JPH04247043A - Suppression of transition of gamma-alumina to alpha-alumina and production of olefins using the same alumina - Google Patents

Abstract

PURPOSE:To obtain an olefin useful as for various organic synthetic raw materials and polymer raw materials from a lower alcohol by a simple device in high yield and in high selectivity for a long period of time by using a specific catalyst. CONSTITUTION:In producing an olefin by dehydrating 2-4c alcohol, the objective compound is industrially and advantageously obtained preferably under a pressure condition so a to liquefy the compound at a normal temperature at 150-500 deg.C, preferably 250-400 deg.C by using a catalyst prepared by blending gamma-alumina catalyst with 0.5-5wt.%, preferably 0.5-3wt.% SiO2 and suppressing the transition of crystal phase from gamma-alumina to alpha-alumina and not making the reaction product into a heavy substance without deteriorating the catalyst for many hours.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing olefins by dehydrating lower alcohols having 2 to 4 carbon atoms using a specific catalyst.

0002

BACKGROUND OF THE INVENTION As a method for producing olefins, a method has long been known in which alcohols are dehydrated in the presence of a strong acid such as sulfuric acid. However, since this method uses a strong acid, it is necessary to use acid-resistant production equipment, and it is difficult to dispose of the waste sulfuric acid discharged after the reaction, so this method has rarely been adopted in recent years.

[0003] In recent years, the mainstream method for producing olefins is to crack naphtha. For example, industrially important olefins such as ethylene, propylene, butenes and butadienes are produced by this method.

However, recently, in order to diversify the raw materials for producing olefins or to obtain highly pure olefins, the method of producing olefins by dehydrating alcohols has been reviewed. Various methods have been proposed for producing olefins.

For example, a method for producing ethylene by dehydrating ethanol (Japanese Patent Publication No. 40057/1982, Japanese Patent Publication No. 19927/1982), a method for producing high purity isobutylene by dehydrating tertiary butanol (Japanese Patent Publication No. 59-40057, Japanese Patent Publication No. 59-19927), 6
1-23771, Japanese Unexamined Patent Publication No. 61-26), etc. have been proposed. Furthermore, a method has been proposed in which solid acid catalysts such as alumina, silica, silica alumina, zeolites, and solid phosphoric acid are used as catalysts when producing ethylene by dehydrating ethanol (Japanese Patent Laid-Open No. 64-34929
Publication No.).

[0006]

However, as mentioned above, the method using a strong acid as a catalyst requires the use of expensive corrosion-resistant manufacturing equipment, and it is also difficult to treat the waste liquid. Also,
The produced olefins may react in the presence of a strong acid and cause isomerization, or polymerize and increase the molecular weight, resulting in unintended compounds, which may reduce the yield.

On the other hand, when the dehydration reaction is carried out using a solid acid as a catalyst, since the dehydration reaction of alcohol is a highly endothermic reaction, a reaction temperature of 250 to 300°C or higher is required.
Solid acid catalysts such as silica alumina, zeolites, and solid phosphoric acid are strongly acidic, so when these catalysts are used, the produced olefins polymerize and become heavy, leading to a decrease in the yield of olefins. Further, heavy substances adhere to the catalyst surface and cause a decrease in catalyst activity, which is not preferable.

[0008] If γ-alumina is used as a catalyst, it is advantageous because γ-alumina is weakly acidic and the produced olefins do not become heavy.
It was found that when used in a reaction at 300 to 350°C, a part of the crystal phase transitions from the γ form to the inactive α form, resulting in a significant decrease in catalytic activity. Furthermore, since this tendency becomes more pronounced as the pressure increases, it is difficult to use the γ-alumina catalyst industrially under pressurized conditions.

Conventionally, it has been known that γ-alumina transforms into the α form at high temperatures of 1000°C or higher, and as a means of suppressing this transition, La2O3, MgO, and S are added to the catalyst.
A method of adding a metal oxide such as iO2 as a second component is generally known. However, the phenomenon of crystal phase transition at a temperature of about 300° C. is completely unknown and the mechanism is unknown, so it is difficult to apply conventional methods for suppressing crystal phase transition at high temperatures.

[0010]Although it is possible to carry out the dehydration reaction without applying pressure, the produced olefins having 2 to 4 carbon atoms are gaseous at normal temperature and pressure, and must be liquefied for purification such as distillation. If it is obtained as a gas, it must be liquefied by cooling with a refrigerator or pressurizing with a booster, which increases the number of steps in the process, complicates the operation, and is economically disadvantageous. It is.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing olefins from lower alcohols over a long period of time with high yield and high selectivity using a simple apparatus.

