CN110152648B - Preparation method of tin catalyst, tin catalyst and application thereof - Google Patents
Preparation method of tin catalyst, tin catalyst and application thereof Download PDFInfo
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- CN110152648B CN110152648B CN201810143953.1A CN201810143953A CN110152648B CN 110152648 B CN110152648 B CN 110152648B CN 201810143953 A CN201810143953 A CN 201810143953A CN 110152648 B CN110152648 B CN 110152648B
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- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
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- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/02—Impregnation, coating or precipitation
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- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
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- C07C67/00—Preparation of carboxylic acid esters
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Abstract
The invention relates to a preparation method of a tin catalyst, the tin catalyst and application thereof, wherein the catalyst contains Sn-O-Si bonds; in its Raman spectrum, at 237cm‑1A characteristic peak exists nearby and is 110cm‑1Near and 211cm‑1No characteristic peak or relative peak exists nearbyCharacteristic peaks with smaller intensity. The catalyst of the invention is suitable for catalyzing esterification reaction of alcohol and carboxylic acid or ester exchange reaction of alcohol and carboxylic ester, has high catalytic activity and selectivity, and can maintain good catalytic performance for a long time.
Description
Technical Field
The invention relates to a preparation method of a tin catalyst, the tin catalyst and application thereof.
Background
Esterification is one of the most important organic reactions, and products thereof are widely used in various fields of chemical industry. The esterification reaction generally requires the use of a catalyst, and the catalysts used can be divided into acidic catalysts and non-acidic catalysts. The acidic catalyst is some inorganic acids and organic acids, and has the main disadvantages of poor reaction selectivity, corrosion, pollution, incapability of recycling the catalyst, difficulty in product aftertreatment and the like. The non-acidic catalyst is mainly compounds of metals such as aluminum, titanium, zirconium, tin, zinc, magnesium, antimony, bismuth and the like, and the compounds can be used alone or can be prepared into a composite catalyst, so that the catalyst is generally non-corrosive and has relatively high reaction selectivity. Titanates are a non-acidic homogeneous catalyst and, despite their high catalytic activity, require removal of the catalyst from the reaction product, making the work-up of the product difficult. Stannous oxide has high catalytic activity as an esterification catalyst, but stannous oxide is easy to refine and has quick inactivation when catalyzing the esterification reaction of alcohol acid, which is not favorable for long-period operation of continuous esterification process and repeated use of catalyst of intermittent esterification process.
CN1760339A, CN1740277A disclose supported catalysts of divalent tin and are used for esterification decarboxylation of high acid crude oil or distillate oil. US3520915 also discloses supported catalysts of divalent tin, which catalysts are used for the preparation of unsaturated aliphatic nitriles. Wenlei Xie et al disclose Supported Catalysts of tetravalent Tin, which Catalysts are used in the Transesterification of Soybean Oil (silicon-Supported Tin Oxides as a heterologous Acid Catalysts for Transesterification of Soybean Oil, Ind. Eng. chem. Res.2012,51, 225-phase 231). None of these catalysts solves the problems of catalyst refinement and deactivation well. Vinicius et al disclose a complex oxide of aluminum and divalent tin and use it for the esterification of soybean oil fatty acids, and the results show that "the catalytic activity of the complex oxide is reduced compared to stannous oxide" (Metal oxides as a heterologous catalysts for esterification of fatty acids from soybean oil, Fuel Processing Technology, 2011, 92, 53-57). Zhang et al discloses a silica-supported organotin catalyst and its use in the reaction of dimethyl carbonate with phenol (influence of silicon hydroxyl groups on the catalytic performance of silica-supported organotin transesterification, journal of chemical industry, Vol.68 No.5, 1892-1898).
Disclosure of Invention
The invention aims to provide a tin catalyst and application thereof, wherein the tin catalyst has higher catalytic activity, selectivity and better stability when catalyzing the esterification reaction of alcohol and carboxylic acid.
The second purpose of the invention is to solve the refining problem of the existing tin catalyst.
The invention also aims to provide a preparation method of the tin catalyst.
Specifically, the present invention mainly includes the following contents:
1. a method for producing a tin catalyst, characterized by comprising a step of coprecipitating a tin salt dissolved in water and a silicate in the presence of a carrier; in said water, an acid (preferably hydrochloric acid, sulfuric acid or nitric acid) is dissolved or not dissolved; in the water, a metal salt other than tin is dissolved or not dissolved.
2. The preparation method according to 1, characterized in that the carrier is selected from one or more of activated carbon, alumina, molecular sieve and silica gel.
3. The production method according to any one of the above aspects, wherein the charging ratio of the silicate to the tin salt is 0.8 to 6 (preferably 1.5 to 5) in terms of the molar amount of silicon atoms to tin atoms.
4. The preparation method according to any one of the preceding claims, characterized in that the feed ratio of the raw materials is such that the mass fraction of tin in the catalyst is 15% to 45% (preferably 20% to 35%).
5. The preparation method according to any one of the preceding claims, characterized in that the other metal salt is selected from one or more of aluminum salt, titanium salt, zirconium salt, tin salt, zinc salt, magnesium salt, antimony salt and bismuth salt.
6. The preparation method according to any one of the preceding claims, characterized in that the tin salt is selected from one or more of stannous chloride, stannic chloride and stannous sulfate.
7. The preparation method according to any one of the preceding claims, characterized in that the silicate is selected from one or more of sodium silicate and potassium silicate.
