Stabilizing asphaltene in crude oil using waste plastic antifoulants

Abstract

A method for stabilizing asphaltenes in petroleum feedstocks such as crude oil includes adding to the feedstock an effective amount of an additive containing at least one waste plastic. Suitable waste plastics include, but are not necessarily limited to, polyethylene, polyethylene terephthalate, polystyrene, polycarbonate, polyamide, and polyurethane, and combinations thereof. By stabilizing is meant keeping the asphaltenes in solution in the petroleum feedstocks.

Claims

1. A method for stabilizing asphaltenes in a petroleum feedstock comprising: evaluating the stability of asphaltenes in the petroleum feedstock; obtaining at least one waste plastic from plastic bottles or plastic packaging; reducing the size of the at least one waste plastic into chips; preparing at least one additive comprising the at least one waste plastic, wherein the step of preparing the at least one additive further comprises the step of dissolving the chips in a solvent; and adding to the petroleum feedstock an effective amount of up to about 1 wt % of the at least one additive to improve the stability of asphaltenes in the petroleum feedstock.

2. The method of claim 1 where the petroleum feedstock is selected from the group consisting of crude oils, heavy oils, coker feedstocks, visbreaker feedstocks, vacuum tower bottoms, fuel oils, diesel oils, bunker fuel oils, and mixtures thereof.

3. The method of claim 1 where the at least one waste plastic is selected from the group of waste plastics consisting of polyethylene, polyethylene terephthalate, polystyrene, polycarbonate, polyamide, and polyurethane, and combinations thereof.

4. The method of claim 1 where the at least one additive comprises at least one waste plastic selected from the group of waste plastics consisting of polyethylene, polyethylene terephthalate, and combinations thereof.

5. The method of claim 1 where the solvent is selected from the group consisting of refinery gasoil, a hydrocarbon refinery stream, gasoline, fluid catalytic coking heavy cycle oil, light cycle oil, delayed coker heavy gasoil, xylene, benzene, and combinations thereof.

6. The method of claim 1 where the effective amount of waste plastic in the petroleum feedstock ranges from about 0.01 wt. % to about 1 wt. %.

7. The method of claim 1 where the effective amount of waste plastic in the petroleum feedstock ranges from about 0.01 wt. % to about 0.5 wt. % and where the petroleum feedstock is crude oil.

8. The method of claim 1 where the effective amount of waste plastic in the petroleum feedstock ranges from about 0.01 wt. % to 0.33 wt. %.

9. A method for stabilizing asphaltenes in a petroleum feedstock comprising: evaluating the stability of asphaltenes in the petroleum feedstock; obtaining at least one waste plastic from plastic bottles or plastic packaging; reducing the size of the at least one waste plastic into chips; preparing at least one additive comprising the at least one waste plastic, wherein the step of preparing the at least one additive further comprises the step of dissolving the chips in a solvent; and adding to the petroleum feedstock an effective amount of up to about 0.5 wt % at least one additive to improve the stability of asphaltenes in the petroleum feedstock; where the petroleum feedstock is selected from the group consisting of crude oils, heavy oils, coker feedstocks, visbreaker feedstocks, vacuum tower bottoms, fuel oils, diesel oils, bunker fuel oils, and mixtures thereof; and where the at least one waste plastic is selected from the group of waste plastics consisting of polyethylene, polyethylene terephthalate, polystyrene, polycarbonate, polyamide, and polyurethane, and combinations thereof.

10. The method of claim 9 where the solvent is selected from the group consisting of refinery gasoil, a hydrocarbon refinery stream, gasoline, fluid catalytic coking heavy cycle oil, light cycle oil, delayed coker heavy gasoil, xylene, benzene, and combinations thereof.

11. The method of claim 9 where the effective amount of waste plastic in the petroleum feedstock ranges from about 0.01 wt. % to about 0.5 wt. %.

