Kinetic, thermodynamic, FT-IR, and primary constitution analysis of Sargassum spp from Mexico: Potential for hydrogen generation

Abstract

Pyrolyzed sargassum can be processed to produce important chemical products and hydrogen gas (H2) from its residual fractions. This article reports the results of a study of the kinetics of the thermogravimetric process (TGA) of sargassum using pyrolysis. Pyrolysis was performed in a temperature interval of 25–900 °C in N2 atmosphere at several heating velocities: 10, 15, 20, 25, 30, 35, and 40 °C/min. Considering a conversion range of 10–90%, the kinetics of this non-isothermal process were evaluated using six models: Friedman, FWO, KAS, Starink, Popescu, and Kissinger. Following this order, the average activation energies for the six methods were 213.92, 203.35, 203.55, 203.81, 206.25, and 178.63 kJ/mol. The sargassum's thermodynamic behavior was determined by four analyses: A, ΔH, ΔG, and ΔS. Observations of the thermal behavior revealed a pyrolytic process that occurred through a multi-stage reaction. Using an algorithm obtained with SciLab software, deconvolution of DTG was performed to compare the results of the proximal and compositional analyses of the sargassum. Results of the kinetic and thermodynamic analyses, the higher heating value (HHV) close to 17 MJ/kg, low ash content of 12.77%, and high volatile matter content, 82.93%, constitute excellent conditions for generating a pyrolytic design based on sargassum as a raw material for generating green hydrogen as a form of bioenergy. According to the results, it is feasible to expect the production of hydrogen from the pyrolysis of sargassum.