A sulfur-tolerant methane dry reforming catalyst, a preparation method and use thereof

Abstract

The application provides a sulfur-resistant methane dry reforming catalyst, a preparation method and application thereof, the catalyst has a structural formula of Ni@Ni3P / NiAl-LDO, an active center of the catalyst is a Ni@Ni3P composite nanoparticle uniformly dispersed on a NiAl-LDO carrier, and the particle size of the catalyst is 5-30 nm. The special core-shell structure in the catalyst is realized by using specific raw materials, specific proportions and a specific preparation method, the structure unexpectedly resists the poisoning of SO2 on Ni particles, thereby the stability of the catalyst can be improved, the efficiency of converting CH4 and CO2 into synthesis gas in the presence of SO2 can be greatly improved, in addition, the NiAl-LDO has a strong metal-carrier interaction, the sintering of Ni in the reaction process can be inhibited, the catalyst is more suitable for a DRM reaction requiring high temperature, and the catalyst has great industrialization prospects; the initial conversion rate of CH4 is less than or equal to 94, and the initial conversion rate of CO2 is less than or equal to 94 within 12 hours of reaction time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of anti-sulfur catalysts, in particular to an anti-sulfur methane dry reforming catalyst, a preparation method and an application thereof, more particularly to an anti-sulfur nickel-based methane dry reforming catalyst with a core-shell structure, a preparation method and an application thereof. BACKGROUND

[0002] Carbon dioxide (CO2) is the largest greenhouse gas in the world, which stays in the atmosphere for a long time and contributes greatly to the global temperature rise. Methane (CH4) is the second largest greenhouse gas in the world, which is more active than carbon dioxide in the atmosphere. The methane in the global atmosphere belongs to trace gas, and a slight increase in its emission will lead to a significant increase in the content of methane in the atmosphere. The greenhouse effect of methane is significant, and its driving effect on global warming in the short term cannot be underestimated. Excessive emission of CO2 and CH4 is the most important reason for global warming, which has triggered a series of ecological problems, such as melting of glaciers and rising of sea level threatening coastal areas; frequent extreme climate events, floods, droughts, heat waves and other disasters have brought great challenges to human life.

[0003] Methane and carbon dioxide dry reforming (DRM) technology can convert these two greenhouse gases into valuable synthesis gas industrial raw materials with an equal molar H2 / CO ratio, and then prepare high-value chemicals and liquid fuels through Fischer-Tropsch synthesis process. DRM technology can turn waste into treasure, reduce greenhouse gas emissions while achieving effective use of resources, and has important significance for alleviating global warming. Catalyst is the core of methane dry reforming technology, and noble metal has high activity and stability, but its high price limits its wide application. Non-noble metal nickel has strong ability to break C-H and C-O bonds, and has industrial application prospect in DRM technology.

[0004] However, the nickel-based catalyst inevitably has problems of sintering and carbon deposition during use. At present, the research on DRM catalysts mainly focuses on solving the problem of activity decline caused by nickel particle sintering and carbon deposition. However, the actual conditions of DRM inevitably involve the presence of sulfur compounds, and the negative effects of sulfides are less studied. Sulfur species are easily combined with the metal active sites of the catalyst to form stable metal-sulfur bonds (Me-S), leading to catalyst poisoning. Current DRM mainly focuses on solving the deactivation problem of Ni catalyst caused by Ni particle sintering and carbon deposition, and less attention is paid to the negative effects of sulfur poisoning. Obviously, in metal catalysts, active Ni sites are highly sensitive to sulfur species, and even exposure to ppm-level sulfur can cause partial or complete deactivation of Ni-based catalysts. Currently, the DRM technology usually requires a desulfurization process, which makes the operation process complex and increases additional costs. Therefore, it is an urgent technical problem to provide a DRM catalyst with high activity, high selectivity, and resistance to sulfur poisoning.

[0005] CN118904347A discloses a carbon deposition resistant nickel-based catalyst for methane carbon dioxide dry reforming, a preparation method and applications thereof. The catalyst is prepared by combining an innovative formula with a process, using a metal organic framework material derived nanotube as a precursor, impregnating nickel salt and zirconium salt, and has excellent carbon deposition resistance in DRM reaction, while the catalytic activity is highly maintained, the CO2 conversion rate is stabilized at about 90%, and the CH4 conversion rate is maintained at more than 93%, effectively overcoming the problems of carbon deposition and deactivation of traditional nickel-based catalysts in the reaction. The preparation process is simple and mild, and has good industrial application potential. However, further research and improvement are still needed in reducing carbon deposition, expanding the adaptability of reaction conditions, and comprehensively evaluating long-term stability.

