Method for recovering hydrogen during hydroprocessing of feedstocks

Abstract

The present disclosure relates to a process for hydrotreating a feedstock comprising oxygenates comprising the steps of: a. Directing the feedstock, an amount of supplemental hydrogen and a recycle gas in contact with a catalyst having hydrotreating activity under active hydrotreating conditions to provide a hydrotreated product stream, b. Separating a vapor product fraction and a liquid product fraction from the hydrotreating product stream by gas-liquid separation at a pressure of 80% or more and a temperature of 200 DEG C or more under active hydrotreating conditions, c. Separating a liquid product fraction from the hydrotreating product stream by gas-liquid separation at a pressure of 80% or more and a temperature of 100 DEG C or less under the active hydrotreating conditions, separating a gaseous product fraction and a light liquid product fraction from the vapour product fraction by gas / liquid separation, d. Directing at least an amount of the gaseous product fraction to a gas purification device to provide a hydrogen-rich gas fraction in which molecules having a molecular weight of 12 g / mole or more are relatively lean and a hydrogen-lean gas fraction in which molecules having a molecular weight of 12 g / mole or more are relatively lean, and d. Separating the gaseous product fraction from the vapour product fraction by gas / liquid separation. The hydrogen-depleted gas fraction is rich in molecules having a molecular weight of 12 g / mole or more, and e. Providing at least an amount of the hydrogen-rich gas fraction as a part of the recycle gas or supplemental hydrogen. This has the related advantage of being able to provide pure recycle gas even for a partially hydrotreated product stream, which has a low ability to capture CO2, CO and CH4.

Description

Technical Field

[0001] The present invention relates to the field of upgrading liquids derived from the pyrolysis of solid feedstocks.

[0002] Technical Problem

[0003] The pyrolysis of solid feedstocks (such as mixed municipal waste, mixed or sorted plastic waste, and forestry waste) can produce a liquid product (referred to as pyrolysis oil or crude pyrolysis oil for simplicity), which can be upgraded to high-quality hydrocarbons and used as transportation fuel or petrochemical feedstock. The oxygenate content of this product may be higher than the common requirements for hydrocarbons, and it may be desirable to perform subsequent hydrotreating at different locations or intentionally use such oxygenate-rich products.

[0004] When the final product is rich in polar oxygenates, its processing conditions and intermediate products will be different from other hydrotreating processes, in which the intermediate products and the final product are quantitatively converted to non-polar hydrocarbons. Compared with products rich in non-polar hydrocarbons, products rich in polar oxygenates have lower solubility in non-polar carbon dioxide and carbon monoxide. Therefore, compared with a similar situation of products substantially free of oxygenates, intermediate low-temperature high-pressure gas / liquid separation will direct more carbon dioxide into the gas phase. In addition, large (high-boiling) molecules generally have lower solubility in gases than small (low-boiling) molecules. The effect of this reduced solubility is that if the gas phase is recycled, the partial pressure of hydrogen in it will be reduced, which will in turn lead to a decrease in process reactivity, or an increase in the purge rate from the recycle loop is required to maintain reactivity.

[0005] At present, we have determined that an economically effective solution to this problem is to provide a gas separation method. The preferred method is membrane-supported separation, which will allow the extraction of the retentate gas containing a low concentration of hydrogen and the recycling of the permeate gas with a high concentration of hydrogen.

[0006] Other gas separation methods can also be considered, including the sponge oil process, the CO2 amine washing process, and absorption-based processes (such as pressure swing absorption).

[0007] Definitions

[0008] It should be understood that the unit "MPag" represents gauge pressure in MPa, i.e., the pressure above the ambient pressure.

[0009] It should be understood that the unit Nm 3 represents "standard" cubic meters, i.e., the volume occupied by a gas at 0 °C and 1 atmosphere of pressure.

[0010] The term "hydrogen-oil ratio" or "H2:oil ratio" as used herein refers to the volume ratio of the hydrogen gas flow to the liquid oil flow, and its reported unit is Nm 3 / m 3, where, according to the practice in the art, the gas phase is reported under standard conditions (0 °C and 1 atmosphere), e.g., standard cubic meters Nm 3 , and the liquid phase is reported under standard conditions (25 °C and 1 atmosphere), e.g., standard cubic meters Sm 3 . For convenience, if the liquid phase has no significant pressure or temperature dependence, then Sm 3 and m 3 can be used interchangeably.

[0011] Whenever the concentration is expressed in wt%, it should be understood as weight / weight percentage.

[0012] Whenever the concentration is expressed in vol%, it should be understood as gas phase volume / volume percentage.

[0013] As used herein, for convenience, the terms "thermal decomposition" and "thermochemical decomposition" will be widely used to refer to any decomposition process in which a solid material undergoes partial decomposition at elevated temperatures (usually from 250 °C to 800 °C, even up to 1000 °C) in the presence of sub-stoichiometric O2 (including the case of no added oxygen). The products are typically a mixed stream of liquids and gases, as well as a certain amount of solid carbon. This term should be interpreted to include processes known as pyrolysis and hydrothermal liquefaction, whether or not a catalyst is present. For convenience, the products of such a thermal decomposition process may be referred to as pyrolysis oil, but should be understood to cover any thermal decomposition process.

[0014] Hereinafter, the term "hydrocarbon-containing feedstock" shall be used to refer to a feedstock rich in molecules containing hydrogen and carbon, but the feedstock may also contain heteroatoms, i.e., other elements such as oxygen, sulfur, and nitrogen.

[0015] In this document, the term "section" refers to a physical section that includes a single unit or a combination of multiple units, and is used to perform one or more steps and / or sub-steps.

[0016] The term "feedstock from plastics or polymers" or "waste plastics or polymers" may be understood to include mixed or sorted waste that contains at least 50 wt%, 80 wt%, or 90 wt% of plastics and other synthetic polymers.

