DE102014011213A1 - Process for synthesis gas production - Google Patents

Abstract

The invention relates to a method for producing a synthesis gas (100) containing H2 and CO, comprising the steps of: providing a feed stream (10) comprising methane and CO2, and reforming methane and CO2 in the presence of a suitable first catalyst (K) producing a synthesis gas stream (100) comprising H2 and CO, wherein the H2 / CO ratio is in the range of 0.5 to 3.0.

Description

The invention relates to a method for producing a synthesis gas according to claim 1.

There are various approaches for the production of H ₂ and CO-containing synthesis gases. Depending on the required H ₂ / CO ratio for the respective product, there are the (catalytic) partial oxidation (CPOX or POX), the autothermal reforming (ATR), the steam reforming (SMR) and combinations thereof.

H ₂ / CO ratios below 3: 1 can be achieved with the POX and ATR technologies, which is sufficient for the Fischer-Tropsch synthesis. By using or combining different technologies, it is possible to achieve a ratio H ₂ / CO of 2: 1. However, for both the POX and ATR processes, air separation units must be provided which provide the oxygen required for the particular process, which adds cost.

Furthermore, existing steam reforming processes require a significant amount of water vapor to avoid coke formation on the catalyst used. Coke formation usually blocks and destroys the catalyst used, so it must be replaced frequently. In addition, the generation of water vapor requires the provision of appropriate energy and the apparatus and the piping must be sized according to the increased due to the water vapor feed stream.

Furthermore, processes such as the CALCOR process are required for the production of CO with reduced water vapor demand ( G. Kurz, S. Teubner, petroleum. Kohl, 43 (1990) 171 ) and the SPARG process. While the CALCOR technology is only applicable at pressures below 5 bar, the SPARG process uses sulfur in the feed (eg in the form of H ₂ S) to suppress the formation of coke. However, sulfur is a typical catalyst poison and reduces the efficiency of the reformer and downstream catalysts used.

These known methods for the production of synthesis gas with a high CO content can not be applied at elevated pressures of 10 bar and more. Typical reforming or downstream processes usually take place at 30 bar to 50 bar, so that the synthesis gas must be compressed in these known methods, with the disadvantage that a corresponding compressor adversely affects the cost.

Furthermore, using conventional catalysts for steam reforming of methane, more energy efficient processes with a low vapor to carbon ratio (so-called S / C ratio) of 0.5 to 2.0 mol / mol are not possible because of the high Risk of coking in the reformer tubes.

Finally, high CO and low vapor content in the product gas can cause problems with the materials used for the equipment / piping (eg, scale, corrosion).

On this basis, the present invention has the object to provide a method for producing a synthesis gas which is relatively inexpensive and can be operated in particular at higher pressures, in particular with little steam and in particular the production of a H ₂ - and CO-containing synthesis gas allowed with a low H ₂ / CO ratio.

This object is achieved by a method having the features of claim 1. Advantageous embodiments of the invention are u. a. in the subclaims and are described below.

According to claim 1, the method according to the invention for producing an H ₂ and CO-containing synthesis gas provides the following steps:

• - Providing a feed stream comprising methane, and
• Dry reforming of methane with CO ₂ in the presence of a first catalyst to produce a synthesis gas stream comprising H ₂ and CO, wherein the H ₂ / CO ratio is in the range of 0.5 to 3.0.

The dry reforming of methane and CO ₂ is advantageously carried out in the presence of a soot-resistant first catalyst. This is a first according to the invention A catalyst comprising a nickel-magnesium mixed oxide and a magnesium spinel or a first catalyst comprising a hexaaluminate (see below).

The first catalyst comprising at least one nickel-magnesium mixed oxide and a magnesium spinel may optionally comprise an aluminum oxide hydroxide, the nickel-magnesium mixed oxide having an average crystallite size of less than 100 nm, preferably less than 70 nm, preferably less than 40 nm, and wherein the magnesium spinel phase has an average crystallite size smaller than 100 nm, preferably smaller than 70 nm, preferably smaller than 40 nm, and wherein the content of nickel in the first catalyst is in the range of 30 mol%, and wherein the content of magnesium is in the range of 8 mol% to 38 mol%, preferably 23 mol% to 35 mol%, and wherein the content of aluminum is in the range of 50 mol% to 70 mol%, and wherein the intensity of the Diffraction reflectivity of the first catalyst at 43.09 ° 2θ is less than or equal to the intensity of the diffraction reflection at 44.82 ° 2θ, with preferably the intensity of the diffraction reflection at 43.08 ° 2 θ is smaller than the intensity of the reflex at 44.72 ° 2θ.

