• Energy Research

Abstract Due to the increasing thrust on third generation biofuels, algal research has gained a lot of importance in the recent years. Effective utilization of algal biomass in a single step is necessary as it can produce fungible hydrocarbons in addition to a variety of valuable products. Hydrothermal liquefaction does not require the energy intensive drying steps and is an attractive approach for the conversion of algae which has high moisture content. The objective of this study is to understand the effect of compositional changes of macro algae samples Ulva fasciata (MA’UF), Enteromorpha sp. (MA’E) and Sargassum tenerrimum (MA’ST) on product distribution and nature of products. Various macro algae samples were converted to bio-oil by hydrothermal liquefaction in a batch reactor at 280 °C for 15 min with biomass:water ratio of 1:6. The liquefaction products were separated into ether soluble fraction (bio-oil1), water-soluble fraction, solid residue and gaseous fraction. Maximum conversion of 81% was observed with macro algae (MA) UF. The effect of varying feedstock compositions were reflected in the bio-oil and bio-residue yields. The maximum conversion and bio-oil yield was observed with MA’UF due to the presence of higher carbohydrate content than other feeds. FTIR and NMR spectra showed high percentage of aliphatic functional groups for all bio-oils.

The thermal decomposition of the byproducts of the biodiesel process was studied by thermoanalytical methods. Deoiled algae cake and jatropha seed deoiled cake were pyrolyzed and the catalytic effects of silica supported iron catalysts (Fe/FSM-16 and Fe/SBA-15) and magnetite (Fe3O4) were tested. The evolution profiles of the decomposition products as well as the thermal stability of the samples were determined by thermogravimetry/mass spectrometry (TG/MS). The formation of the volatile products was monitored by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The composition and the amounts of the gaseous products changed significantly in the presence of the silica supported iron catalysts: the yield of hydrogen and carbon monoxide considerably increased above the decomposition temperature of 400 °C. Both silica supported iron catalysts had important effects on the yield of the products originating from carbohydrates and lignins. The formation of anhydrosugars and phenolic compounds was hindered...

The only sustainable environmental friendly source of carbon for liquid fuel production is biomass, which is fixed by plants using atmospheric CO2. However, a major challenge for biomass-based routes is to economically produce the enormous quantities of liquid hydrocarbons needed by the transportation and chemical sector. The fast pyrolysis oil possesses many undesirable properties making it chemically far from a crude oil replacement. In hydropyrolysis process, bio-oil formed is of better quality than that formed under inert atmosphere and has relatively low oxygen content. At present, there are no systematic studies on the hydropyrolysis of biomass, which can give a detailed insight into the mechanistic aspects of the process. In addition to this, only several concepts have been proposed, which can be experimented. This review aims to provide a clear insight of the existing hydropyrolysis concepts and experiments carried out by different groups so far, along with the challenges and opportunities in the area.

The increasing concerns over the depletion of fossil resources and its associated geo-political issues have driven the entire world to move toward sustainable forms of energy. Pretreatment is the first step in any biochemical conversion process for the production of valuable fuels/chemicals from lignocellulosic biomass to eliminate the lignin and produce fermentable sugars by hydrolysis. Conventional techniques have several limitations which can be addressed by using them in tandem with non-conventional methods for biomass pretreatment. Electron beam and γ (gamma)-irradiation, microwave and ultrasound energies have certain advantages over conventional source of energy and there is an opportunity that these energies can be exploited for biomass pretreatment.

Thermal and catalytic hydrothermal liquefaction of water hyacinth was performed at temperatures from 250 to 300 °C under various water hyacinth:H2O ratio of 1:3, 1:6 and 1:12. Reactions were also carried out under various residence times (15-60 min) as well as catalytic conditions (KOH and K2CO3). The use of alkaline catalysts significantly increased the bio-oil yield. Maximum bio-oil yield (23 wt%) comprising of bio-oil1 and bio-oil2 as well as conversion (89%) were observed with 1N KOH solution. (1)H NMR and (13)C NMR data showed that both bio-oil1 and bio-oil2 have high aliphatic carbon content. FTIR of bio-residue indicated that the usage of alkaline catalyst resulted in bio-residue samples with lesser oxygen functionality indicating that catalyst has a marked effect on nature of the bio-residue and helps to decompose biomass to a greater extent compared to thermal case.

Hydrothermal liquefaction of lignin was performed using methanol and ethanol at various temperatures (200, 250 and 280°C) and residence times of 15, 30 and 45min. Maximum liquid product yield (85%) was observed at 200°C and 15min residence time using methanol. Increase in temperature was seen to decrease the liquid products yield. With increase in residence time, liquid yields first increased and then decreased. FTIR and (1)H NMR showed the presence of substituted phenols and aromatic ethers in liquid products and breakage of β-O-4 or/and α-O-4 ether bonds present in lignin during hydrothermal liquefaction was confirmed through FTIR of bio-residue. In comparison to the existing literature information, higher lignin conversion to liquid products and maximum carbon conversion (72%) was achieved in this study.

There is an increasing demand of hydrocarbons owing to the fluctuations in crude oil prices and reduced fossil resources. Lignocellulosic biomass is seen as a potential renewable source of sustainable hydrocarbons. The hydropyrolysis of jatropha seed de-oiled cake has been carried out at various hydropyrolysis temperatures (300, 350, 400 and 450 °C) and pressures of hydrogen (1, 20, 40 and 52 bar). It has been observed that the liquid bio-oil yields have increased with pyrolysis temperature and pressure. It was also found that 40 bar is the optimum value of hydrogen pressure for the hydropyrolysis reactions at 450 °C to obtain maximum liquid yield (17 wt.%) in the given experimental setup. The frequency factor of 98 s−1 and activation energy of 29 kJ/mol are the lowest at 40 bar reaffirming the fact that heat and mass transfer limitations are the least at 40 bar pressure.