WO2018202829A1

WO2018202829A1 - Integrated process for producing c2+ hydrocarbons and a process system for such a process

Info

Publication number: WO2018202829A1
Application number: PCT/EP2018/061455
Authority: WO
Inventors: Guhan Mathivanan; Krister Fagerstolt; Tuomas Ouni; Eberhard Dreher
Original assignee: Borealis Ag
Priority date: 2017-05-05
Filing date: 2018-05-04
Publication date: 2018-11-08

Abstract

The present invention relates to an integrated process for producing C2+ hydrocarbons, preferably C2+ saturated and unsaturated hydrocarbons, comprising a process for oxidative coupling of methane (OCM) which comprises the steps of - producing C2+ hydrocarbons from methane and at least one oxidizing agent, preferably oxygen, and from ethane in at least one OCM reactor comprising at least one OCM catalyst unit and at least one cracking unit; - transferring the OCM effluent from the at least one OCM reactor to at least one fractionation system for separating the C2+ hydrocarbons in one or more hydrocarbon product streams, wherein the fractionation system comprises at least one demethanizer unit (114) for separating methane from C2+ hydrocarbons, at least one C2 splitter unit (121) for separating ethane and ethene, and/or at least one deethanizer unit (118) for separating C2 hydrocarbons from C3+ hydrocarbons, and a propane dehydrogenation process which comprises the steps of - producing propene from propane in at least one dehydrogenation reactor (201); - transferring the dehydrogenation reactor effluent from the at least one dehydrogenation reactor to at least one fractionation system for separating propene from the reactor effluent, wherein the fractionation system comprises at least one deethanizer unit (204) for separating C2 hydrocarbons, from C3+ hydrocarbons, and at least one C3 splitter unit (205) for separating propane and propene, wherein the C3 hydrocarbon effluent from the at least one deethanizer unit (118) in the OCM process is fed into the at least one C3 splitter unit (205) in the propane dehydrogenation process and/or the C2+ hydrocarbon effluent from the at least one demethanizer unit (107) in the OCM process is fed into the at least one deethanizer unit (204) in the propane dehydrogenation process and the C2 hydrocarbon effluent from the at least one deethanizer unit (204) in the propane dehydrogenation process is fed to the at least one C2 splitter unit (121) in the OCM process.

Description

INTEGRATED PROCESS FOR PRODUCING C2+ HYDROCARBONS AND A

PROCESS SYSTEM FOR SUCH A PROCESS

The present invention relates to an integrated process for producing C₂₊ hydrocarbons and a process system for conducting the same.

Description

C₂₊ Hydrocarbons comprising two or more carbon atoms and including saturated C₂₊ hydrocarbons or alkanes (such as ethane, propane, butane, pentane etc.) and unsaturated C₂₊ hydrocarbons or alkenes (such as ethylene, propylene, butylene etc.) may be produced in different processes, such as by oxidative coupling of alkanes, in particular the oxidative coupling of methane (also known as OCM process). OCM process

The oxidative coupling of alkanes, in particular the oxidative coupling of methane, converts methane to valuable products as for example ethane and ethene. In the course of the oxidative coupling process methane is oxidized according to the following equation:

2 CH₄ + 0₂→ C₂H₄ + 2 H₂0. This reaction is exothermic and is typically conducted at high temperatures in the range between 750 °C to 950^. In the course of the reaction methane is activated on the catalytic surface forming methyl radicals, which subsequently react in the gas phase with each other forming higher, long chain hydrocarbons such as ethane or dehydrogenation products thereof such as ethene.

Suitable catalysts for OCM include various forms of iron oxide, manganese oxide, magnesium oxide, molybdenium oxide, cobalt oxide and others on various supports. Number of doping elements have also been proven to be useful in combination with the above catalysts. The methane feedstock for the OCM reactor can be provided from various sources such as natural gas or from a methanizer in which carbon dioxide and hydrogen are reacted to me same. Besides a catalyst unit for oxidative coupling of methane the OCM reactor may also comprise a cracking unit for generating unsaturated alkenes, in particular ethene, from ethane. Ethane is thermally dehydrogenated via the following reaction:

This reaction is endothermic (ΔΗ = -144 kJ/mol) and can utilize the exothermic reaction heat produced during methane conversion in the OCM catalyst unit.

The OCM process provides primarily ethene (or ethylene) that is an important chemical intermediate for the production of different plastics and compounds such as polyethylene plastics, polyvinylchloride, ethylene oxide, ethylbenzene, alcohols and other alkanes and alkenes.

Besides ethene a variety of other hydrocarbons such as hydrocarbons with saturated or unsaturated carbon-carbon bonds may also be obtained as side products. Saturated hydrocarbons can include alkanes such as ethane, propane, butane, pentane and hexane. Unsaturated hydrocarbons may include C₃₊ hydrocarbons, such as propene.

The C₂₊ hydrocarbons produced in the OCM process are separated from methane in a demethanizer unit and are typically fed in a subsequent step to a deethanizer unit for separating C₂ hydrocarbons, such as ethane and ethene, from C₃₊ hydrocarbons comprising three or more carbon atoms, such as propane and propene.

Propene (or propylene) and propane that are produced as side products in the OCM process can be sold as refinery grade propylene (RGP) which is normally less valued than polymer grade propylene (PGP).

