EP0078249A1 - Additive with a combustion promoting and soot inhibiting activity for furnace oils, diesel fuels and other liquid combustion and fuel substances, as well as the aforesaid liquid combustion and fuel substances - Google Patents

Abstract

1. Additive with a combustion-promoting and soot-inhibiting action for fuel oils, diesel motor fuels and other liquid burner fuels and motor fuels, especially those having a final boiling point above 300 C under normal pressure, the additive containing one or more oil-soluble and/or oil-dispersible compounds, which are active in catalysing combustion, of transition metals, such as iron, manganese, molybdenum, cobalt, nickel or copper, and/or alkaline earth metals and one or more inhibitors of polymerization and oxidation of hydrocarbons, characterized in that the oil-soluble and/or oil-dispersible compounds, which are active in catalysing combustion, of alkaline earth metals are those of calcium, strontium and/or barium and that the inhibitor present is an oxidation and polymerization inhibitor based on sterically hindered, heat-stable alkylphenols of an average molecular weight of 280 or based on N-phenylnaphthylamine (molecular weight 219), the inhibitor having such a heat stability that, as a result of its vapour pressure and/or its decomposition temperature, it can be exposed at least for short periods under normal pressure to temperatures of 300 C and higher without loss of its polymerization-inhibiting action.

Description

The invention relates to an additive with a combustion-promoting and soot-inhibiting effect on heating oils, diesel fuels and other liquid fuels, in particular with a boiling point at normal pressure above 300 ° C., and liquid fuels with such an additive.

Due to the increase in crude oil prices in the years since 1973, the best possible combustion and utilization of the heat content of heating oils and diesel fuels became an economic necessity. Environmental protection has also become an increasingly important concern of the population. The avoidance of soot and smoke formation during combustion processes with the least possible excess of air meets both of the above requirements, namely increasing economic efficiency and avoiding environmental damage and nuisance.

Excess air is known to be one of the most important factors affecting the thermal efficiency of a combustion. plant influenced. The more excess air is unnecessarily heated, the greater the waste heat losses. Through the minimie The loss of usable heat is reduced by the excess air, but at the same time the tendency towards increased soot formation is increased. This formation of incompletely burned, carbon-enriched solid particles affects the heat transfer on the transfer surfaces and the dynamics of the exhaust system.

The soot deposits, which due to their large surface area also adsorb acidic components, especially sulfuric acid, also cause increased corrosion and thus material losses in the exhaust system of such systems.

The deterioration of the heat yield in the case of soot formation increases over time, as the formation of deposits, corrosion, etc. increases continuously. A study of over 100,000 burner units in a large city has shown that the decrease in operating efficiency during an heating period averaged 10 relative percent. Ongoing cleaning of such heating systems would therefore be necessary, which is not only expensive, but also does not always lead to the desired success. Wear of the burners and weather conditions (storms, low-pressure periods, etc.) mean that the soot formation from incomplete combustion can very quickly resume even after cleaning. It has therefore been intensively investigated, particularly in recent years, what possibilities exist to achieve a more complete combustion without unnecessary excess air using chemical additives.

When burning heating oils and diesel fuels, the oil is usually sprayed into the combustion zone in the form of finely divided droplets (except for small gasification burners). The individual droplets are quickly heated up in this hot zone and at least partially evaporated. Around the droplets, these vaporized hydrocarbons mix with the atmospheric oxygen and maintain the flame formation, whereby the corresponding combustion products are formed. While this Droplets migrate through the combustion zone, their size continuously decreases until the volatile constituents have evaporated (and burned). Depending on the composition of the individual fuels, a small or large remnant of non-volatile constituents remains, which consist of high-polymer organic compounds, carbon and impurities. When hydrocarbons are heated strongly, they crack, whereby larger molecules are broken down into smaller ones. Lighter hydrocarbons, hydrogen etc., as well as reactive unsaturated compounds, which can polymerize further, are formed here. In contrast to hydrogen and light hydrocarbons, these tarry residues up to carbon burn much more heavily and often incompletely. Due to the slower oxidation of these residues by atmospheric oxygen, the time in the hot combustion zone is not sufficient for complete, residue-free combustion.

