Extraction of Co-Products from Biomass: Example of Thermal Degradation of Silymarin Compounds in Subcritical Water |
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Authors: | Lijun Duan Sunny N Wallace Abigail Engelberth Justin K Lovelady Edgar C Clausen Jerry W King Danielle Julie Carrier |
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Institution: | (1) Ralph E. Martin Department of Chemical Engineering, University of Arkansas, 3202 Bell Engineering Center, Fayetteville, AR 72701, USA;(2) Department of Biological and Agricultural Engineering, University of Arkansas, 203 Engineering Hall, Fayetteville, 72701, USA |
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Abstract: | In an effort to increase revenues from a given feedstock, valuable co-products could be extracted prior to biochemical or
thermochemical conversion with subcritical water. Although subcritical water shows significant promise in replacing organic
solvents as an extraction solvent, compound degradation has been observed at elevated extraction temperatures. First order
thermal degradation kinetics from a model system, silymarin extracted from Silybum marianum, in water at pH 5.1 and 100, 120, 140, and 160 °C were investigated. Water pressure was maintained slightly above its vapor
pressure. Silymarin is a mixture of taxifolin, silichristin, silidianin, silibinin, and isosilibinin. The degradation rate
constants ranged from 0.0104 min−1 at 100 °C for silichristin to a maximum of 0.0840 min−1 at 160 °C for silybin B. Half-lives, calculated from the rate constants, ranged from a low of 6.2 min at 160 °C to a high
of 58.3 min at 100 °C, both for silichristin. The respective activation energies for the compounds ranged from 37.2 kJ/gmole
for silidianin to 45.2 kJ/gmole for silichristin. In extracting the silymarin with pure ethanol at 140 °C, no degradation
was observed. However, when extracting with ethanol/water mixtures at and 140 °C, degradation increased exponentially as the
concentration of water increased.
An erratum to this article can be found at |
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Keywords: | Extraction Kinetics Silymarin Subcritical water Thermal degradation |
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