EP0049804B1 - Process for the production of motor fuel fractions - Google Patents

Description

The present invention relates to a method for producing gasoline cuts with an engine octane number of at least 80 by hydrogenating a hydrocarbon fraction with olefinic fractions and their use as an admixture with the fuel for carburetor engines and the fuels obtainable thereby.

The thermal cracking of mineral oil fractions, such as naphtha, gas oil and vacuum oils, produces the well-known petrochemicals, such as ethylene, propylene, butenes, butadiene and aromatics, as well as liquid hydrocarbon fractions that cannot be economically processed into their individual components. These fractions are normally added to the petrol as so-called pyrolysis gasoline, optionally after stabilization by removing the diolefins and acetylenes. This occurs above all with the fraction boiling in front of the benzene with a boiling range of 25 to 75 ° C, which arises during the aromatics extraction and is still rich in olefins after stabilization by hydrogenation of the diolefins and acetylenes.

However, the motor properties of this fraction are unsatisfactory, especially the motor octane number (MOZ), which is around 76. This means that only a limited admixture with petrol is possible. High demands on fuel quality due to new energy-saving engines as well as for reasons of lead-free or limited lead in gasoline make it necessary to improve the existing fuel sources by appropriate measures in their engine behavior. In addition to olefins and paraffins, the aforementioned fraction also contains naphthenes and to a lesser extent aromatics. The olefins as well as the paraffins of this fraction consist of C ₄ -Cg hydrocarbons, with the CS-C6 hydrocarbons and especially the C ₅ portion predominating.

For the hydrogenation of olefinic compounds, such as hexene-1, hexene-2, heptene-3, 4-vinyl-1-cyclohexene, 1,3-pentadiene or 1,5-cyclooctadiene, catalysts have become known according to US Pat. No. 3,917,737 a solid, acidic carrier, nickel acetyl acetonate, diisobutyl aluminum hydride and optionally an electron donor, such as a tertiary phosphine.

It is also known to increase the motor octane number of a C ₅ -C ₆ mixture to over 78 by contacting part of the C ₆ part with a zeolite of the ZSM-5 type, the C _{5 part} and the remaining C _s portion treated with a palladium / HY-type zeolite / Al ₂ 0 ₃ contact and then combined both parts of this mixture again (DE-OS 29 34 460). This process does not involve hydrogenation.

Finally, the production of high-octane gasoline by separate treatment of the C ₃ and C ₄ cuts from the catalytic cracking of hydrocarbons is known, the propylene of the C ₃ fraction being present in the presence of a catalyst which may contain nickel in addition to an organoaluminum compound, is oligomerized, the C _{4 cut is} partially oligomerized on a Si0 ₂ -A1 ₂ 0 ₃ catalyst and the non-oligomerized C ₄ components are alkylated by reaction of isobutane and C ₄ -butenes in the presence of hydrogen fluoride and the three portions thus treated are then mixed (DE-OS 29 38 697). This process also does not include hydrogenation.

A process for the production of a gasoline cut with an engine octane number of at least 80 was found, which is characterized in that a hydrocarbon fraction with C ₄ -C ₈ hydrocarbons and a boiling range from about 25 to about 75 ° C, the particularly monoolefinic and in addition contains diolefinic and optionally higher olefinic and acetylenic components, hydrogenated with hydrogen at a temperature of 100 to 400 ° C. and a pressure of 5 to 80 bar in the presence of a supported nickel catalyst which contains 20 to 80% by weight of nickel in the unreduced state, for this purpose, a ratio of 0.3 to 30 moles of hydrogen per mole of hydrocarbon mixture is set, the number of moles of the hydrocarbon mixture being an average of the number of moles of the various hydrocarbons in accordance with their quantity in the mixture and a space / time velocity (weight hourly space velocity ; WHSV) from 0.5 to 8 g reaction mixture per g contact filling per hour sets.

The C ₄ -C ₈ hydrocarbons (KW) which can be used according to the invention originate, for example, from a hydrocarbon fraction such as is obtained in the thermal cracking of naphtha or gas oil. Such a hydrocarbon fraction is generally obtained before aromatics are separated from a pyrolysis mixture. The boiling range is about 25 to about 75 ° C. Such fractions which can be used according to the invention contain straight-chain or branched paraffinic, mono- or poly-olefinically unsaturated or acetylenically unsaturated hydrocarbons having 4 to 8 carbon atoms, such as the various isomeric butanes, butenes or butynes, pentanes, pentenes or pentynes up to the octanes, octets and octynes , butadiene, pentadiene, up to octadienes. In technically relevant compositions of such a KW electricity according to the invention, the proportion of C ₄ -KW is up to about 10% by weight, for example 0.1 to 8% by weight, the pentane proportion is up to about 45% by weight, for example 5 to 40% by weight, the proportion of n-pentenes up to approximately 35% by weight, for example 10 to 30% by weight, the proportion of isoamylenes up to approximately 45% by weight, for example 10 to 40% by weight, the proportion of cyclopentene up to approximately 22% by weight, for example 2 to 20% by weight, the proportion of cyclopentene up to approximately 35% by weight, for example 3 to 30% by weight, and the proportion of C ₆ -KW up to about 40% by weight, for example 3 to 30% by weight. Of course, small amounts of unsaturated hydrocarbons can also be present which contain more than two olefinic bonds or acetylenic as well as olefinic bonds. Such hydrocarbon fractions can also contain small amounts of hydrocarbons with less than 4 carbon atoms or small amounts of hydrocarbons with more than 8 carbon atoms and small amounts of aromatics entrained in the distillation. Similar hydrocarbon mixtures of other origins can of course also be used according to the invention.

