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Lignin is the utmost abundant source of renewable aromatics hence its depolymerization into functionalized aromatics is attractive but challenging as well. A lot of interest is diverting to photocatalysis as a promising sustainable approach to depolymerizing lignin. In the present studies, photocatalytic lignin depolymerization has been investigated under UV-light irradiation using i -propylamine lead chloride perovskites (AS1-AS3) as catalysts. These catalysts were characterized by Powder X-ray Diffraction, Scanning Electron Microscopy, Ultraviolet–Visible, Photoluminescence, and Fourier Transform Infra-Red Spectroscopic techniques to evaluate crystallite size, surface morphology, band gaps, and quantum yields. Depolymerization of lignin was monitored by taking UV spectra and catalytic pathways were studied through various kinetic models. The depolymerization extent was monitored for different catalyst doses (0.05g–0.1 g), lignin concentration (50ppm–200 ppm), and temperatures (25–100 °C). More than 50% depolymerization rate was obtained for each catalyst using 100 ppm lignin concentration. AS3 has shown maximum efficiency in depolymerizing lignin. Pseudo-first order and modified Freundlich were found to be best-fitted kinetic models for experimental data of lignin depolymerization. The activation energy (E a) for the depolymerization reaction was calculated to be 6.8 kJ/mol which is extraordinarily less than conventional depolymerization of lignin exhibiting significant catalytic competencies of synthesized catalysts. One of the products (L-AS3) of lignin depolymerization activity carried out at room temperature was characterized through GCMS analysis which indicated the breakdown of the polymeric structure of lignin into small monomeric functionalities. 2-methoxy-4-methylphenol (9%), benzene (4%), cyclohexene (16%), phenol (6%), catechol (12%) and 2-methoxy-5-propenyl phenol (10%) were detected by GCMS analysis of lignin depolymerization product. • Isopropylamine PbClx perovskites were tested as photocatalysts for lignin depolymerization under UV light. • More than 50% depolymerization rate was obtained for each catalyst. • Activation energy was 6.8 kJ/mol i.e. remarkably less than conventional depolymerization. • GCMS analysis indicated breakdown of lignin structure into monomeric functionalities. • Methoxy phenols (9 and 10%), benzene (4%), cyclohexene (16%), and catechol (12%) were detected. [ABSTRACT FROM AUTHOR]

Dye removal through photocatalytic degradation employing nanomaterials as catalysts is a growing research area. In current studies, photocatalytic alizarin red (AR) dye degradation has been investigated by designing a series of Cr based manganese oxide nanomaterials (MH1–MH5). Synthesized nanomaterials were characterized by powder X-ray diffraction, scanning electron microscopy/energy dispersive x-ray, Brunauer–Emmett–Teller, and photoluminescence techniques and were utilized for photocatalytic AR dye degradation under UV light. AR dye degradation was monitored by UV–visible spectroscopy and percent degradation was studied for the effect of time, catalyst dose, different dye concentrations, and different pH values of dye solution. All the catalysts have shown more than 80% dye degradation exhibiting good catalytic efficiencies for dye removal. The catalytic pathway was analyzed by applying the kinetic model. A pseudo second-order model was found the best fitted kinetic model indicating a chemically-rate controlled mechanism. Values of constant R2 for all the factors studied were close to unity depicting a good correlation between experimental data. [ABSTRACT FROM AUTHOR]

Lignin depolymerization for the purpose of synthesizing aromatic molecules is a growing focus of research to find alternative energy sources. In current studies, the photocatalytic depolymerization of lignin has been investigated by two new iso-propylamine-based lead chloride perovskite nanomaterials (SK9 and SK10), synthesized by the facile hydrothermal method. Characterization was done by Powder X-Ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), UV-Visible (UV-Vis), Photoluminescence (PL), and Fourier-Transform Infrared (FTIR) Spectroscopy and was used for the photocatalytic depolymerization of lignin under UV light. Lignin depolymerization was monitored by taking absorption spectra and catalytic paths studied by applying kinetic models. The %depolymerization was calculated for factors such as catalyst dose variation, initial concentration of lignin, and varying temperatures. Pseudo-second order was the best suited kinetic model, exhibiting a mechanism for lignin depolymerization that was chemically rate controlled. The activation energy (Ea) for the depolymerization reaction was found to be 15 kJ/mol, which is remarkably less than conventional depolymerization of the lignin, i.e., 59.75 kJ/mol, exhibiting significant catalytic efficiencies of synthesized perovskites. Products of lignin depolymerization obtained after photocatalytic activity at room temperature (20 °C) and at 90 °C were characterized by GC-MS analysis, indicating an increase in catalytic lignin depolymerization structural subunits into small monomeric functionalities at higher temperatures. Specifically, 2-methoxy-4-methylphenol (39%), benzene (17%), phenol (10%) and catechol (7%) were detected by GC-MS analysis of lignin depolymerization products. [ABSTRACT FROM AUTHOR]

• Bi doped ZnO have shown excellent stability and efficiency for lignin depolymerization. • The effect of soft templates on the catalytic efficiencies Bi doped ZnO has been explored. • 97% of lignin depolymerization was achieved under sunlight. • Successful conversion of lignin into smaller subunits have been monitored. • The found E a (11 kJ/mol) was remarkably lower than the conventional E a (59.75 kJ/mol). Lignin depolymerization is a growing research area for the synthesis of aromatic molecules. In current studies, photocatalytic lignin depolymerization has been investigated by designing a series of soft template-based Zn 0.95 Bi 0.05 O nano-materials (SK1-SK5). Synthesized nano-materials were characterized by PXRD, SEM/EDX, BET, FTIR and utilized for photocatalytic lignin depolymerization in the presence of direct sunlight. Lignin depolymerization was monitored by UV–Visible Spectroscopy and catalytic pathway analyzed by different kinetic models. Percent depolymerization was studied for the effect of catalyst dose, starting lignin concentration and different temperatures. Pseudo second order was found the best fitted kinetic model indicating chemically rate controlled mechanism. Activation energy (E a) for the reaction was found to be 11 kJ/mol that is remarkably lower than conventional lignin depolymerization i.e. 59.75 kJ/mol depicting better catalytic efficiencies of tested materials. Lignin depolymerization products were characterized by HPLC and FTIR Spectroscopy and their analysis indicated the conversion of lignin into smaller subunits like syringaldehyde, sinapyl alcohol, phthalates, and 4-hydroxy-benzoic acid. Specifically, phenol (21%) and 2-methoxy-4-methylphenol (16%) were detected by GCMS analysis in the products of lignin depolymerization by SK2. [ABSTRACT FROM AUTHOR]