Generation of H2, CH4, CO and CO2 shows that reaction mechanisms
(1)–(3) co-exist during heating of PVC milled with CaO and Ni(OH)2.
Reaction mechanism (1) represents primary water–gas shift reaction,
and, for secondary water–gas shift reaction (Eq. (2)) to proceed,
4 moles water is required, however, in the current system only
(x = 0.1–2.0) moles water is provided by Ni(OH)2 (0.5–2.0 moles
Ni(OH)2 used). Also from TG-MS profiles, loss of H2O was observed
before 400 ◦C during heating, indicating that there is insufficient
H2O mole between 400 and 550 ◦C where H2 peaks appear.