EP2780435B1 - Tertiobutyl hydroperoxide (tbhp) as a diesel additive - Google Patents

Description

The invention corresponds to the claims.

The present disclosure relates to the use of tert-butyl hydroperoxide (TBHP) and mixtures thereof as a fuel additive and in particular as an additive to diesel fuels.

The cetane number is a characteristic parameter for the combustion quality of diesel fuel. The cetane number is a measure of the ignition readiness or ignition delay, i.e. the time between the start of fuel injection and the start of combustion. Rapid ignition, followed by even and as complete a combustion as possible, is beneficial. The higher the cetane number, the shorter the ignition delay and the better the combustion quality.

Various additives are used to increase the cetane number. At present, almost exclusively 2-EHN (2-ethylhexyl nitrate) is used on a commercial scale. Problems with this additive are its high toxicity, poor storage stability, safety-critical properties and considerable additional costs. The use of 2-EHN is problematic in particular because of its explosiveness. Furthermore, the nitrogen content can lead to increased, undesirable NOX emissions.

Additives that increase cetane number are also used, for example, in U.S. 2,763,537 described, including alkyl nitrates, nitrites, nitroso compounds, diazo compounds and organic peroxides. With the exception of small amounts of DTBP (di-tert-butyl peroxide), organic peroxides are currently not used commercially as diesel additives. This for reasons of cost, security and compatibility.

For example, commercially available peroxide preparations often contain considerable amounts of water as phlegmatizers, are thermally or chemically too unstable, cannot be used commercially as fuel additives due to the raw materials or production processes used, or contain aromatic residues that have a negative impact on pollutant emissions. Peroxides phlegmatized with water are unsuitable as a fuel additive because water does not mix with the fuel, but rather forms a two-phase system.

Organic peroxides are thermally unstable compounds that decompose exothermically, splitting the peroxidic oxygen-oxygen bond. Therefore, for safety reasons, organic peroxides often have to be phlegmatized for safe handling or safe transport or are already technically produced in dilution.

In this respect, some anhydrous peroxides are not available, or only obtainable with great technical effort

WO 99/21942 discloses increasing cetane number through the use of a diesel fuel additive comprising zinc peroxide and TBHP in a liquid carrier.

It was an object of the present disclosure to provide an improved fuel additive, in particular with regard to pollutant emissions, effectiveness, manageability and costs.

The disclosure therefore relates to a fuel comprising anhydrous tert-butyl hydroperoxide (TBHP) as an additive, the additive containing TBHP in tert-butanol, the TBHP in an amount of 0.01% by weight to 10% by weight, based on the Total weight of the hydrogen is present and the base fuel is selected from diesel fuel, petrol, rapeseed methyl ester, kerosene and rocket fuels.

The disclosure relates to a fuel comprising tert-butyl hydroperoxide (TBHP) as an additive component in a mixture of TBHP with other organic peroxides, in particular other organic anhydrous peroxides such as, for example, di-tert-butyl peroxide (DTBP).

It has surprisingly been found that tert-butyl hydroperoxide, in particular in anhydrous form, is suitable as a fuel additive. By The use of TBHP as an additive increases, in particular, the cetane number of the fuel and, compared with the base fuel, preferably by a value of at least 2, more preferably at least 3, even more preferably at least 4 and most preferably at least 5. The cetane number can be determined according to ASTM 0613, for example. An increase in the cetane number is a measure of the improvement in the ignitability of the fuel.

Furthermore, it was found that with the same consumption, the pollutant emissions, in particular the hydrocarbon emissions and / or the carbon monoxide emissions, are significantly reduced, while at the same time the NOx emissions are not increased significantly.

These advantages are obtained in vehicles without a catalytic converter, but surprisingly also in vehicles with a catalytic converter.

Surprisingly, it was possible to determine reduced pollutant emissions both upstream of a downstream exhaust gas catalytic converter and also after a downstream exhaust gas catalytic converter. A reduction in pollutant emissions after the catalytic converter was found especially in phase 1 (cycle 1 to 4) of the NEDC driving cycle, in which low speeds of up to 50 km / h are driven and in which the catalytic converter has not yet reached full operating temperature. In this respect, TBHP, in particular anhydrous TBHP, and mixtures thereof are of very high interest in regions in which the catalyst density in the existing vehicle fleets is already very high, such as Europe, since a large number of journeys are made in vehicles in which the catalyst is not has reached full operating temperature. TBHP, in particular anhydrous TBHP and mixtures thereof as a fuel additive consequently reduce the emission of pollutants, in particular the emission of hydrocarbons and carbon monoxide, regardless of the prevalence of catalytic converters.

