EP4638654A1

EP4638654A1 - A process for recovery of hydrogen during hydroprocessing of a feedstock comprising oxygenates

Info

Publication number: EP4638654A1
Application number: EP23836855.9A
Authority: EP
Inventors: Stefan ANDERSEN
Original assignee: Haldor Topsoe AS
Current assignee: Topsoe AS
Priority date: 2022-12-21
Filing date: 2023-12-21
Publication date: 2025-10-29
Also published as: CN120380108A; AU2023413763A1; WO2024133632A1

Abstract

The present disclosure relates to a process for hydroprocessing a feedstock comprising oxygenates, comprising the steps of a. directing said feedstock, an amount of make-up hydrogen and a recycle gas to contact a catalyst active in hydroprocessing under active hydroprocessing conditions, to provide a hydroprocessed product stream, b. separating from the hydroprocessed product stream a vapor product fraction and a liquid product fraction by gas liquid separation at a pressure above 80% of said active hydroprocessing conditions and a temperature above 200°C, c. separating from the vapor product fraction a gaseous product fraction and a light liquid product fraction by gas/liquid separation at a pressure above 80% of said active hydroprocessing conditions and a temperature below 100°C, d. directing at least an amount of said gaseous product fraction to a means of gas purification to provide a hydrogen rich gas fraction depleted in molecules with a molecular weight above 12 g/mole and a hydrogen depleted gaseous fraction enriched in molecules with a molecular weight above 12 g/mole, e. providing at least an amount of said hydrogen rich gas fraction as a portion of said recycle gas or make-up hydrogen. This has the associated benefit of providing a pure recycle gas also for partially hydroprocessed product streams, which have a low capacity for capturing CO₂, CO and CH₄.

Description

Title of Invention: A process for recovery of hydrogen during hydroprocessing of a feedstock comprising oxygenates

Technical Field

[0001] The present invention relates to the field of upgrading liquids originating from thermal decomposition of solid feedstocks.

Technical Problem

[0002] Thermal decomposition of solid feedstocks, such as mixed municipal waste, mixed or sorted plastic waste and forestry waste provides a liquid product (for simplicity pyrolysis oil or raw pyrolysis oil) which may be upgraded to quality hydrocarbons and be used as transportation fuels or petrochemical raw materials. The product may be richer in oxygenates content than commonly required for hydrocarbons, either in the expectation of subsequent hydrotreatment at a different site or in the intention of using such an oxygenate rich product.

[0003] When the final product is rich in polar oxygenates, the processing conditions and intermediate products will differ from other hydrotreatment processes where intermediate and final products are quantitatively converted to non-polar hydrocarbons. Products rich in polar oxygenates will have a lower solubility for non-polar carbon dioxide and carbon monoxide compared to non-polar hydrocarbon rich products, and thus, intermediate cold high pressure gas/liquid separation will direct more carbon dioxide to the gas phase compared to the similar case for products substantially free of oxygenates. In addition large (high boiling) molecules may typically have a lower solubility for gases than small (low boiling) molecules . The effect of this reduced solubility is that if the gas phase is recycled, it will have a lower partial pressure of hydrogen, and a related lower process reactivity, or a requirement for increased purge from the recycle loop to maintain reactivity.

[0004] We have now identified that a cost effective solution to this problem is the provision of a means of separation of the gas phase. A preferred method is a membrane supported separation, which will allow withdrawal of a retentate gas comprising a low concentration of hydrogen and recycle of a permeate gas with a high concentration of hydrogen.

[0005] Alternative means of gas separation may also be considered, including sponge oil processes, amine wash of CO2 and absorption based processes, such as pressure swing absorption.

Definitions

[0006] It would be understood that the unit “MPag” denotes MPa gauge, i.e. pressure above surroundings.

[0007] It would be understood, that the unit Nm³ means “normal” m³, i.e. the amount of gas taken up this volume at 0°C and 1 atmosphere.

[0008] As used herein, the term “hydrogen to liquid oil ratio” or “H2:oil ratio” means the volume ratio of hydrogen gas stream to the liquid oil stream, and is reported as Nm³/m³, where the gas phase is reported at normal conditions (0°C and 1 atmosphere) e.g. as normal cubic meters Nm³ and the liquid phase is reported at standard conditions (25°C and 1 atmosphere) e.g. as standard cubic meters Sm³ in accordance with practice of the field. For convenience Sm³ and m³ may be used interchangingly if liquid phases do not have a significant pressure or temperature dependence.

[0009] Where concentrations are stated in wt% this shall be understood as weight/weight %.

[0010] Where concentrations are stated in vol% this shall be understood as gas phase volume/volume %.

[0011 ] As used herein, the terms “thermal decomposition” and “thermochemical decomposition” shall for convenience be used broadly for any decomposition process, in which a solid material is partially decomposed at elevated temperature (typically 250°C to 800°C or even 1000°C), in the presence of substoichiometric amount of O2 (including no added oxygen). The product will typically be a combined liquid and gaseous stream, as well as an amount of solid char. The term shall be construed to include processes known as pyrolysis and hydrothermal liquefaction, both in the presence and absence of a catalyst. For convenience the product of such a thermal decomposition process may be called pyrolysis oil but shall be understood to cover any thermal decomposition process.

[0012] In the following a hydrocarbonaceous feedstock shall be used to signify a feedstock rich in molecules comprising hydrogen and carbon, but possibly also heteroatoms, i.e. other elements, such as oxygen, sulfur and nitrogen.

