NO125493B - - Google Patents

Description

Procedure for the production of lubricating oils

with a very high viscosity index.

The present invention relates to a method for the production of lubricating oils with a very high viscosity index, - by hydrogen treatment of a hydrocarbon starting material. More specifically, the invention relates to a method by which solvent-refined, asphalt-free, waxy hydrocarbon oils are hydrogenated at specific temperatures and pressures for the production of lubricating oils that satisfy the "SAE 10 W/30" requirements for multi-category oils ("all-season oils" ).

Lubricating oils for car engines, including diesel engines as well

such as petrol engines, are classified according to a scheme proposed by the Society of Automotive Engineers, according to which the viscosity

measured in Seconds Saybolt Universal (SSU) at 99°C is indicated by an SAE number.

Originally seven categories of oils were proposed, of which the three lightest, namely the "SAE 5 W", "SAE 10 W" and "SAE 20 W" oils, are known as winter oils (W = Winter). These winter oils meet the same viscosity requirements at 99°C, but must also meet certain viscosity requirements at -17.8°C, which requirements increase from the "5W" oils to the "20W" oils. The other four oil categories, namely "SAE 20", "SAE 30", "SAE 4-0" and "SAE 50", have increasing values for the viscosity at 99°C but must not fulfill any requirement for the viscosity at -17.8 °C. In recent years, however, multi-category oils have been developed for use as lubricating oils for car engines, and which fall within more than one SAE category. They are both a winter oil and a normal oil in one and the same oil and thus ensure both good lubrication at high temperatures and sufficiently high fluidity at low temperatures. They are designated by double SAE designations such as 5 W/20, 10 W/20, 20 W/20, 5 W/30, 10 W/30, 10 W/30, 20 W/30, etc.

Pure mineral lubricating oils usually do not meet the requirements set, and to achieve the desired multi-category oil it is common to add viscosity index improvers (VI) to improve the viscosity/temperature characteristic and/or thickeners to increase the viscosity . In addition, other oil additives can be added, such as pour point depressants, antioxidants, corrosion inhibitors, cleaning agents and the like, so that the universal oils available on the market are usually compound oils. Particularly preferred multi-grade oils are "10 W/30" oils and "10 W/4-0" oils.

It is a well-known fact that lubricating oils deteriorate with prolonged use for many reasons. One of these is that the viscosity index improving agent and the thickening medium, which are usually high molecular polymers, gradually break down under the influence of the shearing forces in the engine, which results in a permanent reduction of the viscosity index and of the viscosity. Finally, the oil must be replaced with fresh multi-category oil. Furthermore, the multi-category oil also exhibits a temporary reduction in viscosity during use, because the polymer!sat molecules align with each other, which leads to a reduction in internal friction and consequently a reduction in viscosity. This phenomenon is often referred to as "temporary depolymerisation". With increasing cutting forces, the viscosity of the compound oil will approach the viscosity of the base oil with a lubricating effect.

As a result of the above, it would be very advantageous if multi-category oils could be provided containing only small amounts or none at all of viscosity index improvers or thickeners, because such oils would fulfill their purpose in engines in much longer, while they would show no reduction in viscosity or working conditions. Although for certain SAE grades it has already been shown to be possible to produce direct mineral lubricating oils that meet the requirements of a specific multi-category oil according to the SAE classification system, it has not been possible up to now to produce a real "10 W/30 "-multi-category oil from a hydrocarbon starting material.

It is the aim of the present invention to provide a method for the production of a multi-category oil which meets the requirements of a "10 W/30" oil, without the need to add additives. It is a further aim of the invention to provide such an oil by hydrotreating a hydrocarbon oil on a petroleum basis, in the presence of a catalyst. It is further an aim of the invention to provide multi-category oils with a "clear" viscosity index (VI) of at least 132 and a "clear" viscosity at 99°C of at least 9.6 centistokes, which oils can be mixed to "10 W/4-0" - multi-category oils with the addition of a relatively small amount of viscosity index improvers and/or thickeners.

