CN110586062A - Si-Mg-Zr-Zn composite metal oxide catalyst and preparation method and application thereof - Google Patents

Abstract

The invention discloses a multifunctional Mg _a Zr _b Zn _c Si _d O _e composite metal oxide catalyst, a preparation method and an application in the preparation of enol compounds. The multifunctional Mg _a Zr _b Zn _c Si _d O _e composite metal oxide catalyst is obtained by adding a Si source to the original Mg-Zr-Zn composite metal oxide catalyst. While ensuring the catalytic activity of the catalyst, the reaction activity hardly decreased after 800 hours; while using the original Mg-Zr-Zn composite metal oxide catalyst (CN107398264A), under the same conditions, after 800 hours, the conversion of the reaction raw materials The yield was reduced from the initial 18% to less than 5%, and the selectivity of propenol in the reaction product was also reduced from the initial 87% to 32%. It shows that the stability of the catalyst during the reaction can be significantly improved by adding Si components.

Description

A Si-Mg-Zr-Zn composite metal oxide catalyst and preparation method thereof application

technical field

The invention belongs to the field of fine chemicals, in particular to a multi-component Si-Mg-Zr-Zn composite metal oxide catalyst and its application in preparing enol compounds.

Background technique

Enols can participate in various reactions such as oxidation, reduction, esterification, etherification, coupling, polymerization, etc., because of their molecular structure containing double bonds and hydroxyl groups. A series of downstream products are widely used. Synthetic fragrances, resins, etc., are an important class of fine chemical raw materials and organic synthesis intermediates. Common enols mainly include: propenol, isobutenol, crotyl alcohol, etc. For example, isobutenol, also known as 2-methallyl alcohol, is a colorless and transparent liquid with a boiling point of 114.5°C. Methallyl polyoxyethylene ether (TPEG) can be synthesized from isobutenol and ethylene oxide as raw materials for use in A new generation of high performance concrete water reducer. Acrylic alcohol, also known as allyl alcohol, is the raw material for the production of diallyl phthalate resin and bis(2,3-dibromopropyl) fumarate.

For example, the industrial methods for preparing isobutenol mainly include isobutene chlorination hydrolysis method and oxidation method. Many domestic companies have adopted the isobutene chlorination hydrolysis method. The isobutene undergoes a two-step reaction. The first step is the reaction of isobutene with chlorine to generate chloroisobutene, and the by-product is hydrogen chloride. It is hydrolyzed to generate isobutenol, and at the same time, a large amount of salty and oily wastewater is produced. The oxidation method generally uses isobutene as the raw material to synthesize methalylaldehyde by oxidation, and the methalylaldehyde is hydrogenated to form methallyl alcohol (isobutenol). The current production process of allyl alcohol includes the isomerization of propylene oxide, the selective reduction of acrolein, the hydrolysis of allyl chloride and the hydrolysis of allyl acetate, etc., which require catalysts or additives such as acids and bases.

The above method has the disadvantages of cumbersome operation steps, large energy consumption, heavy pollution, and difficult to handle by-products. Therefore, it is imminent to develop a new process for preparing enol products. In view of the current state of the art, in the Chinese invention patent (CN107398264A) previously submitted by the applicant, a Mg-Zr-Zn composite metal oxide catalyst and a preparation method thereof are disclosed, and are applied to methanol and n-propanol as raw materials The reaction generates isobutenol in the reaction. However, although the catalyst disclosed in the invention patent (CN107398264A) can show good stability within 200 hours, the conversion rate and product distribution of the reaction raw materials do not change much. However, in the application for a longer time, such as extending to more than 400 hours, the deactivation of the catalyst is gradually obvious, and the conversion rate of the raw material is reduced, and the selectivity of isobutenol is also reduced. The long-term stability of the catalyst is very important for the actual production process. In view of this problem in the aforementioned invention patent, the present invention discloses a method for improving the stability of the catalyst.

In the present invention, Si source is added to the original Mg-Zr-Zn composite metal oxide catalyst to form a multifunctional Si-Mg _x Zr _y Zn _z O composite metal oxide catalyst. Taking the reaction process of preparing allyl alcohol as an example, the specific reaction steps are as follows: methanol and ethanol undergo rapid dehydrogenation and aldol under the action of a multifunctional Si-Mg _{x Zry} Zn _z O composite metal oxide catalyst in a fixed bed reactor. Cross-condensation and hydrogenation finally produce allyl alcohol. After the Si source is introduced into the Mg-Zr-Zn composite metal oxide, the high selectivity of allyl alcohol can be ensured, the stability of the catalyst can be greatly improved, and the service life can be prolonged.

