This application claims priority to U.S. provisional application N°.

62/315949 filed on March 31, 2016 and to European application N°. 16306635.0 filed on December 07, 2016, the whole content of each of these applications being incorporated herein by reference for all purposes.

Technical field

The present invention relates to a process for converting plastic into waxes by cracking. The process comprises the steps of introducing the plastic within a reactor; allowing at least a portion of the plastic to be converted to waxes, the waxes being part of a pyrolysis gas formed within the reactor; and removing a product stream containing said waxes from the reactor.

The invention also relates to a mixture of hydrocarbons obtainable by that process.

Prior art

In view of the increasing importance of polymers as substitutes for conventional materials of construction, such as glass, metal, paper and wood, the perceived need to safe non-renewable resources such as petroleum and dwindling amounts of landfilled capacity available for the disposal of waste products, considerable attention has been devoted in recent years to the problem of recovering, reclaiming, recycling or in some way reusing waste plastic.

It has been proposed to pyrolize or catalytically crack the waste plastic so as to convert high molecular weight polymers into volatile compounds having much lower molecular weight. The volatile compounds, depending on the process employed, can be either relatively high-boiling liquid hydrocarbons useful as fuel oils or fuel oil supplements or light- to medium-boiling carbon atoms useful as gasoline-type fuels or as other chemicals. Furthermore, the volatile compounds can be or at least can include waxes.

Catalytic cracking of a mixed waste plastic is a process well-known to the person skilled in the art. For example, US 5,216,149 discloses a method for controlling the pyrolysis of complex waste stream of plastics to convert such stream into useful high- value monomers or other chemicals, by identifying catalyst and temperature conditions that permit decomposition of a given polymer.

Research has been conducted in an effort to optimize process parameters with respect to an increased yield of desired cracking products. For example, US 2015/0247096 Al describes a method for converting a waste plastic to wax by adding hydrogen to the reaction chamber and heating the waste plastic and hydrogen sufficiently to thermally depolymerize the waste plastic to form a wax product, comprising paraffin and olefin compounds. Cracking is conducted at a temperature of about 300°C to about 500°C for a duration of about 1 minute to about 45 minutes, sufficient to cause thermal degradation of substantially all of the melted plastic feed stock.

US 6,150,577 and US 6,143,940 disclose a method for making a heavy wax composition from waste plastics in a pyro lysis zone at sub-atmospheric pressure forming a pyro lysis zone effluent including 1 -olefins and n-paraffins. Pyrolysis is conducted at a temperature of from 500 to 700°C.

M. Arabiourrutia et al. describe in Journal of Analytical and applied pyrolysis 94 (2012) 230-237 the characterization of waxes obtained by the pyrolysis of polyolefin plastics. The authors investigated the influence of the cracking temperature on the yields of waxes and volatiles obtained from different polyolefins. It was found that increasing the cracking temperature from 450°C to 600°C results for example for LDPE (low-density polyethylene) in a decrease in the obtained waxes from 80 wt. % to 51 wt. %. At the same time the amount of obtained volatiles increases from 20 wt. % to 49 wt. %. These findings support the general understanding that increasing the temperature favors the cracking rate towards the formation of shorter chain products.

There is, however, still a need for further improving the cracking of plastic in particular with respect to the yield of specific products, such as waxes and the composition of such products. In certain applications it is, for example, desirable to obtain a high yield of waxes from plastic. Furthermore, it can be desirable to obtain waxes having an increased average carbon chain length.

Brief description of the invention

The present inventors now found that contrary to the above expectation that with increasing cracking temperature the yield of waxes is decreasing, the yield of waxes is surprisingly increased even at high cracking temperatures if the pyrolysis gas which is formed during the cracking of the plastic and which contains the volatile cracking products has only a short residence time at a temperature above 370°C.

Furthermore, the present inventors found that under the specific process conditions a novel mixture of hydrocarbons comprising predominantly waxes is obtained wherein the hydrocarbons have a high number of carbon atoms, are predominantly linear hydrocarbons and have a unique ratio of n-paraffins to alpha-olefms.

Detailed description of the invention

The present invention therefore relates to a process for converting plastic into waxes by cracking, the process comprising:

introducing the plastic within a reactor;

allowing at least a portion of the plastic to be converted to waxes, the waxes being part of the pyrolysis gas formed within the reactor; and

removing a product stream containing said waxes from the reactor;

characterized in that the pyrolysis gas has a residence time at a temperature above 370°C of less than 60 seconds.

The present invention furthermore relates to a mixture of hydrocarbons, characterized in that the hydrocarbons exhibit a cumulative distribution of their number of carbon atoms such that 20 < d20 and 50 > d50;

> 50 mol % of the hydrocarbons are linear hydrocarbons;

and the molar ratio of n-paraffins to alpha-olefms among the hydrocarbons is in the range of 0.1 to 10.

Furthermore, the present invention relates to a process for producing said mixture wherein in the above described process for converting plastic into waxes said mixture is obtained by removing the product stream containing the waxes from the reactor.

In the catalytic cracking of plastic several fractions of chemical compounds are obtained. Usually, there is a gas fraction containing light-weight chemical compounds with less than 5 carbon atoms. The gasoline fraction contains compounds having a low boiling point of for example below 150°C. This fractions includes compounds having 5 to 9 carbon atoms. The kerosene and diesel fraction has a higher boiling point of for example 150°C to 359°C. This fraction generally contains compounds having 10 to 21 carbon atoms. The even higher-boiling fractions are generally designated as heavy cycle oil (or HCO) and waxes. In all these fractions, the compounds are hydrocarbons which optionally comprise heteroatoms, such as N, O, etc. "Waxes" in the sense of the present invention therefore designate hydrocarbons which optionally contain heteroatoms. In most cases, they are solid at room temperature (23°C) and have a softening point of generally above 26°C. A definition of the obtained fractions is provided in the experimental section below.