The present invention therefore relates to a method for the production of lubricating oils with a very high viscosity index, which method involves hydrogenating a solvent-refined, asphalt-free, waxy hydrocarbon oil in the presence of a sulphided catalyst comprising a metal of group VI and/or group VIII on a predominantly non-acidic low-melting cracking carrier at a temperature in the range between 4-20° and 4-60°C and a pressure between 165" and 225 kg/cm , and recovers a dewaxed lubricating oil with a viscosity index of at least 132 and viscosity at 99°C of at least 9.6 centistokes from the hydioger-treated waxy oil by fractionation and dewaxing.

In the following description, the viscosity indices refer to values determined according to ASTM method D-567, unless otherwise stated.

It has already been proposed to produce lubricating oils with a viscosity index of at least 125, ve(3 hydrogen treatment of a raffinate obtained by solvent extraction of a hydrocarbon starting material to a content of aromatic compounds corresponding to an occurrence of carbon atoms in aromatic rings of less than less stringent, and the lubricating oils obtained have a viscosity at 99°C that is well below 9.0 centistokes (cS).

U.S. patent document no. 2,967. 14-7 describes a hydrogen treatment of a lubricating oil which has previously been deasphalted, solvent-refined and dewaxed, where the hydrogen treatment is carried out at a relatively low temperature within the range of 20<4>--371°C. However, the viscosity indices of the products obtained are low (approx. 98).

Furthermore, the U.S. describes patent document no. 2.917.4-4-8 a method for hydrogen treatment of a lubricant oil which is deasphalted and wax-free, but which is not solvent refined, where the hydrogen treatment is carried out at a temperature within the range of 363_399°C and a pressure within, the range of 14-0- 280 kg/cm. However, the product produced only has a viscosity at 99°C of 6.8 centistokes, although its viscosity index is 125.

Among the publications that mention the use of other types of output material, special mention should be made of the U.S. patent document no. 3-328,287. According to this patent, a residual fraction material containing a resinous extract and aromatic compounds is hydrogenated.

As a result of using such a starting material, lubricating oils with relatively poor viscosity indices and/or viscosities are obtained. Although some of the products produced have viscosity indices above 132, the viscosity at 99°C is not greater than 6.8 centi stoke.

British patent document no. 1,008,019 can also be mentioned, where a starting material is used which is not solvent-refined and which is preferably dewaxed. According to modern standards, the obtained products have a relatively poor viscosity index (52-100).

Furthermore, it has been proposed to hydrogenate deasphalted oils at a pressure of at least 175 kg/cm and a temperature between 390 and 4-4-0°C and to extract lubricating oils with a viscosity index of at least 115 from the hydrogenated product. Thus- describes the U.S. patent document no. 3,078,222 hydrogen treatment of a deasphalted oil at a temperature between 390-4-4-0°C and a pressure within the range 175-280 kg/cm . The starting material is not solvent refined. The lubricating oils thus obtained have a viscosity index lower than 125 and do not satisfy the requirements of a "10 W/30" multi-category oil. The required quality of the manufactured lubricating oils can only be achieved by using a purification step including urea adduct formation. Even after this step, none of the manufactured products have properties that satisfy the requirements of a real 10 W/30 lubricating oil. However, they can be used as "10 W/20", "20 W/30" or "20 W/4-0" oils.

The method according to the invention has the advantage that, in addition to the "10 W/30" multi-category oil, a significant yield of light and medium machine oils with a very high viscosity index is obtained as a by-product.

is, while the remaining part of the hydrocarbon starting material over-

is fed into a valuable fuel material that mainly boils below 375°C

The advantages of the lubricating oils with a very high viscosity index, which are obtained by the method according to the invention, are that viscosity-improving agents or thickeners do not need to be added to form a "10 W/30" multi-category oil. If it is desired to develop

quiet multi-category oils that meet the requirements of "5 W/30"-,

'10 W/4-0" or "10 W/50" oils, which must have higher viscosity

index and/or viscosity, only minor additions of the aforementioned compounds are sufficient. Additional oil additives, such as pour point depressants, antioxidants, corrosion inhibitors, cleaning agents and the like can be added if desired to form multi-category oils that meet the requirements of other specifications.

