The present invention relates to a method for reducing mutagenicity in petroleum products. In particular, it relates to a method to reduce mutagenicity in distillate extracts from refining processes.

In oil refineries, mixtures are extracted from crude oils by a system of distillation and/or chemical separation by solvents. This produces a range of different chemical mixtures. Where the mixtures contain polyaromatic hydrocarbons of say 3-9 rings, these mixtures may be carcinogenic.

Examples of such oils are light cycle oil from catalytic cracking of distillation streams (light cycle oil or clarified slurry oil), vacuum distillates (non solvent treated) and main column bottoms.

Atmospheric residuum is produced by atmospheric distillation. In lubrication oil refinery processes, in order to convert this residuum to a useful product, it is generally fractionated under vacuum to convert it into hydrocarbon streams of different molecular size and composition. These fractions are generally classified in terms of their viscosity. The viscosity is measured by an efflux method in terms of second(s). Fractions may be for example in the range of from say 100s (or lower) to 850s (or higher) dependent upon its viscosity.

These fractions are then extracted by use of solvents to remove the aromatic oils. This produces materials termed distillate extracts which are generally termed with respect to their viscosity classification, for example; Extract of 100s. These organic extracts are used for such purposes as the manufacture of, or in combination with, bitumen products, rubber extender oils or solvents.

Solvent refining may also be used in bitumen production in which the vacuum tower bottoms are separated by solvent systems, for example butane or propane deasphalting or rose fluid supercritical extraction, in which an oil is

extracted, for example a deasphalted oil and a residuum propane deasphalted tar (PDA or PPA). The oil may then be solvent extracted to extract the aromatic component. A typical solvent may be furfural. All of the streams so produced may have polyaromatic hydrocarbons of the type described above and be carcinogenic. This is a technique for reducing the mutagenicity index for bitumens.

The highly aromatic nature of these distillate extracts may mean that they have carcinogenic properties. The carcinogenic properties may be measured by the modified Ames test that determines mutagenicity or the propensity for the substance to cause mutations, for example cancer. Generally, these extracts are required to be labelled as carcinogens.

It is therefore highly desirable to reduce the mutagenicity of these extracts. It has been established that, if radical formation sites can be blocked by alkylation then biological activity can be greatly reduced. The present invention concerns another method of achieving the reduction in the biological activity and mutagenicity of aromatic and polyaromatic species.

The present invention aims to overcome or at least alleviate one or more of the difficulties associated with the use and handling of such distillate extracts.

The present invention resides in a method of reducing the mutagenicity effect in petroleum products having a high aromatic nature said method including the step of subjecting the petroleum product to an oxidation process.

The process is particularly applicable for reducing the biological activity of the aromatic content of extracts from refinery processes, particularly distillate extracts from the atmospheric residuum produced in oil refineries.

The oxidation may be achieved by blowing air, oxygen, ozone, mixtures of air or oxygen with carbon dioxide, nitrogen, nitrogen oxides or sulphur oxides, or

other oxidizing sources. The blowing agent may include a gaseous catalyst, for example SeS, SOCI ₂ , S0 ₂ F ₂ , POCI ₃ , PSF ₃ , HSiF ₃ , POF ₃ , Cl ₂ , Cl ₂ 0, COS, NO, N0 ₂ , H ₂ S, H ₂ Se, S0 ₂ , S0 ₃ , mercaptans, of which ethyl or N butyl are examples.

A preferred method is to contact the organic material with fine bubbles of air at elevated temperatures for set periods of time, and at a range of pressures. The air rate is preferably in the range of from 0.1 to 3.0 kg/hr, most preferably about 1.0 kg/hr.

The reaction may be carried out with or without the presence of a catalyst.

Catalysts may be used in order to accelerate the reaction rate. Suitable catalysts include manganese dioxide, mineral acids, metallic persulphates or perborates, phosphorous compounds, including P ₂ 0 ₅ , P ₂ S ₅ , P ₄ S ₃ , P ₄ F ₇ or mixtures of phosphorous compounds with copolymers of isobutylene or styrene, phosphoric acid, boron trifluoride, fluorides or sulphates of zinc, aluminium, iron, copper or antimony optionally with finely divided metals, including, iron, aluminium, magnesium, manganese, copper or lead oxides.

The preferred temperature range for the reaction to take place is from about 100 to about 300°C, preferably between 160°C to 260°C. The pressure may vary from 0.0 bar to about 3.0 bar (gauge pressure), preferably from 1.5 bar to 2.5 bar and most preferably 2.0 bar. It is preferred that the temperature and pressure remain substantially constant during the reaction and are generally determined by the starting materials to be used. Residence times may vary from about 10 minutes to about 10 hours preferably from about 1 to 4 hours.

