Process for producing diesel fuel from olefinic refinery feedstreams

Abstract

An integrated refinery process for producing diesel fuel blending stock from olefinic heavy naphtha streams that contain gasoline and compounds with carbon numbers in the range of from 9-14 are oxidized and converted into their corresponding oxides in the presence of a homogeneous or heterogeneous catalyst, or both, and optionally an acid phase transfer agent for the liquid reactants, the product oxides having boiling points about 34° C. higher than the corresponding olefins, and as a result, in the diesel blending component boiling point range. The oxygenates produced have lubricating properties that enhance the typically poor lubricity characteristics of ultra-low sulfur diesels and reduce the need for additives to improve the lubricity of the blended diesel fuels.

Claims

1. An integrated refinery process for producing diesel fuel blending components, the process comprising: a. contacting an olefinic heavy naphtha hydrocarbon feedstock with a gaseous oxidant and an oxidation catalyst in an oxidation reactor for a predetermined period of time that is sufficient to oxidize all or substantially all of the olefinic compounds in the feedstock to form their oxides; b. passing the liquid reaction mixture and any unreacted gaseous oxidant to a separation zone and separating any gaseous oxidant and an aqueous phase to form a hydrocarbon reaction mixture and discharging the gaseous oxidant and aqueous phase; c. recovering and passing the hydrocarbon reaction mixture to a hydrocarbon separation zone and separating gasoline range blending components from diesel range blending components based on their respective boiling point ranges; and d. recovering the diesel range blending components.

2. The process of claim of claim 1 in which the feedstock is derived from a catalytic cracking unit or a thermal cracking unit.

3. The process of claim 2 in which the catalytic cracking unit is a fluidized catalytic cracking (FCC) unit.

4. The process of claim 2 in which the olefinic heavy naphtha hydrocarbon feedstock includes gasoline.

5. The process of claim 2 in which the FCC gasoline is a mixture of hydrocarbons comprising paraffins, aromatics, olefins and naphthenes boiling in the range from 36 to 240° C.

6. The process of claim 2 in which the thermal cracking unit is a delayed coking unit.

7. The process of claim 1 in which the oxidant is selected from the group consisting of oxygen, air, oxides of nitrogen, and mixtures thereof.

8. The process of claim 1 in which the oxidation catalyst is an oil soluble homogeneous catalyst selected from the group consisting of sodium tungstate, molybdenum acetylacetone and molybdenum hexacarbonyl.

9. The process of claim 1 in which the oxidation catalyst is selected from the group consisting of MoO3, Fe2O3, V2O5, ZrO2, TiO2.

10. The process of claim 1 in which the oxidation catalyst includes salts of transition metal oxides, wherein the salts are selected from IUPAC Groups 1 and 2 of the Periodic Table and includes Na+, K+, Ca++, Mg++, or mixtures thereof.

11. The process of claim 1 in which the oxidation reactor is a fixed bed catalytic reactor and the hydrocarbon feedstock is introduced into the top of the catalyst bed and the oxidant is introduced into the bottom of the reactor for contact in counter-current flow with the feedstock, and the oxidized reaction products and any partially converted or unconverted feedstock is recovered from the bottom of the reactor.

12. The process of claim 1 in which the oxidation catalyst comprises a support and a metal selected from the group consisting of IUPAC Groups 4-10 of the Periodic Table.

13. The process of claim 1 in which the reaction is conducted in a three-phase reactor selected from the group consisting of fixed bed, ebullated bed, slurry bed and moving bed reactors.

14. The process of claim 1 in which the oxides formed by the catalytic oxidation of the olefins are oxygenates.

15. The process of claim 14 in which oxygenates are formed in the reaction mixture that increase the lubricity of the diesel fuel blending components.

16. The process of claim 1 in which the oxides formed by the catalytic oxidation of the oxygenates are epoxides of the olefins.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The current process will be described in further detail below and with reference to the drawings that follow in which the same numerals are used to refer to the same and similar elements, and where:

(2) FIG. 1 is a simplified schematic diagram of an embodiment of the oxidation process utilizing a homogeneous catalyst;

(3) FIG. 2 is a simplified schematic diagram of another embodiment of the process utilizing a heterogeneous catalyst; and

(4) FIG. 3 is the plot of a simulated distillation curve for a feedstock and the oxidized products of the feedstock.

