METHOD FOR PRODUCING A DIESEL FUEL
A method relating to oil refining, which can be used to produce low-sulfur diesel fuel, comprising oil demineralization and distillation, and extraction and mixing of diesel fractions, followed by hydrogen refining of the mixture. In an atmospheric tower, two diesel fractions that boil at 171-341° C. and 199-360° C. are extracted. The 199-360° C. fraction is sent for liquid extraction to purify it from benzalkylthiophens. Amide, a product of organic amine interaction with organic acid, is used as the extractant. Fractions are then mixed, maintaining the balance ratio (based on the output) of 171-341° C. and 199-360 ° C. after refining. When refined using the ASTM D-86 method, the mixture of these fractions has an end boiling point no higher than 360° C. The technical result is production of diesel fuel with a 171-360° C. fractional composition and sulfur content of no higher than 10 ppm.
This application is a national stage application and claims the benefit of the priority filing date in PCT/RU2012/000475 referenced in WIPO Publication WO2012/177180 filed on Jun. 19, 2012. The earliest priority date claimed is Jun. 22, 2011.
FEDERALLY SPONSORED RESEARCHNot Applicable
SEQUENCE LISTING OR PROGRAMNot Applicable
BACKGROUNDThe invention relates to oil refining and can be used in production of low-sulfur diesel fuel which is being increasingly used in Russia and Europe.
The projected fuel demand in Europe (“ ” [Oil and Gas Technology] magazine, No. 6, 2007, p. 94) indicates increasing production of diesel fuel and decreasing production of gasoline:
Dieselization of vehicular transport is due to the fact that a diesel engine is 25-30% more cost effective than a gasoline one.
According to technical regulations On Fuel Requirements (RF Government Decree No. 118 of Feb. 27, 2008), the sulfur content of diesel fuel produced after December 2012 shall not exceed 10 ppm.
Known is the method for production of diesel fuel (RF patent No. 2247140) comprising single-stage hydrogen refining of light gas-oil fraction (end boiling point no higher than 300° C.) and two-stage hydrogen refining of heavy gas- oil fraction (initial boiling point not below 300° C.) using an aluminum-nickel- molybdenum of aluminum-cobalt-molybdenum catalyst. Hydrogen refining is performed at an elevated temperature and pressure with subsequent compounding of hydrogen-refined fractions. The sulfur content of the produced diesel fuel exceeds 10 ppm.
Also known is the method for production of low-sulfur diesel fuel described in the RF patent No. 2303624. According to this method, fuel is produced using two-stage catalytic hydrogen refining of the 180-360° C. diesel fraction using hydrogen-rich gas at elevated temperature and pressure wherein vapor and liquid phases of the first stage hydrogenator are produced. The liquid phase of the first stage hydrogenator is hydrogen-refined at the second stage, producing a second- stage hydrogenator which is then combined with the vapor phase of the first stage hydrogenator. This method does not provide diesel fuel sulfur content lower than 10 ppm.
The disadvantage of the known methods is that they are not designed for producing fuel with sulfur content no higher than 10 ppm.
The closest to the claimed invention in technical essence is a method for production of diesel fuel described in the RF patent No. 2387700; the authors have selected this method as the prototype.
According to the method described in the RF patent No. 2387700, after oil is demineralized it is distilled. Here, diesel fraction with a 171-341° C. boiling temperature is extracted from an atmospheric tower. Fractions with a boiling temperature above 341° C. together with fuel oil are fed to a vacuum column for further refining. Fractions with a 181-304° C. and 226-326° C. boiling temperature are extracted from a vacuum column and mixed with diesel fraction from the atmospheric tower while maintaining a balance ratio, wherein the end boiling point (EBP) of the balanced mixture of these fractions, when refined using the ASTM D-86 method, does not exceed 340° C. The mixture is hydrogen refined, producing low-sulfur diesel fuel with a sulfur content no higher than 10 ppm. The technical result is that the method per the invention makes it possible to produce diesel fuel with a sulfur content no higher than 10 ppm.
This effect is due to the fact that sulfur, which is a component of alkylbenzothiophens (ABT) and is sterically hindered by polyaromatic rings, is removed from diesel fuel by fractionation.
Known from literature (for instance, Salvatore Torrisi, Michael Gunter, “Petroleum Technology Quartlerly” magazine, 2004, vol. 9, No. 4, pp. 29-35) is that fractions with EBP above 340° C. contain sulfur compounds of ABT where sulfur is combined with sterically hindered polyaromatic rings, and its extraction during hydrogen refining is impeded due to sterical hindering of the sulfur atom. To remove sterically hindered sulfur, it is necessary to increase the temperature of the hydrogen refining process, which facilitates catalyst coking and shortens the plant service cycle.
