CN105709837A - Heteropoly acid ammonium salt catalyst and preparation method thereof - Google Patents
Heteropoly acid ammonium salt catalyst and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a heteropoly acid ammonium salt catalyst and a preparation method thereof. The catalyst comprises an active component, an assistant and a carrier. The active component is heteropoly acid ammonium salt, the assistant is nickel oxide, and the carrier is silicon oxide. The catalyst provided by the invention is especially suitable for the reaction of preparing ethylene by dehydration with low concentration ethanol aqueous solution as the raw material. The catalyst not only has the characteristics of high low temperature activity, good selectivity, and strong carbon deposition resistant ability, but also has good stability.
Description
Technical field
The present invention relates to a kind of heteropoly acid ammonium salt catalyst and method for making thereof, particularly relate to a kind of carried heteropoly acid ammonium salt in catalysis agent for producing ethylene by ethanol dehydration and method for making thereof.
Background technology
Ethylene is as the flagship product of basic Organic Chemicals and petro chemical industry, and the chemical products of about 75% prepare with ethylene for raw material, and therefore the size of ethylene yield has become as the important symbol weighing a national oil development of chemical industry level.Traditional ethylene obtains mainly by light petroleum fraction cracking, heavy dependence petroleum resources.Along with the day of international energy situation is becoming tight, petroleum resources are increasingly exhausted, and developing new renewable alternative energy source has been the task of top priority.
Many-sided advantages such as recently, ethanol particularly recyclable organism preparing ethylene by dehydrating ethanol is increasingly subject to people's attention, and it has green, sustainable, reaction condition is gentle and product ethylene purity is high.Bio-ethanol is mainly derived from the fermentation of agricultural byproducts, can avoid the dependence to petroleum resources, continues to use this method in the country that some petroleum resources such as Brazil, India, Pakistan are deficient always and produces ethylene, and more there is realistic meaning in the country of oil-poor and few oil by this point.Preparing ethylene by dehydrating ethanol has the great potential partly or entirely replacing obtaining ethylene from oil.Therefore, research producing ethylene from dehydration of ethanol has great economic worth and strategic importance.
Catalyst for ethanol delydration to ethylene report is a lot, mainly activated alumina, molecular sieve and heteropoly acid etc..Activated alumina is as catalyst low price, and activity and selectivity is better, but reaction temperature is high, and reaction velocity is low, and energy consumption is high, and utilization rate of equipment and installations is low.The catalysis activity and selectivity of molecular sieve is high, stable；Reaction temperature is low, and reaction velocity is big, but catalyst life is short, and amplification is little, limits its industrialized production.Heteropoly acid is with certain structure oxygen-containing polyprotic acid by oxygen atom ligand bridging by central atom and coordination atom, has the advantages such as highly acid.In producing ethylene from dehydration of ethanol reacts, it is low that heteropolyacid catalyst has reaction temperature, the feature that selectivity is high and yield is high.
Li Benxiang etc. [Chemical Engineering Technology and exploitation, 2010,5 (39): 7-9] report the article being entitled as MCM-41 load Catalyzed by Silicotungstic Acid producing ethylene from dehydration of ethanol, and catalyst adopts infusion process to prepare.CN200910057539.X discloses the catalyst of a kind of producing ethylene from dehydration of ethanol.This catalyst is with aluminium oxide for carrier, and active component is heteropoly acid, adopts kneading method to prepare.Above-mentioned catalyst, when with high concentration ethanol for raw material, shows higher catalysis activity and selectivity, but when with low-concentration ethanol for raw material, catalyst activity is decreased obviously, and stability is bad.
Summary of the invention
In order to overcome weak point of the prior art, the invention provides a kind of heteropoly acid ammonium salt catalyst and method for making thereof.The feature that this catalyst not only has low temperature active height, selectivity is good, carbon accumulation resisting ability is strong, and good stability.
Heteropoly acid ammonium salt catalyst of the present invention, including active component, auxiliary agent and carrier, active component is that ammonium heteropoly acids is shown in formula (1), and auxiliary agent is nickel oxide, and carrier is silicon oxide；With the weight of catalyst for benchmark, the content of ammonium heteropoly acids is 3% ~ 35%, it is preferred to 12% ~ 30%, more preferably 18% ~ 30%, the content that auxiliary agent is counted with oxide is for 3% ~ 18%, it is preferred to 5% ~ 15%, the content of carrier is 47% ~ 94%, it is preferred to 55% ~ 83%, more preferably 55% ~ 77%；
Hm(NH4)nYX12O40(1)
Wherein X represents W or Mo, Y and represents Si or P；When Y represents Si, m+n=4, n value is 0.1 ~ 1.0；When Y represents P, m+n=3, n value is 0.1 ~ 1.0.
