CN102794167A - Catalyst for preparing isobutene by isobutane dehydrogenation and preparation method for catalyst - Google Patents

Abstract

The invention provides a catalyst for preparing isobutene by isobutane dehydrogenation and a preparation method for the catalyst. The catalyst comprises the following components in percentage by mass: 60 to 90 percent of Cr2O3, 3 to 12 percent of CaO, 0.5 to 3.0 percent of K2O and 5 to 36.5 percent of Al2O3. The preparation method comprises the following steps of: adding Cr2O3, CaO, K2O and Al2O3 into an aqueous solution of diluted nitric acid in an abundance ratio, baking, introducing nitrogen, roasting, decomposing nitrate and performing solid ion exchange, and thus obtaining the Cr2O3-CaO-K2O-Al2O3 catalyst. The invention has the advantages that the preparation flow of the catalyst is simple, and preparation and use of the catalyst and the waste catalyst do not pollute the environment; the catalyst for preparing the isobutene by the isobutane dehydrogenation has activity and stability, and particularly has excellent isobutene selectivity; and the conversion per pass of isobutane is over 50 percent, and the selectivity of the isobutene serving as a target product is over 98 percent.

Description

Catalyst used for preparing isobutene from isobutane dehydrogenation and preparation method thereof

technical field

The invention relates to the preparation of a catalyst, in particular to a catalyst used for isobutane dehydrogenation to prepare isobutene and a preparation method thereof.

Background technique

Isobutene is a very important organic chemical intermediate, mainly used in the preparation of methyl tert-butyl ether (MTBE, high-octane clean gasoline blending component), butyl rubber, polyisobutylene, methacrylate, tert-butyl Various organic raw materials and fine chemicals such as phenol, tert-butylamine, 1,4-butanediol, ABS resin, etc.

With the continuous development of isobutene downstream products and its derivatives, the demand for isobutene is increasing day by day. Due to the limitation of its own production technology, the conventional steam cracking process restricts the increase of isobutene production. In addition, with the development of the natural gas industry, the market for liquefied petroleum gas used as civil fuel in the petroleum refining industry is gradually shrinking. The development of chemical utilization technology for liquefied petroleum gas is one of the keys for the petroleum refining industry to improve efficiency and resource utilization. Liquefied petroleum gas contains a large amount of isobutane resources, so the development of isobutane dehydrogenation to produce isobutene is an important way to expand the source of isobutene raw materials and improve the efficiency of petroleum refining industry.

At present, there are several sets of industrialized isobutane dehydrogenation technology to prepare isobutene in the world, including the oleflex process of UOP Company in the United States, the catofin process of ABB Lummus, the star process of Phillips Company, the FBD-4 of Snamprogetti SPA Company in Italy and the Linde Company in Germany Linde Craft. Catalysts for isobutane dehydrogenation to isobutene are mainly divided into two categories, chromium-based catalysts and platinum-group noble metal catalysts. For example, USP4506032, USP4595673, etc. disclose catalysts and preparation methods for supporting precious metal platinum on alumina carriers; such as Hakuli et al., on 11%CrOx/SiO2 (mass fraction in terms of Cr) catalysts, 18% of them were obtained at 540°C The yield of isobutene is high, but the selectivity of isobutene is low (72%), and there is serious carbon deposition, which leads to catalyst deactivation (A. Hakuli, et al. J. Catal., 1999,184:349-356). These traditional methods for preparing isobutene by dehydrogenating isobutane have low target product selectivity and easy deactivation of the catalyst due to problems such as high reaction temperature, low reaction space velocity and easy carbon deposition on the surface of the catalyst.

