CN102814193A - Copper-composite molecular sieve catalyst used for synthesis of diethyl carbonate through gas-phase oxidative carbonylation and its preparation method - Google Patents

Abstract

The invention discloses a catalyst for ethanol gas-phase carbonylation of diethyl carbonate and a preparation method thereof. A copper-composite molecular sieve catalyst is prepared by using a composite molecular sieve Yβ through a solid ion exchange method and applied to oxidative carbonylation to synthesize diethyl carbonate. The ester reaction system uses the unique acidity and pore structure of the composite molecular sieve to improve the performance of the catalyst. The catalyst prepared by the method has high selectivity, long service life, low preparation cost and relatively simple process.

Description

Copper-composite molecular sieve catalyst for gas-phase oxidative carbonyl synthesis of diethyl carbonate and its preparation method

technical field

The invention belongs to the gas-phase synthesis catalytic technology for synthesizing diethyl carbonate, and more specifically, relates to a catalyst for ethanol gas-phase carbonylation of diethyl carbonate and a preparation method thereof.

Background technique

Diethyl carbonate (DEC) is an environmentally friendly and widely used green chemical. Due to its active chemical properties, DEC can be used as an important organic synthesis intermediate and widely used in many fields such as synthetic pesticides, medicines, paints, spices, etc., and has good industrial prospects. DEC can be used as a green solvent, surfactant and lithium battery fluid additive, etc. Electronic-grade pure DEC can be used as a cleaning agent for color TV picture tubes. In addition, as one of the substitutes for MTBE, DEC has more competitive advantages than dimethyl carbonate (DMC) and ethanol, and is the potential maximum use. The existing synthesis processes of DEC mainly include phosgene method, transesterification method, direct synthesis of ethanol carbon dioxide, urea alcoholysis method, ethanol gas-phase oxidative carbonylation method, etc. The reactants of the traditional phosgene method are highly toxic and cause serious environmental pollution; the product hydrogen chloride is easy to corrode equipment. Therefore, the non-phosgene process has received more and more attention. Among them, the gas-phase oxidative carbonylation of ethanol has high atomic economy and harmless by-products, which conforms to the principles of green chemistry and has great industrial prospects. The process reaction is as follows:

At present, the reports of catalysts for this reaction system are increasing year by year. Among them, the initial activity and selectivity of the Wacker-type catalysts loaded with CuCl ₂ -PdCl ₂ on carbon supports are better, but at the same time, there are problems of catalyst deactivation and equipment corrosion caused by chlorine loss.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, to provide a catalyst for the synthesis of DEC by the oxidative carbonylation of ethanol, for the first time to use the composite molecular sieve Yβ to prepare the copper-composite molecular sieve catalyst through the solid ion exchange method and apply it to the oxidative carbonylation The diethyl carbonate reaction system is synthesized, and the unique acidity and pore structure of the composite molecular sieve are used to improve the performance of the catalyst. The catalyst prepared by the method has high selectivity, long service life, low preparation cost and relatively simple process.

The technical purpose of the present invention is achieved through the following technical solutions.

Gas-phase oxidative carbonylation synthesis diethyl carbonate copper-composite molecular sieve catalyst and preparation method thereof are prepared according to the following method:

First, the preparation of Yβ composite molecular sieve carrier

1. Configure the system for preparing β molecular sieve, which is composed of template agent, ammonia water, sodium hydroxide, sodium metaaluminate, silica sol and water, wherein the volume ratio of ammonia water to water is 2~10, silicon dioxide and trioxide The molar ratio of dialuminum is 20-50, preferably 21-45; the molar ratio of hydroxide ion to silicon dioxide is 0.2-2.5, preferably 0.2-2.2; the molar ratio of template agent to silicon dioxide is 0.3-0.4 ; Then add NaY molecular sieve powder to the above system, stir the suspension prepared for 0.5~2h

Wherein said templating agent is tetraethylammonium bromide (TEAB), and the mol ratio of silicon dioxide and aluminum oxide is silicon-aluminum ratio, and silica sol provides silicon dioxide in the system (that is, the quality of silica sol is multiplied by The mass percent of silicon dioxide in the silica sol), sodium metaaluminate provides aluminum oxide (that is, the consumption of sodium metaaluminate is converted into the molar number of aluminum oxide); the hydroxide ion and silicon dioxide The molar ratio is the alkalinity, and the hydroxide radicals are provided by sodium hydroxide and ammonia in the system, that is, the sum of the moles of sodium hydroxide and _NH3 in ammonia.

