Disclosure of Invention
It is a first object of the present invention to provide a catalyst for glycerol carbonate by introducing an alkali/alkaline earth metal oxide to TiO2The perovskite titanate catalyst with high activity and high stability is obtained by the lattice structure, so that the technical problems of difficult catalyst recovery and poor reusability in the process of synthesizing the glycerol carbonate by the existing ester exchange method can be solved.
In order to realize the purpose, the adopted technical scheme is as follows:
a catalyst for glycerol carbonate, said catalyst being a perovskite titanate of formula A2TiO3、BTiO3Or A2-2xBxTiO3(x is more than or equal to 0 and less than or equal to 1); wherein A is one of Na, K and Cs, and B is one of Mg and Ca.
Further, the perovskite type titanate is CaTiO3。
The second object of the present invention is to provide a method for preparing a catalyst for glycerol carbonate.
In order to realize the purpose, the adopted technical scheme is as follows:
the preparation method of the catalyst is a citric acid complexing method.
Further, the citric acid complexation method comprises the following steps: uniformly mixing the solution 1 and the solution 2, evaporating to form yellow gel, and roasting to obtain the catalyst;
wherein, the solution 1 is: adding titanate into absolute ethyl alcohol, and uniformly mixing to obtain a solution 1;
the solution 2 is as follows: dissolving alkali/alkaline earth metal salt, citric acid and glacial acetic acid in water, and uniformly stirring to obtain a solution 2.
Still further, the molar ratio of the alkali/alkaline earth metal salt to the citric acid to the glacial acetic acid is 1: 4: 1;
the evaporation temperature is 60-100 ℃;
the roasting temperature is 500-1200 ℃, and the time is 1-10 h;
the alkali/alkaline earth metal salt is NaNO3、KNO3、CsNO3、Mg(NO3)、Ca(NO3)2、CH3COONa、CH3COOK、CH3COCs、Ca(CH3COO)2、Mg(CH3COO)2At least one of;
the titanate is tetraethyl titanate, isopropyl titanate and tetrabutyl titanate.
The third purpose of the invention is to provide a synthetic method for glycerol carbonate, which has the advantages of high GC selectivity, good stability and the like.
In order to realize the purpose, the adopted technical scheme is as follows:
the synthesis method for the glycerol carbonate comprises the following steps: the above catalyst was used for synthesis by the transesterification method.
Further, the ester exchange method comprises the following steps: and (2) uniformly mixing the organic carbonate and the glycerol, adding the catalyst, and carrying out reflux reaction at the temperature of 40-120 ℃ for 1-10h to obtain the glycerol carbonate.
Still further, the organic carbonate is at least one of dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, dibutyl carbonate and diphenyl carbonate;
the molar ratio of the organic carbonate to the glycerol is 1-6: 1;
the dosage of the catalyst is 0.1-15 wt% of that of the glycerol.
The fourth object of the present invention is to provide a novel use of glycerol carbonate. According to the structural characteristics of GC, the polylactic acid/polylactic acid copolymer is used as a plasticizer for plasticizing PLA and PGA of full-biodegradable materials, has excellent plasticizing effect and solvent extraction resistance, and also maintains the excellent environmental friendliness of the materials.
In order to realize the purpose, the adopted technical scheme is as follows:
use of glycerol carbonate as a bio-based plasticizer.
Further, the glycerol carbonate is used to plasticize PLA and PGA.
Compared with the prior art, the invention has the beneficial effects that:
1. the perovskite titanate is used as the catalyst, the strong basicity of alkali metal and alkaline earth metal is reserved, the alkali metal/alkaline earth metal and titanium react to generate solid solution, so that the catalyst has excellent stability, and the catalyst has excellent catalytic activity and reusability in the GC synthesis reaction by the ester exchange method.
