Dilute Acid Hydrolysis of Softwoods(Scientific Note)

Nguyen, Quang; Tucker, Melvin P.; Keller, Fred A.; Beaty, Delicia A.; Connors, Kevin M.; Eddy, Fannie P.

doi:10.1385/abab:77:1-3:133

Cited by 89 publications

(18 citation statements)

References 4 publications

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“…Seven 15-kg batches of corn stover feedstock were impregnated with dilute sulfuric acid (2.0 wt%) for 3 h using a recirculating bath, and then combined and mixed by a modified method of coning and quartering [36,37]. The mixed impregnated feedstock was dewatered using a horizontal tapered screw-press to 60% total solids prior to pretreatment, and then mixed again by coning and quartering.…”

Section: Methodsmentioning

confidence: 99%

Effect of mechanical disruption on the effectiveness of three reactors used for dilute acid pretreatment of corn stover Part 1: chemical and physical substrate analysis

Wang

Chen

Donohoe

et al. 2014

Biotechnol Biofuels

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BackgroundThere is considerable interest in the conversion of lignocellulosic biomass to liquid fuels to provide substitutes for fossil fuels. Pretreatments, conducted to reduce biomass recalcitrance, usually remove at least some of the hemicellulose and/or lignin in cell walls. The hypothesis that led to this research was that reactor type could have a profound effect on the properties of pretreated materials and impact subsequent cellulose hydrolysis.ResultsCorn stover was dilute-acid pretreated using commercially relevant reactor types (ZipperClave® (ZC), Steam Gun (SG) and Horizontal Screw (HS)) under the same nominal conditions. Samples produced in the SG and HS achieved much higher cellulose digestibilities (88% and 95%, respectively), compared to the ZC sample (68%). Characterization, by chemical, physical, spectroscopic and electron microscopy methods, was used to gain an understanding of the effects causing the digestibility differences. Chemical differences were small; however, particle size differences appeared significant. Sum-frequency generation vibrational spectra indicated larger inter-fibrillar spacing or randomization of cellulose microfibrils in the HS sample. Simons’ staining indicated increased cellulose accessibility for the SG and HS samples. Electron microscopy showed that the SG and HS samples were more porous and fibrillated because of mechanical grinding and explosive depressurization occurring with these two reactors. These structural changes most likely permitted increased cellulose accessibility to enzymes, enhancing saccharification.ConclusionsDilute-acid pretreatment of corn stover using three different reactors under the same nominal conditions gave samples with very different digestibilities, although chemical differences in the pretreated substrates were small. The results of the physical and chemical analyses of the samples indicate that the explosive depressurization and mechanical grinding with these reactors increased enzyme accessibility. Pretreatment reactors using physical force to disrupt cell walls increase the effectiveness of the pretreatment process.

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Section: Methodsmentioning

confidence: 99%

Effect of mechanical disruption on the effectiveness of three reactors used for dilute acid pretreatment of corn stover Part 1: chemical and physical substrate analysis

Wang

Chen

Donohoe

et al. 2014

Biotechnol Biofuels

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“…conducted two-stage DAH at 200°C for 5 min with 0.4% H 2 SO 4 ; 215°C for 3 min at 0.4% H 2 SO 4 ; 190°C for 3 min at 0.7% H 2 SO 4 ; and 215°C for 3 min at 0.4% H 2 SO 4 [13]. The reported glucose yields were 16.7 and 16.0 g per 100 g raw material, which was only slightly lower than the maximum 17 g per 100 g raw material we found in this study.…”

Section: Resultsmentioning

confidence: 99%

“…Pretreatment of softwood has previously been investigated using methods such as impregnation with acid catalysts, (for example, SO 2 and H 2 SO 4 ) before steam pretreatment, and also DAH [11,12]. A two-step DAH method using H 2 SO 4 and a two-step pretreatment method of an acid-impregnated lignocellulosic substrate followed by EH have been thoroughly explored [13-16]. The advantage of the two-step process was an increase in the hemicellulose yield, although the glucose yield remained the same [17].…”

Section: Introductionmentioning

confidence: 99%

Impact of dual temperature profile in dilute acid hydrolysis of spruce for ethanol production

Bösch

Wallberg

Joelsson

et al. 2010

Biotechnol Biofuels

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BackgroundThe two-step dilute acid hydrolysis (DAH) of softwood is costly in energy demands and capital costs. However, it has the advantage that hydrolysis and subsequent removal of hemicellulose-derived sugars can be carried out under conditions of low severity, resulting in a reduction in the level of sugar degradation products during the more severe subsequent steps of cellulose hydrolysis. In this paper, we discuss a single-step DAH method that incorporates a temperature profile at two levels. This profile should simulate the two-step process while removing its major disadvantage, that is, the washing step between the runs, which leads to increased energy demand.ResultsThe experiments were conducted in a reactor with a controlled temperature profile. The total dry matter content of the hydrolysate was up to 21.1% w/w, corresponding to a content of 15.5% w/w of water insoluble solids. The highest measured glucose yield, (18.3 g glucose per 100 g dry raw material), was obtained after DAH cycles of 3 min at 209°C and 6 min at 211°C with 1% H2SO4, which resulted in a total of 26.3 g solubilized C6 sugars per 100 g dry raw material. To estimate the remaining sugar potential, enzymatic hydrolysis (EH) of the solid fraction was also performed. EH of the solid residue increased the total level of solubilized C6 sugars to a maximum of 35.5 g per 100 g dry raw material when DAH was performed as described above (3 min at 210°C and 2 min at 211°C with 1% H2SO4).ConclusionThe dual-temperature DAH method did not yield decisively better results than the single-temperature, one-step DAH. When we compared the results with those of earlier studies, the hydrolysis performance was better than with the one-step DAH but not as well as that of the two-step, single-temperature DAH. Additional enzymatic hydrolysis resulted in lower levels of solubilized sugars compared with other studies on one-step DAH and two-step DAH followed by enzymatic hydrolysis. A two-step steam pretreatment with EH gave rise to a considerably higher sugar yield in this study.

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“…Despite the low acid consumption in dilute-acid processes, the high hydrolysis temperature causes corrosion and saccharide degradation (Jones and Semrau, 1984 ). Saccharide degradation can be reduced by applying a two-stage process in which hemicellulose is hydrolyzed in a first step (150 -190 ° C) and cellulose subsequently is hydrolyzed in a second step at more severe conditions (190 -230 ° C) (Nguyen et al, 1999 ;Wayman et al, 1984 ). The two-stage process may also be considered a thermo-chemical pretreatment (see below), followed by an acid hydrolysis of the cellulose fraction ( Fig …”

Section: Acid Hydrolysis Of Lignocellulosementioning

confidence: 99%