The course of the combustion process is further delayed by the masking effect which the oil mist has on the heat transfer and by the reduction in the oxygen content in the immediate vicinity of the burning oil droplets. During the period in which the heating of the oil droplets and evaporation of the light parts takes place, the polymerization and pyrolysis in the remaining oil part is promoted accordingly.

The course of the chemical reactions described above is greatly accelerated at temperatures of over 300 ° C., so that the fuel components with an overlying boiling range are more exposed to such polymerization during combustion. For economic reasons as well as for reasons of availability, extra-light heating oils and diesel fuels are cut in the production process in such a way that the parts boiling above 300 ° C. under normal pressure become ever larger. If you previously had a boiling point of 320/350 ° C for the above products depending on the seasonal quality, this is often already the case at 380 ° C. Due to the rapid development in the construction and use of conversion systems for converting residues into lighter products, the proportion of unsaturated and thus also thermally unstable molecules in the middle distillates customary on the market continues to increase. These components, which tend to polymerize, therefore also form a source of higher soot formation.

Both tendencies, namely a higher boiling point and more unsaturated components, which will increase further in the next few years, complicate the complete combustion with the air volumes that are as close as possible to stoichiometric. To remedy this situation, chemical additives have been investigated and investigated for a long time in order to catalytically favor the combustion of heating oils and diesel fuels, i.e. to achieve complete combustion in the shortest possible time or at lower temperatures.

It is known that organometallic, organic and inorganic compounds can serve as combustion-promoting additives. Thus, organometallic compounds have proven to be favorable as combustion catalysts of hydrocarbons in certain cases, since on the one hand they can be finely divided into solution / dispersion in oil-soluble / oil-dispersible form and on the other hand compounds of transition and / or alkaline earth metals have shown good effects as combustion catalysts.

Gas phase catalysis to split hydrogen and water molecules onto hydrogen atoms is a hypothesis of the effect of alkaline earths (calcium, strontium, barium) and probably also of molybdenum as a combustion promoter. The latter react rapidly with the water vapor present to form hydroxide radicals, which react with the carbon of the soot. The transition metals, on the other hand, should act as metal oxides and accelerate the formation of CO and CO ₂ from carbon in the already cooler zone of the combustion, where there is also a greater supply of oxygen. It is known and measurable that the Combustion of carbon (soot) can take place at lower temperatures if catalysts of the transition metals are present in a suitable form. The simultaneous use of alkaline earth and transition metals has proven to be advantageous during combustion, since the two groups can develop their catalytic effect one after the other in the hotter zone and then again colder but more oxygen-rich.

The addition of purely organic compounds (without metal content) has also been investigated for a long time, but when added in the usual small amounts of additives has not brought about any significant combustion-promoting effects. For example, alcohols, phenols, esters, low aromatics, hydrazine derivatives, organic amines, naphthenic and carboxylic acids were tested without changing the combustion or influencing smoke formation.

Another problem with the use of heating oils and diesel fuels (from petroleum or synthetic oils) is the stabilization thereof during storage. The aim is to ensure that the application properties of these hydrocarbons do not deteriorate over time as a result of oxidation and polymerization. For this purpose, inhibitors can be added, which are widely used in practice especially in the case of carburetor fuels and lubricating oils, but can also be used in heating oils and diesel fuels, see below.

