CN1814577A - Method for preparing phenylethylene by oxidation-dehydrogenation of ethyl benzene - Google Patents

Abstract

The invention discloses a method for preparing styrene by oxidative dehydrogenation of ethylbenzene, which is characterized in that the method is to contact ethylbenzene with a catalyst under a carbon dioxide atmosphere, wherein the molar ratio of carbon dioxide to ethylbenzene is 5-15, and the reaction temperature is 673K-873K, the liquid volume space velocity of ethylbenzene is 0.1-2.0h ^-1 , and the catalyst is a molecular sieve containing vanadium element in the skeleton structure. The method can effectively prolong the stable operation time under high ethylbenzene conversion rate and styrene selectivity.

Description

A kind of method for preparing styrene by oxidative dehydrogenation of ethylbenzene

Technical field

The present invention relates to a method for preparing styrene by oxidative dehydrogenation of ethylbenzene, more specifically a method for preparing styrene by oxidative dehydrogenation of ethylbenzene under a carbon dioxide atmosphere.

Background technique

Styrene is an important chemical raw material, and 90% of its output is produced by the direct dehydrogenation of ethylbenzene on an iron oxide catalyst. This method requires a large amount of superheated steam, which is condensed into a liquid after the reaction, and the latent heat of vaporization of the water vapor is not recycled, so the energy consumption is relatively large, and the method has the disadvantage that the yield of styrene is limited by thermodynamic equilibrium. In this reaction system, if carbon dioxide is used to replace water vapor, the equilibrium conversion rate of ethylbenzene can be increased and energy consumption can be reduced (the energy consumption for producing 1 ton of styrene can be reduced from 1.5×10 ⁹ cal/t to 1.9×10 ⁸ cal/t), therefore, the method of preparing styrene by dehydrogenation of ethylbenzene under carbon dioxide atmosphere has become a research hotspot in recent years.

Since the activity of Fe-K catalysts in the industrial production of direct dehydrogenation of ethylbenzene to styrene is very low under _CO2 atmosphere, it cannot meet the demand. Therefore, it is necessary to develop new and efficient catalysts suitable for application under CO2 atmosphere. The supports of such catalysts reported in the literature include Al ₂ O ₃ , ZnO, WO ₃ , SiO ₂ , ZrO ₂ , ZSM-5 and activated carbon (AC), etc., and the active components include Fe, V, Cr, Ce, Cu, Ni Oxides of transition metals such as Co and Co, additives include alkali metals such as Li, Na, K, alkaline earth metals such as Ca and Mg, and rare earth metals such as La; spinel-like ferrite, ZrO ₂ and hydrotalcite can also be used directly Type Mg-Al-Fe material as catalyst. Among them, the catalysts with better dehydrogenation performance mainly include Fe-based and V-based catalysts.

N.Mimura et al reported in the article "Dehydrogenation of ethylbenzene to styrene over Fe ₂ O ₃ /Al ₂ O ₃ catalysts in the presence of carbon dioxide" in "Catalyst Letter" 1999, volume 58, pages 59-62. The Fe ₂ O ₃ (10wt%)/Al ₂ O ₃ (90wt%) catalyst prepared by the method is 823K, the molar ratio of CO ₂ /EB is 11, and the W/F is 3.89g-cat h/mol. The yield of ethylene was 33.2%, and the selectivity to styrene was 95.7%.

Zhang Weiguang et al reported the Fe- Na/AC catalyst. The catalyst has a ethylbenzene conversion rate of 63.8% and a styrene selectivity of 93.5% under the condition that the ethylbenzene mass space velocity is 1.28 ^-1 and the CO ₂ flow rate is 38ml/min.

In "Applied Catalysis A: General" 2000, volume 192, "Dehydrogenation of ethylbenzene with an activatedcarbon-supported vanadium catalyst" on pages 281 to 288, Y.Sakurai et al reported the V/AC prepared by impregnation method (loading capacity is 1.0mmol/g AC) catalyst, the catalyst has the highest activity at 823K, the molar ratio of CO ₂ /EB is 50-70, and W/F is 70g-cat h/mol, and the yield of styrene is 54.2%. The selectivity is 80.8%, but the activity is poor.

