DE2819791C2 - Process for the selective hydrogenation of C 2 -minus fractions - Google Patents

Description

he) the commissioning of fresh catalytic converters or the recommissioning of used catalytic converters with a carbon monoxide _{concentration in the C 2} -mlnus crude fraction between the process-related content and a maximum of 3500 ppm by volume,

ß) keeps the space velocity at least 3000, preferably 3500 to 4000 v / vh, and
γ) the reaction inlet temperature is increased in small steps within 1 to 6 hours, preferably within 2 to 3 hours.

12. The method according to claim 1, paragraph f,), to claim 11, characterized in that the - "restarting a used catalyst with a carbon monoxide _{concentration in the C 2} -mlnus crude fraction between process-related Gehall and 3000 vol.-ppm undertakes.

13. The method according to claim 1, paragraph g) to claim 12, characterized in that the reactor inlet temperature changes in small steps, but a maximum of 20 K / h, at least 10 K / h.

14. The method according to claim 1, paragraph h), to claim 13, characterized in that the cooling 2S Medium temperature in small steps, but in total by a maximum of 10 K / h and preferably by a maximum 5 K / h, changes.

The process for the selective hydrogenation of C ₂ -minus-Fraktlonen concerns a heterogeneously catalyzed, chemical process, with which in the context of the technical production of ethylene from fission gases of the gasoline pyrolysis the acetylene contained in the crude fraction and interfering with the processing of the olefin is removed as far as possible, without a substantial loss of ethylene occurring.

Characteristics of the known technical solutions.

The production of ethylene, as an intermediate product for the production of plastics, has achieved enormous technical importance. It is preferably obtained by separating and refining the fission gases from gasoline pyrolysis. The selective hydrogenation of the acetylenic bond has proven to be an almost universal refining process. Such selective hydrogenation processes require that they break down the acetylene of -tii, as a rule 0.3 to 2.0 ¹ V ₁ in the crude fraction, to less than 3 ppm, without substantial amounts of the ethylene present in large excess being hydrogenated.

For energetic reasons and to the extent of the polymer formation on the catalyst as little as To keep it possible, the aim is generally to keep the working temperature as low as possible, since, as is known, the Polymer formation, regardless of the specific catalyst system used, increases with increasing temperature favored and the deactivation of the catalyst is accelerated. In addition, the ethylene losses increase in the case of an excess of hydrogen, on extremely quickly with increasing temperature, even if Selectivity-increasing moderators, such as carbon monoxide, are present. Nevertheless, the selective hydrogenation offers of acetylene in so-called C2-minus-Fraktlonen on palladium catalysts, d. H. in an input product that in addition to acetylene, ethylene and ethane, carbon monoxide, methane and a large excess of hydrogen like that contains a number of technological advantages when designing the separation of the cracked gas mixture.

It is known that the hydrogenation process at temperatures from 323 to 473 K, pressures from 0.1 to 4 MPa, preferably 2.5 to 3.5 MPh, and loads of up to 10,000 v / vh, the reactor temperature being preferred is limited upwards to about 423 K (US-PS 33 25 556, DE-AS 11 73 455 and DE-AS 12 49 228).

Catalysts with palladium concentrations of up to approx. 0.5% by mass are used for this process (US-PS 35 49 720 and DE-AS 12 49 228). It is known that the temperature control of such processes in the presence a large excess of hydrogen is critical (W. K. Lam and L. Lloyd, Oil Gas Journal 1972 [March 27] 66 to 70).

For this reason, in the known technical solutions, the temperature rise in the catalyst bed even in the presence of carbon monoxide to below 303 K, In US-PS 34 12 169 z. B. to values below 294 K fto limited. The required carbon monoxide concentration ranges from 0.1 to approx. 1.0% (US Pat. No. 3,549,720, US Pat 33 25 556).

In order to increase the operational stability of such processes, it is known to use catalysts to increase the selectivity z. B. with silver and elsenic oxide (US-PS 29 27 141 and DD-PS 26 099) or copper and silver (DE-AS 10 52 979) to pronote. The selectivity achieved through the doctorate is limited and with a < >> Decrease in activity associated.

The known processes also relate to macroporous, low-surface palladium catalysts (DE-AS 12 01 330. DE-AS 12 49 228 and US-PS 1 13 980). However, the activity of the proposed catalysts is

with surfaces below ISmVg, in particular below 10m ² / g, comparatively low. For example, a palladium catalyst promoted with silver and iron oxide on a corundum support, even in the absence of carbon monoxide, already requires operating temperatures of at least 373 K. DE-AS 12 49 228 shows that palladium-alpha-aluminum supported catalysts with 0.045% by mass Palladium and a specific surface area of

11 m ² / g or less despite a high excess of hydrogen and the absence of carbon monoxide at temperatures of 363 to 368 K only break down 90% of the acetylene, but already 0.5 to 1.0% of ethylene hydrates.

