A process for removing silicon-containing impurities from a feedstock

Abstract

The invention relates to a process for removing one or more silicon-containing impurities from a hydrocarbon feedstock, the process comprising the step of contacting the hydrocarbon feedstock with a guard bed comprising a porous material comprising gamma-alumina, the porous material having a total pore volume of 600-850 ml / kg, as measured by mercury intrusion porosimetry (HgPV), and a BET-surface area of 100-500 m2 / g, thereby providing a purified hydrocarbon feedstock.

Description

[0001] TITLE: A PROCESS FOR REMOVING SILICON-CONTAINING IMPURITIES FROM A FEEDSTOCK

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a process for removing Si impurities from a feedstock such as a renewable feedstock by contacting the feedstock with a guard bed comprising a porous material.

[0004] BACKGROUND

[0005] Renewable fuels can be produced from a broad variety of hydrocarbon sources, including, e.g., pyrolysis oil, spent lube oil, other non-edible compounds, animal fats, vegetable oils, etc. Before feedstocks derived from renewable organic material can be used in conventional automobile engines, aviation turbines, marine engines, or other engines, and distributed using existing fuel infrastructure, it is desirable to convert the material into hydrocarbons similar to those present in petroleum-derived transportation fuels.

[0006] One well-established method for upgrading feedstocks is by employing a hydrotreating process. This kind of process can be used, e.g., for converting vegetable oils into normal paraffins in the gasoline, jet fuel, or diesel boiling range. In a hydrotreating / hydrotreatment process, the feedstock is reacted with hydrogen at elevated temperature and pressure in a catalytic reactor.

[0007] A particular problem with renewable feedstocks is that they contain high amounts of impurities such as silicon-containing and phosphorus-containing species. Si is typically present in high amounts in pyrolysis-derived feedstocks (both from plastics and bio / waste mass) and spent lube oil. Si can be derived from anti-foaming additives made of polydimethylsiloxanes (PDMS). In pyrolysis-derived feedstocks, sources can also be additives for plastics and cosmetic products. P-containing species in feedstocks may take the form of phospholipids such as lecithin, from seed oils. Waste lube oils can also contain species such as zinc dialkyl dithio phosphates (ZDDP), which acts as an anti-wear additive in such lubricants.

[0008] The amounts of Si seen in pyrolysis-derived feedstocks can be very high compared to cokernaphtha (e.g., 50-200 ppm Si vs. <5 ppm Si). Furthermore, the size of PDMS molecules in pyrolysis-derived feedstocks can range from sizes seen in coker-naphtha feedstock to much bigger rings. Large Si-containing molecules limit the pore size that can be used in Si-guards and the pick-up capacity at a given volume. Existing Si guards either do not allow for maximum penetration due to too small pores or have too big pores and thus too small specific surface area, resulting in insufficient Si pick-up capacity for feedstocks containing high Si amounts. For example, Si guards with high Si pickup capacity designed for coker-naphtha often do not perform optimally for pyrolysis- derived feedstocks or spent lube oil. The pores tend to clog up, leaving the inside of the extrudate un-utilized. This results in their full capacity not being utilized.

[0009] Si guards in fossil service will typically treat a distilled fraction of the feed which will define the molecular size of hydrocarbons as well as Si species. However, pyrolysis oils may unstable and polymerize during heating, such that distillation of unprocessed feedstock is not possible. This means that the Si guard must be able to handle a broader range of Si species compared to fossil service.

[0010] Si- and P-containing species quickly deactivate conventional catalysts for hydrotreating and reduce cycle length dramatically. The refiners processing renewable feedstocks are therefore typically forced to load more material for guarding the hydrotreating catalyst compared to fossil fuel-based refining processes.

[0011] It is predicted that the renewable fuels market will be moving towards processing more difficult feedstocks (i.e., tallow, biomass, plastic) that contain higher levels of Si and P contaminants. Furthermore, refiners are continuously interested in increasing cycle length of processing renewables.

