EP0441195B1 - Process for the preparation of base oils and middle distillates stabilized against oxydation and low temperatures - Google Patents

Description

The invention relates to the production of middle distillates in the boiling range from 180 to 360 ° C on the one hand and an oxidation-stable residue suitable as a base oil for lubricating oils on the other hand by treating mineral oil fractions with a boiling range above 350 ° C in a first stage by hydrocracking and in a second stage Hydrogenation with a catalyst based on a borosilicate zeolite.

Due to the constant further development of engine oils, ever increasing demands are made on the base oils that form the basis for these engine oils. The production of fuel-saving low-viscosity engine oils requires the provision of low-viscosity base oils that are thin at low temperatures and thus reduce cold start wear, and that remain sufficiently viscous at high temperatures to ensure adequate lubrication. A slight dependence of the viscosity on the temperature and therefore a high viscosity index (VI) is necessary. Oxidation stability and sufficient fluidity at low temperatures are further important quality requirements for base oils.

Base oils with very high viscosity indices (VHVI [very high viscosity index] oils) can be obtained by hydrocracking vacuum gas oils. Here, components with low VI are either split into low-boiling components or converted into compounds with high VI by hydrogenation, ring cleavage and isomerization.

The subsequent dewaxing serves to improve the fluidity at low temperatures. Long-chain, unbranched and little branched hydrocarbons are separated. This separation can take place physically by precipitating the paraffin crystals at low temperatures using a mixture of solvents or by hydrogenating cleavage of these compounds on shape-selective catalysts. To assess fluidity, e.g. the determination of the pour point according to DIN 51 597 is used.

The oxidation stability can be adjusted by hydrogenating the base oil or by adding stabilizers. The test can be carried out according to DIN 51 352, for example, by increasing the Conradson coke residue after aging by passing air through it.

US Pat. No. 4,347,121 describes a process in which base oils for the production of lubricating oil are obtained in succession by hydrocracking, hydrofinishing and catalytic dewaxing with viscosity indices of approximately 100 which are stable to oxidation and sufficiently flowable at low temperatures.

The subject of US Pat. No. 4,561,967 is a single-stage, catalytic process for the production of light neutral oils with good UV stability, using hydrocracking products.

DE-PS 2 613 877 relates to a process for the production of lubricating oil in which lubricating oils with a low pour point and a VI of 95 are obtained via two hydrocracking stages and a catalytic dewaxing stage.

The viscosity index of the base oil obtained in all these processes is not sufficient to produce high-quality lubricating oils from these base oils.

It was therefore the task to propose a process with which it is possible to produce oxidation-stable VHVI oils.

This object was achieved with a two-stage process for the production of oxidation-stable base oils with a VI (viscosity index) 110 to 135 (VHVI oils) and very good fluidity at low temperature by using heavy mineral oil fractions with a boiling range above 350 ° C on one Hydrocracking catalyst converted under hydrocracking conditions to 20 to 80 wt .-% in portions that boil below 360 ° C, the reactor discharge, if necessary, in a high pressure separator into liquid and gas phase, the entire reactor discharge or only the liquid phase, directly, or after distilling off the bottom 360 ° C boiling in a second stage treated with hydrogen in the presence of a catalyst at 200 to 450 ° C and 20 to 150 bar, which is a crystalline borosilicate zeolite of the pentasil type, aluminum oxide and / or amorphous aluminosilicate as a carrier material and one or more metals from the Group VIb and / or Group VIII of the Periodic Table and Pho sphor contains, and after distillation of the hydrogenation products a middle distillate in the boiling range of 180 to 360 ° C with a pour point below -30 ° C and an oxidation-stable residue with a boiling point> 360 ° C, a viscosity index between 110 and 135 and a pour point of below - Wins 12 ° C.

The first stage is generally carried out at pressures of 40 to 150 bar, temperatures of 300 to 450 ° C. and specific catalyst loads of 0.1 to 4 kg / lxh with hydrogen in the presence of a catalyst, the support of which is preferably made of aluminum oxide, a amorphous aluminosilicate and / or a dealuminated Y zeolite, and which contains as hydrogenation components one or more metals from group VI b and / or VIII of the periodic table and phosphorus. The entire liquid outflow from the first stage is fed directly to the second stage without intermediate relaxation or after the parts boiling below 360 ° C. have been distilled off, with printing of e.g. 20 to 150 bar, temperatures of e.g. 200 to 450 ° C and specific catalyst loads of 0.1 to 4 kg / l x h treated with hydrogen in the presence of a catalyst which contains a borosilicate zeolite of the pentasil type in addition to aluminum oxide and / or aluminosilicate or silicon dioxide. One or more metals from group VI b and / or group VIII of the periodic table are applied to the catalyst for the hydrogenative stabilization of the oils.

