CN116786138A - CO low-temperature selective methanation bimetallic catalyst and preparation method and application thereof - Google Patents
CO low-temperature selective methanation bimetallic catalyst and preparation method and application thereof Download PDFInfo
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- KBJMLQFLOWQJNF-UHFFFAOYSA-N nickel(ii) nitrate Chemical compound [Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O KBJMLQFLOWQJNF-UHFFFAOYSA-N 0.000 claims description 2
- 239000012716 precipitator Substances 0.000 claims description 2
- OJLCQGGSMYKWEK-UHFFFAOYSA-K ruthenium(3+);triacetate Chemical compound [Ru+3].CC([O-])=O.CC([O-])=O.CC([O-])=O OJLCQGGSMYKWEK-UHFFFAOYSA-K 0.000 claims description 2
- 239000007787 solid Substances 0.000 claims description 2
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- HZEWFHLRYVTOIW-UHFFFAOYSA-N [Ti].[Ni] Chemical compound [Ti].[Ni] HZEWFHLRYVTOIW-UHFFFAOYSA-N 0.000 description 11
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- MKYBYDHXWVHEJW-UHFFFAOYSA-N N-[1-oxo-1-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propan-2-yl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(C(C)NC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 MKYBYDHXWVHEJW-UHFFFAOYSA-N 0.000 description 2
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Abstract
The invention belongs to the field of heterogeneous catalysis, and discloses a CO low-temperature selective methanation bimetallic catalyst, a preparation method and application thereof. The invention relates to a CO low-temperature selective methanation bimetallic catalyst which is a metal supported catalyst taking Ru and Ni as active components and NiTi-LDH as a carrier. The catalyst disclosed by the invention is simple to prepare, the noble metal Ru is low in dosage and good in low-temperature activity, CO in hydrogen-rich gas can be deeply removed to below 10ppm at 180-260 ℃ and the reaction selectivity is higher than 50%; can be used for deeply removing trace CO in hydrogen-rich gas.
Description
Technical Field
The invention belongs to the field of heterogeneous catalysis, and particularly relates to a CO low-temperature selective methanation bimetallic catalyst, and a preparation method and application thereof.
Background
The Proton Exchange Membrane Fuel Cell (PEMFC) has the advantages of high efficiency, small pollution, low working temperature, quick start, high power density and the like, and is expected to be used in the fields of new energy automobiles, distributed power generation and the like. The fuel of PEMFC is mainly hydrogen or hydrogen-rich gas, and the hydrogen fuel is mainly derived from hydrogen-rich compound such as AReforming alkane, methanol, dimethyl ether, etc., and then producing by water vapor conversion, but the hydrogen fuel obtained by this method contains 20vol.% CO 2 And 0.5-2vol.% CO, etc., and a trace amount of CO can poison the anode material Pt of the PEMFC to degrade the battery performance. In order to ensure the normal operation of the PEMFC and improve the battery life thereof, deep removal of CO in the hydrogen fuel is required. Current chemical methods for deep and efficient removal of CO are the selective methanation of CO (CO-SMET) and the selective oxidation of CO. Compared with the CO selective oxidation method, the CO selective methanation method does not need to introduce oxygen or air into the system, the process is simpler, and nitrogen is not introduced into hydrogen fuel to reduce the content of hydrogen. Currently, the difficulty of CO selective methanation is the development of highly active and highly selective catalysts.
