A PROCESS AND TWO-STEP CATALYTIC REACTOR SYSTEM FOR THE PRODUCTION OF LIQUID HYDROCARBONS FROM PLASTIC WASTE

Abstract

The present invention relates to a process and a system for the production of liquid hydrocarbons by thermo-catalytic cracking of plastic waste. The invention relates to a technique for efficiently producing high-quality liquid fuel using designed reactor setup for the cracking of waste plastic. The invention also relates to a thermo-catalytic cracking method, which occurs in the presence of zeolite-based catalysts, more preferably the zeolite catalysts impregnated with transition metals which remain catalytically active up to 8-10 sets of reactions with higher selectivity of petroleum range hydrocarbons. The present invention also relates to a two-step approach system for the production of liquid hydrocarbons.

Claims

1. process for the production of liquid hydrocarbon from plastic waste comprising the steps of: (i) thermally cracking plastic waste in a thermal cracking zone at a temperature of about 200 to 400° C. forming hydrocarbon vapors; (ii) catalytically cracking said hydrocarbon vapors in a catalytic cracking zone with a zeolite catalyst impregnated with a transition metal selected from the group consisting of Fe, Cu, Co, or Ni at a temperature of about 300 to 400° C.; and (iii) condensing the hydrocarbon vapors at a temperature of about −5 to about 15° C. forming fuel-like hydrocarbon having C.sub.5 to C.sub.28 hydrocarbon fractions; wherein 60-80% of fuel-like hydrocarbon formed are liquids and 20-35% are gases.

2. The process as claimed in claim 1, wherein the zeolite catalyst is impregnated with copper or iron.

3. The process as claimed in claim 1, wherein the ratio of the catalyst to plastic waste is in the range of 1:10 to 1:30.

4. The process as claimed in claim 1, wherein fuel-like hydrocarbons have C5 to C18 hydrocarbon fractions.

5. The process as claimed in claim 1, wherein the fuel-like hydrocarbon has calorific value in the range of 42 to 45 MJ/kg.

6. The process as claimed in claim 1, wherein the catalyst retains reactivity for about 8-10 sets of reactions.

7. The process as claimed in claim 1, wherein the thermal cracking and catalytic cracking reaction is completed in 10 to 25 minutes.

8. The process as claimed in 1, further comprises the steps of separating, sizing, pelletizing and/or processing the plastic waste prior to thermal cracking.

9. A two-stage hatch reactor system for producing a fuel-like hydrocarbons from plastic waste comprising: (i) a thermal cracking zone adapted to receive plastic waste; (ii) a catalytic cracking zone arranged vertically and connected to said thermal cracking zone and comprising zeolite catalytic bed; wherein the zeolite catalyst is impregnated with a transition metal selected from the group consisting of Fe, Cu, Co, or Ni; and (iii) a condenser connected to said catalytic cracking zone maintained at about −5 to about 15° C. temperature range.

10. The system as claimed in claim 9, wherein the catalytic cracking zone is arranged vertically about 20-30 mm above the thermal cracking zone, having L/D ratio in the range of 70-40 mm such that there is an immediate interaction of vapor from the thermal cracking zone and the catalyst bed.

11. The system as claimed in claim 9, further comprises an inert gas cylinder supplying inert gas to the thermal cracking zone.

12. The system as claimed in claim 9, further comprises a hydrocarbon gas collector and a hydrocarbon liquid collector connected to said condenser.

Description

BRIEF DESCRIPTION OF DRAWING

[0028] FIG. 1 depicts the process steps of the present invention.

[0029] FIG. 2 illustrates the block diagram of the process of production of liquid fuel from waste plastic for the present invention.

[0030] FIG. 3 illustrates the batch reactor system following a two-step approach for the thermo-catalytic cracking of waste plastic.

DETAILED DESCRIPTION OF THE INVENTION

[0031] The following is a detailed description of embodiments of the invention. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.

[0032] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the “invention” may in some cases refer to certain specific embodiments only. In other cases, it will be recognized that references to the “invention” will refer to subject matter recited in one or more, but not necessarily all, of the claims. Unless the context requires otherwise, throughout the specification which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”

[0033] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0034] As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

[0035] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[0036] The title and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.

[0037] The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus, if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.

[0038] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.