[0013] As used herein, the term “section” means a physical section comprising a unit or combination of units for conducting one or more steps and/or sub-steps.

[0014] The terms a “feedstock of plastic or polymeric origin” or “waste plastic or polymer” may be understood as including a mixed or sorted waste comprising at least 50 wt%, 80 wt% or 90 wt% plastic and other synthetic polymers.

[0015] A feedstock of biological origin may be defined by tracing the origin, but it may also be defined by the ¹⁴C content being above 0.5 parts per trillion of the total carbon content.

[0016] Where hydrogen and hydrogen concentration is mentioned this shall in general be understood as molecular elemental hydrogen, unless it is implied that hydrogen is part of other molecules.

[0017] Where oxygen content is mentioned this shall in general be understood as atomic oxygen is part of other molecules, unless it is implied that is relates to molecular elemental oxygen.

[0018] Where polarity and non-polarity of compounds are discussed, the compounds labelled “polar” shall be understood as more polar than compounds labelled “nonpolar”, with related properties such as solubility of non-polar compounds being affected, but the terms shall not be understood as absolute terms, indicating e.g. non-miscibility.

Solution to Problem

[0019] The provision of sufficiently pure recycle gas is proposed to be based on gas purification, and in specific embodiments on purification schemes optimizing the pressure characteristics of the process, including embodiments where a membrane purification employs gas pressurization in the make-up gas compressor. [0020] A hydrocarbonaceous feedstock according to the present disclosure may be provided by a thermochemical decomposition process plant section which may be one of many variants, including rotary oven, fluidized bed, transported bed, or circulating fluid bed, as is well known in the art. This decomposition converts a pyrolysis feedstock into a solid (char), a high boiling liquid (tar) and fraction being gaseous at elevated temperatures. The gaseous fraction comprises a fraction condensable at standard temperature (pyrolysis oil or condensate, C5+ compounds) and a non-condensable fraction (pyrolysis gas, including pyrolysis off-gas). For instance, the thermochemical decomposition process plant section (the pyrolysis section) may comprise a pyrolizer unit (pyrolysis reactor), cyclone(s) and/or filters to remove particulate solids such as char, and a cooling unit for thereby producing pyrolysis off-gas stream and said pyrolysis oil stream, i.e. condensed pyrolysis oil. The pyrolysis gas stream comprises light hydrocarbons e.g. C1 -C4 hydrocarbons, and commonly also H2O, CO and CO2. Typically, the term pyrolysis oil comprises condensate and tar, and the pyrolysis oil stream from pyrolysis of biomass may also be referred to as bio-oil or biocrude. The pyrolysis oil is a liquid substance rich in blends of molecules, usually consisting of more than two hundred different compounds mainly oxygenates such as acids, sugars, alcohols, phenols, guaiacols, syringols, aldehydes, ketones, furans, and other mixed oxygenates, resulting from the depolymerization of the solids treated in pyrolysis. Thermochemical decomposition of non- biological waste comprising suitable compositions, such as plastic fractions or rubber, including end of life tires will in general only provide products which have low contents of oxygen, unless O2 is added to the decomposition process and will commonly provide a hydrocarbonaceous feedstock which has a structure reflecting the solid pyrolysis feedstock.

[0021 ] For the purposes of the present invention, the pyrolysis section may be fast pyrolysis, also referred to in the art as flash pyrolysis. Fast pyrolysis means the thermochemical decomposition of a solid feedstock typically in the absence of O2, at temperatures typically in the range 350-650°C e.g. about 500°C and reaction times of 10 seconds or less, such as 5 seconds or less, e.g. about 2 sec. Fast pyrolysis may for instance be conducted by autothermal operation e.g. in a fluidized bed reactor. The latter is also referred to as autothermal pyrolysis and is characterized by employing air, optionally with an inert gas or recycle gas, as the fluidizing gas. Thereby, the partial oxidation of pyrolysis compounds being produced in the pyrolysis reactor (autothermal reactor) provides the energy for pyrolysis while at the same time improving heat transfer. In so-called catalytic fast pyrolysis, a catalyst may be used. An acid catalyst, commonly comprising a zeolite, without active metals, may be used to upgrade the pyrolysis vapors, and it can both be operated in an in-situ mode (the catalyst is located in the pyrolysis reactor) and an ex-situ mode (the catalyst is placed in a separate reactor). The use of a catalyst conveys the advantage of helping to stabilize the pyrolysis oil and thereby making it easier to hydroprocess. In addition, increased selectivity towards desired pyrolysis oil compounds may be achieved.

[0022] In some cases, hydrogen is added to the catalytic pyrolysis which is then called reactive catalytic fast pyrolysis. If the catalytic pyrolysis is conducted at a high hydrogen pressure, such as above 0.5 MPa, it is often called catalytic hydropyrolysis. The catalyst for upgrading in the presence of hydrogen, will typically comprise one or more metals active in hydrogenation, such as a metal from Group 6 or Group 8,9 or 10.

[0023] The pyrolysis stage may be fast pyrolysis which is conducted without the presence of a catalyst and hydrogen, i.e. the fast pyrolysis stage is not catalytic fast pyrolysis, hydropyrolysis or catalytic hydropyrolysis. This enables a much simpler and inexpensive process.

