Hydrogen production by supercritical water gasification of valine over Ni/activated charcoal catalyst modified with Y, Pt, and Pd

Abstract

Hydrogen production by supercritical water gasification (SCWG) of valine as a model for protein was examined in a fixed-bed reactor at 28 MPa. The effect of reaction temperature (500–710 °C), type of catalyst (AC, Ni–Y/AC, Ni–Pt/AC, and Ni–Pd/AC), and LHSV (24–72 h−1) on the extent of gasification and gas composition was investigated. Total gas yield increased with increasing temperature up to 710 °C while carbon gasification efficiency (CGE) reached the highest value of 98.1% at 600 °C over the Ni–Y/AC catalyst. The three Ni-based catalysts promoted hydrogen formation reactions greater than the AC. In particular the Ni–Pt/AC and Ni–Pd/AC catalysts effectively reformed C2+ hydrocarbons intermediates to H2 and CO2. The Ni–Y/AC catalyst at 650 °C completely destroyed nitrogen-containing organic intermediates such as amines in the liquid effluent. The presence of Pt and Pd significantly suppressed the crystallization of Ni metal supported on AC in supercritical water.