[0012] WO 2024 / 165222 discloses a phosphorous guard material having large pores.

[0013] WO 2022 / 008508 discloses a reactive catalyst for use downstream guards.

[0014] There is a need for a process for capture and improved capture of particularly Si-containing species in feedstocks such as renewable feedstocks, to remove Si-containing impurities from the feedstocks. It is an object of embodiments of the invention disclosed herein to solve this problem.

[0015] SUMMARY

[0016] The disclosure relates to a process for removing one or more silicon-containing impurities from a hydrocarbon feedstock, the process comprising the step of contacting the hydrocarbon feedstock with a guard bed comprising a porous material comprising gamma-alumina, the porous material having a total pore volume of 600-850 ml / kg, as measured by mercury intrusion porosimetry (HgPV), and a BET-surface area of 100-500 m2 / g, thereby providing a purified hydrocarbon feedstock.

[0017] Specifically, a process is disclosed for removing one or more silicon-containing impurities from a hydrocarbon feedstock, the process comprising the step of contacting the hydrocarbon feedstock with a guard bed comprising a porous material comprising gamma-alumina, the porous material having a total pore volume of 600-850 ml / kg, as measured by mercury intrusion porosimetry (HgPV), and a BET-surface area of 100-500 m2 / g, and of the pore volume in pores having a radius from 10 A to 1000 A, at least 50 vol% of the pore volume is in pores with a radius in the range of between 25 A and 70 A.

[0018] Further details of the invention are provided in the following description and figures.

[0019] BRIEF DESCRIPTION OF THE FIGURES

[0020] Fig. 1 shows SEM (scanning electron microscope) images of Si-capture in two different samples of porous material.

[0021] Fig. 2 shows SEM images of Si- and P-capture in two different samples of porous material.

[0022] Fig. 3 shows examples of different polysiloxanes that may be present in pyrolysis oil and / or coker-naphtha feedstock.

[0023] Fig. 4 shows the pore size distribution (PSD) by mercury intrusion porosimetry of different samples of porous material.

[0024] Fig. 5 shows the penetration of a number of elements, including Si and P, into different samples of porous material, along a cross-section of each sample.

[0025] DETAILED DESCRIPTION

[0026] In the following, mercury intrusion porosimetry is conducted according to ASTM D4284, BET-surface area is measured according to ASTM D3663, i.e. multi-point determination of surface area by the BET equation.

[0027] A process for removing one or more silicon-containing impurities from a hydrocarbon feedstock is provided, the process comprising the step of contacting the hydrocarbon feedstock with a guard bed comprising a porous material comprising gamma-alumina, the porous material having a total pore volume of 600-850 ml / kg, as measured by mercury intrusion porosimetry (HgPV), and a BET-surface area of 100-500 m2 / g, thereby providing a purified hydrocarbon feedstock.

[0028] The hydrocarbon feedstock that is contacted with the guard bed is a feedstock comprising hydrocarbons and optionally impurities, such as Si-containing species. The feedstock comprises hydrocarbons and optionally heteroatoms, i.e. other elements, such as oxygen, sulfur, nitrogen, silicon phosphorous, and / or metals. The term "hydrocarbon feedstock" is understood as a feedstock rich in molecules comprising hydrogen and carbon. Additionally, the feedstock may comprise heteroatoms, i.e. other elements, such as oxygen, sulfur, nitrogen, silicon, phosphorous, and metals. The heteroatoms may be incorporated into molecules containing hydrogen and carbon. The feedstock may be a combination of molecules comprising only hydrogen and carbon and molecules comprising hydrogen and carbon and heteroatoms. Some heteroatoms such as oxygen may be present in the feedstock in amounts up to 10 wt% or even up to 50 wt%.