[0024] In an embodiment, the thermal decomposition is hydrothermal liquefaction. Hydrothermal liquefaction means the thermochemical conversion of solid feedstocks, such as plastic waste, biomass, municipal solid waste or sewer sludge into liquid fuels by processing in a hot, pressurized water environment for sufficient time to break down the solid biopolymeric structure to mainly liquid components. Typical hydrothermal processing conditions are temperatures in the range of 200-500°C, especially 300-450°C and operating pressures in the range of 4-40 MPag, especially 25-35 MPag. This technology offers the advantage of operation of a lower temperature, higher energy efficiency and lower yield of high boiling product compared to pyrolysis, e.g. fast pyrolysis. [0025] In an embodiment, the thermal decomposition further comprises passing said solid feedstock through a solid feedstock preparation section comprising for instance drying for removing water and/or comminution for reduction of particle size. Any water/moisture in the solid feedstock which vaporizes in for instance the pyrolysis section condenses in the pyrolysis oil stream and is thereby carried out in the process, which may be undesirable. Furthermore, the heat used for the vaporization of water withdraws heat which otherwise is necessary for the pyrolysis. By removing water and also providing a smaller particle size in the solid feedstock the thermal efficiency of the pyrolysis section is increased.

[0026] Finally, other relevant thermochemical decomposition methods are intermediate or slow pyrolysis, in which the conditions involve a lower temperature and commonly higher residence times - these methods may also be known as carbonization or torrefaction. The major benefit of these thermochemical decomposition methods is a lower investment, but they may also have specific benefits for specific feedstocks or for specific product requirements, such as a desire for bio-char as an associated product.

[0027] When high amounts of solid product are produced, such as processes producing bio-char or when retrieval of unconverted carbon black particles from thermochemical conversion of end-of-life tires is desired, it may be beneficial to filter the liquid product as part of the thermochemical conversion process, which will also have the benefit of minimizing deactivation of downstream catalyst.

[0028] The liquid feedstocks resulting from thermochemical decomposition are not of sufficient quality for use as e.g. transportation fuels. They may suffer from a too elevated boiling point, poor stability and presence of undesired heteroatoms, and therefore they require hydrotreatment to be upgraded to feedstocks of practical and economical value.

[0029] Accordingly, we propose a process for hydrotreating a liquid oil stream by reacting the liquid oil stream with hydrogen in the presence of a hydrotreatment catalyst having resistance to sulfur poisoning. This catalyst may be a sulfided catalyst comprising one or more of nickel, cobalt, molybdenum and tungsten typically operating at an inlet temperature of 130-200°C or it may be a metallic catalyst comprising one or more of nickel, palladium and platinum typically operating at an inlet temperature of 80-130°C. In most cases the pressure may be 0.5-2 MPa, but it may be up to 15 MPa, and the liquid hourly space velocity (LHSV) of 0.1 -5 h^-1, which conditions enable forming a stabilized liquid oil stream.

[0030] In an embodiment, the hydrotreatment catalyst is in sulfided form, e.g. NiMoS or CoMoS. The catalyst may be pre-sulfided by exposure of to a sulfur containing stream or it may be sulfided in-situ i.e. during or immediately prior to operation, for instance by sulfur present in the pyrolysis oil, such that the sulfided catalyst remains sulfided and thus active due to the presence of sulfur.

[0031 ] The material catalytically active in initial hydrotreating especially of conjugated double bonds, e.g. hydrogenation, typically comprises an active metal (sulfided base metals such as nickel, cobalt, tungsten and/or molybdenum, but possibly also either elemental metals both nickel and noble metals such as platinum and/or palladium) and a refractory support (such as alumina, silica or titania, or combinations thereof). Initial hydrotreating conditions may involve a moderate temperature in the interval 120-200°C, a moderate pressure in the interval 0.5-5 MPa, and a liquid hourly space velocity (LHSV) in the interval 0.1-5. For certain conditions an elevated pressure up to 15 MPa may be required.

[0032] Final hydrotreating e.g. hydrogenation conditions commonly involve a higher temperature in the interval 250-400°C, a higher pressure in the interval 3-20 MPa, and a liquid hourly space velocity (LHSV) in the interval 0.1-4, optionally together with intermediate cooling by quenching with cold hydrogen, feed or product.

[0033] In general the process is moderately exothermic thus a raise in temperature of 5-20°C typically occurs, but depending on the extent of hydrogenation and hydrodeoxygenation it may be highly exothermic, with a raise of temperature up to 100°C.

[0034] In addition to hydrotreatment to remove heteroatoms, additional steps may be desired to obtain a product of appropriate quality. These steps may especially involve isomerization, hydrocracking and hydrodearomatization, depending on feedstock properties and product requirements.

[0035] The material catalytically active in isomerization typically comprises an active metal (either elemental noble metals such as platinum and/or palladium or sulfided base metals such as nickel, cobalt, tungsten and/or molybdenum), an acidic support (typically a molecular sieve showing high shape selectivity, and having a topology such as MOR, FER, MRE, MWW, AEL, TON and MTT) and a refractory support (such as alumina, silica or titania, or combinations thereof).

[0036] Isomerization conditions involve a temperature in the interval 250-400°C, a pressure in the interval 2-15 MPa, and a liquid hourly space velocity (LHSV) in the interval 0.5-8.

[0037] The material catalytically active in hydrocracking is of similar nature to the material catalytically active in isomerization, and it typically comprises an active metal (either elemental noble metals such as platinum and/or palladium or sulfided base metals such as nickel, cobalt, tungsten and/or molybdenum), an acidic support (either silica-alumina or a molecular sieve showing high cracking activity, and having a topology such as MFI, BEA and FAU) and a refractory support (such as alumina, silica or titania, or combinations thereof). The difference over materials catalytically active in isomerization is typically the nature of the acidic support, which may be of a different structure (even amorphous silica-alumina may be used for hydrocracking) or have a different acidity e.g. due to silica:alumina ratio.

