JP2000005599A - Selective oxidation catalyst of hydrogen, selective oxidizing method of hydrogen and dehydrogenating method of hydrocarbon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst with which hydrogen is selectively oxidized to release the restriction coming from the equilibrium of the reaction in the dehydrogenation of hydrocarbons, and that loss of the source material and dehydrated hydrocarbons by combustion can be suppressed to a low level which practically causes no problem. SOLUTION: This catalyst is used to selectively oxidize hydrogen in a mixture gas containing hydrogen and hydrocarbons when the mixture gas is brought into contact with an oxygen-contg. gas. The catalyst contains platinum group elements and one or more kinds of group VI elements in the periodical table. In the selective oxidizing method of hydrogen, the catalyst above described is used. Also the catalyst is used in the dehydrogenating method of hydrocarbons.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst for selectively oxidizing hydrogen present in a produced mixed gas when a hydrocarbon is dehydrogenated to produce a dehydrogenated hydrocarbon, The present invention also relates to a method for selectively oxidizing hydrogen using hydrogen and a method for dehydrogenating hydrocarbons using the catalyst.

[0002]

2. Description of the Related Art Processes for dehydrogenating hydrocarbons to produce dehydrogenated hydrocarbons have been described in many documents. For example, a process of synthesizing styrene by dehydrogenating ethylbenzene is industrially performed using an iron-based catalyst. However, in general, in a dehydrogenation reaction, a high yield cannot be obtained due to strong restrictions of equilibrium. Further, in the reaction in the adiabatic reactor, the dehydrogenation reaction is an endothermic reaction, so that the reaction temperature decreases with the reaction, and it is difficult to obtain the target product in a high yield.

[0003] Under such circumstances, several methods have already been proposed. For example, JP-A-49-56930 discloses a process and a catalyst for selectively oxidizing hydrogen in a mixed gas containing unreacted ethylbenzene, styrene and hydrogen after dehydrogenating ethylbenzene. Although this method is an effective method for styrene synthesis, A-type zeolite or alumina carrying platinum is used as a selective oxidation catalyst for hydrogen, and the performance of oxidizing only hydrogen is not always satisfactory.

US Pat. No. 4,565,898 also discloses a method using a catalyst in which platinum, tin, lithium and the like are supported on alumina by a similar process. However, this catalyst cannot be said to have a sufficient ability to oxidize only hydrogen. Also, Japanese Patent Application Laid-Open No. 9-2905
Japanese Patent Laid-Open Publication No. H11-157,086 discloses a method using a catalyst in which platinum is supported on niobium oxide in a similar process. However, since niobium, which is relatively expensive as an element, is used as the entire amount of the carrier, it becomes expensive as a catalyst, which is economically disadvantageous.

[0005]

An object of the present invention is to selectively oxidize hydrogen in a mixed gas containing unreacted hydrocarbons, dehydrogenated hydrocarbons, and hydrogen produced by the dehydrogenation of hydrocarbons. As described above, conventionally known catalysts are not satisfactory in performance of oxidizing only hydrogen, and are also satisfactory as industrial catalysts from the economical point of view because a relatively large amount of expensive elements are used. It was not something.
Therefore, an object of the present invention is to provide a novel catalyst that can more selectively oxidize hydrogen present in the mixed gas.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that platinum group elements and periodic table 6
The present inventors have found that a catalyst containing a component carrying one or more of the group III elements performs selective oxidation of hydrogen with high performance, and have completed the present invention. That is, Claim 1 of the present invention is a catalyst for selectively oxidizing hydrogen in a mixed gas by contacting a mixed gas containing hydrogen and a hydrocarbon with an oxygen-containing gas, The present invention relates to a selective oxidation catalyst for hydrogen containing a group III element and one or more elements from group VI of the periodic table.