[0029] The feedstock may consist, for example, of at least 40% vol. hydrocarbons, such as at least 50% vol. hydrocarbons, such as at least 60% vol. hydrocarbons, such as at least 70% vol. hydrocarbons, such as at least 80% vol. hydrocarbons, such as at least 90% vol. hydrocarbons, such as at least 95% vol. hydrocarbons, such as at least 98% vol. hydrocarbons. For example, the feedstock may be a combination of a recycle feed that is close to pure hydrocarbons and a fresh feed that is close 100% molecules that comprise heteroatoms. Ratios of such dilution by recycle from 1 : 1 to 30: 1 are reported in the literature, depending on the nature of feedstocks.

[0030] The hydrocarbon feedstock is understood as the stream that enters the reactor wherein the one or more silicon-impurities are removed from the hydrocarbon feedstock. The hydrocarbon feedstock may have undergone various steps, such as pre-treatment, heating, and / or mixing, before entering the reactor (i.e., before being contacted with the guard bed). In an embodiment, the hydrocarbon feedstock is or essentially is: a pyrolysis oil, spent lube oil, diesel, kerosene, or a combination of two or more thereof, optionally with other components added thereto. In an embodiment, the hydrocarbon feedstock is a renewable hydrocarbon feedstock. In an embodiment, the pyrolysis oil is provided by thermal decomposition of a solid renewable feedstock, such as plastics or bio / waste mass.

[0031] In an embodiment, the feedstock is renewable feedstock, a fossil fuel feedstock, or a combination thereof. Suitably, the feedstock is a renewable feedstock or a combination of a renewable feedstock and a fossil fuel feedstock.

[0032] In an embodiment, the feedstock is: i) a renewable source obtained from a raw material of renewable origin, such as originating from plants, algae, animals, fish, vegetable oil refining, domestic waste, waste rich in plastic, industrial organic waste like tall oil or black liquor, or a feedstock derived from one or more oxygenates taken from the group consisting of triglycerides, fatty acids, resin acids, ketones, aldehydes or alcohols where said oxygenates originate from one or more of a biological source, a gasification process, a pyrolysis process, Fischer-Tropsch synthesis, or methanol based synthesis. The oxygenates may also originate from a further synthesis process. Some of these feedstocks may contain aromatics; especially products from pyrolysis processes or waste products from e.g. frying oil. Any combinations of the above feedstocks are also envisaged.

[0033] The feedstock can also be: ii) a feedstock originating from a fossil fuel, such as diesel, kerosene, naphtha, vacuum gas oil (VGO), spent lube oil, or combinations thereof; or iii) a feedstock originating from combining a renewable source according to i) and a feedstock originating from a fossil fuel according to ii)

[0034] In the context of the present invention, the terms "renewable source" and "renewable feed" or "renewable feedstock", are used interchangeably. The terms "feedstock originating from a fossil fuel" and "fossil fuel feedstock" are also used interchangeably.

[0035] A renewable feedstock may be sourced from waste or be of biological origin, and may be defined by tracing the origin. Biological origin may also be defined by the14C content being above 0.5 parts per trillion of the total carbon content. Commonly pyrolysis oil originating from thermal decomposition of a solid renewable material, comprises 40-85 wt% C and 3-50 wt% O and an atomic ratio between H and C of less than 1.8 or 1.6.

[0036] Commonly pyrolysis oil originating from thermal decomposition of artificial polymers may involve 0.5-5 wt% or 0.5-10 wt% of conjugated di-olefins and as much as 30-90 wt% such as 65 wt% olefins. The atomic oxygen content may typically be below 1 wt% such as from 500 ppmwt, but it may be up to 15 wt%.

[0037] In an embodiment, the portion of the feedstock originating from a renewable source is 5-60 wt%, such as 10-50 wt%. In another particular embodiment, the portion of the feedstock originating from a renewable source is higher than 60 wt%, for instance 70-90 wt%.

