Low-sulfur fuel and process of making

[0002] This case claims benefit of U.S. Provisional Application No. 60/245,281 filed Nov. 2, 2000.

[0003] The invention relates to a process for forming a low-sulfur motor gasoline and the product made therefrom. In one embodiment, process involves separating a catalytically cracked naphtha into at least a light fraction boiling below about 165° F. and a heavy fraction boiling above about 165° F. The light fraction is treated to remove sulfur by a non-hydrotreating method, and the heavy fraction is hydrotreated to remove sulfur to a level of less than about 100 ppm.

[0004] Catalytically cracked naphtha (“cat naphtha”) boiling in the gasoline boiling range is generally high in octane number resulting from the olefinic species contained therein. Cat naphtha may also contain sulfur impurities in sufficient quantity to warrant removal by hydroprocesssing, for example, in order to comply with product specifications and environmental regulations.

[0005] While hydroprocessing is a common method for sulfur removal, it also results in saturation of the desirable olefin species leading to a loss in cat naphtha octane number.

[0006] Some conventional processes attempt to remove the sulfur while maintaining octane number by separating the naphtha into at least a light fraction and a heavy fraction. Such processes take advantage of the observation that the olefins are concentrated in the light fraction and the sulfur in the heavy fraction. Accordingly, the light fraction is not hydroprocessed to preserve the olefin content and may be subsequently combined with the hydroprocessed heavy fraction to provide a naphtha having less sulfur without too great an octane number reduction. Unfortunately, some sulfur, such as mercaptan and thiophene sulfur, is often present in the light fraction, so further sulfur removal from the naphtha would be desirable.

[0007] At least one conventional process attempts to overcome this difficulty by treating the light fraction with a cobalt group metal chelate catalyst in an alkaline medium to oxidize the mercaptans to disulfides which are separated from the light fraction. Even so, such a treatment would not remove the thiophene from the light fraction, and further sulfur removal would therefore be desirable.

[0008] In another conventional process, reactive separation is employed to provide a relatively sulfur-free light fraction and a heavy fraction that contains monosulfides (“converted monosulfides”) resulting from the reactive conversion. While the light fraction would then contain less sulfur, the hydroprocessing of the heavy fraction must be conducted at greater severity in order to remove the converted monosulfides, which leads to an undesirable loss in octane number from olefin saturation.

[0009] Yet another conventional process seeks to restore octane number in the hydroprocessed heavy fraction by subsequently cracking the hydroprocessed fraction with an acidic catalyst such as ZSM-5. While octane number may be improved, the amount of desirable olefin species in the heavy fraction will still be diminished. Moreover, in order to avoid poisoning the acidic catalyst, the hydroprocessing is generally conducted at high severity to remove nitrogen impurities, leading to even more olefin saturation.

[0010] There is, therefore, a need for a process for forming a low-sulfur naphtha for gasoline blending from a cat naphtha without undesirable olefin saturation.

[0011] In one embodiment, the invention relates to a method for forming a low-sulfur, high-octane naphtha suitable for gasoline blending, the process comprising:

[0012] (a) separating a catalytically cracked naptha into at least a light fraction and a heavy fraction;

[0013] (b) treating the light fraction to remove sulfur at a hydrogen partial pressure of less than about 50 psig H₂to form a treated light fraction having a sulfur content less than about 150 ppm; and then

[0014] (c) treating the heavy fraction in the presence of a catalytically effective amount of a hydroprocessing catalyst under catalytic conversion condition in order to form a treated heavy fraction having a sulfur content less than about 150 ppm, based on the weight of the heavy fraction, and wherein the treated heavy fraction has at least 10% of the C₆+ olefin in the heavy fraction.

[0015] In another embodiment, the invention relates to a product formed in accordance with such a process.

[0016] In another embodiment, the invention relates to a naphtha-boiling-range hydrocarbon suitable for gasoline blending, the hydrocarbon comprising olefins having at least 5 carbon atoms wherein

[0017] (i) the hydrocarbon contains no more than about 13 wt. % olefins, based on the weight of the hydrocarbon;

[0018] (ii) the percentage of olefins having at least 5 carbon atoms that are C₅and C₆olefins ranges from about 45% to about 65%; and

[0019] (iii) the hydrocarbon contains less than about 60 ppm sulfur, based on the weight of the hydrocarbon.