From the above, it will appear that a "10 W/30" oil mix-

ing on the basis of a real "10 W/30" lubricating oil produced according to the method according to the invention is not subjected to any permanent reduction in viscosity under the influence of shearing forces nor is it subjected to any temporary reduction in viscosity. If a "10 W/30" multi-category oil has been prepared on the basis of the oil produced according to the method of the invention, using a smaller amount of a thickener, the multi-category oil will never fall outside its SAE classification , as the base oil is a true "10 W/30" oil. Moreover, they will thus

stilted multi-category oils exhibit a measured viscosity at -17.8°C which

is practically the same as the extrapolated viscosity at

-17.8°C, due to the absence of polymers in the oil.

In Table I, the viscosity required by the SAE specifications is given in SSU units for some two-category oils.

In the following description, however, the viscosity is preferably stated as kinematic, expressed in centistokes (cS), instead of in SSU units. As is known, such viscosities can be easily converted to each other, or the corresponding values can be taken from viscosity conversion tables. Reference is made to the table in Handbook of Chemistry and Physics, 4-3. edition of The Chemical Rubber Publishing Co., page 2210.

In the attached drawing, the two-category oils are shown graphically, with the kinematic viscosity (cS) plotted along the abscissa. Oils with SAE number 20, 30, h0 and 50 have kinematic viscosity respectively between 5.6 and 9.6, between 9.6 and 13.0, between 13.0 and 17.0 and between 17.0 and 20, 3 at 99°C. The viscosity range for oils with a given SAE number is also indicated along the horizontal axis. Along the vertical axis or ordinate axis, the viscosity index, determined according to ASTM-D 567, is given, 80 being the lowest value for oils with a high viscosity index. The right side of the drawing shows the SAE Is types, with the area above the top curve indicating the 5 W type, while the area between the top curve and the middle curve indicates the 10 W type, and the area between the middle curve and the bottom curve indicates 20 W type. The area between the vertical line starting at 9.6 cS, the vertical line starting at 13 cS, the right curve and the middle curve indicates "10 W/30" oils obtained by the process of the invention. These oils are new products.

In order to produce the desired two-category oil, it is essential to use a solvent-refined and asphalt-free hydrocarbon oil as starting material. The oil must also be a waxy oil. The hydrocarbon oil may be a waxy distillate obtained by vacuum distillation or similar distillation of a crude oil, a reduced crude oil or a fraction thereof, which has been subjected to solvent refining.

The hydrocarbon oil is preferably a residual oil obtained by deasphalting a vacuum-reduced crude oil, i.e. a crude oil residue obtained by vacuum distillation or similar distillation of a crude crude oil, or a drained crude oil or crude oil fraction, with a low-boiling hydrocarbon such as propane, and solvent refining of the deasphalted oil for to remove aromatic compounds. The solvent-refined, asphalt-free, waxy hydrocarbon oil may also be a synthetic oil obtained from shale oil.

Although any of the usual solvents capable of selectively removing aromatic hydrocarbons can be used, it is preferred to use a furfural raffinate as starting material, i.e. a furfural-refined waxy oil. However, other solvents which are selective towards aromatic hydrocarbons, such as liquid sulfur dioxide, phenol, cresol, bis-(3-chloroethyl ether) and the like, can also be used. The deasphalting can be carried out using any suitable solvent. Preferred solvents

agents are the lower boiling paraffinic hydrocarbons, such as ethane, propane, butane or pentane or mixtures thereof, propane being preferred. If a high yield of deasphalted oil is desired,

pentane is the most suitable solvent. Mixtures of the above-mentioned lower-boiling hydrocarbons with alcohols such as methanol and isopropane-0.1 can also be used as deasphalting solvents.