8. The process according to any of the preceding claims, characterized by comprising the step of adjusting the pH of the aqueous phase (typically adjusting the pH of the aqueous phase to 2 to 12, preferably 4 to 8, more preferably 4 to 7).
9. The process according to any one of the preceding claims, further comprising a step of heat treatment at 80 ℃ to 600 ℃ (preferably 200 ℃ to 500 ℃, more preferably 250 ℃ to 350 ℃) (said heat treatment is preferably carried out under an inert gas atmosphere).
10. A method of preparing a tin catalyst, comprising: (1) a step of impregnating the support with an aqueous solution in which a tin salt, an optional acid and an optional other metal salt are dissolved; and (2) a step of treating the carrier obtained in (1) with a silicate.
11. The preparation method according to 10, characterized in that the carrier is selected from one or more of activated carbon, alumina, molecular sieves and silica gel.
12. The production method according to 10 or 11, characterized in that the charging ratio of the silicate to the tin salt is 0.8 to 6 (preferably 1.5 to 5) in terms of the molar amount of silicon atoms to tin atoms.
13. The preparation method according to any one of 10 to 12, characterized in that the feed ratio of the raw materials is such that the mass fraction of tin in the catalyst is 15% to 45% (preferably 20% to 35%).
14. The preparation method according to any one of 10 to 13, characterized in that the other metal salt is one or more selected from aluminum salt, titanium salt, zirconium salt, tin salt, zinc salt, magnesium salt, antimony salt and bismuth salt.
15. The preparation method according to any one of claims 10 to 14, characterized in that the tin salt is one or more selected from stannous chloride, stannic chloride and stannous sulfate.
16. The preparation method according to any one of claims 10 to 15, characterized in that the silicate is one or more selected from sodium silicate and potassium silicate.
17. The production method according to any one of claims 10 to 16, characterized by comprising an operation of adjusting the pH of the aqueous phase (generally, adjusting the pH of the aqueous phase to 2 to 12, preferably 4 to 8, more preferably 4 to 7).
18. The production method according to any one of claims 10 to 17, characterized by comprising a step of heat treatment at 80 ℃ to 600 ℃ (preferably 200 ℃ to 500 ℃, more preferably 250 ℃ to 350 ℃) (the heat treatment is preferably performed under an inert gas atmosphere).
19. A tin catalyst, characterized by being obtained by any one of the aforementioned production methods.
20. An inorganic tin catalyst, characterized in that the catalyst contains Sn-O-Si bonds; under the protection of nitrogen, after the catalyst is roasted for 3 hours at 500 ℃, the XRD spectrum has no characteristic peaks of stannic oxide crystals and stannous oxide crystals.
21. A catalyst according to any one of the preceding claims, characterized in that the Raman spectrum of the catalyst after calcination at 300 ℃ for 3h under nitrogen protection is 237cm-1A characteristic peak exists nearby and is 110cm-1Near and 211cm-1No characteristic peak nearby or small relative intensityCharacteristic peak of (2).
22. A tin catalyst, characterized in that the catalyst contains Sn-O-Si bonds; under the protection of nitrogen, the catalyst is calcined at 300 ℃ for 3h, and the Raman spectrum of the catalyst is 237cm-1A characteristic peak exists nearby and is 110cm-1Near and 211cm-1There is no characteristic peak or a characteristic peak with relatively small intensity in the vicinity.
23. A catalyst according to any of the preceding claims, characterized in that in the catalyst the valence state of tin is divalent or tetravalent.
24. A catalyst according to any one of the preceding claims, characterised in that the catalyst is an amorphous solid.
25. A catalyst according to any one of the preceding claims, characterised in that the catalyst comprises a support (the support preferably being selected from one or more of activated carbon, alumina, molecular sieves and silica gel).
26. Use of any of the foregoing catalysts for catalyzing an esterification reaction of an alcohol with a carboxylic acid or a transesterification reaction of an alcohol with a carboxylic acid ester.
27. A process for producing a carboxylic acid ester by reacting an alcohol and a carboxylic acid, characterized by using any of the catalysts described above.
28. The process according to claim 26 or 27, comprising the step of separating the catalyst after the reaction is completed and reusing the catalyst for the reaction.
In the prior art, stannous oxide is a better non-acidic esterification catalyst, but the catalyst has the problem of quick inactivation, more seriously, the catalyst is easy to refine, so that the catalyst is difficult to separate from a reaction product, great difficulty is brought to actual production, and the problems can not be ideally solved by loading or preparing a composite metal oxide in the prior art. The inventor unexpectedly discovers in tests that the high-temperature esterification catalyst which has higher activity and better selectivity and is not thinned can be prepared by coprecipitation of silicate and tin salt; it is also unexpected that the tetravalent tin catalysts obtained by this process also have good activity, selectivity and thermal stability. The present inventors have proposed and completed the present invention on the basis of this finding.
The catalyst of the invention contains new tin species, and the combination of silicon, tin and oxygen is firmer, so that the catalyst of the invention has the following advantages: the catalyst has higher catalytic activity and selectivity, and can keep good catalytic performance for a longer time; the catalyst of the invention is easy to separate from the reaction product, and the separated catalyst can still keep good catalytic performance without heating and activating, thereby being greatly beneficial to the reuse of the catalyst; the catalyst of the invention has higher thermal stability and basically does not change at high temperature. In addition, the preparation method of the catalyst is simple and easy to industrialize.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
FIG. 1 is an XPS photoelectron spectrum of stannous oxide and stannic oxide.
