Reactivity of [formula omitted] and [formula omitted] toward steam reforming of palm fatty acid distilled (PFAD) with co-fed oxygen and hydrogen

Abstract

Steam reforming of three types free fatty acids (i.e. palmitic, oleic and linoleic acids) and palm fatty acid distilled (PFAD) were studied over ceria-based materials prepared by precipitation and cationic surfactant-assisted methods with/without Zr doping with an aim to develop good reforming catalyst for converting PFAD to hydrogen with high reforming reactivity and low carbon deposition. Among all catalysts, high surface area (HSA) Ce–ZrO 2 (with Ce/Zr ratio of 3/1) prepared by cationic surfactant-assisted method provided the highest steam reforming reactivity with greatest resistance toward carbon deposition; due to the high oxygen storage capacity (OSC) of this material. During steam reforming, the redox reactions between absorbed hydrocarbons (forming intermediate surface hydrocarbon species) with lattice oxygen ( O O x ) at Ce–ZrO 2 surface take place. The rapid redox reactions between surface carbon ( C * ) forming via the adsorptions of hydrocarbon with lattice oxygen ( O O x ) prevents the formation of carbon species from decomposition of hydrocarbons. At 1173 K, the main products from the steam reforming of PFAD over this catalyst are H 2 , CO, and CO 2 with some amounts of CH 4 and C 2 H 4 generated; the formations of these high hydrocarbons can be eliminated by increasing temperature up to 1273 K. The addition of either oxygen or hydrogen together with PFAD and steam considerably reduced the degree of carbon deposition. The presence of oxygen also reduced the formations of hydrocarbons, on the other hand, these formations increased when hydrogen was introduced at the feed. The negative effect of hydrogen is due to hydrogenation reaction as well as the reduction of lattice oxygen by hydrogen, which consequently inhibits the reaction of lattice oxygen with surface hydrocarbon species.