12. The method of claim 9 where the effective amount of waste plastic in the petroleum feedstock ranges from about 0.02 wt. % to 0.33 wt. %.

13. A stabilized petroleum feedstock comprising: a petroleum feedstock having asphaltenes and a corresponding baseline asphaltene stability index; and an effective amount of at least one additive of up to about 1 wt. % based on the petroleum feedstock to improve the stability of asphaltenes in the petroleum feedstock, where the at least one additive comprises at least one waste plastic selected from polyethylene terephthalate, polystyrene, polycarbonate, polyamide, and polyurethane, wherein the effective amount of the least one additive increases the baseline asphaltene stability index of the petroleum feedstock, and wherein the additive comprises the waste plastics dissolved in a solvent selected from the group consisting of refinery gasoil, fluid catalytic coking heavy cycle oil, light cycle oil, delayed coker heavy gasoil, xylene, benzene, and combinations thereof.

14. The stabilized petroleum feedstock of claim 13 where the petroleum feedstock is selected from the group consisting of crude oils, heavy oils, coker feedstocks, visbreaker feedstocks, vacuum tower bottoms, fuel oils, diesel oils, bunker fuel oils, and mixtures thereof.

15. The stabilized petroleum feedstock of claim 13 where the at least one waste plastic is polyethylene terephthalate.

16. The stabilized petroleum feedstock of claim 13 where the effective amount of waste plastic in the petroleum feedstock ranges from about 0.01 wt. % to about 1 wt. %.

17. The stabilized petroleum feedstock of claim 13 where the effective amount of waste plastic in the petroleum feedstock ranges from about 0.01 wt. % to about 0.5 wt. % and where the petroleum feedstock is crude oil.

18. The stabilized petroleum feedstock of claim 13 where the effective amount of waste plastic in the petroleum feedstock ranges from about 0.01 wt. % to 0.33 wt. %.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a graph of stability measured by Asphaltene Stability Index (ASI) by light scattering in the near infrared for a Middle East crude oil having low to moderate stability, where ASI=70.9 using no dispersant or flocculant;

(2) FIG. 2 is a graph of stability measured by ASI by light scattering for the Middle East crude of FIG. 1 containing 1 wt. % polystyrene dispersant/flocculant from waste plastics where ASI=67.1;

(3) FIG. 3 is a graph of stability measured by ASI by light scattering for the Middle East crude of FIG. 1 containing 0.5 wt. % polyethylene dispersant/flocculant from waste plastics where ASI=71.2 indicating a marginal increase in stability over the FIG. 1 result;

(4) FIG. 4 is a graph of stability measured by ASI by light scattering for the Middle East crude of FIG. 1 containing 0.16 wt. % polyethylene dispersant/flocculant from waste plastics where ASI=72.6 indicating a slight increase in stability over the FIG. 1 result; and

(5) FIG. 5 is a graph of stability measured by ASI by light scattering for the Middle East crude of FIG. 1 containing 0.08 wt. % polyethylene dispersant/flocculant and 0.25 wt. % polyethylene terephthalate from waste plastics where ASI=85.3 indicating a marked increase in stability over the FIG. 1 result.

DETAILED DESCRIPTION

(6) It has been discovered that waste plastics dissolved in a solvent can stabilize the asphaltenes in petroleum feedstocks by adding effective amounts of a plastics to the petroleum feedstock to act as a dispersant or an antifoulant. This method can reduce fouling and consequent fuel increase costs, as well as reduce CO.sub.2 and other emissions from refinery-fired heaters. The waste plastics that were tested can be processed at low percentages in refineries as they are partly thermally cracked to distillates while they produce some residuum and eventually acceptable levels of coke and residual metals from catalysts used in their manufacture. The method can also reduce downtime and costs for cleaning equipment that would be otherwise fouled.

(7) The fouling-causing components may include asphaltenes. Other materials that may cause fouling include, but are not necessarily limited to, solids particles, resins, organic acids, polymers, oxides, sulfides, metals, waxes, and combinations thereof. The methods of stabilizing asphaltenes may or may not stabilize these other materials and/or keep them from fouling as well.

