Category Archives: Additive blending

Additives for fuel economy: a modern view

Fuel additives. A private car doesn’t just give you the pleasure of a quick and comfortable ride, but it also requires everyday expenses for maintenance, and the biggest expense is the cost of fuel. The question of saving on fuel is very relevant.

The Internet offers many tips. One of the ways to save fuel is to use special additives. But experience shows that these additives have both advantages and disadvantages. Let’s try to understand where the additives can be used, and where they are  better avoided.

The advantages and disadvantages depend on the active ingredients of the additives and their main characteristics.

Tetraethyl reduces smoke emissions, reduces engine noise and has a positive impact on engine performance. Tetraethyl additives are often added to gasoline to improve gasoline quality. The main drawback of these additives is evaporation of lead compounds hazardous health and potentially deadly.

Fuel additives. Adding alcohol into the fuel can increase the octane number and improve the flammability index. The main disadvantage of alcohol application is its degrading effect on seals and rubber or plastic parts.

Naphthalene, even in relatively small amounts, increases the quality of fuel and thus reduces its consumption. However, the use of naphthalene additives lead to the formation of deposits in the engine.

Acetone can both reduce fuel consumption and increase it. It all depends on the selected dosage.

Manganese additives have good performance, but they increase smoke opacity, which affects the spark plugs.

Ferrocene additives lead to the formation of sludge, which is very dangerous for moving mechanisms.

Additives containing monomethylamine and methyl tertiary butyl ether can also help save fuel. But their side effect is corrosive destruction of metal surfaces. With increased detonation, these additives can also cause foaming of fuel and formation of sludge.

Multifunctional Cleaning Additives

Multifunctional Cleaning Additives. Modern oil refining cannot directly produce diesel fuel which can also clean the engine and the fuel system in the process of operation. Engine operation can be disrupted even by a small amount of desposits, degrading its efficiency and economy.

That is why mutifunction cleaning additives were developed. They improve performance and environmental parameters of diesel fuel. This type of additive reduces fuel consumption by 3-5%, while decreasing exhaust toxicity by 10-15%. In combination, this reduces the risk of premature replacement of post-combustion catalysts and soot filters. However, this is not the primary objective of using the cleaning additives. Their main purpose is to ensure even spraying of fuel by preventing deposits on the spraying nozzles.

Although the deposits in diesel engines are similar in composition and structure to those formed in gasoline engines, they are far more dangerous. This is due to the possible disruption of the entire high pressure fuel system operation.

The modern diesel vehicles are mostly equipped with the Common-rail injection system. It improves the efficiency of the multifunctional cleaning additives. The main features of the Common-rail engines are:

  • fuel supply pressure is 2500 atm, compared to just 100-400 atm in a regular engine;
  • fuel is injected into the combustion chamber in two portions. The small portion initiates combustion. This makes the combustion even, and fuel economy reaches 20%.

The main component of cleaning additives is cyclic amines, with the molecular weight of the alkyl radical above 1000. They have high thermal stability and therefore are well suited for diesel fuel. The solvents are volatile hydrocarbon fractions which easily solve the active components of the additives, improving dosage.

A cleaning additive is usually a package of components, including the main component (thermally stable surfactant), corrosion inhibitor, antioxidant, demulsifier and anti-foaming additive. If necessary, the additive may also contain solvent, friction modifier and anti-wear components.

The efficiency of the cleaning is evaluated by the nozzle gumming rate.

Thus, the test is run by BASF. The cleaning performance of basic fuel and fuel with additives is compared on a Peugeot XUD9 A/L engine (1.9 l, 4 tacts, 4 cylinders) according to the most commonly used 10 hour test method according to the CEC-F23-A-01 standard on the motor bench in Ludwigshafen, Germany. The standard minimum, according to the world fuel charter, is 85% (limitation of the flow with fuel needle raised 0.1 mm).

Cleaning additives operate just as any other surfactant: the bind the molecules on the surface to their hydrophilic part. The polar part of the molecules are oriented towards the fuel.

How Depressor Additives Operate

Depressor Additives. The first suggestions about the mechanism in which depressor additives affect fuel were first made in the 1930s-1950s. The modern theory explains the efficiency of the depressors by the presence of n-akanes in the fuel. These components crystallize when the temperature drops. These crystals cause clouding of diesel fuel. The crystals grow in size. At a certain point, a spacial framework forms. The fuel loses fluidity and cannot be pumped through filters and piping.

