Catalytic performance optimization method for preparing 1, 4-dioxane by catalyzing diethylene glycol with solid acid

Abstract

The invention discloses a catalytic performance optimization method for preparing 1, 4-dioxane by catalyzing diethylene glycol with solid acid, and belongs to the technical field of organic synthesis catalysis. Comprising the following steps: a, loading a solid acid catalyst into a fixed bed reactor, heating to a reaction activation temperature, and keeping the temperature; b, a raw material mixed solution is introduced into the reactor, and the raw material mixed solution is composed of diethylene glycol and a mutual soluble solvent of the diethylene glycol. A diethylene glycol raw material mixed solvent method is adopted, the activity and stability of the molecular sieve catalyst can be greatly improved, especially when water which is low in cost, free of pollution and high in stability is preferably selected as a solvent, under the optimal condition, the average conversion rate of diethylene glycol is 95%, the average selectivity of DOX is 91%, the stable operation time can reach up to 1000 h, and the molecular sieve catalyst is suitable for industrial production. And a foundation is laid for green industrial synthesis of 1, 4-dioxane.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for optimizing the catalytic performance of 1,4-dioxane prepared by a heterogeneous catalytic reaction, in particular to a method for optimizing the catalytic performance of solid acid catalysis of diethylene glycol to prepare 1,4-dioxane. BACKGROUND

[0002] 1,4-dioxane (DOX) is a six-membered heterocyclic compound containing two oxygen atoms, which is a widely used excellent organic solvent. It is mainly used as a solvent, reaction medium, extractant in the production of pharmaceuticals, spices, dyes, cosmetics and other fine chemicals, and as a peeling agent in coatings, as well as a metal surface treatment agent.

[0003] 1,4-dioxane is usually prepared from ethylene glycol or diethylene glycol (DEG), and diethylene glycol is a byproduct of ethylene glycol production. Therefore, it is more economically beneficial to produce 1,4-dioxane from diethylene glycol than from ethylene glycol. The traditional synthesis method is to synthesize it under the catalysis of liquid acid such as sulfuric acid or phosphoric acid. Liquid acid catalytic synthesis of 1,4-dioxane has the disadvantages of corrosion of equipment, complex product follow-up treatment, environmental pollution, etc., which is not conducive to the development of green chemical technology.

[0004] The reaction equation is as follows:

[0005] Compared with the traditional liquid acid catalysis, the molecular sieve catalyst overcomes the disadvantages of high pollution and strong corrosion, and is a green route for synthesizing 1,4-dioxane. However, at present, the diethylene glycol raw material occurs intermolecular dehydration and polycondensation on the acid sites of the molecular sieve solid acid catalyst, forming triethylene glycol, tetraethylene glycol, and large molecular polycondensates, which block the molecular sieve pores and acid sites, leading to catalyst deactivation and poor catalyst stability, thus limiting the industrial application of solid acid catalysts for catalyzing diethylene glycol to prepare 1,4-dioxane.

[0006] Sun D L et al. studied the catalytic performance of several solid acid catalysts (such as Al2O3, SiO2-Al2O3, β zeolite and MFI zeolite) for the gas phase cyclization dehydration reaction of diethylene glycol to prepare 1,4-dioxane. Cyclodehydration of diethylene glycol over Ag - modified Al2O3 catalyst The study showed that the activity of all catalysts gradually decreased with the extension of reaction time, especially the β zeolite and MFI zeolite with strong acidity. At the same time, it was found that the Ag-modified Al2O3 catalyst could effectively inhibit carbon deposition and stabilize the catalytic activity, especially under the reaction condition of 250℃, the DEG conversion rate of the catalyst was 100%, and the DOX selectivity was 90%.

[0007] US4760154A pointed out that diethylene glycol can be converted to commercial solvent 1,4-dioxane with high conversion rate in fixed bed device using ZSM-5 or β zeolite as catalyst, and 1,4-dioxane yield can reach 90%, but the patent did not mention reaction time and stability of molecular sieve catalyst, wherein 1,4-dioxane yield = DEG conversion rate x 1,4-dioxane selectivity.