Deasphalting and solvent refining are methods that

in and of themselves are known in the field. The conditions used during these operations to bring the starting material into the desired condition for use in the method according to the invention, i.e. to give it the desired temperature, the desired quantity ratio solvent/oil, etc., are the conventional conditions, which it would not be necessary to explain in more detail here.

The conditions of the hydrogery treatment operation are preferably chosen so that a dewaxed spreading oil is finally obtained with a viscosity index in the range between 130 and 160 and with a kinematic viscosity at 99°C in the range between 9.5 and 13.0 (cS). Preferably, however, such strict conditions are used that a dewaxed lubricating oil is obtained with a viscosity index of at least 132 and viscosity at 99°0 and at least 9.6 cS, so that the SAE specifications for a "10 W/30" oil are met.

The temperature and pressure used during the hydrotreatment of the waxy raffinate are preferably respectively between 4-30° and Mf5°C - these temperatures being average reactor temperatures - and between 170 and 185 kg/cm . The applied space velocities per hours are preferably rather low, thereby making the conditions for the treatment more stringent. Particularly preferred space velocities are those in the range between 0.4 and 1.7 kg per liter per hour. However, the hydrogen gas production rate can vary within a wide range and is preferably between 500 and 5000 NI hydrogen per kg. starting material.

The catalyst used in the process must have a mainly non-acidic, low-melting cracking carrier to avoid excessive cracking at the indicated reactor conditions. Acidity of the cracking carrier promotes the hydrocarbon conversions which involve the formation of carbonium ions, for example dealkylation and hydro-cracking. For the purposes of the invention, suitable non-acidic cracking carriers are certain metal oxides, such as aluminum oxide, boron oxide, silicon dioxide, magnesium oxide and zirconium oxide. Likewise, mixtures of some of these oxides can be used, such as mixtures of aluminum oxide and magnesium oxide or mixtures of magnesium oxide and zirconium oxide, while metal oxide mixtures containing silicon dioxide are unsuitable. Aluminum oxide is particularly preferred as a cracking carrier. The aluminum oxide carrier may contain minor amounts of alkali metal or alkaline earth metal to ensure the non-acidity of the carrier. Preferred amounts are 0.05-1.5% by weight, expressed as metal oxide. Commercial aluminum oxides containing silicon dioxide in amounts greater than 5% by weight, and/or halogen such as fluorine and/or chlorine, are unsuitable.

■Preferred group VI and group VIII metals are molybdenum, tungsten, cobalt, nickel and platinum. The non-precious metals can be present on the cracking carrier either in the form of the sulphide or in the form of the oxide. The catalysts containing these metals are, however, preferably used in the sulphided form. The sulphidation of the catalyst can be carried out using any technique known in the art. Particularly suitable catalysts for use in the method according to the invention are the commercially available hydrodesulfurization catalysts which contain between 1 and 5% nickel and between 3 and 20% molybdenum and an aluminum oxide carrier.

The effluent from hydrogen treatment will contain lower-boiling reaction products such as petrol, kerosene and gas oil. These lower-boiling products without a spreading effect must be separated from the spreading oil. Generally, the products that boil higher than 375°C will be recovered as the spread oil fraction. This lubricating oil fraction will then be further fractionated into different base lubricating oils. The base oils with a very high viscosity index, which form the object of the present invention, will suitably be the fraction that boils higher than <1>+80°C. However, the lower boiling point for these oils with a very high viscosity index can vary in the range between 460° and 515°C.

