Method for producing hydrogen from CO-rich gas

Abstract

The present invention relates to a method for enriching a synthesis gas with hydrogen by contacting the synthesis gas with a water gas shift catalyst, wherein the synthesis gas is a CO-rich synthesis gas comprising at least 15% by volume CO and at least 1 ppmv of sulfur, and the water gas shift catalyst comprises Zn, Al, optionally Cu, and an alkali metal or alkali metal compound; the water gas shift catalyst is chromium (Cr) and iron (Fe) free and has a pore volume of 240 ml / kg or more as determined by mercury porosimetry.

Description

[Technical Field]

[0001] The present invention relates to a method for enriching synthesis gas with hydrogen by a water-gas shift reaction, in special cases of CO-rich gases having a substantial amount of sulfur (S), i.e., gases containing at least 15 volume% CO and at least 1 ppmv of sulfur, for example 15 ppmv, 250 ppmv, or 5 volume% sulfur (these are particularly demanding for water-gas shift catalysts, for example, in terms of mechanical stability and selectivity). Such CO-rich gases are produced, for example, from the gasification of waste, biomass, or other carbonaceous materials, or, for example, from the partial oxidation of hydrocarbons. More specifically, the present invention relates to a method for enriching synthesis gas containing at least 15 volume% CO and at least 1 ppmv of S with hydrogen by using an iron-free water-gas shift catalyst. [Background technology]

[0002] The water-gas shift is a well-known method for increasing the hydrogen content of synthesis gas, which is a gas produced, for example, by steam reforming of hydrocarbon feedstocks, and which contains hydrogen and carbon monoxide. The water-gas shift allows for an increase in the hydrogen yield of synthesis gas and a decrease in the carbon monoxide content through the following equilibrium reaction: CO + H2O = CO2 + H2

[0003] Synthesis gas used as a feed material for water-gas shift reactions can be obtained by various methods, for example, by steam reforming of hydrocarbon feed material gases, such as natural gas or naphtha, by partial oxidation or autothermal reforming of hydrocarbon feed material gases, or by gasification of solid carbonaceous materials such as biomass, waste, or petroleum coke. Such gases can also be obtained as pyrrolysis-off gases from the thermal decomposition of carbonaceous materials. The CO content of synthesis gas varies considerably depending on the feed material source and the conditions of synthesis gas preparation. For example, synthesis gas obtained by gasification or partial oxidation almost always has a high CO content. This invention relates to such CO-rich gases having a CO concentration of 15% by volume or more. Furthermore, significant amounts of sulfur are present, namely at least 1 ppmv, e.g., 15 ppmv, 250 ppmv, or 5% by volume of sulfur.

[0004] Typically, hydrogen yield is optimized by performing an exothermic water-gas shift in separate reactors, such as separate adiabatic reactors with interstage cooling. Often, the first reactor is a high-temperature shift (HTS) reactor with an HTS catalyst inside, and the second reactor is a low-temperature shift (LTS) reactor with an LTS catalyst inside. A medium-temperature shift (MTS) reactor may also be included, and it may be used alone or in combination with an HTS or LTS reactor. Typically, HTS reactors are operated in the range of 300–570°C, and LTS reactors in the range of 180–240°C. MTS reactors are usually operated in the temperature range of 210–330°C.

[0005] The established types of HTS catalysts widely available on the market are Fe-based catalysts, typically based on the iron / chromium (Fe / Cr) system, with small amounts of other components (typically including copper). However, when operated with CO-rich gas, Fe-based catalysts are prone to over-reduction and thus form undesirable iron carbides: Fe-based HTS catalysts have inherent problems when operated with synthesis gas that has a high carbon monoxide content and / or a low oxygen-to-carbon ratio. This is due to the possibility that the over-reduction of the catalyst will result in its complete or partial iron carbide or conversion of elements to iron, which leads to decreased selectivity (increased hydrocarbon formation) and loss of mechanical strength of the molded catalyst, which can result in increased pressure drop throughout the reactor. This issue is discussed in detail in [L. Lloyd, DE Ridler and MV Twigg Ch. 6, 283-339 in MV Twigg (ed.) Catalyst Handbook 2nd ed. Manson Publishing, Frome, England 1996] (Non-Patent Literature 1) and in [PE Hojlund-Nielsen and J. Bogild-Hansen “Conversion limitations in hydrocarbon synthesis”, Journal of Molecular Catalysis 17 (1982), 183-193] (Non-Patent Literature 2).

[0006] To overcome these problems, for example, US9365421 (Patent Document 1) discloses a reactor design in which a portion of the shifted synthesis gas is recycled to the inlet of a water-gas shift reactor, thereby reducing the carbon monoxide concentration. This allows for the use of iron-based catalysts, but increases the capital expenditures (Capex) and operating expenses (Opex) of the plant in which they are used.

[0007] US7510696 (Patent Document 2) solves the problem of avoiding over-reduction of Fe-based shift catalysts in a different way, namely by adding an oxidizing gas to the material supplied to the water-gas shift reactor.

[0008] Applicant US10549991 (Patent Document 3) discloses a recycling of product gases for operating a water-gas shift reactor in a manner that can handle aggressive and reactive synthesis gases, such as gases having high CO and H2 content.