[0006] Hu et al. loaded BaTiO3 on the surface of γ -Al2O3 using a sol-gel method, synthesized composite carriers BaTiO3 / γ -Al2O3 with different mass percentages of BaTiO3, and studied the structure of the composite carrier BaTiO3 / γ -Al2O3 using XRD and IR techniques, investigated the carbon deposition resistance and stability of the nickel-based catalyst Ni / BaTiO3 / γ -Al2O3 in the CH4-CO2 reforming reaction; the results showed that the BaTiO3 particles were dispersed in a discontinuous manner on the surface of γ -Al2O3, resulting in Ni / BaTiO3 / γThe electron-donating strength of the Al2O3 catalyst is relatively weakened, which inhibits the disproportionation reaction of CO in the CH4-CO2 reforming process, and the Ni / 25.4%BaTiO3 / γ The carbon deposition resistance and stability of the Al2O3 catalyst at a low reforming reaction temperature of 700 DEG C are obviously superior to those of the Ni / BaTiO3 and Ni / γ However, the applicability under different temperature conditions is still unclear, the catalyst stability needs to be further improved, and the catalyst application range needs to be further widened. SUMMARY

[0007] To solve the above problems, the application provides a sulfur-resistant methane dry reforming catalyst with a hydrotalcite precursor: a nickel aluminum hydrotalcite (NiAl-LDH) precursor is calcined under an inert gas atmosphere to obtain a layered double metal oxide (NiAl-LDO) matrix, the NiAl-LDO is mixed with sodium hypophosphite, and is calcined under an inert gas atmosphere to obtain the catalyst. Due to phosphorization, a layer of Ni3P shell is formed on the surface of the Ni particles, and the active ingredient has a core-shell structure of Ni@Ni3P, which can resist the poisoning of SO2 to the Ni particles, thereby realizing the efficient and stable conversion of CH4 and CO2 into synthesis gas in the presence of SO2. In addition, the NiAl-LDO has a strong metal-support interaction, which can inhibit the sintering of Ni during the reaction. The specific technical scheme is as follows:

[0008] A sulfur-resistant methane dry reforming catalyst, which is composed of a nickel aluminum double metal oxide matrix loaded with a core-shell structure active center Ni@Ni3P, and has a structure formula of Ni@Ni3P / NiAl-LDO. In the catalyst, the molar ratio of P, Al and Ni is (0.2-0.8):(0.4-0.6):1. In the XRD spectrum of the catalyst, the characteristic diffraction peaks of (031), (231), (330), (112), (240), (202), (141), (222), (132), (611), (233) of Ni3P appear at 2θ angles of 36.4 o , 41.8 o , 42.8 o , 43.6 o , 45.2 o , 46.0 o , 46.6 o , 50.6 o , 52.7 o , 66.9 o , 75.3 o

[0009] ​Further, from the HRTEM characterization, it can be seen that there is a specific Ni@Ni3P core-shell structure in the catalyst.

[0010] Further, in the TEM characterization, the ratio of P, Ni in the catalyst is (0.2-0.8):1, and it can be observed that the active center of the catalyst is the Ni@Ni3P composite nanoparticles uniformly dispersed on the NiAl-LDO carrier, and the particle size of the catalyst is 5-30 nm.

[0011] Further, the ICP test shows that, based on the total weight of the catalyst, the Ni content in the active center Ni@Ni3P is 40-60wt% in terms of metal elements.

[0012] Further, the BET test shows that the specific surface area of the catalyst is 60.9-75.5m 2 / g.

[0013] Further, the SEM characterization can show that the catalyst always maintains the morphology of the specific hexagonal nanosheet of hydrotalcite.

