Residues solvent separation

Deasphalting is a liquid-liquid separation operation that extracts the last of the easily convertible hydrocarbons from the vacuum residue. Solvents enipl ec) are light paraffins propane, butane, and pentane. The yimd In deasphalted oil increases with the molecular weight of the solvent, but its quality decreases. 5 uxct... 

British Coal Corp. is developing a gasoline-from-coal process at a faciUty at Point of Ayr (Scotiand). This process involves treatment with Hquid recycle solvents, digestion at 450—500°C, filtration to separate unconverted residues, and separation into two fractions. The lighter fraction is mildly hydrotreated, and the heavier one is hydrocracked (56). 

The reaction takes place at low temperature (40-60 °C), without any solvent, in two (or more, up to four) well-mixed reactors in series. The pressure is sufficient to maintain the reactants in the liquid phase (no gas phase). Mixing and heat removal are ensured by an external circulation loop. The two components of the catalytic system are injected separately into this reaction loop with precise flow control. The residence time could be between 5 and 10 hours. At the output of the reaction section, the effluent containing the catalyst is chemically neutralized and the catalyst residue is separated from the products by aqueous washing. The catalyst components are not recycled. Unconverted olefin and inert hydrocarbons are separated from the octenes by distillation columns. The catalytic system is sensitive to impurities that can coordinate strongly to the nickel metal center or can react with the alkylaluminium derivative (polyunsaturated hydrocarbons and polar compounds such as water). 

Solvent extraction may also be used to reduce asphaltenes and metals from heavy fractions and residues before using them in catalytic cracking. The organic solvent separates the resids into demetallized oil with lower metal and asphaltene content than the feed, and asphalt with high metal content. Figure 3-2 shows the IFP deasphalting process and Table 3-2 shows the analysis of feed before and after solvent treatment. Solvent extraction is used extensively in the petroleum refining industry. Each process uses its selective solvent, but, the basic principle is the same as above. 

There are generally two types of analyses that are requested with reference to solvents. The first is the identification of residual solvents in products, and the second is the identification of impurities in common industrial solvents. Certain GC conditions have been found to separate most of the common solvents. Always examine the mass spectra at the front and back of the GC peaks to determine if they are homogeneous. Also remember that isomers may not be detected by this approach if they are not separated. 

Nearly all polymerization processes and products require a post-reaction process to remove and reduce to an acceptable level residual monomer(s), solvent or diluent. End use properties can be adversely affected by high levels of residuals through toxicity, odor, or poor physical properties. In the cases of residual solvent or diluent, a separation process involving the evaporation of the volatile components (devolatilization) can be used. Devolatilization can be used for residual monomer removal, but completing the polymerization of monomer is an attractive alternative when applicable. Polymerization finishing is usually accomplished with an increase in temperature to kick-off a finishing initiator or the addition of an initiator. (D For the dispersion... 

Microcapsules of PCL and its copolymers may be prepared by aircoating (fluidized bed), mechanical, and, most commonly, solution methods. Typically, the solution method has involved emulsification of the polymer and drug in a two-phase solvent-nonsolvent mixture (e.g., CH2Cl2/water) in the presence of a surfactant such as polyvinyl alcohol. Residual solvent is removed from the tnicrocapsules by evaporation or by extraction (70). Alternatively, the solvent combination can be miscible provided one of the solvents is high-boiling (e.g., mineral spirits) phase separation is then achieved by evaporation of the volatile solvent (71). The products of solution methods should more accurately be called microspheres, for they... 

Singh, R. Khwaja, A. R. Gupta, B. Tandon, S. N. Extraction and separation of nickel(II) using bis(2,4,4-trimethylpentyl) dithiophosphinic acid (Cyanex 301) and its recovery from spent catalyst and electroplating bath residue. Solvent Extr. Ion Exch. 1999, 17, 367-390. 

Property measurements of fullerenes are made either on powder samples, films or single crystals. Microcrystalline C6o powder containing small amounts of residual solvent is obtained by vacuum evaporation of the solvent from the solution used in the extraction and separation steps. Pristine Cgo films used for property measurements are typically deposited onto a variety of substrates (< . , a clean silicon (100) surface to achieve lattice matching between the crystalline C60 and the substrate) by sublimation of the Cr,o powder in an inert atmosphere (e.g., Ar) or in vacuum. Single crystals can be grown either from solution using solvents such as CS and toluene, or by vacuum sublimation [16, 17, 18], The sublimation method yields solvent-free crystals, and is the method of choice. 

Thus, P.Y.108 is commercially produced by heating l,9-anthrapyrimidine-2-carboxylic acid with 1-aminoanthraquinone and thionyl chloride in a high boiling solvent, such as o-dichlorobenzene or nitrobenzene, to 140 to 160°C. The product is separated, washed with methanol, and residual solvent removed by steam distillation. The aqueous suspension is then boiled down with sodium hypochlorite solution. 

Figure 4.4 Effect of TFA concentration on peptide retention. A series of five synthetic peptides containing 0, 1,2, 4, or 6 basic residues were separated on an octadecyl reversed-phase column using a 1%/min linear gradient from water to acetonitrile. Both solvents contained TFA at the indicated concentrations. (Reproduced from D. Guo, C.T. Mant, and R.S. Hodges, J. Chromatogr., 386 205 [1987]. With permission from Elsevier Science.)...

In common with all capillary-based techniques, modem GC offers high-efficiency separations, allowing analyte resolution even with relatively low selectivity differences. Flame ionisation is now the most common form of detection used for organic analytes in GC and is universal for hydrocarbon-containing species. Although achiral GC is used widely in the pharmaceutical industry for the analysis of residual solvents and volatile analytes, its apphcation to chiral analysis tends to be limited to chiral raw materials and smaller intermediates. As the mobile phase is a gas, only volatile analytes are applicable to analysis by GC, often precluding its use for the analysis of relatively large, complex API molecules. Moreover, analyte molecules also need to be thermally stable to the temperatures required to ensure volatilisation [114]. 

Residual solvents are organic volatile chemicals that remain in active substances, excipients, and other pharmaceutical products after processing. In spite of their toxic properties, solvents play an important role in the production of pharmaceuticals, during the synthesis, separation, or purification, and their use cannot be avoided. Solvents in this category do not include those used as excipients. 

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