WO2004058665A2

WO2004058665A2 - Method for the hydration of hydrocarbon compounds

Info

Publication number: WO2004058665A2
Application number: PCT/EP2003/014291
Authority: WO
Inventors: Thomas Hill; Harald Dialer; Ana Alba Perez; Peter Zehner; Jörg UNGER; Luis Martinez Thomas; Heinrich Laib
Original assignee: Basf Aktiengesellschaft
Priority date: 2002-12-20
Filing date: 2003-12-16
Publication date: 2004-07-15
Also published as: AU2003294860A1; AU2003294860A8; DE10259858A1; WO2004058665A3

Abstract

Disclosed is a method for hydrating hydrocarbon compounds selected among the group comprising alkynes, dienes, alkenynes, and polyenes (hydrocarbons I). According to the inventive method, a gas stream containing hydrogen and a hydrocarbon I is directed through a hydration zone containing a hydration catalyst. The beginning of the hydration zone is located at a point whose geodetic height is lower than that of the end of the hydration zone.

Description

Process for the hydrogenation of hydrocarbon compounds

description

The invention relates to processes for the hydrogenation of hydrocarbon compounds, selected from the group consisting of alkynes, dienes, alkenins and polyenes (hydrocarbons I), by passing a gas stream comprising hydrogen and a hydrocarbon I through a hydrogenation zone containing a hydrogenation catalyst, the beginning of the hydrogenation zone is in a location with a lower geodetic height than the end of the hydrogenation zone.

In refineries and petrochemical plants, hydrocarbon flows are generated, stored and processed on a large scale. These hydrocarbon streams often contain highly unsaturated compounds, the presence of which is known to cause problems, particularly during processing and / or storage, or which are not the desired product of value and which are therefore undesirable components of the corresponding hydrocarbon streams. These highly unsaturated compounds are alkynes, dienes, alkenins and / or polyenes, which are generally more highly unsaturated homologues of the product of value contained in the hydrocarbon stream in question, which is usually a monounsaturated olefin or 1,3-butadiene. In this text, homologs or homologous compounds are compounds which do not differ in the number of carbon atoms but only in the degree of unsaturation. For example, the secondary component ethyne (trivial name "acetylene") is undesirable in C ₂ streams of steam crackers and ethene (common name ethylene ") is the homologous product of value, in C ₃ streams the secondary components are propyne and propadiene (common name" methylacetylene "and "Allen", respectively) undesirable and propene (common name "propylene") is the homologous product of value, and in C ₄ streams the secondary components are 1-butyne, but-3-en-1-in (common name "vinyl acetylene") and 1 , 2-butadiene undesirable if 1, 3-butadiene is to be obtained as a homologous product of value and further processed, as well as the mentioned secondary components and 1,3-butadiene even in cases where 1-butene or 2-butene (in the and / or trans form) are the desired homologous value products. Analogous problems arise with hydrocarbon streams which originate from an FCC cracker or a reformer instead of a steam cracker.

Considerable demands are placed on processes for the depletion of alkynes, dienes, alkenins and / or polyenes in an olefin-containing carbon stream. For example, the acetylene contained in the C ₂ stream of a steam cracker disrupts the polymerization of ethylene, so that the acetylene content in the C ₂ stream, which is typically 0.3 to 1.5% by volume, is below 1% by volume. ppm must be reduced. From the C ₃ stream of a steam cracker, propyne and propadiene, which are typically contained in an amount of 2 to 3% by volume, usually have to have a residual content of at most at least 20 ppm by volume for chemical applications or at most 5 ppm by volume for polymer applications. For the C ₄ hydrocarbon stream of a steam cracker, the task with respect to C ₄ alkynes or C ₄ alkenines is similar to that for a C ₃ stream when 1,3-butadiene is to be extracted from the hydrocarbon stream as a valuable product, or flow in a hydrocarbon that is already freed from 1,3-butadiene, also with reference to its maximum residual 1,3-butadiene content for further processing. However, if 1- or 2-butene is the desired product of value, besides the alkynes, alkynenes and other di- and polyenes, 1,3-butadiene, which is typically present in an amount of 30 to 50 vol.% In the C ₄ stream is contained, down to a residual content of at most 10 vol. ppm.

Alkynes, dienes, alkenins and / or polyenes are usually removed from an olefin-containing carbon stream by selective catalytic hydrogenation. For this purpose, C ₂ streams are generally subjected to a gas phase hydrogenation, C ₅ and higher carbon hydrogen streams are generally subjected to a liquid phase hydrogenation, both gas phase and liquid phase processes are known for C ₃ and C streams. The catalysts used are usually copper catalysts or supported catalysts containing noble metals, with palladium catalysts or silver-doped palladium catalysts mostly being used today. Depending on the content of the compounds to be removed in the hydrocarbon stream to be treated and their maximum permissible concentration, the hydrogenation is carried out in only one or - more often - in several reactors connected in series. An overview of the processing of hydrocarbon streams from a steam cracker is given, for example, by A. Watson in The Oil and Gas Journal, Nov. 8, 1976, pp. 179-182.

