Precise Depolymerization of Poly(3-hydoxybutyrate) by Pyrolysis

Direct Production of Propene from the Thermolysis of Poly(β-hydroxybutyrate) (PHB). An Experimental and DFT Investigation

“…The thermal depolymerization of PHB has been studied over a range of temperatures (170–250 °C) and heating rates (1–50 °C min –1 ), which has led to a wide range of estimates of the activation energy E a (111–550 kJ mol –1 ) . The work by Nishida et al represents a comprehensive review regarding the pyrolysis of PHB and subcategorizes the large range of activation energies into three groups. The first of these has a range of 111–140 kJ mol –1 , calculated from the weight loss of PHB under multiple constant heating rate methodologies. ,,, The second group is characterized by activation energies ranging between 178 and 247 kJ mol –1 , as determined by isothermal degradation analyses based on changes in the molecular weight. ,,,, The last group has the highest ranging activation energies, 235–550 kJ mol –1 , which were calculated from weight loss data obtained from single constant heating routines. ,,,, The ensuing discussion details both the nonisothermal experimental and isothermal computational efforts of the present work as a first step in understanding the mechanistic aspect of PHB depolymerization and the identification of possible experimental strategies to improve conversion of PHB to crotonic acid.…”

“…The thermal depolymerization of PHB has been studied over a range of temperatures (170–250 °C) and heating rates (1–50 °C min –1 ), which has led to a wide range of estimates of the activation energy E a (111–550 kJ mol –1 ) . The work by Nishida et al represents a comprehensive review regarding the pyrolysis of PHB and subcategorizes the large range of activation energies into three groups.…”

“…The thermal depolymerization of PHB has been studied over a range of temperatures (170−250 °C) and heating rates (1−50 °C min −1 ), which has led to a wide range of estimates of the activation energy E a (111−550 kJ mol −1 ). 41 The work by Nishida et al 41 multiple constant heating rate methodologies. 9,32,35,39 The second group is characterized by activation energies ranging between 178 and 247 kJ mol −1 , as determined by isothermal degradation analyses based on changes in the molecular weight.…”

“…The thermal conversion of PHB to crotonic acid has been studied ,,− using various analytical procedures, including thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), nuclear magnetic resonance spectroscopy (NMR), among others. A comprehensive summary of this work identifying the various techniques is provided by Nishida . These studies indicate that PHB thermally degrades primarily through a statistical intramolecular β-elimination process that results in the production of an olefin and a carboxylic acid.…”

Παρασκευή Και Μελέτη Ιδιοτήτων Νέων Νανομιγμάτων Και Νανοσύνθετων Πολυμερικών Υλικών Με Βάση Βιοδιασπώμενους Πολυεστέρες Των Υδροξυκαρβοξυλικών Οξέων Για Βιοϊατρικές Εφαρμογές Και Πιθανή Αντικατάσταση Συμβατικών Πολυμερών

“…Πιθανότερα προϊόντα της πυρόλυσης του καθαρού PHB και των νανοσύνθετων του με τροποποιητή C 16 MMT, σε περιεκτικότητα 5% κβ και βαθμό τροποποίησης ισοδύναμο με 50%, 150% και 250% CEC του ορυκτού Τα υδρογόνα του μεθυλενίου ενεργοποιούνται από τη γειτονική καρβοξυλική ομάδα, αυξάνοντας την οξύτητα τους με συνέπεια να δημιουργείται κροτονικό οξύ(2-ολεφίνη). Επίσης είναι γνωστό από τη βιβλιογραφία ότι η παρουσία των κατιόντων μαγνησίου ευνοεί στερεοχημικά το σχηματισμό του κροτονικού οξέος[215]. οκτάεδρων και τετράεδρων στο ορυκτό.…”