0012

[Means for Solving the Problems] In developing a method for producing olefins by dehydrating lower alcohols, the present inventors focused on the use of solid acid catalysts, and as a result of intensive studies, they arrived at the present invention. .

That is, in the method of the present invention, when producing olefins by dehydrating lower alcohols having 2 to 4 carbon atoms, γ- containing 0.5 to 5% by weight of SiO2 is used.
This is a method for producing olefins characterized by using an alumina catalyst.

Another method is to contain 0.5 to 5% by weight of SiO2 in the γ-alumina catalyst used in the dehydration reaction to suppress the transition of γ-alumina to the α form.

The present invention will be explained in detail below. The alcohol used as the starting material of the present invention is a lower alcohol having 2 to 4 carbon atoms, such as ethanol, n-propanol, i-propanol, n-butanol, i-butanol, or a mixture thereof. Either alcohol or tertiary alcohol may be used.

The method of the present invention is characterized by the catalyst used in the dehydration reaction. This catalyst is a γ-alumina catalyst and is a SiO
0.5 to 5% by weight, preferably 0.5 to 3% by weight of
contains. When the amount of SiO2 is within this range, the crystal phase transition from the γ-form to the α-form can be suppressed without making the product heavier due to acidity.

[0017] γ-alumina containing a predetermined amount of SiO2 is produced by adding SiO2 during the production stage of γ-alumina or when using it as a catalyst. SiO
2 may be added at any part of the production stage of γ-alumina. For example, the SiO2 source may be added to boehmite, pseudoboehmite, etc., which are raw materials for γ-alumina, or may be added at the stage of raw materials for γ-alumina, such as aluminum sulfate or sodium aluminate. It may also be added to this γ-alumina powder as a final product. In order to obtain a sufficient effect of adding SiO2, SiO2 is added to γ-alumina.
It is necessary to disperse them evenly to some extent. Also,
If the additive is ultimately in the form of SiO2,
Any SiO2 source may be used. For example, SiO
It can be added in the form of a hydrogel or hydrosol, or an alkyl compound such as ethyl silicate.

Other metal oxides, such as La2O3, which is known to be effective in suppressing the transition to the alpha form at high temperatures.
On the contrary, the addition of substances such as MgO or MgO causes premature deterioration of the catalyst, so it is preferable to avoid mixing them as much as possible.

The method for producing the γ-alumina catalyst used in the present invention is not particularly limited. Generally known methods include, for example, a manufacturing method of mixing aluminum sulfate and sodium aluminate, a method of hydrolyzing an organic aluminum compound, and a method of mixing aluminum sulfate and calcium carbonate. Other physical properties of γ-alumina are not particularly limited, but preferably have an average pore diameter of 50 to 150
Å, specific surface area 100-350m2/g, Na, Fe,
The total amount of impurities such as SO4 ions is preferably 0.8% by weight or less.

The shape of the catalyst may be either powder or granule. It may be compressed into pellets and used as a fixed bed. Although pretreatment of the catalyst is not particularly necessary, pretreatment such as calcination treatment may be performed.

The olefins produced by the method of the present invention are ethylene, propylene, 1-butene, 2-butene, and isobutene. Preferably, ethylene, propylene, and isobutene are produced.

[0022] Preferred conditions for the dehydration reaction in the method of the present invention are as follows. The reaction temperature is 150-500°C, preferably 250-400°C. The reason for this range is that the reaction proceeds in high yield and industrial production is possible. The reaction pressure may be reduced pressure, normal pressure, or increased pressure, but in consideration of purification as described above, it is preferable to carry out the reaction under a pressure such that the olefins produced are liquefied at room temperature. The amount of raw material supplied to the reactor is 0 as LHSV.
．． 1-20 hr-1, preferably 0.5-10 hr-1
It is. The reason for setting this range is that if it is smaller than this, the productivity will be low and a large equipment will be required, and if it is larger than this, the reaction yield will decrease and energy will be required to separate and recover the product, which is not economical.

In the method of the present invention, an inert gaseous substance may be mixed into the dehydration reaction in order to quickly discharge the olefin produced in the reaction from the system. Examples of such gaseous substances include nitrogen, helium, argon, methane, ethane, propane, and butane. However, since water may accelerate the crystal phase transition of the catalyst, it is preferable to avoid its presence as much as possible. Further, the gaseous substances include substances that are liquid before being supplied to the reactor but become gaseous under the reaction conditions within the reactor. Examples of such substances include aliphatic hydrocarbons such as pentane, hexane, heptane, cyclopentane, and cyclohexane; aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cumene.

