Optimal use of glycerol co-solvent to enhance product yield and its quality from hydrothermal liquefaction of refuse-derived fuel.

Refuse-derived fuels (RDF) are rich in resources that make them an attractive feedstock for the production of energy and biofuels. Hydrothermal liquefaction (HTL) is a promising thermochemical conversion technology to handle wet feedstocks and convert them to valuable bio-crude, bio-char and aqueous products. This study highlights the advantages of using glycerol as the co-solvent along with water in different proportions to produce bio-crude from RDF via HTL. The ratio of water:glycerol (vol.%:vol.%) was varied for each experiment (100:0, 90:10, 80:20, 70:30, 60:40, 50:50), and the product yields and their quality were studied. The results demonstrate that increasing the proportion of glycerol until 50 vol.% in the solvent enhances the bio-crude yield (36.2 wt.%) and its higher heating value (HHV) (30.9 MJ kg-1). Deoxygenation achieved in the bio-crude was 42%. The production of bio-char was minimum (9.5 wt.%) at 50 vol.% glycerol with HHV of 31.9 MJ kg-1. The selectivity to phenolic compounds in the bio-crude increased, while that of cyclic oxygenates decreased when the glycerol content was more than 20 vol.%. The gas-phase analysis revealed that the major deoxygenation pathway was decarboxylation. The yield of aqueous products drastically increased with the addition of glycerol. The minimum amount of glycerol in the co-solvent that favours an energetically feasible process with low carbon footprint is 30 vol.%. Using 50 vol.% glycerol resulted in the highest energy recovery in the bio-crude and bio-char (80%), the lowest energy consumption ratio (0.43) and lowest environmental factor (0.1). The mass-based process mass intensity factor, calculated based on only bio-crude and bio-char as the valuable products, decreased with an increase in addition of glycerol, while it was close to unity when the aqueous phase is also considered as a valuable product.

Effect of water quality on the yield and quality of the products from hydrothermal liquefaction and carbonization of rice straw.

The need for fresh water limits the application and scale-up of hydrothermal technologies to convert waste biomass to energy and chemicals. In an effort to demonstrate the use of wastewater for sustainable process development, this work is focused on hydrothermal liquefaction (HTL) (350 °C, 18 MPa, 30 min) and carbonization (HTC) (200 °C, 7 MPa, 4 h) of rice straw with water from various sources (milli-Q water, tap water, seawater, recycled wastewater and industrial wastewater). The bio-crude yield from HTL was maximum (36.4 wt%) with industrial wastewater, while the yield of hydrochar from HTC was maximum (74.5 wt%) with seawater. The ions like K+, PO43- and NH4+ accumulated in the aqueous phase from rice straw. The hydrochars from HTL experiments contained significantly higher amount of ash compared to that from HTC experiments. Cyclopentenones and phenols were the major constituents of the bio-crude, whose HHV was 26.3 MJ/kg using seawater.

Valorization of red macroalgae biomass via hydrothermal liquefaction using homogeneous catalysts.

Hydrothermal liquefaction of red macroalgae species, Kappaphycus alvarezii (KA) and Eucheuma denticulatum (ED), was performed at 350 °C in the presence of 5 wt% neutral and alkali catalysts like Na2CO3, K2CO3, CaCO3, Na2SO4, NaOH, and KOH. The maximum bio-crude yield of 26.7 wt% and 18.5 wt%, on a dry ash-free basis, was obtained from Na2CO3 treatment of KA and KOH treatment of ED, respectively. The bio-crude from both feedstocks mainly consisted of cyclic oxygenates, whose selectivities were maximum in K2CO3 and CaCO3 treatments. The calorific value of the bio-crude was 38.5 MJ/kg from KA and 30.8 MJ/kg from ED, while that of biochars was 20-24 MJ/kg. A high degree of deoxygenation (64.2%) was observed in bio-crude produced from Na2SO4 treatment of KA biomass. Salts of Cl-, SO42- and K+ constituted the major inorganic portion of the aqueous phase. Maximum energy recovery (99%) was observed from the Na2CO3 treatment of ED.

Effects of aqueous phase recirculation on product yields and quality from hydrothermal liquefaction of rice straw.

Aqueous phase (AP) recirculation is a promising process intensification strategy to improve the yield and quality of the products and cost efficiency of the hydrothermal liquefaction (HTL) process by replacing the fresh water used in the experiments. The results demonstrate that AP recirculation in the HTL of rice straw decreases the bio-crude yield from 32.6 wt% to 9.1 wt% after the third recycle, while enhancing the bio-char yield up to 64.1 wt%. The bio-crude and bio-char show improved carbon and hydrogen content with AP recirculation. The decrease in selectivity to aliphatic hydrocarbons in the bio-crude and bio-char, coupled with increase in H2 content in the gaseous phase, suggests the prevalence of dehydrogenation reactions. The bio-char achieved better thermal stability, water retention and cation exchange capacity with AP recirculation. There was a significant accumulation of K+, Ca2+ and Cl- with a concomitant decrease in silicates, sulfate and phosphate in the AP.

Strain-mediated effects of oxygen deficiency and variation in non-Fermi liquid behavior of epitaxial PrNiO3-δ thin films.

To understand the effects of oxygen variation in combination with different strains in perovskite nickelates, three sets of PrNiO3-δ thin films S 1, S 2 and S 3 were deposited on (0 0 1) oriented single-crystal wafers of SrTiO3, LSAT [(LaAlO3)0.3(Sr2TaAlO6)0.7] and LaAlO3, respectively. Two sets of films, S 1 and S 2, have tensile strain whereas the films of S 3 show compressive strain. For each set, two thin films of fixed thickness (5 nm) were deposited; one film was annealed in situ in oxygen partial pressure just after deposition, the other film was not annealed. The difference in oxygen stoichiometry caused a different state of epitaxial strain in the films. So, the strain was induced in the films due to lattice mismatch with substrate, which modified due to oxygen deficiency. These films show non-Fermi liquid (NFL) behavior in the metallic state. The fitting parameters to power-law equation show a systematic tuning of NFL fitting parameters because of variations in strain. Our results show that not only lattice mismatch induced strain, but also oxygen stoichiometry are crucial parameters in changing the state of strain and hence the NFL behavior and electronic properties of perovskite nickelates.