Background technology
The discharge reducing volatile gas (VOCs) is one of main target of Air Pollution Control.In the solvent that building materials of house fitting-up use, the alcohol gas of slow releasing is the main source of indoor ethanol pollution, the alcohol gas discharged in the motor-vehicle tail-gas that use ethanol fuel is power is the important component of tail gas pollution of motor-driven vehicle, both forms significant damage to health.Catalytic oxidation is the method that atmosphere pollution controls economical and efficient the most.Therefore the efficient catalysis technique eliminating ethanol pollution of research, the catalysis material of development environment close friend, has become the urgent task improving people's living environment quality.
The existing catalyst for complete oxidation ethanol is mainly divided into noble metal catalyst and metal oxide catalyst.With Pd/Al in noble metal catalyst
2o
3the catalytic activity of catalyst is best, can by the alcohol gas complete oxidation of 20000ppm (F á bio B.Noronha, Marcelo C. when 200 DEG C
lucia G. Appel etc., The role of Ni on the performance of automotive catalysts:evluating the ethanoloxidation reaction.Catal.Today, 85 (2003), 13-21); Metal oxide catalyst is with CuO, activity better (the H.Idriss of MnOx and Cu-MnOx composite oxide catalysts, E.G.Seebauer, Reactions ofethanol over metal oxides.J.Mol.Catal.A:Chem.152 (2000) 201-212; L.Lamaita, Miguel A.Peluso, Horacio J.Thomas, Synthwsis and characterization ofmanganese oxides employed in VOCs abatement.Appl.Catal.B:Environ.61 (2005) 114-119; M.Roxana Morales, B.P.Barbero, Luis E.Cad ú s, Total oxidation of theethanol and propane over Mn-Cu mixed oxide catalysts.Appl.Catal.B:Environ.67 (2006) 229-236).But the cost of noble metal catalyst is higher, is unfavorable for commercial application.
The problems such as catalytic oxidation of alcohol catalyst disclosed in prior art exists that complete conversion temperature is high, poor selectivity, life-span are short, select suitable method to obtain the catalyst for catalytic oxidation of alcohol of excellent performance particularly important.
In existing research, the Mn oxide with the OMS-2 structure of pore passage structure is a kind of catalyst (Renhu Wang, Junhua Li, Environ.Sci.Technol.2010,44,4282 – 4287) with efficient removal VOCs activity.Manganese oxide octahedral molecular sieve (contracting claims OMS-2) is since 20th century came out, with its distinctive loose structure, the manganese of mixed valence, gentle surface acidic-basic property and ion exchangeable, become another the new study hotspot after zeolite type tetrahedron molecular sieve.It is by octahedra MnO
6with common seamed edge to be connected with altogether corner angle formation be about 2 × 2 one dimension tunnel structure, pore size is about 0.46nm.Manganese element is with mixed valence (Mn
4+, Mn
3+, Mn
2+) be arranged in octahedra skeleton, K in tunnel
+play a part balancing charge with a small amount of water and stablize tunnel structure, wherein, K
+with external cation generation ion-exchange, thus electricity and the catalytic performance of OMS-2 can be improved.Because nature contains abundant promoter manganese, and price is cheap, and therefore, R and D OMS-2 has obvious economic advantages.
The preparation method of OMS-2 is a lot, mainly contains: circumfluence method, hydrothermal synthesis method, sol-gel process, microwave method, solventless method, water softening method, ultrasonic wave and high temperature method etc.Sol-gal process also exists high temperature easy-sintering, shrinks the shortcomings such as large time dry, comparatively strict to conditional requests such as reactant stoichiometric proportion, calcination temperatures; Solventless method is owing to being a kind of physical mixing processes, and catalyst granules is rendered as micelle form, and the decentralization between component and uniformity are not as other method; Catalyst stabilization prepared by microwave method is indifferent, and with impurity.
Find gentle controlled catalyst preparing means become this research emphasis in order to prepare manganese-base oxide catalyst, wherein, the low in raw material price of hydrothermal synthesis method, preparation method is simple, and can realize producing in enormous quantities, the manganese-base oxide catalyst therefore adopting hydrothermal synthesis method to prepare is the effective catalyst that the ethanol low-temperature oxidation with better application prospect is decomposed.