FIG. 2 shows the photoelectron spectra of catalyst A in preparative example 1 and catalyst G in preparative comparative example 1.
Fig. 3 is a raman spectrum of catalyst a in preparative example 1, catalyst G in preparative comparative example 1, and stannous oxide.
FIG. 4 is a scanning electron micrograph of stannous oxide.
FIG. 5 is a scanning electron micrograph of catalyst A from preparation example 1.
Fig. 6 is a scanning electron micrograph of catalyst G prepared in comparative example 1.
Figure 7 is an XRD pattern of stannous oxide.
Fig. 8 is an XRD pattern of catalyst J in preparation comparative example 4.
Fig. 9 is an XRD pattern of catalyst E in preparative example 5.
Fig. 10 is an XRD pattern of catalyst B in preparative example 2.
Detailed Description
The present invention will be described in detail with reference to the following embodiments, but it should be understood that the scope of the present invention is not limited by these embodiments and the principle of the present invention, but is defined by the claims.
In the present invention, anything or matters not mentioned is directly applicable to those known in the art without any change except those explicitly described. Moreover, any embodiment described herein may be freely combined with one or more other embodiments described herein, and the technical solutions or ideas thus formed are considered part of the original disclosure or original description of the present invention, and should not be considered as new matters not disclosed or contemplated herein, unless a person skilled in the art would consider such combination to be clearly unreasonable.
All of the features disclosed in this invention can be combined in any combination and these combinations should be understood as disclosed or described herein unless a person skilled in the art would consider the combination to be clearly unreasonable, for example in the present invention, a combination of "any range of molar ratios of silicon to tin" and "any range of tin content in the catalyst" should be considered as specifically disclosed and described herein. The numerical points disclosed in the present specification include not only the numerical points specifically disclosed in the examples but also the endpoints of each numerical range in the specification, and ranges in which any combination of the numerical points is disclosed or recited should be considered as ranges of the present invention.
Technical and scientific terms used herein are to be defined only in accordance with their definitions, and are to be understood as having ordinary meanings in the art without any definitions.
In the present invention, "optionally" means including or not including, for example, "optionally a" means including a or not including a.
In the present invention, the inert gas means a gas having no adverse effect on the performance of the catalyst.
In the catalyst of the invention, the sum of the contents of all the components is 100%.
In the present invention, "inorganic tin" means that tin is not directly linked to a hydrocarbon group or a substituted hydrocarbon group.
First, the catalyst of the present invention
The invention provides an inorganic tin catalyst, which contains Sn-O-Si bonds; under the protection of nitrogen, after the catalyst is roasted for 3 hours at 500 ℃, the XRD spectrum has no characteristic peaks of stannic oxide crystals and stannous oxide crystals.
According to the inorganic tin catalyst, after roasting for 3 hours at 500 ℃ under the protection of nitrogen, no sharp crystal characteristic peak exists between 5 and 70 degrees in an XRD (X-ray diffraction) pattern; the existing silica gel supported tin catalyst has sharp crystal characteristic peak in the range after being treated under the same conditions.
The inorganic tin catalyst may or may not contain a carrier.
The invention also provides another tin catalyst comprising Sn-O-Si bonds; under the protection of nitrogen, the catalyst is calcined at 300 ℃ for 3h, and the Raman spectrum of the catalyst is 237cm-1A characteristic peak exists nearby and is 110cm-1Near and 211cm-1There is no characteristic peak nearby or a characteristic peak with relatively small intensity (preferably at 110 cm)-1Near and 211cm-1No characteristic peak nearby). Wherein, the relative intensities of the two characteristic peaks are compared according to the peak area sizes of the two characteristic peaks, the relative intensity of the characteristic peak with a large peak area is larger, and the relative intensity of the characteristic peak with a small peak area is smaller.
According to the tin catalyst, under the protection of nitrogen, the Raman spectrum of the catalyst is 237cm after being calcined at 300 ℃ for 3 hours-1A characteristic peak exists nearby; the existing silica gel supported tin catalyst does not have the characteristic peak nearby or has the characteristic peak of 110cm after being treated under the same conditions-1Characteristic peaks nearby and 211cm-1The characteristic peaks in the vicinity are smaller than the characteristic peaks having smaller relative intensities.
In one case, the Raman spectrum of the tin catalyst is 110cm after the tin catalyst is roasted for 3 hours at 300 ℃ under the protection of nitrogen-1Near and 211cm-1No characteristic peak is nearby; the existing silica gel supported tin catalyst is treated under the same conditions and is 110cm-1Near and 211cm-1And each has a distinct characteristic peak nearby.
In another case, after the tin catalyst is roasted for 3 hours at 300 ℃ under the protection of nitrogen, the Raman spectrum of the tin catalyst is 110cm-1NearbyAnd 211cm-1There is a characteristic peak nearby, but the characteristic peak is 237cm-1The relative intensity is small compared with the characteristic peak nearby (such as 110 cm)-1Near and 211cm-1There is a characteristic peak near each, any one of the characteristic peaks is at 237cm-1The peak area ratios of nearby characteristic peaks are all less than 1/2); the existing silica gel supported tin catalyst is treated under the same conditions, if the concentration is 237cm-1A characteristic peak exists nearby, and is 110cm-1Near and 211cm-1Any characteristic peak appearing nearby has large relative intensity compared with the characteristic peak, and the ratio of peak areas is far larger than 1.