SUMMARY OF THE INVENTION

In view of the problems in the aforementioned invention patents, one object of the present application is to provide a multifunctional Si-Mg _a Zr _b Zn _c O _d composite metal oxide catalyst, which can significantly improve the prepared Si-Mg a Zr b Zn c O d composite metal oxide catalyst. the stability of the catalyst. In the Mg _a Zr _b Zn _c Si _d O _e composite oxide catalyst, a, b, c and d are the molar ratios of the active components of Mg, Zr, Zn and Si, respectively, and e is the stoichiometric ratio of O atoms, where Mg:Zr:Zn:Si=0.1-10:0.01-1:0.01-1:0.01-1, preferably 0.1-10:0.1-1:0.01-0.1:0.1-1, more preferably 1-10:0.1 ~1:0.01~0.1:0.1~1.

According to another aspect of the present invention, there is provided a preparation method of a multi-component Mg _a Zr _b Zn _c Si _d O _e composite metal oxide catalyst, the method comprising the following steps:

(1) After adding metal salts, metal oxides or metal hydroxides containing metal active components Mg, Zr and Zn into the solvent to dissolve and/or disperse, stir to fully mix, the total concentration of the metal precursor mixed solution is 1 to 3 mol·L ^-1 , and heated to reflux;

(2) adding a Si-containing compound to the mixed solution obtained in step (1), continuing to stir until fully mixed, and heating to reflux;

(3) The mixed solution obtained in step (2) is subjected to rotary evaporation to remove solvent, drying and high temperature calcination to obtain the multi-component Mg _a Zr _b Zn _c Si _d O _e composite metal oxide catalyst.

Preferably, in step (1), the active component metal salt is selected from at least one of nitrate, carbonate, bicarbonate, chloride, acetate, sulfate, and lower metal alkoxide. Wherein, the lower metal alkoxide represents an alkoxy organometallic compound formed by replacing the hydroxyl hydrogen of an alcohol molecule with a metal, and the alcohol can be at least one of ethanol, propanol or butanol.

Preferably, the metal oxide and metal hydroxide in step (1) can be commercial products, and can be used directly without any pretreatment.

Preferably, in the step (1), the solvent is water, or a mixed solvent of water and a unit lower alcohol, and the unit lower alcohol is selected from at least one of methanol, ethanol, propanol and butanol, preferably methanol , at least one of ethanol and propanol. The volume percentage of the unit lower alcohol in the co-solvent is 1-50%, preferably 20-50%.

Preferably, in step (1), the heating reflux temperature of the active component mixture is 50-90° C., and the reflux time is not less than 2 hours. More preferably, the heating and refluxing time in step (1) is 2-8 hours.

Preferably, the Si-containing compound in step (2) is selected from silica powder or organosilicon monomer.

Further preferably, the Si-containing compound in step (2) is selected from tetraethyl orthosilicate and tetrabutyl orthosilicate.

Further preferably, the Si-containing compound in step (2) is silica powder with a particle size of 10 microns to 100 microns.

Preferably, when the Si-containing compound in step (2) is an organosilicon monomer selected from tetraethyl orthosilicate and tetrabutyl orthosilicate, the Si-containing compound is gradually added dropwise in the mixed solution of step (1).

Preferably, when the Si-containing compound is silicon dioxide powder in step (2), the silicon dioxide powder is added to the mixed solution in step (1) in a batchwise manner.

Preferably, in step (3), the temperature for removing the solvent by rotary evaporation is 50-90° C., the drying temperature is 100-150° C., and the drying time is 4-12 hours, preferably 6-10 hours; the roasting temperature is 400-100° C. At 800°C, the calcination time is 1 to 12 hours, preferably 2 to 8 hours.

According to another aspect of the present invention, use of the multifunctional Mg-Zr-Zn-Si composite metal oxide catalyst in preparing an enol compound is provided. The prepared enol compound may include: at least one of propenol, crotyl alcohol, isobutenol, 2-ethyl-propenol, 2-propyl-propenol, and 2-butyl-propenol.

According to another aspect of the present invention, there is provided a method for directly preparing an enol compound from a unit alcohol, the method adopts a fixed bed reactor, and the Mg _a according to the present invention is installed in the fixed bed reactor A Zr _b Zn _c Si _d O _e composite metal oxide catalyst is carried out by loading one or more unit lower alcohols with nitrogen to react to prepare an enol compound, wherein the catalyst usage amount is 0.1-10 g, and the injection rate is 0.1-10 g. 5mL·h ^-1 , the temperature is 150～350℃, and the pressure is 0.1～2MPa.