[0017] Feedstocks of biological origin can be defined by tracing their origin, or can be defined by their 14 C content being more than one part per trillion of the total carbon content.

[0018] Whenever hydrogen and hydrogen concentration are mentioned, unless specifically stated that hydrogen is part of other molecules, it should generally be understood as elemental hydrogen molecules.

[0019] Whenever oxygen content is mentioned, unless specifically stated to refer to molecular elemental oxygen molecules, it should generally be understood as atomic oxygen as part of other molecules.

[0020] When discussing the polarity and non-polarity of compounds, the compounds labeled "polar" should be understood to be more polar than those labeled "non-polar", and the relevant properties (such as the solubility of non-polar compounds) will be affected, but these terms should not be understood as absolute terms, for example, indicating complete immiscibility.

[0021] Solution to the problem

[0022] It is proposed to provide a recycled gas of sufficient purity based on gas purification, and in a specific embodiment, a purification scheme based on optimizing the pressure characteristics of the process, including an embodiment of membrane purification using gas pressurization in a make-up gas compressor.

[0023] According to the present disclosure, a hydrocarbon-containing feedstock can be provided by a thermochemical decomposition process equipment section, which can be one of various variants, including a rotary kiln, a fluidized bed, a transport bed, or a circulating fluidized bed, which are well known in the art. This decomposition converts the pyrolysis feedstock into a solid (char), a high-boiling liquid (tar), and a gaseous fraction that is gaseous at elevated temperatures. The gaseous fraction includes a condensable fraction (pyrolysis oil or condensate, C5+ compounds) and a non-condensable fraction (pyrolysis gas, including pyrolysis off-gas) at standard temperature. For example, the thermochemical decomposition process equipment section (i.e., the pyrolysis section) can include a pyrolyzer unit (pyrolysis reactor), a cyclone separator, and / or a filter to remove particulate solids such as char, and a cooling unit, thereby producing a pyrolysis off-gas stream and the pyrolysis oil stream, i.e., condensed pyrolysis oil. The pyrolysis gas stream contains light hydrocarbons, such as C1-C4 hydrocarbons, and typically also contains H2O, CO, and CO2. Generally, the term "pyrolysis oil" includes condensate and tar, and the pyrolysis oil stream produced by the pyrolysis of biomass can also be referred to as bio-oil or biocrude. Pyrolysis oil is a liquid substance rich in a mixture of various molecules, usually composed of more than two hundred different compounds, mainly oxygen-containing compounds, such as acids, sugars, alcohols, phenols, guaiacol, eugenol, aldehydes, ketones, furans, and other mixed oxygen-containing compounds, which are generated by the depolymerization reaction of solids during pyrolysis treatment. For the thermochemical decomposition of non-biological waste containing appropriate components (such as plastic fragments or rubber, including waste tires), usually only products with a low oxygen content can be provided unless O2 is added during the decomposition, and usually a hydrocarbon-containing feedstock is provided whose structure reflects the structure of the solid pyrolysis feedstock.

[0024] For the purposes of the present invention, the pyrolysis section may be fast pyrolysis, also known as flash pyrolysis in the art. Fast pyrolysis refers to the thermochemical decomposition of a solid feedstock under conditions typically free of O2, at a temperature in the range of typically 350 - 650 °C (e.g., about 500 °C) and a reaction time of 10 seconds or less (e.g., 5 seconds or less, e.g., about 2 seconds). Fast pyrolysis can be carried out, for example, in an autothermal manner, such as in a fluidized bed reactor. The latter is also known as autothermal pyrolysis and is characterized by the use of air (optionally together with an inert gas or recycle gas) as the fluidizing gas. Thus, the partial oxidation of the pyrolysis compounds produced in the pyrolysis reactor (autothermal reactor) provides energy for the pyrolysis process while improving heat transfer. In so-called catalytic fast pyrolysis, a catalyst can be used. An acidic catalyst, typically comprising a zeolite and free of active metals, can be used to enhance the quality of the pyrolysis gas, and it can be operated in an in-situ mode (the catalyst is located in the pyrolysis reactor) or an ex-situ mode (the catalyst is placed in a separate reactor). The advantages obtained by using the catalyst are that it helps to stabilize the pyrolysis oil, making it more amenable to hydrotreating. In addition, the selectivity to the desired pyrolysis oil compounds can be increased.

[0025] In some cases, hydrogen is added during the catalytic pyrolysis process, which is referred to as reactive catalytic fast pyrolysis. If the catalytic pyrolysis is carried out at a high hydrogen pressure, e.g., above 0.5 MPa, it is often referred to as catalytic hydro-pyrolysis. Catalysts for upgrading in the presence of hydrogen typically contain one or more metals with hydrogenation activity, such as metals of Group 6 or Groups 8, 9, or 10.

[0026] The pyrolysis stage can be fast pyrolysis, which is carried out in the absence of a catalyst and hydrogen, i.e., the fast pyrolysis stage is not catalytic fast pyrolysis, hydro-pyrolysis, or catalytic hydro-pyrolysis. This makes the process simpler and more economical.

[0027] In one embodiment, the thermal decomposition is hydrothermal liquefaction. Hydrothermal liquefaction refers to the thermochemical conversion process of treating a solid feedstock (such as plastic waste, biomass, municipal solid waste, or sewage sludge) in a high-temperature, pressurized aqueous environment for a sufficient time to decompose the solid biopolymer structure into mainly liquid components. Typical hydrothermal treatment conditions are: a temperature range of 200 - 500 °C, especially 300 - 450 °C; an operating pressure range of 4 - 40 MPag, especially 25 - 35 MPag. Compared with pyrolysis (e.g., fast pyrolysis), this technology has the advantages of lower operating temperature, higher energy efficiency, and lower yields of high-boiling products.