The tin catalyst may contain no stannous oxide or a small amount of stannous oxide.
The two catalysts described above are collectively described below.
According to the catalyst of the present invention, in one embodiment, the catalyst is an amorphous solid.
The catalyst according to the present invention may contain, as an optional component, an element other than tin. These elements are not particularly limited in the present invention and may be incorporated in the preparation of the catalyst as long as they do not have a significant adverse effect or other benefit on the catalyst performance, including but not limited to one or more of aluminum, titanium, zirconium, tin, zinc, magnesium, antimony, and bismuth.
The catalyst according to the present invention may contain impurities as long as the kind and content thereof do not significantly degrade the catalyst performance. Generally, the catalyst of the present invention has a sodium mass fraction of less than 0.03% based on sodium oxide.
The catalyst according to the invention may or may not contain a support. The carrier can be one or more selected from activated carbon, alumina, molecular sieve and silica gel.
According to the catalyst of the present invention, the molar ratio of silicon to tin may be 0.5 to 22, preferably 0.8 to 6, more preferably 1 to 5, and still more preferably 1.5 to 5.
When the catalyst of the present invention does not contain a carrier, the mass fraction of tin may be 8% to 72%, preferably 23% to 65%, more preferably 26% to 61%, and still more preferably 26% to 53%.
When the catalyst of the present invention contains a carrier, the mass fraction of tin may be 15% to 45%, preferably 20% to 35%.
According to the catalyst of the present invention, the valence of tin may be divalent and/or tetravalent, preferably divalent.
The XPS analysis of the catalyst according to the present invention shows that the reaction of the silicate with the tin salt results in the production of new tin species, thereby improving the performance of the tin catalyst, allowing the catalyst of the present invention to have better catalytic activity, selectivity and stability, and allowing the catalyst to be easily separated from the reaction product. The molar ratio of silicon to tin is not particularly limited in the present invention, and it is critical to adjust the amount of silicon modified with tin during the catalyst preparation process, and one skilled in the art can easily select an appropriate silicon to tin molar ratio based on this teaching.
Secondly, the preparation method of the catalyst of the invention
The invention provides a preparation method of a tin catalyst, which comprises the step of coprecipitation of tin salt and silicate dissolved in water in the presence of a carrier; in said water, an acid (preferably hydrochloric acid, sulfuric acid or nitric acid) is dissolved or not dissolved; in the water, a metal salt other than tin is dissolved or not dissolved.
According to the catalyst preparation method of the present invention, the carrier is preferably selected from one or more of activated carbon, alumina, molecular sieves and silica gel.
According to the catalyst preparation method of the present invention, the manner of coprecipitation is not particularly limited, and any suitable manner can be adopted. For example, the aqueous solution of the tin salt may be added to the aqueous solution of the silicate, the aqueous solution of the silicate may be added to the aqueous solution of the tin salt, the aqueous solution of the silicate and the aqueous solution of the tin salt may be directly mixed or mixed by dropping them at the same time, and then the mixture may be completely precipitated. If an acid is added, it is preferable to add the acid to the aqueous tin salt solution and then mix the aqueous tin salt solution with the aqueous silicate solution; if other metal salts are added, it is also preferable to add the other metal salts to the aqueous tin salt solution and then mix the aqueous tin salt solution with the aqueous silicate solution.
According to the catalyst preparation method of the present invention, the silicate is generally one or more of sodium silicate and potassium silicate.
According to the catalyst preparation method of the present invention, the tin salt is generally one or more of stannous chloride (including anhydrous stannous chloride or stannous chloride dihydrate), stannic chloride (including anhydrous stannic chloride or stannic chloride pentahydrate) and stannous sulfate.
According to the preparation method of the catalyst, the charging ratio of the silicate to the tin salt can be 0.5-22, preferably 0.8-6, more preferably 1-5, and even more preferably 1.5-5 based on the molar amount of the silicon atom and the tin atom.
According to the preparation method of the catalyst, the feeding ratio of all raw materials is that the mass fraction of tin in the catalyst is 15-45% (preferably 20-35%).
According to the catalyst preparation method of the present invention, the silicate and the tin salt are used in the molar amounts of silicon atoms and tin atoms, respectively, the acid is used in the molar amount of releasable protons, and the silicate, the tin salt and the acid preferably satisfy the following relational expressions: mSi-MSn＝2×MProton(s)。
According to the catalyst preparation method of the present invention, there is no particular limitation on the kind and amount of the other metal salt, and an appropriate amount of the other metal salt may be introduced in preparing the catalyst as long as there is no significant adverse effect or other benefit on the catalyst performance. The other metal salt is preferably one or more selected from aluminum salt, titanium salt, zirconium salt, tin salt, zinc salt, magnesium salt, antimony salt and bismuth salt.
According to the catalyst preparation method of the present invention, the temperature of the coprecipitation is generally around room temperature (for example, 25 ℃ to 40 ℃).
According to the catalyst preparation method, the method also comprises the operation of adjusting the pH value of the water phase after the reactants are mixed. The pH value of the water phase is generally adjusted to 2-12, preferably 4-8, and more preferably 4-7. The invention has no special limitation on the medicament and the mode for adjusting the pH value of the water phase, and the pH value of the system can be adjusted by using the common alkaline aqueous solution, such as NaOH aqueous solution, KOH aqueous solution or ammonia aqueous solution.
