Summary of the invention
The purpose of this invention is to provide a kind of carbon-based solid acid catalyst that is easy in liquid-phase reaction system, disperse and preparation method thereof.
The preparation method of carbon-based solid acid catalyst provided by the invention comprises the steps:
1) metal oxide is placed carries out carbonization behind organic aqueous solution dipping and the evaporate to dryness and obtain carbon/complex oxide;
2) described carbon/complex oxide is carried out sulfonating reaction and obtain sulfonation carbon/complex oxide;
3) described sulfonation carbon/complex oxide and acid or alkali reaction are promptly got described carbon-based solid acid catalyst.
Among the above-mentioned preparation method, the described metal oxide of step 1) can be Al
2O
3, SiO
2And TiO
2In at least a; The particle diameter of described metal oxide and aperture can be 2nm-100nm and 5nm-15nm respectively.
Among the above-mentioned preparation method, the organic matter in the described organic aqueous solution of step 1) can be sucrose or starch; The quality percentage composition that described organic matter accounts for described organic aqueous solution can be 35%-40%, as 37.5%.
Among the above-mentioned preparation method, the time of the described dipping of step 1) can be 30 minutes-50 minutes, as 30 minutes or 45 minutes; Described evaporate to dryness carries out under water-bath; The temperature of described water-bath is 75 ℃-85 ℃, as 80 ℃.
Among the above-mentioned preparation method, the described carbonization of step 1) is carried out under inert gas, as nitrogen; The temperature of described carbonization is 500 ℃-800 ℃, as 500 ℃, 600 ℃ or 800 ℃; The time of described carbonization was 0.5 hour-1 hour, as 0.5 hour or 1 hour.
Among the above-mentioned preparation method, step 2) sulfonating agent of described sulfonating reaction is the benzene sulfonic acid diazol; The ratio of quality and the number of copies of carbon/complex oxide and sulfonating agent is (18-31) in the described sulfonating reaction: 1, as 31: 1 or 17: 1; The temperature of described sulfonating reaction is 0 ℃~5 ℃, as 0 ℃, 3 ℃ or 5 ℃; The time of described sulfonating reaction was 2 hours-8 hours, as 3 hours; The solvent of described sulfonating reaction is a water.
Among the above-mentioned preparation method, described benzene sulfonic acid diazol can be prepared by diazo-reaction by sulfanilic acid.
Among the above-mentioned preparation method, step 2) also comprise described sulfonation carbon/complex oxide is filtered, washs and dry step; The solvent of described washing is followed successively by water, N, dinethylformamide and acetone; The temperature of described drying is 100 ℃-120 ℃, as 110 ℃; The time of described drying is 6 hours-9 hours.
Among the above-mentioned preparation method, the described acid of step 3) can be hydrofluoric acid, and described alkali can be NaOH; Described sulfonation carbon/complex oxide can be 1 with the ratio of quality and the number of copies of acid: (5-10), and as 1: 7 or 1: 10; The ratio of quality and the number of copies of described sulfonation carbon/complex oxide and alkali can be 7: 4; The time of described reaction can be 2 hours-4 hours, as 3 hours; Described reaction also comprises filters described carbon-based solid acid catalyst, wash and dry step; The temperature of described drying is 100 ℃-120 ℃, as 110 ℃; The time of described drying was 6 hours-9 hours, as 8 hours.
Among the above-mentioned preparation method, step 1) also comprise one or many place described organic aqueous solution to flood described carbon/complex oxide and evaporate to dryness after the step of carbonization.Can obtain the different carbon/complex oxide of phosphorus content by carrying out the one or many above-mentioned steps, in order to the different carbon-based solid acid catalyst of preparation granularity.
The present invention also provides the carbon-based solid acid catalyst by method for preparing, and sulfonic content is 1.4mmol/g-1.7mmol/g in the described carbon-based solid acid catalyst, as 1.41mmol/g, 1.5mmol/g or 1.7mmol/g.
The preparation method of carbon-based solid acid catalyst provided by the invention all adopts raw material cheap and easy to get; Carbon-based solid acid catalyst by this method preparation has following advantage: 1) good dispersion, the dynamic laser scattering analysis shows, the carbon-based solid acid catalyst that the present invention makes can partly be dispersed into the granule of particle diameter tens to the hundreds of nanometer in the liquid phase methylalcohol reaction system.Transmission electron microscope photo shows that the granule that is dispersed into has the structure of thin-walled porous.Compare with the sulfonation active carbon, catalyst of the present invention has better dispersiveness in methyl alcohol, helps contacting of reactant and catalytic active center.Therefore, though active sites density is close with the sulfonation active carbon, catalyst of the present invention demonstrates higher activity in the esterification of oleic acid and methyl alcohol.2) catalytic activity height, Amberlyst-15 compares with the conventional solid acid catalyst, activity of such catalysts bit density of the present invention has only 1/3rd of Amberlyst-15, but in the esterification of oleic acid and methyl alcohol, reactant transformation frequency (TOF) is seven times of Amberlyst-15.This is not only because catalyst of the present invention has good dispersiveness, and also because carbon-based solid acid is compared with resin, surface hydrophobic is stronger, and the water that more helps the esterification generation is from the catalyst surface desorption, thus the raising reaction rate.
