CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is related to and claims priority benefit to U.S. Provisional Appl. Ser. No. 63/398,148, filed on Aug. 15, 2022, herein incorporated in its entirety.

FIELD OF THE INVENTION

[0002] The present disclosure relates to a process for preparing normal alkane enriched products by selective adsorption, separation, and isomerization of non-normal alkanes. The normal alkane enriched product is useful as a steam cracking feed.

BACKGROUND OF THE INVENTION

[0003] In the petrochemical industry, olefins, especially light olefins such as ethene, propene, and butene, are important precursors for downstream processes. Normal alkanes are preferred feeds to steam crackers as they provide a higher yield of light olefins compared to iso-alkanes, cyclo-alkanes, and aromatics.

[0004] Hydrocarbon mixtures containing mixtures of normal alkanes with other alkanes and other hydrocarbons are readily available in the oil refining and petrochemical industries. Many hydrocarbon mixtures can comprise a wide range of molecular weights and molecular species. It would be advantageous to have efficient processes for the separation and recovery of normal alkanes from hydrocarbon mixtures, in particular, for certain beneficial uses, such as feedstocks to steam crackers for the production of light olefins.

[0005] Isomerization and conversion of non-normal alkanes to normal alkanes to enrich the normal alkane content in a normal alkane feedstream would also be beneficial, e.g., in the case of steam cracking, potentially resulting in an increase in the yield of light olefins in the steam cracker.

[0006] Certain adsorption processes using materials like molecular sieves are known to provide for the separation of normal alkanes from hydrocarbon mixtures. Such processes for separating normal alkanes from other alkane isomers have not, however, been integrated with processes for the conversion of non-normal alkanes to normal alkenes. A solution that provides an increase in the overall utilization of normal alkanes derived from hydrocarbon mixtures would offer a commercially beneficial improvement, particularly in steam cracking processes.

SUMMARY OF THE INVENTION

[0007] The present invention is generally directed to a process for producing an enriched normal alkane product from a hydrocarbon mixture, particularly a product being suitable for use as an enriched normal alkane steam cracker feedstock. The process generally comprises contacting a hydrocarbon mixture comprising normal alkanes and two or more non-normal alkanes selected from iso-alkanes, cycloalkanes, or aromatics, with normal alkane-selective adsorption media to produce a normal alkane product from the hydrocarbon mixture and a non-normal alkane product; contacting the non-normal alkane product with a hydroconversion catalyst to produce a hydroconversion product comprising normal alkanes produced from the non-normal alkanes; and, combining the normal alkanes produced from the non-normal alkanes with the normal alkane product to provide an enriched normal alkane product.

[0008] The invention also relates to the use of the enriched normal alkane product, e.g., in a process for producing a steam cracker olefin product from the enriched normal alkane feedstream. The process generally comprises separately contacting a hydrocarbon feedstream comprising normal alkanes and two or more non-normal alkanes selected from iso-alkanes, cycloalkanes, or aromatics, with normal alkane-selective adsorption media to produce a normal alkane feedstream product and a non-normal alkane feedstream product from the hydrocarbon feedstream; contacting the non-normal alkane feedstream product with a hydroconversion catalyst under hydroconversion conditions to produce a hydroconversion feedstream product comprising normal alkanes produced from the non-normal alkanes; and, feeding the hydroconversion feedstream product normal alkanes produced from the non- normal alkanes and the normal alkane feedstream product to a steam cracker to produce an olefin product.

[0009] In general, the process provides an enriched normal alkane product that can be advantageously used to improve the feedstream normal alkane content for any suitable process. While steam cracking is one useful application, other areas may also benefit, such as for blending with other feedstocks, including gasoline stocks, and in the production of olefins and petrochemicals.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 illustrates a basic separation unit process for producing an n-paraffins rich stream.

[0011] FIG. la illustrates a separation unit process for n-paraffin recovery integrated with an isomerization process unit.

[0012] FIG. lb illustrates a separation unit process for n-paraffin recovery integrated with an isomerization process unit combined with isomerization unit recycle.

[0013] FIG. 2 illustrates a first integrated separation/isomerization process configuration scheme. [0014] FIG. 3 illustrates a second integrated separation/isomerization process configuration scheme. [0015] FIG. 4 illustrates a third integrated separation/isomerization process configuration scheme. [0016] FIG. 5 illustrates an integrated separation/isomerization process configuration scheme with recycle.

[0017] FIG. 6 illustrates a prior art combined hydrocracking and steam cracking process. [0018] FIG. 7 illustrates a combined hydrocracking and steam cracking process according to the invention.

[0019] FIG. 8 illustrates the experimental set up used to obtain breakthrough curves as described in the Examples.

[0020] FIG. 9 illustrates breakthrough curves at 420 psig and 175s°C for hydrotreated feed, LHSV= 0.9 hr ¹ as described in Example 1.

[0021] FIG. 10 illustrates breakthrough curves for the n-alkanes at space velocities 0.9 and 5 hr ¹ at 420 psig and 175°C as described in Example 1.

[0022] FIG. 11 illustrates process scheme for treating 100,000 BblD (barrel per day) hydrocarbon feed to produce a stream of n-alkane product as described in Example 2.

[0023] FIG. 12 illustrates a three-bed adsorption process design to treat 100,000 BblD (barrel per day) containing 23% n-alkanes (n-paraffins) as described in Example 3.

DETAILED DESCRIPTION

[0024] Although illustrative embodiments of one or more aspects are provided herein, the disclosed processes may be implemented using any number of techniques. The disclosure is not limited to the illustrative or specific embodiments, any drawings, and any techniques illustrated herein, including any exemplary designs and embodiments illustrated and described herein, and may be modified within the scope of the appended claims along with their full scope of equivalents.

[0025] The following description of embodiments provides non-limiting representative examples referencing numerals to particularly describe features and teachings of different aspects of the invention. The embodiments described should be recognized as capable of implementation separately, or in combination, with other embodiments from the description of the embodiments. A person of ordinary skill in the art reviewing the description of embodiments should be able to learn and understand the different described aspects of the invention. The description of embodiments should facilitate understanding of the invention to such an extent that other implementations, not specifically covered but within the knowledge of a person of skill in the art having read the description of embodiments, would be understood to be consistent with an application of the invention.