[0008] CN103193758A disclosed a preparation method of 1,4-dioxane, which used solid super strong acid resin to catalyze diethylene glycol to prepare 1,4-dioxane, and used isopropyl ether to extract and dehydrate crude product in high efficiency extraction tower, and then treated waste water by cation resin tower, which successfully overcame many shortcomings of traditional process and realized long-term pollution-free production of product. However, the patent did not mention the catalytic performance and stability of the catalyst, the performance of the catalyst in long period operation was not clear, and the solid super strong acid resin catalyst was expensive and could not be regenerated and recycled.

[0009] At present, the synthesis process of 1,4-dioxane at home and abroad depends on liquid acid catalyst such as concentrated sulfuric acid, which has problems of equipment corrosion and environmental pollution. And the new type of solid acid catalyst is easy to be deactivated due to carbon deposition in the reaction process, which restricts its industrial application. Therefore, it has good industrial application prospect to develop a new method and new process of modified molecular sieve catalytic diethylene glycol to synthesize 1,4-dioxane with high stability and high activity. SUMMARY

[0010] In order to solve the problem of deactivation of the existing solid acid catalyst, the present application provides a method for optimizing the catalytic performance of solid acid catalyst for preparing 1,4-dioxane from diethylene glycol. Specifically, by using diethylene glycol raw material mixed solvent method, strictly selecting the solvent miscible with diethylene glycol, and accurately controlling the mass ratio of diethylene glycol and its miscible solvent, the activity and service life of the catalyst are significantly improved; at the same time, by further modifying the solid acid catalyst and accurately controlling the mass space velocity of diethylene glycol, the activity and service life of the catalyst are greatly improved, and the catalytic efficiency is improved, which provides industrial basis for green synthesis of 1,4-dioxane.

[0011] In the present application, the performance evaluation of the catalyst mainly focuses on three key indicators: DEG conversion rate, DOX selectivity and catalyst stability, DEG conversion rate and DOX selectivity directly reflect the activity level of the catalyst, and the stability of the catalyst is measured by its stable running time. The specific evaluation method of catalyst stability is: in the continuous reaction process, the distribution of products under different time conditions is analyzed to obtain the DEG conversion rate and DOX selectivity in real time, and then the activity state of the catalyst under different time conditions is evaluated. When the decrease rate of DEG conversion rate is significantly increased and the catalytic activity is significantly weakened compared with the initial activity, the time point is determined as the end point of the stable running time of the catalyst. This method can accurately reflect the performance change of the catalyst in the whole use process.

[0012] The technical scheme of the present application is as follows: A method for optimizing the catalytic performance of a solid acid catalyst for preparing 1,4-dioxane from diethylene glycol, characterized in that it comprises the following steps in sequence: a. loading the solid acid catalyst into a reactor, heating to the reaction activation temperature and keeping; b. feeding a raw material mixed solution into the reactor, wherein the raw material mixed solution is composed of diethylene glycol and a mutually soluble solvent.

[0013] Preferably, the configuration of the raw material mixed solution is completed in a storage tank.

[0014] Preferably, the mutually soluble solvent is one or more of water, 1,4-dioxane, gamma-butyrolactone, diethylene glycol monomethyl ether and diethylene glycol diethyl ether.

[0015] More preferably, the mutually soluble solvent is water, which is low-cost, pollution-free and highly stable. Mixing water with diethylene glycol can greatly improve the activity and stability of the molecular sieve catalyst (from 50h to 1000h), and the promoting effect mainly manifests as the hydrogen bond interaction between water molecules and diethylene glycol.

[0016] Preferably, the mass ratio of diethylene glycol to the mutually soluble solvent is 1:3-2:1; since the mutually soluble solvent does not participate in the reaction, the more solvent, the higher the cost, and more preferably, the mass ratio of diethylene glycol to the mutually soluble solvent is 1:2-1:1.

[0017] Preferably, the reactor is a fixed bed reactor, the feeding mode is up-in and down-out, the fixed bed is filled with an appropriate amount of solid acid catalyst, the mixed raw material is pumped into the fixed bed reactor at a certain flow rate by a metering pump, the reaction is a continuous feeding reaction, and the catalyst loading and the raw material flow rate can be adjusted according to the mass space velocity of diethylene glycol in the mixed solution.