2. After hydrothermally crystallizing the above suspension at 120-150°C for 120-200 hours, preferably 160-200 hours; filter and wash until neutral and then dry, for example, for 8-12 hours; Raise the temperature to 500~650°C per minute, keep the temperature constant for 4~8h, and make sodium Yβ molecular sieve after natural cooling.

3. Add the prepared sodium-type Yβ molecular sieve powder into 0.1~1.0mol/L NH ₄ NO ₃ or NH ₄ Cl aqueous solution, stir at 30~80°C for 4~12h, wash, filter and dry and repeat once; 450~550°C Calcining at lower temperature for 2-5 hours to obtain H-type Yβ composite molecular sieve carrier.

Second, the loading of active components

The catalyst was prepared by the solid ion exchange method, and the CuCl and Yβ composite molecular sieve carriers were mixed and ground according to the mass ratio of 1:10~1:2, and then placed in the quartz glass tube of the tubular heating furnace, and the flow rate was 30~100mL/min. Inject _N2 gas, heat to 350-700°C at a heating rate of 1-10°C/min, keep the temperature for 4-15 hours, and cool to room temperature (20-25°C) naturally to prepare the catalyst.

In the technical scheme of the present invention, Yβ molecular sieves are firstly synthesized and protonated, and then used as a catalyst carrier for synthesis of DEC by gas-phase oxidative carbonylation of ethanol, at a raw material feed molar ratio n(CO):n(O ₂ )=5 :1~15:1, n(CH ₃ CH ₂ OH):n(CO)=1:10~1:2, the reaction temperature is 100~150℃, the reaction pressure is 0.3~1.0MPa and the catalyst exists. To achieve reaction synthesis, N ₂ is used as the balance gas, and the partial pressure of N ₂ is 1/9 to 1/2 of the total pressure. When the ethanol feed space velocity is 2000~5000h ^-1 , the catalyst dosage is 0.3~0.7g.

The advantage of the technical solution of the present invention is that the Yβ composite molecular sieve is used as the carrier, which can effectively adjust the ratio of the two molecular sieves, regulate the carrier composition, pore structure and surface acidity, so that the structure of the catalyst prepared by the solid ion exchange method is stable and better. activity and selectivity. Compared with the traditional wacker-type catalyst with CuCl ₂ -PdCl ₂ supported on carbon carrier, the service life can reach 100 h, and avoids the use of precious metal Pd and equipment corrosion problems caused by chlorine loss.

Description of drawings

Figure 1 XRD patterns of composite molecular sieves under different crystallization times.

Figure 2 is the XRD characterization chart of NaYβ obtained by changing the SiO ₂ /Al ₂ O ₃ preparation system of β molecular sieve.

Fig. 3 is the XRD characterization diagram of NaYβ obtained by changing the basicity of the β molecular sieve preparation system.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with specific embodiments.

【Example 1】

The preparation method of the Yβ carrier is as follows: add 4.5g of the template agent tetraethylammonium bromide (TEAB) into 8mL of 25% ammonia (density 0.91g/mL) solution, then add 1mL of water, stir to dissolve, and then Add 0.3g NaAlO ₂ , 0.3g NaOH and 7.5mL H ₂ O and stir until completely dissolved, then add 13g silica sol (the mass fraction of SiO ₂ is 30%) and 2mL H ₂ O at one time, and form a suspension after vigorous stirring for 1 hour solution, where n(SiO ₂ )/n(Al ₂ O ₃ )=36 and n(NH ₃ +NaOH)/n(SiO ₂ )=1.8 in the β-gel. Then add 2g of commercially available NaY molecular sieve powder (Nankai Catalyst Factory, n(SiO ₂ )/n(Al ₂ O ₃ )=5) and 25mL of H ₂ O, stir for 0.5h, then move to a crystallization kettle, and place in water at 140°C After thermal crystallization for 180 hours, filter and wash until the filtrate is neutral. After drying at 120°C for 8 hours, put it into a muffle furnace to raise the temperature to 590°C at a rate of 2°C/min, keep the temperature for 6 hours, and then cool down to room temperature naturally to obtain the sodium composite molecular sieve NaYβ.

Add 3g of NaYβ molecular sieve to 30mL of 0.5mol/L NH ₄ NO ₃ aqueous solution, stir in a water bath at 60°C for 6h, filter and wash, dry in vacuum at 120°C for 4h, and repeat the above process once. The obtained solid was placed in a muffle furnace to raise the temperature to 500°C at a rate of 2°C/min, and then cooled down to room temperature naturally after constant temperature for 3 hours to obtain a hydrogen-type composite molecular sieve HYβ.