In described catalyst, ammonium heteropoly acids is the distribution in eggshell type on silica support, and namely ammonium heteropoly acids is distributed in the outer surface of silica support, and is substantially free of ammonium heteropoly acids in catalyst duct.
The character of described silica support is as follows: specific surface area is 500 ~ 820m2/ g, pore volume is 0.62 ~ 0.92mL/g, and average pore diameter is 4.6 ~ 6.6nm.
The preparation method of described heteropoly acid ammonium salt catalyst, including:
(1) auxiliary agent precursor water solution is joined in silica support, stir at 60 DEG C ~ 90 DEG C to solution and be evaporated；
(2) solid step (1) obtained is at 90 DEG C ~ 120 DEG C dry 3h ~ 12h, then at 300 DEG C ~ 500 DEG C roasting 2h ~ 6h, prepares catalyst precarsor A；
(3) catalyst precarsor A is joined in autoclave, adopt hydrogen that it is carried out reduction treatment；
(4) polyhydric alcohol solutions is driven in autoclave, then regulates Hydrogen Vapor Pressure to 2～4MPa, at 200～300 DEG C, react 0.5～5.0h；
(5) catalyst precarsor A reacted in step (4) is filtered out, at 20 DEG C ~ 50 DEG C, it is preferred to be dried at 30 DEG C ~ 50 DEG C, until sample surfaces is without liquid phase, obtain catalyst precarsor B；
(6) the catalyst precarsor B that step (5) obtains is joined in aqueous solutions of organic acids, stir at 60 DEG C ~ 90 DEG C and be evaporated to solution, obtain catalyst precarsor C；
(7) the catalyst precarsor C that step (6) obtains is joined in the alkaline solution containing ammonium, through filtering, dry at 50 DEG C ~ 90 DEG C；Or material step (6) obtained adsorbs ammonia at 50 DEG C ~ 90 DEG C, obtains catalyst precarsor D；
(8) aqueous solution of heteropoly acid is joined in the catalyst precarsor D that step (7) obtains, stir at 60 DEG C ~ 90 DEG C to solution and be evaporated；
(9) solid step (8) obtained is at 90 DEG C ~ 120 DEG C dry 3h ~ 12h, then at 300 DEG C ~ 550 DEG C roasting 2h ~ 6h, obtains catalyst.
Silica support described in step (1) is adopted and is prepared with the following method:
A, template is joined containing in organic acid aqueous solution, obtain solution I；
B, silicon source is joined in solution I, obtain solution II, then stir to becoming gel at 60 DEG C ~ 90 DEG C；
C, by gel aging 8h ~ 24h, drying at 20 DEG C ~ 50 DEG C, make silica support.
In step A, described template is cetyl trimethylammonium bromide, hexadecyltrimethylammonium chloride, sodium lauryl sulphate, triblock polymer P123, triblock polymer F127, triblock polymer F108, molecular weight be 1000 ~ 10000 Polyethylene Glycol in one or more, described template and SiO in carrier2Mol ratio be 0.01 ~ 1.2；Described organic acid is one or more in citric acid, tartaric acid, malic acid, SiO in described organic acid and carrier2Mol ratio be 0.1 ~ 1.2.
In step B, described silicon source is one or more in tetraethyl orthosilicate, Ludox.
In step C, described silica support can make the silica support of molding, it is also possible to being the silica support not needing molding, those skilled in the art determine according to selected technique.The silica support of molding, it is possible to adopt existing conventional molding techniques to carry out molding, such as extruded moulding, compression molding etc., shape can be bar shaped, spherical, lamellar etc..In forming process, it is possible to adding binding agent and shaping assistant as required, binding agent is generally adopted little porous aluminum oxide.Shaping assistant is peptizer, extrusion aid etc. such as.After step C dries, it is possible to through molding or without molding, obtain silica support then through high-temperature roasting.
