CA2202941A1 - Depolymerization - Google Patents

Abstract

Thermoplastic waste may be depolymerized by heating the thermoplastic to a temperature from about 623°K to 773°K at a low pressure for a time of at least 30 minutes in the presence of a catalyst.
Optionally the depolymerization may be conducted in the presence of hydrogen and in the presence of other hydrocarbon streams. The product is suitable to go into a petroleum refinery product stream or into a petrochemical plant as feedstock, e.g. a naphtha steam cracker for the production of ethylene and coproducts. The invention provides a method to "recycle" plastics to valuable feedstocks.

Description

' CA 02202941 1997-04-17 Depolv,., e ri,alion FIELD OF THE INVENTION
The present invention relates to the treatment of waste thermoplastic material and more particularly the recovery of hydrocarbon streams from waste thermoplastic. More particularly the present invention relates to the "depolymerization" of waste thermoplastic material, optionally in the presence of vacuum distillates or pyrolysis fuel oil (PFO).
BACKGROUND OF THE INVENTION
The article "Wasfe plastic yields high-quality fuel O;/n in Science News, Vol.144, page 134 teaches that waste thermoplastic may be converted into a hydrocarbon stream similar to a light crude oil by heating a mixture of zeolite catalysts, tetralin (i.e. tetrahydronaphthalene) and waste thermoplastic in a sand bath and then feeding the mixture to a "tubing-bomb" and heating to 693~K (420~C) in the presence of hydrogen for about an hour. The present invention does not contemplate the use of a "sand bed" nor does it require the use of tetralin.
United States patent 5,364,995, issued November 15,1994, assigned to BP Chemicals Limited teaches producing waxes from thermoplastic material by feeding the thermoplastic to a fluidized bed of infusible material such as quartz sand, silica, ceramics, carbon black and aluminosilicates and the like, together with a fluidizing gas free of molecular oxygen such as nitrogen or refinery fuel gas and maintaining the bed at a temperature of above 573~K (300~C) and below 963~K (690~C).
As noted above the present invention does not contemplate the presence tt/jm/spec/91 29can.doc 2 of an infusible material, nor does the reaction take place in a fluidized bed reactor.
United States patent 4,851,601, issued July 25,1989, assigned to Mobil Oil Corporation teaches a two stage process for cracking thermoplastics to produce an oil. In the first step the thermoplastic is thermally cracked at a temperature of at least 633~K (360~C), preferably in the presence of particulate porous material to a vaporous overhead stream which is then contacted with an acidic intermediate pore size zeolite at an elevated temperature of at least 523~K (250~C) to produce a hydrocarbon oil having a low pour point. The present invention does not contemplate such a two stage reaction.
The present invention seeks to provide a simple direct reaction in the absence of an inert particulate material to depolymerize waste thermoplastic to one or more hydrocarbon streams which are useful per se or may be further refined.
SUMMARY OF THE INVENTION
The present invention provides a process to recover hydrocarbons from waste thermoplastic material comprising:
(i) heating clean particulate thermoplastic waste material comprising at least 85 weight % of one or more polymers selected from the group consisting of:
(A) polymers comprising from 85 to 100 weight % of ethylene and from 0 to 15 weight % of one or more C4 12 alpha olefins, (B) polymers comprising 55 weight % of ethylene and up to 45 weight % of vinyl acetate;

tVjm/spec/9129can.doc 3 (C) polymers comprising from 50 to 80 weight % of propylene and from 50 to 30 weight % of ethylene;
(D) polymers comprising from 100 to 50 weight % of one or more C8 12 vinyl aromatic monomers which are unsubstituted or substituted by a C14 alkyl radical and from 0 to 50 weight %
of one or more monomers selected from the group consisting of C14 alkyl esters of C3-6 ethylenically unsaturated carboxylic acids; and maleic anhydride; and (E) polyesters selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthenate, and up to 15 weight % of one or more polymers selected from the group consisting of:

(F) polymers comprising from 100 to 50 weight % of one or more C8 12 vinyl aromatic monomers which are unsubstituted or substituted by a C14 alkyl radical and from 0 to 50 weight %
of one or more monomers selected from the group consisting of C14 alkyl esters of C3-6 ethylenically unsaturated carboxylic acids; and maleic anhydride which have been grafted on to up to 20 weight % of one or more rubbers selected from the group consisting of:
(1 ) polymers comprising from 40 to 60 weight % of one or more C8 12 vinyl aromatic monomers which are unsubstituted or substituted by a C14 alkyl radical, tt/jm/spec/9129can.doc 4 and from 60 to 40 weight % of one or more C4-6 conjugated diolefins;