[0038] Hydrocracking conditions may involve a temperature in the interval 200- 400°C, a pressure in the interval 3-20MPa, and a liquid hourly space velocity (LHSV) in the interval 0.5-8, optionally together with intermediate cooling by quenching with cold hydrogen, feed or product. If the catalyst comprises the more active noble metals the temperature will commonly be at the lower end of the range.

[0039] Other types of hydroprocessing are also envisaged, for instance hydrodearomatization (HDA). The material catalytically active in hydrodearomatization typically comprises an active metal (typically elemental noble metals such as platinum and/or palladium but possibly also sulfided base metals such as nickel, cobalt, tungsten and/or molybdenum) and a refractory support (such as amorphous silica-alumina, alumina, silica or titania, or combinations thereof). [0040] Hydrodearomatization conditions involve a temperature in the interval 200 - 350°C, a pressure in the interval 2-10 MPa, and a liquid hourly space velocity (LHSV) in the interval 0.5-8.

[0041] The provision of hydrogen for hydroprocessing is a significant cost, and the reduction of the requirements for hydrogen may be a driver for cost reduction as well as for reducing the overall CO2 emissions of the process. In hydroprocessing, an amount of hydrogen is consumed per volume of oil, which is termed the H2:oil consumption ratio. Depending on the nature of the raw product, for complete hydroprocessing the H2: oil consumption ratio may be from 50 Nm³/m³ to 1000 Nm³/m³. However, to minimize the risk of coke deposits on the catalyst due to hydrogen deprivation, it is common to operate with a safety factor of 2, 4 or even 8, such that an H2: oil consumption ratio of 200 Nm³/m³ results in operation with up to 1600 Nm³/m³ H2:oil

[0042] Hydrotreatment in general and especially in processing of oxygenate feedstocks is carried out in excess of hydrogen to increase reaction rate and to minimize the risk of coke deposition on the catalyst. The excess hydrogen is typically recycled, to minimize the hydrogen consumption and the related cost. However, as the reaction rate and process equilibrium depend on the partial pressure of hydrogen, presence of other compounds such as methane and carbon dioxide in the recycle gas will lower this effect of hydrogen or require an increased total pressure, at the cost of more expensive equipment. As an example, an H2:oil consumption ratio of 200 Nm³/m³ will, if the purity of the H2 rich gas in the process is only 80 vol%, result in a gas:oil ratio of 500 Nm³/m³ if a safety factor of 2 was employed.

[0043] The product stream from hydroprocessing will be a two phase gas/l iquid stream. The liquid phase will be a product which has appropriate qualities for use in a final product or for downstream processing and may comprise a high amount of high boiling hydrocarbons and oxygenates, whereas the hot gas phase will comprise unreacted hydrogen and gaseous products. The gaseous products will mainly be released heteroatoms, including oxygen (as H2O or CO and CO2), nitrogen (as NH3), sulfur (as H2S) as well as halides such as chloride (as HCI or NH4CI). In addition, light hydrocarbons and oxygenates may also be present in the hot gas phase, especially if hydrogenation, hydroprocessing and hydrotreatment is not complete. Due to the excess amount of hydrogen and the related cost, recycling of hydrogen is desirable. Incomplete hydroprocessing may have the benefit of lower OPEX including hydrogen consumption, reduced equipment cost and possibly higher yields. Obtaining incomplete hydrotreatment is not the focus of the present invention and a wide range of means known to the skilled person are available alone or in combination, such as selecting process parameters to limit conversion, including but not limited to the availability of hydrogen, the partial pressure of hydrogen, the temperature, the activity of catalyst and the space velocity. Due to the incomplete hydroprocessing of a feedstock comprising oxygenates, the hydroprocessed product stream will still comprise oxygenates, but in a lower amount than the feedstock comprising oxygenates.

[0044] A high boiling liquid phase may be separated from the gas phase in a hot high pressure separator (operating close to process conditions) e.g. at 11 MPa and 240°C. If all catalysts are sulfided and the process operates in the presence of sulfur, this separation may be carried out downstream the full hydroprocessing process, but commonly only the initial step of hydrotreatment employs a sulfided catalyst, and in this case a first step of separation is carried out downstream hydrodeoxygenation and upstream noble metal isomerization or hydrocracking catalysts. If additional (or all) catalysts are sulfided, the separation is commonly made after all sulfided catalysts.

[0045] The two phase product stream or the separated gas phase will comprise excess H2, small heteroatomic molecules such as H2O, CO, CO2, NH3, H2S and HCI as well as C1 -C5 hydrocarbons and oxygenates. To separate excess H2from the remainder of the gas phase, the gas phase is cooled to e.g. 50°C, and separated in a high pressure cold separator.

[0046] If the hot gas phase comprises water and light hydrocarbons, the condensation in the cold separator will result in three phases; a gas phase, a liquid non-polar phase rich in hydrocarbons, and a liquid polar phase rich in water. Most non-polar gases, such as CO2, CO and paraffins, will have a high but limited solubility in the liquid non-polar phase, especially if it is rich in small (low boiling) molecules and salts such as NH4CI will have a high and almost unlimited solubility in the polar phase, and thereby these compounds may be withdrawn with the liquid condensates from the high pressure cold separator, whereas H2 will mainly remain in the gas phase as the solubility of H2 is low. To avoid clogging by deposition of solidified salts an amount of wash water may be added to the hot gas phase, in addition to the water produced by hydrodeoxygenation, such that when the temperature is decreased, salts will not solidify but instead be dissolved in condensed water. In a similar manner, a significant amount of nonpolar gases will be dissolved in the condensed non-polar hydrocarbon phase.