A particular storage problem arises in products which contain organometallic compounds of the transition metals, such as, in particular, copper, manganese, cobalt, nickel and iron compounds, since these accelerate aging particularly in the case of unsaturated hydrocarbons. It has also been shown that aging deterioration can occur even in the presence of these metals in complex form, such as, for example, when middle distillates and heavy fuel oils are added with methylcyclopentadienyl manganese tricarbonyl (abbreviated NMT) or dicyclopenta dienyl iron (ferrocene). A well-known short method for determining the stability of middle distillates is the accelerated stability test (also EDM diesel test, Union Pacific or Nalco and Du Pont test) at 149 ° C (300 ° Fahrenheit). This test determines the relative stability of middle distillates under short-term aging conditions at high temperature and ingress of air. The procedure consists in aging the distillate sample at 149 ° C (300 ° Fahrenheit) for 90 minutes with the entry of air and filtering off the residues formed. Depending on the thickness and color, the filter covering is rated with numbers from 1 to 20 and provides a comparison of the aging stability of the distillates tested. The lower the rating number, the more stable the distillate, whereby a number up to a maximum of 7 is usually considered to be satisfactory. In addition to the filter evaluation, the color of the distillate is also determined according to ASIM (D - 1500 - 58 T) before and after aging, which also allows a relative evaluation of the stability.

Use of this test showed significant increases in the rating numbers after aging when copper, manganese, cobalt, nickel and iron compounds (such as naphthenates, octoates, sulfonates, but also complex compounds) were added to the middle distillates. There were increases of several points - depending on the composition of the middle distillate - with a content of the above metals of 10 - 25 parts per million parts of hydrocarbon (ppm).

In practice, when excess burner oil is returned from the burner to the tank, these fuels are exposed to a higher than usual storage temperature, which further increases and often accelerates the tendency to polymerize and oxidize and thus causes a deterioration in the quality of the heating oils.

It can therefore be seen that, according to the prior art, combustion can be improved by catalytically active oil-soluble and / or oil-dispersible metal compounds. but at the same time this is associated with the disadvantage of increased aging of the heating oils and diesel fuels treated with it. In many cases, the economic advantage of promoting combustion is thereby nullified and converted into even greater disadvantages, such as burner and line laying.

Polymerization and oxidation inhibitors are known per se and are used in a wide variety of products such as e.g. Food, cosmetics, plastics, rubber and also used in mineral oil derivatives. It has been shown that these ingredients for promoting combustion are largely ineffective in the products in question here. In the case of mineral oil distillates and residual oils, specific inhibitors have also been used to improve storage stability. All of these known oxidation and polymerization inhibitors have hitherto been used to stabilize the products at customary storage temperatures. A temperature load of these heating oil and diesel fuel inhibitors of over 150 ° C has not been provided.

The object of the invention is to provide an additive for heating oils and diesel fuels and other liquid fuels, which hinders the polymerization at temperatures of in particular 300 ° C. and above. As already stated, there is a sharp increase in the reaction rate at temperatures of over 300 ° C., the tendency of unsaturated hydrocarbons to polymerize being significantly further favored by the presence of metal compounds, in particular the transition group. It is therefore of particular interest to hinder precisely these high-temperature reactions, since they lead to the increased formation of unburned carbon and high-molecular tarry hydrocarbon compounds (which usually also contain polycyclic aromatics), which can have cancerogenic properties.

In order to be able to exert a hindrance to polymerization even at temperatures of 300 ° C and above, the inhibitors did not decompose or evaporate at this temperature at normal pressure (boiling point or sublimation above 300 ° C). As a result, the antioxidants and antipolymerizers which are already known for the stabilization of heating oils and distillates cannot be used for the present purposes since they do not meet these conditions. For example, 2,4-dimethyl-6-tert-butylphenol, 2,6-di-tert-butyl-p-cresol (BHT), sterically hindered xylenols and trimethylphenols, butylated hydroxyanisoles (BHA) are often used to stabilize the storage of light and middle distillates. , Mono-tert-butylhydroquinone (TBHQ), para-cresols and aromatic amines are used. These inhibitors are only suitable for temperature ranges up to approximately 150 ° C.

Oxidation and polymerization inhibitors, which are also intended for higher temperature loads, have already been used to stabilize plastics, lubricating oils and asphalts. An anti-aging agent known for heat resistant rubber articles is e.g. the zinc salt of 2-mercapto-benzimidazole. However, this inhibitor is also decomposed at temperatures of 300 ° C and is not suitable for higher temperatures.