A plastic is mostly constituted of a particular polymer and the plastic is generally named by this particular polymer. Preferably, a plastic contains more than 25 % by weight of its total weight of the particular polymer, preferably more than 40 % by weight and more preferably more than 50 % by weight. Other components in plastic are for example additives, such as fillers, re-enforcers, processing aids, plasticizers, pigments, light stabilizers, lubricants, impact modifiers, antistatic agents, inks, antioxidants, etc. Generally, a plastic comprises more than one additive.

Plastics used in the process of the present invention include polyolefms and polystyrene, such as high-density polyethylene (HDPE), low-density polyethylene (LDPE), ethylene-propylene-diene monomer (EPDM),

polypropylene (PP) and polystyrene (PS). Mixed plastics mostly constituted of polyolefm and polystyrene are preferred.

Other plastics, such as polyvinyl chloride, polyvinylidene chloride, polyethylene terephthalate, polyurethane (PU), acrylonitrile-butadiene-styrene (ABS), nylon and fluorinated polymers are less desirable. If present in the plastic, they are preferably present in a minor amount of less than 50 % by weight, preferably less than 30 % by weight, more preferably less than 20 % by weight, even more preferably less than 10 % by weight of the total weight of the dry weight plastic.

Preferably, the plastic comprises one or more thermoplastic polymers and is essentially free of thermosetting polymers. Essentially free in this regard is intended to denote a content of thermosetting polymers of less than 15, preferably less than 10 and even more preferably less than 5 % by weight of the plastic starting material.

Usually, waste plastic contains other non-desired components, namely foreign materials such as paper, glass, stone, metal, etc.

The plastic used in the process of the present invention can be selected among:

single waste plastic, single virgin plastic on spec or off spec, mixed waste plastic, rubber waste, organic waste, biomass or a mixture thereof. Single plastic waste, single virgin plastic off spec, mixed waste plastic, rubber waste or a mixture thereof are preferred. Single virgin plastic off-spec, mixed waste plastic or a mixture thereof particularly preferred. Mixed plastic waste gives usually good results.

Limited quantity of unpyrolysable component such as water, glass, stone, metal and the like as contaminant of inlet raw material are acceptable. A "low content" preferably means a minor amount of less than 50 % by weight, preferably less than 20 % by weight, more preferably less than 10 % of the total weight of the dry plastic. Preferably, the individual content of any less desirable plastic is less than 5 % by weight, more preferably less than 2 % by weight based on the total weight of the dry plastic.

Preliminary to the pyro lysis, the raw material can be pretreated by a physico-chemical process including one or more operations as size reduction, grinding, shredding, screening, chipping, metal removal, foreign material removal, dust removal, drying, degasing, melting, solidifying and agglomerating.

The pretreatment can be conducted at a temperature lower or equal to 350°C, preferably lower or equal to 330°C. Gaseous degradation products occurring during the pretreatment are advantageously removed. Examples of gaseous degradation products are hydrochloric acid, hydrobromic acid, hydrofluorhydric acid, CO, C02, small carbon containing molecules with no more than 4 C-atoms such as methane, ethane, butane, ethylene, acetylene, propane, propylene, butene, methanol, formic acid, formaldehyde, acetic acid, acetaldehyde, ethanol, acetone and the like.

Some of these degradation products might react with other materials present in the plastic and produce undesired reaction products. Examples of such materials are fillers, for instance alkaline fillers such as PCC (precipitated calcium carbonate) or chalk, lime, soda lime, sodium carbonate, sodium bicarbonate, alumina, titanium oxide, magnesium oxide, calcium oxide, and the like.

At the outlet of the pretreatment, the raw material can be solid or melted, preferably melted. Optionally, an acid capturing component can be added for the pretreatment. Examples of acid capturing components are fillers, for instance alkaline fillers such as PCC (precipitated calcium carbonate), alumina, titanium oxide, magnesium oxide, calcium oxide, and the like.

The present inventors surprisingly found that waxes can be obtained at high yield from the cracking of plastics even at high de-polymerization temperature if the pyrolysis reactor and the operation conditions ensure a short residence time of less than 60 second of the pyrolysis gas at a high temperature of above 370°C. This finding is particularly surprising because a high cracking temperature should favor cracking rate towards the formation of shorter-chain products. In other words, lower content of the wax mixture should be found at higher temperatures.

Additionally, the present inventors found that at short residence time of the pyrolysis gas at high temperature not only more of the wax mixture is produced but also the average carbon chain length of the wax is increased. This allows carrying out the cracking process at rather high temperatures which ensures high conversions of the raw material and a low residue of for example less than 50 g/kg plastic raw material but nevertheless allows the production of an increased amount of waxes having even an increased average carbon chain length.

In the cracking reactor the plastic is generally present in a molten state at cracking temperature. The cracking reaction results in a de-polymerization of the plastic yielding lower molecular weight products. At the temperature in the cracking reactor these lower molecular weight products evaporate forming a pyrolysis gas within the reactor. This gas comprises the volatile pyrolysis fractions, such as light-weight hydrocarbons, diesel, kerosene and waxes. The invention is based on the finding that the pyrolysis gas should be quickly removed from the hot cracking reaction zone and it was found that high yields of waxes are obtained if the pyrolysis gas has a residence time at a temperature above 370°C of less than 60 seconds, preferably less than 50 seconds, more preferably less than 40 seconds, even more preferably less than 30 seconds, furthermore preferably less than 25 seconds and most preferably less than 20 seconds, such as less than 15 or even less than 10 seconds.