The oxidative dehydrogenation of low-carbon alkanes is an exothermic reaction, which can be carried out at a lower temperature, and because the introduction of oxygen can eliminate the carbon on the surface of the catalyst, so the oxidative dehydrogenation of isobutane to prepare isobutene has attracted attention. Such as CN101138738B, CN1044787C, CN101439292A, CN101618319A and other patents all disclose catalysts and processes for preparing isobutene by oxidative dehydrogenation of isobutane. However, in the presence of oxygen, the target product olefins of isobutane oxidative dehydrogenation and the raw material isobutane are prone to deep oxidation reactions, resulting in low selectivity of raw material isobutane and target product olefins. Therefore, it is of great significance to develop a high-selectivity and high-conversion catalyst for isobutane dehydrogenation to isobutene.

Contents of the invention

The object of the present invention is to overcome the shortcomings in the prior art, and provide a catalyst for preparing isobutene by dehydrogenation of isobutane with high activity and high selectivity and a preparation method thereof.

The object of the present invention can be realized by the following measures: isobutane dehydrogenation prepares the catalyst used for isobutene, the catalyst Cr _{2 O} The content is 60-90% of the catalyst mass fraction, and the CaO content is 3-12% of the catalyst mass fraction %, the content of K ₂ O is 0.5-3.0% of the mass fraction of the catalyst, and the content of Al ₂ O ₃ is 5-36.5% of the mass fraction of the catalyst.

The active component dichromium trioxide is introduced in the form of dichromium trioxide powder; calcium oxide and potassium oxide are introduced in the form of calcium nitrate salt and potassium nitrate salt; aluminum oxide is introduced in the form of active alumina powder Form introduction.

The preparation method of the catalyst used in the preparation of isobutene from isobutane dehydrogenation, the method, according to the content ratio of Cr ₂ O ₃ , CaO, K ₂ O, Al ₂ O ₃ , weighs chromium trioxide powder, activated alumina powder , calcium nitrate salt, and potassium nitrate, added to dilute nitric acid aqueous solution with a mass concentration of 10%, mixed and kneaded evenly, extruded, baked in an oven at 120°C for 24 hours, passed nitrogen in a resistance furnace, and roasted at 540°C for 4 hours. The nitrate is decomposed and solid-state ion exchange is realized to obtain Cr ₂ O ₃ -CaO-K ₂ O-Al ₂ O ₃ isobutane dehydrogenation to prepare isobutene catalyst.

In the reaction of isobutane dehydrogenation to prepare isobutene, the trivalent chromium species has excellent dehydrogenation activity, and the acidity strength and distribution of the catalyst are the main factors affecting the selectivity, so the activity of the isobutane dehydrogenation catalyst should be improved and selectivity, it is necessary to stabilize the trivalent chromium species on the catalyst, adjust the acid distribution and acid strength of the catalyst; at the same time, trivalent chromium is harmless to the environment, and stabilizing the valence state of the catalyst chromium species can not only make the catalyst have a high isotropic Butane dehydrogenation activity and activity stability, and eliminate the pollution of hexavalent chromium to the environment. The present invention is to provide a solid _Cr2O3 - _CaO - _K2O - _Al2O3 isobutane dehydrogenation preparation of isobutene catalyst and its method by solid-state ion exchange _{, Cr2O3} is _the active component of the catalyst; K ₂ O is an electronic additive that modulates the electronic form of the active component Cr ₂ O ₃ ; CaO interacts with Al ₂ O ₃ to modulate the acidic strength and distribution of Al ₂ O ₃ as a binder to achieve high activity Synthesis of active and stable, environmentally friendly catalysts for the dehydrogenation of isobutane to isobutene.

Compared with the prior art, the present invention has the following advantages:

1. The catalyst preparation process is simple, and the catalyst preparation, use and waste catalyst will not cause environmental pollution;

2. The catalyst has high activity and stability for preparing isobutene from isobutane dehydrogenation, and especially has excellent isobutene selectivity; under certain reaction conditions, the single-pass conversion rate of isobutane can be more than 50%, and the selectivity to the target product isobutene Reach more than 98%.

Detailed ways

The following examples are further detailed descriptions of the present invention, but the present invention is not limited by these examples.

