An asphaltene flocculant composition, its preparation and use

Abstract

The application discloses an asphaltene flocculant composition and a preparation method and application thereof. The asphaltene flocculant composition comprises the following components in the asphaltene flocculant composition by weight: 75wt%-85wt% of at least one selected from waste plastics and waste rubber powder; 5wt%-15wt% of deoiled asphalt; 2wt%-10wt% of waste biological oil; 1wt%-10wt% of Span-80; 1wt%-10wt% of Tween-80; and 1wt%-2wt% of sulfonic acid. The asphaltene flocculant composition is suitable for production of deasphalted oil by solvent deasphalting of petroleum residue oil, and can effectively improve extraction efficiency and extraction quality.

Description

Technical Field

[0001] This invention belongs to the field of solvent deasphalting, specifically relating to an asphalt flocculant composition, its preparation method, and its application. Background Technology

[0002] Petroleum asphaltene is the most complex solid component of crude oil, possessing diverse molecular structures and high molecular weights, making it prone to instability and deposition due to various factors. Its main hazards include: petroleum asphaltene containing acidic functional groups tends to aggregate during refining, corroding pipelines and equipment; asphaltene containing heteroatoms (such as nitrogen and sulfur) and heavy metals (such as vanadium and nickel) reduces catalyst activity, leading to deactivation; polycyclic aromatic hydrocarbons (PAHs) in asphaltene easily coke at high temperatures, clogging reactors and pipelines; and asphalt fumes contain carcinogenic PAHs, such as benzo[a]pyrene, harming the environment and health.

[0003] Currently, solvent deasphalting (SDA) technology is the mainstream method for separating petroleum asphaltenes. This technology uses light hydrocarbons such as propane, butane, and pentane as solvents. Based on the differences in the solvent's solubility for different components of vacuum residue, it separates vacuum residue into deasphalted oil (DAO) rich in saturated hydrocarbons and deoiled asphalt (DOA) rich in gums and asphaltenes. Due to its simple process flow and strong adaptability to raw materials, SDA technology is widely used in the pretreatment stage of vacuum residue.

[0004] However, with the increase in global crude oil processing capacity and the growing volume of low-quality resources such as vacuum residue, the existing solvent deasphalting units can no longer meet production demands. Refineries face a mismatch between equipment processing capacity and resource processing needs. Traditional solutions, such as capacity expansion or new construction, involve high investment costs and long construction periods, making it difficult to solve the problem in the short term.

[0005] Therefore, developing a new method that improves extraction quality and unit throughput without adding external equipment has become a key need in the oil refining industry. This new method needs to be technologically innovative and economically feasible to meet the needs of refineries to improve efficiency, reduce costs, and ensure stable equipment operation. Introducing new asphaltenes-based flocculants to enhance separation technology holds promise for breaking through existing bottlenecks and providing technical support for heavy oil processing and utilization.

[0006] In summary, existing technologies offer limited solutions for improving extraction quality during solvent deasphalting and require further investigation. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides an asphaltene flocculant composition, its preparation method, and its application. The asphaltene flocculant composition is suitable for solvent deasphalting of petroleum residue to produce deasphalted oil, improving extraction efficiency and extraction quality.

[0008] A first aspect of the present invention provides an asphaltene flocculant composition. The flocculant composition, based on the weight of the asphaltene flocculant composition, comprises:

[0009] 75wt% to 85wt% is selected from at least one of waste plastics and waste rubber powder;

[0010] 5wt% to 15wt% deoiled bitumen;

[0011] 2wt% to 10wt% of waste bio-oil;

[0012] 1wt% to 10wt% of Span-80;

[0013] 1 wt% to 10 wt% Tween-80;

[0014] 1wt% to 2wt% sulfonic acid.

[0015] According to the present invention, the waste plastic is selected from at least one of polystyrene waste plastic, polycarbonate waste plastic, polyurethane waste plastic, and polymethyl methacrylate waste plastic. The density of the waste plastic at 23±0.5℃ is 1.00~1.30 g / cm³. -3 .

[0016] According to the present invention, the waste rubber powder is waste tire rubber powder. Preferably, the mesh size of the waste tire rubber powder is 60-80 mesh. More preferably, the waste tire rubber powder is truck waste tire rubber powder.

