Marion Carrier

Impact of the lignocellulosic material on fast pyrolysis yields and product quality

The paper describes the fast pyrolysis conversion of lignocellulosic materials inside a bubbling fluidized bed. The impact of biopolymers distribution in the biomass feed, namely hemicelluloses, cellulose and lignin, on the yields and properties of pyrolytic bio-oils and chars was investigated. Although it is not possible to deconvoluate chemical phenomena from transfer phenomena using bubbling fluidized bed reactors, the key role of hemicelluloses in biomass feedstocks was illustrated by: (i) its influence on the production of pyrolytic water, (ii) its impact on the production of organics, apparently due to its bonding relationship with the lignin and (iii) its ability to inhibit the development of chars porosity, while the cellulose appeared to be the precursor for the microporous character of the biochars. These results are of interest for the selection of suitable feedstocks aimed at producing bio-oil and char as fuels and soil amendment, respectively.

Photocatalytic Degradation of Diuron: Experimental Analyses and Simulation of HO° Radical Attacks by Density Functional Theory Calculations

The photocatalytic oxidation of diuron has been performed in presence of TiO(2) suspensions. To better understand the mechanistic details of the hydroxyl radical attack on diuron, computational methods were carried out. The combination of experimental and computational methods has been employed to establish the main degradation pathways of diuron. After identification of the majority of first byproduct, the experimental study underlined that substitution of chlorines and hydroxylation by hydroxyl radicals are the main diuron degradation pathways, in agreement with MOPAC and DFT simulations carried out in the gas phase. In addition, these calculations revealed that the aromatic ring attack is led by a HO degrees addition and not a hydrogen abstraction and the main first byproduct, monochlorohydroxylated compounds, are obtained by concerted reactions.

Structural and chemical modifications of typical South African biomasses during torrefaction

Torrefaction experiments were carried out for three typical South African biomass samples (softwood chips, hardwood chips and sweet sorghum bagasse) to a weight loss of 30 wt.%. During torrefaction, moisture, non-structural carbohydrates and hemicelluloses were reduced, resulting in a structurally modified torrefaction product. There was a reduction in the average crystalline diameter (La) (XRD), an increase in the aromatic fraction and a reduction in aliphatics (substituted and unsubstituted) (CPMAS (13)C NMR). The decrease in the aliphatic components of the lignocellulosic material under the torrefaction conditions also resulted in a slight ordering of the carbon lattice. The degradation of hemicelluloses and non-structural carbohydrates increased the inclusive surface area of sweet sorghum bagasse, while it did not change significantly for the woody biomasses.

Biomass Conversion to Bioenergy Products

The rendering of bioenergy products such as heat, fuel and electricity requires the conversion of sustainably produced biomass feedstock by means of thermochemical and biological processes. Such processes convert feedstocks into higher energy-value products amenable to industrial and domestic applications. This chapter deals with the nature of the conversion processes, the biomass feedstock requirements for these processes and the resulting quality of bioenergy products. In addition, the present chapter will also consider the application potential of different conversion technologies to both industrial and rural areas in the Southern Hemisphere.

Quantitative insights into the fast pyrolysis of extracted cellulose, hemicelluloses and lignin

Abstract The transformation of lignocellulosic biomass into bio‐based commodity chemicals is technically possible. Among thermochemical processes, fast pyrolysis, a relatively mature technology that has now reached a commercial level, produces a high yield of an organic‐rich liquid stream. Despite recent efforts to elucidate the degradation paths of biomass during pyrolysis, the selectivity and recovery rates of bio‐compounds remain low. In an attempt to clarify the general degradation scheme of biomass fast pyrolysis and provide a quantitative insight, the use of fast pyrolysis microreactors is combined with spectroscopic techniques (i.e., mass spectrometry and NMR spectroscopy) and mixtures of unlabeled and 13C‐enriched materials. The first stage of the work aimed to select the type of reactor to use to ensure control of the pyrolysis regime. A comparison of the chemical fragmentation patterns of “primary” fast pyrolysis volatiles detected by using GC‐MS between two small‐scale microreactors showed the inevitable occurrence of secondary reactions. In the second stage, liquid fractions that are also made of primary fast pyrolysis condensates were analyzed by using quantitative liquid‐state 13C NMR spectroscopy to provide a quantitative distribution of functional groups. The compilation of these results into a map that displays the distribution of functional groups according to the individual and main constituents of biomass (i.e., hemicelluloses, cellulose and lignin) confirmed the origin of individual chemicals within the fast pyrolysis liquids.

Chemical and structural characterization of char development during lignocellulosic biomass pyrolysis

The chemical and structural changes of three lignocellulosic biomass samples during pyrolysis were investigated using both conventional and advanced characterization techniques. The use of ATR-FTIR as a characterization tool is extended by the proposal of a method to determine aromaticity, the calculation of both CH2/CH3 ratio and the degree of aromatic ring condensation ((R/C)u). With increasing temperature, the H/C and O/C ratios, XA and CH2/CH3 ratio decreased, while (R/C)u and aromaticity increased. The micropore network developed with increasing temperature, until the coalescence of pores at 1100°C, which can be linked to increasing carbon densification, extent of aromatization and/or graphitization of the biomass chars. WAXRD-CFA measurements indicated the gradual formation of nearly parallel basic structural units with increasing carbonization temperature. The char development can be considered to occur in two steps: elimination of aliphatic compounds at low temperatures, and hydrogen abstraction and aromatic ring condensation at high temperatures.