WO2015140300A1

WO2015140300A1 - Method and device for producing olefins

Info

Publication number: WO2015140300A1
Application number: PCT/EP2015/055933
Authority: WO
Inventors: Torben HÖFEL; Harald SCHMADERER; Andreas Peschel
Original assignee: Linde Aktiengesellschaft
Priority date: 2014-03-20
Filing date: 2015-03-20
Publication date: 2015-09-24

Abstract

The invention relates to a method (100) for producing olefins, wherein oxygenates are produced in one or more oxygenate synthesis steps (1, 2) by using hydrocarbons, hydrogen being obtained in the process, which oxygenates are then at least partially converted into hydrocarbons in one or more oxygenate conversion steps (3), and wherein in one or more steam cracking steps (4) hydrocarbons are produced, wherein some of the hydrocarbons from the one or more oxygenate conversion steps (3) and/or some of the hydrocarbons from the one or more steam cracking steps (4) are reacted with hydrogen in one or more hydrogenation steps (6). According to the invention the hydrogen obtained in the one or more oxygenate synthesis steps (1, 2) is at least partially used in the one or more hydrogenation steps (6). The invention further relates to a corresponding plant.

Description

description

Process and apparatus for producing olefins

The present invention relates to a method and an apparatus for producing olefins according to the preambles of the independent claims.

State of the art

Short chain olefins such as ethylene and propylene can be prepared by steam cracking

Hydrocarbons are prepared, as explained in detail below. An alternative route to such short chain olefins are the so-called oxygenate to olefin (Oxygenates to Olefins, OTO) processes.

Oxygenates are oxygen-containing compounds derived from saturated hydrocarbons, in particular ethers and alcohols. Oxygenates are used, for example, as fuel additives for increasing the octane number and as a lead substitute (see D. Barcelo (ed.): Fuel Oxygenates.) In: D. Barcelo and AG Kostianoy (ed.): The Handbook of Environmental Chemistry, Vol. 5. Heidelberg: Springer, 2007). The addition of oxygenates in fuels causes, among other things, a cleaner combustion in the engine and thus reduces emissions.

The corresponding oxygenates are typically ethers and

Alcohols. In addition to methyl tert-butyl ether (MTBE, engl, methyl tertiary butyl ether), for example, tert-amyl methyl ether (TAME, tertiary amyl methyl ether), tert-amyl ethyl ether (TAEE, tertiary amyl ethyl ether), ethyl tert-butyl ether (ETBE, ethyl tertiary butyl ether) and diisopropyl ether (DIPE, diisopropyl ether) are used. When

Alcohols are, for example, methanol, ethanol and tert-butanol (TBA, tertiary butyl alcohol) used. In particular, the oxygenates include the dimethyl ether explained below (DME, dimethyl ether). The invention is not limited to said fuel additives, but is equally suitable for use with other oxygenates.

According to a common definition which also applies here, oxygenates are compounds which are at least one covalent to an oxygen atom having bound alkyl group. The at least one alkyl group may have up to five, up to four or up to three carbon atoms. In particular, the oxygenates of interest in the present invention are

Alkyl groups having one or two carbon atoms, in particular are methyl groups. Of particular interest are monohydric alcohols and dialkyl ethers such as methanol and dimethyl ether or corresponding mixtures.

In oxygenate-to-olefin processes, corresponding oxygenates such as methanol or dimethyl ether are introduced into a reaction zone of a reactor in which a catalyst suitable for reacting the oxygenates is provided. The catalyst typically contains a molecular sieve. Under the action of the catalyst, the oxygenates are converted into, for example, ethylene and propylene. The catalysts and reaction conditions used in oxygenate-to-olefin processes are basically known to the person skilled in the art.

For example, the running in known oxygenate-to-olefin process

Reactions are also referred to hereinafter by the term "oxygenate replacement steps." The one or more oxygenate replacement steps have at least one oxygenate converted to one or more other oxygenates or one or more nonoxygenates understood ongoing reactions in which in particular paraffinic

Compounds are converted to olefinic compounds. The invention can work with different catalysts for the realization of the or the Sauerstoffomatsetzungsschritte. For example, zeolites such as ZSM-5 or SAPO-34 or functionally comparable materials can be used. When ZSM-5 or a comparable material is used, comparatively large amounts of relatively long-chain (C3plus) hydrocarbons and comparatively small amounts of shorter-chain (C2minus) hydrocarbons are formed. By contrast, when using SAPO-34 or comparable materials, significant amounts of shorter-chain (C 2 -min) hydrocarbons are also formed.

Also integrated processes and plants ("compound plants") for the production of hydrocarbons, the one or more steam cracking steps and one or more implementing several oxygenate replacement steps or include corresponding cracking furnaces and reactors are known and described for example in WO 201 1/057975 A2 or US 2013/172627 A1. US 2004/0122268 A1 discloses a process for the removal of methyl acetylene and / or propadiene from a

Propylene stream and / or a butylene stream by means of a two-step fractionation. This avoids the avoidance of a hydrogenation reactor and allows the

Methylacetylene and / or the propadiene from the process to win.