It is also known (DE-OS 22 25 215, DE-OS 23 15 025), the selective hydrogenation process in one with Carry out catalyst-filled tubular reactor, the gas stream being guided from the bottom to the top and the coolant level in the reactor jacket is regulated so that, depending on the operating conditions and catalyst properties a more or less large upper part of the catalyst bed In the tubes, if necessary Also in the upper vapor space of the reactor, the jacket side is not surrounded by the cooling liquid. on this way, a lower, worldwide isothermally operated stage and an upper, essentially adiabatic stage working stage Combined in one and the same reactor. A significant disadvantage of these procedural principles is that special reactors or catalysts are required, which are significant compared to conventional types cause more costs.

It is also known that the start-up of fresh catalytic converters in particular is problematic. she have a strong tendency to overheat as a result of high olefin hydrogenation (W. K. Lam and L. Lloyd, Oll Gas J. 1972 [March 27] 66 to 77). This disadvantage can be avoided by pretreating the catalyst with carbon monoxide in a special procedure can be reduced during commissioning. It is also known that the initial

^{! n} selectivity of palladium catalysts by a special hydrogen treatment at a pressure of at least 0.5 MPa and a temperature at least 30 K above the normal operating temperature is to be improved (DD-PS 29 285).

Object of the invention

The aim of the invention is to provide a process for the selective hydrogenation of Cj mlnus fractions

develop, through which the ethylene loss compared to known processes is reduced. It is also a goal the invention to expand the stability range of the hydrler process and thus the operational reliability of the To increase the process considerably compared to known processes and to shorten the commissioning phase.

· "'Zen and reduce its characteristic instability.

Explain the essence of the invention

The invention is based on the object of developing a process for the selective hydrogenation of C ₂ -mlnus fractions with optimal process management including an active palladium-supported catalyst with high intrinsic selectivity, since the main causes of the ethylene losses and the limited stability range of the process the operating parameters lie on the one hand in the catalyst and on the other hand in the process conditions. It is known that palladium catalysts catalyze both acetylene and ethylene hydrogenation. The high selectivity of these catalysts under suitable conditions is due to the fact that the chemisorption equilibrium is grown, even in the presence of a large excess of olefin. is practically completely on the side of the acetylene, so that this is hydrogenated with high selectivity. However, if the acetylene content falls below a certain limit concentration, the absolute value of which also depends, among other things, on the catalyst used and the process conditions, the hydrogenation of ethylene begins to an increasing extent.
This state is, since a practically complete removal of the acetylene is required, under tech-

^A > nical conditions achieved and exceeded in any case. The loss of ethylene is also increased if diffusion processes on or in the shaped catalyst pieces determine or help determine the course of the reaction.

The carbon monoxide increases the selectivity of the process as it makes the ethylene hydrogenation much stronger inhibits acetyl hydration. However, its effect depends on the temperature. It sinks quickly with increasing temperature, so that large temperature gradients in the catalyst bed deteriorate Selectivity and the stability of the process cause 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 that is due to its pore structure and the distribution of the active components excludes diffusion processes as far as possible and thereby, without reducing its activity, a large compared with known catalysts

^ Temperature gradient allows, as well as to design the process in such a way that the katalysatorseltlg allowable temperature gradient, which inevitably occurs as a result of the acetylene hydration, optimally used in terms of the process and thereby a high effectiveness and stability of the hydration process is achieved. Another task of the Invention consists in making the commissioning conditions so that in a short period of time with process-related or minimal increase in the carbon monoxide concentration, the required acetylene degradation and a high selec-

⁽¹ "tlvitäi can be achieved.

The subject of the invention is thus the method indicated in the preceding claims. To the selective hydrogenation of C2 nut fractions.

An expedient embodiment of the inventive method comprises a heat exchanger, a Vorhci / er, a tubular reactor, a cooler as well as a GrUnökibschcldcr. It also enables

'' - Infeed of cold raw construction /. Between the curtain and the reactor and the flow through the heat exchanger with the hot, refined ('walnut-l'ractlon. As a favorable insulation of the catalyst tube The inside diameter of the reactor is from 25 to 55 mm, preferably from 40 to 51 mm. and a length of 4000 proven up to 8000 mm. In the heat exchanger, the k.Ulc Cj-minus raw fraction is replaced by the hot, hydrogenated

Preheated product stream from the reactor. With the help of the Vorhei / crs and, if necessary, by pumping of a substream of the cold crude fraction, the required reactor inlet temperature is set. The pipes of the reactor are filled to about 90% with catalyst and are covered with a boiling liquid chilled. The cooling medium vapors are condensed in a vapor cooler and flow over a storage vessel back into the cooling jacket of the reactor. The KUhlmlttelsland is regulated so that the catalyst bed In the pipes are completely surrounded by a jacket with coolant. The reactor temperature is mainly Controlled via the coolant pressure. The coolant should have a boiling point that is as low as possible and a high one Have heat of vaporization. Cooling of liquid, low-molecular hydrocarbon fractions is considered beneficial or methanol and at temperatures significantly above 373 K with methanol-water mixtures proven. The hot, refined C; -minus fraction usually first gives some of its heat to the ι » cold crude fraction, and after intensive cooling, the very small amounts of Ollgomerisat Im Green oil separator removed. '

