Thallada Bhaskar

Thermal decomposition of flame-retarded high-impact polystyrene

The thermal decomposition of four high-impact polystyrene (HIPS) samples containing brominated flame retardants has been studied. Decabromodiphenyl ether (Br10-DPE) and decabromodibenzyl (Br10-DB) were used as flame retardants and two samples contained antimony trioxide (Sb2O3) synergist besides the brominated additives. The thermal decomposition of HIPS samples was studied by thermogravimetry/mass spectrometry (TG/MS), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and pyrolysis-mass spectrometry (Py-MS). It was established that the brominated additives themselves do not change the decomposition temperature of polystyrene (PS). However, Sb2O3 reduces the thermal stability of the samples indicating that Sb2O3 initiates the decomposition of the flame retardants and PS. Water and styrene products were detected during the first stage of decomposition from HIPS samples containing Sb2O3. Nevertheless, the majority of PS decomposes at a higher temperature. The two brominated flame retardants decompose by different pathways. The scission of CC bonds, resulting in the formation of bromotoluenes, is the most important reaction of Br10-DB additives. In contrast, Br10-DPE decomposes by an intermolecular ring closure pathway producing brominated dibenzofurans (DBF).

Non isothermal model free kinetics for pyrolysis of rice straw

The kinetics of thermal decomposition of rice straw was studied by thermogravimetry. Non-isothermal thermogravimetric data of rice straw decomposition in nitrogen atmosphere at six different heating rates of 5-40 °C/min was used for evaluating kinetics using several model free kinetic methods. The results showed that the decomposition process exhibited two zones of constant apparent activation energies. The values ranged from 142 to 170 kJ/mol (E(avg) = 155.787 kJ/mol), and 170 to 270 kJ/mol (E(avg) = 236.743 kJ/mol) in the conversion range of 5-60% and 61-90% respectively. These values were used to determine the reaction mechanism of process using master plots and compensation parameters. The results show that the reaction mechanism of whole process can be kinetically characterized by two successive reactions, a diffusion reaction followed by a third order rate equation. The kinetic results were validated using isothermal predictions. The results derived are useful for development and optimization of biomass thermochemical conversion systems.

Effective catalytic conversion of cellulose into high yields of methyl glucosides over sulfonated carbon based catalyst.

An amorphous carbon based catalyst was prepared by sulfonation of the bio-char obtained from fast pyrolysis (N(2) atm; ≈ 550°C) of biomass. The sulfonated carbon catalyst contained high acidity of 6.28 mmol/g as determined by temperature programmed desorption of ammonia of sulfonated carbon catalyst and exhibited high catalytic performance for the hydrolysis of cellulose. Amorphous carbon based catalyst containing -SO(3)H groups was successfully tested and the complete conversion of cellulose in methanol at moderate temperatures with high yields ca. ≥ 90% of α, β-methyl glucosides in short reaction times was achieved. The methyl glucosides formed in methanol are more stable for further conversion than the products formed in water. The carbon catalyst was demonstrated to be stable for five cycles with slight loss in catalytic activity. The utilization of bio-char as a sulfonated carbon catalyst provides a green and efficient process for cellulose conversion.

Novel calcium based sorbent (Ca-C) for the dehalogenation (Br, Cl) process during halogenated mixed plastic (PP/PE/PS/PVC and HIPS-Br) pyrolysis

A calcium carbonate carbon composite sorbent (Ca-C) was prepared by using 90 wt% of calcium carbonate and 10 wt% phenol resin. The Ca-C sorbent was successfully utilised for the dechlorination and debromination process during halogenated (Cl, Br) mixed waste plastic (PP/PE/PS/PVC/HIPS-Br: 3∶3∶2∶1∶1) pyrolysis at 430 °C and produced halogen free liquid products.

Pyrolysis of Mesua ferrea and Pongamia glabra seed cover: Characterization of bio-oil and its sub-fractions

In the present study, pyrolysis of Mesua ferrea seed cover (MFSC) and Pongamia glabra seed cover (PGSC) was performed to investigate the characteristics of bio-oil and its sub fractions. In a fixed bed reactor, the effect of temperature (range of 350-650 °C) on product yield and quality of solid product were monitored. The maximum bio-oil yield of 28.5 wt.% and 29.6 wt.% for PGSC and MFSC respectively was obtained at 550 °C at heating rate of 40 °C/min. The chemical composition of bio-oil and its sub fractions were investigated using FTIR and (1)H NMR. GC-MS was performed for both PGSC and MFSC bio-oils and their corresponding n-hexane fractions. The results showed that bio-oil from the feedstocks and its sub-fractions might be a potential source of renewable fuel and value added chemicals.

Hydrothermal conversion of lignin to substituted phenols and aromatic ethers

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.

Recycling of waste lubricant oil into chemical feedstock or fuel oil over supported iron oxide catalysts

The recycling of waste lubricant oil from automobile industry was found to be best alternative to incineration. Silica (SiO2), alumina (Al2O3), silica–alumina (SiO2–Al2O3) supported iron oxide (10 wt% Fe) catalysts were prepared by wet impregnation method and used for the desulphurisation of waste lubricant oil into fuel oil. The extent of sulphur removal increases in the sequence of Fe/SiO2–Al2O3<Fe/Al2O3<Fe/SiO2 and this might be due to the presence of smaller crystalline size (7.4 nm) of Fe2O3 in Fe/SiO2 catalyst. X-ray diffraction results suggest the presence of iron sulphide in the used catalyst. Gas chromatography with thermal conductivity detector analysis confirms the presence of H2S in gaseous products. In addition, Fe/SiO2 catalyst facilitated the formation of lower hydrocarbons by cracking higher hydrocarbons (≈C40) present in waste lubricant oil.

Catalytic hydrothermal liquefaction of water hyacinth.

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.

Opportunities for utilization of non-conventional energy sources for biomass pretreatment

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.

Thermogravimetric and decomposition kinetic studies of Mesua ferrea L. deoiled cake

The present study aims to explore the physico-chemical properties of Mesua ferrea L. (Iron wood tree) deoiled cake (MFDC) and decomposition parameters for thermochemical methods of conversion. The physico-chemical characteristics of MFDC were investigated by bomb calorimetry, TG/DTA (10, 20 and 40°C min(-1)), elemental analysis (CHN) and FTIR spectroscopy. The proximate composition was calculated using standard ASTM methodology. The temperature profile, activation energy (E), pre-exponential factor (A) and reaction order (n) for the active pyrolysis zone of the species under investigation have been provided for the respective heating rates using Arrhenius, Coats-Redfern, Flynn-Wall-Ozawa (FWO) and Global independent reactions model. The current investigation suggests that within the realm of existing biomass conversion technologies, MFDC can be used as a feedstock for thermochemical conversion.