Method and equipment for producing hydrocarbons by catalytic decomposition of plastic waste products in a single step

Abstract

A method having the following steps: subjecting plastic waste material to a thermal pre-treatment in order to produce a liquid plastic mass, wherein the thermal pre-treatment of the plastic material is carried out in an inert gas atmosphere at a temperature that varies between 110 C. and 310 C.; simultaneously feeding the liquid plastic mass to a reaction apparatus; bringing the plastic mass into contact with a bed of particles of inorganic porous material contained inside the reaction apparatus at a temperature of between 300 and 600 C.; inducing thermocatalytic decomposition reactions at a temperature of between 300 and 600 C. in order to generate a mixture of hydrocarbons in a vapor phase; and separating the hydrocarbons from the vapor phase current generated inside the reaction means in order to produce a liquid mixture of hydrocarbons.

Claims

1. A continuous process for the production of aliphatic and aromatic hydrocarbons comprising: i.) thermally pretreating a plastic waste material contaminated with oils and/or pigments in an inert gas atmosphere at a temperature between 260 C. and 325 C. to produce a contaminated liquid plastic mass, wherein the plastic waste material contaminated with oils and/or pigments is a single plastic or a mixture of different plastics; ii.) homogenizing the contaminated liquid plastic mass to produce a homogenized contaminated liquid plastic mass; iii.) feeding the homogenized contaminated liquid plastic mass to a reaction apparatus containing a bed of particles of porous material, wherein the reaction apparatus is selected from the group consisting of a packed bed reactor, a fluidized bed reactor, and a mixed flow reactor and wherein the particles of porous material comprise both natural porous aluminosilicates and spent porous synthetic aluminosilicates; iv.) thermocatalytically decomposing the homogenized contaminated liquid plastic mass by contacting the homogenized contaminated liquid plastic mass with the bed of particles of porous material at a temperature between 460 C. and 550 C. and at atmospheric pressure to generate a gaseous mixture containing aliphatic hydrocarbons having between 1 and 44 carbon atoms and aromatic hydrocarbons having between 1 and 44 carbon atoms; and v.) separating the gaseous mixture to obtain a liquid mixture of hydrocarbons and a non-condensable stream of hydrocarbons.

2. The process according to claim 1, wherein the gaseous mixture comprises hydrocarbons having between 3 and 35 carbon atoms.

3. The process according to claim 1, wherein the size of the particles in the bed of particles of porous material is in the range of 30 to 10,000 microns.

4. The process according to claim 1, wherein the natural aluminosilicates and spent porous synthetic aluminosilicates each have the following characteristics: (i) a Si/Al molar ratio between 3 and 40, (ii) a pore diameter between 0.5 and 50 nm, and (iii) a specific surface area between 15 and 1000 m.sup.2/g.

5. The process according to claim 1, wherein modification of the relative proportion of natural porous aluminosilicates to spent porous synthetic aluminosilicates adjusts the composition of the liquid mixture of hydrocarbons.

6. The process according to claim 1, wherein the liquid mixture of hydrocarbons comprises hydrocarbons having between 5 and 44 carbon atoms.

7. The process according to claim 1, wherein the separating step comprises fractionating the gaseous mixture by distillation to produce a gasoline fraction, a jet fuel fraction, a kerosene fraction, a gas oil fraction, and/or a fuel oil fraction.

8. The process according to claim 1, wherein the plastic waste material contaminated with oils and/or pigments is composed primarily of polypropylene, polyethylene, polystyrene, polyethylene terephthalate, or a mixture thereof.

9. The process according to claim 8, wherein the plastic waste material contaminated with oils and/or pigments is composed primarily of polypropylene and polyethylene.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The aspects that are considered to be characteristic of the present invention shall be established in particular in the appended claims. Nevertheless, the invention itself, both in its organization and in its method of operation, together with other objects and advantages of the same, shall be better understood in the following description of certain embodiments, taken in conjunction with the accompanying drawings, in which:

(2) FIG. 1 is a block diagram showing the stages of the thermal-catalytic decomposition reaction generating a mixture of hydrocarbons in the vapor phase.