In order to upgrade refinery grade propylene (RGP) to polymer grade propylene (PGP) propene and propane needs to be separated from each other. Such a separation is typically done in a so called C₃ splitter. A heat pump is sometimes installed in C₃ splitter to save energy. It is not always necessary, it is only installed to save operating expenses. C₃ splitter itself is a very big distillation tower and expensive as such. Alkane dehydrogenation process

Dehydrogenation of hydrocarbons or alkanes, in particular aliphatic hydrocarbons, to convert them into to their respective olefins is a well-known process. For example, the hydrocarbons propane, butane, isobutane, butenes and ethyl benzene are well known catalytically dehydrogenated to produce the respective propylene, butene, isobutene, butadiene and styrene. Dehydrogenation reactions are strongly endothermic and thus, an increase of the heat supply favours the olefin conversion.

In particular, dehydrogenation of paraffinic and other hydrocarbons such as propane dehydrogenation (reaction 1 ) or butane dehydrogenation (reaction 2) or i-butane dehydrogenation (reaction 3) are well known: C₃H₈ ^ C₃H₆ + H₂ (1 ) C₄H_W ^ C₄H₆ + 2H₂ (2) i - C₄H_W i - C₄H_S + H₂ (3)

Houdry CATOFIN^® and Oleflex™ are well known dehydrogenation processes where propene is produced from propane using a dehydrogenation catalyst.

The product mixture or effluent leaving the propane dehydrogenation reactor comprises besides the main product propene also hydrogen, ethane, ethene and methane.

In order to optimize the Capex intensive propane dehydrogenation process and OCM process, it would be beneficial to integrate or share process units of PDH process with OCM process.

It is thus an object of the present invention to provide an integrated process that allows the synthesis of C₂₊ hydrocarbons and is at the same time less cost intensive and more efficient.

This object is being solved by an integrated process for producing C₂₊ hydrocarbons and a process system for conducting such a process as defined in the claims. Accordingly, an integrated process for producing C₂₊ hydrocarbons, preferably C₂₊ saturated and unsaturated hydrocarbons (i.e. hydrocarbons having 2 and more carbon atoms), is provided, wherein the integrated process comprises a process for oxidative coupling of methane (OCM) which comprises the steps of

- producing C₂₊ hydrocarbons from methane and at least one oxidizing agent, preferably oxygen, and from ethane in at least one OCM reactor comprising at least one OCM catalyst unit and at least one cracking unit,

- transferring at least one OCM effluent from the at least one OCM reactor to at least one fractionation system for separating the C₂₊ hydrocarbons in one or more hydrocarbon product streams, wherein the fractionation system comprises - at least one demethanizer unit for separating methane from C₂₊ hydrocarbons, and

- at least one C₂ splitter unit for separating ethane and ethene, and/or

- at least one deethanizer unit for separating C₂ hydrocarbons from C₃₊ hydrocarbons, and a propane dehydrogenation process which comprises the steps of

- producing propene from propane in at least one dehydrogenation reactor, - transferring at least one dehydrogenation reactor effluent from the at least one dehydrogenation reactor to at least one fractionation system for separating propene from the reactor effluent, wherein the fractionation system comprises

- at least one deethanizer unit for separating C₂ hydrocarbons, such as ethane and ethene, from C₃₊ hydrocarbons,

- at least one C₃ splitter unit for separating propane and propene, and

- optionally at least one depropanizer for separating C₄₊ hydrocarbons. According to the invention the integrated process comprises the steps of

- feeding the C₃₊ hydrocarbon effluent from the at least one deethanizer unit in the OCM process into the at least one C₃ splitter unit in the propane dehydrogenation process and/or

- feeding the C2₊ hydrocarbon effluent from the at least one demethanizer unit in the OCM process into the at least one deethanizer unit in the propane dehydrogenation process, and

- feeding the C₂ hydrocarbon effluent from the at least one deethanizer unit in the propane dehydrogenation process to the at least one C₂ splitter unit in the OCM process. Specifically, a process is provided that allows the integration of an OCM process and a propane dehydrogenation process in such a manner that specific process units are now used for both process.

On the one hand a C₃ splitter typically used in a propane dehydrogenation process is now also used for products of the OCM process. In the present integrated process the C₃ splitter has now two different feeds one from the OCM process and one from the propane dehydrogenation depicted in the following scheme:

C₃ hydrocarbons as side

products from the OCM

process

Polymer grade

C₃ splitter propylene

PDH process

propane/propylene

In a preferred embodiment the C₃ hydrocarbon feed from the OCM process would be introduced into the C₃ splitter at least one tray above the tray where the C₃₊ hydrocarbon feed from the propane dehydrogenation process is introduced into the C₃ splitter. On the other hand, by feeding the C2₊ hydrocarbon effluent from the demethanizer unit in the OCM process to the deethanizer unit in a propane dehydrogenation process a deethanizer unit (and also a depropanizer unit) in the OCM process may be at least reduced or is even no longer required. This is depicted in the following scheme:

OCM reactor Demethanizer unit C₂₊ hydrocarbon

effluent (OCM process) effluent

Deethanizer unit Dehydrogenation (dehydrogenation process)

reactor effluent

C₂ hydrocarbon

effluent hydrocarbon effluent

C₂ Splitter C₃ Splitter

(OCM process) (dehydrogenation process)

By integrating these units of a dehydrogenation process with an OCM process additional investment cost of PDH/OCM process can be decreased.