(2) polymers comprising co- or homopolymers of one or more C4-6 conjugated diolefins; and

(3) polymers comprising one or more C4-8 alkyl esters of acrylic or methacrylic acid, and (G) polyvinylchloride, in a non-oxidizing atmosphere to produce a melt;
(ii) contacting in a reactor said melt with one or more catalysts selected from the group consisting of natural zeolites, synthetic zeolites, bauxite, the residue produced by the removal of aluminum from bauxite, alkali oxides, alkaline metal earth oxides, aluminum phosphates, transition metal oxides, and mixtures thereof to provide a weight ratio of said melt to said one or more catalysts of from 100:1 to 5:1 at a pressure from 10 to 507 kPa (0.1 to 5 atmospheres) under a non-oxidizing atmosphere at a temperature from 623~K to 773~K (350 to 500~ C) for a period of time from 10 minutes to 180 minutes and a conversion of at least 20%; and (iii) removing from said reactor a gaseous stream comprising hydrogen and one or more C14, preferably C13, saturated and unsaturated hydrocarbons; a liquid stream comprising one or more members selected from the group consisting of C4 12 saturated and unsaturated hydrocarbons; and removing as a bottom stream paraffin wax and a stream of unreacted thermoplastic.

tt/jm/spec/9129can.doc 5 The process of the present invention may be useful with other polymers which may contain acrylonitrile or methacrylonitrile (e.g. styrene acrylonitrile (SAN) or styrene methacrylonitrile type products), sulphur (e.g.
rubbers or rubber containing products) or PVC which tend to poison catalysts and in particular zeolite catalysts. Such polymers may be used in accordance with the present invention if there is a pretreatment to remove nitrogen N, S, and halides (e.g. chlorides) or to reduce the amount of such polymer in the feed to less than about 15 weight %, preferably less than about 10 weight %.
DETAILED DESCRIPTION
There are a number of waste thermoplastics which may be used in the process of the present invention. These thermoplastics need not be sorted and may be commingled in the process of the present invention.

The thermoplastics may be selected from the group consisting of polyolefins such as polyethylene and polypropylene; styrenic polymers such as polystyrene, styrene acrylics. The thermoplastic may be predominantly (i.e. at least 50 weight %) polyethylene.
The polyolefins may comprise homopolymers of ethylene and copolymers comprising from 85 to 100 weight % of ethylene and from 0 up to 15 weight % of one or more C4 12, preferably C4 10 olefins, preferably alpha olefins. Suitable alpha olefin copolymers include 1-butene, 1-pentene, 1-hexene, 1-octene and 1-decene. The alpha olefin comonomer may also be an isomer such a methyl pentene monomer.
However, the polyolefin could also include other alpha olefin monomers such as C2 8 ethylenically unsaturated carboxylic acids such as tt/jm/spec/91 29can.doc 6 CA 0220294l l997-04-l7 methacrylic acid, acrylic acid and itaconic acid, preferably acrylic acid and methacrylic acid and C14 alkyl esters of such acids. Such polymers also include metal salts of the resulting polymer such as sodium, potassium and calcium salts (e.g. SURLYNTM type materials). The copolymer could be a vinyl ester of a lower C14, preferably C2 carboxylic acid such as vinyl acetate. In the case of ethylene vinyl acetate copolymers, the vinyl o acetate may be present in amounts of greater than 15 weight % up to 45 weight % of the polymer. The polymer could be obtained from the manufacturing process such as low molecular weight (Mw less than about