On the other hand, cracking reactions still occur in the pyrolysis gas as long as the temperature is high enough. Therefore, if the residence time of the pyrolysis gas at a temperature above 370°C is too short, the obtained products can also have undesirable characteristics, for example with respect to carbon chain length, content of branched hydrocarbons, content of aromatics, etc.

Therefore, in certain embodiments it can be desirable if the residence time of the pyrolysis gas at a temperature above 370°C is more than 2 seconds, preferably more than 5 seconds, even more preferably more than 10 seconds, such as more than 15 or even more than 20 seconds.

Fast removal of the pyrolysis gas allows high pyrolysis temperatures for cracking the plastic. This has the further advantage that conversion of the plastic can be high and undesired residues are low. For example, the temperature at which at least a portion of the plastic is converted to waxes is at least 370°C, preferably at least 400°C, more preferably at least 425°C, even more preferably at least 440°C. The temperature at which the plastic is converted can be as high as desired, for example up to 850°C, preferably up to 700°C, more preferably up to 600°C, even more preferably up to 500°C, such as up to 480°C or up to 470°C. In preferred embodiments the temperature at which the plastic is converted ranges from 400 to 650°C, preferably from 425 to 550°C, preferably from 440 to 520°C, even more preferable 440 to 470°C. Most preferably the temperature at which the plastic is converted ranges from 400 to less than 500°C.

The required low residence time of the pyro lysis gas at a temperature of above 370°C can be obtained by any suitable means, such as reducing the residence time of the pyrolysis gas in the reactor by operating the reactor under vacuum, by dilution of the pyrolysis gas in the reactor itself, by design of the reactor for example by limiting the volume of the gas phase, or by increasing the percentage of the reactor volume filled by liquid and (if present) solid, or by a combination of these measures. Generally, it is preferred to combine several of these measures in order to obtain the desired low residence time.

In one embodiment the reactor is operated at a pressure of less than or equal to 1200 mbar, preferably less than or equal to 1000 mbar, more preferably less than or equal to 950 mbar and even more preferably less than or equal to 900 mbar. The pressure in the reactor can be as low as 0.5 mbar, preferably 1 mbar, preferably 10 mbar, preferably 40 mbar, preferably 50 mbar, more preferably 60 mbar and even more preferably 80 mbar. For example the reactor can be operated at a pressure in the range of 0.5 to 1200 mbar, preferably 10 to 1100 mbar, preferably 50 to 1000 mbar, more preferably 60 to 950 mbar and even more preferably 80 to 900 mbar.

In an alternative or additional embodiment the pyrolysis gas can be diluted with a diluent. Such diluent is not particularly limited but should not adversely affect the pyrolysis reaction or the desired reaction products. In particular, the diluent should have a low oxygen (02) content as described below. Examples of suitable diluents are nitrogen, hydrogen, steam, carbon dioxide, combustion gas, hydrocarbon gas and mixtures thereof. The hydrocarbon gas preferably comprises one or more hydrocarbons having less than 5 carbon atoms. Nitrogen, carbon dioxide, combustion gas and hydrocarbon gas with less than 5 carbon

atoms are preferred. Combustion gas and hydrocarbon gas with less than 5 carbon atoms are particularly preferred.

The diluent preferably has a low oxygen (02) content, such as less than

4 % vol, preferably less than 2 % vol, more preferably less than 1 % vol, each based on the volume of the dry gas. Combustion gas with less than 0.1 % vol oxygen based on the dry gas gives particularly good results.

The dilution level is not particularly limited and can be selected according to the requirements. For example, the molar ratio of diluent to pyrolysis product in the pyrolysis gas can be above 0.5, preferably above 0.7, more preferably above 0.8, and even more preferably above 1. A molar ratio of diluent to pyrolysis products in the pyrolysis gas of above 50 is less preferred.

Advantageously, this ratio is up to 40, more preferably up to 20. Preferred molar ratios of diluent to pyrolysis products in the pyrolysis gas are in the range of 0.5 to 50, preferably 0.7 to 40 and more preferably 0.8 to 20, such as 1 to 10 or even 1 to 7.

The diluent may be introduced into the reactor at any position. For example, an inlet for the diluent can be positioned in the top of the reactor so that the diluent basically only comes into contact with the pyrolysis gas but not with the plastic melt under reaction conditions. In an alternative embodiment the diluent inlet can be positioned for example in the bottom part of the reactor so that the diluent comes into contact with the plastic melt under reaction conditions. A combination of two or more different inlets may be used.

Preferably at least one diluent inlet is positioned in the bottom part of the reactor. It has been found that in this case the pyrolysis gas is effectively removed from the hot plastic melt thereby effectively reducing the residence time of the pyrolysis gas at a temperature above 370°C. Most preferably a combination of a diluent inlet positioned in the top of the reactor and a diluent inlet positioned in the bottom part of the reactor is employed.

In a particularly preferred embodiment the reactor is operated at a reduced pressure and diluent is used. In this case the molar ratio D of diluent to pyrolysis products in the pyrolysis gas and the absolute pressure P at which the reactor is operated can be adjusted such that D/P is in the range of 2 to 50 mol/mol/bar, particularly in the range of 3 to 30 mol/mol/bar, more particularly in the range of

5 to 20 mol/mol/bar.

In one embodiment of the process of the present invention the conversion of at least a portion of the plastic to waxes is conducted in the presence of a heat carrier. Examples of suitable heat carriers are sand (such as silica), stone, gravel, metal, metal oxides, glass, ceramic, etc. Any metal having a melting point above the temperature at which cracking of the plastic is conducted can be employed. Suitable metals are for example iron and steel, such as forged steel and refractory steel. Sand, metal, such as steel or iron, gravel, and glass are preferred. Sand and steel are particularly preferred.

The carrier may be a catalyst for the cracking of the plastic. In a preferred embodiment the heat carrier is, however, not a catalyst for gas-phase cracking of hydrocarbons.