[0018] Preferably, the mass space velocity of diethylene glycol in the raw material mixed solution is 0.1h -1-20h -1 ; more preferably, the mass space velocity of diethylene glycol in the raw material mixed solution is 1h -1 -6h -1 . Wherein, the mass space velocity refers to the mass of reactants passing through a unit mass of catalyst per unit time, which is usually used to describe the residence time of reactants on the catalyst and the reaction rate. In the synthesis of 1,4-dioxane and the evaluation of catalyst stability, the mass space velocity is an important process parameter, which affects the stability of the catalyst and the yield of the product.

[0019] In order to better improve the activity and service life of the catalyst, and improve the catalytic efficiency, further, before step a, the solid acid catalyst is modified by using an acid with a concentration of 0.1mol / L-1mol / L.

[0020] Preferably, the solid acid catalyst is one or more of Beta type molecular sieve, ZSM-5 molecular sieve, MCM-22 molecular sieve, and γ-Al2O3; more preferably, the solid acid catalyst is Beta type molecular sieve.

[0021] Preferably, the modification process of the catalyst is to use an organic acid or an inorganic acid with a concentration of 0.1mol / L-1mol / L for modification, and the treatment time is 24h. After modification, the molecular sieve catalyst is washed with ultrapure water until it is neutral, then it is dried and calcined at 500℃ for 4h.

[0022] More preferably, the organic acid is one or more of citric acid, tartaric acid, and coffee acid.

[0023] More preferably, the inorganic acid is one or more of sulfuric acid, hydrochloric acid, and nitric acid.

[0024] In order to better improve the activity and service life of the catalyst, and improve the catalytic efficiency, further, the reaction is carried out at normal pressure, and the reaction activation temperature of the catalyst is 200-300℃; more preferably, nitrogen can be introduced during the reaction, and by controlling the flow rate of nitrogen in the fixed bed reactor, the entire catalytic reaction is always in a nitrogen protection state.

[0025] Particularly preferably, a method for optimizing the catalytic performance of a solid acid catalyst for preparing 1,4-dioxane from diethylene glycol, characterized in that it comprises the following steps in sequence: a. 3g of Beta type molecular sieve is modified by using 0.1mol / L citric acid; b. The modified Beta type molecular sieve is loaded into a fixed bed reactor, and the reaction is carried out at normal pressure, and the temperature is raised to 200℃ and maintained; c. A raw material mixed solution of diethylene glycol:water (mass ratio) 1:1.5 is introduced into the reactor, wherein the mass space velocity of diethylene glycol is 1.0h-1 .

[0026] The reacted product flows from the fixed bed outlet into a condensation separation tank, and after cooling and separation, flows into a storage tank, and the organic phase of the crude product can be analyzed by gas chromatography, and the water content can be analyzed by a Karl Fischer water tester.

[0027] Compared with the prior art, the application has the following prominent features: 1. The diethylene glycol raw material mixed solvent method used in the application can greatly improve the activity and stability of the molecular sieve catalyst, and the stability is much higher than that of the prior art of 55h. In particular, when water, which is low-cost, non-polluting and high-stability, is used as the solvent, the average conversion rate of diethylene glycol is 95%, the average selectivity of DOX is 91%, and the stable operation time is as high as 1000h under the optimal experimental conditions (Example 1), which lays a foundation for the green industrial synthesis of 1,4-dioxane.

[0028] 2. The application uses solid acid as a catalyst to carry out dehydration reaction on diethylene glycol in a fixed bed reactor, realizes the continuous production of 1,4-dioxane under normal pressure, and is suitable for industrial large-scale production. The process is significantly superior to the batch reaction concentrated sulfuric acid method in terms of environmental protection, catalyst efficiency, economy and safety. The technology not only conforms to the development trend of green chemistry, but also effectively reduces the comprehensive production cost, and provides a better solution for the industrial production of 1,4-dioxane. DETAILED DESCRIPTION

[0029] The specific examples listed in the application are only as examples of the application, and the application is not limited to the specific examples described below. Any equivalent modifications and alternatives to the examples described below are also within the scope of the application for those skilled in the art. Therefore, any equivalent transformation and modification without departing from the spirit and scope of the application should be included in the scope of the application. If no specific conditions are specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If no manufacturer is specified for all reagents or instruments, they are all conventional products that can be purchased on the market. In order to better illustrate the application, numerous specific details are given in the following detailed description. Those skilled in the art should understand that the application can also be implemented without some specific details. In some other examples, methods, means, apparatus and steps that are well known to those skilled in the art are not described in detail, in order to highlight the main idea of the application.