[0026] Unless otherwise indicated, the following terms have the meanings as defined hereinbelow. [0027] The term "hydroconversion" refers to processes or steps performed in the presence of hydrogen for the hydrocracking, hydrogenation, hydrodeoxygenation, hydrodesulfurization, hydrodenitrogenation, hydrodemetallation, hydrodechlorination, hydrodecarboxylation, hydrodecarbonylation and/or hydrodearomatization (e.g., impurities) of a hydrocarbon or biomass feedstock, and/or for the hydrogenation of unsaturated compounds in the feedstock. [0028] The term "hydrocracking" refers to processes or steps performed in the presence of hydrogen for the hydrocracking, hydrodeoxygenation, hydrodesulfurization, hydrodenitrogenation, hydrodemetallation, hydrodechlorination, and/or hydrodearomatization of components (e.g., impurities) of a hydrocarbon feedstock, and/or for the hydrogenation of unsaturated compounds in the feedstock. Depending on the type of hydrocracking and the reaction conditions, products of hydrocracking processes may have improved aromatic content, viscosities, viscosity indices, saturates content, low temperature properties, volatilities, and depolarization, for example. Hydrocracking is a catalytic chemical process performed using a hydrocracker in petroleum refineries for converting the high-boiling constituent hydrocarbons in petroleum crude oils to more valuable lower-boiling products such as gasoline, kerosene, jet, and diesel. Hydrocracking typically takes place in a hydrogen-rich atmosphere at elevated temperatures (260-425°C) and pressures (35-200 bar). Hydrocracking converts the high-boiling, high molecular weight hydrocarbons into lower-boiling, lower molecular weight olefinic and aromatic hydrocarbons and then hydrogenates them. Any sulfur and nitrogen present in the hydrocracking feedstock are, to a large extent, also hydrogenated and form gaseous hydrogen sulfide (H2S) and ammonia (NH3) which are subsequently removed. The result is that the hydrocracked products are essentially free of sulfur and nitrogen impurities and consist of predominantly paraffinic hydrocarbons (n-paraffins and isoparaffins) and remaining cycloparaffins, or aromatics.

[0029] A "full conversion hydrocracker" converts essentially all the feed, e.g., VGO, that is fed into the full conversion hydrocracker into products with a boiling point range below 371°C.

[0030] "Isomerization" refers to the chemical process by which a hydrocarbon molecule is transformed into any of its isomeric forms, i.e., forms with the same chemical composition but with different structure or configuration and, hence, generally with different physical and chemical properties. For example, isomerization can transform an n-paraffin into an isoparaffin or an isoparaffin into an n-paraffin and the transformation is controlled by the careful selection of an isomerization catalyst and isomerization process conditions in an isomerization reactor.

[0031] The term "normal alkane-selective separation" refers to a selective separation process that allows more normal alkanes to pass through but stops or limits other hydrocarbons from passing through. Likewise, a "normal alkane-enriched stream" refers to a hydrocarbon stream that has passed through the separation unit and/or the isomerization unit.

[0032] "TBP" refers to the boiling point of a hydrocarbon mixture or product, as determined by ASTM D2887-18.

[0033] "Distillates" include the following products and typical boiling point ranges: Light Naphtha C ₅ - 180°F (C ₅ - 82°C); Heavy Naphtha 180-300°F (82-149°C); Jet 300-380°F (149-193°C); Kerosene 380-530°F (193-277°C); Diesel 530-700°F (277-371°C); Vacuum Gas Oil (VGO) 700-1150°F (371-621°C). [0034] "Naphtha" in the context of this disclosure refers to petroleum naphtha that is an intermediate hydrocarbon liquid stream derived from the refining of crude oil. It can have a carbon number within the range from C5 to C12.

[0035] "Heavy hydrocarbons" in the context of this disclosure refers to distillates with boiling point ranges of diesel and/or VGO.

[0036] "Fuel oil" is a fraction obtained from petroleum distillation, either as a distillate or a residue. It is made of long hydrocarbon chains, particularly alkanes, cycloalkanes, and aromatics.

[0037] The term "molecular sieve" refers to a crystalline material containing pores, cavities, or interstitial spaces of a uniform size in which molecules small enough to pass through the pores, cavities, or interstitial spaces are adsorbed while larger molecules are not. Examples of molecular sieves include zeolites and non-zeolite molecular sieves such as zeolite analogs including, but not limited to, SAPOs (silicoaluminophosphates), MeAPOs (metalloalummophosphates), AIPO ₄ , and ELAPOs (nonmetal substituted aluminophosphates).

[0038] The term "catalyst support" is used in the conventional sense according to the normal usage in the art and includes typical catalyst support materials such as alumina, silica-alumina, zeolites and nonzeolite molecular sieves, and the like.

[0039] The Periodic Table of the Elements referred to in this disclosure is the CAS version published by the Chemical Abstract Service in the Handbook of Chemistry and Physics, 72nd edition (1991-1992). [0040] Unless otherwise specified, the recitation of a genus of elements, materials, or other components from which an individual component or mixture of components can be selected is intended to include all possible sub-generic combinations of the listed components and mixtures thereof. Also, "include" and its variants are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that may also be useful in the materials, compositions, and methods of this invention.

[0041] In one aspect, the present invention relates to a new use of a normal alkane-selective separation process to provide a normal alkane enriched product from a hydrocarbon mixture in an integrated refining unit. The process uses a combination of selective adsorption and separation over molecular sieves and catalytic hydrocracking and isomerization to increase the normal alkane content derived from a hydrocarbon mixture. While not limited thereto, one of the beneficial uses is to provide an enriched normal alkane feedstream to a steam cracker.