Such integrated methods are advantageous, for example, because in the or the oxygenate replacement steps typically not exclusively the

desired short-chain olefins are formed. An essential part of

Oxygenate is converted to paraffins and C4plus olefins (see below for designation). At the same time, not all of the furnace charge is split into short-chain olefins during steam cracking. In particular, unreacted paraffins may be present in the cracking gas of corresponding cracking furnaces. Further, typically C4plus olefins are found here, including diolefins such as butadiene. The compounds obtained in both cases depend on the used inserts and reaction conditions. In the in WO201 1/057975 A2 and US 2013/172627 A1 proposed

Methods, the cracking gas of a cracking furnace and the effluent of an oxygenate to olefin reactor are combined in a common separation unit and fractionated. A C4 fraction may, for example after hydrogenation or separation of butadiene, again be subjected to one or more steam cracking steps and / or one or more oxygenate reduction steps, optionally after separation into predominantly olefinic and predominantly paraffinic fraction fractions.

In particular, the efficiency of corresponding integrated methods, however, does not always prove to be satisfactory, in particular due to the complicated hydrogen to be provided for the hydrogenation. There is therefore room for improvement.

Disclosure of the invention

Against this background, the present invention proposes a method and an apparatus for producing olefins according to the features of the independent Claims. Preferred embodiments are subject of the dependent claims and the following description.

Before explaining the advantages of the present invention, its principles and the terms used will be explained.

The used in the context of this application in the usual way

Abbreviations for hydrocarbon mixtures or hydrocarbon fractions are based on the carbon number of the respectively predominantly or exclusively contained compounds. Thus, a "C1 fraction" is a fraction which contains predominantly or exclusively methane (but conventionally under certain circumstances also hydrogen, then also called "Cl minus fraction"). By contrast, a "C2 fraction" contains predominantly or exclusively ethane, ethylene and / or acetylene. A "C3 fraction" contains predominantly propane, propylene, methyl acetylene and / or propadiene. A "C4 fraction" contains predominantly or exclusively butane, butene, butadiene and / or butyne, it being possible for the respective isomers to be present in different proportions, depending on the source of the C4 fraction. The same applies to the "C5 fraction" and the higher fractions. Several such fractions can also be summarized in terms of process and / or notation. For example, a "C2plus fraction" contains predominantly or exclusively hydrocarbons having two or more and a "C2minus fraction" predominantly or exclusively hydrocarbons having one or two carbon atoms and hydrogen. The term "predominantly" refers to a content of at least 50%, 60%, 70%, 80%, 90%, 95% or 99% on a molar, weight or volume basis.

Steam cracking processes and apparatuses of

Hydrocarbons are known and, for example, in the article "Ethylene" in

Ullmann's Encyclopedia of Industrial Chemistry, online since April 15, 2007, DOI 10.1002 / 14356007.a10_045.pub2.

Steam cracking processes are predominantly used on a commercial scale

Tubular reactors carried out, the reaction tubes, the so-called coils, individually or in groups can be operated at the same or different gap conditions. Under the same or comparable fission conditions operated reaction tubes or groups of reaction tubes, but optionally also below Overall, tubular reactors operated in accordance with uniform nip conditions are referred to below as "cracking furnaces". A cracking furnace in the language used here is thus a structural unit used for the vapor cracking, which equates to a furnace insert or exposes it to comparable cracking conditions. A steam cracking plant may have one or more cracking furnaces.

It is possible that there is a subdivision into two or more cracking furnaces in a total furnace. One then often speaks of furnace cells. Several, one

Oven furnaces belonging to the total furnace generally have independent radiation zones and a common convection zone as well as a common smoke outlet. In these cases, each furnace cell can be operated with its own gap conditions. Each furnace cell is thus a structural unit used for steam columns, which are similar or comparable to a furnace insert

Cleavage conditions exposes and is therefore referred to here as cracking furnace. The total furnace then has several corresponding units or, in other words, several cracking furnaces. If there is only one furnace cell, this is the splitting unit and thus the cracking furnace. Cracking furnaces can be combined into groups, which are supplied, for example, with the same furnace insert. The fission conditions within a furnace group are usually set the same or similar.

In recent processes and devices for steam cracking increasingly mild cracking conditions are used (see below), because in this particular so-called value products such as propylene or butadiene can win in a relatively larger amount.

The term "furnace insert" here refers to one or more liquid and / or gaseous streams which are fed to one or more cracking furnaces. Also, streams obtained by a corresponding steam cracking process, as explained below, may be recycled to one or more cracking furnaces and reused as

Oven insert can be used. As a furnace insert is a variety of

Hydrocarbons and hydrocarbon mixtures of ethane to gas oil up to a boiling point of typically 600 Ό.

A furnace insert may consist of a so-called "fresh use", ie from an insert provided externally and for example from one or more several petroleum fractions, natural gas and / or natural gas condensates is obtained. A furnace insert can also consist of one or more so-called "recycle streams", ie streams that are generated in the plant itself and returned to a corresponding cracking furnace. A furnace insert may also consist of a mixture of one or more fresh feeds with one or more recycle streams.

The furnace insert is at least partially reacted in the respective cracking furnace and leaves the cracking furnace as a so-called "raw gas", which can be subjected to post-treatment steps. Such aftertreatment steps comprise first a treatment of the raw gas, for example by quenching, compacting,

Liquefying, cooling and drying, whereby a so-called "cracking gas" is obtained. Sometimes, the raw gas is already referred to as cracking gas.