This first catalyst is in detail in WO2013 / 068905 All the preferred variants and production methods given there can also be used in the context of the present invention.

• (i) Bereitstellung einer Aluminiumquelle, vorzugsweise einer feinteiligen Aluminiumoxid- und/oder Aluminiumhydroxidmodifkation,
• (ii) Inkontaktbringen der feinteiligen Aluminiumquelle mit einer aufschmelzbaren beziehungsweise löslichen Co-haltigen Verbindung und zumindest mit einem weiteren auflösbarem oder aufschmelzbarem Metallsalz ausgewählt aus der Gruppe Ba, La Sr,
• (iii) innige Durchmischung der Aluminiumquelle und der gelösten beziehungsweise aufgeschmolzenen Metallsalze,
• (iv) Trocknung des Gemisches,
• (v) Tieftemperaturkalzinierung des Gemisches,
• (vi) Abformung beziehungsweise Formgebung,
• (vii) Hochtemperaturkalzinierung.

In the case of the first catalyst comprising a hexaaluminate, it is provided that the hexaaluminate-containing phase contains cobalt and at least one further metal from the group Ba, Sr, La, the Co content being in the range from 2 mol% to 15 mol%, preferably from 3 mol% to 10 mol% and more preferably in the range of 4 mol% to 8 mol%, the content of further metal from the group Ba, Sr, La in a range from 2 mol% to 25 mol%, preferably from 3 mol% to 15 mol%, more preferably from 4 mol% to 10 mol%, and the content of Al is in the range of 70 mol% to 90 mol%, and the first catalyst is an oxide minor phase in the range of 0 wt% to 50 Wt .-%, preferably 3 wt .-% to 40 wt .-%, more preferably 5 wt .-% to 30 wt .-%, preferably selected from the group of theta-alumina, alpha-alumina, LaAlO ₃ , BaAl ₂ O ₄ , SrAl ₂ O ₄ , CoAl ₂ O ₄ , La-stabilized alumina, La-stabilized alumina hydroxide, and the BET surface area of hexaaluminate igen catalyst greater than 2 m ² / g, preferably greater than 4 m ² / g, more preferably greater than 8 m ² / g and especially preferably greater than 15 m ² / g. This first catalyst is preferably preparable by the following process:

• (i) providing an aluminum source, preferably a finely divided aluminum oxide and / or aluminum hydroxide modification,
• (ii) contacting the finely divided aluminum source with a fusible or soluble Co-containing compound and at least one further dissolvable or fusible metal salt selected from the group Ba, La Sr,
• (iii) thorough mixing of the aluminum source and the dissolved or molten metal salts,
• (iv) drying the mixture,
• (v) cryogenic calcination of the mixture,
• (vi) impression or shaping,
• (vii) high temperature calcination.

This first hexaaluminate-containing catalyst is described in detail in FIG WO2013 / 118078 All the preferred variants and production methods given there can also be used in the context of the present invention.

Dry reforming in the sense of the invention is understood to mean the conversion of methane (or natural gas) and CO ₂ under heat supply and optionally in the absence of water to synthesis gas having a stoichiometric ratio of H ₂ and CO of preferably 1: 1: CH ₄ + CO ₂ ↔ 2CO + 2H ₂

The dry reforming in the context of the invention also includes the reaction of CH ₄ (or natural gas) and CO ₂ in the presence of water vapor, wherein water vapor is in the ratios given below to methane.

According to a preferred embodiment of the process according to the invention, it is provided that at least one hydrocarbon heavier than CH _{4 is} steam reformed together with steam in the presence of another, second catalyst upstream of the dry reforming to produce that CH ₄ which is then subjected to dry reforming becomes. The second catalyst may be a nickel-based catalyst suitable for steam reforming. Here, ordinary, known catalysts can be used.