[0014] A preparation method of a sulfur-resistant methane dry reforming catalyst, the method comprising the following steps:

[0015] Step 1, preparing NiAl-LDH

[0016] Take Ni(NO3)2·6H2O and Al(NO3)3·9H2O and place them in a beaker, add deionized water and stir until uniform to obtain a metal salt solution, wherein the molar ratio of Ni 2+ / Al 3+ is (1-4):1; take urea and NH4F and place them in a beaker, add deionized water and stir until uniform to obtain a mixed alkali solution, wherein the molar ratio of urea and NH4F is (2.5-10):1, pour the metal salt solution and the mixed alkali solution into an autoclave, and statically crystallize at 60-120℃ for 4-24h to obtain a precipitate, filter, wash, and then place it in an oven for drying, set the temperature to 60-80℃, and the time to 12-24h to obtain NiAl-LDH;

[0017] Step 2, preparing NiAl-LDO

[0018] Take the NiAl-LDH obtained in step 1, calcine it under an inert gas atmosphere, the initial temperature is room temperature, the temperature is raised to 800-1000℃ at a rate of 2-10℃ / min, the calcination time is 2-5h, and the inert gas flow rate is 10-40mL / min to obtain NiAl-LDO;

[0019] Step 3, preparing a sulfur-resistant methane dry reforming catalyst

[0020] Mixing the NiAl-LDO obtained in step 2 with sodium hypophosphite, wherein the molar ratio of P:Ni is (0.1-1):1, and calcining under an inert gas atmosphere, with an initial temperature of room temperature, and a temperature rising rate of 2-10℃ / min to 800-1000℃, and a calcining time of 2-5h, and an inert gas flow rate of 10-40mL / min, to obtain the sulfur-resistant methane dry reforming catalyst, denoted as Ni@Ni3P / NiAl-LDO.

[0021] Further, in step 1, the XRD spectrum of the NiAl-LDH is observed to have characteristic diffraction peaks of (003), (006), (012), (015), (018), (1010), (0111), (110), (113), (1013) and (116) of nickel-aluminum hydrotalcite at 2θ angles of 11.3 o , 22.8 o , 34.7 o , 39.1 o , 46.4 o , 52.2 o , 55.5 o , 60.6 o , 61.9 o , 62.5 and 65.7 o , respectively, and no other diffraction peaks are observed in addition to the characteristic peaks of hydrotalcite.

[0022] Further, in step 2, the inert gas is any one of N2, Ar and He.

[0023] A method for using the aforementioned sulfur-resistant methane dry reforming catalyst for a methane dry reforming reaction, taking the catalyst, granulating to 40-60 mesh, and loading into a reactor, with a reaction temperature of 600-800℃, first purging with H2 for 0.5-2h, with a flow rate of H2 of 30-50mL / min / g, and then passing a raw gas containing SO2 into the reactor, wherein the raw gas is a mixed gas of CH4 and CO2, setting the reaction pressure to 0.1-2MPa, setting the space velocity to 3000-12000mL·g −1 ·h −1 , and a reaction time of 12-100h, and the product is CO and H2, wherein the initial conversion rate of CH4 is ≤94, and the initial conversion rate of CO2 is ≤94.

[0024] Further, in the mixed gas, the volume ratio of SO2, CH4 and CO2 is (1-10):(100-5000):(100-5000) based on the total volume of the mixed gas.

[0025] Further, the reactor is a fixed bed reactor with a length of 200-350 mm and an inner diameter of 5-10 mm.

[0026] The beneficial effects of the present application are as follows:

[0027] 1. In the catalyst of the present application, by ingeniously introducing sodium hypophosphite, phosphorization occurs on the surface of Ni particles to form a layer of Ni3P shell, forming a package for Ni metal atoms, so that the active ingredient of the catalyst of the present application has a core-shell structure of Ni@Ni3P, which unexpectedly resists the poisoning of SO2 to Ni particles, thereby improving the stability of the catalyst, greatly improving the efficiency of converting CH4 and CO2 into synthesis gas in the presence of SO2, and the NiAl-LDO has a strong metal-support interaction, which can inhibit the sintering of Ni during the reaction, and is more suitable for DRM reaction which requires high temperature, so that the catalyst of the present application has great industrialization prospect;

[0028] 2. The catalyst preparation method of the present application is relatively simple, and the raw material cost is low. The NiAl-LDH precursor is prepared by hydrothermal method using common metal salt and alkali solution, and then the target catalyst is obtained through the steps of calcination and mixing with sodium hypophosphite and calcination again. The whole process does not need complex equipment and harsh reaction conditions, and is easy to mass industrial production, which is beneficial to reduce the production cost.