The preferred parameters of the invention indicated in the above description have been found to be appropriate for laboratory scale reactors of 10 to 15 kg batch size. The method may be carried out on large scale reaction vessels in plant situations with a scaling of the reaction parameters, although the temperature and pressure rates are likely to be consistent to give the correct reaction time and air to charge ratio.

The present invention also relates to petroleum products having reduced biological activity, produced by the method of subjecting the petroleum product to an oxidation step. Such products will have reduced mutagenicity and may avoid the need for them to be labelled as carcinogens.

The method of the invention may take place in a biturox™ reactor however any standard air blowing device may be used.

In a preferred method, the organic material, which may for example consist of organic extracts from heavy lube distillates, is stirred by a mixer and cooled by a water shower, steam injection or by a heat exchange system where the air is mixed with the water at a rate of, for example, 0.2 to 1.0 kg/hr, and injected down a pipe or pipes into the reactor.

The components of the biturox™ are illustrated in Figure 1. The attached figures are illustrative of preferred embodiments of the invention, and the generality of the invention should not be considered to be limited thereto.

The features of the biturox™ reactor (1) illustrated in Figure 1 , include an air inlet (2) and water inlet (3) in close proximity which allows for appropriate heat exchange when the air is mixed with the water and injected into the reactor through pipes (4).

Generally, organic material, for example a distillate extract is fed into the reaction cylinder (5) through inlet (6) and is heated to within the preferred temperature range of between 160°C to 260°C and at a pressure of between 1.5 bar to 2.5 bar. The temperature is generally maintained at a constant temperature by a combination of air and water. Air is bubbled through the organic material through inlet (2) at a rate of about 1 kg/hr, and is mixed through the organic material, with the assistance of air distribution impellers (7) and coalescing devices (8). The impellers are driven by electric device (9). Waste gas exits

through exit (10) while the oxidised organic material exits through either exit (11) or (12).

The oxidation of the organic material is able to reduce the biological activity of the aromatic and polyaromatic species. This results in a significant lowering of the Mutagenicity Index as measured by the modified Ames test.

The reaction may also take place in a conventional reactor which is illustrated in Figure 2. Generally, maintaining the reaction temperature in this case is initiated by steam injection through inlet (23). Air is bubbled through the reactor (25) via inlet (22) through pipe (24) to outlet (21), where it is able to react with the organic material . Distribution of the air is assisted through air distribution spider (29). The oxidised organic material is generally exited through exit (31) and waste gas will exit through exit (30).

The following Examples are illustrative of the present invention, and the generality of the invention should not be considered to be limited by the specific nature of the Examples.

Example 1

Base Stock:: Turbine Oil 750 s extract. Viscosity 40°C : 2.3 Pa.s

Air was bubbled through the petroleum product using a biturox™ pilot plant with the following criteria:

Air rate : 1.0 kg/hr Reaction Temperature : 160°C Reactor Pressure : 200 kPa. Water Rate : 0.35 kg/hr Charge : 14 kg

Agitator speed : 840 rpm Reaction Time : 4 hrs.

Final Viscosity : 4.4 Pa.s at 40°C

Initial Mutagenicity index 1.6 Final Mutagenicity index : 1.1

Example 2

Bitumen: Combination of Propane Deasphalted Tar (89%) by weight; Bright Stock Furfural Extract (11%) by weight.

Air was bubbled through the petroleum product using a biturox™ pilot plant with the following criteria.

Charge : 14 kg

Reaction Temperature : 260°C Air rate : 1.0 kg/hr Reactor Pressure : 200 kPa Water Rate : 0.35 kg/hr Agitator Speed 860 rpm.

Reaction time : 1 hour.

Penetration 25°C of feed : 135 units Penetration of final product : 35 units

Mutagenicity index of initial feed : greater than 1.0 Mutagenicity index of final product : 0.6

Examples 3 to 8

The following table includes results from further tests with various organic extracts. In each case, air was bubbled through the organic extract, using a biturox™ reactor.

ORGANIC EXTRACT INITIAL FINAL UTAGENCTTY MUTAβENJCITY

.NDEX INDEX

100s 20 8

300s 5 1

850s 3 1

Deasphalted Oil 1 0.1

Light Cycle Oil 1200 700

Bright Stock Furfural 0.7 0.3 Extract

Conditions for each of the above tests were varied depending on the starting material. The blowing temperature in each case was below the auto ignition temperature, and varied depending upon the pressures which were employed.

Finally, it is to be understood that various other modifications and/or alterations may be made without departing from the spirit or ambit of the present invention.