In a first preferred embodiment the present integrated process comprises the following aspects:

- transferring the OCM effluent to at least one fractionation system for separating the C₂₊ hydrocarbons in one or more hydrocarbon product streams, wherein the fractionation system comprises

- at least one demethanizer unit for separating methane from C₂₊ hydrocarbons, - at least one deethanizer unit for separating C₂ hydrocarbons from C₃₊ hydrocarbons,

- at least one one depropanizer unit for separating C₃ hydrocarbons, such as propane and propene, from C₄₊ hydrocarbons, and

- producing propene from propane in at least one propane dehydrogenation reactor,

- transferring the dehydrogenation reactor effluent to at least one fractionation system for separating propene from the reactor effluent, wherein the fractionation system comprises

- at least one deethanizer unit for separating C₂ hydrocarbons, such as ethane and ethene, from C₃₊ hydrocarbons, - at least one C₃ splitter unit for separating propane and propene, and

- optionally at least one depropanizer for separating C_4+; and feeding the C₃ hydrocarbon effluent from the at least one deethanizer unit (and optionally depropanizer unit) in the OCM process into the at least one C₃ splitter unit in the propane dehydrogenation process In a second preferred embodiment the present integrated process comprises:

- transferring the OCM effluent to at least one fractionation system for separating the C₂₊ hydrocarbons in one or more hydrocarbon product streams, wherein the fractionation system comprises - at least one demethanizer unit for separating methane from C₂₊ hydrocarbons, and

- at least one C₂ splitter unit for separating ethane and ethene, - producing propene from propane in at least one propane dehydrogenation reactor,

- at least one deethanizer unit for separating C₂ hydrocarbons, such as ethane and ethene, from C₃₊ hydrocarbons, and

- feeding the C2+ hydrocarbon effluent from the at least one demethanizer unit in the OCM process into the at least one deethanizer unit in the propane dehydrogenation process, and

- feeding the C₂ hydrocarbon effluent from the at least one deethanizer unit in the propane dehydrogenation process to the at least one C₂ splitter unit in the OCM process. In another embodiment of the present integrated process the OCM reactor effluent is fed to at least one compression unit that is arranged downstream of the OCM reactor before entering the at least one fractionation system.

Typically, in an OCM process the effluent leaving the OCM reactor comprises at least one C₂₊ hydrocarbons (such as ethane, ethene but also higher hydrocarbons), carbon dioxide, carbon monoxide, hydrogen and methane. The OCM effluent is subsequently separated into i) one first stream comprising at least a part of the C₂₊ hydrocarbons and ii) a second stream comprising carbon monoxide (CO), carbon dioxide (C0₂), hydrogen (H₂) and methane (CH₄). The separation of the OCM effluent into stream i) and stream ii) is preferably done in a least one C0₂ removal unit that is arranged downstream of the OCM reactor and the compression unit.

The first stream i) leaving the C0₂ removal unit comprising ethane as C₂₊ compound is fed further into the fractionation system.

Here, in a further embodiment of the present process at least demethanizer unit as part of the fractionation system is arranged downstream of the C0₂ removal unit. The methane separated in the demethanizer unit is fed to at least one methanation unit and further recycled back into the OCM reactor. The second stream ii) leaving the C0₂ removal unit is fed into at least one methanation unit to generate a first OCM reactor feed comprising CH₄ from H₂ and C0₂ and/or CO. Besides the second stream a third stream iii) comprising CH₄ and H₂ from the demethanizer unit (De-C1 ) is fed into a methanation unit.

Hydrogen reacts with carbon monoxide and carbon dioxide in the methanation unit (as part of the OCM process) to methane in exothermic processes. The heat generated may be used as heat input to other process units or for preheating reactants such as methane and/or an oxidizing agent prior to an OCM reaction.

The methanation reaction can take place in one or more reactors in series. In an embodiment the methanation unit comprises a first reactor and the second reactor that can be operated as adiabatic reactors. The methanation reaction requires a suitable catalyst. For example, nickel-based catalysts can be used that may include nickel supported on alumina. A methanation catalyst can be tableted or extruded. The shapes of such catalysts can be for example cylindrical, spherical or ring structure. Methane synthesized in the at least one methanation unit is fed subsequently to at least one pre-heating unit before recycled back into the OCM reactor. Besides methane from the methanation unit further methane from natural gas may be used for the OCM reactor.

In a further variant of the present integrated process the C₂₊ hydrocarbon effluent leaving the demethanizer unit is fed into at least one deethanizer unit for separating C₂ hydrocarbons, such as ethane and ethene, from C₃₊ hydrocarbons.

It is further preferred, if the C₂ hydrocarbon effluent leaving the at least one deethanizer unit and that is fed to the at least one C₂ splitter comprises ethane, ethene and further methane. The ethane leaving the at least one C₂ splitter unit may be subsequently recycled back to the

OCM reactor, preferably to the cracking unit of the OCM reactor.

In the dehydrogenation process propane is reacted in an endothermic dehydrogenation reactor in the presence of a suitable catalyst such as chromium oxide or Pt-Sn based catalyst. A typical Chromium oxide dehydrogenation catalyst manufactured on an alumina support comprises from about 17wt% to about 22 wt% Cr₂0₃. These type of dehydrogenation catalyst are known for instance under the name Catofin® Standard catalyst (US 2008/0097134 A1 ). The product gas mixture or dehdyrogenation reactor effluent leaving the dehydrogenation reactor goes to at least one separating unit comprising at least one cold box unit and at least one pressure swing adsorption unit (psa unit) that are arranged downstream of the propane dehydrogenation reactor. The light gases including hydrogen are separated in the cold box unit or cold section unit. The hydrogen from the light gases is then further separated from the remaining light gases using a pressure swing adsorption unit.

The liquid products from the cold box are sent further to at least one de-ethaniser unit as part of a fractionation system where components lighter than propene (for example ethane and ethene) are removed at the top. Propene and the other heavier components are sent to the C₃ unit (a C₃ splitter tower) where propene is obtained at the top.

The bottom stream or effluent of the C₃ splitter unit is then fed to at least one depropaniser unit as part of the dehydrogenation process where the components heavier (C₄₊ hydrocarbons) then propane are removed at the bottom. The propane leaving the at least one de-propanizing unit is recycled back into the propane dehydrogenation reactor.

