Patent Grant
10844303
The invention relates to refining fuel in general and to refining fuel oil in particular.
During the catalytic cracking process of crude oil refining, a residual product is produced. These are simply the materials left after catalytic cracking has been performed on crude oil. These residuals are commonly referred to as “bottoms,” as they are the heavier components of crude oil. Residuals typically have a high British Thermal Unit (BTU) value. However, they are difficult to use because they are commonly high in solid content; asphalt, asphaltoid, and asphaltene content; and paraffin content. It is usually very viscous, making handling difficult. Depending on the content of the particular bottom, viscosities on the order of 6,000 to 400,000 mm2/s at ambient temperature are not uncommon.
Residuals or refining bottoms will typically be between about 50 to 90 percent asphaltenes, asphaltoids, high molecular weight (above about 1,000,000 mw) paraffins, and solids.
These residuals are commonly used to make asphalt. However, another use is to convert the residual to fuel oil. The high BTU value makes this a suitable use for residuals, but the high viscosity makes it problematic.
To convert the residuals into fuel oil, a cutter is added. Typically, the cutter is diesel oil of number 2 quality. A significant amount of diesel is required. Up to a third of the overall volume of the finished fuel oil will frequently be diesel oil. The finished product will be a number 4 to number 6 grade fuel oil.
Diesel is, of course, a type of fuel oil. Thus, number 2 diesel is more valuable than no. 4 and especially no. 6 fuel oil. When the price disparity between no. 2 diesel and no. 6 fuel oil gets too wide, it ceases to make financial sense to blend up to a ⅓ of a more valuable commodity into the residuals in order to obtain a larger volume of lower value commodity.
In view of the foregoing, a more efficient method of converting petroleum refining residuals into fuel oil is desired.
A method making fuel oil from refining residuals is disclosed. The refining residuals, petrochemicals comprising about 50 to 90 percent asphaltenes, asphaltoids, high molecular weight (above about 1,000,000 mw) paraffins, and solids are mixed with a diluent and an additive. (As used herein, the term “about” means+/−ten percent, unless otherwise indicated.) When necessary, the refining residuals are heated to render them flowable—typically to between about 160° to 220° F. Once the residuals have been liquified, they are combined with a mixture of the diluent and the additive. Preferred diluents include diesel and reformed naphtha and combinations thereof.
The additive is believed to be a cross-linked cyclic anhydride copolymer having an intrinsic viscosity (limiting viscosity, η) of between about 0.10 and 3.0 deciliters per gram. The anhydride copolymer has an average molecular weight between about 3,000 and 3,000,000. The additive also includes excess aromatic hydrocarbons and a surfactant. In the preferred embodiment, the additive (about 0.10 to 0.25 percent by weight) is introduced to a mixture comprising about three quarters residuals and one quarter diluent (˜3:1 ratio by weight). The result will be a fuel oil having a viscosity that is about 25 to as much as about 70 percent lower than the viscosity of a mixture of the same refining residuals and diluent without the additive.
Another difficult product to utilize in the refining field are a subset of reformed naphthas, that is naphthas that have undergone thermal and/or catalytic reformation. Reformed naphthas with an aromatic content below about 28 percent are suitable for making gasoline. Reformed naphthas above about 48 percent in aromatic content are suitable for use as a feed stock for manufacturing aromatic chemicals. However, reformed naphthas whose aromatic content is above about 28 percent but below about 48 percent have few good commercial uses. It contains too many aromatics for use in gasoline but not enough to be a good, or at least efficient, feedstock for aromatic chemical production.
Reformed naphtha with 28-48 percent aromatics is thus a low cost refining product that would be attractive for use as a diluent to convert refining residuals into fuel oil. However, reformed naphtha is too volatile for this application. Fuel oil requires a flash point between about 125° F. and about 210° F., and most preferably about 145° F. The use of reformed naphtha as a diluent would result in an end product having a flash point too low for use as fuel oil.
The inventor has developed an additive which can be used with reformed naphtha. The additive allows the reformed naphtha to be used as a diluent for refinery bottoms to produce fuel oil. This significantly reduces the cost of manufacturing the fuel oil because of the lower cost of reformed naphtha vs. diesel and other common cutter stocks. It also reduces the overall amount of diluent required, regardless of which diluent is used.
