@article {44393, title = {Effect of structural properties of organosolv lignins isolated from different rice husks on their liquefaction using acidic ionic liquids}, journal = {Clean Technologies and Environmental Policy}, volume = {20}, year = {2018}, month = {MAY}, pages = {739-750}, abstract = {Lignin is the only naturally available sustainable resource of aromatic compound on the Earth. Depending on the properties of lignin and the reaction conditions employed for the liquefaction, it is observed that the product distribution alters. Since ionic liquids (ILs) are considered as green and have tuneable properties, in the current work, imidazolium-based acidic ILs were employed to liquefy organosolv lignins derived from different varieties of rice husks. When liquefaction was carried out at 120 A degrees C for 1 h 36\% yield for EtOAc- and DEE-soluble products with high mass balance (97 +/- 3\%) was observed. The detailed characterisations of lignins and organic solvent-soluble products were done by variety of techniques [GC-MS, FT-IR, UV-Vis, 2D (HSQC) NMR], and based on this, the correlation between activity and properties of catalyst and lignin was established. Depolymerisation of organosolv lignin (derived from three rice husks) into aromatic product was done, and experimental correlation studies were performed in both. }, doi = {10.1007/s10098-017-1435-9}, author = {Singh, Sandip K. and Dhepe, Paresh L.} } @article {45406, title = { Efficient method for cyclopentanone synthesis from furfural: understanding the role of solvents and solubility in a bimetallic catalytic system}, journal = {Catalysis Science \& Technology}, volume = {8}, year = {2018}, month = {OCT}, pages = {5259-5269}, type = {Article}, abstract = {The platform chemical, furfural (FAL), is obtained from C5 stream of biomass, and effective conversion into various chemicals including cyclopentanone (CPO) would find many industrial applications. It is desirable to convert FAL to CPO under low H-2 pressure with high selectivity. In the current work, bimetallic catalysts with Pt as the base metal supported on carbon are evaluated in the synthesis of CPO using a biphasic solvent system. By tuning the solvent ratio, with toluene/water (3:4 v/v), 75\% yield of CPO is achieved under 1 MPa H-2 at 180 degrees C. The difference in solubility of the substrate, intermediates and products, along with the optimum ratio of Pt and Co metals plays a crucial role in achieving better yields.}, issn = { 2044-4753}, doi = {10.1039/c8cy01468j}, author = {Dohade, Manisha and Dhepe, Paresh L.} } @article {44344, title = { Experimental evidences for existence of varying moieties and functional groups in assorted crop waste derived organosolv lignins}, journal = {Industrial Crops and Products}, volume = {119}, year = {2018}, month = {SEP}, pages = {144-151}, type = {Article}, abstract = {Isolation of organosolv lignins (ORGLs, water:ethanol, 180 degrees C, 1 h, 93 +/- 5\% mass balance) from various lignocellulosic materials like rice husk (RH), wheat straw (WS), bagasse (BG) \& wood chips (WC) was done and experimental evidences are provided to perceive the differences in the structures of isolated lignins. To achieve this on bulk level, lignins were characterized by XRD, GPC, TGA \& elemental analysis and on molecular level using UV-vis, ATR, 1D/2D HSQC NMR techniques. Besides isolated lignins, crop wastes and pulps were also characterized to divulge details on their properties. It was revealed that lignins have varying concentrations of sinapyl (S), coniferyl (G) and p-coumaryl alcohols (H) and tricin (T) moieties. While, Tricin (T) type lignin moieties are observed only in RH and WS derived lignins, RH derived lignin has higher concentration of side chains than other isolated lignins. Additionally, it is discovered that most lignins have G as main moiety.}, doi = {10.1016/j.indcrop.2018.04.002}, author = {Singh, Sandip K. and Dhepe, Paresh L.} } @article {47109, title = {Efficient catalytic transfer hydrogenation-hydrodeoxygenation of lignin derived monomers: investigating catalyst properties-activity correlation}, journal = {Catalysis Communications}, volume = {149}, year = {2021}, month = {JAN }, pages = {106220}, type = {Article}, abstract = {

Reduction of O/C ratio of lignin derived monomers via hydrodeoxygenation (HDO) pathway is conventionally furnished using molecular hydrogen under severe conditions. Nonetheless, due to a prerequisite to accomplish HDO through commercially attractive methodology we report, HDO reactions of various phenolic compounds via catalytic transfer hydrogenation (CTH) pathway using very low loading of Ru (0.5 wt\%) on neutral and acidic Al2O3 under nitrogen atmosphere. With guaiacol as a substrate, 74\% cyclohexanol yield at 225 degrees C in the presence of IPA is realized. Bi-functionality of metal state, acidity of support and nature of alcohol are perceived to be responsible for the variation in activity.

