JPS6223726B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a method for selectively separating and recovering 1,3-butadiene from a _C3 to _C5 hydrocarbon stream containing 1,3-butadiene and acetylenic hydrocarbons, particularly from a hydrocarbon stream rich in _C4 hydrocarbons. ,1,
The acetylenic hydrocarbon-rich fraction separated from the main hydrocarbon stream rich in 3-butadiene is subjected to a selective hydrogenation reaction in the liquid phase in the presence of a specific catalyst to produce acetylenic hydrocarbons. The present invention relates to a process for increasing the yield of 1,3-butadiene by converting 1,3-butadiene into an alkadiene or alkene and then returning the hydrogenation reaction product to the main hydrocarbon stream. Traditionally, hydrocarbon streams containing 1,3-butadiene, acetylenic hydrocarbons and _C3 - _C5 fractions, especially
From a hydrocarbon stream rich in _C4 hydrocarbons, 1,3
-Separation and recovery of butadiene is widely practiced. However, in the conventional method of separating and recovering 1,3-butadiene from a hydrocarbon stream rich in _C4 hydrocarbons, a main hydrocarbon stream rich in 1,3-butadiene and a fraction rich in acetylenic hydrocarbons are separated. Hydrocarbon streams rich in acetylenic hydrocarbons, which must be separated, require special precautions in handling due to the explosive and polymerizable nature of acetylenic compounds. That is, since the explosion hazard of acetylenic compounds increases when they are highly concentrated, the fraction rich in acetylenic hydrocarbons is separated from the main hydrocarbon stream to the extent that it does not pose a danger in handling. It is then diluted with inert hydrocarbons to a point where it is then usually burned off. Furthermore, as described in JP-A No. 51-127006, the fraction rich in acetylene hydrocarbons is separated from the 1,3- It is often diluted in such a way that separation from butadiene is incomplete. Therefore, the 1,3-butadiene that accompanies the acetylenic hydrocarbons due to dilution will not be used effectively and will be discarded by combustion.
In a process aimed at separating and purifying butadiene, it must be said that the economic disadvantage of such loss of 1,3-butadiene is significant. For this reason, in JP-A-51-127006, fractions rich in acetylenic hydrocarbons are
In particular, a method is proposed in which the fraction is subjected to a catalytic hydrogenation reaction using palladium as a catalyst and then recycled to the feedstock C ₄ hydrocarbon mixture stream. However, when the concentration of acetylenic hydrocarbons in the stream subjected to catalytic hydrogenation reaction increases beyond a certain level, good results cannot always be obtained with the palladium-based catalyst normally used for hydrogenation to carbon-carbon double bonds. The inventors have found that there is no such thing. That is, when a palladium-based catalyst commonly used in the known technology was subjected to a catalytic hydrogenation reaction in the liquid phase of a stream containing a relatively high concentration of acetylenic hydrocarbons, the initial activity was good, but an unexpected result was observed. In particular, it was found that the activity of the catalyst decreased significantly within a short period of time, making it impossible to put it to practical use. Therefore, we diligently investigated the cause and found that it was due to palladium being desorbed from the carrier. This phenomenon is hardly observed when a stream with a low concentration of acetylenic hydrocarbons of about 2% or less is subjected to a catalytic hydrogenation reaction. This phenomenon was presumed to be unique to catalytic hydrogenation reactions in streams containing relatively high concentrations. The above was experimentally confirmed by the following reference examples. These experiments investigated the effect of the acetylenic hydrocarbon concentration in the hydrocarbon stream used in the catalytic hydrogenation reaction on the palladium-based catalyst. Reference example 1 Commercially available PGC catalyst (manufactured by Nippon Engelhard Co., Ltd.,
(contains 0.30 wt% Pd) and G-68B (made by Nissan Girdler, 0.47 wt% Pd and 0.50 wt% Cr)
) into a SUS304 reaction tube with an inner diameter of 13.8 mm and a 65 c.c.