[0009] Applicant US2019039886A1 (Patent Document 4) discloses an ammonia process and plant based on an ATR-self-thermal reformer. Synthesis gas is produced by reforming, for example, about 27 volume% CO, and shifted in a high-temperature shift utilizing an accelerated zinc-aluminum oxide catalyst (HTS catalyst) at a steam-to-carbon ratio of less than 2.6 in the reforming. More specifically, the HTS catalyst, in its active form, includes a Zn / Al molar ratio in the range of 0.5 to 1.0, and an alkali metal content in the range of 0.4 to 8.0 wt% and a copper content in the range of 0 to 10%, based on the weight of the oxidized catalyst. This cited document does not mention, at least, the provision of a sulfur-containing gas supply material in the shift step.

[0010] Applicant US2010000155A1 (Patent Document 5) discloses a chromium-free aqueous gas shift catalyst, particularly an HTS catalyst comprising a mixture of zinc alumina spinel and zinc oxide in combination with an alkali metal selected from the group consisting of Na, K, Rb, Cs and mixtures thereof, in its active form, the catalyst having a Zn / Al molar ratio in the range of 0.5 to 1.0 and an alkali metal content in the range of 0.4 to 8.0 wt% based on the weight of the oxidized catalyst. The synthesis gas to HTS is said to typically contain 5 to 50 volume% CO. The HTS catalyst is resistant to impurities present at low concentrations, such as sulfur, i.e., H2S up to 0.4 ppm. In Example 28, 1.8 g / cm³ 3The catalyst having a density is exposed to 10% H2S to sulfurize the catalyst; therefore, this H2S is not part of the gas supplied when carrying out the water-gas shift. Accordingly, this cited literature also does not mention supplying a gas containing a significant amount of sulfur, i.e., significantly higher than 0.4 ppm of H2S, to the shift step.

[0011] Applicant EP2300359B1 (Patent Document 6) discloses a method for operating an HTS reactor under conditions in which the synthesis gas entering the reactor has a specific range of oxygen-to-carbon molar ratio (O / C ratio) of 1.69 to 2.25. The catalyst, in its active form, comprises a mixture of zinc alumina spinel and zinc oxide, combined with a co-catalyst in the form of an alkali metal selected from the group consisting of Na, K, Rb, Cs and mixtures thereof, wherein the catalyst has a Zn / Al molar ratio in the range of 0.5 to 1.0 and an alkali metal content in the range of 0.4 to 8.0% by weight based on the weight of the oxidized catalyst, and the catalyst is 1.8 g / cm³ 3 It has a density of [value missing]. Synthesis gas for HTS is said to typically contain 5-50 volume% CO. This cited literature does not mention, at least, the supply of sulfur-containing feed gas in the shift step.

[0012] US2006002848A1 (Patent Document 7) discloses a method for carrying out an equilibrium-limited chemical reaction in a single-step process channel. This method is suitable for carrying out a water-gas shift reaction using a catalyst containing copper, zinc, and aluminum, and using a feed material gas with a high CO content, i.e., 1 to 20 mol% CO. This cited document does not mention, at least, the use of a feed material gas containing sulfur in the shift step. [Prior art documents] [Patent Documents]

[0013] [Patent Document 1] US9365421

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Non-Patent Document

[0014]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0015] [[ID=4G]] Therefore, an object of the present invention is to provide a method for the operation of water-gas shift conversion that overcomes the above problems of over-reduction of Fe-based water-gas shift catalysts in a simple manner.

[0016] Another object of the present invention is to provide an excellent water-gas shift conversion method, particularly an HTS method, that can tolerate a feed material gas containing not only high levels of CO but also high levels of S, such as H2S.

[0017] Another object of the present invention is to provide a simpler and, by extension, less expensive water-gas shift conversion method than prior art methods, particularly the HTS method. [Means for solving the problem]

[0018] These and other objectives are addressed by the present invention.

[0019] Accordingly, the present invention relates to a method for enriching synthesis gas with hydrogen by contacting the synthesis gas with a water-gas shift catalyst, wherein the synthesis gas is a CO-rich synthesis gas containing at least 15 volume% CO and at least 1 ppmv, e.g., 15 ppmv, 250 ppmv, or 5 volume% sulfur, the water-gas shift catalyst comprises Zn, Al, optionally Cu, and alkali metals or alkali metal compounds, the water-gas shift catalyst does not contain chromium (Cr) or iron (Fe), and the water-gas shift catalyst has a pore volume of 240 ml / kg or more, e.g., 250 ml / kg or more, e.g., 240-380 ml / kg or 300-600 ml / kg, as determined by mercury intrusion.

[0020] Mercury intrusion is carried out in accordance with ASTM D4284.

[0021] For the purposes of this application, unless otherwise stated, the percentage of a given compound or combination of compounds in a gas is given on a volume basis and on a wet basis. For example, 15 vol% CO means 15 vol% on a wet basis.

[0022] As used herein, the phrase "chromium-free and iron-free" means that the Fe content is less than 1% by weight, or the Cr content is less than 1% by weight. For example, the Fe or Cr content is undetectable.

[0023] In one embodiment, the synthesis gas contains 1 ppmv to 5 volume% sulfur.

[0024] As used herein, sulfur means H2S and / or COS, i.e., sulfur is assumed to exist as H2S, COS, or a combination thereof. Synthesis gas could be subjected to desulfurization, for example, by passing it over a ZnO guard, but equilibrium slip of sulfur exists from such a guard. The type of catalyst used in the method of the present invention is not only capable of handling CO-rich gases but is also resistant to exposure to sulfur and can be used in sulfur-containing gases as well.

