WO2006114114A1

WO2006114114A1 - Method for the integrated hydrogenation and distillation of hydrocarbons

Info

Publication number: WO2006114114A1
Application number: PCT/EP2005/004466
Authority: WO
Inventors: Holger Schmigalle
Original assignee: Linde Aktiengesellschaft
Priority date: 2005-04-26
Filing date: 2005-04-26
Publication date: 2006-11-02

Abstract

Disclosed is a method for the integrated hydrogenation and distillation of hydrocarbons, in which a hydrogenation catalyst (5) is assigned to a distillation column (2). Said hydrogenation catalyst (5) can be accommodated in the distillation column (2), the hydrogenation step and the distillation step being carried out in a common component. Alternatively, the hydrogenation step can be carried out in a spatially separate hydrogenation reactor. The hydrogenation step and the distillation step are functionally disconnected from each other in both cases.

Description

description

Process for the integrated hydrogenation and distillation of hydrocarbons

The invention relates to a process for the integrated hydrogenation and distillation of hydrocarbons, wherein a distillation column is associated with a hydrogenation catalyst.

Hydrogenation and distillation are common process steps in the chemical and petrochemical industry. In particular, in the oil and gas processing these basic methods for fractionation and conversion of hydrocarbon streams are used. For example, in olefin plants, the separator contains numerous distillation columns and various hydrogenations. In the previous systems, these process steps are implemented in separate apparatus or assemblies. In this case, conventional distillation columns and hydrogenation reactors equipped with catalyst beds are used for the fractionation. However, this means a high

Investment cost requirement, requires a high energy consumption and allows only short running times.

An alternative to this standard is the so-called reactive distillation. In contrast to the conventional variant, in the case of reactive distillation, also called catalytic distillation, the catalyst beds are integrated in the distillation column. These catalyst beds work simultaneously as reactors and as separation stages of the distillation. 'Advantageous in this variant are the lower investment costs due to a smaller number of devices, lower energy costs through the use of heat of reaction for separation by distillation and extended runtimes of the reactor beds by continuous and clean rinsing. Moreover, this variant allows a reduced number of plates in the distillation column by additional theoretical plates due to the catalyst beds. In addition, distillation limits (azeotropes) can be overcome.

A decisive disadvantage, however, is that the reaction and distillation conditions are coupled in the distillation column. Provided Reserve beds are desired, these can only be realized with high costs. In addition, such a distillation column is difficult to calculate.

A process for catalytic distillation is described, for example, in WO 99/09118. In practice, however, such a method is so far only rarely used, in particular olefin plants are so far realized almost exclusively in the conventional construction with separate apparatus for distillation and hydrogenation.

The present invention has for its object to provide a method of the type mentioned above in such a way that the mentioned disadvantages of previous methods are avoided.

This object is achieved in that the process steps hydrogenation and distillation are functionally decoupled from each other.

The process steps hydrogenation and distillation are advantageously carried out in a common distillation column. In this case, one can speak of column-integrated hydrogenations, the hydrogenation reactors being laid in the distillation column as in the catalytic distillation. The main difference, however, is that the catalyst is decoupled from the separation process. Whereas in the catalytic distillation reaction and distillation proceed simultaneously via the catalyst, in the column-integrated hydrogenation distillation part and reaction part are connected in series by compartmentalization of the catalyst. For example, a distillation column may be provided in the upper part with a gas phase hydrogenation and in the lower part with a Flüssigphaseπhydrierung.

In the gas-phase hydrogenation, the liquid coming from above is conducted past the hydrogenation catalyst by suitable constructive measures. The gas stream coming from below is hydrogenated and passed on to the upper distillation part of the column.

In Flüssigphasenhydriemng the gas stream coming from below is passed by appropriate design measures on the Hydrierkatalyssator. Of the The liquid stream coming from the upper part of the column is hydrogenated with additionally supplied hydrogen and passed to the lower part of the column.

In principle, the use of gas-phase and liquid-phase hydrogenation in the upper or lower part of the distillation column is possible.

By serial arrangements of catalyst compartments can also be realized reserve beds. By constructive measures, in addition to the variation of liquid and gas phase hydrogenation, the current conduction can also be varied between countercurrent and direct current.

According to a development of the inventive concept, the hydrogenation can also be carried out in a hydrogenation reactor assigned to the distillation column but spatially outsourced. Distillation columns with outsourced hydrogenation catalyst operate on the principle of column-integrated hydrogenation. The only difference is that the hydrogenation reactor is taken out of the column jacket, but is still coupled via the inlet and outlet with the column system. Since such a distillation column with externalized hydrogenation catalyst, in particular outsourced catalyst bed, is technically equal to the column-integrated hydrogenation, the same applies to the reaction phase (liquid phase hydrogenation / gas phase hydrogenation) and flow direction (countercurrent / direct current) as for the column-integrated hydrogenation.