}, keywords = {Catalytic transfer hydrogenation (CTH), Cyclohexanol, Hydrodeoxygenation, lignin, Supported metal catalysts}, issn = {1566-7367}, doi = {10.1016/j.catcom.2020.106220}, author = {Singh, Dheerendra and Dhepe, Paresh L.} } @article {47439, title = {Elucidating the effect of solid base on the hydrogenation of C5 and C6 sugars over Pt{\textendash}Sn bimetallic catalyst at room temperature}, journal = {Carbohydrate Research}, volume = {505}, year = {2021}, month = {JUL}, pages = {108341}, type = {Article}, abstract = {

Conversion of sugars into\ sugar alcohols\ at room temperature with exceedingly high yields are achieved over Pt{\textendash}Sn/γ-Al2O3\ catalyst in the presence of calcined\ hydrotalcite. pH of the reaction mixture significantly affects the conversion and selectivity for sugar alcohols. Selection of a suitable base is the key to achieve optimum yields. Various solid bases in combination with Pt{\textendash}Sn/γ-Al2O3\ catalysts were evaluated for hydrogenation of sugars. Amongst all combinations, the mixture (1:1\ wt/wt) of Pt{\textendash}Sn/γ-Al2O3\ and calcined hydrotalcite showed the best results. Hydrotalcite helps to make the pH of reaction mixture alkaline at which sugar molecules undergo ring opening. The sugar molecule in open chain form has\ carbonyl group\ which can be polarized by Sn in Pt{\textendash}Sn/γ-Al2O3\ and Pt facilitates the hydrogenation. In the current work, effect of both; solid base and Sn as a promoter has been studied to improve the yields of sugar alcohols from various C5 and C6 sugars at very mild reaction conditions.

}, keywords = {Bimetallic catalyst, Hydrogenation, Hydrotalcites, Sugar, Sugar alcohols}, issn = {0008-6215}, doi = {10.1016/j.carres.2021.108341}, author = {Tathod, Anup P. and Dhepe, Paresh L.} } @article {49787, title = {Experimental investigation and lumped kinetic modeling studies for upcycling of polyolefins}, journal = {Journal of the Indian Chemical Society}, volume = {102}, year = {2025}, month = {NOV}, pages = {102127}, type = {Article}, abstract = {

The present work discusses on comparative kinetic analysis of the pyrolysis of polypropylene (PP), high-density polyethylene (HDPE), and low-density polyethylene (LDPE) using sophisticated lumped models. Unlike many previous studies that focused on single-polymer kinetic models or employed simplified reaction schemes, this study develops an enhanced multistep reaction network that explicitly considers both primary decomposition and secondary cracking pathways, thereby improving the accuracy of product distribution predictions. By integrating this detailed reaction framework with a robust nonlinear regression approach using LSQNONLIN and ODE45 solvers in MATLAB, the study achieved greater accuracy in estimating kinetic parameters than traditional curve-fitting methods. The findings reveal that HDPE exhibits the highest activation energy (222.97 kJ mol(-1)), indicating it is more thermally stable than LDPE (193.44 kJ mol(-1)) and PP (62.16 kJ mol(-1)). One of the highlights of the present work is that lower pyrolysis temperature (400 degrees C) is found to be optimum for liquid yield by reducing secondary cracking, which aligns with the sustainable fuel production principles. The study also emphasizes on the limitations of previous lumped models that overlooked wax decomposition pathways, which are crucial for optimizing the hydrocarbon distribution. Future research should investigate catalytic interventions and reactor design modifications to enhance the product selectivity and scalability. This study offers a more comprehensive kinetic framework for advancing the valorization of plastic waste through pyrolysis, aiding the development of efficient waste-to-fuel conversion strategies.

}, keywords = {Lumped kinetic modeling, Plastic pyrolysis, Rate constants, Reaction pathways, Secondary cracking reactions, Temperature-dependent product distributions}, issn = {0019-4522}, doi = {10.1016/j.jics.2025.102127}, author = {Kavade, Omkar G. and Dhepe, Paresh L. and Devi, Nandini R. and Vasireddy, Satyam Naidu} }