A sixth aspect of the present invention is to contact a mixed gas containing hydrogen and a hydrocarbon with an oxygen-containing gas in the presence of an oxidation catalyst to selectively oxidize hydrogen in the mixed gas. The present invention relates to the use of a catalyst containing a platinum group element and one or more elements from group 6 of the periodic table as an oxidation catalyst. Further, claim 8 of the present invention relates to a mixed solution containing a dehydrogenated hydrocarbon, an unreacted raw material hydrocarbon, and hydrogen obtained by subjecting a raw hydrocarbon to a dehydrogenation reaction in the presence of a dehydrogenation catalyst. The gas is brought into contact with an oxygen-containing gas in the presence of an oxidation catalyst to selectively oxidize hydrogen in the mixed gas and further dehydrogenate the hydrocarbon-containing gas obtained by the oxidation reaction. In the elementary method, the present invention relates to the use of a catalyst containing a platinum group element and one or more elements from Group 6 of the periodic table as an oxidation catalyst.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The hydrogen selective oxidation catalyst used in the present invention is a catalyst containing a platinum group element and at least one element from group 6 of the periodic table. Platinum group elements are
Platinum, palladium, ruthenium, iridium, rhodium and osmium, of which the preferred elements are platinum and palladium. Although the content of the platinum group element is not particularly limited, if the amount is too small, the activity of the oxidation reaction tends to decrease.If the amount is too large, the reaction characteristics are hardly affected. Is disadvantageous in terms of cost, so is preferably 0.001 to 10% by weight, more preferably 0.05 to 5% by weight, based on the total amount of the catalyst. In preparing a catalyst containing a platinum group element, the platinum group element is used as a raw material salt. The raw material salt is not particularly limited, but can be used as an oxide, a halide, an organic complex, or the like.

Next, the elements of Group 6 of the periodic table are tungsten, molybdenum and chromium. Of these, tungsten and / or molybdenum are preferred, and tungsten is more preferred. Group 6 elements of the periodic table are also used as raw material salts when preparing the catalyst. The raw material salt is not particularly limited, and can be used as an oxide, a halide, a hydroxide, a sulfate, an organic salt, and the like.
The content of one or more elements of Group 6 of the periodic table is
In the case of consisting only of the platinum group element and the sixth group of the periodic table, it is sufficient that these two elements be 100% by weight.
Preferably, it is 90 to 99.999% by weight, more preferably 95 to 99.95% by weight.

[0010] In order to prepare a catalyst from a platinum group element and one or more elements of group 6 of the periodic table, a catalyst can be prepared by a conventionally known method. Specifically, for example, after sintering a raw material salt of one or more elements of the elements of Group 6 of the periodic table at an appropriate temperature to obtain a solid component such as an oxide, impregnating a solution containing a platinum group and drying, It can be prepared by firing.

[0011] The catalyst of the present invention comprises a platinum group element and Periodic Table 6
What is necessary is just to contain at least one element from the group elements,
In addition to preparation from these two elements, these elements can be used by being supported on a heat-resistant inorganic carrier. The heat-resistant inorganic carrier is used for the purpose of, for example, optimizing heat generation by diluting an active ingredient, reducing the price by diluting an expensive element, and improving catalyst strength.

The heat-resistant inorganic carrier includes aluminum oxide,
Examples include silicon oxide, titanium oxide, germanium oxide, tin oxide, and gallium oxide. Of these, aluminum oxide, silicon oxide and titanium oxide are preferred. Further, two or more of these heat-resistant inorganic carriers may be used. Here, the aluminum oxide is preferably aluminum trivalent aluminum oxide, and the crystal form includes alpha aluminum oxide, gamma aluminum oxide and the like, and preferably alpha aluminum oxide. Silicon oxide is preferably silicon tetravalent silicon oxide, and amorphous silicon oxide, crystalline silicon oxide, or the like can be used as the crystal form. The titanium oxide is preferably titanium tetravalent titanium oxide, and amorphous titanium oxide, crystalline titanium oxide, or the like can be used as the crystal form.