[0042] The hydrocarbon mixture may generally have a carbon number of C5+. The hydrocarbon mixture may, e.g., comprise hydrocarbons having a diesel boiling point range and a vacuum gas oil (VGO) boiling point range. The hydrocarbon mixture may comprise various distillate components, such as naphtha, kerosene, and/or diesel components, or a mixture thereof. [0043] Steam cracking is the principal industrial method for producing lighter alkenes (olefins), including ethylene and propylene. Steam cracking performs petrochemical hydroprocessing by breaking down saturated hydrocarbons in a feed into smaller, often unsaturated, hydrocarbons. Gaseous or liquid hydrocarbon feed to a steam cracker is diluted with steam and then briefly heated in a furnace, without the presence of oxygen. The steam cracking reaction temperature is typically very hot (around 850°C), but the reaction is only allowed to take place very briefly. In modern steam crackers, the residence time can be reduced to milliseconds (resulting in gas velocities reaching speeds beyond the speed of sound) to improve the yield of desired products. After the steam cracking temperature has been reached, the gas is quickly quenched to stop the reaction in a transfer line exchanger. The products produced in the reaction depend on the composition of the feed, on the hydrocarbon to steam ratio and on the cracking temperature and furnace residence time.

[0044] In one aspect, a process is provided for producing an enriched normal alkane product from a hydrocarbon mixture, the product being suitable for use as an enriched normal alkane steam cracker feedstock. The process generally comprises contacting a hydrocarbon mixture comprising normal alkanes and non-normal alkanes selected from iso-alkanes, cycloalkanes, or aromatics, with normal alkane-selective adsorption media to produce a normal alkane product from the hydrocarbon mixture and a non-normal alkane product; contacting the non-normal alkane product with a hydroconversion catalyst to produce a hydroconversion product comprising normal alkanes produced from the non- normal alkanes; and, combining the normal alkanes produced from the non-normal alkanes with the normal alkane product to provide an enriched normal alkane product.

[0045] In another aspect, a process is provided for producing a steam cracker olefin product from an enriched normal paraffin feedstream to a steam cracker. The process generally comprises separately contacting a hydrocarbon feedstream comprising normal alkanes and non-normal alkanes selected from iso-alkanes, cycloalkanes, or aromatics, with normal alkane-selective adsorption media to produce a normal alkane feedstream product and a non-normal alkane feedstream product from the hydrocarbon feedstream; contacting the non-normal alkane feedstream product with a hydroconversion catalyst under hydroconversion conditions to produce a hydroconversion feedstream product comprising normal alkanes produced from the non-normal alkanes; and feeding the hydroconversion feedstream product normal alkanes produced from the non-normal alkanes and the normal alkane feedstream product to a steam cracker to produce an olefin product.

[0046] The normal alkane-selective adsorption media useful in the process generally comprises a normal alkane selective zeolite. Non-limiting examples of the normal alkane selective zeolite include ZSM-5, zeolite 5a, or a combination thereof. [0047] Suitable hydrocarbon mixtures are typically those used as steam cracker feeds, e.g., feeds comprising LPG, naphtha, kerosene, diesel, or a mixture thereof. Hydrocarbon mixtures produced as a hydrocracker product from a hydrocracking process may be used as well, particularly where the hydrocracker product comprises naphtha, kerosene, or diesel product components, or a mixture thereof.

[0048] Useful hydroconversion catalysts typically comprise a hydrocracking and/or an isomerization catalyst, with the hydroconversion conditions including corresponding hydrocracking and/or isomerization conditions. Suitable catalysts and process conditions generally include any known in the art.

[0049] The hydroconversion product typically includes an isomerization product comprising iso- and normal alkanes. The isomerization product may be partially or completely recycled with the hydrocarbon mixture and contacted with the normal alkane selective adsorption media. The hydroconversion catalyst may also comprise a hydrocracking catalyst and/or an isomerization catalyst arranged in a sequential configuration.

[0050] The hydroconversion product may be contacted with a hydrocracking catalyst to produce a hydrocracking product and further contacted with normal alkane-selective adsorption media to produce a second normal alkane product from the hydroconversion product and a second non-normal alkane product comprising non-normal alkanes. The second non-normal alkane product may then be further contacted with a hydrocracking catalyst to produce a second hydrocracking product comprising C6- normal and iso-paraffins.

[0051] The process may comprise a plurality of normal alkane-selective adsorption media zones, wherein at least one zone operates in normal alkane adsorption mode and at least one zone operates in normal alkane desorption regeneration mode. The normal alkane desorption regeneration mode typically comprises contacting a regeneration fluid with the normal alkane adsorption media of one or more of the normal alkane-selective adsorption media zones, the adsorption media having normal alkanes adsorbed thereon, to desorb the adsorbed normal alkanes and form a mixture of the desorbed normal alkanes and regeneration fluid; separating the normal alkane regeneration fluid from the mixture of the desorbed normal alkanes and regeneration fluid; and combining the desorbed normal alkanes with the normal alkanes produced from the non-normal alkanes and with the normal alkane product to provide the enriched normal alkane product. While not limited thereto, the regeneration fluid may be selected from C5-C8 normal alkanes, LPG, C1-C8 alcohols, ammonia, or a combination thereof.

[0052] The general aspects and specifics of the process are illustrated in the accompanying figures. FIG. 1 illustrates a basic separation unit process for producing an n-paraffins rich stream from a mixed feed comprising n- and iso-paraffins and other hydrocarbon feed components. In FIG. 1, feedstream 50 comprising n-paraffins, iso-paraffins, cyclo-aromatics and aromatics is fed to separation unit 60 resulting in n-paraffins rich product stream 70 and reject stream 80 containing iso- and cyclo-paraffins and aromatics.

[0053] FIG. la illustrates an integrated separation and isomerization process in which the separation scheme illustrated in FIG. 1 is combined with a process for ring opening and skeletal isomerization of reject stream. In FIG. la, feedstream 50a (e.g., diesel and VGO streams) comprising n-paraffins, isoparaffins, cyclo-aromatics and aromatics is fed to separation unit 60a resulting in n-paraffins rich product stream 70a and reject stream 80a containing iso- and cyclo-paraffins and aromatics. Stream 80a is subjected to cracking conditions in hydrocracker 90a, resulting in ring opening of cyclic compounds and isomerization to produce normal paraffins from iso-paraffins. The iso- and n-paraffins 100a are combined 110a with the n-paraffins stream 70a from separation unit 60a, with the combined stream 120a available for further processes, including use as a feed to a steam cracker.