In step C, described dry and roasting adopts usual manner to carry out, and the dry condition being generally adopted is as follows: 90 DEG C ~ 120 DEG C dry 3h ~ 12h, roasting is typically in 300 DEG C ~ 800 DEG C roasting 2h ~ 6h.
In step (1), the described nickel salt that auxiliary agent presoma is solubility, be generally in nickel nitrate, nickel acetate one or more.
In step (3), described reduction treatment process is as follows: catalyst precarsor is warming up under hydrogen atmosphere 300 DEG C～600 DEG C, processes 4h～8h under 0.1MPa～0.5MPa.Wherein reduction treatment can adopt pure hydrogen, it would however also be possible to employ the hydrogen containing noble gas, and hydrogen volume concentration is 30% ~ 100%.
In step (4), described polyhydric alcohol is one or more in C5～C10 polyhydric alcohol, it is preferable that one or more in xylitol, sorbitol, mannitol, arabitol；The mass concentration of polyhydric alcohol solutions is 5%～30%.The mass ratio of the addition of polyhydric alcohol and catalyst precarsor A is 3:1 ~ 10:1.
In step (6), described organic acid is one or more in citric acid, tartaric acid, malic acid.Described organic acid and SiO in carrier2Mol ratio be 0.05 ~ 0.50.
In step (7), being joined in the alkaline solution containing ammonium by the catalyst precarsor C that step (6) obtains and impregnate, dip time is generally 5min ~ 30min.Catalyst precarsor C step (6) obtained adsorbs ammonia, and adsorption time is generally 5min ~ 30min.In step (7), the described alkaline solution containing ammonium is one or more in ammonia, sal volatile, ammonium bicarbonate soln.
In step (7), described ammonia can adopt pure ammonia, it would however also be possible to employ the gaseous mixture containing ammonia, and in mixing gas except ammonia, other is one or more in noble gas such as nitrogen, argon etc..
In step (8), described heteropoly acid is one or more in phosphotungstic acid, silico-tungstic acid, phosphomolybdic acid.
Can also adding mesopore molecular sieve, one or more in such as SBA-15, SBA-3, MCM-41 etc. in described silica support, molecular sieve weight content in the carrier, below 10%, is generally 1% ~ 8%.Mesopore molecular sieve can introduce before silicon oxide plastic, it is also possible to introduces in plastic process, it is also possible to introduces after silicon oxide plastic, it is also possible in silica support forming process, kneading introduces.
A kind of method that present invention also offers producing ethylene by ethanol dehydration, wherein adopts the catalyst of the present invention.Catalyst of the present invention is particularly well-suited to the Dehydration ethylene reaction that low-concentration ethanol aqueous solution is raw material, and ethanol water concentration is 5wt% ~ 40wt%.The method of described producing ethylene by ethanol dehydration can adopt fixed-bed process, and its reaction condition is as follows: mass space velocity 0.5h-1~12.0h-1, reaction temperature 180 DEG C ~ 400 DEG C.
Catalyst of the present invention adopts the silica support of bigger serface, utilize the hydrogenation of auxiliary agent nickel, catalytic polyol liquid-phase hydrogenatin in autoclave, mainly there are two aspect effects: the liquid alkane that first polyhydric alcohol liquid-phase hydrogenatin generates adsorbs on a catalyst support, can effectively block the duct of carrier, make the heteropoly acid ammonium of follow-up load be distributed on carrier outer surface；On the other hand, polyhydric alcohol liquid-phase hydrogenatin can produce carbon distribution on carrier, the acidity of carrier can be weakened to a certain extent, reduce the quantity of support acidity position absorption ammonia, make heteropoly acid main and ammonium salt organic acid reacts generation ammonium heteropoly acids, contribute to ammonium heteropoly acids dispersed at carrier outer surface, and above-mentioned carbon deposit can be removed through follow-up high-temperature roasting, so effectively remain this Component Vectors acidic site.The feature that the catalyst that the inventive method obtains not only has low temperature active height, selectivity is good, carbon accumulation resisting ability is strong, and good stability.
Detailed description of the invention
Below in conjunction with embodiment, the present invention is described in detail.In the present invention, wt% is mass fraction.