2. The invention uses the glycerol carbonate to replace esters and polyalcohol plasticizers to plasticize fully biodegradable polymers PLA and PGA, and expands a new application field of the glycerol carbonate. Under the synergistic effect of ester group and hydroxyl bifunctional group, the compatibility and interaction strength of the glycerol carbonate and the ester macromolecules can be obviously improved, the plasticizing effect and excellent extraction resistance of polylactic acid (PLA) and polyglycolic acid (PGA) are enhanced, and the environmental friendliness of the system can be maintained.
Detailed Description
In order to further illustrate the catalyst, the synthesis method and the application of the present invention for glycerol carbonate, and to achieve the intended purpose, the following detailed description is given for the catalyst, the synthesis method and the application of glycerol carbonate according to the present invention, together with the preferred embodiments, the detailed description, the structure, the characteristics and the efficacy thereof. In the following description, different "one embodiment" or "an embodiment" refers to not necessarily the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
The catalyst, synthesis method and application of glycerol carbonate according to the present invention will be further described in detail with reference to the following specific examples:
the technical scheme of the invention is as follows:
a catalyst for glycerol carbonate, said catalyst being a perovskite titanate of formula A2TiO3、BTiO3Or A2-2xBxTiO3(x is more than or equal to 0 and less than or equal to 1); wherein A is one of Na, K and Cs, and B is one of Mg and Ca.
Preferably, the perovskite type titanate is CaTiO3。
The preparation method of the catalyst is a citric acid complexing method.
Preferably, the citric acid complexation method comprises the following steps: uniformly mixing the solution 1 and the solution 2, evaporating to form yellow gel, and roasting to obtain the catalyst;
wherein, the solution 1 is: adding titanate into absolute ethyl alcohol, and uniformly mixing to obtain a solution 1;
the solution 2 is as follows: dissolving alkali/alkaline earth metal salt, citric acid and glacial acetic acid in water, and uniformly stirring to obtain a solution 2.
Further preferably, the molar ratio of the alkali/alkaline earth metal salt to the citric acid to the glacial acetic acid is 1: 4: 1;
the evaporation temperature is 60-100 ℃;
the roasting temperature is 500-1200 ℃, and the time is 1-10 h;
the alkali/alkaline earth metal salt is NaNO3、KNO3、CsNO3、Mg(NO3)、Ca(NO3)2、CH3COONa、CH3COOK、CH3COCs、Ca(CH3COO)2、Mg(CH3COO)2At least one of (1). Preferably Ca (NO)3)2And Ca (CH)3COO)2。
The titanate is one of tetraethyl titanate, isopropyl titanate and tetrabutyl titanate.
The invention adopts high-temperature treatment to introduce alkali/alkaline earth metal into TiO2The composite oxide with the perovskite structure formed by the lattice structure retains the excellent catalytic activity of alkali metal and alkaline earth metal on one hand, can well inhibit the loss of active sites on the other hand, and obviously improves the stability and the reusability of the catalyst.
The synthesis method for the glycerol carbonate comprises the following steps: the above catalyst was used for synthesis by the transesterification method.
Preferably, the ester exchange method comprises the following steps: and (2) uniformly mixing the organic carbonate and the glycerol, adding the catalyst, and carrying out reflux reaction at the temperature of 40-120 ℃ for 1-10h to obtain the glycerol carbonate.
More preferably, the organic carbonate is at least one of dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, dibutyl carbonate and diphenyl carbonate;
the molar ratio of the organic carbonate to the glycerol is 1-6: 1;
the dosage of the catalyst is 0.1-15 wt% of that of the glycerol.
Use of glycerol carbonate as a bio-based plasticizer.
Further preferably, the glycerol carbonate is used to plasticize PLA and PGA.
The specific method comprises the following steps: mixing the glycerol carbonate and the high molecular polymer on a high-speed mixer until the mixture is uniform, wherein the mixing temperature is 150 ℃ and 250 ℃, and the mixing time is 10-20min, putting the mixed material into an extruder, and performing extrusion granulation to obtain the glycerol carbonate plasticized high molecular material.
