DD131644B1 - METHOD FOR THE SELECTIVE HYDROGENATION OF C TWO MINUS FRACTIONS - Google Patents

Description

Field of application of the invention

The process for the selective hydrogenation of CL-Einus fractions relates to a heterogeneously catalyzed, cheraiochen process, as part of the technical extraction of ethylene from fission gases by gasoline pyrolysis contained in the crude fraction and in the processing of the olefin ßtoerende acetylene is largely removed, without that a substantial loss of ethylene occurs ·

Characteristic of the known technical solutions

The production of ethylene, as an intermediate for the production of plastics, has gained enormous technical importance. It is obtained preferentially by separation and refining of fission gases cup of Вгпзіпрзтоіузе. As an almost universal KaffinationDverfahren has the selective hydrogenation o ^ ev acptylerdochen binding proven "is required of such selective hydrogenation processes that they acetylene of usually 0.3 to 2.0% in the

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Reduce crude fraction to less than 3 ppm, without significant amounts of the present in large excess of ethylene are hydrogenated. For energetic reasons and to keep the extent of polymer formation on the catalyst as low as possible, the lowest possible working temperature is generally sought, since, as is known, the polymer formation, independently of the specially used catalyst system, is increasingly favored with increasing temperature and the deactivation of the Catalyst is accelerated. In addition, the ethylene losses in an excess of hydrogen increase extremely rapidly with increasing temperature, even when selectivity enhancing moderators such as carbon monoxide are present. Nevertheless, the selective hydrogenation of the acetylene in so-called. Cp-minus fractions of palladium catalysts, d. h # in a feedstock containing, in addition to acetylene, ethylene and ethane, carbon monoxide, methane and a large excess of hydrogen, a series of technological advantages in the design of the separation of the cracked gas mixture.

It is known to carry out the hydrogenation process at temperatures of 50 to 200 ⁰ C, pressures of 1 to 40 kp / cm, preferably 25 to 35 kp / cm ² , and loads up to 10 000 v / vh, the reactor temperature is preferably up about 150 ⁰ C is limited (US-PS 3 325 556, DT-AS 1 173 455 and DT-AS 1 249 228).

Ftier these methods are catalysts with palladium concentrations up to about 0.5% by mass used (US Patent 3,549,720 and DT-AS 1 249 228). It is known that the temperature control of such processes in the presence of a large excess of hydrogen is critical (W.K. Lam and L. Lloyd, Oil Gas Journal 1972 (March 27) 66-70).

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For this reason, v / ill be in the known technical solutions the temperature rise in the catalyst bed itself in the opposite? / Art of carbon monoxide to less than 3O ⁰ C, in US Patent No. 3,412,169 for example * to values below 21 ⁰ C limited. The required carbon monoxide concentration ranges from 0.1 to about 1.0 % (U.S. Patent 3,549,720, U.S. Patent 3,556).

In order to increase the operational stability of such processes, it is known to increase the selectivity of the catalysts e.g. with silver and iron oxide (US Patent 2,927,141 and DL-PS 26 099 or copper and silver (DT-AS 1 052 979). The selectivity gain achieved by the promotion is limited and associated with a decrease in activity.

The known methods also apply to macroporous, surface-active palladium urea catalysts (DT-AS 1 201 330, DT-AS 1 249 228 and US Pat. No. 3,113,980). However, the activity of the proposed catalysts with upper

2 2

less than 15m / g, in particular less than 10 g / g, comparatively low. Thus, a promo-oriented with silver and iron oxide Palladiurakatalysator requires on a Korundtraeger, even in the absence of carbon monoxide, already operating temperatures of at least 100 ⁰ C * In the DT-AS 1,249,228 it is shown that palladium-alpha-Aluminiumtraegerkatalysatoren with 0.045% by mass of palladium and a specific surface of 11 m / g or less, despite a high excess of water and absence of carbon monoxide at temperatures of 90 to 95 ⁰ G, only 90 % of the acetylone, but already hydrogenate 0.5 to 1.0 % ethylene.

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Furthermore, it is still known (DT-OS 2,225,215, DT-OS 2,315,025) to drive through the selective hydrogenation in a filled with catalysts tube reactor, the gas flow is guided from bottom to top and the coolant level is controlled in the reactor jacket so that Depending on the operating conditions and catalyst properties, a more or less large upper part of the catalyst bed in the tubes, possibly also in the upper Bruederraum of the reactor, shell side is not surrounded by the Kuehlfluessigkeit. In this way, a lower, largely isothermally operated stage and an upper, essentially adiabatically operating stage is combined in one and the same reactor. A significant part of these process principles is that special reactors or catalysts are required, which cause considerably more costs compared to conventional types.

It is also known that the commissioning of especially fresh catalysts is problematic. They have a strong tendency to hot run as a result of high olefin hydrogenation (WK Lam and L. Lloyd, Oil Gas J, 1972 (March 27) 66-77). This disadvantage can be reduced by pretreating the catalyst with carbon monoxide in a specific start-up procedure. It is also known to improve the initial selectivity of palladium catalysts by a special hydrogen treatment at a pressure of at least 5 at and a temperature which is at least 30 ^° C. above the normal operating temperature (DL 29 285).