[0020] In one embodiment, the olefins having a carbon number of at least C₅are present in an amount ranging from about 13 wt. % to about 30 wt. %, based on the weight of the hydrocarbon, and about 25% to about 45% of the olefins having a carbon number of at least C₅are C₅olefins.

[0021] The FIGURE illustrates the olefin content and distribution for representative naphthas produced in accordance with one embodiment of the process of the invention and in accordance with conventional processes. The abscissa is the wt. % of total olefins present in the desulfurized cat naphtha, based on the total weight of the desulfurized cat naphtha. The ordinate is the fraction (represented as a percent) of the total olefins having a carbon number of at least 5 that are C₅and C₆olefins.

[0022] The invention is based in part on the discovery that a low-sulfur, high-octane cat naphtha may be provided by regulating the cut point in a cat naphtha separation to provide a light fraction containing mercaptan sulfur and a heavy fraction containing thiophene sulfur. The light fraction is then processed using no more than a 50 psig hydrogen partial pressure to remove the mercaptan and other sulfur to a level of less than about 150 ppm. The heavy fraction is hydroprocessed to remove thiophene and other sulfur to a level of less than about 150 ppm, but the hydroprocessing is regulated to provide for retention of a substantial amount of C₅, C₆, and higher molecular weight olefins in order to ameliorate octane number loss. The desulfurized light and heavy fractions may be used alone and in combination as blendstock for low-sulfur, high-octane gasoline.

[0023] In one embodiment, cat naphtha feeds are employed that have a boiling range from about 65° F. to about 430° F. The naphtha can be any stream predominantly boiling in the naphtha boiling range and containing olefins, for example, a thermally cracked or a catalytically cracked naphtha. Such streams can be derived from any appropriate source, for example, they can be derived, for example, from the fluid catalytic cracking (“FCC”) of gas oils and resids from delayed or fluid coking of resids, and from steam cracking and related processes. The naphtha streams used may be derived from the fluid catalytic cracking of gas oils and resids. Such naphtha typically contains hydrocarbon species such as paraffins, olefins, naphthenes, and aromatics. Such naphtha may also and generally does contain heteroatom, e.g., sulfur and nitrogen, species. Heteroatom species include, for example, mercaptans and thiophenes. Undesirably, significant amounts of such heteroatom species may be present. FCC cat naphtha typically contains 20 to 40 wt. % olefins, based on the weight of the cat naphtha. Of these olefins, C₅olefins are typically present as 20% to about 30% of the total amount of olefins, and combined C₅and C₆olefin content is typically about 45% to about 65% of the total C₅+ olefins present.

[0024] The cat naphtha feed may be separated by methods such as splitting and fractionation in order to provide at least a light cat naphtha fraction and a heavy cat naphtha fraction. In one embodiment, the separation cut point between the light and heavy fraction is regulated so that a substantial amount of the mercaptan and olefins having fewer than six carbons (“C₆⁻⁼”) are present in the light fraction and a substantial amount of the thiophene and the olefins having 6 or more carbons (“C₆⁻⁼”) are present in the heavy fraction. Accordingly, the cut point is regulated so that light fraction boils in the range of about 65° F. to about 165° F., preferably from about 65° F. to about 150° F., and more preferably in the range of about 65° F. to about 115° F. Thus the heavy fraction may have a boiling point in the range of about 165° F. to about 430° F., preferably 150° F. to about 430° F., and more preferably from about 115° F. to about 430° F. Those skilled in the art are aware that hydrocarbon separations are imperfect and, consequently, some overlap in the boiling points of the light and heavy fractions may occur near the cut point. Even so, the light fraction will typically contain more than 50% of the C₅olefins contained in the cat naphtha feed. The heavy fraction will typically contain more than 50% of the C₆olefin contained in the cat naphtha feed. For an FCC cat naphtha, about 10 wt. % to about 40 wt. % of the total weight of the cat naphtha is in the light fraction and about 90% to about 60 wt. % of the total weight of the cat naphtha is in the heavy fraction.

