DE1171901B - Process for the removal of acetylenes and diolefins from hydrocarbon gases or their mixtures by selective hydrogenation - Google Patents

Description

Process for removing acetylenes and diolefins from hydrocarbon gases or mixtures thereof by selective hydrogenation. The invention relates to a process for the removal of hydrocarbon gases or their mixtures with a high olefin content contained Athinen and Diolefinen by selective hydrogenation in the presence of a specific palladium-alumina catalyst.

Because of their great reactivity, there is a hydrogen attachment with athenes and diolefins per se more easily feasible than with olefins. the selective hydrogenation of these ethynes and diolefins contained in olefin gas mixtures is generally carried out in the presence of an activated catalyst. at however, the amount of hydrogen to be added must be exactly within this process defined limits are kept and continuously monitored. If only small amounts Athine and diolefin impurities are present in these gases, one encounters in the general to great difficulty, especially when an almost perfect one Hydrogenation of the ethynes and diolefins should be achieved without changing the olefin content of the gases by hydrogenation noticeably decrease. In the production of gases, that are to be used as intermediates for organic syntheses is this of highest importance. It is known, for example, that gas mixtures which are used in the manufacture of polyethylenes are used and which in general mainly consist of ethylenes consist of no more than about 0.025 ° lo of highly unsaturated impurities, such as, therefore, methylethine, propadiene or other diolefins with low molecular weight, may contain. With the new polymerisation processes it has been found necessary proven to use only olefin gases with a content of acetylene and diolefin of 0.010% does not exceed.

It is already known that by using catalysts with selective effect of the content of unsaturated compounds in crude oil mixtures can be reduced. For this purpose, a catalyst was made from pumice stone, inactive Aluminum oxide, diatomaceous earth, asbestos, coke or charcoal on or. stored Palladium is used, but it is still used as an activating metal, either copper or gold or contains silver. In addition, in this known palladium catalyst the content of catalytic metals 0.1 to 5 percent by weight with a palladium content from 99 to 60 and a copper, silver or gold content of 1 to 40 percent by weight.

It has also already been recognized that the activity of such a Catalyst can be improved if the distribution of the metal compounds, from which the metal is then formed, one if possible even on and in that inert carrier material is. This was sought by circulating the appropriate salt solutions, in which the inert carrier material is located during the drying process to reach. The firing of the impregnated and dried moldings should be at the decomposition temperatures of the metal salts, approximately between 325 and 4500 C, however not above 5000 C, in order to rule out severe damage to the activity.

The invention is also based on the use of a palladium-alumina catalyst, by means of the same the selective hydrogen addition to contained in olefin gas mixtures Acetylenes or diolefins is carried out without a noticeable amount of Olefins is hydrogenated. The hydrogen attachments carried out with this catalyst give very favorable results, especially with anhydrous olefin mixtures, because it is at relatively low temperatures and with a very low stoichiometric Excess of hydrogen achieved an almost complete hydrogenation, so that the remaining Remainder of acetylenes and / or diolefins in the purified gas not more than a few a few particles per million particles of gas.

The catalyst used according to the invention consists of a metallic one Palladium on an alumina support greater than 0.01 and up to 0.09, preferably until contains to 0.05 percent by weight metallic palladium, which is mainly on the Surface layer of the alumina carrier is deposited, and the alumina carrier Has pore volume of not more than 0.4 cm3 / g and the diameter of the pores is not greater than 800 Å. In such an alumina carrier, the amount exceeds of the inner pores lying below the surface is the amount of surface pores, measured at the same point, around 0.02 to 0.05 cm3 / g. This catalyst is extremely stable, d. i.e., its effect is also repeated and long-lasting Usage not noticeably reduced under normal process conditions. He tolerates also repeated regenerations without noticeably weakening its effect. This regeneration but only needs to take place within a period of about two weeks, to remove polymer layers formed on the catalyst surface. These Refreshment can be carried out several times without affecting the physical condition, catalytic effect or selectivity are impaired.

To produce the alumina carrier, alumina balls are used, which have the aforementioned surface pore volume. The clay used is made of from known fine powder mixtures of a-alumina monohydrate and alumina trihydrates, which are either tabletted or shaped into bodies by means of extrusion presses. In addition, alumina is a well-known carrier material for catalysts. The palladium is sprayed on in the form of a concentrated palladium salt solution. The amount of palladium salt sprayed on varies from one part to 5 to 12 Particles of clay, this ratio being chosen in each case so that the finished Catalyst more than 0.01 up to 0.09, preferably up to 0.05 weight percent contains metallic palladium.

