JPS6146035B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for selectively hydrogenating dienes and acetylenes to monoenes. More specifically, an unsaturated hydrocarbon mixture having 4 or more carbon atoms containing an unsaturated hydrocarbon having 2 or more double bonds and/or 1 or more triple bond in the molecule (hereinafter referred to as highly unsaturated hydrocarbon) is brought into contact with hydrogen in the presence of a catalyst using a fixed bed reactor,
The present invention relates to a method for converting only highly unsaturated hydrocarbons into corresponding hydrocarbons with a low degree of unsaturation without double bond isomerization. A mixture of unsaturated hydrocarbons with a carbon number of 4 or more, including highly unsaturated hydrocarbons, is reacted with hydrogen in the presence of a hydrogenation catalyst, and the highly unsaturated hydrocarbons are selected as corresponding hydrocarbons with a low degree of unsaturation. Hydrogenation is widely known, for example, dienes such as butadiene and methylalene, acetylenes such as dimethylacetylene, ethyl acetylene, and vinyl acetylene, and monoolefins such as 1-butene, 2-butene, and isobutene. There is an industrial method for selectively hydrogenating only dienes and acetylenes by reacting an unsaturated hydrocarbon mixture containing 4 carbon atoms with hydrogen in the presence of a hydrogenation catalyst such as palladium, platinum, or nickel. It has also been adopted. However, in these known selective hydrogenation methods, intramolecular movement of double bonds easily occurs at the same time as selective hydrogenation of highly unsaturated bonds such as two or more double bonds and one or more triple bonds. The drawback was that the composition of the reaction product changed significantly. For example, when performing a selective hydrogenation reaction of unsaturated hydrocarbons with 4 carbon atoms including butadienes and butynes, selective hydrogenation of butadienes and butynes to butenes and simultaneous hydrogenation of 1-butene to 2-butene. The isomerization of 1-butene easily proceeds, resulting in a large decrease in the 1-butene concentration in the reaction product. 1-Butene is important as a monomer for producing polyolefins, and in order to effectively utilize 1-butene in a mixture of hydrocarbons with 4 carbon atoms, only highly unsaturated hydrocarbons are selected without isomerization. There has been a strong desire for a method that can perform hydrogenation. The present inventors have conducted extensive research into a method for selective hydrogenation of highly unsaturated hydrocarbons that does not involve isomerization of olefins, and have arrived at the present invention. The present inventors conducted intensive research on a method for selective hydrogenation of highly unsaturated hydrocarbons in the presence of a catalyst without isomerization of olefins using a fixed bed reactor, and found a surprising result. In particular, a supported palladium catalyst whose catalyst particle size is 25% or less of the inner diameter of the reaction tube of the fixed bed reactor is used as a catalyst, and the raw hydrocarbon mixture is transported at a linear velocity (blank column standard, hereinafter referred to as LV).
It has been found that selective hydrogenation of highly unsaturated hydrocarbons occurs with almost no isomerization of olefins by passing through the catalyst bed at a rate of 100 m/hr or less. It is generally known that when the catalyst particle size becomes larger than the reaction tube diameter, the wall surface of the reaction tube affects the reaction, and it is also known that when the LV value falls below a certain level, it affects the reaction. However, it was completely unexpected that these effects would appear strongly only in specific reactions as in the method of the present invention. A method for selectively hydrogenating highly unsaturated hydrocarbons without isomerizing olefins.
A method of performing a selective hydrogenation reaction using _H2 gas containing CO gas (Japanese Patent Publication No. 46-30808), or a method of hydrogenating in a gas-liquid mixed phase in the first step, and hydrogenating in a liquid phase in the second step. (Special Publication No. 52-16082) has been proposed, but each has drawbacks such as the need to use expensive CO gas and the complicated process. The method of the present invention does not require the use of expensive auxiliary raw materials and provides a method for selectively hydrogenating highly unsaturated hydrocarbons without isomerizing olefins in a relatively simple process. It has great industrial significance. The hydrocarbon mixture containing highly unsaturated hydrocarbons and having a carbon number of 4 or more and having a low degree of unsaturation used in the present invention includes butadiene, butene, so-called C ₄ fraction obtained by steam cracking of naphtha, etc. , a C ₄ hydrocarbon mixture consisting of butane, etc., and a so-called spent product obtained by removing most of the butadiene from this C ₄ fraction by extraction.
A _C4 hydrocarbon mixture called the BB fraction, and the main components are 1-butene and 2-butene, which are obtained by removing isobutene from this spent BB fraction.
Examples include C ₄ hydrocarbon mixtures and hydrocarbon mixtures mainly composed of C ₅ hydrocarbons such as isoprene. Highly unsaturated hydrocarbons contained in these hydrocarbon mixtures include propadiene, methylacetylene, 1,2-butadiene, 1,3-butadiene, ethylacetylene, vinylacetylene,
There are pentadiene, etc. The catalyst used in the method of the present invention is a supported palladium catalyst whose catalyst particle size is 25% or less of the reaction tube diameter of the fixed bed reactor. As the supported palladium catalyst, one in which palladium is supported on a known carrier is used. Alumina is usually used as the carrier, and the preferred amount of palladium supported is 0.02 to 2% by weight. In the present invention, the catalyst particle size is defined as the diameter of a sphere for a spherical catalyst, and the diameter of a sphere having the same volume as that of a catalyst other than a sphere, such as a cylindrical catalyst. If the catalyst particle size has a distribution, the average particle size of the catalyst is defined as the catalyst particle size.
A fixed bed reactor is used as the reactor, but
As the fixed bed reactor, either an adiabatic reactor or an isothermal reactor can be used. In the method of the present invention, the feedstock hydrocarbon mixture is LV
(Air column standard, gas phase) It is necessary to pass through the catalyst layer at a speed of 100 m/hr or more. More preferably, the catalyst layer is allowed to pass through the catalyst layer at a speed of 200 m/hr or more on LV (empty column basis, gas phase). In addition, in the present invention
The value of LV is defined as the value under reaction conditions when the raw material hydrocarbon mixture is an ideal gas. In the process of the invention, the feedstock hydrocarbon mixture is hydrogenated substantially in the gas phase, but in some cases hydrogenation may be
There is no problem even if the part exists in a liquid phase state. The reaction temperature and other conditions for selectively hydrogenating highly unsaturated hydrocarbons are not particularly limited, but the reaction temperature is usually 10°C to 150°C and the reaction pressure is normal pressure to 30 atmospheres for raw material carbonization. The pressure is below that at which most of the hydrogen mixture remains in the gas phase. Hydrogen gas is generally used in a molar ratio of 1 to 10, preferably 1 to 2, to the highly unsaturated hydrocarbon. Furthermore, there is no problem even if the hydrogen gas used contains methane or other gas. The space velocity (space velocity based on the sky column, hereinafter referred to as SV) of the raw material hydrocarbon mixture is 1000hr ^-1 to 10000hr ^-1 in terms of NTP.
and preferably 2000 hr ^-1 to 5000 hr ^-1 . The method of the present invention will be explained below using Examples, but the scope of the present invention is not limited thereto. Example 1 A so-called spent BB fraction, which was obtained by applying a fraction mainly composed of hydrocarbons having 4 carbon atoms produced as a by-product from an ethylene production device to a butadiene extraction device to remove most of the butadiene, was used as a raw material. The composition of the raw materials is shown in the raw material column of Table 1. As a catalyst, alumina with an average particle size of 3 mm is used.
A material on which % by weight of palladium was supported was used.
200 ml of this palladium catalyst was filled into a vertically arranged reaction tube with an inner diameter of 20 mm, and the temperature was 50°C and the pressure was 4 kg/kg.
1 kg/hr of the spent BB fraction under the condition of cm ² G.
(SV=2000hr ^-1 , NTP conversion) 10% hydrogen gas
It was introduced into the reactor at a feed rate of (in terms of NTP)/hr to perform a selective hydrogenation reaction. The composition of the obtained product was as shown in the product column of Table 1. Also, the LV at this time was 377m/hr.