The unit lower alcohols include: methanol, ethanol, propanol, butanol, amyl alcohol, hexanol, phenethyl alcohol, phenylpropanol, etc., preferably methanol, ethanol, propanol, butanol, amyl alcohol, hexanol.

When the unit lower alcohol is a mixture of methanol and other unit lower alcohols, the mass percentage of other unit lower alcohols is 1% to 50%, preferably, the mass percentage of other unit lower alcohols is 2% to 50%. 20%.

beneficial effect

In the present invention, Si source is added to the original Mg-Zr-Zn composite metal oxide catalyst to form a multi-component Mg _a Zr _b Zn _c Si _d O _e composite metal oxide catalyst. While ensuring the catalytic activity of the catalyst, the reaction activity almost did not decrease after 800 hours; while using the original Mg-Zr-Zn composite metal oxide catalyst (CN107398264A), under the same conditions, after 800 hours, the conversion of the reaction raw materials The yield was reduced from the initial 18% to less than 5%, and the selectivity of propenol in the reaction product was also reduced from the initial 87% to 32%. It shows that the stability of the catalyst during the reaction can be significantly improved by adding Si components.

Detailed ways

Hereinafter, the present invention will be described in detail. Before proceeding with the description, it should be understood that the terms used in this specification and the appended claims should not be construed to be limited to ordinary and dictionary meanings, but should be used in the context of allowing the inventor to properly define the terms for best interpretation On the basis of the principles of the present invention, explanations are made according to meanings and concepts corresponding to the technical aspects of the present invention. Accordingly, the descriptions presented herein are merely preferred examples for illustrative purposes and are not intended to limit the scope of the present invention, whereby it is to be understood that others, etc., may be derived therefrom without departing from the spirit and scope of the present invention. price or improvement.

The key of the present invention is that the previously developed multifunctional Mg-Zr-Zn composite oxide catalyst is doped with Si element material, which successfully improves the long-term use stability of the catalyst. The inventors of the present invention found that when a specific ratio of three metals Mg-Zr-Zn and Si elements are used as catalyst active components, the unit lower alcohol can be converted into an enol compound with a high selectivity and at the same time, the Improve the long-term stability of the catalyst. In the multi-component Mg _a Zr _b Zn _c Si _d O _e composite oxide catalyst prepared by the invention, a, b, c and d are the molar ratios of the active components of Mg, Zr, Zn and Si respectively, and e is an O atom The stoichiometric ratio of Mg:Zr:Zn:Si=0.1～10:0.01～1:0.01～1:0.01～1, preferably 0.1～10:0.1～1:0.01～0.1:0.1～1, more preferably 1 to 10: 0.1 to 1: 0.01 to 0.1: 0.1 to 1.

The addition of the Si-containing material is different from that of the other three metal elements. In the preparation method of the multi-component Mg _a Zr _b Zn _c Si _d O _e composite oxide catalyst according to the present invention, in step (1), first The precursors containing the elements Mg, Zr and Zn are mixed and heated to reflux, so that the precursors of the three elements are thoroughly mixed, and then the Si-containing substances are added.

Especially when the added Si-containing material is an organosilicon monomer selected from tetraethyl orthosilicate and tetrabutyl orthosilicate, a slow dropwise addition operation is required. So that the organic silicon monomer is fully flocculated and mixed with the other three metal element precursors. If the organosilicon monomer is added at one time, it is easy to cause serious local flocculation, and the performance of the final catalyst product is not uniform.

The inventors of the present invention have surprisingly found that when the molar ratio of the four elements is controlled within the range of the present invention, and at the same time, specific preparation steps are used for preparation, the purpose of improving the long-term use stability of the catalyst can be achieved.

The following examples are only listed as examples of embodiments of the present invention, and do not constitute any limitation to the present invention. Those skilled in the art can understand that modifications within the scope of the spirit and concept of the present invention are all within the protection of the present invention. scope. Unless otherwise specified, the reagents and instruments used in the following examples are commercially available products.

Examples 1 to 5: Preparation of catalysts CAT-1 to CAT-5

Dissolve and disperse Mg, Zr, Zn metal salts according to the calculated amounts in Table 1 in 50 mL of alkaline hydroalcoholic mixed solution, stir vigorously for 15 minutes at 35 ° C, continue stirring for 30 minutes, and then select and add Si source according to Table 1 below . Continue stirring, and heat to reflux at 70°C. The washed and dried catalyst is calcined at high temperature and sealed for later use.