4,000) fractions obtained in some processes to produce polyolefins, sometimes referred to as polymer "grease" or off specification polymer.
The waste thermoplastic may be polypropylene. Generally, such polymers comprise from 50 to 80 weight % of propylene and from 50 to 30 weight % of one or more copolymerisable comonomers. The comonomer may be an alpha olefin such as ethylene. However, the comonomer may be a conjugated diolefin such as butadiene, hexadiene, dicyclopentadiene, and ethylidene norbornene (ENB).
The copolymer may be a styrenic polymer. The styrenic polymer may be a homopolymer of a C8 ,2 vinyl aromatic monomer which are unsubstituted or substituted by a C14 alkyl radical such as styrene, alpha methylstyrene, p-tert-butyl styrene, preferably styrene. The styrenic polymer may be a copolymer of one or more C8 ,2 vinyl aromatic monomers and one or more monomers selected from the group consisting of C1 8, preferably C14 alkyl esters of a C3-6 ethylenically unsaturated carboxylic acid; and maleic anhydride. Suitable esters include methyl ~jm/spec/91 29can.doc 7 methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate and ethylhexyl acrylate. Typically the copolymers will comprise at least 50 weight % of the vinyl aromatic monomer and the balance of one or more comonomers. For the vinyl aromatic (meth)acrylate ester polymers the (meth)acrylate monomer may be present in amounts of from about 15 to about 50 weight %. For the copolymers containing maleic lo anhydride, the anhydride is present in amounts typically from about 5 to 25, preferably 5 to about 15 weight %.
The thermoplastic may be a polyester such as polyethylene terephthalate (PET), polybuylene terephthalate (PBT), or polyethylene naphthenate.
Typically the plastic is introduced into the reactor, which may be a cracking column, as a particulate. The plastic may be shredded to a particle size of less than 5 cm. In a preferred embodiment the plastic may be pelletized. Typically the pellets could have a size from 0.1 to 10, preferably about 5 mm. Generally, the pelletizing would be used to make it easier to feed the thermoplastic into the first stage of the process - the melting stage - by suitable means such as a conveyor.
In the process of the present invention the thermoplastic waste is melted typically at temperatures from about 623~K to 773~K (350~C to 500~C), preferably from 663~K to 723~K (390 to 450~C).
In a further embodiment of the invention the thermoplastic is fed to the reactor together with one or more members selected from the group consisting of vacuum gas oils (VGO), pyrolysis fuel oil (PFO), and waste or contaminated solvent from a solution polymerization process (e.g. the tt/jm/spec/91 29can.doc 8 solvent from a solution polyethylene process which contains polymer grease). VGO typically boils in the true boiling range of 61 3~K to 81 3~K
(340~C to 540~C), while PFO boils in the range of 473~K to 81 3~K (200~C
to 540~C). Generally these oils comprise a C20 to C100 fraction having a high aromatic content. The waste solvent from a solution polymerization process would generally comprise a C5 to C80 stream.

The melt is then directly contacted with one or more catalysts selected from the group consisting of natural zeolites, synthetic zeolites, bauxite, the residue produced by the removal of aluminum from bauxite, alkali oxides, alkaline metal earth oxides, aluminum phosphates, transition metal oxides, and mixtures thereof to provide a weight ratio of said polymer melt to said catalysts of from 100:1 to 5:1, preferably from 80:1 to 20:1. Generally the catalyst is used together with a binder in the form of pellets having a particle size from 0.1 to 10 mm.
Suitable alkali oxides include sodium and potassium oxide.
Suitable alkaline earth metal oxides include calcium oxide. Suitable transition metal oxides include oxides of iron, copper, titanium, vanadium, chromium, nickel, zirconium, ruthenium, and palladium.
A good discussion of zeolites is contained in The Kirk Othmer Encyclopedia of Chemical Technology, in the third edition, volume 15, pages 638-668, and in the fourth edition, volume 16, pages 888-925.
Zeolites are based on a framework of Al04 and SiO4 tetrahedra linked together by shared oxygen atoms having the empirical formula M2/nO~AI2O3~ySiO2 wH2O in which y is 2 or greater, n is the valence of the cation M (typically an alkali or alkaline earth metal (e.g. Na, K, Ca and tt/jm/spec/9129can.doc 9 Mg), and w is the water contained in the voids within the zeolite.
Structurally zeolites are based on a crystal unit cell having a smallest unit of structure of the formula Mx/n[(AlO2)x(SiO2)y].wH2O in which n is the valence of the cation M, x and y are the total number of tetrahedra in the unit cell and w is the water entrained in the zeolite. Generally the ratio y/x may range from 1 to 100. The entrained water (w) may range from about 10 to 275. Natural zeolites include chabazite (in the structural unit formula M is Ca, x is 4, y is 8 and w is 13), mordenite (in the structural unit formula M is Na, x is 8, y is 40 and w is 24), erionite (in the structural unit formula M may be Ca, Mg, Na2, or K2, x is 9, y is 27 and w is 27), faujasite (in the structural unit formula M may be Ca, Mg, Na2, K2, x is 59, y is 133 and w is 235), clinoptilolite (in the structural unit formula M is Na2, x is 6, y is 30 and w is 24). Synthetic zeolites generally have the same unit cell structure except that the cation may in some instances be replaced by a complex of an alkali metal, typically Na and tetramethyl ammonium (TMA) or the cation may be a tetrapropylammonium (TPA). Synthetic zeolites include zeolite A (in the structural unit formula M is Na2, x is 12, y is 12 and w is 27), zeolite X (in the structural unit formula M is Na2, x is 86, y is 106 and w is 264), zeolite Y (in the structural unit formula M is Na2, x is 56, y is 136and w is 250), zeolite L (in the structural unit formula M is K2, x is 9, y is 27 and w is 22), zeolite omega (in the structural unit formula M is Na68TMA1.6, x is 8, y is 28 and w is 21) and other zeolites wherein in the structural unit formula M is Na2 or TPA2, x is 3, y is 93 and w is 16.
Preferred zeolites have an intermediate pore size typically from about 5 to 10 angstroms (having a constrainf index of 1 to 12 as described in U.S.