Embodiment 1
(1) preparation of carrier:
Weigh 145.8g cetyl trimethylammonium bromide and 205g citric acid is made into mixed solution, 302mL tetraethyl orthosilicate is joined in mixed solution, stirring 2h, then stirs to becoming gel, by gel aging 12h at 40 DEG C at 70 DEG C, then dry 8h at 110 DEG C, after compression molding, at 580 DEG C of roasting 3h, obtain silica support, wherein cetyl trimethylammonium bromide is 0.3 with the mol ratio of silicon oxide, and the mol ratio of citric acid and silicon oxide is 0.8.Support is: specific surface area is 525m2/ g, pore volume is 0.64mL/g, and average pore diameter is 4.9nm.
(2) preparation of catalyst:
31.1g nickel nitrate is dissolved in deionized water, join in 77g silica support, stir at 70 DEG C to solution and be evaporated, by the solid that obtains at 110 DEG C of dry 8.0h, then at 400 DEG C of roasting 3.0h, prepare catalyst precarsor A, it is then added in autoclave, 450 DEG C it are warming up under hydrogen atmosphere, 4h is processed under 0.3MPa, it is down to reaction temperature, adding 400g mass concentration is the sorbitol solution of 20%, then Hydrogen Vapor Pressure is regulated to 3MPa, 3h is reacted at 260 DEG C, after reaction terminates, by catalyst filtration out, carrier surface it is dried to without liquid phase at 40 DEG C；It is then added to containing in 37.0g Fructus Citri Limoniae aqueous acid, stirs at 70 DEG C to solution and be evaporated；The material obtained joins dipping 10min in sal volatile, dry at 60 DEG C after filtration；It is then added in the aqueous solution containing 15.6g phosphotungstic acid, stirs at 70 DEG C to solution and be evaporated；By the solid that obtains at 110 DEG C of dry 8.0h, then at 500 DEG C of roasting 3.0h, prepare (NH4)0.5H2.5PW12O40-NiO/SiO2Catalyst, wherein NiO content is 8wt%, (NH4)0.5H2.5PW12O40Content is 15wt%.
(3) catalyst characterization:
Surrounding and centre in catalyst granules cross section take a little, by SEM, each point is carried out elementary analysis, result shows: the heteropoly acid ammonium salt content at surrounding each point place is substantially suitable, and centre each point is not detected by ammonium heteropoly acids, the catalyst adopting the method to prepare is described, the dispersion that ammonium heteropoly acids has had on catalyst surface, and be not impregnated with in duct.
(4) evaluation of catalyst:
Evaluating catalyst carries out in atmospheric fixed bed tubular reactor, and raw material is 20wt% ethanol water, mass space velocity 4h-1, reaction temperature 250 DEG C.Before reaction, catalyst is at N2Activating 2h in 400 DEG C under protection, be then down to after reaction temperature starts to react 4 hours, product is analyzed by gas chromatogram, calculates ethanol conversion and ethylene selectivity, and result is in Table 1.
Embodiment 2
(1) preparation of carrier:
Weigh 200g cetyl trimethylammonium bromide and 105.7g citric acid is made into mixed solution, 250mL tetraethyl orthosilicate is joined in mixed solution, stirring 2h, then stir at 70 DEG C to becoming gel, by gel aging 12h at 40 DEG C, then dry 8h at 110 DEG C, at 600 DEG C of roasting 3h after compression molding, obtaining silica support, wherein cetyl trimethylammonium bromide is 0.5 with the mol ratio of silicon oxide, and the mol ratio of citric acid and silicon oxide is 0.5.Support is: specific surface area is 570m2/ g, pore volume is 0.72mL/g, and average pore diameter is 5.1nm.
(2) preparation of catalyst:
38.9g nickel nitrate is dissolved in deionized water, join in 70g silica support, stir at 70 DEG C to solution and be evaporated, by the solid that obtains at 110 DEG C of dry 8.0h, then at 400 DEG C of roasting 3.0h, prepare catalyst precarsor A, it is then added in autoclave, 450 DEG C it are warming up under hydrogen atmosphere, 4h is processed under 0.3MPa, it is down to reaction temperature, adding 400g mass concentration is the sorbitol solution of 20%, then Hydrogen Vapor Pressure is regulated to 3MPa, 2h is reacted at 300 DEG C, after reaction terminates, by catalyst filtration out, carrier surface it is dried to without liquid phase at 40 DEG C；It is then added to containing in 56.0g Fructus Citri Limoniae aqueous acid, stirs at 70 DEG C to solution and be evaporated；The material obtained joins dipping 10min in sal volatile, dry at 60 DEG C after filtration；It is then added in the aqueous solution containing 20.7g phosphotungstic acid, stirs at 70 DEG C to solution and be evaporated；By the solid that obtains at 110 DEG C of dry 8.0h, then at 470 DEG C of roasting 3.0h, prepare (NH4)0.7H2.3PW12O40-NiO/SiO2Catalyst, wherein NiO content is 10wt%, (NH4)0.7H2.3PW12O40Content is 20wt%.