The VI from 110 to 135 in base oil with a boiling point> 360 ° C is set in the first stage using different degrees of conversion. The degree of conversion is the quotient of the portion boiling below 360 ° C and the total hydrocarbon portion. In the second stage, the reaction conditions (pressure, temperature and specific catalyst load) are selected so that the resulting base oil with a start of boiling above 360 ° C is stable to oxidation and has a pour point below -12 ° C.

A further surprising advantage of the method according to the invention is the finding that the base oils according to the method respond better to pour point improvers than base oils which have been dewaxed with solvents.

In addition, the middle distillates obtained in this process, with a boiling range of 180 to 360 ° C, have excellent cooling properties. The pour point is always below -30 ° C. Such middle distillates are valuable mixed components for the production of low-temperature diesel fuels.

The preparation of catalysts for the hydrocracking stage of the process according to the invention can be carried out by mixing an aluminum oxide component with a silicon oxide component or an aluminosilicate, optionally with the addition of a dealuminated zeolite of the Y type with an SiO₂ / Al₂O₃ molar ratio in the range from 7 to 150 and a peptizing agent, such as for example formic acid. As a SiO₂ component, a hydrogel with a SiO₂ content of 10 to 20% by weight is particularly suitable Bands in the IR spectrum at wavenumbers of 1,630 and 960 cm ,¹, a Na content of less than 0.01% by weight and a BET surface area of more than 400 m² / g. The dealumination of the Y zeolite can be carried out by acid treatment, for example according to DE-PS 2 435 716. 20 to 95% by weight of aluminum oxide, preferably 30 to 60% by weight and 5 to 50% by weight of silicon dioxide, preferably 20 to 40% by weight, can be used in amorphous carrier fractions. The weight fraction of dealuminated Y zeolite in the carrier can be varied in the range from 0 to 30. After intensive mixing, the paste is extruded through a die with a diameter between 1 and 3 mm and then dried and calcined at elevated temperatures.

The carrier composition of the catalyst used in the second stage, the dewaxing and stabilization stage, of the process according to the invention can expediently vary in the range from 10 to 90% by weight of boron zeolite of the pentasil type, 10 to 90% by weight of aluminum oxide and 20 to 40% by weight. -% silicon oxide.

The borosilicate zeolites of the pentasil type are characterized by a high SiO₂ / B₂O₃ ratio and by pore sizes between those of type A zeolites and those of type X or Y. You will e.g. synthesized at 90 to 200 ° C under autogenous pressure by using a boron compound e.g. H₃BO₃ with a silicon compound, preferably highly disperse silicon dioxide in aqueous amine solution, in particular in 1,6-hexanediamine or 1,3-propanediamine or triethylenetetramine solution with and in particular without addition of alkali or alkaline earth metal to the reaction. These also include the isotactic zeolites according to EP-A-34 727 and EP-A-46 504. Such borosilicate zeolites can also be prepared if the reaction is carried out in ethereal solution, e.g. Diethylene glycol dimethyl ether or in alcoholic solution, e.g. 1,6-hexanediol. The synthesis of borosilicate zeolites in aqueous polyamine solution without the addition of alkali is essential and particularly advantageous. After their isolation, drying at 100 ° C. to 160 ° C., preferably 110 ° C. and calcination at 450 to 550 ° C., preferably 500 ° C., the zeolites thus produced can be shaped together with the other carrier materials.

The hydrogenation components for the catalysts in both stages of the process according to the invention can be incorporated into the moist carrier mixture and / or applied to the catalyst carrier by impregnation. For this purpose, the catalyst particles are brought into contact, for example, one or more times with a solution which contains the desired hydrogenation components. The amount of solution corresponds to the previously determined water absorption of the catalyst particles. On hydrogenation metal components preferably Co, Ni, Mo, and W, for example in the form of ammonium heptamolybdate, nickel nitrate, ammonium metatungstate, cobalt nitrate. The finished catalyst is obtained after renewed drying and calcination and can contain 2 to 10 wt .-% nickel or cobalt oxide and 10 to 25 wt .-% molybdenum or tungsten, calculated as MoO₃ and WO₃. Phosphorus components can also be added to the catalysts, both when the carrier components are mixed and as part of the impregnation solution. Amounts in the range of 1 to 12% by weight of P₂O₅ based on the finished catalyst are usually added.