[0025] This represents a significant advantage because the alkali-accelerated Zn-Al oxide catalyst used in the method of the present invention is far less expensive than Co-Mo-based catalysts, i.e., sour shift catalysts typically used to carry out water-gas shift reactions in the presence of sulfur compounds.

[0026] Therefore, it is found that the present invention not only eliminates problems associated with catalytic over-reduction, but also eliminates the need to use expensive CoMo catalysts or to adapt expensive and cumbersome process schemes involving recycling and dilution, as disclosed in the prior art. Thus, an excellent process is provided.

[0027] CO-rich gases often contain sulfur. Therefore, it is significant that, surprisingly, the catalyst used in the present invention retained most of its initial activity, e.g., over 70%, after 445 hours of operation at 380°C, even when exposed to synthesis gas containing a significant amount of sulfur, e.g., 15 ppmv of H2S. Furthermore, deactivation did not follow a linear path and was most pronounced at the start of the experiment. Thus, an exponential deactivation model that fits the data very well showed a residual activity of 48% of the initial activity. This means that even after longer periods, e.g., after several years of exposure to synthesis gas containing 15 ppmv of sulfur, the catalyst would still retain 48% of its initial activity.

[0028] A characteristic feature of such gases containing high amounts of CO and S, i.e., at least 15 vol% CO and at least 1 ppmv, e.g., 15 ppmv, 250 ppmv, or 5 vol% sulfur, is the higher equilibrium content of COS. Equilibrium calculations show that in CO / H2O gases moving from 100 vol% H2O to 50 / 50 CO / H2O, the COS / H2S ratio increases from 0 to 0.0128 (300°C, 25 bar). This ratio is independent of the total sulfur content in the gas. Therefore, the COS content in gases containing CO, H2O, and S increases with increasing CO content.

[0029] Recently, other chromium-free HTS catalysts have emerged, such as those described in [M. Zhu and IE Wachs, Catalysis Today 311 (2018), 2-7], but these are iron-based as the active metal and therefore suffer from the same selectivity and mechanical strength problems as Fe / Cr and Cu / Fe / Cr catalysts. Furthermore, CO-rich synthesis gas used as a feed material for HTS catalysts often contains sulfur, as mentioned earlier, which leads to catalyst deactivation. As described above, the catalyst of the present invention is not highly susceptible to sulfur poisoning at the relevant operating temperatures. In the case of high-temperature shifts, the operating temperature is typically in the range of 300-570°C or 300-550°C.

[0030] The present invention enables a method for enriching such CO-rich synthesis gas with hydrogen by a water-gas shift reaction using an iron-free and chromium-free catalyst.

[0031] This also provides a more sustainable and environmentally friendly method because the catalyst does not contain Cr. Furthermore, the catalyst, which does not contain Fe, significantly reduces or even eliminates the undesirable formation of hydrocarbons, such as methane, in the process.

[0032] The catalyst of the present invention has also been found to be more heat-resistant and free from the risk of excessive loss of mechanical strength due to over-reduction. Therefore, the present invention enables the execution of a water-gas shift process with both a lower risk of pressure drop across the HTS reactor and the possibility of operation at lower recycling rates or even without recycling, compared to operation using an Fe-based catalyst. Thus, the present invention offers potential economic advantages compared to current state-of-the-art processes.

[0033] Fe-based catalysts, such as Fe / Cr catalysts, and Zn-Al-based catalysts, both possess a spinel structure and are well known to promote reduction. Therefore, when ZnO is exposed to temperatures above 500°C, for example, 550°C, 570°C, or 600°C, it becomes oxygen-deficient even in air, i.e., ZnO is reduced to ZnO 1-x It is well known that it is converted to [a certain substance]. Furthermore, unexpectedly, it was found that the catalyst is thermally stable at these temperatures.

[0034] The term "thermally stable" means that the space-time yield (STY) (mol / kg / h), as a function of the catalyst's flow time, remains substantially unchanged for most of the flow time, for example, for more than 70% of that time, e.g., within 5%.

[0035] In addition, compared to, for example, the use of an Fe / Cr catalyst, the present invention achieves a more robust process because it has higher resistance to exposure to synthesis gas with a low oxygen / carbon ratio. The term "low oxygen / carbon ratio" refers to a highly reducing gas with a low O / C molar ratio, i.e., 1.5 or less. The O / C ratio is calculated as O / C = ([CO] + 2*[CO2] + [H2O]) / ([CO] + [CO2]).

[0036] The method of the present invention, particularly the method for HTS, can tolerate lower steam / dry gas levels in the feed material gas (synthesis gas) than conventional methods using, for example, Fe / Cr catalysts, thereby reducing the risk of catalyst damage that would otherwise cause pressure drop problems. This means that it may be possible to operate with a smaller percentage of recirculation or even without recirculation, resulting in better savings by reducing capital expenditures and operating costs. Thus, it will be understood that lower steam / dry gas levels mean lower O / C ratios.