The used catalyst from the dehydrogenation step may be regenerated in a regeneration step .

The present integrated process is conducted in an integrated process system for conducting a process for producing C₂₊ hydrocarbons, wherein the process system comprises at least one OCM system comprising

- at least one OCM reactor comprising at least one OCM catalyst unit for generating C₂₊ hydrocarbons from methane and at least one cracking unit for generating C₂₊ hydrocarbons, preferably ethene, from ethane; - at least one fractionation system for separating the C₂₊ hydrocarbons in one or more hydrocarbon products streams, wherein the fractionation system comprises at least one demethanizer unit for separating methane from C₂₊ hydrocarbons, and at least one C₂ splitter unit for separating ethane and ethene, and/or

at least one deethanizer unit for separating C₂ hydrocarbons from C₃₊ hydrocarbons, and at least one propane dehydrogenation system comprising

- at least one propane dehydrogenation reactor for producing propene from propane,

- at least one fractionation system for separating propene from the reactor effluent, wherein the fractionation system comprises at least one deethanizer unit for separating C₂ hydrocarbons, such as ethane and ethene, from C₃₊ hydrocarbons, and at least one C₃ splitter unit for separating propane and propene, wherein the at least one depropanizer unit in the OCM system is in fluid connection to the at least one C₃ splitter unit in the propane dehydrogenation system for feeding the C₃₊ hydrocarbon effluent from the at least one deethanizer unit in the OCM system into the at least one C₃ splitter unit in the propane dehydrogenation system, and/or the at least one demethanizer unit in the OCM system is in fluid connection to the at least one deethanizer unit in the propane dehydrogenation system for feeding the C₂₊ hydrocarbon effluent from the demethanizer unit in the OCM system into the deethanizer unit in the propane dehydrogenation system and feeding the C₂ hydrocarbon effluent from the at least one deethanizer unit in the propane dehydrogenation system to the at least one C₂ splitter unit in the OCM system. In a first preferred embodiment the present integrated process system comprises the following aspects: at least one OCM system comprising - at least one OCM reactor comprising at least one OCM catalyst unit for generating C₂₊ hydrocarbons from methane and at least one cracking unit for generating C₂₊ hydrocarbons, preferably ethene, from ethane; - optionally at least one C0₂ removal unit for removing C0₂ from the OCM reactor effluent,

- at least one fractionation system for separating the C₂₊ hydrocarbons in one or more hydrocarbon products streams, wherein the fractionation system comprises at least one demethanizer unit for separating methane from C₂₊ hydrocarbons, at least one deethanizer unit for separating C₂ hydrocarbons from C₃₊ hydrocarbons, at least one depropanizer unit for separating C₃ hydrocarbons, such as propane and propene, from C₄₊ hydrocarbons, and at least one propane dehydrogenation system comprising

- at least one fractionation system for separating propene from the reactor effluent, wherein the fractionation system comprises at least one deethanizer unit for separating C₂ hydrocarbons, such as ethane and ethene, from C₃₊ hydrocarbons, and at least one C₃ splitter unit for separating propane and propene, wherein the at least one depropanizer unit in the OCM system is in fluid connection to the at least one C₃ splitter unit in the propane dehydrogenation system for feeding the C₃ hydrocarbon effluent from the at least one depropanizer unit in the OCM system into the at least one C₃ splitter unit in the propane dehydrogenation system,

In a second preferred embodiment the present integrated process system comprises: at least one OCM system comprising - at least one OCM reactor comprising at least one OCM catalyst unit for generating C₂₊ hydrocarbons from methane and at least one cracking unit for generating C₂₊ hydrocarbons, preferably ethene, from ethane; - at least one fractionation system for separating the C₂₊ hydrocarbons in one or more hydrocarbon products streams, wherein the fractionation system comprises at least one demethanizer unit for separating methane from C₂₊ hydrocarbons, at least one C₂ splitter unit for separating ethane and ethene, and at least one propane dehydrogenation system comprising - at least one propane dehydrogenation reactor for producing propene from propane,

- at least one fractionation system for separating propene from the reactor effluent, wherein the fractionation system comprises at least one deethanizer unit for separating C₂ hydrocarbons, such as ethane and ethene, from C₃₊ hydrocarbons, and at least one C₃ splitter unit for separating propane and propene, wherein the at least one demethanizer unit in the OCM system is in fluid connection to the at least one deethanizer unit in the propane dehydrogenation system for feeding the C₂₊ hydrocarbon effluent from the demethanizer unit in the OCM system into the deethanizer unit in the propane dehydrogenation system and feeding the C₂ hydrocarbon effluent from the at least one deethanizer unit in the propane dehydrogenation system to the at least one C₂ splitter unit in the OCM system.

In a variant of the integrated process system at least one at least one compression unit and at least C0₂ removal unit (as part of the OCM system) are arranged downstream of the OCM reactor and upstream of the at least one fractionation system. It is furthermore preferred that as part of the OCM system at least one methanation unit is arranged downstream of the at least one demethanizer unit. Downstream of the at least one demethanizer unit at least one deethanizer unit and at least one depropanizer unit are provide as further part of the OCM system described previously.

In a further embodiment of the present integrated system the dehydrogenation system comprises at least one separation unit arranged downstream of the propane dehydrogenation reactor. The separation unit in the dehydrogenation system comprises at least one cold box for separating light gases from the product mixture leaving the propane dehydrogenation reactor and at least one pressure swing unit (psa) for further separating hydrogen from the light gases leaving the psa unit. Cold box unit and psa unit are in thereby in fluid communication with each other.

In yet another embodiment of the present process system the at least one de-ethanizer unit is arranged downstream of the at least separating unit in the propane dehydrogenation system.