[0025] In one embodiment, the light fraction is processed to remove sulfur while preserving the olefin content to maintain octane number. Accordingly, the light fraction is desulfurized via a non-hydrotreating process (i.e., a process employing no more than 50 psig hydrogen partial pressure) to remove sulfur species such as mercaptan. Preferably, the desulfurized light fraction has a sulfur content of less than about 100 ppm, more preferably less than 75 ppm, and still more preferably less than about 50 ppm, based on the weight of the light fraction. A substantial portion of the olefins in the light fraction (mostly C₅olefins but generally also some C₆olefins) can be preserved during sulfur removal. In an embodiment, more than 75% of the C₅olefins are retained following sulfur removal, preferably more than 90%, based on the total weight of C₅olefins in the light fraction. MEROX™ and EXTRACTIVE MEROX™, Universal Oil Products, Des Plaines, Ill., are suitable processes for removing sulfur while preserving olefin content, as are sulfur absorption processes set forth, for example, in U.S. Pat. No. 5,843,300. It should be noted that such processes are representative, and that any non-hydrotreating process capable of removing sulfur to a level lower than 150 ppm can be employed.

[0026] In one embodiment, the heavy fraction is hydrodesulfurized, for example via catalytic hydroprocessing, with a hydrogen partial pressure greater than 50 psig in order to remove sulfur-containing species such as thiophene. The desulfurized heavy fraction typically has a sulfur content of less than about 100 ppm, more preferably less than about 75 ppm, and still more preferably less than about 50 ppm. In one embodiment, the hydroprocessing is conducted under selective hydroprocessing conditions in order to remove sulfur-containing species while minimizing olefin saturation. In regulatory environments where motor gasoline olefin content is limited, there is an incentive to preserve the amount of those olefins making the greatest contribution to octane number. Accordingly, for highest MON and RON values, the amount of C₅and C₆olefin should be preserved in the heavy fraction during hydroprocessing by, for example, selective hydroprocessing.

[0027] The term “hydroprocessing” is used broadly herein and includes processes such as hydrofining, hydrotreating, and hydrocracking. As is known by those of skill in the art, the degree of hydroprocessing can be controlled through proper selection of catalyst as well as by optimizing operating conditions. Hydroprocessing may be conducted under conditions, set forth in detail below, that do not result in converting a substantial portion of olefins into paraffins, but that do result in the removal of objectionable species including non-hydrocarbyl species that may contain sulfur, nitrogen, oxygen, halides, and certain metals. Such conditions are referred to herein as “selective hydroprocessing” conditions.

[0028] Accordingly, the selective hydroprocessing reaction can be conducted in one or more stages at a temperature ranging from about 200° C. to about 400° C., more preferably from about 250° C. to about 375° C. The reaction pressure preferably ranges from about 50 to about 1000 psig, more preferably from about 50 to about 300 psig. The hourly space velocity preferably ranges from about 0.1 to about 10 V/V/Hr, more preferably from about 2 to about 7 V/V/Hr, where V/V/Hr is defined as the volume of oil per hour per volume of catalyst. The hydrogen containing gas can be added to establish a hydrogen charge rate ranging from about 500 to about 5000 standard cubic feet per barrel (SCF/B), more preferably from about 1000 to about 3000 SCF/B. When more than one stage is used, sulfur, typically in the form of H₂S, may be removed from the process between successive stages. Successive stages may be operated under similar hydroprocessing conditions. Lower sulfur concentration in downstream stages is believed to result in diminished mercaptan reversion in the presence of olefins that were selectively retained in the upstream selective hydroprocessing stages.

