Advanced characterization unravels the structure and reactivity of wood-based chars

Abstract

This study aims at understanding the structural changes occurring in the carbonaceous matrix of wood-based chars during their thermal conversion. Although chars are routinely characterized by porosity measurements or scanning electron microscopy, the composition and structure of the carbonaceous matrix is often not investigated. Here, advanced characterization using X-ray synchrotron microtomography, transmission electron microscopy, Raman spectroscopy and X-ray diffraction provided a precise description of the char properties, allowing for an accurate discussion of their catalytic properties. Two chars were produced by slow pyrolysis of wood waste (400 and 700°C) and a third one was fabricated by activation under steam at 850°C of the char obtained at 700°C. The results show that the pyrolysis temperature and the activation performed did not affect the macrostructure of the chars and that the pores were interconnected at the macroscopic scale. However, at 700°C, the micro-and nanostructures were modified: short-range organized graphene fringes were observed. The activated char showed a homogeneous microstructure similar to that of its precursor. Besides, the ratio of graphene-like structures, the local organization of graphene sheets, and the imperfections in graphene-like sheets were clearly improved by the post-treatment. To our knowledge, this is the first time that such an approach, combining various tools, is applied for the study of pyrolysis chars.

Fertilizer and soil conditioner value of broiler manure biochars

“…Contrary to our initial estimate, none of the imaged biochar particles were pure bedding material, but the different components surprisingly seemed evenly mixed. While X-ray microtomography has been used to image biochar derived from plant-based materials (Berhanu et al 2018;Bird et al 2008;Hyväluoma et al 2018b;Jeffery et al 2015;Jones et al 2015;Schnee et al 2016), to our knowledge this is the first study using X-ray microtomography to study the structure of broiler manure biochar. Previously, scanning electron microscopy (SEM) has been used to visually study the structure of broiler manure biochar (Glazunova et al 2018;Liang et al 2016;Lima et al 2015;Qiu and Guo 2010;Song and Guo 2012).…”

“…e.g. Berhanu et al 2018;Hyväluoma et al 2018a). However, further research on this topic is required.…”

Reactivity and deactivation mechanisms of pyrolysis chars from bio-waste during catalytic cracking of tar

“…Chars can represent 12-30 wt% of the initial biomass [2]. These solid residues are carbonaceous materials with complex properties [3] and containing several inorganic species [4], depending on the initial waste.…”

Effect of Weathering on Surface Functional Groups of Charred Norway Spruce Cladding Panels

“…Under the torch, temperatures exceed 1000 • C, and while obtaining a homogeneous surface may be difficult, the char formed is very aromatic. At above 700 • C, onion-like (ordered) and graphite structures may be formed [25][26][27] that may react entirely differently to UV-radiation.…”