Recycling of plastics in a steam cracker

Chemistry of hydrocarbon compounds – Production of hydrocarbon mixture from refuse or vegetation – From synthetic resin or rubber

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585648, 208130, C07C 100, C07C 422

Patent

active

057314837

DESCRIPTION:

BRIEF SUMMARY
This application is a 371 of PCT/EP94/01647 filed on Sep. 20, 1994.
The present invention relates to a process for recycling plastics in a steam cracker.
It is possible by means of the process according to the invention to convert plastics, for example pure polymeric plastic waste, mixed plastic waste or sheet waste, including possible soiling, sticky label materials, fillers, residual contents etc., into high-value feed materials for the known steam cracking process. These feed materials are in turn converted in the known steam cracking process, into cracked products such as ethylene, propylene, C.sub.4 mixtures, pyrolysis gasoline etc., and these are produced in yields which are almost the same as or even higher than when the steam cracker is operated with the traditional feed materials such as naphtha, liquid petroleum gas (LPG) and gas oil. It is therefore possible by means of the process according to the invention to replace in the steam cracking process the abovementioned traditional feed materials by feed materials obtained from plastic waste, it being unnecessary to admix naphtha, LPG or gas oil with the feed materials obtained from plastic waste.
The process according to the invention therefore makes a considerable contribution to the economic recycling of plastics.
The known steam cracking process is usually understood as evaporation and heating of the feed materials at up to 650.degree. C. with subsequent treatment at in general from 700.degree. to 1100.degree. C., for example from 780.degree. to 860.degree. C., in the course of, usually, from 0.02 to 10, for example from 0.1 to 2, seconds in the presence of steam.
It is known that the plastic wastes obtained as garbage consist of about 70% by weight of polyolefins, such as polyethylene and polypropylene, about 15% by weight of styrene polymers, about 10% by weight of PVC and minor amounts of about 5% by weight of other plastics, such as polyurethane, polyester and polyamide. These plastic wastes are generally soiled, ie. they also contain sticky label materials, fillers, residual contents, etc. The plastic wastes are usually sorted and are therefore obtained in various fractions known per se. The bottle or blow molded fraction composed of bottles, containers, etc., which essentially consist of polyolefins, such as polyethylene or polypropylene, a mixed plastic fraction, consisting essentially of polyethelene (PE), polypropylene (PP), styrene polymer, such as polystyrene (PS), and polyvinyl chloride (PVC); a sheet fraction consisting essentially of PE and PP, etc., and a light fraction consisting essentially of PE, PP and PS, in each case possibly with adherent soiling, sticky label materials, fillers, residual contents, etc., may be mentioned. Essentially, the fractions contain plastics other than the stated ones only in minor amounts, for example less than 10% by weight, in many cases less than 5% by weight, in particular less than 2% by weight.
A number of processes have been described in the patent literature for converting plastic waste into products for further processing, for example catalytic or thermal processes, hydrocracking processes, extrusion processes etc. For example, Europ. Patent Application 0 502 618 describes a process in which plastic waste, specifically polyolefins, is converted into lower hydrocarbons. This entails the plastic waste being reacted in a fluidized bed apparatus at about 300.degree.-630.degree. C. The resulting lower hydrocarbons, such as paraffins or waxes, can be converted by means of the known steam cracking process into olefins. Plastic waste can be converted by the combination of fluidized bed apparatus and known steam cracking process into these olefins.
An evident disadvantage of this process is that for the steam cracking process it is necessary to add naphtha to the feed materials obtained, ie. it is not possible to convert the plastic waste into cracked products such as ethylene, propylene etc. without adding traditional feed materials. Furthermore, the handling of the solids in the fluidized bed alw

REFERENCES:
patent: 5364995 (1994-11-01), Kirkwood et al.

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