Method for producing high quality base oils using two stage hydrofinishing

Abstract

This describes a process for economically and / or efficiently producing base oils with, for example, lower aromatics and other modified properties. In some embodiments, the process relates to a two-stage (or more-stage) hydrorefining process, which advantageously provides base oils with lower aromatics than comparable one-stage processes.

Description

[Technical Field]

[0001] This disclosure relates to a method for producing high-quality base oils using, for example, a novel multi-stage hydrorefining method. [Previous Technology]

[0002] Modern refining processes for producing lubricating oils from crude oil typically utilize numerous hydrogen processes. These processes are used to produce lubricating oils with suitable lubricating properties over a wide range of operating conditions. Hydrotreating / hydrocracking is typically an advanced process used to increase the viscosity index by removing low-viscosity-index molecules, including those containing sulfur and nitrogen. Hydrodewaxing is typically a process used to improve low-temperature properties by isomerizing long-chain waxy molecules, which, if not removed, can negatively affect the pour point and cloud point of the fraction. Hydrorefining is typically described as a process used to further enhance the quality of lubricating base oils, including color and oxidation stability, often by saturating aromatic molecules. However, in many cases, base oils may still contain undesirable levels of aromatics, residual organic sulfur, and / or nitrogen. Therefore, additional or alternative processes may be necessary to economically and efficiently produce base oils with one or more modified properties. [Summary of the Invention]

[0004] Advantageously, the process of the present invention economically and / or efficiently produces base oils having, for example, lower aromaticity levels and a plurality of modified properties. In one embodiment, the process includes a process for producing low-aromatic base oils, the process comprising: firstly contacting an SSZ-91 isomerization feedstock with a precious metal hydrorefining catalyst under first hydrorefining conditions to provide a first hydrorefined feedstock; and nextly contacting the first hydrorefined feedstock with a second precious metal hydrorefining catalyst under second hydrorefining conditions to provide a second hydrorefined feedstock. Typically, the second hydrorefining conditions include temperatures lower than the first hydrorefining conditions.

[0005] In another embodiment, this application relates to a process for producing low-aromatic base oils. The process includes first contacting a hydrocarbon feedstock with hydrogen and a catalyst comprising crystalline molecular sieve SSZ-91 and platinum under hydroisomerization dewaxing conditions to provide an isomerization stream. Then, under first hydrorefining conditions, the isomerization stream is contacted with a catalyst comprising a silica-alumina support and a noble metal selected from palladium, platinum, or combinations thereof. The catalyst may contain about 0.1 to about 0.6% by weight of the noble metal. Then, under second hydrorefining conditions, the first hydrorefined stream is contacted with a catalyst comprising a silica-alumina support and a noble metal selected from palladium, platinum, or combinations thereof. This catalyst may contain about 0.1 to about 0.6% by weight of the noble metal. Typically, the second hydrorefining conditions involve temperatures lower than the first hydrorefining conditions. Advantageously, base oils produced by this process often contain at least about 40% less aromatics by weight than comparable processes that use a single hydrorefining step.

[0006] Further features of the disclosed design and the advantages therefrom will be explained in more detail below with reference to specific example embodiments illustrated in the accompanying drawings.

Implementation Method

[0009] Cross-reference to related applications

[0010] This application claims the benefit of priority to the entire disclosure herein in U.S. Provisional Application No. 63 / 138,810, filed January 19, 2021, and U.S. Patent Application No. 17 / 153,865, filed January 20, 2021.

[0011] Although one or more illustrative embodiments are provided herein, any number of techniques may be used to implement the disclosed process. The disclosure is not limited to the illustrative or specific embodiments, drawings and techniques described herein, but includes any exemplary designs and embodiments illustrated and described herein, and modifications may be made within the scope of the appended technical solutions and their equivalents.

[0012] The following description of the embodiments provides reference numerals to specifically describe the features of different aspects of the invention and to teach non-limiting representative examples. The described embodiments should be considered as being able to be implemented alone or in combination with other embodiments based on the description of the embodiments. Those skilled in the art who review the description of the embodiments should be able to learn and understand the different descriptive aspects of the invention. The description of the embodiments should help to understand the invention to the extent that other implementations not specifically covered but within the knowledge of those skilled in the art who have read the description of the embodiments will be understood to be consistent with the application of the invention. Definitions

[0013] Unless otherwise stated, the following terms as used herein have the meanings as defined herein.

[0014] The term "hydrotreating" refers to a process or step performed in the presence of hydrogen to achieve hydrodesulfurization, hydrodenitrogenation, hydrodemetallization, and / or hydroaromaticization of components (e.g., impurities) of a hydrocarbon feedstock and / or to achieve hydrogenation of unsaturated compounds in the feedstock. Depending on the type of hydrotreating and the reaction conditions, the products of hydrotreating processes may have, for example, modified aromatic content, viscosity, viscosity index, saturated hydrocarbon content, low-temperature properties, volatility, and depolarization.

[0015] As used herein, the term "molecular sieve" refers to a crystalline material containing pores, cavities, or interstitial spaces of uniform size, in which molecules small enough to pass through the pores, cavities, or interstitial spaces are adsorbed, while larger molecules are not adsorbed. Examples of molecular sieves include zeolite and non-zeolite molecular sieves, such as zeolite analogues, including but not limited to SAPO (silica aluminum phosphate), MeAPO (metallic aluminum phosphate), AlPO4, and ELAPO (a family of nonmetallic substituted aluminum phosphates).

[0016] As used herein, the term "pour point" refers to the temperature at which an oil begins to flow under controlled conditions. Pour point can be determined by, for example, ASTM D5950.

[0017] "Target pour point" means the desired or required pour point of a lubricant base oil product. Target pour points are typically less than about -10°C, and are typically in the range of about -10°C to -50°C, and in some embodiments, about -5°C to about 20°C.

[0018] As used herein, "cloud point" refers to the temperature at which a lubricating oil sample begins to become cloudy when cooled under specified conditions. The cloud point of a lubricating oil base oil is complementary to its pour point. The cloud point can be determined by, for example, ASTM D5773.

