, holding time of 3 h, and heating rate of 5°C / min. Grind the calcined product for 30 min to obtain the Pt-Re / Al2O3 catalyst (0.2wt% of Pt, 0.4wt% of Re, 99.94wt% of γ-Al2O3 carrier).

[0063] In this embodiment, when the platinum-rhenium is extracted at different pH (1, 2, 3, 5, 7) by using 30% N235+10% TBP complexing extractant, the extraction rate of platinum is 98.99% and the extraction rate of rhenium is 97.96% at pH=2, O:A=1:1, and extraction time of 5 min, which is the highest co-extraction. The Pt:Re in the platinum-rhenium mixed solution is 1:2, and it is found that different extraction pH does not affect the ratio of Pt to Re in the platinum-rhenium mixed solution.

[0064] Example 3

[0065] According to the flowchart as shown in Figure 1 , platinum-rhenium is recovered and Pt-Re / Al2O3 catalyst is prepared, and the specific steps are as follows:

[0066] (1) The waste Pt-Re / Al2O3 reforming catalyst is calcined at 400°C for 4 h, then 2.0M HCl+5% H2O2 solution is added to the calcined sample at liquid-solid ratio of 5g:1mL, and leaching is performed at 120°C for 3 h, and the leaching solution is collected. 1000ml of waste reforming catalyst leaching solution is measured, in which the concentration of Pt ion is 100ppm, the concentration of Re ion is 200ppm, and the concentration of Al ion is 900ppm. 20% N235+10% TBP extractant is prepared, 2mol / L HCl solution and 4mol / L NaOH solution are used to adjust pH, and extraction is performed at O:A=1.5:1 when pH is 1, 2, 3, 5, and 7, and the extraction time is controlled at 5 min to obtain an organic phase containing platinum-rhenium. When pH is 3, the extraction rate of platinum-rhenium is the highest, and the specific data are shown in Table 1.

[0067] (2) 20% ammonia solution is prepared to back-extract the organic phase after extraction, the back-extraction time is 5 min, O:A=1.5:1, and the platinum-rhenium mixed solution is obtained by separating funnel at pH=3, and the mass ratio of platinum-rhenium in the mixed solution is Pt:Re=1:1.

[0068] (3) Take 100 ml of platinum-rhenium mixed solution, weigh 5 g of γ-Al2O3 carrier into a beaker, set the temperature to 80°C on the constant temperature stirrer, and stir for 9 h. Put the stirred product into a constant temperature drying box and dry for 12 h, set the temperature to 80°C, and grind the dried product in a mortar for 30 min. Place in a muffle furnace and calcine at 400°C for 3 h, with a heating rate of 5°C / min.

[0069] (4) Put the calcined product into a tube furnace and calcine under H2 atmosphere, with a H2 flow rate of 30 sccm, a temperature setting of 400°C, a holding time of 3 h, and a heating rate of 5°C / min. Grind the calcined product for 30 min to obtain a Pt-Re / Al2O3 catalyst (0.2 wt% Pt, 0.2 wt% Re, 99.96 wt% γ-Al2O3 carrier).

[0070] In this embodiment, when platinum-rhenium is extracted at different pH (1, 2, 3, 5, 7) using 20% N235 + 10% TBP complexing extractant, the extraction rate of platinum is 98.89% and the extraction rate of rhenium is 47.65% at pH = 3, O:A = 1.5:1, and extraction time of 5 min, which is the highest co-extraction rate. The Pt:Re ratio in the platinum-rhenium mixed solution is 1:1, and it is found that different extraction pH does not affect the Pt:Re ratio in the platinum-rhenium mixed solution.

[0071] Example 4

[0072] According to the flowchart shown in Figure 1 , platinum-rhenium is recovered and a Pt-Re / Al2O3 catalyst is prepared, with the specific steps as follows:

[0073] (1) The waste Pt-Re / Al2O3 reforming catalyst is calcined at 400°C for 4 h, then a 2.0M HCl + 5% H2O2 solution is added to the calcined sample at a liquid-solid ratio of 5g:1mL, and leached at 120°C for 3 h, and the leaching solution is collected. Take 1000 ml of waste reforming catalyst leaching solution, with a Pt ion concentration of 100 ppm, a Re ion concentration of 200 ppm, and an Al ion concentration of 900 ppm. Prepare a 20% N235 + 5% TBP extractant, adjust the pH with 2 mol / L HCl solution and 4 mol / L NaOH solution, and extract at O:A = 1.5:1 when the pH is 1, 2, 3, 5, and 7, with an extraction time of 10 min. The organic phase containing platinum-rhenium is obtained, and the extraction rate of platinum-rhenium is the highest at pH = 3. The specific data are shown in Table 1.