According to the catalyst preparation method of the invention, after coprecipitation, the precipitate is preferably kept in water for a period of time, generally 0.1 h-8 h (preferably 0.5 h-5 h); the temperature maintained in the water is generally from 25 ℃ to 70 ℃, preferably the temperature at which precipitation takes place.
According to the catalyst preparation method of the present invention, the precipitate can be easily separated from the aqueous phase by filtration.
According to the catalyst preparation method of the present invention, the precipitate is preferably subjected to washing (typically water washing), heat treatment, and then the catalyst of the present invention is obtained.
According to the catalyst preparation method of the present invention, the temperature of the heat treatment is generally 80 to 600 ℃, preferably 200 to 500 ℃, and more preferably 250 to 350 ℃. The heat treatment is preferably carried out under the protection of an inert gas, such as nitrogen or argon. The time for the heat treatment is generally 2 to 5 hours, preferably 3 to 5 hours.
The invention also provides another preparation method of the tin catalyst, which comprises the following steps: (1) a step of impregnating the support with an aqueous solution in which a tin salt, an optional acid and an optional other metal salt are dissolved; and (2) a step of treating the carrier obtained in (1) with a silicate.
According to the catalyst preparation method of the present invention, the carrier is preferably selected from one or more of activated carbon, alumina, molecular sieves and silica gel.
According to the catalyst preparation method of the present invention, if an acid is added, it is preferable to add the acid to the tin salt aqueous solution first, and then impregnate the carrier with the tin salt aqueous solution; if other metal salts are added, the preferable mode is that other metal salts are firstly added into the tin salt aqueous solution, and then the carrier is impregnated by the tin salt aqueous solution; if the acid and the other metal salt are added simultaneously, it is preferable to add both the acid and the other metal salt to the aqueous tin salt solution and then impregnate the carrier with the aqueous tin salt solution.
According to the catalyst preparation method of the present invention, the silicate is generally one or more of sodium silicate and potassium silicate.
According to the catalyst preparation method of the present invention, the tin salt is generally one or more of stannous chloride (including anhydrous stannous chloride or stannous chloride dihydrate), stannic chloride (including anhydrous stannic chloride or stannic chloride pentahydrate) and stannous sulfate.
According to the catalyst preparation method of the present invention, the acid is preferably hydrochloric acid, sulfuric acid, or nitric acid.
According to the catalyst preparation method of the present invention, there is no particular limitation on the kind and amount of the other metal salt, and an appropriate amount of the other metal salt may be introduced in preparing the catalyst as long as there is no significant adverse effect or other benefit on the catalyst performance. The other metal salt is preferably one or more selected from aluminum salt, titanium salt, zirconium salt, tin salt, zinc salt, magnesium salt, antimony salt and bismuth salt.
According to the preparation method of the catalyst, the charging ratio of the silicate to the tin salt can be 0.5-22, preferably 0.8-6, more preferably 1-5, and even more preferably 1.5-5 based on the molar amount of the silicon atom and the tin atom.
According to the preparation method of the catalyst, the feeding ratio of all raw materials is that the mass fraction of tin in the catalyst is 15-45% (preferably 20-35%).
According to the catalyst preparation method of the present invention, the silicate and the tin salt are used in the molar amounts of silicon atoms and tin atoms, respectively, the acid is used in the molar amount of releasable protons, and the silicate, the tin salt and the acid preferably satisfy the following relational expressions: mSi-MSn＝2×MProton(s)。
According to the catalyst preparation method of the present invention, the temperature for treating the carrier obtained in (1) with silicate is generally around room temperature (e.g., 25 ℃ C. to 40 ℃ C.).
According to the catalyst preparation method of the present invention, the method further comprises the operation of adjusting the pH of the aqueous phase when treating the carrier obtained in (1) with a silicate. The pH value of the water phase is generally adjusted to 2-12, preferably 4-8, and more preferably 4-7. The invention has no special limitation on the medicament and the mode for adjusting the pH value of the water phase, and the pH value of the system can be adjusted by using the common alkaline aqueous solution, such as NaOH aqueous solution, KOH aqueous solution or ammonia aqueous solution.
According to the preparation method of the catalyst, after the silicate is added, the silicate is preferably kept in water for a period of time, and the time is generally kept between 0.1 and 8 hours (preferably between 0.5 and 5 hours); the temperature maintained in the water is generally from 25 ℃ to 70 ℃, preferably the temperature at which precipitation takes place.
According to the catalyst preparation method of the present invention, the product can be easily separated from the aqueous phase by filtration.
According to the catalyst preparation method of the present invention, the product is preferably obtained after washing (generally water washing), filtration, heat treatment.
According to the catalyst preparation method of the present invention, the temperature of the heat treatment is generally 80 to 600 ℃, preferably 100 to 400 ℃, and more preferably 200 to 350 ℃. The heat treatment is preferably carried out under the protection of an inert gas, such as nitrogen or argon. The time for the heat treatment is generally 2 to 5 hours, preferably 3 to 5 hours.
The invention also provides a catalyst obtained by any one of the aforementioned methods.
Third, the application of the catalyst of the invention
The invention also provides the application of any one of the catalysts in catalyzing the esterification reaction of alcohol and carboxylic acid or the ester exchange reaction of alcohol and carboxylic ester.
Specifically, the present invention provides a process for producing a carboxylic ester by reacting an alcohol and a carboxylic acid, characterized by using any one of the catalysts described above.