The CO selective methanation active component generally adopts noble metal Ru and non-noble metal Ni, the noble metal Ru has better catalytic activity under the low-temperature condition, and the non-noble metal Ni has the problems of difficult reduction of the active component, higher reaction temperature, easy agglomeration and sintering and the like. TiO (titanium dioxide) 2 Has semiconductor property and can generate stronger metal-carrier interaction with the load metal. Tada et al (Effect of metal addition to Ru/TiO) 2 catalyst on selective CO metal.catalysis Today,2014, 232:16-21.) etc. by directly loading 5wt% Ru and Ni to commercial TiO 2 The CO outlet concentration can be reduced to below 500ppm within the range of 200-290 ℃. Li et al (hydrogenic TiO) 2 supported Ru for selective methanation of CO in practical conditions, applied Catalysis B: environmental,2021, 298:120597) to treat TiO 2 Calcining in hydrogen atmosphere at 400 deg.c for 3 hr to obtain modified H 2 -TiO 2 Then loading 1.1wt% Ru to obtain Ru/H 2 -TiO 2 The catalyst can reduce CO to below 10ppm in the temperature range of 200-260 ℃ and simultaneously maintain the selectivity above 50%. Ping et al (Ni-doped TiO) 2 nanotubes supported Ru catalysts for CO selective methanation in H 2 -rich reformate gases.Reaction Kinetics Mechanisms&Catalyst, 2018.) Ru/Ni-TNT catalyst prepared by loading 1wt% Ru and 5wt% Ni onto Titanium Nano (TNT) tube, can be in the range of 210-270 DEG CThe CO outlet concentration was reduced to below 10ppm while maintaining selectivity above 50%. Shore Steel et al (grant bulletin No. CN 101607198B) supported 0.2-2wt% Ru to ZrO 2 CeO (CeO) 2 On a composite oxide carrier of (a) to obtain Ru/ZrO 2 -CeO 2 Has good activity in 220-300 ℃, but can only reduce the CO outlet concentration to 25ppm. Dong Xinfa (bulletin No. CN 113398935B) is prepared by synthesizing graphene oxide-nickel aluminum hydrotalcite hydrogel layer by layer self-assembly, freeze-drying and roasting to obtain graphene-composite metal oxide aerogel carrier, loading Ru on the carrier, and reducing the concentration of hydrogen-rich CO outlet containing 1vol% CO to below 10ppm at 220-290 ℃ while keeping the selectivity above 50%.
The catalyst prepared by the method generally has the defects of large Ru consumption (the Ru consumption is more than or equal to 1 wt%) of noble metal, poor low-temperature activity (the initial temperature of a reaction window is higher than 200 ℃), incomplete CO reaction (the concentration of CO outlet cannot be reduced to below 10 ppm) and the like.
Disclosure of Invention
In order to overcome the defects and shortcomings of the prior art, the primary purpose of the invention is to provide a bimetallic catalyst for low-temperature selective methanation of CO.
The invention also aims to provide a preparation method of the CO low-temperature selective methanation bimetallic catalyst.
The invention also aims to provide the application of the CO low-temperature selective methanation bimetallic catalyst in deep removal of trace CO in hydrogen-rich gas.
The aim of the invention is achieved by the following scheme:
a CO low-temperature selective methanation bimetallic catalyst is a metal supported catalyst taking Ru and Ni as active components and nickel titanium hydrotalcite (NiTi-LDH) as a carrier, wherein the active components are derived from Ru reduced by ruthenium salt and Ni partially reduced by NiTi-LDH.
The molar ratio of Ni to Ti in the NiTi-LDH is 2-3; ru loading is 0.3wt% to 1.2wt% of NiTi-LDH; preferably, the loading of Ru is 0.3wt%.
The preparation method of the CO low-temperature selective methanation bimetallic catalyst comprises the following steps: the preparation method comprises the steps of preparing a NiTi-LDHs catalyst carrier by a coprecipitation method, loading active component Ru by an impregnation method, drying and reducing to obtain the Ru-Ni/NiTi-LDH catalyst.
The preparation method of the CO low-temperature selective methanation bimetallic catalyst specifically comprises the following steps:
(1) Preparing a NiTi-LDH carrier by a coprecipitation method: dissolving nickel salt in water to obtain nickel salt solution (I); tiCl is added to the mixture 4 Mixing with concentrated hydrochloric acid to obtain colorless or yellow clear solution (II); adding the solution (II) into the solution (I) to obtain a mixed solution (III); preparing NaOH and Na 2 CO 3 The mixed solution (IV) is a precipitator; adding the solution (IV) into the solution (III), stirring uniformly until the solution is completely precipitated, aging the precipitate, filtering and drying to obtain a solid NiTi-LDH carrier;
(2) And (3) taking the NiTi-LDH carrier obtained in the step (1), immersing in ruthenium salt solution, drying and reducing to obtain the Ru-Ni/NiTi-LDH catalyst.