(3) evaluation of catalyst:
Evaluating catalyst carries out in atmospheric fixed bed tubular reactor, and raw material is 20wt% ethanol water, mass space velocity 4h-1, reaction temperature 240 DEG C.Before reaction, catalyst is at N2Activating 2h in 400 DEG C under protection, be then down to after reaction temperature starts to react 4 hours, product is analyzed by gas chromatogram, calculates ethanol conversion and ethylene selectivity, and result is in Table 1.
Embodiment 3
(1) preparation of carrier:
Weigh 316g cetyl trimethylammonium bromide and 62.4g citric acid is made into mixed solution, 246mL tetraethyl orthosilicate is joined in mixed solution, stirring 2h, then stir at 70 DEG C to becoming gel, by gel aging 12h at 40 DEG C, then dry 8h at 110 DEG C, at 650 DEG C of roasting 3h after compression molding, obtaining silica support, wherein cetyl trimethylammonium bromide is 0.8 with the mol ratio of silicon oxide, and the mol ratio of citric acid and silicon oxide is 0.3.Support is: specific surface area is 630m2/ g, pore volume is 0.81mL/g, and average pore diameter is 5.1nm.
(2) preparation of catalyst:
46.7g nickel nitrate is dissolved in deionized water, join in 63g silica support, stir at 70 DEG C to solution and be evaporated, by the solid that obtains at 110 DEG C of dry 8.0h, then at 400 DEG C of roasting 3.0h, prepare catalyst precarsor A, it is then added in autoclave, 450 DEG C it are warming up under hydrogen atmosphere, 4h is processed under 0.3MPa, it is down to reaction temperature, adding 400g mass concentration is the sorbitol solution of 20%, then Hydrogen Vapor Pressure is regulated to 3MPa, 2h is reacted at 300 DEG C, after reaction terminates, by catalyst filtration out, carrier surface it is dried to without liquid phase at 40 DEG C；It is then added to containing in 70.6g Fructus Citri Limoniae aqueous acid, stirs at 70 DEG C to solution and be evaporated；The material obtained joins dipping 10min in sal volatile, dry at 60 DEG C after filtration；It is then added in the aqueous solution containing 25.9g phosphotungstic acid, stirs at 70 DEG C to solution and be evaporated；By the solid that obtains at 110 DEG C of dry 8.0h, then at 520 DEG C of roasting 3.0h, prepare (NH4)0.2H2.8PW12O40-NiO/SiO2Catalyst, wherein NiO content is 12wt%, (NH4)0.2H2.8PW12O40Content is 25wt%.
(3) evaluation of catalyst:
Evaluating catalyst carries out in atmospheric fixed bed tubular reactor, and raw material is 20wt% ethanol water, mass space velocity 7h-1, reaction temperature 240 DEG C.Before reaction, catalyst is at N2Activating 2h in 400 DEG C under protection, be then down to after reaction temperature starts to react 4 hours, product is analyzed by gas chromatogram, calculates ethanol conversion and ethylene selectivity, and result is in Table 1.
Embodiment 4
In embodiment 3, changing cetyl trimethylammonium bromide into 628gP123, all the other are with embodiment 3, and gained catalyst is (NH4)0.2H2.8PW12O40-NiO/SiO2Catalyst, wherein NiO content is 12wt%, (NH4)0.2H2.8PW12O40Content is 25wt%, P123 and SiO2Mol ratio be 0.1.Support is: specific surface area is 610m2/ g, pore volume is 0.84mL/g, and average pore diameter is 5.5nm.
The evaluation of catalyst with embodiment 3, ethanol conversion and ethylene selectivity result in Table 1.
Embodiment 5
In embodiment 3, change phosphotungstic acid into silico-tungstic acid, sal volatile impregnates 10min and changes suction into
Attached 10v%NH3/ Ar gaseous mixture 10min, all the other are with embodiment 3, and gained catalyst is (NH4)0.2H3.8SiW12O40-NiO/SiO2, wherein NiO content is 12wt%, (NH4)0.2H3.8SiW12O40Content is 25wt%.