tVjm/spec/9129can.doc 10 patent 4,016,218). Synthetic zeolites are prepared by gel process (sodium silicate and alumina) or a clay process (kaolin) which form a matrix to which a zeolite is added. Some commercially available synthetic zeolites are described in U.S. patent 4,851,601). The zeolites may undergo ion exchange to entrain a catalytic metal or may be made acidic by ion exchange with ammonium ions and subsequent deammoniation (see the Kirk Othmer reference above). A hydrogenation metal component such as platinum, palladium, nickel or other transition metals such as group Vlll metals may be present in (e.g. entrained within the pores) or exchanged or impregnated into the zeolite in amounts from 0.1 to 10 weight %.
Combinations of catalysts may be used in accordance with the present invention. One useful combination is a mixture of one or more alkali or alkaline earth metal oxides and one or more zeolites. Preferably the zeolites are selected from the group consisting of one or more intermediate pore size zeolites (as noted above). The catalyst may be mixed in the sense of being commingled or it may be mixed in the sense of being a layered bed of two or more catalysts.
The thermoplastic is contacted with the above noted catalysts for a period of time from 10 to 180, preferably from 20 to 90 minutes. The reaction may take place under pressure or under a partial vacuum. The pressure in the reactor may be from 10 to 507, preferably from 76 to 304 kPa (0.1 to 5, preferably from 0.75 to 3 atmospheres). The melt is under a non-oxidizing atmosphere preferably selected from the group consisting of hydrogen, helium, nitrogen, argon and mixtures thereof.

tVjm/spec/91 29can.doc 1 1 The process of the present invention may be a batch or continuous process, preferably batch. If the process is operated continuously the reactor is preferably a cracker, most preferably a cracking column. If the process is a batch process the reactor is preferably a stirred tank reactor (STR). In an STR the thermoplastic is subjected to shear, typically by a turbine or "paddle" stirrer. The thermoplastic should be heated to lo temperatures of at least about 523~K (250~C), preferably greater than 623~K (350~C). The agitation rate may be low, about 200 rpm (typically at lower temperatures) or may be high, greater than 500 rpm, preferably greater than about 700 rpm at the higher temperatures.
The residence time in the reactor is such to provide at least a 20%
conversion of thermoplastic and if present one or more members selected from the group consisting of vacuum gas oils, pyrolysis fuel oil and waste solvent from a solution or bulk polymerization. Preferably in a continuous process the per pass conversion should be in the range from 50 to 90%.
The thermoplastic and if present one or more members selected from the group consisting of vacuum gas oils, pyrolysis fuel oil and waste solvent from a solution or bulk polymerization, in the reactor (cracking column) under the above noted conditions produces three product 30 streams. There is a gaseous overhead stream comprising hydrogen and C14, preferably C13, saturated and unsaturated hydrocarbons. There is a liquid stream taken off at an intermediate level within the reactor which comprises C412, preferably C48, saturated and unsaturated hydrocarbons.
Finally, there is a bottom stream comprising a paraffin wax and a stream of unreacted thermoplastic polymer. The unreacted thermoplastic polymer tt/jm/spec/9129can.doc 12 is typically fed back into the reactor, preferably after blending with fresh thermoplastic.
The catalyst is not consumed during the reaction but will have to be regenerated periodically depending upon the conditions in the reactor.
Additionally, there may be some coke generated during the reaction which will have to be removed when the reactor is shut down.