According to the invention, the reaction temperature for the esterification or transesterification is 160 ℃ to 230 ℃, preferably 180 ℃ to 210 ℃.
According to the invention, the method comprises the steps of separating the catalyst (for example, by filtration) after the reaction is finished, and reusing the catalyst for the reaction.
Examples section
The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.
In the context of the present specification, all medicaments and raw materials are either commercially available or can be manufactured according to established knowledge. In the following examples and comparative examples, all reagents used were analytical reagents unless otherwise specified.
In the context of the present specification, including the following examples and comparative examples, the stannous oxide in the tests and analyses was subjected to a "calcination at 200 ℃ for 3 hours under nitrogen atmosphere" treatment unless otherwise specified; the tin oxide in the test and analysis was treated by "baking at 500 ℃ for 3 hours under nitrogen atmosphere" unless otherwise specified.
In the context of the present description, including the examples and comparative examples below, X-ray photoelectron spectroscopy (XPS) uses an X-ray photoelectron spectrometer of the model ESCALB 220i-XL, manufactured by VG Scientific, Inc. (test conditions: the excitation light source is monochromatized Al K alpha X-ray, the power is 300W, and the basic vacuum is 3X 10-9mbar, electron binding energy was corrected by the C1s peak of elemental carbon. ).
In the context of the present specification, including the following examples and comparative examples, X-ray fluorescence spectroscopy (XRF) quantitative and semi-quantitative analysis of element content was carried out by external standard method using a 3271E type X-ray fluorescence spectrometer manufactured by Nippon Denshi electric motors industries, Ltd, to detect the line intensity with a scintillation counter and a proportional counter (test conditions: powder tablet molding, rhodium-palladium, excitation voltage 50kV, and excitation current 50 mA).
In the context of the present specification, including the examples and comparative examples below, atomic emission spectrometry (ICP-AES) was performed using an Atom Scan model 16 inductively coupled plasma emission spectrometry, USA (test conditions: dissolution of the catalyst in a solution of HCl to HF volume ratio of 50:1, digestion using a microwave digestion instrument manufactured by CEM, USA.).
In the context of the present description, including the examples and comparative examples below, Raman spectroscopy was performed using a LAM-800 laser confocal Raman spectrometer (test conditions) from the French JY company: incident light of 532nm and resolution of 4cm-1The scanning range is 100-1200 cm-1)。
In the context of the present specification, including the following examples and comparative examples, Scanning Electron Microscopy (SEM) employed a Quanta 200F scanning electron microscope manufactured by FEI corporation (test conditions: drying of the sample followed by vacuum evaporation of the metal spray to increase conductivity and contrast, analytical electron microscope acceleration voltage of 20.0KV, magnification of 1-30 k).
In the context of the present specification, including the following examples and comparative examples, X-ray powder diffraction (XRD) was carried out using an X-ray diffractometer model D5005 (test conditions: Cu target, Ka radiation, Ni filter, tube voltage 35kV, tube current 45mA, scanning range 2 θ 5-70 °) manufactured by Siemens of Germany.
In the following examples and comparative examples, the esterification ratio was calculated as follows:
the acid value in the esterification rate calculation method is determined by the method specified in GB-1668-2008-T.
In the following examples and comparative examples, the esterification reaction selectivity was determined using an Agilent 7890A gas chromatograph, U.S.A., under chromatographic conditions: capillary column (50m × 0.2mm × 0.5 μm), FID detector, detection chamber temperature of 280 deg.C, column temperature programmed from 60 deg.C to 260 deg.C, gasification chamber temperature of 280 deg.C, hydrogen flow rate of 30mL/min, air flow rate of 400mL/min, and nitrogen pressure of 10 MPa.
The calculation method is as follows:
preparation of example 1
2.26g of stannous chloride dihydrate (SnCl)2·2H2O) was dissolved in 10ml of deionized water, Na was taken2O·SiO2·9H2O is dissolved in deionized water. At 30 DEG CThen adding the two solutions into a flask at the same time, regulating the pH value to 6 by adding an ammonia water solution, continuously keeping the solution at 50 ℃ for 2 hours after the precipitation is completed, filtering, washing with water, drying at 80 ℃, and roasting at 300 ℃ for 3 hours under the protection of nitrogen to obtain the tin catalyst, namely the tin catalyst with the number of A.
The catalyst had a Si/Sn molar ratio of 0.96 by XRF analysis.
XPS analysis shows that the mass fraction of tin atoms on the surface of the catalyst is 5.12%; by ICP analysis, the mass fraction of tin in the catalyst was 63.5%.
Preparation of example 2
2.26g of stannous chloride dihydrate (SnCl)2·2H2O) is dissolved in 40ml of water, 4g of silica gel carrier is added into the water, and the mixture is soaked for 5 hours; then slowly add Na dissolved in 2.84g2O·SiO2·9H2An aqueous solution of O; stirring for 3 hours at 30 ℃, filtering, washing, drying at 80 ℃, and then roasting for 3 hours at 500 ℃ under the protection of nitrogen to obtain the tin catalyst, number B.
By ICP analysis, the mass fraction of tin in the catalyst was 19.6%.