[0037] The water-gas shift catalyst has pore volumes of 240–380 ml / kg, 250–380 ml / kg, or 300–600 ml / kg, as determined by mercury intrusion. Apart from catalysts with these pore volumes that enable handling variable gas supply materials rich in CO and sulfur, the use of these pore volumes allows the HTS reactor to operate with reduced or no leaching of alkali metals or alkali metal compounds, even in transient conditions, such as during startup. Thus, the water-gas shift catalyst does not lose activity to a significant degree due to alkali or alkali metal compounds that are no longer present, for example.

[0038] In another embodiment, the pore volume is measured by mercury intrusion and is in the range of 300-500 ml / kg, for example, 300, 350, 400, 450 or 500 ml / kg, or in the range of 320-430 ml / kg.

[0039] In one embodiment, the water-gas shift catalyst is a high-temperature shift (HTS) catalyst, and the water-gas shift reactor is an HTS reactor that operates at a temperature in the range of 300 to 570°C and also optionally at a pressure in the range of 2.0 to 6.5 MPa.

[0040] The synthesis gas converted on the HTS catalyst according to the present invention may be further converted to optimize hydrogen yield. However, it may also be used directly in the synthesis of important compounds, such as methanol, dimethyl ether, olefins, or aromatic compounds, or it may be converted into hydrocarbon products, i.e., synthetic fuels (synthetic fuels or synfuels), in Fischer-Tropsch (FT) synthesis or other chemical synthesis processes.

[0041] According to the present invention, a simple HTS reactor, preferably an adiabatic HTS reactor without recycling, can also be used for CO-rich gases containing at least 15 vol% CO, for example, at least 20 vol% CO, for example, at least 40 vol% CO, or more CO, for example, 50 vol% or 60 vol% CO, provided that the catalyst is a co-catalyst of appropriate composition and content, such as a Zn / Al type having copper and alkali metal compounds, as described in any of the embodiments above or below.

[0042] In one embodiment, the CO-rich synthesis gas contains at least 20% by volume of CO, but no more than 60% by volume of CO or no more than 50% by volume of CO. For example, the CO content can be 25%, 30%, 40%, 45%, or 50% by volume. The upper limit of the CO concentration is preferably 50% by volume, which may be a stoichiometric gas resulting from a water-gas shift reaction containing 50% by volume of CO and 50% by volume of H2O.

[0043] In a particular embodiment, the CO-rich synthesis gas includes: CO 30-60% by volume, H2O 30-50% by volume, CO20-5% by volume, and H2O-20% by volume.

[0044] In one embodiment, the method further includes a step for producing the synthesis gas, the step being one of the following: - Steam reforming (i.e., steam methane reforming (SMR)) of hydrocarbon feedstock gases, such as natural gas or naphtha, for example by electro-heated reforming (e-SMR); by partial oxidation of hydrocarbon feedstock gases; and autothermal reforming (ATR) of hydrocarbon feedstock gases. - Solid carbonaceous materials: for example, petroleum coke or renewable supply raw materials including biomass and / or waste, including gasification or pyrolysis of carbonaceous materials; - By combining them, for example, by combining e-SMR and ATR.

[0045] The above technology is well known in this field. For details on the more recent technology, e-SMR, please refer to applicant WO2019 / 228797A1.

[0046] In certain embodiments, pyrolysis is hydrothermal liquefaction. In another specific embodiment, pyrolysis is pyrolysis. In yet another specific embodiment, pyrolysis is gasification. Thus, in yet another specific embodiment, synthesis gas is pyrolysis-off gas from the pyrolysis of solid renewable feedstock. In yet another specific embodiment, the solid renewable feedstock is: - Lignocellulosic biomass including wood products, forestry waste and agricultural residues; and / or - Municipal waste, that is, municipal solid waste, especially its organic components.

[0047] As used herein, the term “pyrolysis” shall, for convenience, be used broadly to any decomposition process in which a material is partially decomposed at an elevated temperature (typically 250°C to 800°C or even 1000°C) in the presence (or absence of) a substoichiometric amount of oxygen. The products are typically a combined liquid and gas stream, as well as some amount of solid char. The term should be interpreted to include processes known as pyrrolysis and hydrothermal liquefaction, both in the presence and absence of a catalyst.

[0048] As used herein, "pyrolysis" also includes gasification, i.e., the gasification process. It will be understood that pyrolysis takes place in the absence of air, while gasification takes place in the presence of air.

[0049] As used herein, the term “lignocellulosic biomass” means biomass that also includes cellulose, hemicellulose, and optionally lignin. Lignin or a substantial portion thereof may be removed, for example, by a prior bleaching step. Lignocellulosic biomass is forestry waste and / or agricultural residue and includes biomass derived from plants, such as grass, e.g., natural grass (grass originating from the natural surface), wheat, e.g., wheat straw, oats, rye, reeds, bamboo, sugarcane or sugarcane derivatives, e.g., bagasse, maize, and other cereals.

[0050] As used herein, the term “urban solid waste” means waste or scraps discarded as everyday items from homes, schools, hospitals, and businesses. Urban solid waste includes packaging, newspapers, clothing, utensils, and food scraps.

[0051] In another embodiment, the method includes adding water vapor to the synthesis gas, thereby shifting the WGS reaction toward producing more hydrogen.

[0052] In one embodiment, the aqueous gas shift catalyst is a Zn / Al-based catalyst in its active form, comprising a mixture of zinc aluminum spinel and optionally zinc oxide, combined with an alkali metal compound selected from K, Rb, Cs, Na, Li and mixtures thereof, where the Zn / Al molar ratio is in the range of 0.3 to 1.5, and the alkali metal compound content is in the range of 0.3 to 10% by weight, based on the weight of the oxidized catalyst.