The nickel salt in the step (1) is one or more of nickel chloride, nickel nitrate and nickel oxalate; ni in the solution (I) 2+ The concentration of (C) is 0.1-0.4 mol.L -1 Preferred Ni 2+ The concentration of (C) is 0.3 mol.L -1 。
The mass fraction of the concentrated hydrochloric acid in the solution (II) in the step (1) is 36-38%, preferably 37%; tiCl 4 With concentrated hydrochloric acid in a volume ratio of 0.5 to 1, preferably TiCl 4 The volume ratio of the acid to the concentrated hydrochloric acid is 0.5.
The total concentration of metal cations in the mixed solution (III) in the step (1) is 0.2 to 0.5 mol.L -1 ，Ni 2+ With Ti 4+ The molar ratio of (2) to (3): 1, preferably, the cation concentration in the solution is 0.4 mol.L -1 ，Ni 2+ With Ti 4+ Molar ratio 3:1.
na in the precipitant in step (1) + The total concentration is 1.2-1.6mol.L -1 ，Na 2 CO 3 The mol ratio of the catalyst to NaOH is 0.3-0.5:1, preferably, na in the precipitant + The total concentration is 1.2-1.4 mol.L -1 ，Na 2 CO 3 The mol ratio of NaOH to NaOH is 0.375-0.5:1.
the pH of the mixed solution at the time of complete precipitation in step (1) is=9.0 to 10.0, preferably, the pH at the time of complete precipitation is=9.5.
The aging time in the step (1) is 20-30 hours, and the aging temperature is 80-95 ℃; preferably, the aging time is 24 hours and the aging temperature is 90 ℃.
The ruthenium salt in the step (2) is ruthenium trichloride or ruthenium acetate, preferably ruthenium trichloride; ru in ruthenium salt solution 3+ The concentration is 0.2-0.82 mg.mL -1 Preferably 0.204 mg/mL -1 。
The temperature of the impregnation in the step (2) is room temperature; the time is 12-24 hours, preferably the impregnation time is 20 hours.
The drying temperatures in the step (1) and the step (2) are 50-70 ℃, and the drying temperatures are preferably 60 ℃.
The composition of the reducing gas of the reduction in the step (2) is V N2 ：V H2 =1: 0.8-1.2:1, preferably V N2 ：N H2 =1: 1, a step of; the space velocity of the reducing gas is 6000-7200 mL.h -1 ·g -1 Preferably, the reducing gas space velocity is: 7200 mL.h -1 ·g -1
The temperature of the reduction in step (2) is 330-370 ℃, preferably 350 ℃; the reduction time is 1 to 3 hours, preferably 1.5 hours.
The application of the CO low-temperature selective methanation bimetallic catalyst in deep removal of trace CO in hydrogen-rich gas, wherein the concentration of CO in the hydrogen-rich gas is 0.5-1vol.%.
Further, the reaction temperature of the catalyst for removing trace CO is 180-260 ℃.
The mechanism of the invention is as follows:
the invention provides a preparation method and application of a Ru-Ni/NiTi-LDH supported bimetallic catalyst taking NiTi-LDH as a carrier and under the synergistic effect of noble metal Ru and non-noble metal Ni. Ru-Ni/NiTi-LDH is in a sheet structure, and cations on the hydrotalcite sheet layer can be uniformly distributed, so that the dispersity of Ni on the surface of the catalyst is high. Hydrogen overflow effect exists between Ru and Ni on the surface of the catalyst, and RuCl 3 The reduction temperature of (2) is lower, ru is reduced firstly in the reduction process,H 2 the catalyst is characterized in that the catalyst is dissociated into active H on Ru, and overflows to NiO, so that the NiO is reduced at a lower temperature, the reduction temperature of Ni is reduced, more Ni is reduced, and the activity of the catalyst is obviously improved. The catalyst prepared by the invention can reduce the concentration of CO in hydrogen-rich gas to below 10ppm in a reaction window (180-260 ℃) with a lower reaction temperature and a wider reaction window, and the selectivity is higher than 50%, so that the requirements of the fuel cell electric automobile on high-quality hydrogen source fuel are better met.
