CN104084210B - A kind of preparation method of double-doped composite oxides methyl hydride combustion catalyst - Google Patents
A kind of preparation method of double-doped composite oxides methyl hydride combustion catalyst Download PDFInfo
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Abstract
The invention discloses a kind of preparation method of double-doped composite oxide catalysts, and by this catalyst application in low-concentration methane catalyst combustion reaction.This catalyst utilizes with the raw method preparation coexisted, complexing agent is made with citric acid, by the original solution simultaneous reactions complexing containing La, Mg, Sn and Co element, at 900 DEG C, roasting forms double-doped composite oxide catalysts in 3 hours, selected Mg foreign atom and the mol ratio of La atom are 0 ~ 0.2: 2 ~ 1.8, the mol ratio of Co foreign atom and Sn atom is 0 ~ 0.3: 2 ~ 1.7, and the optimum molar ratio of La, Mg, Sn and Co atom example is La: Mg: Sn: Co=1.8: 0.2: 1.7: 0.3.This method for preparing catalyst is simple, with low cost, pollution-free, has higher catalytic activity and good structural stability for low-concentration methane catalytic combustion.
Description
Technical field
The present invention relates to a kind of preparation method of double-doped composite oxide catalysts, refer to the preparation method of a kind of double-doped composite oxides for the catalyst of low-concentration methane catalyst combustion reaction especially.
Background technology
China's coal bed gas resource is very abundant, but utilizes the very large deficiency of existence to the exploitation of coal bed gas at present, and total extraction rate less than 50%, and after extraction, is still had a greater part of coal bed gas to be directly discharged in air by mine ventilation, is called wind resource assessment.Containing methane gas in wind resource assessment, according to according to a preliminary estimate, the methane of annual China's coal-mine wind resource assessment loss is 16,100,000,000 m
3~ 200 hundred million m
3chase after its reason, mainly because methane content in wind resource assessment is general not higher than 3%, because methane concentration is too low, utilize technical difficulty large, at present, wind resource assessment primary discharge, in air, is not almost also fully utilized in countries in the world, although the concentration of methane is low in wind resource assessment, but total amount is huge especially, is equivalent to have 2,160 ten thousand t ~ 2,700 ten thousand t standard coals to be wasted every year like this, and creates serious environmental pollution (CH
4the greenhouse effects formed are CO
226 times).If effectively can be utilized wind resource assessment, huge economic benefit, social benefit and environmental benefit will be produced.In recent years, scientists proposes the effective utilization of method realization to wind resource assessment of low-concentration methane burning, and one of key realizing this technology is the research and development of low-concentration methane combustion catalyst.
At present, applying more catalyst in methane catalytic combustion reaction is noble metal catalyst, and it can effectively reduce methyl hydride combustion temperature, just burning is complete between 200 ~ 400 DEG C to make methane, but because noble metal is expensive, heat endurance is poor, therefore and be not suitable for large-scale application.Old friends expand cheap and easy to get, the research of the catalyst of transition metal oxide that oxygen storage capacity is stronger, as the oxide of Ce, Mn, Fe, Cu, but these oxides are as methyl hydride combustion catalyst, heat resistance is poor, easily react to each other between component when high temperature, reduce the catalytic activity of catalyst.So people turn one's attention to stable in properties again and the non-noble metal composite oxide catalyst of low temperature not easy-sintering, such as hexa-aluminate oxide, double negative property, spinel oxide etc.These composite oxide of metal all comprise A, B two kinds of metallic elements, wherein A bit element is generally alkaline-earth metal, thulium, B position is generally transition metal, therefore selects suitable preparation method can improve its catalytic activity to prepare some specific composite oxide of metal as methyl hydride combustion catalyst.
In existing research, someone adopts infusion process that active constituent loading is prepared methyl hydride combustion catalyst to the larger carrier of specific area; Also have people to prepare methyl hydride combustion catalyst by coprecipitation, but it is relative less as the research of methyl hydride combustion catalyst with the pyrochlore-type composite metal oxide adulterated in B position simultaneously that the same raw coexistence method of employing at present prepare A position.Therefore this patent provides a kind of preparation method of double-doped O composite metallic oxide catalyst, the methyl hydride combustion for low concentration reacts, and significantly can improve the catalytic activity of methyl hydride combustion catalyst.