The process according to the invention is preferably carried out at a pressure of 2.5 to 3.5 MPa and a space velocity of 3000 to 7000 v / vh. The catalyst support used consists largely or entirely of alpha-aluminum oxide. No more than 10% of its pore volume should consist of pores 15 _; ^:

with a radius of less than 10 nm. It contains a total of 0.0005 to 0.25% by mass of promoters from the Elsen and / or first subgroup of the periodic table of the elements (= copper, silver). Vorzugswelse will a catalyst is used which has a specific surface area of 3 to 15 m '/ g and especially from 3 to 10 mVg which contains no pores with radii below 10 nm, in which at least 75% of the pore volume on pores with radii over 50 nm are omitted, the 0.01 to 0.05% by mass of palladium and 0.003 to 0.05% by mass of nickel, 2 « Copper and / or silver or their oxides and 0.03 to 0.2% by mass of iron (IH) or Elsen (II, III) oxide. In addition, the palladium in the catalyst preferred according to the invention is in a maximum of 1.5 mm, but preferably in an up to 1.0 mm thick pearlescent layer of the shaped catalyst pieces and lies independently of the penetration of the active components in the carrier form, in a comparatively homogeneous and stable structure under the reaction conditions.

The optimal palladium concentration in the catalyst depends on the process conditions. In the case of high exposure and high acetylene concentrations, it is preferably in the upper part of the specified range. In addition, the required operating temperature of the catalyst can be reduced by increasing the palladium content. If the catalyst used according to the invention contains no promoters, the palladium contained in it is distributed over the entire support form 11 ng and / or the specific surface area is over ^-10 20 m ² / g, palladium concentrations below 0.040% by mass are preferred. With increasing palladium content, increasing specific surface area, especially above 20 mVg, and increasing penetration depth of the palladium, the ethylene balance of the process deteriorates under comparable conditions and the requirements with regard to compliance with the temperature conditions increase, especially when the temperature is lower. Normally process-related carbon monoxide concentration, ie the stability of the hydration process decreases. When using catalysts with specific surface areas above 50 mVg or palladium concentrations above 0.1% by mass, ethylene losses due to the hydration process are unavoidable under technical conditions, the temperature control is critical and the failure at start-up is unsatisfactory. The hydration process is difficult or impossible to control with such catalysts, even with very high carbon monoxide concentrations. The selectivity of the catalyst is also adversely affected by micropores. ■ »»

The dimensions of the shaped catalyst pieces depend primarily on the inside diameter of the catalyst tubes. It has been found that the favorable ratio of the inner diameter of the pipes to the diameter or to the height of the shaped catalyst pieces between 8 and 25, preferably between 10 and 15: 1.

According to the process according to the invention, the feedstock flows at a rate of 0.3 to 3.0 m / s, preferably from 0.5 to 2.0 m / s, through the catalyst tubes. The one for dimensioning the reactor tubes The most important determinants are the acetylene concentration in the crude fraction, the one to be expected Load range and the performance of the cooling system. As the load on the catalytic converter falls, it falls The cooling capacity and increasing acetylene concentration must be controlled by the flow rate to achieve optimal results increase. In the case of acetylene concentrations above 1% by mass, it should not be below 0.8 m / s sink and are preferably between 1.0 and 2.0 m / s. In these cases it is also beneficial if thanks to a comparatively small pipe diameter for a sufficiently fast dissipation of the heat of hydrogenation is taken care of.

The best results are achieved with the method according to the invention when in the axial direction of the Catalyst tubes as large a temperature difference as possible between the reactor outlet and reactor inlet:

is striving. It has been found that, when the catalyst described above is used, this difference can be up to> - ^s + 60K without ethylene losses occurring or the hydrogenation process becoming unstable. Even with ■

negative values of this temperature difference down to -15 K the result is not or not significantly impaired, if the acetylene concentration in the C2 nut crude fraction is below 1.0% by mass. Above -15 K occur at constant carbon monoxide concentration with increasing negative temperature gradient and; »

^{increasing acetylene concentration,} especially above 1.0% by mass ethylene losses, and the process stability wl v ^? sinks. In the process according to the invention, the inlet temperature is preferably 50 to 5 K below J.

Outlet temperature. In addition, according to the invention, the reactor inlet temperature is up to 20 K below the? ^;

The light-off temperature of the catalytic converter is maintained, the light-off temperature being understood as the temperature ({

in which the catalyst just begins to hydrate the acetylene under the given process conditions. Of the ;

axial and radial temperature gradient between any point in the catalyst bed and the temperature must not exceed ⁶⁵ Kühlmitteltempe- invention +60 K. The most favorable for a special application; /;

The temperature difference depends mainly on the current Akiivltäts level of the catalyst used and the Dimensioning of the reactor. In the case of large, clear worlds of the catalytic converter tubes and in the case of very active catalytic converters -

In the interests of the ethylene yield and process stability, it should preferably be 45 K and during £

the start-up of fresh catalytic converters, at carbon monoxide concentration cn = 2000 ppm by volume, preferably not exceeding 30 K. _: - \

Above all, this temperature control, compared with all previously known methods, despite the

> Permissible large temperature gradients, a significantly better selectivity and a considerably higher stability ^! ,.

of the hydrler process.