[0019] The “pour point / cloud point distribution” or “pour-cloud point distribution” of a base oil refers to the distribution or difference between the cloud point and the pour point, and is defined as the cloud point minus the pour point, measured in °C. Generally, it is desirable to minimize the distribution between the pour point and the cloud point.

[0020] The periodic table mentioned in this disclosure is the CAS version published by the Chemical Abstracts Service in the Handbook of Chemistry and Physics (72nd edition, 1991-1992).

[0021] "Group VIII metals" refers to metals selected from Group VIII of the periodic table and / or metal compounds containing such metals.

[0022] Unless otherwise specified, the “feed rate” of hydrocarbons or other feedstocks fed to the catalytic reaction zone is expressed herein as the feed volume per hour per volume of catalyst, which may be referred to as the liquid space time (LHSV) in reciprocal hours (h-1).

[0023] The term "hydroisomerization" refers to the process of isomerizing n-alkanes (n-alkanes) into their more branched counterparts in the presence of hydrogen via a hydroisomerization (dewaxing) catalyst.

[0024] Unless otherwise specified, descriptions of the kinds of elements, materials, or other components from which a single component or mixture of components may be selected are intended to include all possible subgenus combinations of the listed components and mixtures thereof. Furthermore, "comprising" and its variations are intended to be non-limiting, such that descriptions of items in the list do not exclude other similar items that may also be used in the materials, compositions, and methods of the present invention. The properties of the materials described herein may be determined in some embodiments as follows:

[0025] (a) SiO2 / Al2O3 ratio (SAR): Determined by ICP elemental analysis. An infinite (∞) SAR indicates that there is no aluminum in the zeolite, that is, the molar ratio of silicon oxide to aluminum oxide is infinite. In that case, the molecular sieve is essentially composed entirely of silicon oxide.

[0026] (b) Surface area: determined by the amount of N2 adsorbed at boiling temperature. BET surface area was calculated using a 5-point method at P / P0 = 0.050, 0.088, 0.125, 0.163 and 0.200. The sample was first pretreated at 400°C for 6 hours in the presence of flowing dry N2 to remove any adsorbed volatiles, such as water or organic matter.

[0027] (c) Micropore volume: determined by the amount of N2 adsorbed at boiling temperature. The micropore volume was calculated using the t-plot method at P / P0 = 0.050, 0.088, 0.125, 0.163, and 0.200. The sample was first pretreated at 400°C for 6 hours in the presence of flowing dry N2 to eliminate any adsorbed volatiles, such as water or organic matter.

[0028] (d) Mesopore size: determined by the amount of N2 adsorbed at boiling temperature. The mesopore size was calculated using the BJH method based on the N2 isotherm, which is described in "The determination of pore volume and area distributions in porous substances. I. Computations from nitrogen isotherms" by EP Barrett, LG Joyner, and PP Halenda (J. Am. Chem. Soc. 1951 73, 373-380). The sample was first pretreated at 400°C for 6 hours in the presence of flowing dry N2 to eliminate any adsorbed volatiles, such as water or organic matter.

[0029] (e) Total pore volume: determined by the amount of N2 adsorbed at the boiling temperature with P / P0 = 0.990. The sample was first pretreated at 400°C for 6 hours in the presence of flowing dry N2 to remove any adsorbed volatiles, such as water or organic matter.

[0030] (f) The percentage of aromatics by weight is determined by the amount of UV absorption at wavelengths from 220 nm to 400 nm, as in ASTM D2008.

[0031] Where permitted, all publications, patents and patent applications cited in this application are incorporated herein by reference in their entirety, provided that such disclosure does not contradict this invention. The general process of this application using the first and second hydrorefining feed streams.

[0032] The processes described in this application typically include hydrorefining processes, which comprise two or more stages or steps for producing low-aromatic base oils, the stages or steps having varying conditions, such as temperature. Typically, these processes involve contacting the isomerization feed stream with a noble metal hydrorefining catalyst under first hydrorefining conditions to provide a first hydrorefining feed stream.

[0033] The first hydrorefined feed stream is then contacted with a second precious metal hydrorefining catalyst under the second hydrorefining conditions to provide the second hydrorefined feed stream. The first and second hydrorefining conditions (and the third, fourth or more hydrorefining conditions, if used) may be selected from those conditions for hydrorefining described below and may vary depending on the feedstock and the desired base oil product and properties.

[0034] Although other first and second hydrorefining conditions such as pressure, feed rate, catalyst, and the like may be the same or different, typically, in some embodiments of this application, these second hydrorefining conditions involve temperatures lower than those of the first hydrorefining conditions. This often results in unexpectedly low levels of aromatics in the produced base oil, as illustrated in the following examples.

[0035] The temperature difference between the first and second hydrorefining processes can be selected based on the required yield, the desired product and properties, the equipment used, and other process parameters. In some embodiments, the second hydrorefining conditions include a temperature lower than the first hydrorefining conditions, wherein the temperature of the second hydrorefining conditions may be at least about 80℉, or at least about 90℉, or at least about 100℉, or at least about 120℉, or at least about 140℉, or at least about 160℉, or at least about 180℉, or at least about 200℉, or at least about 220℉, or at least about 250℉, up to a maximum temperature difference not exceeding about 450℉, or not exceeding about 350℉, or not exceeding about 325℉, or not exceeding about 300℉.

[0036] The specific temperatures used in the first hydrorefining conditions and the specific lower temperatures used in the second hydrorefining conditions may vary depending on the required production volume, the desired product and properties, the equipment used, and other process parameters. Typically, the first hydrorefining conditions may include the following temperatures: about 475℉, or about 500℉, or about 510℉, or about 520℉, or about 530℉, or about 540℉, or about 560℉, or about 580℉, or about 600℉, or about 625℉, or about 650℉, up to about 800℉, or up to about 750℉, or up to about 700℉.

[0037] The second hydrorefining conditions typically involve temperatures lower than the first hydrorefining conditions, and the specific lower temperature used in the second hydrorefining conditions may vary based on many factors as described above. Typically, the second hydrorefining lower temperature conditions include the temperature difference as described above. With regard to the absolute temperature of the second hydrorefining lower temperature conditions, the temperature may include one of the following: about 370℉, or about 380℉, at most about 390℉, or at most about 410℉, or at most about 430℉, or at most about 455℉, or at most about 460℉, or at most about 465℉.