Grind and mix 2g of HYβ molecular sieve and 1g of CuCl powder and move it into a tube furnace quartz glass tube with N flow rate _of 60mL/min, heating rate of 2°C/min to 550°C, constant temperature for 6h and natural cooling to obtain CuYβ catalyst.

[Example 2-4]

In the case that other experimental conditions are exactly the same as in Example 1, the crystallization time in the preparation process of the sodium-type Yβ composite molecular sieve is changed to 160h, 190h, and 200h, wherein the mix state refers to the situation of Comparative Example 1, that is, the two molecular sieves Condition after physical mixing. The XRD spectrum of the obtained NaYβ molecular sieve and physically mixed NaY-β molecular sieve is shown in Figure 1 (XRD is measured by Rigaku D/max2500v/pc diffractometer of Rigaku, using Cu/K-alphal rays as light source. The target is a copper target, the 2θ angle measurement range is 20~80°, the scanning speed is 8°/min, and the test samples are all powder, the same below). When the crystallization time is longer than 160h, the crystal phases of Y and β molecular sieves can appear at the same time, indicating that the composite molecular sieve has been successfully prepared. Further prolonging the time, the characteristic diffraction peak of β molecular sieve is enhanced, and the characteristic diffraction peak of Y molecular sieve is weakened, indicating that the composition of the composite molecular sieve can be effectively adjusted by controlling the crystallization time, thereby affecting the catalyst activity.

[Example 5-7]

In the case that other experimental conditions are exactly the same as those in Example 1, the quality of NaAlO ₂ added to the β molecular sieve system during the preparation of NaYβ composite molecular sieve is changed, that is, the ratio n(SiO ₂ ) of SiO ₂ /Al ₂ O ₃ is changed /n(Al ₂ O ₃ )=21, 27, 45. The obtained NaYβ molecular sieve and the XRD spectrum of Example 1 are shown in FIG. 2 . When the ratio of n(SiO ₂ )/n(Al ₂ O ₃ ) is between 21 and 45, NaYβ composite molecular sieves can be successfully synthesized, and the higher the ratio, the higher the proportion of β crystal phase in the composite molecular sieve. high. Therefore, by controlling the ratio of SiO ₂ /Al ₂ O ₃ , the proportion of the crystal phase of β molecular sieve in the composite molecular sieve can be changed.

【Example 8-12】

In the case that other experimental conditions are exactly the same as in Example 6, the amount of ammonia water in the β molecular sieve system during the preparation of the NaYβ composite molecular sieve is changed, that is, the alkalinity n(NH ₃ +NaOH)/n(SiO ₂ ) is changed, respectively for 0.2, 0.5, 1.0, 1.4, 2.2. The XRD spectrum of the obtained NaYβ molecular sieve is shown in FIG. 3 . The change of alkalinity will affect the crystallinity of the composite molecular sieve and the composition of the crystal phases of the two molecular sieves, which will further affect the performance of the catalyst.

[Example 13]

Catalyst activity evaluation was carried out in a pressurized micro-reaction system. The reactants were fed with 40mL/min CO, 4mL/min O ₂ and carrier gas 26mL/minN ₂ . Ethanol was passed through the gasification chamber by a micropump at a constant flow rate of 0.05mL/min. After gasification, enter the reactor, use 1.0mL of the catalyst of Example 1, react at 140°C, 0.7Mpa, and analyze the product by gas chromatography. The conversion rate of ethanol was 1.5%, the selectivity of ethanol to DEC was 34.1%, and the space-time yield of DEC was 31.1mg/g·h.

[Example 14-24]

Under the same situation as other reaction conditions and embodiment 13, adopt the catalyst among the embodiment 2-12 to carry out the activity evaluation of synthesizing diethyl carbonate. Taking the conversion rate of ethanol, the selectivity of ethanol to DEC and the space-time yield of DEC as indicators, the obtained reaction performance is shown in Table 1.

Table 1 Catalyst oxidation carbonyl synthesis diethyl carbonate reaction result

[Example 25-28]

When other reaction conditions were the same as in Example 13, the catalyst prepared under the preparation conditions of Example 6 was used, and the reaction temperatures were changed to 120, 130, 150, and 160° C. to evaluate the performance of the catalyst. Taking the conversion rate of ethanol, the selectivity of ethanol to DEC and the space-time yield of DEC as indicators, the obtained reaction performance is shown in Table 2.