[0028] In one embodiment, the pyrolysis also includes passing the solid feedstock through a solid feedstock preparation section, which includes, for example, drying to remove moisture and / or pulverizing to reduce the particle size. Any moisture / wetness in the solid feedstock will condense in the pyrolysis oil stream after evaporation, for example, in the pyrolysis section, and thus be carried out of the process flow, which may be undesirable. In addition, the heat consumed by the evaporation of moisture will carry away the thermal energy that is originally necessary for pyrolysis. By removing the moisture in the solid feedstock and reducing the particle size of the solid feedstock, the thermal efficiency of the pyrolysis section is improved.

[0029] Finally, other related thermochemical decomposition methods include medium or slow pyrolysis, where the conditions include lower temperatures and usually longer residence times - these methods may also be referred to as carbonization or calcination. The main advantages of these thermochemical decomposition methods are lower investment costs, and there may also be special advantages for specific feedstocks or specific product requirements (for example, when biochar is desired as the relevant product).

[0030] When a large amount of solid product is produced, such as in the process of producing biochar or when it is desired to recover unreacted carbon black particles from the thermochemical conversion process of waste tires, filtering the liquid product as part of the thermochemical conversion process may be beneficial, which also has the advantage of minimizing downstream catalyst deactivation.

[0031] The quality of the liquid feedstock produced by thermochemical decomposition is not sufficient to be used as, for example, a transportation fuel. They may have problems such as too high boiling points, poor stability, and containing undesirable heteroatoms, so hydrotreating is required to upgrade them into feedstocks with practical and economic value.

[0032] Therefore, we propose a method for hydrotreating a liquid oil stream, that is, reacting the liquid oil stream with hydrogen in the presence of a hydrotreating catalyst with sulfur poisoning resistance. The catalyst can be a sulfided catalyst containing one or more of nickel, cobalt, molybdenum, and tungsten, usually operating at an inlet temperature of 130 - 200 °C; or it can be a metal catalyst containing one or more of nickel, palladium, and platinum, usually operating at an inlet temperature of 80 - 130 °C. In most cases, the pressure can be 0.5 - 2 MPa, but can reach up to 15 MPa, and the liquid hourly space velocity (LHSV) is 0.1 - 5 h-1. These conditions can achieve the formation of a stable liquid oil stream.

[0033] In one embodiment, the hydrotreating catalyst is in sulfided form, such as NiMoS or CoMoS. The catalyst can be pre-sulfided by exposure to a sulfur-containing stream, or in-situ sulfided during operation or just before operation (for example, using the sulfur present in the pyrolysis oil), so that the sulfided catalyst remains in a sulfided state and maintains its activity due to the presence of sulfur.

[0034] Materials that are catalytically active in the initial hydrotreating (e.g., hydrogenation), especially of conjugated double bonds, typically comprise an active metal (sulfided base metals such as nickel, cobalt, tungsten, and / or molybdenum, but may also be elemental metals such as nickel and noble metals such as platinum and / or palladium) and a heat-resistant support (such as alumina, silica, or titania, or combinations thereof). The initial hydrotreating conditions may include: a moderate temperature in the range of 120 - 200 °C; a moderate pressure in the range of 0.5 - 5 MPa; and a liquid hourly space velocity (LHSV) in the range of 0.1 - 5. In some cases, a higher pressure of up to 15 MPa may be required.

[0035] The conditions for the final hydrotreating (e.g., hydrogenation) typically include: a higher temperature in the range of 250 - 400 °C; a higher pressure in the range of 3 - 20 MPa; and a liquid hourly space velocity (LHSV) in the range of 0.1 - 4, optionally with intermediate cooling by quenching with cold hydrogen, feed, or product.

[0036] Generally, the process is moderately exothermic, with the temperature typically rising by 5 - 20 °C; however, depending on the degree of hydrogenation and hydrodeoxygenation, the reaction may be highly exothermic, with a temperature rise of up to 100 °C.

[0037] In addition to removing heteroatoms by hydrotreating, other steps may be required to obtain a product of appropriate quality. Depending on the feedstock properties and product requirements, these steps may particularly involve isomerization, hydrocracking, and hydrodearomatization.

[0038] Materials that are catalytically active in isomerization typically comprise an active metal (which can be elemental noble metals such as platinum and / or palladium or sulfided base metals such as nickel, cobalt, tungsten, and / or molybdenum), an acidic support (usually a molecular sieve with high shape selectivity, whose topological structure is, for example, MOR, FER, MRE, MWW, AEL, TON, and MTT), and a heat-resistant support (such as alumina, silica, or titania, or combinations thereof).

[0039] The isomerization conditions include: a temperature range of 250 - 400 °C, a pressure range of 2 - 15 MPa, and a liquid hourly space velocity (LHSV) range of 0.5 - 8.

[0040] Materials catalytically active in hydrocracking have similar properties to those catalytically active in isomerization and generally comprise an active metal (which may be a noble metal in elemental form such as platinum and / or palladium, or a base metal sulfide such as nickel, cobalt, tungsten and / or molybdenum), an acidic support (silica-alumina or zeolite with high cracking activity, the topological structure of which is for example MFI, BEA and FAU), and a heat-resistant support (such as alumina, silica, titania, or a combination thereof). The difference from materials catalytically active in isomerization generally lies in the nature of the acidic support, which may have a different structure (even amorphous silica-alumina can be used for hydrocracking) or a different acidity, for example due to the silica:alumina ratio.

[0041] Hydrocracking conditions may include: a temperature in the range of 200 - 400 °C, a pressure in the range of 3 - 20 MPa, a liquid hourly space velocity (LHSV) in the range of 0.5 - 8, and optionally intermediate cooling by quenching with cold hydrogen, feed or product. If the catalyst contains a more active noble metal, the temperature is generally at the lower end of this range.