[0074] (2) The 20% ammonia solution was prepared and used to back-extract the organic phase after extraction, the back-extraction time was 5 min, O:A = 1.5:1, and the platinum-rhenium mixed solution was obtained by a separatory funnel under the condition of pH = 3, the mass ratio of platinum-rhenium in the mixed solution was 1:1.

[0075] (3) 100 ml of the platinum-rhenium mixed solution was measured, 5 g of γ-Al2O3 carrier was weighed and put into a beaker, the temperature of the constant temperature stirrer was set to 80℃, and the stirring was carried out for 12 h. The stirred product was dried in a constant temperature drying box for 12 h, the temperature was set to 80℃, and the dried product was ground in a mortar for 30 min. The calcination was carried out in a muffle furnace, the temperature was set to 400℃, the holding time was 3 h, and the heating rate was 5℃ / min.

[0076] (4) The calcined product was placed in a tube furnace and calcined under H2 atmosphere, the H2 flow rate was 30 sccm, the temperature was set to 400℃, the holding time was 3 h, and the heating rate was 5℃ / min. The calcined product was ground for 30 min to obtain the Pt-Re / Al2O3 catalyst (0.2wt% of Pt, 0.2wt% of Re, 99.96wt% of γ-Al2O3 carrier).

[0077] In this embodiment, when the platinum-rhenium was extracted by the 20% N235+5% TBP complexing extractant under different pH (1, 2, 3, 5, 7), the extraction rate of platinum was 96.76% and the extraction rate of rhenium was 48.13% under the condition of pH = 3, O:A = 1.5:1, and extraction time of 10 min, the co-extraction rate was the highest; the Pt:Re in the platinum-rhenium mixed solution was 1:1, and it was found that different extraction pH did not affect the ratio of Pt to Re in the platinum-rhenium mixed solution.

[0078] Example 5

[0079] According to the flow chart as shown in Figure 1 , platinum-rhenium was recovered and Pt-Re / Al2O3 catalyst was prepared, and the specific steps were as follows:

[0080] (1) The waste Pt-Re / Al2O3 reforming catalyst was calcined at 400℃ for 4h, then 2.0M HCl+5% H2O2 solution was added into the calcined sample at a liquid-solid ratio of 5g:1mL, and leaching was carried out at 120℃ for 3h, and the leaching solution was collected. 1000ml of the waste reforming catalyst leaching solution was measured, in which the concentration of Pt ions was 100ppm, the concentration of Re ions was 200ppm, and the concentration of Al ions was 900ppm. A 10% N235+5% TBP extractant was prepared, and the pH was adjusted using 2mol / L HCl solution and 4mol / L NaOH solution. Extraction was carried out at pH 1, 2, 3, 5, and 7, respectively, with O:A=1.5:1, and the extraction time was controlled at 5min. The organic phase containing platinum and rhenium was obtained, and the extraction rate of platinum and rhenium was the highest at pH=5. The specific data are shown in Table 1.

[0081] (2) A 20% ammonia solution was prepared to back-extract the organic phase after extraction, the back-extraction time was 5min, O:A=1.5:1, and the platinum-rhenium mixed solution was obtained by separating funnel at pH=5. The mass ratio of platinum to rhenium in the mixed solution was Pt:Re=1:0.5.

[0082] (3) 100ml of the platinum-rhenium mixed solution was measured, 5g of γ-Al2O3 carrier was weighed and put into a beaker, and the temperature was set to 80℃ on the constant temperature stirrer and stirred for 12h. The stirred product was dried in a constant temperature drying box for 12h, and the temperature was set to 80℃. The dried product was ground in a mortar for 30min. The product was calcined in a muffle furnace, the temperature was set to 400℃, the holding time was 3h, and the heating rate was 5℃ / min.