When a heat-resistant inorganic carrier is used in addition to the platinum group element and one or more elements of group 6 of the periodic table,
Of the 100% by weight, the required amount of the platinum group element is preferably 0.001 to 10% by weight, more preferably 0.1 to 10% by weight.
It is sufficient that the remaining weight% of 05 to 5% by weight is the sum of at least one element of Group 6 elements of the periodic table and the heat-resistant inorganic carrier. A catalyst in which a platinum group element and one or more elements of Group 6 of the periodic table are supported on a heat-resistant inorganic carrier can be prepared by various methods. As a method for preparing the catalyst, for example, a method in which a platinum group element and one or more elements of Group 6 of the Periodic Table are supported on the heat-resistant inorganic carrier at one time, and one or more elements of Group 6 of the Periodic Table are used. A method of supporting a platinum group element on a solid component containing a metal and a heat-resistant inorganic carrier, and supporting one or more elements of Group 6 of the periodic table on a solid component containing a platinum group element and a heat-resistant inorganic carrier Can be used.

A method for preparing a solid component containing at least one element from Group 6 of the periodic table and a heat-resistant inorganic carrier is as follows:
A method in which a heat-resistant inorganic carrier is impregnated with a compound solution of at least one element of Group 6 of the periodic table, dried and calcined, a compound of at least one element of Group 6 of the periodic table and the heat-resistant inorganic carrier And a method of combining and baking them, and a method of combining these, and any method can be used. A solid component containing a platinum group element and a heat-resistant inorganic carrier can be prepared by a method in which a solution of a compound of a platinum group element is impregnated into a heat-resistant inorganic carrier, dried, and fired.

A catalyst containing the white metal element obtained by the above-described catalyst preparation method and one or more elements of Group 6 of the periodic table, and a catalyst having these supported on a heat-resistant inorganic carrier. The state of the white metal element such as platinum and palladium is divalent or zero-valent, and is usually an oxide as divalent, and zero-valent is a metal or an alloy. Among the elements of Group 6 of the periodic table, the state of tungsten is as follows:
For example, it contains one or more of the group consisting of hexavalent, tetravalent, divalent and zero-valent tungsten, and preferably
It is hexavalent and in this case it is usually an oxide, and in this case it is a metal or an alloy.

Next, the state of molybdenum is, for example, one containing at least one member of the group consisting of hexavalent, tetravalent and divalent molybdenum, preferably hexavalent, in which case it is usually an oxide. is there. Further, the state of chromium is preferably trivalent chromium, in which case it is usually an oxide. Hexavalent chromium is not very suitable as an industrial catalyst because of its high toxicity.

The oxidation catalyst of the present invention is used for a reaction in which a mixed gas containing hydrogen and a hydrocarbon is brought into contact with an oxygen-containing gas to selectively oxidize hydrogen in the mixed gas.
When the temperature is too high, the selectivity of hydrogen tends to decrease and the combustion of hydrocarbons tends to increase when the temperature is too high, and when the temperature is too low, the selectivity does not affect much but the activity is insufficient. Therefore, the temperature is preferably from 300 to 800 ° C., and more preferably from 400 to 700 ° C.

The mixed gas containing hydrogen and hydrocarbons is composed of dehydrogenated hydrocarbons obtained by subjecting raw material hydrocarbons to a dehydrogenation reaction with a dehydrogenation catalyst, unreacted raw material hydrocarbons and hydrogen. . The oxygen-containing gas is
A gas containing 1 to 100% of molecular oxygen is used, and specifically, air, oxygen-enriched air, air diluted with an inert gas, and the like are preferably used. Further, water vapor can be contained in the oxygen-containing gas.

It is known that coking on a catalyst occurs in a process in which hydrocarbons and oxygen are introduced in a normal process and reacted in a reactor to consume all oxygen. In the oxidation catalyst of the present invention, when all the oxygen is consumed by using the hydrogen in the selective oxidation method and the hydrocarbon dehydrogenation method, coking occurs on the catalyst, but the selectivity to selectively oxidize hydrogen is obtained. Can be used without any problem.

