CN1128664C - Compound metal oxide catalyst for synthesizing diphenyl carbonate by using ester exchange method and its preparation method - Google Patents

Abstract

A composite metal oxide catalyst for synthesizing diphenyl carbonate by transesterification and a preparation method thereof mainly solve the problems of difficult separation and recovery of the catalyst and low yield of diphenyl carbonate. The catalyst is basically composed of lead oxide and zinc oxide, wherein the weight ratio of lead and zinc is: Pb:Zn=100:2~85, the calcination temperature is 200~700°C, the matrix is lead salt and zinc salt, and the preparation method adopts coprecipitation method or mechanical grinding. The catalyst has high catalytic activity and good selectivity for the synthesis of diphenyl carbonate by transesterification, and the yield of diphenyl carbonate is greater than 40%. In particular, it has the advantages of no pollution to the environment, no corrosion to equipment, easy separation, recovery and preparation, etc., and can be widely used in the production of diphenyl carbonate.

Description

Composite metal oxide catalyst for synthesizing diphenyl carbonate by transesterification method and preparation method thereof

Technical field of the present invention:

The invention belongs to a composite metal oxide catalyst and a preparation method thereof, in particular to a lead oxide-zinc oxide composite metal oxide catalyst for synthesizing diphenyl carbonate by transesterification and a preparation method thereof.

Background technology of the present invention:

Diphenyl carbonate is an important organic chemical raw material, which can be used to synthesize many important organic compounds and polymer materials, especially polycarbonate which can replace highly toxic phosgene and bisphenol A to produce excellent performance. The synthesis methods of diphenyl carbonate include phosgene method, transesterification method and phenol oxidative carbonylation method. Because phosgene is highly toxic and seriously pollutes the environment, it is gradually being eliminated; the catalyst used in the oxidative carbonylation of phenol is expensive and the catalytic efficiency is not high, and no industrialization report has been seen yet; The suitable method is that in the presence of a catalyst, phenol reacts with dimethyl carbonate to generate diphenyl carbonate and simultaneously produces a synthetic route of methanol. As far as the current synthesis of diphenyl carbonate by transesterification is concerned, there are problems such as low equilibrium conversion rate, difficulty in separation and recovery of catalyst and product when using a homogeneous catalyst. Therefore, it is of great significance to develop efficient and environmentally friendly solid-phase catalysts and suitable reaction processes.

At present, most of the catalysts used for the synthesis of diphenyl carbonate by transesterification of phenol and dimethyl carbonate are homogeneous catalysts. In the JP 56-25138 document, alkali or alkali metal compound catalysts are used, but the reaction speed of this type of catalyst is slow and a large amount of CO _and anisole are produced by-product, and the yield of diphenyl carbonate is low. In DE 2528412 and JP51-105032 documents, the Lewis acid catalysts adopted, such as AlX ₃ , TiX ₃ , TiX ₄ , VOX ₃ , VX ₅ , ZnX ₂ , FeX ₃ , SnX ₄ (wherein X is halogen, acetoxy, alkoxy, aryloxy), the yield of diphenyl carbonate is slightly improved but not more than 37%, and its strong corrosiveness brings difficulties to industrialization. In the DE 344552 and JP63-92662 documents, it is disclosed that the catalysts used in the synthesis of diphenyl carbonate by transesterification are mostly metal organic compounds of titanium and tin, such as butyl titanate [Ti(OC ₄ H ₉ ) ₄ ], dibutyltin oxide [(C ₄ H ₉ ) ₂ SnO], aluminum phenoxide [Al(OPh) ₃ ], butyltin trichloride [C ₄ H ₉ SnCl ₃ ] and polyhydroxybutylene Stannous ane [(OH)(C ₄ H ₉ ) ₂ SnH] _n and so on. These two types of catalysts are homogeneous catalysts with good effect, and the yield of diphenyl carbonate can reach 34% to 52%. The disadvantage is that it is difficult to separate the catalyst from the product and recycle it, and the price is relatively expensive.

Although the productive rate of diphenyl carbonate on the homogeneous catalyst is higher, there are problems such as separation, recovery and environmental pollution, Akinobu et al. The mixed oxide catalysts of Group IIIB metals have diphenyl carbonate yields of 13.6% and 8.5%, respectively. In order to facilitate the separation of catalysts, Akinobu et al. (JP 09-241217) studied heterogeneous microporous catalysts containing IVB group metals, and the yields of methyl phenyl carbonate and diphenyl carbonate were 11.5% and 0.2% respectively .