[0029] Selective hydroprocessing conditions can be maintained by use of any of several types of hydroprocessing reactors. Trickle bed reactors are most commonly employed in petroleum refining applications with co-current downflow of liquid and gas phases over a fixed bed of catalyst particles. It can be advantageous to utilize alternative reactor technologies. Countercurrent-flow reactors, in which the liquid phase passes down through a fixed bed of catalyst against upward-moving treat gas, can be employed to obtain higher reaction rates and to alleviate aromatics hydrogenation equilibrium limitations inherent in co-current flow trickle bed reactors. Moving bed reactors can be employed to increase tolerance for metals and particulates in the hydroprocessor feed stream. Moving bed reactor types generally include reactors wherein a captive bed of catalyst particles is contacted by upward-flowing liquid and treat gas. The catalyst bed can be slightly expanded by the upward flow or substantially expanded or fluidized by increasing flow rate, for example, via liquid recirculation (expanded bed or ebullating bed), use of smaller size catalyst particles which are more easily fluidized (slurry bed), or both. In any case, catalyst can be removed from a moving bed reactor during onstream operation, enabling economic application when high levels of metals in feed would otherwise lead to short run lengths in the alternative fixed bed designs. Furthermore, expanded or slurry bed reactors with upward-flowing liquid and gas phases would enable economic operation with feedstocks containing significant levels of particulate solids, by permitting long run lengths without risk of shutdown due to fouling. Moving bed reactors utilizing downward-flowing liquid and gas can also be applied, as they would enable onstream catalyst replacement.

[0030] In one embodiment, the hydroprocessing catalyst contains at least one Group VIII metal and a Group VI metal on an inorganic refractory support, which is preferably alumina or alumina-silica. The Group VIII and Group VI compounds are well known to those of ordinary skill in the art and are well defined in the Periodic Table of the Elements. For example, these compounds are listed in the Periodic Table found at the last page of Advanced Inorganic Chemistry, 2nd Edition 1966, Interscience Publishers, by Cotton and Wilkinson. The Group VIII metal is preferably present in an amount ranging from 0.5 to 20 wt. %, preferably 1 to 12 wt. %. Preferred Group VIII metals include Co, Ni, and Fe, with Co and Ni being most preferred. The preferred Group VI metal is Mo which is present in an amount ranging from 1 to 50 wt. %, preferably 1.5 to 40 wt. %, and more preferably from 2 to 30 wt. %.

[0031] Where selective hydroprocessing is employed, and especially where selective hydrodesulfurization (“selective HDS”) is employed, a representative hydroprocessing catalyst can contain 1 to 10 wt. % MoO₃and 0.1 to 5 wt. % CoO supported on alumina, silica-alumina, or other conventional support materials. Generally, the support surface area may range from about 100 to about 400 m²/g. The catalyst may contain small amounts of iron and SO₄. The total surface area of the catalyst may range from about 150 to about 350 m²/g, while the pore volume may range from about 0.5 to about 1.0 cm³/g, as measured by mercury intrusion. When metals are impregnated into or on to the support, the impregnation should be conducted to provide a final catalyst composition having oxygen chemisorption values set forth in the range of Table 1. The catalyst may also contain about 0 to about 10 wt. % phosphorus which may be added at any time during catalyst preparation.

[0032] In the selective hydrotreating process, the catalyst may be loaded into the hydrotreating reactor in the oxidized form and sulfided by conventional methods prior to treating the cracked naphtha.

[0033] In an embodiment, the selective hydroprocessing catalyst may contain about 0 to about 5 wt. % Group IA elements, especially potassium, for activity, selectivity, or a combination of activity and selectivity enhancements. The elements may be added at any time during the preparation of the catalyst.

[0034] The selective hydroprocessing catalyst when used in accordance with the selective hydroprocessing conditions set forth herein provides both high activity and selectivity for selective naphtha hydroprocessing. The high selectivity of the catalyst provides abated olefin hydrogenation at a given sulfur removal level as compared to conventional hydroprocessing catalysts. The olefin hydrogenation abatement leads to reduced hydrogen consumption and substantially diminishes octane losses in the hydrotreated heavy fraction.

[0035] All metals and metal oxide weight percents given are on support. The term “on support” means that the percents are based on the weight of the support. For example, if a support weighs 100 g, then 20 wt. % Group VIII metal means that 20 g of the Group VIII metal is on the support.