The additive according to the invention is primarily characterized in that it comprises one or more oil-soluble and / or dispersible compounds of transition metals and / or alkaline earths and one or more inhibitors against polymerization and oxidation of hydrocarbons, these inhibitors being heat-stable and due to their vapor pressure and / or their decomposition temperature can be exposed to temperatures of 300 ^P C and above at normal pressure for at least a short time without losing their polymerization-inhibiting effect. The liquid fuel and fuel according to the invention is characterized in that the metal content is 0.1 to 1000 parts by weight per million parts by weight of the fuels mentioned. Further preferred embodiments of the invention are characterized in the remaining subclaims.

The addition according to the invention on the one hand improves the shelf life of the fuels mentioned and on the other hand also effectively inhibits the polymerizations described above, which are accelerated enormously at temperatures of over 300 ° C. At the same time, the advantage of more complete combustion is achieved even with less air excess. This is all the more important since the aforementioned trend towards using heavier cuts and products from conversion plants, in particular catalytic and thermal crackers and coking plants, in heating oils and diesel fuels is constantly increasing.

The polymerization inhibitors used according to the present invention are also effective at temperatures above 300 ° C. With such heat effects, they are not only thermally stable as long as the hydrocarbon droplet to be burned travels through the combustion zone, but they also advantageously provide effective protection against oxidation for heating oils and diesel fuels at the normal normal storage temperatures. Such inhibitors are e.g. high-boiling phenols with longer-chain, sterically hindering alkyl groups, e.g. Nonyls. Also higher molecular weight organic amine compounds such as e.g. N-phenyl-2-naphthylamine, meet the present condition. In practice, of course, any carcinogenic effects must always be observed and the additives that are harmful to health must be preferred, although heating oils and diesel fuels should normally not come into contact with the skin or with food.

Selected metal (eg zinc, molybdenum) alkyl dithiophosphates, dithiocarbamates and imidazoles, as well as other metal compounds, can also meet the thermal stability requirements as such suitable inhibitors. Inhibitors based on highly alkylated or polymeric sterically hindered phenol compounds have proven to be particularly economical and advantageously do not result in any increases in pollutants by SO ₂ / SO ₃ or nitrogen oxides, phosphorus compounds, etc. in the exhaust gas.

The following examples are intended to further illustrate the present invention.

example 1

Dark heating oil with the analysis data below is heated with and without additives according to this invention in a Pieren boiler with Olymp 8D and Unitherm mat 5 burners.

When this non-additized heating oil was burned with the Olymp burner, the soot number according to Bacharach was 3 with an air number of 1.4. A soot number of 3.3 was measured for the Unitherm burner with the same air ratio. The boiler efficiency, measured with the heat quantity measuring device, was 76.0 - 76.3% and 75.8 - 76.2% for the burners mentioned.

By adding 1 part by weight of an additive of the following composition to 1,000 parts by weight of this dark heating oil, the soot number for the Olymp burner improved to 1.5 for the same air ratio (1.4) and even to 1.2 for the Unitherm burner. The boiler efficiency of the additive heating oil was found to be 79.5 - 80.0% (Olymp burner) and 82.0 - 83.0% (Unitherm burner) when using the same heat measuring device. The average gain in efficiency was 3.6 and 6.5% due to the additives.

The composition of the additive according to the invention was:

Example 2

Extra-light, light heating oil with the following analysis data is, with and without additives, according to the invention in a Voßmann, Duo Paro-1a-E, steel boiler with a Weishaupt oil burner type WL 2/3 with a heat output of max. 81 kW burned.

When this middle distillate was burned without an additive, a soot number according to Bacharach of 2.9 - 3 was obtained with an exhaust gas content of 12.3 - 12.4% CO ₂ , 16.4% CO ₂ + O _{2 '} under 0.01% CO. 2 found. At 12.6% CO ₂ , 16.1 - 16.2% CO ₂ + O ₂ , below 0.01% CO in the flue gases, the soot number was 4.