Natural gas is preferably used as the input or feed stream, which has methane as its main constituent. In the event that this natural gas or the feed stream contains a certain proportion of higher hydrocarbons (eg ethane, propane, etc.) or naphtha (in particular hydrocarbons having 5 to 12 carbon atoms) is used as the feed stream or its component , can be converted by the above-described (optional) steam reforming the heavier hydrocarbons to methane, which is then further reacted in the actual dry reforming step to the synthesis gas.

Furthermore, according to a preferred embodiment of the method according to the invention, it is provided that CO ₂ contained in the synthesis gas stream is separated off (eg by means of PSA or washing by means of a suitable detergent, eg an amine- or methanol-containing detergent) and at least partially (or completely ) is recycled to the feed stream, preferably upstream of the steam and / or dry reforming.

However, the CO ₂ added to the feedstream may also be partly or completely derived from another source (import), where e.g. B. CO _{2 is} recycled from other processes.

The dry reforming is preferably carried out at a pressure in the range from 2 bar to 70 bar, preferably at a pressure in the range from 10 bar to 40 bar, most preferably at a pressure in the range from 20 to 40 bar.

Furthermore, it is preferably provided that the feed stream has a CH ₄ content in the range of 20 vol .-% to 45 vol .-%. The CO ₂ content of the feed stream is preferably in the range from 20% by volume to 45% by volume. When water vapor is used in the dry reforming, the water vapor content of the feed gas is preferably in the range of 0% by volume to 40% by volume. Furthermore, the feed stream can have 0% by volume to 40% by volume of hydrogen.

Furthermore, it is preferably provided that the molar CO ₂ / CH ₄ ratio is in the range from 0 to 1.5, preferably in the range of 0.3 to 1.4, preferably in the range of 0.5 to 1.3, on most preferably in the range of 0.7 to 1.2.

Finally, it is preferably provided that when using steam, the H ₂ O / CH ₄ ratio in the feed stream is less than 2.0, preferably less than 1.5, preferably less than 1.0, most preferably less than 0.9.

According to a further embodiment of the invention, it is provided that the dry reforming of methane and CO _{2 is carried out} in the presence of the first catalyst in at least one reactor tube, wherein the first catalyst forms a first layer of a catalyst bed arranged in the reactor tube and wherein said catalyst bed at least one further Layer of another (third) catalyst, which is different from the first catalyst.

The advantage of such a 2-layer reactor filling, in which the (soot-resistant) first catalyst is arranged in the inlet region of the reactor and then a conventional further (third) catalyst (eg a known nickel-based reforming catalyst), usually to the exit is applied to a synthesis gas with high CO content, is that the conventional additional or third catalyst can bring the reaction closer to the thermodynamic equilibrium, so that a higher conversion can be achieved, which is exploited that at the reactor exit slightly uncritical conditions prevail in terms of the risk of coking. Furthermore, comparatively inexpensive conventional (third) catalysts can be used, which reduces costs (compared to using only the first catalyst). Unless the optional steam reforming is carried out (see above) and accordingly no second catalyst is present, the third catalyst is also referred to as the second catalyst.

According to a preferred variant of the method according to the invention, it is provided that when using the nickel-magnesium mixed oxide and magnesium spinel-containing first catalyst, the synthesis gas stream produced has a H2 / CO ratio in the range of 1.0 to 2.0.

Furthermore, according to a preferred variant of the method according to the invention, when the hexaaluminate-containing first catalyst is used, the generated synthesis gas stream has an H2 / CO ratio in the range from 0.5 to 2.0.

Preference is further provided that the generated synthesis gas stream, in particular when using the hexaaluminate-containing first catalyst after the dry reforming is abruptly or rapidly cooled, z. Example, by applying / quenching the synthesis gas stream with a cooling medium (eg., Water) to avoid side reactions, especially a coking according to Boudouard reaction (2CO ↔ CO ₂ + C) by the high CO content in the gas. Even when using the two-layer catalyst (see above), the cooling is preferably carried out downstream of the reactor.