[0042] Other types of hydrotreating are also envisaged, such as hydrodearomatization (HDA). Materials catalytically active in hydrodearomatization generally comprise an active metal (usually a noble metal in elemental form, such as platinum and / or palladium, but may also be a base metal sulfide such as nickel, cobalt, tungsten and / or molybdenum) and a refractory support (such as amorphous silica-alumina, alumina, silica or titania, or a combination thereof).

[0043] Hydrodearomatization conditions include: a temperature between 200 - 350 °C, a pressure between 2 - 10 MPa, and a liquid hourly space velocity (LHSV) between 0.5 - 8.

[0044] Providing hydrogen for hydrotreating is an important cost, and reducing the need for hydrogen can be a driver for cost reduction and for reducing the overall CO2 emissions of the process. In hydrotreating, the amount of hydrogen consumed per unit volume of oil is called the H2:oil consumption ratio. Depending on the nature of the crude product, for full hydrotreating, the H2:oil consumption ratio may be between 50 Nm 3 / m 3 and 1000 Nm 3 / m 3 However, in order to minimize the risk of coke deposition on the catalyst due to hydrogen deficiency, a safety factor of 2, 4 or even 8 is usually used in operation, such that a H2:oil consumption ratio of 200 Nm 3 / m 3 results in an actual operation of up to 1600 Nm 3 / m 3H2: oil ratio.

[0045] Generally, hydrotreating (especially the treatment of oxygenate-containing feeds) is carried out under excess hydrogen conditions to increase the reaction rate and minimize the risk of coke deposition on the catalyst. The excess hydrogen is typically recycled to minimize hydrogen consumption and associated costs. However, since the reaction rate and process equilibrium depend on the partial pressure of hydrogen, the presence of other compounds such as methane and carbon dioxide in the recycle gas reduces this effect of hydrogen, or requires an increase in the total pressure at the expense of higher equipment costs. For example, if the H2:oil consumption ratio is 200 Nm 3 / m 3 , and the purity of the hydrogen-rich gas in the process is only 80 vol%, then with a safety factor of 2, the gas:oil ratio will reach 500 Nm 3 / m 3 .

[0046] The product stream from hydrotreating will be a gas / liquid two-phase flow. The liquid phase will be the product with suitable quality for the final product or downstream processing and may contain a large amount of high-boiling hydrocarbons and oxygenates, while the hot gas phase will contain unreacted hydrogen and gaseous products. The gaseous products are mainly released heteroatoms, including oxygen (in the form of H2O or CO and CO2), nitrogen (in the form of NH3), sulfur (in the form of H2S), and halides such as chlorides (in the form of HCl or NH4Cl). In addition, light hydrocarbons and oxygenates may also be present in the hot gas phase, especially in cases where hydrogenation, hydroprocessing, and hydrotreating are incomplete. Due to the excess of hydrogen and associated costs, hydrogen recycling is desirable. Incomplete hydrotreating may have the advantages of reducing OPEX (including hydrogen consumption), reducing equipment costs, and possibly increasing the yield. Achieving incomplete hydrotreating is not the focus of the present invention, and those skilled in the art can use a variety of known means alone or in combination to achieve it, such as selecting process parameters to limit the conversion rate, including but not limited to the supply of hydrogen, hydrogen partial pressure, temperature, catalyst activity, and space velocity. Due to the incomplete hydrotreating of the oxygenate-containing feed, the hydrotreating product stream will still contain oxygenates, but in a lower amount than in the oxygenate-containing feed.

[0047] In a high-temperature and high-pressure separator (operating conditions close to the process conditions, such as 11 MPa and 240 °C), the high-boiling liquid phase can be separated from the gas phase. If all the catalysts are sulfided and the process is carried out in the presence of sulfur, this separation can be carried out downstream of the entire hydrotreating process. However, usually only the initial step of hydrotreating uses sulfided catalysts. In this case, the first step of separation is carried out downstream of hydrodeoxygenation and upstream of noble metal isomerization or hydrocracking catalysts. If additional (or all) catalysts are sulfided, the separation is usually carried out after all the sulfided catalysts.

[0048] The two-phase product stream or the separated gas phase will contain excess H2, small heteroatom molecules such as H2O, CO, CO2, NH3, H2S and HCl, as well as C1-C5 hydrocarbons and oxygenates. To separate the excess H2 from the rest of the gas phase, the gas phase is cooled to, for example, 50 °C and separated in a high-pressure and low-temperature separator.

[0049] If the hot gas phase contains water and light hydrocarbons, the condensation in the low-temperature separator will produce three phases: a gas phase, a non-polar liquid phase rich in hydrocarbons, and a polar liquid phase rich in water. Most non-polar gases, such as CO2, CO and alkanes, have a relatively high but limited solubility in the non-polar liquid phase, especially when the non-polar liquid phase is rich in small (low-boiling) molecules; while salts, such as NH4Cl, have a very high and almost infinite solubility in the polar phase. Therefore, these compounds may be withdrawn from the high-pressure and low-temperature separator with the liquid condensate, while H2 is mainly retained in the gas phase because of its low solubility. To avoid blockage caused by the deposition of solidified salts, in addition to the water produced by hydrodeoxygenation, a certain amount of wash water can be added to the hot gas phase so that when the temperature drops, the salts will not solidify but dissolve in the condensed water. In a similar way, a large amount of non-polar gases will dissolve in the condensed non-polar hydrocarbon phase.