[0054] FIG. lb illustrates an integrated separation and isomerization process in which the separation scheme illustrated in FIG. 1 is combined with a process for ring opening and skeletal isomerization of reject stream, coupled with recycling of iso- and normal paraffins produced thereby for further separation. In FIG. lb, feedstream 50b (e.g., diesel and VGO streams) comprising n-paraffins, isoparaffins, cyclo-aromatics and aromatics is combined with recycled iso- and normal paraffins produced under cracking conditions in hydrocracker 90b and fed 55b to separation unit 60b resulting in n- paraffins rich product stream 70b and reject stream 80b containing iso- and cyclo-paraffins and aromatics. Stream 80b is subjected to cracking conditions in 90b, resulting in ring opening of cyclic compounds and isomerization to produce normal paraffins from iso-paraffins. The iso- and n-paraffins 100b are combined 110b with the n-paraffins stream 70b from separation unit 60b, with the combined stream 120b available for further processes, including use as a feed to a steam cracker.

[0055] An integrated separation and hydrocracking scheme for producing an n-paraffins rich stream with recycle is further shown in FIG. 2, wherein feedstream 50c, e.g., a diesel and VGO range stream, is fed to a full conversion hydrocracker 25c, with C2 to C4 light products being recovered for use (e.g., in a steam cracker) and heavier products, e.g., naphtha, kerosene and diesel, being combined with recycle stream 95c and fed 55c to separation unit 60c, which produces n-paraffin stream 70c and reject stream 80c. Stream 80c is fed to hydrocracker 92c to produce iso- and n-paraffins stream 125c with C2 to C4 light ends 100c combined with streams 30c and 70c and collected 110c and/or passed 120c to a further process units, such as a steam cracker. Product stream 125c comprising iso- and n-paraffins may have a product stream withdrawn 130c for use in other processes with the remainder recycled/combined with stream 40c and fed 55c to separation unit 60c. [0056] The process may further comprise alternative schemes of feeding the separation reject stream to a hydrocracker (as is generally shown in FIGs. 3 and 4). Feeding the separation reject stream to the hydrocracker can be used to open naphthenic rings and break carbon-carbon bonds in the separation reject stream to improve this stream for further processing. Any hydrocracking catalyst useful to open naphthenic rings, break carbon-carbon bonds, or both can be used in the hydrocracker. One example of a catalyst that can be used in the hydrocracker is mordenite.

[0057] In FIG. 3, feedstream 50d, e.g., a diesel and VGO range stream, is fed to a full conversion hydrocracker 25d, with C2 to C4 light products being recovered for use (e.g., in a steam cracker) and heavier products, e.g., naphtha, kerosene and diesel, being fed 40d to separation unit 60d, which produces n-paraffin stream 70d and reject stream 80d. Stream 80d is fed to hydrocracker 92d to produce iso- and n-paraffins stream 95d with C2 to C4 light ends 93d combined with stream 70d and, along with C2 to C4 stream 30d and n-paraffin stream lOOd, collected HOd and/or passed 120dto further process units, such as a steam cracker. Product stream 95d comprising iso- and n-paraffins may have a product stream withdrawn 130d for use in other processes with the remainder fed subjected to isomerization conditions 98d to produce n-paraffins that are combined with the other n-paraffin and C2 to C4 streams.

[0058] FIG. 4 illustrates the use of more than one separation and cracking step to increase the amount of n-paraffins produced and available for steam cracking. Feedstream 50e, e.g., a diesel and VGO range stream, is first separated in separation unit 60e to separate n-paraffin stream 30e and produce reject stream 80e containing iso- and cyclo-paraffins and aromatics. Stream 80e is fed to a full conversion hydrocracker 25e, with mostly iso- and n-paraffin products being fed 85e to separation unit 65e, which produces n-paraffin stream 70e and reject stream 75e. Stream 75e is fed to hydrocracker 98e to produce C6 and lower carbon number iso- and n-paraffins stream 105e. N-paraffin streams 70e and 30e are collected IlOe and/or passed 120e to further process units, such as a steam cracker.

[0059] FIG. 5 illustrates a full recycle scheme in which the recycle stream shown is FIG. 2 is recycled for further separation. In FIG. 2, feedstream 50f, e.g., a diesel and VGO range stream, is fed to a full conversion hydrocracker 25f, with C2 to C4 light products being recovered for use (e.g., in a steam cracker) and heavier products, e.g., naphtha, kerosene and diesel, being combined with recycle stream 95f and fed 55/ to separation unit 60f, which produces n-paraffin stream 70f and reject stream 80f. Stream 80f is fed to hydrocracker 90f to produce iso- and n-paraffins stream 95f with iso- and n-paraffins bleed stream lOOf combined with streams 30f (C2 to C4)and 70f (n-paraffins) and collected IlOf and/or passed 120fto a further process units, such as a steam cracker.

[0060] FIG. 6 shows a typical conventional integrated refining unit comprising a full-conversion hydrocracker and a steam cracker, but without any inter-stage process to produce a normal alkane- enriched stream that is fed to the steam cracker. The full conversion hydrocracker converts larger hydrocarbon molecules into smaller molecules. Depending on the economics for hydrocracker product streams, some of these streams can be used as feedstocks to a steam cracker, e.g., C2-C4, naphtha, kerosene, and diesel. The normal alkane isomers in the hydrocracker product streams provide high yields to olefins in the steam cracker, however the other isomers that remain in the hydrocracker product streams (isoparaffins, cycloparaffins, and/or aromatics) provide lower yields to olefins and higher yields to less desired products like heavy aromatics, fuel oil, and pyrolysis oil. Light hydrocarbon feeds (such as ethane, LPG, or light naphthas) give product streams rich in the lighter alkenes, including ethylene, propylene, and butadiene. Heavier hydrocarbon (full range and heavy naphthas as well as other refinery products such as kerosene or diesel) feeds give some of these lighter alkenes, but also give other products rich in aromatic hydrocarbons and hydrocarbons suitable for inclusion in gasoline or fuel oil. In FIG. 6, conventional feeds, such as diesel and VGO, 50g are fed along with hydrogen to a hydrocracker 25g, resulting in products streams such as C2 to C442g, naphtha 44g, kerosene 46g, and diesel 48g. In a conventional process, each of cracking product streams 42g to 48g are fed to steam cracker 150g to produce ethylene and other products 160g.