Finally, the wax present is removed by dewaxing. The dewaxing can be carried out according to any conventional method for the dewaxing of oils. Preferably, the lubricant oils are dewaxed to a pour point lower than -12.2%, and most preferably they are dewaxed to a pour point below -15°C With decreasing temperature during the dewaxing of the lubricant oil, the yield is reduced, as the reduction in yield can be as great as 30$ for the oil fraction that boils higher than 4-80°C. There is a corresponding reduction in the viscosity index of approx. 2-3 units. In a typical, satisfactory dewaxing process, the oil is dissolved in a solvent such as propane, methyl ethyl ketone or toluene or in a mixture of the two latter solvents, after which the oil solution is cooled and then filtered. The dewaxing solvent can be removed: by distillation.

The "10 W/30" multi-category oil obtained by the method according to the invention can be mixed into multi-category oils containing a larger proportion of a real "10 W/30" multi-category oil and a smaller proportion of one or more lubricating oil additives as mentioned above. Usually these additives are added in an amount of between 1 and 10% by weight.

Examples of additives that can be mixed into the "10 W/30" oil are the known viscosity index improving agents, such as isobutylene polymers, polyacrylates, polymethacrylates and the like, cleaning agents or detergents of the type metal sulfonates, metal phenates and metal naphthenates, and polymer dispersants, such as poly -ethylene glycol-substituted polymethacrylates and the like. The antioxidants include compounds such as zinc dithiophosphates and alkylated phenols, and examples of known corrosion inhibitors are amine-derived succinic anhydrides.

The following examples will illustrate the invention. In the experiments described, the lubricating oil fractions were dewaxed to a pour point as low as -19°C to show that the results obtained by means of the method according to the invention are not dependent on the dewaxing temperatures used.

Example 1

A propane deasphalted oil obtained from a crude oil from the Middle East was solvent refined with furfural at a temperature of approx. 120°C and a solvent/oil ratio of 5/1. The resulting waxy raffinate (60%, calculated on the deasphalted oil) was used as starting material for the production of base lubricating oils during the hydrotreatment. The waxy raffinate 'had the following characteristics?

Distillation

area

The waxy raffinate was contacted with hydrogen in a laboratory reactor of total capacity 250 ml, in the presence of a commercially available hydrodesulfurization catalyst. The catalyst was used in the form of 1.5 ml extrudates and had the following composition: 17.6 parts by weight MoO^ and h, 0 parts by weight NiO on 100 parts by weight Al2Oy The liquid effluent from the reactor was fractionated, and the material which boiled at temperatures above <4>-80 °C, was extracted as waxy lubricating oil. This waxy lubricating oil was dewaxed at ~30°C with a mixture of methyl ethyl ketone and toluene (in the volume ratio 50/50), so that the oil had a pour point of -19°C. The catalyst was presulfided by making a cold start using a gas oil obtained from a crude oil from the Middle East (1.6 wt% sulphur) as sulphiding agent. The waxy raffinate was treated at two different reactor temperatures. The results are given in Table II.

The data in the table show that a certain minimum temperature and a certain strictness of the conditions are required to obtain an oil with a viscosity index (VI) of at least 132.

Despite. that a hydrocarbon oil refined with furfural was used as the starting material, the lubricating oil obtained had a low viscosity index.

Example II

The experiments described in Example I were repeated using more stringent conditions in a semi-industrial scale plant, using the same starting material and catalyst. The reactor had a capacity of approx. 7 liters and was adapted for operation with recirculation of the hydrogen gas. The catalyst was presulfided for 21 hours with a gas oil (1.6 wt# sulfur), making a cold start. The effluent from the reactor was processed in the same way as in the described experiments 1 and 2. The results are listed in Table III below. This table also provides data for the frying oil fractions with a boiling range of 375° - 4-80°C, which fractions are obtained in addition to the frying oil with a boiling range above V80°C.

The oil obtained in test 5 is a true "10 W/30" multi-category oil that meets the SAE requirements for viscosity and viscosity index. The data show that, by applying the given data, a lubricating oil with a viscosity index higher than 132 and a viscosity at 99°C higher than 9.6 can be produced from a furfural-extracted deasphalted oil.