[0047] However, due to the nature of product which is only partially hydrotreated or comprising little low boiling product, the sponge capacity for gases in the low amount of low boiling product will be low, especially if the product is high boiling, since in this case the majority of product which is liquid at cold separator conditions will have been withdrawn in the high pressure high temperature separator. Furthermore, if the moderate amount of condensed non-polar hydrocarbons, is dominated by a high amount of polar compounds, such as light oxygenates, the capacity for dissolving non-polar gases in the small volume will be low. As a result, the withdrawal of CO2, CO and CH4 from the cold gas phase will be low, and therefore the purity of recycle gas will also be low. Finally a two stage process will have higher recycle gas purity, as it typically involves a high pressure stripper and a cold separator between stages and a cold separator before fractionation, which will withdraw more CO2 from the gas loop.

[0048] A common method for purification of gas streams in hydroprocessing plants is the use of amine scrubbers, in which especially CO2 and H2S are reversibly captured in an aqueous amine solution. However, if the gas to be purified also comprises water soluble compounds such as methanol, ethanol and formic acid, these compounds will also be captured in an amine scrubber, but not reversibly, and therefore embodiments of the present invention include embodiments with purification of recycle gas in other means than gas scrubbers using scrubbing solutions in which product oxygenates may be dissolved.

[0049] The use of an amine scrubber for gas purification involves a very low pressure drop, and therefore a scrubber may be positioned in line with a recycle gas compressor, which is tasked with pressurizing high pressure gas to match process pressure, compensating for the reactor pressure drop of perhaps 1 MPa.

[0050] Other means of purifying recycle gas are commonly related to a more significant pressure drop. A membrane unit may be used to purify gases, and will provide some purification at moderate pressure drop, and more purification with increasing pressure drop. Therefore, if moderate purification of the H2 rich gas is required, membrane purification may be a cost effective alternative to an amine scrubber, if it is configured in a low pressure drop configuration, withdrawing a moderate amount of gas and forming a separate loop around the recycle gas compressor.

[0051] When the amount of impurities to be removed is higher, such as a total amount of CO2, CO and CH4 above 1 vol%, 3 vol% or even 5 vol%, it may be beneficial or even required to operate at a higher pressure drop, where the purified recycle gas is directed to the make-up gas compressor, since hydrogen is typically provided at moderately high pressure such as 2 MPag from a hydrogen plant. Such a configuration of the purification of recycle gas may enable a high pressure drop, such as 9 MPa pressure drop from 11 MPag to 2 MPag, and the recycle gas may either be withdrawn prior to compression of the recycle gas between the cold separator and a knock-out drum or after compression of the recycle gas. This configuration has a higher capital cost and a higher operating cost, since a larger make up gas compressor is required which also will have a high energy consumption as a high volume must undergo high pressurization.

Brief Description of Drawings

[0052] Fig.1 shows a process for hydroprocessing of a feedstock comprising oxygenates, with membrane purification in the recycle gas loop.

[0053] Fig.2 shows a process for hydroprocessing of a feedstock comprising oxygenates, with membrane purification between the cold separator and the make-up gas compressor. [0054] Fig.3 shows a process for hydroprocessing of a feedstock comprising oxygenates, with membrane purification between the recycle gas compressor and the make-up gas compressor.

Fig.1

[0055] In Fig.1 a feedstock comprising oxygenates (2) is pressurized in a feedstock pump (FP) and combined with a hydrogen rich gas (10) comprising make up hydrogen gas (4) and recycle gas (8). This feedstock stream (12) is after heating by heat exchange with the reactor effluent (16) in a heat exchanger (HX) combined with additional recycle gas directed as a reactor feed stream (14) to a reactor (R) comprising one or more catalysts configured, by control of conditions including composition, temperature, pressure and space velocity, to provide a desired hydroprocessing conversion of the reactor feed stream (14). The conditions may be chosen to only support a limited extent of reaction, e.g. by limiting the temperature or the availability of hydrogen. The reactor effluent (16) is cooled in heat exchanger (HX) and directed to a hot high-pressure separator (HHPS) providing a first product stream (18) and a vapor stream (20), which is cooled in cooler (C) and directed to a cold high-pressure separator (CHPS) from which sour water (22) and light liquid product (24) are separated from light gases (26). The light gases are combined with a purified gas stream (36) and directed to the knock-out drum (KOD) for removal of liquid, and further to a recycle gas compressor (RC). A gas stream for purification (28) is split from the light gases and is directed to a membrane separator (M) providing a retentate gas (30) depleted in hydrogen and a purified gas stream (36) rich in hydrogen. The remainder of the light gases (34) is directed as recycle gas and split in an amount of recycle gas (8) combined with the feedstock comprising oxygenates (2) prior to heating and an amount directed to the reactor (R).