Even with vehicles that are operated without a catalytic converter, pollutant emissions are higher in phase 1 (cycle 1 to 4) of the NEDC driving cycle than in phase 2 (cycle 5). In phase 1, the reduction in hydrocarbon and carbon monoxide emissions is particularly high with fuels that contain TBHP, in particular anhydrous TBHP, as an additive. This is the desired effect, especially for short-haul traffic. In principle, the pollutant emissions of e.g. hydrocarbons and carbon monoxide are higher when burning low-quality fuel than with higher-quality fuel.

It has now been found, surprisingly, that TBHP as an additive reduces the pollutant emissions of e.g. hydrocarbons and carbon monoxide when using higher quality diesel grades, such as a commercially available Euro4 diesel, more than when using lower quality diesel grades, such as a commercially available US diesel. In this respect, TBHP is also especially suitable as a fuel additive for regions in which higher quality fuel is typically used.

Anhydrous TBHP is used as a fuel additive. Anhydrous means that the water content in the TBHP composition is <5% by weight, in particular <1% by weight, even more preferably <0.3% by weight.

The use of anhydrous TBHP, which is miscible with fuel and in particular with diesel fuel, prevents an undesired, second aqueous phase from forming. TBHP is preferably used as an additive in an anhydrous organic solvent. Polar and non-polar solvents can be used. Examples of suitable non-polar solvents are alkyls and, in particular, aliphatic hydrocarbons, in particular isododecane, isooctane, decane, and nonane or / and n-octane or mixtures of different aliphatics. Examples of polar solvents are, in particular, oxygen-containing solvents such as alcohols and / or ethers. Alkyl alcohols are preferably used as solvents, in particular C1-C8-alkyl alcohols, more preferably C2-C6-alkyl alcohols, even more preferably butanol and most preferably tert-butanol. By using alcohols and in particular tert-butanol, the proportion of oxygen in the fuel additive is increased further, which is desirable and contributes to improved combustion due to the oxygen enrichment and thus to a reduction in pollutant emissions.

A significant reduction in soot and pollutant emissions was observed especially when using a fuel additive comprising TBHP in tert-butanol (TBA).

The amount of TBHP in the additive is preferably at least 10% by weight, more preferably at least 30% by weight, even more preferably at least 40% by weight and most preferably at least 50% by weight. Pure TBHP is not preferred for safety reasons. The amount of TBHP in the additive is therefore preferably up to 90% by weight, more preferably up to 75% by weight and most preferably up to 60% by weight. The proportion of anhydrous organic solvents, in particular of alcohols and preferably of tert-butanol, is correspondingly at least 10% by weight, more preferably at least 25% by weight and most preferably at least 40% by weight and up to 90% by weight, more preferably up to 70% by weight and most preferably up to 50% by weight.

An additive which contains 30 to 70% by weight of TBHP in 70 to 30% by weight of tert-butanol has proven to be particularly suitable and thus most preferred. Even more preferred is an additive which contains 50 to 60 wt% TBHP in 50 to 40 wt% tert-butanol. Most preferred is an additive which contains 55% by weight TBHP and 45% by weight TBA. By phlegmatizing TBHP in an oxygen-containing solvent, preferably in an alcohol and in particular in tert-butanol, the safety is increased during the technical TBHP production, the transport and the further handling.

Further particularly preferred solvents are ethers and polyethers, particularly preferably aliphatic or cyclic ethers and / or polyethers.

On the basis of phlegmatization with an oxygen-containing solvent, preferably an alcohol and in particular tert-butyl alcohol, the oxygen content of the additive is also increased in order to reduce pollutants in the exhaust gas. For example, an oxygen content of about 29.3% by weight of oxygen, of which about 9.8% by weight of active oxygen is contained in a mixture of 55% by weight of TBHP and 45% by weight of TBA.

The fuel can contain fuels or fuels known as the base fuel, such as petrol, in particular gasoline, super, etc., diesel fuels such as diesel, biodiesel or similar, but also very low diesel grades, such as various marine diesel grades, rapeseed methyl ester, oxymethylene ether, kerosene or Rocket fuel. The fuel, in particular a diesel fuel or kerosene, can be provided, for example, for diesel units in, for example, motor vehicles, ships or for stationary diesel engines for generating electricity or also for aircraft or rocket engines.

In particular, the additive increases the ignitability of the fuel. Furthermore, the emission of soot and hydrocarbons and carbon monoxide in the internal combustion engine is significantly reduced, in particular with constant or almost constant NOx emissions. The fuel particularly preferably comprises a high-quality diesel as the base fuel which meets the Euro4 diesel requirements.