Every change in the reactor inlet temperature takes place in small steps, with a total of 20 K / h and ßi

preferably 10 K / h are not exceeded, regardless of whether it is an increase or; >!

Lowering the temperature. According to the invention, the coolant temperature is also only in small |;

Steps changed, in which case the change does not exceed a total of 10 K / h and preferably 5 K / h

increases. As the operating period of the catalytic converter increases, the rate of temperature changes ||

increase.

The temperature increase must be particularly careful and slow when starting up fresh catalytic converters or in the range around and above the light-off temperature of the catalyst used when the vehicle is started up done by reactors. It is also essential that changes in temperatures or the Carbon monoxide concentration with careful analytical control of the hydrogenation process be performed.

A reactor filled with fresh catalyst is started up according to the invention with a Carbon monoxide concentration in the crude fraction, which is between process-related and a maximum of 5000 ppm by volume,

^{: u} preferably between process-related and 3500 ppm by volume Hegt. When a catalytic converter is restarted, a carbon monoxide content between the process-related concentration and a maximum of 3000 ppm by volume is preferably used. The carbon monoxide concentration that is favorable for a specific case depends above all on the dimensions 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 acetylene concentration in the crude fraction of CVmlnus, with low performance of the cooling system, with low load and / or with a catalyst with high activity, it is advantageous in the interests of a short start-up period, the process stability and the ethylene yield Carbon monoxide content in the raw fraction temporarily during the inhalation phase. To increase within the limits defined according to the invention.

The space velocity must not be below 3000 v / vh at start-up and is preferably 3500 to 4000 v / vh in this phase Load with minimal consumption of crude fraction.
When starting up, according to the invention, the Cj-minus crude fraction is at a temperature of 278 to

■ "303 K, preferably 288 to 303 K, introduced into the reactor. Then within 1 to 6 h, preferably ₍

within 2 h to 3, the Eintrlttstemperaiur in small steps up to 50 to 20 K under the Ansprlngtem- j

temperature increased. Expediently, the temperature increase is just below or at the starting temperature '*

door interrupted for 30 to 60 minutes until the temperature gradient in the reactor largely offset _t

shark. As soon as the acetylene is hydrogenated to a small extent, the reactor temperature increases in small steps

■ w is increased via the coolant pressure and under careful analytical control until the residual acetylene content is below _l

3 ppm. After the hydrogenation process has stabilized, the carbon monoxide concentration increases, if necessary gradually reduced in accordance with the ethylene balance down to the process-related value. As soon as ethylene hydrogenation is noticeable, the reactor temperature is set parallel to the carbon monoxide content,

lowered. £ i

· *> The method according to the invention has a number of essentials compared to the previously known methods Advantages that are extremely beneficial to the economy and the stability of the hydrler process as well as the affect the investment required for its realization. Due to the high self-selectivity of the used Catalysts and the process conditions tailored to them is one compared to the known processes, very high temperature difference in the catalyst bed or from the catalyst bed to the cooling medium

5 "dium is permissible without the reactor tending to run away or to hydrogenate ethylene. Quite the contrary the ethylene losses in the process according to the invention are well below those previously usual. This is the natural protein concentration required in the crude fraction is low, without any process-related deviations in the composition of the CVmlnus fraction and / or in the event of fluctuations in the process parameters significant ethylene losses occur or the acetylene is no longer sufficiently hydrogenated. With the so far

5 * known methods, however, as already explained, this temperature difference must be below 30 K, in in most cases even to 21 K and below, in order to keep the ethylene losses within limits and to achieve a sufficient stability of the process (see. US-PS 34 12 169). Usually must also an increased moderator concentration may still be required. Another major advantage of the invention Process resulting from the high permissible temperature levels within the catalyst tubes in

^wl radial and axial direction, the high Eigencnselektlvliät of the catalysts used and the optimally matched process conditions, consists in the fact that it can be carried out in appropriately dimensioned, conventional tubular reactors and possibly also in intercooled bed reactors with the same or better effectiveness with regard to the operating result than the process described in DE-OS 22 25 213 and DE-OS 23 15 025, the special reactors with high investment costs

<>> wall and requires a complicated process management with increased susceptibility to failure. It is also advantageous that the method according to the invention when commissioning in a short period of time, with minimal ethylene loss or Raw material salt and a minimal additional carbon monoxide requirement must be of the required purity (acetylene 3 ppm) corresponding selectively hydrogenated Cj-minus-Fraktlon ran.

Some expedient and advantageous embodiments of the method according to the invention are given in the shown in the following examples.

Example I.

