Hydrothermal liquefaction of biomass: A review of subcritical water technologies

Gas solubility in ionic liquids.

Thermal degradation of PVC: A review.

The electrochemical reduction of CO2 is a promising route to convert intermittent renewable energy to storable fuels and valuable chemical feedstocks. To scale this technology for industrial implementation, a deepened understanding of how the CO2 reduction reaction (CO2 RR) proceeds will help converge on optimal operating parameters. Here, a techno-economic analysis is presented with the goal of identifying maximally profitable products and the performance targets that must be met to ensure economic viability-metrics that include current density, Faradaic efficiency, energy efficiency, and stability. The latest computational understanding of the CO2 RR is discussed along with how this can contribute to the rational design of efficient, selective, and stable electrocatalysts. Catalyst materials are classified according to their selectivity for products of interest and their potential to achieve performance targets is assessed. The recent progress and opportunities in system design for CO2 electroreduction are described. To conclude, the remaining technological challenges are highlighted, suggesting full-cell energy efficiency as a guiding performance metric for industrial impact.

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Electrochemical CO2 Reduction into Chemical Feedstocks: From Mechanistic Electrocatalysis Models to System Design.

The potential of hot and supercritical water in applications to produce useful products, or to process unwanted compounds into environmentally compatible materials is reviewed. The potential of hot and supercritical water is high. Water changes its character from a solvent for ionic species at ambient conditions to a solvent for non-ionic species at supercritical conditions. Water at temperatures higher than ambient boiling temperature can be applied for extraction. At modest temperatures, ionic and polar species will be extracted. At higher temperatures, in particular approaching the critical temperature, nonpolar substances are readily dissolved and extracted. Hot pressurized water has a high reactivity. The reactions are commonly summarized as “hydrolysis reactions” which are catalyzed by acids, or may arise from simply hydrothermal transformations. Since CO2, dissolved in water increases the availability of protons, the addition of CO2 to liquid water catalyses hydrolysis reactions. Hydrolysis of natural plant materials provides a route to obtain fuel from non-food plant material. However, difficulties associated with operating conditions have so far limited the large scale implementations.

Near critical and supercritical water. Part I. Hydrolytic and hydrothermal processes

Supercritical water oxidation (SCWO) technology presents important environmental advantages for the treatment of industrial wastes and sludges. The homogeneous reaction that takes place between the oxidizable materials and oxygen, at temperatures and pressures above the critical point of the water (647.3 K and 22.12 MPa), is well known. Specific equations of state for water and aqueous mixtures, gases, and organics have been developed. The process is not having the expected industrial development. Some new plants have been closed by corrosion and operational problems related with high temperature, high pressure, and oxidative atmosphere inside of the equipments. To overcome these technical difficulties more research focused on solving operational problems is necessary. This article presents an overview of the technical aspects of the supercritical water oxidation process. Reactors design, construction materials, corrosion, salts precipitation problems, and industrial applications are discussed. © 2006 American Institute of Chemical Engineers AIChE J, 2006

Supercritical water oxidation: A technical review

Absorption refrigerators are alternative systems to conventional compression cycles in which the energy necessary for the refrigeration is provided by heating instead of mechanical power. Commercial absorption refrigerators use two absorbent/refrigerant pairs: NH3–H2O and H2O–LiBr. These systems have some limitations due to the difficulty of separating absorbent and refrigerant, the narrow refrigeration temperature range, or the possibility of corrosion and salt deposition. The application of ionic liquids as absorbents with supercritical carbon dioxide as refrigerant can solve some of these problems because separation of ionic liquid from CO2 is easy due to the negligible vapor pressure of ionic liquids. In this work, suitable ionic liquids–CO2 pairs have been selected considering their phase equilibrium properties, calculated with the Group-Contribution equation of state developed by Skjold-Jorgensen. The energetic efficiency of the process with ionic liquids has been estimated by calculation of the Coefficient of Performance (COP) of the process. It has been found that the process with ionic liquids has a lower COP than conventional NH3–H2O systems due to the necessity of operating with a higher solution flowrate. Nevertheless, near-optimum performance is obtained in a wide range of process conditions.

M.D. Bermejo

Papers

Supercritical water oxidation: A technical review

Thermodynamic analysis of absorption refrigeration cycles using ionic liquid + supercritical CO2 pairs

A process for generating power from the oxidation of coal in supercritical water

Supercritical water oxidation of feeds with high ammonia concentrations: Pilot plant experimental results and modeling

Simultaneous and selective recovery of cellulose and hemicellulose fractions from wheat bran by supercritical water hydrolysis