Won Bae Kim and Jae Sung Lee (WBKim, JSLee.CatalysisLetter, 59(1999): 83-88) studied titanium oxide catalysts and other IIIB, IVB, VB, VIB metal oxide catalysts on different supports such as activated carbon and silicon dioxide. On the catalytic activity of transesterification reaction between dimethyl carbonate and phenol, the catalysts include (MoO _x , CrO _x , WO _x , VO _x , TiO ₂ )/(Al ₂ O ₃ , SiO ₂ , MgO, C), they It was found that the TiO ₂ /SiO ₂ catalyst had the highest activity, the conversion of phenol was 37.2%, the yield of methyl phenyl carbonate was 31.7%, and the yield of diphenyl carbonate was 1.7%. Fu and Ono (ZH.Fuand Y.Ono, J.Mol.Catal.A 118(1997): 293) studied supported MoO ₃ , Ga ₂ O ₃ , V ₂ O ₅ , PbO, ZrO ₂ , TiO ₂ , Catalytic performance of CdO, Sm ₂ O ₃ , Fe ₂ O ₃ , CuO and other catalysts, MoO ₃ /SiO ₂ catalyst has the highest activity, but the main product is methyl phenyl carbonate, and the yield of diphenyl carbonate is very low (The highest yield of diphenyl carbonate on PbO/ _SiO2 catalyst was only 2.2%).

Technical content of the present invention:

The present invention solves the problems existing in the prior art, thereby providing a composite metal oxide catalyst for synthesizing diphenyl carbonate by transesterification and a preparation method thereof

Technical solution of the present invention is as follows:

The composite metal oxide catalyst for synthesizing diphenyl carbonate by transesterification is made up of lead oxide and zinc oxide, and wherein the weight ratio of lead and zinc is: Pb: Zn=100: 2～85; Preferred weight ratio is: Pb: Zn= 100: 3~18.

Prepare the steps of composite metal oxide catalysts for synthesizing diphenyl carbonate by transesterification with precipitation method as follows:

(1) dissolving parent lead salt and zinc salt in distilled water respectively to form a solution of 10% to 40% (mass percentage);

(2) be made into the ammonia solution of 2%～5% (volume percent) with distilled water and ammoniacal liquor;

(3) The above three solutions are mixed and stirred by the parallel flow method, precipitated, and vacuum filtered;

(4) drying the obtained precipitate in an oven at 90-120° C. for 5-10 hours;

(5) Calcining the dried precipitate in a muffle furnace at a temperature of 200-700° C. for 2-10 hours, taking it out to obtain a composite metal oxide catalyst.

Said parent lead salt in the precipitation method is lead nitrate, lead acetate, and parent zinc salt is zinc nitrate, zinc acetate, zinc stearate.

The step that prepares transesterification synthesis diphenyl carbonate composite metal oxide catalyst with mechanical grinding method is as follows:

(1) dissolving parent lead salt and zinc salt in distilled water respectively to form a solution of 10% to 40% (mass percentage);

(2) prepare 2%～5% (volume percent) ammonia solution with distilled water and ammoniacal liquor;

(3) Mix and stir the prepared lead salt solution and ammonia solution according to the co-current method to form lead hydroxide precipitate, and vacuum filter;

(4) Mix and stir the zinc salt solution and the ammonia solution according to the co-current method to form a zinc hydroxide precipitate and vacuum filter;

(5) Wash and dry the precipitate obtained after filtering in (3) and (4) respectively;

(6) Grinding the two hydroxides prepared in (5) in a mortar and mixing uniformly;

(7) Calcining the ground mixture in a muffle furnace at a temperature of 200-700° C. for 2-10 hours, and taking it out to obtain a composite metal oxide catalyst.

Said parent lead salt in the grinding method is lead nitrate, lead acetate, and parent zinc salt is zinc nitrate, zinc acetate, zinc stearate.

The preferred calcination temperature in the above two preparation methods is 400-600°C.

Compared with the prior art, the present invention has the following beneficial effects:

1. High catalytic activity. The lead oxide-zinc oxide composite metal oxide catalyst of the invention has high catalytic activity for the reaction of synthesizing diphenyl carbonate by transesterification. The yield of diphenyl carbonate is comparable to that of n-Bu ₂ SnO homogeneous catalyst with the best catalytic activity at present.

2. The catalyst is easy to separate and recycle. Homogeneous catalysts have problems such as product separation, difficulty in recovery and reuse, and have a certain impact on product quality, while the catalyst of the present invention is very easy to separate from the product.