Preferably, the heat carrier has a particle size higher than the particle size of the filler used in the plastic.

In one embodiment the heat carrier comprises particles, preferably free-flowing particles, for instance granular round particles, near spherical particles, full balls, hollow balls, and the like. Preferably, the heat carrier particles have a higher particle size than standard US mesh 632, preferably higher than standard US mesh 400. Also preferably the heat carrier particles have a particle size lower or equal to about 5 cm, preferably lower or equal to about 2.5 cm.

When the heat carrier is sand, the heat carrier particles are advantageously fine or medium sand according to ISO 14688-1 :2002. Preferably the heat carrier particles are fine sand.

When the heat carrier is metal, such as iron or steel, they are preferably in the form of full balls. The particle size can be between 1 and 50 mm, preferably between 10 and 30 mm. When the heat carrier is glass, the particles are advantageously glass bead or glass balls having a size of between 0.5 and 20 mm, preferably of between 0.6 and 6 mm.

When the heat carrier is gravel, it is preferably fine or medium gravel according to ISO 14688-1 :2002, preferably fine gravel.

The residence time of the pyrolysis gas in the reactor is expressed as the gas hold-up of the reactor (in other words, the volume of the reactor occupied by the gaseous material and expressed in m3) divided by the flow of gas exiting the reactor and expressed in m3/min. To take into account thermal gas expansion, gases are considered to be at the same temperature of the pyrolysis reactor. If used, gas exiting the reactor comprise the diluent.

The residence time of the condensed material in the reactor is expressed as the condensed material hold-up of the reactor (in other words, the volume of the reactor occupied by the condensed material and expressed in m3) divided by the

outlet condensed material flow expressed in m3/min. Temperature expansion of condensed material is neglected. This residence time is not particularly limited but usually is in the range of 1 to 600 minutes, preferably in the range of 2 to 400 minutes, more preferably in the range of 3 to 250 minutes. By "condensed material" the total amount of unconverted raw material in the liquid or solid form, liquid and solid products obtained from the reactions (such as for example coke, ashes) and, if used, the heat carrier is understood.

The process of the present invention can be conducted batchwise or continuously. Conducting the process continuously is preferred.

The skilled person is aware of suitable apparatus and equipment for carrying out the process in accordance with the present invention and he will select the suitable system based on his professional experience, so that no further extensive details need to be given here.

Examples of suitable reactor types are fluidized bed, entrained bed, spouted bed, downcomer, fixed bed, rotating drum, rotating cone, screw cone, screw auger, extruder, molecular distillation, thin film evaporator, kneader, cyclone and the like. Fluidized bed, entrained bed, spouted bed, screw auger and rotating drum are preferred. Screw auger and rotating drum are particularly preferred. Rotating drum gives good results.

Gas exiting the pyrolysis reactor may be cleaned from dust in any de-dusting device. Examples of de-dusting devices are cyclone, multi-cyclone, helical separator, grid separator, swirl tube, electrostatic filter, settling chamber, scroll collector, shutter collector, wet washer and the like. Cyclone, multi-cyclone, helical separator and swirl tube are preferred. Multi-cyclone is particularly preferred.

Separation of the incondensable gas is realized by any ways known by a person skilled in the art. Incondensable gas are meant here as component not condensed at the operating pressure at a temperature of 25°C. Examples of separation devices are quench, organic quench, aqueous quench, spray column, fractionation column, cyclone and the like. Organic quench is preferred.

Organic quench operated at a temperature between 110 and 250°C is preferred, between 125 and 220°C being particularly preferred. Between 140 and 180°C being even more preferred.

Vacuum can be provided by any device known by the man skilled in the art. Examples of vacuum devices are liquid ring pump, dry vacuum pump, steam ejector, gas ejector, water ejector and any combination.

Combustion is made in any device known by the man skilled in the art.

Separation of the waxes from the fuel is made by any method known by the man skilled in the art. Examples are evaporation, distillation, crystallization, liquid extraction or a combination. Combination of evaporation and solvent extraction gives good results. Example of solvent are hexane, benzene, toluene, methylethylketone (MEK), methylisobutylketone (MIBK). MEK and MIBK are preferred.

The condensate material separate at the outlet of the reactor may be extracted by any means known by the man skilled in the art. Examples of means are screw, rotating valve and the like. Screw is preferred.

In order to avoid spontaneous ignition, the condensated material may be extracted in an atmosphere with low oxygen content. Less than 2 % 02 in the gas phase surrounding the condensed material is preferred. The condensate material may be cooled down by any means known to the man skilled in the art. Examples are double wall screw conveyor, screw conveyor with water injection, extruder, screw auger and the like. Screw conveyor with water injection is preferred.

Optionally, the condensed material may be sent to a burner to burn the combustible unconverted raw material and the coke. Particularly in the case of having a heat carrier. Optionally, the ashes and the heat carrier are heated in a furnace at a temperature between 500 and 1000°C, preferably between 600 and 800°C. Optionally, at least a portion of the hot ashes and heat carrier is sent to the pyrolysis reactor. Preferably, at least a portion of the ashes are separated from the heat carrier. The separation is made by any method known by the man skilled in the art. Examples of methods are cycloning, elutriation, screening, sieving, centrifuging and the like. The ratio of the heat carrier flow to the raw material flow is usually comprised 0.1 and 10 in weight. Preferably between 0.2 and 8. A ratio higher than 0.25 gives particularly good results.

The process of the present invention yields high- value waxes and mixtures of hydrocarbons comprising predominantly these waxes to be used for example in applications such as candles, adhesives, packaging, rubber, cosmetics, fire logs, bituminous mixtures, superficial wear coatings, asphalt, sealing coatings, etc.