(3) FIG. 2 is a block diagram showing the stage of separation of the hydrocarbons from the vapor phase current.

(4) FIG. 3 is an illustration showing schematically the equipment for carrying out the process of catalytic decomposition in continuous duty.

(5) FIG. 4 is an illustration showing schematically one embodiment of the equipment to carry out the process of catalytic decomposition in a continuous manner.

(6) FIG. 5 is an illustration showing schematically one additional embodiment of the equipment for carrying out the process of catalytic decomposition in a continuous manner.

DETAILED DESCRIPTION OF THE INVENTION

(7) The present invention comprises a process and equipment for decomposing plastic material and converting it into hydrocarbons (fuels and/or chemicals of industrial utility). Said decomposition is of a catalytic nature, wherein the plastic material is subjected to a thermal pretreatment accompanied by an inert gas to produce a liquid mass, which is fed simultaneously into a packed bed reactor to bring the pretreated plastic material in the liquid state into contact with particles of catalytic material in order to perform the catalytic conversion in this way, taking care to control the different temperatures in order to obtain a mixture of hydrocarbons in the vapor phase, so that afterwards liquid products that can be used as chemicals or fuels can be obtained.

(8) Generally, the plastic material used in the process that has been developed can come from any origin; however, it is emphasized that the process is able to convert plastic waste products including plastics contaminated with oils and pigments, since these constitute a serious environmental problem. Also disclosed is equipment in which the process can be carried out, without this disclosure representing a limitation on the type of equipment required to carry out the process. Both the process and the equipment of the present invention are described below.

(9) In one embodiment, the process of the present invention comprises the steps of subjecting to thermal pretreatment 1 the plastic waste material 10 in order to produce a liquid plastic mass, wherein the thermal pretreatment of the plastic material is carried out in an inert gas atmosphere 11 at a temperature varying between 110 C. and 310 C., and wherein the pretreatment time depends on the type of plastic material and the plastic mass being liquefied. The purpose of the pretreatment under an inert gas atmosphere is to avoid any oxidation and consequently to avoid a premature degradation into unwanted compounds such as synthesis gas or compounds of low molecular weight. When the plastic material feedstock is composed of a mixture of different plastics, the process typically includes an additional step of homogenization of the liquid plastic mass in order to produce a mixture of hydrocarbons of consistent composition during the process.

(10) The homogenized liquid plastic mass is simultaneously fed to a reaction apparatus 2, such as a closed tank, reactor, or the like. In a preferred embodiment, the reaction apparatus is a packed bed reactor, a fluidized bed reactor, or a mixed flow reactor. As the liquid plastic mass flows inside the reaction medium of packed bed type, the plastic mass is brought into contact with the bed of particles of inorganic porous material with catalytic activity in a medium free of oxygen at a temperature of 300 C. to 600 C. In this way, reactions of thermocatalytic decomposition are induced, generating a mixture 12 containing hydrocarbons in the vapor phase (see FIG. 1). The decomposition reactions occur at temperatures ranging from 300 C. to 600 C., preferably at a temperature varying between 450 C. and 550 C.

(11) The particle size of the bed of inorganic porous material can be between 30 and 10,000 microns, preferably between 50 and 2000 microns, and more preferably between 60 and 1500 microns. This material can be composed of synthetic or natural aluminosilicates or a combination of the two. Aluminosilicates are porous materials with acidic active centers which give them very good catalytic activity, so that they are active in carrying out the decomposition of the liquid mass in the process of the present invention. Preferably, the natural aluminosilicates and the spent synthetic ones have the following characteristics: Si/Al molar ratios between 3 and 40 and pore diameters between 0.5 and 50 nm and specific surface area between 15 and 1000 m.sup.2/g.

(12) The vapor phase generated by the thermocatalytic decomposition reaction comprises hydrocarbons of between 1 and 44 carbon atoms in their structure, preferably between 1 and 4 carbon atoms in their structure (non-condensable) and between 5 and 44 carbon atoms in their structure (condensable).

