Process Engineering

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Browsing Process Engineering by Subject "Acid hydrolysis"

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    Extraction, Characterization, and Optimization of Cellulose Nanocrystals from Corncob
    (Addis Ababa University, 2020-10) Getahun, Esubalew; Hundessa, Dessalegn (PhD)
    In this study cellulose nanocrystals were extracted from corncob by the method of sulfuric acid hydrolysis, followed by separation using centrifugation, dialysis, and ultrasonication with the objective of achieving maximum yield. The maximum yield (41.8%) of cellulose nanocrystal was found at the parameter interaction of 65wt.% sulfuric acid concentration,45℃ reaction temperature, and 60 minutes of hydrolysis time. The effect of process parameters (acid concentration, temperature, and hydrolysis time) on the yield of cellulose nanocrystals was optimized using response surface methodology(RSM) and gave 41.74% of cellulose nanocrystals yield with the sulfuric acid concentration 61.66wt.%, the reaction temperature 45℃, and the hydrolysis time 59. 92minutes.The experimental yield was 40.94±0.25% after doing triple experiments using the optimal conditions are acid concentration (61.66wt.%), reaction time (59.93 min), and temperature (45℃). The size and surface morphology of cellulose nanocrystals were characterized by particle size analyzer and scanning electron microscopy respectively. Fourier transform infrared showed that the structural change occurs by the chemical treatments (by alkaline treatment and bleaching) due to most of the lignin and hemicellulose were removed from the raw corncob. The result reveals Cellulose nanocrystals prepared from the hydrolysis of the isolated cellulose in the sulfuric acid had needle-shaped morphology, an average length of 170.3nm, and a crystallinity index of 79.3%. The crystallinity index obtained from x-ray diffraction for cellulose nanocrystal was found higher than extracted cellulose with a value of 79.3% and 76.4% respectively.Thermal stability by thermogravimetric analysis showed that the degradation temperature of the cellulose nanocrystals reached around 327℃, which was higher than that of the raw corncob and extracted corncob cellulose. These results showed that corncob cellulose and cellulose nanocrystals (CNCS) were successfully extracted from corncob by sulfuric acid and might be potentially used for different applications.
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    Production of Cellulosic Ethanol from Wood Sawdust
    (Addis Ababa University, 2016-07) Gebreyohannes, Gebrehiwot; Jabasingh, S. Anuradha (PhD)
    Production of cellulosic ethanol was investigated in this study. The wood sawdust has lignocelluloses content, which make it suitable as fermentable sugars, when hydrolyzed. The dried sawdust with uniform particle size was hydrolyzed with sulfuric acid for breaking the bond that binds sugar monomers together. The black residue or lignin was removed and the reduced sugars were neutralized for catalyst activity in the fermentation process. Four experimental parameters were investigated during hydrolysis. They are particle size (1-3mm), acid concentration (3-7%), temperature (90-110oC) and time (120-240 minutes). The total reduced sugars content of hydrolyzed solutions were analyzed using phenol sulfuric acid method. The result of stastical analysis showed a maximum sugar content of 72.51% (w/w) during the hydrolysis of 10% (w/v) wood sawdust of 2mm particle size at 5% (v/v) sulfuric acid concentration at 100oC and 180 minutes. The minimum yield of 41.24% (w/w) was achieved at 1mm particle size, 3% (v/v) sulfuric acid concentration, 90oC and 120 minutes. The reduced sugars were fermented using Saccharomyces cerevisiae in anaerobic condition and the residual solutions were distilled every 150 minutes by rotary evaporator. The ethanol concentrations were measured by Alcoholmeter. And maximum and minimum ethanol concentrations of 73.10% (v/v) and 35.20% (v/v) with 90% (0.46 g/g) of the theoretical conversion (0.51g/g) in 72 hours were achieved respectively. Response surface methodology (RSM) employing the central composite design (CCD) was used to optimize the total reduced sugar using acid hydrolysis. The optimum result was obtained at 1.72mm particle size, 4.21% (v/v) acid concentration, 102.46oC and 156.60 minutes. The total reduced sugar yield of 67.56% (w/w) was achieved under these conditions. The rough feasibility analysis evaluation indicates that, this project is beneficial. The cost estimation studies provide the rate of return on investment as 52.4%. The payback period shows the return of the total investment cost in 3 years with the net present value of 22.73 million Birr.