[0029] 3. The catalyst of the present application shows good stability under the condition of raw material gas containing SO2. In the methane dry reforming reaction, even if exposed to a sulfur-containing environment for a long time (12-100 h), the activity of the catalyst can still be maintained, and the conversion rate of CH4 and CO2 does not decrease obviously during the reaction, which provides an effective solution for treating sulfur-containing greenhouse gases in actual industrial production, avoiding the problems of cost increase and production interruption caused by frequent replacement of catalyst due to catalyst deactivation. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 XRD pattern of the sample of the present application

[0031] Figure 1 (a) in the figure is the test result of XRD of NiAl-LDH prepared by urea method, and the 2θ angle is 11.3 o , 22.8 o , 34.7 o , 39.1 o , 46.4 o , 52.2 o , 55.5 o , 60.6 o , 61.9 o, 62.5 and 65.7 o The characteristic diffraction peaks of (003), (006), (012), (015), (018), (1010), (0111), (110), (113), (1013) and (116) of hydrotalcite were observed obviously, and no other diffraction peaks appeared except the characteristic peaks of hydrotalcite, indicating that the hydrotalcite sample with complete crystal form and no impurities was prepared;

[0032] Figure 1 (b) in the above are respectively the products after calcination using different proportions of sodium hypophosphite, red phosphorus and no phosphorus source, and are respectively recorded as: Ni@Ni3P / NiAl-LDO, Ni2P / NiAl-LDO and NiAl-LDO; the uppermost curve is the XRD pattern of NiAl-LDO, and only the characteristic peak of NiAl-LDO at a 2θ angle of 44.5 o , 51.8 o , 76.4 o The characteristic peaks of Ni (111), (200) and (220) were observed at 44.5 o , 44.6 o , 47.3 o , 54.2 o , 54.9 o , 66.2 o , 72.7 o , 76.7 o The characteristic peaks of Ni2P (111), (201), (210), (300), (211), (310), (311) and (400) were observed at 36.4 o , 41.8 o , 42.8 o , 43.6 o , 45.2 o , 46.0 o , 46.6 o , 50.6 o , 52.7 o , 66.9 o , 75.3 o , 44.5 o , 51.8 o , 76.4 oThe characteristic peaks of Ni@Ni3P (031), (231), (330), (112), (240), (202), (141), (222), (132), (611), (233) and the characteristic peaks of Ni (111), (200), (220) are observed, and thus the specific core-shell structure in the catalyst can be realized under specific raw materials, specific ratio and specific preparation method.

[0033] Figure 2 SEM images of samples of the present application

[0034] Figure 2 (a) in the figure is the product Ni@Ni3P / NiAl-LDO calcined by using sodium hypophosphite as the phosphorus source, Figure 2 (b) in the figure is the product Ni2P / NiAl-LDO calcined by using red phosphorus as the phosphorus source, Figure 2 (c) in the figure is the product NiAl-LDO calcined without adding the phosphorus source, and it can be seen that all the catalyst samples maintain the morphology of the hexagonal nanosheet of hydrotalcite.

[0035] Figure 3 TEM images of samples of the present application

[0036] Figure 3 (a) in the figure is the product Ni@Ni3P / NiAl-LDO calcined by using sodium hypophosphite as the phosphorus source, and it can be seen that the size of the metal particles is 5.4-28.1 nm; Figure 3 (b) in the figure is the product Ni2P / NiAl-LDO calcined by using red phosphorus as the phosphorus source, and it can be seen that the size of the metal particles is 5.1-25.2 nm; Figure 3 (c) in the figure is the product NiAl-LDO calcined without adding the phosphorus source, and it can be seen that the size of the metal particles is 5.2-36.5 nm.

[0037] Figure 4 HRTEM images of samples of the present application

[0038] Figure 4 (a) in the figure is the product Ni@Ni3P / NiAl-LDO calcined by using sodium hypophosphite as the phosphorus source, and it can be seen that the metal particles have obvious core-shell structure, in which the core is Ni and the shell is Ni3P; Figure 4 (b) in the figure is the product Ni2P / NiAl-LDO calcined by using red phosphorus as the phosphorus source, and only single metal particles on the carrier can be seen, and the metal particles are Ni2P; Figure 4 (c) in the figure is the product NiAl-LDO calcined without adding the phosphorus source, and only single metal particles on the carrier can be seen, and the metal particles are Ni.