[0039] The present invention relates to a two-step approach to control the immediate deactivation of the catalyst, as instead of plastic melt, hydrocarbon vapors will interact with the catalyst surface at the temperature below 400° C. with high liquid yield (60-80%) by using substantially minimal amount of catalyst. The developed two step approach leads to substantially 100% conversion of plastic waste into value added products comprising 60-80% liquids, and 20-35% gases.

[0040] Moreover, the current invention promotes the gasoline and diesel fraction formation from the waste plastic in considerable amount and efficient manner. By this means, it contributes towards resource reclamation and environment protection.

[0041] In an embodiment, the present invention provides a process for the production of hydrocarbon from plastic waste is provided. The process according to the present invention comprises the steps of: (i) thermally cracking plastic waste in a thermal cracking zone (120) at a temperature of about 200 to 400° C. forming hydrocarbon vapors; (ii) catalytically cracking said hydrocarbon vapors with a zeolite catalyst impregnated with a transition metals selected from the group consisting of Fe, Cu, Co, and/or Ni in a catalytic cracking zone (130) at a temperature of about 300 to 400° C.; and (iii) condensing the hydrocarbon vapors at a temperature of about −5 to about 15° C. forming fuel-like hydrocarbon having C5 to C28 hydrocarbon fractions; wherein 60-80% of fuel-like hydrocarbon formed are liquids and 20-35% are gases.

[0042] In a preferred embodiment, the zeolite catalyst can be impregnated with copper or iron. The as synthesized zeolite catalyst impregnated with transition metal plays a crucial role in tuning the fraction of hydrocarbons formed. The usage of the zeolite catalyst impregnated with transition metal shows an added advantage of reducing the cracking temperature as well as tailoring the selectivity. In an embodiment, the temperature of the catalyst bed in the catalytic zone can be maintained between 100-400° C. for the further cracking of thermally cracked vapors. Preferably, the ratio of the catalyst to plastic waste can be in the range of 1:10 to 1:30. The lower consumption of catalyst was one of the challenges in the catalytic cracking of plastic. The present invention shows that a minimal ratio of zeolite to a polymer (1:10-1:30) was found to be efficient for the reaction.

[0043] In an embodiment, the thermal cracking and catalytic cracking reaction can be completed in 10 to 25 minutes. The catalyst retains reactivity for about 8-10 sets of reactions. Thus, the present invention provides substantially faster means for the formation of fuel like liquid. Further, the catalyst has delayed the coke formation on its surface with good recyclability, and hence the process is cost effective as well.

[0044] The process of the present invention further includes the steps of separating, sizing, pelletizing and/or processing the plastic waste prior to thermal cracking.

[0045] FIG. 2 shows the block diagram describing the process of the present invention. In a preferred embodiment, the plastic waste, such as those sourced from municipal solid waste (MSW) can be used as a raw material for the process of the present invention. Preferably, the plastic material used in the invention can have a composition of polypropylene (PP), low-density polyethylene (LDPE), and high-density polyethylene (HDPE) which can account for about 50% of the total municipal plastic waste. The MSW from a storage (Block 1) is separated (Block 1A) sized and pelletized (Block 2B) and supplied to a shredder where the plastic waste is shredded and pelletized (Block 2). The shredded and pelletized is fed (Block 3A) to thermal cracking (Block 4) through a hopper (Block 3). Thermal cracking of the plastic waste is carried out in a thermal cracking zone (4, FIG. 3) at a temperature of about 200 to 400° C. (Block 4A and 4B) forming hydrocarbon vapors. The hydrocarbon vapors from thermal cracking (Block 4) is then passed to the catalytic cracking (Block 5) which is preferably arranged vertically about 20-30 mm above the thermal cracking zone (Block 4, FIG. 2 and FIG. 3 (130)). Catalytic cracking of previously formed vapors occurs in the presence of zeolite catalyst impregnated with a transition metal selected from the group consisting of Fe, Cu, Co, or Ni at temperature range of 300-400° C. Condensing the hydrocarbon vapors (Block 6A) at a temperature of about −5 to about 15° C. (Block 6) forming fuel-like hydrocarbon having C5 to C28 hydrocarbon fractions; wherein 60-80% of fuel-like hydrocarbon formed are liquids and 20-35% are gases. The condensed liquid from Block 6 formed can be collected in an air tight glass bottled for further analysis (Block 8). The uncondensed gases from Block 6 can be collected (Block 7) for further analysis using GC-FID. Preferably, the uncondensed gases can be collected in tedlar bags.