7.2 l of catalyst are installed in an experimental reactor. The reactor is part of an experimental plant, Consists of a pre-heater, reactor, cooling system and the corresponding mechanical and control equipment including the devices for the release of measured values. The tubular reactor is surrounded by a cooling jacket and has a clear width of 51 mm (outside diameter 57 mm, wall thickness 2.9 mm). The catalyst fill level is 3500 mm. The preheater is operated with low steam pressure. The cooling system consists of the cooling jacket of the reactor, a water cooler and a storage vessel for the cooling liquid. As a cooling medium boiling methanol is used. The required d-mlnus fraction is taken directly from a technical Plant for ethylene production taken over. Increased carbon monoxide concentrations can be caused by a additional carbon monoxide flushing at the entrance of the test facility can be set in a targeted manner. The reactor inlet temperature is via the preheater and the coolant temperature via the methanol pressure in the The cooling system is regulated by the amount of cooling water in the methanol condenser. The analyzes are made using usual gas chromatographic methods.

The C ₂ -mlnus Fraktlon used had the following average composition in% by mass:

Acetylene 0.75%

Ethylene 50.0%

Ethane 13.5%

Hydrogen 1.65%

Methane 34.8%

Carbon monoxide 1000 to 1800 ppm (V _o |.)

The catalyst is characterized by the following data:

Bulky weight burst pressure composition

0.90 kg / l 17.3 +4.0 MPa Pd 0.034 mass% CuO 0.020 mass% Ix ₂ C)., 0.028 mass% Carrier material rest alpha alumina 0.37 cmVg 0.0 cm-Vg 0.04 cm Vg 0.33 cm Vg 8 Λ m - '/ u

Structure of the support total pore volume

r <10 nm 10 <r <50 nm

r> 50 nm

specific surface

_t catalyst form tablets with a diameter of

j 4.56 ± 0.15 mm and a height of

* 4.6 ± 0.2mm ^

Palladium distribution approx. 0.8 mm thick peripheral layer

Before start-up, the reactor filled with catalyst was increased with nitrogen inert and in the C ₂ - <* minus crude fraction by feeding in additional carbon monoxide, the carbon monoxide concentration to 3000 ppm. _{The C 2} -minus fraction was then passed into the reactor at an inlet temperature of 303 K and a pressure of 2.8 MPa. The flow rate through the catalyst tube was 0.45 m / s and the loading was 3500 v / vh. The inlet temperature was increased in small steps to 333 K within 2 hours. At this temperature, the hydrogenation reaction began, as indicated by the increasing coolant pressure and the results of the analysis. Under analytical control, the inlet temperature was increased in small steps to 343 K and the coolant pressure to 0.02 to 0.025 MPa. Under these conditions the acetylene was already broken down to 2 ppm. There were no ethylene losses. After being stable

Having set operating conditions, the carbon monoxide concentration was gradually reduced to the process-affected value of 1600 to 1800 ppm. Thereby, as soon as the analyzes were carried out, minor ethylene losses
revealed, the reactor temperature was also lowered in parallel.

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

The process conditions were then varied within the following limits.

pressure Coolant 2.8 to 3.0 MPa C \ H., - balance sheet, related temperature pressure 318 to 393 K to C ₃ H _{4 used} Coolant pressure MP; i 0.1 to 0.46 MPa ±% load 2 2200 to 7000 v / vh 5 Table 1 0.02 + 1.15 temperature 0.025 load CO- + 0.98 Reassignment 0.025 Kun / .cnlralinn + 1.27 K 0.025 v / vh Ppm by volume + 0.70 1 0.40 3 4th ± 0.0 343 0.03 3500 3000 + 1.41 343 0.08 3500 2500 + 0.82 343 0.075 3500 2000 + 0.71 343 0.125 3500 1700 + 0.29 343 0.09 3500 1700 + 0.66 345 0.09 4400 1700 + 1.34 355 0.092 5800 2000 + 1.28 355 0.23 5800 1700 + 1.06 361 0.395 7000 1700 + 1.63 333 5800 1700 323 5800 1700 318 5800 1800 318 5800 1800 318 5800 1800

By systematically changing the reactor temperature with the aid of the coolant pressure, inter alia at constant, process-related carbon monoxide concentration, the process stability and the inclination of the catalyst for "runaway" (i.e., for hydration), tested. Characteristic values are summarized in Table 1. After an operating time of 142 hours it was switched off and again under essentially analogous conditions approached as described above. The carbon monoxide concentration in the crude fraction was 2050 ppm. Already after 4.5 hours. stable operating conditions were achieved. The residual acetylene content was at 1 ppm. Based on the ethylene used, ethylene yields between 0.93 and 1.496 were achieved.

Example 2

7.2 l of the catalyst according to Example 1 were installed in the test system described there. 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. For testing of the activity-time behavior of the catalytic converter, the conditions were due to the relatively high operating temperature consciously tightened. The process-related carbon monoxide concentration fluctuated between 1000 and 1300 ppm by volume. The stability of the hydrogenation process and the run-through behavior of the catalyst were improved several times different operating times as in example 1 tested. Furthermore, in the course of the experiment, the Reactor shut down and started up six times as planned. The start-up was carried out according to Example 1 with loads of 220 to 7000 v / vh and carbon monoxide concentration from 1000 to 2500 ppm by volume. Characteristic results are summarized in Table 2. The residual acetylene content was in all cases <2 ppm. After an effective operating time of 774 hours, the test was aborted without one hour after the 100th operating hour Decrease in activity was seen.