[0024] When this gaseous substance is mixed with alcohol and supplied to the reactor, the amount used is usually preferably in the range of 0.05 to 10 moles per mole of alcohol. If too much gaseous material is used, it becomes necessary to separate and reuse the gaseous material from the mixture of olefins and water, which is the reaction product, resulting in economic problems such as increased production costs of olefins. causing a disadvantage.

[0025] In the method of the present invention, a continuous reaction is preferable, and a fixed bed type using a granular catalyst is preferable as a reactor type.

[0026]

[Examples] The present invention will be specifically explained below with reference to Examples and Comparative Examples, but the present invention is not limited by these in any way. In addition, whether or not the γ-alumina catalyst causes a crystal phase transition was investigated using the following simple method.

(Catalyst steam resistance test method) 1 g of catalyst
Take ~50g and transfer it to 200 mesh SUS316
wrapped in a mesh and filled into a 2000cc autoclave with a SUS316 coiled filler (helipak). At this time, the catalyst should be located as centrally as possible. Thereafter, it is heated to 400°C in an electric furnace, and water is fed using a high-pressure pump to raise the pressure to 80kg/cm2G. After 6 hours, the catalyst is taken out and subjected to X-ray analysis to examine the crystal phase. In addition, the specific surface area of the catalyst taken out is measured and the catalytic activity for olefin production is evaluated as necessary.

(Preparation of Catalyst 1) A commercially available aqueous solution of aluminum sulfate and an aqueous sodium aluminate solution were mixed and a precipitate was collected. After adding 3% by weight of silica sol (trade name: Snowtex) to the precipitate, the pH was adjusted to 13.
The mixture was stirred all day and night in an ammonia aqueous solution adjusted to . After the precipitate was filtered and washed with water, it was calcined in an electric furnace at 600°C for 5 hours. Analysis of the obtained alumina revealed that the SiO2 content was approximately 2% by weight. The generated alumina is 3m long
It was molded into a tablet of m x 3 mm.

(Preparation of Comparative Catalyst 1) Comparative Catalyst 1 was prepared in the same manner as the preparation method of Catalyst 1 except that silica sol was not added.

(Preparation of Comparative Catalyst 2) A commercially available aqueous solution of aluminum sulfate and an aqueous sodium aluminate solution were mixed and a precipitate was collected. After adding 10% by weight of silica sol (trade name: Snowtex) to the precipitate, the pH
The mixture was stirred all day and night with an ammonia aqueous solution adjusted to a concentration of 13. After the precipitate was filtered and washed with water, it was calcined in an electric furnace at 600°C for 5 hours. As a result of analyzing the obtained alumina, SiO2
The content was about 7% by weight. The produced alumina was molded into a 3 mm x 3 mm tablet.

(Preparation of Catalyst 2) A commercially available γ-alumina catalyst (trade name, Sumitomo Chemical: KHO-24) was pulverized, 3% by weight of commercially available silica gel (Kanto Kagaku Products) was added, and an appropriate amount of water was added. While adding the mixture, thoroughly mix it in a mortar. This is 3m
It was molded into a tablet of m x 3 mm.

(Example 1) Inner diameter 2 with electric furnace outside
A vertical tubular reaction tube made of SUS316 with a diameter of 5.4 mm and a length of 50 cm was filled with 40 cc of catalyst 1, and the temperature of the electric furnace was set to 32
The temperature was set at 0°C. Isopropanol to LHSV1hr-
1, feed from the top of the reactor column, and the pressure inside the reaction tube is 1
The reaction was carried out at 8 kg/cm2G. The gas-liquid mixture discharged from the bottom of the reactor was separated into a liquid phase and a gas phase. Five hours after the start of the experiment, the reaction results were an isopropanol conversion rate of 90% and a propylene selectivity of 92%. The by-product was diisopropyl ether.

Next, the above-mentioned steam resistance test was conducted on Catalyst 1. As a result of X-ray measurement, no metastasis to the α-form was observed. After this steam resistance test, the catalyst 1 was
A reactor similar to that used in the experiment described above was charged with 40 cc. The reaction was carried out under the same reaction conditions as in Example 1. The gas-liquid mixture discharged from the bottom of the reactor was separated into a liquid phase and a gas phase. Five hours after the start of the experiment, the reaction results were an isopropanol conversion rate of 87% and a propylene selectivity of 90%. The by-product was diisopropyl ether.