Before using the catalysts, they are sulfurized from the oxidic to the more active sulfidic form, e.g. by passing a mixture of hydrogen and H₂S converted.

Suitable feedstocks for the process are heavy gas oils, vacuum gas oils, deasphalted residue oils and mixtures thereof in the boiling range above 350 ° C. A prior breakdown of the organic sulfur and nitrogen compounds is not necessary, but is advantageous in certain cases.

In detail, the procedure is appropriately such that the feed is added to the hydrocracking reactor together with hydrogen and brought to the reaction temperature. The conversion rate for a boiling temperature <360 ° C is set between 20 and 80%. The effluent from the hydrocracking reactor is separated into a liquid and gas phase in a high pressure separator. Ammonia and hydrogen sulfide, which are contained in the gas phase, are optionally separated in a downstream wash, and the hydrogen is returned to the reaction zone. The liquid portion is fed to the second reactor at the same pressure level, where dewaxing and hydrating stabilization take place. If the sulfur content in the liquid fraction is below 100 mg / kg, the addition of a sulfur component, for example dimethyl disulfide (DMDS), is necessary before entering the second reactor in order to prevent desulfurization of the catalyst. After the separation of the gas phase, the effluent from the second reactor is separated in a further high-pressure separator in a downstream distillation into liquid gas, naphtha, middle distillate and a residue with a boiling point> 360 ° C. Due to its viscosity index between 110 and 135, its oxidation stability and its pour point below -12 ° C, this residue is ideal as a base oil for the production of high-quality lubricating oils. It was also found that the base oils obtained by the process according to the invention respond much better to pour point improvers than, for example, base oils dewaxed with solvents. It won't just be requires smaller amounts of pour point improver to set a given pour point, but also reaches lower-lying pour points than was possible using conventional methods.

Since the middle distillates in the boiling range 180 to 360 ° C are only separated after the dewaxing stage, this results in excellent cold properties for these middle distillates. With a pour point of <-30 ° C, the distillates also meet extreme requirements, e.g. for diesel fuel in winter operation.

The process conditions for both catalytic stages can generally be varied within the following ranges:

example 1

Preparation of the catalyst for the hydrocracking stage:

A moist carrier mixture is prepared by mixing 227 g of hydrogel (SiO₂ content 15%) with 102 g of aluminum oxide and 10 g of formic acid, adding 18 g of phosphoric acid, 16.2 g of nickel nitrate and 309 g of ammonium heptamolybdate dissolved in 150 ml of water. The carrier mixture is extruded through a 1.5 mm die, then dried at 150 ° C. and calcined at 500 ° C. for 5 hours. The moldings are impregnated with a solution consisting of nickel nitrate and ammonium heptamolybdate and dried and calcined again. The finished catalyst has the following composition (wt .-%): Al₂O₃ 51, SiO₂ 17, MoO₃ 18, NiO 5, [PO₄] ³⁻9.

Example 2

Preparation of the dewaxing and hydrating stabilization catalyst:
Synthesis of borosilicate zeolite:

A borosilicate zeolite of the pentasil type is in a hydrothermal synthesis from 640 g of highly disperse SiO₂, 122 g of H₃BO₃, 8000 g of an aqueous 1,6-hexanediamine solution (mixture 50:50 wt .-%) at 170 ° C under autogenous pressure in a stirred autoclave without added alkali. After filtering off and washing out, the crystalline reaction product is dried at 100 ° C./24 h and calcined at 500 ° C./24 h. This borosilicate zeolite is composed of 94.2 wt .-% SiO₂ and 2.3 wt .-% B₂O₃ (loss on ignition: 3.5 wt .-%).