Table 3

lalicllc ? Operational time

in h

lcmperalur Küliliniilcl- exposure Cl ι-Kim-C.illj-Biianz, related

Reaklorcingang pressure / cniralion aul 'inserted CjII ₄ K Ml'a v / vh vol.ppm +%

103 368 138 367 190 368 269 368 404 386 412 366 570 371 613 358 647 358 708 376 729 368 753 373 770 379

0.16 5800 2300 + 1.4 0.335 58W) 2 (KHl ± 0 0.115 5800 HHH) + 1.02 0.19 5800 2000 + 1.14 0.22 5800 2500 + 0.65 0.35 5800 i200 -0.55 0.15 7000 1100 + 1.24 0.085 2900 1200 + 0.86 0.4 2900 1000 - 1.79 0.4 2200 1000 -3.18 0.15 5800 1000 + 0.96 0.175 7000 1000 + 0.63 0.23 5800 250 (1 0.08

Catalyst for Example 3 Example 4 Example 5

Bulk weight in kg / l 0.84 0.86 1.05 Burst pressure in MPa 38.2 ± 8.0 39.1 ± 8.5 18.3 ± 10.5 Composition in mass% Pd 0.032 0.025 0.035 CuO 0.018 0.017 - Fe ₂ O ₃ 0.044 0.06 0.1 Carrier material rest rest rest X-ray structure of the carrier material alpha-AljO ₃ alpha-AhO.? alpha-AhO.i with shares of theta and kappa subscription Pore volume in cnWg total 0.44 0.52 0.35 Radii <10 nm 0.0 0.03 0.07 Radii 10 to 50 nm 0.13 0.09 0.15 Radii> 50 nm 0.33 0.40 0.13

specific surface in m ² / g

distribution

of the active components

in the Triigerformlingcn

12.0

1.0

32

peripheral, Hindringtiel'e approx. 0.6 mm

peripheral, Penetration depth approx. 0.8 mm

evenly all in one Lazy rl'orml ing

Catalyst shape 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 test facility described in example 1 used for the selective hydrogenation of a technical Cj-mlnus-Fraktlon. The carbon mono-

28 19 791 Coolant load
pressure v / vh CO- CjHrBalance, related
Concentration on the C2H4 used Coolant
pressure el-load ■ '1 Kiililmi
pressure IcI exposure ', Vi Ci) - (Mli-Hil; in /, related
Concentration; iul inserted (ΛΙΙ4 5 oxide concentration between 1730 and 6300 ppm by volume, the loads between 2800 and 7000 v / vh, the reac
door inlet temperature between 340 and 377 K and the coolant pressure between 0.03 and 0.255 MPa.
The reactor pressure varied between 2.68 and 2.83 MPa.
The conduct of the experiment corresponded to that described in Example 1. The characteristic results are In
Table 4 summarized. The residual acetylene content was 2 ppm in all cases. MPa 5800 Vol.ppm ±% Ml'a v / vh CO- CiIl ₄ -BiIaIiZ, related to If
Concentration of CjH _{4 used} Ml'a v / vh Vol.ppm: *: % Table 4 0.055 5800 6300 + 0.08 0.17 5X00 Ppm by volume ±% P 0.035 3500 IWK) + 0.62 10 temperature
Reactor entrance 0.050 5800 3600 +1.22 0.16 5800 1900 + 1.24 I. 0.0X0 5X00 IX (H) + 0.94 K 0.053 7000 2500 +0.61 0.15 5800 1700 +1.5 || 359 0.085 4400 2500 -2.02 0.13 4400 1500 + 0.83 || 15th 349 0.094 2900 2400 -2.55 0.12 2900 2100 +1.19 H. 345 0.095 5800 5000 +1.05 0.155 7000 2100 +1.19 || 356 0.25 2600 -5.46 0.35 5800 1500 +1.32 § 353 ι
Example 4 1
Si 1400 -0.24 J,: j
ti * " 353 The catalyst characterized in Table 3, Column 2, was used in the test procedure described in Example 1
used for the selective hydrogenation of a technical Cj-mlnus-Fraktlon. The feed mixture contained |
1200 to 2500 ppm by volume carbon monoxide. The other process parameters were within the limits given in Example 3.
led boundaries varied. The reactor was started up as in Example 2. The characteristic. Jf
Test results are summarized in Table 5, the residual acetylene concentration was in all cases ^: |
at 2 ppm. f i
Example 5 § 368 Table 5 The catalyst characterized in table 3, column 3, was elnge in the experimental reactor according to example 1
builds. The start-up was carried out as in Example 1, but with a carbon monoxide concentration of 1600 vol. ':'
ppm. The further implementation of the experiment corresponded to Examples 3 and 4. The results summarized in Table 6 ;; {
Nits are characteristic of this attempt. The acetylene was broken down to 3 ppm in each case. The f \
Hydrogenation reaction starts at 360 K. _; ; 25th temperature
Reactor entrance Table 6 30th K temperature
Reaklorcingjng 363 K 363 345 363 ■ (41) M- 363 360 366 367 ■ • ι ι Ν>

continuation

temperature
Reactor entrance

Coolant load pressure

Ml'a

v / vh

Konzen'.ralinn

Vol.ppm

('.1I ₄ -BiIaH /. Based on CiH ₄

358 0.095 58 (H) 12 (H) 4 0.78 359 0.15 5100 1200 0.52 358 0.25 5100 1250 - 1.5 360 0.295 5800 1300 -4.36 example 6th Comparative example