[0038] In some embodiments, a base oil with low aromatics can be obtained by employing two or more subsequent hydrorefining stages at lower temperatures. That is, in some embodiments, the base oil produced by the process described herein may contain less than about 0.9% or less than about 0.8% or less than about 0.7% or less than about 0.6% or less than about 0.5% or less than about 0.4% or less than about 0.3% of aromatics by weight. In other embodiments, the total aromatics in the base oil produced by this process may be at least about 30%, or at least about 35%, or at least about 40%, or at least about 45%, or at least about 50% less than those in a comparable process employing a single hydrorefining step.

[0039] Comparable processes employing a single hydrorefining step include those shown in the comparable examples, wherein the temperature used in the single hydrorefining step in its single stage is the same as, or within 2 degrees, the temperature used in the second hydrorefining condition, or within 4 degrees. That is, the temperature used in the first hydrorefining condition is higher than the temperature in the second hydrorefining condition and the single hydrorefining step, while other conditions in the single-step and two-step or multi-step hydrorefining steps are similar or the same.

[0040] The useful hydrorefining conditions and catalysts used for the first and second hydrorefining conditions, as well as the isomers prior to hydrorefining, are described below. Hydrorefining unit

[0041] Typically, the isomerization feedstock is fed to one or more hydrorefining units to produce a first hydrorefining stream and a second hydrorefining stream, ultimately providing the desired quality and yield of the base oil product. This or such hydrorefining step can remove trace amounts of any aromatics, olefins, chromophores, and the like from the base oil product. The hydrorefining unit may include a hydrorefining catalyst comprising a silica-alumina support and a noble metal, typically palladium, or platinum combined with palladium. In one embodiment, the noble metal content of the hydrorefining catalyst is typically in the range of about 0.1 to about 1.0% by weight, typically about 0.1 to about 0.6% by weight, and often about 0.2 to about 0.5% by weight. The isomerization stream and the hydrorefining stream may be contacted with the first and second catalysts in the same hydrorefining unit or in separate units in series. The catalyst contacted with the isomerization stream and the catalyst contacted with the first hydrorefining stream may be the same or different catalysts.

[0042] As known in the art, hydrorefining can be carried out in the presence of a hydrogenation catalyst, which may also be referred to as a hydrorefining catalyst. The hydrogenation catalyst used for hydrorefining may comprise, for example, platinum, palladium, or a combination thereof on a silica-alumina support. Hydrorefining can be carried out at temperatures ranging from about 400℉ to about 650℉ (204°C to 343°C) and at pressures ranging from about 400 psig to about 4000 psig (2.76 to 27.58 MPa). Hydrorefining for the production of lubricating oils is described, for example, in U.S. Patent No. 3,852,207, the disclosure of which is incorporated herein by reference.

[0043] Within the reactor, the feed may be contacted with a hydrotreating catalyst under hydrotreating conditions. Contacting the feed with the hydrotreating catalyst is used to effectively hydrogenate the aromatics in the feed and, in some cases, remove N and S-containing compounds from the feed. "Effectively hydrogenating aromatics" means that the hydrotreating catalyst can reduce the aromatic content of the feed by at least about 20%. The hydrogenated feed may typically contain C10+ n-alkanes and slightly branched isoalkanes, with a wax content typically at least about 20%. The hydrogenated feed may first be contacted with a hydroisomerization catalyst under hydroisomerization dewaxing conditions to provide an isomerization stream. The hydrotreating and hydroisomerization conditions used in the catalytic dewaxing process of this invention are described herein. Hydrorefining catalyst

[0044] In one embodiment, the catalyst system of the present invention may include hydrorefining, which may also be referred to as hydrotreatment or hydrogenation catalyst. Hydrotreatment catalysts used in the present invention may comprise a refractory inorganic oxide support and a Group VIII metal. The oxide support may also be referred to herein as a binder. The support for the hydrotreatment catalyst may be prepared from alumina, silicon oxide, silicon oxide / alumina, titanium oxide, magnesium oxide, zirconium oxide, and the like or combinations thereof, or may comprise alumina, silicon oxide, silicon oxide / alumina, titanium oxide, magnesium oxide, zirconium oxide, and the like or combinations thereof. The catalyst support may comprise amorphous materials, crystalline materials, or combinations thereof. Examples of amorphous materials include, but are not limited to, amorphous alumina, amorphous silicon oxide, amorphous silicon oxide-alumina, and the like.

[0045] In one embodiment, the support may comprise amorphous alumina. When a combination of silicon oxide and alumina is used, the distribution of silicon oxide and alumina in the support may be homogeneous or heterogeneous. In some embodiments, the support may consist of an alumina gel in which silicon oxide, silicon oxide / alumina, or an alumina-based material is dispersed. The support may also contain refractory materials other than alumina or silicon oxide, such as, for example, other inorganic oxides or clay particles, provided that such materials do not adversely affect the hydrogenation activity of the final catalyst or cause harmful degradation of the feedstock.

[0046] In one embodiment, the silicon oxide and / or alumina will typically comprise at least about 90% by weight of the support for the hydrotreating catalyst, and in some embodiments, the support may be at least substantially entirely silicon oxide or entirely alumina. Regardless of the type of support material in the hydrotreating catalyst, the hydrotreating catalyst used in the process and catalyst system of the present invention will typically have low acidity. Where appropriate, the acidity of the support can be reduced by treatment with alkali metal and / or alkaline earth metal cations.

[0047] Various crystalline and non-crystalline catalyst support materials that can be used to practice the present invention, as well as the quantification of the acidity level of such materials and methods for neutralizing acid sites in the catalyst support, are described in U.S. Patent Application Publication No. 2011 / 0079540, which is co-application and commonly assigned, and whose disclosure is incorporated herein by reference in its entirety.

