Browsing by Author "Bhattacharya, S"

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    Evolution of functional group of lignocellulosic biomass and its delignified form during thermal conversion using synchrotron-based THz and laboratory-based in-situ DRIFT spectroscopy
    (Elsevier, 2023-05-05) Kundu, C; Biswas, S; Thomas, BS; Appadoo, D; Duan, A; Bhattacharya, S
    In the industry, platform chemicals are traditionally synthesized from non-renewable resources. In order to determine the ideal temperature range and associated emissions for the production of platform chemicals from biomass, which is a renewable resource, mechanistic insights into the thermochemical conversion of biomass are needed. Here, the high-resolution synchrotron-based gas-phase THz (Far-IR) spectra and lab-based in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) spectra of both raw and delignified biomass have been studied to identify real-time evolution of the functional groups and any gas-phase secondary reactions during the thermochemical conversion as a function of temperature; these are linked to weight loss measurements through differential thermogravimetry. The high-resolution synchrotron-based technique and DRIFTS were used to acquire the spectra in two different wavenumber ranges of 50–600 cm−1 and 500–4500 cm−1, respectively. The synchrotron-based spectra were used to identify the major gaseous components between 300 and 500 °C of methane, ethane, acetylene and formaldehyde, and their generation followed the order 300 > 400 > 500 °C. The DRIFTS spectra showed that the covalent hydrogen bonds of both raw and delignified biomass was cleaved below 250 °C, between 250 and 300 °C the decarboxylation reaction took place, whereas between 300 and 400 °C platform chemicals (furan, levoglucosan, levoglucosenone) and aromatic compounds were formed from the dehydration of the cellulosic part of the biomass. No changes in the DRIFTS spectra were observed above 400 °C. These results suggest that 300–400 °C is the ideal temperature range for the thermochemical conversion of biomass to platform chemicals. Pyrolysis-gas chromatography/mass spectrometry (Py-GCMS) results demonstrated that the identification of platform chemicals laid the groundwork for large-scale operation. © 2023 The Author(s). Published by Elsevier Ltd.
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    In situ studies of structural changes in DME synthesis catalyst with synchrotron powder diffraction
    (Elsevier, 2014-09-22) Kabir, KB; Maynard-Casely, HE; Bhattacharya, S
    Structural changes in a bi-functional dimethyl ether synthesis catalyst (CuO-ZnO-Al2O3-MgO + γ-Al2O3, BFC), a methanol synthesis catalyst (CuO-ZnO-Al2O3-MgO, MSC) and a methanol dehydration catalyst (γ-Al2O3, MDC), were studied using X-ray synchrotron powder diffraction. The catalysts were first reduced in 10% H2/He and then treated in a gas containing CO, H2 and CO2. Measurements were taken at temperatures between 50 °C and 500 °C. These measurements were complemented by ex-situ techniques—thermogravimetry (TG) and scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDS). The X-ray diffraction (XRD) results showed that the copper oxide phase, present in methanol synthesis and bi-functional catalysts, reduced to form Cu0 after reduction. No further chemical changes were observed for these catalysts. γ-Al2O3 was resistant to structural and chemical changes. The copper crystallite sizes of the methanol and bi-functional catalysts were found to increase with temperature. The extent of deactivation was higher for CuO-ZnO-Al2O3-MgO + γ-Al2O3 compared to CuO-ZnO-Al2O3-MgO. © 2014, Elsevier B.V.