[0038] In an embodiment, the process is a process for removing one or more silicon-containing impurities and, optionally, one or more phosphorous-containing impurities from a hydrocarbon feedstock, the process comprising the step of contacting the hydrocarbon feedstock with a guard bed comprising a porous material comprising gamma-alumina, the porous material having a total pore volume of 600-850 ml / kg, as measured by mercury intrusion porosimetry (HgPV), and a BET-surface area of 100-500 m2 / g, and of the pore volume in pores having a radius from 10 A to 1000 A, at least 50 vol% of the pore volume is in pores with a radius in the range of between 25 A and 70 A. thereby providing a purified hydrocarbon feedstock.

[0039] In an embodiment, the process is used for purifying a hydrocarbon feedstock containing 0.5- 1000 ppm Si, such as 1-10 ppm Si, 1-100 ppm Si, 1-200 ppm Si, 1-300 ppm Si, 1-400 ppm Si, 1-500 ppm Si, 1-600 ppm Si, 1-700 ppm Si, 1-800 ppm Si, 1-900 ppm Si, 10-900 ppm Si, 5-200 ppm Si, 5-400 ppm Si, 5-900 ppm Si, 10-200 ppm Si, 10-400 ppm Si, 10-900 ppm Si, or 50-900 ppm Si,. The content of Si may vary significantly depending on the feedstock. For example, a fossil coker naphtha feedstock may have 1-2 ppm Si while a pyrolysis oil feedstock may have from 5 to 500 ppm Si, depending on the raw material source, which may be either fossil feedstock, typically with low amounts of Si or pyrolysis oil.

[0040] In an embodiment, the feedstock contains 0.5-1000 ppm P. The content of P may vary significantly depending on the feedstock. For instance, 50-60 ppm P in oils derived from oxygenates originated from a pyrolysis process e.g. pyrolysis oil, or 100-300 ppm, or 50-300 ppm, e.g. 200 ppm for a feedstock originating from animals, particularly animal fat. It is understood that the ppm units are on weight basis, i.e. ppm-wt.

[0041] The guard bed used in the process is designed to remove contaminants, including Si- containing impurities and optionally also P-containing impurities, from the hydrocarbon feedstock, thereby protecting any downstream or bulk catalyst(s). Absent the guard bed, downstream catalyst beds would be exposed to the high amounts of Si and P present in, for example, renewable feedstock, resulting in contamination of the catalyst and thus accelerated deactivation due to poisoning, and a shortening of the cycle length.

[0042] In essence, the higher the surface area / volume (specific surface area (SSA)) of the alumina of the guard bed, the higher the pick-up capacity of the guard bed at a given volume. Large Si-containing molecules present in the feedstock limit the pore size that can be used in Si- guards and do not allow to go for maximum SSA due to these pore size restraints.

[0043] The total pore size volume and BET-surface and the pore radius are linked, such that, for example, the pore radius is determined by the total pore size volume and the BET-surface. This means that the pore size cannot be freely adjusted without affecting the other two.

[0044] As described in the background section of this application, a particular problem with renewable feedstocks is that they contain high amounts of impurities such as silicon- containing species and phosphorus-containing species. The amounts of Si seen in pyrolysis- derived feedstocks can be very high compared to coker-naphtha (typically 50-200 ppm Si vs. <5 ppm Si). Furthermore, the size of PDMS molecules in pyrolysis-derived feedstocks can range from the sizes seen in coker-naphtha feedstock to significantly bigger sizes. The relatively small pores of the guard beds typically used for coker-naphtha feedstock therefore tend to clog up if the PDMS molecules are large, not allowing for their full capacity to be utilized. The same can occur due to large P-containing molecules in the feedstock.

[0045] In an embodiment, at least 10%, such as 20%, of the Si atoms present in the hydrocarbon feedstock are present in molecules with a molar mass above 300 g / mole.