[0050] However, due to the nature that the product is only partially hydrotreated or contains few low-boiling products, the adsorption capacity of the gas in a small amount of low-boiling products will be very low, especially when the product is high-boiling, because in this case, most of the products that are liquid under the conditions of the low-temperature separator have been withdrawn in the high-pressure and high-temperature separator. In addition, if the amount of a moderate amount of condensed non-polar hydrocarbons is far exceeded by a large amount of polar compounds (such as light oxygenates), the ability to dissolve non-polar gases in a small volume will be very low. Therefore, the amounts of CO2, CO and CH4 withdrawn from the cold gas phase will be very low, resulting in a very low purity of the recycle gas. Eventually, the two-stage process will have a higher purity of the recycle gas because it usually includes a high-pressure stripper and an inter-stage low-temperature separator, as well as a low-temperature separator before fractionation, which will remove more CO2 from the gas cycle.

[0051] A common method for purifying a gas stream in a hydrotreating unit is to use an amine scrubber, in which CO2 and H2S are particularly reversibly captured in an aqueous solution of an amine. However, if the gas to be purified also contains water-soluble compounds such as methanol, ethanol, and formic acid, these compounds will also be captured (but irreversibly) in the amine scrubber. Therefore, embodiments of the present invention include embodiments for purifying the recycle gas in a manner different from a gas scrubber using a wash liquid that may dissolve product oxygenates.

[0052] Gas purification using an amine scrubber involves a very low pressure drop, so the scrubber can be arranged in series with a recycle gas compressor, the task of which is to pressurize the high-pressure gas to match the process pressure to compensate for a pressure drop of about 1 MPa in the reactor.

[0053] Other means of purifying the recycle gas usually result in a more significant pressure drop. Membrane units can be used to purify the gas, providing a certain degree of purification at a moderate pressure drop and more purification at an increased pressure drop. Therefore, if a moderate purification of a H2-rich gas is required, membrane purification may be a cost-effective alternative to an amine scrubber if it is configured with a low pressure drop, extracts an appropriate amount of gas, and bypasses the recycle gas compressor to form an independent loop.

[0054] When the content of impurities to be removed is high, such as when the total amount of CO2, CO, and CH4 is 1 vol%, 3 vol%, or even more than 5 vol%, it may be advantageous or even necessary to operate at a higher pressure drop, where the purified recycle gas is directed to a make-up gas compressor, since hydrogen is usually provided from a hydrogen production unit at a moderate high pressure (e.g., 2 MPag). This purification configuration of the recycle gas may result in a relatively high pressure drop, such as a 9 MPa pressure drop from 11 MPag to 2 MPag, and the recycle gas can be withdrawn either before the recycle gas compression between the cold separator and the knock-out drum or after the recycle gas compression. This configuration has a relatively high capital cost and a relatively high operating cost because a larger make-up gas compressor is required, which will also have a relatively high energy consumption because a large volume needs to be treated at a high pressure.

[0055] Brief Description of the Drawings

[0056] Figure 1 Shows a process for hydrotreating a feedstock containing oxygenates, in which membrane purification is carried out in a recycle gas loop.

[0057] Figure 2 Shows a process for hydrotreating a feedstock containing oxygenates, in which membrane purification is carried out between a cold separator and a make-up gas compressor.

[0058] Figure 3 A process for hydrotreating a feedstock containing oxygenates is shown, in which membrane purification is carried out between a recycle gas compressor and a make-up gas compressor.

[0059] Figure 1

[0060] In Figure 1 this process, a feedstock (2) containing oxygenates is pressurized by a feed pump (FP) and combined with a hydrogen-rich gas (10) which includes make-up hydrogen (4) and recycle gas (8). After being heated in a heat exchanger (HX) by heat exchange with the reactor effluent (16), this feed stream (12) is combined with additional recycle gas and led as a reactor feed stream (14) to a reactor (R). The reactor (R) contains one or more catalysts which are configured to provide a desired hydrotreating conversion of the reactor feed stream (14) by controlling conditions including composition, temperature, pressure and space velocity. Conditions can be selected, such as limiting the temperature or the supply of hydrogen, to support only a limited degree of reaction. The reactor effluent (16) is cooled in the heat exchanger (HX) and sent to a high-temperature high-pressure separator (HHPS), thereby providing a first product stream (18) and a vapor stream (20) which is cooled in a cooler (C) and then led to a cold high-pressure separator (CHPS), in which acid water (22) and a light liquid product (24) are separated from a light gas (26). The light gas is combined with a purified gas stream (36) and led to a separation drum (KOD) to remove liquid, and then further led to a recycle gas compressor (RC). A gas stream (28) for purification is branched off from the light gas and led to a membrane separator (M) to provide a hydrogen-lean retentate gas (30) and a hydrogen-rich purified gas stream (36). The remaining light gas (34) is led as recycle gas and divided into two parts: one part of the recycle gas (8) is combined with the feedstock (2) containing oxygenates before heating; the other part is led to the reactor (R).

[0061] In an alternative embodiment, the purified gas (36) can also be led to a location upstream of the cooler (C) or to a location between the cooler and the cold high-pressure separator (CHPS).

[0062] Figure 2

[0063] In Figure 2In this process, a feedstock (2) containing oxygenates is pressurized by a feed pump (FP) and combined with a hydrogen-rich gas (10) which contains make-up hydrogen (4), a purge gas (6), and a recycle gas (8). After being heated in a heat exchanger (HX) by heat exchange with a reactor effluent (16), the feed stream (12) is combined with additional recycle gas and directed as a reactor feed stream (14) to a reactor (R) which contains one or more catalysts configured to provide a desired hydrotreating conversion of the reactor feed stream (14) by controlling conditions including composition, temperature, pressure, and space velocity. Conditions can be selected, such as limiting the temperature or the supply of hydrogen, to support only a limited degree of reaction. The reactor effluent (16) is cooled in the heat exchanger (HX) and directed to a high-temperature and high-pressure separator (HHPS), thereby providing a first product stream (18) and a vapor stream (20) which is cooled in a cooler (C) and then directed to a cold high-pressure separator (CHPS) where acidic water (22) and a light liquid product (24) are separated from a light gas (26). The light gas (26) is split into a gas stream (28) for purification and a stream (32) which is directed to a knockout drum (KOD) to remove liquid and then further directed to a recycle gas compressor (RC). A gas stream (28) for purification is separated from the light gas (26) and directed to a membrane separator (M) to provide a hydrogen-lean retentate gas (30) and a hydrogen-rich purge gas stream (36). The remaining light gas (34) is directed as a recycle gas and split into two parts: one part of the recycle gas (8) is mixed with the feedstock (2) containing oxygenates before heating; the other part is directed to the reactor (R).