[0048] The Group VIII metal component of the hydrotreatment catalyst may include platinum, palladium, or a combination thereof. In one embodiment, the hydrotreatment catalyst includes platinum and palladium, with a Pt:Pd ratio ranging from about 5:1 to about 1:5, typically from about 3:1 to about 1:3, and often from about 1:1 to about 1:2. The Group VIII metal content of the hydrotreatment catalyst is typically in the range of about 0.01 wt% to about 5 wt%, typically from about 0.2 wt% to about 2 wt%. In one embodiment, the hydrotreatment catalyst may include platinum in a concentration ranging from about 0.1 to about 1.0 wt%, and palladium in a concentration ranging from about 0.2 to about 1.5 wt%.

[0049] In one embodiment, the hydrotreating catalyst may comprise about 0.3% by weight of platinum and about 0.6% by weight of palladium. The hydrotreating catalyst of the present invention typically exhibits sulfur resistance and high catalytic activity.

[0050] In one embodiment, the Group VIII metal of the hydrotreating catalyst may be dispersed on an inorganic oxide support. Many methods are known in this art for depositing platinum and / or palladium metals or compounds containing platinum and / or palladium onto a support; such methods include ion exchange, impregnation, and coprecipitation. In one embodiment, impregnation of the support with platinum and / or palladium metal may be performed at a controlled pH. Typically, platinum and / or palladium systems are added to the impregnation solution as metal salts (such as halide salts, and / or amine complexes, and / or inorganic acid salts). Ammonium salts have been found particularly useful in preparing solutions for impregnating Group VIII metals. Other examples of metal salts that may be used include nitrates, carbonates, and bicarbonates, as well as carboxylates, such as acetates, citrates, and formates.

[0051] Optionally, the impregnated support may be allowed to stand with the impregnation solution for a period of time, for example, from about 2 to about 24 hours. After impregnating the oxide support with a Group VIII metal, the impregnated support may be dried and / or calcined. After the hydrotreated catalyst has been dried and calcined, the prepared catalyst can be reduced with hydrogen, as is known in the art, and put into use.

[0052] Typically, the hydrotreating catalyst can account for about 5% to about 20% of the total catalyst volume, and usually about 5% to about 15% of the total catalyst volume. Isomerization feed stream, catalyst and reaction conditions

[0053] Typically, the isomerization stream for the first hydrorefining step can be obtained in any convenient manner, which may vary depending on the specific conditions of the feedstock, the desired properties of the base oil, and other factors. There are no specific limitations on the available isomerization streams, and they can vary depending on the desired product, isomerization, hydrorefining and / or other conditions, the catalyst used, etc. Isomerization conditions and catalysts can vary considerably. Typically, the hydrocarbon feedstock is contacted with a hydroisomerization catalyst under hydroisomerization dewaxing conditions to provide the isomerization stream. The isomerization stream can be produced by contacting the hydrocarbon feedstock with hydrogen and a precious metal hydroisomerization catalyst under hydroisomerization dewaxing conditions.

[0054] The noble metal hydroisomerization catalyst can be varied, but in some embodiments it comprises crystalline molecular sieve SSZ-91 and platinum. Such SSZ-91 catalysts are described in detail in U.S. Patent No. 10,618,816 entitled "Molecular sieve SSZ-91, methods for preparing SSZ-91, and uses for SSZ-91", which is incorporated herein by reference. Similarly, the hydroisomerization dewaxing conditions can be varied, but in some embodiments they comprise temperatures of about 550℉ to about 700℉, and preferably 590℉ to about 675℉. In some embodiments, the hydroisomerization dewaxing conditions comprise pressures in the range of about 15 to about 3000 psig, and preferably in the range of about 100 to about 2500 psig.

[0055] Hydroisomerization dewaxing conditions may include a hydrocarbon feed rate in the presence of hydrogen in the range of about 0.1 to about 20 hr⁻¹ LHSV, wherein the hydrogen to hydrocarbon ratio is in the range of about 2,000 to about 10,000 standard cubic feet per barrel of hydrocarbons. In other embodiments, the hydrocarbon feed rate may be about 0.1 to about 5 hr⁻¹ LHSV. In some embodiments, the hydrogen to hydrocarbon ratio may be about 2,500 to about 5,000 standard cubic feet per barrel of hydrocarbons.

[0056] The hydroisomerization catalyst may comprise a one-dimensional 10-ring molecular sieve and a Group VIII metal, for example, substantially as described above in the section "Hydroisomerization Catalysts". The hydroisomerization catalyst may exhibit selectivity for the isomerization of n-alkane in the feedstock, causing the feedstock component to preferentially isomerize rather than crack. Hydroisomerization Catalyst

[0057] In one embodiment, the process of the present invention uses a hydroisomerization catalyst that is selective for the isomerization of n-alkane in a hydrocarbon feed. A useful hydroisomerization catalyst may comprise a molecular sieve and a Group VIII metal. In one embodiment, the molecular sieve of the hydroisomerization catalyst may comprise a one-dimensional 10-ring molecular sieve. The Group VIII metal of the first and second hydroisomerization catalysts may comprise platinum, palladium, or a combination thereof. In one embodiment, the hydroisomerization catalyst may comprise about 0.1 to about 1.5 wt% of a Group VIII metal, typically about 0.2 to about 1.0 wt%, and generally about 0.325 to about 1.0 wt% of a Group VIII metal. In one embodiment, the hydroisomerization catalyst may further comprise a metal modifier selected from the group consisting of Mg, Ca, Sr, Ba, K, La, Pr, Nd, Cr, and combinations thereof, substantially as described below.

[0058] Typically, the hydroisomerization catalyst will further comprise a support or binder. The support may comprise a refractory inorganic oxide. Suitable inorganic oxide supports for hydroisomerization catalysts include silicon oxide, alumina, titanium oxide, magnesium oxide, zirconium oxide, silicon-alumina, silicon-magnesium oxide, silicon-titanium oxide, and the like, and combinations thereof. The hydroisomerization catalyst may comprise about 5 to about 95% by weight or more of a molecular sieve component, typically about 15 to about 85% by weight, and usually about 25 to about 75% by weight. Generally, for economic reasons, it is advantageous to minimize the molecular sieve component, provided that the catalyst maintains the required levels of activity and selectivity. The hydroisomerization catalyst may comprise about 0 to about 95% by weight of support material, and more typically about 5 to about 90% by weight.