[0036] Any suitable inorganic oxide support materials may be used for the hydroprocessing catalyst of the present invention, including the selective hydroprocessing catalyst. Alumina and silica-alumina, including crystalline alumino-silicate such as zeolite are representative supports. Alumina is employed in one embodiment. The silica content of the silica-alumina support can be from about 2 to about 30 wt. %, preferably about 3 to about 20 wt. %, and more preferably about 5 to about 19 wt. %. Other refractory inorganic compounds may also be used, non-limiting examples of which include zirconia, titania, magnesia, and the like. The alumina can be any of the aluminas conventionally used for hydroprocessing catalysts. Such aluminas are generally porous amorphous alumina having an average pore size from about 50 to about 200 Å, preferably about 70 to about 150 Å, and a surface area from about 50 to about 450 m²/g.

[0037] In one embodiment, the hydroprocessed heavy fraction has a boiling point in the range of about 115° F. to about 430° F. and retains at least about 45%, and more preferably at least about 75% of the olefins present in the heavy fraction before hydroprocessing. Still more preferably, at least about 50% to about 90% of the olefins present in the heavy fraction are preserved during hydroprocessing and are present in the hydroprocessed heavy fraction.

[0038] It is within the scope of the invention to further process the hydroprocessed heavy fraction by, for example, sulfur absorption and catalytic reforming.

[0039] In one embodiment, the heavy fraction comprises an intermediate cat naphtha portion (“ICN”) and a heavy cat naphtha portion (“HCN”). The initial boiling point for the HCN portion ranges from about 115° F. to about 165° F. (preferably about 115° F.), and is in the range of about 350° F. to about 380° F. (preferably about 365° F.) for the HCN. The final boiling point ranges from about 350° F. to about 380° F. (preferably about 365° F.) for the ICN and from about 410° F. to about 480° F. for the HCN (preferably about 430° F.). The ICN and HCN can be processed independently to remove sulfur. Accordingly, in one embodiment, the ICN portion is selectively hydroprocessed and the HCN is non-selectively hydroprocessed. All or a portion of the hydroprocessed ICN and HCN can be combined to form the desulfurized heavy fraction.

[0040] In one embodiment, all or a portion of desulfurized light and heavy fractions may be combined or, alternatively, independently selected for blending to form a motor gasoline. In an embodiment where the process' light and heavy fractions are combined to form a product, preferably no more than about 20% of the total olefins in that product would be heavier than C₅and C₆olefins, based on the total amount of olefins in that product. Preferably, at least about 10% of the hydroprocessed heavy fraction's C₅+ olefins are C₅and C₆olefins, and still more preferably about 40% to about 70% of the hydroprocessed heavy fraction's C₅+ olefins are C₅and C₆olefins. Motor gasoline blending is known to those skilled in the art. Representative hydrocarbons that may be blended with the desulfurized light fraction, desulfurized heavy fraction, or some combination thereof include alkylate, butanes, reformate, light virgin naphtha, and isomerate.

[0041] One product that may be formed from the process of the invention comprises at least a portion of the desulfurized light fraction and at least a portion of the desulfurized heavy fraction.

[0042] Another product that may be formed in the process of the invention is a naphtha that may be used for motor gasoline blending comprising about 30 wt. % to about 50 wt. % of a combination of the desulfurized light fraction and desulfurized heavy fractions, based on the weight of the naphtha. Preferably, the desulfurized light fraction is present in an amount ranging from about 5 wt. % to about 30 wt. %, based on the weight of the combined fractions, the balance of the combined light and heavy product being the desulfurized heavy fraction. Preferably, for this naphtha, the percentage of C₅and C₆olefins in the combined fractions ranges from about 5 wt. % to about 8 wt. % and from about 3 wt. % to about 9 wt. % respectively, based on the weight of the combined fractions. The balance of the naphtha may contain about 50 wt. % to about 70 wt. % of other motor gasoline blendstocks (including conventional blendstocks such as light virgin naphtha, reformate, isomerate, alkylate, and butanes) which together would generally contain no more than about 50 ppm sulfur and about 5 wt. % olefins, based on the weight of the naphtha. The resulting naphtha product would, therefore, comprise about 5 to about 15 wt. % total olefins where greater than 25%, preferably greater than 35%, and more preferably greater than 40% of the total weight of olefins in the naphtha are C₅olefins and where greater than 50%, preferably greater than 60%, and more preferably greater than 70% of the total weight of olefins in the naphtha are C₅plus C₆olefins.