If a pour point depressor is mixed into the fuel, the process of crystal formation changes. The additive accumulates on the surface of the crystals, preventing their further growth. However, the exact nature of the process is not entirely known. There are two competing theories. One suggests that co-crystallization of paraffin and the additive occurs, integrating the depressor molecule (its neutral part) in the crystal. The polar part of the molecule remains outside the crystal and prevents other paraffin molecules from attaching to the crystal. The other theory stipulates that the polar part of the molecule is adsorbed on the surface of the crystal, while the neutral part remains outside and isolates the crystal preventing their flocculation and formation of a larger structure.

Both theories confirm the interaction of the depressor additive with the growing crystal. Therefore, the depressor only acts when crystals start to form. This is why this type of additives has no effect on fuel cloud point. Without the additive, paraffin crystal size grows to tens of microns. When the additive is used, crystal size is reduced by an order of magnitude.

With time, depressor additives which can lower the cloud point of the fuel have been developed. Their principle of operation involves integration of polymer into paraffins with the subsequent formation of accosiations, which is possible due to similar solubility of paraffins and the additive. The additive in the paraffins prevents clouding, delays crystallization and reduces the cloud point.

Depressant and Depressant-Dispersion Additives

Depressant-Dispersion Additives. The low temperature properties of diesel fuel have always been a focus of the oil refining industry and motorists alike. They are especially important in cold climates, where the demand for arctic and winter diesel fuel is high.

The main method of adjusting low temperature properties of diesel is the use of special depressor and depressor-dispersion additives. This approach is considered the most economical, and it increases oil processing efficiency and flexibility.

Traditional pour point depressor additives reduce the pour point and the filter point of diesel. In most cases, these additives are injected into fuel at refineries. However, the end used can also use depressors to improve fuel quality.

The development of depressor additives for fuel began forty years ago, while the same additives for oil were first developed 80 years ago. So why did they come into use relatively late? The main reason is that these additives do reduce the pour point, but have little effect on cloud point. For a long time, the latter was considered the main parameter of diesel usability in the cold seasons. Depressor additives do not prevent formation of initial n-alkane crystals, but limit their growth. The fact that filtration temperature is the main parameter for the use of diesel fuel in winter became the beginning of active development of depressor additives.

At this time, the most commonly used depressors are:

  • ethylene copolymers with polar monomers (ethylene polymer with vinyl acetate, ethylene copolymer with acrylic acid ether);
  • alkyl methacrylate and polyalkyl methacrylate copolymers;
  • polyolefin type copolymers (ethylene-propylene and ethylene-propylene-diene copolymers and the products of their destruction, α-olefin copolymers and modified polyolefins);
  • maleic anhydride copolymers;
  • polymers of vinyl acetate with fumaric acid;
  • aromatic hydrocarbon copolymers, which consist of two or three monomeres;
  • non-polymer chemicals (alkyl naphthalene; polyacid ethers and alcohols, amides containing long alkyles).

Most depressor additives are polymers of ethylene with vinyl acetate.

In long storage, small crystals precipitate in diesel fuel. The fuel then consists of two visible layers: clear at the top and clouded at the bottom. It is at the bottom where small paraffin crystals deposit. Both layers are quite fluid, but taking fuel from the top layer does significantly complicate engine start and running, while taking fuel from the bottom layer means the engine will not start at all.

Pour point depressors cannot prevent fuel stratification, so dispersing additives are also used. This is a relatively new type of additive, first introduced by Exxon Chem in 1989. Disperser additives prevent fuel stratification in cold storage. Good paraffin dispersers are high molecular amides and imides of carboxylic acids, quaternary ammonium salts  and polyalkylene polyamine type amines.

A depressor-dispersion additive is a mix of components each improving a certain aspect of the fuel. Thus, the depressor determines the filtration and cloud point, the disperser prevent flocculation of paraffins at low temperatures, preserving fuel stability. Therefore, a depressor-disperser additive has two functions:

  • improvement of diesel fuel cold performance;
  • improvement of diesel stability at low temperature.

A specific additive is selected for each specific fuel type. This is the only way to mutually amplify the performance of each component.

A basic criteria for the efficiency of a depressor-disperser additive is the sedimentation stability of fuel at temperatures below the cloud point.