[0064] Figure 3

[0065] In Figure 3In it, a raw material (2) containing an oxygenate is pressurized by a raw material pump (FP) and combined with a hydrogen-rich gas (10), which contains make-up hydrogen (4), a purified gas (6), and a recycle gas (8). After being heated by heat exchange with a reactor effluent (16) in a heat exchanger (HX), the raw material stream (12) is combined with additional recycle gas and led as a reactor feed stream (14) to a reactor (R), which contains one or more catalysts configured to provide a desired hydrotreating conversion of the reactor feed stream (14) by controlling conditions including composition, temperature, pressure, and space velocity. Conditions can be selected, such as limiting the temperature or the supply of hydrogen, to support only a limited degree of reaction. The reactor effluent (16) is cooled in the heat exchanger (HX) and led to a high-temperature and high-pressure separator (HHPS), thereby providing a first product stream (18) and a vapor stream (20), which is cooled in a cooler (C) and then led to a cold high-pressure separator (CHPS), where acidic water (22) and a light liquid product (24) are separated from a light gas (26). The light gas (26) is led to a separation drum (KOD) to remove liquid and then further led to a recycle gas compressor (RC). Downstream of the recycle gas compressor (RC), a gas stream (28) for purification is separated from the light gas (26) and led to a membrane separator (M) to provide a hydrogen-lean retentate gas (30) and a hydrogen-rich purified gas (6). The remaining light gas (34) is led as a recycle gas and divided into two parts: one part of the recycle gas (8) is mixed with the raw material (2) containing an oxygenate before heating; the other part is led to the reactor (R).

[0066] Description of the embodiment

[0067] A first aspect of the present disclosure relates to a method for hydrotreating a raw material containing an oxygenate, which comprises the following steps:

[0068] a. Leading the raw material, a certain amount of make-up hydrogen, and a recycle gas into contact with a catalyst having hydrotreating activity under active hydrotreating conditions to provide a hydrotreating product stream,

[0069] b. Separating a vapor product fraction and a liquid product fraction from the hydrotreating product stream by gas-liquid separation under a pressure of more than 80% of the active hydrotreating conditions and a temperature of more than 200 °C,

[0070] c. Separating a gaseous product fraction and a light liquid product fraction from the vapor product fraction by gas / liquid separation under a pressure of more than 80% of the active hydrotreating conditions and a temperature of 100 °C or less,

[0071] d. Direct at least a certain amount of the gaseous product fraction to a gas purification device to provide a hydrogen-rich gas fraction and a hydrogen-lean gaseous fraction, wherein the hydrogen-rich gas fraction is depleted in molecules with a molecular weight of 12 g / mole or more, and the hydrogen-lean gaseous fraction is enriched in molecules with a molecular weight of 12 g / mole or more.

[0072] e. Provide at least a certain amount of the hydrogen-rich gas fraction as part of the recycle gas or make-up hydrogen.

[0073] This has the related advantage that: this is the case even when the hydrotreated product stream is only partially hydrotreated, such that the ability of the liquid phase to capture CO2, CO, and CH4 is low, and it is still possible to provide a pure recycle gas.

[0074] A second aspect of the present disclosure relates to the method according to the first aspect, characterized in that the hydrotreated product stream contains at least 2% of organically bound oxygen.

[0075] This has the related advantage that: such a method supports the removal of undesirable CH4 and CO2 from the recycle gas, even when the solubility of CH4 and CO2 in such a partially hydrotreated product is moderate.

[0076] A third aspect of the present disclosure relates to the method according to one of the above aspects, characterized in that the volume ratio of the gaseous product fraction to the light liquid product fraction is greater than 2000 Nm 3 / m 3 .

[0077] This has the related advantage that: such a method supports the removal of undesirable CH4 and CO2 from the recycle gas, even when the adsorption capacity of CH4 and CO2 in such a moderately sized light liquid product is very low.

[0078] A fourth aspect of the present disclosure relates to the method according to one of the above aspects, characterized in that 10 - 90% of the gaseous fraction is directed to the separation device, and 80 - 100% of the remaining gaseous fraction is directed as another part of the recycle gas.

[0079] This has the related advantage that: it is possible to purify the gaseous fraction to provide favorable process conditions.

[0080] A fifth aspect of the present disclosure relates to the method according to one of the above aspects, characterized in that the gaseous fraction contains 30 - 90 vol% hydrogen.

[0081] This has the related advantage that: even if the gaseous fraction contains a large amount of, for example, CO2, it is possible to effectively utilize the hydrogen resource.

[0082] The sixth aspect of the present disclosure relates to the method according to one of the above aspects, characterized in that the gaseous fraction comprises a combination of at least 1 vol%, 3 vol% or 5 vol% of CO2, CO and CH4.

[0083] The related advantage of this is that even if the gaseous fraction contains a large amount of CO2, CO and CH4, the effective utilization of hydrogen resources can be achieved.

[0084] The seventh aspect of the present disclosure relates to the method according to one of the above aspects, characterized in that the recycle gas comprises 70 - 95% hydrogen.

[0085] The related advantage of this is that there is an effective balance between the cost and benefit of hydrogen purification.

[0086] The eighth aspect of the present disclosure relates to the method according to one of the above aspects, characterized in that the gauge pressure at the outlet of the gas purification device is 10 - 100% of the pressure of the active hydrotreating conditions.