The evaluation of catalyst with embodiment 3, ethanol conversion and ethylene selectivity result in Table 1.
Embodiment 6
(1) carrier of embodiment 3 preparation is selected:
(2) preparation of catalyst:
50.6g nickel nitrate is dissolved in deionized water, join in 59g silica support, stir at 70 DEG C to solution and be evaporated, by the solid that obtains at 110 DEG C of dry 8.0h, then at 400 DEG C of roasting 3.0h, prepare catalyst precarsor A, it is then added in autoclave, 450 DEG C it are warming up under hydrogen atmosphere, 4h is processed under 0.3MPa, it is down to reaction temperature, adding 400g mass concentration is the sorbitol solution of 20%, then Hydrogen Vapor Pressure is regulated to 3MPa, 2h is reacted at 300 DEG C, after reaction terminates, by catalyst filtration out, carrier surface it is dried to without liquid phase at 40 DEG C；It is then added to containing in 66.1g Fructus Citri Limoniae aqueous acid, stirs at 70 DEG C to solution and be evaporated；The material obtained joins dipping 10min in sal volatile, dry at 60 DEG C after filtration；It is then added in the aqueous solution containing 29.0g phosphotungstic acid, stirs at 70 DEG C to solution and be evaporated；By the solid that obtains at 110 DEG C of dry 8.0h, then at 520 DEG C of roasting 3.0h, prepare (NH4)0.2H2.8PW12O40-NiO/SiO2Catalyst, wherein NiO content is 13wt%, (NH4)0.2H2.8PW12O40Content is 28wt%.
(4) evaluation of catalyst:
Evaluating catalyst carries out in atmospheric fixed bed tubular reactor, and raw material is 20wt% ethanol water, mass space velocity 8h-1, reaction temperature 240 DEG C.Before reaction, catalyst is at N2Activating 2h in 400 DEG C under protection, be then down to after reaction temperature starts to react 4 hours, product is analyzed by gas chromatogram, calculates ethanol conversion and ethylene selectivity, and result is in Table 1.
Embodiment 7
Preparing catalyst according to embodiment 3, catalyst has carried out according to the appreciation condition of embodiment 3 the estimation of stability experiment of 100h, ethanol conversion and ethylene selectivity result are in Table 2.
Comparative example 1
In embodiment 3, carrier is added directly in the mixed aqueous solution containing 46.7g nickel nitrate and 25.9g phosphotungstic acid, stirs at 70 DEG C to solution and be evaporated；By the solid that obtains at 110 DEG C of dry 8.0h, then at 350 DEG C of roasting 3.0h, prepare H3PW12O40-NiO/SiO2Catalyst, wherein NiO content is 12wt%, H3PW12O40Content is 25wt%.
The evaluation of catalyst with embodiment 3, ethanol conversion and ethylene selectivity result in Table 1.
Comparative example 2
The silica support 63g of preparation in embodiment 3 is joined in C6 alkane solvent, impregnates 10min, then filter, at 40 DEG C, be dried to carrier surface without liquid phase；It is then added to containing in 70.6g Fructus Citri Limoniae aqueous acid, stirs at 70 DEG C to solution and be evaporated；The material obtained joins dipping 10min in sal volatile, dry at 60 DEG C after filtration；It is then added in the mixed aqueous solution containing 46.7g nickel nitrate and 25.9g phosphotungstic acid, stirs at 70 DEG C to solution and be evaporated；By the solid that obtains at 110 DEG C of dry 8.0h, then at 520 DEG C of roasting 3.0h, prepare (NH4)0.2H2.8PW12O40-NiO/SiO2Catalyst, wherein NiO content is 12wt%, (NH4)0.2H2.8PW12O40Content is 25wt%.
The evaluation of catalyst with embodiment 3, ethanol conversion and ethylene selectivity result in Table 1.
Comparative example 3
Preparing catalyst according to comparative example 1, catalyst has carried out according to the appreciation condition of embodiment 3 the estimation of stability experiment of 100h, ethanol conversion and ethylene selectivity result are in Table 2.