[0046] The guard bed used in the process according to the invention has a capacity for Si which significantly exceeds that of existing guard beds, and it captures Si effectively. The effective removal of impurities from the hydrocarbon feedstock by the guard bed has the effect of extending the life cycle of a downstream catalyst(s). This effect is achieved by the composition, the pore size, the total pore size volume, and the specific surface area of the guard bed. Due to the particular pore size of the porous material of the guard bed used in the process according to the present invention, there is no clogging of the pore system by big Si molecules, thus allowing for deep Si penetration. The pores serve for Si impurity capture, and optionally also P impurity capture. Too small pores would lead to clogging. At the same time, bigger pores lower the surface area of the porous material of the guard bed, thus lowering the Si pick-up capacity of the guard bed. In addition there may be a competition between capture of the two elements such that the pore size may beneficially be selected to match the dominating impurity.

[0047] The right balance between pore size and specific surface area is essential to achieve the desired effect of effective Si impurity removal and optionally also P impurity removal by the guard bed. The fact that the process disclosed herein is also effective for removal of P impurities has the advantage that the process can be used to remove both Si and P impurities, rather than having to perform two different processes to remove first Si impurities and second P impurities, or vice versa.

[0048] The preferable pore size depends on the size of the Si impurities present in the feedstock. If only small Si impurities are present, the pore size should be small, compared to the pore size needed if larger Si impurities were present. If both Si and P impurities are present, and the P impurities are larger than the Si impurities, larger pores (meaning larger than if only the Si impurities were present) are preferable to achieve effective pickup of both Si and P impurities.

[0049] The described porous material is especially well suited for feedstocks boiling in an intermediate range of 200-300°C and for feedstocks which are not fractionated.

[0050] When the feedstock is fractionated, such that hydrocarbons as well as Si species boil below 200°C, a guard material is preferred which of the pore volume in pores having a radius from 10 A to 1000 A, has at least 30 vol%, 50 vol% or 80 vol% of the pore volume is in pores with a radius in the range of between 15 A and 30 A, due to the size of molecules concerned.

[0051] Such a material will typically have a high surface area above 290 m2 / g BET e.g. 290, 300 or 320 m2 / g BET to 350, 370 or 400 m2 / g BET, and the alumina will be at least 80 wt%, such as 90 wt% and up to 100 wt% gamma-alumina.

[0052] When the feedstock is fractionated, such that hydrocarbons as well as Si species boil above 300°C, a guard material is preferred which of the pore volume in pores having a radius from 10 A to 1000 A, has at least 30 vol%, 50 vol% or 80 vol% of the pore volume is in pores with a radius in the range of between 50 A and 80 A, due to the size of molecules concerned.

[0053] Such a material will typically have a high surface area between 120, 150 or 170 m2 / g BET to 180 or 200 m2 / g BET and the alumina will be at less than 30 wt%, such as 10 wt% and down to 0 wt% gamma-alumina.

[0054] In an embodiment, the porous material has a pore size distribution (PSD) with less than 10 vol% with a radius above 250 A. This has the associated benefit of minimizing the volume in larges pores, having a low contribution to surface area.

[0055] In an embodiment, of the pore volume in pores having a radius from 10 A to 1000 A, at least 30 vol% of the pore volume is in pores with a radius in the range of between 30 A and 65 A, between 30 A and 50 A, or between 35 A and 60 A.

[0056] In an embodiment, of the pore volume in pores having a radius from 10 A to 1000 A, at least 50 vol% of the pore volume is in pores with a radius in the range of between 30 A and 65 A, between 30 A and 50 A, or between 35 A and 60 A.

[0057] In an embodiment, of the pore volume in pores having a radius from 10 A to 1000 A, at least 80 vol% of the pore volume is in pores with a radius in the range of between 25 A and 70 A, between 30 A and 65 A, between 30 A and 50 A, or between 35 A and 60 A.

[0058] It has surprisingly been found that the above pore size ranges provide an optimal balance between penetration and surface area, i.e. maximizing the volume in intermediate size pores, having a high contribution to surface area and a low tendency to plugging.