The following composition may be mentioned as an example of such a hydrocarbon fraction:

The process according to the invention is carried out on a nickel carrier catalyst. This has a nickel content of 20 to 80 wt .-%, preferably 40 to 70 wt .-% nickel. As carriers are Si0 ₂ -A1 ₂ 0 ₃ mixtures with Si: AI molar ratios of 10- ² to 10 ^2, preferably 0.1 to 50, particularly preferably 0.5 to 50, is used. Si0 ₂ is preferably used in the form of kieselguhr and A1 ₂ 0 ₃ preferably in the form of kaolin. Both components can also be used in the form of an aluminosilicate. Kaolin can also be used as a carrier. By doping with 0.2 to 5% by weight of oxides of the 1st and 2nd main group of the Periodic Table of the Elements (Mendeleev) such as Li ₂ 0, K ₂ 0, Na ₂ 0, Rb ₂ 0, Cs ₂ 0, MgO, CuO, SrO, BaO, the contact is made slightly alkaline. In addition, the catalyst support can contain 0.1 to 3% by weight of transition metal oxides, such as iron oxides or titanium oxide.

Such catalysts have a long service life, for example over 2,000 hours, and are furthermore distinguished by good regenerability. The regeneration is carried out, for example, as follows: after the reaction zone has been rendered inert with nitrogen, the contact can be regenerated oxidatively by slowly metering in air at temperatures of around 400.degree. Temperature peaks in the catalyst bed above 500 ° C are less favorable. The contact is then activated in a hydrogen stream at 350-420 ° C and 5-80 bar for 48 hours.

The hydrogen is used in an equivalent or excess amount, based on the equivalents of double and triple bonds. An excess amount of hydrogen is preferred here because it achieves a uniform flow distribution, thorough mixing of the reaction mixture and uniform wetting of the catalytically active contact surfaces. For example, an amount of 0.3 to 30 moles, preferably 0.5 to 10.0 moles, particularly preferably 1.5 to 5 moles, of hydrogen per mole of hydrocarbon may be mentioned, the number of moles of the hydrocarbon mixture being an average of the number of moles of the various hydrocarbons means according to their amount in the mixture. At the same time, experience is taken into account that such a hydrocarbon mixture contains no more than 1% by weight of polyunsaturated olefins and of acetylenes.

According to the invention, pure or technical hydrogen can be used. Technical hydrogen can contain impurities such as methane (up to 25% by volume), CO (up to approx. 0.5% by volume) and ethylene (up to approx. 0.2% by volume).

The process according to the invention is carried out at a temperature of 100 to 400 ° C., preferably 150 to 250 ° C., particularly preferably 170 to 220 ° C. and at a pressure of 5 to 80 bar, preferably 15 to 30 bar. According to the invention, a space-time-velocity (Weight-Hourly-Space-Velocity; WHSV) of 0.5 to 8, preferably 1.5 to 4 g of reaction mixture per g of contact filling per hour is also set.

The process according to the invention can be carried out in the gas phase, the liquid phase or the trickle phase, the catalyst being able to be arranged in a fixed manner, being operated in a fluidized bed or being arranged in tubular reactors. The hydrocarbon fraction and the hydrogen are passed in cocurrent from top to bottom or from bottom to top of the contact. Among the process variants resulting from this, working in the trickle phase on a fixedly arranged catalyst in the direct current of hydrocarbons and hydrogen is preferred.

According to the invention, the proportion of the olefinically and acetylenically unsaturated components in the hydrocarbon fraction used is reduced to 0.1 to 8, preferably 0.2 to 5, particularly preferably 0.5 to 3% by weight of its original value. Any small amounts of aromatic compounds present are also largely hydrogenated to the associated saturated compounds, for example benzene to cyclohexane. This hydrogenation of the aromatic compounds takes place, for example, up to a value from the detectable limit of the aromatics up to a content of about 10% by weight of the original content of aromatics, preferably up to a value of 0.1 to 5% by weight of the original Aromatic content.

