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- Sultana, Nazmun, et al.
(författare)
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Kinetics of Periodate-Mediated Oxidation of Cellulose
- 2024
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Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 16:3
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Tidskriftsartikel (refereegranskat)abstract
- The oxidation of cellulose to dialdehyde cellulose (DAC) is a process that has received increased interest during recent years. Herein, kinetic modeling of the reaction with sodium periodate as an oxidizing agent was performed to quantify rate-limiting steps and overall kinetics of the cellulose oxidation reaction. Considering a pseudo-first-order reaction, a general rate expression was derived to elucidate the impact of pH, periodate concentration, and temperature on the oxidation of cellulose and concurrent formation of cellulose degradation products. Experimental concentration profiles were utilized to determine the rate constants for the formation of DAC (k1), degradation constant of cellulose (k2), and degradation of DAC (k3), confirming that the oxidation follows a pseudo-first-order reaction. Notably, the increase in temperature has a more pronounced effect on k1 compared to the influence of IO4− concentration. In contrast, k2 and k3 display minimal changes in response to IO4− concentration but increase significantly with increasing temperature. The kinetic model developed may help with understanding the rate-limiting steps and overall kinetics of the cellulose oxidation reaction, providing valuable information for optimizing the process toward a faster reaction with higher yield of the target product.
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| 2. |
- Sultana, Nazmun, et al.
(författare)
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Synthesis and kinetic analysis of green AA-type monomers using linoleic acid through bromide promoted transition metal-catalyzed oxidation with air
- 2023
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Ingår i: Chemical engineering research & design. - : Elsevier BV. - 0263-8762 .- 1744-3563. ; 190, s. 536-549
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Tidskriftsartikel (refereegranskat)abstract
- The present study explores the renewable route to synthesize AA-type monomers for condensation polymerization, namely adipic and azelaic acid, from linoleic acid (LA) using a bromide-promoted transition metal catalyst. For this, liquid-phase catalytic oxidation of LA is carried out using a catalyst system involving the acetates of Cobalt(II) and Manganese(II) and hydrogen bromide in an acetic acid green solvent at temperature: 393-423 K and a pressure of 5.8-8.8 bar in the air. The oxidation products are confirmed by a gas chromatography-mass spectrometer and carbon dioxide analyzer. At the early stage of LA oxidation (i.e., < 5.0 h), the identified major products are malonic acid, azelaic acid, and adipic acid, whereas malonic acid decomposes to carbon dioxide after increasing oxidation time. The influence of process variables, i.e., (i) the loading of LA, bromide, Cobalt(II), and Manganese(II), (ii) temperature, and (iii) pressure on LA conversion and yield of adipic acid and azelaic acid have also been carried out, and the loading of catalyst, pressure, and temperature plays a vital role on the LA conversion and product yields. The temperature-dependent kinetic parameters are also determined, and the rate-controlling step for LA oxidation is analyzed and further extended by evaluating the Hatta number and enhancement factor. The lower values of the Hatta numbers and enhancement fac-tors suggest that the oxidation using air is controlled by the diffusion of oxygen and re-action in the film, and adequate gas-liquid mixing will improve the rate of LA oxidation.
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