The numbers of the obtained samples and the corresponding preparation conditions are shown in Table 1.

Table 1: Preparation of CAT-1 to CAT-5 catalysts

Comparative Examples 1 and 2: Preparation of catalysts CAT-6 and CAT-7

Dissolve and disperse the metal salts of Mg, Zr and Zn according to the calculated amounts in Table 2 in 50 mL of alkaline hydroalcoholic mixed solution, stir vigorously for 15 minutes at 35°C, continue stirring for 30 minutes, and heat to reflux at 70°C. The washed and dried catalyst is calcined at high temperature and sealed for later use.

The numbers of the obtained samples and the corresponding preparation conditions are shown in Table 2.

Table 2: Preparation of CAT-6 and CAT-7 catalysts

Test Example 1: Evaluation of Catalytic Performance of Multifunctional Mg _a Zr _b Zn _c Si _d O Composite Oxide Catalyst in Direct Preparation of Allyl Alcohol from Methanol and Ethanol

The catalyst tablets prepared in Examples 1 to 5 and Comparative Examples 1 and 2 were sieved, and 20-60 mesh particles were taken for later use. Take 2 g of catalyst and load it into a fixed-bed reactor with an inner diameter of 10 mm. The mixed solution of methanol and ethanol is used as the reaction raw material, the mass concentration of ethanol is 10%, and nitrogen is used as the carrier gas. The injection rate is 1.2 mL·h ^-1 . The reaction was carried out at a reaction temperature of 300° C. and a carrier gas pressure of 1.5 MPa. The collected reaction solution was quantitatively detected by gas chromatograph (equipped with FID detector, Rtx-WAX chromatographic column, 30m×0.25μm×0.32mm), and the obtained product was qualitatively analyzed by GC-MS instrument. The initial reactivity of different catalysts is shown in Table 2; after the reaction was continuously operated for 800 h, the reaction product was detected and analyzed to test the stability of the catalyst, and the test results after 800 h were shown in Table 3.

Table 2: Evaluation of catalytic performance of multifunctional Mg _a Zr _b Zn _c Si _d O composite oxide catalysts in the preparation of allyl alcohol

catalyst Ethanol conversion (%) Allyl alcohol selectivity (%) CAT-1 twenty three 86 CAT-2 25 85 CAT-3 twenty two 85 CAT-4 26 90 CAT-5 twenty two 87 CAT-6 19 85 CAT-7 18 87

It can be seen from the data in Table 2 that the initial reaction activity of the multifunctional Mg _a Zr _b Zn _c Si _d O composite oxide catalyst according to the present invention is not much different from that of the composite oxide catalyst without Si addition, both of which can achieve allyl alcohol. high selectivity with a slight increase in ethanol conversion.

Table 3: Performance evaluation of multifunctional Mg _a Zr _b Zn _c Si _d O composite oxide catalysts after reaction for 800 h

catalyst Ethanol conversion (%) Allyl alcohol selectivity (%) CAT-1 twenty two 85 CAT-2 26 85 CAT-3 twenty one 86 CAT-4 25 89 CAT-5 twenty one 87 CAT-6 4 30 CAT-7 4 32

However, it can be seen from the data in Table 3 that the multifunctional Mg _a Zr _b Zn _c Si _d O composite oxide catalyst according to the present invention has no effect on the selectivity of propenol or the conversion of ethanol after 800 hours of continuous operation. The rates were not significantly different from the initial reactivity. However, after 800 hours of continuous operation of the composite oxide catalyst without Si addition, the selectivity to propylene alcohol and the conversion rate of ethanol decreased significantly. Therefore, the multifunctional Mg _a Zr _b Zn _c Si _d O composite oxide catalyst prepared according to the present invention has more excellent long-term use stability.

The above embodiments do not limit the content of the present invention in any form. Although the embodiments of the present invention only disclose the application of the catalytic conversion of methanol and ethanol mixed solution to prepare propenol compounds, the prepared catalyst is used to catalyze lower alcohols or methanol and lower alcohols. The application of preparing the enol compound is not limited by this example. Any changes to the technical content by any skilled person who are familiar with this profession, without departing from the scope of the technical solution of the present invention, are equivalent to the implementation case, and belong to the technical solution.