The functionalities of the process system units and further system units are described in detail above. The invention is further described in more detail by means of examples with reference to the figures. It shows:

Figure 1 A a scheme of a conventional stand-alone OCM process;

Figure 1 B a scheme of a conventional Oleflex stand-alone propane dehydrogenation process;

Figure 1 C a scheme of a conventional Catofin stand-alone propane dehydrogenation process;

Figure 2A a scheme of a first embodiment of the present process;

Figure 2B a scheme of a second embodiment of the present process; Figure 3A a scheme of a third embodiment of the present process; and

Figure 3B a scheme of a fourth embodiment of the present process; Example 1 :

Fig. 1 A shows a schematic overview of a conventional OCM process.

The OCM process system 100 comprises an OCM reactor unit 101 with an OCM catalytic unit and the post-bed cracking unit (PBC) for generating olefins (for example ethene) from alkanes (for example ethane and/or propane). OCM catalytic unit and PBC unit can be situated in separate reactors or can be integrated into the same reactor.

Methane (stream A 104) and oxygen (stream 103) as oxidizing agent are injected into the catalytic unit and ethane can be injected into the PBC unit. In the catalytic unit methane is converted to C₂₊ compounds and is subsequently directed to PBC unit in which one alkanes are converted to alkenes. The stream A13 leaving the OCM reactor unit 101 is directed to a TLE and Quench tower (not shown) and further to a compression unit 107.

In the quench tower the OCM effluent gases are quenched with a cooling medium and any process condensates are condensed and removed. The cooled OCM effluent is then set to the compression unit 107, which can comprise a single or multiple stages of compression. The compression unit 107 can also comprise coolers and separator vessels which wasted pressure of the OCM effluent stream and water from the OCM effluent stream.

The product stream leaving the compression unit 107 is further transported to a carbon dioxide removal unit 1 10 which can remove carbon dioxide from the OCM product stream. At least a portion of the carbon dioxide can be directed to a methanation unit 1 1 1 . The other portion of the carbon dioxide can be directed for other uses (stream 1 13).

The carbon dioxide removal unit 1 10 can comprise pressure swing absorption unit (PSA) or can be based on any other membrane separation processes. The effluent from the carbon dioxide removal unit can be treated (for example in the molecular sieve dryer).

Next the OCM product stream can be directed from the carbon dioxide removal unit 1 10 to a CDC and turboexpander unit (not shown). CDC (compression, drying, chilling) train in OCM first precools C0₂-free gas from C0₂ removal, then removes any water by molecular sieve absorbents and the cools down the process gas in order to be able to separate methane from C₂₊ by distillation. The Turboexpander is used to provide cooling for chilling unit by expanding the pressurized demethaniser overhead to lower pressure and consequently to much lower temperature. This very low temp methane stream is then used to cool down the process gas through a heat exchanger.

The OCM product stream leaving the CDC / turboexpander unit is subsequently introduced to a demethanizer unit (De-C1 ) 1 14 which can separate all recover methane from higher molecular weight hydrocarbons (such as ethane, ethene, propene). The demethanizer unit 1 14 may include one or more distillation columns.

The methane (stream 1 17) separated in the demethanizer unit 1 14 (and after PSA purge stream 1 15) can then be directed to the methanation unit 1 1 1 . In the methanation unit 1 1 1 further methane is generated from carbon dioxide, carbon monoxide and hydrogen. Methane generated in the methanation unit 1 1 1 can then be directed to the OCM catalytic unit 101 .

In side reactions of the OCM significant amounts of hydrogen, carbon monoxide and carbon dioxide are formed and are thus contained in the OCM effluent stream. Hydrogen content in the effluent stream can range between 5% and about 15%. The content of carbon monoxide and carbon dioxide can range between one and 5%.

In some cases this effluent stream is directly recycled to the OCM reactor 101 . However, if carbon monoxide and hydrogen are recycled to the OCM reactor 101 along with methane they can react with oxygen to produce carbon dioxide and water causing negative impact to the overall process.

Thus, in order to make effectively use of the side products the stream comprising carbon dioxide, carbon monoxide and hydrogen is fed (after removal from the product stream in the carbon dioxide removal unit) to a methanation unit 1 1 1 .

In the methanation unit 1 1 1 carbon monoxide and carbon dioxide react with hydrogen to methane in exothermic processes. The heat generated may be used as heat input to other process units or for preheating reactants such as methane and/or an oxidizing agent prior to an OCM reaction.

The methanation reaction can take place in two or more reactors in series. In an embodiment the methanation unit 1 1 1 comprises a first reactor and the second reactor that can be operated as adiabatic reactors. The methanation reaction 1 1 1 requires a suitable catalyst. For example, nickel-based catalysts can be used that may include nickel supported on alumina.

The methanation reaction can produce water. Thus it is desirable to remove this water prior to recycling the methanation effluent to the OCM a reactor. This can be accomplished by lowering the temperature of the methanation effluent or applying any separation procedure for removing the water.in some embodiments at least about 70%, at least about 80% at least about 90% or at least about 99% of the water is removed from the methanation effluent prior to the OCM reactor. Removing the water can increase the lifetime and/or performance of the OCM catalyst.

