Hydrogen production from aqueous-phase reforming of glycerol, sorbitol, and glycine over Pt/Al2O3 catalyst in a fixed-bed reactor

Abstract

Aqueous-phase reforming (APR) is an interesting technique for generating hydrogen (H₂) from biofeeds. In this work, APR of model compounds of wet biomass for H₂ production was investigated. Glycerol, sorbitol, and glycine were the chosen model compounds. They represent polyols and amino acids in wet biomass such as waste sludge and microalgal biomass. The Pt/Al₂O₃ catalyst was preferred and it was characterized using nitrogen adsorption–desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS) techniques. APR trials were performed in a continuous fixed-bed reactor. The reaction conditions chosen for this work were: temperature (T) 453–498 K, pressure (P) 1.2–2.4 MPa, feed concentration 5–15 wt%, and weight hourly space velocity (WHSV) 0.15–0.6 g reactant/(g catalyst h). The best conditions for H₂ production by the APR process were found to be T = 498 K, P = 2.4 MPa, and feed concentration = 15 wt%. Among the chosen model compounds, glycerol exhibited the highest H₂ selectivity (82.7%) and H₂ yield (21.6%) at 498 K. The analysis of kinetic data suggested first-order reaction kinetics for all the model compounds. The values of activation energy for the reactions with glycerol (55.4 kJ/mol), sorbitol (51.6 kJ/mol), and glycine (45.7 kJ/mol) were determined. Thus, APR is a promising route for effectively producing H₂-bearing gaseous products with high heating value from wet biomass.