Claims (10)

1. A multifunctional Mg _a Zr _b Zn _c Si _d O _e composite metal oxide catalyst, wherein a, b, c and d are the molar ratios of Mg, Zr, Zn and Si active components respectively, and e is O The stoichiometric ratio of atoms, wherein Mg:Zr:Zn:Si=0.1～10:0.01～1:0.01～1:0.01～1, preferably 0.1～10:0.1～1:0.01～0.1:0.1～1, more It is preferably 1 to 10:0.1 to 1:0.01 to 0.1:0.1 to 1. 2. the preparation method of Mg _a Zr _b Zn _c Si _d O _e composite metal oxide catalyst according to claim 1, described method comprises the following steps: (1) After adding metal salts, metal oxides or metal hydroxides containing metal active components Mg, Zr and Zn into the solvent to dissolve and/or disperse, stir to fully mix, the total concentration of the metal precursor mixed solution is 1 to 3 mol·L ^-1 , and heated to reflux; (2) adding a Si-containing compound to the mixed solution obtained in step (1), continuing to stir until fully mixed, and heating to reflux; (3) The mixed solution obtained in step (2) is subjected to rotary evaporation to remove solvent, drying and high temperature calcination to obtain the multi-component Mg _a Zr _b Zn _c Si _d O _e composite metal oxide catalyst. 3. preparation method according to claim 2 is characterized in that, in step (1), active component metal salt is selected from nitrate, carbonate, bicarbonate, chloride, acetate, sulfate, lower grade At least one of metal alkoxides; wherein, the lower metal alkoxide represents an alkoxy organometallic compound generated by replacing the hydroxyl hydrogen of an alcohol molecule with a metal, and the alcohol is at least one of ethanol, propanol or butanol A sort of. 4 . The preparation method according to claim 2 , wherein the metal oxide and metal hydroxide described in step (1) are commercial products and can be used directly without any pretreatment. 5 . 5. preparation method according to claim 2 is characterized in that, solvent described in step (1) is water, or the mixed solvent of water and unit lower alcohol, and described unit lower alcohol is selected from methyl alcohol, ethanol, propanol and At least one of butanol is preferably at least one selected from methanol, ethanol and propanol; the volume percentage of unit lower alcohol in the co-solvent is 1-50%, preferably 20-50%. 6. preparation method according to claim 2 is characterized in that, in step (1), the heating reflux temperature of active component mixed solution is 50～90 ℃, and reflux time is not less than 2 hours; More preferably, step ( The heating reflux time in 1) is 2 to 8 hours. 7. The preparation method according to claim 2, wherein the Si-containing compound described in step (2) is selected from silicon dioxide powder or organosilicon monomer; Further preferably, the Si-containing compound described in step (2) is selected from tetraethylorthosilicate and tetrabutylorthosilicate; Further preferably, the Si-containing compound described in step (2) is silicon dioxide powder with a particle size of 10 to 100 microns; Further preferably, when the Si-containing compound in step (2) is an organosilicon monomer selected from tetraethyl orthosilicate and tetrabutyl orthosilicate, the Si-containing compound is gradually added dropwise. Add in the mixed solution of step (1); Preferably, when the Si-containing compound is silicon dioxide powder in step (2), the silicon dioxide powder is added to the mixed solution in step (1) in a batchwise manner. 8. preparation method according to claim 2, is characterized in that, in step (3), the temperature of rotary evaporation to remove solvent is 50～90 ℃, drying temperature is 100～150 ℃, drying time is 4～12 hours, preferably The calcination temperature is 400 to 800°C, and the calcination time is 1 to 12 hours, preferably 2 to 8 hours. 9. purposes of the Mg _a Zr _b Zn _c Si _d O _e composite metal oxide catalyst according to claim 1 in the preparation of an enol compound, the enol compound comprising: propenol, crotyl alcohol, isobutenol, 2 -At least one of ethyl-propenol, 2-propyl-propenol, 2-butyl-propenol. 10. a method for directly preparing an enol compound from a unit alcohol, the method adopts a fixed bed reactor, in which the Mg _a Zr _b Zn _c Si _d O according to claim 1 is housed _e Composite metal oxide catalyst, the enol compound is prepared by loading one or more unit lower alcohols with nitrogen for reaction, wherein the catalyst is used in an amount of 0.1-10 g, the injection rate is 0.1-5 mL·h ^-1 , and the temperature The temperature is 150～350℃, and the pressure is 0.1～2MPa; Preferably, the unit lower alcohols include: methanol, ethanol, propanol, butanol, pentanol, hexanol, phenethyl alcohol, phenylpropyl alcohol, etc., preferably methanol, ethanol, propanol, butanol, amyl alcohol, hexyl alcohol, etc. alcohol; Preferably, when the unit lower alcohol is a mixed solution of methanol and other unit lower alcohol, the mass percentage of other unit lower alcohol is 1% to 50%, further preferably, the mass percentage of other unit lower alcohol 2% to 20%.