However, decreasing the diesel fraction EBP from 360° C. to 340° C. reduces potential extraction of diesel fuel.
SUMMARYThe technical result of the claimed invention is the production of diesel fuel with a sulfur content no higher than 10 ppm with broad fractional composition at 171-360° C.
The stated technical result is achieved using a method for production of diesel fuel comprising oil demineralization and distillation, and extraction of two diesel fractions with boiling temperature of 171-341° C. and 199-360° C. in an atmospheric tower. The 199-360° C. fraction is sent for extraction of ABT using the liquid extraction method, followed by mixing the refined 199-360° C. fraction with the 171-341° C. fraction. Then, the fractions mixture is sent for hydrogen refining on an aluminum-cobalt-molybdenum or aluminum-nickel-molybdenum catalyst. Hydrogen refining of the fractions mixture is performed in a single stage.
The method for production of diesel fuel proposed as the invention solves this problem by removing ABT using the liquid extraction method.
DESCRIPTIONThe proposed method is realized as follows. Demineralized oil is fed to an atmospheric tower for distillation. In addition to gasoline and kerosene fractions, two diesel fractions with 171-341° C. and 199-360° C. boiling point are extracted. The 199-360° C. fraction is sent for removing ABT using the liquid extraction method, followed by mixing the refined 199-360° C. fraction (raffinate) with the 171-341° C. fraction. Then, the fractions mixture is sent for hydrogen refining on an aluminum- cobalt-molybdenum or aluminum-nickel-molybdenum catalyst. When refined using the ASTM D-86 method, the EBP of the balanced mixture of these fractions (output-based mixing) is no higher than 360° C.
The process parameters of the atmospheric tower during extraction of diesel fractions conform to design standards:
- tower pressure—no more than 2.5 kg/cm,
- tower top temperature—120-170° C.,
- tower bottom temperature—no more than 360° C.
Parameters of hydrogen refining of diesel fuel depends on the catalyst type and activity, the quality of feedstock and requirements to the end product, and is selected according to the design solution. For instance, for aluminum-cobalt-molybdenum or aluminum-nickel-molybdenum catalyst: pressure—20-60 kg/cm2, temperature—340-400° C., feedstock volumetric feed rate—1-3 hour−1, hydrogen-bearing gas circulation rate—200-600 nm3/m3, circulating gas hydrogen content—8595% by volume.
Reduction of sulfur in diesel fuel results in decreasing its fuel lubricity. So to produce diesel fuel meeting regulatory requirements, it is necessary to introduce lubricating and depressor-dispersive additives to meet operational specifications in terms of low-temperature characteristics, detergent additives, etc.
Adding the additives does not affect the amount of sulfur in finished fuel. The proposed method for removing ABT from diesel fuel—the feedstock for a hydrogen refining plant—has been developed on a pilot plant using diesel fuel fractions produced in a commercial plant.
Invention Embodiments Including the Best Invention Embodiment. Results of the experiments that were conducted are shown in Table 1. They demonstrate the following.
All experiments were conducted at 40-45° C. This temperature range ensures good mixing of diesel fuel and extractant. The temperature is sufficient for reducing viscosity of initial components—the 199-360° C. diesel fraction and extractant.
The feedstock:extractant mass ratio varied from 1:1 to 1:4. At the 1:1 feedstock:extractant ratio, maximum residual ABT was observed. The 1:2 to 1:3 feedstock:extractant ratio was selected as the optimum ratio. Increasing the feedstock:extractant ratio to 1:4 does not result in further decrease of ABT.
The selected optimum contact—mixing—time was 2-3 hours. However, based on results of the ABT content analysis, one hour of mixing is not enough (experiment 1), and increasing mixing time to 4 hours does not reduce the ABT content (experiment 4).
The optimum parameters are:
- temperature—40-45° C.,
- feedstock:extractant mass ratio—1:2 to 1:3,
- mixing time—2-3 hours
The detailed description of experiments 1-6 is provided below: Example No. 1. According to the claimed method, demineralized oil is fed to an atmospheric tower for distillation.
During distillation, two diesel fractions with 171-341° C. and 199-360° C. boiling point are extracted. The 199-360° C. fraction is sent for ABT extraction using the liquid extraction method.