- 5 LP 7726 Aim of the invention

The object of the invention is to develop a process for the selective hydrogenation of C2-minus fractions, which reduces the loss of ethylene compared to known processes. In addition, it is the object of the invention to extend the stability range of the hydrogenation process and thus significantly increase the reliability of the process compared to known processes, as well as to shorten the period during which the reaction is initiated and to reduce the characteristic instability associated therewith.

Explanation of the essence of the invention

The invention has for its object to provide a process for the selective hydrogenation of C ^ minus fractions with optimal Prosesrfuchrung incorporating an active palladium traeger catalyst with high Eigonselektivitaet to develop, since the main causes of the Aethylenverlusbe and the limited stability of the process the operating parameters are on the one hand the catalyst, on the other hand in the process conditions. As is known, palladium catalysts catalyze both the acetylenic and ethylene hydrogenation. The high selectivity of these catalysts under suitable conditions results from the fact that the chemisorption equilibrium, even in the presence of a large amount of olefin excess, is practically completely on the side of the acetylenes, so that this is hydrogenated with high selectivity "If the acetylene content falls below a certain limit concentration, whose absolute value u. a »also depends on the catalyst used and the process conditions, the ethylene hydrogenation is increasingly used.

LP 7726

This condition is, since a virtually complete removal of Acetylene is required under technical conditions in any case reached and exceeded. The loss of ethylene also increases when diffusion processes on or in the catalyst moldings determine or co-determine the course of the reaction »

The carbon monoxide increases the selectivity of the process, since it inhibits the Aethylenhydrierung much stronger than the acetylene "However, its effect on temperature is tacked _# You decreases rapidly with increasing temperature, so that large temperature gradients in the catalyst bed deterioration of selectivity and stability of the process and, in extreme cases, even the cause of a very high ethylene hydrogenation, as a result of which the hydrogenation process gets out of control.

The invention is therefore also based on the object of using a catalyst which largely excludes diffusion processes due to its pore structure and the distribution of Aktivkompoenten and thereby, without reducing its activity, allowing a large compared with known catalysts temperature gradient, and the method so too design that the catalyst-permissible temperature gradient, which inevitably sets as a result of acetylene hydrogenation, procedurally optimally utilized and thereby high effectiveness and Stability of the hydrogenation is achieved * Another object of the invention is to make the commissioning conditions so that in a short time if the carbon monoxide concentration is increased by a process-related or a minimal increase, the required acetylene decomposition and a

- 7 LP 7726 high selectivity can be achieved.

For the selective hydrogenation of a Cp-minus fraction containing 0.3 to 2.0% by mass of acetylene, at least 1% by mass of hydrogen and generally from 1 000 to 2 000 ppm by volume of carbon monoxide, in a shell-cooled tubular reactor These pressures are achieved according to the invention by a pressure of 1 to 40 kp / cm 2, a rate of 2500 to 10 000 v / vh and a reactor tempature of 35 to 105 ° C, the ancestor can be replaced by a copper, silver, nickel and, if appropriate, nitrobenzene or promoted iron or its compounds, essentially macroporous palladium-supported catalyst having a specific surface area of at most 50 cm / g, wherein at least 33 % of the 6

SOO

Pore volume attributable to pores and the radii uebervAE, and a palladium concentration of 0.005 to 0.1 mass'% conducted vrird _e Erfincltingsgeiaaeßs If the Strcemungßgeechwindigkeit of C ₂ -minus-fraction through the tubes of the reactor from 0.3 to 3.0 m / s and The ratio of the internal diameter of the catalyst tubes to the Durander or »to the catalyst moldings is between 8 and 25. According to the invention, the method continues with temperature differences between the reactor outlet and reactor inlet of + 60 ° to - 15 ⁰ C and between reactor outlet or any point in the catalyst bed and the Kuehlmedium

from 0 to + 6O ⁰ C performed. The start-up of the hydrogenation is carried out in the inventive process with process-related or up to a maximum of 5000 Vol _e ppm elevated carbon monoxide concentration, and a space velocity of at least 3,000 v / vh, the reactor entry temperature within 1 to 6 hours to just below or up гш: light-off temperature dep catalyst increased and then, if appropriate, under Einsohiebung a holding time of 30 to 60 minutes, at substantially

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constant inlet temperature by gradual increase of the coolant pressure of the required Acetylenabbau is set, Erfindungsgemaes.s temperature changes are carried out in the reactor at a rate of up to 20 ° C / h maximum.