The by-products include large amounts of light and medium machine oils with a high viscosity index (fractions 375-44-0°C and 4-4-0-1+80°C), which make the method according to the invention a competitive process.

Example III

This example shows how important it is to perform a solvent refining to obtain a "10 W/30" oil.

The deasphalted oil from Example I was used as starting material in the hydrotreatment, the solvent refining step with furfural being omitted. The hydrotreatment step was carried out at three different temperatures, the same catalyst being used as in Example I. The conditions used were a pressure of 200 kg/cm 2 , a space velocity of 1 kg per liters per hour and a hydrogen:oil quantity ratio of 3000 Nl/1.

The results obtained are given in Table IV below.

The lubricating oil fraction with a boiling range above 375°C from trials

Nos. 6 and 8 were further fractionated into 3 separate lubricating oil fractions, namely into a fraction with a boiling range of 4-00-4-4-0°C, a fraction with a boiling range of 4-4-0-4-80°C and a fraction with a boiling range above 4-80°C. The fractions obtained after the dewaxing are listed with their viscosity and viscosity index in Table V below.

The results show that the fraction with a boiling range above 4-80°C from trial 8 has the required viscosity higher than 9.6 cS, but that its viscosity index is far lower than 132. This fraction thus does not satisfy the requirements of a "10 W/30" -butter oil.

Example IV

In an experiment extending over a longer period, a larger batch of true "10 W/30" lubricating oil was produced. The same starting material and the same catalyst were used as in Example I. The reactor, which was on a semi-industrial scale, contained 15.12 kg of catalyst. The catalyst was presulfided by a cold start with a subsequent buy-in period under hydrodesulfurization conditions with a sulfur-containing gas oil. The conditions used during the long-term trial remained fairly constant. Table VI below indicates the results obtained at the beginning of the experiment and towards the end of the experiment (approx. 600 hours). The butter oil fractions were dewaxed to a pour point of -19°C.

The fractions boiling above 4-80°C do not fully meet the "10 W/30" specifications. However, it will be clear to a person skilled in the art that by changing the lower fractionation limit below

the fractionation of the fraction ion > 4-80°C will result in such a multi-category oil. After the end of the experiment, the smoreol ef raks ions<1>+4-0-4-80° and }<4>-80°C were redistilled under laboratory conditions. A "10 W/30" lubricating oil with a viscosity at 99°C of 956 cS and a viscosity index of 133.5 was obtained, in a yield of approx. 6.2% calculated on the waxy raffinate.

Claims (7)

1. Process - in the production of lubricating oils with a viscosity index of at least 132 and a viscosity at 99°C of at least 9.6 centistokes, by hydrotreating a solvent-refined, asphalt-free, waxy hydrocarbon oil in the presence of a sulfided catalyst comprising a metal from group VI and/ or group VIII on a mainly non-acidic, low-melting carrier at elevated temperature, at a pressure between 165°g 225 kg/cm and a space velocity between 0.25°g 2.25 kg oil per liter of catalyst per hour, and the hydrogen-treated oil is fractionated and dewaxed, characterized in that the hydrogen treatment is carried out at a temperature in the range 4-20 - 4-60°C. 2. Procedure according to claim 1, characterized in that a temperature between 4-30° and 4-'+5°C is used. 3. Method according to one of claims 1-2, characterized in that a pressure between 170 and 185 kg/cm<2> is used. 4-. Method according to one of claims 1 - 3, characterized in that a space velocity between 0.4 and 1.7 kg per liters per hour. 5. Method according to one of the claims - 1 - 4 -, characterized in that hydrogen is supplied in an amount of between 500 and 5000 NI per kg starting material. 6. Method according to one of the claims 1-5, characterized in that after the fractionation the spreading oil is dewaxed to a pour point lower than -12.2°C. 7. Method according to one of claims 1-6, characterized in that the catalyst comprises an aluminum oxide-based carrier and contains nickel and molybdenum as the metals.