Further features and advantages of the present invention will be explained in the following description of embodiments of the invention with reference to the figures. It shows:

1 a scheme of the method according to the invention; and

2 a reactor tube with a two-bed catalyst bed used in the process.

1 shows a block diagram of the inventive method. In the examples described below, H ₂ and CO-containing synthesis gas (GHSV preferably in the range from 500 to 5000 based on the dried synthesis gas) are produced in the presence of the above-described first catalyst, wherein in principle for the production of the synthesis gas the above-mentioned compositions, pressures ( preferably in the range from 2 bar to 70 bar) and temperatures (preferably 700 ° C. to 980 ° C. at the outlet of the dry reforming 50 ) can be used.

The feed stream 10 is preheated first 20 , This can be z. B. be made in a convection zone of a furnace used by means of a heat exchanger, the feed stream 10 preheated against combustion heat. Unless the use 10 initially composed of heavier hydrocarbons, these are by means of an optional steam reforming 30 upstream of the actual dry reforming 50 converted to methane (preferably using a known or conventional second catalyst), which then as part of the feed stream 10 preferably in turn preheated 40 (for example in the convection zone one for dry reforming 50 used furnace by means of a heat exchanger against combustion heat) and then in the dry reforming 50 is driven. Indicates the feed stream 10 from the outset, no heavier hydrocarbons, but methane, the feed stream 10 after preheating 20 (eg in the oven of dry reforming 50 , see above) (directly) into the dry reforming 50 where methane in the presence of the above-described first catalyst K with the in the feed stream 10 existing CO _{2 is converted} to a H ₂ and CO-containing synthesis gas stream. The dry reforming 50 can z. B. in one or more vertically oriented reactor tubes 51 (see eg. 2 ) are made, the z. B. are arranged in a radiation zone of the furnace and heated by combustion heat (eg., Provided by one or more burners). In the reactor tubes 51 is the first catalyst according to the invention, for. B. in the form of a bed or a catalyst bed. According to an embodiment variant, which in 2 is shown, it can be provided that the catalyst bed B has at least two (horizontal) layers, of which a first layer which is closer to the reactor tube inlet, through the first catalyst K according to the invention and the further second layer by a further, third catalyst K 'is formed, which is different from the first catalyst K. The third catalyst K 'may in particular be a known, conventional (eg nickel-based) catalyst for steam reforming.

After the reform 50 the synthesis gas stream is cooled 60 , z. B. by applying water, and existing in the synthesis gas stream CO ₂ is separated from the synthesis gas stream 70 and into the feed stream 10 returned (CO ₂ -recycle) 80 , Possibly. can additionally fresh CO ₂ 90 the feed stream 10 be added. The released from CO ₂ synthesis gas stream 100 is further dried and fed as a product stream for further use.

Example 1:

According to a first example, a feed stream 10 comprising 34% by volume of CH ₄ , 22% by volume of CO ₂ , 44% by volume of H ₂ O preheated to a temperature of 500 ° C. and into dry reforming 50 where methane at a temperature of 875 ° C and a pressure of 30 bar in the presence of the above-described first catalyst K, the nickel-magnesium mixed oxide and the magnesium spinel having, in the feed stream 10 existing CO ₂ to a synthesis gas stream 100 is reacted, which in the present case has a H ₂ / CO ratio of 2: 1. That in the synthesis gas 100 contained CO ₂ is separated 70 and the feed stream 10 partially or completely added 80 ,

Example 2:

According to another example, a feed stream 10 comprising 46 vol .-% CH ₄ , 36 vol .-% CO ₂ , 18 vol .-% H ₂ O preheated to a temperature of 500 ° C. 20 and in dry reforming 50 driven, where methane at a temperature in the amount of 875 ° C and a pressure of 30 bar in the presence of the hexaaluminate-containing first catalyst K described above with the in the feed stream 10 existing CO ₂ to a synthesis gas stream 100 is reacted, which in the present case has a H ₂ / CO ratio of 1: 1. That in the synthesis gas 100 contained CO ₂ is separated 70 and the feed stream 10 at least partially or completely added 80 , LIST OF REFERENCE NUMBERS 10 feed stream 20 preheating 30 Optional steam reforming 40 preheating 50 dry reforming 51 Reactor or reactor tube 60 cooling 70 CO ₂ removal 80 CO ₂ recycling 90 CO ₂ feed 100 Synthesis gas stream B catalyst bed K First catalyst K ' Third catalyst