[0059] In an exemplary catalyst system for dewaxing hydrocarbon feedstocks according to the process of the present invention, each hydroisomerization catalyst may comprise a one-dimensional 10-ring molecular sieve and a Group VIII metal. The molecular sieve of the hydroisomerization catalyst may comprise a medium-porosity zeolite, for example, a zeolite with a pore size in the range of about 0.39 nm to about 0.7 nm. In one embodiment, each hydroisomerization catalyst may further comprise about 0.325 wt% to about 1 wt% platinum.

[0060] Examples of molecular sieves that can be used to formulate hydroisomerization catalysts include molecular sieves with AEL frame type codes such as SAPO-11, SAPO-31, SM-3, and SM-6; and zeolite-type materials with MTT or TON codes. MTT code molecular sieves include ZSM-23, SSZ-32, EU-13, ISI-4, and KZ-1. TON code molecular sieves that can be used to practice this invention include Theta-1, ISI-1, KZ-2, NU-10, and ZSM-22. Parameters of MTT and TON type molecular sieves are further described in the zeolite frame type map published by the International Zeolite Association (IZA). In one embodiment, the hydroisomerization catalyst contains zeolite SSZ-32. In a sub-embodiment, the hydroisomerization catalyst contains SSZ-32. The process of this invention is not limited to any specific hydroisomerization catalyst formulation. Metal support of the catalyst.

[0061] In one embodiment, the hydroisomerization catalyst may further comprise one or more metal modifiers. Typically, the metal modifier may be selected from the group consisting of Mg, Ca, Sr, Ba, K, La, Pr, Nd, Cr, and combinations thereof. In one sub-embodiment, the metal modifier may comprise Mg. As a non-limiting example, the hydroisomerization catalyst may comprise: a one-dimensional 10-ring molecular sieve, such as SSZ-32; a Group VIII noble metal, such as platinum; and in some embodiments, a metal modifier, such as magnesium. In one embodiment, the metal-modified catalyst of the present invention may comprise about 0.5 to about 3.5% by weight of Mg or other metal modifiers, typically about 0.5 to about 2.5% by weight and generally about 0.9 to about 2.5% by weight of Mg or other metal modifiers.

[0062] When formulating a catalyst or catalyst system for the dewaxing process of the present invention, the mixture of molecular sieve and oxide binder can be formed into particles or extrusions having a wide range of solid shapes and sizes. In one embodiment, the extrusions or particles are dried and calcined before metal loading. Calcination can typically be performed at a temperature ranging from about 390℉ to about 1100℉ (199°C to 593°C) for a period of about 0.5 to about 5 hours or longer. The calcined extrusions or formed particles can then be loaded with at least one metal modifier selected from the group consisting of Ca, Cr, Mg, La, Na, Pr, Sr, K, Nd, and combinations thereof. While not bound by theory, such metals can effectively reduce the number of acid sites on the molecular sieve of a metal-modified hydroisomerization catalyst, thereby improving the catalyst's selectivity for isomerization (relative to cracking) of n-alkanes in the feed. The loading of the modifier metal onto the catalyst can be achieved by techniques known in this art, such as impregnation or ion exchange. Ion exchange technology typically involves contacting an extrudate or particle with a solution containing a salt of a desired metal cation. Various metal salts can be used for this purpose, such as halides, nitrates, and sulfates. After contact with the solution of the desired metal cation, the extrudate or particle can be dried, for example, at a temperature ranging from about 150℉ to about 800℉ (66°C to 427°C). Subsequently, the extrudate or particle can be further loaded with a Group VIII metal component of a catalyst.

[0063] In one embodiment, the molecular sieve or catalyst of the present invention may be co-impregnated with a modified metal and a Group VIII metal. After loading the Group VIII metal and the modified metal, the catalyst may be calcined in air or an inert gas at a temperature ranging from about 500℉ to about 900℉ (260°C to 482°C). The preparation of molecular sieve catalysts containing metal modifiers is disclosed in commonly assigned U.S. Patent No. 7,141,529 and U.S. Patent Application Publication No. 2008 / 0083657, the disclosures of which are incorporated herein by reference in their entirety. Isomerization and Hydrorefining Reaction Conditions

[0064] The conditions for carrying out the process of the present invention will generally include temperatures in the range of about 390℉ to about 800℉ (199°C to 427°C). In one embodiment, the hydroisomerization dewaxing conditions include temperatures in the range of about 550℉ to about 700℉ (288°C to 371°C). In yet another embodiment, the temperature may be in the range of about 590℉ to about 675℉ (310°C to 357°C). The pressure may be in the range of about 15 to about 3000 psig (0.10 to 20.68 MPa), and typically in the range of about 100 to about 2500 psig (0.69 to 17.24 MPa).

[0065] Typically, the feed rate to the catalyst system / reactor during the dewaxing process of the present invention can be in the range of about 0.1 to about 20 hr⁻¹ LHSV, and typically about 0.1 to about 5 hr⁻¹ LHSV. Typically, the dewaxing process of the present invention is performed in the presence of hydrogen. Typically, the hydrogen to hydrocarbon ratio can be in the range of about 2000 to about 10,000 standard cubic feet per barrel of hydrocarbons, and typically about 2500 to about 5000 standard cubic feet per barrel of hydrocarbons.

[0066] The above conditions are applicable to the hydrotreating conditions in the hydrotreating zone and the hydroisomerization conditions in the hydroisomerization zone. Reactor temperature and other process parameters may vary depending on factors such as the properties of the hydrocarbon feedstock used and the required characteristics of the base oil product (e.g., pour point, cloud point, VI) and yield.

[0067] Hydroisomerization catalysts may contain one-dimensional 10-ring molecular sieves and Group VIII metals, for example, substantially as described above in the section "Hydroisomerization Catalysts". Hydroisomerization catalysts can be selective for the isomerization of n-alkanes in the feedstock, allowing the feedstock components to preferentially isomerize rather than crack. Base oil products

[0068] The pour point of the base oil product may not exceed about -9°C, typically not exceed about -12°C, and usually not exceed about -14°C. The cloud point of the base oil product may not exceed about -5°C, typically not exceed about -7°C, and usually not exceed about -12°C. The pour turbidity dispersion of the base oil product may not exceed about 7°C, typically not exceed about 5°C, and usually not exceed about 3°C. In one embodiment, a base oil product having the above properties can be obtained in a yield of at least about 89%.

