JPH0227390B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for selective hydrogenation of 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 contacted with hydrogen in the presence of a catalyst in a fixed bed reactor to produce hydrocarbons with a low degree of unsaturation, contrasting only with highly unsaturated hydrocarbons, without double bond isomerization. It is about how to transform. 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, methyl allene, etc.
Acetylenes such as dimethylacetylene, ethylacetylene, vinylacetylene, and 1-butene,
A mixture of unsaturated hydrocarbons having 4 carbon atoms containing monoolefins such as 2-butene and isobutene is reacted with hydrogen in the presence of a hydrogenation catalyst such as palladium, platinum, or nickel to produce only dienes and acetylenes. Selective hydrogenation methods are also employed industrially. 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 having 4 carbon atoms, including butadienes and butynes, it is possible to selectively hydrogenate from butadienes and butynes to butenes, and simultaneously convert 1-butene to 2-butene. The isomerization to 1-butene easily proceeds, resulting in a large decrease in the concentration of 1-butene 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 without isomerizing olefins in the presence of a catalyst using a fixed bed reactor, and found a surprising result. In particular, a supported palladium catalyst whose catalyst particle size is 20% 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 fed at a linear velocity (blank column standard, hereinafter referred to as LV) of 5 m/hr or more. It has been found that selective hydrogenation of highly unsaturated hydrocarbons can occur with almost no isomerization of olefins by passing them through a catalyst layer and carrying out the hydrogenation reaction in the liquid phase. It is generally known that when the catalyst particle size becomes larger than the diameter of the reaction tube, the wall surface of the reaction tube will affect the reaction, and it is also known that the LV will have an effect on the reaction if its value falls below a certain level. However, it was completely unexpected that these effects would appear strongly only in specific reactions as in the method of the present invention. As a method for selectively hydrogenating highly unsaturated hydrocarbons without isomerizing olefins, a selective hydrogenation reaction using H ₂ gas containing a large amount of CO gas (specifically Japanese Patent Publication No. 16082/1983) or hydrogenation in a gas-liquid mixed phase in the first stage and liquid phase in the second stage (Japanese Patent Publication No. 16082/1982) has been proposed, but each method requires expensive CO gas. However, it has the disadvantages that it is necessary to use it and that the process is complicated. 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. Its industrial significance is great. The hydrocarbon mixture containing highly unsaturated hydrocarbons and having a low degree of unsaturation, having 4 or more carbon atoms, used in the present invention is a so-called C ₄ fraction obtained by steam cracking of naphtha, etc. A C ₄ hydrocarbon mixture called the spent BB fraction, most of which has been removed by extraction, and a C ₄ hydrocarbon whose main components are 1-butene and 2-butene, which are obtained by further removing isobutene from the spent BB fraction. Examples include mixtures and hydrocarbon mixtures based on C ₅ hydrocarbons such as isobutene. Highly unsaturated hydrocarbons contained in these hydrocarbon mixtures include propadiene, methylacetylene, 1,2-butadiene,
Examples include 1,3-butadiene, ethylacetylene, vinylacetylene, and pentadiene. The catalyst used in the method of the present invention is a supported palladium catalyst whose catalyst particle size is 20% 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 non-spherical catalyst 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 either an adiabatic reactor or an isothermal reactor can be used as the fixed bed reactor. In the method of the present invention, the feedstock hydrocarbon mixture is LV5
It is necessary to allow the liquid phase to pass through the catalyst layer at a speed of m/hr or more. More preferably LV10m/
Pass through the catalyst layer at a speed of hr or more. The raw material hydrocarbon mixture may be brought into contact with the catalyst bed in an upward flow, or may be brought into contact with the catalyst bed in a downward flow. The reaction temperature and other conditions for selectively hydrogenating highly unsaturated hydrocarbons are not particularly limited, but the reaction temperature is usually -30°C to 120°C and the reaction pressure is normal pressure to 50 atm. The reaction is carried out at a pressure that keeps the hydrocarbon mixture in the liquid phase. In addition, the liquid hourly space velocity (hereinafter referred to as LHSV) of the raw material hydrocarbon mixture is usually 1 to 1.
100 hr ⁻¹ , preferably 5 to 50 hr ⁻¹ . 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 method of the present invention will be explained below using Examples, but the scope of the present invention is not limited by these. 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. The supported palladium catalyst has a diameter of 2 mm.
Alumina containing 0.05% by weight of palladium was used. 100ml of this palladium catalyst was filled into a vertically arranged reaction tube with an inner diameter of 20mm, and the temperature
Under the conditions of 40℃ and 20 atm pressure, the above spent BB fraction was added at 4/hr (LHSV=40hr ^-1 ) and hydrogen gas was added at 30%
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 12.7m/hr.

【table】

[Table] In this way, when the catalyst particle size is 10% of the reaction tube diameter, the LV is
At 12.7m/hr, butadiene, propadiene,
Most of the highly unsaturated hydrocarbons such as vinyl acetylene were hydrogenated, and the isomerization rate of 1-butene was about 4%. Examples 2-3, Comparative Examples 1-2 Alumina with particle sizes listed in Table 2
100ml of catalyst supported with 0.05% by weight of palladium
was filled into a reaction tube with an inner diameter of 15 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 4 A reaction tube with an inner diameter of 30 mm was filled with 100 ml of the supported palladium catalyst used in Comparative Example 1, and a selective hydrogenation reaction of the spent BB fraction was carried out at a reaction temperature of 40°C. 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 5 to 6, Comparative Example 3 Example 1 was placed in a vertically arranged reaction tube with an inner diameter of 20 mm.
The amount of the catalyst used in Table 4 was charged, and selective hydrogenation of the spent BB fraction was carried out at a reaction temperature of 40° C. and a reaction pressure of 20 atm. 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 LHSV=40 hr ^-1 . Hydrogen gas was also introduced into the reactor at the feed rates listed in Table 4. The results were as shown in Table 4.

【table】

Claims (1)

[Claims] 1. A mixture of highly unsaturated hydrocarbons with a carbon number of 4 or more and a low degree of unsaturation is brought into contact with hydrogen in the presence of a catalyst using a fixed bed reactor to produce the highly unsaturated carbonization. In a method of selectively hydrogenating hydrogen, a supported palladium catalyst with a catalyst particle size of 20% or less of the inner diameter of the reaction tube of a fixed bed reactor is used as a catalyst, and the raw material hydrocarbon mixture is Phase) A selective hydrogenation method without isomerization characterized by passing through a catalyst layer at a rate of 5 m/hr or more and carrying out the hydrogenation reaction in a liquid phase.