The TBHP used as an additive is also significantly easier to handle in terms of safety compared to the additives usually used, such as 2-EHN. The use of TBHP in anhydrous form, in particular in an anhydrous organic solvent, avoids the formation of two separate phases and only then enables TBHP to be used as a fuel additive.

Compared to the conventionally used 2-EHN, the use of TBHP as an additive improves combustion (especially lower hydrocarbon, carbon monoxide and soot emissions). Furthermore, TBHP does not contain any nitrogen, so that the problems associated therewith and in particular the problem of the formation of nitrogen oxides are reduced according to the invention. TBHP is still significantly safer than 2-EHN in terms of safety, especially with regard to decomposition.

The Koenen test is a measure of the rate of decomposition and the pressure build-up during decomposition of a product. The larger the Koenen value, the more violent the decomposition takes place.

The coefficient for 2-EHN = 1.0 while the coefficient for a TBHP phlegmatized with TBA is <1.

The energy released during the decomposition of 2-EHN with ΔH = 2210 J / g is also significantly higher than that of a TBHP-TBA mixture with ΔH = 729 J / g.

Compared to the di-tert-butyl peroxide (DTBP) already used as a fuel additive, TBHP advantageously has a higher flash point of 21 ° C. The flash point of DTBP, for example, is significantly lower than that of TBHP and below room temperature at <0 ° C. Furthermore, the conductivity of DTBP is extremely low at <3 pS / m, so that transfer processes of DTBP due to possible charge separations are very critical from a safety point of view, since these charge separations can generate sufficient ignition energy to ignite DTBP, since DTBP only has a very low ignition energy of < 0.1 mJ required. The energy released during the decomposition of DTBP with ΔH = 1370 J / g is also significantly higher than that of the TBHP desensitized with TBA with ΔH = 729 J / g.

In contrast to the non-polar DTBP, the polar TBHP is conductive (> 1000 pS / m) and thus such charge separations do not occur, so that the TBHP can be handled much more safely than DTBP.

The fuel has 0.01 wt% to 10 wt%, preferably up to 5 wt%, and most preferably 0.01 wt% to 2 wt% TBHP.

It was found that a reduction in pollutant emissions can be achieved even with small amounts of additive. The fuel therefore particularly preferably has up to 0.5% by weight TBHP, even more preferably up to 0.25% by weight TBHP and most preferably up to 0.15% by weight.

It is also possible to combine the additive containing TBHP with other additives. For example, the combination with other peroxides, in particular with other organic peroxides and preferably with other anhydrous organic peroxides, and in particular with di-tert-butyl peroxide (DTBP), is preferred. An additive which comprises TBHP and DTPB is particularly preferred. Most preferred is an additive comprising TBHP, DTPB and TBA.

For the combination of anhydrous TBHP with DTBP as an additive, surprisingly, synergistic effects have been found, so that the Combination of anhydrous TBHP with DTBP leads to a higher pollutant reduction than can be achieved with comparable amounts of TBHP or DTBP alone.

The weight ratio of TBHP and DTPB is preferably from 10:90 to 90:10, in particular from 20:80 to 80:20 and even more preferably from 30:70 to 70:30.

The amount of TBHP and DTPB in the additive is preferably at least 10% by weight, more preferably at least 30% by weight, even more preferably at least 40% by weight and most preferably at least 50% by weight. Furthermore, the amount of TBHP and DTPB in the additive is preferably up to 90% by weight, more preferably up to 75% by weight and most preferably up to 60% by weight. The proportion of anhydrous organic solvents, in particular of alcohols and preferably of tert-butanol, is correspondingly at least 10% by weight, more preferably at least 25% by weight and most preferably at least 40% by weight and up to 90% by weight, more preferably up to 70% by weight and most preferably up to 50% by weight.

The manufacture of TBHP can take place according to known manufacturing processes.

The fuel additive contains in particular anhydrous TBHP and preferably TBHP in an organic solvent. The organic solvent is preferably an alcohol, especially tert-butanol. Particularly preferred is an additive comprising 30 to 70% by weight of TBHP in 70 to 30% by weight of organic solvent, in particular TBA, more preferably 50 to 60% by weight of TBHP in 50 to 40% by weight of organic solvent, especially TBA.

Also particularly preferred is a fuel additive which, in addition to TBHP, comprises a further organic peroxide, in particular a further anhydrous organic peroxide. Most preferred is an additive comprising TBHP and DTBP. In a particularly preferred embodiment, the peroxides are present in the additive in an alcohol, in particular in TBA.