(13) In one embodiment of the process where natural aluminosilicates are used, the condensable hydrocarbons obtained are primarily aliphatic. In the embodiment of the process using spent synthetic aluminosilicates, one obtains a greater quantity of aromatic hydrocarbons in the condensable fraction. Ideally, one can use combinations of natural aluminosilicates and spent synthetic aluminosilicates in the process, being able to modify the proportions of these as well as the operating conditions to adjust the composition of the final mixture of hydrocarbons (see Examples 1 to 3).

(14) The process for decomposing the plastic material and converting it into hydrocarbons and/or chemicals of industrial utility includes the step of separating the hydrocarbons 3 having between 5 and 44 carbon atoms from the vapor phase current 13 generated within the reaction medium to produce a liquid mixture 14 of hydrocarbons (see FIG. 2). The separation can be carried out by any physical or chemical method which allows a condensation of this mixture, preferably by indirect heat exchange with a refrigerant fluid. The non-condensable vapors can be used to generate electrical energy or even thermal energy by combustion, or they can be treated in order to be separated by known physical or chemical techniques (such as liquefaction). The liquid mixture of hydrocarbons can be subjected to an additional fractionation stage, preferably by distillation, in order to separate liquid chemicals and/or hydrocarbons with value as industrial chemicals or with characteristics classified as gasoline, jet fuel, kerosene, gas oil and/or fuel oil.

(15) The equipment designed to carry out the process of catalytic decomposition preferably operates in a continuous manner. The equipment for the production of hydrocarbons by catalytic decomposition of plastic waste products in a single step comprises: an apparatus 1 for thermal treatment of the plastic waste material to produce a liquid plastic mass; an apparatus 2 to carry out the catalytic decomposition of the liquid plastic mass and produce a mixture of hydrocarbons in the vapor phase; and an apparatus 3 for separating the hydrocarbons with 5 to 44 carbon atoms from the vapor phase current generated inside the apparatus carrying out the catalytic decomposition to produce a liquid mixture of hydrocarbons. In one embodiment, the equipment for the production of hydrocarbons by catalytic decomposition of plastic waste products can include a second separator apparatus to separate the condensable fraction of the gaseous product (see FIG. 4). Optionally, the separated liquid goes to a fractionation apparatus, such as a fractionation column, in which a fractional distillation occurs to separate the components of interest or liquid fuels such as gasoline, jet fuel, kerosene, gas oil and fuel oil.

(16) The apparatus for heat treatment of the material comprises means of feeding an inert gas to generate an inert gas atmosphere and heating means for heat treatment of the plastic waste material at a temperature that can lie between 110 C. and 310 C. and thereby to produce a liquid plastic mass.

(17) In a particularly preferred embodiment of the present invention, the apparatus to carry out the catalytic decomposition of the liquid plastic mass and produce a mixture of hydrocarbons in the vapor phase can be selected from among a packed bed reactor, a fluidized bed reactor, or a mixed flow reactor. FIG. 3 shows a preferred apparatus 30 for carrying out the catalytic decomposition in accordance with the present invention, being a tubular packed bed reactor 31. The tubular packed bed reactor comprises a heating source 32 to heat the reactor in a uniform manner and to provide the adequate quantity of heat to maintain the reaction temperature (preferably 300 C. to 600 C.) in the packed bed. The reactor can be heated indirectly with steam, combustion gases, or any other heating fluid, although combustion gases are used preferably. An inert gas 33 is used to maintain a reduced or oxygen-free atmosphere inside the reactor. The plastic material 34, pretreated and in the liquid state, which is treated in the apparatus for heat treatment of the material, is then fed in and flows through the packed bed 35 inside the reactor where it is brought into contact with the particles of catalytic material to bring about the catalytic conversion in this way, making sure to control the different temperatures in order to obtain a mixture of hydrocarbons in the vapor phase, after which one can obtain liquid products that can be used as chemicals or fuels. At the exit from the reactor, a gaseous current 36 is obtained, which can optionally be taken to a second module 40 composed of a condenser to separate the condensable fraction 41 from the gaseous product 36 (see FIG. 4). Optionally, the separated liquid goes to a third module 50, composed of a fractionation column in which a fractional distillation is performed to separate the components of interest or liquid fuels such as gasoline, jet fuel, kerosene, gas oil and/or fuel oil (See FIG. 5).