[0083] (4) The calcined product was placed in a tube furnace and calcined in a H2 atmosphere, the H2 flow rate was 30sccm, the temperature was set to 400℃, the holding time was 3h, and the heating rate was 5℃ / min. The calcined product was ground for 30min to obtain a Pt-Re / Al2O3 catalyst (0.2wt% Pt, 0.1wt% Re, 99.97wt% γ-Al2O3 carrier).

[0084] In this example, when the platinum and rhenium were extracted at different pH (1, 2, 3, 5, 7) using a 10% N235+5% TBP complex extractant, the extraction rate of platinum was 80.45% and the extraction rate of rhenium was 21.75% at pH=5, O:A=1.5:1, and the extraction time was 5min, and the co-extraction rate was the highest. The mass ratio of platinum to rhenium in the platinum-rhenium mixed solution was Pt:Re=1:0.5, and it was found that different extraction pH did not affect the ratio of Pt to Re in the platinum-rhenium mixed solution.

[0085] Example 6

[0086] According to the above Figure 1The flow chart shown recovers platinum and rhenium and prepares a Pt-Re / Al2O3 catalyst, and the specific steps are as follows:

[0087] (1) The waste Pt-Re / Al2O3 reforming catalyst is calcined at 400°C for 4h, then a 2.0M HCl+5% H2O2 solution is added to the calcined sample at a liquid-solid ratio of 5g:1ml, and leaching is carried out at 120°C for 3h, and the leaching solution is collected. 1000ml of the waste reforming catalyst leaching solution is measured, in which the concentration of Pt ions is 100ppm, the concentration of Re ions is 200ppm, and the concentration of Al ions is 900ppm. A 10% N235+10% TBP extractant is prepared, and the pH is adjusted to 1, 2, 3, 5, and 7 using 2mol / L HCl and 4mol / L NaOH solutions, and extraction is carried out at O:A=1.5:1, and the extraction time is controlled at 5min, and an organic phase containing platinum and rhenium is obtained, and the recovery rate of platinum and rhenium is the highest at pH=5, and the specific data are shown in Table 1.

[0088] (2) A 10% ammonia solution is prepared to back-extract the organic phase after extraction, the back-extraction time is 5min, O:A=1.5:1, and the platinum and rhenium mixed solution is obtained through a separatory funnel at pH=5, and the mass ratio of platinum and rhenium in the mixed solution is 1:0.5.

[0089] (3) 100ml of the platinum and rhenium mixed solution is measured, 5g of γ-Al2O3 carrier is weighed into a beaker, the temperature is set to 80°C on a constant temperature stirrer, and stirring is carried out for 12h. The stirred product is placed in a constant temperature drying box for drying for 12h, the temperature is set to 80°C, and the dried product is ground in a mortar for 30min. It is placed in a muffle furnace for calcination, the temperature is set to 400°C, the holding time is 3h, and the heating rate is 5°C / min.

[0090] (4) The calcined product is placed in a tube furnace and calcined in a H2 atmosphere, the H2 flow rate is 30sccm, the temperature is set to 400°C, the holding time is 3h, and the heating rate is 5°C / min. The calcined product is ground for 30min to obtain a Pt-Re / Al2O3 catalyst (0.2wt% Pt, 0.1wt% Re, 99.97wt% γ-Al2O3 carrier).

[0091] In this embodiment, when the 10% N235+10% TBP complex extractant is used to extract platinum and rhenium at different pH (1, 2, 3, 5, 7), the extraction rate of platinum is 78.67% and the extraction rate of rhenium is 19.15% at pH=5, O:A=1.5:1, and the extraction time is 5min, the co-extraction rate is the highest; the mass ratio of Pt:Re in the platinum and rhenium mixed solution is 1:0.5, and it is found that different extraction pH does not affect the ratio of Pt to Re in the platinum and rhenium mixed solution.

[0092] Example 7

[0093] According to the flow chart as shown in Figure 1 Pt-Re / Al2O3 catalyst was prepared by recovering platinum and rhenium, and adjusting the O:A ratio and extraction time in step (1), the calcination conditions in step (3) and the calcination conditions in step (4) compared with Example 1, and the specific steps are as follows:

[0094] (1) The spent Pt-Re / Al2O3 reforming catalyst was calcined at 400°C for 4h, then a 2.0M HC1+5% H2O2 solution was added to the calcined sample at a liquid-solid ratio of 5g:1ml, and leaching was carried out at 120°C for 3h, and the leaching solution was collected. 1000ml of the spent reforming catalyst leaching solution was measured, in which the concentration of Pt ions was 100ppm, the concentration of Re ions was 200ppm, and the concentration of Al ions was 900ppm. A complex extractant of 30% N235+5% TBP was prepared, and extraction was carried out at pH 2 with O:A=1.5:1, and the extraction time was controlled at 10min, and an organic phase containing platinum and rhenium was obtained.