Methane synthesized in the methanation unit 1 1 1 is subsequently mixed and replenished with fresh methane from natural gas (stream 108). The mixed methane stream 104 enters then the catalytic unit of the OCM reactor 101 . Higher molecular weight hydrocarbons separated from methane in the demethanizer unit 1 14 can then be directed to a deethanizer unit (De-C2 unit) 1 18. In the deethanizer unit 1 18 C₂ compounds (such as ethane and ethene) are separated from C₃₊ compounds (such as propane and propene). C₂ compounds are then directed from the deethanizer unit 1 18 to a C₂ splitter 121 which can separate ethane from ethene. The C₂ splitter 121 can be a distillation column. The C₂ splitter 121 can also be coupled to an acetylene converter 1 16 where acetylene (C₂H₂) is reacted with hydrogen to generate ethane and/or ethene. Recovered ethene (stream 122) can be employed for any downstream use (like polymer production) whereas ethane is subsequently recycled from the C₂ splitter 121 to the OCM reactor unit 101 , preferably to the cracking unit (PBC unit).

C₃₊ compounds separated in the deethanizer unit 1 18 from the C₂ compounds are further directed to a depropanizer unit (De-C3 unit) 123 in which C₃ compounds are separated from

C₄₊ compounds comprising 4 and more carbon atoms. The C₃ compounds stream (stream 120) comprises predominantly propene and propane.

The ethane (stream 105) recycled from the C₂ splitter 121 to the OCM reactor unit 101 is mixed and replenished with fresh ethane form a natural gas source (stream 102). Recycled ethane and fresh ethane enter the reactor unit as combined streams. Table 1 below depicts the flow rate of the different streams in a conventional OCM process (as for example described in WO 2015/106023 A1 )

Table 1 : Flow table OCM unit streams (in Ib/hr) Example 2:

Fig. 1 B is schematic view of the known Oleflex propane dehydrogenation process.

Fresh propane feed is mixed with the recycle propane feed to form a combined feed and fed to a heater (not shown). The heated feed is then reacts in dehydrogenation reactor 201 in the presence of a catalyst. The product gas mixture along with unreacted propane goes to a compressor 210 and subsequently to the cold section or cold box 202 where light gases are separated. The hydrogen from the light gases is then separated from the remaining light gases using a pressure swing adsorption (PSA) unit 203. Hydrogen and the other light gases exit the dehydrogenation system 200 as stream 21 1 .

The liquid from the cold box 202 is then sent to a de-ethaniser 204 where components lighter than propene (such as methane and ethane) are removed at the top for export (stream 213). Propene and the other heavier components are sent to a C₃ splitter tower 205 where propene is obtained (stream 212). The bottom stream of C₃ splitter 205 is then fed to depropaniser (De-C3) 207 where the components heavier then propane (such as C₄₊ compounds) are removed at the bottom (stream 209). Propane together with freshly injected propane (stream 203) is recycled back from the De-C3 unit 207 to the dehydrogenation reactor 201 .

The used catalyst from the dehydrogenation reactor 201 is regenerated in a regeneration section (not shown) and recycled back to the dehydrogenation reactor 201 .

Table 2 below depicts the flow rate of the different streams in a conventional propane dehydrogenation process.

The flow values in the Table 2 are based on reactor effluent stream composition given by Chin et al. (Int. J. Chem., Nucl., Metallurgic. and Materials Engineering; 201 1 , Vol. 5; No. 4, pages 1 9-25) for a 500 kilo ton per year basis. It is assumed that all the H₂ and methane are separated in coldbox from C2+ components. In case of using PSA further, it can be assumed that H₂ will be further purified from methane. Also it is assumed that ethane and ethylene are separated from C₃₊ components in deethaniser and polymer grade propylene is separated from the remaining components in C₃ splitter.

Table 2: Flow table PDH unit streams

Fig. 1 C depicts a scheme of the known Catofin propane dehydrogenation process 200. The CATOFIN propane dehydrogenation process is a cyclic process where during regeneration and reduction steps, heat is supplied to the catalyst bed and during dehydrogenation step catalyst bed cools down due to the endothermic dehydrogenation reaction. Propylene production is normally controlled by equilibrium at the bottom section (US 2,41 9,997). According to the scheme of Fig. 1 C fresh propane is mixed with the recycle propane feed to form a combined feed and fed to a fired heater (not shown). The heated feed is then reacts in dehydrogenation reactor 201 in the presence of a catalyst. The product gas mixture along with unreacted propane goes to a compressor 210 and subsequently to the cold section or cold box 202 where light gases are separated. The hydrogen from the light gases is then separated from the remaining light gases using a pressure swing adsorption unit 203. Hydrogen and the other light gases exit the dehydrogenation system 200 as stream 21 1 and are typically used as fuel gas.

The liquid from the cold box 202 is then sent to a de-ethaniser 204 where components lighter than propene (such as methane and ethane) are removed at the top for export (stream 213). Propene and the other heavier components are sent to a C3 splitter tower 205 where propene is obtained (stream 212).

The bottom stream of C3 splitter 205 is recycled back then together with freshly injected propane (stream 203) to the dehydrogenation reactor 201 .

Example 3:

Fig. 2A illustrates a first embodiment of the present process.

As in the conventional OCM process of Fig. 1 A ethane and oxygen enter the OCM reactor 101 . The OCM reactor effluent (stream 106) is fed into the C0₂ removal unit 1 10. Part of the removed C0₂ will be guided into the methanation unit, whereas the remaining C0₂ part is vented out of the system (not shown).

Next the OCM product stream is directed from the carbon dioxide removal unit 1 1 1 to further work up units. In a first step the OCM product stream enters as a demethanizer unit (De-C1 ) 1 14 which separates and recovers methane from higher molecular weight C₂₊ hydrocarbons

(such as ethane, ethene, propene). The recovered methane is fed to the methanation unit (not shown).

The C₂₊ hydrocarbon effluent is further directed from the demethanizer unit 1 14 to the deethanizer unit 1 18 for separating C₂ hydrocarbons (such as ethane and ethene) from C₃₊ hydrocarbons. The separated C₂ hydrocarbons are then transferred to a C₂ splitter (not shown). The C₃₊ hydrocarbons (stream 120) leaving the deethanizer unit 1 18 in the OCM process are now transferred to a C₃ splitter unit 205 in the propane dehydrogenation system.