3. It will not pollute the environment and corrode equipment. During the catalytic reaction of Lewis acid catalyst, a large amount of hydrochloric acid will be produced by-product, which will pollute the environment and seriously corrode the equipment. However, the catalyst of the present invention neither pollutes the environment nor corrodes equipment during use.

4. Easy regeneration and good stability. The catalyst of the invention belongs to composite metal oxide, can be reused for many times, and can recover activity only by simple roasting. However, the supported n-Bu ₂ SnO catalyst has the loss of active components and the change of active structure, and it is difficult to restore the initial activity after regeneration.

5. The particle size of the catalyst reaches the nanometer level.

The specific embodiment of the present invention is as follows:

Example 1

Preparation of Composite Metal Oxide Catalysts

1. Take 14.8g of Pb(NO ₃ ) ₂ and add 59.2g of distilled water to make a 20% (mass percentage) solution;

Take 9.8g Zn(Ac) ₂ and add 39.2g distilled water to make a 20% (mass percentage) solution;

2. Take 14.6ml of 25% ammonia water and add 715.4ml of distilled water to make a 2% (volume percentage) solution;

3. Add the three solutions together into the beaker, stir at the same time, stir for 10 minutes, and vacuum filter;

4. After filtration, the obtained precipitate was dried in an oven at 90°C for 10 hours;

5. Calcining the dried precipitate in a muffle furnace at 500° C. for 8 hours to prepare a composite metal oxide catalyst, which is taken out and placed in a desiccator for later use.

The prepared catalyst samples were taken for XRD characterization, and it was found that the catalyst was basically composed of lead oxide, trilead tetroxide and zinc oxide; and atomic absorption analysis showed that the mass ratio of Pb to Zn was 100:11.

Example 2

Catalyst prepared with embodiment 1 adopts transesterification method to synthesize diphenyl carbonate

1, in the four-neck flask that is connected with the constant pressure dropping funnel, the rectifying column that is equipped with distillation head, nitrogen inlet pipe and thermometer, after feeding nitrogen, add the catalyst 0.49g that makes in the embodiment 1, phenol 15.0 g;

2. When heated to 180°C, start to add dimethyl carbonate (DMC) dropwise. The total amount of DMC added is 17.0ml. The time when DMC is started to be added dropwise is the reaction start time, and the reaction is carried out for 8 hours; Distillation column evaporates methanol and dimethyl carbonate mixed fraction;

3. The overhead fraction of the rectification column was analyzed by 3420 type gas chromatograph, the reaction solution containing the main product diphenyl carbonate was analyzed by SQ-206 type gas chromatograph, the content of each component in the sample was determined by external standard method, and the diphenyl carbonate was measured. The phenyl ester yield was 40.8%.

4. Vacuum filtration to separate the catalyst from the reaction solution. After repeated washing, the catalyst was dried at 90°C for 10 hours, then roasted in a muffle furnace at 500°C for 8 hours, and then taken out and put into a desiccator for next use.

Example 3

The preparation steps of the composite metal oxide catalyst are the same as in Example 1, but the calcination temperature is different, as shown in Table 1. Using the prepared catalyst to synthesize diphenyl carbonate by transesterification, the reaction conditions are the same as in Example 2, and its catalytic performance is shown in Table 1.

The impact of table 1 calcination temperature on catalyst activity Calcination temperature/℃ 350 450 500 550 600 DPC ^* Yield/% 23.2 35.6 40.8 24.0 22.5

*DPC: diphenyl carbonate

Example 4

The preparation steps of the composite metal oxide catalyst are the same as in Example 1, but the amount of the precursor is changed, so that the mass ratio of Pb and Zn in the prepared catalyst is also changed, as shown in Table 2. Using the prepared catalyst to synthesize diphenyl carbonate by transesterification, the reaction conditions are the same as in Example 2, and the catalytic performance results are shown in Table 2.

Table 2 _{Effects of different} lead-zinc ratios on catalyst activity :3 100:6 100:13 100:83 100:45DPC ^* Yield/% 37.8 42.3 39.6 26.8 14.9

*DPC: diphenyl carbonate

Example 5

The preparation steps of the composite metal oxide catalyst and the parent molar mass consumption are the same as in Example 1, but different lead and zinc compounds are used as the parent, and the mass ratio of lead and zinc in the prepared catalyst is Pb:Zn=100:5 ~80. Using the prepared catalyst to synthesize diphenyl carbonate by transesterification, the reaction conditions are the same as in Example 2. The catalytic performance results are shown in Table 3.