[0030] Example 1 Into a 10 mL fixed bed reactor, 3 g of 0.1 mol / L citric acid modified Beta type molecular sieve was loaded, 20 mL / min of nitrogen was introduced as a carrier gas, the reaction was carried out at normal pressure, the temperature was raised to 200°C and kept, a raw material mixed solution of diethylene glycol: water (mass ratio) 1:1.5 was introduced into the fixed bed, the mass space velocity of diethylene glycol was 1.0 h-1 -1 .

[0031] Example 2 Into a 10 mL fixed bed reactor, 2 g of 0.5 mol / L tartaric acid modified ZSM-5 molecular sieve was loaded, 20 mL / min of nitrogen was introduced as a carrier gas, the reaction was carried out at normal pressure, the temperature was raised to 200°C and kept, a raw material mixed solution of diethylene glycol: γ-butyrolactone (mass ratio) 1:1 was introduced into the fixed bed, the mass space velocity of diethylene glycol was 6.0 h-1 -1 .

[0032] Example 3 Into a 50 mL fixed bed reactor, 25 g of 1 mol / L caffeic acid modified MCM-22 molecular sieve was loaded, 50 mL / min of nitrogen was introduced as a carrier gas, the reaction was carried out at normal pressure, the temperature was raised to 280°C and kept, a raw material mixed solution of diethylene glycol: diethylene glycol monomethyl ether (mass ratio) 1:3 was introduced into the fixed bed, the mass space velocity of diethylene glycol was 1.0 h-1 -1 .

[0033] Example 4 Into a 50 mL fixed bed reactor, 20 g of 0.5 mol / L dilute hydrochloric acid modified γ-Al2O3 molecular sieve was loaded, 50 mL / min of nitrogen was introduced as a carrier gas, the reaction was carried out at normal pressure, the temperature was raised to 300°C and kept, a raw material mixed solution of diethylene glycol: diethylene glycol diethyl ether (mass ratio) 1:2 was introduced into the fixed bed, the mass space velocity of diethylene glycol was 1.0 h-1 -1 .

[0034] Example 5 Into a 50 mL fixed bed reactor, 28 g of 0.2 mol / L dilute nitric acid modified Beta type molecular sieve was loaded, 50 mL / min of nitrogen was introduced as a carrier gas, the reaction was carried out at normal pressure, the temperature was raised to 200°C and kept, a raw material mixed solution of diethylene glycol: 1,4-dioxane (mass ratio) 1:2 was introduced into the fixed bed, the mass space velocity of diethylene glycol was 1.0 h-1 -1 .

[0035] Comparative Example 1 The conditions were the same as in Example 1 except that no solvent miscible with diethylene glycol was added.

[0036] Comparative Example 2 The rest of the conditions are the same as those in Example 1 except that the catalyst is replaced by an unmodified Beta-type molecular sieve catalyst.

[0037] Comparative Example 3 The rest of the conditions are the same as those in Example 1 except that the mass ratio of diethylene glycol: water is changed to 1:3.

[0038] Comparative Example 4 The rest of the conditions are the same as those in Example 1 except that the diethylene glycol mass space velocity is changed to 3.0 h -1

[0039] The specific evaluation method of the stable running time of the catalyst is discussed in detail taking the product distribution at different times during the reaction process in Example 1 (Table 1) as an example. The data in Table 1 are all real-time data.

[0040] Table 1 Product distribution at different reaction times in Example 1

[0041] As can be seen from Table 1, when the reaction time is 1000 h, the content of diethylene glycol in the product component distribution increases significantly, and the decline rate of the DEG conversion rate accelerates significantly, so 1000 h is determined as the stable running time of the reaction.

[0042] The performance parameters of Examples 1-5 are shown in Table 2.

[0043] Table 2 Performance parameters of Examples 1-5

[0044] The performance parameters of Example 1 and Comparative Examples 1-4 are shown in Table 3.