(8) It is typical to have petroleum feedstock blend in a tank that when added to a different petroleum feedstock blend in a different tank induces significant destabilization in the new blend or mixture. This destabilization may be controlled and avoided with proper selection of effective amounts of a biological source oil and/or a chemical additive.

(9) Inhibit is defined herein to mean that the waste plastic additive may suppress or reduce the ability of the asphaltenes in the petroleum feedstocks to precipitate, flocculate or agglomerate in a problematic way if there are actually any asphaltenes present within the petroleum feedstocks. Without being limited to any particular explanation or mechanism, it is believed that this is accomplished by the asphaltenes remaining in solution in the petroleum feedstocks. Prevent is defined herein to mean entirely preventing any asphaltene precipitation, flocculation or agglomeration, or in other words, complete stability. However, it is not necessary for fouling to be entirely prevented for the methods and compositions discussed herein to be considered effective, although complete prevention and complete stabilization are desirable goals. All that is necessary is for asphaltenes to be more stabilized as compared with an identical petroleum feedstock absent the effective amount of the waste plastic.

(10) The asphaltenes may be stabilized in the petroleum feedstocks by one or more different mechanisms, such as but not limited to a stabilization mechanism, a dispersant mechanism, including solvation/micellization by additives coating asphaltenes aggregates while providing a more oil/hydrocarbon soluble outer layer, generation of repulsive electrical charges on asphaltene aggregates reducing their agglomeration tendency, introduction of steric hindrance by polymeric stabilizing additives, a radical inhibition mechanism, or combinations thereof. Polystyrene has a structure that is not so different from asphaltenes (i.e., archipelago asphaltenes model of interacting polycyclic aromatic hydrocarbons (PAHs)), and might treated as a sort of asphaltenic material, which likely directly interacts with asphaltenes by polar/polar interactions of the aromatic rings. Polyethylene terephthalate has both esters (polar groups) and paraffinic short chains and aromatic cores, and thus might be expected to interact with asphaltenes (interaction of asphaltenes polar groups with the ones of Polyethylene terephthalate).

(11) The stabilization mechanism may be performed in a petroleum feedstock at a temperature ranging from about ambient and/or room temperature (defined herein as 22? C. (72? F.) independently to about 1000? C., or alternatively from about 200? C. independently to about 800? C. once the waste plastic additive has been added to the base fluid. The effective amount of the waste plastic additive added to the petroleum for the stabilization effect to occur, can range from about 0.01 to about 5 wt. %; alternatively, from about 0.08 wt. % independently to about 2 wt. %; and in another non-restrictive embodiment from about 0.1 wt. % to about 1 wt. %, based on the petroleum feedstock. Independently is defined herein to mean that any lower threshold may be used together with any upper threshold to give a suitable alternative range. In a non-limiting example, another suitable dosage range would be from about 0.08 wt. % to about 1 wt. %. An effective amount is defined herein as an amount added that inhibits or prevents the asphaltenes from agglomerating, precipitating or flocculating together.

(12) The petroleum feedstocks may include, but are not necessarily be limited to, crude oils, heavy oils, coker feedstocks, visbreaker feedstocks, vacuum tower bottoms, fuel oils, diesel oils, bunker fuel oils (including, but not limited to, #6 oils), and the like and mixtures thereof. Petroleum feedstocks suitable herein include variations of those listed, including, but not necessarily limited to, heavy crude oil, heavy oil, heavy fuel oil and the like.

(13) Temperature can be a factor in the method described herein only for resids (residual oil products that remain after petroleum has been distilled) or very viscous feeds; in general, the temperature of the petroleum feedstock is not expected to be a factor.