[0046] The process of thermally cracking plastic waste in a thermal cracking zone (120) and then conducting a catalytic cracking reaction in a separate catalytic cracking zone (130) controls the immediate deactivation of the catalyst and leads to higher selectivity for the production of liquids in the petroleum range as compared to the formation of gaseous fraction which can also be used as a source of heat and thus, overall process supports the economic viability of the invention. Furthermore, no external hydrogen source/hydrogen donor solvent has been used during or post reaction.

[0047] The experimental results suggest that, the carbon chain length can be narrowed to C5-C28 when the zeolite catalysts were employed, as well as a significant yield of aromatics can be obtained with substantially major percentage of naphthalene indicating that the obtained liquids are fuel-like products. The physical properties of the fuel like liquid formed are comparable with the commercially available liquid fuel which shows that the liquid formed can be used as an alternative fuel. The liquid product formed is cost effective and thus, supports the economic viability of the present invention.

[0048] The process according to the present invention produces fuel-like hydrocarbons preferably that have C5 to C18 hydrocarbon fractions. The fuel-like hydrocarbon of the present invention can have a calorific value in the range of 42 to 45 MJ/kg. The fuel like liquid formed in the present invention can be directly used for the engine operation without further up-gradation.

[0049] The process according to the present invention for the treatment of waste plastic does not involve the use of any organic or inorganic solvent for the formation of fuel like liquid. Furthermore, no external hydrogen source/hydrogen donor solvent has been used during or post reaction. Thus, the process is cost-effective, simple operating, substantially no secondary pollution, energy saving and most importantly the value product formation through the safe and reliable operation. In another embodiment of the present invention, a two-stage batch reactor system for producing a fuel-like hydrocarbons from plastic waste is provided. FIG. 3 shows the two-stage batch reactor system (100) of the present invention. The two-stage batch reactor system of the present invention comprises: a thermal cracking zone (120) adapted to receive plastic waste; a catalytic cracking zone (130) arranged vertically and connected to said thermal cracking zone (120) and comprising zeolite catalytic bed (132); wherein the zeolite catalyst is impregnated with a transition metal selected from the group consisting of Fe, Cu, Co, or Ni; and a condenser (140) connected to said catalytic cracking zone (130) maintained at about −5 to about 15° C. temperature range.

[0050] The thermal cracking zone (120) is the first heating zone and is adapted to receive the plastic waste. Preferably, the spherical reactor volume of around 300-600 cm.sup.3 can be considered for the uniform heating of plastic. The thermal cracking zone (120) contains raw material in the form of plastic beads for the first step of degradation in the thermal cracking zone. In one embodiment, the plastic waste of around 10-250 g can be loaded in the reactor. The plastic waste obtained from MSW can be shredded and pelletized before feeding to the thermal cracking zone (120). The pelletized plastic waste can be fed through a hopper (not shown in figure) to the thermal cracking zone. The process of formation of vapors (122) starts in this zone from about 200 to about 400° C. An inert gas cylinder (110), preferably a nitrogen gas cylinder with 99.99% purity supplies inert gas to the thermal cracking zone (120). The inert gas can be used as an inert media to avoid the side reactions and also as a medium for vapor transfer supplies to the catalytic cracking zone (130). The flow of inert gas to the thermal cracking zone (120) can be regulated via a regulator (112) and a flow meter (114). The flow rate of the inert gas can be in the range of 0.6-3.0 L/hour.

[0051] The vapors (122) from the thermal cracking zone (120) can be passed to the catalytic cracking zone (130) arranged vertically and connected to said thermal cracking zone (120) and comprising zeolite catalytic bed (132); wherein the zeolite catalyst is impregnated with a transition metal selected from the group consisting of Fe, Cu, Co, or Ni. The catalytic cracking zone (130) is preferably vertical about 20-30 mm above the thermal cracking zone (120), having L/D ratio in the range of 70-40 mm such that there is an immediate interaction of vapor (122) from the thermal cracking zone (120) and the catalyst bed (132). Thus, the travel path of the vapors from thermal cracking to catalytic zone is short, regarding the design of the reactor system and thereby leading to immediate interaction with the catalyst bed. This also reduces the time taken for the reaction to occur in two stage process.