Example 1

Weigh 60g of chromium trioxide powder (produced by Tianjin Chemical Plant), the content of Cr ₂ O ₃ is 60% of the mass fraction of the catalyst; 36.5g of active alumina (produced by Sinopec Changling Catalyst Factory), Al ₂ O ₃ The content of CaO is 36.5% of the mass fraction of the catalyst; 8.78g calcium nitrate (Beijing Chemical Reagent Company), the content of CaO is 3.0% of the catalyst mass fraction; and 0.54g potassium nitrate (Beijing Chemical Reagent Company), the content of K ₂ O is 0.5% of the mass fraction of the catalyst, after grinding and adding dropwise 10 g of dilute nitric acid aqueous solution with a mass concentration of 10%, stirring and kneading, and then extruding on an extruder with a plate hole diameter of 0.5 mm. Dry the extruded mixture strip at 120°C for 24 hours, and then roast the dried alumina strip at 540°C for 4 hours under nitrogen gas to obtain 100g of a solid ion-exchanged solid, whose composition is Cr ₂ O ₃ : CaO : K ₂ O: Al ₂ O ₃ with a mass ratio of 60:3:0.5:36.5, cut into 10-20 mesh particles, called catalyst A, and set aside. The content of each raw material in the following examples can be deduced by analogy.

Example 2

Weigh 70g of chromium trioxide powder (produced by Tianjin Chemical Plant), 23g of activated alumina (produced by Sinopec Changling Catalyst Plant), 17.56g of calcium nitrate (produced by Beijing Chemical Reagent Company) and 1.07g of potassium nitrate (produced by Beijing Chemical Reagent Company) company), after grinding and adding dropwise 15g of dilute nitric acid aqueous solution with a mass concentration of 10%, stirring, kneading, and then extruding on an extrusion machine with a plate hole diameter of 0.5 mm. Dry the extruded mixture strip at 120°C for 24 hours, and then roast the dried alumina strip at 540°C for 4 hours under nitrogen gas to obtain 100g of a solid ion-exchanged solid, whose composition is Cr ₂ O ₃ : CaO : K ₂ O: Al ₂ O ₃ with a mass ratio of 70:6:1.0:23, cut into 10-20 mesh particles, called catalyst B, and set aside.

Example 3

Weigh 70g of chromium trioxide powder (produced by Tianjin Chemical Plant), 16g of activated alumina (produced by Sinopec Changling Catalyst Factory), 35.11g of calcium nitrate (produced by Beijing Chemical Reagent Company) and 2.15g of potassium nitrate (produced by Beijing Chemical Reagent Company) company), after grinding and adding dropwise 15g of dilute nitric acid aqueous solution with a mass concentration of 10%, stirring, kneading, and then extruding on an extrusion machine with a plate hole diameter of 0.5 mm. Dry the extruded mixture strip at 120°C for 24 hours, and then roast the dried alumina strip at 540°C for 4 hours under nitrogen gas to obtain 100g of a solid ion-exchanged solid, whose composition is Cr ₂ O ₃ : CaO : K ₂ O: Al ₂ O ₃ with a mass ratio of 70:12:2.0:16, cut into 10-20 mesh particles, called catalyst C, and set aside.

Example 4

Weigh 80g of chromium trioxide powder (produced by Tianjin Chemical Plant), 11g of activated alumina (produced by Sinopec Changling Catalyst Factory), 17.56g of calcium nitrate (produced by Beijing Chemical Reagent Company) and 3.22g of potassium nitrate (produced by Beijing Chemical Reagent Company) company), after grinding and adding dropwise 15g of dilute nitric acid aqueous solution with a mass concentration of 10%, stirring, kneading, and then extruding on an extrusion machine with a plate hole diameter of 0.5 mm. Dry the extruded mixture strip at 120°C for 24 hours, and then roast the dried alumina strip at 540°C for 4 hours under nitrogen gas to obtain 100g of a solid ion-exchanged solid, whose composition is Cr ₂ O ₃ : CaO : K ₂ O: Al ₂ O ₃ with a mass ratio of 80:6:3.0:11, cut into 10-20 mesh particles, called catalyst D, and set aside.