CN1431045A discloses a vanadium-loaded catalyst prepared with activated carbon or alumina as a carrier, the conversion rate of ethylbenzene can reach more than 60%, and the selectivity of styrene is higher than 96%.

US2003/0166984A1 discloses a catalyst containing vanadium, iron and antimony prepared with zirconia and alumina as a carrier. The catalyst is prepared at 873K, the molar ratio of CO ₂ /EB is 5, and the mass space velocity of ethylbenzene is 1 Under the conditions, the conversion rate of ethylbenzene is as high as 90.8%, and the selectivity of styrene is 95.7%.

So far, there is no report on the dehydrogenation of ethylbenzene to prepare styrene using molecular sieves with vanadium as the framework element as the catalyst.

Contents of Invention

The object of the present invention is to provide a method for preparing styrene by dehydrogenation of ethylbenzene catalyzed by new materials under carbon dioxide atmosphere.

The method for preparing styrene by ethylbenzene dehydrogenation provided by the invention is characterized in that the method is to contact ethylbenzene with a catalyst under a carbon dioxide atmosphere, wherein the molar ratio (CO ₂ /EB) of carbon dioxide to ethylbenzene is 5-15, Preferably 7~11, the reaction temperature is 673K~873K, preferably 723K~873K, the liquid volume space velocity of ethylbenzene is 0.1~2.0h ^-1 , preferably 0.3~1.0h ^-1 , and the catalyst is vanadium-containing in the skeleton structure Elemental molecular sieves.

In the method provided by the invention, said catalyst is a molecular sieve containing vanadium element in the framework structure (abbreviated as vanadium-containing molecular sieve), they refer to that vanadium element enters the framework of molecular sieve, and is combined in the molecular sieve framework with ^V form, as Molecular sieves of framework elements, the presence of vanadium are characterized by FT-IR, ESR and NMR (refer to literature Vanadosilicate catalysts prepared from different vanadium sources and their characteristics in methanol to conversion (A.Miyamoto, D.Medhanavyn and T.Inui, Applied Catalysis, 28(1986)89-103), Synthesis and Characterization of the Vanadium-incorporated MolecularSieve VAPO-5 (SHJhung, YSUH and H. Chon, Applied Catalysis 62(1990)61-72) and Synthesis, characterization and catalytic properties of vanadium silicates with a ZSM-48 structure (A. Tuel and Y. Ben Taarit, Applied Catalysis A: General, 102(1993) 201-204)).

Vanadium-containing molecular sieves can be vanadium-silicon molecular sieves (such as VS-1 and VS-2), wherein vanadium and silicon are used as framework elements, and the mass percent of vanadium is preferably 3 to 6%; vanadium-containing molecular sieves can also be vanadium-aluminum phosphate molecular sieves (such as VAPO -5, VAPO-11, VAPO-31 and VAPO-17, etc.), wherein vanadium, aluminum, phosphorus are used as framework elements, and likewise, the mass percentage of vanadium is preferably 3 to 6%; it can also be vanadium silicoaluminum phosphate, silicon and aluminum The ratio of is arbitrary, and at this time, silicon-aluminum is used as a framework element at the same time, and the content of vanadium in the framework is characterized by the mass percentage of vanadium.

The method provided by the present invention is carried out by using vanadium-containing molecular sieves as ethylbenzene oxidative dehydrogenation catalysts. In said vanadium-containing molecular sieves, vanadium elements enter the molecular sieve framework to form isolated redox centers. The active components are highly dispersed and the pore size distribution is Consistent, so the dispersion of vanadium species and the specific surface area of the catalyst are improved, and the stability is better, so when reflected in the reaction, the stable operation time under high ethylbenzene conversion and styrene selectivity can be effectively extended (see Attached).

Description of drawings

Accompanying drawing is embodiment 1 and use V/ The comparison diagram of the method of AC (the loading is 1.0mmol/g AC) catalyst, in the figure, (■) represents V/AC, (▲) represents VAPO-5.

Detailed ways

The present invention will be further described below by embodiment, but content of the present invention is not limited thereby.

In the examples, the elemental composition of the vanadium-silicon molecular sieve or vanadium-aluminum phosphate molecular sieve in the catalyst is quantitatively analyzed by X-ray fluorescence spectroscopy, and its crystal phase and crystallinity are determined by XRD.