[0069] In some embodiments, the process of the present invention provides high-value, high-quality lubricating oils in good yields from low-value waxy hydrocarbon feedstocks. The pour point of the lubricating oil may be less than about -9°C, typically less than about -12°C, and often less than about -14°C, for example, as measured by ASTM D97. In one embodiment, the pour point of the lubricating oil product may be in the range of about -10°C to about -30°C. The product may have a viscosity in the range of 3 to 30 cSt at 100°C and a VI in the range of about 95 to about 170, as measured by ASTM D445. Feedstock for base oil production.

[0070] This invention can be used with a wide variety of hydrocarbon feedstocks, including crude oil, distillate residue, vacuum tower residue, circulating oil, synthetic crude oil, gas-generating oil, vacuum gas-generating oil, foot oil, Fischer-Tropsch derivative waxes, and the like. In one embodiment, the hydrocarbon feedstock can be described as a waxy feedstock having a pour point generally above about 0°C and a tendency to solidify, precipitate, or otherwise form solid particles upon cooling to about 0°C. Straight-chain n-alkanes having 16 or more carbon atoms, alone or together with only slightly branched alkanes, may be referred to herein as waxes. The feedstock is generally a C10+ feedstock with a generally boiling point above about 350°F (177°C).

[0071] In one embodiment, the feedstock may comprise a heavy feed. In this document, the term "heavy feed" may be used to refer to a hydrocarbon feedstock wherein at least about 80% of the components have a boiling point above about 900℉ (482°C). Examples of heavy feedstocks suitable for practicing the present invention include heavy neutral (600N) and bright feedstocks.

[0072] In one embodiment, the hydrocarbon feedstock of the present invention typically has a pour point above 0°C and, in some embodiments, above about 20°C. In contrast, the base oil products of the process of the present invention typically have a pour point below 0°C, typically below about -12°C, and often below about -14°C.

[0073] In one embodiment, the raw material used in the process of the present invention may be a wax-containing raw material containing more than about 20% wax, more than about 50% wax, or even more than about 70% wax. More typically, the feed will contain about 5% to about 30% wax. As used herein, the term "wax-containing hydrocarbon raw material" may include plant waxes other than petroleum-derived waxes and animal-derived waxes.

[0074] According to one embodiment of the present invention, a wide variety of feedstocks can be used to produce lubricant base oils with good performance characteristics, including low aromatics, low pour point, low cloud point, low pour-cloud dispersion, and high viscosity index. The quality and yield of the lubricant base oil products of the present invention can vary depending on many factors, including but not limited to the hydrorefining steps and conditions described herein. Comparative Examples

[0075] As shown in Figure 1, a comparative example is provided using dewaxing 101, a one-stage hydrorefining 102, and subsequent product separation systems 201, 202, and 203. A noble metal hydroisomerization catalyst is installed in 101. This noble metal catalyst is combined with crystalline SSZ-91 and platinum. The second reactor 102 (one-stage hydrorefining) is loaded with a Pd / Pt catalyst to further improve the quality of the lubricating oil product.

[0076] Legend of Figure 1: 101-Dewaxing; 102-One-stage hydrorefining; 201-High-pressure separator; 202-Distillation system; 203-Butane removal tower

[0077] A "heavy neutral" feed was used to evaluate this process configuration, and its properties are described in Table 1 below. The feed and reaction conditions are described in WO2012 / 005980, which is incorporated herein by reference. Table 1 Feed Properties nature value API proportion 29.6 Nitrogen, ppm 1 Sulfur, ppm 32 Aromatics, lv% 18 SIMDIST TBP (wt%), ℉ TBP @0.5 716 TBP @5 808 TBP @10 842 TBP @30 909 TBP @50 950 TBP @70 990 TBP @90 1043 TBP @95 1065 TBP @99.5 1110

[0078] The reaction was carried out in a micro-unit with the described configuration and at a total pressure of 2100 psig. The catalyst was activated by a standard reduction procedure prior to feed. The HN feed was passed through a hydrodewaxing reactor at an LHSV of 1.2 hr⁻¹, followed by hydrorefining at 102. The hydrogen-to-oil ratio was approximately 3000 scfb. The base oil product was separated from the fuel via a distillation section. The aromatic content of the product was determined.

[0079] 101 is operated at 600-650℉ to convert wax molecules to achieve the product pour point target, while 201 is operated at 450℉ to improve product quality. The results are shown in Table 2 below. Example 1

[0080] Example 1 consists of dewaxing 101, two-stage hydrorefining 102 and 103, and subsequent product separation systems 201, 202, and 203, as shown in Figure 2. A noble metal hydroisomerization catalyst is installed in the first-stage reactor. After passing through the dewaxing reactor, the effluent is first treated in 102 and then sent to 103 for further refining. Both 102 and 103 are loaded with Pd / Pt catalysts to saturate aromatics and further remove impurities. The hydrogen-to-oil ratio is approximately 3000 scfb. The lubricating oil product is separated from the fuel via a distillation section. The aromatic content of the product is determined.

[0081] Legend of Figure 2: 101-Dewaxing; 102-Stage 1 Hydrogenation Refining; 103-Stage 2 Hydrogenation Refining; 201-High Pressure Separator; 202-Distillation System; 203-Butane Removal Column

[0082] In Example 1, 101 is operated at 600-650℉ to convert wax molecules to achieve the product pour point target. 102 is operated at approximately 500℉ and 103 is operated at 450℉ to saturate monocyclic and polycyclic aromatic hydrocarbons to improve product quality and stability.