Compared with the prior art, the invention has the following advantages:
according to the invention, ni and Ti elements are firstly introduced into hydrotalcite to prepare a NiTi-LDH carrier, and Ru is loaded on the NiTi-LDH carrier to prepare the Ru-Ni/NiTi-LDH catalyst. The Ru loading of the catalyst is as low as 0.3wt%, and the outlet concentration containing 1vol.% CO can be reduced to below 10ppm within a temperature window of 180-260 ℃ while the selectivity is maintained above 50%.
(1) The CO selective methanation Ru-Ni/NiTi-LDH bimetallic catalyst has good low-temperature activity, can reduce CO in hydrogen-rich gas to below 10ppm in a wider reaction temperature window of 180-260 ℃ under the synergistic effect of Ni and Ru bimetallic, and has selectivity higher than 50%.
(2) The CO selective methanation Ru-Ni/NiTi-LDH bimetallic catalyst is low in cost and economical, and the active component in the catalyst consists of Ni and noble metal Ru, but the load of the noble metal Ru is only about 0.3 wt.%.
(3) According to the invention, hydrogen overflow effect exists between Ru and NiO on the Ru-Ni/NiTi-LDH bimetallic catalyst by CO selective methanation, and the required reduction temperature is low.
(4) The Ru-Ni/NiTi-LDH bimetallic catalyst for CO selective methanation has the advantages that the layered structure of the LDH plays a role in limiting the domain, and the dispersity of the active component Ni can be increased.
Drawings
Figure 1 is an XRD pattern for different nickel-titanium ratio hydrotalcite supports.
FIG. 2 is a schematic representation of CO and CH selective methanation over a catalyst of comparative example 1 4 Concentration versus temperature profile.
FIG. 3 is a comparative example2 CO selective methanation of CO and CH over catalyst 4 Concentration versus temperature profile.
FIG. 4 is a schematic illustration of CO and CH selective methanation over a catalyst of example 1 4 Concentration versus temperature profile.
FIG. 5 is a schematic illustration of CO and CH selective methanation over a catalyst of examples 2-5 4 Concentration versus temperature profile.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but embodiments of the present invention are not limited thereto. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
The reagents used in the examples are commercially available as usual unless otherwise specified.
Catalyst performance test method: tabletting and pulverizing the catalyst, selecting 0.2g of 40-60 mesh catalyst, loading into quartz reaction tube with inner diameter of 6mm, and controlling the space velocity to 6000 mL-g -1 ·h -1 Introducing a mixture containing 79vol% of H 2 、20vol.％CO 2 And 1vol.% CO, and the reaction temperature is 150-320 ℃, and the reaction product is detected on line by gas chromatography after being dried.
Comparative example 1
8.724g of Ni (NO) 3 ) 2 ·6H 2 O is added into 100mL of deionized water, and is dissolved to obtain Ni (NO) 3 ) 2 A solution; under the condition of ice-water bath, 1.09mL of the solution with the concentration of 9.084 mol.L -1 TiCl of (2) 4 Rapidly dripping into 3.8mL of concentrated hydrochloric acid to form TiCl 4 A solution; tiCl is added to the mixture 4 Dropwise adding the solution to Ni (NO) 3 ) 2 The solution was stirred at room temperature for 3h. 6.3594g of Na 2 CO 3 And 6.4g of NaOH are added into 200mL of deionized water, and stirred at room temperature to prepare a precipitant. The precipitant is then slowly added dropwise to TiCl 4 And Ni (NO) 3 ) 2 Dropwise adding and stirring until the pH of the solution is 9.5 to obtain greenColor suspension. The suspension was aged at 90℃for 24h. Filtering, washing and drying the obtained green precipitate at 60 ℃ to obtain NiTi-LDH with nickel-titanium ratio of 3, wherein XRD spectrum of the NiTi-LDH is shown in curve a of figure 1, and PDF #15-0087 of figure 1 is a standard card of hydrotalcite.