Example 1

Synthesis of VAPO-5 molecular sieve: 15g dry rubber powder (Al ₂ O ₃ content 65.8%, produced by Changling Catalyst Factory), add water 60mL beating for 60 minutes, slowly add 14g orthophosphoric acid solution (phosphoric acid content 85%, Beijing reagent factory production). After stirring for 10 minutes, add 2.3 grams of vanadyl sulfate pentahydrate (22% by weight of vanadium content, dissolved in 2g of water), continue stirring at room temperature for 60 minutes, then add 16mL template triethylamine (content of 98%, produced by Beijing Reagent Factory). After continuing to stir for 1 hour, place in a crystallization kettle for dynamic crystallization at 175° C. for 72 hours. The obtained product was washed with water and dried at 80°C, and the sample was roasted at a temperature program in flowing air (120°C, 1 hour; 3°C/min to 550°C; kept for 4 hours and then slowly cooled to room temperature). The X-ray diffraction (XRD) spectrum of the obtained product has the characteristics of VAPO-5 molecular sieve, wherein the mass percentage of vanadium is 3%, which is recorded as catalyst A.

The operating conditions of the method for preparing styrene by dehydrogenation of ethylbenzene are as follows: the reaction temperature is 813K, the space velocity of ethylbenzene is 1.0h ^-1 , and the molar ratio of CO ₂ /EB is 10.

The reaction gas phase product was analyzed by 13X molecular sieve column, and the liquid phase product was analyzed by capillary column. The capillary column model is: Innowax, 30m×0.25mm×0.25μm, hydrogen flame detector.

The reaction results are shown in Table 1.

Taking catalyst A as an example, V/AC( Loading capacity is that 1.0mmol/g AC) catalyst is compared, illustrates the stability of method provided by the present invention with this. The reaction conditions are 823K, W/F: 70g-cat h/mol, V in each gram of catalyst A is 0.3mmol.

The comparison results are shown in the attached figure. It can be seen from the figure that the method provided by the present invention is obviously superior to the method using catalyst V/AC both in terms of the initial activity of the catalyst and the stable operation time.

Example 2

The difference from catalyst A is that the mass percent of vanadium in the VAPO-5 molecular sieve used is 1%, which is referred to as catalyst B. The operating conditions are: the reaction temperature is 873K, the space velocity of ethylbenzene is 0.6h ^-1 , the molar ratio of CO ₂ /EB is 7, and other conditions are the same as in Example 1.

The reaction results are shown in Table 1.

Example 3

The difference from catalyst A is that the mass percent of vanadium in the VAPO-5 molecular sieve used is 2%, which is referred to as catalyst C. The operating conditions are: the reaction temperature is 723K, the space velocity of ethylbenzene is 0.3h ^-1 , and the molar ratio of CO ₂ /EB is 11. Other conditions are with embodiment 1.

The reaction results are shown in Table 1.

Example 4

The difference from catalyst A is that the mass percent of vanadium in the VAPO-5 molecular sieve used is 4%, which is referred to as catalyst D. The operating conditions are: the reaction temperature is 813K, the space velocity of ethylbenzene is 0.6h ^-1 , and the molar ratio of CO ₂ /EB is 7. Other conditions are with embodiment 1.

The reaction results are shown in Table 1.

Example 5

The difference from catalyst A is that the mass percent of vanadium in the VAPO-5 molecular sieve used is 5%, which is referred to as catalyst E. The operating conditions are: the reaction temperature is 773K, the space velocity of ethylbenzene is 1.0h ^-1 , and the molar ratio of CO ₂ /EB is 15. Other conditions are with embodiment 1.

The reaction results are shown in Table 1.

Example 6

The difference from catalyst A is that the mass percentage of vanadium in the VAPO-5 molecular sieve used is 6%, which is referred to as catalyst F. The operating conditions are: the reaction temperature is 813K, the space velocity of ethylbenzene is 0.1h ^-1 , and the molar ratio of CO ₂ /EB is 5. Other conditions are with embodiment 1.

The reaction results are shown in Table 1.