(Example 2) A vertical tubular reaction tube made of SUS316 with an inner diameter of 38.1 mm and a length of 4300 mm and having an oil heating tank outside was filled with 4550 cc of catalyst 1, and the temperature of the heating tank was set at 315°C. did. Isopropanol was fed from the top of the reactor column at a LHSV of 1 hr-1, and the reaction was carried out so that the pressure inside the reaction tube was 18 kg/cm2G. The gas-liquid mixture discharged from the bottom of the reactor was separated into a liquid phase and a gas phase. After 10 hours from the start of the experiment, the reaction result was 89% isopropanol conversion.
, the propylene selectivity was 95%. The by-product was diisopropyl ether. Furthermore, after the start of the experiment, 300
At 0 hours, the reaction result was 85% isopropanol conversion.
, the propylene selectivity was 92%. After the reaction was completed, the extracted catalyst was examined with X-rays, and it was found that it remained in the γ form, and there was no transition to the α form of the catalyst even after a long reaction period, and there was no decrease in activity.

(Comparative Example 1) 40 cc of Comparative Catalyst 1 was charged and a reaction was carried out under the same reaction conditions as in Example 1. The gas-liquid mixture discharged from the bottom of the reactor was separated into a liquid phase and a gas phase. Five hours after the start of the experiment, the reaction results were an isopropanol conversion rate of 73% and a propylene selectivity of 88%. The by-product was diisopropyl ether.

Next, when the above-mentioned steam resistance test was conducted on Comparative Catalyst 1, the conversion to the α-form measured by X-rays was about 30%. After this steam resistance test, Comparative Catalyst 1 was subjected to a reaction in the same reactor as used in Example 1 under the same reaction conditions. The gas-liquid mixture discharged from the bottom of the reactor was separated into a liquid phase and a gas phase. After starting the experiment,
After 5 hours, the reaction results were an isopropanol conversion rate of 48% and a propylene selectivity of 75%. The by-product was diisopropyl ether. A water resistance test revealed that the catalyst had been transferred to the alpha form, resulting in a decrease in catalytic activity.

(Comparative Example 2) 40 cc of Comparative Catalyst 2 was charged and a reaction was carried out under the same reaction conditions as in Example 1. The gas-liquid mixture discharged from the bottom of the reactor was separated into a liquid phase and a gas phase. Five hours after the start of the experiment, the reaction results were an isopropanol conversion rate of 92% and a propylene selectivity of 65%. The by-products were heavy substances. 100
After 0 hours, the isopropanol conversion rate decreased to 43%. The removed catalyst showed no transition to the α-form, but a large amount of carbon was attached to the surface.

(Comparative Example 3) A vertical tubular reaction tube made of SUS316 with an inner diameter of 38.1 mm and a length of 4300 mm and having an oil heating tank outside was filled with 4550 cc of Comparative Catalyst 1, and the temperature of the heating tank was set to 315°C. Set. Isopropanol was fed from the top of the reactor column at a LHSV of 1 hr-1, and the reaction was carried out so that the pressure inside the reaction tube was 18 kg/cm2G. The gas-liquid mixture discharged from the bottom of the reactor was separated into a liquid phase and a gas phase. After 10 hours from the start of the experiment, the reaction result was an isopropanol conversion rate of 84.
%, and the propylene selectivity was 90%. The by-product was diisopropyl ether. Furthermore, 30 minutes after the start of the experiment
At 00 hours, the reaction result was an isopropanol conversion of 54
%, and the propylene selectivity was 84%. After the reaction was completed, the extracted catalyst was examined with X-rays, and it was found that the transition to the α-form was approximately 2
I was awake 0%.

(Example 3) 40 cc of Catalyst 2 was charged into the reactor used in Example 1, and the temperature of the electric furnace was set at 400°C. Ethanol was fed from the top of the reactor column at LHSV 0.5 hr-1, and the pressure inside the reaction tube was 18 kg/cm.
The reaction was carried out to give 2G. The gas-liquid mixture discharged from the bottom of the reactor was separated into a liquid phase and a gas phase. Five hours after the start of the experiment, the reaction results were 82% ethanol conversion and 95% ethylene selectivity. The by-product was diethyl ether.

