Description:FIELD:
The present disclosure relates to a diesel and middle distillate fuels and additive compositions to enhance overall performance of these fuels such as improved combustion characteristics, reduced emissions and improving overall fuel efficiency in diesel engine along with lowering of deposit formation.

BACKGROUND:
Middle distillate fuels especially diesel fuels are widely used in transportation sector and energy sector as main energy source. Thus, the quality and performance of diesel fuels are very crucial to utilize its high energy and worth full output performance. Further, combustion of diesel fuel in an internal combustion engine result in formation and accumulation of deposits on various parts of the combustion chamber as well as in the fuel intake and on the exhaust systems of the engine.

Further, the additive compositions/packages can improve the quality of diesel fuel and can enhance the combustion properties by reducing deposit formation. There are several additive compositions/packages reported in the literature which can reduce deposit formation in the fuel intake and on the exhaust systems of the engine and such additive compositions are mainly nitrogen containing polymeric compounds. Further, literature showed that the usage of nitrogen containing polymer especially polyisobutylene succinimide in combination of some active chemicals has improved the reduction in deposits in combustion chamber. Most of active chemicals used in the literature are Mannich bases, polyalkylamines and polyether amines prepared from different oil soluble raw materials.

US2006/0277819 discloses development of synergistic additive package with PIBSI in combination of Mannich base of p-Nonyl phenol/p-dodecyl phenol and hydrogenated cashew nutshell liquid (CNSL) reaction with alkylated base with at least one NH bond. The document has explored limited properties of the additised diesel fuels and not studied combustion properties, fuel efficiency and noise parameters. Since both the components i.e., Mannich base and PIBSI contain nitrogen atoms which may leads to the increase in NOx in the exhaust emissions. Some of the examples of additive packages of combination PIBSI and other chemicals are reported in this document.
US5752989 discloses a diesel fuel additive composition comprising of major proportion of compression ignition dye and a minor proportion of additive, and the additive comprises a dispersant and a carrying oil, wherein, the dispersant comprises at least one ingredient of succinimides and polyalkyl amine. Higher nitrogen content in the additive package may lead to increase in the NOx emission. The additive composition reduces injector deposits in internal combustion-compression ignition engines.

WO2017/075203A1 discloses the development of additive package for reduction in nozzles deposits in diesel fuel combustion engines. The additive package contains nonyl phenol based polyether amine compound (80-100%) in diluents (0-20%). In this document high dosages of additive (1:1000) was used for reduction of nozzle deposits of diesel engines.

US20170029738A1 discloses a lubricant additive concentrate containing a dispersant-detergent colloid complex, including a polybutenyl succinimide dispersant (61 mass%) and one/more surfactants selected from sulfonate. Additionally, it comprises synthetic lubricating oils comprising the esters of dicarboxylic acids with a variety of alcohols (i.e., 2-ethylhexyl diester of linoleic acid dimer). As a friction modifier, it comprises butane diol ester of a dimerized unsaturated fatty acid and as a viscosity improver it comprises C4 to C10 di-carboxylic acid with an unsaturated nitrogen-containing monomer having 4 to 20 carbon atoms.

US20030171225A1 discloses a composition for reducing sludge and degradation of elastomer seals in engines, the composition comprising nitrogen-containing dispersant (polyisobutene) and synthetic lubricating oils comprising mixed C3-C8 fatty acid esters (2-ethylhexyl diester of linoleic acid dimer).

US6719814B1 discloses a lubricity additive comprising an ester of an acid and an alcohol. As a dispersant, it comprises pentaerythritol diester of polyisobutylene-substituted succinic acid or linear or branched hydrocarbyl amines.

US20090077869A1 discloses an additive composition comprising at least one antistatic agent (5-25 wt.% polysulfone); ester lubricity additive (ethylene glycol diester of dimer acid); nitrogen-containing compound; dehazer and aromatic solvent.

Most of the prior art additive compositions/packages was focused only on decreasing the deposit of engine parts. However, still there is requirement of an additive composition which can provide comprehensive solution regarding improvements in fuel combustion and fuel efficiency, reducing harmful emissions of doped diesel fuel and reducing deposit formation. Further, there is also requirement of an additive composition which can improve quality of doped diesel fuel, especially, improving properties like lubricity, conductivity, cetane number, corrosion protection and storage stability.

SUMMARY OF THE INVENTION:
The present disclosure provides an additive composition which works and acts as a performance enhancer for low sulphur diesel and middle distillate fuels. The additive composition includes 30-60 wt.% of polyisobutylene succinimide, 5-30 wt.% of a reaction product of C8-C16 dimeric acid and alkylated ether, and 0.1-0.5 wt.% of polysulfone. Further, the additive composition also includes a chemical component selected from a dehazer, a cetane improver, or a combination thereof. The dehazer concentration ranges 0.5-4 wt.% which is based on alkoxylated phenolic resins. The cetane improver ranges 0-50 wt.% and the cetane improver is 2-ethyl hexyl nitrate. Specifically, the cetane improver is 25-50 wt.%.
To get the desired results, 100-1000 ppm of the additive composition is dopped with low sulphur diesel and middle distillate fuels.
The reaction product of C8-C16 dimeric acid and alkylated ether is a non-amine based complex, wherein, the non-amine based complex is a dimeric acid ether (DAE) complex represented by the formula 1.