[0061] FIG. 7 illustrates one processing scheme that can be used for combining hydrocracking with steam cracking. In FIG. 7, feeds such as VGO 51h and diesel 52h are fed along with hydrogen 54h to hydrocracker 25h to produce product streams C2 to C4, 42h, naphtha 44h, kerosene 46h, and diesel 48h. Streams 44h to 48h are separately distilled into fractions and each fraction is passed through a normal alkane-selective separation unit 61h, 62h, and 63h in a single stage to produce normal alkane- enriched streams that are fed to a steam cracker 150h to produce olefins and other products 160h. The reject streams (normal-paraffin depleted) can be collected 90h for further use, processed further 91h, or fed lOOh to a steam cracker 150h. For example, the separation reject streams may be useful as fuels, as recycle to the full conversion hydrocracker, or isomerized. The diesel stream that comes into the integrated refining unit can be converted entirely in the full conversion hydrocracker, converted in part in the full conversion hydrocracker, or fed entirely or in part to the normal alkane-selective separation, as shown.

[0062] In one embodiment, the process additionally comprises recycling an amount of the isoparaffins and the n-paraffins from the hydrocracker to either the hydrocarbon mixture that is passed through the normal alkane-selective separation (as shown in FIG. 3) or to the full conversion hydrocracker. Recycling the amount of the isoparaffins and the n-paraffins from the hydrocracker further enriches the normal- alkane enriched stream that is fed to the steam cracker to produce olefins. The portion of the isoparaffins and the n-paraffins from the hydrocracker that is not recycled can be sent to other downstream processes. [0063] In one embodiment, the process comprises feeding the separation reject stream to a hydrocracker and additionally separating an effluent from the hydrocracker into a C2-C4 hydrocarbon fraction and a hydrocracked fraction that comprise the n-paraffins and the isoparaffins; feeding the C2-C4 hydrocarbon fraction to the steam cracker; and skeletally isomerizing at least a portion of the hydrocracked fraction to produce a second normal alkane-enriched stream that is fed to the steam cracker. This embodiment is illustrated in FIG. 4.

[0064] In one embodiment, the process additionally comprises feeding a stream of heavy hydrocarbons to a full-conversion hydrocracker that produces a low-boiling C2-C4 hydrocarbon fraction and at least one higher-boiling hydrocarbon fraction that is the hydrocarbon mixture that passes through the normal alkane-selective separation; and feeding the normal alkane-enriched stream and the low-boiling C2-C4 hydrocarbon fraction to the steam cracker. This embodiment is illustrated in FIGs. 3 and 4.

[0065] In one embodiment, where a full-conversion hydrocracker is used, the at least one higher- boiling hydrocarbon fraction produced in the full-conversion hydrocracker is distilled into two or more intermediate streams and each of the two or more intermediate streams is separately passed through the normal alkane-selective separation. Examples of these intermediate streams can include naphtha, light naphtha, heavy naphtha, jet, kerosene, and diesel, and mixtures thereof. In this embodiment, at least two (or even all) of the separation reject streams produced from each of the two or more intermediate streams can be fed to the steam cracker. These embodiments are illustrated in FIG. 7. [0066] In one embodiment, different normal alkane-selective separations can be used for the different two or more intermediate streams, and the different normal alkane-selective separations can be selected to optimize the separation of the n-paraffins into the normal alkane-enriched stream from each of the different normal alkane-selective separations. For example, the two or more intermediate streams could comprise a naphtha stream, a kerosene stream and a diesel stream; and after separately passing the two or more intermediate streams through a first normal alkane-selective separation that is selected for the naphtha stream, a second normal alkane-selective separation that is selected for the kerosene stream, and a third normal alkane-selective separation that is selected for the diesel stream; a naphtha n-paraffins stream is fed to the steam cracker, a kerosene n-paraffins stream is fed to the steam cracker, and a diesel n-paraffins stream is fed to the steam cracker. In another related embodiment, a first normal alkane-enriched stream from a first normal alkane-selective separation, a second normal alkane-enriched stream from a second normal alkane-selective separation, and a third normal alkane-enriched stream from a third normal alkane-selective separation are fed to the steam cracker; a first separation reject stream the first normal alkane-selective separation, a second separation reject stream from the second normal alkane-selective separation, and a third separation reject stream from the third normal alkane selective separation are sent to an intermediate-range hydrocracker that elutes a hydrocracked intermediate stream that is fed to the steam cracker. This integrated scheme is shown in FIG. 6.

[0067] In one embodiment, the hydrocarbon mixture that is passed though the normal alkane selective separation unit is, in part or entirely, fed directly to the normal alkane-selective separation unit without previously passing through a full conversion hydrocracker or another hydrocracker. Examples of hydrocarbon mixtures that could be fed directly to the normal alkane-selective separation in this manner include light naphtha, heavy naphtha, naphtha, kerosene, jet, and diesel. These hydrocarbon mixtures could be obtained from other equipment in the same refinery that comprises the integrated refining unit or brought in from other sources.

[0068] In general, the processes provide significantly increased yields of olefins when using a steam cracker. Yields of olefins using the same steam cracker can be increased by greater than 5 wt%, such as from 10 to 50 wt%, or from 13 to 42 wt% compared to an alternative process without the passing of the hydrocarbon mixture through the normal alkane-selective separation in the single stage, whereby the hydrocarbon mixture is passed directly to the steam cracker in the alternative process.