[0017] According to the present invention, the aromatic content of the deoiled bitumen is 25 wt% to 35 wt%. As a non-limiting example, the aromatic content of the deoiled bitumen can be any value among 25 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, 32 wt%, etc.

[0018] According to the present invention, the water content of the waste bio-oil is less than 0.7 wt% by mass percentage.

[0019] A second aspect of the present invention provides a method for preparing the asphalt flocculant composition. The method comprises: uniformly mixing at least one selected from waste plastics, waste rubber powder, deoiled asphalt, waste bio-oil, Span-80, Tween-80, and sulfonic acid to obtain the asphalt flocculant composition.

[0020] According to the present invention, in the preparation method of the asphalt-based flocculant composition, waste plastics and / or waste rubber powder are pulverized and melted before being mixed with other raw materials. Preferably, the waste plastics can be washed before pulverization. The washing solvent is water.

[0021] According to the present invention, in the method for preparing the asphalt flocculant composition, the source of the deoiled asphalt is the heavy component obtained after vacuum residue is passed through a solvent deasphalting device. The vacuum residue includes at least one of light, medium, and heavy vacuum residue. Preferably, the solvent is butane. The operating conditions for solvent deasphalting are: operating pressure of 4.0 MPa to 9.0 MPa, operating temperature of 110°C to 150°C at the top of the tower, 105°C to 140°C in the middle of the tower, and 100°C to 140°C at the bottom of the tower, with the temperature decreasing sequentially from top to bottom; the yield of the deoiled asphalt is controlled to be 40 wt% to 60 wt%. The aromatic content of the deoiled asphalt is 25 wt% to 35 wt%. As a non-limiting example, the aromatic content of the deoiled asphalt can be any value among 25 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, and 32 wt%.

[0022] According to the present invention, in the preparation method of the asphaltene flocculant composition, the mixing is carried out under stirring. Preferably, the stirring speed is 100-500 r / min. The mixing pressure is 0.5-2 MPa. The mixing temperature is 150-300°C. The mixing time is 30-90 min. The mixing equipment is a reaction vessel.

[0023] A third aspect of the present invention provides the application of the asphalt flocculant composition in the production of deasphalted oil.

[0024] According to the present invention, the method of application includes: using petroleum residue oil as feedstock; using an alkane solvent as an extractant; using the extractant to extract the feedstock oil containing an asphaltene flocculant composition, and the resulting extract is deasphalted oil.

[0025] According to the present invention, the petroleum residue is the residue obtained from crude oil distillation under normal or reduced pressure. The properties of the petroleum residue are as follows: asphaltenes content of 5 wt% to 12 wt%; 10% distillation point ≥ 500℃, preferably 500 to 530℃; heavy metal content of 100 to 400 mg / kg, wherein the heavy metals are calculated as the sum of Ni and V; and carbon residue value of 10 wt% to 25 wt%.

[0026] According to the present invention, the alkane solvent is an alkane having 3 to 5 carbon atoms. Preferably, the alkane solvent includes at least one selected from propane, butane, and pentane, with butane being the most preferred.

[0027] According to the present invention, the amount of the asphaltene flocculant composition added is 1.0 wt% to 8.0 wt% of the mass of petroleum residue oil, preferably 1.0 wt% to 5.0 wt%. As a non-limiting example, the proportion of the asphaltene flocculant composition added to the mass of petroleum residue oil can be 3 wt%, 4 wt%, 5 wt%, or 6 wt%.

[0028] According to the present invention, the mass ratio (solvent-to-oil ratio) of alkane solvent to petroleum residue oil is 3:1 to 8:1.

[0029] According to the present invention, the extraction process is preferably carried out in an extraction tower. The operating pressure of the extraction is 3.8–10.0 MPa. The extraction temperature is 50–190°C. Preferably, the extraction tower is operated under constant pressure and cooling conditions. The temperature ranges at various points in the extraction tower are as follows: top 70–190°C, middle 60–180°C, bottom 50–170°C, preferably top 100–140°C, middle 90–130°C, and bottom 80–120°C. Preferably, the temperature at various points in the extraction tower is: top at least 10–30°C higher than middle; middle at least 10–30°C higher than bottom.