[0039] Figure 5 CH4and CO2conversion rate graph

[0040] Figure 5 The curves P:Ni=0.26:1, P:Ni=0.5:1, and P:Ni=0.8:1 in FIG. 1 are products with core-shell structures Ni@Ni3P / NiAl-LDO obtained by calcination using sodium hypophosphite as a phosphorus source, and the conversion rates of CH4and CO2are high, and there is no obvious decline in performance within 12h of reaction time; Figure 5 The curve P:Ni=1:1 in FIG. 1 is a supported catalyst Ni2P / NiAl-LDO obtained by calcination using red phosphorus as a phosphorus source, and the conversion rate is lower than that of Ni@Ni3P / NiAl-LDO, and within 12h of reaction time, the conversion rates of CH4and CO2decrease, and the sample is partially deactivated; Figure 5 The curve P:Ni=0:1 in FIG. 1 is a supported catalyst NiAl-LDO obtained by calcination without adding a phosphorus source, and the conversion rates of CH4and CO2are significantly lower than those of Ni@Ni3P / NiAl-LDO, and within 12h of reaction time, the conversion rates decrease significantly, and the sample is severely deactivated. DETAILED DESCRIPTION

[0041] The technical solutions of the present application will be described in detail below in combination with specific embodiments of the present application, and the described embodiments are only a part of the present application, and the present application is not limited to the following described embodiments.

[0042] Example 1

[0043] A sulfur-resistant methane dry reforming catalyst, the molar ratio of P, Al and Ni in the catalyst is 0.26:0.5:1;

[0044] Step 1, preparation of NiAl-LDH

[0045] Weigh 3.8g of Ni(NO3)2 6H2O and 1.6g of Al(NO3)3 9H2O and dissolve them in 350mL of deionized water, stir uniformly to obtain a metal salt solution; weigh 5.1g of urea and 0.9g of NH4F and dissolve them in 350mL of deionized water, stir uniformly to obtain a mixed alkali solution; pour the metal salt solution and the mixed alkali solution into the hydrothermal kettle at the same time, control the crystallization temperature to be 90℃, and the crystallization time to be 4h, the precipitate is filtered, washed and dried in a 60℃ oven for 12h to obtain NiAl-LDH;

[0046] Step 2, preparation of NiAl-LDO

[0047] Take 1 g of NiAl-LDH obtained in step 1, and calcine under H2 atmosphere for 5 h, set the temperature to 500℃, the initial temperature to room temperature, the temperature rising rate to 2℃ / min, and the gas flow rate to 30 mL / min, to obtain NiAl-LDO;

[0048] Step 3, preparation of a sulfur-tolerant methane dry reforming catalyst

[0049] Take 1 g of NiAl-LDO obtained in step 2 and 0.28 g of sodium hypophosphite, mix them uniformly, and calcine under H2 atmosphere for 5 h, set the temperature to 1000℃, the initial temperature to room temperature, the temperature rising rate to 10℃ / min, and the gas flow rate to 30 mL / min, to obtain the sulfur-tolerant methane dry reforming catalyst 1, denoted as Ni@Ni3P / NiAl-LDO;

[0050] Example 2

[0051] A sulfur-tolerant methane dry reforming catalyst, the molar ratio of P, Al and Ni in the catalyst being 0.5:0.5:1;

[0052] Step 1, preparation of NiAl-LDH

[0053] Take 4.0 g of Ni(NO3)2 6H2O and 1.8 g of Al(NO3)3 9H2O, dissolve them in 350 mL of deionized water, and stir to obtain a metal salt solution; take 5.1 g of urea and 0.9 g of NH4F, dissolve them in 350 mL of deionized water, and stir to obtain a mixed alkali solution; pour the metal salt solution and the mixed alkali solution into a hydrothermal kettle at the same time, control the crystallization temperature to be 90℃, and the crystallization time to be 4 h; after the precipitate is filtered, washed, and dried in an oven at 60℃ for 12 h, NiAl-LDH is obtained;

[0054] Step 2, preparation of NiAl-LDO

[0055] Take 1 g of NiAl-LDH obtained in step 1, and calcine under H2 atmosphere for 5 h, set the temperature to 500℃, the initial temperature to room temperature, the temperature rising rate to 2℃ / min, and the gas flow rate to 30 mL / min, to obtain NiAl-LDO;

