JPH0148317B2 - - Google Patents

Description

[Detailed description of the invention]

In the present invention, acetylenes and dienes contained in a sulfur-free hydrocarbon mixture mainly composed of hydrocarbons having 4 carbon atoms obtained by steam cracking of hydrocarbons are selected in the presence of a palladium catalyst. The present invention relates to a method for hydrogenation. More specifically, hydrogenation is a method for selectively hydrogenating acetylenes and dienes contained in a sulfur-free _C4 hydrocarbon mixture obtained by steam cracking of hydrocarbons in the presence of a palladium catalyst. The sulfur-free feedstock hydrocarbon mixture to be subjected to alumina,
The present invention relates to a hydrogenation method for preventing a decrease in the activity of a palladium catalyst by hydrogenating the palladium catalyst after contacting it with at least one solid adsorbent selected from zeolite and activated carbon. Steam cracking of hydrocarbons such as naphtha produces unsaturated hydrocarbons such as ethylene, propylene, butadiene, and butenes, as well as hydrocarbons boiling in the gasoline boiling point range.
These can be distilled into ethylene, propylene,
Separated into _C4 fraction and others. In addition to paraffins and olefins such as n-butane, i-butane, 1-butene, 2-butene, and i-butene, the _C4 fraction usually contains 1,3-butadiene, 1,2-butadiene, vinyl acetylene, 4 carbon atoms such as ethyl acetylene
Contains dienes and acetylenes. In addition, trace amounts of C3 dienes and acetylenes such as propadiene and methylacetylene may also be included. The 1,3-butadiene contained in the _C4 fraction is separated and purified from other C4 hydrocarbons by _an extraction method and is widely used industrially.
With the exception of a few other components contained in the distillate, they are hardly used industrially. Among these, 1-butene is industrially important as a monomer for producing polyolefins, but 1-butene is
When butene is used as a monomer for producing polyolefins, the concentration of dienes and acetylenes in 1-butene is strictly limited. Therefore, it is necessary to remove dienes and acetylenes from the C ₄ hydrocarbon mixture by selectively hydrogenating the dienes and acetylenes contained in the C ₄ hydrocarbon mixture. Selective hydrogenation of acetylene in the ethylene fraction obtained by steam cracking of hydrocarbons and selective hydrogenation of methylacetylene and propadiene in the propylene fraction are widely carried out industrially using palladium catalysts. It is
Furthermore, various methods have been proposed for selectively hydrogenating dienes and acetylenes in a hydrocarbon mixture having 4 carbon atoms in the presence of a palladium, platinum, or nickel catalyst. The present inventors have demonstrated the palladium-catalyzed selection of dienes and acetylenes contained in the so-called spent BB fraction, in which most of the butadiene was removed by extraction from the _C4 fraction obtained by steam cracking. When investigating hydrogenation, it was found that the catalytic activity of palladium catalysts decreased rapidly over a short period of time. Therefore, the present invention was achieved through intensive research into a method of preventing the activity of the palladium catalyst from decreasing and performing a selective hydrogenation reaction stably over a long period of time. That is, in a method of selectively hydrogenating acetylenes and dienes contained in a sulfur-free _C4 hydrocarbon mixture obtained by steam cracking of hydrocarbons in the presence of a palladium catalyst, A sulfur-free mixture mainly composed of hydrocarbons having 4 carbon atoms to be supplied is brought into contact with at least one solid adsorbent selected from alumina, zeolite, and activated carbon, and then hydrogenated to form a palladium catalyst. It has been discovered that the selective hydrogenation reaction can be carried out stably for a long period of time with almost no decrease in activity. The raw material hydrocarbon containing dienes and acetylene used in the method of the present invention is a sulfur-free fraction (C ₄ fraction)
It is. More preferably used is the so-called spent BB fraction, which is obtained by separating and removing most of the butadiene from the _C4 fraction by an extraction method, which contains sulfur mainly composed of hydrocarbons with 4 carbon atoms, including diene and acetylenes. This is a sulfur-free C ₄ hydrocarbon mixture obtained by further separating and removing isobutylene from this spent BB fraction. The solid adsorbent used in the method of the present invention is at least one solid adsorbent selected from alumina, zeolite, and activated carbon. As the alumina, γ-alumina is usually preferably used.
Further, as the zeolite, type A zeolite, type X zeolite, etc. are used, and examples of preferable zeolites include type 3A zeolite, type 10X zeolite,
There are 13X type zeolites, etc. The contact conditions between the _C4 fraction or the spent BB fraction and the solid adsorbent are not particularly limited, but
Usually, the temperature is -20°C to 150°C and the pressure is normal pressure to 50 atmospheres. The contact method is to collect _C4 fraction or spent BB in a fixed bed packed with solid adsorbent.
Although it is preferable to pass a fraction, etc., in some cases, a solid adsorbent may be brought into contact with a liquid phase C ₄ fraction, etc. in a suspended state. Usually C ₄ fraction or spent BB
The fraction etc. is brought into contact with a solid adsorbent before being mixed with hydrogen gas, but depending on the case, it may be brought into contact in the presence of hydrogen gas. It is generally known that sulfur compounds such as mercaptans are poisonous substances for palladium catalysts.
_C4 fraction or spent BB free of sulfur compounds
A decrease in the activity of the palladium catalyst was also observed in the fraction. Although the cause of the decrease in palladium catalyst activity is unknown, it is surprisingly possible to improve palladium catalyst activity by contacting _C4 fraction or spent BB fraction, which does not contain sulfur, with a solid adsorbent such as alumina, zeolite, or activated carbon. was able to prevent a decrease in activity. The palladium catalyst used in the method of the present invention includes palladium metal, palladium compounds such as palladium chlorides, oxides, and sulfides, and those supported on known carriers. Preferably, palladium is supported on known carriers. A supported palladium catalyst having a loading of 0.005 to 5% by weight is used. The reaction conditions for selectively hydrogenating dienes and acetylenes are not particularly limited, but are usually carried out in a fixed bed reactor at a reaction temperature of -10°C to 150°C and a pressure of normal pressure to 50 atm. It is carried out in liquid phase or gas phase. When selectively hydrogenating dienes and acetylenes in the _C4 fraction or spent BB fraction, 1-butene contained in the _C4 fraction or spent BB fraction is easily isomerized to 2-butene. move on. Therefore 1
- When selectively hydrogenating dienes and acetylenes while suppressing the isomerization of butenes, it is necessary to strictly control the reaction conditions, and even a slight decrease in the activity of the catalyst will cause the dienes and acetylenes to deteriorate after selective hydrogenation. The remaining amount of will increase. By the method of the present invention, the selective hydrogenation reaction of dienes and acetylenes in a C ₄ hydrocarbon mixture can be carried out stably for a long time, and its industrial significance is great. The method of the present invention will be explained in more detail below using Examples, but the scope of the present invention is not limited by these. Example 1 A so-called spent product in which a sulfur-free fraction mainly composed of hydrocarbons with a carbon number of 4 produced as a by-product from an ethylene production unit (steam cracker) is passed through a butadiene extraction unit to remove most of the butadiene.
BB fraction was used as the raw material. The composition of the raw materials is the first
Shown in the raw material column of the table. γ-Alumina (trade name KHD-24, manufactured by Sumitomo Aluminum) was used as a treatment agent for the spent BB fraction. 20 ml of γ-alumina was filled into a vertically arranged tube with an inner diameter of 12 mm. The palladium catalyst used was one in which 0.1% by weight of palladium was supported on alumina. 20ml of this palladium catalyst with an inner diameter of 18mm
The mixture was filled into a vertically arranged reaction tube. Spent
The BB fraction is first introduced into a tube filled with γ-alumina, and then into a reaction tube filled with palladium catalyst.
- The pipe was arranged so that the alumina was mixed with the spent BB fraction when it exited the pipe. Spent BB fraction is 800ml/hr and hydrogen gas is
A selective hydrogenation reaction was carried out by introducing it into the reactor at a feed rate of 10 (in terms of NTP)/hr. The conditions for treating the spent BB fraction with γ-alumina were a temperature of 30°C and a pressure of 10 atm, and conditions for selective hydrogenation using a palladium catalyst were a temperature of 50°C and a pressure of 10 atm. The composition of the product obtained 4 hours after the start of the reaction was as shown in the product column of Table 1.