An advantage of the process variant with outsourced hydrogenation reactor over the column-integrated hydrogenation is the ability to build renewable regenerable reactors can. Another advantage is that it is possible to separate the hydrogenation conditions such as temperature and pressure from the distillation column conditions by means of additional equipment such as pumps and heat exchangers.

Conveniently, the hydrogenation catalyst is formed as a fixed bed, wherein the usual materials in Hydnervorgängen materials come into question as a catalyst material.

In principle, the process according to the invention is suitable for all possible hydrogenations of hydrocarbons, in particular C ₂ , C ₃ , C ₄ , C ₅ and C ₆ + hydrogenations, both as selective hydrogenation and as full hydrogenation. Likewise, all combination hydrogenations such as Cs, C ₃ C ₄ , C ₅ C ₆ +, C ₄ C ₅ , C ₄ -, etc., as selective or full hydrogenations.

As distillation columns in which the hydrogenations can be integrated, in the case of olefin plants, in principle all distillation columns are suitable, in particular demethanizing, deethanizing, depropanizing, debutanizing or depentanizing columns and C ₃ splinters etc. In this case, any separation sequences of these columns are possible. For example, the circuits may begin with a demethanizer, deethanizer, depropanizer, debutanizer or depentanizer column. In addition to the first column giving the name to the circuit, the subsequent columns can also be varied as desired and used as an integration column for the hydrogenation.

Column-integrated hydrogenations or columns with an outsourced catalyst bed can be used in all ethylene plants with gas feed, liquid feed and mixed gas-liquid feed. The composition of the feed streams to be hydrogenated may contain the components hydrogen, methane, C ₂ to C ₆ paraffins, C ₂ to C ₆ olefins and polyunsaturated components having this carbon number, aromatics, all hydrocarbons heavier than C ₆ and various trace components.

Column-integrated hydrogenations or columns with an outsourced catalyst bed can furthermore be used in the so-called front-end service, ie. H. be used in hydrogen-rich process gas, as well as in the so-called tail end service, so with additional addition of hydrogen.

In addition to an application in olefin plants, the invention can also be used in all conceivable processes in which distillation and hydrogenation slurries are required.

In the following, the invention will be explained in more detail with reference to embodiments shown schematically in the figures.

Show it Figure 1 is a flow diagram of a method for conventional hydrogenation and

distillation

Figure 2 is a column for catalytic distillation

FIG. 3 shows a comparison between catalytic distillation and column-integrated hydrogenation

FIG. 4 shows a distillation column with column-integrated hydrogenation

FIG. 5 shows a distillation column with liquid-phase hydrogenation

FIG. 6 shows a column with an outsourced catalyst bed

Figure 7 shows a column with outsourced catalyst bed with pressure decoupling

Figure 8 shows a column with paged catalyst bed in the return

The flow chart shown in FIG. 1 is a conventional version of conventional hydrogenation and distillation in ethylene plants. In this variant, the process steps separation of the components by means of distillation and hydrogenation are carried out in different apparatuses. In this case, the feed stream 1 containing the hydrocarbons is fed to a conventional distillation column 2. Top product 3 and bottom product 4 are fed separately from one another via various intermediate steps, not described in detail, to a hydrogenation reactor 5 and 6. The hydrogenation reactors 5 and 6 contain catalyst beds of a catalyst material which is usually used for the hydrogenation of hydrocarbons. About leads 7 and 8 of the hydrogen necessary for the hydrogenation is supplied. This state of the art reproducing variant has a high investment requirement and requires a high Engergieverbrauch. In addition, it allows only low maturity.

FIG. 2 shows a variant of the prior art relating to catalytic distillation. In contrast to the conventional variant according to FIG. 1, in the case of the catalytic distillation illustrated here, the catalyst beds 5 and 6 are in the Column 2 integrated. These beds work simultaneously as reactors and as separation stages of the distillation. The hydrocarbon-containing feed stream is fed via line 1 of the column 2. Via line 7 of the hydrogen necessary for the hydrogenation is supplied. The top product is withdrawn via line 3 and the bottom product via line 4 from the column. The decisive disadvantage of this variant is that the reaction and distillation conditions are coupled in the column.