Table 2 Oxidation carbonyl synthesis reaction result of diethyl carbonate at different reaction temperatures

[Comparative Example 1]

Take commercially available Y molecular sieves (Nankai Catalyst Factory, n(SiO ₂ )/n(Al ₂ O ₃ )=5), β molecular sieves (using the formula and process of Example 1 to prepare β gels, and do not compare with commercially available Y molecular sieves are compounded, and the same process is used to obtain β molecular sieves), each 1g is mixed, and then ball milled with water for 8 hours at a speed of 200r/min. After the ball-milled NaY-β molecular sieve was dried at 120°C, it was added to a 0.5mol/L NH ₄ NO ₃ aqueous solution, stirred in a water bath at 60°C for 6 hours, filtered and washed, dried in vacuum at 120°C for 4 hours, and the above process repeated. The obtained solid was placed in a muffle furnace to raise the temperature to 500°C at a rate of 2°C/min, and then cooled down to room temperature naturally after constant temperature for 3 hours to obtain a hydrogen-type composite molecular sieve HY-β.

Grind and mix 2g HY-β molecular sieve with 1g CuCl powder and move it into a tube furnace quartz glass tube, the _N2 flow rate is 60mL/min, the heating rate is 2°C/min, rise to 550°C, keep the temperature for 6h, and then cool naturally to obtain CuY-β catalyst. The activity test was carried out under the reaction conditions of Example 13. The conversion rate of ethanol is 1.0%, the selectivity of ethanol to DEC is 32.5% and the space-time yield of DEC is 19.7mg/g·h.

[Comparative Example 2]

Take 5g of commercially available Y molecular sieve, add it to 50mL0.5mol/L NH ₄ NO ₃ aqueous solution, stir in a water bath at 60°C for 6h, filter and wash, dry in vacuum at 120°C for 4h, repeat the above process once. The obtained solid was placed in a muffle furnace to raise the temperature to 500°C at a rate of 2°C/min, and then cooled down to room temperature naturally after constant temperature for 3 hours to obtain a hydrogen-type composite molecular sieve HY.

Grind and mix 2g HY molecular sieve and 1g CuCl powder and move it into a tube furnace quartz glass tube, the _N2 flow rate is 60mL/min, the heating rate is 2°C/min, rise to 550°C, keep the temperature for 6h, and then cool naturally to obtain the CuY catalyst. The activity test was carried out under the reaction conditions of Example 13. The conversion rate of ethanol is 1.6%, the selectivity of ethanol to DEC is 29.2% and the space-time yield of DEC is 28.4mg/g·h.

[Comparative Example 3]

The experimental conditions are exactly the same as those of Comparative Example 19, except that the molecular sieve is changed to beta molecular sieve (the formula and process of Example 1 are used to prepare the beta gel, and the commercially available Y molecular sieve is not compounded, and the same process is used to obtain the beta molecular sieve), The conversion rate of ethanol is 0.7%, the selectivity of ethanol to DEC is 49.2% and the space-time yield of DEC is 20.9mg/g·h.

The present invention has been described as an example above, and it should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacements that can be made by those skilled in the art without creative labor all fall within the scope of this invention. protection scope of the invention.

Claims (6)

1. gaseous oxidation carbonyl synthesizing diethyl carbonate copper-composite molecular sieve catalyst is characterized in that, utilizes composite molecular screen Y β to prepare copper-composite molecular sieve catalyst through the solid ion exchange process, prepares according to following step:

The first, the preparation of Y β composite molecular screen carrier

Configuration is used to prepare the system of beta-molecular sieve, is made up of template, ammoniacal liquor, NaOH, sodium metaaluminate, Ludox and water, and wherein the volume ratio of ammoniacal liquor and water is 2 ~ 10, and the mol ratio of silica and alundum (Al is 20-50; The mol ratio of hydroxide ion and silica is 0.2-2.5; The mol ratio of template and silica is 0.3-0.4; In above-mentioned system, add the NaY molecular sieve powder then, stir the suspension that 0.5 ~ 2h makes; Above-mentioned suspension behind 120 ~ 150 ℃ of following hydrothermal crystallizing 120-200h, is preferably 160-200 hours; Filtration washing is dry to neutral back; The gained solid is warming up to 500 ~ 650 ℃ with 2 ℃/min under air atmosphere, constant temperature 4 ~ 8h makes sodium type Y beta-molecular sieve after the cooling naturally; The sodium type Y beta-molecular sieve powder that makes adds the NH of 0.1 ~ 1.0mol/L ₄NO ₃Perhaps NH ₄In the Cl aqueous solution, 30 ~ 80 ℃ are stirred 4 ~ 12h down, repeat behind the washing, filtering and drying once; 450 ~ 550 ℃ of following roasting 2 ~ 5h obtain H type Y β composite molecular screen carrier;