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2013/068905 [0014]
• WO 2013/118078 [0016]

Cited non-patent literature

• G. Kurz, S. Teubner, petroleum. Kohl, 43 (1990) 171 [0005]

Claims (14)

Process for producing a H ₂ and CO-containing synthesis gas ( 100 ), comprising the steps: - providing a feedstream ( 10 ) comprising methane, and - reforming ( 50 ) of methane of the feedstream ( 10 ) with CO ₂ in the presence of a first catalyst (K) comprising a nickel-magnesium mixed oxide and a magnesium spinel or having a hexaaluminate, to produce a synthesis gas stream comprising H ₂ and CO, wherein the H ₂ / CO ratio in the range from 0.5 to 3.0. Process according to claim 1, characterized in that the feedstream ( 10 ) Comprises natural gas and / or naphtha. A method according to claim 1 or 2, characterized in that the feed stream ( 10 ) together with water vapor in the presence of a second catalyst of a steam reforming ( 30 ), before the said reforming ( 50 ) of methane with CO ₂ , wherein at least one hydrocarbon of the feed stream ( 10 ), which is heavier than methane, is converted to methane, which is subsequently converted to the synthesis gas in the reforming with CO ₂ . Method according to one of the preceding claims, characterized in that CO _{2 is added} to the feed stream ( 80 . 90 ). A method according to claim 4, characterized in that at least part of the CO ₂ entering the feedstream ( 10 ), is separated from the synthesis gas stream ( 70 ), and / or that at least part of the CO ₂ entering the feedstream ( 10 ), and in particular not reforming ( 50 ) and / or steam reforming ( 30 ) comes from. Method according to one of the preceding claims, characterized in that the reforming ( 50 ) of methane and CO ₂ in the presence of the first catalyst (K) in at least one reactor tube ( 51 ), wherein the first catalyst (K) has a first layer in the reactor tube ( 50 ) and wherein said catalyst bed (B) has at least one further layer having a further, third catalyst (K ') different from the first catalyst (K). Method according to one of the preceding claims, characterized in that the reforming ( 50 ) is carried out in a temperature range from 500 ° C to 1100 ° C, preferably from 650 ° C to 1000 ° C, most preferably from 700 ° C to 980 ° C. Method according to one of the preceding claims, characterized in that the reforming ( 50 ) is carried out at a pressure in the range from 2 bar to 70 bar, preferably at a pressure in the range from 10 bar to 40 bar, most preferably at a pressure in the range from 20 to 40 bar. Method according to one of the preceding claims, characterized in that the feed stream ( 10 ) a CH ₄ content in the range of 20% to 45% by volume, a CO ₂ content in the range of 20% to 45% by volume, a water vapor content in the range of 0% by volume. % to 40 vol .-% and in particular has a hydrogen content in the range of 0 vol .-% to 40 vol .-%. Method according to one of the preceding claims, characterized in that the molar CO ₂ / CH ₄ ratio in the feed stream ( 10 ) is in the range of 0 to 1.5, preferably in the range of 0.3 to 1.4, preferably in the range of 0.5 to 1.3, most preferably in the range of 0.7 to 1.2, Method according to one of the preceding claims, characterized in that the H ₂ O / CH ₄ ratio in the feed stream ( 10 ) is less than 2.0, preferably less than 1.5, preferably less than 1.0, most preferably less than 0.9. Method according to one of the preceding claims, characterized in that when using the nickel-magnesium mixed oxide and a magnesium spinel having the first catalyst (K), the generated synthesis gas stream has a H ₂ / CO ratio in the range of 1.0 to 2.0. Method according to one of the preceding claims, characterized in that when using the hexaaluminate having the first catalyst (K) of the generated synthesis gas stream has a H ₂ / CO ratio in the range of 0.5 to 2.0. Method according to one of the preceding claims, characterized in that the generated synthesis gas stream is cooled ( 60 ).

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