It was filled and used for experiments. A jacket through which cooling water flowed was provided on the outside of the reaction tube. A stream rich in acetylenic hydrocarbons having the following composition was heated at 30℃ for 6
When subjected to a catalytic hydrogenation reaction under the conditions of Kg/cm ² G, hydrogen/acetylenes = 1.2 mol/mol, and liquid hourly space velocity (LHSV) = 4.6 hr ^-1 , all catalysts showed good initial activity. However, after 60 hours, the conversion rate of acetylenes decreased significantly, and the palladium content in the catalyst particles decreased to 0.05% by weight and 0.11% by weight, respectively. C ₃ hydrocarbons 0.3% by weight Butanes 2.1 Butenes 38.5 1,3-butadiene 12.0 1,2-butadiene 7.2 Methylacetylene 0.2 Ethylacetylene 6.8 Vinyl acetylene 32.5 C ₅ hydrocarbons 0.4 Reference example 2 Hydrocarbons subjected to catalytic hydrogenation reaction A mixture having the following composition was used, the hydrogen flow rate was maintained at the same amount as in Reference Example 1, and the reaction was conducted under the same conditions as in Reference Example 1 except for the following conditions. In addition to acetylenes, a hydrogenation reaction of 1,3-butadiene occurred, but there was almost no decrease in activity even after 60 hours of reaction, and no change was observed in the palladium content in the catalyst particles. _C3 hydrocarbons 0.3% Butanes 6.3 Butenes 49.9 1,3-butadiene 42.6 1,2-butadiene 0.1 Methylacetylene 0.1 Ethylacetylene 0.1 Vinyl acetylene 0.5 _C5 hydrocarbons 0.1 Rich in acetylenes as shown in Reference Example 1 It is clear that when a hydrocarbon is subjected to a catalytic hydrogenation reaction, the activity decreases in a short period of time due to the elimination of palladium, which cannot be used practically as an industrial catalyst. As a result of various studies to solve the above problems, the present inventors added at least one element selected from arsenic, selenium, antimony, and tellurium to palladium, in particular antimony and/or tellurium, and supported it on alumina. It has been discovered that palladium can be suppressed from being eluted from the catalyst by using novel catalysts that have been developed. Acetylenic hydrocarbons can be safely and easily removed by hydrogenation, and vinyl acetylene can be removed by selective hydrogenation.
By using 3-butadiene, it is possible to improve the recovery rate of 1,3-butadiene in a butadiene separation and recovery device. In the present invention, the main hydrocarbon stream containing 1,3-butadiene is a hydrocarbon stream containing C ₄ and small amounts of C ₃ and C ₅ fractions, including butane, isobutane, butene,
It contains isobutene, 1,3-butadiene, 1,2-butadiene, ethyl acetylene, vinyl acetylene and small amounts of C ₃ and C ₅ hydrocarbons. From these mixtures, 1,3-butadiene is extracted and separated using a selective solvent, while a fraction rich in acetylenic hydrocarbons, namely vinylacetylene, ethylacetylene and methylacetylene, is separated. The acetylenic hydrocarbon stream subjected to the selective hydrogenation reaction in the present invention is a fraction rich in vinyl acetylene, ethyl acetylene and methyl acetylene, usually 20 to 80%, especially 30 to 75%
% of acetylenic hydrocarbons. When acetylenic hydrocarbons are subjected to a hydrogenation reaction, a large amount of reaction heat is generated, so it is important to remove this heat. The higher the temperature of acetylenic hydrocarbons, the greater the risk of explosion and the easier the formation of polymers, so sufficient care must be taken in removing the heat of reaction. For this purpose, a multi-tubular reactor is used and the reaction is carried out isothermally while being cooled with cooling water, or alternatively, a method can be adopted in which the hydrogenated hydrocarbon stream is cooled and a portion is refluxed to the reactor. . The refluxed hydrocarbon stream has a volume ratio of 1 to 200 times, in particular 2 to 100 times, the volume of the feed hydrocarbon stream. The hydrogen used in the hydrogenation reaction may be industrial hydrogen commonly used in hydrogenation reactions. The hydrogenation reaction takes place in the liquid phase and is carried out isothermally or adiabatically.
The reaction temperature is suitably between 0 and 70 DEG C., especially between 5 and 50 DEG C., and a pressure of 2 to 15 atmospheres, especially 3 to 10 atmospheres, sufficient to maintain the hydrocarbon stream in essentially liquid phase is used. Hydrogen and a hydrocarbon liquid, which are reaction raw materials, are preferably introduced in parallel flow and passed through the reactor in an upward flow or a downward flow, with an upward flow being particularly suitable. The hydrogenation catalyst is extremely important in the present invention. Palladium is used as the active metal. The metal responsible for hydrogenation activity is usually a group metal in the periodic table, and it is well known that palladium is effective in the selective hydrogenation reaction from triple bonds to double bonds. There is. In the present invention, palladium is also the most suitable metal having selective hydrogenation activity. arsenic,
At least one element selected from selenium, antimony, and tellurium is preferably 10 ^-5 to 10 times the weight of palladium.