(14) Suitable waste plastics can include, but are not necessarily limited to, polyethylene (PE), polyethylene terephthalate (PETE), polystyrene (PS), polycarbonate (PC), polyamide (Nylon class), and polyurethane, and combinations thereof. By waste plastics it is to be understood that the plastics were used to make some other article that has outlived its usefulness and is considered waste, in a non-limiting example, plastic bottles or PETE packaging. In one non-limiting embodiment the only dispersant or antifoulant is one or more waste plastic.

(15) A first step is to reduce the size of the plastic, in a non-limiting example by grinding the bottles or other articles to a suitable size, such as into chips a few millimeters in size. Then the particles are dissolved in a suitable solvent. In one non-limiting embodiment, a solvent can include, but is not necessarily limited to, refinery gasoil, a hydrocarbon refinery stream, gasoline, fluid catalytic coking heavy cycle oil, light cycle oil, delayed coker heavy gasoil, xylene, benzene, and combinations thereof. In one non-limiting embodiment, the waste plastic dispersed in solvent is likely captured, suspended, or dispersed by London dispersion forces, also loosely known as van der Waals forces.

(16) Waste plastic can be converted at high percentages by thermal cracking that is typical of hydrocarbon processing above 400? C., and blended into hydrocarbon distillates which can be used as fuel, particularly when integrated with gasoline or diesel, or after different processing sent to a petrochemical steam cracker for the production of more monomers.

(17) In another non-limiting embodiment, the method for stabilizing asphaltenes in a petroleum feedstock involves a number of steps, including, but not necessarily limited to: 1. evaluating the petroleum feedstock or blend of feedstocks (petroleum derived refinery streams) for asphaltene stability; 2. when the petroleum feedstock exhibits asphaltene instability, introducing the additive containing waste plastics into the petroleum feedstock; and 3. evaluating the additive for asphaltene stability of the petroleum feedstock.

(18) Evaluating a petroleum feedstock for asphaltene stability may be performed using any of a number of known and proprietary evaluation and analytical methods, including, but not necessarily limited to, ASTM D7060 (Shell P-value method), ASTM-D7157 (S-value), ASTM D4312 (Toluene Equivalents Test), ASTM D2781 (the Spot Test), and the Baker Hughes Field ASI Test (ASIt). ASIt is a laboratory testing method based on the application of light scattering flocculation titration with an asphaltene paraffin precipitant, typically heptane or other suitable precipitant. The determination of stability by light scattering is very accurate and reliable, and ASIt is the preferred test method herein.

(19) It will be appreciated that, as previously noted, petroleum feedstocks, such as crude oils, may vary widely in composition from one to another, and the waste plastic additive, and its proportion that is optimal for one petroleum feedstock, may not be the type or amount of waste plastic additive optimal for a different petroleum feedstock.

(20) Advantages of the method described herein over conventional, synthetic fouling control additives include, but are not limited to, the re-use of a waste stream, and use of a low-cost raw material.

(21) The invention will now be described with respect to particular embodiments which are not intended to limit the invention in any way, but which are simply to further highlight or illustrate the invention. All percentages (%) are weight percentages unless otherwise noted.

EXAMPLES 1-5

(22) A Middle East crude oil was used in all Examples, alone and then with the indicated additives. An Asphaltene Stability Index (ASI) for each was measured using a proprietary evaluation technique.

(23) In Example 1, the ASI of the Middle East crude, which had low to moderate stability on its own, was measured with no additive. The results are presented in FIG. 1. ASI=70.9, which is shown by the peak of the curve. This result may be considered a baseline or a blank.

(24) In Example 2, 1 wt. % polystyrene dispersant/flocculant from waste plastics was added to the Middle East crude. FIG. 2 is a graph of stability measured by ASI by light scattering, where ASI=67.1. This transmission indicated scattering, which was likely aggregation of the polystyrene with asphaltenes before the precipitation in the ASIt. In this case, the polystyrene was destabilizing, and stability decreased (67.1 being less than the 70.9 baseline) and the amount of precipitate increased. Thus, while polystyrene was not suitable for this crude, polystyrene may have positive interactions with other crudes and/or at different dosages. For example, waste polystyrene may be suitable lighter crudes with less total asphaltenes and/or crudes having asphaltenes that are more soluble.