[0069] In one embodiment the yield of olefins, such as light C4- olefins from a steam cracker is significantly increased, e.g., from greater than 5 wt% to 25 wt%, or to 30 wt%, using the processes of this disclosure. In one embodiment, a yield of total olefins can be increased by 10 wt% to 50 wt%. For example, the passing of the hydrocarbon mixture through the normal alkane-selective separation can increase a yield of ethylene, propylene, or a mixture thereof in the steam cracker. Ethylene and propylene are important sources of industrial chemicals and polymer products. They can also be used as feeds to alkylation processes. Ethylene is used as a ripening stimulant.

[0070] In one embodiment, the process increases a yield of ethylene and/or propylene in the steam cracker and lowers the production of fuel oil by decreasing an amount of isoparaffins, cycloparaffins, and aromatics in the feed to the steam cracker. For example, the yield of ethylene and/or propylene can be increased by from greater than 5 wt% to 50 wt% (such as from 10 wt% to 50 wt%) and the production of fuel oil can be decreased by from greater than 5 wt% to 90 wt% (such as from 30 to 90 wt%).

[0071] In one embodiment, the process additionally comprises isomerizing at least a portion of the separation reject stream. The isomerizing can be used to produce additional n-paraffins that can be fed to the steam cracker. One example of this embodiment is shown in FIG. 4, in which the portion of the separation reject stream additionally passes through an intermediate-range hydrocracker before it is sent to the isomerization reactor. In another embodiment, the isomerizing can be used to transform n-paraffins into isoparaffins. Skeletal isomerization can introduce branching into n-paraffins, by converting them to isoparaffins, to produce higher quality fuels. EXAMPLES

[0072] Adsorption experiments were carried out to obtain breakthrough curve data using different hydrocarbon feeds at conditions relevant to the process. The n-alkanes were removed by the adsorbent in a fixed-bed adsorber and desorbed by swinging the from feed to regeneration fluid in co-current operation mode.

[0073] The experimental lab set up, illustrated in FIG. 8, was composed of two metering pumps (ISCO) 50i, 54i, one for the feed 52i and one for the desorbent 56i, a three-way valve 57i to control the selection of the adsorption column feed 58i, an adsorption column containing the adsorbent material 60i having a cover 62i, and a back pressure regulator to control the pressure 64i. Samples leaving the adsorption column 64i were collected in glass vials and analyzed via GC x GC methodology. Typical adsorption bed dimensions are provided in Table 1.

Table 1 - Adsorption bed dimensions and adsorbent size

Bed Geometry Characteristic Value

Length (L) 0.1397 m

Internal Diameter (D) 0.127 m

Adsorbent particle radius (Rp) 0.001 m

L/D 11

Bed to particle diameter ratio (D/Dp) 6.4

[0074] The experiment was typically carried out by maintaining the adsorption column at the intended process conditions under desorbent flow. The hydrocarbon feed was introduced at time zero and dead volumes were previously determined and taken into the account.

[0075] Using ZSM-5 extrudates, we conducted adsorption/desorption experiments with diesel feed at LHSV 1 hr ¹ and 420 psig and 175°C. The same adsorption and desorption flowrate was used. FIG. 8 shows the lab experimental set up used to obtain breakthrough curves.

Example 1

[0076] Using a hydrotreated diesel feed with boiling point range of 320-915°F (composition in Table 2), breakthrough curves for ZSM-5 material at LHSV 0.9 hr ¹ were generated (see FIG. 9 showing breakthrough curves at 420 psig and 175°C for hydrotreated feed, LHSV= 0.9 hr ¹ ). The material was desorbed with n-pentane. Iso-alkanes, cycloalkanes and aromatic compounds eluted together before the n-alkanes which led to an effective separation; n-alkanes adsorbed into ZSM-5 and rejection of the other compounds in the raffinate stream Table 2 - Composition of hydrotreated feed

Compound Class wt. % n-paraffins (n-alkanes) 23%

Iso-paraffins 24% cycloparaffins 40% aromatics 13%

[0077] The throughput was increased by flowing the hydrocarbon feed at space velocity of 5 hr ¹ and a similar breakthrough profile during both adsorption and desorption phase was demonstrated (see FIG. 10 showing breakthrough curves for the n-alkanes at space velocities 0.9 and 5 hr ¹ at 420 psig and 175°C). The plots suggest that a purge step with a normal alkane, such as n-pentane, will greatly improve the recovery and purity of n-alkanes. The desorption step showed a similar pattern for n-paraffins in both runs. The space velocity did not change the mass transfer behavior. The mass transfer for n-pentane was different during desorption - much less sharp breakthrough at lower space velocity, which suggests that a purge step will be helpful.

Example 2

[0078] To illustrate the integration between the adsorption process and steam cracker, a hydrocarbon feed was fed into an adsorber containing ZSM-5 material and the adsorbent was regenerated using light gasoline (49-175°F). The process conditions were 420 psig and 175°C. In this process, about 20% of the feed was adsorbed (extract) as n-alkanes. FIG. 11 illustrates a process scheme for treating 100,000 BBLD (barrel per day) hydrocarbon feed to produce a stream of n-alkane product. Adsorption section A and desorption section D are shown in FIG. 11. Hydrocarbon feed 50j (e.g., 100k Bbld diesel and light VGO) is fed to adsorber 60j, producing n-paraffin enriched stream 70j and reject stream 80j, the latter is then passed to hydrocracker 90j, wherein hydrogen is also introduced 52j, producing i-paraffin stream lOOj (having a higher octane number). N-paraffin enriched stream 70j may be combined with the hydrocracker product i-paraffin stream lOOj, with the combined stream 72j fed to a steam cracker llOj. Steam cracker product stream 120j shows an increased C2 production, e.g., a 30% increase, due to the enriched n-paraffin feed.