0.2g of NiTi-LDH with a nickel-titanium ratio of 3 is taken and the space velocity is 7200 mL.h -1 ·g -1 50vol% H of 2 And 50vol% N 2 The activity of the catalyst is evaluated after the catalyst is reduced for 1.5 hours at 350 ℃ in the mixed gas, the test result of the catalyst is shown in figure 2, and as can be seen from figure 2, the NiTi-LDH with the nickel-titanium ratio of 3 can reduce the concentration of CO outlet to below 10ppm at 180-220 ℃ and simultaneously maintain the selectivity of more than 50%.
Comparative example 2
(1) 2.9079g of Ni (NO) 3 ) 2 ·6H 2 O is added into 100mL of deionized water, and is fully dissolved to obtain Ni (NO) 3 ) 2 A solution; under the condition of ice-water bath, 1.09mL of the solution with the concentration of 9.084 mol.L -1 TiCl of (2) 4 Rapidly dripping into 3.8mL of concentrated hydrochloric acid to form TiCl 4 A solution; tiCl is added to the mixture 4 Dropwise adding the solution to Ni (NO) 3 ) 2 The solution was stirred well at room temperature for 3h. Weigh Na of 6.3594 2 CO 3 And 3.2g of NaOH, and dissolving with 200mL of deionized water at room temperature to prepare alkali liquor. Subsequently, the lye is slowly and dropwise added to TiCl 4 And Ni (NO) 3 ) 2 To the mixture of (2) was added dropwise while stirring until the pH of the solution became 9.5, to obtain a green suspension. The suspension was aged at 90℃for 24h. The green precipitate obtained was filtered, washed and then dried at 60℃to give a NiTi-LDH having a nickel-to-titanium ratio of 1, the XRD spectrum of which was shown in detail in FIG. 1, curve c.
(2) 3mL of RuCl was measured with a pipette 3 Solution (wherein Ru) 3+ The concentration of (C) is 0.338 mg.mL -1 ). Placing 0.2g of NiTi-LDH carrier with nickel-titanium ratio of 1 in RuCl 3 Soaking in the solution at room temperature for 20 hr, drying at 60deg.C, and drying at air speed of 7200 mL.h -1 ·g -1 50vol% H of 2 And 50vol% N 2 Strips at 350 ℃ in the mixture of (c)And (3) reducing for 1.5 hours under the piece to obtain the Ru-Ni/NiTi-LDHs catalyst. Wherein the ratio of nickel to titanium is 1, and the Ru loading is 0.5wt% of the NiTi-LDH mass.
As can be seen from FIG. 3, the catalyst prepared in this example can reduce the CO outlet concentration to below 10ppm at 210-240 deg.C while maintaining selectivity above 50%.
Example 1
(1) 5.8158g of Ni (NO) 3 ) 2 ·6H 2 O is added into 100mL of deionized water, and is fully dissolved to obtain Ni (NO) 3 ) 2 A solution; under the condition of ice-water bath, 1.09mL of the solution with the concentration of 9.084 mol/L -1 TiCl of (2) 4 Rapidly dripping into 3.8mL of concentrated hydrochloric acid to form TiCl 4 A solution; tiCl is added to the mixture 4 Dropwise adding the solution to Ni (NO) 3 ) 2 The solution was stirred well at room temperature for 3h. 6.3594g of Na 2 CO 3 And 4.8g of NaOH, and dissolving with 200mL of deionized water at room temperature to prepare alkali liquor. Subsequently, the lye is slowly and dropwise added to TiCl 4 And Ni (NO) 3 ) 2 To the mixture of (2) was added dropwise while stirring until the pH of the solution became 9.5, to obtain a green suspension. The suspension was aged at 90℃for 24h. The green precipitate obtained was filtered, washed and then dried at 60℃to give a NiTi-LDH having a nickel to titanium ratio of 2, the XRD spectrum of which was shown in detail in FIG. 1, curve b.
(2) 3mL of RuCl was measured with a pipette 3 Solution (wherein Ru) 3+ The concentration of (C) is 0.338 mg.mL -1 ). Placing 0.2g of NiTi-LDH carrier with nickel-titanium ratio of 2 in RuCl 3 Soaking in the solution at room temperature for 20 hr, drying at 60deg.C, and drying at air speed of 7200 mL.h -1 ·g -1 50vol% H of 2 And 50vol% N 2 Reducing for 1.5h at 350 ℃ to obtain the Ru-Ni/NiTi-LDHs catalyst. Wherein the ratio of nickel to titanium is 2, and the load of Ru is 0.5wt% of the mass of NiTi-LDH.