The mentioned "cracking conditions" in a cracking furnace include, inter alia, the partial pressure of the furnace insert, which can be influenced by the addition of different amounts of steam and the set pressure in the cracking furnace, the residence time in the cracking furnace and the temperatures and temperature profiles used therein. The furnace geometry and furnace design also play a role. For the production of ethylene, a cracking furnace is typically operated at an oven inlet temperature of 500 to 680 Ό and at a furnace outlet temperature of 77 5 to 875 ° C. Here, the "furnace exit temperature" is the temperature of a gas stream at the end of one or more reaction tubes. Typically, this is the maximum temperature to which the corresponding gas stream is heated. The pressure used, also measured at the end of one or more reaction tubes, is typically 165 to 225 kPa. The furnace insert is admixed with steam in a ratio of typically 0.25 to 0.85 kg of steam per kg of dry feed. The values used are of the furnace used and the desired

Fission products dependent. Since the values mentioned influence each other at least partially on each other, the term "cracking severity" has been used to characterize the fission conditions. For liquid oven inserts, so longer-chained

Hydrocarbons, the gap resolution on the ratio of propylene to ethylene (P / E) or as the ratio of methane to propylene (M / P) in the cracking gas on a weight basis (kg / kg) can be described. The P / E and M / P ratios are directly dependent on the temperature, but in contrast to the real temperature in or at the output of a cracking furnace can be measured more accurately and used for example as a controlled variable in a control method. For gaseous furnace inserts, the conversion or conversion of a respective considered component of the furnace insert can be specified as a measure of the gap resolution. In particular, for the C4 fractions or C4 substreams used in the present case, a description of the resolution of the gap over the reaction of

Key components such as n-butane well suited and customary.

The splitting or cleavage conditions are "sharp" when more than 92% of n-butane is reacted in a corresponding fraction. At even sharper cleavage conditions, n-butane may also be converted to greater than 93%, 94% or 95%. A conversion of n-butane to 100% typically does not occur. The upper limit of the "sharp" splitting or cleavage conditions is therefore for example 99%, 98%, 97% or 96% conversion of n-butane.

On the other hand, the splitting or cleavage conditions are "mild" when n-butane is converted to less than 92%. With less than 91%, less than 90%, less than 89%, less than 88% or less than 87% conversion of n-butane, increasingly milder splitting or cleavage conditions are present. With less than 86% conversion of n-butane, the gap-sharpening or cleavage conditions are referred to herein as "very mild". Very mild splitting or cleavage conditions also include, for example, a conversion of n-butane to less than 85%, 80% or 75% and more than 50% or 60%.

The mentioned gap sharpening or cleavage conditions depend in particular on the above-explained furnace outlet temperature at the end of the reaction tube or slit furnaces used in each case. The higher this is, the "sharper", the lower, the "milder" the gap sharpening or gap conditions.

It is further understood that the reaction of other components need not be identical to that of n-butane. With a percentage conversion of a

However, the key component, in this case n-butane, is in each case one kiln outlet temperature and the respective percentage conversions of the other components in use connected. This furnace outlet temperature is in turn dependent, among other things, on the cracking furnace. The offset between the respective percentage conversions depends on a number of other factors. Advantages of the invention

The present invention proposes a process for producing olefins in which oxygenates are produced in one or more oxygenate synthesis steps using hydrocarbons and yielding hydrogen. These oxygenates are then in one or more

Oxygenatumsetzungsschritten at least partially converted to hydrocarbons. In parallel, in one or more steam splitting steps

Hydrocarbons generated. A portion of the hydrocarbons from the or the Sauerstoffuminasetzungsschritten and / or a portion of the hydrocarbons from the one or more steam cracking steps are subjected to one or more hydrogenation steps, in which they are reacted with hydrogen.

As already explained at the beginning, methods of this type are known in principle. For example, DE 32 20 996 A1 discloses the combining of gases from a steam cracking process and an oxygenate-to-olefin process. The same is also illustrated in US 2005/0038304 A1. Here are individual

Product fractions may also be recycled to a steam cracking process and / or an oxygenate to olefin process. Thus, DE 32 20 999 A1, WO 83/04249 A1, EP 0 090 232 A1, WO 2009/039948 A1, US 201 1/01 12344 A1 and US 201 1/01 12345 A1 corresponding methods disclosed. Integration concepts in plant complexes for the production of olefins with an oxygenate-to-olefin process and a vapor cracking process are also shown in US 201 1/0137095 A1 and US 201 1/01 12314 A1. From the prior art, for example, US 201 1/91 12314 A1, is the

Recycling hydrogen from a common separator of an oxygenate to olefin process and a steam cracking process to an oxygenate synthesis step. Further, the separation of an insert consisting of methane, ethane and carbon dioxide has been proposed to separate the individual fractions in each case a synthesis gas generating unit, a steam cracking step, and a

Oxygenate synthesis step to lead.