An expedient embodiment of the process according to the invention comprises a heat exchanger, a preheater, a tubular reactor, a cooler and a green oil separator. In addition, it enables the feed of cold crude fraction between the preheater and the reactor and the circulation of the yawarm shear with the hot, refined Cg -minus fraction, As a favorable sizing of the catalyst tubes in the reactor has a clear width of 25 to 55 mm, preferably from 40 to 51 mm, and a length of 4000 to 8000 mm proved. In the heat exchanger, the cold CL minus crude fraction is pre-heated by the hot, hydrogenated product stream from the reactor. The requisite reactor inlet temperature is set with the aid of the preheater and, if appropriate, by feeding a partial stream of the cold crude fraction. The tubes of the reactor are filled to about 90 % with catalyst and are cooled on the shell side by a boiling Pluessigkeit. The coolant mixtures are condensed in a Bruedenkuehler and flow back through a Vorratsgefaess back into the cooling jacket of the reactor, the coolant level is controlled so that the Katalysatorschuettung in the tubes is fully surrounded on the shell side with Kuehlfluessigkeit. The reactor temperature is mainly controlled by the coolant pressure. The Coolant should have ungswaerme a possible low boiling point and a high evaporator ,, A favorable cooling has, liquid, low molecular weight hydrocarbon fractions or methanol, and at temperatures substantially above 100 ⁰ C.

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proved with methanol-water mixtures. The hot, refined Cp-minus-praxis usually gives off part of their heat to the cold crude fraction, and after intensive cooling they remove the very small amounts of oligomerizate in the green oil separator.

Preferably, the inventive method is in a

Pressure of 25 bio 35 kp / cm and a space velocity of 3000 to 7000 v / vh performed. The used Katolysatortraeger consists to a large extent or completely of alpha-alumina. It should not be more than 10% of its pore volume of pores having a radius below 100 AE, He contains in the sum of 0.0005 to 0.25 mass% promoters from the iron and / or first subgroup of the Periodic Table of the Elements. Preferably, a catalyst is used which has a specific surface area of from 3 to 15 m / g and especially from 3 to 10 m / g, which does not contain pores with radii below 100 AU, in which at least 75 % of the pore volume on pores Radii of over 500 AU, containing 0.01 to 0.05% by mass of palladium and 0.003 to 0.05% by mass of nickel, copper and / or silver or their oxides and 0.03 to 0.2% by mass of iron ( III) - or iron (IJ, III) oxide contains. In addition, the palladium in the preferred catalyst according to the invention is in a maximum of 1.5 mm, but preferably in a 1.0 mm, thick peripheral layer of the catalyst particles and, independently of the penetration depth of the active components in the carrier molding, is relatively homogeneous and stable structure under the reaction conditions.

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The optimum palladium concentration in the catalyst depends on the process conditions. At high load and high acetylene concentrations, it is preferably in the upper part of the stated range. In addition, an increase in the palladium content can lower the required operating temperature of the catalyst. If the catalyst used according to the invention contains no promoters, the palladium contained in it is distributed over the entire carrier molding and / or if the specific surface area is above 20 m / g, palladium concentrations below 0.040 mass% are preferred. With increasing palladium content, increasing specific surface area, in particular above 20 m 2 / g, and increasing penetration depth of the palladium, the ethylene balance of the process deteriorates under comparable conditions and the requirements with regard to the maintenance of the temperature increase.

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conditions, especially at low, in the case of normal process-related carbon monoxide concentration, i. the stability of the hydrogenation process decreases. When using catalysts with specific surface areas above 50 m / g or palladium concentrations above 0.1 mass%, ethylene losses due to the hydrogenation process under technical conditions are unavoidable, the temperature control is critical and the starting behavior is unsatisfactory. The hydrogenation process can only be so or not with such catalysts even with high carbon monoxide concentrations. The selectivity of the catalyst is also unfavorably influenced by micropores.

The Afcmessung the catalyst moldings depends primarily on the clear width of the catalyst tubes. It has been found that the most favorable ratio of internal diameter of the tubes to the diameter or height of the catalyst pieces is between 8 and 25, preferably between 10 and 15.

According to the process of the invention, the feedstock flows through the catalyst tubes at a rate of from 0.3 to 3.0 m / s, preferably from 0.5 to 2.0 m / s. The most important parameters for the dimensioning of the reactor tubes are the acetylene concentration in the crude fraction, the expected load range and the performance of the cooling system. With decreasing catalyst load, decreasing cooling performance and increasing acetylene concentration, the flow rate must be increased to achieve optimum results. * At acetylene concentrations above 1% by mass, it should not fall below 0.8 m / s and preferably between 1.0 and 2.0 m / s lie. It is also true in other cases, when a comparatively small pipe

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sufficient fast removal of hydrogenation heat is ensured.

The best results are achieved by the method according to the invention when a very high temperature difference between reactor outlet and reactor inlet is desired in the axial direction of the catalyst tubes. It has been found that when using the catalyst described above, this difference can be up to + 60C without ethylene losses or the hydrogenation process becoming unstable. Even with negative values of this temperature difference down to -15 ° C, the result is not or not significantly affected if the acetylene concentration in the Cp-minus crude fraction is below 1.0 mass $. Above -15 ° C occur at constant carbon monoxide with increasing negative temperature gradient and increasing acetylene concentration, especially above 1.0 mass% ethylene losses, and the process stability decreases. Preferably, the inlet st emperature process of the invention from 50 to 5 ⁰ C below the exit temperature. In addition, the reactor inlet temperature erfindungsgemaess is maintained up to 20 C under the light-off temperature of the catalyst, the temperature is understood as a light-off temperature, particularly to hydrogenate the acetylene at the aer catalyst under the given Prczessbedingungen begins * during the commissioning phase and in catalysts with relatively low current Aktivitaetsniveau For example, the reactor inlet temperature is preferably maintained at or above the light-off temperature. In continuous operation, especially in the presence of a catalyst with a high current Aktivitaetsniveau, the inlet temperature is preferably up to 20 ⁰ C below the light-off temperature. The axial and radial temperature gradient between any point in the catalyst bed and the coolant temperature may be