As can be seen from FIG. 4, the catalyst prepared in this example can reduce the CO outlet concentration to below 10ppm at 190-260 ℃ while maintaining selectivity above 50%.
Example 2
(1) 8.724g of Ni (NO) 3 ) 2 ·6H 2 O is added into 100mL of deionized water, and is fully dissolved to obtain Ni (NO) 3 ) 2 A solution; under the condition of ice-water bath, 1.09mL of the solution with the concentration of 9.084 mol.L -1 TiCl of (2) 4 Rapidly dripping into 3.8mL of concentrated hydrochloric acid to form TiCl 4 A solution; tiCl is added to the mixture 4 Dropwise adding the solution to Ni (NO) 3 ) 2 The solution was stirred well at room temperature for 3h. 6.3594g of Na 2 CO 3 And 6.4g of NaOH, and dissolving with 200mL of deionized water at room temperature to prepare alkali liquor. Subsequently, the lye is slowly and dropwise added to TiCl 4 And Ni (NO) 3 ) 2 To the mixture of (2) was added dropwise while stirring until the pH of the solution became 9.5, to obtain a green suspension. The suspension was aged at 90℃for 24h. The green precipitate obtained was filtered, washed and then dried at 60℃to give a NiTi-LDH having a nickel to titanium ratio of 3, the XRD spectrum of which was shown in detail in FIG. 1, curve a.
(2) 3mL of RuCl was measured with a pipette 3 Solution (wherein Ru) 3+ The concentration of (C) is 0.204 mg.mL -1 ). Placing 0.2g of NiTi-LDH carrier with nickel-titanium ratio of 3 in diluted RuCl 3 Soaking in the solution at room temperature for 20 hr, drying at 60deg.C, and drying at air speed of 7200 mL.h -1 ·g -1 50vol% H of 2 And 50vol% N 2 Reducing for 1.5h at 350 ℃ to obtain the Ru-Ni/NiTi-LDHs catalyst. Wherein the ratio of nickel to titanium is 3, and the load of Ru is 0.3wt% of the mass of NiTi-LDH.
As can be seen from FIG. 5, the catalyst prepared in this example can reduce the CO outlet concentration to below 10ppm at 180-260 deg.C while maintaining selectivity above 50%.
Example 3
(1) 8.724g of Ni (NO) 3 ) 2 ·6H 2 O is added into 100mL of deionized water, and is fully dissolved to obtain Ni (NO) 3 ) 2 A solution; under the condition of ice-water bath, 1.09mL of the solution with the concentration of 9.084mol·L -1 TiCl of (2) 4 Rapidly dripping into 3.8mL of concentrated hydrochloric acid to form TiCl 4 A solution; tiCl is added to the mixture 4 Dropwise adding the solution to Ni (NO) 3 ) 2 The solution was stirred well at room temperature for 3h. 6.3594g of Na 2 CO 3 And 6.4g of NaOH, and dissolving with 200mL of deionized water at room temperature to prepare alkali liquor. Subsequently, the lye is slowly and dropwise added to TiCl 4 And Ni (NO) 3 ) 2 To the mixture of (2) was added dropwise while stirring until the pH of the solution became 9.5, to obtain a green suspension. The suspension was aged at 90℃for 24h. The green precipitate obtained was filtered, washed and then dried at 60℃to give a NiTi-LDH having a nickel to titanium ratio of 3, the XRD spectrum of which was shown in detail in FIG. 1, curve a.
(2) 3mL of RuCl was measured with a pipette 3 Solution (wherein Ru) 3+ The concentration of (C) is 0.338 mg.mL -1 ). Taking 0.2g of NiTi-LDH carrier with nickel-titanium ratio of 3 and placing RuCl 3 Soaking in the solution at room temperature for 20 hr, drying at 60deg.C, and drying at air speed of 7200 mL.h -1 ·g -1 50vol.% H of (C) 2 And 50vol.% N 2 Reducing for 1.5h at 350 ℃ to obtain the Ru-Ni/NiTi-LDHs catalyst. Wherein the ratio of nickel to titanium is 3, and the load of Ru is 0.5wt% of the mass of NiTi-LDH.