The glycerol carbonate has both ester group and hydroxyl group, is easy to generate hydrogen bond with carbonyl group in polyester high molecular polymer structure, and has the characteristics of ester and polyether polyol compound. In view of special structural characteristics, the invention also uses glycerol carbonate as a plasticizer to replace ester and polyether polyol compounds for plasticizing and modifying PLA and PGA, and improves the flexibility of the polymer. The glycerol carbonate has excellent degradation characteristics, and can be used as a plasticizer to efficiently plasticize and modify a polymer and maintain the environmental friendliness of a system.
In the following examples, the glycerol conversion and glycerol carbonate yield were determined by gas chromatography (GC-2014), and specific methods were referred to in the literature (Applied Catalysis A General,2017,542: 174-181). The catalyst and reaction product are then separated, washed and dried for further performance testing for reusability, as described in Journal of the Taiwan Institute of Chemical Engineers,2018,87: 131-.
Example 1.
The specific operation steps are as follows:
(1) preparing a catalyst:
adding titanate into absolute ethyl alcohol to form a uniform solution 1, and mixing the titanate with the absolute ethyl alcohol according to a molar ratio of 1: 4: dissolving the alkali/alkaline earth metal salt of 1, citric acid and glacial acetic acid in water, uniformly stirring to obtain a solution 2, mixing the solutions 1 and 2 under rapid stirring, and rapidly stirring to form a uniformly mixed solution. Evaporating at 60-100 ℃ to form yellow gel, and roasting the yellow gel at 500-1200 ℃ for 1-10h to obtain the perovskite titanate catalyst.
Wherein the perovskite titanate has a general formula A2TiO3、BTiO3And A2-2xBxTiO3(x is more than or equal to 0 and less than or equal to 1), wherein A is one of Na, K and Cs, and B is one of Mg and Ca.
The alkali/alkaline earth metal salt is NaNO3、KNO3、CsNO3、Mg(NO3)、Ca(NO3)2、CH3COONa、CH3COOK、CH3COOCs、Ca(CH3COO)2And Mg (CH)3COO)2At least one of (1).
The titanate is one of tetraethyl titanate, isopropyl titanate and tetrabutyl titanate.
(2) Synthesis of glycerol carbonate:
adding organic carbonate and glycerol in a certain material ratio into a reactor, heating to a set temperature, uniformly stirring, then adding a perovskite titanate catalyst, and continuously stirring and refluxing at 40-120 ℃ for 1-10h to obtain a glycerol carbonate product.
Wherein the organic carbonate is at least one of dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, dibutyl carbonate and diphenyl carbonate.
The molar ratio of organic carbonate to glycerol is 1-6: 1.
The amount of the catalyst is 0.1-15 wt% of the amount of the glycerol.
(3) Applications of
Mixing 10-50 parts of glycerol carbonate and 100 parts of high molecular polymer on a high-speed mixer until the mixture is uniform, wherein the mixing temperature is 150 ℃ and 250 ℃, the mixing time is 10-20min, putting the mixed material into an extruder, and performing extrusion granulation to obtain the glycerol carbonate plasticized high molecular material.
Example 2.
6.81g of tetrabutyl titanate was added to absolute ethanol to form a homogeneous solution 1, the molar ratio was 1: 4: dissolving the calcium nitrate, the citric acid and the glacial acetic acid of the solution 1 in water, and uniformly stirring to obtain a solution 2. And (3) mixing and stirring the solution 1 and the solution 2 under rapid stirring to form a uniform mixed solution, wherein the molar ratio of titanium to calcium in the mixed solution is 1: 1. evaporating at 80 deg.C to form yellow gel, and calcining the yellow gel at 700 deg.C for 3.0h to obtain CaTiO3A catalyst.