[0083] The following Examples 2 to 9 were performed in the same manner, except that the temperature varied as described below. The results are shown in Table 2 and Figure 3 below. Example 2:

[0084] Regarding the catalyst and process system of Example 1, 102 operates at approximately 510℉ and 103 operates at 400℉. Example 3:

[0085] Regarding the catalyst and process system of Example 1, 102 operates at approximately 550℉ and 103 operates at 400℉. Example 4:

[0086] Regarding the catalyst and process system of Example 1, 102 operates at approximately 550℉ and 103 operates at 370℉. Example 5:

[0087] Regarding the catalyst and process system of Example 1, 102 operates at approximately 580℉ and 103 operates at 380℉. Example 6:

[0088] Regarding the catalyst and process system of Example 1, 102 operates at approximately 600℉ and 103 operates at 380℉. Example 7:

[0089] Regarding the catalyst and process system of Example 1, 102 operates at approximately 625℉ and 103 operates at 380℉. Example 8:

[0090] Regarding the catalyst and process system of Example 1, 102 operates at approximately 625℉ and 103 operates at 410℉. Example 9:

[0091] Regarding the catalyst and process system of Example 1, 102 operates at approximately 650℉ and 103 operates at 410℉. Table 2 – Comparative Results of Examples 2 to 9 Example Comparison Examples 1 2 3 4 5 6 7 8 9 Stage 1 HDF CAT,℉ 450 500 510 550 550 580 600 625 625 650 Stage 2 HDF CAT,℉ 450 400 400 370 380 380 380 410 410 Base oil products aromatics, weight % 0.93 0.8 0.81 0.67 0.55 0.61 0.53 0.52 0.35 0.38 system

[0092] The systems used in the above processes and examples are also taken into consideration in this application and are further described below in the embodiments numbered below.

[0093] 1. A system for producing low-aromatic base oils, the system comprising: an isomerization zone including a precious metal SSZ-91 hydroisomerization catalyst for producing an SSZ-91 isomerization feed stream; a first hydrorefining zone for contacting the SSZ-91 isomerization feed stream with a precious metal hydrorefining catalyst under first hydrorefining conditions to provide a first hydrorefined feed stream; and a second hydrorefining zone for contacting the first hydrorefined feed stream with a second precious metal hydrorefining catalyst under second hydrorefining conditions to provide a second hydrorefined feed stream, wherein the second hydrorefining conditions include a temperature lower than the first hydrorefining conditions.

[0094] 2. The system of Example 1, wherein the base oil produced by the system contains less than 0.9% aromatics by weight.

[0095] 3. The system of Example 1, wherein the base oil produced by the system has a pour point of about -5°C to about -20°C.

[0096] 4. The system of Example 1, wherein the base oil produced by the system contains at least about 30% less total aromatics than a comparable system using a single hydrorefining step.

[0097] 5. The system of Example 1, wherein the SSZ-91 isomerization feedstock is produced by the following steps: contacting the hydrocarbon feedstock with hydrogen and the noble metal SSZ-91 hydroisomerization catalyst under hydroisomerization dewaxing conditions to provide the isomerization feedstock.

[0098] 6. The system of Example 5, wherein the noble metal SSZ-91 hydroisomerization catalyst comprises crystalline molecular sieve SSZ-91 and platinum.

[0099] 7. The system of Example 1, wherein the precious metal hydrorefining catalyst and the second precious metal hydrorefining catalyst each comprise a silica-alumina support and a precious metal selected from palladium, platinum or a combination thereof.

[0100] 8. The system of Example 1, wherein the precious metal hydrorefining catalyst and the second precious metal hydrorefining catalyst are the same.

[0101] 9. The system of Example 1, wherein the precious metal hydrorefining catalyst and the second precious metal hydrorefining catalyst each contain about 0.1 to about 1.0% by weight of precious metal.

[0102] 10. The system of Example 1, wherein the first hydrorefining conditions include a temperature of about 475℉ to about 700℉.

[0103] 11. The system of Example 1, wherein the second hydrorefining conditions include a temperature of about 370℉ to about 475℉.

[0104] 12. The system of Example 5, wherein the hydroisomerization dewaxing conditions include a temperature of about 550℉ to about 700℉.

[0105] 13. The system of Example 5, wherein the hydroisomerization dewaxing conditions are contained in a pressure range of about 15 to about 3000 psig.

[0106] 14. The system of Example 5, wherein the hydroisomerization dewaxing conditions include a hydrocarbon feed rate in the range of about 0.1 to about 20 hr-1 LHSV in the presence of hydrogen, wherein the hydrogen to hydrocarbon ratio is in the range of about 2,000 to about 10,000 standard cubic feet per barrel of hydrocarbon.

[0107] 15. The system of Example 1, wherein the first hydrorefining conditions and the second hydrorefining conditions are contained in a pressure range of about 15 to about 3000 psig.

[0108] 16. The system of Example 1, wherein the first hydrorefining conditions and the second hydrorefining conditions comprise a first hydrorefining feed rate of about 0.1 to about 20 hr-1 LHSV and a second hydrorefining feed rate.

[0109] 17. A system for producing low aromatic base oils, the system comprising: an isomerization zone for contacting a hydrocarbon feedstock with hydrogen and a catalyst comprising crystalline molecular sieve SSZ-91 and platinum under hydroisomerization dewaxing conditions to provide an isomerization feedstock; A first hydrorefining zone, wherein the first hydrorefining zone is used to contact the isomerized feed stream with a catalyst comprising a silica-alumina support and a noble metal selected from palladium, platinum, or combinations thereof, wherein the catalyst contains about 0.1 to about 0.6% by weight of the noble metal under first hydrorefining conditions to provide the first hydrorefined feed stream; and a second hydrorefining zone, wherein the second hydrorefining zone is used to contact the first hydrorefined feed stream with a catalyst comprising a silica-alumina support and a noble metal selected from palladium, platinum, or combinations thereof, wherein the catalyst contains about 0.1 to about 0.6% by weight of the noble metal under second hydrorefining conditions to provide the second hydrorefined feed stream, wherein the second hydrorefining conditions include a lower temperature than the first hydrorefining conditions and wherein the base oil produced by the system contains at least about 40% less aromatics by weight than a comparable system employing a single hydrorefining step.

[0110] 18. The system of Example 17, wherein the base oil produced by the system contains less than 0.8% aromatics by weight.

[0111] 19. The system of Example 17, wherein the base oil produced by the system has a pour point of not more than about -12°C.