Are hydrocarbons from at least one steam cracking step and

Hydrocarbons combined from at least one oxygenate conversion step and fed to a common separation part may have an amount therein

corresponding hydrocarbons are formed, which makes it possible to dispense with fresh inserts for the or the steam gap steps. Conventional methods of the type explained have in common that in these

typically not only propane and ethane to a steam cracking process

but also hydrocarbons with four or more

Carbon atoms with low added value. Such components include olefins which, as in the context of the present invention, before a

corresponding recycling typically be hydrogenated.

For the hydrogenation and hydroisomerization of olefins or olefin-containing

Hydrocarbon mixtures are known from the prior art numerous catalytic processes, which can also be used in the context of the present invention. Hydrogenation catalysts have as the hydrogenation-active component one or more elements of the 6th, 7th or 8th subgroup of the Periodic Table in

elementary or bound form. As Hydroisomerisierungskatalysatoren typically noble metals of the 8th subgroup are used in elemental form. They can be endowed with different additions to specific ones

Catalyst properties, such as lifetime, resistance to certain catalyst poisons, selectivity or regenerability affect. The hydrogenation and hydroisomerization catalysts often contain the active component on supports, for example, mordenites, zeolites, dialuminium trioxide modifications, silica modifications, and others.

For the substantial hydrogenation of olefins are in general

Reaction temperatures of 150 to 250 Ό applied, the hydroisomerization takes place at significantly lower temperatures. The thermodynamic equilibrium is at these lower temperatures on the side of the internal olefins, here 2-butene. The present invention now proposes that at least part of the hydrogen used in the hydrogenation step or steps is used in the hydrogenation step (s)

Is obtained oxygenate synthesis steps. As has been found, even with a separation of the hydrocarbons in a common separation part of the hydrogen separated here often is not sufficient for the hydrogenation. It proves to be particularly favorable, instead of additional, fed from the investment limit

Hydrogen to use the hydrogen obtained in the oxygenate synthesis. The invention makes it possible, due to the measures described, to dispense with additional hydrogen from the plant boundary, so that such a

Process is particularly simple and efficient.

It is here said that the hydrogen in the one or more Oxygenatsyntheseschritten "won", or that or the

Oxygenatsynthesehtritte "under recovery of hydrogen" are carried out, it is understood that this hydrogen is already there and not in a common separation part is obtained. Advantageously, the hydrogen obtained in the or the oxygenate synthesis steps is upstream of the or

Separated oxygenate replacement steps. In both cases, by the recovery of hydrogen in the or

Oxygenatsyntheseschritten or by the implementation of or

Oxygenatsynthesehritte to yield hydrogen significantly improves the overall efficiency of the process. Instead of recovering the hydrogen in a downstream separation section into which an effluent of the or

Oxygenierungssetzungsschritte and / or the or the vapor cracking steps is fed, the recovery of hydrogen in the or

Oxygenatsyntheseschritten or the implementation of or

Oxygenatsyntheseschritte to produce hydrogen much easier and less expensive to perform. For example, the recovery of hydrogen from a synthesis gas, which in one

Oxygenate synthesis step is used, which is essentially a three-component mixture, much easier than from a

Multi-component mixture, as they downstream of the or

Oxygenatumsetzungsschritte and / or the steam cracking steps present occur.

The same applies to an oxygenate-containing gas from an oxygenate synthesis step, the still represents a much less complex mixture than the mentioned effluents. In particular, due to an upstream

Hydrogen production, the separators used for the effluent of the oxygenation step (s) and / or the vapor splitting step (s) will be designed for lower volumes, significantly reducing the investment cost of constructing a corresponding plant.

Although the present invention is based on the finding that the recovery of hydrogen in the or the Sauerstoffatsyntheseschritten or performing the oxygenate or the synthesis steps to give hydrogen and the at least partial use of this hydrogen in the or

Hydrogenation steps is particularly advantageous, this does not exclude that further hydrogen, for example hydrogen, from an effluent of or

Oxygenate reaction steps and / or the steam-cracking steps in one

downstream separation step is obtained, can also be used for the hydrogenation. This hydrogen may be, for example, hydrogen generated in the vapor splitting step (s). However, the present invention always uses hydrogen, which, as mentioned above, is obtained upstream thereof in the oxygenate synthesis step (s). The recovery of hydrogen at different stages of the process significantly increases flexibility because each hydrogen extraction step can be customized to meet the specific technical needs of downstream units or units

Process steps can be met. This is of particular advantage when retrofitting existing plants, because in such cases the existing separation capacities designed for a particular purpose often do not correspond to the quantities that will be available after retrofitting. The provision of several adjustment options in the form of additional hydrogen recovery points solves this problem. If, for example, an existing steam cracking process is extended by an oxygenate-to-olefin process, a separation device for the separation of

Hydrogen from the collected effluents of both processes can not be extended if the recovery of hydrogen in the or the Sauerstoffatsyntheseschritten or performing the oxygenate or the synthesis steps to obtain Hydrogen occurs because then the effluent of the oxygenate synthesis and / or oxygenate reduction steps is poorer in hydrogen.