It is added at a ratio of 10 ^-4 to 1 times, more preferably 10 ^-3 to 1 times. If the amount added is less than the above ratio, the effect of suppressing palladium elution will be insufficient, and if it is more than the above ratio, the activity of the catalyst will be inhibited, which is not preferable. Activated carbon, silica, alumina, and calcium carbonate are used as the catalyst carrier, and alumina is particularly suitable. Palladium is
It is contained in a proportion of 0.001 to 10% by weight, preferably 0.01 to 5.0% by weight. A particularly preferred catalyst in the present invention is one in which palladium, antimony and/or tellurium are supported on alumina. The present invention will be explained below with reference to the drawings, but the present invention is not limited thereto. Also, in order to simplify the diagram, most of the pumps, heat exchangers, etc. are omitted and only the main parts are shown. The area surrounded by the broken line in Figure 1 is an example of the butadiene separation and purification process (Hydrocarbon
Processing vol. 46 No. 5 p. 166), and is not limited to this process as long as it produces a by-product of a fraction rich in acetylene hydrocarbons. The raw C ₄ hydrocarbon mixture containing 1,3-butadiene, C ₄ acetylenes, etc. is fed via conduit 1, while the hydrogenation reaction product is also added via conduit 29 before entering the butadiene recovery unit. It is supplied to the distillation column 2 of one extractive distillation zone (consisting of the distillation column 2 and the stripping column 7). An extractive distillation solvent composed of a polar solvent is supplied to the vicinity of the top of the distillation column 2 via a conduit 3, and a portion of the top vapor stream of the solvent stripping column 7 is supplied to the bottom of the column via a conduit 4. Butanes and butenes, which have a lower affinity for solvents than 1,3-butadiene, are discharged from the top of the column via conduit 5. On the other hand, from the bottom of the tower, 1, containing a small amount of butenes,
Components having a strong affinity for solvents, such as 3-butadiene, 1,2-butadiene, and C ₄ acetylenes, are discharged together with the solvent and supplied to a solvent stripping tower 7 through a conduit 6. In the stripping tower 7, hydrocarbons are stripped from the solvent by a reboiler (not shown) installed at the bottom of the tower, distilled from the top of the tower, a part of which is recycled to the distillation tower 2, and the rest is passed through a conduit 8 to the second extractive distillation. It is supplied to the distillation column 9 in the zone (composed of the distillation column 9 and the stripping column 14). On the other hand, a solvent substantially free of hydrocarbons is discharged from the bottom of stripping column 7, and this stream is recycled via line 3 to distillation column 2. Near the top of the distillation column 9, the same solvent normally used in the first extractive distillation zone is supplied via conduit 10, and at the bottom of the column, a portion of the overhead vapor stream from the solvent stripping column 14 is fed through conduit 11. The fraction mainly composed of 1,3-butadiene, which has a relatively low affinity for solvents, is discharged from the top of the column via conduit 12, while the bottom of the column is rich in acetylenes, which have a stronger affinity for solvents. The resulting fraction is discharged together with the solvent and supplied to a stripping tower 14 via a conduit 13. In the stripping tower 14 , hydrocarbons are stripped from the solvent by a reboiler (not shown) provided at the bottom of the tower and distilled from the top of the tower, a portion of which is circulated to the distillation tower 9 and the remainder is passed through a conduit 15 . It is supplied to the catalytic hydrogenation reactor 24. This stream is composed of vinyl acetylene, ethylacetylene, 1,3-butadiene, 1,2-butadiene, etc. On the other hand, a solvent substantially free of hydrocarbons is discharged from the bottom of the stripping column 14, and this stream is passed through the conduit 1.
0 and then circulated to the distillation column 9. The crude 1,3-butadiene fraction obtained from the top of distillation column 9 via conduit 12 is fed to distillation column 16 of the final purification zone (consisting of distillation column 16 and distillation column 19). From the top of the distillation column 16, crude 1,3-
Substantially all of the methylacetylene mixed into the butadiene is distilled out, but 1,3-butadiene is distilled out at the same time to prevent the concentration of acetylenes in the distillate from increasing excessively. The concentration of methylacetylene in the fraction discharged from conduit 17 is normally 60
%, but the remainder is essentially 1,3-butadiene, so it is preferable to subject this fraction to the catalytic hydrogenation reaction because it can increase the recovery rate of 1,3-butadiene (dotted line). 17a). On the other hand, a fraction mainly consisting of 1,3-butadiene from which methylacetylene has been substantially removed is discharged from the bottom of the distillation column 16 and supplied to the distillation column 19 via a conduit 18. Here, 1,3-butadiene is finally purified and obtained through a conduit 20 from the top of the column, and heavy substances are discharged from the bottom of the column through a conduit 21. The acetylene-rich fraction discharged from the butadiene recovery device (streams in conduit 15 and conduit 17a) is fed in liquid form to the catalytic hydrogenation reactor 24.