It is surprising that the increase in the number of motor octanes according to the invention to values of at least 80 with a nickel-containing catalyst, that is to say without catalysts containing noble metals, is possible under the mild reaction conditions described, in which splitting or oligomerization of individual components of the hydrocarbon mixture used is avoided.

The effect of the high octane gain of the high octane gasoline cut according to the invention when the method according to the invention is carried out is completely surprising, since a calculated determination of the motor octane number from the analysis of the treated hydrocarbon fractions does not increase the motor octane number between the state before the method according to the invention was carried out and the state after Was expected hydrogenation according to the invention to paraffins and cycloparaffins. Correlation equations developed from regression analyzes are used for such MOZ calculations from the composition of hydrocarbon mixtures. (Lit .: W. C. Healey, Jr., C. W. Maassen and R. T. Peterson, API Midyear Meeting Div. Of Ref., May 27, 1955).

The following table illustrates the surprising effect on knocking behavior by comparing calculated and measured MOZ.

The high-octane gasoline cuts obtainable according to the invention are suitable, for example, as an additive to automotive gasoline, the number of engine octanes and its knock resistance being improved. The invention therefore also relates to the use of these gasoline cuts as an admixture to the fuel for carburetor engines.

example 1

In a tubular reactor with a catalyst content of 200 cm ³ , in the trickle phase, H _{2 was passed} in cocurrent over a nickel catalyst with a Ni content of 50% by weight on an SiO ₂ -AI ₂ O _{3 support} containing 89.7% by weight. % SiO ₂ , 3.7% by weight Al ₂ O ₃ , 2% by weight oxides of the 1st and 2nd main group of the Periodic Table of the Elements (Mendeleev) (CaO; MgO; Na ₂ O; K ₂ O) and 1.1% by weight Fe ₂ O ₃ and 0.1% by weight TiO ₂ (loss on ignition 3.5%) at a temperature of 210 ° C and a total pressure of 26 bar (H ₂ content of the hydrogenation gas 80 vol .-%), a WHSV of 2 (200 g KW over 100 g catalyst in one hour) and a ratio H ₂ / throughput of 120 I / h, the results listed in the table.

Example 2

The procedure was the same as in Example 1, the catalyst used was a nickel catalyst with a Ni content of 68% by weight on an SiO ₂ -Al ₂ O _{3 support} containing 73.1% by weight Al ₂ O ₃ , 20.9% by weight Si0 ₂ , 1.5% by weight oxides of the 1st and 2nd main group of the Periodic Table of the Elements (Mendeleev) (CaO; MgO; Na ₂ O; K ₂ O;) and 1 , 0 wt .-% Fe ₂ O ₃ and 0.08 wt .-% TiO ₂ (loss on ignition 3.42%) used.

The results are shown in the table.

Claims (8)

1. Process for the preparation of a petrol cut with a motor octane number of at least 80, characterised in that a hydrocarbon fraction of C₄-C_s-hydrocarbons which has a boiling range from about 25°C to about 75 °C and contains, in particular, monoolefinic and also diolefinic and, where relevant, higher-olefinic and acetylenic and, where relevant, higher-olefinic and acetylenic components, is hydrogenated with hydrogen at a temperature of 100 to 400 °C and under a pressure of 5 to 80 bars in the presence of a supported nickel catalyst which, in the non-reduced state, contains 20 to 80 % by weight of nickel, a ratio of 0.3 to 30 Mol of hydrogen per mol of hydrocarbon mixture being established for the process, the number of mols of hydrocarbon mixture being a mean value of the number of mols of the various hydrocarbons according to the amount thereof in the mixture, and a weight hourly space velocity WHSV of 0.5 to 8 g of reaction mixture per g of catalyst per hour being established.

2. Process according to Claim 1, characterised in that the hydrogenation is carried out at 150 to 250 °C.

3. Process according to Claims 1 and 2, characterised in that the hydrogenation is carried out under a pressure of 15 to 30 bars.

4. Process according to Claims 1 to 3, characterised in that, in the non-reduced state, the catalyst contains 40 to 70 % by weight of nickel on Si0₂/AI₂0₃ supports with Si : AI molar ratios of 10-² to 10², preferably 0.1 to 50.

5. Process according to Claims 1 to 4, characterised in that the catalyst support has been rendered slightly alkaline by being doped with 0.2 to 5 % by weight of oxides of main groups 1 and 2 of the periodic system of the elements.

6. Process according to Claims 1 to 5, characterised in that the catalyst support contains 0.1 to 3 % by weight of transition metal oxides.

7. Process according to Claims 1 to 6, characterised in that a ratio of 0.4 to 6 mols of hydrogen per mol of hydrocarbon mixture is established.

8. Process according to Claims 1 to 7, characterised in that it is carried out in the trickle phase on a fixed-bed catalyst with hydrogen and the hydrocarbon mixture in cocurrent.