[0095] (2) A 20% ammonia solution was prepared to back-extract the organic phase after extraction, the back-extraction time was 10min, O:A=1.5:1, and the platinum and rhenium mixture was obtained by separating funnel at pH=2, and the mass ratio of platinum and rhenium in the mixture was 1:2.

[0096] (3) 100ml of the platinum and rhenium mixture was measured, 5g of γ-Al2O3 carrier was weighed into a beaker, and the temperature was set to 80°C on a constant temperature stirrer, and stirring was carried out for 12h. The stirred product was placed in a constant temperature drying oven for drying for 12h, and the temperature was set to 60°C, and the dried product was ground in a mortar for 30min. It was placed in a muffle furnace and calcined at a temperature of 500°C for 4h, and the heating rate was 5°C / min.

[0097] (4) The calcined product was placed in a tube furnace and calcined in a H2 atmosphere, the H2 flow rate was 30sccm, the temperature was set to 500°C, the holding time was 4h, and the heating rate was 5°C / min. The calcined product was ground in a mortar for 30min to obtain a Pt-Re / Al2O3 catalyst (0.2wt% Pt, 0.4wt% Re, 99.94wt% γ-Al2O3 carrier).

[0098] Example 8

[0099] According to the flow chart as shown in Figure 1 Pt-Re / Al2O3 catalyst was prepared by recovering platinum and rhenium, and adjusting the O:A ratio and extraction time in step (1), the calcination conditions in step (3) and the calcination conditions in step (4) compared with Example 1, and the specific steps are as follows:

[0100] (1) Waste Pt-Re / Al203reforming catalyst was calcined at 400 °C for 4 h, then 2.0 M HC1 + 5% H202solution was added into the calcined sample with liquid-solid ratio of 5 g: 1 mL, leaching at 120 °C for 3 h, and the leaching solution was collected. 1000 ml of waste reforming catalyst leaching solution was measured, in which the concentration of Pt ion was 100 ppm, the concentration of Re ion was 200 ppm, and the concentration of Al ion was 900 ppm. 30% N235 + 5% TBP complex extractant was prepared, and extraction was carried out at pH 2 with O:A = 1.5:1, the extraction time was controlled at 15 min, and the organic phase containing platinum and rhenium was obtained.

[0101] (2) 20% ammonia solution was prepared to strip the organic phase after extraction, the stripping time was 15 min, O:A = 1.5:1, and the platinum-rhenium mixed solution was obtained by separating funnel at pH = 2, and the mass ratio of platinum-rhenium in the mixed solution was Pt:Re = 1:2.

[0102] (3) 100 ml of platinum-rhenium mixed solution was measured, 5 g of γ-Al203carrier was weighed and put into a beaker, the temperature of constant temperature stirrer was set to 80 °C, and stirring was carried out for 12 h. The stirred product was placed in a constant temperature drying box for drying for 12 h, and the temperature was set to 60 °C. The dried product was ground in a mortar for 30 min. It was placed in a muffle furnace and calcined at 600 °C for 5 h, with a heating rate of 5 °C / min.

[0103] (4) The calcined product was placed in a tube furnace and calcined in H2atmosphere, with H2flow rate of 30 sccm, temperature set to 600 °C, and holding time of 5 h, with a heating rate of 5 °C / min. The calcined product was ground in a mortar for 30 min to obtain Pt-Re / Al203catalyst (0.2wt% Pt, 0.4wt% Re, 99.94wt% γ-Al203carrier).