The second, the load of active component

Adopt the solid ion exchange process to prepare catalyst, CuCl and Y β composite molecular screen carrier are placed in the quartz glass tube of tubular heater according to mass ratio 1:10 ~ 1:2 mixed grinding, with the flow velocity feeding N of 30 ~ 100mL/min ₂Gas, and be heated to 350 ~ 700 ℃ with 1 ~ 10 ℃/min heating rate, behind constant temperature 4 ~ 15h, naturally cool to 20-25 ℃ of room temperatures, can make catalyst.

2. gaseous oxidation carbonyl synthesizing diethyl carbonate copper-composite molecular sieve catalyst according to claim 1 is characterized in that the mol ratio of said silica and alundum (Al is 21-45; The mol ratio of hydroxide ion and silica is 0.2-2.2.

3. the preparation method of gaseous oxidation carbonyl synthesizing diethyl carbonate copper-composite molecular sieve catalyst is characterized in that, prepares according to following method:

The first, the preparation of Y β composite molecular screen carrier

Configuration is used to prepare the system of beta-molecular sieve, is made up of template, ammoniacal liquor, NaOH, sodium metaaluminate, Ludox and water, and wherein the volume ratio of ammoniacal liquor and water is 2 ~ 10, and the mol ratio of silica and alundum (Al is 20-50; The mol ratio of hydroxide ion and silica is 0.2-2.5; The mol ratio of template and silica is 0.3-0.4; In above-mentioned system, add the NaY molecular sieve powder then, stir the suspension that 0.5 ~ 2h makes; Above-mentioned suspension behind 120 ~ 150 ℃ of following hydrothermal crystallizing 120-200h, is preferably 160-200 hours; Filtration washing is dry to neutral back; The gained solid is warming up to 500 ~ 650 ℃ with 2 ℃/min under air atmosphere, constant temperature 4 ~ 8h makes sodium type Y beta-molecular sieve after the cooling naturally; The sodium type Y beta-molecular sieve powder that makes adds the NH of 0.1 ~ 1.0mol/L ₄NO ₃Perhaps NH ₄In the Cl aqueous solution, 30 ~ 80 ℃ are stirred 4 ~ 12h down, repeat behind the washing, filtering and drying once; 450 ~ 550 ℃ of following roasting 2 ~ 5h obtain H type Y β composite molecular screen carrier;

The second, the load of active component

Adopt the solid ion exchange process to prepare catalyst, CuCl and Y β composite molecular screen carrier are placed in the quartz glass tube of tubular heater according to mass ratio 1:10 ~ 1:2 mixed grinding, with the flow velocity feeding N of 30 ~ 100mL/min ₂Gas, and be heated to 350 ~ 700 ℃ with 1 ~ 10 ℃/min heating rate, behind constant temperature 4 ~ 15h, naturally cool to 20-25 ℃ of room temperatures, can make catalyst.

4. the preparation method of gaseous oxidation carbonyl synthesizing diethyl carbonate copper-composite molecular sieve catalyst according to claim 3 is characterized in that the mol ratio of said silica and alundum (Al is 21-45; The mol ratio of hydroxide ion and silica is 0.2-2.2.

5. like the application in the synthetic diethyl carbonate of ethanol gas phase oxidation carbonylation of claim 1 or 2 described catalyst, it is characterized in that, at raw material charging mole proportioning n (CO): n (O ₂)=5:1 ~ 15:1, n (CH ₃CH ₂OH): n (CO)=1:10 ~ 1:2, reaction temperature is 100 ~ 150 ℃, and reaction pressure is under 0.3 ~ 1.0MPa and the catalyst existence condition, and realization response is synthetic, adopts N ₂Be balanced gas, N ₂Dividing potential drop is 1/9 ~ 1/2 of a stagnation pressure.

6. the application of catalyst according to claim 5 in the synthetic diethyl carbonate of ethanol gas phase oxidation carbonylation is characterized in that, when ethanol charging air speed is 2000 ~ 5000h ^-1The time, catalyst amount is 0.3 ~ 0.7g.

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