Mass transfer and chemical reaction in gas-liquid-liquid systems

Gas-liquid-liquid reaction systems may be encountered in several important fields of application as e.g. hydroformylation, alkylation, carboxylation, polymerisation, hydrometallurgy, biochemical processes and fine chemicals manufacturing. However, the reaction engineering aspects of these systems have only been considered occasionally. For systems with very slow reaction kinetics this is not surprising, as the three phases will be at physical equilibrium. In reaction systems with fast parallel and consecutive reactions the effects of mass transfer and mixing on the product yield can be significant. A fascinating example of such a reaction system is the Koch synthesis of Pivalic Acid. In this work this reaction system was chosen as model system to study these effects

Biogas Upgrading Using Cation-Exchanged Bentonite Clay

The separation of CH4 and CO2 in biogas, known as biogas upgrading, can produce two valuable gas products and prevent greenhouse gas emissions. One method hereto is (vacuum-)pressure swing adsorption that involves the selective adsorption of CO2 on a sorbent. This work evaluates three montmorillonite-rich bentonite clay sorbents (cesium-, monomethylammonium-, and tetramethylammonium-exchanged). These layered materials were specifically selected for their interlayer spacing that nearly matches the molecular size of CO2 and hence can exclude the larger CH4 molecule. Adsorption isotherms of CO2 and CH4 and breakthrough measurements of the gas mixture determined for powders and particles demonstrate unambiguously the ability to separate both gases. The sorbents show a CO2/CH4 selectivity at 20-30 °C and PCO2 = PCH4 = 0.5 bar in the range of ∼35 to 7, decreasing with increasing cation size. While diffusional transport inside cesium- and tetramethylammonium-bentonite particles is fast, it is severely hindered in the case of monomethylammonium-bentonite particles. Desorption with nitrogen-purge, at room temperature and without external heating, demonstrates fast regeneration, typically within several minutes for cesium- and tetramethylammonium-bentonite particles. Based on the fast kinetics and their good selectivity, cation-exchanged clays are considered a promising alternative for conventional sorbents that often suffer from a trade-off between adsorption and desorption kinetics and selectivity.</p

Microalgae wet extraction using N-ethyl butylamine for fatty acid production

AbstractMicroalgae are considered a promising feedstock for the production of food ingredients, cosmetics, pharmaceutical products and biofuels. The energy intensity of drying and cell breaking of algae and solvent recovery afterwards hindered the route of algae biorefinery. In this work the influences of freeze drying and cell breaking to the extraction efficiency of crude lipid yield and fatty acid yield were investigated. Results showed that drying and cell breaking are not necessary for N-ethyl butylamine extraction, because good yields were obtained without. Crude lipid yield and fatty acid yield using N-ethyl butylamine were comparable with Bligh & Dyer extraction, making N-ethyl butylamine a candidate for further development of an energy efficient lipid extraction technology for non-broken microalgae

Toward Redox-Free Reverse Electrodialysis with Carbon-Based Slurry Electrodes

Clean and renewable salinity gradient energy can be harvested using reverse electrodialysis (RED). The electrode system is an essential part to convert ionic current into electrical current. In this study, a typical 0.10 × 0.10 m2 RED stack with a cross-flow configuration was used to test carbon-based slurry electrodes (CSEs) to replace the usual redox solutions, like hexacyanoferrate, to enhance the RED process’ sustainability, stability, and economic value. Six different slurry compositions comprising activated carbon, carbon black, and graphite powder were tested. The CSE characteristics were systematically studied by measuring viscosity, electrode compartment pressure drop, maximum current density, stability, and performance of power density and energy efficiency. Using a single membrane configuration, the CSE ran continuously for 17 days with a stable output. The application of CSEs for RED, with artificial seawater and river water, using mixing activated carbon and carbon black at a total concentration of 20 wt %, resulted in the best performance with a net power density of 0.7 W·m-2. Moreover, higher current densities up to 350 A·m-2 were tested for ED and shown to be feasible until 150 A·m-2. CSEs show promising versatility for different application modes

A novel condensation reactor for efficient CO2 to methanol conversion for storage of renewable electric energy

A novel reactor design for the conversion of CO2 and H2 to methanol is developed. The conversion limitations because of thermodynamic equilibrium are bypassed via in situ condensation of a water/methanol mixture. Two temperatures zones inside the reactor ensure optimal catalyst activity (high temperature) and full conversion by condensation at a lower temperature in a separate zone. Due to this full gas conversion there is no need for an external recycle of reactants. Experimental work confirmed full carbon conversion (>99.5%) and high methanol selectivity (>99.5% on carbon basis). Additionally, it was shown that due the temperature gradient inside the reactor significant reaction rates are achieved under natural convection conditions

Solubility of CO2 in Aqueous Solution of Newly Developed Absorbents

The solubility of CO2 in various aqueous amine based solvents was determined at lower CO2 partial pressures. Cyclic capacity of various potential aqueous amine based solvents at 10 kPa CO2 partial pressure was determined by performing CO2 absorption at 30 ∘C, regeneration at 90oC and at 1 atmosphere. 1,7-Diaminoheptane and 1,6-Hexanediamine, N,N’-dimethyl was found to be having high cyclic loading of 0.81 and 0.85 moles CO2/moles amine respectively. Aqueous solution of 1,6-Hexanediamine, N,N’-dimethyl of 0.5 and 2.55 Mole/L concentration was selected for solubility study of CO2 at different partial pressure ranging from 1 up to 40 kPa, 30 ∘C and at 1 atmosphere. The solubilities of CO2 in aqueous 1,6-Hexanediamine, N,N’-dimethyl at 30oC were compared with those in aqueous solution of MEA with similar solution concentrations. The solubility of CO2 in 2.55 Mole/L 1,6-Hexanediamine, N,N’-dimethyl was found to be higher when compared to the 2.5 Mole/L MEA at lower CO2 partial pressure