EP2748290A1

EP2748290A1 - Liquid fuel compositions

Info

Publication number: EP2748290A1
Application number: EP12753744.7A
Authority: EP
Inventors: Felix Johannes BALTHASAR; Ingo Torsen MAHLKE
Original assignee: Shell Internationale Research Maatschappij BV
Current assignee: Shell Internationale Research Maatschappij BV
Priority date: 2011-09-06
Filing date: 2012-09-06
Publication date: 2014-07-02
Also published as: WO2013034617A1

Abstract

Use of Heavy Cycle Oil (HCO) in a diesel fuel composition for reducing power loss, e.g. due to injector fouling, in an engine into which the fuel composition is introduced.

Description

LIQUID FUEL COMPOSITIONS

Field of the Invention

The present invention relates to a liquid fuel composition. In particular, the present invention relates to a liquid diesel fuel composition comprising Heavy Cycle Oil for providing reduced power loss, e.g. due to injector fouling, in a diesel engine.

Background of the Invention

A known problem that affects high performance diesel engines is deposit formation. Particularly stubborn deposits form at and around the injector valve seat and nozzle. This phenomenon, also referred to as injector fouling, often results in injector drift, power loss and an increase in smoke emissions.

Diesel fuel injectors have always been prone to injector fouling, however improvements in the design of fuel injection equipment to meet increasing regulatory and consumer demands may mean that the fuel injection equipment is more sensitive to fouling.

New injection systems are being designed to run at higher pressures with smaller fuel injector nozzle sizes and multiple injections, to allow for smoother running, better combustion and to enable sophisticated after treatment devices such as diesel particulate filters.

Tighter tolerances and nozzle hole sizes in the order of 100 microns mean that fouling can have a more significant impact on power, emissions and fuel economy.

US 2005/0241216 Al demonstrates, in the Exanples, that a Fischer-Tropsch derived fuel, and in particular a

Fischer-Tropsch gas oil, leads to markedly lower engine deposits compared to petroleum derived fuels, and may be used to ^xclean-up' fouled injectors to remove deposits built up through use of another fuel (Examples 1 and 2) .

Heavy Cycle Oil is a petroleum-derived

hydrocarbonaceous fraction obtained from a fluid

catalytic cracker (FCC) unit. It has now surprisingly been found by the present inventors that by introducing Heavy Cycle Oil into a diesel fuel composition, reduced power loss, e.g. due to reduced injector fouling, can be achieved .

Summary of the Invention

The present invention provides the use of Heavy Cycle Oil in a diesel fuel composition for reducing injector fouling or reducing power loss in a compression ignition (diesel) engine to which the diesel fuel composition is introduced.

The present invention further provides a method for reducing injector fouling or reducing power loss of an engine, the method comprising introducing into a

combustion chamber of the engine a diesel fuel

composition comprising Heavy Cycle Oil.

The present invention also provides a diesel fuel composition which comprises a diesel base fuel and in the range of from 0.05 wt% to 5 wt% of Heavy Cycle Oil, by weight of the diesel fuel composition, and a process for its preparation by the addition of Heavy Cycle Oil to a diesel base fuel in the appropriate amount.

Detailed Description of the Invention

As used herein the term "reducing power loss" or "reduced power loss" means the reduction of loss of power in an engine. This is directly proportional to a decrease in torque for the engine run at constant engine speed or at fixed throttle conditions. As used herein the term "reducing injector fouling" or "reduced injector fouling" means a reduction of deposits formed at and around the injector valve seat and/or nozzle.

The liquid diesel fuel composition of the present invention comprises a base fuel suitable for use in a compression ignition engine and a Heavy Cycle Oil.

The term "Heavy Cycle Oil" is well known to those skilled in the art. Heavy Cycle Oil is a petroleum- derived hydrocarbaceous fraction obtained from an FCC

(fluid catalytic cracking) unit.

The product from the FCC unit contains fractions of light olefins, gasoline, Light Cycle Oil (LCO) and a heavy hydrocarbon fraction, such as slurry oil or Heavy Cycle Oil (HCO) . The heavy hydrocarbon fraction remaining in the bottoms of the FCC unit is removed. The resulting energy density of this heavy hydrocarbon fraction can be affected by the operation of the FCC unit. Operation of the FCC unit at relatively high severity, for example, higher temperatures with a higher catalyst to hydrocarbon ratio, will yield products with higher energy densities and higher carbon to hydrogen ratios.

