Compositions, Methods and Uses

The present invention relates to pyrolysis oils and methods and uses relating thereto. In particular the invention relates to additives for improving the stability of compositions comprising waste rubber pyrolysis oils or waste plastic pyrolysis oils.

Pyrolysis oils are the fluids generated from the pyrolysis of waste, for example plastic waste, used tyres, waste rubber, biomass for example agricultural waste, forestry waste, waste cooking oils and algae waste. Examples of waste plastic which may be pyrolysed to produce plastic pyrolysis oils include polyethylene, polypropylene, polystyrene, polyethylene terephthalates (PET) and mixtures thereof. Oils obtained from the pyrolysis of plastics are commonly referred to as waste plastic pyrolysis oils (WPPOs). Oils obtained from the pyrolysis of rubber (e.g. from tyres) are commonly referred to as waste rubber pyrolysis oils (WRPOs). The organic liquid produced by pyrolysis of rubber, plastics and other waste materials has a very dark colour, an unpleasant odour and is unstable. However there is a strong desire to find a use for such oils to avoid such waste being sent to landfill or polluting oceans.

Pyrolysis oils can be used as a feedstock for chemical processing, for example in the production of polymers such as polyethylene. They may also be used in fuel oils. The use of pyrolysis oils to produce polymers represents a sustainable alternative to the use of crude oil feedstocks.

The utility of pyrolysis oils is limited due to their poor oxidation stability. This is believed to be due to oxidation of oxygen or nitrogen containing species present in the oil. The nature of these oils and their method of production means that they typically comprise a greater proportion of components that are susceptible to oxidation than mineral derived middle distillate fuels.

Pyrolysis oils can be optionally hydrotreated or cracked before subsequent use. Such processes may increase their oxidation stability. Alternatively they may be treated with chemical additives to improve their stability.

The present inventors have found that certain compounds are effective at improving the oxidation stability of compositions comprising pyrolysis oils. Furthermore, the inventors have found that such compounds are effective at improving the storage stability of compositions comprising pyrolysis oils.

According to a first aspect of the present invention there is provided a composition comprising a pyrolysis oil and, as an additive:

The first aspect of the present invention relates to a composition comprising a pyrolysis oil. The pyrolysis oil may be obtained from the pyrolysis of any type of waste. The components of the oil and the properties thereof will depend on the types of waste that was pyrolysed and the pyrolysis conditions. For example the pyrolysis oil may be obtained from the pyrolysis of plastic waste, rubber waste, agricultural waste, forestry waste, waste cooking oils and algae waste.

Preferably the pyrolysis oil comprises a plastic pyrolysis oil. The plastic pyrolysis oil may be obtained from the pyrolysis of any type of plastic.

Preferred plastic pyrolysis oils are obtained from the more pyrolysis of one or more polymers selected from polyethylene, polypropylene, PET, rubber and mixtures thereof.

Preferred plastic pyrolysis oils are obtained from the more pyrolysis of one or more polymers selected from polyethylene, polypropylene, PET, rubber, used tyres and mixtures thereof.

In one especially preferred embodiment the pyrolysis oil is obtained from the pyrolysis of rubber. For example, the pyrolysis oil may be obtained from the pyrolysis of used tyres.

In some embodiments the pyrolysis oil in the composition of the first aspect may be a hydrotreated pyrolysis oil.

In some embodiments the pyrolysis oil in the composition of the first aspect have been treated using a cracking process.

In preferred embodiments the composition of the first aspect comprises a pyrolysis oil directly obtained from a pyrolysis plant without purification or further treatment.

In some embodiments the pyrolysis oil has and n-paraffin content of less than 15 wt %. Preferably less than 10 wt %, for example less than 6 wt %.

In some embodiments the pyrolysis oil has an asphaltene content of less than 5 wt %. Preferably less than 2 wt %, for example less than 1 wt %.

In some embodiments the composition of the first aspect may comprise a blended fuel oil comprising a pyrolysis oil and one or more fuel oils from hydrocarbon and/or renewable sources. Preferably the pyrolysis oil is a waste plastic pyrolysis oil (WPPO) or a waste rubber pyrolysis oil (WRPO).