[0104] Comparative Example 1

[0105] The extractant in Example 1 was replaced by only using N235, and the specific steps were as follows:

[0106] (1) The waste Pt-Re / Al2O3 reforming catalyst was calcined at 400℃ for 4h, then 2.0M HCl + 5% H2O2 solution was added to the calcined sample at a liquid-solid ratio of 5g:1ml, and leached at 120℃ for 3h, and the leaching solution was collected. 1000ml of waste reforming catalyst leaching solution was measured, in which the concentration of Pt ion was 100ppm, the concentration of Re ion was 200ppm, and the concentration of Al ion was 900ppm. 30% N235 extractant was prepared, and the pH was adjusted by using 2mol / L HCl solution and 4mol / L NaOH solution, and the extraction was carried out at pH 1, 2, 3, 5 and 7 with O:A=1:1, and the extraction time was controlled at 5min, and the organic phase containing platinum and rhenium was obtained. At pH=5, the extraction rate of platinum and rhenium is the highest, and the specific data is shown in Table 1.

[0107] (2) The organic phase after extraction was stripped with 20% ammonia solution, the stripping time was 5min, O:A=1.5:1, and the platinum and rhenium mixed solution was obtained by separating funnel at pH=5, and the mass ratio of platinum and rhenium in the mixed solution was Pt:Re=1:1.

[0108] (3) 100ml of platinum and rhenium mixed solution was measured, and 5g of γ-Al2O3 carrier (0.2wt% of Pt, 0.2wt% of Re, 99.96wt% of γ-Al2O3 carrier) was weighed. Put it into a beaker, set the temperature to 80℃ on the constant temperature stirrer, and stir for 9h. Put the stirred product into a constant temperature drying box for drying for 12h, and set the temperature to 80℃, and grind the dried product in a mortar for 30min. Put it in a muffle furnace for calcination, set the temperature to 400℃, and keep the temperature for 3h, and the heating rate is 5℃ / min.

[0109] (4) The calcined product was placed in a tube furnace and calcined in H2 atmosphere, the H2 flow rate was 30sccm, the temperature was set to 400℃, the holding time was 3h, and the heating rate was 5℃ / min. The calcined product was ground for 30min to obtain Pt-Re / Al2O3 catalyst.

[0110] Comparative Example 2

[0111] The extractant in Example 1 was replaced with TBP only, and the specific steps were as follows:

[0112] (1) The waste Pt-Re / Al2O3 reforming catalyst was calcined at 400°C for 4h, then 2.0M HCl+5% H2O2 solution was added to the calcined sample at a liquid-solid ratio of 5g:1ml, and leaching was carried out at 120°C for 3h, and the leaching solution was collected. 1000ml of the waste reforming catalyst leaching solution was measured, in which the concentration of Pt ions was 100ppm, the concentration of Re ions was 200ppm, and the concentration of Al ions was 900ppm. A 5% TBP extractant was prepared, and the pH was adjusted using 2mol / L HCl solution and 4mol / L NaOH solution. Extraction was carried out at pH 1, 2, 3, 5, and 7 with O:A=1:1, and the extraction time was controlled at 5min to obtain an organic phase containing platinum and rhenium. At pH=3, the extraction rate of platinum and rhenium was the highest, and the specific data are shown in Table 1.

[0113] (2) A 20% ammonia solution was prepared to strip the extracted organic phase, the stripping time was 5min, O:A=1.5:1, and the platinum and rhenium mixed solution was obtained at pH=3 through a separatory funnel. The mass ratio of platinum to rhenium in the mixed solution was Pt:Re=1:1.

[0114] (3) 100ml of the platinum and rhenium mixed solution was measured, and 5g of γ-Al2O3 carrier (0.2wt% Pt, 0.2wt% Re, 99.96wt% γ-Al2O3 carrier) was weighed. It was placed in a beaker, and the temperature was set to 80°C on a constant temperature stirrer for 9h. The stirred product was placed in a constant temperature drying box for drying for 12h, and the temperature was set to 80°C. The dried product was ground in a mortar for 30min. It was placed in a muffle furnace for calcination, the temperature was set to 400°C, the holding time was 3h, and the heating rate was 5°C / min.

[0115] (4) The calcined product was placed in a tube furnace and calcined in a H2 atmosphere, the H2 flow rate was 30sccm, the temperature was set to 400°C, the holding time was 3h, and the heating rate was 5°C / min. The calcined product was ground for 30min to obtain a Pt-Re / Al2O3 catalyst.