Furthermore, a fuel additive is also included which, in addition to TBHP, contains another known fuel additive such as 2-EHN. In a particularly preferred embodiment, the TBHP is present in an alcohol, in particular in TBA.

The preferred proportions of TBHP, optionally further organic peroxide such as DTBP and organic solvent, in particular TBA, are as described hereinbefore.

Furthermore, it was found according to the invention that the pollutant emissions can be reduced by using the fuel additive or a fuel comprising the fuel additive. The disclosure therefore also relates to the use of TBHP for reducing pollutants, in particular for reducing hydrocarbon emissions and / or carbon monoxide emissions. The disclosure particularly preferably relates to the use of TBHP to emit pollutants in vehicles with a catalytic converter. Most preferred is the use of an additive comprising TBHP, DTBP and TBA to reduce pollutants.

The disclosure also relates to the use of TBHP or the fuel additives described herein to increase the cetane number.

The disclosure also relates to the use of TBHP or the fuel additives described herein for reducing pollutants, in particular for reducing the emission of hydrocarbons and / or carbon monoxide.

example 1 Fuel comprising TBHP as an additive

A conventional US base diesel fuel has a cetane number of 45.2. An additive consisting of 55% by weight of TBHP and 45% by weight of tert-butanol in a concentration based on TBHP of 0.026% by weight of additive and in a concentration of 0.11% by weight is added to this fuel.

By adding 0.026% by weight of TBHP, the CETAN number increases from 45.2 to 47.4. With a further addition of a total of 0.11% by weight of TBHP, the CETAN number is increased to 50.0.

Comparative emission and consumption measurements were made with a conventional US base diesel fuel (cetane number 45.2) and a conventional EU4 base diesel fuel (cetane number 54.6) with and without the addition of TBHP on a roller dynamometer according to the standardized NEDC driving cycle.

A Mercedes C 220 CDI, 4 cylinder, 110 KW power, built in 2005 with a 5-speed automatic transmission and a mileage of around 140,000 km was used as the test vehicle. The vehicle is equipped with a particle filter and catalytic converter. The emissions were determined in multiple measurements before and after the catalytic converter.

By adding 0.11% by weight of TBHP to a conventional EU base diesel fuel with a CETAN number of 54.6, the raw emissions upstream of the catalytic converter could be reduced as follows while the average consumption remained the same: EU4 basic diesel Measured values upstream of the catalytic converter 0.11 wt% TBHP Phase 1 Phase 2 (Cycle 1 - 4 NEDC) (Cycle 5 NEDC) Hydrocarbons (HC) -10.0% -7.0% Carbon monoxide (CO) -9.7% -5.2% Carbon dioxide (CO2) 0.0% 0.0%

The NO _x emissions increase only very slightly by 6.1% in phase 1 and 2.9% in phase 2.

The positive influence of the emission reduction in phase 1, the cold start phase in NEDC cycle 1 to 4, is particularly important and pronounced. US base diesel Readings after 0.11 wt% TBHP the catalyst Phase 1 (cycle 1 - 4 NEDC) Hydrocarbons (HC) -43.7% Carbon monoxide (CO) -30.2% Carbon dioxide (CO2) 0.0%

By adding 0.11% by weight of TBHP to a conventional US base diesel fuel with a cetane number of 45.2, the following raw emissions could be observed upstream of the catalytic converter with a constant average consumption: US base diesel Measured values upstream of the catalytic converter 0.11 wt% TBHP Phase 1 (cycle 1 - 4 NEDC) Phase 2 (cycle 5 NEDC) Hydrocarbons (HC) -8.4% 0.5% Carbon monoxide (CO) -8.0% 4.2% Carbon dioxide (CO2) 0.0% 0.0%

The NO _x emissions rise below the measurement tolerance.

Especially in phase 1 (cycle 1 - 4 NEDC), a very strong reduction in emissions was measured downstream of the catalytic converter, as it does not yet have the required operating temperature: US base diesel Readings after 0.11 wt% TBHP the catalyst Phase 1 (cycle 1 - 4 NEDC) Hydrocarbons (HC) -17.5% Carbon monoxide (CO) -16.9% Carbon dioxide (CO2) 0.0%

