Kinetics of cellulose pyrolysis after a pressurized heat treatment

Abstract

A hot pressure treatment (HPT) converts celluloses into an advantageous feedstock for activated carbon preparation. Other ways of utilization may also emerge in the future. In the present paper the pyrolysis kinetics of three HPT cellulose samples were studied by thermogravimetric analysis (TGA) at linear and stepwise temperature programs. A distributed activation energy model was used assuming two partial reactions. Nine experiments on three samples were evaluated simultaneously by the method of least squares. 20 unknown parameters were determined in this way. Good fits were obtained at the linear and stepwise temperature programs alike. The evaluations were also carried out by non-constant preexponential factors that depended on the activation energy. The considerations and evaluation methods of the paper are hoped to help the investigations of other biomass materials, too. The results showed that part of the cellulose remained unconverted and another part only partially converted at the mildest pretreatment conditions of this study. The cellulose was wholly transformed in the pretreatment when either the pressure or the temperature was increased.

Influence of Cellulose Characteristics on Pyrolysis Suitability

“…As it can be observed in Table 4, the Ea for the studied celluloses ranged from 180.07 kJ mol −1 to 285.30 kJ mol −1 and its pre-exponential factor natural logarithms ranged from 21.86 log (1/s) to 13.04 log (1/s). These values are within the range of values found by other authors [17][18][19][20][21][22]. On the contrary, Jin et al [55] found values of 381 kJ mol −1 for cellulose activation energy under isothermal heating conditions.…”

“…Although fitting to a first-order reaction has been shown to provide higher values than true A and Ea values [16], it can be used in a comparative study among celluloses with different characteristics. In this sense, Antal et al [17] found an Ea value of 228 kJ mol −1 and Wu et al [18] reported values between 214.5 and 275.1 kJ mol −1 both for commercial ash-free celluloses. Amutio et al [19] described an Ea value of 206 kJ mol −1 for pine wood sawdust cellulose, whereas Cai et al [20] found values between 204.2 and 212.5 kJ mol −1 for several celluloses extracted from different raw materials, such as corn stover, cotton stalk, palm oil husk, pine wood, red oak, sugarcane bagasse, switchgrass, and wheat straw.…”

Biomass pyrolysis: A review of the process development and challenges from initial researches up to the commercialisation stage

“…The employed pretreatment resulted in the decomposition of the feedstock material in a wide temperature range. They also used distributed activation energy model with Gaussian distribution for the pyrolysis kinetics [55] . Lin et al used both TGA and pyrolysis reactor experiments to study the cellulose pyrolysis.…”

Torrefaction of Sorghum Straw Pellets in a Stationary Reactor with a Feeding Screw

“…However, the high hydrophilicity, low energy density, and low calorific value of agricultural residues make it not yet comparable to fossil fuels . A variety of methods, including chemical, physical, and biological, have been investigated to improve the availability and flammability of crop residues. Torrefaction, heating biomass at 200–300 °C in an inert atmosphere, is a commonly used thermochemical method to improve the grindability, hydrophobicity, and calorific value of biomass. , Yu et al found that the grindability of torrefied biomass increased with the increasing torrefaction degree.…”