The people such as Ge Xin (Ge Xin, Zhou Zhenyu, toluene low-temp. selective oxidation producing benzaldehyde---the research of V-Ag/OMS-2 catalytic performance, Chemical Industry and Engineering Society of China petrochemical industry Annual Conferences in 2008 and Beijing Chemical Research Institute's establishment 50 anniversary symposium collection of thesis, 2008) in disclose a kind of method adopting hydro-thermal method to prepare OMS-2 catalyst.Described method comprises: in HAc-KAc cushioning liquid, add MnAc
2the aqueous solution, and by KMnO
4solution under agitation slowly adds in above-mentioned mixed solution; The pH controlling solution is 4.5, is then slowly heated to 110 DEG C, and backflow 24h, is cooled to room temperature under stirring, by sedimentation and filtration, after washing, in 120 DEG C of dry 8h, then at 400 DEG C of roasting 4h.The method uses MnAc
2for manganous salt Kaolinite Preparation of Catalyst, described method reaction temperature is high, and energy consumption of reaction is high, and needs buffer solution in preparation process, and method is complicated, and repeatability is low.
Summary of the invention
For the deficiencies in the prior art, for solve high, the poor selectivity of complete conversion temperature that existing catalytic oxidation of alcohol catalyst exists, life-span short, use that noble metal high cost, catalyst preparing energy consumption are high, the problem of complicated operation, poor repeatability, the invention provides a kind of manganese-base oxide Catalysts and its preparation method, can be used for the elimination of indoor alcohol gas and the remaining alcohol gas of motor-vehicle tail-gas.
In order to achieve the above object, present invention employs following technical scheme:
For a preparation method for the manganese-base oxide catalyst of catalytic oxidation of alcohol, described method is hydrothermal synthesis method, comprises the steps:
(1) by manganous salt and oxidant mixing, water-soluble, adjust ph is 0 ~ 2, and the bivalent manganese in manganous salt and the mol ratio of oxidant are 0.5 ~ 2.0;
(2) after mixed solution stirring at room temperature step (1) obtained, at 80 ~ 200 DEG C of reaction 1 ~ 36h;
(3) step (2) products therefrom is washed, dry;
(4) by dried product roasting, the manganese-base oxide catalyst for catalytic oxidation of alcohol is obtained.
Different from the preparation method of traditional OMS-2, the present invention adopts the hydrothermal synthesis method of simple and effective more to prepare OMS-2 catalyst, preparation condition is gentle, controllability, reappearance are high, and catalyst has the activity being better than Mn oxide prepared by traditional co-precipitation method, circumfluence method, citric acid complex method and pyrolysismethod.
Preferably, manganese salt of the present invention is soluble manganese salt, the mixture of any one or at least two kinds in preferred manganese chloride, manganese nitrate, manganese sulfate or manganese acetate, the mixture of described mixture such as manganese chloride and manganese nitrate, the mixture of manganese nitrate and manganese sulfate, the mixture of manganese sulfate and manganese acetate, the mixture of manganese chloride, manganese nitrate and manganese sulfate, the mixture of manganese nitrate, manganese sulfate and manganese acetate, further preferably sulfuric acid manganese and/or manganese nitrate, most preferably manganese sulfate.Employing manganese sulfate is that the catalytic activity of the manganese-base oxide for catalytic oxidation of alcohol that manganous salt prepares is the highest.
Preferably, described oxidant is any one or at least two kinds of mixtures in potassium permanganate, sodium thiosulfate or sodium chlorate, the mixture of described mixture such as sodium chlorate and sodium thiosulfate, the mixture of potassium permanganate and sodium chlorate, the mixture of sodium thiosulfate and potassium permanganate, the mixture of sodium chlorate, sodium thiosulfate and potassium permanganate, preferred potassium permanganate.
The present invention utilizes MnO4 (MnO
4 -, Mn
7+) and manganous salt in manganese element (Mn
2+) automatic oxidation reduction reaction, prepare highly active manganese-base oxide catalyst.
Because MnO4 has different oxidation potentials when different pH value, in Crystallization process, the pH value of environment has important impact to crystal morphology, be 0 ~ 2 by adjust ph, such as pH is regulated to be 0.1,0.2,0.4,0.6,0.8,1,1.2,1.4,1.6,1.8, cause the automatic oxidation reaction between MnO4 and manganous salt, prepare the manganese-base oxide catalyst with OMS-2 structure, described manganese-base oxide catalyst has high activity to catalytic oxidation of alcohol.