[0052] In this zone (130), further cracking of previously formed vapors (122) occurs. The vapors (122) are preferably continuously passed to the catalytic cracking zone (130). Temperature of the catalyst bed in the catalytic zone can be maintained between 100-400° C. for the further cracking of thermally cracked vapors. Temperature sensors (117) are connected to both the reactors (120) and (130) to the PID controller (116).

[0053] The vapors from the catalytic cracking zone (130) are allowed to pass through the condenser (140) connected to said catalytic cracking zone (130) and maintained at about −5 to about 15° C. temperature range. A cryostat (118) can be used which behaves as a source for cooling media to the condenser (140). A gas outlet is connected where the uncondensed gases are released and collected (150) for further analysis in gas chromatograph. The uncondensed gases can be collected in tedlar bags. The condensed vapors can be collected in the form of liquid (160) at room temperature.

[0054] The two-step reactor design of the improved batch reactor system with two separate heating zones accounts to low power consumption for the complete degradation of plastic and thus, supports the first point towards the economic viability of the proposed process. The two separate zones for material treatment restricts the direct contact of polymer melt with the catalyst; thereby, the delay in coke formation is observed. The two-step reactor design of the improved batch reactor system of the present invention retains the reactivity of the catalysts for the longer period of time.

[0055] The two-step approach reactor set-up of the present invention also leads to higher selectivity for the production of liquids in the petroleum range as compared to the formation of gaseous fraction which can also be used as a source of heat and thus, overall process supports the economic viability of the invention. In addition, the further distillation of the crude product is not required and can be directly employed for the engine operation with the blend which is supported with the calorific value and GC-MS analysis of the product obtained.

[0056] The reactor system of the present invention has easy operation, and minimal maintenance and increases productivity and can be economical.

[0057] The examples used here in this invention are merely intended to facilitate the understanding of ways in which the embodiments herein may be practiced, however; the scope of the invention is not limited to them.

Examples

[0058] The plastics used herein are the waste plastics from the municipality. The poly-bags are collected, cleaned, shredded and then used for the cracking process. The plastic material used here in this invention has the composition of PP, LDPE, and HDPE which accounts for around 50% of the total municipal plastic waste. The novel catalyst prepared in the laboratory is used in very minimal amount. First heating zone is the thermal heating zone which is filled with the waste plastic in terms of raw material. For this zone, the spherical reactor volume of around 300-600 cm.sup.3 is considered for the uniform heating of plastic. Thermal heating zone has the waste plastic feed of around 10-250 g in the reactor. Reaction is performed in the presence of an inert atmosphere to suppress the side reactions due to oxygen in the atmosphere. The heating rate is varied from 5 to 30° C./min. Vapors formed in the thermal cracking zone are allowed to pass towards the catalytic zone in continuous mode. In reference to the catalytic zone, the catalytic bed of as prepared zeolite catalyst (HZSM-5), impregnated with transition metals such as, Cu/ZSM-5, and Fe/ZSM-5 are equipped with bed volume of around 20-30 cm.sup.3.

[0059] In the catalytic zone, thermally cracked vapors are further cracked catalytically for the controlled formation of vapors. Temperature of the catalyst bed in the catalytic zone is maintained between 100-400° C. for the further cracking of thermally cracked vapors. The catalytically cracked vapors are allowed to pass through the helical coiled condenser maintained between −5 to 15° C. temperature range for the condensation of the higher hydrocarbons formed in the heating zone.

[0060] The condensed vapors are converted into fuel like liquid and are collected at the bottom in the barrel. Uncondensed gases pass through the gas sampler for further testing through gas chromatography.

[0061] Table 1 shows the liquid yield percentage for the plastic mixture with higher selectivity of liquid range hydrocarbons for modified zeolites.

TABLE-US-00001 TABLE 1 Liquid Calorific Sr. Yield Selectivity (%) Value No. Feed Catalysts (%) C5-C12 C13-C18 C19-C28 (MJ/kg) 1 PP + — 70 15 19 58 38.45 LDPE + HDPE 2 PP + HZSM-5 60 30 46 12 40.39 LDPE + HDPE 3 PP + Cu/ZSM-5 65 38 40 8 41.16 LDPE + HDPE 4 PP + Fe/ZSM-5 65 45 42 5 42.78 LDPE + HDPE

[0062] The quality of the fuel like liquid formed is enhanced greatly with the application of two-step approach for plastic degradation. A two-step approach has the advantage of simple operation, easy to handle, cost effective, less power consumption and can be considered as an economically viable process.