The design of surfactants for CO/oil emulsions has been elusive given the low CO-oil interfacial tension, and consequently, low driving force for surfactant adsorption. Our hypothesis is that waterless, high pressure CO/oil emulsions can be stabilized by hydrophobic comb polymer surfactants that adsorb at the interface and sterically stabilize the CO droplets. The emulsions were formed by mixing with an impeller or by co-injecting CO and oil through a beadpack (CO volume fractions (ϕ) of 0.50-0.90). Emulsions were generated with comb polymer surfactants with a polydimethylsiloxane (PDMS) backbone and pendant linear alkyl chains. The C alkyl chains are CO-insoluble but oil soluble (oleophilic), whereas PDMS with more than 50 repeat units is CO-philic but only partially oleophilic. The adsorbed surfactants sterically stabilized CO droplets against Ostwald ripening and coalescence. The optimum surfactant adsorption was obtained with a PDMS degree of polymerization of ∼88 and seven C side chains. The emulsion apparent viscosity reached 18 cP at a ϕ of 0.70, several orders of magnitude higher than the viscosity of pure CO, with CO droplets in the 10-150 µm range. These environmentally benign waterless emulsions are of interest for hydraulic fracturing, especially in water-sensitive formations.

Direct contact membrane distillation (DCMD) has immense potential in the desalination of highly saline wastewaters where reverse osmosis is not feasible. This study evaluated the potential of DCMD for treatment of produced water generated during extraction of natural gas from unconventional (shale) reservoirs. Exhaust stream from Natural Gas Compressor Station (NG CS), which has been identified as a potential waste heat source, can be used to operate DCMD thereby providing economically viable option to treat high salinity produced water. An ASPEN Plus simulation of DCMD for the desalination of produced/saline water was developed in this study and calibrated using laboratory-scale experiments. This model was used to optimize the design and operation of large scale systems and estimate energy requirements of the DCMD process. The concept of minimum temperature approach used in heat exchanger design was

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The production of biodiesel via the transesterification of triglycerides by low molecular weight alcohols is generally inhibited by the poor mutual miscibility of the polar alcohol and the nonpolar oil. To overcome the hindrance that the initial phase separation imposes on the reactivity of such systems, some research groups have added carbon dioxide as a cosolvent, where this strategy allows for complete conversion of the triglyceride at moderate temperatures and relatively short reaction times. To date, however, it has not been clear what the best conditions for operating such a reaction might be. To explore this, the Polar-PC-SAFT and Group-Contribution-Polar-PC-SAFT were used to predict the phase equilibria of biodiesel related molecules at the very beginnings of the reaction (time t = 0). Depending upon temperature, pressure, and concentration conditions, the CO 2 + methanol + triolein system exhibits shifts between LLV, LL, and LV equilibria. It was found that if a particular concentration of CO 2 was employed, the ratio of methanol to triolein in the oil-rich phase could be maximized. A range of pressures (4 to 50 MPa) and temperatures (20−200 °C) have been investigated, and such optimal CO 2 composition values have been provided for each set of conditions.