In an optional embodiment the melt of the thermoplastic may be subjected to shear, typically by a turbine or "paddle stirrer". The polymer should be heated to temperatures of at least about 523~K (250~C), preferably greater than 623~K (350~C). The agitation rate may be low, about 200 rpm (typically at lower temperatures) or may be high, greater than 500 rpm, preferably greater than about 700 rpm, at the higher temperatures.

The paraffin stream may be further processed for example by dissolving it in a light oil or naphtha and feeding the resulting stream to a naphtha cracker. The liquid stream may be fed to a gasoline refiner, or blended with gas oil and feeding the resulting stream to a steam cracker or separated into various streams or components through distillation. The liquid stream may be fed to a naphtha (steam) cracker for the production of ethylene and coproducts.
As noted above, care should be used when practicing the present invention with polymers which contain nitrogen, sulphur or halides (e.g.
polyvinyl chloride) unless treated to remove the nitrogen, sulphur or halides. It may not be practical to remove nitrogen from acrylonitrile polymers such as styrene acrylonitrile (SAN) or styrene methacrylonitrile tt/jm/spec/9129can.doc 1 3 polymers or impact modified polymers such as acrylonitrile butadiene styrene (ABS) polymers (typically for copolymers of the vinyl aromatic monomer and one or more nitriles, the nitrile monomer may be present in amounts from about 15 to 45 weight %). If present in commingled thermoplastic waste such polymers should be present in amounts not greater than about 15 weight %, preferably not greater than 10 weight %, o of the plastic to be treated. However, impact modified styrenic polymers such as the styrenic polymers identified in group (C) modified with rubber that does not contain sulphur may be suitable for treatment in accordance with the present invention. Such polymers would be the polymers of group (C) noted above which have been grafted to up to 20 weight % of a rubbery phase selected from the group consisting of:

(i) polymers comprising from 40 to 60 weight % of one or more ~0 C8 12 vinyl aromatic monomers which are unsubstituted or substituted by a C14 alkyl radical, and from 60 to 40 weight % of one or more C4-6 conjugated diolefins;
(ii) polymers comprising co- or homopolymers of one or more C4-6 conjugated diolefins; and (iii) polymers comprising one or more C4-8 alkyl esters of acrylic or methacrylic acid.
The rubber may be a copolymer comprising from about 40 to 60 weight % of one or more C6 8 vinyl aromatic monomers which are unsubstituted or substituted by a C14 alkyl radical and from 60 to 40 weight % of one or more C4-6 conjugated diolefins. Suitable vinyl aromatic monomers have been listed above. Suitable conjugated diolefins include tVjm/spec/9129can.doc 1 4 butadiene and isoprene. The rubber may be a homopolymer of one or more C4-6 conjugated diolefin monomers. Suitable diolefin monomers have been listed above. Preferred diolefin rubbers are homopolymers of butadiene rubber. The polymer may have a stereo configuration such as high cis rubber having over 90, most preferably over 95%, of the polymer in the cis configuration or medium cis rubbers having about 50 to 65, o preferably from about 50 to 60%, of the polymer in the cis configuration.
The rubber may be a rubbery acrylate comprising one or more C4-8 alkyl esters of acrylic or methacrylic acid. Preferred esters are butyl and ethylhexyl acrylate.
The broad aspects of the present invention have been disclosed above. Following the above teaching, specific combinations of time, temperature, catalyst, and feedstock may be determined by non-inventive testing.
The present invention will now be illustrated by the following non-limiting examples in which, unless otherwise specified, parts is parts by weight and % is weight %
Example 1 The experiments were conducted in a batch catalytic cracking unit (BCCU) consisting of a two liter high pressure autoclave designed to operate at temperatures up to 773~K (500~C); at a pressure of up to 35,000 kPa (about 5,000 psi) at 773~K (500~C). The autoclave had a removable top through which a stirrer shaft extended. In operation the stirrer was driven by an electric motor. The reactor was heated by two high temperature electric heaters. At the bottom of the reactor was an tt/jm/spec/9129can.doc 15 inlet line for hydrogen. (Although the hydrogen could be replaced by an inert gas such as nitrogen or if the valve is kept closed no gas would be introduced into the reactor.) The hydrogen pressure was controlled by a pressure controller at the exit of a knock-out drum also having a valve in the bottom, up-stream of the upper outlet of the reactor. The reactor had two outlets. An outlet in the top of the reactor permitted gaseous products to be drawn off. A valve in the bottom of the reactor permitted liquid products to be drawn off.
The catalyst was conditioned overnight in a vacuum oven at 353~K
(80~C) under a reduced pressure of 6.5 kPa (28 inches of mercury (torr)).
The conditioned catalyst was then placed in a desiccator and allowed to cool to room temperature. The reactor was loaded with about 1500 g of polymer. First, about 30 grams of polymer was placed in the reactor and then the catalyst was added in an amount to provide a weight ratio of catalyst to total polymer of 0.05. Then the remainder of polymer was fed to the reactor (in an amount not to exceed a total volume of polymer of 1500 cc).
The reactor was then pressurized to 6990 kPa (1000 psig) with nitrogen to check for leaks and then purged with nitrogen. The reactor was heated at a rate to provide a temperature increase of 100~K (100~C) per hour for the first four hours and a rate to provide a temperature increase of 50~K (50~C) per hour for the last hour to provide a final operating temperature of 773~K (500~C). During the heat-up cycle the hydrogen pressure was set and the flow rate of about 2500 cc/min is maintained through out the reaction. The stirrer started at a low speed of tVjm/spec/9129can.doc 16 about 200 rpm when the temperature reaches 523~K (250~C) and the rate is increased to about 800 rpm when the temperature is 633~K (360~C).
The run time is recorded when the reactor reaches the desired reaction temperature (773~K (500~C)). At the end of the reaction heaters are turned off. The hydrogen flow is maintained to prevent the hydrogen inlet from becoming plugged with the waxy residue from the polymer. The knock-out drum is separated from the reactor and depressurized and the contents emptied into a sampling bottle and weighed. The waxy residue from the polymer is scooped out of the reactor when cool and solidified and weighed. The recovered streams from the reaction were then analyzed for their components.
A series of screening runs were conducted initially with virgin high density polyethylene resin and repeated with recycled high density polyethylene resin obtained from Montreal and Toronto to determine a useful combination of residence time, reaction pressure, and temperature.
These were found to be 45 minutes, 345 kPa (50 psig) and 678~K
(405~C), respectively.
A sample of commingled plastics obtained from the Edmonton Recycling Society typically comprising: 60% Polyethylene (PE); 15%

Polystyrene(PS); 10% Polyvinyl chloride (PVC); 5% Polypropylene (PP);

5% Polyethylene terephthalate (PET); and 5% others, shredded into 5-10 mm flakes, was washed and dried (overnight at 353~K (80~C)). The sample was treated under the above conditions with aluminum phosphate gel as the catalyst. The results of the analysis of the recovered streams is set forth in table 1 below.

tVjm/spec/91 29can.doc 17 Table 1 Component Wt. % Component Wt. %
Cl to C3 1.44 Benzene 0.023 Isobutane Non-aromatic C7's1.21 n-Butane 0.267 Isobutene/1-Butene<0.002 Toluene 4.38 t-2-Butene 0.109 c-2-Butene 0.087 Non-aromatic C8's4.11 1 o 1,2-Butadiene <0.002 1,3-Butadiene 1.30 Ethyl Benzene 0.58 1-Butyne <0.002 m,p-Xylene 0.200 2-Butyne <0.002 o-Xylene 0.08 Total C4's 1.77 Styrene 2.63 Total Aromatic C8's 3.49 Pentanes 4.41 Pentenes 0.80 Non-aromatic C9's18.5 Pentadienes 0.054 Isoprene 0.013 Propylbenzene 0.194 Cyclopentane 0.008 m,p-Ethyl Toluene0.190 Cyclopentene <0.002 o-Ethyl Toluene 0.56 Cyclopentadiene 0.003 Other Aromatic C9's 1.85 2 o Other C5's 0.213 Total Aromatic C9's 2.80 Total C5's 5.5 Dicyclopentadiene 0.066 1-Hexene 0.148 Indene <0.002 t-2-Hexene 0.140 Naphthalene 0.077 c-2-Hexene 0.08 Cyclohexane 0.08 C9+ by difference 48.3 Cyclohexene 0.029 Other C6's 7.8 Total Non-aromatic C6's 8.3 The results of the experiment show that commingled plastic can be catalytically converted to streams suitable for refining and use in the petrochemical business to produce a mixture of products such as naphtha, jet fuel, diesel fuel and gas oil.