[0045] Table 3 Performance parameters of Example 1 and Comparative Examples 1-4

[0046] As can be seen from Tables 2 and 3, the stable running time of Comparative Example 1 (the traditional method) is only 55 h, while in the method of the present application (Examples 1-5, Comparative Examples 2-4), the catalyst stability is greatly improved under different catalysts and different experimental conditions, and under the optimal (Example 1) conditions, the stable running time of the catalyst can be improved to 1000 h.

[0047] As can be seen from Tables 1 and 2, the stable running time, DOX selectivity and DEG conversion rate of Comparative Example 2 (unmodified Beta-type molecular sieve catalyst) are all significantly lower than those of Example 1 (modified Beta-type molecular sieve catalyst), which shows that the acid modification treatment of the catalyst can significantly improve the activity and service life of the catalyst, and thus improve the catalytic efficiency. ​

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. Units used in the specification are those commonly employed in the art and the numerical values and ranges appearing in the present application should be understood to be inclusive of systemically error inherent in the manufacturing process.

[0049] The features and characteristics of the present application will be further described with reference to the following examples.

[0050] The above examples only express the specific implementation of the present application, which is described in more detail and specifically, but it should not be understood as a limitation to the protection scope of the present application. It should be noted that for those skilled in the art, without departing from the technical concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application.

Claims

1. A method for optimizing the catalytic performance of a solid acid catalyst for the preparation of 1,4-dioxane from diethylene glycol, characterized in that, Comprise the following steps in turn: a. loading solid acid catalyst into the reactor, heating to reaction activation temperature and keeping; b. feeding raw material mixed solution into the reactor, The raw material mixed solution is composed of diethylene glycol and its mutually soluble solvent.

2. The process for optimization of catalytic performance of solid acid catalyst for the preparation of 1,4-dioxane from diethylene glycol as claimed in claim 1, wherein, The mutually soluble solvent is one or more of water, 1,4-dioxane, gamma-butyrolactone, diethylene glycol monomethyl ether, diethylene glycol diethyl ether.

3. The process for optimization of catalytic performance of solid acid catalysts for the preparation of 1,4-dioxane from diethylene glycol as claimed in claim 2, wherein, The mass ratio of diethylene glycol and its mutually soluble solvent is 1:3-2:

1.

4. The process for optimization of catalytic performance of solid acid catalyst for the preparation of 1,4-dioxane from diethylene glycol as claimed in claim 3, wherein, The mass ratio of diethylene glycol and its mutually soluble solvent is 1:2-1:

1.

5. The process for optimization of catalytic performance of solid acid catalyst for the preparation of 1,4-dioxane from diethylene glycol as claimed in claim 4, wherein the process is carried out at a temperature in the range of 80-100°C. The mass space velocity of diethylene glycol in the raw material mixed solution is 0.1 h -1 -20 h -1 .

6. The process for optimization of catalytic performance of solid acid catalyst for the preparation of 1,4-dioxane from diethylene glycol as claimed in claim 5, wherein, The mass space velocity of diethylene glycol in the raw material mixed solution is 1 h -1 -6h -1 .

7. The process for optimization of catalytic performance of solid acid catalysts for the preparation of 1,4-dioxane from diethylene glycol as claimed in any one of claims 1 to 6, wherein the process is characterized by, Before step a, the solid acid catalyst is modified with an acid with a concentration of 0.1mol / L-1mol / L.

8. The process for optimization of catalytic performance of solid acid catalyst for the preparation of 1,4-dioxane from diethylene glycol as claimed in claim 7, wherein, The solid acid catalyst is one or more of Beta type molecular sieve, ZSM-5 type molecular sieve, MCM-22 molecular sieve, gamma-Al2O3.

9. The process for optimization of catalytic performance of solid acid catalyst for the preparation of 1,4-dioxane from diethylene glycol as claimed in claim 8, wherein the process is carried out at a temperature in the range of 80-120°C. The acid is one or more of citric acid, tartaric acid, coffee acid.

10. The process for optimization of catalytic performance of solid acid catalyst for the preparation of 1,4-dioxane from diethylene glycol as claimed in claim 8, wherein the process is characterized by, The acid is one or more of sulfuric acid, hydrochloric acid, nitric acid.

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