PEFTEC - Abstract

Abstract Information :

Polyolefins make up 50 of consumed plastics in Western Europe 1. Chemical recycling is an interesting and preferred method to recycle plastic waste by cracking it into basic chemical substances which can be reused in the petrochemical industry 2. Pyrolysis of polyolefins very specifically results in pyrolysis oils with a high alkene content. Its composition is markedly different from the composition of fossil oil. Characterizing alkenes in polyolefin pyrolysis oil is hence important in order to introduce it into the classical petrochemical industry. Knowing the type and concentration of the alkenes will support decisions on the chemical route and amount of reagents for processes necessary to connect to the petrochemical industry. However, characterization is not easy because of the presence of a wide variety of different molecules and functionalities after the pyrolytic cracking process. Polyolefin feedstock for pyrolysis can come from LLDPE, HDPE, PP, or mixtures of them. This leads to a big challenge to characterize each type of alkene and the corresponding concentration in waste polyolefin pyrolysis oil. Moreover, classical methods, i.e. 2D-GC-MS or iodine titration are time consuming, laborious and costly. A simple, reliable but still highly differentiating and quantifying method, relying on one single analytical technique is thus of high value. rnrnWe proposed 3 a simple method using FTIR to determine the kind and quantity of double bonds in PE-based pyrolysis oils. By studying characteristic absorption peaks of unsaturated hydrocarbons in the fingerprint region of the IR spectrum between known and unknown samples, together with the estimated carbon number and molecular weight of those materials through the mass of methylene group CH2, an equation was proposed to determine the moles of double bonds per gram of sample DBM. rn rnStandard substituted and unsubstituted alkenes and alkanes were used to create mixtures with different double bondcarbon DBC content and yielded calibration curves that allowed to determine the DBM content in unknown PE-based pyrolysis samples. NMR confirmed the accuracy of the method lt;10 deviation in DBC concentration within the C10-C20 range.rnrnHowever PP-based pyrolysis oil is markedly different from PE-based pyrolysis oil. The latter has a continuous MW-distribution profile, whereas PP-based pyrolysis oil shows no continuous MW distribution profile but a profile with predominant molecular entities due to the difference in backbone structure. For PE the MW is directly correlated to the CH2-content, whereas in the case of PP and PPPE mixtures, the presence of side groups has to be taken into account.rnrnAn improved method, equation and calibration approach based on FTIR is proposed to make accurate DBM determinations for PP and mixed PPPE based pyrolysis oils. The new proposed approach also allows to determine the type of alkenes and their corresponding content by an easy, low cost and efficient analytical method, based on quantitative ATR-FTIR.rnrnReferencesrn1.Plastics Europe Market Research Group PEMRG and Conversion Market amp; Strategy GmbH 2019rn2.Sasse, F. E. et al. 1998. Chemical Recycling of Polymer Materials. Chemical Engineering amp; Technology, 2110, 777-789rn3.Trang Thi Bui et al. 2021 A new analytical method to characterize saturated and unsaturated hydrocarbons in pyrolysis oil of waste polyethylene, The 8th International Conference on Engineering for Waste and Biomass Valorisation, May 31 - June 4, 2021.rn