In the propane dehydrogenation system propane is reacted to propene in the dehydrogenation reactor 201 . The reactor effluent is subsequently fed to a separation unit (not shown) for separating light gases and a deethanizer unit 204. The C₃₊ hydrocarbon effluent leaving the deethanizer unit 204 is guided into a C₃ splitter for separating propane and propene. The separated propene stream 212 consists essentially of polymer grade propene (PG propene). The OCM process and the dehydrogenation system are thus combined such that C₃ hydrocarbon stream 120a as side product in the OCM process is tunneled into the C₃ splitter in the dehydrogenation process. This allows for providing high value propane.

Example 4

Fig. 2B illustrates a second embodiment of the present process. Reference is made to the schemes shown in Figs. 1 A, 1 B and 1 C.

Here, the C₃ hydrocarbon stream 120a leaving the depropanizer unit 123 in the OCM process are tunneled to the C₃ splitter 205 in the propane dehydrogenation process.

As a result the amount of fresh propane (C3 LPG feed stream 203) that is required can be reduced by 20,7 kg per tonne OCM ethylene capacity. Moreover, the amount of polymer grade propene (stream 212) that can be obtained is increased by 39,1 kg per tonne OCM ethylene capacity. Besides, the OCM refinery grade propylene product is upgraded into polymer grade propylene and propane.

Example 5 Fig. 3A illustrates a third embodiment of the present process.

As in the conventional OCM process of Fig. 1 A ethane and oxygen enter the OCM reactor 101 . The OCM reactor effluent (stream 106) is fed into the C0₂ removal unit 1 10. Part of the removed C0₂ will be guided into the methanation unit, whereas the remaining C0₂ part is vented out of the system (not shown). Next the OCM product stream is directed from the carbon dioxide removal unit 1 10 to further work up units. In a first step the OCM product stream enters as a demethanizer unit (De-C1 ) 1 14 which separates and recovers methane from higher molecular weight C2₊ hydrocarbons (such as ethane, ethene, propene). The recovered methane is fed to the methanation unit (not shown).

The C2₊ hydrocarbon effluent from the demethanizer unit 1 14 in the OCM system is now directed to the deethanizer unit 204 as part of the propane dehydrogenation system for separating C₂ hydrocarbons (such as ethane and ethene) from C₃₊ hydrocarbons.

The separated C₂ hydrocarbon stream 213 from the deethanizer unit 204 in the dehydrogenation system is then transferred back into the OCM system, more particular to the C₂ splitter 121 . In the C₂ splitter 121 ethane and ethene are separated from each other. While ethene is used for further purposes such as for polymerisation, ethane (stream 105) is recycled back to the cracking unit of the OCM reactor 101 .

In the propane dehydrogenation system propane is reacted to propene in the dehydrogenation reactor 201 . The reactor effluent is subsequently fed to a separation unit (not shown) for separating light gases and a deethanizer unit 204. The C₃₊ hydrocarbon effluent leaving the deethanizer unit 204 is guided into a C₃ splitter for separating propane and propene. The separated propene stream 212 consists essentially of polymer grade propene (PG propene). The OCM process and the dehydrogenation system are thus combined such that C₂₊ hydrocarbon stream from the OCM process is tunneled into the deethanizer unit in the dehydrogenation process and after separating off the C₃₊ hydrocarbons the C2 hydrocarbons are tunneled back into the OCM system. This allows the use of one common deethanizer unit 204 for both processes.

Example 6

Fig. 3B illustrates a fourth embodiment of the present process. Reference is made to the schemes shown in Figs. 1 A, 1 B and 1 C.

Here, the C₂₊ hydrocarbon effluent from the demethanizer unit 1 14 in the OCM process is fed into the dehydrogenation process, specifically into the deethanizer unit 204 in the dehydrogenation process. The separated C2 hydrocarbon stream 213 from the deethanizer unit 204 in the dehydrogenation system is then transferred back into the OCM system, more particular to the C2 splitter 121 . In the 02 splitter 121 ethane and ethene are separated from each other. While ethene is used for further purposes such as for polymerisation, ethane (stream 105) is recycled back to the cracking unit of the OCM reactor 101 . OCM ethylene production capacity is increased by 9,3 kg per tonne PDH propylene capacity and OCM fresh ethane feed is decreased by 83,3 kg per tonne PDH propylene capacity.

Besides, a de-ethaniser is no longer required in the OCM process.

Claims

An integrated process for producing C₂₊ hydrocarbons preferably C₂₊ saturated and unsaturated hydrocarbons, comprising a process for oxidative coupling of methane (OCM) which comprises the steps of

- producing C₂₊ hydrocarbons from methane and at least one oxidizing agent, preferably oxygen, and from ethane in at least one OCM reactor (101 ) comprising at least one OCM catalyst unit and at least one cracking unit,

- transferring at least one OCM effluent (106) from the at least one OCM reactor (101 ) to at least one fractionation system for separating the C₂₊ hydrocarbons in one or more hydrocarbon product streams, wherein the fractionation system comprises at least one demethanizer unit (1 14) for separating methane from C₂₊ hydrocarbons, and

at least one C₂ splitter unit (121 ) for separating ethane and ethene, and/or

at least one deethaniser unit (1 18) for separating C₂ hydrocarbons, from C₃₊ hydrocarbons, and a propane dehydrogenation process which comprises the steps of