By adding an additive of the following composition in the ratio of 1 part by weight of addition to 2 500 parts by weight of extra-light heating oil, the soot number at 12.3 - 12.4% CO ₂ and 16.4% CO ₂ + O ₂ , under 0.01% CO in the exhaust gas reduced to an average of 1.06, ie improved by 2 points. At 12.6% CO ₂ , 16.1 - 16.2% CO ₂ + O ₂ , below 0.01% CO in the flue gas, the average number of soot was 1.63, ie one Improvement of approximately 2.4 points.

The additive included:

Example 3

Gas oil with the following analysis data was burned under the conditions of Example 2 with and without an additive.

This gas oil complies with the European regulations for use as diesel fuel.

The following additives according to the invention were added to the gas oil, alkylated phenol according to Examples 1 and 2, sterically hindered tert-nonyl-cresols, N-phenyl-2-naphthylamines and other highly evaporative polymerization and oxidation inhibitors with a boiling point (boiling range) of over 300 ⁹ C at normal pressure were included. The finished additive was added with 1 part by weight of addition to 2,000 parts by weight of gas oil. The following improvements in the number of carbon blacks were achieved for the following metal contents in the additive according to the invention:

It can be clearly seen that all additive combinations significantly favor the more complete combustion and the original soot numbers of 3-4 are drastically - partly

below 1 - could be reduced. In this way, lower-soot combustion conditions can be achieved even with a reduced excess of air with a corresponding improvement in the thermal efficiency.

Example 4

Dieses Coker-Gasöl (ohne Additiv) wurde dem eingangs beschriebenen beschleunigten Alterungstext bei 149°C (300° Fahrenheit) 90 Minuten unterworfen. Die Farbzahl ergab 9. Bei Anwesenheit von Ferrocen in einer solchen Menge, daß der Fe-Gehalt im Produkt 15 ppm betrug, wurde bei gleicher beschleunigter Alterung die Farbzahl auf 14, bei Anwesenheit von 15 ppm Mangan (aus MMT) auf 16 und bei 15 ppm Kupfer (aus Kupfernaphtenat) auf 18 erhöht.The polymerization and oxidation inhibitors according to the invention with a temperature resistance of over 300 ° C. also give very good anti-aging effects at lower (storage) temperatures. A coker gas oil with the following analysis data was used:

This coker gas oil (without additive) was subjected to the accelerated aging text described above at 149 ° C (300 ° Fahrenheit) for 90 minutes. The color number was 9. In the presence of ferrocene in such an amount that the Fe content in the product was 15 ppm, the color number became 14 with the same accelerated aging, to 16 in the presence of 15 ppm manganese (from MMT) and in 15 ppm copper (from copper naphtenate) increased to 18.

By adding additives according to the invention, each with 3% by weight of iron (one from ferrocene, the other time from iron naphtenate) and 6% by weight of alkylated phenols according to Examples 1 and 2 as inhibitors, the remainder to 100% heavy petroleum cut, in a ratio of 1% by weight Part of the additive per 1,000 parts by weight of coker gas oil was again adjusted to an Fe content of 15 ppm in the product for the comparison test with the additive according to the invention. The same accelerated aging test as before gave color numbers of 3-4 for these additive coker gas oils.

When the aging conditions were tightened to double the operating time of 180 minutes at 149 ° C (300 ° Fahrenheit), color numbers of 5 were found. It was found that by using the additives according to the invention, the desired aging number of less than 7 could be achieved even with middle distillates from thermal conversion.

Example 5

The non-additive coker gas oil described in Example 4 was used in trucks as diesel fuel. Practical operation of these motor vehicles was not possible with the product, however, as these diesel engines showed very strong and unreasonable smoke emissions not only at full load, but also during normal operation, which may be due to the high content of aromatics and unsaturated hydrocarbons.