The concentrated palladium salt solution appears to be the strongest adsorbed by the smallest diameter micropores. The small amounts of the applied palladium salt solution as well as the way in which the palladium salt is applied to the alumina carrier according to the invention, promote deposition of the metal on the surface of the support, whereby the metal does not pass through homogeneously the entire carrier body is distributed. It was surprisingly found that apart from those occurring as a result of the incorporation of the palladium salt or the palladium Reducing the surface pores also reduces the amount of internal pores that originally formed the Exceeded the amount of external pores, in a corresponding to the original pore ratio Ratio decreases, although there is no significant metal insert in the inner Pores is done. This reduction in the amount of internal pores is essential for the stability and long-term effectiveness of the catalyst. As the little micro pores on the surface of the support due to the applied catalyst metal for the most part have been sealed, no charring products can be deposited in it. As a result, it is very difficult for polymers to adhere to the surface of the catalyst and form within the catalyst body, which then convert into charring products.

Although the processes of palladium deposition are not easy can be interpreted, they are decisive for the hydrogen attachment to the Acetylenes and diolefins, since the catalyst produced in this way is perfect Effective at relatively very low temperatures, e.g. B. below the Freezing point of water. This effectiveness remains undiminished, even when using concentrated olefin gas mixtures without additional water vapor will.

The effect of the catalyst according to the invention is also not weakened at temperatures of 38 C and 520 C up to 204-C, so that a substantial reduction of the acetylenes and diolefins present, that only a few fractions per million parts of gas remain in these. With the catalyst according to the invention such hydrogen attachments with relatively low stoichiometric Excess of hydrogen. z. B. 300 / o carried out.

Example 1 In a 0.505% solution of Pd (NO3) 2 in distilled Alumina tablets with a total weight of 1000 g were added to the water Fired beforehand for 8 hours at a temperature of 5000 C, then stored in water and air dried. The pore volume of these tablets was 0.35 cm3 / g, and the pores had an opening diameter of less than 800 Å. After putting these tablets in Pd (NO) solution for 15 minutes to soak were left, they were separated from the solution, drained for 30 minutes and then dried.

The soaked catalyst tablets were then 8 hours at 5000 Fired C and treated with hydrogen. The determined palladium content gave a Bulk concentration of 0.02ovo Pd.

A dry gas mixture of the following composition was passed through a layer of such a catalyst used in an isothermal fractionation column: propylene. . . 78.00 ovo propadien. 0.32 ovo hydrogen. 4.50% nitrogen. . 10.00 0 / o propane .. 7,000 / o and the following results were obtained: Table I. Through- C, H4 1o duration temperature pressure pressure running duration and temperature Hours ° C atmospheric input output 16 118 18.2 300 3200 35 22 121 18.2 580 3200 1 165 25 152 18.8 502 5450 190 43 152 19.6 575 5450 210 Flow rate = amount of gas, based on the catalyst area per hour, calculated at 160 ° C. and 1 ata.

The catalyst worked perfectly during the first 16 hours, so that the propadiene content has been reduced to approximately 0.00350 / 0. After this period of time, however, the effectiveness of the catalyst decreased quickly, and it could not return to its original state even with temperature increases Height to be brought.

Another charge of the same catalyst was made after expiration made the first attempt. The reaction column was then operated for 8 hours flushed with hydrogen at a temperature of about 398 to 4000 C. Afterward was a raw gas mixture of the same composition as in the first attempt passed the catalyst layer. The throughput speed was per hour about 500 times the amount of catalyst mass. The pressure will be 19.3 atmospheres set. When the process was carried out for the first full day, the temperature was in the reaction column 1040 C. The exhaust gas was during the course of the process still 0.00450 / 0 propadiene.

On the second day the propadiene content increased to 0.0130 / 0, and on the third day at a temperature of 1210 C it was 0.0325 per cent.

A study of the amount of pores showed that the amount of internal pores and Surface pore amount in the catalyst is by and large the same. the Relationship of the amount of pores to each other was exactly due to the ratio between alumina and palladium metal that was originally applied. Accordingly the amount of pores was between 0.35 and 0.36% per cubic centimeter and gram, with it was pores with a surface diameter of up to 800 Å. Included the ratio was approximately 0.33 cc / g for surface pores and 0.34 cc / g for the internal pores that had an outer diameter of 270 Å or less.

Example 2 By a spherical clay tablets im Example 1 given composition, but by spraying a palladium solution, which is about 9.3 g as PdCl2. in 1000 cm3 distilled water acidified with HCI contained, subsequent firing and reducing produced, 0.050 / 0 palladium containing, located in a reaction column catalyst was without preceding Hydrogen treatment for one month with a gas mixture of the following composition directed: ethylene. . 70,000 / 0 methane. . 27.00% propylene. 1.200 / 0 Athin 0.35 ° / o hydrogen. . 0.70% The process temperatures varied between 54 and 660 C at a pressure of 365 atm. The throughput speed was 500 times Volume of gas and more per hour, based on the volume of the catalyst bed. While Over the course of the process, the catalyst was repeatedly regenerated to ensure its durability to be demonstrated after each regeneration. In general, the regeneration carried out in such a way that one consists of 950/0 water vapor and 50/0 air Gas mixture at a flow rate of 1000 volumes of gas, based on the catalyst bed volume, at a temperature of about 4820 C through the catalyst bed and then for 8 hours with hydrogen at minimum temperatures was treated at about 4000 C.