[0059] In an embodiment, the porous material has a BET-surface area of 150-380 m2 / g, such as 200-350 m2 / g, such as 250-320 m2 / g.

[0060] In an embodiment, the porous material has a BET-surface area of about 290-315 m2 / g BET.

[0061] In an embodiment, the porous material has a total pore volume of 650-800 ml / kg as measured by HgPV. In an embodiment, the porous material has a total pore volume of about 720 ml / kg as measured by HgPV.

[0062] In an embodiment, the porous material comprises one or more metals selected from Co, Mo, Ni, W, and combinations of two or more thereof. The presence of one or more of these metals gives the guard bed hydrotreating activity, such as hydrodesulfurization activity and / or hydrodenitrogenation activity. The metal(s) also result in an exotherm that facilitates better Si uptake as higher temperatures help with the reaction of Si molecules with the alumina surface of the porous material. The metal(s) can vary in amount. If loaded too much, the metal(s) may decrease the Si capacity, meaning the Si pick-up, of the guard bed.

[0063] When the porous material is suitably loaded with a suitable metal, the resulting hydrotreating activity will prevent coking. However, if loaded too much, the hydrotreating activity may get too high, resulting in coking promotion, which affects the Si pick-up capacity of the guard bed.

[0064] In an embodiment, the content of the one or more metals in the porous material is 0.1-20 wt%. In an embodiment, the porous material comprises NiMo. In an embodiment, the porous material comprises 0.1-5 wt% Ni and 0.1-10 wt% Mo, preferably 0.5-3.5 wt% Ni and 2-8 wt% Mo, more preferably 1.5-2.5 wt% Ni and 4-7.5 wt% Mo, most preferably 1.6-2.0 wt% Ni and 5.5-7.0 wt% Mo.

[0065] In an embodiment, the content of gamma-alumina in the porous material is 20-99 wt%.

[0066] In an embodiment, the porous material contains at least 50 wt%, 80 wt%, 90 wt%, 99 wt% or 100 wt% gamma alumina. This has the associated benefit of gamma-alumina providing a pore structure with small or moderate size pores.

[0067] In an embodiment, the porous material further comprises beta-alumina and / or thetaalumina. In this way, a guard bed having a particularly desirable surface area, reactivity, and / or stability can be obtained.

[0068] In an embodiment, the porous material is an extruded or tabletized pellet having a shape selected from trilobal, tetralobal, pentalobal, cylindrical, spherical, hollow such as hollow rings or hollow cylinders, and combinations thereof. Pellets having tetralobal shape, as for instance shown in Fig. 1 (left image) below, can be particularly advantageous, due to improved outer surface area to volume ratio.

[0069] In an embodiment the initial boiling point of the hydrocarbon feedstock is less than 100°C, 150°C or 180°C and the final boiling point of the hydrocarbon feedstock is greater than 200°C, 250°C, 350°C or 400°C. Such a process with a broad boiling range feedstock is especially benefitting from an intermediate pore radius range.

[0070] In an embodiment, the process is for removing one or more polydimethyl siloxane impurities (PDMS molecules) from the hydrocarbon feedstock. In an embodiment, the process is carried out at high temperature such as 100-400°C, for instance 250-350°C, optionally in the presence of a reducing agent such as hydrogen.

[0071] In an embodiment, the purified feedstock is subsequently processed in a hydrotreatment stage in the presence of a hydrotreatment catalyst.