DETAILED DESCRIPTION OF THE INVENTION

(5) Referring now to FIG. 1, a process in accordance with the present disclosure is illustrated in which a feedstock from a source (11) such as described above containing cracked gasoline, and a liquid oxidant (12) are added to a two-phase oxidation reactor (10). One or more solubilized homogeneous catalysts (13) and, optionally, an acid phase transfer agent (13A) are introduced into the oxidation reactor (10) where they are thoroughly mixed for a time that is sufficient for the olefins present in the cracked gasoline (11) to be catalytically oxidized into their respective oxide forms.

(6) The mixing is continued in oxidation reactor (10) for a predetermined period of time and under conditions that will permit the oxidation of all, or substantially all, of the olefinic compounds present in the feedstock (11). Suitable operating conditions for the homogeneously catalyzed oxidation reactions employing liquid oxidants are temperatures in the range of from 20° C. to 100° C., preferably from 20° C. to 80° C., and most preferably from 20° C. to 60° C., and a pressure of from 1 bars to 10 bars, preferably from 1 to 5 bars, and most preferably from 1 to 3 bars.

(7) The reaction mixture is then passed to a two-phase liquid-liquid separator (20) for separation of the water from the hydrocarbons. As illustrated, the aqueous phase settles and is withdrawn as aqueous stream (16). The hydrocarbons are passed from the liquid-liquid separator (20) as treated hydrocarbon stream (15) and introduced into a separation zone (30). The separation zone (30) can include a stripper, a fractionator or a flash unit, or a combination of two or more of these devices.

(8) The lighter gasoline blending components (17) boiling in the range of 36° C. to 180° C. are removed from the upper portion of the separation zone (30) and the heavier diesel blending components (18) boiling in the range of from 180° C. to 370° C. are removed from the lower portion of the separation zone (30). The separated components are sent, respectively, to the gasoline blending pool and the diesel blending pool.

(9) Referring now to the simplified schematic diagram of FIG. 2, a process in accordance with the present disclosure employing one or more heterogeneous catalysts will be described. The solid catalyst (13) is preloaded into the two-phase oxidation reactor (100) and the cracked gasoline feedstock (11), a liquid oxidant (12) and, optionally, an acid phase transfer agent (13A) are introduced into the top of the oxidation reactor and, as illustrated, flow downwardly through the solid catalyst (13) at a predetermined rate that is sufficient to effect the oxidation of all, or substantially all of the olefinic compounds while in the reactor (100).

(10) As will be understood by one of ordinary skill in the art, the downstream processing steps in FIG. 2 of the hydrocarbon stream containing the reaction products and water are the same as those described above in connection with FIG. 1.

(11) When one or more gas phase oxidants are used, the gaseous oxidants are introduced into a gas distribution reactor (not shown) in place of reactor (10) in which the gas is intimately contacted with the liquid mixture in the form of small bubbles and preferably as micro bubbles. The liquid-liquid separation vessel (20) is replaced with a gas-liquid separation vessel and any remaining oxidant gases separated are recycled back to the oxidation reactor (10).

(12) Suitable operating conditions for the heterogeneously catalyzed oxidation reactions in the solid catalyst-containing reactor (100) using liquid oxidants are a temperature in the range of from 20° C. to 100° C. and a pressure in the range of from one bar to 30 bars.

(13) The oxidation agents can be added directly to the catalytic reactor or formed in situ in accordance with methods known in the art, such as in the in situ formation of organic peroxides, e.g., as disclosed in US 2013 026062, the disclosure of which is incorporated in its entirety by reference. For example, the in situ generation of an organic peroxide, or peroxides, can be conducted in an apparatus that includes an inlet for receiving an olefinic heavy naphtha hydrocarbon stream, a gas inlet for receiving a gaseous oxidant stream, and an oxidant outlet for discharging an effluent that can include the organic peroxide and any unreacted, unconverted or partially converted hydrocarbons and heteroatom-containing hydrocarbons including organosulfur and organonitrogen compounds. The organic peroxide generating apparatus contains a quantity of heterogeneous catalyst material that is effective to promote the generation of the organic peroxide. In an alternative embodiment, in combination with the heterogeneous catalyst, the apparatus can also include an inlet for receiving another stream that contains a concentration of a homogeneous catalyst in a liquid stream that is also effective to promote the generation of the organic peroxide. In a further embodiment (not shown), only the homogeneous catalyst is employed to promote the generation of the organic peroxide.

(14) In alternative processes (not shown), the gaseous oxidant and/or homogeneous catalyst can be mixed with the olefinic-rich stream, and the combined feed is charged to the organic peroxide generation apparatus.