tt/jm/spec/9129can.doc 1 8 ' CA 02202941 1997-04-17 Example 2 The above experiment was then repeated with an intermediate pore size zeolite without the use of hydrogen and it was found that although there was a change in the ratio of gas to liquid components in the product streams (i.e. the gas went from 20.33 weight % to 18.33 weight % and the liquids went from 79.67 weight % to 81.67 weight %) the resulting product stream could still be used as a feed stock in petrochemical operations.

tVjm/spec/9129can.doc 1 9

Claims (36)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process to recover hydrocarbons from waste thermoplastic material comprising:
(i) heating clean particulate thermoplastic waste material comprising at least 85 weight % of one or more polymers selected from the group consisting of:
(A) polymers comprising from 85 to 100 weight % of ethylene and from 0 to 15 weight % of one or more C4-12 alpha olefins, (B) polymers comprising 55 weight % of ethylene and up to 45 weight % of vinyl acetate;
(C) polymers comprising from 50 to 80 weight % of propylene and from 50 to 30 weight % of ethylene;
(D) polymers comprising from 100 to 50 weight % of one or more C8-12 vinyl aromatic monomers which are unsubstituted or substituted by a C1-4 alkyl radical and from 0 to 50 weight %
of one or more monomers selected from the group consisting of C1-4 alkyl esters of C3-6 ethylenically unsaturated carboxylic acids; and maleic anhydride; and (E) polyesters selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthenate, and up to 15 weight % of one or more polymers selected from the group consisting of:

(F) polymers comprising from 100 to 50 weight % of one or more C8-12 vinyl aromatic monomers which are unsubstituted or substituted by a C1-4 alkyl radical and from 0 to 50 weight %
of one or more monomers selected from the group consisting of C1-4 alkyl esters of C3-6 ethylenically unsaturated carboxylic acids; and maleic anhydride which have been grafted on to up to 20 weight % of one or more rubbers selected from the group consisting of:
(1) polymers comprising from 40 to 60 weight % of one or more C8-12 vinyl aromatic monomers which are unsubstituted or substituted by a C1-4 alkyl radical, and from 60 to 40 weight % of one or more C4-6 conjugated diolefins;
(2) polymers comprising co- or homopolymers of one or more C4-6 conjugated diolefins; and (3) polymers comprising one or more C4-8 alkyl esters of acrylic or methacrylic acid, and (G) polyvinyl chloride, in a non-oxidizing atmosphere to produce a melt;
(ii) contacting in a reactor said melt with one or more catalysts selected from the group consisting of natural zeolites, synthetic zeolites, bauxite, the residue produced by the removal of aluminum from bauxite, alkali oxides, alkaline metal earth oxides, aluminum phosphates, transition metal oxides, and mixtures thereof to provide a weight ratio of said melt to said one or more catalysts of from 100:1 to 5:1 at a pressure from 10 to 507 kPa under a non-oxidizing atmosphere at a temperature from 623°K to 773°K for a period of time from 10 minutes to 180 minutes and a conversion of at least 20%;
(iii) removing from said reactor a gaseous stream comprising hydrogen and one or more C1-4 saturated and unsaturated hydrocarbons; a liquid stream comprising one or more members selected from the group consisting of C4-12 saturated and unsaturated hydrocarbons;
and removing as a bottom stream paraffin wax and a stream of unreacted thermoplastic.

2. The process according to claim 1, wherein the pressure is from 76 to 304 kPa.

3. The process according to claim 2, wherein the temperature is from 663°K to 723°K.

4. The process according to claim 3, wherein the time of contact between said melt and said catalyst is from 20 minutes to 90 minutes.