Preparation of example 3
4.52g of stannous chloride dihydrate (SnCl) are taken2·2H2O) was dissolved in 50ml of deionized water, Na was taken2O·SiO2·9H2O5.68 g was dissolved in 50ml of deionized water. Adding the two solutions into a flask at 30 ℃, adding 5g of silica gel carrier, adding ammonia water solution to adjust the pH value to 7, stirring and reacting for 4 hours at 30 ℃, filtering, washing, drying at 80 ℃, and roasting for 3 hours at 300 ℃ under the protection of nitrogen to obtain the tin catalyst, wherein the number is C.
By ICP analysis, the mass fraction of tin in the catalyst was 26.5%.
Preparation of example 4
Dissolving 2.15g stannous sulfate in 40ml 1mol/L hydrochloric acid water solution, and collecting K2O·SiO2Dissolved in deionized water. Adding the two solutions into a flask at 30 deg.C, feeding Si/Sn ratio of 3, addingAdjusting the pH value of the ammonia water solution to 7, keeping the solution at 30 ℃ for 2 hours after the precipitation is completed, filtering, washing, drying at 80 ℃, and roasting at 250 ℃ for 4 hours under the protection of nitrogen to obtain the tin catalyst, namely the number D.
The catalyst had a Si/Sn molar ratio of 3.02 by XRF analysis.
By ICP analysis, the mass fraction of tin in the catalyst was 37.3%.
Preparation of example 5
2.26g of stannous chloride dihydrate (SnCl)2·2H2O) is dissolved in 80ml of hydrochloric acid aqueous solution with the concentration of 1mol/L, K is taken2O·SiO2Dissolved in deionized water. Adding the two solutions into a flask at 30 ℃ simultaneously, regulating the pH value to 7 by adding an ammonia water solution with the feeding Si/Sn ratio of 5, continuously keeping the solution at 30 ℃ for 4 hours after complete precipitation, filtering, washing, drying at 80 ℃, and roasting at 500 ℃ for 3 hours under the protection of nitrogen to obtain the tin catalyst, namely the number E.
By ICP analysis, the mass fraction of tin in the catalyst was 27.1%.
Preparation of example 6
3.51g of tin tetrachloride pentahydrate (SnCl) are taken4·5H2O) was dissolved in 10ml of deionized water, Na was taken2O·SiO2·9H2O is dissolved in deionized water. Adding the two solutions into a flask at 30 ℃, simultaneously adding the feeding Si/Sn ratio of 2, adding an ammonia water solution to adjust the pH value to 7, continuously keeping the solution at 50 ℃ for 0.5 hour after the precipitation is completed, filtering, washing, drying at 80 ℃, and roasting at 200 ℃ for 3 hours under the protection of nitrogen to obtain the tin catalyst, wherein the number of the tin catalyst is F.
By ICP analysis, the mass fraction of tin in the catalyst was 44.0%.
Preparation of comparative example 1
5g of stannous chloride dihydrate (SnCl)2·2H2O) to SnCl2Adding 10g of silica gel into 10% aqueous solution by mass, stirring for 10h, adding 20% ammonia water solution by mass, stirring uniformly, washing, filtering, drying, and performing nitrogen protectionThen roasted for 3 hours at 300 ℃ to obtain the comparative tin catalyst, No. G.
By ICP analysis, the mass fraction of tin in the catalyst was 20.1%.
Preparation of comparative example 2
The catalyst was prepared by the same method as that for the preparation of comparative example 1, except that: stannous chloride dihydrate (SnCl)2·2H2O) was used in an amount of 4 g. The catalyst number is H.
By ICP analysis, the mass fraction of tin in the catalyst was 16.4%.
Preparation of comparative example 3
The catalyst was prepared by the same method as that for the preparation of comparative example 1, except that: stannous chloride dihydrate (SnCl)2·2H2O) was used in an amount of 7 g. The catalyst is numbered I.
By ICP analysis, the mass fraction of tin in the catalyst was 25.3%.
Preparation of comparative example 4
The catalyst was prepared by the same method as that for the preparation of comparative example 1, except that: calcining at 500 deg.C for 3 hr under nitrogen protection. Catalyst number J.
By ICP analysis, the mass fraction of tin in the catalyst was 20.1%.
Reaction example 1
In the reaction system, the molar ratio of the benzoic acid to the diethylene glycol is 2:1.15, n-butyl ether accounting for 25% of the total mass of reactants is added as a water-carrying agent, and a catalyst accounting for 1.5% of the total mass of the reactants is added. Heating to reflux, refluxing and water distributing while reacting, and stirring for reacting for 3 hours. After the reaction is finished, stopping stirring, standing for 10 minutes, sampling, observing an upper liquid phase, and separating a liquid phase product from the catalyst. And (5) analyzing the liquid phase product, and calculating the esterification rate and the selectivity.
The reaction results are shown in Table 1.
Reaction example 2
This example serves to illustrate the comparative effect of the tin catalyst, supported tin catalyst and stannous oxide of the present invention on reuse.
The procedure of reaction example 1 was followed except that: except for using the catalyst A, G and stannous oxide in the first reaction, the catalyst recovered in the last reaction is reused in the catalyst of each subsequent reaction; wherein, the series test of the catalyst A adopts a filtration mode to recover, and the series test of the catalyst G and the stannous oxide adopts a centrifugation mode to recover the catalyst due to the difficult filtration and the loss of the catalyst.
The reaction results are shown in Table 2.