Example 7

The synthesis of VAPO-11: 15g dry rubber powder (Al ₂ O ₃ content 65.8%, Changling Catalyst Factory production), add water 60mL beating for 60 minutes and slowly add 14g orthophosphoric acid solution (phosphoric acid content 85%, Beijing Reagent Factory Production). After stirring for 10 minutes, add 2.1g of vanadyl sulfate pentahydrate (V content 22%, dissolved in 2g of water), continue stirring at room temperature for 60 minutes, then add 13.6mL of template agent dipropylamine (content 98%, Beijing Reagent factory production). After continuing to stir for 1 hour, it was placed in a crystallization tank at 200°C for dynamic crystallization for 96 hours. The X-ray diffraction (XRD) spectrum of the obtained product has the characteristics of VAPO-11 molecular sieve, and the mass percentage of vanadium is 3%, which is recorded as catalyst G.

The operating conditions are as follows: the reaction temperature is 873K, the space velocity of ethylbenzene is 2.0h ^-1 , and the molar ratio of CO ₂ /EB is 10. Other conditions are with embodiment 1.

The reaction results are shown in Table 1.

Example 8

Synthesis of VS-1: Dissolve 1.0 g of V ₂ O ₅ in 50 g of tetrabutylammonium hydroxide, then add 15 g of silica gel as a silicon source, stir evenly, crystallize at 160°C for 10 days, and bake at 530°C for 5 hours to obtain the product The X-ray diffraction (XRD) spectrogram has the characteristic of VS-1 molecular sieve, and the mass percent of vanadium is 3%, is recorded as catalyst H.

The operating conditions are: the reaction temperature is 673K, the space velocity of ethylbenzene is 0.6h ^-1 , and the molar ratio of CO ₂ /EB is 15. Other conditions are with embodiment 1.

The reaction results are shown in Table 1.

Example 9

Synthesis of VS-2: Dissolve 1.8 grams of V ₂ O ₅ in 30 grams of tetrabutylammonium hydroxide and 10 grams of water, then add 15 grams of silica gel as a silicon source, stir evenly, crystallize at 180°C for 10 days, and bake at 530°C for 5 hours Use afterward, obtain former powder, the X-ray diffraction (XRD) spectrogram of gained product has the characteristic of VS-2 molecular sieve, and the mass percentage of vanadium is 3%, is recorded as catalyst I.

The operating conditions are: the reaction temperature is 673K, the space velocity of ethylbenzene is 1.0h ^-1 , and the molar ratio of CO ₂ /EB is 10. Other conditions are with embodiment 1.

The reaction results are shown in Table 1.

Table 1 Example Catalyst number Ethylbenzene conversion % Styrene selectivity % Styrene yield% 123456789 ABCDEFGHI 42.530.135.143.443.844.416.99.412.0 98.495.395.897.298.496.992.590.493.1 41.828.733.642.243.143.015.68.511.2

Claims (7)

1. the method for a preparing phenylethylene by oxidation-dehydrogenation of ethyl benzene, it is characterized in that this method is that ethylbenzene is contacted with catalyzer, wherein the mol ratio of carbonic acid gas and ethylbenzene is 5～15, temperature of reaction is 673K～873K, and the liquid volume air speed of ethylbenzene is 0.1～2.0h ^-1, said catalyzer is the molecular sieve that contains v element in the skeleton structure.

2. according to the method for claim 1, the molecular sieve that contains v element in the said skeleton structure is phosphoric acid vanadium aluminum molecular screen or V-Si molecular sieve.

3. according to the method for claim 2, said phosphoric acid vanadium aluminum molecular screen is selected from one or more among VAPO-5, VAPO-11, VAPO-17 and the VAPO-34.

4. according to the method for claim 3, said phosphoric acid vanadium aluminum molecular screen be with vanadium, aluminium, phosphorus as backbone element, the mass percent of vanadium is 3～6%.

5. according to the method for claim 2, said V-Si molecular sieve is VS-1 and/or VS-2.

6. according to the method for claim 5, said V-Si molecular sieve be vanadium and silicon as backbone element, the mass percent of vanadium is 3～6%.

7. according to the method for claim 1, it is characterized in that this method is that the liquid volume air speed that mol ratio at carbonic acid gas and ethylbenzene is 7～11, temperature of reaction is 723K～873K, ethylbenzene is 0.3～1.0h ^-1Under carry out.