(15) In a further alternative process (not shown), a mixer can be provided in a vessel upstream of the peroxide generation apparatus in which gaseous oxidant, the olefinic-rich fraction and homogeneous catalyst are admixed prior to being introduced into the organic peroxide generation apparatus.

EXAMPLE

(16) In a laboratory-scale example, a sample of 20 g of FCC naphtha was oxidized in a vessel containing using 0.3 g of sodium tungstate (Na.sub.2WO.sub.4.2H.sub.2O) in aqueous solution, 1.3 grams of acetic acid and 24 grams of hydrogen peroxide. The mixture was stirred in a round bottom flask and reacted for 60 minutes at 20° C. The reaction mixture was maintained at a reflux condition to prevent any vapor release from the system. At the end of sixty minutes, the reflux was stopped and the hydrocarbon phase was separated from the aqueous phase.

(17) The feedstock and product were analyzed by simulated distillation in accordance with ASTM D2887 and the results are presented in the diagrammatic plot of FIG. 3. As shown, the uppermost line is a plot of the FCC naphtha stream following the catalytic oxidation reaction and the line immediately below is a plot of the original boiling points of the untreated FCC naphtha stream. The bottom line is an independent plot along the X-axis of the increase in the boiling point temperatures between the untreated FCC naphtha and the oxidized FCC naphtha product stream, where the numerical values represent the increase in boiling point in degrees centigrade at the respective data points. At any given point along the respective plot lines, the horizontal distance between the plots of the FCC naphtha oxidized and untreated streams corresponds to the percentage of the weight shift from the gasoline to the diesel range blending components in the respective streams.

(18) As shown by the plots of FIG. 3, there is clear shift in boiling point, with 14 W % of the gasoline boiling range material shifted to diesel boiling range components. Thus, the problem of satisfying the increasing demand for middle distillate fuel is addressed by the present invention which shifts the gasoline range products to the distillate fuel, or diesel range, thereby increasing the production of distillate fuels.

(19) The FCC naphtha gasoline and the oxidized hydrocarbon product were subjected to PIONA analyses for paraffins (n-P), isoparaffins (i-P), olefins (O), naphthenes (N) and aromatics (A), and the results are reported in Table 1 and Table 2, respectively. As can be seen, the olefin content was reduced from 31.5 W % to 18.5 W % which indicated the extent of the oxidation reactions.

(20) TABLE-US-00001 TABLE 1 PIONA Analysis of FCC Gasoline C# n-P i-P O N A Total 4 1.0 0.6 1.4 0.0 0.0 3.0 5 0.8 5.2 8.5 0.1 0.0 14.6 6 0.6 5.3 6.0 1.3 0.8 14.0 7 0.7 4.2 6.4 2.2 2.1 15.6 8 0.8 3.9 2.4 2.5 5.1 14.8 9 0.3 2.7 1.0 1.3 6.1 11.3 10-14 1.0 5.0 5.7 1.1 14.0 26.8 Total 5.2 26.7 31.5 8.4 28.2 100.0

(21) TABLE-US-00002 TABLE 2 PIONA Analysis of oxidized FCC Gasoline C# n-P i-P O N A Total 4 0.0 0.0 0.0 0.0 0.0 0.0 5 0.0 0.0 0.0 0.0 0.0 0.0 6 0.0 0.0 0.2 0.0 0.0 0.2 7 0.0 0.0 0.2 0.1 0.6 0.9 8 0.7 1.5 1.5 1.5 7.3 12.5 9 0.5 3.7 2.1 2.0 13.5 21.9 10-14 2.4 11.4 14.4 2.2 34.1 64.5 Total 3.6 16.6 18.3 5.8 55.6 100.0

(22) As will be understood from the above, the catalyzed oxidation of an olefinic heavy naphtha refinery stream in accordance with the present process shifts the boiling point of the feedstream from the gasoline range to the diesel range and permits the refinery operator to relatively quickly and efficiently change the slate in order to meet an increase in the market demand for diesel fuel. An additional benefit realized from the oxygen-containing diesel blending components produced by this process are the lubricating properties of these oxygenates, which result in the reduction or elimination of the need for lubricity additives in the final blend of the diesel fuel products.

(23) Although the present invention has been described with reference to various examples and embodiments, other modifications and variations will be apparent to those of ordinary skill in the art from the above description, and the scope of protection for the invention is to be determined by the claims that follow.