Formula 1: dimeric acid ether (DAE) complex

Further, the present disclosure provides a process for preparing the said additive composition, wherein, the process includes dissolving polyisobutylene succinimide in an aromatic rich refinery stream at an ambient temperature of 20-40 oC to produce a first reaction mixture. Wherein, 30-60 wt.% of polyisobutylene succinimide is dissolved in 10-60 wt.% of aromatic rich refinery stream to produce the first reaction mixture. Then separately preparing a reaction product of C8-C16 dimeric acid and alkylated ether, wherein, the reaction product is a non-amine based complex. Then blending 30-60 wt.% of the first reaction mixture, 5-30 wt.% of the said non-amine based complex, and 0.1-0.5 wt.% of polysulfone, wherein, the blending is carried out at an ambient temperature of 20-40 oC to get a blend of additive composition. Stirring the blend of additive composition at 500-1000 rpm by mechanical stirrer at the ambient temperature of 20-40 oC for a period of 2 hours. The non-amine based complex is synthesized by reacting C8-C16 dimeric acid and alkylated ether in a batch reactor in a molar ratio ranging from 0.05:1 to 0.2:1, and then heated in a Dean-Stark apparatus in the presence of an acid.

Further, other component such as a dehazer, a cetane improver, or a combination thereof is also added in the said additive composition. Wherein, the dehazer is 0.5-4 wt.% and the dehazer is selected from phenolic resins, esters, polyamines, sulphonates, polyol resins and reaction products of alcohol and epoxides. The cetane improver is 0-50 wt.% and the cetane improver is selected from an alkylated nitrate, an alkylated peroxide, wherein, the cetane improver is 2-ethyl hexyl nitrate. Specifically, the cetane improver is 25-50 wt.%

Further, the additive composition also contains corrosion inhibitors selected from a carboxylic acid, an anhydride, an amine, or an amine salt of carboxylic acid.

TECHNICAL ADVANTAGES:
One advantage of the present disclosure is to provide an additive composition which when blended with the diesel improves the performance properties of normal diesel.

Another advantage of the present disclosure is to provide an additive composition which acts as a single package for improving multiple properties of diesel fuel and internal combustion engines like fuel economy benefits, better emission characteristics, improved power, enhanced corrosion protection and better fuel lubricity.

OBJECTIVE:
It is the primary objective of the present disclosure to provide an additive composition which works and acts as a performance enhancer for low sulphur diesel and middle distillate fuels.

It is further objective of the present disclosure to provide an additive composition which is prepared by using cost effective indigenous components.

It is further objective of the present disclosure to provide an additive composition which is compatible with other fuel additives to enhance the quality of diesel fuel.

It is further objective of the present disclosure to provide a comprehensive additive package which improves fuel combustion, fuel efficiency and reduces harmful emissions of doped diesel fuel.

It is further objective of the present disclosure is to provide a comprehensive additive package which improves the quality of the doped diesel fuel for properties like lubricity, conductivity, cetane number, corrosion protection and storage stability.

It is further objective of the present disclosure is to provide a comprehensive additive package which had excellent dispersancy-detergency property which reduces the injectors deposits as well as clean the existing deposits.

It is further objective of the present disclosure to provide an additive package which is compatible with all other fuel additives like cold flow improvers, dehazers, cetane improver etc.

BRIEF DESCRIPTION OF THE DRAWING:
To further clarify advantages and aspects of the disclosure, and aspects of the present additive composition, a more particular description of the present additive composition will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawing(s). It is appreciated that the drawing(s) depicts only typical embodiments of the invention and are therefore not to be considered limiting of its scope.

Figure 1: illustrates an IR spectrum of the DAE product.

DESCRIPTION OF THE INVENTION:
The present disclosure provides an additive composition which works and acts as a performance enhancer for low sulphur diesel and middle distillate fuels. The additive composition includes 30-60 wt.% of polyisobutylene succinimide, 5-30 wt.% of a reaction product of C8-C16 dimeric acid and alkylated ether, and 0.1-0.5 wt.% of polysulfone. Further, the additive composition also includes a chemical component selected from a dehazer, a cetane improver, or a combination thereof. The dehazer is 0.5-4 wt.% and the dehazer is selected from phenolic resins, esters, polyamines, sulphonates, polyol resins and reaction products of alcohol and epoxides. The cetane improver is 0-50 wt.% and the cetane improver is selected from an alkylated nitrate, an alkylated peroxide, wherein, the cetane improver is 2-ethyl hexyl nitrate. In an embodiment, the cetane improver is 25-50 wt.%.
To get the desired results, 100-1000 ppm of the additive composition is dopped with low sulphur diesel and middle distillate fuels.
The reaction product of C8-C16 dimeric acid and alkylated ether is a non-amine based complex, wherein, the non-amine based complex is a dimeric acid ether (DAE) complex represented by the formula 1.

Formula 1: Dimeric Acid Ether (DAE) complex
Further, the present disclosure provides a process for preparing the said additive composition, wherein, the process includes dissolving polyisobutylene succinimide in an aromatic rich refinery stream at an ambient temperature of 20-40 oC to produce a first reaction mixture. Wherein, 30-60 wt.% of polyisobutylene succinimide is dissolved in 10-60 wt.% of aromatic rich refinery stream to produce the first reaction mixture. Then separately preparing a reaction product of C8-C16 dimeric acid and alkylated ether, wherein, the reaction product is a non-amine based complex. Then blending 30-60 wt.% of the first reaction mixture, 5-30 wt.% of the said non-amine based complex, and 0.1-0.5 wt.% of polysulfone, wherein, the blending is carried out at an ambient temperature of 20-40 oC to get a blend of additive composition. Stirring the blend of additive composition at 500-1000 rpm by mechanical stirrer at the ambient temperature of 20-40 oC for a period of 2 hours. The non-amine based complex is synthesized by reacting C8-C16 dimeric acid and alkylated ether in a batch reactor in a molar ratio ranging from 0.05:1 to 0.2:1, and then heated in a Dean-Stark apparatus in the presence of an acid.

Further, other component such as a dehazer, a cetane improver, or a combination thereof is also added in the said additive composition. Wherein, the dehazer is 0.5-4 wt.% and the dehazer is selected from alkoxylated phenolic resins. The cetane improver is 0-50 wt.% and the cetane improver is selected from an alkylated nitrate, an alkylated peroxide, wherein, the cetane improver is 2-ethyl hexyl nitrate. In an embodiment, the cetane improver is 25-50 wt.%.