[0116] Test Example

[0117] The dry reforming of methane thermal catalytic performance of the Pt-Re / Al2O3 catalyst prepared in the above examples and comparative examples was tested, and the test conditions were as follows: 200.0mg of the catalyst was weighed and placed in a quartz tube, and then placed in a fixed field reactor for thermal catalytic performance test. H2 was passed for reduction and vacuum treatment before the test, then CH4 and CO2 were passed into the quartz tube at a gas concentration ratio of CH4:CO2:N2=1:1:8, the flow rate of CH4 and CO2 was 2ml / min, and the flow rate of N2 was 16ml / min. The thermal catalytic performance of the catalyst was tested at temperatures of 400°C, 500°C, 600°C, 700°C, 800°C, and 850°C, respectively.

[0118] The CH4 conversion rate at a test temperature of 800℃ is shown in Table 1-2.

[0119] Table 1 Extraction rate and thermal catalytic performance of different extraction systems

[0120] Complexing extractant Pt extraction efficiency (%) Re extraction efficiency (%) Pt:Re CH4conversion rate (%) Example 1 30% N235 + 5% TBP 99.99 99.99 1:2 99.96 Example 2 30% N235 + 10% TBP 98.99 97.96 1:2 96.17 Example 3 20% N235 + 10% TBP 98.89 47.65 1:1 90.12 Example 4 20% N235 + 5% TBP 96.76 48.13 1:1 91.07 Example 5 10% N235 + 5% TBP 80.45 21.75 1:0.5 87.41 Example 6 10% N235 + 10% TBP 78.67 19.15 1:0.5 88.65 Comparative Example 1 30％N235 40.12 41.43 1:1 89.71 Comparative Example 2 5% TBP 38.13 32.04 1:1 89.15

[0121] Table 2 Thermal catalytic performance of different catalysts

[0122] Complexing extractant Pt:Re Calcination temperature (°C) Calcination time (h) CH4conversion rate (%) Example 1 30% N235 + 5% TBP 1:2 400 3 99.96 Example 7 30% N235 + 5% TBP 1:2 500 4 98.97 Example 8 30% N235 + 5% TBP 1:2 600 5 98.65

[0123] Table 1 shows that using 30% N235 + 5% TBP exhibits stronger platinum-rhenium co-extraction capability compared to using N235 or TBP alone, and this composite extractant shows the best extraction effect among the N235 and TBP concentration ratios. Furthermore, the synthesized catalyst achieves the highest methane conversion rate and best thermal catalytic performance when the platinum-rhenium mass ratio is controlled at 1:2. Table 2 shows that the calcination temperature and time have little impact on catalyst performance. Preferably, maintaining the calcination temperature at 400℃ and the calcination time at 3 hours results in a catalyst with good performance and low carbon footprint.

[0124] The thermal catalytic performance of the Pt-Re / Al2O3 catalyst for methane dry reforming in Example 1 is shown in the figure below. Figure 3 and Figure 4 As shown. From Figure 3 It can be seen that the conversion rates of CH4 and CO2 increase with increasing temperature. At 800℃, the conversion rate of CH4 reaches a maximum of 99.99%, and remains stable with further increases in temperature. The conversion rate of CO2 also continuously increases, reaching 98.96% at 800℃, and then stabilizes without changing with further temperature increases. Figure 4 As shown, the yields of CO and H2 also increase with increasing temperature, and the H2 / CO ratio approaches 1.

[0125] Therefore, the Pt-Re / Al2O3 catalyst synthesized by the present invention has good and stable thermal catalytic performance, and strong CH4 and CO2 conversion and carbon fixation performance.

[0126] The application has been described in detail. For those skilled in the art, the application can be implemented in a wider range with equivalent parameters, concentrations and conditions without departing from the spirit and scope of the application. Although the application gives specific examples, it should be understood that further improvements can be made to the application. In general, according to the principle of the application, the application is intended to include any changes, uses or improvements of the application, including changes made by using conventional techniques known in the art, which are outside the scope disclosed in the application.