The present invention therefore also relates to a wax or a mixture of hydrocarbons obtainable by the invented process.

The waxes and mixtures of hydrocarbons have the advantage of having a rather high chain length, in particular a linear carbon chain. Furthermore, the obtained waxes are generally a wax mixture mainly containing n-paraffins and alpha-olefins. The percentage of alpha-olefins in the wax can be from about 25 to 75 wt. %, preferably from about 40 to 60 wt. %, more preferably about 50 wt. %, each based on the total weight of the wax.

The present invention therefore also relates to a mixture of hydrocarbons, characterized in that the hydrocarbons exhibit a cumulative distribution of their number of carbon atoms such that 20 < d20 and 50 > d50;

> 50 mol % of the hydrocarbons are linear hydrocarbons;

and the molar ratio of n-paraffins to alpha-olefins among the hydrocarbons is in the range of 0.1 to 10.

The mixture of hydrocarbons according to the invention predominantly comprises waxes, i.e. hydrocarbons having 20 or more carbon atoms. The mixture may, however, also contain a small amount of hydrocarbons having less than 20 carbon atoms. Preferably, the mixture comprises less than 5 mol %, more preferably less than 3 mol %, even more preferably less than 2 mol % and most preferably less than 1 mol % of hydrocarbons having less than 20 carbon atoms. Here and anywhere else throughout this application "mol % of the hydrocarbons" refers to the total amount of hydrocarbons in the mixture of hydrocarbons.

In preferred embodiments, the hydrocarbons in the mixture of

hydrocarbons exhibit a cumulative distribution of their number of carbon atoms such that 22 < d20, preferably 25 < d20.

In a further embodiment, the hydrocarbons in the mixture of hydrocarbons exhibit a cumulative distribution of their number of carbon atoms such that d20 < 40, more preferably d20 < 35, even more preferably d20 < 30.

In a further embodiment, the hydrocarbons in the mixture of hydrocarbons exhibit a cumulative distribution of their number of carbon atoms such that 20 < d20 < 40, preferably 22 < d20 < 35, more preferably 25 < d20 < 30.

In a further embodiment, the hydrocarbons in the mixture of hydrocarbons exhibit a cumulative distribution of their number of carbon atoms such that 45 > d50, preferably 40 > d50.

In a further embodiment, the hydrocarbons in the mixture of hydrocarbons exhibit a cumulative distribution of their number of carbon atoms such that 50 > d50 > 20, preferably 40 > d50 > 22.

In preferred embodiments, the hydrocarbons in the mixture of

hydrocarbons exhibit a cumulative distribution of their number of carbon atoms such that 20 < d20 < 40 and 50 > d50 > 20, more preferably 22 < d20 < 25 and 40 > d50 > 22.

Besides the high number of carbon atoms, the hydrocarbons in the mixture of hydrocarbons according to the invention have the advantage that they comprise a high molar amount of linear hydrocarbons. Preferably, > 60 mol %, more preferably > 70 mol % of the total amount of hydrocarbons in the mixture of hydrocarbons are linear hydrocarbons.

A further advantage of the hydrocarbons in the mixture of hydrocarbons according to the invention is that they have a certain molar ratio of n-paraffins to alpha-olefms in the range of 0.1 to 10, preferably in the range of 0.2 to 5, more preferably in the range of 0.5 to 2. In the context of the present invention, n-paraffins are linear saturated hydrocarbons while alpha-olefms are linear and branched hydrocarbons, which contain at least one alpha-double bond.

A further advantage of the hydrocarbons in the mixture of hydrocarbons according to the invention is that the unsaturated hydrocarbons comprise a high amount of alpha-olefms. Preferably, > 40 mol %, more preferably > 45 mol %, even more preferably > 50 mol % of the total amount of the unsaturated hydrocarbons are alpha-olefms.

In a further embodiment, the mixture of hydrocarbons has a iodine number of > 10, preferably of > 25, more preferably of > 40.

In a further embodiment, the mixture of hydrocarbons has a iodine number of < 150, preferably of < 100, more preferably of < 70.

In preferred embodiments, the mixture of hydrocarbons has a iodine number in the range of 1 to 150, more preferably in the range of 25 to 100, and even more preferably in the range of 40 to 70.

A further advantage of the mixture of hydrocarbons according to the invention is that the mixture can have a relatively high drop point of for example > 25°C, preferably of > 40°C, more preferably of > 50°C.

The mixture of hydrocarbons according to the invention can consist of hydrocarbons which do not contain any heteroatoms. However, depending on the plastic from which the mixture of hydrocarbons is produced, it is well possible that at least a portion of the hydrocarbons contains one or more heteroatoms, such as oxygen, sulfur, nitrogen or halogen, such as fluorine, chlorine, bromine or iodine. Other heteroatoms are possible as well.

The mixture of hydrocarbons according to the invention can be obtained by the above described process by catalytic cracking of plastic. If the product stream removed from the reactor is selected such that it contains only hydrocarbons with at least 20 carbon atoms, waxes are obtained. However, in practice and in particular on a technical scale, the product stream will usually contain minor amounts of hydrocarbons having less than 20 carbon atoms. In this case, the above described mixture of hydrocarbons is obtained.

Figures

Figure 1 schematically shows a first embodiment of the process of the present invention.

Figure 2 schematically shows a second embodiment of the process of the present invention.

Figure 3 shows the evolution of conversion (as %, y-axis) as function of reaction time (expressed in minutes, x-axis) at different temperatures: 425°C (square-marked line), 450°C (circle-marked line) and 465°C (triangular-marked line).

Figure 4 shows the cumulative selectivity (expressed as %, y-axis) of the different reaction products (listed in the x-axis) at different temperatures: 425°C (white bars), 450°C (black-white pattern fill bars) and 465°C (black bars).