For comparison with the results obtained in Examples 1 to 5 according to the invention, In the in example ί described experimental plant 7.2 l of an industrially manufactured and selective hydrogenation of d-minus-Fraktlon technically proven catalyst installed and according to the in Examples 1 to 5 applied principle and essentially tested under analogous conditions. The comparative catalyst is characterized by the following data

Bulk weight Structure of the carrier 0.75 kg / 1 Burst pressure 35.6 ± 29.0 Ml'a Composition I'd Pore volume, total 0.034 mass- '^1;. CuO for r <10 nm 0.01 Fc ₂ O, for 10 <r <50 nm 0.54 NOK lur r> 50 nm <0.015 specific surface Mixture of alpha- and theta- Catalyst shape Alumina 0.60 cnvVg 0.25 cmVg 0.25 cm Vg 0.10 cnvVg 82 ni-Vg Tablets with a diameter of 6.0 ± 0.8 mm and a height of 3.2 ± 1.1 mm

When commissioning, the crude fraction with a carbon monoxide content of 3800 ppm and a Temperature of 298 K set on the reactor. The exposure was 5800 v / vh. The inlet temperature was increased to 333 K in small steps within 3 hours and held for less than 1 hour until the Reactor outlet temperature had adjusted worldwide as far as possible. Then the temperature increased at a rate from 6 K / h weller increased. The hydration reaction started at 345 K. The required acetylene degradation to 3 The ppm was approx. 7.5 hours after the reactor had been charged with the Cj-minus fraction at an inlet temperature of 353 K and a coolant pressure of 0.08 MPa. The reactor pressure fluctuated between 2.6 and 2.8 MPa. The other parameters were varied within the limits given in Example 1. It became the Characteristic values summarized in Table 7 were obtained.

Table 7 Coolant
pressure
Ml'a liclaslung
v / vh CO-
Kun / entratum
Ppm by volume C-Ili-Biliiii /. be / .ogcn
with inserted C _- -Il ₄ temperature
Rcaktorcingang
K 0.08
0.08 5800
5800 1,800
2220 + 0.20
- 0.32 355
353

continuation

Temperature reactor inlet

Coolant load pressure

MPa

v / vh

CO-

Concentration

Vol-npm

based on C ₂ H _{4 used}

348 0.08 2900 1600 - 0.75 355 0.15 5800 1500 - 3.66 355 0.20 5800 1500 -41.0 (more complete Consumption of H2) 347 0.12 2800 1500 - 4.29 378 0.07 2800 1600 - 1.58 357 0.08 7000 1500 - 1.5

The start-up of the catalyst with carbon monoxide concentrations below 2000 ppm was not possible, because he tends to run away. In addition, the achievable process stability was compared with the examples 1 to 5, considerably less. Even a relatively small increase in the reactor temperature (especially via the coolant pressure) or a reduction in the carbon monoxide concentration led to rapidly increasing ethylene losses and finally even going through the reactor. This becomes particularly evident when comparing them the results summarized in Table 8 with regard to process lability and runaway behavior of the catalysts.

Table 8

Example temperature coolant load CO- C ₂ Il ₄ -BiIaHz, related

Reactor inlet pressure concentration of the C ₂ H _{4 used}

K Ml'a v / vh vol.ppm ±%

I. 343 318 2 366 358 376 3 368 4th 367 5 360 6th 355 355

0.40 1500 1700 0.39 5800 1800 0.35 5800 1200 0.40 2900 1000 0.40 2200 1000 0.25 5800 2600 0.35 5800 1400 0.29 5800 1300 0.15 5800 1500 0.20 5800 1500

± 0.0 + 1.63

- 0.55

- 1.79

- 3.19

- 5.46

- 0.24

- 4.36

- 3.66

-41.0 (total hydrogenation)

summary

Process for the selective hydrogenation of C ₂ -mlnus-Fraktlonen. The invention relates to a process for the selective hydrogenation of acetylene in a gaseous C ₂ -nus fraction from gasoline pyrolysis on a special palladium-supported catalyst. The goals are to reduce ethylene losses, expand the stability range and improve the commissioning process.

The invention consists in the fact that a macroporous catalyst with a specific surface area of a maximum of 50 m ^! / g and a palladium concentration of 0.005 to 0.1 mass-'V>, optionally in combination or compounds of the Elsen and / or 1st subgroup, In a tubular reactor is used that the flow rate through the tubes / wipe 0.3 to 3.0 m / s, the maximum temperature difference between the catalyst bed and the cooling medium does not exceed 60 K and the temperature difference between the reactor outlet and the reactor is kept between -15 and +60 K.