[0112] 20. The system of Example 17, wherein the base oil product is obtained at a yield of at least about 85%.

[0113] 21. The system of Example 17, wherein the second hydrorefining conditions include a temperature that is about 50℉ to about 450℉ lower than the first hydrorefining conditions.

[0114] This disclosure is not limited to the specific embodiments described in this application, which are intended as illustrations of various forms. It will be apparent that many modifications and variations can be made without departing from the spirit and scope of this disclosure. Functionally equivalent methods and systems within the scope of this disclosure will be apparent from the preceding representative descriptions, in addition to the methods and systems listed herein. Such modifications and variations are intended to fall within the scope of the appended representative solutions. This disclosure will be limited only to the terms of the appended representative solutions and the full scope of their equivalents. It will also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be restrictive.

[0115] The foregoing description and associated embodiments have been presented for illustrative purposes only. This description is not exhaustive and does not limit the invention to the precise forms disclosed. Those skilled in the art will understand from the foregoing description that modifications and variations are possible based on the above teachings, or may be obtained by practicing the disclosed embodiments. For example, the described steps need not be performed in the same order or with the same degree of separation. Similarly, various steps may be omitted, repeated, or combined as needed to achieve the same or similar objectives. Therefore, the invention is not limited to the above embodiments, but is instead defined by the appended technical solutions according to their full equivalent scope.

[0116] Various preferred embodiments have been described in the foregoing description with reference to the accompanying drawings. However, it will be apparent that various modifications and changes can be made to these embodiments, and additional embodiments can be implemented without departing from the broader scope of the invention as set forth in the following claims. The description and drawings are therefore to be regarded as illustrative rather than restrictive. [Simplified Explanation of the Diagram]

[0008] Figure 1 depicts a simplified process flow scheme with one-stage hydrorefining. Figure 2 depicts a simplified process flow scheme with two-stage hydrorefining.

Claims

1. A process for producing low-aromatic base oil, the process comprising: contacting an SSZ-91 isomerization feedstock with a precious metal hydrorefining catalyst under first hydrorefining conditions to provide a first hydrorefining feedstock, wherein the first hydrorefining conditions include a temperature range of 500℉ to 650℉; and contacting the first hydrorefining feedstock with a second precious metal hydrorefining catalyst under second hydrorefining conditions to provide a second hydrorefining feedstock, wherein the second hydrorefining conditions include a temperature range of 370℉ to 450℉; wherein the base oil produced by the process contains less than 0.9% aromatics by weight, and wherein the SSZ-91 isomerization feedstock is produced by the following step: contacting a hydrocarbon feedstock with hydrogen and a precious metal SSZ-91 hydroisomerization catalyst under hydroisomerization dewaxing conditions to provide the isomerization feedstock.

2. The process of claim 1, wherein the base oil produced by the process contains 0.35% to 0.81% aromatics by weight.

3. The process described in claim 1, wherein the base oil produced by the process has a pour point of about -5°C to about -20°C.

4. The process described in claim 1, wherein the total aromatics content of the base oil produced by the process is at least about 30% lower than that of a comparable process using a single hydrorefining step.

5. The process of claim 1, wherein the precious metal SSZ-91 hydroisomerization catalyst comprises crystalline molecular sieve SSZ-91 and platinum.

6. The process of claim 1, wherein the precious metal hydrorefining catalyst and the second precious metal hydrorefining catalyst each comprise a silica-alumina support and a precious metal selected from palladium, platinum or a combination thereof.

7. The process of claim 1, wherein the precious metal hydrorefining catalyst and the second precious metal hydrorefining catalyst are the same.

8. The process of claim 1, wherein the precious metal hydrorefining catalyst and the second precious metal hydrorefining catalyst each contain about 0.1 to about 1.0% by weight of precious metal.

9. The process of claim 1, wherein the hydroisomerization dewaxing conditions include a temperature of about 550℉ to about 700℉.

10. The process of claim 1, wherein the hydroisomerization dewaxing conditions are contained in a pressure range of about 15 to about 3000 psig.

11. The process of claim 1, wherein the hydroisomerization dewaxing conditions include a hydrocarbon feed rate in the presence of hydrogen in the range of about 0.1 to about 20 hr⁻¹ liquid space time (LHSV), wherein the hydrogen to hydrocarbon ratio is in the range of about 2,000 to about 10,000 standard cubic feet per barrel of hydrocarbons.

12. The process of claim 1, wherein the first and second hydrorefining conditions are contained in a pressure range of about 15 to about 3000 psig.

13. The process of claim 1, wherein the first hydrorefining conditions and the second hydrorefining conditions include a first hydrorefining feed rate and a second hydrorefining feed rate of about 0.1 to about 20 hr⁻¹ liquid space velocity (LHSV).

14. A process for producing low-aromatic base oils, the process comprising: contacting a hydrocarbon feedstock with hydrogen and a catalyst comprising crystalline molecular sieve SSZ-91 and platinum under hydroisomerization dewaxing conditions to provide an isomerization stream; contacting the isomerization stream with a catalyst comprising a silica-alumina support and a noble metal selected from palladium, platinum, or combinations thereof under first hydrorefining conditions to provide a first hydrorefining stream, wherein the catalyst comprises about 0.1 to about 0.6% by weight of a noble metal, wherein the first hydrorefining conditions comprise a temperature ranging from 500℉ to 650℉; and contacting the first hydrorefining stream with a catalyst comprising a silica-alumina support and a noble metal selected from palladium, platinum, or combinations thereof under second hydrorefining conditions to provide a second hydrorefining stream, wherein the catalyst comprises about 0.1 to about 0.6% by weight of a noble metal, wherein the second hydrorefining conditions comprise a temperature ranging from 370℉ to 450℉; The base oil produced by this process contains less than 0.8% by weight of aromatics and at least about 40% by weight less aromatics than comparable processes that use a single hydrorefining step.

15. The process of claim 14, wherein the base oil produced by the process contains at least 0.8% aromatics by weight, ranging from 0.35% to 0.8%.

16. The process of claim 14, wherein the base oil produced by the process has a pour point of not more than about -12°C.

17. The process described in claim 14, wherein the base oil product is obtained at a yield of at least about 85%.

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