At this point, it should be emphasized that the skilled person would have in the design of a combined process that includes the oxygenate synthesis, the oxygenation and the steam cleavage would not have caused hydrogen separately in the Oxygenatsynthese, ie from a gas mixture, the one

Oxygenate synthesis step is or has already been subjected to it to win upstream of an Oxynatumsetzungsschritts (for example, upstream of an oxygenate to olefin process). In any case, since in such plants hydrogen is obtained from a effluent of the oxygenate reaction step (s) in a downstream reaction step, for example as part of a so-called "tail gas", the most obvious decision would be to use all of the hydrogen separation in one

perform downstream separation step. One of skill in the art would therefore have been discouraged from using another upstream separation step because it requires additional devices for separation. However, as has been found according to the invention, the expense of obtaining hydrogen in the oxygenate synthesis is more than offset by the advantages mentioned, for example by the increased flexibility which was explained above.

For obtaining hydrogen, means may be provided which are adapted to hydrogen during or after the or the oxygenate synthesis steps, for example from synthesis gas or from an effluent of a

Oxygenatsynthesereaktors containing, for example, at least oxygenates and hydrogen to separate. These agents may be in the form of, for example

Low-temperature or cryogenic separation devices or devices that operate due to adsorptive or absorptive principles, for example, using pressure swing adsorption (PSA), be realized. It may be of particular advantage in one or more different steps of the

Process according to the present invention to recover a crude gas mixture which is enriched in hydrogen. Such a crude gas mixture may be, for example, the said tail gas, which essentially contains hydrogen and methane, and from which hydrogen is obtained, for example by means of PSA. Corresponding crude gas mixtures from different steps of the method according to the present invention can also be combined and a common

Hydrogen extraction step are subjected. This is considered to be particularly advantageous because in this case only a single device needs to be provided for this purpose, for example a single PSA unit. However, according to the present invention, a portion of the raw hydrogen fed to such a common unit is previously separated, i. in the one or the other

Oxygenate synthesis steps, won.

As has been determined according to the invention, the hydrogen which is formed, for example, during vapor cracking is typically insufficient in quantity in order to carry out the required hydrogenation steps. In contrast, the hydrogen present in the oxygenate synthesis step (s), which includes the formation of synthesis gas by, for example, steam reforming and / or partial oxidation, is present in an amount greater than that required to carry out the synthesis of the or Oxygenate is required, ie in a superstoichiometric amount. Therefore, especially in the case of the combination of steam columns and oxygenate synthesis carried out in the context of the invention, excess hydrogen can be removed from the

Oxygenate synthesis can be used advantageously in the hydrogenation. Hydrogen also typically is by-produced in other processes for producing olefins, for example in the dehydrogenation of propane. Also, such hydrogen can be used with advantage in the context of the method according to the invention. As already explained, in the context of the present invention advantageously hydrocarbons having four and / or five carbon atoms from the or the Sauerstoffumsetzungsschritten and / or hydrocarbons having four and / or five carbon atoms from the or the steam cracking steps in the or

Hydrogenation steps reacted with hydrogen. This allows a meaningful use of corresponding hydrocarbons in a steam cracking process and thus the simple and cost-effective extraction of value-added products.

Advantageously, the hydrocarbons from the or

Oxygenatumsetzungsschritten and / or the hydrocarbons from the or Steam splitting steps thereby at least partially subjected to one or more common separation steps, as already explained above.

Advantageously, it is further contemplated that the oxygenate synthesis step (s) comprises a synthesis gas generating step and / or a syngas conversion step. In the former, synthesis gas is generated, for example, from hydrocarbons or other organic uses, which in the latter example is catalytically converted to the oxygenates. In both steps, hydrogen may be generated, which can be used according to the invention. The hydrogen may also be hydrogen in the synthesis gas used for the

Oxygenatsyntheseschritte is not needed.

Synthesis gas generation steps and synthesis gas conversion steps are

basically known. For example, allothermal or autothermal reforming processes can be used for synthesis gas production. Also combined

Procedures can be used. The synthesis gas conversion to the oxygenate (s) typically occurs catalytically in one or more

Reaction steps. Synthesis gas is typically produced using single or multistage processes. Here, for example, tube bundle reactors are used as synthesis gas reactors whose reaction tubes conventionally fired from the outside and operated at 850 to 900 wer who the. The reaction tubes are filled with a suitable catalyst and are flowed through by the mixed with the process steam insert. The invention can be used in addition to the conventional

Steam reforming (SMR, steam methane reforming) but also in autothermal reforming (ATR, autothermal reforming) and combined

Reforming process from conventional steam reforming and autothermal reforming are used. Another field of application of the invention are processes for steam reforming with carbon dioxide import.

Dimethyl ether can be obtained by a two-stage synthesis of synthesis gas via methanol as an intermediate. Corresponding methods are described, for example from page 171 in the DME Handbook of the Japan DME Forum, ISBN 978-4-9903839-0-9, 2007. The two-step recovery of dimethyl ether from synthesis gas is characterized, as mentioned, by the fact that first methanol is obtained from synthesis gas, then the unreacted synthesis gas from the

Condensates (methanol and water) is separated, and the methanol is then dehydrated in another reactor to yield dimethyl ether and water. Methods for obtaining other oxygenates can be found in

be carried out in a comparable manner.

The patent literature already 1973 (DE 23 62 944 A1, US 4 098 809 A) describes the direct or single-stage recovery of dimethyl ether from synthesis gas. This is characterized by a common reaction stage in which methanol and dimethyl ether are jointly obtained from hydrogen, carbon monoxide and carbon dioxide. Based on this, further methods have been described in the literature.