[Table] The degree of oxidation was quantified, but it was not detected.
As is clear from Table 1, dienes and acetylenes such as butadiene, propadiene, and vinyl acetylene are almost completely hydrogenated. Therefore, a long-term continuous experiment was conducted under these conditions, and the results shown in Table 2 were obtained.

[Table] Even after 1000 hours, the butadiene hydrogenation activity of the palladium catalyst has hardly decreased, and stable operation for a long time is possible. Examples 2 and 3 Instead of the γ-alumina used in Example 1, 20 ml of zeolite (Molecular Sieve 4A) and activated carbon were filled to create a sulfur-free spent BB.
After processing the fraction, a selective hydrogenation reaction was carried out. The raw material spent BB fraction, hydrogenation catalyst, and other reaction conditions were the same as described in Example 1. The results are shown in Table 3.

[Table] Comparative Example 1 A selective hydrogenation reaction was carried out without treating the spent BB fraction with a solid adsorbent, and the results shown in Table 4 were obtained. Note that the raw material spent BB fraction hydrogenation catalyst and other conditions were the same as described in Example 1.

【table】

Claims (1)

[Claims] 1 Selective treatment of acetylenes and dienes contained in a sulfur-free hydrocarbon mixture mainly composed of hydrocarbons having 4 carbon atoms obtained by steam cracking of hydrocarbons in the presence of a palladium catalyst. This method is characterized in that the sulfur-free hydrocarbon mixture, which is mainly composed of hydrocarbons having 4 carbon atoms, to be subjected to hydrogenation is brought into contact with a solid adsorbent in advance, and then hydrogenation is carried out. hydrogenation method.