[0087] The related advantage of this is that there is an effective balance between the purification effect and the cost of pressurizing the recycle gas. For example, to achieve efficient purification, a pressure drop is required from the active hydrotreating conditions at 15 MPa to the make-up gas supply pressure at 2 MPa.

[0088] The ninth aspect of the present disclosure relates to the method according to one of the above aspects, characterized in that the gas purification device is a membrane separator.

[0089] The related advantage of this is that the membrane separator is an economical and efficient solution for separating CO2 from H2. Based on molecular size or physicochemical properties, the membrane material can be selective.

[0090] The tenth aspect of the present disclosure relates to the method according to one of the above aspects, characterized in that the gas purification device is a sponge oil separator, which uses a sponge oil different from the hydrotreating product stream, such as a fraction separated from the hydrotreating product in a downstream separation.

[0091] The related advantage of this is that using sponge oil as an economical and efficient separation device because it is convenient to mix with the process product.

[0092] The eleventh aspect of the present disclosure relates to the method according to one of the above aspects, wherein the hydrogen-rich gas fraction is combined with the certain amount of make-up hydrogen and pressurized by at least 5 MPa before contacting the catalyst.

[0093] This has the associated advantage that by increasing the pressure of the hydrogen-rich gas by at least 5 MPa, a process with a high pressure drop in the gas purification device can be achieved, which enables the use of, for example, a membrane separator with a high purification effect.

[0094] The eleventh aspect of the present disclosure relates to a method according to one of the foregoing ten aspects, wherein the hydrogen-rich gas fraction is pressurized by at least 1 MPa and less than 5 MPa before being combined with other streams.

[0095] This has the associated advantage that by increasing the pressure of the hydrogen-rich gas by 1 - 5 MPa, a process with a low pressure drop in the gas purification device can be achieved, so that it can be pressurized together with the unpurified recycle gas.

[0096] Another aspect of the present disclosure relates to a process equipment configured to perform the method of any of the foregoing aspects. Examples

[0097] The effects of the present invention are illustrated by two sets of examples, showing the gas circulation efficiency for complete deoxygenation of a triglyceride-based raw material in the case of high hydrogen consumption, and the gas circulation efficiency for partial deoxygenation of pyrolysis oil in the case of low hydrogen consumption. In both cases, the separation will be carried out by two separators operating at the reactor pressure. Table 1 lists the flow rates of the vapor stream and the liquid stream coming out of the low-temperature high-pressure separator, as well as the selected dissolved gas concentrations in the liquid stream (streams 24 and 26 in all three figures).

[0098] The hydrogen consumption for the process designed for complete deoxygenation (complete HDO in Table 1) is 440 Nm 3 / m 3 . The oxygen content in the light liquid product is less than 100 ppm wt , and under the conditions of the high-temperature high-pressure separator and the low-temperature high-pressure separator (5.9 MPag, 240 °C / 50 °C), the gas:liquid ratio produced is 1686 Nm 3 / m 3 .

[0099] For the process designed for partial deoxygenation, the hydrogen consumption is 82 Nm 3 / m 3 . The light liquid product contains approximately 4 wt% oxygen. Under the conditions of the high-temperature high-pressure separator and the low-temperature high-pressure separator (11 MPag, 240 °C / 50 °C), the amount of the light liquid product is 1.27 m 3 / h, and the gas amount is 8,157 Nm 3 / h, resulting in a gas:liquid ratio of 6414 Nm 3 / m 3。The concentration of CO2 in the liquid from the low-temperature high-pressure separator is 14.3 g / kg, compared with 2.1 g / kg for the full deoxygenation process.

[0100] Table 2 shows that for the full deoxygenation process, without purification, to achieve a satisfactory recycled gas hydrogen purity of 80.5 vol%, it is necessary to purge the light gas containing 248 kmol / h of H2, which is equivalent to 22% of the H2 chemical consumption (1114 kmol / h).

[0101] If it is desired to obtain the same recycled gas purity by membrane separation, placing the membrane in the recycle loop, as Figure 1 shown, will provide sufficient purification at a low driving pressure of 2.0 MPa. In this case, the make-up hydrogen compressor and the recycle gas compressor together will consume 613 kW.

[0102] If it is desired to obtain the same recycled gas purity by membrane separation, placing the membrane between the recycle low-temperature high-pressure separator and the make-up gas compressor, as Figure 2 shown, sufficient purification can be obtained with a driving pressure of 3.2 MPa. In this case, the make-up hydrogen compressor and the recycle gas compressor together will consume 670 kW.

[0103] If it is desired to obtain the same recycled gas purity by membrane separation, placing the membrane between the recycle compressor and the make-up gas compressor, as Figure 3 shown, sufficient purification can be obtained with a driving pressure of 5.3 MPa. In this case, the make-up hydrogen compressor and the recycle gas compressor together will consume 670 kW.

[0104] In this case, only moderate purification is required, and the lowest-cost and simplest process is to install a membrane in the recycle loop. For many similar cases, moderate purging may be the most effective way to maintain a high hydrogen concentration.

[0105] Table 3 shows the partial deoxygenation process. Without purification, to achieve a satisfactory recycled gas purity of 82 vol% hydrogen, it is necessary to purge the light gas containing 16 kmol / h of H2, which is equivalent to 33% of the H2 chemical consumption (48 kmol / h).

[0106] If it is desired to obtain the same recycled gas purity by membrane separation, placing the membrane in the recycle loop, as Figure 1 shown, will provide sufficient purification at a low driving pressure of 2.3 MPa. In this case, the make-up hydrogen compressor and the recycle gas compressor together will consume 149 kW.