The following table shows the almost complete removal of the ethine. Table II Day temperature | Passage C2H2 Regen- Remarks Day ° C speed C2H2 ration 1 54 500 00 0 2 54 1000 0.00100 0 4 54 1000 0.00050 1 13 66 1000 0.00000 4 17 66 2000 0.00013 6 regeneration, but without hydrotreating 18 54 1000 00 6 Pressure: 365 atmospheres. Example 3 Alumina spheres of the order of magnitude 4.7 4.7 4.7 mm were treated as indicated in Example 2, and the catalyst prepared and containing 0.05 0.05% metallic palladium incorporated in the alumina was treated then treated for 8 hours at a temperature of 3990 C with hydrogen of high moisture content in such an amount that 1000 times the catalyst volume was passed hourly through the catalyst. A gas mixture containing 85.5% propylene, 0.50 / 0 methyl ether, 10 / o propadiene, 10% nitrogen and 90/0 hydrogen was then passed through the catalyst layer. A pressure of 275 atmospheres and temperatures between about 51 and 1490 ° C. were maintained, with the throughput speed changing. The result can be seen from the following table.

Table III Selective Hydrogenation of Methyl Ethine and Propadiene Procedure-Run-Methyl-Sample duration temperature speed in grams Hours ° C ity *)% 149 510 0.0003 119 **) 5 135 490 0.0005 160 81.2 131 450 0.00005 40 10 102 440 217 151.2 66 450 194 27 52 425 194 37 52 1600 200 40 52 490 175 Constant pressure: 275 atü B) Throughput speed determined on the basis of the weights of the samples.

[8) Analysis of the samples showed that they contained 0.020/0 propadiene. During the course of the process, the temperature fell to 380 ° C. for a short time, and the amount of methylethine contained in the effluent rose to 0.070%. From it it can be concluded that the lowest temperature at which the catalyst is still its showed complete effectiveness, is above 380 ° C.

In further experiments gas mixtures were used, the carbon monoxide contained. Such gas mixtures must be treated at temperatures that higher by about 150 C when the same level of selective hydrogenation is reached shall be.

In the selective hydrogenation of the gas mixture according to Example 2, which, however, still contained 2.5% CO, with the same catalyst and at a pressure of 275 atmospheres, the following results were obtained: Table IV Selective hydrogenation of methyl ether in the presence of carbon monoxide Ver Tem By- Methyl- Fahrens- - Lauf- äthin- sample H2 temperature speed gram maximum duration Hours ° C dity% 4 121 470 153 4.5 71.12 121 720 0.0019 339 4.5 341/2 66 440 160 4.5 381z2 38 485 0.075 r 247 4.5 44 52 475 0.0113 230 4.5 4912 63 900 0.0031 147 1 4.5 Table IV (continued) Ver Tem- By- Methyl- driving temperature running ether- sample H2 maximum- continuous temperature speed gram maximum Hours c digkeit oo 511/4 63 900 0.2 320 517 2.2 631/4 63 580 0.1950 355 2.0 703 / r 66 390 0.065 73 3.0 811/4 93 490 197 3.0 853/4 204 640 335 3.0 Constant pressure: 275 atm. The highly effective catalyst according to the invention is not only suitable for the hydrogenation of the propadiene contained in a propylene gas mixture, but also for the hydrogenation of the ethine in ethylene gas mixtures (see Table 1). Although the gas mixtures used were completely dry and anhydrous, the effect of the catalyst was unrestrictedly high and uniform for the entire duration of the process. The catalyst according to the invention shows this excellent effectiveness at only 400 ° C. and at flow rates of 1600 times the gas per hour, based on the catalyst volume.

The pore amount measurements mentioned in the examples were made according to the method of Benesi, Bonnar and Lee (Analytical Chemistry, p. 1963 December 1955). It is a carbon tetrachloride absorption process.

Approximately 250 cmS of a 0.040 / 0 palladium contained according to the example 1 manufactured catalyst in spherical shape were placed in a rotating drum with a diameter of 25 cm and a length of approximately 15 cm. Inside the drum is a racket is attached, the racket of which is about 5 cm wide and the length runs along the drum. The drum rotated at a speed of sixty rotations per minute. For 4 hours the beads were both exposed to friction exposed to each other as well as to the club.