The PIBSI based additive packages are generally combined with Mannich based products to improve its performance for deposit cleanliness, whereas, in the present disclosure, the PIBSI in combination of non-amine based Dimeric acid ether complex showed tremendous improvement of injectors cleanliness along with improvement in fuel combustion characteristics, fuel efficiency and emissions reduction.

Further, the prior art of PIBSI based additives packages was focused only on the decrease in deposit of engine parts. Further, in the present disclosure, the developed additive composition/package blended diesel was explored for the improvements of fuel characteristics after like lubricity, conductivity, cetane number, corrosion protection and storage stability. Further, hereinbelow all the advantage of additive composition/package while doping in diesel fuels have been described in detail.

Materials (Chemical) and methods:
Following components (chemicals) were used for the development of novel and effective additive composition/package for improving quality and performance of low sulfur diesel/middle distillate fuels.
Component A: Polyisobutylene succinimide (PIBSI, 1800-2500 MW) was purchased from suppliers in India.
Component B: Reaction product of (C8-C16) dimeric acid and alkylated ether complex (DAE product) is prepared in the laboratory (~1000 MW) as per the process described herein in the present disclosure. C8-C16 Dimeric acid complex is procured from vendor in India and alkylated ether complex purchased from supplier in India.
Component C: Polysulfone from 1-Decene is prepared in the laboratory (<50000 MW) as described in the literature, especially in US patent number US3811848 (1974). Polysulfone was prepared by reacting equimolar of 1-decene and SO2 in presence of catalytic amount of t-butyl hydrogen peroxide as catalyst at temperature 5-10 oC.
Component D: Dehazer additive is selected from phenolic resins, esters, polyamines, sulphonates, polyol resins and reaction products of alcohol and epoxides.
Component E: Cetane improver, 2-ethyl hexyl nitrate purchased from vendor in India.
Diluents: Refinery stream with boiling point range of 150-350 oC.
Test Diesel fuel: Collected from Indian refineries meeting BSV diesel specification (IS: 1460 – 2017). Below table 1 describes the properties of the test diesel meeting the BSV diesel specification.
Table 1: Properties of Test diesel meeting BSV diesel specification
Characteristics Test method Properties of Test Diesel as per BS VI standard
Appearance
Visual Light yellow, bright and visually free from solid matter and un-dissolved water at ambient fuel temperature
Acidity Inorganic ASTM D974 Nil
Total acidity, mg KOH/g, Max ASTM D974 0.2
Total contamination, mg/kg, Max IP440 24
Density, at 15 oC, kg/m3 ASTM D 4052 815-845
Distillation, 95% v/v, recovery, oC Max ASTM D 86 370
Total Sulphur, w/w ppm, Max ASTM D5453 10
Copper Corrosion Strip test (for 3 h @50°C), Max ASTM D130 Not More Than No.1
Cetane number, min ASTM D613 51.0
Cetane index, Min ASTM D4737 46.0
Lubricity, HFRR at 60°C, Max ISO 12156-1 460 micron
Kin. Viscosity, cSt at 40°C ASTM D445 2.0 - 4.5
Flash point, Abel, °C, Min ASTM D93 35
Water content, ppm, w/w, Max ASTM D6304 200
Cold filter plugging point, oC, Max
• Winter
• Summer ASTM D6371 6 oC
18 oC
Pour point, oC, Max
• Winter
• Summer ASTM D97 3 oC
15 oC
PAH, % by mass, Max ASTM D 6591 8

Preparation of Dimeric acid ether (DAE) complex:
The synthesis process for production of DAE complex has been conducted by adding optimum quantities of desired C8-C16 dimeric acid compound (lab prepared as described in US patent US6797021) and alkylated ether complex in batch reactor in molar ratio ranging from (0.05:1 to 0.2:1) and heated in presence of an acid in a Dean-Stark apparatus. The product was collected after reaction as viscous liquid. The structure and molecular weight of the Dimeric acid ether product (DAE product) were confirmed by analytical techniques and the IR spectrum of DAE product is described in Figure 1. In figure 1, the IR analysis of the reaction product confirmed the formation of DAE product by appearance of 1735 cm-1 peak of ester C=O instead of acid C=O peak at 1710 cm-1 presented in dimeric acid compound.

Analytical characterizations of DAE product:
The InfraRed (FTIR) spectroscopy of the DAE product was recorded on Shimadzu IR Prestige 25 FTIR instrument. About 2-3 mg of sample was filmed on KBr pallet uniformly and subjected for analysis. The IR spectra were recorded in 4000-400 cm-1 region at 4 cm-1 resolution, 50 scans.

Figure 1 provides that the IR analysis of the reaction product confirmed the formation of DAE product by appearance of 1735 cm-1 peak of ester C=O instead of acid C=O peak at 1710 cm-1 presented in dimeric acid compound.
Process development for novel additive composition:
The novel additive composition was prepared after evaluating different combinations of chemical components of different chemistry and established the compatibility and superior activity. The novel additive composition was formulated using optimized ratios of high performing additives.

The novel additive package is prepared by dissolving polyisobutylene succinimide (PIBSI, 1800-2500 MW, 30-60% wt/wt) in aromatic rich refinery stream as diluents (10-60% wt/wt) at ambient temperature i.e., 20-40oC. To this mixture added reaction product of C8-C16 dimeric acid and alkylated ether (DAE product) (1500-4000 MW, 5-30% wt/wt) and polysulfone (0.1-0.5% wt/wt) at ambient temperature. The mixture was stirred at 500-1000 rpm by mechanical stirrer at an ambient temperature i.e., 20-40 oC for a period of 2 hours. The other additives like dehazer (0.5-4.0% wt/wt) and cetane improver (0-50% wt/wt) were also added in the additive composition to improve the water shedding and cetane number of the diesel fuels.

