We demonstrate that removal of oxygen and metals from crude algae oils produced by hydrothermal treatment processes is possible by thermal means alone and without the use of catalysts or hydrogen. Thermal treatment can reduce the total amounts of acids in the crude algae oil and thus decrease the total acidity of the oil. Thermal treatment also reduces the boiling point range of crude algae oils, making them more volatile and less viscous, benefitting shipping and upgrading. Trace metals are significantly reduced as the thermal treatment temperature increases. The results obtained in this study are consistent with existing theories of the formation of petroleum crude oils and create a link between the upgrading of crude algae oils and the mechanisms involved in the formation of conventional fossil fuels. The results and possible pathways of the reaction mechanisms are presented.

ABSTRACT:The sorption and transport of water vapor in five dense polyimide membranes were studied by thermogravimetry. The sorption isotherms of water vapor in the polyimides could be successfully interpreted by both the dualmode sorption model and the Guggenheim-Anderson-de Boer equation. The water vapor diffusion behavior was found to be nearly Fickian at higher water vapor activities, whereas non-Fickian diffusion was observed at lower water activities. The phenomena could be well described by the mechanism of combined Fickian and time-dependent diffusion. The diffusion coefficient and water vapor uptake in the polyimides were strongly dependent on the polymer molecular structure. Except for the polyimide prepared from 3,3Ј,4,4Ј-diphenylsulfone tetracarboxylic dianhydride and 1,3-bis(4-aminophenoxy) benzene, the permeability of water vapor in the dense polyimide membranes predicted from the sorption measurement at 30°C corresponded well with the water vapor permeability measured at 85°C. Among the polyimides studied, pyromellitic dianhydride-4,4Ј-diaminophenylsulfone (50 mol%)/4,4Ј-oxydianiline (50 mol%) showed both high water sorption and diffusion and, therefore, high water vapor permeability, which for vapor permeation membranes is necessary for the separation of water vapor from gas streams.

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Asymmetric integrally skinned capillary tubes were produced from the polymers PEI (polyetherimide) and PVP (polyvinylpyrrolidone) for vapour permeation modules which were applied for the separation of water from organic compounds and gases. Water treatment and recovery of desirable organic compounds was achieved. The capillary tubes had intrinsic permeability coefficients of 7.5 x I@' mol/m2+Pa for water and 1.6 x IC9 mol/rn'.s.Pa for 1 -propano1 for a 1 : 1 mass ratio vapour feed mixture under pyrolysis conditions. The vapour was fed at the interior of the capillary tubes with total pressure of 30 kPa; the permeate total pressure was 14 kPa, and the temperature was 86°C. Modules, with surface areas up to 1.0 m2, were constructed and tested with feed flow rates as high as 4 kg/h with a process development unit. Tests were performed with the vapours from wood chips and contaminated soils subjected to vacuum pyrolysis. he application of vapour permeation membranes to T industry is very recent. However, it is rapidly growing, aided by previous experience with reverse osmosis and pervaporation technology. The first industrial vapour permeation application was in 1989 (Sander and Janssen, 1991; Sander, 199 1) using flat sheet composite membranes originally designed for pervaporation for the dehydration of ethanol from 94% to 99.9%. Will and Lichtenthaler (1 992a,b) showed that polyvinyl alcohol/polyacrylonitrile composite membranes can be used for the separation of water/alcohol mixtures by pervaporation and vapour permeation. Deng et al. (1995) prepared flat sheet asymmetric polyetherimide (PEI) membranes and studied the recovery of solvents from air exhaust streams. Tanihara et al. (1992) prepared polyimide hollow fibers to study the separation of alcohol/water mixtures by vapour permeation.Regarding the effect of polyvinylpyrrolidone (PVP) additive to the casting solution, Cabasso et al. (1 976) made an intensive study. Miyano et al. (1990) showed that residual PVP remained in the membrane even after extraction of PVP in the gelation bath.

Attempts were made to develop solvent-resistant polyimide capillary membranes with integrally skinned asymmetric structure to be used for the treatment of wood dryer emissions or vacuum pyrolysis aqueous effluents. Model mixtures of 1-propanol (1-PrOH)/H 2 O and acetic acid (AA)/H 2 O, with concentrations of 10 -90 wt % of organic components, were used as vaporous feeds. Solvent-resistant membranes with good mechanical and excellent vapor separation properties were prepared from polyimides based on PMDA and BPDA by the dry/wet phase-inversion technique. Molecular structure largely influences membrane properties. For the asymmetric polyimide membranes studied, a tendency similar to that of homogeneous dense membrane was found. Membranes prepared from polyimides with diamine and dianhydride moieties, both containing rigid backbone and aromatic rings, displayed higher permeability and selectivity. Test conditions exhibited influences on membrane separation performance. Membranes prepared from copolyimide BPDA-50DDS/50ODA and PMDA-50DDS/ 50ODA exhibited the best mechanical and chemical properties as well as water vapor separation properties, which are considered to be of practical usefulness for applications of these membranes in the removal of water from water/organic mixtures. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 139 -152, 2002