An additive according to the invention, consisting of 15% by weight of MMT, 20% by weight of alkylated phenols according to Examples 1 and 2 and 65% by weight of paraffin-based petroleum, was used in the ratio of 1 part by weight of additive to 700 parts by weight of coker gas oil admitted. The manganese content was 52.8 ppm, of the high-boiling alkylated phenols 28.6 ppm in the coker gas oil. The smoke development of the diesel engines operated with it was drastically reduced and averaged 20 Hartridge units. The residues in the combustion cylinders of the engines operated with it were negligible even after several months of use and the injection in excellent condition.

Example 6

Residual heating oils containing heavy parts from visbreakers had the following analysis data:

The low-soot combustion of this additive-free residue oil was only possible with a very large excess of air and precisely adjustable burners, mostly with water vapor injection.

This heavy residual oil was treated with 100 ppm manganese (from manganese naphtenate) and silicon dioxide obtained by flame hydrolysis of silicon tetrachloride with a BET surface area of approx. 200 (Aerosil 200) in an amount of 50 ppm plus aluminum oxide with a BET surface area of approx. 100 ( Aluminum oxide-C) also added in an amount of 50 ppm.

The low-soot combustion in normal industrial burners was possible without difficulty at air ratios of 1.2 and below if the above-added residual oil was used.

The silanol groups on the surface of the highly disperse silicic acid as well as analogous aluminum hydroxides in the case of the highly disperse aluminum oxide are likely to contribute to the polymerization inhibition Temperatures above 300 ° C may be responsible, while the manganese may have catalytically favored the combustion of carbon or carbon-enriched particles in the colder zone of the combustion. It shows that the inorganic polymerization inhibitors according to the invention can also be used advantageously for the present purposes.

Claims (11)

1. Addition with combustion-promoting and soot-inhibiting effect to heating oils, diesel fuels and other liquid fuels, in particular with boiling point at normal pressure of over 300 ° C, characterized in that the addition one or more oil-soluble and / or dispersible compounds of transition metals and / or alkaline earths as well as one or more inhibitors against polymerization and oxidation of hydrocarbons, these inhibitors being heat-stable and, due to their vapor pressure and / or their decomposition temperature, temperatures of 300 ° C. and above at normal pressure can be exposed at least for a short time without loss of their polymerization-preventing action. 2. Additive according to claim 1, characterized in that the weight ratio of metal: inhibitor = 1: 0.1 to 10. 3. Additive according to claim 1 or 2, characterized in that it comprises at least one compound of iron, manganese, molybdenum, cobalt, nickel or copper. 4. Additive according to claim 1 or 2, characterized in that it comprises at least one compound of calcium, strontium or barium. 5. Additive according to claim 1 or 2, characterized in that it comprises at least one compound of iron, manganese, molybdenum, cobalt, nickel or copper and at least one compound of calcium, strontium or barium. 6. Additive according to one of the preceding claims 1 to 5, characterized in that an oxidation and polymerization inhibitor based on heat-stable alkylphenols is contained as an inhibitor. 7. Additive according to one of the preceding claims 1 to 5, characterized in that various organic polymerization and oxidation inhibitors, such as heat-stable amines, dithiophosphates, dithiocarbamates and / or imidazoles are contained as inhibitors of phenols. 8. Additive according to one of the preceding claims 1 to 5, characterized in that inorganic polymerization and oxidation inhibitors, such as finely dispersible oxides and / or hydroxides of at least one metal from the group consisting of aluminum, magnesium, silicon and other light metals are contained as inhibitors. 9. Additive according to one of the preceding claims 1 to 5, characterized in that an oxidation and polymerization inhibitor based on aminophenols is contained as an inhibitor. 10. Liquid fuels, especially those with a boiling end at normal pressure of over 300 ° C, such as heating oils and diesel fuels, characterized in that they contain an additive according to one or more of claims 1 to 9. 11. Liquid fuels according to claim 10, characterized in that the metal content is 0.1 to 1000 parts by weight per million parts by weight of the said fuels.