Water-in-Oil Pickering Emulsions Stabilized by Hydrophobized Protein Microspheres

Water-in-oil (w/o) Pickering emulsions have gained considerable attention in colloid science and daily applications. However, for the formation of w/o emulsions, especially those with high internal water content, the particulate stabilizers are required to be sufficiently hydrophobic, and synthetic or chemically modified particles have been mostly reported until now, which are not biocompatible and sustainable. We present a zein protein-based microsphere derived from the Pickering emulsion template, in which protein microspheres are feasibly in situ hydrophobized by silica nanoparticles, enabling the stabilization of w/o Pickering emulsions. The effects of microsphere concentration, water/oil volume ratio, oil types, and pH on the stabilization of prepared w/o emulsions are systematically studied, revealing prominent characteristics of the controllable size, high water fraction, universal adaptation of oils, as well as broad pH stability. As a demonstration, the Pickering emulsion effectively encapsulates vitamin C and shows high stability for long storage duration against ultraviolet radiation/heat. Therefore, this novel proteinaceous particle-stabilized w/o Pickering emulsion has great potential in the delivery and protection of water-soluble bioactive substrates

Synthesis of Fluorenes Starting from 2‑Iodobiphenyls and CH₂Br₂ through Palladium-Catalyzed Dual C–C Bond Formation

A facile and efficient approach is developed for the synthesis of fluorene and its derivatives starting from 2-iodobiphenyls and CH₂Br₂. A range of fluorene derivatives can be synthesized under relatively mild conditions. The reaction proceeds via a tandem palladium-catalyzed dual C–C bond formation sequence through the key dibenzo­pallada­cyclo­pentadiene intermediates, which are obtained from 2-iodobiphenyls through palladium-catalyzed C–H activation

Air Injection for Enhanced Oil Recovery: <i>In Situ</i> Monitoring the Low-Temperature Oxidation of Oil through Thermogravimetry/Differential Scanning Calorimetry and Pressure Differential Scanning Calorimetry

Low-temperature oxidation (LTO) of oil plays an important role in air-injection based oil recovery processes. Systematic investigations on the regularities of LTO reactions, especially those decoupled with the influences of mass transfer, were highly expected to improve field application and even to develop new strategies for heavy oil recovery. In this contribution, both thermogravimetry/differential scanning calorimeter and pressure differential scanning calorimeter were employed as microreactors to <i>in situ</i> monitoring the heat release and mass loss performances of the LTO process under different oxygen partial pressures. The total amount of heat resulted from LTO reactions of oil was observed in a linear relationship with oxygen partial pressure. A one-step reaction model was proposed to simulate the low-temperature mass loss behavior. The kinetic parameters were calculated based on the Arrhenius expression and the assumption of distributed activation energy. These results indicated the feasibility of <i>in situ</i> generated heat during low-temperature oxidation by the promotion of oxygen partial pressure and the contact between oil and oxygen with little loss of deposited oil

Phase Behavior of Pickering Emulsions Stabilized by Graphene Oxide Sheets and Resins

Graphene oxide is preferable to form stable water-in-oil (W/O) emulsions with crude oil, owing to its exceptional structure, including 1 nm in thickness, several micrometers in diameter, and −COOH, −OH, C-O, C-O-C, and CO groups on the surface. The properties of the as-prepared emulsions are strongly dependent on the GO concentrations (<i>C</i>_GO) and volume fraction of water to oil. At a volume ratio of 1:1, the GO dispersions and crude oil can be miscible into stable W/O emulsions accompanying with largely increased viscosity even when the GO concentration reduces to 0.0001%. Notably, when the concentration of GO ranges from 0.005% to 0.01%, the viscosity of W/O emulsions increases to several hundred mPa·s with the increased shear time, which is ascribed to the coalescence of the emulsions under shear. The volume fraction of water in the mixtures (<i>F</i>_w) also affects the phase behavior of the emulsions. At <i>C</i>_GO = 0.0001%, 0.001%, and 0.01%, GO dispersions and crude oil are miscible into one phase completely at <i>F</i>_w < 0.7. In the range between 0.1 and 0.7, viscosity of the emulsion increases as increasing the volume ratio of water to oil. More interestingly, high internal phase emulsions can be obtained in the range of 0.0005–0.008% at <i>F</i>_w = 0.75, in which case viscosity of the emulsions reaches the maximum, i.e., nearly 200 times higher than that of crude oil, due to the high internal phase volume fractions. These results show that the GO dispersions are favorable to form stable W/O emulsions with high internal phase volume fraction, and have a great potential in improving oil displacement efficiency of chemical flooding