Selective phenol recovery via simultaneous hydrogenation/dealkylation of isopropyl- and isopropenyl-phenols employing an H2 generator combined with tandem micro-reactor GC/MS

Latest Trends in Pyrolysis Gas Chromatography for Analytical and Applied Pyrolysis of Plastics

Pyrolysis is considered to be a promising method for polymer characterization (in the field of analytical pyrolysis) and for chemical feedstock recovery from plastic wastes (in the field of applied pyrolysis) because it can decompose any polymeric material into smaller molecules by applying heat alone in an inert atmosphere. Pyrolysis-gas chromatography (Py-GC) involves pyrolyzing polymeric materials in a micropyrolyzer and a subsequent direct GC analysis of pyrolyzates. Py-GC has immense potential for applications in the fields of both analytical and applied pyrolysis, as it allows for rapid and accurate analysis of pyrolyzates. This is beneficial for elucidating microstructure and composition of polymers and for a rapid screening of pyrolysis conditions for designing feedstock recycling processes. In this review, we examined the latest research trends in Py-GC applications for polymer characterization, analysis of plastics in the environment, and chemical feedstock recovery from plastics.

Direct Gas-Phase Derivatization by Employing Tandem μ-Reactor-Gas Chromatography/Mass Spectrometry: Case Study of Trifluoroacetylation of 4,4'-Methylenedianiline

Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) is a promising technique allowing the rapid characterization of the polymer structure and additives of microgram-scale plastics. However, the Py-GC/MS analysis of polymers with urethane bonds is challenging because they produce highly reactive pyrolyzates such as amines and isocyanates polymerizing in the GC column, which limits the efforts to elucidate the pyrolysis mechanism and plastic characterization by online GC analysis. Herein, a novel pyrolysis-gas-phase derivatization-GC/MS (Py-GPD-GC/MS) technique was developed, allowing the pyrolysis of polymers and the subsequent direct gas-phase derivatization of pyrolyzates, employing a modified tandem μ-reactor-GC/MS system. This work conducted the gas-phase trifluoroacetylation of 4,4'-methylenedianiline (MDA), which is one of the major polyurethane (PU) pyrolyzates, using N-methyl-bis-trifluoroacetamide (MBTFA) as a derivatization agent. The trifluoroacetylation gas-phase reaction was monitored by in situ GC/MS analysis and the effects of derivatization conditions were investigated. The highest MDA conversion observed was 65.6 area %. Furthermore, the sequential PU pyrolysis and direct trifluoroacetylation of PU pyrolyzates in the first μ-reactor and second μ-reactor, respectively, were successfully operated, achieving the inhibited polymerization and detection of trifluoroacetylated derivatives. Thus, the Py-GPD-GC/MS method has a significant potential to be applied for other combinations of pyrolyzates and derivatization reactions, enabling deeper characterization of plastics producing highly reactive pyrolyzates that cannot be accurately analyzed by conventional Py-GC/MS analysis.

Hydrogen and steam injected tandem μ-reactor GC/FID system: phenol recovery from bisphenol A and alkylphenols using Ni/Y zeolite

Hydrogen and steam injected tandem μ-reactor-GC/FID system achieved online quantification of products from hydrogenation and dealkylation of bisphenol A and alkylphenols using Ni/Y zeolite.