The specific embodiment
Employed experimental technique is conventional method if no special instructions among the following embodiment.
Used material, reagent etc. if no special instructions, all can obtain from commercial channels among the following embodiment.
Used active carbon is available from Beijing Fine Chemical Works energetically in the following Comparative Examples of the present invention; Used sulfonic group ion exchange resin Amberlyst-15 is available from Acros Organics company.
The particle diameter of used silica, aluminium oxide and titanium oxide is 2nm-100nm among the following embodiment of the present invention; The aperture is 5nm-15nm.
The preparation of embodiment 1, carbon-based solid acid catalyst and the catalytic effect in catalytic esterification thereof
1) the 9g aluminium oxide is placed the aqueous sucrose solution (the quality percentage composition of sucrose is 37.5%) that contains 2.7g sucrose, left standstill after the stirring 45 minutes, evaporate to dryness obtains pressed powder under 80 ℃ of water-baths.The gained pressed powder is carried out carbonization 1 hour under under the nitrogen protection 600 ℃, obtain the black solid powder and be carbon/alumina compound 9.3g;
2) get the 0.22g sulfanilic acid, make its dissolving with 4ml hydrochloric acid (1mol/L) and 30ml deionized water, and place 0 ℃ of ice-water bath, add the 88mg natrium nitrosum again, leave standstill after the stirring and it was fully reacted in 15 minutes, obtain containing the settled solution of 0.22g benzene sulfonic acid diazol;
Get the black solid powder 6.7g of step 1), add the 40ml deionized water, place 0 ℃ of ice-water bath; Add above-mentioned settled solution (wherein under the electromagnetic agitation, the mass ratio of carbon/alumina compound and benzene sulfonic acid diazol is 31: 1), continue stirring reaction after 3 hours, filter, the gained black powder is used deionized water, N successively, dinethylformamide and acetone washing are dried down in 110 ℃ then and were promptly got sulfonation carbon/alumina compound 6.9g in 8 hours;
3) with step 2) sulfonation carbon/alumina compound 6.9g mix with 50ml hydrofluoric acid (sulfonation carbon/alumina compound is 1: 7 with the mass ratio of hydrofluoric acid) and stirred 3 hours, filter once more, spend deionised water to neutral, promptly got carbon-based solid acid catalyst in 8 hours in 110 ℃ of oven dry, wherein, sulfonic content is 1.41mmol/g.
Get above-mentioned solid acid 50mg, add in the 20ml hydrothermal reaction kettle with 8ml absolute methanol and 1g oleic acid, reaction is 2 hours under 77 ℃ of water-bath electromagnetic agitation, obtains methyl oleate, and the productive rate that gets methyl oleate is 91%.System to above-mentioned esterification is carried out the laser light scattering analysis, and Fig. 2 is the following particle diameter distribution map of dynamic light scattering 1 μ m of the carbon-based solid acid of present embodiment preparation.Analyzed as can be known by this, the hydrodynamic radius of this carbon-based solid acid mainly is distributed between the 57nm-1149nm, and mean radius is 265nm.System to above-mentioned esterification is carried out transmission electron microscope analysis, and Fig. 1 is the transmission electron microscope photo of the carbon-based solid acid of present embodiment preparation, and this photo shows that this carbon-based solid acid has the granule of thin-walled loose structure.