[0053] In one embodiment, the aqueous gas shift catalyst comprises only Zn, Al, optionally Cu, and alkali metals or alkali metal compounds.

[0054] This type of HTS catalyst typically also contains copper as another co-catalyst. This type of HTS catalyst, i.e., Cu-enhanced HTS catalyst, is described, for example, in the applicant's patents US7998897B2, US8404156B2, and US8119099B2. The catalyst of the method of the present invention differs from those catalysts in that it has a pore volume of at least 240 ml / kg, for example 250 ml / kg, for example 240-380 ml / kg or 250-380 ml / kg or 300-600 ml / kg, thereby enabling it to handle variable gas supply materials rich in CO and sulfur coming from, for example, a gasification process, without relying on expensive sour shift catalysts.

[0055] In one embodiment, the Zn / Al molar ratio is in the range of 0.5 to 1.0, and the alkali metal content is in the range of 0.4 to 8% by weight, based on the weight of the oxidized catalyst.

[0056] In one embodiment, the alkali metal content, preferably K, is in the range of 1 to 6% by weight, for example, 1 to 5% by weight or 2.5 to 5% by weight. In particular, in the latter range, the HTS operation exhibits an alkali buffering effect, and as a result, catalytic activity is maintained or even increased even if some alkali leaches out or is lost during the HTS operation (which is startup or normal operation).

[0057] In one embodiment, the Cu content ranges from 0.1 to 10 wt%, for example 1 to 5 wt%, based on the weight of the oxidized catalyst.

[0058] In one embodiment, the water gas shift catalyst is in the form of pellets, extrudates or tablets, and the particle density is 1.25 - 1.75 g / cm 3 or 1.55 - 18.85 g / cm 3 , for example 1.3 - 1.8 g / cm 3 , or for example 1.4, 1.5, 1.6, 1.7 g / cm 3 . The lower the particle density, the greater the pore volume. The term "particle" means pellets, extrudates or tablets, which are compacted, for example, by pelletizing or tabletizing from a starting catalyst material, for example from a powder, to the tablets. The density is simply measured, for example, by dividing the weight of the tablet by its geometric volume.

[0059] Typically, the density of catalyst particles, for example HTS catalysts as in the applicant's US7998897 or US8404156, is close to 2 g / cm 3 , for example up to 2.5 g / cm 3 , or about 1.8 or 1.9 g / cm 3 . These relatively high densities contribute significantly to the mechanical strength of the particles, for example tablets, and as a result, they can withstand the impact when loaded into an HTS reactor, for example from a considerable height, for example 5 m. Therefore, it is usually desirable to have a high particle density, for example 1.8 g / cm 3 or higher. Now, by compacting into a lower density shape, for example tabletizing, the pore volume of the particles increases, thereby solving the leaching problem mentioned above, and at the same time, the particles maintain sufficient mechanical strength to withstand the impact during loading or normal operation, and it has also been found that it avoids an increase in the pressure drop across the reactor during normal operation (continuous operation) due to particle breakage.

[0060] In one embodiment, the catalyst is in the form of pellets, extruded materials, or tablets, and its mechanical strength is ACS: 30-750 kp / cm². 2 For example, 130-700 kp / cm² 2 or 30-350 kp / cm² 2 It falls within the following range. ACS stands for Axial Crush Strength. Alternatively, the mechanical strength measured as SCS is in the range of 4 to 100, for example, 20 to 90 kp / cm or 40 kp / cm. SCS is an abbreviation for Side Crush Strength, also known as Radial Crush Strength. For a given tablet density, the mechanical strength can vary considerably depending on the machine used to compact the catalyst powder. A lower range of mechanical strength (ACS or SCS), for example, up to ACS: 300 or 350 kp / cm 2 A maximum SCS of 40 kp / cm corresponds to what can be obtained by a small (approximately 100 g / h) manually fed tablet machine, a so-called Manesty machine. A higher range of mechanical strength, for example, up to ACS: 750 kp / cm 2 , or SCS:90kp / cm, corresponds to what is obtained using an automated full-scale device (100kg / h), such as a Kilian RX machine equipped with a rotary press. ACS and SPS are measured in the oxidation form of the catalyst. Mechanical strength is also measured in accordance with ASTM D4179-11.

[0061] In one embodiment, the method further includes contacting the first shift gas, i.e., hydrogen-enriched synthesis gas, taken from the HTS reactor with an intermediate-temperature shift (MTS) catalyst in an MTS reactor or a low-temperature shift (LTS) catalyst in an LTS reactor. This yields a further hydrogen-enriched synthesis gas. Preferably, the hydrogen-enriched synthesis gas is passed through a CO2 removal section, such as an amine absorber, and hydrogen purification in, for example, a pressure swing adsorption unit (PSA unit), to provide hydrogen products.

[0062] A water-gas shift reactor can also function as a reverse water-gas shift reactor, thereby allowing a hydrogen and carbon dioxide-rich feed gas to undergo a reverse water-gas shift reaction. CO2 + H2 = CO + H2O It is converted to carbon monoxide and water accordingly. Using the catalyst in the method of the present invention, a high CO concentration can be tolerated in the outlet gas of the reverse water-gas shift reactor, which is not possible with Fe-based catalysts.