Preferably, by adding solubility acid for adjusting pH, the acid of described solubility is selected from the mixture of any one or at least two kinds in sulfuric acid, hydrochloric acid, acetic acid or nitric acid, the mixture of described mixture such as sulfuric acid and hydrochloric acid, the mixture of acetic acid and nitric acid, the mixture of sulfuric acid, hydrochloric acid and acetic acid, the mixture of hydrochloric acid, acetic acid and nitric acid, further preferred nitric acid.
Because oxidant needs by self appraising at the current rate the manganese salt of divalence to be oxidized to the state being about 4 valencys, therefore require that the mol ratio of manganous salt and oxidant is within a suitable scope, so that the valence state that manganese element obtains being suitable for forms OMS-2 crystalline form.Bivalent manganese in manganous salt of the present invention and the mol ratio of oxidant are 0.5 ~ 2.0, such as 0.6,0.7,0.8,0.9,1.0,1.2,1.4,1.6,1.8,1.9.
Preferably, mixed solution stirring at room temperature 0.5 ~ 2h step (1) obtained, reaction raw materials is mixed to get in water more even, augmenting response area, improves reaction efficiency.
Preferably, after mixed solution stirring at room temperature 0.5 ~ 2h step (1) obtained, solution being moved to liner is react in the stainless steel cauldron of polytetrafluoroethylene (PTFE).
Preferably, the temperature of described reaction is 80 ~ 180 DEG C, such as 88 DEG C, 90 DEG C, 100 DEG C, 122 DEG C, 125 DEG C, 130 DEG C, 140 DEG C, 160 DEG C, 170 DEG C, preferably 100 ~ 120 DEG C further.
Preferably, the described reaction time is 2 ~ 23h, such as 3h, 4h, 7h, 9h, 11h, 14h, 17h, 21h, 22h, preferably 5 ~ 20h.
Described washing is centrifuge washing, and the number of times of centrifuge washing is 1 ~ 5 time, such as 2 times, 3 times, 4 times.
The temperature of described drying is 60 ~ 200 DEG C, such as 65 DEG C, 75 DEG C, 85 DEG C, 95 DEG C, 115 DEG C, 125 DEG C, 140 DEG C, 160 DEG C, 170 DEG C, preferably 70 ~ 180 DEG C, preferably 80 ~ 110 DEG C further.
The time of described drying is 10 ~ 30 hours, such as 12 hours, 14 hours, 16 hours, 19 hours, 22 hours, 25 hours, 28 hours, preferably 12 ~ 28 hours, preferably 15 ~ 25 hours further.
Described roasting is carried out in air atmosphere, and the temperature of roasting is 300 ~ 900 DEG C, such as 350 DEG C, 410 DEG C, 520 DEG C, 630 DEG C, 740 DEG C, 850 DEG C, preferably 300 ~ 550 DEG C, preferably 350 ~ 500 DEG C further.
For a preparation method for the manganese-base oxide catalyst of catalytic oxidation of alcohol, described method comprises the steps:
(1 '), water-soluble, adding solubility acid-conditioning solution pH value was 0 ~ 2, and the manganese wherein in manganous salt and the mol ratio of oxidant are 0.5 ~ 2.0 by manganous salt and oxidant mixing;
After mixed solution stirring at room temperature 0.5 ~ 2h that step (1 ') obtains by (2 '), solution is moved in stainless steel cauldron that liner is polytetrafluoroethylene (PTFE), under 80 ~ 200 DEG C of conditions, react 1 ~ 36h;
(3 ') by step (2 ') products therefrom centrifuge washing 1 ~ 5 time, dry 10 ~ 30h at 60 ~ 200 DEG C;
Dried product in 300 ~ 900 DEG C of air atmosphere roastings, is obtained the manganese-base oxide catalyst for catalytic oxidation of alcohol by (4 ').
Preferably, described method comprises the steps:
(1 ") by MnSO
4and KMnO
4mixing, water-soluble, adding solubility acid-conditioning solution pH value is 0 ~ 2, wherein MnSO
4in manganese and KMnO
4mol ratio be 0.5 ~ 2.0;
After mixed solution stirring at room temperature 0.5 ~ 2h that step (1 ") obtains by (2 "), solution is moved in stainless steel cauldron that liner is polytetrafluoroethylene (PTFE), under 80 ~ 200 DEG C of conditions, react 1 ~ 36h;
(3 ") by step (2 ") products therefrom centrifuge washing 1 ~ 5 time, dry 10 ~ 30h at 60 ~ 200 DEG C;
Dried product in 300 ~ 900 DEG C of air atmosphere roastings, is obtained the manganese-base oxide catalyst for catalytic oxidation of alcohol by (4 ").