[0107] If the same recycle gas purity is desired through membrane separation, place the membrane between the recycle cryogenic high-pressure separator and the make-up gas compressor, as Figure 2 shown, sufficient purification can be achieved with a driving pressure of 8.7 MPa. In this case, the make-up hydrogen compressor and the recycle gas compressor together will consume 136 kW.

[0108] If the same recycle gas purity is desired through membrane separation, place the membrane between the recycle compressor and the make-up gas compressor, as Figure 3 shown, sufficient purification can be achieved with a driving pressure of 11.0 MPa. In this case, the make-up hydrogen compressor and the recycle gas compressor together will consume 141 kW.

[0109] The comparison between Table 2 and Table 3 shows that the hydrogen consumption of the process with only partial deoxidation is greatly reduced, but since CO2 is not captured by the liquid product, the H2 purity coming out of the cryogenic high-pressure separator is also lower.

[0110] In the case of complete deoxidation and CO2 capture in the liquid product, only the scenario of using a membrane for purification in the recycle loop ( Figure 1 ) can reduce the total compressor power and the purge amount of H2.

[0111] In the case of partial deoxidation and poor CO2 capture in the liquid product, all three layouts of using a membrane for purification are beneficial, but the layout with the membrane in the make-up gas circuit ( Figure 2 and Figure 3 ) is the most favorable, which can reduce the energy consumption by 14% and 11% respectively. In addition, in this layout, the loss of hydrogen as a purge gas or retentate is also lower.

[0112] Table 1

[0113] Complete HDO Partial HDO Gas velocity <![CDATA[Nm 3 / h]]> 111,997 8,157 Liquid <![CDATA[Sm 3 / h]]> 66.44 1.27 Gas / oil <![CDATA[Nm 3 / h]]> 1,686 6,414 <![CDATA[H2]]> g / kg 0.57 1.38 <![CDATA[CH4]]> g / kg 3.08 5.95 <![CDATA[CO2]]> g / kg 1.22 14.30

[0114] Table 2

[0115] Only purge Figure 1 Figure 2 Figure 3 Feed rate BPSD 2000 2000 2000 2000 Chemical hydrogen consumption <![CDATA[Nm 3 / m 3 > 440 440 440 440 Chemical hydrogen consumption <![CDATA[Nm 3 > 5548 5548 5548 5548 Recycle gas purity downstream of the membrane vol% 80.5 80.5 80.5 80.5 Rate into the membrane kmol / h 101.6 81.8 81.8 Recycle compressor power kW 350 339 343 346 Makeup gas compressor power kW 310 274 324 324 Total compressor power kW 660 613 667 670 Membrane dP Mpa 20.4 32.3 52.7 <![CDATA[H2 loss in the retentate or purge gas]]> kmol / h 55.1 16.4 4.0 4.0

[0116] Table 3

[0117]

[0118]

Claims

1. A method for hydrotreating a feedstock containing oxygenates, comprising the following steps: a. guiding the feedstock, a certain amount of make-up hydrogen, and recycle gas into contact with a catalyst having hydrotreating activity under active hydrotreating conditions to provide a hydrotreated product stream containing oxygenates, but in an amount lower than that in the feedstock containing oxygenates, b. separating a vapor product fraction and a liquid product fraction from the hydrotreated product stream by gas-liquid separation at a pressure above 80% of the active hydrotreating conditions and a temperature above 200 °C, c. separating a gaseous product fraction and a light liquid product fraction from the vapor product fraction by gas / liquid separation at a pressure above 80% of the active hydrotreating conditions and a temperature below 100 °C, d. guiding at least a certain amount of the gaseous product fraction to a gas purification device to provide a hydrogen-rich gas fraction and a hydrogen-lean gaseous fraction, wherein molecules with a molecular weight of 12 g / mole or more are less abundant in the hydrogen-rich gas fraction, and molecules with a molecular weight of 12 g / mole or more are more enriched in the hydrogen-lean gaseous fraction, e. providing at least a certain amount of the hydrogen-rich gas fraction as part of the recycle gas or make-up hydrogen.

2. The method according to claim 1, characterized in that The hydrotreated product stream contains at least 2% of organically bound oxygen.

3. The method according to claim 1 or 2, characterized in that, The volume ratio of the gaseous product fraction to the light liquid product fraction is greater than 2000 Nm 3 / m 3 .

4. The method according to claim 1, 2 or 3, characterized in that, 10 - 90% of the gaseous fraction is guided to the separation device, and 80 - 100% of the remaining gas fraction is guided as another part of the recycle gas.

5. The method according to claim 1, 2, 3 or 4, characterized in that The gaseous fraction contains 30 - 90 vol% of hydrogen.

6. The method according to claim 1, 2, 3, 4 or 5, characterized in that, The gaseous fraction contains at least 1 vol%, 3 vol%, or 5 vol% of a combination of CO2, CO, and CH4.

7. The method according to claim 1, 2, 3, 4, 5 or 6, characterized in that The recycle gas contains 70 - 95% of hydrogen.

8. The method according to claim 1, 2, 3, 4, 5, 6 or 7, characterized in that, The gauge pressure at the outlet of the gas purification device is 30 - 100% of the pressure of the active hydrotreating conditions.

9. The method according to claim 1, 2, 3, 4, 5, 6, 7 or 8, characterized in that The gas purification device is a membrane separator.

10. The method according to claim 1, 2, 3, 4, 5, 6, 7, 8 or 9, characterized in that, The gas purification device is a sponge oil separator that uses a sponge oil different from the hydrotreated product stream.

11. The method according to any one of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, wherein the hydrogen-rich gas fraction is combined with the certain amount of make-up hydrogen and pressurized by at least 5 MPa before contacting the catalyst.

12. The method according to any one of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, wherein the hydrogen-rich gas fraction is pressurized by at least 1 MPa and less than 5 MPa before being combined with other streams.

13. A process equipment for performing the method according to any one of the above claims.

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