Throughout this specification, the term “comprising” or “comprises” means including the component(s) specified but not to the exclusion of the presence of other components. The term “consisting essentially of” or “consists essentially of” means including the components specified but excluding other components except for components added for a purpose other than achieving the technical effect of the invention. The term “consisting of” or “consists of” means including the components specified but excluding other components.

Whenever appropriate, depending upon the context, the use of the term “comprises” or “comprising” may also be taken to include the meaning “consists essentially of” or “consisting essentially of”, and also may also be taken to include the meaning “consists of” or “consisting of”.

In some embodiments the composition of the first aspect comprises a blended fuel oil comprising a pyrolysis oil (preferably a WPPO or WRPO) and a middle distillate fuel oil.

The middle distillate fuel oil may comprise a petroleum-based fuel oil, especially a middle distillate fuel oil. Such distillate fuel oils generally boil within the range of from 110° C. to 500° C., e.g. 150° C. to 400° C. The middle distillate fuel oil may comprise atmospheric distillate or vacuum distillate, cracked gas oil, or a blend in any proportion of straight run and refinery streams such as thermally and/or catalytically cracked and hydro-cracked distillates.

The middle distillate fuel oil may comprise non-renewable Fischer-Tropsch fuels such as those described as GTL (gas-to-liquid) fuels, CTL (coal-to-liquid) fuels and OTL (oil sands-to-liquid).

The middle distillate fuel oil may comprise a renewable fuel such as a biofuel composition or biodiesel composition.

The middle distillate fuel oil may comprise 1st generation biodiesel. First generation biodiesel contains esters of, for example, vegetable oils, animal fats and used cooking fats. This form of biodiesel may be obtained by transesterification of oils, for example rapeseed oil, soybean oil, safflower oil, palm oil, palm kernel oil, corn oil, peanut oil, cotton seed oil, tallow, coconut oil, physic nut oil (Jatropha), sunflower seed oil, used cooking oils, hydrogenated vegetable oils or any mixture thereof, with an alcohol, usually a monoalcohol, in the presence of a catalyst.

The middle distillate fuel oil may comprise second generation biodiesel. Second generation biodiesel is derived from renewable resources such as vegetable oils and animal fats and processed, often in the refinery, often using hydroprocessing such as the H-Bio process developed by Petrobras. Second generation biodiesel may be similar in properties and quality to petroleum based fuel oil streams, for example renewable diesel produced from vegetable oils, animal fats etc. and marketed by ConocoPhillips as Renewable Diesel and by Neste as NExBTL.

The middle distillate fuel oil used in the present invention may comprise third generation biodiesel. Third generation biodiesel utilises gasification and Fischer-Tropsch technology including those described as BTL (biomass-to-liquid) fuels. Third generation biodiesel does not differ widely from some second generation biodiesel, but aims to exploit the whole plant (biomass) and thereby widens the feedstock base.

The middle distillate fuel oil may contain blends of any or all of the above diesel fuel oils.

In some embodiments the middle distillate fuel oil may be a blended diesel fuel comprising bio-diesel. In such blends the bio-diesel may be present in an amount of, for example up to 0.5%, up to 1%, up to 2%, up to 3%, up to 4%, up to 5%, up to 10%, up to 20%, up to 30%, up to 40%, up to 50%, up to 60%, up to 70%, up to 80%, up to 90%, up to 95% or up to 99%.

In some embodiments the middle distillate fuel oil may comprise a secondary fuel, for example ethanol. Preferably however the diesel fuel composition does not contain ethanol.

The middle distillate fuel oil may contain a relatively high sulphur content, for example greater than 0.05% by weight, such as 0.1% or 0.2%.

However in preferred embodiments the middle distillate fuel oil has a sulphur content of at most 0.05% by weight, more preferably of at most 0.035% by weight, especially of at most 0.015%.

Fuels with even lower levels of sulphur are also suitable such as, fuels with less than 50 ppm sulphur by weight, preferably less than 20 ppm, for example 10 ppm or less.