Claims

1. A method for preparing a methane dry reforming catalyst by recycling spent reforming catalysts, comprising the following steps: (1) calcining a spent Pt-Re / Al 2 O 3 reforming catalyst, and then immersing the calcined catalyst in a solution composed of an acid, hydrogen peroxide and water to obtain a spent reforming catalyst leaching solution containing Pt ions, Re ions and Al ions; (2) co-extracting Pt and Re in the spent reforming catalyst leaching solution with an N235+TBP complexing extractant to obtain an organic phase containing Pt and Re; the N235+TBP complexing extractant is composed of N235, TBP and a diluent; the diluent is petroleum ether; the concentration of the N235 extractant in the N235+TBP complexing extractant is 10%-30% by mass fraction, the concentration of the TBP is 5%-20% by mass fraction, and the concentration of the diluent is 50%-85% by mass fraction; in the co-extraction step, the phase ratio A / O is 1:(1-1.5), and the co-extraction time is 5-20 min; the pH of the co-extraction system is adjusted to 1-7; (3) stripping the organic phase containing Pt and Re with NH 3 ·H 2 O to obtain a Pt-Re mixed solution; (4) adding a γ-Al 2 O 3 carrier to the Pt-Re mixed solution, stirring and immersing to obtain an impregnated product, and then sequentially performing drying, grinding and calcination on the impregnated product; (5) calcining the product obtained in the calcination step in a H 2 atmosphere to obtain the methane dry reforming catalyst Pt-Re / Al 2 O 3. In the calcination step in step (1), the temperature is 400℃, and the time is 4h; in the solution composed of an acid, hydrogen peroxide and water, the concentration of the acid is 2.0 M, and the mass concentration of H 2 O 2 is 5%; in the immersion step, the liquid-solid ratio is 5g:1mL, the immersion temperature is 120℃, and the immersion time is 3h. The concentration of NH 3 ·H 2 O is 10%-20% by mass fraction; in the stripping step, the phase ratio A / O is 1:(1-1.5), and the stripping time is 5-20 min; the method further comprises, after stripping, adjusting the pH of the system to the pH of the co-extraction step, and then separating the aqueous phase and the organic phase. In the Pt-Re mixed solution, the mass fraction ratio of Pt to Re is 1:(0.5-2); in the methane dry reforming catalyst, the mass fraction of the γ-Al 2 O 3 carrier is 80%-99.97%; in the methane dry reforming catalyst, the mass fraction of the γ-Al 2 O 3 carrier is 99.94%-99.97%; in the impregnation step, the solid-liquid ratio is 1:20, the temperature is 80℃, and the stirring time is 9h-12h; in the drying step, the drying temperature is 50℃-80℃, and the drying time is 12h; in the calcination step, the calcination time is 3-5h, and the calcination temperature is 400℃-600℃. In the calcination step, the H 2 flow rate is 30sccm; in the calcination step, the calcination temperature is 400℃-600℃, and the calcination time is 3-5h. ​ ​ ​ ​ ​ ​ The method further comprises, before the co-extraction: ​ ​ ​ ​ 2. The method for recovering and reusing the spent reforming catalyst to prepare a methane dry reforming catalyst according to claim 1, characterized in that: ​ ​ ​ 3. The process for the recovery and reuse of spent reforming catalysts to prepare a dry methane reforming catalyst according to any one of claims 1-2, characterized in that: ​ ​ ​ 4. The process for the recovery and reuse of spent reforming catalysts to prepare a dry methane reforming catalyst according to any one of claims 1-2, characterized in that: ​ ​ 5. The method of claim 4, wherein the waste reforming catalyst is recovered and reused to prepare a methane dry reforming catalyst. ​ 6. The process for the recovery and reuse of spent reforming catalysts to prepare a dry methane reforming catalyst according to any one of claims 1-2, characterized in that: ​ ​ ​ 7. The process for the recovery and reuse of spent reforming catalysts to prepare a dry methane reforming catalyst according to any one of claims 1-2, characterized in that: ​ ​ 8. The methane dry reforming catalyst Pt-Re / Al203 prepared by the method of any one of claims 1-7.

9. A methane dry reforming method, comprising the following steps: reacting a mixed gas containing methane and carbon dioxide with a methane dry reforming catalyst Pt-Re / Al203 in a fixed bed reactor, wherein the methane dry reforming catalyst Pt-Re / Al203 is the catalyst of claim 8.

10. The dry methane reforming method according to claim 9, characterized in that: In the mixed gas, the volume ratio of methane to carbon dioxide is 1: (1-2) ; The flow rate of methane and carbon dioxide corresponding to 0.2 g of the catalyst is (2-4) ml / min; The reaction temperature is 400-850 ℃; The mixed gas is balanced with nitrogen or argon, and the volume fraction of methane and carbon dioxide in the mixed gas is 10%-20%.

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