A 0.3% weight loss was noted after the treatment. The powder that collects on the bottom is to be regarded as part of the outer surface, while the remaining shaped bodies form the inner surface or the core of the catalyst carrier body form. The latter were then also powdered. The powder amounts then became 11 Dried for 2 hours at a temperature of 130 C and a surface pore quantity determination subjected. The values obtained are shown in Table V.

Table V Measurements of pore quantities on the surface Amount of pores per cubic centimeter and gram Sample at 800 Å at 270 Å Interior surface interior t surface Manufactured according to example 1 *) ... 0.31 to 0.31 0.27 to 0.29 Manufactured according to example 2 *) ... 0.31 to 0.31 Manufactured according to example 3 **) .. 0.36 to 0.36 0.35 to 0.34 0.34 to 0.34 0.33 to 0.33 Manufactured according to example 4 ***) 0.36 to 0.35 0.35 to 0.35 1) Palladium salt solution sprayed on.

**) Soaking the alumina carrier with the palladium salt solution.

: * :) When preparing sample 4, the pH of the soaking solution was decreased to 0.2 to prevent hydrolysis of the palladium salt on the surface of the catalyst body to prevent.

From the table it can be seen that the catalyst body is on the surface 1 and 2, which are produced by spraying the palladium salt solution onto the alumina support the number of pores is always less than the number of pores inside, while the values for internal pore quantities and external surface pore quantities at the Catalyst samples 3 and 4, the alumina supports of which were soaked with palladium solution, are roughly the same. The internal pore size is comparative in samples 1 and 2 smaller than the internal pore amount of samples 3 and 4, which suggests that that when spraying more palladium solution is deposited in the interior of the carrier than while soaking. The difference in the number of pores is somewhat more pronounced between interior and surface in samples 1 and 2 with pore diameters of 270 Å versus those with a diameter of 800 Å.

The pore quantity values must not exceed 0.5 cm8 / g with a pore diameter not exceeding 800 A. When firing with the sprayed-on palladium The catalyst body soaked in salt solution is distributed on the surface of the support Palladium salt converted into palladium oxide and thereby the amount of pores both on the surface as well as inside the catalyst body is reduced. The palladium oxide is then reduced to palladium with hydrogen.

40 days represent the longest possible duration of the procedure if used of the freshly made catalyst sators according to the invention, with the best Results can still be obtained at a temperature of about 930 ° C.

The exhausted catalyst is regenerated by a Treatment with steam for 8 hours at a temperature of about 4000 C, followed by the reduction using bottled hydrogen and then cooled will. The regenerated catalyst works again in a 20 day process time the 95 to 1000 / above removal of the propadiene contained in raw gas mixtures. During the process, the active zone in the catalyst layer shifts from the gas entry zone at the same speed as in the process with the Fresh catalyst after the gas outlet zone. The total duration of the procedure with the fresh and once regenerated catalyst is thus 60 days, the attrition strength the catalyst body remained the same as before.

When the catalyst layer was discharged, no disintegrated or broken catalyst body was found.

Compared to the known activated by copper, silver or gold Palladium catalysts, the catalyst according to the invention represents a non-activated one Catalyst that has a higher selectivity for hydrogen addition to acetylenes for the purpose of converting them into olefins, as shown in the comparison table below can be found.

Table VI Selective hydrogenation of methyl acetylene and propadiene in a propylene gas mixture Output gas residual content Catalyst used methylacetylene t propadiene methylacetylene 1 propadiene o / OI Olo o / OI Olo U.S. Patent 2,802,889, Example 2 1.0! 0.3 0.3 0.054 0.036 Catalyst according to example 3 of the invention (0.05 o / o Pd) 1.6 0.2 j 0.0085 0.005 Pressure: 350 atü;

Claims (2)

Temperature: 55 to 660 C; Ratio of H2 to C3H4 = 1.9: 1; Throughput speed: 800 volumes of gas per volume of catalyst per hour; Claims: 1. Method for removing small amounts of acetylenes and / or diolefins from a predominantly Gas mixture containing monoolefins by selective hydrogenation over a palladium-alumina support catalyst in the presence of a slight excess of hydrogen, indicated by that as a catalyst support alumina with a pore volume of not more than 0.4 cmS / g is used, the diameter of the pores not being greater than 800 Å, and that the palladium content of the catalyst is 0.01 and up to 0.09, preferably up to 0.05 percent by weight, the Amount of catalyst: 50 cms; Gas composition: 0.5 o / o propadiene, 1.0 ovo methylacetylene, 1.5 ovo propane, 3 O / o H2., 80 ovo propylene, 14 o / o methane. Metal is mainly deposited on the surface layer. 2. The method according to claim 1, characterized in that the Gases or the gas mixture at a minimum temperature of 380 C and a space velocity of not less than 425 per liter of catalyst per hour over the catalyst bed directs. Considered publications: German Patent Specifications No. 4566, 253160, 534475; U.S. Patent No. 802889.