Various metal species may be present in the middle distillate fuel oil. This may be due to contamination of the fuel during manufacture, storage, transport or use or due to contamination of fuel additives. Metal species may also be added to fuels deliberately. For example transition metals are sometimes added as fuel borne catalysts, for example to improve the performance of diesel particulate filters.

In preferred embodiments the middle distillate fuel oil used in the present invention comprise sodium and/or calcium. Preferably they comprise sodium. The sodium and/or calcium is typically present in a total amount of from 0.01 to 50 ppm, preferably from 0.05 to 5 ppm preferably 0.1 to 2 ppm, such as 0.1 to 1 ppm.

Other metal-containing species may also be present as a contaminant, for example through the corrosion of metal and metal oxide surfaces by acidic species present in the fuel or from lubricating oil. In use, fuels such as diesel fuels routinely come into contact with metal surfaces for example, in vehicle fueling systems, fuel tanks, fuel transportation means etc. Typically, metal-containing contamination may comprise transition metals such as zinc, iron and copper; other group I or group II metals and other metals such as lead.

In addition to metal-containing contamination which may be present in middle distillate fuel oils there are circumstances where metal-containing species may deliberately be added to the fuel. For example, as is known in the art, metal-containing fuel-borne catalyst species may be added to aid with the regeneration of particulate traps.

Metal-containing contamination, depending on its source, may be in the form of insoluble particulates or soluble compounds or complexes. Metal-containing fuel-borne catalysts are often soluble compounds or complexes or colloidal species.

In some embodiments, the middle distillate fuel oil may comprise metal-containing species comprising a fuel-borne catalyst. Preferably, the fuel borne catalyst comprises one or more metals selected from iron, cerium, platinum, manganese, Group I and Group II metals e.g., calcium and strontium. Most preferably the fuel borne catalyst comprises a metal selected from iron and cerium.

In some embodiments, the middle distillate fuel oil may comprise metal-containing species comprising zinc. Zinc may be present in an amount of from 0.01 to 50 ppm, preferably from 0.05 to 5 ppm, more preferably 0.1 to 1.5 ppm.

The composition of the first aspect comprises (a) one or more nitrogen containing antioxidants.

Any suitable nitrogen containing antioxidant may be used.

Suitable nitrogen containing antioxidants will be known to the person skilled in the art.

Suitable amino based antioxidants include aromatic amines, hindered amines, N-oxides, substituted hydroxylamines, and acylated nitrogen compounds.

Suitable aromatic amines include diaminobenzene and alkylated diamino benzenes, especially dialkylated and trialkylated diaminobenzenes, for example p-phenylenediamine, 3,5-diethyltoluene-2,4-diamine; 3,5-diethyltoluene-2,2-diamine; 2,4,6-triethylbenzene-2,6-diamine alkylated diphenyl amines; diphenylamines and alkylated diphenylamines, for example N,N-diphenyl-1,4-phenylenediamines; and naphthylamines, for example N-phenyl-1-napthylamine and N-phenyl-2-naphthylamine.

Suitable hindered amines include secondary and tertiary aliphatic amines, for example dimethyl cyclohexylamine.

Suitable N-oxides include TEMPO and derivatives thereof.

Preferably the one or more nitrogen containing antioxidants (a) are selected from:

Suitable acylated nitrogen compounds (i) may be made by reacting a carboxylic acid acylating agent with an amine and are known to those skilled in the art. In such compounds the acylating agent is linked to the amino compound through an imido, amido, amidine or acyloxy ammonium linkage.

Preferred acylated nitrogen-containing compounds are hydrocarbyl substituted. The hydrocarbyl substituent may be in either the carboxylic acid acylating agent derived portion of the molecule or in the amine derived portion of the molecule, or both. Preferably, however, it is in the acylating agent portion. A preferred class of acylated nitrogen-containing compounds suitable for use in the present invention are those formed by the reaction of an acylating agent having a hydrocarbyl substituent of at least 8 carbon atoms and a compound comprising at least one primary or secondary amine group.