Mixing a mixture of 1: 2 glycerol and dimethyl carbonate are put into a reactor, and then CaTiO is added3The catalyst accounts for 3 wt% of the mass of the glycerol, and the glycerol carbonate product can be obtained after reflux reaction for 2 hours at the temperature of 80 ℃.
Example 3.
Preparation of the catalyst CaTiO was prepared in the same manner as in example 23A catalyst.
Mixing a mixture of 1: 3 glycerol and dimethyl carbonate are put into a reactor, and then CaTiO is added3The catalyst accounts for 5 wt% of the mass of the glycerol, and the glycerol carbonate product can be obtained after reflux reaction for 5 hours at the temperature of 100 ℃.
Example 4.
The catalyst was prepared as in example 2.
Mixing a mixture of 1: 4 glycerol and dimethyl carbonate are put into a reactor, and then CaTiO is added3The mass of the catalyst is 4 wt% of that of the glycerol, and the glycerol carbonate product can be obtained after reflux reaction for 3 hours at the temperature of 90 ℃.
Example 5.
The catalyst preparation procedure was the same as in example 2, except that: the potassium nitrate 4.04g is used to replace the calcium acetate to prepare the K2TiO3A catalyst.
Mixing a mixture of 1: 3 glycerol and dimethyl carbonate are fed into a reactor, and then K is added2TiO3The mass of the catalyst is 3 wt% of that of the glycerol, and the glycerol carbonate product can be obtained after reflux reaction for 2 hours at the temperature of 85 ℃.
Example 6.
The catalyst was prepared as in example 2, with a molar ratio of 1: 5 glycerol and dimethyl carbonate are fed into a reactor, and then CaTiO is added3And the mass of the catalyst is 7 wt% of that of the glycerol, and the glycerol carbonate product can be obtained after reflux reaction for 4 hours at the temperature of 85 ℃.
Example 7.
6.81g of tetrabutyl titanate was added to absolute ethanol to form a homogeneous solution 1, the molar ratio was 0.4: 1.2: 4: dissolving the calcium acetate, the potassium nitrate, the citric acid and the glacial acetic acid of the solution 1 in water, and uniformly stirring to obtain a solution 2. Then under the condition of rapid stirring, mixing and stirring the solution 1 and the solution 2 to form a uniform mixed solution, evaporating at 80 ℃ to form yellow gel, roasting the yellow gel at 700 ℃ for 3.0h to obtain K1.2Ca0.4TiO3A catalyst.
Mixing a mixture of 1: 2 glycerol and dimethyl carbonate are fed into a reactor, and then K is added1.2Ca0.4TiO3The mass of the catalyst is 3 wt% of that of the glycerol, and the glycerol carbonate product can be obtained after reflux reaction for 2 hours at the temperature of 80 ℃.
Example 8.
The catalyst was prepared as in example 2.
Mixing a mixture of 1: 3 isPutting glycerol and diethyl carbonate into a reactor, uniformly mixing, and adding CaTiO3And the mass of the catalyst is 7 wt% of that of the glycerol, and the glycerol carbonate product can be obtained after reflux reaction for 2 hours at the temperature of 80 ℃.
Example 9.
5.71g of isopropyl titanate was added to absolute ethanol to form a homogeneous solution 1, the molar ratio was 1: 4: dissolving the calcium acetate, the citric acid and the glacial acetic acid of the solution 1 in water, and uniformly stirring to obtain a solution 2. Under rapid stirring, the solution 1 and the solution 2 are mixed and stirred to form a uniform mixed solution. Evaporating at 80 deg.C to form yellow gel, and calcining the yellow gel at set temperature (500, 600, 700, 800, 900, 1000, 1100 deg.C) for 3.0h to obtain CaTiO3A catalyst.
Mixing a mixture of 1: 3, adding glycerol and dimethyl carbonate into a reactor, and then adding CaTiO at different roasting temperatures3The mass of the catalyst is 3 wt% of that of the glycerol, and the glycerol carbonate product can be obtained after reflux reaction for 2 hours at the temperature of 80 ℃.
