Showing papers by "Sushil Adhikari published in 2017"

Synthesis and Characterization of Bio-oil-Based Self-Curing Epoxy Resin

Abstract: A novel self-curing epoxy resin was synthesized using bio-oil. Bio-oil was produced by hydrothermal liquefaction of loblolly pine and utilized as a biopolyol in the synthesis of bio-oil-based epoxy resin (BOBER) for the first time. Hydroxyl groups in bio-oil were analyzed by quantitative 31P NMR. It was found that not only does the total hydroxyl number of bio-oil influence the yield and epoxy equivalent weight of BOBER, but also the distribution of hydroxyl groups within bio-oil (aliphatic, phenolic, and acidic OH) played an important role in the determination of the optimum amount of catalyst in the synthesis of BOBER. Differential scanning calorimetry analysis proved the self-curing phenomena of BOBER, and Fourier transform infrared spectroscopy suggested that etherification reaction was the dominate reaction during the self-curing. Glass transition temperature, cross-linking density, and the storage modulus of self-cured BOBER were calculated using a dynamic mechanical analyzer.

Kinetics and Mechanisms for Copyrolysis of Palm Empty Fruit Bunch Fiber (EFBF) with Palm Oil Mill Effluent (POME) Sludge

Abstract: Copyrolysis of biomass is one of the potential options to improve the quality of bio-oil. In this study, different types of feedstock, palm empty fruit bunches fiber (EFBF) and palm oil mill effluent (POME) sludge, were conducted via thermogravimetric analysis. The thermogravimetric behavior of EFBF and POME sludge blends (EFBF:POME sludge mass ratio of 100, 90, 75, 50, 25, and 0%) were subjected to different heating rates of (5, 10, 20, 30, 40 °C/min) with a nitrogen (N2) purge of 20 mL/min to simulate pyrolysis conditions. As the percentage of POME sludge in the blend increases, the thermogravimetric data and thermogravimetric derivative profiles shifted from EFBF to that of POME sludge gradually. A higher mass loss rate of EFBF upon devolatilization indicates the higher reactivity than that of POME sludge. During copyrolysis, a positive synergistic effect was observed. All the samples experienced three pyrolysis stages, and for each stage, the mechanisms responsible were determined. The third order kin...

Catalytic upgrading of fractionated microalgae bio-oil (Nannochloropsis oculata) using a noble metal (Pd/C) catalyst

Abstract: Pyrolytic bio-oil was chemically upgraded after physically distilled upgrades to meet the petroleum transportation fuel substitute. A Pd/C catalyst was used to upgrade the microalgae pyrolytic bio-oil to determine the effect of different distillation fractions and catalytic upgrading conditions on the yields and properties. The middle distillation fraction (F2) was upgraded under various temperature (130 to 250 °C) and pressure (4.1 to 8.3 MPa) conditions based on response surface methodology (RSM). The light distillation fraction (F1) and raw bio-oil were also catalytically upgraded for the comparison. The distillation step prior to catalytic upgrading led to a better quality of upgraded bio-oil compared to the direct bio-oil upgrades. Both the oxygen and hydrogen contents of light and middle fraction upgrades were improved, while the upgraded raw bio-oil showed limited improvement. The other properties of HHV and TAN with the middle fraction upgrades were improved to 42.9 MJ/kg and 1.09 mg KOH/g, respectively, at the severe condition as most of the ketones in upgrades were removed. Also, paraffin and aromatic chemical groups were significantly produced at the expense of the olefin groups through hydrogenation and hydrodeoxygenation. Thus, the catalytic upgrading after a distillation stage enhanced the quality of biofuel that can be a petroleum fuels substitute or additives.

Chemometric modeling of thermogravimetric data for the compositional analysis of forest biomass.

Abstract: The objective of this study was to investigated the use of chemometric modeling of thermogravimetric (TG) data as an alternative approach to estimate the chemical and proximate (i.e. volatile matter, fixed carbon and ash contents) composition of lignocellulosic biomass. Since these properties affect the conversion pathway, processing costs, yield and / or quality of products, a capability to rapidly determine these for biomass feedstock entering the process stream will be useful in the success and efficiency of bioconversion technologies. The 38-minute long methodology developed in this study enabled the simultaneous prediction of both the chemical and proximate properties of forest-derived biomass from the same TG data. Conventionally, two separate experiments had to be conducted to obtain such information. In addition, the chemometric models constructed with normalized TG data outperformed models developed via the traditional deconvolution of TG data. PLS and PCR models were especially robust in predicting the volatile matter (R2–0.92; RPD– 3.58) and lignin (R2–0.82; RPD– 2.40) contents of the biomass. The application of chemometrics to TG data also made it possible to predict some monomeric sugars in this study. Elucidation of PC loadings obtained from chemometric models also provided some insights into the thermal decomposition behavior of the chemical constituents of lignocellulosic biomass. For instance, similar loadings were noted for volatile matter and cellulose, and for fixed carbon and lignin. The findings indicate that common latent variables are shared between these chemical and thermal reactivity properties. Results from this study buttresses literature that have reported that the less thermally stable polysaccharides are responsible for the yield of volatiles whereas the more recalcitrant lignin with its higher percentage of elementary carbon contributes to the yield of fixed carbon.