Antiwear Additives

Antiwear Additives. Fuel system parts wear down with time, so antiwear additives are mixed into diesel fuel.

Originally, diesel fuel has certain anti-wear properties due to the presence of naphthenic hydrocarbons. Many sulfuric compounds in diesel fuel also have such properties (benzothiophenes and sulfides). However, environmental considerations dictate limitations of sulfur content, making it impossible to ensure the required degree of wear protection by sulfur only. Special additives are required.

The most common element of such additives is carboxylic acid. These are usually fatty acids of tall oil and their fractions, which are obtained from wood. However, the acid contains resinous acids, which degrade stability and performance of diesel. Beside the fatty acids, additives also contain corrosion inhibitor and a demulsifier. Alkyl salicylic acids are also quite efficient.

Antiwear additives create a layer on the surface of metal, distributing the loads more evenly and thus reducing the possible wear. The layer contains products of mechanical and chemical transformation of the additive. The lubricity of the additives is due to adsorption on the metal surface as well as chemical activity of the additive to the material of the friction parts.

Additives by BASF, Clariant, Lubrizol are based on tall oil acids with various supplementary components, additives by Infinеum are based on complex esters of mono and diglycerol and fatty acids with С12-С18 chains.

Anticorrosion Additives

Anticorrosion Additives. Anticorrosion additives are special substances mixed with fuel to give it protective properties. The result is the formation of a protective film on metal surfaces, preventing corrosion.

There are two types of anticorrosion additives. The first type includes alkyl sulfonate and nitrate oil. These promote the creation of a strong chemisorption layer on the protected surface, isolating air and moisture. The second type are the salts of organic acids and esters, which reduce the interfacial tension on the boundary between fuel and water and improve the affinity of metal and fuel.

The corrosive properties of diesel fuel are determined by the presence of chemicals, which cause electrochemical and chemical corrosion of fuel system components. Fuel can also become contaminated by the products of corrosion, reducing  system throughput, as well as lubricity of the fuel.

In standard diesel fuel the amount of contaminants which may cause corrosion of metal parts is strictly limited. Such contaminants as bases, water-soluble acids and hydrogen sulfide are prohibited.

Electrochemical corrosion is usually caused by water and electrolytes. When oil products are shipped from the refinery, their copper strip test must be negative. This is only possible in the absence of hydrogen sulfide or free sulfur or their presence in such concentrations which cause no chemical corrosion of metal surfaces in the fuel system.

Modern oil refining technologies do not involve separate mixing of anticorrosion additives into diesel fuel. This is due to the fact that such additives are already present in lubricating and multifunctional additives.

Cetane Improver Additives

Cetane Improver Additives. One of the ways to improve diesel fuel cetane number is to mix it with cetane improver additives. These additives reduce ignition lag of the fuel mixture.

There are two types of cetane improver additives:

  • alkyd
  • peroxide.

The additives cause homolytic molecule breaking and formation of free radicals, which provoke fuel ignition. The additives are only effective in the first stages of combustion.

Adding of up to 1% cetane improver raises the cetane number by 10-12 units. Previously, alkyl nitrates were used for this purpose, but their efficiency was accompanied by significant drawbacks, such as corrosive properties, reduction of wear-protective additive efficiency and lubricity of the fuel. Storage of fuel with nitrate additives for over six months reduces additive concentration due to its oxidation reactions with hydrocarbons, dropping the cetane number by 4-6. The above limitations are why research into the development of cetane improvers is ongoing.

Organic compounds based on peroxides, such as diaryl and dialkyl peroxides, are of particular interest. Some of the advantages of these substances is stability in storage and at higher temperatures, as well as stability in contact with water and other materials present in diesel fuel in the market.

Today, the most popular peroxide is ditertiary butyl peroxide. The general advantages of peroxides are compatibility with antiwear additives, lower toxicity and explosion hazard, as well as no corrosion effects. Diesel fuel in the United States are expected to be produced with peroxides, due to the stricter requirements to nitric compound content in diesel fuel.

Additives for Fuel Economy

In our time, the possession of a private vehicle is costly, especially if it does not participate in any business processes.  The main item of expenditure is not even wear and replacement of various parts, but high prices for fuel.  The situation is complicated by the fact that not all engines consume fuel sparingly.  Therefore, car owners have to look for some method to save their money. One of them is using special fuel additives.