US -A-6,039,771 discloses the use of a hydrocarbon component, which is the distillate from the distillation of Heavy Cycle Oil to remove, inter alia, contaminants, as an additive blend component to combine with a diesel fuel component to form an energy fortified diesel fuel for off-highway compression ignition engines. The

distillate is used in quantities from about 10% to about 90% of said diesel fuel. US-A-6, 039, 771 reports attempts to use LCO-diesel fuel blends in on-highway compression ignition engines, which were unsuccessful even when using stabilizers; Column 3, lines 26 to 31, note that the findings using LCO-diesel blends cause the industry to expect that HCO-diesel blends would be even less stable.

The diesel fuel compositions used herein comprise from 0.05 wt% to 5 wt%, preferably 0.1 wt% to 1 wt~6 , more preferably 0.2 wt% to 0.7 wt%, of HCO, by weight of the diesel fuel composition.

In the diesel fuel compositions of the present invention, the base fuel used is a diesel fuel, and includes diesel fuels for use in automotive compression ignition engines, as well as in other types of engine such as for example off road, marine, railroad and stationary engines. The diesel fuel used as the base fuel in the diesel fuel composition of the present invention may conveniently also be referred to as iesel base fuel' .

The diesel base fuel may itself comprise a mixture of two or more different diesel fuel components, and/or be additivated as described below.

Such diesel fuels will contain one or more base fuels which may typically comprise liquid hydrocarbon middle distillate gas oil (s) , for instance petroleum derived gas oils. Such fuels will typically have boiling points within the usual diesel range of 150 to 400°C, depending on grade and use. They will typically have a density from 750 to 1000 kg/m³, preferably from 780 to

860 kg/m³, at 15°C (e.g. ASTM D4502 or IP 365) and a cetane number (ASTM D613) of from 35 to 120, more

preferably from 40 to 85. They will typically have an initial boiling point in the range 150 to 230°C and a final boiling point in the range 290 to 400°C. Their kinematic viscosity at 40°C (ASTM D445) might suitably be from 1.2 to 4.5 mm^/s. An example of a petroleum derived gas oil is a

Swedish Class 1 base fuel, which will have a density from

800 to 820 kg/m³ at 15°C (SS-EN ISO 3675, SS-EN ISO

12185), a T95 of 320°C or less (SS-EN ISO 3405) and a kinematic viscosity at 40°C (SS-EN ISO 3104) from 1.4 to

4.0 mm^/s, as defined by the Swedish national

specification ECl .

Optionally, non-mineral oil based fuels, such as biofuels or Fischer-Tropsch derived fuels, may also form or be present in the diesel fuel. Such Fischer-Tropsch fuels may for example be derived from natural gas, natural gas liquids, petroleum or shale oil, petroleum or shale oil processing residues, coal or biomass.

The amount of Fischer-Tropsch derived fuel used in the diesel fuel may be from 0% to 100%v of the overall diesel fuel, preferably from 5% to 100%v, more preferably from 5% to 75%v. It may be desirable for such a diesel fuel to contain 10%v or greater, more preferably 20 ΐν or greater, still more preferably 30%v or greater, of the Fischer-Tropsch derived fuel. It is particularly

preferred for such diesel fuels to contain 30 to 75%v, and particularly 30 to 70%v, of the Fischer-Tropsch derived fuel. The balance of the diesel fuel is made up of one or more other diesel fuel components.

Such a Fischer-Tropsch derived fuel component is any fraction of the middle distillate fuel range, which can be isolated from the (optionally hydrocracked)

Fischer-Tropsch synthesis product. Typical fractions will boil in the naphtha, kerosene or gas oil range.

Preferably, a Fischer-Tropsch product boiling in the kerosene or gas oil range is used because these products are easier to handle in for example domestic

environments. Such products will suitably comprise a fraction larger than 90 wt% which boils between 160 and 400°C, preferably to about 370°C. Examples of Fischer- Tropsch derived kerosene and gas oils are described in EP-A-0583836, WO-A- 97 / 14768 , WO-A- 97 / 14769 ,

WO-A-00/11116, WO-A- 00 / 11117 , WO-A- 01 / 83406 ,

WO-A-01/83648, WO-A- 01 / 83647 , WO-A- 01 / 83641 ,

WO-A-00/20535, WO-A- 00 /20534 , EP-A-1101813 , US-A-5766274 , US-A-5378348, US-A-5888376 and US-A-6204426.

