Solvent-based recovery

Fig. 1. General overview of a PHA production process. All PHA production processes consist of a fermentation and a recovery step, followed by polymer processing for specific applications. In many cases the fermentation is divided into two stages, a biomass production and a PHA accumulation stage (for further detail see text). Several methods for recovery of the material have been described, of which solvent-based and non-solvent-based recovery protocols are illustrated...

ZENECA has developed a non-solvent based recovery process as an alternative to solvent extraction for the commercial production of poly(3HB) and poly(3HB-co-3V) by A. eutrophus [94,95], In this process the cells were first exposed to a temperature of 80 °C and subsequently treated with a cocktail of various hydrolytic enzymes consisting of lysozyme, phospholipase, lecithinase, the proteinase alcalase, and others. Most of the cellular components were hy-... 

Recovery and Purification. AH processes for the recovery and refining of maleic anhydride must deal with the efficient separation of maleic anhydride from the large amount of water produced in the reaction process. Recovery systems can be separated into two general categories aqueous- and nonaqueous-based absorption systems. Solvent-based systems have a higher recovery of maleic anhydride and are more energy efficient than water-based systems. 

Sample Cleanup. The recoveries from a quick cleanup method for waste solvents based on sample filtration through a Elorisd and sodium sulfate column are given in Table 2 (40). This method offers an alternative for analysts who need to confirm the presence or absence of pesticides or PCBs. 

In contrast, the Biotechnologische Forschungsgesellschaft has used a solvent-based process for the recovery of poly(3HB) from A. latus. The cells were harvested by centrifugation and the poly(3HB) was subsequently extracted from the suspended cells with methylene chloride and precipitated from the solvent by the addition of water. After drying a polyester with 99% purity was obtained [15]. The process also included the recovery of the solvent. 

OGR [Off-gas recovery] A solvent-based technology for recovering olefins and/or hydrogen from FCC or coker off-gases. Developed by KTI. 

Thus there is considerable incentive to find extractants that could tolerate higher quantities of solids in H2SO4 leach liquors. Stripping of uranium from the Amex process extractant and subsequent regeneration of the amine solvent also consume considerable quantities of acid and base. Recovery of uranium from H2SO4 solutions would be simplified if a convenient neutral extractant could be found. An extractant with better selectivity for vanadium and molybdenum than HDEHP and long-chain amines is also desirable. 

A method for determining CDDs in municipal incinerator fly ash has been reported (Alexandrou and Pawliszyn 1990). The method uses supercritical fluid extraction (SFE) to recover CDDs from fly ash samples prior to GC. Supercritical fluid extraction is faster and less expensive than the typically used Soxhlet extraction and gives quantitative removal of CDDs and CDFs from fly ash. Extracts obtained using SFE will still require additional clean-up steps prior to analysis. Supercritical C02 has also been used to assist solvent-based extraction of CDDs from soils (Friedrich and Kleibohmer 1997). In this case, the supercritical fluid was combined with accelerated solvent extraction (liquid extractions conducted under elevated temperature and pressure) to provide good recoveries relative to Soxhlet extractions. 

Several recommendations arose from the interlaboratory smdy to minimize analytical challenges and to ensure data quality. As discussed above, it is recommended that mass labelled PFCs be employed as internal standards [93, 97]. It should be noted, however, that some electrospray ionization suppression may still occur if these internal standards are used at high concentrations [97]. Matrix effects can also be minimized by employing matrix-matched calibration standards in lieu of solvent-based calibration standards [97]. Unfortunately, matrix-matched standards can be impractical when an appropriate clean matrix cannot be found [94]. Other quality assurance and quality control measures, such as spike and recovery analyses of an analyte added to the sample matrix, repetitive analysis of samples to determine precision and comparison of internal standard quantitation to quantitation via standard additions, are also useful in determining data quality [94]. 

These inks contain high concentrations of low-boiling solvents, and the usual practice is to dilute them further in the press room. The large volume of solvents emitted makes incineration impractical, but these solvents may be absorbed on activated charcoal, and removed l steam distillation when the charcoal is saturated. The recovered solvents may be re-used or sold however, it may be impractical to fractionate some recovered solvent blend that boil in the same temperature range, which lessens their value considerably. Therefore, although this approach is also technically and economically feasible, the difficulty in procuring the solvents used for dilution may restrict the continued use of these solvent-based inks and, hence, the adoption of solvent recovery approach. 

This case study involves the recovery of highly valued and high demand ethylbenzene (EB) and mixed-xylenes (comprising of p-xylene (PX), m-xylene (MX) and o-xylene (OX)) from a C8-aromatics mixture (C8A). As point out above, C8A is isomers mixture, so their separation (recovery) is not simple, that why there is only one commercial process of liquid-phase adsorptive separation available for EB recovery from C8A. [8] However, this process requires high investment cost and generates huge volume of waste adsorbent that may become an environmental problem. Therefore, another green process should be considered for the EB purification. The ratio of various properties of the key components (EB and PX) were tested to examine the possibly alternatives. The result showed, by vapor pressure ratio, the solvent-based extractive distillation can be employed for their purification. [7]... 

Murphy (1981) reported the analysis of genistin, daidzin and their aglycones and coumestrol in toasted, defatted soy flakes by HPLC without the use of external standards. Twelve extraction combinations with methanol, chloroform-methanol, acetonitrile and acetone, with or without water, and HC1 were compared. The addition of water or HC1 to the extraction solvents improved recoveries. Acetonitrile-HCl-water was found to co-extract less impurity. Based on the studies, three best... 

Research on solvent based polymer separation processes is by no means in its infancy. One of Ae first studies on mixed plastics was conducted by Sperber and Rosen [24,25] in the mid 1970 s. These investigators used a blend of xylene and cyclohexanone to separate a mixture of polystyrene (PS), poly(vinyl chloride) (PVC), high density polyethylene (HOPE), low density polyethylene (LDPE), and polypropylene (PP) into three separate phases. In adAtion, many United States and foreign patents dating from the 1970 s were granted for the solvent recovery of thermoplastic jwlymers [26-30]. The interest in solvent processes waned in the late 1970 s as the oil crisis eased, but the growing need to develop solutions to Ae solid waste problem has renewed Ae research effort [31-33]. 

A. M. Baniel, A. M. Eyal, and J. Mizrahi, Acid-base solvents in recovery of mineral acids from waste streams, Proceedings of 2nd Int. Conf Sep. Sci.,... 

The Pd is leaching and is redeposited at the end of the reaction, which provides an excellent recovery of the precious metal from the reaction mixture. The precipitation of the catalyst at the end of the reaction significantly changes its state and decreases its activity, however, making its re-use unattractive. Kohler et al. also showed that optimization of the Pd/C catalyst (temperature, solvent, base and Pd loading) allows turnover frequencies (TOFs) of up to 9000 to be reached and Pd concentration down to 0.005 mol% to be developed for the Heck reaction of unac-tivited bromobenzene at 140 °C [44]. The turnover numbers (TONs) are surpassed, however, by those of the best homogeneous catalysts. 

---