FIG. 3 shows a comparison between the known catalytic distillation and the column-integrated hydrogenation according to the invention. On the left side of the figure, a schematic cross section through a conventional distillation column with catalytic distillation is shown, while on the right side of the figure, a cross section through a distillation column according to the invention with column-integrated hydrogenation is shown. In both distillation columns, the liquid 9 is passed from top to bottom through the distillation column, while the gaseous flow 10 is directed from bottom to top. In the case of the catalytic distillation packing are used for distillation, which also serve as a catalyst bed 5, 6. As a result, catalytic hydrogenation and distillation occur simultaneously. In contrast, the catalyst bed 6 is decoupled from the distillation in the column-integrated hydrogenation. This is achieved in that the upward gas stream 10 is passed via a bypass line 11, bypassing the catalyst bed 6 directly into the upper part of the distillation column 2. In contrast, the liquid flow 9 directed downwards is passed over the catalyst bed 6 for liquid-phase hydrogenation and is conducted into the lower part of the distillation column 2 via a line 12 which extracts the hydrogenated liquid phase below the catalyst bed 6.

The distillation column shown in Figure 4 with column-integrated hydrogenation is provided in the upper part with a gas phase hydrogenation and in the lower part with a liquid phase hydrogenation. In the gas-phase hydrogenation, the liquid coming from above is guided past the hydrogenation catalyst 6 by means of appropriate internals. The gas stream coming from below is passed over the hydrogenation catalyst 6 and passed on to the upper distillation part of the column. In the liquid phase hydrogenation, the gas stream coming from below is guided past the hydrogenation catalyst 5 by means of suitable internals. The one from the upper part of the Column incoming liquid stream is hydrogenated via line 7 additionally supplied hydrogen and passed to the lower part of the column. The column shown in FIG. 5 differs from that shown in FIG. 4 only in that liquid phase hydrogenations take place both in the upper part and in the lower part of the column 2. In each case, the liquid coming from above is guided past the hydrogenation catalysts 5 and 6 by means of suitable internals, while the gas stream coming from below, which is supplied with hydrogen via lines 7 and 8, is guided respectively via the hydrogenation catalysts 5 and 6.

FIG. 6 shows a column with an outsourced catalyst bed. In this embodiment, it is a pure liquid hydrogenation. In this case, the gas stream coming from below is conducted upwards for distillation in the column, while the liquid stream coming from above via line 13, 14 is withdrawn from the column 2 and passed to the hydrogenation via paged catalyst beds 5, 6. The hydrogenated streams are finally recycled via line 15, 16 back into the column 2.

Finally, FIG. 7 also shows a column with an outsourced catalyst bed with decoupling of pressure. This variant differs from that shown in FIG. 6 in that a pump 17, which makes it possible to set a pressure independent of the column 2 in the catalyst bed 5, is inserted in the line 14.

FIG. 8 shows a sub-variant of FIG. 7. This variant differs from that in FIG. 7 in that the hydrogenation reactor 5 is positioned directly in the return of the column 2. The pump 17 for the return is thus simultaneously the pump for the reactor inlet. By this variation, a pump can be saved in comparison to Figure 7.

Claims

claims

1. A process for the integrated hydrogenation and distillation of hydrocarbons, wherein a distillation column is associated with a hydrogenation catalyst, characterized in that the process steps hydrogenation and distillation are functionally decoupled from each other.

2. The method according to claim 1, characterized in that the process steps hydrogenation and distillation are carried out in a common distillation column.

3. The method according to claim 1 or 2, characterized in that the hydrogenation in one of the distillation column associated, but spatially outsourced hydrogenation reactor is performed.

4. The method according to any one of claims 1 to 3, characterized in that for carrying out a gas phase hydrogenation in the distillation column from above coming liquid is passed to the hydrogenation catalyst, wherein the gas stream coming from below for hydrogenation over the hydrogenation catalyst is conducted and to the upper part the distillation column is passed.

5. The method according to any one of claims 1 to 4, characterized in that for carrying out a liquid phase hydrogen in the distillation column from below gas stream is passed to the hydrogenation catalyst, while the coming from above liquid stream is fed to the hydrogenation via the hydrogenation catalyst and to the lower part the distillation column is passed.

6. The method according to claim 4 or 5, characterized in that gas phase hydrogenation and liquid phase hydrogenation are carried out in the same distillation column.

7. The method according to any one of claims 1 to 6, characterized in that the hydrogenation catalyst is formed as a fixed bed.

8. The method according to any one of claims 1 to 7, characterized in that the integrated hydrogenation and distillation of hydrocarbons is used in processes for olefin production.

9. The method according to claim 8, characterized in that the streams to be hydrogenated as components of hydrogen and / or methane and / or C ₂ to Ce olefins and / or polyunsaturated components having this carbon number and / or aromatics and / or all hydrocarbons heavier than C ₆ and / or trace components included.