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

Abstract

The pyrolysis of bisphenol A (BPA), an essential process ingredient used in industry and many everyday life products, helps produce low-industrial-demand chemicals such as isopropenyl- and isopropyl-phenols (IPP and iPrP). In this study, tandem micro-reactor gas chromatography/mass spectrometry combined with an H2 generator (H2-TR-GC/MS) was employed for the first time to investigate the selective recovery of phenol via simultaneous hydrogenation/dealkylation of IPP and iPrP. After investigating the iPrP dealkylation performances of several zeolites, we obtained full iPrP conversion with over 99% phenol selectivity using the Y-zeolite at 350 °C. In contrast, when applied to IPP, the zeolite acid centres caused IPP polymerisation and subsequent IPP-polymer cracking, resulting in many byproducts and reduced phenol selectivity. This challenge was overcome by the addition of 0.3 wt% Ni on the Y-zeolite (0.3Ni/Y), which enabled the hydrogenation of IPP into iPrP and subsequent dealkylation into phenol (full IPP conversion with 92% phenol selectivity). Moreover, the catalyst deactivation and product distribution over repetitive catalytic use were successfully monitored using the H2-TR-GC/MS system. We believe that the findings presented herein could allow the recovery of phenol-rich products from polymeric waste with BPA macro skeleton.

Catalytic Pyrolysis of Poly(ethylene terephthalate) in the Presence of Metal Oxides for Aromatic Hydrocarbon Recovery Using Tandem μ-Reactor-GC/MS

“…A tandem μ-reactor was previously used to investigate the simple catalytic pyrolysis of biomass and plastic − in terms of qualitative and semiquantitative product analysis based on the GC/MS area. TR also permits the additional introduction of H 2 for evaluating hydrogenation − and of H 2 + CO for Fischer–Tropsch reaction monitoring . Thermogravimetry–mass spectrometry (TG–MS) and TG–Fourier-transform infrared spectrometry (TG–FTIR) are in-line analytical methods that have previously been used for well-known pyrolysis products of plastics. − However, the following problems were found for PET pyrolysis: (i) TPA with a high boiling point is deposited inside the long transfer tube connecting the TG and MS or FTIR components.…”

Hydrothermal Liquefaction of Polycarbonate (PC) Plastics in Sub-/Supercritical Water and Reaction Pathway Exploration

“…This indicates that IPP may be converted into IPrP and phenol. Kumagai et al studied the recovery of phenol by hydrocracking of IPP and IPrP with several zeolites . The results showed that at the action of acid sites, IPP was converted to IPrP, but during the conversion process of IPrP, only phenol was produced by dealkylation without IPP.…”

“…studied the recovery of phenol by hydrocracking of IPP and IPrP with several zeolites. 46 The results showed that at the action of acid sites, IPP was converted to IPrP, but during the conversion process of IPrP, only phenol was produced by dealkylation without IPP. Although they used zeolite catalysts and hydrogenation in their research, their work can provide us with a reference because sub-/supercritical water plays the role of hydrogen donors and acid−base catalysts.…”

Application of Pyrolysis-Gas Chromatography for the Development of Chemical Recycling Process for Plastics

“…Fig.10(a) GC/MS chromatograms and (b) composition of aromatics and iPrP conversion data obtained from the catalytic conversion of iPrP using zeolites53) …”