[0056] In alternative embodiments the purified gas (36) may also be directed to a position upstream the cooler (C) or between the cooler and the cold high pressure separator (CHPS). Fig.2

[0057] In Fig.2 a feedstock comprising oxygenates (2) is pressurized in a feedstock pump (FP) and combined with a hydrogen rich gas (10) comprising make up hydrogen gas (4), a purified gas (6) and a recycle gas (8). This feedstock stream (12) is after heating by heat exchange with the reactor effluent (16) in a heat exchanger (HX) combined with additional recycle gas directed as a reactor feed stream (14) to a reactor (R) comprising one or more catalysts configured, by control of conditions including composition, temperature, pressure and space velocity, to provide a desired hydroprocessing conversion of the reactor feed stream (14). The conditions may be chosen to only support a limited extent of reaction, e.g. by limiting the temperature or the availability of hydrogen. The reactor effluent (16) is cooled in heat exchanger (HX) and directed to a hot high- pressure separator (HHPS) providing a first product stream (18) and a vapor stream (20), which is cooled in cooler (C) and directed to a cold high-pressure separator (CHPS) from which sour water (22) and light liquid product (24) are separated from light gases (26). The light gases are split in a gas stream for purification (28) and a stream (32) directed to the knock-out drum (KOD) for removal of liquid, and further to a recycle gas compressor (RC). The gas stream for purification (28) is split from the light gases (26) and is directed to a membrane separator (M) providing a retentate gas (30) depleted in hydrogen and a purified gas (6) rich in hydrogen. The remainder of the light gases (34) is directed as recycle gas and split in an amount of recycle gas (8) combined with the feedstock comprising oxygenates (2) prior to heating and an amount directed to the reactor (R).

Fig.3

[0058] In Fig.3 a feedstock comprising oxygenates (2) is pressurized in a feedstock pump (FP) and combined with a hydrogen rich gas (10) comprising make up hydrogen gas (4), a purified gas (6) and a recycle gas (8). This feedstock stream (12) is after heating by heat exchange with the reactor effluent (16) in a heat exchanger (HX) combined with additional recycle gas directed as a reactor feed stream (14) to a reactor (R) comprising one or more catalysts configured, by control of conditions including composition, temperature, pressure and space velocity, to provide a desired hydroprocessing conversion of the reactor feed stream (14). The conditions may be chosen to only support a limited extent of reaction, e.g. by limiting the temperature or the availability of hydrogen. The reactor effluent (16) is cooled in heat exchanger (HX) and directed to a hot high- pressure separator (HHPS) providing a first product stream (18) and a vapor stream (20), which is cooled in cooler (C) and directed to a cold high-pressure separator (CHPS) from which sour water (22) and light liquid product (24) are separated from light gases (26). The light gases (26) are directed to the knockout drum (KOD) for removal of liquid, and further to a recycle gas compressor (RC). Downstream the recycle gas compressor (RC) the gas stream for purification (28) is split from the light gases (26) and is directed to a membrane separator (M) providing a retentate gas (30) depleted in hydrogen and a purified gas (6) rich in hydrogen. The remainder of the light gases (34) is directed as recycle gas and split in an amount combined with the feedstock comprising oxygenates (2) prior to heating and an amount directed to the reactor (R).

Description of Embodiments

[0059] A first aspect of the present disclosure relates to a process for hydroprocessing a feedstock comprising oxygenates, comprising the steps of a. directing said feedstock, an amount of make-up hydrogen and a recycle gas to contact a catalyst active in hydroprocessing under active hydroprocessing conditions, to provide a hydroprocessed product stream, b. separating from the hydroprocessed product stream a vapor product fraction and a liquid product fraction by gas liquid separation at a pressure above 80% of said active hydroprocessing conditions and a temperature above 200°C, c. separating from the vapor product fraction a gaseous product fraction and a light liquid product fraction by gas/liqu id separation at a pressure above 80% of said active hydroprocessing conditions and a temperature below 100°C, d. directing at least an amount of said gaseous product fraction to a means of gas purification to provide a hydrogen rich gas fraction depleted in molecules with a molecular weight above 12 g/mole and a hydrogen depleted gaseous fraction enriched in molecules with a molecular weight above 12 g/mole, e. providing at least an amount of said hydrogen rich gas fraction as a portion of said recycle gas or make-up hydrogen.

[0060] This has the associated benefit of providing a pure recycle gas, also for cases where hydroprocessed product stream is only partially hydroprocessed such that the liquid phase has a low capacity for capturing CO2, CO and CH4.

[0061 ] A second aspect of the present disclosure relates to a process according to the first aspect characterized in characterized in the hydroprocessed product stream comprising at least 2% organically bound oxygen.

[0062] This has the associated benefit of such a process supporting the removal of undesired CH4 and CO2 from the recycle gas, even though the solubility of CH4 and CO2 in such a partially hydroprocessed product is moderate.

[0063] A third aspect of the present disclosure relates to a process according to an aspect above characterized in characterized in the volume ratio of the gaseous product fraction and the light liquid product fraction is more than 2000 Nm³/m³.

[0064] This has the associated benefit of such a process supporting the removal of undesired CH4 and CO2 from the recycle gas, even though the sponge capacity of CH4 and CO2 in such a moderate volume of light liquid product is low.

[0065] A fourth aspect of the present disclosure relates to a process according to an aspect above characterized in 10-90% of said gaseous fraction being directed to said means of separation, and 80-100% of the remaining gaseous fraction being directed as a further portion of said recycle gas.

[0066] This has the associated benefit of enabling purification of the gaseous fraction, to provide favorable process conditions.

[0067] A fifth aspect of the present disclosure relates to a process according to an aspect above characterized in said gaseous fraction comprising 30-90 vol% hydrogen gas.