In a known combination process, the so-called Topsoe process, as described in the DME Handbook from page 185, in particular on page 187, a dual catalyst, with both methanol and dimethyl ether can be formed, is used. There are at least two reactors without intermediate separation used, with a first reactor cooled isothermally and a second reactor is operated adiabatically. There is a parallel production of dimethyl ether and methanol, wherein the methanol can be reacted in a further reactor after separation of the components to dimethyl ether.

The direct synthesis of dimethyl ether can also be carried out, for example, in slurry operation and at comparatively low stoichiometric numbers. This results in the formation of carbon dioxide as a by-product, which must be separated conventionally from the respective unreacted compounds in order to be able to feed the latter as a recycle of the reaction again. The reactions mentioned are included

comparatively low stoichiometric numbers only at low carbon dioxide content with a satisfactory yield.

The invention may also be used with particular advantage in methods and apparatuses for the production of dimethyl ether developed by the Applicant, in which a feed stream with hydrogen, carbon monoxide and carbon dioxide corresponding to a stoichiometric number of more than two and a comparatively high proportion of carbon dioxide is used. The one or more reactors used in this case are operated under exclusively isothermal conditions.

It is particularly advantageous if the hydrocarbons reacted in the hydrogenation step or steps are at least partially recirculated to the vapor splitting step or steps, as likewise explained.

Other recycle streams include, for example, paraffinic hydrocarbons having two to three carbon atoms. It is therefore intended that paraffinic

Hydrocarbons having two to three carbon atoms of the or

Oxygenatumsetzungsschritten and / or paraffinic hydrocarbons having two to three carbon atoms from the or the steam gap steps or the

Steam splitting steps are fed again. It is particularly advantageous if the hydrocarbons from which the oxygenates are produced in the oxygenate synthesis step (s) to form the hydrogen are separated from a gas mixture comprising methane, ethane and

Contains carbon dioxide. Depending on the embodiment of the method according to the invention, it is possible to dispense with the separation of carbon dioxide, in particular if an oxygenater-generating step for the processing is comparatively high

Carbon dioxide levels is set up. Ethane contained in such a gas mixture can be at least partially supplied to the vapor cracking step (s), and carbon dioxide contained in the gaseous mixture can also be fed to the oxygenate synthesis step (s), at least partially separated from other hydrocarbons. For example, corresponding carbon dioxide a

Synthesis gas to be fed.

It can also be advantageous if, if the hydrocarbons from the or the oxygenate reduction steps and / or the hydrocarbons from the vapor splitting step or steps comprise methane, this methane is at least partially supplied to the oxygenate synthesis step (s). The increase in cost of corresponding methane for providing energy in the vapor cracking step (s) is already known. Depending on requirements, according to the invention, methane can thus optionally be used for the provision of energy for the endothermic steam cracking processes (so-called underfiring) and / or be recycled to the oxygenate synthesis step (s), which is a particularly flexible process control allowed. So it will be either one

Energy integration and / or a material integration made.

The vapor splitting step or steps can be carried out using at least two cracking furnaces which can also be operated at different cracking conditions and / or charged with different hydrocarbons. The cracking conditions in the individual cracking furnaces can be matched to the particular use used, for example, hydrocarbons having four carbon atoms, ethane and / or heavier hydrocarbons and optionally milder or sharper.

A plant for the production of olefins is also an object of the present invention. This plant comprises means adapted to generate oxygenates in one or more oxygenate synthesis steps using hydrocarbons and hydrogen to form and then at least partially augmenting them in one or more oxygen conversion steps

Implement hydrocarbons. In addition, the system comprises means adapted to generate hydrocarbons in one or more steam-cracking steps in parallel with the oxygenation step (s), wherein one or more hydrogenation units are arranged to remove some of the hydrocarbons from the oxygenate replacement step (s) or to react some of the hydrocarbons from the one or more steam cracking steps in one or more hydrogenation steps with hydrogen. The facility is characterized by means that are set up, the one or the other

Hydrogen units at least partially feed the hydrogen formed in the or the Sauerstoffatsyntheseschritten.

A corresponding system benefits from the advantages explained above. This is therefore expressly referred to. In particular, such a system is adapted to carry out a method as explained above and has corresponding means for this purpose.

Embodiments of the invention are explained in more detail below with reference to the accompanying drawings with respect to the prior art. Brief description of the drawings

Figure 1 illustrates a process for producing olefins according to the prior art.

Figure 2 illustrates a process for producing olefins according to an embodiment of the invention. Figure 3 illustrates a process for producing olefins according to an embodiment of the invention.

In the figures, corresponding elements carry identical reference numerals and will not be explained repeatedly for the sake of clarity.

Detailed description of the drawings

FIG. 1 schematically illustrates a process for the production of olefins according to the prior art and denotes 1 10 in total.

In the illustrated example, a hydrocarbon-containing feed stream a is first fed to a synthesis gas production step 1, by means of which a

Synthesis gas stream b is formed. The synthesis gas stream b contains at least hydrogen and carbon monoxide and is subjected to a synthesis gas conversion step 2. In the synthesis gas conversion step 2, oxygenates are formed from components of the synthesis gas contained in the stream b and provided in the form of a stream c. The synthesis gas conversion step 2 works under

Use of suitable catalysts and optionally additional feed streams. Hereinafter, steps 1 and 2, d. H. the synthesis gas generating step 1 and the synthesis gas conversion step 2, summarized as

Designated oxygenate synthesis steps.