[0063] Furthermore, iron-containing catalysts are known to need to be operated above a certain steam / carbon molar ratio or oxygen / carbon molar ratio in the synthesis gas entering the HTS reactor to prevent the formation of iron carbides and / or elemental iron, which can lead to a serious loss of mechanical strength and, consequently, an increase in pressure drop across the reactor. Alkali-containing Zn / Al-based catalysts are not sensitive to the oxygen / carbon molar ratio and do not lose mechanical strength as a result of the low steam content in the CO-rich synthesis gas supplied to the HTS reactor during normal operation.

[0064] The advantages of this invention include: - A method, particularly for HTS, that can deal with variable gas supply materials (synthesis gas) derived from gasification, which contain not only high levels of CO (at least 15 vol%) but also sulfur (at least 1 ppmv); - A method that can tolerate lower steam / dry gas in the supply material gas (synthesis gas), thereby reducing the risk of catalyst damage that would cause pressure drop problems, especially for HTS. This means that it may be possible to operate with a smaller percentage of recirculation or even without recirculation, resulting in better savings by reducing capital expenditures and operating expenses. Thus, it will be understood that lower steam / dry gas means a lower O / C ratio; - A process, particularly for HTS, that eliminates the need for expensive CoMo catalysts to address sulfur in the feed gas. [Brief explanation of the drawing]

[0065] The only attached drawing shows a plot of the thermal stability of catalyst A during high-shift operation in Example 2.

[0066] Detailed explanation [Examples]

[0067] example Example 1: Production of Catalyst A - According to an embodiment of the present invention The catalyst was prepared by adjusting the composition according to the procedure described in Example 1 of the applicant's patent US7998897. According to ICP analysis, catalyst A contains 1.99 wt% K, 1.65 wt% Cu, 34.3 wt% Zn, and 21.3 wt% Al. Therefore, the Zn / Al molar ratio is 0.665. The catalyst was molded into 6 × 6 mm tablets. Furthermore, it has a pore volume (PV) of approximately 320 ml / kg and a filtration rate of 1.7 g / cm³. 3 This gives us the tablet density (which is simply measured by dividing the weight of the tablet by its geometric volume).

[0068] Example 2. Thermal stability of Catalyst A The experiment was conducted in a tubular reactor (ID 19 mm) heated by three external electric heaters. A 40 g tablet of catalyst A was loaded. The gas composition was 9.4 vol% CO, 37.6 vol% H2O, 6.1 vol% CO2, 45 vol% H2, and 1.9 vol% Ar. The experiment was conducted at 2.35 MPa. The duty cycles of the three external electric heaters were adjusted to obtain near isothermal conditions. The catalyst bed temperature was measured using 10 internal thermoelectric elements, and the difference between the inlet and outlet temperatures was always less than 2°C. The concentrations of all components were periodically measured in both the inlet and dry outlet gases by GC (calibrated against gas mixtures of known compositions). All measurements were performed at 397°C (outlet temperature) with a gas space velocity GHSV = 20000 Nl / kg / h. Catalyst aging (between measurements) was performed by maintaining all operating parameters except the temperature, which was raised to 570°C. The activity at 397°C, expressed as space-time yield (STY) (mol / kg / h) as a function of flow time, is shown in the attached figure. It is clear that after an initial decrease in activity, the catalyst stabilizes after 400-600 hours and remains substantially unchanged for the remainder of the test.

[0069] In this example, the aging temperature of 570°C was achieved by external heating instead of using a CO-rich gas; that is, this example demonstrates the thermal exposure that would result from the use of a CO-rich gas. This was done because the experimental setup allowed for such much better temperature control. A CO-rich gas with a composition of 35 vol% CO, 45 vol% H2O, 5 vol% CO2, and 15 vol% H2 was equilibrated at an inlet temperature of approximately 350°C, reaching a temperature of 570°C at the outlet of the adiabatic reactor.

[0070] Example 3. Resistance to dry synthesis gas As a test of tolerance to low oxygen / carbon ratios, catalyst A was exposed to dry synthesis gas for 1.4 hours. Dry synthesis gas is a highly reducing gas that does not contain H2O and has a low O / C molar ratio, i.e., 1.5 or less. In this example, the dry synthesis gas contained 47.5 vol% H2, 45.7 vol% CO, 4.8 vol% CO2, and 2.0 vol% Ar, with an oxygen / carbon (O / C) ratio of 1.10. This exposure occurred after 49 hours of operation in normal (wet) synthesis gas. The pressure drop ΔP across the reactor was measured before and after exposure. Before and after exposure, standard (wet) synthesis gas with a composition of 29.7 vol% H2, 28.6 vol% CO, 3.0 vol% CO2, 1.3 vol% Ar, and 37.5 vol% H2O, with an O / C ratio of 2.28, was supplied. The reactor outlet pressure was controlled by a back pressure regulator at a set point of 5.07 MPa. The pressure difference ΔP between the reactor outlet and inlet was measured after exposure to dry synthesis gas, and operation was subsequently repeated with wet synthesis gas at O / C = 2.28. The pressure drop was found to be very small, less than 0.5 bar, and was almost the same before and after exposure to dry synthesis gas.