[0072] Specific embodiments

[0073] Fig. 1

[0074] A sample (sample 1) of the porous material according to the invention was tested for Si uptake properties and its performance compared to a reference sample of porous material from a commercial coker-naphtha Si guard (sample 2). Sample 2 has smaller pores than sample 1. Fig. 1 shows SEM (scanning electron microscope) images of the two samples. The results are shown as Si-maps with brighter meaning more Si. Sample 1 (left image) shows deep penetration of Si into the porous material. Sample 2 (right image) shows low penetration of Si into the porous material. Penetration is understood as the extent to which Si enters into the extrudate, meaning how much of the guard surface is utilized. The porous material of the commercial coker-naphtha Si guard (sample 2) shows a clear lack of Si in the middle of the extrudate, which cannot be explained by the shape difference of the two samples. Due to big Si-molecules present in the feedstock used in the testing of the Si- uptake capacity, sample 2 underperforms. Access to the pores of sample 2 was blocked after a while by the big Si molecules.

[0075] Fig. 2

[0076] Fig. 2 shows SEM images of Si- and P-capture in a sample of the porous material according to the invention (sample 3) and a reference sample (sample 4), with sample 4 having smaller pores than sample 3. The results are shown as Si- and P-maps with brighter meaning more Si / P. Sample 4 managed to pick up Si (bottom right image), but P was not able to penetrate the porous material (top right image). This can affect the Si pick-up capacity as well. By contrast, sample 3 (left images) managed to pick up both Si and P, showing deep penetration of both Si and P. Fig. 3

[0077] Si-specific Gas Chromatography Atomic Emission Detector (GC-AED) analysis was performed on pyrolysis oil derived from sewage sludge, showing presence of a variety of polysiloxanes, including large rings such as 20-membered rings. Fig. 3 shows examples of different polysiloxanes that can be present in pyrolysis oil and / or coker-naphtha feedstocks. The 8- membered ring on the left in Fig. 3 is a common Si-impurity in coker-naphtha feedstocks. The size of PDMS molecules in pyrolysis-derived feedstocks can range from sizes seen in coker-naphtha feedstock to much bigger molecules, such as cyclic PDMS molecules with ring sizes of more than 4 Si-0 units (an 8 membered ring), more than 5 Si-0 units (a 10 membered ring), more than 6 Si-0 units (a 12 membered ring), more than 8 Si-0 units (a 16 membered ring), more than 9 Si-0 units (a 18 membered ring), more than 10 Si-0 units (a 20 membered ring), where the term Si-0 units shall be understood as the number of Si or O atoms in such units, i.e. 8 Si-0 units shall be understood as a ring comprising 8 Si atoms and 8 O atoms.

[0078] Fig. 4

[0079] Fig. 4 shows the pore size distribution (PSD) by mercury intrusion porosimetry of three different samples of the porous material according to the invention (samples 5-7) and a reference sample (sample 8). Note that the X-axis is logarithmic. It is observed that for samples 5-7, a significant portion, or even the majority, of the pores have a pore radius between 25 A and 70 A, between 30 A and 65 A, or between 35 A and 60 A. The preferred Si guard depends on the size of the Si molecules in the hydrocarbon feedstock to be purified. If the pores are bigger than needed to achieve deep penetration of the Si-impurities and optionally P-impurities into the porous material, then potential surface area is unnecessarily lost. The BET surface of samples 5-8 is indicated in the figure.

[0080] Fig. 5

[0081] Fig. 5 shows results from the testing of the pick-up capacity of the porous material according to the invention (bottom graph) and a reference porous material (top graph). The figure shows the distribution of a number of elements, including Si and P, along a cross-section of the porous material, after the porous material has been contacted with a hydrocarbon feedstock comprising different impurities, including heavy Si-molecules. As appears, Si is present essentially evenly through the sample according to the invention (bottom graph), indicating a high Si pick-up capacity, meaning a high Si penetration into the porous material. By comparison, Si shows a hammock distribution profile in the reference sample, with essentially no Si present in the middle of the sample, indicating a low Si pick-up capacity (low Si penetration into the porous material). Furthermore, the porous material according to the invention (bottom graph) shows a high penetration of P, with an essentially even distribution of P across the sample. Examples

[0082] Table 1

[0083] Table 1 shows physical characteristics of three different Si guard bed samples according to the invention. The physical characteristics are: bulk density (abbreviated "d Bulk") [g / ml], Ni wt.%, Mo wt.%, BET surface [m2 / g], and amount of metal per volume of the porous material comprised by the guard bed (gMo / L and gNi / L).