【table】

[Table] In this way, when the catalyst particle size is 15% of the reaction tube diameter, the LV is
At 377m/hr, butadiene, propadiene,
Highly unsaturated hydrocarbons such as vinyl acetylene were mostly hydrogenated and the isomerization rate of 1-butene was less than 3%. Example 2, Comparative Examples 1 and 2 200 ml of a catalyst in which 0.3% by weight of palladium was supported on alumina, each having an average particle size listed in Table 2.
was filled into a reaction tube with an inner diameter of 20 mm, and selective hydrogenation of the spent BB fraction was carried out at the reaction temperature listed in Table 2. For other reaction conditions, see Example 1.
This was done in the same manner as described. The raw materials used were also the same as those used in Example 1. The results were as shown in Table 2.

[Table] Example 3 A reaction tube with an inner diameter of 30 mm was filled with 200 ml of the same supported palladium catalyst used in Comparative Example 1, and the reaction temperature was
Selective hydrogenation of the spent BB fraction was carried out at 50℃. The other reaction conditions were the same as those described in Example 1. The raw materials used were also the same as those used in Example 1. The results are shown in Table 3.

[Table] Examples 4 and 5 Comparative Example 3 Example 1 was placed in a vertically arranged reaction tube with an inner diameter of 20 mm.
Filled with the amount of catalyst used in Table 4,
A selective hydrogenation reaction of the spent BB fraction was carried out at the temperature and pressure listed in the table. In addition, raw material spent BB
The fraction was the same as that used in Example 1, but it was introduced into the reactor at a feed rate of SV = 2000 hr ^-1 (in terms of NTP). Hydrogen gas was also introduced into the reactor at the feed rates listed in Table 4. The results are shown in Table 4.

【table】

Claims (1)

[Claims] 1. A mixture of hydrocarbons with a low degree of unsaturation and having a carbon number of 4 or more, including highly unsaturated hydrocarbons, is brought into contact with hydrogen in the presence of a catalyst using a fixed bed reactor to remove the highly unsaturated hydrocarbons. In the selective hydrogenation method, a supported palladium catalyst with a catalyst particle size of 25% or less of the inner diameter of the reaction tube of the fixed bed reactor is used as a catalyst, and the raw material hydrocarbon mixture is ) A selective hydrogenation method without isomerization characterized by passing through a catalyst bed at a rate of 100 m/hr or more.