[0056] Step 3, preparation of a sulfur-tolerant methane dry reforming catalyst

[0057] Take 1 g of NiAl-LDO obtained in step 2 and 0.53 g of sodium hypophosphite, mix them uniformly, and calcine under H2 atmosphere for 5 h, set the temperature to 1000℃, the initial temperature to room temperature, the temperature rising rate to 10℃ / min, and the gas flow rate to 30 mL / min, to obtain the sulfur-tolerant methane dry reforming catalyst 2, denoted as Ni@Ni3P / NiAl-LDO;

[0058] Example 3

[0059] A sulfur-tolerant methane dry reforming catalyst, the molar ratio of P, Al and Ni in the catalyst is 0.8:0.5:1.

[0060] Step 1, preparation of NiAl-LDH

[0061] Weigh 4.2g of Ni(NO3)2 6H2O and 2g of Al(NO3)3 9H2O and dissolve them in 350mL of deionized water, stir uniformly to obtain a metal salt solution; weigh 5.1g of urea and 0.9g of NH4F and dissolve them in 350mL of deionized water, stir uniformly to obtain a mixed alkali solution; pour the metal salt solution and the mixed alkali solution into the hydrothermal kettle at the same time, control the crystallization temperature to be 90℃, the crystallization time is 4h, the precipitate is filtered, washed and dried in the oven at 60℃ for 12h, to obtain NiAl-LDH;

[0062] Step 2, preparation of NiAl-LDO

[0063] Weigh 1g of NiAl-LDH obtained in step 1, calcine under H2 atmosphere for 5h, set the temperature to be 500℃, the initial temperature is room temperature, the heating rate is 2℃ / min, the gas flow rate is 30mL / min, to obtain NiAl-LDO;

[0064] Step 3, preparation of sulfur-tolerant methane dry reforming catalyst

[0065] Weigh 1g of NiAl-LDO obtained in step 2 and 0.85g of sodium hypophosphite and mix them uniformly, calcine under H2 atmosphere for 5h, set the temperature to be 1000℃, the heating rate is 10℃ / min, the gas flow rate is 30mL / min, to obtain the sulfur-tolerant methane dry reforming catalyst 3, marked as Ni@Ni3P / NiAl-LDO;

[0066] Comparative Example 1

[0067] A water-sliding-lattice-derived supported nickel phosphide DRM catalyst, the molar ratio of P, Al and Ni in the catalyst is 1:0.5:1.

[0068] Step 1, preparation of NiAl-LDH

[0069] Take 2.6 g of Ni(NO3)2 6H2O and 1.2 g of Al(NO3)3 9H2O, dissolve in 350 mL of deionized water, stir uniformly to obtain a metal salt solution; take 5.1 g of urea and 0.9 g of NH4F, dissolve in 350 mL of deionized water, stir uniformly to obtain a mixed alkali solution; pour the metal salt solution and the mixed alkali solution into the hydrothermal kettle at the same time, control the crystallization temperature to be 90℃, the crystallization time is 4h, the precipitate is filtered, washed and dried in a 60℃ oven for 12h to obtain NiAl-LDH;

[0070] Step 2, preparation of NiAl-LDO

[0071] Take 1 g of NiAl-LDH obtained in step 1, calcine under H2 atmosphere for 5h, set the temperature to be 500℃, the initial temperature is room temperature, the heating rate is 2℃ / min, the gas flow rate is 30mL / min, to obtain NiAl-LDO;

[0072] Step 3, preparation of catalyst hydrotalcite-derived supported nickel phosphide DRM catalyst

[0073] Take 1 g of NiAl-LDO obtained in step 2 and 0.31 g of red phosphorus, mix uniformly, calcine under H2 atmosphere for 5h, set the temperature to be 1000℃, the heating rate is 5℃ / min, the gas flow rate is 30mL / min, to obtain hydrotalcite-derived supported nickel phosphide DRM catalyst 4, recorded as Ni2P / NiAl-LDO;

[0074] Comparative example 2

[0075] Take NiAl-LDO as catalyst, the molar ratio of P, Al and Ni in the catalyst is 0:0.4:1;