TABLE 1
| Catalyst and process for preparing same | Degree of esterification/%) | Selectivity/%) | Upper liquid phase |
| A | 99.84 | 99.86 | Clear and bright |
| B | 99.02 | 99.42 | Clear and bright |
| C | 99.24 | 99.44 | Clear and bright |
| D | 99.53 | 99.74 | Clear and bright |
| E | 98.49 | 99.50 | Clear and bright |
| F | 98.12 | 98.73 | Clear and bright |
| G | 99.37 | 99.22 | Slight turbidity |
| H | 99.13 | 98.57 | Slight turbidity |
| I | 99.24 | 98.96 | Slight turbidity |
| J | 98.57 | 99.07 | Slight turbidity |
| Stannous oxide | 99.20 | 99.48 | Is relatively turbid |
TABLE 2
As can be seen from FIG. 1, the binding energy of tin in stannous oxide is at 486.31ev and that of tin in stannic oxide is at 486.53 ev. As can be seen from FIG. 2, the binding energy of tin in the silica-supported catalyst is at 487.89ev, and the binding energy of tin in the catalyst of the present invention is at 488.31 ev. As can be seen from fig. 1 and 2, the binding energy of tin is highest in the catalyst of the present invention.
As can be seen from FIG. 3, at 110cm-1Near and 211cm-1Nearby, the supported catalyst and stannous oxide have two characteristic peaks which are consistent, while the catalyst of the invention does not have the two characteristic peaks, but is at 237cm-1In the vicinity, the catalyst of the present invention has a strong characteristic peak which is not present in both the supported catalyst and the stannous oxide.
As can be seen from fig. 4, stannous oxide (purchased and untreated) is a cuboid particle with a single morphology. As can be seen from fig. 5, the catalyst of the present invention has no clear outline, is clustered together, and is a uniform-appearing substance. As can be seen from fig. 6, in the supported catalyst, the carrier was clearly visible and was a substance having a non-uniform appearance.
As can be seen from fig. 7, 8, 9 and 10, a plurality of sharp crystal characteristic peaks exist between the conventional supported tin catalyst (calcined at 500 ℃ for 3 hours under the protection of nitrogen) and stannous oxide at 5 ° to 70 °, while the catalyst of the present invention has no sharp crystal characteristic peak at 5 ° to 70 °.
Claims (16)
1. An inorganic tin catalyst, characterized in that the catalyst contains Sn-O-Si bonds; under the protection of nitrogen, after the catalyst is roasted for 3 hours at 500 ℃, the XRD spectrum has no characteristic peaks of stannic oxide crystals and stannous oxide crystals; the catalyst is prepared by the following method: in the presence of a carrier, carrying out coprecipitation on a tin salt and a silicate dissolved in water, washing the precipitate, carrying out heat treatment under the protection of inert gas, and then obtaining the catalyst; the water is dissolved or not dissolved with acid; in the water, other metal salts except tin are dissolved or not dissolved; the tin salt is selected from one or more of stannous chloride and stannous sulfate.
2. The catalyst of claim 1, wherein the acid is hydrochloric acid, sulfuric acid or nitric acid in the preparation method of the catalyst.
3. The catalyst of claim 1, wherein in the preparation method of the catalyst, the carrier is selected from one or more of activated carbon, alumina, molecular sieve and silica gel.
4. The catalyst according to claim 1, wherein the catalyst is prepared by a method in which the ratio of the silicate to the tin salt is 0.8 to 6 in terms of the molar amount of silicon atoms to tin atoms.
5. The catalyst according to claim 1, wherein the catalyst is prepared by a method in which the ratio of the silicate to the tin salt is 1.5 to 5 in terms of the molar amount of silicon atoms to tin atoms.
6. The catalyst according to claim 1, wherein in the preparation method of the catalyst, the raw materials are fed in a ratio that the mass fraction of tin in the catalyst is 15-45%.
7. The catalyst according to claim 1, wherein in the preparation method of the catalyst, the other metal salt is one or more selected from the group consisting of aluminum salt, titanium salt, zirconium salt, zinc salt, magnesium salt, antimony salt and bismuth salt.
8. The catalyst according to claim 1, wherein in the preparation method of the catalyst, the silicate is selected from one or more of sodium silicate and potassium silicate.
9. The catalyst according to claim 1, wherein the preparation method of the catalyst comprises the operation of adjusting the pH value of the aqueous phase to 2-12.
10. The catalyst according to claim 1, wherein the preparation method of the catalyst comprises the operation of adjusting the pH value of the aqueous phase to 4-8.
11. The catalyst according to claim 1, wherein the preparation method of the catalyst comprises a step of heat treatment at 80 ℃ to 600 ℃ under the protection of inert gas.
12. The catalyst according to claim 1, wherein the preparation method of the catalyst comprises a step of heat treatment at 200 ℃ to 500 ℃ under the protection of inert gas.
13. The catalyst according to claim 1, wherein the raman spectrum of the catalyst after calcination at 300 ℃ for 3h under nitrogen protection is 237cm-1A characteristic peak exists nearby and is 110cm-1Near and 211cm-1There is no characteristic peak or a characteristic peak with relatively small intensity in the vicinity.
14. Use of a catalyst according to any one of claims 1 to 13 for catalysing the esterification of an alcohol with a carboxylic acid or the transesterification of an alcohol with a carboxylic acid ester.
15. A process for producing a carboxylic acid ester by reacting an alcohol with a carboxylic acid, wherein the catalyst of any one of claims 1 to 13 is used.
16. The method of claim 15 including the step of separating the catalyst after the reaction is complete and reusing the catalyst for the reaction.
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