Following additive packages (as listed in below table 2) were prepared using different components in different ratios to optimize highly efficient and performing additive package:

Table 2: List of developed DMFA packages using different components
Formulations Component-A Component-B Component-C Component-D Cetane improver (E) Diluents
Candidate-1 60 0 0 0 0 47
Candidate-2 60 5 0 0 0 35
Candidate-3 60 10 0 2 0 28
Candidate-4 45 15 0 2 0 38
Candidate-5 30 30 0 2 0 38
Candidate-6 50 30 0.5 2 0 17.5
Candidate-7 40 20 0.5 2 0 37.5
Candidate-8 30 15 0.5 2 0 52.5
Candidate-9 45 10 0.5 2 0 42.5
Candidate-10 30 20 0.5 3 30 16.5
Candidate-11 30 15 1 4 50 0
Candidate-12 60 5 0.1 0.5 10 24.4

Performance Screening of the Additive Composition:
The performance of DMFA formulations was screened at select dosages in BSIV compliant heavy-duty vehicle (Type: BSIV Heavy Duty Vehicle (Truck); Model: Ashok Leyland 1618/4; Engine Size: 5759 cc) as per test procedure mentioned in IS: 11921- Standard Test Method of Evaluation of Fuel Economy. The test vehicle was serviced and during servicing old engine oil, oil filter, air filter and coolant were replaced with new one. Before each test trial, test vehicle was fitted with new injectors and inline fuel flow meter. Injector’s performance was measured with neat BSVI diesel containing Zinc Neo-decanoate under defined test conditions (Ambient Conditions: 15 – 35°C & <75%R.H; Weight: With Gross Weight i.e., 18.5 Tonne; Instrumentation: FC Meter / Data Logger).

Evaluation of base test fuel and additive treated fuel:
Data with base test fuel and additive treated fuel for Fuel Consumption: Test vehicle was loaded to the gross weight with the help of dead weights. In order to stabilise vehicle on base test fuel and additive treated fuel, 100 km was performed on the test track. Test vehicle is then run at constant speed (40 kph & 60kph). A set of 20 readings covering 0.5km in both direction on a starlight track was obtained at constant speeds (40 kph & 60kph) for measuring Fuel Consumption (FC).
Idle Emissions measurements: Smoke density with base test fuel and additive treated fuel was measured through smoke meter of the test vehicle.
Wide Open Throttle (WOT) Power measurements: Test vehicle was mounted on the chassis dynamometer and the equipment settings were kept on speed control mode with base test fuel and additive treated fuel. Test vehicle was then put on full throttle by maintaining the different constant speed(s) say 20kph, 30kph, 40kph, 50kph, 60kph etc. and measurement was done when the chassis dynamometer shows zero acceleration on full throttle mode. The speeds were run on chassis dynamometer till the power curve starts declining as per the power vs. speed fundamental concept.
Acceleration on road measurements: Test vehicle was filled with base test fuel and additive treated fuel and taken on straight, paved and levelled road with a 2km of stretch. Test vehicle was then put on full throttle with appropriate selection of gears (MT Vehicle). Then acceleration measurement in seconds was recorded at different speed intervals such as 0kph, 30kph, 40kph, 50kph, 60kph, 70kph, 80 kph to plot the acceleration graph.

Engine Performance Evaluation:
Further injectors cleaning efficiency of shortlisted candidate 7 and candidate 8 was determined on XUD 9 engine test bench which is one of the tests methods specified in World Wide Fuel Charter (WWFC) for injectors fouling/cleanliness.

Examples:
The following additive packages were developed and evaluated for their properties in diesel fuel as per optimized process.

Candidate-1: Additive package Candidate-I is prepared from component A (PIBSI, 60% wt/wt) dissolved in diluents (47% wt). The reaction mixture stirred as per blending process mentioned hereinabove. This additive package is without addition of component B, DAE product, dehazer and polysulfone.

Candidate-2: Additive package Candidate-II is also prepared from component A (PIBSI, 60% wt/wt) dissolved in diluents (35% wt.) and added slowly component B (5% wt/wt). The reaction mixture stirred as per blending process mentioned hereinabove. This additive package is without the component C, D and E.

Candidate-3: The additive formulation is developed from component A (PIBSI, 60% wt/wt) dissolved in diluents (28% wt/wt) and added slowly component B (10% wt/wt) and component D (2% wt/wt). The reaction mixture stirred as per blending process mentioned above. Candidate-3 additive package has no component C i.e. polysulfone and component E i.e., cetane improver.

Candidate-4: This additive package is prepared from component A (PIBSI, 45% wt/wt), dissolved in diluents (38% wt/wt) and added slowly component B (15% wt/wt) and component D (2% wt/wt). The reaction mixture stirred as per blending process mentioned above. Candidate-4 additive package has no component C and E.

Candidate-5: Additive package is prepared from component A (PIBSI, 30% wt/wt) and component B (DAE, 30% wt/wt) dissolved in diluents (38% wt/wt) and added component D (2% wt/wt). The reaction mixture stirred as per blending process mentioned above. Candidate-5 additive package has no cetane improver and polysulfone.

Candidate-6: Additive package candidate-6 is formulated from component A (PIBSI, 50% wt/wt) and component B (DAE, 30% wt/wt) dissolved in diluents (17.5% wt/wt) and added slowly component C (0.5% wt/wt), and component D (2% wt/wt). The reaction mixture stirred as per blending process mentioned above. Candidate-6 additive package has no cetane improver.

Candidate-7: Additive package candidate-7 is developed from component B (DAE, 20% wt/wt) and component A (PIBSI, 40% wt/wt) dissolved in diluents (37.5% wt/wt) and added slowly component C (0.5% wt/wt) and component D (2% wt/wt). The reaction mixture stirred as per blending process mentioned above. Candidate-7 additive package has no cetane improver.

Candidate-8: Additive package is developed by component A (PIBSI, 30% wt/wt) and component B (DAE, 15% wt/wt) dissolved in diluents (52.5% wt/wt) and added slowly component C (0.5% wt/wt) and component D (2% wt/wt). The reaction mixture stirred as per blending process mentioned above. Candidate-8 additive package has no cetane improver.

