Kinetics of producing vanillin and 4-hydroxy benzaldehyde from the hydrolysis residue of rice straw by photocatalysis
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Kinetics of producing vanillin and 4‑hydroxy benzaldehyde from the hydrolysis residue of rice straw by photocatalysis Kaleem Ahmad1 · Himadri Roy Ghatak1 · S. M. Ahuja1 Received: 22 March 2020 / Accepted: 16 August 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract Alkali soluble lignin present in rice straw hydrolysis residue (RSHR) is subjected to photocatalytic treatment to study its degradation rates and production of different value-added oxygenated organic compounds. T iO2 and ZnO are used as photocatalysts. ZnO could degrade lignin faster than T iO2 in pseudo-first order photocatalytic degradation. The maximum observed photocatalytic lignin degradation is 83.4% using 2 g/L ZnO dose with pseudo-first order rate constant 0.1386 h−1. Vanillin and 4-hydroxy benzaldehyde are the two important value-added products formed during photocatalysis. Both these compounds, themselves, are susceptible to photocatalytic degradation. Vanillin degradation followed pseudo-first order kinetics and the highest rate constant of 0.1415 h−1 is achieved using 2 g/L ZnO as photocatalyst. While the degradation kinetics of 4-hydroxy benzaldehyde is pseudo-first order with TiO2 and ZnO as a photocatalyst. Higher catalyst doses increased the reaction rate constant. With multiple reactions in operation, the concentration of both vanillin and 4-hydroxy benzaldehyde in the reaction mixture first increased, attained their maxima, and thereafter decreased. With 1 g/L TiO2 as a photocatalyst, the maximum attained vanillin concentration is 22.4 mg/L after 7 h photocatalysis. Maximum attained vanillin concentration, after 8 h photocatalysis, is significantly higher at 51.2 mg/L when 2 g/L ZnO is used as a catalyst. 4-Hydroxy benzaldehyde is produced in lesser amounts. Its maximum observed concentration in the reaction mixture is 20.4 mg/L, obtained with 1.5 g/L TiO2 after 10 h photocatalysis. Keywords Rice straw hydrolysis residue · Photocatalysis · Lignin · Vanillin · 4-Hydroxy benzaldehyde · Kinetics
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s1114 4-020-01840-6) contains supplementary material, which is available to authorized users. * Himadri Roy Ghatak [email protected] 1
Department of Chemical Engineering, Sant Longowal Institute of Engineering and Technology, Longowal, Punjab 148106, India
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Reaction Kinetics, Mechanisms and Catalysis
Introduction Sustainable development calls for proper management and optimum utilization of agricultural wastes. The current practice of large-scale stubble burning goes against this notion. It is seriously detrimental to the environment and also prevents the underutilization of the precious renewable resource. One of the options to manage this waste could be the production of second generation bioethanol wherein the carbohydrate fraction of lignocelluloses is hydrolyzed and subsequently fermented to ethanol. Typically, about half the starting material, most of it being lignin, ends up as solid resid
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