Summary of the invention
The technical problem to be solved in the present invention is to provide a kind of preparation method of double-doped composite oxide catalysts, this catalyst utilizes with raw concurrent laws preparation, complexing agent is made with citric acid, will containing A, A ', the original solution simultaneous reactions complexing of B and B ' atom, form double-doped composite oxide catalysts, the methane catalytic combustion of this catalyst application in low concentration is reacted, low-concentration methane can be made to burn completely at a lower temperature.
The preparation method of catalyst of the present invention is with glass putty, lanthanum nitrate, magnesium nitrate, and cobalt nitrate is reactant, and citric acid is complexing agent.Specific features is: the mol ratio of citric acid and each metallic atom is 1: 1, takes glass putty, the La (NO of certain metering ratio
3)
36H
2o, Mg (NO
3)
26H
2o, Co (NO
3)
26H
2o and citric acid are placed in there-necked flask, measuring appropriate 32.5wt% nitric acid again adds wherein, be made into the metal raw solution containing nitric acid, under the condition coexisted with life, several metal raw solution was in 80 ~ 90 DEG C of constant temperature backflows 6 ~ 8 hours, then solution is moved into beaker, again 70 DEG C of water bath with thermostatic control reactions 6 ~ 8 hours, put into 100 DEG C of IR bakes to spend the night oven dry, Muffle furnace 500 DEG C of roastings make Nitrates decompose in 3 hours, then 900 DEG C of roastings 3 hours, make containing lanthanum, magnesium, tin, the codope pyrochlore type multiple oxide catalyst of cobalt element.And utilize chemical analysis to determine the mol ratio of each metallic atom in the catalyst of generation, consistent with the initial rate of charge of various metal nitrate.
Catalyst of the present invention obtains good catalytic effect in methyl hydride combustion process.It is the methane of 2%, the hybrid reaction gas of 18% oxygen and 80% nitrogen that specific experiment operation adopts containing percent by volume, passing into and catalyst granules is housed is 0.25 ~ 0.42mm, consumption is in the fixed-bed quartz reactor (diameter 10mm) of 200mg, control gas flow rate with mass flowmenter, air speed is 48000h
-1, temperature programming speed is 5 DEG C/min, adopts FQ-W type CH
4infrared spectrum analyser analysis, calculate this reaction reach at different temperatures stable after CH
4conversion ratio.In addition, the thing phase composition of the D8ADVANCE type Powder X-ray Diffractometer detecting catalyst adopting German Bruker company to produce, the running parameter of this instrument is as follows: radiation source is CuK
α(λ=0.15406nm), operating voltage is 36kV, and electric current is 20mA, sweep limits 10 ° ~ 80 °, sweep speed 2 °/min.
A, A in double-doped O composite metallic oxide catalyst of the present invention ', B, B ' element specifically refers to La, Mg, Sn, Co element.Have employed and only contrast containing the metal oxide of A, B two kinds of elements, in its methane catalytic combustion active testing, catalytic activity is well below the composite oxide of metal of codope.
The codope metal oxide of the present invention also adopts A, A ', B, B ' element is respectively La, Fe, Sn, Co element contrasts, result shows that the catalytic activity of the codope catalyst containing La, Mg, Sn, Co in methyl hydride combustion active testing is best, and the material of display is single-phase pyrochlore type multiple oxide structure in XRD test, without assorted peak.
The mol ratio of A ' the position foreign atom selected by the present invention and A position atom is the mol ratio of 0 ~ 0.2: 2 ~ 1.8, B ' position foreign atom and B position atom is 0 ~ 0.3: 2 ~ 1.7.
Advantage of the present invention is: the double-doped composite oxide catalysts prepared, has good catalytic activity as methyl hydride combustion catalyst, heat endurance and structural stability.And method for preparing catalyst is simple, with low cost, the intermediate product loss of preparation process is little, and reactant reaction is complete.