(25) In Example 3, 0.5 wt. % polyethylene dispersant/flocculant from waste plastics was introduced into the Middle East crude of Example 1. FIG. 3 is a graph of stability measured by ASI by light scattering where ASI=71.2 indicating a marginal increase in stability over the Example 1 ASI.

(26) In Example 4, 0.16 wt. % polyethylene dispersant/flocculant from waste plastics was added to the Middle East crude of Example 1. FIG. 4 is a graph of stability measured by ASI by light scattering for containing where ASI=72.6 indicating a slight increase in stability over the Example 1 ASI.

(27) In Example 5, a combination of 0.08 wt. % polyethylene and 0.25 wt. % polyethylene terephthalate, both from waste plastics, were added as a dispersant/flocculant to the Middle East crude of Example 1. FIG. 5 is a graph of stability measured by ASI by light scattering for containing where ASI=85.3 indicating a marked increase in stability; the best of the Examples over the Example 1 ASI.

(28) The Examples thus demonstrate how selected waste plastics dissolved in a solvent can function as antifoulants stabilizing asphaltenes in petroleum feedstocks such as crude oil. Laboratory dose rates are typically higher than the ones needed in field applications by a factor of 10 or more. Therefore, the diose rates in field are likely lower than the ones used in laboratory. While waste polystyrene had a negative impact, further research may be done at different dosages and/or with different crudes; it may have a positive effect on some different crudes depending on the asphaltene chemistry in those crudes.

(29) The waste plastics are easily recovered from selective use of plastic bottles, plastic packaging, and other forms. They can be easily introduced into refining processes at the indicated dosage levels. Selection of the plastic used may be performed in several ways, for example, by the use of Near Infrared Analyzers since the NIR spectra correlate with plastic blend composition The method herein also discloses an effective test method based on the application of near infrared turbidimetry and precipitation of asphaltenes by a paraffinic non-solvent.

(30) In the foregoing specification, the invention has been described with reference to specific embodiments thereof, and has been described as effective in providing methods and compositions for stabilizing asphaltenes in petroleum feedstocks such as crude oils. However, it will be evident that various modifications and changes can be made thereto without departing from the broader scope of the invention. Accordingly, the specification is to be regarded in an illustrative rather than a restrictive sense. For example, specific petroleum feedstocks, waste plastic additives, solvents, proportions, treatment conditions, and other components and procedures falling within the claimed parameters, but not specifically identified or tried in a particular method or composition, are expected to be within the scope of this invention.

(31) The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. For instance, there may be provided a method for stabilizing asphaltenes in a petroleum feedstock comprising, consisting essentially of, or consisting of, adding to the petroleum feedstock containing asphaltenes an effective amount to improve the stability of asphaltenes in the petroleum feedstock at least one additive comprising at least one waste plastic, and stabilizing the asphaltenes in the petroleum feedstock.

(32) Alternatively, there may be provided a stabilized petroleum feedstock that comprises, consists essentially of, or consists of a petroleum feedstock, asphaltenes, and an effective amount of at least one additive to improve the stability of asphaltenes in the petroleum feedstock, where the at least one additive comprises at least one waste plastic.

(33) In another non-restrictive version, the only dispersant or antifoulant in the additive is one or more waste plastic as defined herein.

(34) The words comprising and comprises as used throughout, are to be interpreted to mean including but not limited to and includes but not limited to, respectively.

(35) As used herein, the singular forms a, an, and the are intended to include the plural forms as well, unless the context clearly indicates otherwise.

(36) As used herein, the term about in reference to a given parameter is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the given parameter).

(37) As used herein, the term and/or includes any and all combinations of one or more of the associated listed items.