Candidate-9: Additive package candidate-9 is prepared from component A (PIBSI, 45% wt/wt) and component B (DAE, 10% wt/wt) dissolved in diluents (42.5% wt/wt) and added slowly component C (0.5% wt/wt) and component D (2% wt/wt). The reaction mixture stirred as per blending process mentioned above. Candidate-9 additive package has no cetane improver.

Candidate-10: Additive package candidate-10 is prepared formulated from component A (PIBSI, 30% wt/wt) and component B (DAE, 20% wt/wt) dissolved in diluents (16.5% wt/wt) and added slowly component C (0.5% wt/wt), and component D (3% wt/wt). The cetane improver (30% wt/wt) was added. The final additive package candidate-10 is clear, viscous liquid with homogenous mixture.

Candidate-11: Additive package candidate-11 is prepared from component A (PIBSI, 30% wt/wt) and component B (DAE, 15% wt/wt) directly added to component C (1.0% wt/wt) and component D (4% wt/wt). The cetane improver E (50% wt/wt) was added. The final additive package candidate-11 is clear, viscous liquid with homogenous mixture.

Candidate-12: Additive package candidate-12 is prepared from component A (PIBSI, 60% wt/wt) and component B (DAE, 5% wt/wt) dissolved in diluents (24.4% wt/wt) and added slowly component C (0.1% wt/wt) and component D (0.5% wt/wt). The cetane improver E (10% wt/wt) was added. The final additive package candidate-12 is clear, viscous liquid with homogenous mixture.

Results and discussions:
The developed additive packages were evaluated for performance by doping in middle distillate fuel especially low sulfur diesel fuels having different cetane number ranging from 45-51. The dosages of developed additives also optimized in the range of 100-1000 ppm in the diesel fuel. All the performance and quality of doped diesel fuel were evaluated as per ASTM standard test methods and standard methods. The results were summarized as below.

Combustion characteristics of additive treated diesel fuel:
The experiments for deriving combustion characteristics of additive blended diesel fuels in terms of cetane number were conducted in the CFR engine equipment supplied by CFR Engines, Inc., N8 W22577 Johnson Dr., Pewaukee, WI 53186. The standard test conditions used as per the ASTM D613 method. The reference fuel prepared from blending of n-Hexadecane and a-methylnaphthalene separately for high and low cetane numbers. The cetane number of the test fuel derived by using formula
CN = CNLRF + {(HWS-HWLRF)/(HWHRF-HWLRF)}(CNHRF-CNLRF)
Where CN = Cetane number of test fuel
CNLRF = Cetane Number of low reference fuel
CNHRF = Cetane number of high reference fuel
HWS = Handwheel reading of sample
HWLRF = Handwheel reading of low reference fuel
HWHRF = Handwheel reading of high reference fuel

The cetane number results of diesel fuels doped with each component and combination of components are shown below in Table 3.
Table 3: Results of cetane number derived from ASTM D613 method
S. No. Test fuel detail Cetane Number
1 Reference diesel 51.5
2 Diesel +A (PIBSI) 52.2
3 Diesel +B (DAE) 53.2
4 Diesel +C(ASA) 52.2
5 Diesel +D (DH) 52.3
6 Diesel + (A+C) 52.8
7 Diesel + (A+C+D) 52.8
8 Diesel + (A+B) 54.8
9 Diesel + (A+B+C) 54.6
10 Diesel + (A+B+C+D) 54.6
11 Diesel + (A+B+C+D)+ 10% E 54.8
12 Diesel + (A+B+C+D)+ 40% E 56.0

The combustion characteristics of blended diesels were analysed by calculating cetane number of fuels by ASTM D613 method. The results indicated that the base diesel fuel had cetane number of 51.5 which was further improved by doping additive components individually and mixed components. So the components chosen for development of an additive package to improve quality and performance not affecting the combustion characteristics of base fuel. Further the typical combination of these components improved the cetane number from 51.5 to 56.0 which is very essential for improving performance of diesel fuel in IC engines. The maximum cetane number improvement observed in diesel fuel doped with mixture of components A, B, C, D and E at dosage ranges from 100-1000 ppm.

HFRR Lubricity of additive blended Diesel fuel: Lubricity is a critical characteristic of diesel fuel for smooth travelling through fuel pipelines/engine components. Lubricity of diesel fuel measured in terms of wear which is an excessive friction affects the life of engine components like fuel injectors, fuel injection pumps etc. The wear scar diameter (in microns) due to diesel fuel was measured by high-frequency reciprocating rig (HFRR) test as per ISO 121561 method. The test results of wear scar diameter for base diesel fuel and additive blended diesel fuels (dosage of 100-1000 ppm) were compiled in Table 4.

Table 4: HFRR Lubricity performance as per ISO 121561
S. No. Test Diesel fuel and diesel with additive doped @ 100-1000 ppm HFRR Lubricity
WSD (micron)
1 Reference diesel 615
2 Reference Diesel + A (PIBSI) 605
3 Reference Diesel + B (DAE) 525
4 Reference diesel + Candidate-1, 2, 3 510-485
5 Reference diesel + Candidate-4, 5, 6 420 – 450
6 Reference diesel + Candidate-7, 8, 9 410 -430
7 Reference diesel + Candidate-10, 11, 12 390-410

The HFRR test results of the diesel fuel with and without developed additive packages shown that the lubricity of base diesel fuel is high with 615 microns WSD compared to that of additive doped Diesel fuels. The components PIBSI and DAE individually not able to improve the lubricity of the base fuel (605 microns & 535 microns respectively). Whereas the combination of both in appropriate ratios in additive packages has generated synergy and improved the lubricity of the base diesel fuel from 615 micron to 410-415 microns. Excellent performance was achieved with additive packages Candidate-4, Candidate-5 & Candidate-6 in range of 420-450 microns of WSD. The second-best performance in improving lubricity of diesel fuel shown by the additive packages Candidate-7, Candidate-8 and Candidate-9 in the range of 410-430 micron WSD. The additive package candidates 10, 11 and 12 doped in diesel showed excellent performance in HFRR test and resulted in wear reduction of base diesel from 615 microns to 390-410 micron range at dosages of 100-1000 ppm. The presence of cetane improver along with PIBSI and dimeric acid ether (DAE) complex also contributed for the improvement of lubricity of the diesel fuel under HFRR conditions.