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do not exceed + 60 ° C. The most favorable temperature difference for a particular application depends above all on the current activity level of the catalyst used and the dimensioning of the reactor. In the case of large clear widths of the catalyst tubes and in the case of very active catalysts, it should, in the interest of ethylene yield and process stability, preferably not exceed 45 ° C. and during the startup of fresh catalysts at carbon monoxide concentrations <2,000 Vppm, preferably 3O < ⁰ > G.

Especially by this Temperaturfuehrung is achieved compared to all previously known methods, despite the permissible large temperature gradients, a significantly better selectivity and a significantly higher stability of the hydrogenation.

Any change in the reactor inlet temperature occurs in small increments, not exceeding 20 ° C / h and preferably 10 C / h, regardless of whether it is an increase or decrease in temperature. The coolant temperature is changed according to the invention also only in small steps, in which case the change does not exceed a total of 10 ° C / h and preferably 5 ° C / h. With increasing operating time of the catalyst, the speed of temperature changes can be increased.

The temperature increase during commissioning of fresh catalysts or, in the region around and above the light-off temperature of the catalyst used, during the reactivation of reactors must be particularly careful and slow. It is also essential here that changes in the temperatures or in the concentration of carbon dioxide are subject to a very careful analytical procedure

-H-ЬР 7726 control of the hydrogenation process be performed.

The commissioning of a reactor filled with fresh catalyst is carried out according to the invention with a carbon monoxide concentration in the crude fraction, which is between process-conditioned and a maximum of 5000 ppm by volume, preferably between process-related and 3500 ppm by volume. When recommissioning a catalyst, a carbon monoxide content between process-related concentration and a maximum of 3000 ppm by volume is preferably used. The most favorable carbon monoxide concentration for a specific case depends above all on the dimensioning of the reactor, the composition of the crude fraction, the performance of the cooling system and the current activity and selectivity of the catalyst used. With relatively large inside diameters of the catalyst tubes, with high acetone concentration in the Cg minus crude fraction, with low cooling system performance, at low load, and / or with a high activity catalyst, it is advantageous for short start-up time, process stability, and ethylene yield to temporarily increase the carbon monoxide content in the crude fraction during the start-up phase, within the limits defined according to the invention.

The space velocity must not be less than 3000 v / vh at start-up and is preferably 3500 to 4000 v / vh in this phase. Expediently, during the start-up phase, at least part of the co-minus fraction passing through the reactor is returned to this load with minimal consumption to reach crude fraction.

When starting the invention, the Cg-minus crude fraction with a temperature of 5 to 30 ⁰ C, preferably 15 to 30 ⁰ C placed on the reactor. Than it will be

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within 1 to 6 hours, preferably within 2 to 3 hours, the inlet temperature increases in small steps up to the light-off temperature. Expediently, the temperature increase is interrupted just below or at the light-off temperature for 30 to 60 minutes until the temperature in the reactor has largely equalized. Once the acetylene is hydrogenated to a small extent, the reactor temperature is in small increments above the coolant pressure and under careful analytical control increases until the residual Асеtylengehalt is below 3 ppm · After the hydrogenation has stabilized, if necessary, the carbon monoxide concentration is gradually reduced according to the Äethylenbalanz up to the process-related value. As soon as ethylene hydrogenation is noticed, the reactor temperature is lowered in parallel to the carbon monoxide content.

Compared with the previously known processes, the process according to the invention has a number of significant advantages which have an extremely favorable effect on the economy and stability of the hydrogenation process and the capital expenditure required for its realization. Due to the high Eigenselektivitaet of the catalysts used and the process conditions tuned to this is compared to the known method, very high temperature difference in the catalyst bed or catalyst bed to Kushlmedium allowed without the reactor tends to run through or for ethylene hydrogenation. On the contrary, the ethylene losses in the orformungsgemaessen method are significantly lower than the usual. As a result, the moderator concentration required in the crude fraction is low, without fluctuations in the composition of the Cpminus fraction and / or bsi in the process being caused by process-related variations.

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parameter significant ethylene losses occur or the acetylene is no longer sufficiently hydrogenated. In the known method, however, this temperature difference must, as has already been executed to below 3O ⁰ C to achieve sufficient stability of the process in most Paellen even at 21 C and including, limited to keep the Aethylenverluste limited and (see US 3 412 169). In general, an increased moderator concentration must also be required. Another significant advantage of the process according to the invention, which results from the high permissible temperature gradients within the catalyst tubes in the radial and axial directions, the high intrinsic selectivity of the catalysts used and the process conditions optimally adapted to them, is that it is produced in appropriately dimensioned tubular tube reactors and possibly also in intercooled bed reactors with the same or better effectiveness with regard to the operating result can be carried out as proposed in the DT-OS 2,225,231 and DT-OS 2,315,025 proposed process principle, the special reactors with high investment costs and a complicated Prozeßfuehrung with increased Stoeranfaelligkeit requires. A further advantage is that the inventive method at start-up in a short time, with minimal Äethylenverlust or raw material einsät ζ and minimal additional Kohlenraonoxidbedarf one of the required purity (acetylene <3 ppm) corresponding selectively hydrogenated Cp-minus-Praction provides.