Figure 5 shows the wax cumulative selectivity (expressed as %, y-axis) as function of the pyrolysis gas residence time (expressed in seconds, x-axis).

Figure 6 shows the carbon number distribution of the waxes. The plot shows the weight percentage (wt %, y-axis) as function of carbon chain length (expressed as a number, x-axis) for different reaction temperatures: 425°C (square-marked line), 450°C (circle-marked line) and 465°C (triangular-marked line).

Figure 7 shows the conversion (expressed as %, y-axis) as function of reaction time (expressed in minutes) for different temperatures and inlet N2 flow rates: 450°C and 150 mL/min N2 (empty-circle-marked line), 465°C and 150 mL/min N2 (empty-triangular-marked line), 450°C and 1 L/min N2 (full-circle-marked line), 465°C and 1 L/min N2 (full-triangular-marked line), 465°C and 2 L/min N2 (empty-rhombus-marked line), 465°C and 4 L/min N2 (empty-square-marked line).

Figure 8 shows the cumulative selectivity (expressed as %, y-axis) of the different reaction products (listed in the x-axis) at different temperatures and N2 flow rate. Legend: for each product, starting from left to the right the color of the bars refer to 450°C and 150mL/min, 450°C and 1 L/min, 465°C and

150 mL/min, 465°C and 1 L/min, 465°C and 2 L/min, 465°C and 4 L/min.

Figure 9 shows the waxes cumulative selectivity (expressed as %, y-axis) as function of the pyrolysis gas residence time (expressed in seconds, x-axis) for two reaction temperatures: 450°C (circled-marked line) and 465°C (square-marked line).

Figure 10 shows the carbon number distribution of the waxes. The plot shows the weight percentage (wt %, y-axis) as function of carbon chain length (expressed as a number, x-axis) for different reaction temperatures and N2 inlet flow: 450°C and 150 mL/min (circled-marked line), 465°C and 150 mL/min

(triangular-marked line), 450°C and 1 L/min (x-marked line), 465°C and 1 L/min (+-marked line), 465°C and 2 L/min (rhombus-marked line), 465°C and 4 L/min (square-marked line).

Figure 11 shows the conversion (expressed as %, y-axis) as function of reaction time (expressed in minutes) for different type and flows of N2 inlet feed: 150 mL/min up (circle-marked line), 1 L/min up (rhombus-marked line), 1 L/min down (triangular-marked line) and 4 L/min up/down (1 L/min up and 3 L/min down, square-marked line).

Figure 12 shows the cumulative selectivity (expressed as %, y-axis) of the different reaction products (listed in the x-axis) for different type and flows of N2 inlet feed. Legend: for each product, starting from left to the right the color of the bars refer to 150 mL/min up, 1 L/min up, 1 L/min down, 4 L/min up/down (1 L/min up and 3 L/min down).

Figure 13 shows the waxes cumulative selectivity (expressed as %, y-axis) as function of the pyrolysis gas residence time (expressed in seconds, x-axis).

Figure 14 shows the carbon number distribution of the waxes. The plot shows the weight percentage (wt %, y-axis) as function of carbon chain length (expressed as a number, x-axis) ) for different type and flows of N2 inlet feed: 150 mL/min up (circle-marked line), 1 L/min up (rhombus-marked line), 1 L/min down (triangular-marked line) and 4 L/min up/down (1 L/min up and 3 L/min down, square-marked line).

The process of the invention will now be illustrated by way of example with reference to figures 1 and 2.

In a first embodiment, schematically presented in figure 1 , the pyrolysis of the raw material to produce waxes is realized under vacuum in an oxygen depleted atmosphere. The raw material 1 is pretreated by a combination of

physico-chemical treatment 2 that separates an effluent stream 3 and the pretreated raw material 4. The pretreated raw material 4 is introduced with the help of the feeding device 5 in the pyrolysis reactor 10 through the line 6. The pyrolysis reactor is indirectly heated. Without limiting the scope, as example the reactor can be heated by the circulation of a hot stream 7 fed to a suitable heat transfer device 8 and recovered at the outlet as the stream 9. Optionally, a heat carrier stream 11 is introduced in the pyrolysis reactor. The pyrolysis gas 12 is recovered from the pyrolysis reactor and sent to a physic-chemical treatment 20. The residue 13 is recovered through the device 14 where it is treated in an adequate way to produce the stream 15. The residue contains the unconverted raw material, by product and optionally the heat carrier introduced in the pyrolysis reactor through the stream 11. In the physico-chemical treatment the pyrolysis gas is cleaned from dust and other detrimental components recovered in stream 21 and separated as a stream 22 that is sent to the treatment 25 where a incondensable stream 24 is separated from the condensate stream 23. The stream 24 is sent to a vacuum device 26. The effluent 27 from the vacuum device is sent to the combustion chamber 28 together with an adequate quantity of combustion air (29) to produce a hot stream 7. Optionally, an auxiliary fuel 30 is added to the combustion chamber 28. The condensate stream 23 is sent to the separation unit 31 where the waxes stream 32 is separated from the byproducts 33.

