This paper studies the optimization of a batch cultivation process for the production of succinic acidfrom crude glycerol by using Anaerobiospirillum succinicproducens ATCC 29305 encapsulated with sodium cellulose sulfate/poly-dimethyl-diallyl-ammonium chloride. The batch conditions for the flask were optimized by response surface methodology based on a Box-Behnken design. This design was employed to assess the individual and interactive effects of the four main parameters (pH, crude glycerol concentration, shaking speed and temperature) on succinic acid production under anaerobic conditions. Results from the response surface analysis showed that the data were adequately fitted by a second-order polynomial model via a quadratic regression relationship. The final mathematical model after eliminating the insignificant terms and refining the succinic acid production was a quadratic model. For the succinic acid yield it was observed that the interactive effect between crude glycerol and shaking speed was statistically significant. Optimization conditions for maximizing the production were as follows: pH, 6; crude glycerol, 40 g/L; shaking speed, 150 rpm; temperature, 39 o C. Under these conditions, the maximal numerical solution of the model gave a predicted succinic acid level of 34.66 g/L. For the flask, the experimental production of succinic acid was 34.80 g/L with a conversion yield (87%), and a ratio of succinic acid to acetic acid (34:1). Similar experimental results were obtained for the stirred tank bioreactor. Both sets of experimental results were in good agreement with the model predictions.
Excessive dependence on fossil resources to supply the increased energy demands has led to unsustainable growth. Hence, there is a necessity to shift our reliance from non-renewable to renewable resources. In this scenario, lignocellulosic biorefinery gains its importance because lignocellulosic biomass can be converted into various value-added products. However, biomass pretreatment is necessary due to the recalcitrant nature of the biomass. Various pretreatment techniques are employed to convert biomass into a more amenable structure to be utilized in the further steps of biorefinery. Hence, this review concentrates on different chemical pretreatment techniques used currently on biomass along with their modes of action on the biomass. This review will provide a detailed concept of various chemical pretreatments and the recent developments in pretreatment techniques. Despite this, the limitations of the current pretreatment strategies and the difficulties in their industrial applications are also discussed, which could provide innovative ideas to overcome these issues.
High purity molybdenum metal powder is produced commercially from hexavalent molybdenum precursors, viz.: ammonium dimolybdate (ADM) or molybdenum trioxide. One conventional process incorporates first-stage and second-stage flowsheet components, with hydrogen gas serving as reductant. This two-stage strategy is employed in order to minimize the formation of volatile molybdenum species that would otherwise be generated at the high temperature required to obtain molybdenum (Mo) in a single stage conversion of the molybdenum precursor. Although molybdenum powder has been produced commercially for over a century, a comprehensive understanding of the kinetic mechanisms and powder characteristics, e.g. oxygen content and particle morphology, is far from being definitive. In fact, it might be argued that the “art” and engineering, in a commercial context, has advanced ahead of the fine-detail science-derived metallurgical process-engineering. Theoretical contributions presented in this paper are focused primarily on the fundamentals of the conversion process associated with second-stage reduction process – MoO2 to Mo and the factors that contribute to the oxygen content of the molybdenum powder product (1000 to 100 ppm(w) O, range). Thus, equilibrium-configuration details concerning both solid and gas phases are addressed, including the volatile hexavalent molybdenum vapor complexes as well as solubility of oxygen in molybdenum. In regard to the role of a chemical vapor-transport mechanism on powder morphology in second-stage conversion of MoO2 to Mo, it is shown that the partial pressure of the prominent molybdenum hydroxide vapor-complex (MoO2(OH)2) is far too low to support such a mechanism. This contention has been corroborated by employing helium to control the partial pressures of hydrogen and water in the gas phase. Secondarily, a limited assessment of the intrinsic rate-controlling mechanisms that can contribute to the residual oxygen-content of the Mo powder product is also provided. Powder morphology, and its concomitant influence on specific surface-area of the Mo powder product, is found to correlate with the oxygen-content determination of the powder produced during second-stage reduction, and according to the processing strategy employed. Consequently, it has been found cogent to “partition” second-stage reduction into: i) a relatively high-rate Primary Reduction Sequence, and ii) a lower rate Deoxidation Sequence.
Abstract.A polyhydroxybutyrate-co-hydroxyvalerate (PHBV) is mingled with natural rubber latex (R) to develop its mechanical property of the blend. Normally, substantial effects of the PHBV are hard, fragile, and inelastic, whereas the natural rubber is represented itself as very high elastic matter. The mixtures between the PHBV and natural rubber latex (R) are considered in different proportions. The PHBV solutions (w/v) are defined suitability at 1% (P1), 2% (P2), and 3% (P3). Their liquid mixtures of the PHBV to natural rubber latex (P:R) are fabricated the blended films in three different ratios of 2:3, 1:1 and 3:2, respectively. The PHBV blended films are characterized the crystallinity form by x-ray diffractometry (XRD), which are appeared their identity crystals at 13.30 and 16.68 degree (2θ ). Mechanical characterizations of the blends are examined by a universal testing machine (UTM). The average elastic moduli of P1, P2, and P3 mixtures are indicated as 773, 955, and 1,007 kPa, respectively. Their tensile strengths, similarly to elastic moduli, enhance with the PHBV concentrations. The effects of mechanical behaviors and crystallinity reveal that the PHBV blends can be improved their properties by more flexible with natural rubber latex.
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