[0079] In the desorption section D, a normal alkane regeneration fluid (desorbent) 54j (e.g., 17 kBbld light gasoline C5-C6) is fed to an n-paraffin saturated adsorption bed to desorb n-alkanes adsorbed within the bed. The mixture of the desorbed normal alkanes and regeneration fluid 27j can be fed to a steam cracker lllj or the regeneration fluid and desorbed n-alkanes can be separated with the n-alkanes fed to a steam cracker. The outlet of the adsorption bed may be routed momentarily 28j to the front of the adsorption bed 60j to purge feed that was remaining in the void prior to starting the desorption process.

Example 3

[0080] To illustrate an adsorption process design scheme to continuously treat 100,000 BBLD of a hydrocarbon feed at 420 psig and 175°C to produce a process stream containing n-alkanes and a raffinate product containing the feed balance (iso-alkanes, aromatics and cycloalkanes), a three-bed arrangement with one bed in feed mode and the other two in regeneration (desorption) mode was used. Regeneration is done with a closed loop of n-pentane. Regeneration experiments using n-pentane showed that bed regeneration can take twice as long (160 min) as the feed step (80 min) with an equal volumetric flow. The regeneration fluid (n-pentane), which is mixed with the adsorbed phase (n-alkanes) is routed to a recovery column where n-pentane is separated from the n-alkanes from the feed and then sent back to the Regeneration Fluid Tank for reusing as desorbing fluid. A make-up n-pentane stream is added to account for losses during the process. The normal paraffin product from the bottom of the column is removed from the process and routed to the steam cracker. The proposed cycle scheme is presented in Table 3. The three beds alternate between feed (F), idle (I) and regeneration (R) steps and are maintained at 420 psig and 175°C.

Table 3 - Adsorption cycle for a three-bed adsorption process g _ec j Bed Cycle Time (min)

No. 0 80 160 240 320

1 F R R F R

2 1 F R R F

3 1 1 F R R

F = feed mode; R = regeneration mode; I = idle mode

[0081] FIG. 12 illustrates a three-bed adsorption (A) and bed regeneration (R) process design to treat 100 kBblD containing 23% n-alkanes (n-paraffins) that is fed 50k to a first adsorber bed 61k containing ZSM-5 material. Raffinate stream 80k (77 kBblD) is produced from the first bed, having a reduced n-paraffin content (or being n-paraffin free), which may be fed to a hydrocracker. Second 62k and third 63k absorber beds are shown in regeneration mode. Regeneration fluid 142k (n-C5, 200 kBblD) is fed to both the second and third beds to desorb n-alkanes adsorbed within the beds (streams 64k and 65k). The combined extract stream 66k (233 kBblD total) is sent to regeneration fluid recovery column 130k to recover the n-paraffin product 132k (23 kBblD) and recycle the regeneration fluid 134k (n-C5, 200 kBblD). The n-paraffin stream 132k can be sent to a steam cracker with the regeneration fluid 134k sent to regeneration fluid storage 140k along with makeup regeneration fluid 54k. While described herein for continuous feed processing, the system may be operated using one or more of the beds for n-alkanes adsorption with regeneration of one or more of the beds as needed.

[0082] For the avoidance of doubt, the present disclosure is directed to the subject-matter described in the following numbered paragraphs:

1. A process for producing an enriched normal alkane product from a hydrocarbon mixture, the product being suitable for use as an enriched normal alkane steam cracker feedstock, the process comprising: contacting a hydrocarbon mixture comprising normal alkanes and non-normal alkanes selected from iso-alkanes, cycloalkanes, or aromatics, with normal alkane-selective adsorption media to produce a normal alkane product from the hydrocarbon mixture and a non-normal alkane product; contacting the non-normal alkane product with a hydroconversion catalyst to produce a hydroconversion product comprising normal alkanes produced from the non-normal alkanes; and, combining the normal alkanes produced from the non-normal alkanes with the normal alkane product to provide an enriched normal alkane product.

2. The process of paragraph 1, wherein the normal alkane-selective adsorption media comprises a normal alkane selective zeolite.

3. The process of paragraph 2, wherein the normal alkane selective zeolite comprises ZSM-5, zeolite 5a, or a combination thereof.

4. The process of paragraph 1, wherein the hydrocarbon mixture comprises, LPG, naphtha, kerosene, diesel, or a mixture thereof.

5. The process of any one of paragraphs 1-4, wherein the hydroconversion catalyst comprises a hydrocracking and/or an isomerization catalyst and the hydroconversion conditions include corresponding hydrocracking and/or isomerization conditions.

6. The process of any one of paragraphs 1-5, wherein the hydroconversion product includes an isomerization product comprising iso- and normal alkanes and the isomerization product is partially or completely recycled with the hydrocarbon mixture and contacted with the normal alkane selective adsorption media.

7. The process of any one of paragraphs 1-6, wherein the hydrocarbon mixture is produced as a hydrocracker product from a hydrocracking process, the hydrocracker product comprising naphtha, kerosene, or diesel product components, or a mixture thereof.

8. The process of any one of paragraphs 1-6, wherein the hydroconversion catalyst comprises a hydrocracking catalyst and/or an isomerization catalyst arranged in a sequential configuration.

9. The process of any one of paragraphs 1-6, wherein the hydrocracking catalyst and/or isomerization catalyst are arranged in a sequential configuration. 10. The process of any one of paragraphs 1-6, wherein the hydroconversion product is contacted with a hydrocracking catalyst to produce a hydrocracking product and further contacted with normal alkaneselective adsorption media to produce a second normal alkane product from the hydroconversion product and a second non-normal alkane product comprising non-normal alkanes.

11. The process of paragraph 10, wherein the second non-normal alkane product is further contacted with a hydrocracking catalyst to produce a second hydrocracking product comprising C6- normal and iso-paraffins.

12. The process of any one of paragraphs 1-11, the process comprising a plurality of normal alkaneselective adsorption media zones, wherein at least one zone operates in normal alkane adsorption mode and at least one zone operates in normal alkane desorption regeneration mode.