5. The process according to claim 4, wherein said non-oxidizing atmosphere is selected from the group consisting of hydrogen, helium, nitrogen, argon and mixtures thereof.

6. The process according to claim 5, wherein said catalyst together with a binder is in the form of particles or pellets having a size from 0.1 to 10 mm.

7. The process according to claim 6, which is continuous, wherein said reactor is a cracking column; and further comprising step (iv) recycling said stream of unreacted thermoplastic.

8. The process according to claim 6, wherein said process is a batch process carried out in a stirred tank reactor and said thermoplastic and said catalyst are subject to shear after said thermoplastic has been heated to a temperature of 623°K.

9. The process according to claim 7, wherein said thermoplastic is at least 85 weight % of a polymer comprising from 85 to 100 weight % of ethylene and from 0 to 15 weight % of one or more C4-12 alpha olefins.

10. The process according to claim 8, wherein said thermoplastic is at least 85 weight % of a polymer comprising from 85 to 100 weight % of ethylene and from 0 to 15 weight % of one or more C4-12 alpha olefins.

11. The process according to claim 7, wherein in step (i) said thermoplastic waste is in the form of pellets having a size from 0.1 to 10 mm.

12. The process according to claim 7, wherein in step (i) said thermoplastic waste is shredded to a particle size less than 5 cm.

13. The process according to claim 11, wherein said catalyst comprises aluminum phosphate.

14. The process according to claim 12, wherein said catalyst comprises aluminum phosphate.

15. The process according to claim 11, wherein said catalyst comprises a transition metal oxide.

16. The process according to claim 12, wherein said catalyst comprises a transition metal oxide.

17. The process according to claim 11, wherein said catalyst comprises an alkali or alkaline earth metal oxide.

18. The process according to claim 12, wherein said catalyst comprises an alkali or alkaline earth metal oxide.

19. The process according to claim 11, wherein said catalyst comprises bauxite.

20. The process according to claim 12, wherein said catalyst comprises bauxite.

21. The process according to claim 11, wherein said catalyst comprises the residue produced by the removal of aluminum from bauxite.

22. The process according to claim 12, wherein said catalyst comprises the residue produced by the removal of aluminum from bauxite.

23. The process according to claim 11, wherein said catalyst comprises an intermediate pore size zeolite.

24. The process according to claim 12, wherein said catalyst comprises an intermediate pore size zeolite.

25. The process according to claim 23, wherein said catalyst comprises an intermediate pore size zeolite which has entrained or has been ion exchanged with from 0.1 to 10 weight % of a metal selected from the group consisting of platinum, palladium, and nickel.

26. The process according to claim 24, wherein said catalyst comprises an intermediate pore size zeolite which has entrained or has been ion exchanged with from 0.1 to 10 weight % of a metal selected from the group consisting of platinum, palladium, and nickel.

27. The process according to claim 11, wherein said catalyst comprises a mixture of an alkali or alkaline earth metal oxide and one or more intermediate pore size zeolites.

28. The process according to claim 12, wherein said catalyst comprises a mixture of an alkali or alkaline earth metal oxide and one or more intermediate pore size zeolites.

29. The process according to claim 11, wherein said plastic is coprocessed with one or more members selected from the group consisting of vacuum gas oils, pyrolysis fuel oil, and with waste or contaminated solvent from a solution polymerization process.

30. The process according to claim 12, wherein said plastic is coprocessed with one or more members selected from the group consisting of vacuum gas oils, pyrolysis fuel oil, and with waste or contaminated solvent from a solution polymerization process.

31. The process according to claim 11, further comprising dissolving said paraffin wax in light oil or naphtha and feeding the resulting stream to a cracker.

32. The process according to claim 12, further comprising dissolving said paraffin wax in light oil or naphtha and feeding the resulting stream to a cracker.

33. The process according to claim 11, further comprising feeding said liquid stream comprising one or more saturated C4-12 hydrocarbons to a gasoline refiner.

34. The process according to claim 12, further comprising feeding said liquid stream comprising one or more saturated C4-12 hydrocarbons to a gasoline refiner.

35. The process according to claim 11, further comprising feeding said liquid stream to a naphtha steam cracker to produce ethylene and coproducts.

36. The process according to claim 12, further comprising feeding said liquid stream to a naphtha steam cracker to produce ethylene and coproducts.