In a second embodiment, the pyrolysis of the raw material to produce waxes realized under vacuum in the presence of a diluent gas is as an example schematically shown in figure 2. The pyrolysis of the raw material to produce waxes is realized under vacuum in an oxygen depleted atmosphere. The raw material 51 is pretreated by a combination of physico-chemical treatment 52 that separates an effluent stream 53 and the pretreated raw material 54. The pretreated raw material 54 is introduced with the help of the feeding device 55 in the pyrolysis reactor 60 through the line 56. The pyrolysis reactor is indirectly heated. Without limiting the scope, as example the reactor can be heated by the circulation of a hot stream 57 fed to a suitable heat transfer device 58 and recovered at the outlet as the stream 59. Optionally, a heat carrier stream 61 is introduced in the pyrolysis reactor. A gaseous diluent 66 is introduced at a controlled rate in the reactor 60. The pyrolysis gas in mixture with the diluent 62 is recovered from the pyrolysis reactor and sent to a physic-chemical

treatment 70. The residue optionally in mixture with the heat carrier 63 is

recovered through the device 64 where it is treated in an adequate way to produce the stream 65. The residue contains the unconverted raw material, by product and optionally the heat carrier introduced in the pyrolysis reactor through the stream 61. In the physico-chemical treatment the pyrolysis gas is cleaned from dust and other detrimental components recovered in stream 71 and separated as a stream 72 that is sent to the treatment 75 where an incondensable stream 74 is separated from the condensate stream 73. The stream 74 is sent to a vacuum device 76. The effluent 77 from the vacuum device is sent to the combustion chamber 78 together with an adequate quantity of combustion air (79) to produce a hot stream 57. Optionally, an auxiliary fuel 80 is added to the combustion chamber 78. The condensate stream 73 is sent to the separation unit 81 where the waxes stream 82 is separated from the by-products 83.

Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

Examples

General description of the experimental procedure

In each run in semi-batch mode, 30 g of plastic (20 % polypropylene, 80 % polyethylene) were loaded inside the reactor and a defined amount of heat carrier (SiC"2, approximately 20 g) is stored in the heat carrier storage tank. The reactor was closed and heated from room temperature to 200°C during 20 minutes, while simultaneously purging with a 150 mL/min nitrogen flow, which was introduced at the top of the reactor vessel. When the internal temperature reached the melting point of the plastic, stirring was started and slowly increased to 690 rpm. The temperature was held at 200°C for 25-30 minutes. During this heating process, nitrogen coming out from the reactor was not collected. Meanwhile, the heat carrier storage tank containing the heat carrier was purged with nitrogen several times.

After this first pretreatment step, temperature was increased to the reaction temperature at a heating rate of 10°C/min, and the collection of gases and nitrogen in the corresponding gas sampling bag was started. When the internal temperature reached the reaction temperature, the heat carrier was introduced inside the reactor. Depending on the experiments, the nitrogen gas flow was set to 150 mL/min or adjusted to 1, 2 or 4 L/min, and the circulation of the gaseous products was commuted to another pair of glass traps and corresponding gas

sampling bag. This was considered as the zero reaction time. Depending on the experiments, nitrogen can enter the reactor in two ways: at the top of the vessel or bubbled through the melted plastic.

During selected time periods, liquid and gaseous products were collected in a pair of glass traps and their associated gas sampling bag, respectively. At the end of the experiment the reactor was cooled to room temperature. During this cooling step, liquids and gases were also collected.

The reaction products were classified into 3 groups: i) gases, ii) liquid hydrocarbons and iii) residue (waxy compounds, ashes and coke accumulated on the heat carrier). Quantification of the gases was done by gas chromatography (GC) using nitrogen as the internal standard, while quantification of liquids and residue was done by weight. Glass traps (along with their corresponding caps) were weighed before and after the collection of liquids, while the reactor vessel was weighed before and after each run.

The simulated distillation (SIM-DIS) GC method allowed determination of the different fractions in the liquid samples (according to the selected cuts), the detailed hydrocarbon analysis (DHA) GC method allowed determination of the PIONAU components in the gasoline fraction of the last withdrawn sample (C5-C11 : Boiling point < 216.1°C; what includes C5-C6 in the gas sample and C5-C1 1 in the liquid samples), and GCxGC allowed the determination of saturates, mono-, di- and tri-aromatics in the diesel fraction of the last withdrawn liquid samples (C12-C21; 216.1 < BP < 359°C).

In all experimental cases, the residence time of the pyrolysis gas was calculated using a reactor volume of 300 mL, a raw plastic density of 0.94 g/mL, a bulk density of the silica of 1. lg/mL. This leads to a gas hold-up of 250 mL.

In the examples, HCO refers to heavy cycle oil which is considered as hydrocarbon molecules with at least 22 carbon atoms (+C22). Waxes refer to hydrocarbon molecules with at least 20 carbon atoms (+C20). In general:

• Gasolines: contains C5s and C6s in gases + liquids with bp (boiling point) < 150°C (ca. C5-C9)

• Kerosene: liquids with boiling point 150 < bp < 250°C (ca. C10-C14)

• Diesel: liquids with boiling point 250 < bp < 359°C (ca. C15-C21)

• HCO: products with boiling point >359°C (C22 and +)

• Waxes: products with boiling point > 330°C (C20 and +)

Determination of the different fractions is done by gas chromatography by the simulated distillation method and according to the ASTM-D-2887 standard.

General description of the analytical methods

Measurement of the number of carbon atoms

The number of carbon atoms and their distribution in a mixture of hydrocarbons is measured using the ASTM-D-2887 method. This method is a GC method for the simulated-distillation of complex hydrocarbon mixtures. The method allows separation of the hydrocarbon molecules in a complex mixture according to their boiling point. The boiling point is then related to the carbon number according to defined cut points. In the present invention, the relationship between boiling point and carbon number as defined in table 1 below is used.

WE CLAIM

Process for converting plastic into waxes by cracking, the process comprising:

introducing the plastic within a reactor;

allowing at least a portion of the plastic to be converted to waxes, the waxes being part of the pyrolysis gas formed within the reactor; and

removing a product stream containing said waxes from the reactor;

characterized in that the pyrolysis gas has a residence time at a temperature above 370°C of less than 60 seconds.

2. Process according to claim 1, wherein the pyrolysis gas has a residence time at a temperature above 370°C of less than 50 seconds, preferably less than 40 seconds, more preferably less than 30 seconds, even more preferably less than 25 seconds, such as less than 20 seconds.