[0030] According to the present invention, preferably, the feedstock oil can be preheated before entering the extraction tower. The feedstock oil is preheated to 100-180°C.

[0031] According to the present invention, the extraction process is as follows: the extractant enters the tower from the bottom along with the solvent and flows upward, the petroleum residue enters the tower from the middle and flows downward, the petroleum residue and the extractant are in countercurrent convective contact in the tower, the residue is discharged from the bottom of the tower, and the extract flows out from the top of the tower; the extract is the target product, deasphalted oil.

[0032] Compared with the prior art, the beneficial effects of the present invention mainly include:

[0033] (1) The asphaltene flocculant composition of the present invention, based on the weight of the asphaltene flocculant composition, comprises: 75wt% to 85wt% of at least one selected from waste plastics and waste rubber powder; 5wt% to 15wt% of deoiled asphalt; 2wt% to 10wt% of waste bio-oil; 1wt% to 10wt% of Span-80; 1wt% to 10wt% of Tween-80; and 1wt% to 2wt% of sulfonic acid. The asphaltene flocculant composition contains waste plastics and / or waste rubber powder, as well as deoiled asphalt. The waste plastics and / or waste rubber powder act as methylene bridging agents, and the deoiled asphalt acts as a similar compatibility agent. Preferably, the content of aromatic components in the deoiled asphalt is further limited, which is beneficial to the aggregation of dispersed asphaltene in the raw materials. The components with specific compositions and contents in the composition work together to achieve optimal effects. The asphaltene flocculant composition is suitable for solvent deasphalting of petroleum residue oil to produce deasphalted oil, improving extraction quality and extraction efficiency.

[0034] (2) In the preparation method of the asphalt flocculant composition of the present invention, the method includes: mixing waste plastics and / or waste rubber powder, deoiled asphalt, waste bio-oil, Span-80, Tween-80, and sulfonic acid evenly to obtain the asphalt flocculant composition. The asphalt flocculant composition prepared by the method is suitable for solvent deasphalting of petroleum residue oil to produce deasphalted oil.

[0035] (3) In the application of the asphaltene flocculant composition of the present invention, by adding a specific amount of asphaltene flocculant composition to petroleum residue, the presence of methylene chains in the asphaltene flocculant composition and the interaction force between them and the raw material vacuum residue are utilized to accelerate the aggregation of asphaltene. This achieves the goal of improving the solvent deasphalting extraction efficiency and product quality without changing the internal components of the extraction tower, especially by reducing the carbon residue value of the deasphalted oil and reducing the heavy metal content. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to the embodiments, but the present invention is not limited to these embodiments.

[0037] In this invention, the feedstock used in each example is vacuum residue. Its properties are as follows: 10% distillation point is 530°C, asphaltene content is 5.4 wt%, carbon residue is 21.4 wt%, and heavy metal content is 355.3 mg / kg, wherein the heavy metals are calculated as the sum of Ni and V.

[0038] In this invention, the extraction efficiency = (deasphalted oil collection rate / residual oil feed rate) × 100%.

[0039] In this invention, the carbon residue value is tested using the method specified in GB / T17144-1997, "Determination of Carbon Residue in Petroleum Products".

[0040] In this invention, the heavy metal content is tested using the inductively coupled plasma atomic emission spectrometry method according to GB / T 37160-2019.

[0041] In this invention, unless otherwise specified, % refers to mass percentage.

[0042] In this invention, the water content of each waste bio-oil is 0.4 wt%.

[0043] Example 1

[0044] The preparation method of the asphalt flocculant composition is as follows: Take a sample with a density of 1.05 g / cm³. -3 Eighty-five parts of crushed and melted waste polystyrene plastic were added to a reactor, followed by 5 parts of deoiled bitumen with an aromatic content of 25 wt%, 7 parts of waste bio-oil, 1 part of Span-80, 1 part of Tween-80, and 1 part of sulfonic acid. The heating temperature was 250℃, the heating pressure was 2 MPa, and the stirring speed was 200 r / min. After reacting for 30 minutes, the asphalt flocculant composition was obtained.