The additive is prepared by admixing vinyl acetate copolymers with aromatic hydrocarbons. The preferred aromatics are C10-C12 alkylbenzenes and alkylnapthalenes primarily in the form of dimethylethylbenzene and tetramethylbenzene. The vinyl acetates and the aromatics are combined for about ¾ hour at 180 degrees F.
A preferred aromatic formulation is sold under the trade name Atosol 150 by Total Petrochemicals (CAS #64742-94-5). Similar chemicals are available from Chevron, Shell, and Exxon. The aromatic mixture will commonly contain naphthalene (CAS RN 91-20-3) in quantities of less than 10 percent and ethylbenzene and benzene in amounts of less than 1 percent. It also contains about 25 ppm butylated hydroxytoluene as an inhibitor.
The dimethylethylbenzene is believed to include 1, 2-dimethyl-4-ethylbenzene and the tetramethylbenze is believed to include 1, 2, 3, 5-tetramethylbenzene, each of which are illustrated in
Another suitable aromatic blend include C12-C15 alkylnaphthalenes primarily in the form of methylnaphthalenes. The preferred alkylnaphthalenes are sold under the trade name Atosol 200 by Total Petrochemicals (CAS #64742-94-5). This aromatic mixture will also commonly contain naphthalene (CAS RN 91-20-3) in quantities of less than 10 percent and ethylbenzene and benzene in amounts of less than 1.0 percent. It also contains about 25 ppm butylated hydroxytoluene as an inhibitor. An example of methylnaphthalene is shown in
Substituting C12-C15 alkylnaphthalenes for some or all of the C10-C12 alkylbenzenes and alkylnapthalenes, preferably by substituting Atosol 200 for Atosol 150, will increase the flash point of the final product. The appropriate ratio will depend upon the flash point requirements and the composition of the reformed naphtha. In one preferred embodiment, the ratio of Atosol 150 to Atosol 200 is about 1.5:1.
In the preferred embodiment, the vinyl acetate comprises two ethylene vinyl acetates: ethylene vinyl acetate 28-10 and ethylene vinyl acetate 40-30 (CAS 24937-78-8). The 40 and 28 in the foregoing designations refer to the percentage of vinyl acetate in each reactant. The balance in each is ethylene. The ethylene vinyl acetates used in the preferred embodiment are believed to have the structure illustrated in
Maleic anhydride copolymers and a polyether polyol are next added to the mixture. The maleic anhydride copolymers are preferably maleic anhydride amide copolymers. The preferred maleic anhydride amide is available from AkzoNobel under the brand name Armohib PC-308. The maleic anhydride amide copolymer is believed to be comprised primarily of a mixture of molecules having one or both of the structures illustrated in
The preferred polyether polyol is available from AkzoNobel under the brand name Witbreak DRE-8164. The polyether polyol is believed to have the structure illustrated in
Once the maleic anhydride copolymers and the polyether polyol are added, the mixture is heated to at least about 280 degrees F. for about 4 to 5 hours., Continuous mixing is maintained, preferably in a closed container, thereby retaining any distillate. The mixture is then allowed to cool to about 100-110 degrees F., at which point additional aromatics and a surfactant are added.
The additional aromatics are not believed to be critical to the reaction, which is believed to be complete by the time the extra aromatics are added. Rather, the second addition of aromatics is believed to serve primarily as a diluent. Many aromatic and aliphatic compositions would serve equally well in this capacity.
The preferred surfactant is a C 9-C11 ethoxylated alcohol. It is available under the brand name Tomadol 91-2.5 and is sold by Air Products and Chemicals, Inc. of Allentown, Pa. The surfactant has two primary functions in the additive. First, it helps keeps the additive components in solution, keeping the additive fluid during shipping and storage. Second, it helps the additive enter the residuals to convert the residual into a fuel oil.
The preferred relative percentages of each component are provided below. The percentages provided are relative to the entire composition, rather than the individual stages. All percentages are by weight. The aromatics are listed twice because they are preferably added twice.