Claims (11)

Patent claims: 1. Process for the selective hydrogenation of Cj-minus-Fraktlonen, which in addition to ethylene, ethane and methane still 0.3 to 2.0% by weight acetylene, > at least 1.0 wt .-. i hydrogen and Contains 1000 to 2000 ppm by volume of carbon monoxide, at a pressure of 0.10 to 3.92 MPa, a space velocity of 2500 to 10000 v / vh and a reactor temperature of 35 to 150 ° C, characterized in that one ίο a) an essentially macroporous Palladium carrier analyzer uses which ai) has a specific surface area of a maximum of 50 mVg, where a;) at least 33% of the pore volume is accounted for by pores with radii _{above 50 nm, and the a 3} ) a pslladiam concentrate of 0.005 to 0.1% by weight, and a <) optionally with copper, nickel, silver and / or Elsen or ¹ .-. is promoted with compounds of these elements, b) the hydrogenation carried out in a tubular reactor '-'UeI c) the ratio of the inner diameter of the ei -aH ^ tiv. reactor tubes for the diameter or the height of the shaped catalyst pieces between 8 and 25: 1 iy? d) maintains a flow rate of the C ₂ minus fraction through the reactor roll filled with the catalyst between 0.3 and 3.0 m / s, - »ei) the temperature at the reactor outlet does not keep more than 60 K above or 15 K below the temperature of the reactor inlet and
e ₂ ) maintains a temperature difference between any point in the catalyst bed and the coolant of 0 to 60 K, f,) the commissioning or recommissioning of the reactor filled with catalyst with a 2 * Carbon ion oxide concentration in the C2 minus crude fraction between process-related content and 5000 ppm by volume and f ₂ ) with a space velocity of at least 3000 v / vh, g) the reactor inlet temperature during start-up is set to 278 to 303 K, preferably 288 to 303 K, which is then increased within 1 to 6 hours to just below or up to the light-off temperature w of the catalyst, the light-off temperature being understood as the temperature, at the Under the given process conditions, the acetylene begins to hydrate, and then the catalyst if necessary, inserting a holding tent of 30 to 60 minutes at a substantially constant internal temperature, which is up to 20 K below the start-up temperature of the catalytic converter, through gradual Increasing the coolant pressure sets the required acetylene degradation and h) Carries out temperature changes in the reactor at a rate of up to a maximum of 20 K / h. 2. The method according to claim 1, paragraph a), characterized in that a catalyst is used which α) 0.0005 to 0.25 wt .-% copper, nickel, silver and / or iron or their oxides, ■ "' P) contains on a carrier which / Ji) has a specific surface area of 1 to 25 m ² / g and in which ß ₂ ) at least 50% of the total pore volume are accounted for by pores with radii greater than 50 nm and at most 1096 for those with radii of less than 10 nm. ■ *> 3. The method according to claim 1, paragraph a) and claim 2, characterized in that there is a catalyst who uses x) has a specific surface area of 3 to 15, in particular 3 to 10 ni ² / g, and the! || ß) has no pores with radii below 10 nm, with at least 75% of the pore volume on pores with || "" Radii over 50 nm are omitted. ti '"· 4. The method according to claim 1, paragraph a), to 3, characterized in that a catalyst ξνί sets in, the ^ iJ ⁵ ^ ζ) 0.01 to 0.05 wt .-% palladium and! </! ß) as promoters 0.003 to 0.05 wt .-% nickel, copper and / or silver or their oxides and 0.03 to ifi 0.2% by weight Elsendll) - or Eisendl, IID-oxide contains. ti 5. The method according to claim 1, paragraph a) to claim 4, characterized in that a catalyst is used which contains the palladium in a maximum of 1.5 mm. Especially in a maximum 1.0 mm thick ■ <§ contains peripheral layer of the catalyst moldings. $ 6. The method according to claim 1, paragraph a) to claim 5, characterized in that there is a catalyst who uses ⁽¹ * x) 0.005 to 0.05% by weight palladium, /!) contains on a carrier, which consists essentially of ^ -aluminium oxide, the IU) has a specific surface area of 15 to 50 m '/ g and in which / i _; ) at least 33 ″, leaving pore volumes allotted to pores with radii greater than 50 nm. 7. The method according to claim 1, paragraph c) to claim b. characterized in that the hydrogenation is carried out at a ratio of the inner diameter of the individual reactor tubes to the diameter or to the height of the catalyst shape of between 10 and 15: 1. 8. The method according to claim 1, paragraph d) to claim 7, characterized in that a flow rate of the C ₂ minus fraction through the reactor tubes filled with catalyst of 0.5 to 2.0 m / s is maintained. 9. The method according to claim 1, paragraph C ₂ ) to claim 8, characterized in that the temperature is maintained at any point in the catalyst up to a maximum of 45 K above the coolant temperature. 10. The method according to claim 1, paragraph ei) to claim 9, characterized in that the temperature does not hold more than 50 K above or 5 K below the temperature of the reactor inlet at the reactor outlet. 11. The method according to claim 1, paragraph fi), f ₂ ) and g), to claim 10, characterized in that one