A typical process to which the selective oxidation catalyst and the selective oxidation method of the present invention are applied is as follows. For example, a mixed gas containing dehydrogenated hydrocarbons, unreacted raw material hydrocarbons, and hydrogen that is discharged from the first-stage reaction layer after performing a dehydrogenation reaction of raw material hydrocarbons with a dehydrogenation catalyst in a first-stage reactor Is sent to the second reaction layer.
In the second-stage reaction layer, the selective oxidation of hydrogen is performed using a newly introduced oxygen-containing gas in the presence of the selective oxidation catalyst of the present invention. Thus, the temperature decreased by the endothermic dehydrogenation reaction in the first stage is increased by the exothermic reaction, and the equilibrium restriction of the dehydrogenation reaction is eliminated by consuming hydrogen. Further, the gas discharged from the second-stage reaction layer is sent to a third-stage dehydrogenation reaction layer similar to the first-stage reaction layer, and dehydrogenation of unreacted hydrocarbons is performed. Since the temperature required for the reaction has already been recovered in the second-stage reaction layer and the equilibrium restriction has been released, a higher yield can be obtained in the third dehydrogenation reaction layer.

Further, if necessary, the reaction can be carried out by further adding a combination of the above-mentioned selective oxidation reaction layer and dehydrogenation reaction layer. In general, steam is often used in the dehydrogenation reaction, but steam can be used in the above reaction process. The hydrocarbon of the present invention is a compound having an aromatic ring and a hydrocarbon chain which can be further dehydrogenated, and is preferably ethylbenzene, diethylbenzene, ethylnaphthalene, diethylnaphthalene or the like.

A typical example of the above dehydrogenation process is a dehydrogenation process of ethylbenzene. For example, a mixed gas of ethylbenzene and water vapor is sent to a first-stage reaction layer in which an iron-based catalyst containing iron and an alkali metal as main active components is present. The dehydrogenation reaction is performed at a pressure in the range of atmospheric pressure. Thereafter, a mixed gas of unreacted ethylbenzene, generated styrene, hydrogen, and steam is sent to the second-stage reaction layer.
In the second-stage reaction layer, the selective oxidation of hydrogen is performed using the newly introduced oxygen-containing gas in the presence of the oxidation catalyst of the present invention.
Next, this reaction gas is sent to the third reaction layer, where the unreacted ethylbenzene is again dehydrogenated with an iron-based catalyst,
Obtain styrene in higher yield. As described above, when the method of the present invention is used, the equilibrium restriction is removed, and the reduction in the reaction temperature can be recovered, so that styrene can be obtained in a much higher yield as compared with a normal dehydrogenation reaction. be able to.

[0023]

[Example 1]

 (Catalyst preparation) Aluminum oxide having a particle diameter of 1 mm
(Al_TwoO_Three) Was calcined at 1350 ° C. for 8 hours under air.
20 g of this carrier contains 40% by weight of tungsten.
2.5 g of aqueous solution of ammonium metatungstate
A solution to which 7.5 g of exchanged water was added was impregnated. After this,
Dry at 60 ° C for 1 hour under reduced pressure using a rotary evaporator
Dried. Then, after drying at 120 ° C. for 3 hours, 650 under air.
C. for 3 hours. Thus, 5% by weight tungsten is contained.
Of tungsten oxide / aluminum oxide carrier
did. Subsequently, chloroplatinic acid containing 0.04 g of platinum
(H _TwoPtCl₆・ 6H_TwoO) After immersion in 10 g of aqueous solution,
1 hour at 60 ° C under reduced pressure using a rotary evaporator
After drying, it was dried at 120 ° C. for 3 hours in a dryer. That
Then, it is calcined at 650 ° C. for 3 hours under air to obtain platinum / tan oxide.
A gustene / aluminum oxide catalyst was obtained. The loading composition is
0.2 wt% platinum, 5 wt% tungsten, other oxides
Luminium.