The Fischer-Tropsch product will suitably contain more than 80 wt% and more suitably more than 95 wt% iso and normal paraffins and less than 1 wt% aromatics, the balance being naphthenics compounds. The content of sulphur and nitrogen will be very low and normally below the detection limits for such compounds. For this reason the sulphur content of a diesel fuel composition

containing a Fischer-Tropsch product may be very low.

The diesel fuel composition preferably contains no more than 5000ppmw sulphur, more preferably no more than 500ppmw, or no more than 350ppmw, or no more than

150ppmw, or no more than lOOppmw, or no more than 80ppmw.

The composition may contain no more than 70 ppmw, or no more than 50ppmw, or no more than 30ppmw, or no more than 20ppmw, or no more than lOppmw sulphur.

Other diesel fuel components which may be used herein include the so-called "biofuels" which derive from biological materials. Examples include fatty acid alkyl esters (FAAE) , such as fatty acid methyl esters (FAME) . Examples of such components can be found in

WO2008/135602.

The diesel base fuel may itself be additivated

(additive-containing) or unadditivated (additive-free) . If additivated, e.g. at the refinery, it will contain minor amounts of one or more additives selected for example from anti-static agents, pipeline drag reducers, flow improvers (e.g. ethylene/vinyl acetate copolymers or acrylate/maleic anhydride copolymers) , lubricity

additives, antioxidants and wax anti-settling agents.

Detergent-containing diesel fuel additives are known and commercially available. Such additives may be added to diesel fuels at levels intended to reduce, remove, or slow the build-up of engine deposits.

Examples of detergents suitable for use in diesel fuel additives for the present purpose include polyolefin substituted succinimides or succinamides of polyamines, for instance polyisobutylene succinimides or

polyisobutylene amine succinamides, aliphatic amines, Mannich bases or amines and polyolefin (e.g.

polyisobutylene) maleic anhydrides. Succinimide

dispersant additives are described for example in

GB-A-960493, EP-A- 0147240 , EP-A-0482253, EP-A- 0613938 , EP-A-0557516 and WO-A- 98 /42808. Particularly preferred are polyolefin substituted succinimides such as

polyisobutylene succinimides.

The diesel fuel additive mixture may contain other components in addition to the detergent. Examples are lubricity enhancers; dehazers, e.g. alkoxylated phenol formaldehyde polymers; anti-foaming agents (e.g.

polyether-modified polysiloxanes ) ; ignition improvers

(cetane improvers) (e.g. 2-ethylhexyl nitrate (EHN) , cyclohexyl nitrate, di-tert-butyl peroxide and those disclosed in US-A-4208190 at column 2, line 27 to column 3, line 21); anti-rust agents (e.g. a propane-1 , 2-diol semi-ester of tetrapropenyl succinic acid, or polyhydric alcohol esters of a succinic acid derivative, the

succinic acid derivative having on at least one of its alpha-carbon atoms an unsubstituted or substituted aliphatic hydrocarbon group containing from 20 to 500 carbon atoms, e.g. the pentaerythritol diester of

polyisobutylene-substituted succinic acid) ; corrosion inhibitors; reodorants; anti-wear additives;

anti-oxidants (e.g. phenolics such as

2 , 6-di-tert-butylphenol , or phenylenediamines such as N, ' -di-sec-butyl-p-phenylenediamine) ; metal

deactivators; combustion improvers; static dissipator additives; cold flow improvers; and wax anti-settling agents.

The diesel fuel additive mixture may contain a lubricity enhancer, especially when the diesel fuel composition has a low (e.g. 500 ppmw or less) sulphur content. In the additivated diesel fuel composition, the lubricity enhancer is conveniently present at a

concentration of less than 1000 ppmw, preferably between 50 and 1000 ppmw, more preferably between 70 and 1000 ppmw. Suitable commercially available lubricity enhancers include ester- and acid-based additives. Other lubricity enhancers are described in the patent literature, in particular in connection with their use in low sulphur content diesel fuels, for example in:

- the paper by Danping Wei and H.A. Spikes, "The Lubricity of Diesel Fuels", Wear, III (1986) 217-235;

- WO-A-95/33805 - cold flow improvers to enhance lubricity of low sulphur fuels;

- US-A-5490864 - certain dithiophosphoric diester- dialcohols as anti-wear lubricity additives for low sulphur diesel fuels; and

- WO-A-98/01516 - certain alkyl aromatic compounds having at least one carboxyl group attached to their aromatic nuclei, to confer anti-wear lubricity effects particularly in low sulphur diesel fuels. It may also be preferred for the diesel fuel

composition to contain an anti-foaming agent, more preferably in combination with an anti-rust agent and/or a corrosion inhibitor and/or a lubricity enhancing additive.