Alternative Hydrocarbon Biofuel Production via Hydrotreating under a Synthesis Gas Atmosphere

Abstract: Direct use of syngas, a cheaper hydrogen-rich gas, instead of pure hydrogen, as a deoxygenating agent for biohydrogenated diesel (BHD) production is presented in this study. Low-cost palm fatty acid distillate (PFAD), an inedible byproduct from refining palm oil, is used as a feedstock in the presence of a Pd/C catalyst. The results indicate that syngas can be effectively used in BHD production, while the achieved BHD yield is slightly lower than that obtained from pure hydrogen. The liquid products contain mostly n-C15 and n-C17, which fall into a diesel range. Decarbonylation is a prominent pathway under both hydrogen and syngas atmospheres. It was found that CO in syngas can act as a reducing agent, which can remove an oxygen atom from fatty acid molecules to form alkenol that could be further reduced to alkene and then cyclized to cycloparaffins. After reactivation, the activity of the catalyst could be fully recovered for at least 4 reused cycles. Reaction pathways for the catalytic deoxygenation und...

Process Modeling of Fluidized Bed Biomass-CO2 Gasification using ASPEN Plus

Abstract: Gasification is one of the most important thermochemical methods for conversion of biomass to biofuels. In this work, a comprehensive model to simulate the output performance of a bench scale atmospheric fluidized bed gasifier is developed using the ASPEN Plus process simulator. Knowledge about the chemistry and kinetics of the process obtained from experimental results in earlier parts of this study has been incorporated into the model. Different reactor configurations are used to simulate the various stages in a biomass-CO2 gasification process. A dynamically linked FORTRAN subroutine is used to include the kinetic model for the Boudouard reaction. Results from sensitivity analysis performed on the model are compared with the experimental results using parameters like product stream yields, syngas composition, individual gas yields, and carbon conversion are compared to evaluate the validity of the model. The results are further compared to results from a thermodynamic equilibrium model to judge the credibility of using a comprehensive ASPEN model with kinetics.

Inhibition effect of aromatic aldehydes on butanol fermentation by Clostridium acetobutylicum

Abstract: A large number of degradation compounds are formed during biomass pretreatment and they significantly inhibit the efficiency of biomass conversion to biofuels. Of those identified potential inhibitors, aromatic aldehydes play an important role in inhibition activity. Hence the effect of 13 aromatic aldehydes on acetone–butanol–ethanol (ABE) fermentation was assessed at four concentrations in the present work. It was found that the inhibition severity was affected by the ortho substituents (OH > OCH3 > CHO) and strongly related to the position of hydroxyl group instead of the number of hydroxyl groups. The ortho-hydroxyl group significantly contributed to the aromatic aldehyde inhibition. The ortho-substituted 2-hydroxybenzaldehyde caused at least 20-fold stronger inhibition than meta- and para-substituted analogues of 3- and 4-hydroxybenzaldehydes. The presence of ortho-hydroxyl group can form an intramolecular hydrogen bond with carbonyl hydrogen and potentially increase the cell membrane permeability and electrophilicity. Quantitative structure–activity relationship (QSAR) analysis was used to establish a correlation between inhibition activity (IC50) and physicochemical descriptors. A strong correlation was observed between IC50 and the energy of the highest occupied molecular orbital EHOMO.

Moisture effect on fluidization behavior of loblolly pine Wood grinds

Abstract: The impact of moisture content (MC of 8 to 27 % wet basis) on physical properties (particle size distribution, average size using Feret, chord, Martins, surface-volume, and area diameter measurement schemes, bulk density, and particle density), fluidization behavior, and minimum fluidization velocities (U mf) of loblolly pine wood grinds were studied. A new correlation for predicting the U mf of loblolly pine wood grinds at different moisture contents was also developed. Results showed that bulk density, particle density, and porosity of grinds were significantly affected by increase in MC (p < 0.05). Diameter of the grinds measured using Feret measurement scheme was consistently the highest while those measured by surface-volume scheme were consistently the lowest with the measured Feret-based diameter about three times the surface-volume based diameters. Particle size data showed that variations in sizes of particle within a sample reduced with increase in MC (coefficient of variation value was 90 at 8.45 % MC and 40 at 27.02 % MC). Generally, as MC increased, the minimum fluidization velocity values increased. The minimum fluidization velocity (Umf) was found to be 0.2 m/s for 8 % MC, 0.24 m/s at 14.86 % MC, 0.28 m/s at 19.86 % MC, and 0.32 m/s for 27.02 % MC. The correlation developed predicted the experimental data with mean relative deviation that was less than 10 %.

Biomass gasification producer gas cleanup

Abstract: In addition to primary gases, biomass-derived producer gas contains nonnegligible concentrations of undesirable byproducts collectively known as contaminants. Syngas contaminants are composed of tar-, nitrogen-, and sulfur-based compounds and halides and other trace metals that must be minimize their negative impacts on downstream processes or to adhere to environmental regulations. The producer gas cleanup consists of all processes that are employed to reduce the concentration of contaminants in raw producer gas prior to conditioning and utilization in downstream applications. This chapter discusses primary contaminants, the impact of operating conditions on them, their mitigation and regulations governing their emissions. Additionally, best of available technology (BAT) are discussed for select contaminants.