Essential characteristics of the present invention is:
1. adopt the catalyst prepared with raw concurrent laws to be double-doped composite oxide catalysts, this catalyst is used for methane catalytic combustion reaction, initiation temperature and complete conversion temperature are respectively 417.4 DEG C and 670.1 DEG C, and methyl hydride combustion catalytic activity is far superior to unadulterated O composite metallic oxide catalyst.
2. adopting the double-doped O composite metallic oxide catalyst prepared with raw concurrent laws, is single-phase pyrochlore-type O composite metallic oxide catalyst, and produce without dephasign, this catalyst contains La, Mg, Sn, Co metallic element.This catalyst activity is better than the codope pyrochlore type multiple oxide catalyst containing La, Fe, Sn, Co metallic element.
3. adopt the double-doped metal composite oxide catalyst prepared with raw concurrent laws, the Mg element selected is neither alkali metal also non-thulium, widen the range of choice of metallic element, in addition, Co element is variable valency metal element, is doped in Sn ion and more easily redox reaction occurs.And Mg and Co is mutually collaborative has good resistance to elevated temperatures, so the double-doped catalyst be made up of La, Mg, Sn, Co, the catalytic efficiency of methane catalytic combustion can be improved, the stability of catalyst can be kept again at relatively high temperatures.
Accompanying drawing explanation
Fig. 1 is (1) La-Mg-Sn-Co-O double-doped O composite metallic oxide catalyst; (2) La-Fe-Sn-Co-O double-doped O composite metallic oxide catalyst; (3) the methyl hydride combustion catalytic activity resolution chart of La-Sn-O O composite metallic oxide catalyst.
Fig. 2 is (1) La-Mg-Sn-Co-O double-doped O composite metallic oxide catalyst; (2) La-Fe-Sn-Co-O double-doped O composite metallic oxide catalyst; (3) X ray diffracting spectrum of La-Sn-O O composite metallic oxide catalyst.
Table 1 is reaction temperature T corresponding when the methane conversion under different catalysts catalytic condition is respectively 10%, 50%, 90%
10, T
50and T
90.
Detailed description of the invention
Embodiment 1: take 2.0178g glass putty, 7.7944gLa (NO
3)
36H
2o, 0.5128gMg (NO
3)
26H
2o, 0.8731gCo (NO
3)
26H
2o, 8.4056g citric acid is placed in there-necked flask, the nitric acid measuring 80mL32.5wt% again adds wherein, be made into the metal raw solution containing nitric acid, under the condition coexisted with life, several metal raw solution was in 80 ~ 90 DEG C of constant temperature backflows 6 ~ 8 hours, then solution is moved into beaker, again 70 DEG C of water bath with thermostatic control reactions 6 ~ 8 hours, put into 100 DEG C of IR bakes to spend the night and be dried into half xerogel, Muffle furnace 500 DEG C of roastings 3 hours, then 900 DEG C of roastings 3 hours, obtain 0.01molLa-Mg-Sn-Co-O double-doped O composite metallic oxide catalyst.
Comparative example 1: take 2.3742g glass putty, 8.6604gLa (NO
3)
36H
2o, 8.4056g citric acid is placed in there-necked flask, the red fuming nitric acid (RFNA) measuring 80mL32.5wt% adds wherein, be made into the metal raw solution containing nitric acid, under the condition coexisted with life, several metal raw solution was in 80 ~ 90 DEG C of constant temperature backflows 6 ~ 8 hours, then solution is moved into beaker, again 70 DEG C of water bath with thermostatic control reactions 6 ~ 8 hours, put into 100 DEG C of IR bakes to spend the night and be dried into half xerogel, Muffle furnace 500 DEG C of roastings 3 hours, then 900 DEG C of roastings 3 hours, obtain 0.01molLa-Sn-O O composite metallic oxide catalyst.
Comparative example 2: take 2.0178g glass putty, 7.7944gLa (NO
3)
36H
2o, 0.8080gFe (NO
3)
29H
2o, 0.8731gCo (NO
3)
26H
2o, 8.4056g citric acid is placed in there-necked flask, the nitric acid measuring 80mL32.5wt% adds wherein, be made into the metal raw solution containing nitric acid, under the condition coexisted with life, several metal raw solution was in 80 ~ 90 DEG C of constant temperature backflows 6 ~ 8 hours, then solution is moved into beaker, again 70 DEG C of water bath with thermostatic control reactions 6 ~ 8 hours, put into 100 DEG C of IR bakes to spend the night and be dried into half xerogel, Muffle furnace 500 DEG C of roastings 3 hours, then 900 DEG C of roastings 3 hours, obtain 0.01molLa-Fe-Sn-Co-O double-doped O composite metallic oxide catalyst.