(Reaction) Catalyst 2 prepared as described above
The mixture was filled in a quartz reaction tube having an inner diameter of 6.7 mm, which was filled with quartz chips having upper and lower portions with quartz chips having substantially the same particle size as the catalyst, and then placed at 600 ° C. under a mixed gas flow of hydrogen and nitrogen containing 10% hydrogen. Time reduction treatment was performed. Next, a mixed gas of styrene, ethylbenzene, water, hydrogen, and air was introduced into the reaction tube to start the reaction. The mixed gas composition is

[0025]

## EQU1 ## Ethylbenzene / styrene / water / hydrogen / oxygen /
Nitrogen = 1 / 0.4 / 11.5 / 0.43 / 0.18 /
0.69 (molar ratio)

It was. The gas-equivalent space velocity (SV) in the reactor is:

[0027]

SV = 6550 hr ^-1 (0 ° C., 1 atm conversion)

It was. Start reaction at 600 ℃ 2
After time, the gas at the outlet of the reaction tube and the liquid trapped in the liquid receiver were analyzed by gas chromatography,
The hydrogen conversion was 75.7%, the oxygen conversion was 100%, and the styrene and ethylbenzene combustion rates were 0.72%. Here, the styrene and ethylbenzene combustion rate indicates the ratio of the number of moles of styrene and ethylbenzene disappeared by the combustion reaction to the molar ratio of styrene and ethylbenzene supplied to the reaction layer.

Example 2 Acid having a particle size of 1 mm in diameter
Aluminum chloride (Al_TwoO_Three) At 1350 ° C under air for 8
Fired for hours. To 20 g of this carrier, 40 tungsten are added.
Aqueous solution containing ammonium metatungstate
A solution containing 5 g of ion-exchanged water and 5 g of impregnated water was impregnated. this
Then, at 60 ° C under reduced pressure with a rotary evaporator,
Dried for hours. Then, after drying at 120 ° C for 3 hours, 6
It baked at 50 degreeC for 3 hours. Thus, 10% by weight of tungsten
Oxide / aluminum oxide carrier containing oxygen
Was prepared. Subsequently, chloride white containing 0.04 g of platinum
Gold acid (H_TwoPtCl₆・ 6H _TwoO) Immersion in 10 g of aqueous solution
Then, at 60 ° C. under reduced pressure using a rotary evaporator for 1 hour.
After drying for an hour, it was dried in a dryer at 120 ° C. for 3 hours. So
After that, it is baked at 650 ° C. for 3 hours in air to form a platinum / oxide
A Ngsten / aluminum oxide catalyst was obtained. Loading composition
Is platinum 0.2% by weight, tungsten 10% by weight, others are
Aluminum oxide.

The obtained catalyst was subjected to a reaction test in the same manner as in Example 1. Start reaction at 600 ℃ 2
After time, the gas at the outlet of the reaction tube and the liquid trapped in the liquid receiver were analyzed by gas chromatography,
The hydrogen conversion was 77.8%, the oxygen conversion was 100%, and the styrene and ethylbenzene combustion rates were 0.65%.

Example 3 Aluminum oxide (Al ₂ O ₃ ) having a particle diameter of 1 mm was immersed in air at 1350 ° C. for 8 hours.
Fired for hours. To 20 g of this carrier, 5 molybdenum
3.7 g of ammonium paramolybdate hydrate containing 4% by weight was immersed in an aqueous solution in which 10 g of ion-exchanged water was dissolved. Thereafter, drying was performed at 60 ° C. for 1 hour under reduced pressure using a rotary evaporator. Then, after drying at 120 ° C. for 3 hours, it was baked at 650 ° C. for 3 hours under air. Thus, a molybdenum oxide / aluminum oxide support containing 10% by weight molybdenum was prepared. Subsequently, chloroplatinic acid containing platinum _{0.04g (H 2 PtCl 6 · 6H} 2 O) aqueous solution of 1
After immersion in 0 g, use a rotary evaporator to reduce
After drying at 0 ° C. for 1 hour, it was dried at 120 ° C. for 3 hours in a dryer. Then, it was calcined at 650 ° C. for 3 hours under air to obtain a platinum / molybdenum oxide / aluminum oxide catalyst. The loading composition is platinum 0.2% by weight, molybdenum 10% by weight,
The other is aluminum oxide.

