Thermogravimetric kinetics of crude glycerol

Abstract

The pyrolysis of the crude glycerol from a biodiesel production plant was investigated by thermogravimetry coupled with Fourier transform infrared spectroscopy. The main gaseous products are discussed, and the thermogravimetric kinetics derived. There were four distinct phases in the pyrolysis process of the crude glycerol. The presence of water and methanol in the crude glycerol and responsible for the first decomposition phase, were shown to catalyse glycerol decomposition (second phase). Unlike the pure compound, crude glycerol decomposition below 500 K leaves behind a large mass fraction of pyrolysis residues (ca. 15%), which eventually partially eliminate in two phases upon reaching significantly higher temperatures (700 K and 970 K respectively). An improved iterative Coats-Redfern method was used to evaluate non-isothermal kinetic parameters in each phase. The latter were then utilized to model the decomposition behaviour in non-isothermal conditions. The power law model (first order) predicted accurately the main (second) and third phases in the pyrolysis of the crude glycerol. Differences of 10-30 kJ/mol in activation energies between crude and pure glycerol in their main decomposition phase corroborated the catalytic effect of water and methanol in the crude pyrolysis. The 3-D diffusion model more accurately reproduced the 4 th (last) phase, whereas the short initial decomposition phase was poorly simulated despite correlation coefficients ca. 0.95-0.96. The kinetics of the 3 rd and 4 th decomposition phases, attributed to fatty acid methyl esters cracking and pyrolysis tarry residues, were sensitive to the heating rate.3

Determination of the activation energies of beef tallow and crude glycerin combustion using thermogravimetry

“…Such a behavior is attributed to the variations of heat transfer in function of the change in the heating rate. The removal of water and some low-temperature volatiles, such as methanol, the co-reactant in the transesterification reaction, are considered to be the responsible for the mass loss for this first step [24].…”

“…However, studies that concentrate on the determination of kinetic parameters of thermal behavior of beef tallow are hardly found in the literature. TG experiments have also been used for the determination of kinetic parameter of the pyrolysis for crude glycerol [24] and the second phase was chosen as the main region of the thermal decomposition.…”

Samarium Promoted Ni/Al2O3 Catalysts for Syngas Production from Glycerol Pyrolysis

“…The thermal decomposition of glycerol in near-critical and supercritical water has been finalized by Buhler et al [8]. Apart from that, the pyrolysis of the crude glycerol from biodiesel production plant was achieved by thermogravimetry coupled along with Fourier transform infrared spectroscopy in current work [2,11].…”

Steam Reforming of Glycerol for Hydrogen Production over Ni/SiO2 Catalyst

“…At present, glycerol is used in many applications including personal care, food, oral care, tobacco, polymer, and pharmaceutical applications. Besides converting glycerol into value-added chemicals [2][3][4], hydrogen production through reforming is alternative route [5][6][7][8][9][10][11][12]. Aqueous phase reforming of oxygenated hydrocarbons is extensively studied by the Luo et al and Shabaker et al [9,13], and glycerol steam reforming is studied by Czenik et al [14], Pompeo et al [10], and Adhikari et al [6,15] over nickelbased catalysts and noble metal catalysts on different supports [16][17][18][19].…”