Example 6

Catalyst Preparation Using Mechanical Milling

1. a Weigh 22.2g of Pb(NO ₃ ) ₂ , add 88.8g of distilled water to make a 20% (mass percentage) solution;

b Weigh 10.0g Zn(NO ₃ ) ₂ , add 40.0g distilled water to make a 20% (mass percentage) solution;

2. a Take 10.0ml of 25% ammonia water, add 490.0ml of distilled water, and make a 2% (volume percentage) solution;

b get 25% ammoniacal liquor 7.9ml, add 387.1ml distilled water, be made into the solution of 2% (volume percentage);

3. Put the a solution prepared in 1 and the a solution prepared in 2 into the beaker together, stir at the same time, stir for 10 minutes, and carry out vacuum filtration;

Add the b solution prepared in 1 and the b solution prepared in 2 into the beaker together, and stir at the same time, stir for 10 minutes, and perform vacuum filtration;

4. Fully wash the two kinds of precipitates obtained in 3 with distilled water, and then dry them in an oven at 90°C for 10 hours;

5. Grind the lead hydroxide and zinc hydroxide obtained in 4 in a mortar and mix them evenly;

6. The ground mixture is calcined in a muffle furnace at 500°C for 8 hours, and the prepared catalyst is put into a desiccator for later use.

The prepared catalyst sample was taken for XRD characterization, and it was found that the catalyst was basically composed of lead oxide, trilead tetroxide and zinc oxide. Then, atomic absorption analysis was carried out, and the mass ratio of Pb to Zn was measured to be 100:16.

Example 7

With the catalyst prepared in Example 6, diphenyl carbonate was synthesized by transesterification, and the reaction conditions were the same as in Example 2. The catalytic performance results are shown in Table 3.

_{Table 3 Effects of different precursors on catalyst performance _} ^_ _{_} ^- Y-Ac ^- Z-OH ^- *- Catalyst prepared by mechanical grinding

Claims (5)

1, a kind of compound metal oxide catalyst for synthesizing diphenyl carbonate by using ester exchange is characterized in that: catalyzer is made up of plumbous oxide and zinc oxide, and wherein plumbous weight ratio with zinc is: Pb: Zn=100: 2～85.

2, a kind of preparation method as the said O composite metallic oxide catalyst of claim 1, it is characterized in that: the step for preparing O composite metallic oxide catalyst with the precipitator method is as follows:

(1) parent lead salt and zinc salt are dissolved in respectively in the distilled water, are made into the solution of 10%～40% (mass percent);

(2) be made into the ammonia soln of 2%～5% (volume percent) with distilled water and ammoniacal liquor;

(3) with above-mentioned three kinds of solution with cocurrent process mixing stirring, precipitation, vacuum filtration;

(4) with the gained throw out in baking oven 90～120 ℃ dry 5～10 hours down;

(5) with dried throw out in retort furnace in 200～700 ℃ of roasting temperatures 2～10 hours, take out and promptly make O composite metallic oxide catalyst.

3, according to the preparation method of the said O composite metallic oxide catalyst of claim 2, it is characterized in that: said parent lead salt is lead nitrate, lead acetate, and the parent zinc salt is zinc nitrate, zinc acetate, Zinc Stearate.

4, a kind of preparation method as claim 1 or 2 said O composite metallic oxide catalysts, it is characterized in that: the step for preparing O composite metallic oxide catalyst with mechanical milling method is as follows:

(1) parent lead salt and zinc salt are dissolved in respectively in the distilled water, are made into the solution of 10%～40% (mass percent);

(2) use distilled water and ammoniacal liquor to prepare the ammonia soln of 2%～5% (volume percent);

(3) lead salt solution and the ammonia soln for preparing mixed stirring by cocurrent process, form the lead hydroxide precipitation, vacuum filtration;

(4) zinc solution and the ammonia soln for preparing mixed stirring by cocurrent process, form the zinc hydroxide precipitation, vacuum filtration;

(5) will (3), filter back gained throw out in (4), wash respectively, drying;

(6) two kinds of oxyhydroxide that make in (5) are ground in mortar, mix;

(7) mixture after will grinding again in retort furnace in 200～700 ℃ of roasting temperatures 2～10 hours, take out and promptly make O composite metallic oxide catalyst.

5, according to the preparation method of the said O composite metallic oxide catalyst of claim 4, it is characterized in that: said parent lead salt is lead nitrate, lead acetate, and the parent zinc salt is zinc nitrate, zinc acetate, Zinc Stearate.