The hydrogenation should be as selective as possible with regard to the homologous olefins present in the gas stream in addition to the highly unsaturated compounds, such as ethylene, propylene, 1, 3-butadiene or 1- or 2-butene, which are the product of value, in order to hydrogenate the olefins to lose no valuable product to alkanes. If possible, the corresponding homologous olefin should be formed by hydrogenation of the impurities. In practice, however, it is difficult to prevent, in particular under reaction conditions that lead to the desired high selectivity, that so-called green oil (a mixture of different oligomers and polymers), which forms on the catalyst, in the reactor and deposits in downstream parts of the system and thus shorten the catalyst life. This in turn leads to additional maintenance intervals, which are associated with parking times (cf. WO 98/40450, p. 6, lines 33ff). From DE-A-10149631 a method is known in which the green oil formation is suppressed by a combination of various measures, including the use of several hydrogenation zones and a defined hydrogen content.

Other suitable selective hydrogenation processes and catalysts and reactors therefor are described in EP-A-827944.

Regarding the gas phase processes, there is nowhere in the printed prior art whether the beginning of the hydrogenation zone is at a location with a lower geodetic height than the end of the hydrogenation zone or at a higher location, i.e. whether the flow through the reactors is from “top to bottom” (downflow method) or “bottom to top” (upflow method).

In the text, for the sake of brevity, the term "below" is often used instead of "a place with a lower geodetic height" and "above" instead of "a place with a higher geodetic height"

From practice, however, it is only known to operate the reactor in the downflow process.

The object of the present invention was therefore to provide a method for the most selective

To provide hydrogenation of the above impurities in which the catalyst life is extended.

Accordingly, the process described at the outset and an apparatus for carrying out this process were found.

We suspect that the technical effect has the following background:

According to the previously known processes, the gas stream to be hydrogenated is passed through the reaction zone from top to bottom. The green oil is formed where the main turnover takes place. This is the upper part of a fresh catalyst. The green oil formed there is distributed by gravity down over the entire hydrogenation catalyst and thus deactivates not only the parts of the catalyst where it is mainly formed, but also lower parts.

In the process according to the invention, the parts of the catalyst where the main conversion takes place are poisoned by the green oil formation. As already mentioned above, this is only the lower part of a fresh catalyst. Further to the end of the reaction zone, ie further catalyst parts on top are not poisoned by the green oil formed at the beginning, since the liquid green oil flows downwards (against the direction of gas flow) due to gravity. Since the parts of the catalyst at the beginning of the reaction zone poison faster than those at the end, the main reaction zone “migrates” from bottom to top over time. The service life of the reactor is only exhausted here when the main reaction zone has reached the end of the catalyst.

The hydrocarbons I used in the process according to the invention are, for example, C ₂ -alkynes, C-β-alkynes, C _4-8 alkadienes or mixtures of these compounds. Preferably is polyunsaturated C ₂ - ₆ - hydrocarbons, in particular C ₂ ^ hydrocarbons.

According to one embodiment of the invention, these polyunsaturated hydrocarbons are contained in C ₂ , C ₃ , C ₄ , C ₅ or C ₆ streams (hereinafter referred to as “hydrocarbon feed”), preferably in streams from a steam cracker or As described above, these streams generally contain more or less large amounts of the corresponding polyunsaturated C ₂ to C ₆ hydrocarbons.

The hydrocarbon feed which is treated by the process according to the invention is preferably

a) a gas stream (C2 stream) containing acetylene and other C2 hydrocarbon compounds,

b) a gas stream (C3 stream) containing propyne and propadiene and other C3 hydrocarbon compounds, or

c) a gas stream (C4 stream) containing a C4 hydrocarbon compound selected from the group consisting of butyne, but-3-en-1-yne, 1, 2-butadiene, 1, 3-butadiene and other C4 hydrocarbon compounds.

In general, in addition to hydrogen and the hydrocarbons I, the gas stream essentially only contains olefins with only a single double bond, preferably those having 2 to 6 carbon atoms.

The proportion of hydrogen in the feed stream is usually chosen so that the ratio of hydrogen to hydrocarbons is 1 1: 1 to 10: 1. The hydrogenation zone is generally an adiabatically or isothermally operated reactor.

In adiabatic operation, fixed bed reactors or reactors with fixedly mounted catalysts are usually used. The length to diameter ratio of the catalyst zone is typically 0.01 to 50, preferably 0.5 to 5.