As can be seen from FIG. 5, the catalyst prepared in this example can reduce the CO outlet concentration to below 10ppm at 180-260 deg.C while maintaining selectivity above 50%.
Example 4
(1) 8.724g of Ni (NO) 3 ) 2 ·6H 2 O is added into 100mL of deionized water, and is fully dissolved to obtain Ni (NO) 3 ) 2 A solution; under the condition of ice-water bath, 1.09mL of the solution with the concentration of 9.084 mol.L -1 TiCl of (2) 4 Rapidly dripping into 3.8mL of concentrated hydrochloric acid to form TiCl 4 A solution; tiCl is added to the mixture 4 Dropwise adding the solution to Ni (NO) 3 ) 2 The solution was stirred well at room temperature for 3h. 6.3594g of Na 2 CO 3 And 6.4g NaOH, dissolved with 200mL deionized water at room temperaturePreparing alkali liquor. Subsequently, the lye is slowly and dropwise added to TiCl 4 And Ni (NO) 3 ) 2 To the mixture of (2) was added dropwise while stirring until the pH of the solution became 9.5, to obtain a green suspension. The suspension was aged at 90℃for 24h. The green precipitate obtained was filtered, washed and then dried at 60℃to give a NiTi-LDH having a nickel to titanium ratio of 3, the XRD spectrum of which was shown in detail in FIG. 1, curve a.
(2) 3mL of RuCl was measured with a pipette 3 Solution (wherein Ru) 3+ The concentration of (C) is 0.473 mg.mL -1 ). 0.2g of NiTi-LDH carrier with nickel-titanium ratio of 3 is placed in RuCl 3 Soaking in the solution at room temperature for 20 hr, drying at 60deg.C, and drying at air speed of 7200 mL.h -1 ·g -1 50vol.% H of (C) 2 And 50vol.% N 2 Reducing for 1.5h at 350 ℃ to obtain the Ru-Ni/NiTi-LDHs catalyst. Wherein the ratio of nickel to titanium is 3, and the load of Ru is 0.7wt% of the mass of NiTi-LDH.
As can be seen from FIG. 5, the catalyst prepared in this example can reduce the CO outlet concentration to below 10ppm at 180-260 deg.C while maintaining selectivity above 50%.
Example 5
(1) 8.724g of Ni (NO) 3 ) 2 ·6H 2 O is added into 100mL of deionized water, and is fully dissolved to obtain Ni (NO) 3 ) 2 A solution; under the condition of ice-water bath, 1.09mL of the solution with the concentration of 9.084 mol.L -1 TiCl of (2) 4 Rapidly dripping into 3.8mL of concentrated hydrochloric acid to form TiCl 4 A solution; tiCl is added to the mixture 4 Dropwise adding the solution to Ni (NO) 3 ) 2 The solution was stirred well at room temperature for 3h. 6.3594g of Na 2 CO 3 And 6.4g of NaOH, and dissolving with 200mL of deionized water at room temperature to prepare alkali liquor. Subsequently, the lye is slowly and dropwise added to TiCl 4 And Ni (NO) 3 ) 2 To the mixture of (2) was added dropwise while stirring until the pH of the solution became 9.5, to obtain a green suspension. The suspension was aged at 90℃for 24h. Filtering, washing and drying the obtained green precipitate at 60 ℃ to obtain nickelThe XRD spectrum of the NiTi-LDH with the titanium ratio of 3 is shown in a curve a of figure 1.
(2) 3mL of RuCl was measured with a pipette 3 Solution (wherein Ru) 3+ The concentration of (C) is 0.803 mg.mL -1 ). 0.2g of NiTi-LDH carrier with nickel-titanium ratio of 3 is placed in RuCl 3 Soaking in the solution at room temperature for 20 hr, drying at 60deg.C, and drying at air speed of 7200 mL.h -1 ·g -1 50vol.% H of (C) 2 And 50vol.% N 2 Reducing for 1.5h at 350 ℃ to obtain the Ru-Ni/NiTi-LDHs catalyst. Wherein the ratio of nickel to titanium is 3, and the load of Ru is 1.2wt% of the mass of NiTi-LDH.