Some expedient and advantageous Ausfuehrungsvarianten of the inventive method are shown in the following examples.

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- 17 LP 7726 Example 1

7.2 1 of catalyst are installed in a pilot reactor. The reactor is part of a pilot plant consisting of a preheater, reactor, cooling system and the corresponding measuring and control devices including the vessel for measured value acquisition »The tubular reactor is surrounded by a cooling jacket and has a clear width of 51 mm (outer diameter 57 mm , Wall thickness 2.9 mm). The Katalysatorfuellhoehe is 3500 mm. The preheater is offered with IT low pressure steam. The cooling system consists of the cooling jacket of the reactor, a water cooler and a storage vessel for the cooling liquid. Ale cooling medium is boiling methanol. The required Cp-minus action is taken directly from a technical plant for ethylene production. Elevated carbon monoxide concentrations can be adjusted specifically by an additional carbon monoxide feed at the entrance of the pilot plant. The reactor inlet temperature is controlled via the pre-aerator and the coolant temperature via the methanol pressure in the cooling system by the amount of cooling water in the methanol condenser. Analyzes are carried out by conventional chromatographic methods. The CL minus fraction used had the following average composition in mass% t

Acetylene 0.75 %

Ethylene 50.0

Ethane 13.5

Hydrogen 1.65

Methane 34.3

Carbon Monoxide 1 000 to 1 800 ppm (Vol »)

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LP 7726 0.90 kg / 1 Structure of the carrier alpha alumina 173 +40 Jcp / cm ² Total pore volume 0.37 crn - ^ / g The catalyst is characterized by the following data: 0.034 mass% r <100 & 0.0 cwr / s Schuettgewicht 0.020% by mass 100 <r <500 Ä 0.04 cm ³ / g Burst pressure 0.028% by mass r> 500 1 0.33 cm ³ / g Composition Pd Carrier material remainder specific surface 8.4 cm ² / g CuO Cat alysate orform Pills with a through Pe ₂ O knife of 4.65 + 0.15 mm and a height of 4.6 + 0.2 mm Palladiumvert hurry approx. 0.8 mm thick perip here layer

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At the start of operation, the reactor filled with catalyst was rendered inert with nitrogen, and the carbon monoxide concentration in the C "minus" crude fraction was increased to 3000 ppm by feeding in additional carbon monoxide. Then at an inlet temperature of 30 ⁰ C and a pressure of 28.7 at the Cg-minus fraction was placed on the reactor. The flow rate through the catalyst tube was 0.45 m / s and the load 3500 v / vh. In small steps, the inlet temperature within 2 hours up to 6O ⁰ C increased. At this temperature the hydrogenation reaction set in, as the rising coolant pressure and the analysis results auswiesen * Under analytical control, in small steps, the inlet temperature to 70 ⁰ C and the refrigerant pressure at 0.2 to 0.25 kgf /

cm increased. Under these conditions, the acetylene has already been degraded to 6.2 ppm. Aethylene losses did not occur. After setting stable operating conditions, the carbon monoxide concentration was gradually reduced to the process-related value of 1600 to 1-800 ppm. "As soon as the analyzes showed low ethylene losses, the reactor temperature was also lowered in parallel.

Characteristic results of this phase are summarized in Table 1, lines 1 to 4 ».

Subsequently, the process conditions were varied within the following limits,

Pressure 28 - ЗО ata

Temperature 45-120 ⁰ C

Coolant pressure 1.05 to 4.75 ata

Load 2200 to 7000 v / vh

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!Table 1 1 coolant burden CO-Konz, CLEL balance temperature 70 druek v / v h (related to reactor 70 3 employed entrance 70 3500 C ₂ H ₄ ) 70 kp / cm 3500 Vol "ppm +% ⁰ C 70 2 3500 4 5 72 0.2 3500 3000 + 1.15 82 0.25 3500 2500 + 0.98 82 0.25 4400 2000 + 1.27 88 0.25 5800 1700 + 0.70 60 4.0 5800 1700 + 0.0 50 0.3 7000 1700 + 1.41 45 0.8 5800 2000 + 0.82 45 0.75 5800 1700 + 0.71 45 1.25 5800 1700 + 0.29 0.90 5800 1700 + 0.66 0.90 5800 UDO + 1.34 0.92 1800 + 1.28 2.3 1800 + 1.06 3.95 1800 + 1.63

By systematic change of the reactor temperature with the help of the coolant pressure u. a _# at constant, process-related carbon monoxide concentration, the process stability and the tendency of the catalyst to IIDurchgehenlf, (ie for Durohhydrierung) tested. Characteristic values are summarized in Table 1. After an operating time of 142 hours, it was switched off and restarted under essentially analogous conditions as described above "The carbon monoxide concentration in

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the crude fraction was 2050 ppm. After only 4 to 5 hours, stable operating conditions had been achieved. The residual acetylene content was 1 ppm. Ethylene yields between 0.93 and 1.4 % were obtained, based on the ethylene used.