Claims

CLAIMS1. A process for removing one or more silicon-containing impurities from a hydrocarbon feedstock, said process comprising the step of contacting said hydrocarbon feedstock with a guard bed comprising a porous material comprising gamma-alumina, said porous material having a total pore volume of 600-850 ml / kg, as measured by mercury intrusion porosimetry (HgPV), and a BET-surface area of 100-500 m2 / g, and of the pore volume in pores having a radius from 10 A to 1000 A, at least 50 vol% of the pore volume is in pores with a radius in the range of between 25 A and 70 A. thereby providing a purified hydrocarbon feedstock.

2. The process according to claim 1, wherein, of the pore volume in pores having a radius from 10 A to 1000 A, at least 30 vol% of the pore volume is in pores with a radius in the range of between between 30 A and 65 A, between 30 A and 50 A, or between 35 A and 60 A.

3. The process according to any one of the preceding claims, wherein, of the pore volume in pores having a radius from 10 A to 1000 A, at least 80 vol% of the pore volume is in pores with a radius in the range of between 25 A and 70 A, between 30 A and 65 A, between 30 A and 50 A, or between 35 A and 60 A.

4. The process according to any one of the preceding claims, wherein the porous material has a BET-surface area of 150-380 m2 / g, such as 200-350 m2 / g, such as 250-320 m2 / g.

5. The process according to any one of the preceding claims, wherein the porous material has a BET-surface area of about 290-315 m2 / g BET.

6. The process according to any one of the preceding claims, wherein the porous material has a total pore volume of 650-800 ml / kg as measured by HgPV.

7. In an embodiment, the porous material contains at least 50 wt%, 80 wt%, 90 wt%, 99 wt% or 100 wt% gamma alumina.

8. The process according to any one of the preceding claims, wherein the porous material comprises one or more metals selected from Co, Mo, Ni, W, and combinations of two or more thereof.

9. The process according to any one of the preceding claims, wherein the porous material comprises NiMo.

10. The process according to any one of the preceding claims, wherein the porous material comprises 0.1-5 wt% Ni and 0.1-10 wt% Mo, preferably 0.5-3.5 wt% Ni and 2-8 wt% Mo, more preferably 1.5-2.5 wt% Ni and 4-7.5 wt% Mo, most preferably 1.6-2.0 wt% Ni and 5.5-7.0 wt% Mo.

11. The process according to any one of the preceding claims, wherein the hydrocarbon feedstock contains 0.5-1000 ppm Si, such as 1-10 ppm Si, 1-100 ppm Si, 1-200 ppm Si, 1- 300 ppm Si, 1-400 ppm Si, 1-500 ppm Si, 1-600 ppm Si, 1-700 ppm Si, 1-800 ppm Si, 1- 900 ppm Si, 5-200 ppm Si, 5-400 ppm Si, 5-900 ppm Si, 10-200 ppm Si, 10-400 ppm Si, 10-900 ppm Si, or 50-900 ppm Si.

12. The process according to any one of the preceding claims, wherein the initial boiling point of the hydrocarbon feedstock is less than 100°C, 150°C or 180°C and the final boiling point of the hydrocarbon feedstock is greater than 200°C, 250°C, 350°C or 400°C.

13. The process according to any one of the preceding claims, wherein the process is for removing one or more polydimethyl siloxane impurities from the hydrocarbon feedstock.

14. The process according to any one of the preceding claims, which process is carried out at high temperature such as 100-400°C, optionally in the presence of a reducing agent such as hydrogen.

15. The process according to any one of the preceding claims wherein at least 10%, such as 20%, of the Si atoms present in the hydrocarbon feedstock are present in molecules with a molar mass above 300 g / mole.

Images