ILLUSTRATIVE EXAMPLES

Example 1

(18) The method was tested by decomposing a mixture of low density polyethylene, high density polyethylene and polypropylene in mass fractions of 26%, 38% and 36%, respectively, using a natural zeolite as the catalytic material, varying the conditions of reactor temperature and ratio of catalyst weight to flow of plastic feedstock material (W/F), as shown in the following table, along with the composition of condensable product:

(19) TABLE-US-00001 Temperature 515 C. 525 C. 525 C. W/F Composition of 76 min 60 min 46 min condensable product wt. % wt. % wt. % .sub.C.sub.5-C.sub.12 90.9% 83.8% 75.9% C.sub.13-C.sub.14 1.6% 3.8% 3.4% C.sub.15-C.sub.17 2.3% 3.8% 5.6% C.sub.18-C.sub.28 4.7% 7.4% 12.8% >C.sub.29 0.5% 1.2% 2.3%

Example 2

(20) The method was tested by decomposing a mixture of low density polyethylene, high density polyethylene and polypropylene in the same proportions as in Example 1, using a synthetic zeolite as the catalytic material, varying the conditions of reactor temperature and ratio of catalyst weight to flow of plastic feedstock material (W/F), as shown in the following table, along with the composition of condensable product:

(21) TABLE-US-00002 Temperature 500 C. 450 C. 450 C. 425 C. W/F Composition of 213 min 341 min 262 min 339 min condensable product wt. % wt. % wt. % wt. % .sub.C.sub.5-C.sub.12 99.4% 99.5% 99.7% 98.7% C.sub.13-C.sub.14 0.6% 0.5% 0.3% 1.3% C.sub.15-C.sub.17 C.sub.18-C.sub.28 >C.sub.29 Total aliphatic 16.6% 24.5% 26.0% 37.4% Total aromatic 83.4% 75.5% 74.0% 62.6%

Example 3

(22) The method was tested by decomposing a mixture of low density polyethylene, high density polyethylene and polypropylene in the same proportions as in Example 1, using a mixture of synthetic and natural aluminosilicates as the catalytic material in a mass ratio of 2.85:1. The plastic feed rate and the ratio of catalyst weight to flow of plastic feedstock material (W/F) was varied, as shown in the following table, along with the composition of condensable product:

(23) TABLE-US-00003 Temperature 500 C. 500 C. 500 C. W/F Composition of 107 min 67 min 62 min condensable product wt. % wt. % wt. % .sub.C.sub.5-C.sub.12 63.4% 67.5% 70.1% C.sub.13-C.sub.14 3.2% 3.4% C.sub.15-C.sub.17 2.2% 4.5% C.sub.18-C.sub.28 0.4% 4.0% >C.sub.29 Nitrogenated compounds 33.5% 21.6% 13.1% Total aliphatic 29.8% 55.4% 66.0% Total aromatic 67.0% 39.5% 29.2%

Example 4

(24) The method was tested by decomposing expandable polystyrene, using a mixture of natural zeolite as the catalytic material, varying the conditions of reactor temperature and ratio of catalyst weight to flow of plastic feedstock material (W/F), as shown in the following table, along with the composition of condensable product:

(25) TABLE-US-00004 Temperature 475 C. 495 C. W/F Composition of 177 min 132 min condensable product wt. % wt. % Styrene 28.3% 26.4% Ethylbenzene 17.7% 19.7% Methylstyrene 12.3% 13.1% Toluene 11.2% 12.1% Other aromatic compounds 29.7% 28.1% Other aliphatic compounds 0.7% 0.6%

(26) Even though a specific embodiment of the present invention has been shown and described as an example, it should be understood that it is amenable to various modifications and alternative forms, without departing from the spirit and scope of the present invention. Therefore, the intention is not to limit the invention to the particular form described, but rather to include all modifications, equivalents, and alternatives coming under the scope of the invention as stated in the appended claims.