[0071] Example 4. Comparison The Cu-enhanced Fe / Cr catalyst (Catalyst B) was subjected to the same tests as described in Example 3, with the only difference being that exposure to dry synthesis gas was induced 73 hours after normal operation. The increase in pressure drop after exposure to dry synthesis gas was found to be substantially about 15 bar.

[0072] Clearly, catalyst A exhibits very high resistance to low O / C synthesis gas, while catalyst B, i.e., the Cu-promoted Fe / Cr catalyst, exhibits very low resistance. While this application relates to the invention described in the claims, it may also encompass the following other embodiments. 1. A method for enriching synthesis gas with hydrogen by contacting the synthesis gas with a water-gas shift catalyst in a water-gas shift reactor, wherein the synthesis gas is a CO-rich synthesis gas containing at least 15 volume% CO and at least 1 ppmv, for example, 15 ppmv, 250 ppmv, or 5 volume% sulfur, the water-gas shift catalyst contains Zn, Al, optionally Cu, and alkali metals or alkali metal compounds, the water-gas shift catalyst does not contain chromium (Cr) or iron (Fe), and the water-gas shift catalyst has a pore volume of 240 ml / kg or more, for example, 250 ml / kg or more, for example, 240-380 ml / kg or 250-380 ml / kg or 300-600 ml / kg, as determined by mercury intrusion. 2. The method according to 1, wherein the water-gas shift catalyst is a high-temperature shift (HTS) catalyst, and the water-gas shift reactor is an HTS reactor operated at a temperature in the range of 300 to 570°C and also optionally at a pressure in the range of 2.0 to 6.5 MPa. 3. The method according to 2 above, wherein the HTS reactor is a non-recyclable adiabatic HTS reactor. 4. The method according to any one of 1 to 3 above, wherein the CO-rich synthesis gas contains at least 20% by volume of CO, but not exceeding 60% by volume of CO. 5. The CO-rich synthesis gas contains 30-60% by volume of CO and H 2 O at 30-50% by volume, CO 2 0-5% by volume, H 2 The method according to item 4 above, comprising 0 to 20% by volume. 6. The method according to any one of 1 to 5 above, further comprising a step for producing the synthesis gas, wherein the step is one of the following: - Steam reforming (i.e., steam methane reforming (SMR)) of hydrocarbon feedstock gases, such as natural gas or naphtha, for example by electro-heated reforming (e-SMR); by partial oxidation of hydrocarbon feedstock gases; and autothermal reforming (ATR) of hydrocarbon feedstock gases. - Thermal decomposition of carbonaceous materials, including gasification or pyrolysis of solid carbonaceous materials, such as petroleum coke or renewable supply materials including biomass and / or waste; - Combinations of these, for example, combinations of e-SMR and ATR. 7. The method according to any one of 1 to 6 above, wherein the aqueous gas shift catalyst is a Zn / Al-based catalyst comprising, in its active form, a mixture of zinc aluminum spinel and optionally zinc oxide, and an alkali metal compound selected from K, Rb, Cs, Na, Li and mixtures thereof, wherein the Zn / Al molar ratio is in the range of 0.3 to 1.5, and the content of the alkali metal compound is in the range of 0.3 to 10% by weight, based on the weight of the oxidized catalyst. 8. The method according to any one of 1 to 7 above, wherein the aqueous gas shift catalyst comprises only Zn, Al, optionally Cu, and alkali metals or alkali metal compounds. 9. The method according to any one of 1 to 8 above, wherein the Zn / Al molar ratio is in the range of 0.5 to 1.0 and the alkali metal content is in the range of 0.4 to 8% by weight, based on the weight of the oxidized catalyst. 10. The method according to any one of 1 to 9 above, wherein the alkali metal content, preferably K, is in the range of 1 to 6% by weight, for example, 1 to 5% by weight or 2.5 to 5% by weight. 11. The method according to any one of the above 1 to 10, wherein the Cu content is in the range of 0.1 to 10% by weight, for example, 1 to 5% by weight, based on the weight of the oxidized catalyst. 12. When the aqueous gas shift catalyst is in the form of pellets, extruded or tablets, and the particle density is measured, for example, by dividing the weight of the tablet by its volume, then the density is 1.25 to 1.75 g / cm³. 3 The method described in any one of the above 1 to 11. 13. The catalyst is in the form of pellets, extruded products, or tablets, and has a mechanical strength of ACS: 30-750 kp / cm². 2 For example, 130-700 kp / cm² 2 Alternatively, 30-350 kp / cm² 2 The method according to any one of 1 to 12 above, or the method according to any one of 1 to 12 above, wherein the SCS is in the range of 4 to 100 kp / cm, for example, 20 to 90 kp / cm or 4 to 40 kp / cm, and the ACS and SPS are measured in the oxidized form of the catalyst and according to ASTM D4179-11.

Claims

1. A method for enriching synthesis gas with hydrogen by contacting the synthesis gas with a water-gas shift catalyst in a water-gas shift reactor, wherein the synthesis gas is a CO-rich synthesis gas containing at least 15 volume% CO and at least 1 ppmv of sulfur, the water-gas shift catalyst contains Zn, Al, optionally Cu, and an alkali metal or alkali metal compound, the water-gas shift catalyst does not contain chromium (Cr) and iron (Fe), and the water-gas shift catalyst has a pore volume of 240 ml / kg or more as determined by mercury intrusion.