As can be seen from FIG. 5, the catalyst prepared in this example can reduce the CO outlet concentration to below 10ppm at 180-260 deg.C while maintaining selectivity above 50%.
The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the protection scope of the present invention.
Claims (10)
1. A bimetallic catalyst for CO low-temperature selective methanation is characterized in that: the catalyst is a metal supported catalyst taking Ru and Ni as active components and taking NiTi-LDH as a carrier, wherein the active components are derived from Ru reduced by ruthenium salt and Ni partially reduced by NiTi-LDH.
2. The CO low temperature selective methanation bimetallic catalyst according to claim 1, characterized in that: the molar ratio of Ni to Ti in the NiTi-LDH is 2-3; the Ru loading is 0.3wt% to 1.2wt% of the NiTi-LDH.
3. The method for preparing the bimetallic catalyst for low-temperature selective methanation of CO according to claim 1 or 2, which is characterized by comprising the following steps: the preparation method comprises the steps of preparing a NiTi-LDHs catalyst carrier by a coprecipitation method, loading active component Ru by an impregnation method, drying and reducing to obtain the Ru-Ni/NiTi-LDH catalyst.
4. A method of manufacture according to claim 3, characterized in that it comprises the steps of:
(1) Preparing a NiTi-LDH carrier by a coprecipitation method: dissolving nickel salt in water to obtain nickel salt solution (I); tiCl is added to the mixture 4 Mixing with concentrated hydrochloric acid to obtain colorless or yellow clear solution (II); adding the solution (II) into the solution (I) to obtain a mixed solution (III); preparing NaOH and Na 2 CO 3 The mixed solution (IV) is a precipitator; adding the solution (IV) into the solution (III), stirring uniformly until the solution is completely precipitated, aging the precipitate, filtering and drying to obtain a solid NiTi-LDH carrier;
(2) And (3) taking the NiTi-LDH carrier obtained in the step (1), immersing in ruthenium salt solution, drying and reducing to obtain the Ru-Ni/NiTi-LDH catalyst.
5. The method of manufacturing according to claim 4, wherein:
the nickel salt in the step (1) is one or more of nickel chloride, nickel nitrate and nickel oxalate;
ni in the solution (I) in the step (1) 2+ The concentration of (C) is 0.1-0.4 mol.L -1 。
6. The method of manufacturing according to claim 4, wherein:
the total concentration of metal cations in the mixed solution (III) in the step (1) is 0.2 to 0.5 mol.L -1 ；Ni 2+ With Ti 4+ The molar ratio of (2) to (3): 1.
7. the method of manufacturing according to claim 4, wherein:
na in the precipitant in step (1) + The total concentration is 1.2-1.6mol.L -1 ，Na 2 CO 3 The mol ratio of the catalyst to NaOH is 0.3-0.5:1, a step of;
the aging time in the step (1) is 20-30h, and the aging temperature is 80-95 ℃.
8. The method of manufacturing according to claim 4, wherein:
the ruthenium salt in the step (2) is ruthenium trichloride or ruthenium acetate; ru in ruthenium salt solution 3+ The concentration is 0.2-0.82 mg.mL -1 ；
The temperature of the impregnation in the step (2) is room temperature; the time is 12-24h.
9. The method of manufacturing according to claim 4, wherein:
the composition of the reducing gas of the reduction in the step (2) is V N2 ：V H2 =1: 0.8-1.2:1, a step of; the space velocity of the reducing gas is 6000-7200 mL.h -1 ·g -1 ；
The temperature of the reduction in the step (2) is 330-370 ℃; the reduction time is 1-3h.
10. The use of the CO low temperature selective methanation bimetallic catalyst according to claim 1 or 2 for the deep removal of trace CO in hydrogen rich gas, characterized in that:
the concentration of CO in the hydrogen-rich gas is 0.5-1 vol%;
the reaction temperature of the catalyst for removing trace CO is 180-260 ℃.
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