Next, the above-mentioned steam resistance test was conducted on Catalyst 2. As a result of X-ray measurement, no metastasis to the α-form was observed. After this steam resistance test, 40 cc of the catalyst 2 was filled into a reactor similar to that used in the above experiment. The reaction was carried out under the same reaction conditions. The gas-liquid mixture discharged from the bottom of the reactor was separated into a liquid phase and a gas phase. Five hours after the start of the experiment, the reaction results were 79% ethanol conversion and 91% ethylene selectivity. The by-product was diethyl ether.

(Comparative Example 4) The reactor used in Example 1 was filled with 40 cc of Comparative Catalyst 1. The reaction was carried out under the same reaction conditions as in Example 2. The gas-liquid mixture discharged from the bottom of the reactor was separated into a liquid phase and a gas phase. After starting the experiment, 5
After time, the reaction result was ethanol conversion rate of 82.
%, and the ethylene selectivity was 94%. The by-product was diethyl ether.

Next, Comparative Catalyst 1 was subjected to the steam resistance test described above. As a result of X-ray measurement, the transition to the α-form was approximately 40%. After this steam resistance test, 40 cc of Comparative Catalyst 1 was filled into a reactor similar to that used in the above experiment. The reaction was carried out under the same reaction conditions as above. The gas-liquid mixture discharged from the bottom of the reactor was separated into a liquid phase and a gas phase. Five hours after the start of the experiment, the reaction results were 50% ethanol conversion and 79% ethylene selectivity.
Met. The by-product was diethyl ether.

(Example 4) 40 cc of Catalyst 1 was charged into the reactor used in Example 1, and the temperature of the electric furnace was set at 300°C. Isobutanol was fed from the top of the reactor at LHSV 2hr-1, and the pressure in the reaction tube was 8kg/cm2.
The reaction was carried out so that G. The gas-liquid mixture discharged from the bottom of the reactor was separated into a liquid phase and a gas phase. Five hours after the start of the experiment, the reaction results were an isobutanol conversion rate of 86% and an isobutene selectivity of 92%. The by-product was diisobutyl ether.

Next, the above-mentioned steam resistance test was conducted on Catalyst 1. As a result of X-ray measurement, no rearrangement to α-form was observed. After this steam resistance test, 40 cc of Catalyst 1 was filled into a reactor similar to that used in the above experiment. Experiments were conducted using the same reaction conditions. The gas-liquid mixture discharged from the bottom of the reactor was separated into a liquid phase and a gas phase. Five hours after the start of the experiment, the reaction results were an isobutanol conversion rate of 83% and an isobutene selectivity of 90%. The by-product was diisobutyl ether.

(Comparative Example 5) 40 cc of Comparative Catalyst 1 was charged into the reactor used in Example 1, and the temperature of the electric furnace was set at 300°C. Isobutanol is fed from the top of the reactor at LHSV 2hr-1, and the pressure in the reaction tube is 8kg/c.
The reaction was carried out to give m2G. The gas-liquid mixture discharged from the bottom of the reactor was separated into a liquid phase and a gas phase. Five hours after the start of the experiment, the reaction results were an isobutanol conversion rate of 74% and an isobutene selectivity of 87%. The by-product was diisobutyl ether.

Next, Comparative Catalyst 1 was subjected to the steam resistance test described above. As a result of X-ray measurement, the transition to α-form was approximately 30%. After this steam resistance test, 40 cc of Comparative Catalyst 1 was filled into a reactor similar to that used in the above experiment. Experiments were conducted using the same reaction conditions. The gas-liquid mixture discharged from the bottom of the reactor was separated into a liquid phase and a gas phase. Five hours after the start of the experiment, the reaction results were an isobutanol conversion rate of 52% and an isobutene selectivity of 77%. The by-product was diisobutyl ether.

[0047]

Effects of the Invention According to the method of the present invention, olefins can be produced from lower alcohols over a longer period of time than ever before, with high yield and high selectivity. The resulting high-purity olefin is useful as a raw material for various organic synthesis and polymer materials. In addition, according to the method of the present invention, γ-alumina is used as a dehydration catalyst for lower alcohols, and under pressurized conditions, 30 to 3
It can be used for a long time without deterioration at a reaction temperature of 50°C, and is very useful industrially.

Claims (2)

[Claims] Claim 1: In producing olefins by dehydrating lower alcohols having 2 to 4 carbon atoms, SiO2
A method for producing olefins, characterized by using a γ-alumina catalyst containing 0.5 to 5% by weight of olefins. 2. A method for suppressing the transition of γ-alumina to the α form by containing 0.5 to 5% by weight of SiO2 in the γ-alumina catalyst used in the dehydration reaction.