3. Process according to claim 1 or 2, wherein the temperature at which at least a portion of the plastic is converted to waxes is at least 370°C, preferably at least 400°C, more preferably at least 425°C, even more preferably at least 440°C, such as in the range of 400 to 650°C, preferably 425 to 550°C, more preferably 440 to 520°C.

4. Process according to any of the preceding claims, wherein the reactor is operated at a pressure of below or equal to 1200 mbar, preferably below or equal to 1000 mbar, more preferably below or equal to 950 mbar, even more preferably below or equal to 900 mbar, such as in the range of 0.5 to 1200 mbar, preferably 10 to 1100 mbar, more preferably 60 to 950 mbar and even more preferably 80 to 900 mbar.

5. Process according to any of the preceding claims, wherein the pyrolysis gas is diluted with a diluent, where the diluent preferably is selected from nitrogen, hydrogen, steam, carbon dioxide, combustion gas, hydrocarbon gas and mixtures thereof.

6. Process according to claim 5, wherein the molar ratio of diluent to pyrolysis products in the pyrolysis gas is above 0.5, preferably above 0.7, more preferably above 0.8, even more preferably above 1, such as in the range of 0.5 to 50, preferably 0.7 to 40, more preferably 1 to 20.

7. Process according to any of the preceding claims, wherein the conversion of at least a part of the plastic to waxes is conducted in the presence of a heat carrier.

8. Process according to claim 7, wherein the heat carrier comprises particles, preferably free-flowing particles.

9. Process according to claim 7 or 8, wherein the heat carrier is selected from sand (such as silica), stone, gravel, metal, metal oxides, glass, ceramic and mixtures thereof, preferably sand or steel.

10. Process according to any of claims 7 to 9, wherein the heat carrier is a catalyst for the cracking of the plastic.

11. Process according to any of claims 7 to 10, wherein the heat carrier is not a catalyst for gas-phase cracking of hydrocarbons.

12. Process according to any of the preceding claims, wherein the residence time of condensed material in the reactor is between 10 and 600 min, preferably between 20 and 400 min, more preferably between 30 and 250 min.

13. Process according to any of the preceding claims, which is conducted continuously.

14. Process according to any of the preceding claims, wherein the plastic is waste plastic, preferably mixed waste plastic.

15. Process according to claim 14, wherein the waste plastic is selected from post-consumer waste plastic, off-spec plastic and industrial scrap plastic.

16. Mixture of hydrocarbons, characterized in that the hydrocarbons exhibit a cumulative distribution of their number of carbon atoms such that 20 < d20 and 50 > d50;

> 50 mol % of the hydrocarbons are linear hydrocarbons;

and the molar ratio of n-paraffins to alpha-olefins among the hydrocarbons is in the range of 0.1 to 10.

17. Mixture according to claim 16, wherein the hydrocarbons exhibit a cumulative distribution of their number of carbon atoms such that 22 < d20, preferably 25 < d20.

18. Mixture according to claim 16 or 17, wherein the hydrocarbons exhibit a cumulative distribution of their number of carbon atoms such that d20 < 40, preferably d20 < 35, more preferably d20 < 30.

19. Mixture according to any of claims 16 to 18, wherein the

hydrocarbons exhibit a cumulative distribution of their number of carbon atoms such that 20 < d20 < 40, preferably 22 < d20 < 35, more preferably

25 < d20 < 30.

20. Mixture according to any of claims 16 to 19, wherein the

hydrocarbons exhibit a cumulative distribution of their number of carbon atoms such that 45 > d50, preferably 40 > d50.

21. Mixture according to any of claims 16 to 20, wherein the

hydrocarbons exhibit a cumulative distribution of their number of carbon atoms such that 50 > d50 > 20, preferably 40 > d50 > 22.

22. Mixture according to any of claims 16 to 21, wherein the molar ratio of n-paraffins to alpha-olefins among the hydrocarbons is in the range of 0.2 to 5, preferably in the range of 0.5 to 2.

23. Mixture according to any of claims 16 to 22, wherein > 60 mol %, preferably > 70 mol % of the hydrocarbons are linear hydrocarbons.

24. Mixture according to any of claims 16 to 23, wherein > 40 mol %, preferably > 45 mol %, more preferably > 50 mol % of the unsaturated hydrocarbons are alpha-olefins.

25. Mixture according to any of claims 16 to 24, having an iodine number of > 10, preferably of > 25, more preferably of > 40.

26. Mixture according to any of claims 16 to 25, having an iodine number in the range of 10 to 150, preferably in the range of 25 to 100, more preferably in the range of 40 to 70.

27. Mixture according to any of claims 16 to 26, having a drop point of > 25°C, preferably of > 40°C, more preferably of > 50°C.

28. Mixture according to any of claims 16 to 27, wherein at least a portion of the hydrocarbons contains one or more heteroatoms.

29. Wax obtainable by a process according to any of claims 1 to 15.

30. Wax according to claim 29, which is the mixture according to any of claims 16 to 28.

31. Bituminous mixture, superficial wear coating, asphalt or sealing coating comprising a mixture according to any of claims 16 to 28.

32. Process for producing a mixture according to any of claims 16 to 28 by subjecting plastic to cracking, the process comprising:

introducing the plastic within a reactor;

allowing at least a portion of the plastic to be converted to waxes, at least part of the waxes being part of the pyrolysis gas formed within the reactor; and

removing a product stream containing said waxes being part of the pyrolysis gas formed within the reactor from the reactor to obtain said mixture;

characterized in that the pyrolysis gas has a residence time at a temperature above 370°C of less than 60 seconds.

33. Process according to claim 32, which is the process in accordance with any of claims 1 to 15.