[0076] Step 1, preparation of NiAl-LDH

[0077] Take 2.6 g of Ni(NO3)2 6H2O and 1.2 g of Al(NO3)3 9H2O, dissolve in 350 mL of deionized water, stir uniformly to obtain a metal salt solution; take 5.1 g of urea and 0.9 g of NH4F, dissolve in 350 mL of deionized water, stir uniformly to obtain a mixed alkali solution; pour the metal salt solution and the mixed alkali solution into the hydrothermal kettle at the same time, control the crystallization temperature to be 90℃, the crystallization time is 4h, the precipitate is filtered, washed and dried in a 60℃ oven for 12h to obtain NiAl-LDH;

[0078] Step 2, preparation of NiAl-LDO

[0079] The NiAl-LDH obtained in step 1 was weighed at 1 g, calcined under H2 atmosphere for 5 h, the temperature was set at 500 DEG C, the temperature rising rate was 2 DEG C / min, the gas flow rate was 30 mL / min, and NiAl-LDO was obtained, which was recorded as catalyst 5;

[0080] Methane and carbon dioxide dry reforming reaction: tested in a fixed bed reactor with a length of 200 mm and an inner diameter of 8 mm, 0.1 g of the screened catalysts 1-5 were weighed and loaded into a stainless steel reaction tube, fixed with 2-4 μm quartz wool, the reaction temperature was controlled by an intelligent circulating constant temperature controller, the reaction product component content was detected by gas chromatography GC-2014, and the tail gas was discharged after treatment by an absorption device;

[0081] The reaction gas composition is: 500 mg / m 3 of SO2, 100000 mg / m 3 of CH4, 100000 mg / m 3 of CO2, N2 as the balance gas, the reaction space velocity is 6000 mL·g −1 ·h −1 ; the reaction pressure is set at normal pressure, the reaction temperature is 800 DEG C, and the reaction time is 12 h.

[0082] Table 1, examples, comparative examples, conversion rate of methane and carbon dioxide dry reforming reaction catalysis.

[0083] Sample No. Molar ratio of P / Ni initial conversion of CH4 Initial conversion of CO2 12 h catalyst activity Catalyst 1 0.26：1 92% 92% No significant deactivation Catalyst 2 0.5：1 94% 94% No significant deactivation Catalyst 3 0.8：1 91% 91% No significant deactivation Catalyst 4 1：1 90% 90% Deactivation Catalyst 5 0：1 88% 90% Deactivation

[0084] As can be seen from Table 1, the catalyst Ni@Ni3P / NiAl-LDO with core-shell structure obtained by calcining with sodium hypophosphite as phosphorus source in the present embodiment has high initial conversion rate of CH4 and CO2, and the performance does not decrease obviously within 12h of reaction time; the supported catalyst Ni2P / NiAl-LDO obtained by calcining with red phosphorus as phosphorus source in Comparative Example 1 has lower conversion rate than the catalysts in Examples 1-3, and the catalyst is obviously deactivated within 12h of reaction time; the supported catalyst NiAl-LDO obtained by calcining without adding phosphorus source in Comparative Example 2 has lower conversion rate than the catalysts in the present application, and the catalyst is severely deactivated within 12h of reaction time. This is because in the catalysts in the present application, a layer of Ni3P shell is formed on the surface of Ni particles by the ingenious introduction of sodium hypophosphite to form phosphorization, which forms a package to Ni metal atoms, so that the active ingredient of the catalysts in the present application has the core-shell structure of Ni@Ni3P, which unexpectedly realizes the resistance to SO2 poisoning of Ni particles, thereby improving the stability of the catalysts, greatly improving the efficiency of converting CH4 and CO2 into synthesis gas in the presence of SO2, and the strong metal-support interaction of NiAl-LDO can inhibit the sintering of Ni in the reaction process, which is more suitable for the DRM reaction requiring high temperature, so that the catalysts in the present application have great industrialization prospects.

[0085] The above-described examples only express several embodiments of the present application, facilitate specific and detailed understanding of the technical solutions of the present application, but should not be understood as limiting the patent protection scope of the present application. It should be noted that for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, which are all within the protection scope of the present application.