Example 2

7.2 l of the catalyst according to Example 1 were incorporated into the experimental plant described therein. The commissioning was carried out analogously to Example 1 with a load of 5800 v / vh, a flow rate through the catalyst tubes of 0.8 m / sec and a carbon monoxide concentration of 2500 ppm by volume. To test the activity-time behavior of the catalyst, the conditions were deliberately increased by the relatively high operating temperature. The process-related carbon monoxide concentration fluctuated between 1000 and 1300 ppm by volume. The stability of the hydrogenation process and the passage behavior of the catalyst was tested several times after different operating times analogously to Example 1. Furthermore, in the course of the experiment, the reactor was started and stopped six times as planned. The starting was carried out according to Example 1 at loads of 2200 to 7000 v / vh and carbon monoxide concentration of 1000 to 2500 ppm by volume. Characteristic results are summarized in Table 2. The residual acetylene content was <2 ppm in all paellen. After an effective operating time of 774 hours, the attempt was stopped without a decrease in activity compared to the 100 hours of operation.

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Table 2

Operating time Tempera- Coolant load COm conc. ^с о ** 4 ~

in h door pressure v / vh vol. ppm balance,

Reactor kp / cm

eing. turned

translated

⁰ CC ₂ H ₄

103 95 1.6 5800 2300 + 1.4 138 94 3.35 5800 2000 + 0 Oft 190 95 1.15 5800 1000 + 1.02 269 95 1.9 5800 2000 + 1.14 404 113 2.2 5800 2500 + 0.65 412 93 3.5 5800 1200 - 0.55 570 98 1.5 7000 1100 + 1.24 613 85 0.85 2900 1200 + 0.86 647 85 4.0 2900 1000 - 1,79 708 103 4.0 2200 1000 - 3,18 729 95 1.5 5800 1000 + 0.96 753 100 1.75 7000 1000 + 0.63 770 106 2.3 5800 2500 + 0.08

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Table 3 Catalyst for

Example 3 Example 4 Example 5

Shoe weight in kg / l 0.84 0.86 1.05 0.52 with on Bursting pressure in kp / cm 382 + 80 391 + 85 183 + 105 0.03 share from Composition in Ma, -% theta and Pd 0.032 0,025 0,035 0.09 kappa-Al ₂ O, CuO 0,018 0,017 "M" 0.40 Pe ₂ O ₃ 0,044 0.06 0.1 0.35 Traegermat , rest rest rest 11.0 0.07 Roentgen structure of the alpha-AlJD-alpha-Al_0 alpha-AlgO- Traegermaterials 0.15 0.13 32 Pore volumes in cm / g total 0.44 Radii <100 ΛΕ 0.0 Radii 100 to 500 AU 0.13 Radii> 500 AU 0.33 specific surface in m ² / g 1 2.0

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77Р 7726

Distribution of the active components in the

Traegerformlingen

peripheral, peripheral, uniform

Penetration- penetration throughout

deep deep carriers

approx. 0.6 m approx. 0.8 mm formling

Catalyst form Tablets Tablets Tablets Height in mm 4,70 + 0,15 4,75 + 0,15 3,4 + 0,1 Diameter in mm 4,8 + 0,2 4,75 + 0,15 3,6 + 0 2

Example 3

The catalyst characterized in Table 3, column 1, was used in the pilot plant described in Example 1 for the selective hydrogenation of a technical Cg-minus fraction. In this case, the carbon monoxide concentration between 1730 and 63ОО vol.-ppm, the load between 2800 and 7OOO v / vh, the reactor inlet temperature between 67 and 104 ⁰ C and the coolant pressure between 0.3 and 2.55 kp / cm varied. The reactor pressure varied between 26.8 and 28.3 kp / cm ² .

The experimental procedure corresponded to that described in Example 1. The characteristic results are summarized in Table 4. The residual acetate content was ^ .2 ppm in all cases.

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- 25 LP 7726 Table 4

Temperature Coolant load CO concentration G ₃ H. balance, reactor pressure triggers an input CgH.

⁰ C kp / cm v / v h Ppmv +% 86 0.55 5800 6300 + 0.08 76 0.50 5800 3600 + 1.22 72 0.53 5800 2500 + 0.61 83 0.85 7000 2500 - 2.02 80 0.94 4400 2400 - 2.55 80 0.95 2900 5000 + 1.05 95 2.5 5800 2600 - 5,46

Example 4

The catalyst characterized in Table 3, column 2, was used in the pilot plant described in Example 1 for the selective hydrogenation of a technical C2-minus fraction. The feed mixture contained 1200 to 2500 vol. P pm carbon monoxide, the other process parameters were varied within the limits given in Example 3. The commissioning of the reactor was carried out according to Example 2 * The characteristic Versuohsergebnisse are summarized in Table 5, while the Restacetylenkonzentration was in all Paellen at ^ 2 ppm.