Manganous salt is MnSO
4, pH value is 0 ~ 1, and oxidant is KMnO
4, hydrothermal temperature is 100 DEG C, and the hydro-thermal reaction time is 24h, and sintering temperature is 400 DEG C.The manganese-base oxide catalyst for catalytic oxidation of alcohol using this optimum condition to prepare, fixed bed reactors is investigated different manganous salt presoma on the impact of catalyst activity.The consumption of catalyst is 50mg, reacts and carries out at normal pressure, and ethanol entrance port concentration is 800ppm, and gas flow is 50mL/min.Use is furnished with the concentration of chromatography of gases detection Export Ethanol, carbon dioxide and the acetaldehyde byproduct of thermal conductivity detector (TCD) (TCD).Result shows: under catalysis the same terms, with MnSO
4for the manganese-base oxide catalyst that manganous salt prepares, the complete oxidation to ethanol when 120 DEG C, can be realized, when 140 DEG C, CO
2production rate can reach 100%.With Mn (CH
3cOO)
2manganese oxide catalyst for precursor power realizes ethanol complete oxidation being CO
2temperature be 180 DEG C.
Two of object of the present invention is to provide a kind of manganese-base oxide catalyst for catalytic oxidation of alcohol, and described manganese-base oxide catalyst is prepared by method as above.Described manganese-base oxide catalyst has high activity to catalytic oxidation of alcohol, can be used for indoor alcohol gas and the remaining alcohol gas of motor-vehicle tail-gas is eliminated.
Three of object of the present invention is to provide a kind of as above for the purposes of the manganese-base oxide catalyst of catalytic oxidation of alcohol, and described manganese-base oxide catalyst is used for catalytic oxidation of alcohol.Described manganese-base oxide catalyst is preferably applicable to the elimination of indoor alcohol gas and the remaining alcohol gas of motor-vehicle tail-gas.
Preferably, by described manganese-base oxide catalyst cupport on active carbon, metal or ceramic monolith, loaded catalyst is obtained, for catalytic oxidation of alcohol.Manganese-base oxide catalyst of the present invention is active component, active carbon, metal or pottery are as carrier, according to the preparation method of loaded catalyst disclosed in prior art, obtain loaded catalyst, then this loaded catalyst is used for catalytic oxidation of alcohol gas.
Preferably, by described manganese-base oxide catalyst and shaping assistant extruded, for catalytic oxidation of alcohol.Manganese-base oxide catalyst for catalytic oxidation of alcohol of the present invention is oxide catalyst, and it does not need carrier, also can reach corresponding dispersion and catalytic effect.
Compared with prior art, the present invention has following beneficial effect:
(1), when adopting the manganese-base oxide catalyst ethanol for catalytic oxidation of alcohol of the present invention, carrier is not needed can to reach corresponding dispersion and catalytic effect yet;
(2) the manganese-base oxide catalyst for catalytic oxidation of alcohol of the present invention has high activity in low-temperature zone (being less than 150 DEG C), is applicable to the elimination not consuming alcohol gas and indoor alcohol gas completely of motor vehicle worst cold case section;
(3) after improving ethanol gas concentration (5000ppm), manganese-base oxide catalyst for catalytic oxidation of alcohol of the present invention still maintains greater activity, catalyst life is long, the durability experiment test of continuous 50 hours, reactivity does not reduce, after 100h activity rating, catalyst still keeps initial activity;
(4) the manganese-base oxide catalyst for catalytic oxidation of alcohol of the present invention has good anti humility performance, can be used in certain humidity (containing the H of 10%
2o) removal of ethanol under;
(5) described method adopts nontoxic component, decreases the harm to health and ecological environment;
(6) the present invention adopts hydrothermal synthesis method to prepare OMS-2 catalyst for catalytic oxidation of alcohol, and its activity is better than using MnAC
2for catalyst prepared by manganous salt, and hydrothermal synthesis reaction carries out in a kettle., simple to operate, and reaction temperature low (100 DEG C) energy consumption is low, does not need buffer solution, and repeatability is high.