The foregoing process is believed to be a Diels-Alder reaction. It is believed to yield a cross-linked cyclic anhydride copolymer having an intrinsic viscosity (limiting viscosity, of between about 0.10 and 3.0 deciliters per gram. This corresponds to an average molecular weight between about 3,000 and 3,000,000. The aromatic components are believed to serve as catalysts in the above reaction, allowing the maleic anhydride to react with the vinyl acetate.
Once the additive is prepared, it is preferably mixed with reformed naphtha, diesel, or another cutter stock. The amount of both the additive and the cutter stock will depend upon the amount of the residuals to be treated. However, typical amount of the additive will be between 0.10 and 0.25 percent of the final product, by weight.
In operation, the residuals are heated to make them flowable. The temperature will vary depending on the characteristics of the particular residual but temperatures between about 160° to 220° F. are typical. The cutter stock and additive will be added to the residuals. This may be done on a batch basis; however, in a plant setting, adding the additive and cutter stock to the residuals in line will typically be most convenient.
The preferred mixing method utilizes a static mixer. Suitable mixers are available from Sulzer Corp. of Winterthur, Switzerland. The cutter stock and additive are injected into the residual flow line. The preferred flow rate ranges from 2500 gallons per minute to 7000 gallons per minute, with the rate of addition of cutter stock and additive varying accordingly. The components will be thoroughly combined upon passing through the static mixer.
After mixing, the end result is a fuel oil, typically ranging from grade 6 to 4. It will remain liquid, facilitating transport and pumping without the need for heat. Other characteristics of the finished product are discussed below.
The chart in
The residuals tested were a light residual and a heavier vacuum flashed cracked residual (VFCR). Kinematic viscosities were tested using ASTM D 445 c. cSt. All tests were performed at 100° C., except for the test of the pure residuals, which were so viscous that they had to be heated to 150° C. for the test to be performed.
The BTU content was determined for a finished fuel oil manufactured using the additive. The tested fuel oil was 77.5 percent VFCR, 22.25 percent no. 2 diesel, and 0.25 percent additive. The sample was measured to have a heat of combustion of about 18500 BTU/lb. However, use of reformed naphtha as a cutter, in combination with the additive, is expected to increase the BTU of the finished fuel oil by about 20 to 30 percent compared with fuel oil made solely from residuals and a diesel cutter.
The tested samples were 0.25 percent additive. However, the inventor believes that 0.10 to 0.15 percent additive by weight, in combination with the cutter stock, will be sufficient to reduce the viscosity of the residual by 30 to 40 percent.
The tests were performed using no. 2 diesel. However, the additive will reduce the quantity of cutter stock needed to convert the residuals to fuel oil. This will be advantageous regardless of whether naphtha, diesel, or any other cutter stock is used. Less cutter stock used equals lower production cost in the finished fuel oil, regardless of the cutter stock used. Reductions on the order of 25 to 30 percent in the amount of cutter stock needed to convert residuals to fuel oil can be expected using the additive.
The embodiments shown in the drawings and described above are exemplary of numerous embodiments that may be made within the scope of the appended claims. It is contemplated that numerous other formulations may be used, and the material of each component may be selected from numerous materials other than those specifically disclosed. In short, it is the applicant's intention that the scope of the patent issuing herefrom will be limited only by the scope of the appended claims.
This application claims benefit of provisional U.S. Patent Application Ser. No. 62/380,922, filed Aug. 29, 2016, which is hereby incorporated by reference in its entirety.
| Number | Name | Date | Kind |
|---|---|---|---|
| 9299068 | Henry | Mar 2016 | B2 |
| 9369179 | Hariz | Jun 2016 | B2 |
| 9421004 | Roue | Aug 2016 | B2 |
| 9658183 | Wilsey | May 2017 | B2 |
| 9887315 | Kwak | Feb 2018 | B2 |
| 20050172546 | Spivey | Aug 2005 | A1 |
| 20050203232 | Rolland | Sep 2005 | A1 |
| 20070284108 | Roes | Dec 2007 | A1 |
| 20100251604 | Mahling | Oct 2010 | A1 |
| 20160376263 | Patron | Dec 2016 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 62380922 | Aug 2016 | US |