[0068] This has the associated benefit of enabling efficient use of the hydrogen resource even if the gaseous fraction contains high amounts of e.g. CO2. [0069] A sixth aspect of the present disclosure relates to a process according to an aspect above characterized in said gaseous fraction comprising at least 1 vol%, 3 vol% or 5 vol% CO2, CO and CH4 in combination.

[0070] This has the associated benefit of enabling efficient use of the hydrogen resource even if the gaseous fraction contains high amounts of CO2, CO and CH₄.

[0071] A seventh aspect of the present disclosure relates to a process according to an aspect above characterized in said recycle gas comprising 70-95% hydrogen gas.

[0072] This has the associated benefit of an efficient balance between cost and benefit of hydrogen gas purification.

[0073] An eighth aspect of the present disclosure relates to a process according to an aspect above characterized in the gauge pressure at the outlet of said means of gas purification being 10-100% of the pressure of the active hydroprocessing conditions.

[0074] This has the associated benefit of an efficient balance between purification and cost of pressurization of the recycle gas, e.g., enabling an efficient purification requires a pressure loss from active hydroprocessing conditions at 15 MPa to a make-up gas supply pressure at 2 MPa.

[0075] A ninth aspect of the present disclosure relates to a process according to an aspect above characterized in said means of gas purification being a membrane separator.

[0076] This has the associated benefit of a membrane separator being a cost effective separator of CO2 from H2. The membrane material may be selective based on molecular size or physiochemical properties.

[0077] A tenth aspect of the present disclosure relates to a process according to an aspect above characterized in said means of gas purification being a sponge oil separator employing a sponge oil different from said hydroprocessed product stream, such as a fraction separated from said hydroprocessed product in a downstream separation. [0078] This has the associated benefit of employing a sponge oil as a cost effective means of separation as it is useful for blending with the process product.

[0079] An eleventh aspect of the present disclosure relates to a process according to an aspect above wherein said hydrogen rich gas fraction is combined with said amount of make-up hydrogen and pressurized by at least 5 MPa prior to contacting said catalyst.

[0080] This has the associated benefit of enabling a process with a high pressure drop over the means of gas purification by increasing the pressure of the hydrogen rich gas by at least 5 MPa, which enables the use of e.g. a membrane separator with high purification.

[0081] An eleventh aspect of the present disclosure relates to a process according to one of the first ten aspects above wherein the hydrogen rich gas fraction is pressurized by at least 1 MPa and less than 5 MPa prior to being combined with other streams.

[0082] This has the associated benefit of enabling a process with a low pressure drop over the means of gas purification by increasing the pressure of the hydrogen rich gas by 1-5 MPa, such that pressurization may be carried out together with unpurified recycle gas.

[0083] An further aspect of the present disclosure relates to a process plant configured for carrying out a process according to any aspect above.

Examples

[0084] The effect of the invention is illustrated by two series of examples, demonstrating the gas loop efficiency for a high hydrogen consumption case with full deoxygenation of a feedstock dominated by triglycerides and a low hydrogen consumption case with partial deoxygenation of a pyrolysis oil. In both cases separation will be made in two separators operating at reactor pressure, and in Table 1 , flow rates of the vapor and liquid streams out of the cold high pressure separator and selected concentrations of dissolved gasses in the liquid stream are listed (stream 24 and 26 in all 3 figures). [0085] A process designed for full deoxygenation (Full HDO in Table 1) has a consumption of hydrogen is 440 Nm³/m³. The light liquid product contains less than 100 ppm_wt oxygen and at the conditions of the hot and cold high-pressure separators (5.9 MPag, 240°C/50°C) the resulting in a gas: liquid ratio of 1686 Nm³/m³.

[0086] For a process designed for partial deoxygenation the consumption of hydrogen is 82 Nm³/m³. The light liquid product contains around 4 wt% oxygen and at the conditions of the hot and cold high-pressure separators (11 MPag, 240°C/50°C) the amount of light liquid product is 1 .27 m³/h and the amount of gas is 8,157 Nm³/h, resulting in a gas: liquid ratio of 6414 Nm³/m³. The concentration of CO2 in the liquid from the cold high-pressure separator is 14.3 g/kg, compared to the 2.1 g/kg of the full deoxygenation process.

[0087] Table 2 shows for the full deoxygenation process, that without purification, a satisfactory recycle gas hydrogen purity of 80.5 vol% requires a purge of light gases including 248 kmol/h of H2, corresponding to 22% of the chemical consumption of H2, which is 1114 kmol/h.

[0088] If the same recycle gas purity is to be obtained by membrane separation, positioning the membrane in the recycle loop, as illustrated in Fig.1 will provide sufficient purification with a low driving pressure of 2.0 MPa. In combination, the make-up hydrogen compressor and the recycle gas compressor will consume 613 kW according to this case.

[0089] If the same recycle gas purity is to be obtained by membrane separation, positioning the membrane between the recycle cold high pressure separator and the make up gas compressor, as illustrated in Fig.2 sufficient purification may be obtained by a driving pressure of 3.2 MPa. In combination, the make-up hydrogen compressor and the recycle gas compressor will consume 670 kW according to this case.

[0090] If the same recycle gas purity is to be obtained by membrane separation, positioning the membrane between the recycle compressor and the make up gas compressor, as illustrated in Fig.3 sufficient purification may be obtained by a driving pressure of 5.3 MPa. In combination, the make-up hydrogen compressor and the recycle gas compressor will consume 670 kW according to this case.