The stream c formed in the oxygenate synthesis steps 1, 2, which oxygenates methanol and / or dimethyl ether, is in one or more

Oxygenatumsetzungsschritten 3, for example, an initially explained Implement oxygenate-to-olefin processes, converted to hydrocarbons contained in a stream d. The aim of oxygenate-to-olefin process is, as explained above, the formation of olefins. However, a stream d, which in the example shown is present downstream of the or the oxygenate conversion steps 3, contains not only olefins but also other compounds. The current d is therefore supplied to a separation explained below.

In parallel with the steps just described, the method 1 10 comprises one or more steam-gap steps 4, which also have one or more

hydrocarbon-containing feed streams e can be charged. The vapor splitting steps or steps 4 can be carried out using one or more cracking furnaces operated under identical or different cracking conditions. Instead of only one feed stream e further streams can be used in the one or more steam gap steps, as also explained below.

Also by means of or the steam gap steps 4, a hydrocarbon-containing stream, here denoted by f formed. As also explained at the outset, such a current f also does not exclusively comprise the desired connections, so that a subsequent separation is required.

In the example shown, the separation of the components contained in the streams d and f takes place in a common separation unit or a common separation step 5. It is understood that, although only a single separation step 5 is illustrated in FIG Separation step 5 typically comprises a plurality of separation steps or stages. Separation sequences that in the or

common separation steps 5 can be used are basically known from the prior art, for example from the aforementioned article "Ethylene" in Ullmann's Encyclopedia of Industrial Chemistry. The separation step (s) 5 may comprise, for example, sequential demethanizer, deethanizer and depropanizer steps. Any order of such steps is possible.

In the or the separation steps 5 are different fractions of the

Streams d and f formed. These are, for example, a methane- and / or carbon dioxide-containing stream g, which, as illustrated by a solid arrow, into or the steam gap steps 4 for the provision of energy returned or, as illustrated by a dashed arrow, from the

Method 1 10 can be performed. In other words, the energy required for the vapor separation step or steps 4 of the process 1 10 can also be provided with methane-containing recycle streams, which are formed from a corresponding stream g. However, if required for energy balance reasons, another mathanhaltiger feed stream h (natural gas / fuel gas) can be supplied.

As a further product stream of the separation step or steps 5, a stream i can be formed, which predominantly contains ethylene and can be discharged from the process as a product. Another product stream k essentially comprises ethane and is recycled to the vapor splitting step (s) 4 as a recycle stream. The current k can be combined with further currents, as explained below.

For example, a stream I predominantly contains propylene and can also be carried out as a product of the process. A predominantly propane-containing stream m, as the stream k, in the vapor or the steps 4 are recycled.

Another fraction obtained in the separation step or steps 5 is n

illustrated. For example, this faction contains all the others

Components of the streams d and / or f, for example water, oils, heavy

Hydrocarbons and hydrocarbons having four or more carbon atoms, which may include value products such as aromatics, butadiene and the like. Separately, a stream o is illustrated, which contains predominantly the resulting in the separation in the or the separation steps 5 hydrogen.

As mentioned above, in particular, the processing of the four-carbon hydrocarbons contained in the process 10 in the fraction n is often inefficient. The present invention provides a remedy.

FIG. 2 illustrates a method according to a particularly preferred embodiment of the invention, which is denoted overall by 100. FIG. 2 illustrates an additional current p, which is generated in the separating step or steps 5. This is a stream that

contains predominantly hydrocarbons having four and / or more carbon atoms. The current n is no longer present in the composition 100 explained in FIG. 1 in method 100. A current corresponding to the current n, but without the now contained in the stream p hydrocarbons with four and / or more

No longer contains carbon atoms, is designated in Figure 2 with q.

The stream p is fed to a hydrogenation step 6 and hydrogenated there using hydrogen. It is understood that prior to the supply of the stream p to the hydrogenation step 6, it is also possible to separate components from the stream p, for example for obtaining valuable products.

Furthermore, FIG. 2 illustrates two additional hydrogen streams which can be obtained in the oxygenate synthesis steps 1, 2, ie the synthesis gas generation step 1 and the synthesis gas conversion step 2. These are denoted by r and s. The hydrogen streams r and s can thereby in the

Obtain oxygenate synthesis steps 1, 2 as hydrogen-rich or predominantly hydrogen-containing streams, but it is also possible to recover corresponding currents r and s by purification of other components containing mixtures.

The hydrogen contained in the streams r and s is combined with the

Hydrogen of the already explained with reference to the figure 1 stream o used in the hydrogenation step 6. This results, as already explained above, in a particularly efficient implementation of a method 100 according to the invention.

Hydrogenated components in the hydrogenation step or steps 6 can be recycled to the vapor splitting step or steps 4 in the form of the stream t. The or the

Steam splitting steps 4 can also be operated exclusively by using recirculated streams (recycle streams), a so-called fresh application, ie the stream e present in FIG. 1 is not absolutely necessary. This is illustrated in FIG. 2 in the form of a dashed arrow.