Hydrogen gas is supplied from the conduit 23. Reactor 2
4 is an adiabatic reactor filled with a palladium catalyst. Since the hydrogenation reaction is a highly exothermic reaction, a portion of the reaction product is circulated to the reactor through conduit 28 to prevent the temperature at the reactor outlet from rising excessively. The reaction products are discharged from the reactor via conduit 25, cooled in cooler 26, and then transferred to receiver 27.
is supplied to A portion of the hydrocarbon stream leaving the receiver is recycled to the reactor via line 28 and the remainder is returned as hydrogenated product via line 29 to the butadiene recovery unit. Unreacted hydrogen is discharged from the receiver 27 through a conduit 30, but this can also be recycled to the reactor 24 by a compressor if necessary. Although only one reactor is shown in FIG. 1, if it is difficult to control the outlet temperature, a plurality of combinations of reactors 24 and coolers 26 may be arranged in series.
It is also possible to suppress the amount of heat generated per unit. Usually, three or less units are sufficient. FIG. 2 shows a different combination of the butadiene separation and purification process and catalytic hydrogenation process shown in FIG. 1. The fraction rich in acetylenes is transferred to conduit 15 (and or 17a) in FIG.
It is supplied to the reactor 32 through the. Hydrogen gas is supplied from the conduit 31. The reactor 32 is a multi-tubular type, and the inside of the tube is filled with a palladium-based catalyst. Cooling water is supplied outside the tube through a conduit 33 to remove the reaction heat generated by the hydrogenation reaction, and is discharged through a conduit 34. has been done. The reaction product discharged from the reactor through the conduit 35 is circulated through the conduit 29 to the butadiene recovery device after the hydrogen gas stored in the receiver is separated. Note that it is normal for a small amount of C ₅ hydrocarbons and 1,2-butadiene to be mixed into the flow of conduit 29, and depending on the butadiene recovery equipment, they may accumulate during circulation. In such cases, it may be appropriate to distill the C ₅ hydrocarbons and 1,2-butadiene from the stream in line 29. Next, examples of the present invention will be given. The various values used in the Examples and Comparative Examples are defined as follows.

[Table] Example 1 a Preparation of Catalyst A 500 ml of pure water and 20 ml of 36% concentrated hydrochloric acid are added to 6.67 g of palladium chloride, and the mixture is heated to dissolve. Add pure water to this to make the total volume 5. Approximately 2 kg of cylindrical alumina pellets having a diameter of 3 mm x 5 mm are placed in an evaporating dish, and the palladium chloride solution is poured into the dish little by little while being heated in a water bath. After gradually adding a palladium chloride solution and evaporating the entire amount to dryness, this is calcined at 500°C in a nitrogen stream. The fired alumina pellets are placed in the evaporating dish again, and a solution of 0.42 g of tellurium tetrachloride dissolved in 1 part dilute hydrochloric acid solution (0.1 normal) is poured into the dish, and the pellets are again evaporated to dryness in a hot water bath. This was calcined at 500°C in a nitrogen stream to obtain catalyst A. b Catalytic hydrogenation reaction A stream rich in acetylenic hydrocarbons discharged from the second extractive distillation zone (Fig. 1 15) is combined with a stream discharged from the top of the first extractive distillation column (Fig. 1 2) The solution was diluted with a portion of 1, Figure 5) and subjected to a hydrogenation reaction. The type of hydrogenation reaction was carried out according to Fig. 1, and the reaction tube was made of SUS304 with an inner diameter of 42.7 mm.
850 ml of Catalyst A containing 0.02% Te (alumina carrier) was packed. Instead of the cooler 26 in FIG. 1, the reaction tube was of a double tube type, and cooling water was passed through the outer tube for cooling. The C ₄ fraction to be subjected to hydrogenation was supplied to the catalytic hydrogenation reactor at a rate of 332.2 g/H, and at the same time, a portion of the reaction product was supplied as a circulation stream to the reactor at a rate of 6793.2 g/H. Hydrogen gas was supplied to the reactor at a ratio of 59N/H. The reaction was carried out at 35° C. and 5.5 Kg/cm ² G. The composition of the hydrogenated product after the reaction reached steady state is shown in Table 1.