The conversion ratio of each example catalyst of table 1 and selectivity
| Embodiment | Conversion ratio, wt% | Selectivity, wt% |
| Embodiment 1 | 98.3 | 98.0 |
| Embodiment 2 | 98.2 | 98.0 |
| Embodiment 3 | 99.0 | 98.8 |
| Embodiment 4 | 99.4 | 99.2 |
| Embodiment 5 | 98.8 | 98.7 |
| Embodiment 6 | 99.3 | 99.1 |
| Comparative example 1 | 96.0 | 95.1 |
| Comparative example 2 | 96.4 | 96.2 |
Table 2 stability test evaluation result
| Embodiment | Conversion ratio, wt% | Selectivity, wt% |
| Embodiment 7 | 98.8 | 98.6 |
| Comparative example 3 | 83.1 | 82.0 |
From table 1 and table 2 result, the activity of catalyst of the present invention, selectivity and stability are significantly better than comparative example catalyst.
Claims (20)
1. a heteropoly acid ammonium salt catalyst, including active component, auxiliary agent and carrier, active component is that ammonium heteropoly acids is shown in formula (1), and auxiliary agent is nickel oxide, and carrier is silicon oxide；With the weight of catalyst for benchmark, the content of ammonium heteropoly acids is 3% ~ 35%, and the content that auxiliary agent is counted with oxide is for 3% ~ 18%, and the content of carrier is 47% ~ 94%；
Hm(NH4)nYX12O40(1)
Wherein X represents W or Mo, Y and represents Si or P；When Y represents Si, m+n=4, n value is 0.1 ~ 1.0；When Y represents P, m+n=3, n value is 0.1 ~ 1.0.
2. the catalyst described in claim 1, it is characterized in that: with the weight of catalyst for benchmark, the content 12% ~ 30% of ammonium heteropoly acids, the content that auxiliary agent is counted with oxide is for 5% ~ 15%, the content of carrier is 55% ~ 83%, it is preferable that as follows: with the weight of catalyst for benchmark, the content 18% ~ 30% of ammonium heteropoly acids, the content that auxiliary agent is counted with oxide is for 5% ~ 15%, and the content of carrier is 55% ~ 77%.
3. the catalyst described in claim 1, it is characterised in that: the character of described silica support is as follows: specific surface area is 500 ~ 820m2/ g, pore volume is 0.62 ~ 0.92mL/g, and average pore diameter is 4.6 ~ 6.6nm.
4. the catalyst described in claim 1, it is characterised in that: containing one or more in mesoporous molecular sieve SBA-15, SBA-3, MCM-41 in described silica support, molecular sieve weight content in the carrier is below 10%.
5. according to the arbitrary described catalyst of claim 1 ~ 4, it is characterised in that: in described catalyst, ammonium heteropoly acids is the distribution in eggshell type on silica support.
6. the preparation method of the arbitrary described catalyst of claim 1 ~ 5, including:
(1) auxiliary agent precursor water solution is joined in silica support, stir at 60 DEG C ~ 90 DEG C to solution and be evaporated；
(2) solid step (1) obtained is at 90 DEG C ~ 120 DEG C dry 3h ~ 12h, then at 300 DEG C ~ 500 DEG C roasting 2h ~ 6h, prepares catalyst precarsor A；
(3) catalyst precarsor A is joined in autoclave, adopt hydrogen that it is carried out reduction treatment；
(4) polyhydric alcohol solutions is driven in autoclave, then regulates Hydrogen Vapor Pressure to 2～4MPa, at 200～300 DEG C, react 0.5～5.0h；
(5) catalyst precarsor A reacted in step (4) is filtered out, be dried at 20 DEG C ~ 50 DEG C, until sample surfaces is without liquid phase, obtain catalyst precarsor B；
(6) the catalyst precarsor B that step (5) obtains is joined in aqueous solutions of organic acids, stir at 60 DEG C ~ 90 DEG C and be evaporated to solution, obtain catalyst precarsor C；
(7) the catalyst precarsor C that step (6) obtains is joined in the alkaline solution containing ammonium, through filtering, dry at 50 DEG C ~ 90 DEG C；Or material step (6) obtained adsorbs ammonia at 50 DEG C ~ 90 DEG C, obtains catalyst precarsor D；
(8) aqueous solution of heteropoly acid is joined in the catalyst precarsor D that step (7) obtains, stir at 60 DEG C ~ 90 DEG C to solution and be evaporated；
(9) solid step (8) obtained is at 90 DEG C ~ 120 DEG C dry 3h ~ 12h, then at 300 DEG C ~ 550 DEG C roasting 2h ~ 6h, obtains catalyst.