Corrosion protection of additive treated diesel fuel: Corrosion is one of the major issues with hydrocarbon fuels during storage, transportation and utilization. Corrosion problem of diesel fuels can be minimized by addition of corrosion inhibitor. The developed additive packages also examined for reduction of corrosive nature of the diesel fuel by using NACE test as per TM0172 test method. The corrosion test ratings of the diesel fuel with and without additive dosage (100-1000 ppm) were summarized in Table 5.

Table 5: Results of NACE corrosion test as per NACE TM01702
S. No. Test fuel detail NACE corrosion rating
1 Reference diesel E
2 Reference Diesel +A (PIBSI) B
3 Reference Diesel +B (DAE) C
4 Reference diesel + Candidate -1 B
5 Reference diesel + Candidate -2 B+
6 Reference diesel + Candidate -3 B
7 Reference diesel + Candidate -4 B
8 Reference diesel + Candidate -5 B++
9 Reference diesel + Candidate -6, 7, 8 A
10 Reference diesel + Candidate -9 &10 A
11 Reference diesel + Candidate -11 B++
12 Reference diesel + Candidate -12 B

The results in the Table 5 revealed that the base diesel fuel exhibited the corrosion nature with rating of ‘E’ and the tendency was reduced with addition of additives in 100-1000 ppm dosage. The formulation individual components i.e., PIBSI and DAE reduced the corrosiveness of diesel fuel from ‘E’ rating to ‘B’ and ‘C’ rating respectively as against requirement of B++ rating. The developed additive packages using PIBSI along with DAE dimeric alkylated ether complex as well a Component C has drastically reduced the corrosiveness of diesel fuel. The additive packages candidate-6 to candidate-11 showed very good rating in reducing corrosion in diesel fuel at dosage of 100-1000 ppm.

Water shredding performance test of additive treated diesel: Generally, addition of PIBSI based dispersant-detergent additive may form emulsion at interface/hazy appearance due to water ingress in diesel fuels. To improve water shedding property of additized diesel, the additive package was incorporated with de-emulsifier component. Such additive package improves the water shedding property of additized diesel fuel. This is mandatory to ensure the absence of water soluble components in additive doped diesel fuels for better performance. The water shredding performance of additive doped diesel fuels performed as per ATSM D1094 method and results were summarized in Table 6.

Table 6: Water shedding performance as per ASTM D 1094 test method
S. No. Test fuel detail Water Reaction (ASTM D1094)
Separation rating Interface rating
1 Reference diesel 1 1
2 Reference Diesel +A (PIBSI) 2 3
3 Reference Diesel +B (DAE) 2 2
4 Reference diesel + Candidate-1, 2, 3 2 3
5 Reference diesel + Candidate-4, 5, 6 1 1(b)
6 Reference diesel + Candidate-6, 7, 8 1 1(b)
7 Reference diesel + Candidate-9, 10, 11 2 2
8 Reference diesel + Candidate-12 2 2

The water shredding test results in Table 6 indicates that base diesel fuel had no additive which has water soluble components and gave very good phase separation and interface ratings. The doping of components like PIBSI, DAE and developed additive packages at treat rate of 100-1000 ppm in diesel fuel has shown impact in water reaction, interface rating and fuel mixture separation rating. Apart from other additive packages, candidates-4 to candidate-11 showed a similar type of water and diesel separation nature during the test ratings. The remaining additive packages and components affected the interface separation of water and diesel fuel.

Electrical conductivity performance of additive treated diesel fuel: Hydrocarbons are poor conductors of electricity; however, static electricity accumulated during high speed operation can be harmful in presence of ignitable temperatures. Static dissipater is doped in hydrocarbon fuel to improve its conductivity so that the accumulation of static electricity will be nullified. The electrical conductivity of base diesel fuel and developed additive packages doped diesel fuels measured as per ASTM D2624 test method and the results were compiled in Table 7.

Table 7: Electrical conductivity results of additized diesel fuels
S. No. Test fuel detail Electrical conductivity, pS/m (ASTM D2426) at 25°C
1 Reference diesel 3
2 Reference Diesel +A (PIBSI) 15
3 Reference Diesel +B (DAE) 16
4 Reference diesel + Candidate-1 105
5 Reference diesel + Candidate-2 164
6 Reference diesel + Candidate-3 155
7 Reference diesel + Candidate-4 135
8 Reference diesel + Candidate-5 142
9 Reference diesel + Candidate-6 268
10 Reference diesel + Candidate-7 395
11 Reference diesel + Candidate-8 302
12 Reference diesel + Candidate-9 308
13 Reference diesel + Candidate-10 440
14 Reference diesel + Candidate-11 414
15 Reference diesel + Candidate-12 337

The conductivity results of the test diesel fuel with and without doped with developed additive package at treat rates of 100-1000 ppm shown an improved conductivity. The base diesel fuel had 3 pS/m conductivity and it was improved upon addition of components PIBSI and DAE to 15 pS/m and 16 pS/m respectively. Whereas the additive packages prepared using PIBSI and DAE complex and other components C and D showed slight increased conductivity ranges 135 to 164 pS/m. The improvement in conductivity of diesel with doping of candidates 1 to 5 might be due to presence of polar and charged atoms like nitrogen, oxygen and phosphorus. The additive packages/candidate 6 to 12 (especially packages/candidate 10-12) which are having conductivity booster component E showed excellent improvement in conductivity of doped diesel fuels to 268-440 pS/m range. Hence the developed additive packages showed conductivity which is highly essential for low sulphur containing fuels like ultra-low sulphur diesel.

