Molecular-Level Consequences of Biomass Pretreatment by Dilute Sulfuric Acid at Various Temperatures

详细信息    查看全文

• 作者：Takeshi Kobayashi ; Benjamin Kohn ; Lesley Holmes ; Rebecca Faulkner ; Mark Davis ; Gary E. Maciel
• 刊名：Energy & Fuels
• 出版年：2011
• 出版时间：April 21, 2011
• 年：2011
• 卷：25
• 期：4
• 页码：1790-1797
• 全文大小：873K
• 年卷期：v.25,no.4(April 21, 2011)
• ISSN：1520-5029

文摘

Ex situ room-temperature ¹³C nuclear magnetic resonance (NMR) measurements are reported on powdered poplar wood that has been pretreated with dilute sulfuric acid (concentrations up to 1 wt %) for times ranging up to 20 min and at temperatures of 120, 130, 140, and 150 掳C. There are significant, albeit not dramatic, changes in the measured NMR spectra of the biomass as result of dilute sulfuric acid treatment. Values of T₁ for ¹³C and ¹H, as well as T_CH and T_1蟻H, were measured for lignin peaks and cellulose peaks in the ¹³C NMR spectra, as potential indicators of the degree of atomic-level motion. For lignin components, one finds a trend to larger T_CH values as the treatment time or H₂SO₄ concentration is increased for treatment temperatures of 120 and 130 掳C; however, for treatment temperatures of 140 and 150 掳C, T_CH apparently decreases as the treatment time is increased. This higher temperature T_CH behavior implies that the lignin may actually become more rigid at later stages of treatment at temperatures 鈮?40 掳C, which can be explained by cleavages of ether linkages of lignin and subsequent formation of new linkages, i.e., lignin recondensation. T_1C and T_1H measurements are consistent with this interpretation. The relationships between atomic-level mobility of lignin in biomass and treatment temperature is consistent with published relationships between the sugar yield and treatment temperature. The key role of acid treatment as a pretreatment for enzymatic digestion is evident in NMR measurements, including relaxation measurements, even after the treatment.