The effectiveness of ball milling (BM) and wet disk milling (WDM) on treating sugarcane bagasse and straw were compared. Pretreated materials were characterized by wide angle X-ray diffraction analysis, particle-size distribution and scanning electron microscopy and the effectiveness of pretreatments was evaluated by enzymatic hydrolysis and fermentation. Glucose and xylose hydrolysis yields at optimum conditions for BM-treated bagasse and straw were 78.7% and 72.1% and 77.6% and 56.8%, respectively. Maximum glucose and xylose yields for bagasse and straw using WDM were 49.3% and 36.7% and 68.0% and 44.9%, respectively. BM improved the enzymatic hydrolysis by decreasing the crystallinity, while the defibrillation effect observed for WDM samples seems to have favored enzymatic conversion. Bagasse and straw BM hydrolysates were fermented by Saccharomyces cerevisiae strains. Ethanol yields from total fermentable sugars using a C6-fermenting strain reached 89.8% and 91.8% for bagasse and straw hydrolysates, respectively, and 82% and 78% when using a C6/C5 fermenting strain.
Background: Lignocellulosic biomass such as wood is an attractive material for fuel ethanol production. Pretreatment technologies that increase the digestibility of cellulose and hemicellulose in the lignocellulosic biomass have a major influence on the cost of the subsequent enzymatic hydrolysis and ethanol fermentation processes. Pretreatments without chemicals such as acids, bases or organic solvents are less effective for an enzymatic hydrolysis process than those with chemicals, but they have a less negative effect on the environment.
SYNOPSISThermal properties by DSC, stiffness, melt viscosity, tensile properties, and dynamic mechanical properties were measured for the Na+, K', Mg2+, Zn2+, Cu2+, Mn2+, and Co2+ salts of poly (ethylene-co-methacrylic acid) (EMAA) . The changes in the structure and properties with increasing neutralization are larger in the alkaline and alkaline earth metal salts than in the transition metal salts. The stiffness shows a maximum at 33% neutralization in both the alkaline and alkaline earth metal salts, while no maxima are found up to 60% neutralization in the transition metal salts. The microphase separation of salt group aggregates is observed in both the alkaline and alkaline earth metal salts, but is not seen in the transition metal salts. These differences were attributed to both the stronger ionic interactions and the larger number of carboxyl groups associated with the alkaline and alkaline earth metal salts in the ordered structure of ionic salt groups (ionic crystallites). The mechanical properties measured at low strain, such as stiffness and yield stress, strongly depend on the degree of the crystalline order of the ionic crystallites. The high-strain properties, such as tensile strength and elongation at break, depend on the strength of the ionic interactions and the valence of the cation.
The microphase structure of noncrystalline poly(ethylene-co-13.3 mol % methacrylic acid)
(E-0.133MAA) ionomers was investigated by using infrared (IR) spectroscopic, X-ray scattering, differential
scanning calorimetric (DSC), and dielectric measurements. The noncrystallinity was confirmed by small-angle X-ray scattering (SAXS) and DSC studies, which has enabled a quantitative analysis of the SAXS
ionic peak associated with ionic aggregates without being perturbed by the polyethylene lamellae peak.
In 60% neutralized Na ionomer, it was revealed that almost 100% of MAA side groups including
unneutralized COOH are incorporated into the ionic aggregates with an average ionic core radius (R
1) of
∼6 Å. The dielectric relaxation studies showed that the ionic aggregates form a microphase-separated
ionic cluster. Analysis of dielectric strengths indicated the most (∼90%) of the COONa groups are present
in the ionic cluster. On the other hand, in the 60% neutralized Zn ionomer, both SAXS and dielectric
studies indicated that the ionic aggregates with R
1 ∼ 4 Å are almost isolated and dispersed in the matrix;
the formation of ionic cluster was not recognized. Similarly to partly crystalline E-MAA ionomers, all
noncrystalline E-0.133MAA ionomers exhibited an endothermic peak at 320−330 K (labeled T
i) on the
first heating, depending on the aging time at room temperature. Several factors that would be critical
for the DSC T
i peak were discussed. It was concluded that the DSC T
i peak is certainly associated with
changes of the state of ionic aggregate region.
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