[0045] The feedstock oil was preheated to 100°C and fed into the solvent deasphalting unit (extraction tower). The residue oil feed rate was 2 kg / h. Butane was used as the solvent, with a solvent-to-oil ratio of 3:1. The asphaltene flocculant composition was crushed into 80-mesh particles and slowly and evenly added to the vacuum residue oil. The amount of asphaltene flocculant composition added was 3 wt% of the mass of the petroleum residue oil. The extraction conditions were: operating pressure 4.0 MPa, top temperature 120°C, middle temperature 110°C, and bottom temperature 100°C. The deasphalted oil recovery rate was 1.20 kg / h. The carbon residue and heavy metal content of the deasphalted oil were measured. The carbon residue of the deasphalted oil fraction was 4.2 wt%, and the heavy metal content was 26.5 mg / kg.

[0046] Example 2

[0047] The preparation method of the asphalt flocculant composition is as follows: take a sample with a density of 1.20 g / cm³. -3 Eighty parts of crushed and melted waste polycarbonate plastic were added to a reactor, followed by seven parts of deoiled bitumen with an aromatic content of 25%, ten parts of waste bio-oil, one part of Span-80, one part of Tween-80, and one part of sulfonic acid. The reactor was heated to 200℃, the pressure was 2MPa, and the stirring speed was 200r / min. After reacting for 30 minutes, the asphalt flocculant composition was obtained.

[0048] The feedstock oil was preheated to 100°C and fed into the solvent deasphalting unit (extraction tower). The residue oil feed rate was 2 kg / h. Butane was used as the solvent, with a solvent-to-oil ratio of 4:1. The asphaltene flocculant composition was crushed into 80-mesh particles and slowly and evenly added to the vacuum residue oil. The amount of asphaltene flocculant composition added was 1% of the feedstock oil mass. The extraction conditions were: operating pressure 4.2 MPa, tower top temperature 120°C, tower middle temperature 110°C, and tower bottom temperature 100°C. The deasphalted oil recovery rate was 1.08 kg / h. The carbon residue and heavy metal content of the deasphalted oil were measured. The carbon residue of the deasphalted oil fraction was 4.6 wt%, and the heavy metal content of the deasphalted oil was 30.6 mg / kg.

[0049] Example 3

[0050] The preparation method of the asphalt flocculant composition is as follows: take a density of 1.05 g / cm³. -3 Eighty-three parts of crushed and melted waste polyurethane plastic were added to a reactor, followed by 12 parts of deoiled bitumen with an aromatic content of 35%, 2 parts of waste bio-oil, 1 part of Span-80, 1 part of Tween-80, and 1 part of sulfonic acid. The reactor was heated to 150°C, the pressure was 2 MPa, and the stirring speed was 200 r / min. After reacting for 30 minutes, the asphalt flocculant composition was obtained.

[0051] The feedstock oil was preheated to 100°C and fed into the solvent deasphalting unit (extraction tower). The residue oil feed rate was 2 kg / h. Butane was used as the solvent, with a solvent-to-oil ratio of 5:1. The asphaltene flocculant composition was crushed into 80-mesh particles and slowly and evenly added to the vacuum residue oil. The amount of asphaltene flocculant composition added was 1% of the feedstock oil mass. The extraction conditions were: operating pressure 4.0 MPa, tower top temperature 130°C, tower middle temperature 120°C, and tower bottom temperature 110°C. The deasphalted oil recovery rate was 0.96 kg / h. The carbon residue and heavy metal content of the deasphalted oil were measured. The carbon residue of the deasphalted oil fraction was 4.8 wt%, and the heavy metal content of the deasphalted oil was 32.2 mg / kg.

[0052] Example 4

[0053] The preparation method of the asphalt flocculant composition is as follows: 75 parts of 60-80 mesh truck waste tire rubber powder are melted and added to a reaction vessel. Then, 15 parts of deoiled asphalt with an aromatic content of 35%, 5 parts of waste bio-oil, 2 parts of Span-80, 2 parts of Tween-80, and 1 part of sulfonic acid are added sequentially. The heating temperature is 300℃, the pressure is 0.5MPa, the stirring speed is 200r / min, and the reaction is carried out for 60 minutes. The resulting asphalt flocculant composition is then obtained.