The product of interaction of organic amine (for instance, aniline) with organic acid (for instance, acetic acid) is used as extractant. The resulting acetic anilide (extractant) is a dark cherry-colored liquid with a boiling point higher than 300° C. and a 1 kg/dm3 density at 20° C.
The 199-360° C. fraction is mixed with an extractant (anilide) in a 1:1 mass ratio in a mixer. They are mixed thoroughly for one hour at 40° C. After the mixture is cooled, it is drained to a separating funnel where separation into two layers takes place. The top layer—the refined 199-360° C. fraction—raffinate (85%) and saturated ABT—the extractant (15%)—is separated.
To regenerate the extractant, light gasoline fraction NK-85° C. is added to the bottom layer with a 1:2 mass ratio of saturated extractant to NK-85° C. fraction. The mixture is mixed for 0.5 hours at 20° C. and drained to a separating funnel. The bottom layer is separated and used again for extraction.
After the extractant is regenerated, the top layer is separated by distillation into NK-85° C. fraction and a residue (ABT +heavy aromatic hydrocarbons). The NK-85° C. fraction is used again to regenerate a saturated extractant, and the separated ABT+heavy aromatic hydrocarbons (15%) are fed to a vacuum gas oil.
Examples 2-6 which demonstrate the results of the claimed invention are shown in Table 1 together with Example 1.
Experiment conditions were changed according to the residual ABT content in the raffinate—refined diesel fuel.
The mixture of 70-85% of the 171-341° C. fraction and 15-30% of the purified 199-360° C. fraction, the raffinate (experiments 2-6), is sent for hydrogen refining on an aluminum-cobalt-molybdenum or aluminum-nickel-molybdenum catalyst. After refining, the amount of sulfur in diesel fuel is less than 10 ppm.
Industrial Applicability. The proposed method makes it possible to reduce the total sulfur content in straight-run diesel fuel from 1.34% to 0.774% due to reduced ABT content in feedstock for plants for hydrogen refining of diesel fuel using the liquid extraction method. The proposed method also makes it possible to ensure production of hydrogen refined diesel fuel with a sulfur content of not more than 10 ppm with a wide fractional composition of straight-run diesel fuel.
While hydrogen refining the mixture of 70-85% of the 171-341° C. fraction and 15-30% of the 199-360° C. fraction (without ABT extraction) on an aluminum-cobalt-molybdenum or aluminum-nickel-molybdenum catalyst, the sulfur content of diesel fuel after refining reaches over 50 ppm.
The proposed method makes it possible to produce diesel fuel with a sulfur content of not more than 10 ppm, which meets the requirements of international standards. The proposed method also makes it possible to increase the amount of feedstock for production of diesel fuel by widening the fractional composition of diesel fuel from EBP 340° C. to EBP 360° C.
The production process of diesel fuel with a sulfur content of not more than 10 ppm described in the claimed invention can be implemented at oil refineries and will make it possible to produce diesel fuel with a sulfur content of not more than 10 ppm over a wide fractional composition of 170-360° C. diesel fuel.
Parameters of Liquid Extraction and Content of Sulfuric Compounds in Feedstock and Raffinate.
Claims
1. A method for production of diesel fuel comprising oil demineralization and distillation, extraction and mixing of diesel fractions followed by hydrogen refining of a mixture, wherein,
- during distillation in an atmospheric tower, two diesel fractions boiling at 171-341° C. and 199-360° C. are extracted,
- the 199-360° C. fraction is sent for liquid extraction to purify said 199-360° C. fraction from benzalkylthiophens using amide as an extractant, a product of organic amine interaction with organic acid, and
- the 171-341° C. and 199-360° C. fractions are mixed after refining, and wherein a mixture of these fractions, when refined using an ASTM D-86 method, has an end boiling point no higher than 360° C.
2. The method of claim 1, wherein the produced mixture is subject to hydrogen refining on an aluminum-cobalt-molybdenum or aluminum-nickel-molybdenum catalyst.
Type: Application
Filed: Jun 19, 2012
Publication Date: Oct 2, 2014
Inventors: Raushan Gumerovich Telyashev (Moscow), Anna Nikolayevna Obryvalina (Moscow), Valentina Pavlovna Yengulatova (Kstovo Nizhegradskaya obl.), Irina Grigoryevna Nakipova (Kstovo Nizhegradskaya obl.), German Grigoryevich Vasilyev (Kstovo Nizhegradskaya obl.), Nikolay Vasilyevich Gavrilov (Kstovo Nizhegradskaya obl.)
Application Number: 14/119,441
International Classification: C10G 67/14 (20060101);