Unless otherwise stated, the (active matter)

concentration of each such optional additive component in the additivated diesel fuel composition is preferably up to 10000 ppmw, more preferably in the range from 0.1 to 1000 ppmw, advantageously from 0.1 to 300 ppmw, such as from 0.1 to 150 ppmw.

The (active matter) concentration of any dehazer in the diesel fuel composition will preferably be in the range from 0.1 to 20 ppmw, more preferably from 1 to 15 ppmw, still more preferably from 1 to 10 ppmw, and especially from 1 to 5 ppmw. The (active matter)

concentration of any ignition improver present will preferably be 2600 ppmw or less, more preferably 2000 ppmw or less, even more preferably 300 to 1500 ppmw. The (active matter) concentration of any detergent in the diesel fuel composition will preferably be in the range from 5 to 1500 ppmw, more preferably from 10 to 750 ppmw, most preferably from 20 to 500 ppmw.

In the case of a diesel fuel composition, for example, the fuel additive mixture will typically contain a detergent, optionally together with other components as described above, and a diesel fuel-compatible diluent, which may be a mineral oil, a solvent such as those sold by Shell companies under the trade mark "SHELLSOL", a polar solvent such as an ester and, in particular, an alcohol, e.g. hexanol, 2-ethylhexanol, decanol,

isotridecanol and alcohol mixtures such as those sold by Shell companies under the trade mark "LINEVOL", especially LINEVOL 79 alcohol which is a mixture of 07-9 primary alcohols, or a C]_2-14 alcohol mixture which is commercially available.

The total content of the additives in the diesel fuel composition may be suitably between 0 and 10000 ppmw and preferably below 5000 ppmw.

In the above, amounts (concentrations, % vol, ppmw, % wt) of components are of active matter, i.e. exclusive of volatile solvents/diluent materials.

The diesel fuel composition of the present invention is produced by admixing the Heavy Cycle Oil with a diesel base fuel suitable for use in an internal combustion engine .

It has surprisingly been found that the use of a Heavy Cycle Oil in a diesel fuel composition provides benefits in terms of reduced power loss in a diesel engine to which the diesel fuel composition is

introduced .

The present invention therefore provides a method of reducing injector fouling or reducing power loss of a diesel engine, the method comprising introducing into a combustion chamber of the diesel engine a diesel fuel composition comprising Heavy Cycle Oil.

The present invention will be further understood from the following examples. Unless otherwise stated, all amounts and concentrations disclosed in the examples are based on weight of the fully formulated fuel composition. Examples

In order to measure the effect of the diesel fuel compositions of the Examples and Comparative Examples, the following bench engine test was used. The engine used for this test was a VW Euro 4 Engine. The engine used a PD (Pumpe-Duse) electronic unit injector direct Injection system. The Euro 4 engine uses HHE (High-Hydraulic- Efficiency) Siemens VDO (now part of Continental AG) injectors. Table 1 below shows the details of the VW engine used in this test.

Table 1

The test procedure is based on measurements of torque loss (in Nm) that can be due to injector fouling. The test procedure entails alternating the candidate and reference fuels in 10 hour fixed throttle, high part load

(180 Nm) fouling cycle several times summing up to 60 hours in total. Typically, where injector or nozzle fouling occurs, the torque reduces gradually at fixed throttle conditions because of the reduction in fuel flow due to deposit formation. Therefore, the torque loss at fixed throttle conditions can be a direct measure of the fouling propensity of the respective fuel. A statistical model was developed to calculate the torque loss in each 10 hour fouling cycle by fitting linear regression models to the first 60 and the last 80 torque measurements

(taken at 1 Hz intervals) and using these to estimate the start and end points. The resulting decrease in engine power is directly proportional to the decrease in torque as the engine speed is constant (fixed throttle

conditions) .

The total power loss is then given by Equation 1. Equation 1: Power Loss During the Fouling Cycle Power Loss = [1- (Power (end) /Power (start) ] x 100% Brief Description of the Drawings

Figure 1 shows the Fouling Cycle Power Loss for Fuel A and Fuel B in Example 1.

Figure 2 shows the Fouling Cycle Power Loss for Fuel

A and Fuel C in Example 2.