In FIG. 3, a method according to a further embodiment of the invention is illustrated schematically and also designated overall by 100. Method 100 does not differ fundamentally from the method illustrated in FIG. 2 with respect to steps 1-6 and streams h through t. In addition, FIG. 3 shows a further separation step 7, in which a stream u, which can contain, for example, methane, ethane and carbon dioxide, can be separated. In the separation step 7, for example, a methane-rich stream v can be obtained, which can be used together with another stream w to form the feed stream a already explained above. For its part, the current w can, for example, represent a partial flow of the methane-rich current g already explained. The stream v may also contain ethane and / or carbon dioxide.

However, an essential aspect of the process illustrated in FIG. 3 is the separate feed of carbon dioxide, which is separated from the stream u in the separation step 7, into the synthesis gas conversion step 2. This is illustrated by x in FIG. The stream x can be fed to the synthesis gas conversion step 2, because here, as explained above, appropriate conditions are used, as they have proven to be particularly advantageous for the conversion of synthesis gas to oxygenates.

A further aspect of the embodiment illustrated in FIG. 3 is the separation of an ethane-rich stream y from the stream u in the separation step 7. The stream y can be supplied to the vapor splitting stage (s) 4.

Claims

claims

1 . Process (100) for the production of olefins, in which oxygenates are produced in one or more oxygenate synthesis steps (1, 2) using hydrocarbons and hydrogen, followed by at least partial addition in one or more oxygen conversion steps (3)

Hydrocarbons are reacted, and in which in one or more steam cracking steps (4) hydrocarbons are generated, wherein a portion of the hydrocarbons from the or the Sauerstoffatesetzungsschritten (3) and / or a portion of the hydrocarbons from the or the steam gap steps (4) in one or more hydrogenation steps (6) is reacted with hydrogen, characterized in that in the or the hydrogenation steps (6) at least partially the hydrogen is used, in the or

Oxygenatsyntheseschritten (1, 2) is obtained.

2. The method (100) of claim 1, wherein the at the

Oxygenatsyntheseschritten (1, 2) hydrogen is removed upstream of or the oxygenate conversion steps (3).

3. Method (100) according to one of the preceding claims, in which

Hydrocarbons having four and / or five carbon atoms of the or

Oxygenatumsetzungsschritten (3) and / or hydrocarbons having four and / or five carbon atoms from the one or more vapor cracking steps (4) in the hydrogenation step or steps (6) are reacted with hydrogen.

4. Method (100) according to one of the preceding claims, in which the

Hydrocarbons from the or the Sauerstoffuminasetzungsschritten (3) and / or from the or the Dampfspaltschritten (4) are at least partially subjected to one or more common separation steps (5).

5. The method (100) according to any one of the preceding claims, wherein the or

Oxygenate synthesis steps (1, 2) comprise a synthesis gas production step (1) and / or a synthesis gas conversion step (2).

6. Process (100) according to one of the preceding claims, in which the hydrocarbons reacted in the hydrogenation step or steps (6) are at least partially recycled to the vapor splitting step or steps (4).

A method (100) according to any one of the preceding claims, wherein paraffinic hydrocarbons having two to three carbon atoms from the oxygen conversion step (s) (3) and / or the vapor splitting step (s) are recycled to the vapor splitting step (s) (4).

8. The method (100) according to any one of the preceding claims, wherein the

Hydrocarbons from which the oxygenates are produced in the oxygenate synthesis step (s) (1, 2) to yield the hydrogen are separated from a gas mixture containing methane, ethane and carbon dioxide.

9. The method (100) according to claim 8, wherein ethane contained in the gas mixture is at least partially supplied to the one or more steam gap steps (4).

10. The method (100) according to claim 8 or 9, wherein in the gas mixture contained carbon dioxide at least partially separated from other hydrocarbons or the oxygenate synthesis steps (1, 2) is supplied.

1 1. Method (100) according to one of the preceding claims, in which the

Hydrocarbons from the or the Sauerstoffatesetzungsschritten (3) and / or the hydrocarbons from the or the steam cracking steps (4) include methane, wherein the methane or at least partially

Oxygenatsyntheseschritten (1, 2) is supplied.

12. The method (100) according to any one of the preceding claims, wherein the one or more steam-gap steps (4) using at least two cracking furnaces

which are operated at different clearance conditions and / or charged with different hydrocarbons.

13. An olefin production plant comprising means adapted to oxygenate in one or more oxygenate synthesis steps (1, 2) using hydrocarbons and recovering hydrogen and at least partially converts them to hydrocarbons in one or more oxygen conversion steps (3), and comprising means adapted to generate hydrocarbons in one or more steam cracking steps (4), wherein one or more hydrogenation units are provided therefor are to react some of the hydrocarbons from the oxygen conversion step (s) (3) and / or part of the hydrocarbons from the vapor splitting step (s) (4) in one or more hydrogenation steps (6) with hydrogen, characterized by means adapted to the hydrogenation units or at least partially supply the hydrogen, in the or

Oxygenatsyntheseschritten (1, 2) is obtained.

14. A plant according to claim 13, comprising means adapted to carry out a method (100) according to any one of claims 1 to 12.