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- 26 LP 7726 Table 5

Temperature Coolant load CO conc. C ^ H. balance,

Reactor pressure has started

gegang set C ₀ H.

kp / cm

v / v h

VoI, ppm +

90 1.7 5800 1900 + 1.24 90 1.6 5800 1700 + 1.5 90 1.5 5800 1500 + 0.83 90 1.3 4400 2100 + 1.19 87 1.2 2900 2100 + 1.19 93 1.55 7000 1500 + 1.32 94 3.5 5800 1400 - 0.24

Example 5

The catalyst characterized in Table 3, column 3 »was incorporated in the experimental reactor according to Example 1. The commissioning was carried out analogously to Example 1, but with a carbon monoxide concentration of 1600 VoI, ppm. The further experimental procedure corresponded to Examples 3 and 4. The results summarized in Table 6 are characteristic of this experiment. The acetylene was degraded to 3 ppm in each pail. The hydrogenation reaction starts at 57 ° C,

Table 6

Temperature cooling load CO-Konz, CgEL balance, related

reactor inlet

⁰ C 72

medium pressure

kp / cm 0.35

on inserted ° 2 ^H 4

v / vh VoI, ppm +

3500

1600

+ 0.62

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LP 7726 0.80 5800 1800 + 0.94 Table 6 0.95 5800 1200 + 0.78 76 1.5 5Ю0 1200 - 0.52 85 2.5 5100 1250 - 1.5 86 2,95- 5800 1300 - 4.36 85 87

Example 6 - Comparative Example

For comparison with the results obtained in Examples 1 to 5 according to the invention 7.2 1 of industrially produced and in the selective hydrogenation of Cp-minus fraction technically proven catalyst were incorporated into the experimental plant described in Example 1 and after the Examples 1 to 5 approached and essentially tested under analogous conditions « Oqv comparison catalyst is characterized by the following data

Sohuettgewicht 0.75 kg / 1 Barstdruck 356 + 290 kp / cm ² Composition Pd 0.034 mass% CuO 0.01 Fe ₂ O ₃ 0.54 HiO < 0,015 Structure of the carrier Mixture of alpha and theta alumina Total pore volume 0,60 enrVg for r <100 Ä 0.25 H for 100 <r <500 1 0.25 H for> 500 1 0.10 cm ² / g specific surface 82 m ² / g shaped catalyst Tables with a throughput

diameter of 6.0 + 0.8 mm

and a height of 3.2 + 1.1

mm

- 28 -

LP 7726

During commissioning, the crude fraction with a carbon monoxide content of 3800 ppm and a temperature of 25 ⁰ C on the reactor was set. The load was 5800 v / vh. The inlet temperature was increased in small steps within 3 hours, up to 60 ⁰ C and held here for 1 hour until the reactor outlet temperature had largely adjusted. Then the temperature was further increased at a rate of 6 ° C / h. At 72 ° C, the hydrogenation reaction began. The required acetylene degradation to 3 ppm was about 7.5 hours after charging the reactor with the Cg-niinus fraction at an inlet temperature of 80 C and a coolant pressure of 0.8 kp /

2 cm reached. The reactor pressure fluctuated between 26 and

28 kp / cm. The remaining parameters were varied in the limits given in Example 1. The characteristic values summarized in Table 7 were obtained.

Table 7 Cool burden СО-Кош +0.20 temperature medium - 0.32 reactor print - 0.75 entrance 2 kp / cm v / v h - 3.66 ⁰ C 0.8 5800 above sea level. CpKL balance sheet, related - 41.0 (more complete 82 0.8 5800 on inserted Consumption of H ₂ ) 80 0.8 2900 ^C 2 ^H 4 - 4.29 75 1.5 5800 Ppm by volume + % - 1.58 82 2.0 5800 1800 - 1.5 82 2220 1.2 2800 1600 74 0.7 2800 1500 105 0.8 7000 1500 84 1500 1600 1500

- 29 -

-23-

The commissioning of the catalyst with carbon monoxide concentrations below 2000 ppm was not possible because it is prone to go through. In addition, the achievable process stability compared to Examples 1 to 5,

considerably lower · Already a relatively small increase of the reactor temperature (especially over the coolant pressure) bzv /. a reduction of the carbon monoxide concentration led to rapidly increasing ethylene losses and finally even to reactor runaway. "This is particularly evident when comparing the results summarized in Table 8 with regard to process stability and catalyst throughput.

Table 8

Example Temperature Cooling load CO conc. CgH. balance,

based on

Reactor inlet a

print

inserted ° 2 ^H 4

kp / om v / vh ppm by volume + %

1 70 45 4.0 3.95 1.5 2.0 3500 5800 1700 1800 I5OO 1500 + 0.0 + 1.63 2 93 85 103 3.50 4.0 4.0 5800 2900 2200 1200 1000 1000 - 0.55 - 1.79 - 3.19 3 95 2.5 5800 2600 - 5,46 4 94 3.5 5800 1400 - 0.24 5 87 2.95 5800 1300 - 4.36 6 82 82 5800 5800 - 3.66 - 41.0 (total hydrogenation)

Claims (15)