7. in accordance with the method for claim 6, it is characterised in that the silica support described in step (1) is adopted and prepared with the following method:
A, template is joined containing in organic acid aqueous solution, obtain solution I；
B, silicon source is joined in solution I, obtain solution II, then stir to becoming gel at 60 DEG C ~ 90 DEG C；
C, by gel aging 8h ~ 24h, drying at 20 DEG C ~ 50 DEG C, make silica support.
8. in accordance with the method for claim 7, it is characterized in that in step A, described template is cetyl trimethylammonium bromide, hexadecyltrimethylammonium chloride, sodium lauryl sulphate, triblock polymer P123, triblock polymer F127, triblock polymer F108, molecular weight be 1000 ~ 10000 Polyethylene Glycol in one or more, described template and SiO in carrier2Mol ratio be 0.01 ~ 1.2；Described organic acid is one or more in citric acid, tartaric acid, malic acid, SiO in described organic acid and carrier2Mol ratio be 0.1 ~ 1.2.
9. in accordance with the method for claim 7, it is characterised in that in step B, described silicon source is one or more in tetraethyl orthosilicate, Ludox.
10. in accordance with the method for claim 7, it is characterised in that: after step C dries, through molding or without molding, obtain silica support then through high-temperature roasting；In step C, described dry condition is as follows: at 90 DEG C ~ 120 DEG C dry 3h ~ 12h, the condition of roasting is as follows: at 300 DEG C ~ 800 DEG C roasting 2h ~ 6h.
11. in accordance with the method for claim 6, it is characterised in that in step (1), described auxiliary agent presoma is one or more in nickel nitrate, nickel acetate.
12. in accordance with the method for claim 6, it is characterised in that in step (3), described reduction treatment process is as follows: under hydrogen atmosphere, catalyst precarsor is warming up to 300 DEG C～600 DEG C, process 4h～8h under 0.1MPa～0.5MPa；Wherein reduction treatment adopts pure hydrogen, or adopts the hydrogen containing noble gas, and hydrogen volume concentration is 30% ~ 100%.
13. in accordance with the method for claim 6, it is characterised in that in step (4), described polyhydric alcohol is one or more in C5～C10 polyhydric alcohol, the mass concentration of polyhydric alcohol solutions is 5%～30%；The mass ratio of the addition of polyhydric alcohol and catalyst precarsor A is 3:1 ~ 10:1.
14. in accordance with the method for claim 6, it is characterised in that in step (4), described polyhydric alcohol is one or more in xylitol, sorbitol, mannitol, arabitol.
15. in accordance with the method for claim 6, it is characterised in that in step (6), described organic acid is one or more in citric acid, tartaric acid, malic acid, SiO in described organic acid and carrier2Mol ratio be 0.05 ~ 0.50.
16. in accordance with the method for claim 6, it is characterised in that in step (7), being joined in the alkaline solution containing ammonium by the catalyst precarsor C that step (6) obtains and impregnate, dip time is 5min ~ 30min；Catalyst precarsor C step (6) obtained adsorbs ammonia, and adsorption time is 5min ~ 30min；In step (7), the described alkaline solution containing ammonium is one or more in ammonia, sal volatile, ammonium bicarbonate soln；Described ammonia adopts pure ammonia, or adopts the gaseous mixture containing ammonia, and in mixing gas except ammonia, other is one or more in noble gas such as nitrogen, argon.
17. in accordance with the method for claim 6, it is characterised in that in step (8), described heteropoly acid is one or more in phosphotungstic acid, silico-tungstic acid, phosphomolybdic acid.
18. a method for producing ethylene by ethanol dehydration, wherein adopt the arbitrary described catalyst of claim 1 ~ 5.
19. in accordance with the method for claim 18, it is characterised in that: for the Dehydration ethylene reaction that low-concentration ethanol aqueous solution is raw material, ethanol water concentration is 5wt% ~ 40wt%.
20. the method described in claim 18 or 19, it is characterised in that: the reaction condition of described preparing ethylene by dehydrating ethanol is as follows: mass space velocity 0.5h-1~12.0h-1, reaction temperature 180 DEG C ~ 400 DEG C.
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