All known reactors which are suitable for gas-phase reactions with cooled stationary catalyst beds can be used in isothermal operation. Suitable are e.g. Tube bundle reactors, in which the catalyst is located inside the tubes around which the heat transfer medium flows, and reactors in which, conversely, the heat transfer medium flows inside the tubes and the catalyst is located outside the tubes. For example, such reactors are known from DE-A 2848 014 and 3 007202.

The reactors in which the hydrogenation zone is located are usually equipped with the following devices:

a gas inlet for the hydrocarbon feed and the hydrogen, a hydrogenation catalyst, a supporting grate for the hydrogenation catalyst and a gas outlet for the converted gas stream.

The gas outlet is arranged above the catalytic converter and the gas inlet below the catalytic converter.

The reactors may also have an outlet for green oil. Most of the time, however, the green oil is discharged through the gas outlet.

The reactors preferably additionally have the following devices:

in front of the gas inlet (as seen in the direction of flow) a mixing device for hydrogen and the hydrocarbon feed (eg a static mixer or a tube of suitable length) a gas distributor for distributing the gas flow used over the cross section of the reactor. The gas distributor is connected to the gas inlet and is located under the supporting grid of inert balls above and below the catalyst bed a holding grid above the inert balls, which are provided above the catalyst. The holding grid has a mesh size which is suitable for preventing catalyst particles from being whirled up. a green oil separator in the gas outlet, since it cannot always be avoided that a small proportion of the green oil is carried upwards by the gas flow.

The reactors used are usually essentially vertical.

Suitable catalysts are all customary catalysts which are able, as desired, to convert the hydrocarbons I to the corresponding olefins with only a single double bond or alkanes.

Known highly selective catalysts for the hydrogenation of alkynes, dienes, alkenins or polyenes in hydrocarbon streams containing olefins, which can also be used in the process according to the invention, typically contain a metal from group 10 of the Periodic Table of the Elements (nickel, palladium, platinum) and optionally also a metal from group 11 of the periodic table of the elements (copper, silver, gold) on a catalyst support. Palladium catalysts or silver-doped palladium catalysts on a particulate (particulate) oxidic support, often aluminum oxide, are often used. Such catalysts and their preparation are well known, see for example EP-A-992 284 mentioned at the outset and the documents cited therein, to which express reference is hereby made.

In general, a catalyst is used in at least one reaction zone which contains a metal from Group 10 of the Periodic Table of the Elements on a catalyst support. Optionally, this catalyst also contains an element from Group 11 of the Periodic Table of the Elements. The catalyst preferably contains palladium as metal of the 10th group of the periodic table of the elements and silver as metal of the 11th group of the periodic table of the elements. In a likewise preferred manner, the catalyst support is an oxidic catalyst support, for example aluminum oxide.

In a particularly preferred manner, a catalyst is used in the process according to the invention which comprises a metal from group 10 of the periodic table of the elements (nickel, palladium, platinum) and optionally also a metal from group 11 (copper, silver, gold) from the periodic table of the elements a structured catalyst support or monolith composed of wire mesh, knitted fabric, knitted fabric, felt or foils or sheets, which are optionally also perforated. The catalyst preferably contains palladium and optionally also silver. Such catalysts and their preparation are also well known, see for example the single US-A-5,866,734, EP-A-827,944 and EP-A-965,384 and the publications cited therein, to which express reference is hereby made.

In the processes according to the invention, a hydrogenation zone described above is preferably connected to other hydrogenation zones in such a way that further hydrogenation zones are connected upstream or downstream of it. This also includes an embodiment in which both one or more hydrogenation zones are connected upstream and downstream.

The upstream or downstream hydrogenation zones can either be according to the process of the invention, i.e. operated according to the upflow process or according to the prior art process, i.e. according to the downflow process.

The way in which the interconnection is carried out is generally known. A particularly preferred variant is described in DE-A-101 49631. According to a particularly preferred variant of this invention, a plurality of reaction zones are operated and interconnected in the manner described there, although, in contrast to the methods described there, at least one reaction zone, preferably all, are operated by the upflow method.

A partial stream of the product of a reaction zone can also be removed from the product gas stream and fed back to the gas stream to be hydrogenated in front of this reaction zone (in principle, it is also possible to feed it in front of another reaction zone). This so-called "cycle gas procedure" is a measure frequently used in such hydrogenations and is used in particular to set a sufficient conversion in a specific reaction zone, the cycle gas can also be cooled before being recycled, so that the desired conversion is achieved without the product becomes undesirably hot due to the heat of reaction released. Typical reflux conditions (recirculated partial stream to partial stream introduced for the first time in the reaction zone in question) are in the range from 0 to 30.