[0043] In an embodiment at least a portion of the heavy fraction is separated into a second light fraction and a second heavy fraction. The second light fraction is hydroprocessed in the presence of a hydrogen-containing gas and a catalytically effective amount of at least one selective hydroprocessing catalyst under selective hydroprocessing conditions. The second heavy fraction is hydroprocessed in the presence of a hydrogen-containing gas and a catalytically effective amount of a hydroprocessing catalyst under nonselective hydroprocessing conditions.

[0044] In another embodiment, the invention relates to a product formed by hydroprocessing the second light fraction in the presence of a hydrogen-containing gas and a catalytically effective amount of at least one hydroprocessing catalyst under selective hydroprocessing conditions. The invention also relates to a product formed by hydroprocessing the second heavy fraction in the presence of a hydrogen-containing gas and a catalytically effective amount of a hydroprocessing catalyst under nonselective hydroprocessing conditions.

[0045] In yet another embodiment, the invention relates to a light fraction having a boiling point ranging from about 65° F. to about 165° F. and a heavy fraction with a boiling point ranging from about 165° F. to about 430° F., wherein the heavy fraction contains more than about 50% of the C₇olefm contained in the naphtha.

[0046] The naphtha's sulfur content is preferably less than 50 ppm and more preferably less than 30 ppm, based on the weight of the naphtha.

[0047] Six FCC naphtha samples (Examples 1-6) having nominal boiling ranges of 65-430° F. were obtained from conventional catalytic cracking units. The olefin content, sulfur content and amount of olefins having five (C₅olefins) and six (C₆olefins) carbon atoms were measured and are provided in the table below. The percentage of total olefins that are C₅olefins and the percentage that are C₅plus C₆olefins are also provided.

[0048] Samples A-F were each separated by distillation into three fractions having nominal boiling ranges of 65-115° F., 115-365° F., and 365-430° F. These fractions were analyzed in the same manner as above. The results are provided in Table 3 below.

[0049] Samples A-F were also each separated by distillation into fractions having nominal boiling ranges of 65-165° F. and 165-365° F. These fractions were analyzed in the same manner as above. It should be noted that the ICN/HCN cut-point is the same here as in Table 3. For brevity, the HCN data is not repeated. The results are provided in Table 4 below.

[0050] Conventional naphtha hydrodesulfurization technology typically results in high levels of olefin saturation. To illustrate this, it was assumed (based on a process model) that 90% olefin saturation would occur at the high HDS levels required to reduce the sulfur content of the 65-430° F. naphthas A-F to 30 ppm S. The total olefin content and the percentage of total olefins that are C₅olefins and the percentage that are C₅plus C₆olefins following this HDS step are provided in Table 5 below as samples 2-A through 2-F. It should be noted that in accordance with the process model, olefin saturation is independent of olefin molecular weight. As used herein, the percentage of olefins of a particular molecular weight (e.g., percent of C₅olefin) is calculated by dividing the weight percent of that molecular weight olefin by the total weight percent of olefins.

[0051] Another FCC naphtha desulfurization process treats the light cat naphtha stream using commercially available caustic extraction technology and hydrotreats the intermediate and heavy FCC naphtha streams. Caustic extraction removes about 90% of the sulfur and preserves 100% of the olefins present. In a simulation illustrating such a process, 90% of the sulfur was removed while retaining 100% of the olefins in the 65-115° F. streams of Example 1 (G-L). In the simulation, the ICN and HCN streams of Example 1 (M-R and S-X, respectively) underwent severe hydrotreating to reduce the sulfur content to 30 and 10 ppm S, respectively, with complete saturation of the olefins to paraffins. A simulated blending of these streams provided samples 3-A to 3-F in Table 6 below.