Example 1

Example 1 used Fuel A and Fuel B in the procedure above. Fuel A was an EN 590 diesel fuels which promoted deposit formation and served as a reference fuel. Key properties of the EN 590 diesel fuel (Reference Fuel A) are shown in Table 2 below. Fuel B was identical to Fuel A. The results of Example 1 are shown in Table 3 and in Figure 1.

Table 2 Key Properties of the EN590 Diesel Fuel

(Reference Fuel A)

Property Units EN 590

Density Kg/m³ 820-845

Flash Point °C >55

Cetane number >51

HFRR lubricity ym <460

Metal Content mg/kg 0.1

FAME Content %vol <5%

Distillation °C T5, T95

Sulfur mg/kg 10

Viscosity 2-4.5

CFPP °C -20

Table 3

Fuel Time (hours) Power (%)

0 100

Fuel A 10 96.8

Fuel B 20 94.8

Fuel A 30 93.5

Fuel B 40 92.1

Fuel A 50 90.8

Fuel B 60 89.1 Example 2

Example 2 used Fuel C and Fuel A in the procedure above. Fuel C consisted of Fuel A with the addition of 0.6% Heavy Cycle Oil by vol. The Heavy Cycle Oil used was obtained from an FCC unit and had the following

properties: Vapour pressure: <0.1 kPa @ 40°C; Initial boiling point: approximately 150°C; Final boiling point: >600°C; Density: 1010 kg/m3 - 1060 kg/m3; Flash point:> 60C; Kinematic Viscosity: approximately 700 cSt; Sulphur content: 10000 mg/kg. The results of Example 2 are shown in Table 4 and in Figure 2.

Table 4

Discussion

The data shown in Figure 2 demonstrates that the HCO-containing fuel C had a positive impact on the rate of power loss, e.g. due to deposit formation, in

comparison to the base fuel A. In the first 10-hour fouling cycle, the HCO-containing fuel (fuel C) , even gave a steady-state, e.g. a keep-clean, performance.

Claims

C L A I M S

1. Use of Heavy Cycle Oil (HCO) in a diesel fuel composition for reducing power loss in an engine into which the fuel composition is introduced.

2. Use according to Claim 1, wherein the diesel fuel composition comprises in the range of from 0.05 wt% to 5 wt% of Heavy Cycle Oil, by weight of the diesel fuel composition .

3. Use according to Claim 2, wherein the diesel fuel composition comprises in the range of from 0.1 wt% to 1 wt% of Heavy Cycle Oil, by weight of the diesel fuel composition .

4. Use according to Claim 3, wherein the diesel fuel composition comprises in the range of from 0.2 wt% to 0.7 wt% of Heavy Cycle Oil, by weight of the diesel fuel composition.

5. Use according to any one of Claims 1 to 4, wherein the diesel fuel composition also comprises a biofuel.

6. Use according to any one of Claims 1 to 5, wherein the diesel fuel composition also comprises at least 2% w/w fatty acid methyl esters (FAME) .

7. Use of Heavy Cycle Oil (HCO) in a diesel fuel composition for reducing injector fouling, as measured by torque loss at constant engine speed, in an engine into which the fuel composition is introduced.

8. A method of reducing power loss, or reducing

injector fouling in the injectors, of a diesel engine, the method comprising introducing into a combustion chamber of the engine a diesel fuel composition

comprising Heavy Cycle Oil.

9. A method as claimed in claim 8, wherein the diesel fuel composition comprises in the range of from 0.05 wt% to 5 wt% of Heavy Cycle Oil.

10. Diesel fuel composition which comprises a diesel base fuel and in the range of from 0.05 wt% to 5 wt% of Heavy Cycle Oil, by weight of the total total diesel fuel composition .

11. Diesel fuel composition as claimed in claim 10, which comprises in the range of from 0.1 wt% to 1 wt% of Heavy Cycle Oil, by weight of the diesel fuel

composition .

12. Diesel fuel composition as claimed in claim 11, which comprises in the range of from 0.2 wt% to 0.7 wt% of Heavy Cycle Oil, by weight of the diesel fuel

composition .

13. Diesel fuel composition as claimed in any one of claims 10 to 12, which also comprises a biofuel.

14. Diesel fuel composition as claimed in claim 13, wherein the diesel fuel composition also comprises at least 2% w/w fatty acid methyl esters (FAME) .

15. Process for the preparation of a diesel fuel

composition as claimed in any one of claims 10 to 14, which comprises adding in the range of from 0.05 wt% to 5 wt% of Heavy Cycle Oil, by weight of final diesel fuel composition, to a diesel base fuel.