Generally speaking, fuel additives have both advantages and disadvantages.  The effectiveness of additives is caused mainly by the active substances that they contain.  Most additives perform not one, but several functions; but their main function is to increase octane number of gasoline and cetane number of diesel fuel.  Active constituents of these products include:

  • Tetraethyl lead.  This substance reduces smokiness, lowers engine noise and improves the performance.  The main disadvantage is the presence of organic lead compounds that have a negative impact on the human body;
  • Alcohols increase gasoline octane number and improve its combustibility.  If you use alcohol in order to economize fuel, you should not forget that it has a negative effect on gaskets and other rubber (plastic) parts;
  • Naphthalene improves the quality of gasoline, but it contributes to the formation of soot on the walls of the crankcase;
  • Adding acetone can significantly reduce fuel consumption, but an overdose gives the opposite effect;
  • Manganese additives have positive characteristics, but at the same time they also increase smoke emission, which reduces the service life of spark plugs;
  • Combustion products of ferric iron additives form sediment inside of an engine, which is very dangerous for all moving mechanisms.

Virtually any of these substances and can be added to diesel fuel.  But in this case all side effects of additives are stronger.  Therefore, comprehensive means designed to reduce fuel consumption, may contain other components in order to mitigate their harmful effects.

Selection of additives is best done on the basis of practical experience of fellow car owners who you can trust.  When using personal light vehicles, mixing of additives does not cause much difficulty.  But what about large transport organizations, with a large turnover of fuel for refilling?  Manual mixing is not an option, since it requires too much time.  Furthermore, it cannot provide proper fuel homogenization after adding additives.

In this case, it is recommended to use special equipment for mixing, such as the USB-type plant by GlobeCore.

The USB-type plant for mixing and dissolution of any liquid in-line is intended for mixing of two to five individual components, in particular, low-octane gasoline with additives and other components.  When using conventional methods of blending known today, mixed fuel tends to separate.

An important feature of the system is that the use of injection method and hydrodynamic shock can increase the octane (cetane) number of fuel, and the breakdown of the resulting product does not occur for at least 180 days.

Additives for Engine Oils

One of the major tasks of motor oil is to neutralize acidic products formed in an engine cylinder.  That is why it must have sufficient alkalinity, which ranges from 2-3 mg KOH/g for the oils used in gasoline engines, and up to 70-100 mg KOH/g for cylinder oils.

Engine operation involves a change in quality characteristics of motor oils due to oxidation processes.  Special antioxidant additives are used to prevent these processes.  They contribute to the preservation of detergency and dispersing property of motor oils for a long time, thus keeping the engine clean.

Corrosion is also quite a dangerous threat for motors.  For its prevention, anticorrosion additives, which are not subject to water washout, are added to engine oils.  They form special protective films that protect metal surfaces from corrosion.

Beside good viscosity, oil must also feature good lubricating properties that prevent various defects on parts surfaces and reduce their wear.

Different surfactants are often used as anti-wear additives.  Under certain conditions they can come into contact with metal and form protective film on its surface.  These films reduce the intensity of engine wear under unfavorable conditions (increased friction), and prevent occurrence of protruding burrs and adhesion under heavy loads.

Fuel saving additives

Additives are special substances added to gasoline to improve it. There is usually an additive for each type of fuel properties. This article deals with fuel economy additives.

The product may come in the form of liquid of capsules. Fuel saving additives include several active components increasing the octane number. Some of the widely used additives are lead tetraethyl, alcohols, naphthalene, acetone, manganese compounds etc.

lead tetraethyl reduces smoke and noise. Alcohols increase octane number and improve combustion. Naphthalene improves quality of the fuel and improves mileage.

Special equipment should be used in oil refining to mix additives with fuel. Most of the modern methods of mixing do not ensure the required homogeneity and stability of the oil product. This results in stratification and separation in storage.

GlobeCore’s USB units are free from this drawback. These units can mix up to five liquid components. The process occurs in the hydrodynamic mixer, for all components simultaneously, with output to general blending collector, according to blend formula.

The design of the USB units allows the use of injection method and hydrodynamic shock to increase the octane number of gasoline without separation of the blend for at least 180 days.

Some of the advantages of GlobeCore technologies are:

  • precise portioning;
  • fast mixing;
  • no need to use mixing tanks for product homogenization.

GlobeCore’s USB unit is a reliable product for oil refineries and filling stations interested in improving the quality of their gasoline.