LP 7726 Invention claim 1, Verfalaren for the selective hydrogenation of Cp-minus fractions, in addition to ethylene, ethane and methane 0.3 to 2.0 mass% of acetylene, at least 1.0 mass% of hydrogen and 1000 to 2000 ppm by volume of carbon monoxide at a pressure of 1 to 40 kp / cm, a space velocity of 2500 to 10 000 v / vh and a reactor temperature of 35 to 150 ⁰ C, on palladium traker catalysts, optionally with copper, nickel, silver and / or iron or compounds of these elements are promoted, characterized in that a substantially macroporous Traegerkatalysator with a specific Surface of not more than 50 m / g, in which at least 33 % of the pore volume is accounted for by pores with radii of more than 500 AU, and a palladium concentration of 0.005 to 0.1% by mass in a tubular reactor, such that the rate of flow of the Cp-minus Praction of the clear tubes of the reactor tubes to the diameter or the height of the catalyst moldings is between 8 and 25, that the temperature difference between the reactor outlet and the reactor inlet + 60 to - 15 ⁰ C and between any point in the catalyst bed and the cooling medium 0 to + 60 ° C entailed that the commissioning or recommissioning of the catalyst-filled reactor with a carbon monoxide concentration in the Cp-minus crude fraction between process-related content and 5000 ppm by volume and a RaumgesHhwindigkeit of at least 3000 v / vh that the reactor inlet temperature within 1 to 6 h to short un increased above or up to the light-off temperature of the catalyst and then optionally with Ein3chiebung a holding time of 30 to 60 minutes, LP 7726 is set at a substantially constant inlet temperature by gradually increasing the coolant pressure of the required acetylene degradation and that temperature changes in the reactor at a rate up to 2O ° C / h are performed. 2. The method according to item 1, characterized in that the catalyst used 0.005 to 0.1 mass% of palladium and in the sum 0.0005 to 0.25 mass% of copper, nickel, silver and / oror iron or their oxides on a carrier consisting essentially of alpha-alumina with a specific surface of 1 to 25 In addition, at least 50 % of pores with radii above 500 AU and at most 10% of those with radii of less than 100 AU are accounted for by the total pore volume. 3 · Method according to items 1 and 2, characterized in that the catalyst used has a specific surface area ρ ρ from 3 to 15 m / g and especially one from 3 to 10 m / g, has no pores with radii below 100 AU and accounts for at least 75 % of the pore volume on pores with radii over 500 AU. Method according to items 1 to 3f, characterized in that the catalyst used comprises 0.01 to 0.05% by mass of palladium and, as promoters, 0.003 to 0.05% by mass of nickel, copper and / or silver or their oxides, and 0, 03 to 0.2% by mass of iron (III) or iron (II, III) oxide. Method according to items 1 to 4 _t, characterized in that the catalyst used contains the palladium in a maximum of 1.5 mm and in particular in a maximum of 1.0 mm thick peripheral layer of the catalyst moldings. 6. The method according to item 1, characterized in that the catalyst used 0.005 to 0.05 masse-% palladium LP 7726 on a carrier consisting essentially of alpha-alumina contains with a specific surface area of 15 to 50 m / g, wherein at least 33 % of the pore volume accounts for pores with radii over 500 AU, 7th method according to item 1 to 6, characterized in that the ratio of the inner diameter of a catalyst tube to the diameter or the height of the catalyst moldings is between 10 to 15. 8. The method according to item 1 to 7 », characterized in that the flow rate of the Cg-minus fraction through the catalyst pipes 0.5 to 2.0 m / s. 9. Method according to items 1 to 8, characterized by that the temperature at any point in the catalyst bed is maximized;
temperature is. lysator bed up to 45 C above the coolant 10. The method according to item 1 to 9, characterized in that the difference between the reactor outlet and reactor inlet temperature between + 50 and +5 ⁰ C. 11. The method according to item 1 to 10, characterized in that the reactor inlet temperature is kept up to 2O ⁰ C below the light-off temperature of the catalyst used, wherein the light-off temperature is to be understood, in which the catalyst to hydrogenate the acetylene under the given process conditions begins. 12. The method according to item 1 to 11, characterized in that when commissioning fresh catalysts or recommissioning of catalysts, the carbon monoxide concentration in the crude fraction between process LP 7726 conditional and a maximum of 3500 vole ppn is that ßchwindigkait least 3000 below v / vn, preferably 3,500 to 4,000 v / vh, _f is the Reaktoreintrittstenperatur within 1 to 6 hours, preferably within 2 to 3 hours, in small steps bic rate or bit 'gur nnspringtemperatur of the catalyst ε is erhooht, 13 * Process according to items 1 to 12, characterized dsdin * ch, öafis when restarting a catalyst, the Kohlerunonoxidkonzentration in the crude fraction between prozescbedingtem content and 3000 vol. »Ppm 14 · Processes according to items 1 to 13, geker-nzoichnet q? Dur the reactor © ingangstemperntur in small ^ steps, but maximum 20 C / h and preferably 10 C / h. 15. The method according to item 1 to 14 »characterized in that the coolant temperature is changed in k_s_СоСоp step cn, but in total by a maximum of 10 ° C / h and, preferably, a maximum of 5 ° C / h.