No-harm test of additive treated diesel fuel: The critical physico-chemical properties of the diesel fuel before and after doping of additive packages were evaluated as per standard test methods (ASTM test methods and Indian Standard (IS) 1460-2017 specification of automotive diesel fuel. The results of the no-harm test of doped and un-doped diesel fuels were given in Table 8.

Table 8: No harm evaluation results of additive package doped in diesel (critical properties)
Characteristics Critical properties of test Diesel fuel before doping of additive packages Properties of test Diesel fuel before doping of additive packages @ 300ppm, v/v
Cetane number, Min 51 56
Cetane index, Min 46 55.3
Pour point, Max, deg C
a) Winter
b) Summer 3
15 -6
Copper strip corrosion for 3 h at 50 °C Not worse than No. 1 No. 1
Kinematic viscosity, cSt, at 40 °C 2.0 to 4.5 2. 528
Total contamination, mg/kg, Max 24 3.5
Density at 15 deg C, kg/m3 815-845 825.2
Total sulphur, ppm 10 8
Cold filter plugging point (CFPP), Max, °C
a) Winter
b) Summer 6
18 -3
Oxidation stability, g/m3, Max 25 2.0
PAH, % by mass, Max 11 1.2
Lubricity corrected wear scar diameter (WSD) at 60 deg C, microns, Max. 460 414

The critical physico-chemical properties of additive package doped diesel fuels showed no deviation from the properties of base diesel fuel. The specifications of the diesel fuel were not affected by treating with developed additive package at dosage of 100-1000 ppm.

Performance Screening results:
Fuel efficiency performance:
The tests were conducted at two different speed conditions and corresponding fuel consumption was measured for test fuel doped with candidates 4, 7 and 8 at dosage of 100-1000 ppm range. The fuel efficiency achieved with each candidate in test fuel was measured in comparison with that of test fuel without any additive package. The corresponding results summarized in table 8 (a) as mentioned below.

Table 8 (a). FC Performance of candidates 4, 7 & 8 at select treat rate
S. No. Fuel detail Target Test Speed (km/h) Fuel Efficiency (kmpl) % Improvement
1. Test fuel 40 6.14 -
60 4.42
2. Test fuel + Candidate 4 40 6.35 (+) 3.2%
60 4.55
3. Test fuel + Candidate 7 40 6.38 (+) 4.45%
60 4.65
4. Test fuel + Candidate 8 40 6.42 (+) 5.78%
60 4.75

The test results revealed that candidate 4 doped fuels showed average % improvement in FC by 3.2% at constant speed of 40 km/h and 60 km/l in comparison to test fuel. Candidate 7 doped fuels showed better improvement in FC as compared to Candidate 4 doped fuel with average FC improvement of 4.45% at constant speed of 40 km/h and 60 km/l. Amongst, candidate 8 showed highest average FC improvement of 5.78% at constant speed of 40 km/h and 60 km/l in comparison to candidate 7 and 4.

Emissions study:
The emissions performance of candidates 4, 7 and 8 in diesel fuel were explored for CO and NOx emissions and results were summarized in Table 8 (b).

Table 8 (b). Emission Performance of candidates 4, 7 & 8 at select treat rate
S. No. Fuel detail Parameters (%) change in emission additive treated fuel
1 Test fuel + Candidate 4 CO Change (%) (-) 5.10 %
NOx Change (%) (-) 4.55 %
2 Test fuel + Candidate 7 CO Change (%) (-) 5.22 %
NOx Change (%) (-) 4.74 %
3 Test fuel + Candidate 8 CO Change (%) (-) 5.29 %
NOx Change (%) (-) 4.99 %

Emissions study showed that the additized test fuel helps in reducing the exhaust emissions in terms of CO and NOx gases compared to test fuel. Diesel fuel doped with candidate 4 showed reductions in CO and NOx by 5.10% and 4.55%, respectively. Similarly, diesel fuel doped with candidate 7 showed a reduction of 5.22% and 4.74% of CO and NOx respectively compared to test fuel. Candidate 8 showed higher reduction of 5.29% and 4.99 & in CO and NOx emissions respectively as compared to candidates 4 and 7. Hence, the developed additive packages are highly efficient in improving the fuel combustion and reduction of harmful emissions.

WOT Power and Acceleration performance:
Measurements of wide open throttle (WOT) power and acceleration rates by using diesel fuels with and without doped with Candidate 4, 7 & 8 at different speeds from 0 KM to 80 KM. The results of the WOT power test tabulated in Table 8(c).

Table 8 (c): WOT Power studies using diesel fuel doped with candidates 4, 7 & 8 at select treat rate
S. No. Fuel detail
Speed in kph
WOT Power, kW (%) WOT Power
improvement
1 Test fuel 30 24

Reference Baseline Data

40 32
50 43
60 51
70 62
80 50
2 Test fuel + Candidate 4 30 23 (-) 3.43 %
40 31
50 42
60 48
70 60
80 49
3 Test fuel + Candidate 7 30 25 (+) 0.70 %
40 30
50 42
60 52
70 62
80 49
4 Test fuel + Candidate 8 30 25 (+) 4.19 %
40 32
50 46
60 56
70 63
80 51

Test results revealed that additive doped diesel fuels showed very good improvement in power generation under wide open throttle conditions at different speed conditions. Candidate 7 and candidate 8 doped diesel fuels showed appositive power improvement of 0.70% and 4.19% respectively as compared to base diesel fuel. The developed additive packages Candidates 7 & 8 are capable of improving power of the diesel engine under wide open throttle conditions.