13. The process of paragraph 12, wherein the normal alkane desorption regeneration mode comprises contacting a regeneration fluid with the normal alkane adsorption media of one or more of the normal alkane-selective adsorption media zones, the adsorption media having normal alkanes adsorbed thereon, to desorb the adsorbed normal alkanes and form a mixture of the desorbed normal alkanes and regeneration fluid; separating the normal alkane regeneration fluid from the mixture of the desorbed normal alkanes and regeneration fluid; and combining the desorbed normal alkanes with the normal alkanes produced from the non-normal alkanes and with the normal alkane product to provide the enriched normal alkane product.

14. The process of paragraph 13, wherein the regeneration fluid is selected from C5-C8 normal alkanes, LPG, C1-C8 alcohols, ammonia, or a combination thereof.

15. A process for producing a steam cracker olefin product from an enriched normal paraffin feedstream to a steam cracker, the process comprising separately contacting a hydrocarbon feedstream comprising normal alkanes and non-normal alkanes selected from iso-alkanes, cycloalkanes, or aromatics, with normal alkane-selective adsorption media to produce a normal alkane feedstream product and a non-normal alkane feedstream product from the hydrocarbon feedstream; contacting the non-normal alkane feedstream product with a hydroconversion catalyst under hydroconversion conditions to produce a hydroconversion feedstream product comprising normal alkanes produced from the non-normal alkanes; and feeding the hydroconversion feedstream product normal alkanes produced from the non-normal alkanes and the normal alkane feedstream product to a steam cracker to produce an olefin product. 16. The process of paragraph 15, wherein the normal alkane-selective adsorption media comprises a normal alkane selective zeolite.

17. The process of paragraph 16, wherein the normal alkane selective zeolite comprises ZSM-5, zeolite 5a, or a combination thereof.

18. The process of any one of paragraphs 15-17, wherein the hydroconversion catalyst comprises a hydrocracking and/or an isomerization catalyst and the hydroconversion conditions include corresponding hydrocracking and/or isomerization conditions.

19. The process of any one of paragraphs 15-18, wherein the hydroconversion product includes an isomerization product comprising iso- and normal alkanes and the isomerization product is partially or completely recycled with the hydrocarbon mixture and contacted with the normal alkane selective adsorption media.

20. The process of any one of paragraphs 15-19, wherein the hydrocarbon feedstream comprises one or more separate hydrocarbon feedstreams comprising LPG, naphtha, kerosene, diesel, or a mixture thereof.

21. The process of any one of paragraphs 15-20, wherein the hydrocarbon feedstream is produced as a hydrocracker product from a hydrocracking process, the hydrocracker product comprising naphtha, kerosene, or diesel product components, or a mixture thereof.

22. The process of any one of paragraphs 18-21, wherein the hydrocracking catalyst and/or isomerization catalyst are arranged in a sequential configuration.

23. The process of any one of paragraphs 15-22, wherein the hydroconversion feedstream product comprises iso- and normal alkanes and is partially or completely recycled with the hydrocarbon feedstream product and contacted with the normal alkane selective adsorption media.

24. The process of any one of paragraphs 15-23, the process comprising a plurality of normal alkaneselective adsorption media zones, wherein at least one zone operates in normal alkane adsorption mode and/or at least one zone operates in normal alkane desorption regeneration mode.

25. The process of paragraph 24, wherein the normal alkane desorption regeneration mode comprises contacting a regeneration fluid with the normal alkane adsorption media of one or more of the normal alkane-selective adsorption media zones, the adsorption media having normal alkanes adsorbed thereon, to desorb the adsorbed normal alkanes and form a mixture of the desorbed normal alkanes and regeneration fluid; separating the regeneration fluid from the mixture of the desorbed normal alkanes and regeneration fluid; and feeding the desorbed normal alkanes to the steam cracker. 26. The process of paragraph 25, wherein the regeneration fluid is selected from C5-C8 normal alkanes, LPG, C1-C8 alcohols, ammonia, or a combination thereof.

[0083] The present disclosure is not to be limited in terms of the particular embodiments described in this application, which are intended as illustrations of various aspects. Many modifications and variations can be made without departing from its spirit and scope, as may be apparent. Functionally equivalent methods and systems within the scope of the disclosure, in addition to those enumerated herein, may be apparent from the foregoing representative descriptions. Such modifications and variations are intended to fall within the scope of the appended representative claims. The present disclosure is to be limited only by the terms of the appended representative claims, along with the full scope of equivalents to which such representative claims are entitled. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.

[0084] The foregoing description, along with its associated embodiments, has been presented for purposes of illustration only. It is not exhaustive and does not limit the invention to the precise form disclosed. Those skilled in the art may appreciate from the foregoing description that modifications and variations are possible in light of the above teachings or may be acquired from practicing the disclosed embodiments. For example, in some cases, the steps described need not be performed in the same sequence discussed or with the same degree of separation. Likewise various steps may be omitted, repeated, or combined, as necessary, to achieve the same or similar objectives. Accordingly, the invention is not limited to the above-described embodiments, but instead is defined by the appended claims in light of their full scope of equivalents.

[0085] For the purposes of this specification and appended claims, unless otherwise indicated, all numbers expressing quantities, percentages or proportions, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term "about." Furthermore, all ranges disclosed herein are inclusive of the endpoints and are independently combinable. Whenever a numerical range with a lower limit and an upper limit are disclosed, any number falling within the range is also specifically disclosed. Unless otherwise specified, all percentages are in weight percent.

[0086] Any term, abbreviation or shorthand not defined is understood to have the ordinary meaning used by a person skilled in the art at the time the application is filed. The singular forms "a," "an," and "the," include plural references unless expressly and unequivocally limited to one instance. The invention illustratively disclosed herein may be practiced in the absence of any element that is not specifically disclosed herein. [0087] In the preceding specification, various preferred embodiments have been described with references to the accompanying drawings. It may, however, be evident that various modifications and changes may be made thereto, and additional embodiments may be implemented, without departing from the broader scope of the invention as set forth in the claims that follow. The specification and drawings are accordingly to be regarded as an illustrative rather than restrictive.

[0088] Where permitted, all publications, patents and patent applications cited in this application are incorporated by reference herein in their entirety, to the extent such disclosure is not inconsistent with the present invention.