The catalyst was prepared as described in Example 1 with the addition of the borosilicate zeolite. The finished catalyst had the following composition (% by weight): Al₂O₃ = 18, boron pentasil zeolite = 60, MoO₃ = 18, NiO = 4

Dichte 15°C

0,894 g/ml

Viskosität 70°C

14,6 mm²/s

Pourpoint

40°C

Schwefelgehalt

0,34 Gew.-%

Stickstoffgehalt

0,081 Gew.-%

C aromatisch n. Brandes

16,5 Gew.-%

Siedeverlauf ASTM D 1160

SB

260°C

10 Vol.-%

373°C

30 Vol.-%

432°C

50 Vol.-%

455°C

70 Vol.-%

480°C

90 Vol.-%

516°C

SE

548°C

A vacuum gas oil from Amna / Sahara with the following properties was used for the example given here:

Density 15 ° C

0.894 g / ml

Viscosity 70 ° C

14.6 mm² / s

Pour point

40 ° C

Sulfur content

0.34% by weight

Nitrogen content

0.081% by weight

C aromatic after fire

16.5% by weight

Boiling curve ASTM D 1160

SB

260 ° C

10 vol .-%

373 ° C

30 vol .-%

432 ° C

50 vol .-%

455 ° C

70 vol .-%

480 ° C

90 vol .-%

516 ° C

SE

548 ° C

Reaction conditions:

After the hydrocracking stage, the gaseous constituents were separated off in a high-pressure separator and the entire liquid portions were fed to the dewaxing stage.

Product yields (% by weight):

H2S + NH3

0.5

C1 + C2

1.0

C3 + C4

12.2

C5 - 80 ° C

15.7

80-180 ° C

11.2

180 - 360 ° C

26.3

> 360 ° C

35.2

Product features:

Dichte 15°C

0,842 g/ml

Cetanindex

51

Pourpoint

- 42°C

C aromatisch n. Brandes

9,5 Gew.-%

Fraktion > 360°C

Dichte 15°C

0,846 g/ml

Pourpoint

- 13 °C

Viskosität 100°C

4,8 mm2/s

Viskositätsindex

119

Zunahme des Koksrückstands

< 1,2 %

nach DIN 51 352Middle distillate 180 - 360 ° C

Density 15 ° C

0.842 g / ml

Cetane index

51

Pour point

- 42 ° C

C aromatic after fire

9.5% by weight

Fraction> 360 ° C

Density 15 ° C

0.846 g / ml

Pour point

- 13 ° C

Viscosity 100 ° C

4.8 mm2 / s

Viscosity index

119

Increase in coke residue

<1.2%

according to DIN 51 352

Claims (6)

1. A process for the preparation of a base oil and middle distillate which is stable to oxidation and low temperatures from a mineral oil fraction having a boiling range above 350°C, which comprises, in a first step, converting the mineral oil fraction, by means of hydrogen in the presence of a catalyst which has a support composed of aluminium oxide, an amorphous alumosilicate and/or a dealuminated Y zeolite, and which contains, as hydrogenating components, one or more metals from group VIb and/or VIII of the Periodic Table and phosphorus, at from 300 to 450°C and at from 40 to 150 bar, to an extent of from 20 to 80% by weight into fractions which boil below 360°C, separating the reactor effluent, if necessary, into liquid and gas phases in a high-pressure separator, treating the entire reactor effluent or only the liquid phase, directly or after removal of the fractions boiling below 360°C by distillation, in a second step with hydrogen at from 200 to 450°C and at from 20 to 150 bar in the presence of a catalyst which contains a crystalline pentasil-type borosilicate zeolite, alumina and/or amorphous alumosilicate as the carrier material and one or more metals from Group VIb and/or Group VIII of the Periodic Table and phosphorus, and, after distillation of the hydrogenation product, obtaining a middle distillate in the boiling range from 180 to 360°C having a pour point of below -30°C and an oxidation-stable residue having a boiling point >360°C, a viscosity index of from 110 to 135 and a pour point of below -12°C.
2. A process as claimed in claim 1, wherein the hydrocracking catalyst contains from 1 to 40% by weight of dealuminated Y zeolite having an SiO₂:Al₂O₃ molar ratio in the range from 7 to 150.
3. A process as claimed in claim 1, wherein the proportion of crystalline borosilicate zeolite in the catalyst in the second step is from 1 to 90% by weight.
4. A process as claimed in claim 3, wherein the SiO₂ component in the borosilicate zeolite is a hydrogel having an SiO₂ content of from 10 to 20% by weight, characteristic bands in the IR spectrum at wave numbers of 1630 and 960 cm⁻¹, a sodium content of less than 0.01% by weight and a BET surface area of >400 m²/g.
5. A process as claimed in claim 1, wherein the entire reactor effluent from the hydrocracking step, comprising liquid and gas phases, is fed to the 2nd step.
6. The use of a residue obtained as claimed in claim 1 having a boiling point >360°C as a base oil for the preparation of high-quality lubricant oils.