The absolute values of the pollutant emissions related to hydrocarbons and carbon monoxide are in any case lower for the standard EU4 diesel quality than for the standard US basic diesel quality. Nevertheless, with 0.11% TBHP as an additive for the higher-quality, commercially available EU4 diesel fuel quality, an even greater percentage of pollutant emissions could be achieved than with the US base diesel quality: Pollutant fuel Analysis values in mg / kg in front of the catalytic converter after the catalyst Phase 1 Phase 2 Phase 1 Phase 2 Hydrocarbons Euro4 diesel 431.8 334.9 77.4 10.9 Euro4 diesel + 0.11 wt.% TBHP 388.7 311.4 43.6 9.2 reduction 10.0% 7.0% 43.7% 15.9% Carbon monoxide Euro4 diesel 799.7 461.1 199.9 5.1 Euro4 diesel + 0.11 wt.% TBHP 722.2 436.9 139.5 5.3 reduction 9.7% 5.2% 30.2% -2.8% NOX Euro4 diesel 80.8 117.4 Euro4 diesel + 0.11 wt.% TBHP 85.7 120.8 reduction -6.1% -2.9% Pollutant fuel Analysis values in each case in mq / kg in front of the catalytic converter after the catalyst Phase 1 Phase 2 Phase 1 Phase 2 Hydrocarbons US base diesel 587.4 393.8 101.6 US base diesel + 0.11 wt.% TBHP 538.2 395.7 83.8 reduction 8.4% -0.5% 17.5% Carbon monoxide US base diesel 1025.9 533.8 315.2 5.7 US base diesel + 0.11 wt.% TBHP 944.2 511.4 261.9 5.7 reduction 8.0% 4.2% 16.9% 0.0% NOX US base diesel 79.4 118.5 US base diesel + 0.11 wt.% TBHP 85.4 122.0 80.6 121.3 reduction 0.0 0.0

Example 2 Fuel comprising TBHP and DTBP as an additive

An additive consisting of 27.5% by weight of TBHP, 22.5% by weight of TBA and 50% by weight of DTBP is mixed into a conventional US base diesel fuel. Mixture 1 contains 0.013 wt% TBHP and 0.024 wt% DTBP.

Mixture 2 contains 0.052 wt% TBHP and 0.094 wt% DTBP.

The CETAN number of the conventional base diesel fuel is 45.2, that of mixture 1 is 47.9 and that of mixture 2 is 56.7.

Compared to the base fuel, the addition of the additive significantly increases the cetane number and, according to the following table, significantly reduces the pollutant emissions with constant consumption, especially in phase 1. US base diesel Readings before 0.052 wt% TBHP and 0.094 wt% DTBP the catalyst Phase 1 (cycle 1 - 4 NEDC) Phase 2 (cycle 5 NEDC) Hydrocarbons (HC) -22.6% -4.2% Carbon monoxide (CO) -22.0% -11.9% Carbon dioxide (CO2) 0.0% 0.0%

In phase 1 (cycle 1 - 4 NEDC) in particular, a very strong reduction in emissions was measured downstream of the catalytic converter, as it does not yet have the required operating temperature: US base diesel Readings after 0.052 wt% TBHP and 0.094 wt% DTBP the catalyst Phase 1 (cycle 1 - 4 NEDC) Hydrocarbons (HC) -43.0% Carbon monoxide (CO) -39.5% Carbon dioxide (CO2) 0.0%

The NO _x emissions rise below the measurement tolerance.

Claims (8)

1. Fuel comprising anhydrous tert-butyl hydroperoxide (TBHP) as an additive, the additive containing TBHP in tert-butanol, characterised in that the TBHP is present in an amount of 0.01 wt.% to 10 wt.%, based on the total weight of the fuel, and in that the base fuel is selected from diesel fuel.
2. Fuel comprising anhydrous tert-butyl hydroperoxide (TBHP) as an additive according to any of the preceding claims, characterised in that the additive consists of 30 to 70 wt.% of TBHP in 70 to 30 wt.% of organic solvent.
3. Fuel comprising anhydrous tert-butyl hydroperoxide (TBHP) as additive according to either of the preceding claims, characterised in that the fuel comprises di-tert-butyl peroxide as a further additive.
4. Use of anhydrous tert-butyl hydroperoxide (TBHP) in tert-butanol to increase the cetane number.
5. Use of anhydrous tert-butyl hydroperoxide (TBHP) in tert-butanol to reduce carbon monoxide and/or hydrocarbon emissions.
6. Use according to claim 4 of a mixture of anhydrous tert-butyl hydroperoxide (TBHP) and di-tert-butyl peroxide (DTBP) to increase the cetane number.
7. Use according to claim 6 of a mixture of anhydrous tert-butyl hydroperoxide (TBHP) and di-tert-butyl peroxide (DTBP) to reduce carbon monoxide and hydrocarbon emissions.
8. Use of anhydrous tert-butyl hydroperoxide (TBHP) in tert-butanol as a fuel additive, wherein the base fuel is selected from diesel fuel.