Detailed description of the invention
For better the present invention being described, be convenient to understand technical scheme of the present invention, typical but non-limiting embodiment of the present invention is as follows:
Embodiment 1
For a preparation method for the manganese-base oxide catalyst of catalytic oxidation of alcohol, described method is hydrothermal synthesis method, comprises the steps:
(1) by manganese sulfate and potassium permanganate mixing, water-soluble, adjust ph is 0.2, and the bivalent manganese in manganese sulfate and the mol ratio of potassium permanganate are 0.5;
(2) after mixed solution stirring at room temperature 0.5h step (1) obtained, at 80 DEG C of reaction 36h;
(3) by step (2) products therefrom centrifuge washing 1 time, dry 30h in the baking oven of 60 DEG C;
(4) by the roasting in 300 DEG C of air atmospheres of dried product, the manganese-base oxide catalyst for catalytic oxidation of alcohol is obtained.
Fixed bed reactors are investigated the performance of this catalyst.The consumption of catalyst is 50mg, reacts and carries out at normal pressure, and ethanol entrance port concentration is 800ppm, and gas flow is 50mL/min.Use is furnished with the concentration of chromatography of gases detection Export Ethanol, carbon dioxide and the acetaldehyde byproduct of thermal conductivity detector (TCD) (TCD).Result shows: can realize the complete oxidation to ethanol during this catalyst 120 DEG C, when 140 DEG C, and CO
2production rate can reach 100%.
Embodiment 2
For a preparation method for the manganese-base oxide catalyst of catalytic oxidation of alcohol, described method is hydrothermal synthesis method, comprises the steps:
(1) by manganese acetate and sodium thiosulfate mixing, water-soluble, adjust ph is 2, and the bivalent manganese in manganese acetate and the mol ratio of sodium thiosulfate are 2.0;
(2) after mixed solution stirring at room temperature 2h step (1) obtained, at 200 DEG C of reaction 1h;
(3) by step (2) products therefrom centrifuge washing 5 times, dry 10h in the baking oven of 200 DEG C;
(4) by the roasting in 900 DEG C of air atmospheres of dried product, the manganese-base oxide catalyst for catalytic oxidation of alcohol is obtained.
Fixed bed reactors are investigated the performance of this catalyst.The consumption of catalyst is 50mg, reacts and carries out at normal pressure, and ethanol entrance port concentration is 800ppm, and gas flow is 50mL/min.Use is furnished with the concentration of chromatography of gases detection Export Ethanol, carbon dioxide and the acetaldehyde byproduct of thermal conductivity detector (TCD) (TCD).Result shows: can realize the complete oxidation to ethanol during this catalyst 180 DEG C, when 200 DEG C, and CO
2production rate can reach 100%.
Embodiment 3
For a preparation method for the manganese-base oxide catalyst of catalytic oxidation of alcohol, described method is hydrothermal synthesis method, comprises the steps:
(1) by manganese chloride and sodium chlorate mixing, water-soluble, adjust ph is 1, and the bivalent manganese in manganese chloride and the mol ratio of sodium thiosulfate are 1.5;
(2) after mixed solution stirring at room temperature 1h step (1) obtained, at 150 DEG C of reaction 15h;
(3) by step (2) products therefrom centrifuge washing 3 times, dry 16h in the baking oven of 120 DEG C;
(4) by the roasting in 500 DEG C of air atmospheres of dried product, the manganese-base oxide catalyst for catalytic oxidation of alcohol is obtained.
Fixed bed reactors are investigated the performance of this catalyst.The consumption of catalyst is 50mg, reacts and carries out at normal pressure, and ethanol entrance port concentration is 800ppm, and gas flow is 50mL/min.Use is furnished with the concentration of chromatography of gases detection Export Ethanol, carbon dioxide and the acetaldehyde byproduct of thermal conductivity detector (TCD) (TCD).Result shows: can realize the complete oxidation to ethanol during this catalyst 150 DEG C, when 170 DEG C, and CO
2production rate can reach 100%.
It should be noted that and understand, when not departing from the spirit and scope of the present invention required by accompanying claim, various amendment and improvement can be made to the present invention of foregoing detailed description.Therefore, the scope of claimed technical scheme is not by the restriction of given any specific exemplary teachings.
Applicant states, the present invention illustrates method detailed of the present invention by above-described embodiment, but the present invention is not limited to above-mentioned method detailed, does not namely mean that the present invention must rely on above-mentioned method detailed and could implement.Person of ordinary skill in the field should understand, any improvement in the present invention, to equivalence replacement and the interpolation of auxiliary element, the concrete way choice etc. of each raw material of product of the present invention, all drops within protection scope of the present invention and open scope.