[0052] Yet another FCC naphtha desulfurization process treats the light cat naphtha stream using commercially available caustic extraction technology, hydrotreats the ICN at mild conditions with a conventional catalyst, and hydrotreats the HCN at relatively severe conditions, i.e., conditions that result in desulfurization, but also significant olefin saturation. In a simulation illustrating such a process, 90% of the sulfur was removed while retaining 100% of the olefins in the 65-115° F. streams of Example 1 (G-L). In the simulation, the ICN streams of Example 1 (M-R) underwent mild hydrotreating with a conventional catalyst to reduce the sulfur content to 30 ppm S with 80% olefin saturation and the HCN streams of Example 1 (S-X) were severely hydrotreated to 10 ppm S with 100% saturation of the olefins. A simulated blending of the streams provided samples 4-A to 4-F Table 7 below.

[0053] With efficient fractionation, the end point of the LCN can be increased to 165° F. The following simulation illustrates a process employing a higher cut point between the LCN and ICN and 90% sulfur removal with 100% retention of the olefins in the 65-165° F. streams of Example 1 (Y-AD). In accordance with the simulation, the ICN steams of Example 1 (AE-AJ) were mildly hydrotreated with a conventional catalyst to reduce the sulfur content to 30 ppm S with 90% olefin saturation and the HCN streams of Example 1 (S-X) were severely hydrotreated to 10 ppm S with 100% saturation of the olefins. A simulated blending of the streams provided samples 5-A to 5-F in Table 8 below.

[0054] By using a selective catalyst and HDS conditions that remove sulfur while minimizing olefin saturation, the percentage of C₅and C₅+C₆olefins can be altered significantly. In a simulation of such a process, 90% of the sulfur was removed while retaining 100% of the olefins in the 65-115° F. streams of Example 1 (G-L). The ICN streams of Example 1 (M-R) were selectively hydrotreated with a selective catalyst to reduce the sulfur content to 30 ppm S with 12-40% olefin saturation (based on selective hydroprocessing model predictions) and the HCN streams of Example 1 (S-X) were severely hydrotreated to 10 ppm S with 100% saturation of the olefins. A simulated blending of these streams provided samples 6-A to 6-F in Table 9 below.

[0055] The effect of raising the LCN endpoint from 115 to 165° F. in Example 6 was calculated in order to study the effect of 90% sulfur removal while retaining 100% of the olefins in the 65-165° F. streams of Example 1 (Y-AA). In accordance with the simulation, the ICN streams of Example 1 (AE-AJ) were selectively hydrotreated with a selective catalyst to reduce the sulfur content to 30 ppm S with 15-43% olefin saturation (based on selective hydroprocessing model predictions) and the HCN streams of Example 1 (S-X) were severely hydrotreated to 10 ppm S with 100% saturation of the olefins. A simulated blending of these streams provided samples 7-A to 7-F in Table 10 below.

[0056] With selective HDS of the ICN stream, the total sulfur content can be reduced further still while retaining a high percentage of C₅+C₆olefins. To illustrate this effect, a simulation was employed in which 90% of the sulfur was removed while retaining 100% of the olefins in the 65-115° F. streams of Example 1 (G-L). In accordance with the simulation, the ICN streams of Example 1 (M-R) were selectively hydrotreated with a selective catalyst to reduce the sulfur content to 10 ppm S with 25-55% olefin saturation (based on selective hydroprocessing model predictions) and the HCN streams of Example 1 (S-X) were severely hydrotreated to 10 ppm S with 100% saturation of the olefins. A simulated blending of these streams provided samples 8-A to 8-F in Table 11 below.

[0057] The selective hydrotreating of ICN can be improved further still by using two-stage selective hydroprocessing, which further improves olefin retention. In a simulation illustrating such a process, 90% of the sulfur was removed while retaining 100% of the olefins in the 65-115° F. streams of Example 1 (G-L). In accordance with the simulation, the ICN streams of Example 1 (M-R) were selectively hydrotreated in a two-stage process with a selective catalyst to reduce the sulfur content to 30 ppm S with 6-25% olefin saturation (based on selective hydroprocessing model predictions) and the HCN streams of Example 1 (S-X) were severely hydrotreated to 10 ppm S with 100% saturation of the olefins. A simulated blending of these streams provided samples 9-A to 9-F in Table 12 below.