[0091] In this scenario, only modest purification is required, and the least costly and simplest process is the provision of a membrane in the recycle loop. For many similar scenarios a moderate purge may be the most efficient process for maintaining a high hydrogen concentration.

[0092] Table 3 shows for the partial deoxygenation process, that without purification, a satisfactory recycle gas purity of 82 vol% hydrogen requires a purge of light gases including 16 kmol/h of H2, corresponding to 33% of the chemical consumption of H2, which is 48 kmol/h.

[0093] If the same recycle gas purity is to be obtained by membrane separation, positioning the membrane in the recycle loop, as illustrated in Fig.1 will provide sufficient purification with a low driving pressure of 2.3 MPa. In combination, the make-up hydrogen compressor and the recycle gas compressor will consume 149 kW according to this case.

[0094] If the same recycle gas purity is to be obtained by membrane separation, positioning the membrane between the recycle cold high pressure separator and the make up gas compressor, as illustrated in Fig.2 sufficient purification may be obtained by a driving pressure of 8.7 MPa. In combination, the make-up hydrogen compressor and the recycle gas compressor will consume 136 kW according to this case.

[0095] If the same recycle gas purity is to be obtained by membrane separation, positioning the membrane between the recycle compressor and the make up gas compressor, as illustrated in Fig.3 sufficient purification may be obtained by a driving pressure of 11 .0 MPa. In combination, the make-up hydrogen compressor and the recycle gas compressor will consume 141 kW according to this case.

[0096] A comparison of Table 2 and Table 3 shows that a process with only partial deoxygenation has a much reduced hydrogen consumption, but also that the H2 purity out of the cold high pressure separator is lower, since CO2 is not captured in the liquid product. [0097] In the case with full deoxygenation and capture of CO2 in the liquid product, purification by use of a membrane in the recycle loop (Fig.1 ) is the only scenario with a reduction of the total compressor power and reduced purge of H2.

[0098] In the case with partial deoxygenation, and poor capture of CO2 in the liquid product, all three layouts for purification by use of a membrane are beneficial but layouts with the membrane in the make-up gas loop (Fig.2 and Fig.3) are the most beneficial scenarios, resulting in 14 % and 11 % reduction in power consumption. In addition, the loss of hydrogen as purge or retentate is also lower in this layout.

Table 1

Table 2

Table 3

Claims

[Claim 1 ] A process for hydroprocessing a feedstock comprising oxygenates, comprising the steps of a. directing said feedstock, an amount of make-up hydrogen and a recycle gas to contact a catalyst active in hydroprocessing under active hydroprocessing conditions, to provide a hydroprocessed product stream comprising oxygenates but in a lower amount than the feedstock comprising oxygenates, b. separating from the hydroprocessed product stream a vapor product fraction and a liquid product fraction by gas liquid separation at a pressure above 80% of said active hydroprocessing conditions and a temperature above 200°C, c. separating from the vapor product fraction a gaseous product fraction and a light liquid product fraction by gas/liqu id separation at a pressure above 80% of said active hydroprocessing conditions and a temperature below 100°C, d. directing at least an amount of said gaseous product fraction to a means of gas purification to provide a hydrogen rich gas fraction depleted in molecules with a molecular weight above 12 g/mole and a hydrogen depleted gaseous fraction enriched in molecules with a molecular weight above 12 g/mole, e. providing at least an amount of said hydrogen rich gas fraction as a portion of said recycle gas or make-up hydrogen.

[Claim 2] A process according to claim 1 characterized in characterized in the hydroprocessed product stream comprising at least 2% organically bound oxygen.

[Claim 3] A process according to claim 1 or 2 characterized in characterized in the volume ratio of the gaseous product fraction and the light liquid product fraction is more than 2000 Nm³/m³.

[Claim 4] A process according to claim 1 , 2 or 3 characterized in 10-90% of said gaseous fraction being directed to said means of separation, and 80- of said recycle gas.

[Claim 5] A process according to claim 1 , 2, 3 or 4 characterized in said gaseous fraction comprising 30-90 vol% hydrogen gas.

[Claim 6] A process according to claim 1 , 2, 3, 4 or 5 characterized in said gaseous fraction comprising at least 1 vol%, 3 vol% or 5 vol% CO2, CO and CH4 in combination.

[Claim 7] A process according to claim 1 , 2, 3, 4, 5, 6 or characterized in said recycle gas comprising 70-95% hydrogen gas.

[Claim 8] A process according to claim 1 , 2, 3, 4, 5, 6 or 7 characterized in the gauge pressure at the outlet of said means of gas purification being 30- 100% of the pressure of the active hydroprocessing conditions.

[Claim 9] A process according to claim 1 , 2, 3, 4, 5, 6, 7 or 8 characterized in said means of gas purification being a membrane separator.

[Claim 10] A process according to claim 1 , 2, 3, 4, 5, 6, 7, 8 or 9 characterized in said means of gas purification being a sponge oil separator employing a sponge oil different from said hydroprocessed product stream.

[Claim 11 ] A process according to claim 1 , 2, 3, 4, 5, 6, 7, 8, 9 or 10 wherein said hydrogen rich gas fraction is combined with said amount of make-up hydrogen and pressurized by at least 5 MPa prior to contacting said catalyst.

[Claim 12] A process according to claim 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 prior to being combined with other streams.

[Claim 13] A process plant configured for carrying out a process according to any claim above.