Obtained catalyst carries out the test of catalytic activity according to the methods below:
Example 1, the catalyst 200mg that comparative example 1 and 2 is obtained, particle is that 0.25 ~ 0.42mm is placed in fixed-bed quartz reactor (diameter 10mm), first logical nitrogen 10 ~ 15min, the air being used in emptying reactor, it is 30L/h that mass flowmenter controls gas flow rate, until infrared spectrum analyser pointer nulling and stable after, passing into containing percent by volume is the methane of 2%, the hybrid reaction gas of 18% oxygen and 80% nitrogen, Mass Control flowmeter gas flow rate is 20L/h, when infrared spectrum analyser pointed 100 and stable after, start to heat up, temperature programming speed is 5 DEG C/min.Record and calculate reaction and reach the CH after stablizing at different temperatures
4conversion ratio.
Claims (1)
1. the preparation method of a double-doped O composite metallic oxide catalyst, this catalyst adopts with raw concurrent laws preparation, it is characterized in that, complexing agent is made with citric acid, there are four kinds of metallic atoms to participate in reacting and the individual system that coexists simultaneously simultaneously, take the La (NO that molar ratio is La: Mg: Sn: Co=1.8: 0.2: 1.7: 0.3
3)
36H
2o, Mg (NO
3)
26H
2o, glass putty, Co (NO
3)
26H
2o, the mol ratio of citric acid adding amount and each metallic atom is 1: 1, citric acid is placed in there-necked flask, measuring appropriate 32.5wt% nitric acid again adds wherein, be made into the metal raw solution containing nitric acid, under the condition coexisted with life, several metal raw solution was in 80 ~ 90 DEG C of constant temperature backflows 6 ~ 8 hours, then solution is moved into beaker, again 70 DEG C of water bath with thermostatic control reactions 6 ~ 8 hours, put into 100 DEG C of IR bakes to spend the night oven dry, Muffle furnace 500 DEG C of roastings make Nitrates decompose in 3 hours, 900 DEG C of roastings 3 hours again, obtain the codope pyrochlore-type O composite metallic oxide catalyst of a kind of La-Mg-Sn-Co-O, and the methane catalytic combustion of this catalyst application in low concentration is reacted.
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| CN104368327B (en) * | 2014-10-23 | 2016-09-07 | 江西宝安新材料科技有限公司 | A kind of catalyst for Catalytic methane oxidation and preparation method thereof |
| CN107282052A (en) * | 2017-06-20 | 2017-10-24 | 内蒙古大学 | A kind of preparation of nickel Zr catalyst and the technique reacted for methane catalytic combustion |
| CN113275017A (en) * | 2021-05-28 | 2021-08-20 | 内蒙古大学 | Preparation method and application of composite pyrochlore catalyst |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101293201A (en) * | 2008-05-30 | 2008-10-29 | 内蒙古大学 | Method for preparing methyl hydride combustion catalyst |
| CN101879445A (en) * | 2010-07-15 | 2010-11-10 | 济南大学 | Composite rear earth pyrochlore-type oxide catalyst for catalyzing burning for removing soot of diesel vehicle and preparation method thereof |
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2014
- 2014-07-21 CN CN201410346085.9A patent/CN104084210B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101293201A (en) * | 2008-05-30 | 2008-10-29 | 内蒙古大学 | Method for preparing methyl hydride combustion catalyst |
| CN101879445A (en) * | 2010-07-15 | 2010-11-10 | 济南大学 | Composite rear earth pyrochlore-type oxide catalyst for catalyzing burning for removing soot of diesel vehicle and preparation method thereof |
Non-Patent Citations (1)
| Title |
|---|
| Catalytic combustion of methane over cobalt doped lanthanum stannate pyrochlore oxide;Jie Cheng et al;《Catalysis Communications》;20070817;第9卷;690-695 * |
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