[Table] By removing C ₅ hydrocarbons, this hydrogenated product could be supplied to the butadiene separation and purification process. As is clear from Table 1, 1,3 in the hydrogenated product
- The concentration of butadiene is significantly increased compared to that of the reaction feed, so that not only 1,3-butadiene in the acetylenic hydrocarbon-rich stream is recovered, but also a significant amount of vinyl Since acetylene is converted to 1,3-butadiene, the yield of 1,3-butadiene in the butadiene separation and purification process can be further improved. On the other hand, the palladium content in the catalyst particles before use and after continuous operation for one month was measured by fluorescent X-ray analysis, and both were 0.20% by weight, with no separation of palladium from the carrier observed at all. Example 2, Comparative Example 1 A reaction tube made of SUS304 pipe with an inner diameter of 13.8 mm was filled with 70 g of catalyst, and a hydrocarbon fraction rich in acetylenic hydrocarbons having the composition shown in Table 1 was charged.
A reaction was carried out by flowing hydrogen at a rate of 190 g/H and 30/H (calculated at 0° C. and 1 atm). The conditions of 35° C. and 66 kg/cm ² G were maintained by flowing cooling water to the outside of the reaction tube. Regarding the various catalysts shown in Table 2, the palladium content in the catalyst particles before use and after 60 hours of reaction (according to fluorescent X-ray analysis), and the vinyl content 1 hour, 30 hours, and 60 hours after the start of the reaction. The acetylene conversion rate is shown in Table 3. All catalysts B to I were prepared in accordance with the method shown in Example 1. Table 2 Catalyst B: Alumina is used as a carrier, and Pd is applied to the carrier.
Catalyst C: Alumina is used as a support, and Pd is supported on the support.
Catalyst D: Alumina is used as a support, and Pd is supported on the support.
Catalyst E: Alumina is used as a support, and Pd is supported on the support.
Catalyst F: Alumina is used as a support, and Pd is supported on the support.
Catalyst G supported at a ratio of 0.2%: 80% alumina, 20% calcium carbonate
Catalyst H: Pd is supported at a ratio of 0.7% and zinc is supported at a ratio of 3% to the carrier containing alumina.
Catalyst I: Alumina is used as a support, and Pd is supported on the support.
PGC catalyst: Alumina supported catalyst containing 0.3% Pd (manufactured by Nippon Engelhard Co., Ltd.) Catalyst J: Alumina supported catalyst containing 0.5% Pd (manufactured by Nippon Engelhard Co., Ltd.) G-68A catalyst: Alumina supported catalyst containing 0.3% Pd (manufactured by Nissan Girdler) G-68B catalyst: Alumina containing 0.5% Pd and 0.5% Cr Supported catalyst (manufactured by Nissan Girdler)

【table】

[Table] Example 3, Comparative Example 2 In Example 2 and Comparative Example 1, 1,3
-Use a product with a composition of 48.9% butadiene and 51.1% methylacetylene, and set the hydrogen flow rate to 65/H (0
The test was conducted under exactly the same conditions except that the reaction pressure was 7 kg/cm ² G (calculated at 1 atm). The results are shown in Table 4.

【table】 [Brief explanation of the drawing]

1 and 2 are flow sheets of two embodiments of the present invention. 2, 9... extractive distillation column, 7, 14... stripping column,
16, 19... Distillation column, 24, 32... Catalytic hydrogenation reactor, 26... Cooler, 27, 36... Receiver.

Claims (1)

[Scope of Claims] 1. A main hydrocarbon stream rich in 1,3-butadiene in a method for selectively separating and recovering 1,3-butadiene from a hydrocarbon stream containing 1,3-butadiene and acetylenic hydrocarbons. The fraction rich in acetylenic hydrocarbons is separated in the liquid phase in the presence of a supported catalyst containing palladium and at least one element selected from the group consisting of arsenic, selenium, antimony and tellurium. A method for recovering 1,3-butadiene, characterized in that after performing a selective hydrogenation reaction, the hydrogenation reaction product is returned to the main hydrocarbon stream. 2 The supported catalyst is palladium, antimony and/or
The method for recovering 1,3-butadiene according to claim 1, wherein tellurium or tellurium is supported on alumina.