2. The method according to claim 1, wherein the synthesis gas is a CO-rich synthesis gas containing at least 15 volume% CO and at least 15 ppmv of sulfur.

3. The method according to claim 1, wherein the synthesis gas is a CO-rich synthesis gas containing at least 15 volume% CO and at least 250 ppmv of sulfur.

4. The method according to claim 1, wherein the synthesis gas is a CO-rich synthesis gas containing at least 15 volume% CO and at least 5 volume% sulfur.

5. The method according to any one of claims 1 to 4, wherein the pore volume is 250 ml / kg or more.

6. The method according to any one of claims 1 to 4, wherein the pore volume is 240 to 380 ml / kg.

7. The method according to any one of claims 1 to 4, wherein the pore volume is 250 to 380 ml / kg.

8. The method according to any one of claims 1 to 4, wherein the pore volume is 300 to 600 ml / kg.

9. The method according to any one of claims 1 to 8, wherein the water-gas shift catalyst is a high-temperature shift (HTS) catalyst, and the water-gas shift reactor is an HTS reactor operated at a temperature in the range of 300 to 570°C and also optionally at a pressure in the range of 2.0 to 6.5 MPa.

10. The method according to claim 9, wherein the HTS reactor is a non-recyclable adiabatic HTS reactor.

11. The method according to any one of claims 1 to 10, wherein the CO-rich synthesis gas contains 20 to 60 volume percent of CO.

12. The CO-rich synthesis gas contains 30 to 60% by volume of CO and H ２ O at 30-50% by volume, CO ２ 0-5% by volume, H ２ The method according to claim 11, comprising 0 to 20 volume percent of the above.

13. A method according to any one of claims 1 to 12, further comprising a step for producing the synthesis gas, wherein the step is any of the following: - Steam reforming of hydrocarbon feed gases; partial oxidation of hydrocarbon feed gases; thermal reforming (ATR) of hydrocarbon feed gases; - Thermal decomposition of carbonaceous materials, including gasification or pyrolysis of renewable supply materials, including solid carbonaceous materials or biomass and / or waste; - A combination of those.

14. The method according to claim 13, wherein the hydrocarbon supply material gas is natural gas or naphtha.

15. The method according to claim 13 or 14, wherein the steam reforming is performed by electric heating.

16. The method according to any one of claims 13 to 15, wherein the solid carbonaceous material is petroleum coke.

17. The method according to any one of claims 13 to 16, wherein the combination is a combination of electric heating steam methane reforming (e-SMR) and autothermal reforming (ATR).

18. The method according to any one of claims 1 to 17, wherein the aqueous gas shift catalyst is a Zn / Al-based catalyst comprising, in its active form, a mixture of zinc aluminum spinel and optionally zinc oxide, and an alkali metal compound selected from K, Rb, Cs, Na, Li and mixtures thereof, wherein the Zn / Al molar ratio is in the range of 0.3 to 1.5, and the content of the alkali metal compound is in the range of 0.3 to 10% by weight, based on the weight of the oxidized catalyst.

19. The method according to any one of claims 1 to 18, wherein the aqueous gas shift catalyst comprises only Zn, Al, optionally Cu, and an alkali metal or alkali metal compound.

20. The method according to any one of claims 1 to 19, wherein the Zn / Al molar ratio is in the range of 0.5 to 1.0, and the alkali metal content is in the range of 0.4 to 8% by weight, based on the weight of the oxidized catalyst.

21. The method according to any one of claims 1 to 20, wherein the alkali metal content is in the range of 1 to 6% by weight.

22. The method according to claim 21, wherein the alkali metal content is in the range of 1 to 5% by weight.

23. The method according to claim 22, wherein the alkali metal content is in the range of 2.5 to 5% by weight.

24. The method according to any one of claims 21 to 23, wherein the alkali metal is K.

25. The method according to any one of claims 1 to 24, wherein the Cu content is in the range of 0.1 to 10% by weight, based on the weight of the oxidized catalyst.

26. The method according to claim 25, wherein the Cu content is in the range of 1 to 5% by weight, based on the weight of the oxidized catalyst.

27. When the water-gas shift catalyst is in the form of pellets, extruded materials, or tablets, and the particle density is measured by dividing the weight of the water-gas shift catalyst by its volume, the density is 1.25 to 1.75 g / cm³. ３ The method according to any one of claims 1 to 26.

28. When the aqueous gas shift catalyst is in tablet form and the particle density is measured by dividing the weight of the tablet by its volume, the particle density is 1.25 to 1.75 g / cm³. ３ The method according to claim 27.

29. The catalyst is in the form of pellets, extruded materials, or tablets, and has a mechanical strength of ACS: 30–750 kp / cm². ２ The method according to any one of claims 1 to 27, wherein the ACS and SCS are in the range of 4 to 100 kp / cm in the oxidized form of the catalyst and are measured according to ASTM D4179-11.

30. The aforementioned mechanical strength is ACS: 130-700 kp / cm ２ The method according to claim 29, which is within the range.

31. The method according to claim 29, wherein the mechanical strength is in the range of ACS: 30 to 350 kp / cm².

32. The method according to claim 29, wherein the mechanical strength is in the range of SCS: 20 to 90 kp / cm.

33. The method according to claim 29, wherein the mechanical strength is in the range of SCS: 4 to 40 kp / cm.

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