The obtained catalyst was subjected to a reaction test in the same manner as in Example 1. Start reaction at 600 ℃ 2
After time, the gas at the outlet of the reaction tube and the liquid trapped in the liquid receiver were analyzed by gas chromatography,
The hydrogen conversion was 62.9%, the oxygen conversion was 100%, and the styrene and ethylbenzene combustion rates were 0.95%.

[Comparative Example 1] Aluminum oxide (Al ₂ O ₃ ) having a particle diameter of 1 mm was immersed in air at 1350 ° C. for 8 hours.
Fired for hours. This carrier 5g, after immersion in chloroplatinic acid _{(H 2 PtCl 6 · 6H 2} O) aqueous solution 2.4g containing platinum 0.01 g, after drying for one hour under reduced pressure at 60 ° C. on a rotary evaporator dryer At 120 ° C. for 3 hours. Then, it was calcined at 650 ° C. for 3 hours under air to obtain a platinum / aluminum oxide catalyst. The loading composition is
The platinum was 0.2% by weight and the others were aluminum oxide.

At a reaction temperature of 600 ° C., two hours after the start of the reaction, the gas at the outlet of the reaction tube and the liquid trapped in the liquid receiver were analyzed by gas chromatography to find that the hydrogen conversion rate was 41.9% and the oxygen conversion rate was 41.9%. 100%, styrene and ethylbenzene combustion rate 1.12%.

[0035]

The oxidation catalyst of the present invention can selectively oxidize hydrogen, and can suppress the loss of coexisting raw materials and dehydrated hydrocarbons by combustion to a level at which there is substantially no problem. it can.

Continued on the front page F term (reference) 4G069 AA03 BC59A BC60A BC72A BC75A CB18 EA02Y ED06 4H006 AA02 AC12 BA14 BA25 BA26 BA30

Claims (9)

[Claims] A catalyst for selectively oxidizing hydrogen in a mixed gas by contacting a mixed gas containing hydrogen and a hydrocarbon with an oxygen-containing gas, comprising a platinum group element and a periodic table. A selective oxidation catalyst for hydrogen, comprising one or more elements of Group 6 elements. 2. The catalyst according to claim 1, wherein the content of the platinum group element in the whole catalyst is 0.001 to 10% by weight. 3. The catalyst according to claim 1, wherein the platinum group element is platinum and / or palladium, and at least one of the group 6 elements of the periodic table is tungsten and / or molybdenum. 4. The heat-resistant inorganic carrier according to claim 1, wherein the platinum group element and at least one element from group 6 of the periodic table are supported.
4. The catalyst according to any one of the above items 3. 5. The catalyst according to claim 4, wherein the heat-resistant inorganic carrier is aluminum oxide and / or silicon oxide. 6. A method of contacting a mixed gas containing hydrogen and hydrocarbon with an oxygen-containing gas in the presence of an oxidation catalyst to selectively oxidize hydrogen in the mixed gas,
A method for selectively oxidizing hydrogen, comprising using the catalyst according to any one of claims 1 to 5 as an oxidation catalyst. 7. The method according to claim 6, wherein the mixed gas of hydrogen and hydrocarbon is brought into contact with the oxygen-containing gas in a temperature range of 300 to 800 ° C. 8. The method according to claim 8, wherein the raw material hydrocarbon is prepared in the presence of a dehydrogenation catalyst.
A degassed hydrocarbon obtained by the dehydrogenation reaction, a mixed gas containing unreacted raw material hydrocarbons and hydrogen are brought into contact with an oxygen-containing gas in the presence of an oxidation catalyst,
6. A hydrocarbon dehydrogenation method in which hydrogen in the mixed gas is selectively oxidized and the hydrocarbon-containing gas obtained by the oxidation reaction is further dehydrogenated, as a oxidation catalyst according to any one of claims 1 to 5. A method for dehydrogenating a hydrocarbon, comprising using the catalyst described in the above item. 9. The raw material hydrocarbon is ethylbenzene,
9. The method according to claim 8, wherein the dehydrogenated hydrocarbon is styrene.