[0054] The feedstock oil was preheated to 100°C and fed into the solvent deasphalting unit (extraction tower). The residue oil feed rate was 2 kg / h. Butane was used as the solvent, with a solvent-to-oil ratio of 3:1. The asphaltene flocculant composition was crushed into 80-mesh particles and slowly and evenly added to the vacuum residue oil. The amount of asphaltene flocculant composition added was 3% of the feedstock oil mass. The extraction conditions were: operating pressure 4.0 MPa, tower top temperature 120°C, tower middle temperature 110°C, and tower bottom temperature 100°C. The deasphalted oil recovery rate was 1.22 kg / h. The carbon residue and heavy metal content of the deasphalted oil were measured. The carbon residue of the deasphalted oil fraction was 4.1 wt%, and the heavy metal content of the deasphalted oil was 25.0 mg / kg.

[0055] Example 5

[0056] The preparation method of the asphalt flocculant composition is as follows: 85 parts of 60-80 mesh waste truck tire rubber powder are melted and added to a reaction vessel. Then, 5 parts of deoiled asphalt with an aromatic content of 25%, 7 parts of waste bio-oil, 1 part of Span-80, 1 part of Tween-80, and 1 part of sulfonic acid are added sequentially. The heating temperature is 250℃, the pressure is 2MPa, the stirring speed is 200r / min, and the reaction is carried out for 30 minutes. The asphalt flocculant composition is then obtained.

[0057] The feedstock oil was preheated to 100°C and fed into the solvent deasphalting unit (extraction tower). The residue oil feed rate was 2 kg / h. Butane was used as the solvent, with a solvent-to-oil ratio of 3:1. The asphaltene flocculant composition was crushed into 80-mesh particles and slowly and evenly added to the vacuum residue oil. The amount of asphaltene flocculant composition added was 1% of the feedstock oil mass. The extraction conditions were: operating pressure 4.0 MPa, tower top temperature 120°C, tower middle temperature 110°C, and tower bottom temperature 100°C. The deasphalted oil recovery rate was 1.0 kg / h. The carbon residue and heavy metal content of the deasphalted oil were measured. The carbon residue of the deasphalted oil fraction was 4.5 wt%, and the heavy metal content of the deasphalted oil was 29.3 mg / kg.

[0058] Comparative Example 1

[0059] The difference from Example 1 is that no asphalt flocculant composition is added.

[0060] The feedstock oil was preheated to 100°C and fed into the solvent deasphalting unit (extraction tower). The feed rate of the residue oil was 2 kg / h. Butane was used as the solvent, with a solvent-to-oil ratio of 3:1. The extraction conditions were: operating pressure 4.0 MPa, top temperature 120°C, middle temperature 110°C, and bottom temperature 100°C. The deasphalted oil recovery rate was 0.74 kg / h. The carbon residue and heavy metal content of the deasphalted oil were measured. The carbon residue of the deasphalted oil fraction was 6.5 wt%, and the heavy metal content was 48.3 mg / kg.

[0061] Comparative Example 2

[0062] The difference from Example 5 is that no deoiled asphalt is added to the flocculant composition.

[0063] The preparation method of the asphalt flocculant composition is as follows: 85 parts of 60-80 mesh truck waste tire rubber powder are crushed, melted, and added to a reaction vessel. Then, 7 parts of waste bio-oil, 1 part of Span-80, 1 part of Tween-80, and 1 part of sulfonic acid are added sequentially. The heating temperature is 250℃, the pressure is 2MPa, and the stirring speed is 200r / min. After reacting for 30 minutes, the asphalt flocculant composition is obtained.

[0064] The feedstock oil was preheated to 100°C and fed into the solvent deasphalting unit (extraction tower). The residue oil feed rate was 2 kg / h. Butane was used as the solvent, with a solvent-to-oil ratio of 3:1. The asphaltene flocculant composition was crushed into 80-mesh particles and slowly and evenly added to the vacuum residue oil. The amount of asphaltene flocculant composition added was 1% of the feedstock oil mass. The extraction conditions were: operating pressure 4.0 MPa, tower top temperature 120°C, tower middle temperature 110°C, and tower bottom temperature 100°C. The deasphalted oil recovery rate was 0.79 kg / h. The carbon residue and heavy metal content of the deasphalted oil were measured. The carbon residue of the deasphalted oil fraction was 6.0 wt%, and the heavy metal content of the deasphalted oil was 43.5 mg / kg.