Claims

1. A sulfur tolerant methane dry reforming catalyst, characterized by, The catalyst has a specific core-shell structure active center Ni@Ni3P, which is loaded on a nickel-aluminum bimetallic oxide matrix, and the structural formula of the catalyst is Ni@Ni3P / NiAl-LDO; in the catalyst, the molar ratio of P, Al and Ni is (0.2-0.8):(0.4-0.6):1; in the XRD spectrum of the catalyst, the (031), (231), (330), (112), (240), (202), (141), (222), (132), (611), (233) characteristic diffraction peaks of Ni@Ni3P appear at 2θ angles of 36.4°, 41.8°, 42.8°, 43.6°, 45.2°, 46.0°, 46.6°, 50.6°, 52.7°, 66.9°, 75.3°; The particle size of the catalyst is 5-30 nm; the content of Ni in the active center Ni@Ni3P is 40-60 wt% based on the total weight of the catalyst in terms of metal elements; the specific surface area of the catalyst is 60.9-75.5 m 2 / g; the catalyst maintains the morphology of the hexagonal nanosheet of hydrotalcite.

2. A process for the preparation of a sulfur tolerant methane dry reforming catalyst according to claim 1, characterized in that, The method comprises the following steps: Step 1, preparation of NiAl-LDH Take Ni(NO3)2·6H2O and Al(NO3)3·9H2O and place them in a beaker, add deionized water and stir until uniform to obtain a metal salt solution, take urea and NH4F and place them in a beaker, add deionized water and stir until uniform to obtain a mixed alkali solution, pour the metal salt solution and the mixed alkali solution into a hydrothermal kettle, and statically crystallize at 60-120℃ for 4-24h to obtain a precipitate, filter, wash and then dry the precipitate in an oven, set the temperature to 60-80℃ and the time to 12-24h to obtain NiAl-LDH; Step 2, preparation of NiAl-LDO Take the NiAl-LDH obtained in step 1, calcine under an inert gas atmosphere, the initial temperature is room temperature, the temperature is raised to 800-1000℃ at a rate of 2-10℃ / min, the calcination time is 2-5h, and the inert gas flow rate is 10-40mL / min to obtain NiAl-LDO; Step 3, preparation of a sulfur-resistant methane dry reforming catalyst Take the NiAl-LDO obtained in step 2 and mix it with sodium hypophosphite, calcine under an inert gas atmosphere, the initial temperature is room temperature, the temperature is raised to 800-1000℃ at a rate of 2-10℃ / min, the calcination time is 2-5h, and the inert gas flow rate is 10-40mL / min to obtain the sulfur-resistant methane dry reforming catalyst, which is denoted as Ni@Ni3P / NiAl-LDO.

3. The method for preparing a sulfur-resistant methane dry reforming catalyst according to claim 2, characterized by, In step 1, the molar ratio of Ni 2+ / Al 3+ is (1-4):

1.

4. The method for preparing a sulfur tolerant methane dry reforming catalyst according to claim 2, characterized by, In step 1, in the mixed alkali solution, the molar ratio of urea to NH4F is (2.5-10):

1.

5. The method for preparing a sulfur tolerant methane dry reforming catalyst according to claim 2, characterized by, In step 2, the inert gas is any one of N2, Ar and He.

6. The method for preparing a sulfur tolerant methane dry reforming catalyst according to claim 2, characterized by, In step 3, the molar ratio of P to Ni in the mixture of NiAl-LDO and sodium hypophosphite is (0.1-1):

1.

7. A method for the dry reforming of methane using the sulfur tolerant catalyst for dry reforming of methane as claimed in claim 1, wherein, The catalyst is taken, granulated to 40-60 mesh, loaded into a reactor, the reaction temperature is 600-800℃, first purged with H2for 0.5-2h, the flow rate of H2is 30-50mL / min / g, then a raw gas containing SO2is introduced into the reactor, the raw gas is a mixed gas of CH4and CO2, the reaction pressure is set to 0.1-2MPa, the space velocity is set to 3000-12000mL·g -1 ·h -1 , the reaction time is 12-100h, wherein the initial conversion rate of CH4is ≤94%, the initial conversion rate of CO2is ≤94%.

8. Process for the dry reforming of methane according to claim 7, characterized in that, In the mixed gas, the volume ratio of SO2, CH4 and CO2 in the total volume of the mixed gas is (1-10):(100-5000):(100-5000).

9. Process for the dry reforming of methane according to claim 7, characterized in that, The reactor is a fixed bed reactor with a length of 200-350mm and an inner diameter of 5-10mm.

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