The results of phase structure analysis of the catalysts at different calcination temperatures are shown in FIG. 1, and when the temperature is over 600 ℃, CaO enters TiO2Formation of lattice structure CaTiO3CaO-TiO formed at 500-600 ℃2A composite oxide.
The yield of the glycerol carbonate was measured by the catalytic reaction of the catalyst at different calcination temperatures, and the results are shown in FIG. 2. From FIG. 2, it can be seen that the catalyst calcined at 700 ℃ has the best catalytic effect, and the yield corresponding to GC is CaO-TiO25 times of the composite oxide.
Comparative example 1: taking CaO as a catalyst, and mixing the components in a molar ratio of 1: 2, putting the glycerol and the dimethyl carbonate into a reactor, then adding CaO with the glycerol amount of 3 wt%, and carrying out reflux reaction for 2h at the temperature of 80 ℃ to obtain the product glycerol carbonate.
Comparative example 2: with Ba-Li/CeO2As a catalyst, mixing a mixture of 1: 2 into the reactor, and then adding Ba-Li/CeO with the amount of glycerol being 3 wt%2Reflux reaction at 80 deg.c for 2 hr to obtain sweet productAn oily carbonate.
TABLE 1 catalytic Performance and stability of the catalysts in the different examples
Examples
|
Glycerol conversion (%)
|
GC yield (%)
|
GC yield after five-time reuse (%)
|
Example 2
|
88.3
|
87.5
|
86.8
|
Example 3
|
99.8
|
98.7
|
96.4
|
Example 4
|
99.6
|
98.4
|
92.9
|
Example 5
|
98.9
|
97.4
|
93.3
|
Example 6
|
92.5
|
91.3
|
84.4
|
Example 7
|
96.7
|
95.4
|
93.6
|
Example 8
|
88.1
|
86.5
|
78.5
|
Example 9
|
87.4
|
86.3
|
79.4
|
Comparative example 1
|
95.6
|
88.4
|
35.6
|
Comparative example 2
|
75.4
|
73.7
|
36.4 |
As is apparent from table 1, the perovskite titanate prepared according to the present invention shows not only excellent catalytic activity but also excellent stability in the ester exchange process synthesis GC reaction, as compared to CaO and the supported catalyst. Compared with the existing catalyst, the catalyst system of the invention has the advantages of high activity and good reusability, and can still maintain good catalytic activity after being used for many times.
Example 10.
And (3) mixing different amounts of glycerol carbonate with 100 parts of PLA respectively on a high-speed mixer until the mixture is uniform, wherein the mixing temperature is 180 ℃, the mixing time is 15min, putting the mixed material into an extruder, and performing extrusion granulation to obtain the glycerol carbonate plasticized PLA material.
Example 11.
And (3) mixing different amounts of glycerol carbonate and 100 parts of PGA on a high-speed mixer until the mixture is uniform, wherein the mixing temperature is 250 ℃, the mixing time is 10min, feeding the mixed material into an extruder, and performing extrusion granulation to obtain the glycerol carbonate plasticized PGA material.
In examples 9-10, the content of glycerol carbonate was 0, 10, 20, 30, 40, 50%, respectively, and the elongation at break was measured (in a manner conventional in the art), and the results are shown in FIG. 3. As can be seen from fig. 3, the elongation at break of PLA and PGA can be significantly increased after GC is added to PLA, and the plasticizing and toughening effects of GC on PLA and PGA are significant.
Further, in the prior art, PLA is plasticized by adding a plasticizer, and at the same time, PLA cannot be completely degraded. The glycerol carbonate synthesized by the invention has ester group and hydroxyl double-active functional groups, not only can play a good plasticizing effect and excellent extraction resistance for PLA and PGA, but also can maintain the environmental friendliness of the system.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention are within the scope of the technical solution of the present invention.