The preparation of embodiment 2, carbon-based solid acid catalyst and the catalytic effect in catalytic esterification thereof
1) the 6g titanium oxide is placed the aqueous sucrose solution (the quality percentage composition of sucrose is 37.5%) that contains 1.8g sucrose, left standstill after the stirring 45 minutes, evaporate to dryness obtains pressed powder under 80 ℃ of water-baths.The gained pressed powder is carried out carbonization 0.5 hour under under the nitrogen protection 500 ℃, obtain the black solid powder and be carbon/titanium oxide compound 6.2g;
Gained 3g carbon/titanium oxide compound is placed the aqueous sucrose solution (the quality percentage composition of sucrose is 37.5%) that contains 0.9g sucrose once more, left standstill after the stirring 45 minutes, evaporate to dryness obtains pressed powder under 80 ℃ of water-baths.The gained pressed powder is carried out carbonization 0.5 hour under under the nitrogen protection 500 ℃, obtain the black solid powder and be carbon/titanium oxide compound 3.1g;
2) get the black solid powder 3.7g of step 1), add the 40ml deionized water, place 5 ℃ of ice-water baths; Add the settled solution (preparation of benzene sulfonic acid diazol is with step 2 among the embodiment 1) that contains 0.22g benzene sulfonic acid diazol under the electromagnetic agitation, wherein, the mass ratio of carbon/alumina compound and benzene sulfonic acid diazol is 17: 1), continue stirring reaction after 3 hours, filter, the gained black powder is used deionized water, N successively, and dinethylformamide and acetone washing are dried down in 110 ℃ then and promptly got sulfonation carbon/titanium oxide compound 3.9g in 8 hours;
3) with step 2) sulfonation carbon/titanium oxide compound 3.9g mix with 40ml hydrofluoric acid (hydrofluoric acid is 10: 1 with the mass ratio of sulfonation carbon/titanium oxide compound) and stirred 3 hours, filter once more, spend deionised water to neutral, promptly got carbon-based solid acid catalyst in 8 hours in 110 ℃ of oven dry, wherein, sulfonic content is 1.7mmol/g.
Get above-mentioned solid acid 50mg, add in the 20ml hydrothermal reaction kettle with 8ml absolute methanol and 1g oleic acid, reaction is 4.5 hours under 77 ℃ of water-bath electromagnetic agitation, obtains methyl oleate, and the productive rate of methyl oleate is 97%.
The preparation of embodiment 3, carbon-based solid acid catalyst and the catalytic effect in catalytic esterification thereof
1) 9g silica is placed the aqueous sucrose solution (the quality percentage composition of sucrose is 37.5%) that contains 2.7g sucrose, left standstill after the stirring 30 minutes, evaporate to dryness obtains pressed powder under 80 ℃ of water-baths.The gained pressed powder is carried out carbonization 0.5 hour under under the nitrogen protection 800 ℃, obtain the black solid powder and be carbon/silica compound 9.3g;
2) get the black solid powder 6.7g of step 1), add the 40ml deionized water, place 3 ℃ of ice-water baths; Add under the electromagnetic agitation contain 0.22g benzene sulfonic acid diazol settled solution (preparation method of benzene sulfonic acid diazol is with step 2 among the embodiment 1) wherein the mass ratio of carbon/alumina compound and benzene sulfonic acid diazol be 31: 1), continue stirring reaction after 3 hours, filter, the gained black powder is used deionized water, N successively, dinethylformamide and acetone washing are dried down in 110 ℃ then and were promptly got sulfonation carbon/silica compound 6.9g in 6 hours;
3) with step 2) the sulfonation carbon/silica compound 6.9g and the 50ml NaOH aqueous solution (2mol/L) (mass ratio of NaOH and sulfonation carbon/titanium oxide compound is 4: 7), mix and stirred 3 hours, filter once more, spend deionised water to neutral, promptly got carbon-based solid acid catalyst in 8 hours in 110 ℃ of oven dry, wherein, sulfonic content is 1.5mmol/g.
Get above-mentioned solid acid 50mg, add in the 20ml hydrothermal reaction kettle with 8ml absolute methanol and 1g oleic acid, reaction is 3 hours under 77 ℃ of water-bath electromagnetic agitation, obtains methyl oleate, and the productive rate of methyl oleate is 91%.
The preparation of Comparative Examples 1, sulfonation activated carbon and the catalytic effect in catalytic esterification thereof
1) gets the 0.22g sulfanilate, make its dissolving, and place 5 ℃ of ice-water baths, add the 88mg natrium nitrosum again, leave standstill after the stirring and it was fully reacted in 15 minutes, obtain the settled solution of benzene sulfonic acid diazol with 4ml hydrochloric acid (1mol/L) and 30ml deionized water;
2) get active carbon powder 0.54g, add the 40ml deionized water, place 5 ℃ of ice-water baths.The settled solution that adds step 1) under the electromagnetic agitation continued stirring reaction after 3 hours, filtered, and the gained black powder is used deionized water, N successively, and dinethylformamide and acetone washing in 110 ℃ of oven dry, promptly get the sulfonation activated carbon.
Get above-mentioned solid acid 50mg, add in the 20ml hydrothermal reaction kettle with 8ml absolute methanol and 1g oleic acid, reaction is 6 hours under 77 ℃ of water-bath electromagnetic agitation, obtains methyl oleate, and the productive rate that records methyl oleate is 92%.
Comparative Examples 2, the catalytic effect of sulfonic group ion exchange resin in catalytic esterification
Get sulfonic group ion exchange resin Amberlyst-15 50mg, add in the 20ml hydrothermal reaction kettle with 8ml absolute methanol and 1g oleic acid, reaction is 6 hours under 77 ℃ of water-bath electromagnetic agitation, obtains methyl oleate, and the productive rate that records methyl oleate is 75%.