Table 8 (d): Acceleration studies using diesel fuel doped with candidates 4, 7 & 8 at select treat rate
S. No. Fuel detail
Speed in kph Acceleration time in sec. (%) Improvement in Acceleration
1 Test fuel 0 – 30 10

Reference Baseline Data

30 – 40 6
40 – 50 5
50 – 60 4
60 – 70 4
70 – 80 3
2 Test fuel + Candidate 4 0 – 30 11 (+) 12.5 %
30 – 40 6
40 – 50 5
50 – 60 5
60 – 70 5
70 – 80 4
3 Test fuel + Candidate 7 0 – 30 10 (+) 15.625%
30 – 40 8
40 – 50 6
50 – 60 5
60 – 70 4
70 – 80 4
4 Test fuel + Candidate 8 0 – 30 9 (-) 3.125%
30 – 40 6
40 – 50 5
50 – 60 4
60 – 70 4
70 – 80 3

An acceleration study shows the time taken for achieving different speeds with base diesel fuel versus additive doped diesel fuel. The test results indicate that additive Candidate 4 and 7 doped diesel fuels had showed increased time taken for acceleration and achieving speed segments. Whereas Candidate 8 package doped diesel helped in reduction of time taken for achieving corresponding speed segments.

From above results of WOT and acceleration, the best performance of diesel fuel has been achieved by doping developed additive package Candidate 8 at treat rate of 100-1000 ppm power which ultimately leads to achieve speed segments in shorter durations.

Engine Performance:
Further candidate 7 and candidate 8 were doped at 200 ppm concentration separately in diesel fuel and subjected to XUD 9 engine test bench for injectors cleaning efficiency. The results were summarized in Table 9.

Table 9: Engine cleanliness (XUD 9) of optimized combinations/package - Detergency (Peugeot XUD9, CEC-F23-A-01) test
S. No. Test fuel detail Engine XUD 9
Fouling at 0.1mm needle lift
1 Reference fuel 90.6
2 Reference diesel + Candidate-7 @200ppm 34.6
3 Reference diesel + Candidate-8 @200ppm 22.2

The test results again confirmed strongly that Candidate 8 has shown better injectors cleanliness as compared to candidate-7 by reducing fouling from 90.6 of base diesel to 22.2 at 200 ppm dosage.

Hence, proper combination of PIBSI and DAE complex improved the cleanliness and fouling of the diesel engine which further resulted in the achieving fuel economy benefits and emission reduction. , Claims:1. An additive composition for enhancing performance of a low sulphur diesel and middle distillate fuels, wherein, the additive composition comprising:
30-60 wt.% of polyisobutylene succinimide;
5-30 wt.% of a reaction product of C8-C16 dimeric acid and alkylated ether; and
0.1-0.5 wt.% of polysulfone.

2. The additive composition as claimed in claim 1, wherein, the reaction product of C8-C16 dimeric acid and alkylated ether is a non-amine based complex.

3. The additive composition as claimed in claim 1, wherein, the non-amine based complex is a dimeric acid ether (DAE) complex represented by the formula 1:

Formula 1

4. The additive composition as claimed in claim 1, wherein, the additive composition comprises a component selected from a dehazer, a cetane improver, or a combination thereof.

5. The additive composition as claimed in claim 4, wherein, the dehazer is 0.5-4 wt.% and the dehazer is selected from phenolic resins, esters, polyamines, sulphonates, polyol resins and reaction products of alcohol and epoxides and the dehazer is alkoxylated phenol resin.

6. The additive composition as claimed in claim 4, wherein, the cetane improver is 0-50 wt.% and the cetane improver is 2-ethyl hexyl nitrate.

7. The additive composition as claimed in claim 6, wherein, the cetane improver is 25-50 wt.%.

8. The additive composition as claimed in claim 1-7, wherein, 100-1000 ppm of the additive composition is dopped with the low sulphur diesel and middle distillate fuels.

9. A process for preparing the additive composition as claimed in claim 1, wherein, the process comprises:
dissolving polyisobutylene succinimide in an aromatic rich refinery stream at ambient temperature 20-40 oC to produce a first reaction mixture;
preparing a reaction product of C8-C16 dimeric acid and alkylated ether, wherein, the reaction product is a non-amine based complex;
blending 30-60 wt.% of the first reaction mixture, 5-30 wt.% of the said non-amine based complex, and 0.1-0.5 wt.% of polysulfone, wherein, the blending is carried out at an ambient temperature 20-40 oC to get a blend of additive composition; and
stirring the blend of additive composition at 500-1000 rpm by mechanical stirrer at ambient temperature 20-40 oC for a period of 2 hours.

10. The process as claimed in claim 9, wherein, 30-60 wt.% of polyisobutylene succinimide is dissolved in 10-60 wt.% of aromatic rich refinery stream to produce the first reaction mixture.

11. The process as claimed in claim 9, wherein, the non-amine based complex is synthesized by reacting C8-C16 dimeric acid and alkylated ether in a batch reactor in a molar ratio ranging from 0.05:1 to 0.2:1, and then heated in a Dean-Stark apparatus in the presence of an acid, wherein, the non-amine based complex is a dimeric acid ether (DAE) complex represented by the formula 1:

Formula 1

12. The process as claimed in claim 9, wherein, the additive composition further comprises a chemical component selected from a dehazer, a cetane improver, or a combination thereof.

13. The process as claimed in claim 12, wherein, the dehazer is 0.5-4 wt.% and the dehazer is selected from phenolic resins, esters, polyamines, sulphonates, polyol resins and reaction products of alcohol and epoxides and the dehazer is alkoxylated phenolic resin.

14. The process as claimed in claim 12, wherein, the cetane improver is 0-50 wt.% and the cetane improver is 2-ethyl hexyl nitrate.

15. A fuel composition comprising a diesel fuel ranging from 99.90 to 99.98 percent by weight and the additive composition as claimed in claim 1 in range of 0.02 to 0.1 percent by weight.

16. The fuel composition as claimed in claim 15, wherein the diesel fuel has cetane number in the range of 45-51.