- producing propene from propane in at least one dehydrogenation reactor (201 ),

- transferring at least one dehydrogenation reactor effluent from the at least one dehydrogenation reactor (201 ) to at least one fractionation system for separating propene from the reactor effluent, wherein the fractionation system comprises at least one deethanizer unit (204) for separating C₂ hydrocarbons,, from C₃₊ hydrocarbons, and at least one C₃ splitter unit (205) for separating propane and propene, characterized in that the C₃₊ hydrocarbon effluent (120) from the at least one deethanizer unit (1 18) in the OCM process is fed into the at least one 03 splitter unit (205) in the propane dehydrogenation process, and/or the C₂₊ hydrocarbon effluent from the at least one demethanizer unit (1 14) in the OCM process is fed into the at least one deethanizer unit (204) in the propane dehydrogenation process and the C₂ hydrocarbon effluent (213) from the at least one deethanizer unit (204) in the propane dehydrogenation process is fed to the at least one C₂ splitter unit (121 ) in the OCM process.

2. Process according to claim 1 , characterized in that the OCM reactor effluent is fed to at least one compression unit (107) that is arranged downstream of the OCM reactor (101 ) before entering the at least one fractionation system.

3. Process according to at least one of the preceding claims, characterized in that the OCM reactor effluent (106) is fed to at least one C0₂ removal unit (1 10) that is arranged downstream of the OCM reactor (101 ) and the compression unit (107) before entering the at least one fractionation system.

4. Process according to at least one of the preceding claims, characterized in that the methane separated in the demethanizer unit (1 14) is fed to at least one methanation unit (1 1 1 ) and further recycled back into the OCM reactor (101 ).

5. Process according to one of the preceding claims, characterized in that the C₂₊ hydrocarbon effluent leaving the demethanizer unit (1 14) is fed into at least one deethanizer unit (1 18) for separating C₂ hydrocarbonsfrom C₃₊ hydrocarbons.

6. Process according to one of the preceding claims, characterized in that the C₂ hydrocarbon effluent (213) leaving the at least one deethanizer unit (204) and that is fed to the at least one C₂ splitter unit (121 ) comprises ethane, ethene and further methane.

7. Process according to one of the preceding claims, characterized in that the ethane (105) leaving the at least one C₂ splitter unit (121 ) is recycled back to the OCM reactor (101 ), preferably to the cracking unit of the OCM reactor.

8. Process according to one of the preceding claims, characterized in that the dehydrogenation reactor effluent is transferred to at least one separation unit comprising at least one cold box unit (202) and at least one pressure swing adsorption unit (203) arranged downstream of the propane dehydrogenation reactor (201 ) before entering the at least one fractionation system.

9. Process according to one of the preceding claims, characterized in that the effluent of the at least one C₃ splitter unit (205) is fed into at least one depropanizer unit (207) as part of the dehydrogenation process for separating propane from C₄₊ hydrocarbons.

10. Process according to claim 9, characterized in that the propane leaving the at least one de-propanizing unit (207) is recycled back into the propane dehydrogenation reactor (201 ).

1 1 . An integrated process system for conducting a process for producing C₂₊ hydrocarbons according to one of the preceding claims comprising at least one OCM system comprising

- at least one OCM reactor (101 ) comprising at least one OCM catalyst unit for generating C₂₊ hydrocarbons from methane and at least one cracking unit for generating C₂₊ hydrocarbons, preferably ethene, from ethane;

- at least one fractionation system for separating the C₂₊ hydrocarbons in one or more desired hydrocarbon products streams, wherein the fractionation system comprises

at least one demethanizer unit (1 14) for separating methane from C₂₊ hydrocarbons, and at least one C₂ splitter unit (121 ) for separating ethane and ethene, and/or

at least one deethanizer unit (1 18) for separating C₂ hydrocarbons from C₃₊ hydrocarbons, and at least one propane dehydrogenation system comprising

- at least one propane dehydrogenation reactor (201 ) for producing propene from propane,

- at least one fractionation system for separating propene from the reactor effluent, wherein the fractionation system comprises at least one deethanizer unit (204) for separating C₂ hydrocarbons, , from C₃₊ hydrocarbons, and at least one C₃ splitter unit (205) for separating propane and propene, characterized in that the at least one depropanizer unit (1 10) in the OCM system is in fluid connection to the at least one C₃ splitter unit (205) in the propane dehydrogenation system for feeding the C₃ hydrocarbon effluent from the at least one deethanizer unit (1 18) in the OCM system into the at least one C3 splitter unit (205) in the propane dehydrogenation system, and/or the at least one demethanizer unit (1 14) in the OCM system is in fluid connection to the at least one deethanizer unit (204) in the propane dehydrogenation system for feeding the C₂₊ hydrocarbon effluent from the demethanizer unit (1 14) in the OCM system into the deethanizer unit (204) in the propane dehydrogenation system and feeding the C₂ hydrocarbon effluent from the at least one deethanizer unit (204) in the propane dehydrogenation system to the at least one C₂ splitter unit (121 ) in the OCM process.

12. Process system according to claim 1 1 , characterized in that at least one at least one compression unit (107) and at least C0₂ removal unit (1 10) are arranged downstream of the OCM reactor (101 ) and upstream of the at least one fractionation system.

13. Process system according to one of the claims 1 1 to 12, characterized in that at least one methanation unit (1 1 1 ) is arranged downstream of the at least one demethanizer unit (1 14).

14. Process system according to one of the claims 1 1 to 13, characterized in that at least one deethanizer unit (1 18) is arranged downstream of the at least one demethanizer unit (1 14).

15. Process system according to one of the claims 1 1 to 14, characterized in that at least one separation unit comprising at least one cold box unit (202) and at least one pressure swing adsorption unit (203) arranged downstream of the propane dehydrogenation reactor (201 ).