Spatially resolved spectral determination of polysaccharides in hydrothermally carbonized biomass

Abstract

Reliable information on the decomposition of polysaccharides is important to evaluate the evolution and properties of hydrothermally carbonized chars. Hyperspectral imaging offers a quick and robust alternative to expensive and time-consuming laboratory methods to determine the polysaccharide contents of biomass and biomass-derived chars. Here, we show that the decomposition of hemicellulose and cellulose were visible in the acquired hyperspectral images even without image calibration. Image regression based on sample holocellulose, glucan and the sum of xylan, galactan, arabinan and mannan provided good calibration models and enabled visualizing the decomposition of polysaccharides based on carbonization temperature. Hyperspectral imaging thus provides a non-destructive alternative to traditional polysaccharide analyses of hydrochars for laboratory and potential future industrial applications.

Hydrothermal Carbonization Kinetics of Lignocellulosic Agro-Wastes: Experimental Data and Modeling

“…Actually, it is worth noticing that the pre-exponential factors followed exactly the same trend as the activation energies: the higher E a,i , the higher k 0,i . This can be explained by considering the mathematical aspects behind Arrhenius's formulation: the interrelations between k 0,i and E a,i can be expressed as in Equation (19) [59]:…”

“…Equation (19) highlights that a change in activation energy leads to a change in pre-exponential factors, and vice-versa. Such a phenomenon can be also related to the so-called compensation effect [60].…”

“…Under these process conditions, water acts similarly to an organic solvent due to the tremendous changes in its polarity and dielectric constant, and as a catalyst for biomass conversion via hydrolysis, dehydration, and decarboxylation reactions [7][8][9][10][11]. The main product of HTC is a carbon-rich solid material referred to as hydrochar, which finds application as high energy bio-fuel [12][13][14][15][16][17][18][19][20][21], as a pre-treated material for anaerobic digestion enhancement [15,22], as a soil amendment [14,23,24], and as an advanced carbonaceous material [25,26]. The high interest in this wet thermochemical technology, due to its high energy efficiency, relatively mild process conditions, and scalability, has also been testified by the study on its application at the industrial level [27,28].…”

In Deep Analysis on the Behavior of Grape Marc Constituents during Hydrothermal Carbonization

“…Hydrothermal carbonization (HTC) is a thermochemical process through which it is possible to directly transform a wet organic substrate into a useful material called hydrochar. This process has been studied by several authors [2][3][4][5][6][7][8][9][10][11] even in recent years. The HTC solid product is expected to have different applications, for example for renewable energy production [12,13], as a soil improver and conditioner [14], as a precursor for the production of activated carbons [15], for the generation of nanostructured materials, and many more [16,17].…”

Hyperspectral near infrared imaging quantifies the heterogeneity of carbon materials

“…The effects of scattering are however complicated due to the presence of absorbing constituents and variation in physical properties such as particle size and shape, surface properties and sample packing 21 , 22 . Increasing carbonization temperature generally leads to a higher carbon content and a darker sample color, which can manifest as increased absorbance on shorter wavelengths 23 . The O-H and C-O strains and the second overtone of C-O strain can normally be detected at 1830 nm 20 .…”