[0065] Comparative Example 3

[0066] The difference from Example 5 is that no waste truck tire rubber powder is added to the flocculant composition.

[0067] The asphalt flocculant composition was prepared by taking 5 parts of deoiled asphalt with an aromatic content of 25%, 7 parts of waste bio-oil, 1 part of Span-80, 1 part of Tween-80, and 1 part of sulfonic acid, and adding them sequentially to a reaction vessel. The heating temperature was 250℃, the pressure was 2MPa, the stirring speed was 200r / min, and the reaction was carried out for 30 minutes to obtain the asphalt flocculant composition.

[0068] The feedstock oil was preheated to 100°C and fed into the solvent deasphalting unit (extraction tower). The residue oil feed rate was 2 kg / h. Butane was used as the solvent, with a solvent-to-oil ratio of 3:1. The asphaltene flocculant composition was crushed into 80-mesh particles and slowly and evenly added to the vacuum residue oil. The amount of asphaltene flocculant composition added was 1% of the feedstock oil mass. The extraction conditions were: operating pressure 4.0 MPa, tower top temperature 120°C, tower middle temperature 110°C, and tower bottom temperature 100°C. The deasphalted oil recovery rate was 0.75 kg / h. The carbon residue and heavy metal content of the deasphalted oil were measured. The carbon residue of the deasphalted oil fraction was 6.2 wt%, and the heavy metal content was 44.0 mg / kg.

[0069] The specific embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An asphaltene flocculant composition, comprising, based on the weight of the asphaltene flocculant composition: 75wt% to 85wt% is selected from at least one of waste plastics and waste rubber powder; 5wt% to 15wt% deoiled bitumen; 2wt% to 10wt% of waste bio-oil; 1wt% to 10wt% of Span-80; 1 wt% to 10 wt% Tween-80; 1wt% to 2wt% sulfonic acid.

2. The asphalt flocculant composition according to claim 1, characterized in that, The waste plastic is selected from at least one of polystyrene waste plastic, polycarbonate waste plastic, polyurethane waste plastic, and polymethyl methacrylate waste plastic; further, the density of the waste plastic at 23±0.5℃ is 1.00~1.30g / cm³. -3 .

3. The asphalt flocculant composition according to claim 1, characterized in that, The waste rubber powder is waste tire rubber powder; preferably, the mesh size of the waste tire rubber powder is 60-80 mesh.

4. The asphalt flocculant composition according to claim 1, characterized in that, The aromatic content of the deoiled bitumen is 25wt% to 35wt%.

5. A method for preparing the composition according to any one of claims 1 to 4, comprising: A mixture of at least one of waste plastics and waste rubber powder, deoiled asphalt, waste bio-oil, Span-80, Tween-80, and sulfonic acid is prepared to obtain an asphalt flocculant composition.

6. The method according to claim 5, characterized in that, The deoiled bitumen is derived from heavy components obtained by passing vacuum residue oil through a solvent deasphalting unit.

7. The use of the asphalt flocculant composition according to any one of claims 1 to 4 or the asphalt flocculant composition prepared by any one of claims 5 to 6 in the production of deasphalted oil.

8. The application according to claim 7, characterized in that, The method of application includes: using petroleum residue oil as feedstock; using alkane solvent as extractant; using the extractant to extract the feedstock oil containing asphalt flocculant composition, and the resulting extract is deasphalted oil.

9. The application according to claim 8, characterized in that, The petroleum residue is the residue obtained from crude oil under normal or reduced pressure distillation; the properties of the petroleum residue are as follows: asphaltene content is 5wt% to 12wt%; 10% distillation point is ≥500℃, preferably 500 to 530℃; heavy metal content is 100 to 400 mg / kg, wherein the heavy metals are calculated as the sum of Ni and V; and carbon residue value is 10wt% to 25wt%.

10. The application according to claim 8, characterized in that, The amount of the asphalt flocculant composition added is 1.0 wt% to 8.0 wt% of the mass of petroleum residue oil, preferably 1.0 wt% to 5.0 wt%.