Example 5

Weigh 90g of chromium trioxide powder (produced by Tianjin Chemical Plant), 6.5g of activated alumina (produced by Sinopec Changling Catalyst Factory), 8.78g of calcium nitrate (produced by Beijing Chemical Reagent Company) and 0.5g of potassium nitrate (produced by Beijing Chemical Reagent Company), after grinding and adding dropwise 15 g of dilute nitric acid aqueous solution with a mass concentration of 10%, stirring, kneading, and then extruding on an extrusion machine with a plate hole diameter of 0.5 mm. Dry the extruded mixture strip at 120°C for 24 hours, and then roast the dried alumina strip at 540°C for 4 hours under nitrogen gas to obtain 100g of a solid ion-exchanged solid, whose composition is Cr ₂ O ₃ : CaO : K ₂ O: Al ₂ O ₃ with a mass ratio of 90:3:0.5:6.5, cut into 10-20 mesh particles, called catalyst E, and set aside.

Embodiment 6 Catalyst performance evaluation test

The raw material isobutane (Shijiazhuang Oil Refinery) is transported into the fixed bed reactor (stainless steel reactor with an inner diameter of 12mm, the length of the constant temperature zone is 15cm, the particle size of the catalyst is 10-20 mesh, and the thickness of the catalyst bed is 9-10cm) through the feed pump. . After the reaction product is decompressed by the back pressure valve, the pressure drops to normal pressure and flows into the low-pressure product separator. After collection, the product is sent to a gas chromatograph for analysis. The amount of raw material feeding is controlled by the feeding pump. A heated electric furnace provides the temperature required for the reaction.

The reaction temperature is 550°C-650°C, the reaction pressure is 0.1MPa-1.0MPa, and the reaction mass space velocity is within the range of 0.6-2.0 h ^-1 . The reaction results are shown in Table 1.

Table 1 Performance evaluation results of catalysts for isobutane dehydrogenation to isobutene

Catalyst name Conversion rate of isobutane, l% Isobutene selectivity, % A 51.5 98.1 B 53.4 98.5 C 56.4 99.2 D. 52.3 97.8 E. 54.5 98.4

Claims (3)

1. dehydrogenation of isobutane prepares the used catalyst of isobutene, it is characterized in that: this catalyst Cr ₂O ₃Content be that the 60-90% of catalyst quality mark, the content of CaO are 3-12%, the K of catalyst quality mark ₂The content of O is 0.5-3.0%, the Al of catalyst quality mark ₂O ₃Content be the 5-36.5% of catalyst quality mark.

2. dehydrogenation of isobutane according to claim 1 prepares the used catalyst of isobutene, it is characterized in that: the active component chrome green is to introduce with the chrome green powder type; Calcium oxide and potassium oxide be to introduce with the form of nitric acid calcium salt, potassium salt; Alundum (Al is to introduce with the activated alumina form of powder.

3. prepare the used Preparation of catalysts method of isobutene by the described dehydrogenation of isobutane of claim 1, it is characterized in that: this method is according to Cr ₂O ₃, CaO, K ₂O, Al ₂O ₃Content ratio, take by weighing chrome green powder, active oxidation aluminium powder, nitric acid calcium salt, potassium nitrate, join mass concentration and be in 10% the diluted nitric acid aqueous solution; Mix, knead evenly back extrusion; 120 ℃ of baking ovens baking 24 hours, logical nitrogen in resistance furnace, 540 ℃ of roastings 4 hours; Nitrate is decomposed and the exchange of realization solid ionic, obtain Cr ₂O ₃– CaO-K ₂O-Al ₂O ₃Dehydrogenation of isobutane prepares isobutene catalyst.