Understanding fast pyrolysis of biomass

Abstract

Introduction Experimental Method Results and Discussions Conclusions References Supporting Information for Chapter 2 CHAPTER 3 CELLULOSE-HEMICELLULOSE, CELLULOSE-LIGNIN INTERACTIONS DURING FAST PYROLYSIS

Thermogravimetric Analysis−Fourier Transform Infrared Analysis of Palm Oil Waste Pyrolysis

“…Compared to xylan and cellulose, lignin has an extremely low activation energy (∼33 kJ/mol) and its corresponding pre-exponential factor is also very low. Similar observations were previously reported by Varhegyi et al The much lower activation energy of xylan than cellulose is probably caused by the differences in their structures. − Previous publications indicate that the activation energy ( E ) of cellulose in pyrolysis is generally ∼200 kJ/mol; for hemicellulose, it is relatively low, at ∼100 kJ/mol; and for lignin, it is much lower, only ∼30 kJ/mol. − The activation energy of the biomass in pyrolysis is ∼70−100 kJ/mol . Our results are consistent with those of other researchers.…”

“…The different activation energies between palm oil wastes and the three components (particularly cellulose) may be caused by the catalytic effect of mineral matters that occur in the biomass. ,, Moreover, for the three palm oil wastes, the E values of the second range (300−340 °C), referring to the degradation of cellulose, are always larger than those of the first range (220−300 °C), which refers to the degradation of hemicellulose. This difference is possibly caused by their different structures, as discussed previously. − However, further studies are needed to understand this issue better.…”

“…The difference of inherent structures and compositions among the three components possibly accounts for the different behaviors observed. − The cellulose molecule ([C 6 (H 2 O) 5 ] n ) is a very long polymer of glucose units without any branches, and it is crystalline, strong, and resistant to hydrolysis. In contrast, hemicellulose ([C 5 (H 2 O) 4 ] n ) has a random, amorphous structure with little strength.…”

“…Pyrolysis is considered to be one of the promising thermal approaches in converting biomass to energy. − However, it is a highly complex process that is influenced not only by the properties of biomass feedstock, − such as substrate composition, moisture content, and particle size distribution, but also by the operating conditions. − Fundamentals of biomass pyrolysis have been widely investigated using fluidized-bed reactors, fixed-bed reactors and thermogravimetric analysis (TGA), , and other reactors. ,, The use of TGA has the advantage of a fast and repeatable data collection of pyrolysis rate, which facilitates a deep investigation of the kinetic parameters. Previous investigations of biomass pyrolysis were mostly focused on the yields of solid, liquid, and gas products, as a function of the variable parameters, including heating rate, sample size, final temperature, and volatiles residence time. − However, the real-time gas release in the course of pyrolysis, which is believed to be closely related to the mechanisms of biomass decomposition, is rarely studied. A better understanding of the fundamentals and mechanisms in pyrolysis is essential to achieve high yields of the targeted products.…”

In situ and ex situ catalysis in biomass fast pyrolysis

“…Typical acid catalysts comprise zeolites or other silica aluminas and have been discussed previously. Although, other acid catalysts have been tested, such as a SO 2− 4 /ZrO 2 strong acid [103]. In the deoxygenation of cellulose pyrolysis vapors, the strong acid was found to greatly promote dehydration reactions, particularly levoglucosan dehydration to levoglucosenone.…”