The reaction conditions are chosen as usual. For the selective hydrogenation of acetylene in C ₂ streams, the space velocity of the gaseous C ₂ stream is usually from 500 m ³ / m ^{3 *} h, based on the catalyst volume, to 10,000 m ³ / m ³ * h at a temperature of 0 ° C to 250 ° C and a pressure of 0.01 bar to 50 bar (each overpressure, barü, English: "gauge", barg) set and per mole of acetylene in the C ₂ stream total (ie, across all reaction zones) 1 to For the selective hydrogenation of propyne and propadiene in C ₃ streams, a space velocity of the gaseous C ₃ stream of 500 m ³ / m ^{3 *} h, based on the catalyst volume, up to 10000 m ³ / m ³ * is usually used. h at one temperature from 0 ° C to 250 ° C and a pressure of 1 bar to 50 bar and a total of 1 to 3 moles of hydrogen are added per mole of propyne and propadiene in the C ₃ stream. For the selective hydrogenation of alkynes, dienes, alkenins and / or polyenes in C ₄ streams, a space velocity of the gaseous C ₄ stream of 200 m ³ / m ^{3 *} h, based on the catalyst volume, is usually up to 10,000 m ³ / m ³ * h at a temperature of 0 ° C to 300 ° C and a pressure of 1 bar to 30 bar and per mole of carbon-carbon multiple bond to be hydrogenated in the alkynes, dienes, alkenins and / or polyenes 1 to to be removed 10 moles of hydrogen are added.

If several reaction zones are used, the hydrogen can be added completely before the first reaction zone or fed between the individual reaction zones, in each case in portions which are dimensioned in such a way that in the subsequent reaction zone the desired degree of conversion of the alkynes, dienes, to be hydrogenated in this stage , Alkenins and / or polyenes is achieved, but the undesired overhydrogenation of valuable products to alkanes does not occur or at least occurs only to a tolerably small extent.

The required total conversion of alkynes, dienes, alkenins and / or polyenes is predetermined by the tolerable residual amounts of these compounds in the selectively hydrogenated product stream, which in turn are determined by its further use and are typically in the range of a few ppm by volume. A total conversion of exactly 100% (i.e. a residual content of alkynes, dienes, alkenins and / or polyenes of exactly 0 vol.ppm) is usually not set, since this would result in an undesirably high loss of valuable product through hydrogenation to the corresponding alkane. The conversion can be controlled using the number of reaction zones or the chosen reflux ratio.

The other design of the plant for carrying out the process according to the invention, including the determination of the number of reaction zones used, the heat dissipation, any recirculation, and the selection of the temperatures, pressures, space velocities and other process parameters otherwise used in operation is carried out as is customary in such hydrogenation processes.

Claims

claims

1. Process for the hydrogenation of hydrocarbon compounds selected from the

Alkynes, dienes, alkenins and polyenes (hydrocarbons I) group by passing a gas stream containing hydrogen and a hydrocarbon I through a hydrogenation zone containing a hydrogenation catalyst, the beginning of the hydrogenation zone being at a location with a lower geodetic height than the end of the hydrogenation.

2. The method according to claim 1, wherein the gas stream is an acetylene and other C2 hydrocarbon compounds containing gas stream (C2 stream).

3. The method of claim 1, wherein the gas stream is a gas stream containing propyne and propadiene and other C3 hydrocarbon compounds

(C3 current).

4. The method according to claim 1, wherein the gas stream is a C4-hydrocarbon compound selected from the group butyne, but-3-en-1-yne, 1,2-butadiene, 1,3-butadiene and other C4 hydrocarbon compounds containing gas stream (C4 stream).

5. The method of claim 1, wherein the gas stream is a hydrocarbon I and olefins with only one double bond containing gas stream.

6. The method according to claim 1, wherein the hydrogenation zone one or one or more further hydrogenation zones for hydrogenating compounds I are connected upstream or downstream.

7. The method of claim 1, wherein the hydrogenation catalyst is a

Carrier catalyst is in which wire mesh, knitted fabric, knitted fabric, felt or foils or sheets, which are optionally perforated, form the support.

8. The method according to claim 7, wherein hydrogenation catalysts are used which contain a metal from group 10 or 11 of the periodic table of the elements on a catalyst support.

9. The method of claim 1, wherein the hydrogenation zone is in a substantially vertical reactor.

10. The method according to any one of the claims, wherein the hydrocarbons I are converted to olefins, green oil and optionally alkanes.

11. Device for the hydrogenation of hydrocarbons I comprising a hydrogenation zone with a hydrogenation catalyst, this zone having at least one gas inlet, one gas outlet and one outlet for green oil, the gas inlet being located at a location of lower geodetic height than the gas outlet.

12. The apparatus of claim 11, wherein the hydrogenation zone is designed as a reactor with a supported catalyst, in which wire mesh, knitted fabric, knitted fabric, felt or foils or sheets, which are optionally perforated, form the support.