From refining

If one talks henceforth about the necessity of matching an engine and its fuel, the demand for quality in motor fuels has, however, never ceased to be a preoccupation for refiners ever since gasoline became a commodity item. Two main classes of products are added to gasoline coming from refining octane number improvers and detergents. 

Manufacture of Monomers. The monomers of the greatest interest are those produced by oligomerization of ethylene (qv) and propylene (qv). Some olefins are also available as by-products from refining of petroleum products or as the products of hydrocarbon (qv) thermal cracking. 

Minor uses of vanadium chemicals are preparation of vanadium metal from refined pentoxide or vanadium tetrachloride Hquid-phase organic oxidation reactions, eg, production of aniline black dyes for textile use and printing inks color modifiers in mercury-vapor lamps vanadyl fatty acids as driers in paints and varnish and ammonium or sodium vanadates as corrosion inhibitors in flue-gas scmbbers. 

Dissolved Air Flotation. Dissolved air flotation (DAF) is used to separate suspended soflds and oil and grease from aqueous streams and to concentrate or thicken sludges. Air bubbles carry or float these materials to the surface where they can be removed. The air bubbles are formed by pressurizing either the influent wastewater or a portion of the effluent in the presence of air. When the pressurized stream enters the flotation tank which is at atmospheric pressure, the dissolved air comes out of solution as tiny, microscopic bubbles. Dissolved air flotation is used in many wastewater treatment systems, but in the United States it is perhaps best known with respect to hazardous waste because it is associated with the Hsted waste, K048, DAF flotation soflds from petroleum refining wastewaters. Of course, the process itself is not what is hazardous, but the materials it helps to remove from refining wastewaters. 

Positional parameters of the non-hydrogen atoms obtained from refinements I and II are in good agreement with those of SC (1980) or Dam, Harkema and Feil (hereafter DHF) [16] from X-ray data as well as those from neutron data [13, 17]. 

Waste-derived fuels from refining processes Fuels produced by refining oil-bearing hazardous wastes with normal process streams at petroleum refining facilities are exempt if such wastes resulted from normal petroleum refining, production, and transportation practices. For these wastes to be considered as refined, they must be inserted into a part of the process designed to remove contaminants. This would typically mean insertion prior to distillation. 

Many of the above processes may potentially be applicable to desulfurization of gaseous effluent streams produced from refining operations. The economics of the processes will have to be compared with existing processes to evaluate their commercialization potential. 

Fig. 4.—Alpha dextrose monohydrate from refined starch conversion liquor. Magnification, 50.

Cathode The primary functions of the cathode are catalyzing the O2 reduction and transporting the O2 ions to the electrolyte. Furthermore, the cathode should possess sufficient electronic conductivity to lead the electrons from the interconnect to the reaction sites. At practical operating conditions, the ionic conductivity of LSM is several orders of magnitude lower than its electronic conductivity. Therefore, in the single-phase and two-phase LSM type cathodes presented in the introduction the reaction sites are essentially at the TPBs of air, YSZ and LSM. Mixing the LSM with YSZ is one means, apart from refining the micro-... 

In summary, there are three important generalizations about error estimation in protein crystallography. The first is that the level of information varies enormously as a function primarily of resolution, but also of sequence knowledge and extent of refinement. The second generalization is that no single item of information is completely immune from possible error. If the electron density map is available or indicators such as temperature factors are known from refinement, then it is possible to tell which parameters are most at risk. The third important generalization is that errors occur at a very low absolute rate 95% of the reported information is completely accurate, and it represents a detailed and objective storehouse of knowledge with which all other studies of proteins must be reconciled. 

Fig. 40. A classic j8 bulge the model and electron density from refined trypsin residues Ser-214, Trp-215, and Val-227. Courtesy of Chambers and Stroud.

Fig. 47. The Xi angles observed for disulfides in protein structures. The examples from refined, high-resolution structures are shown separately at the top.

J Anharmonic in this table refers to the Fe atom only harmonic temperature parameters of the other atoms are fixed at values from refinement I. 

Ruthenium is derived from platinum metal ores. Method of production depends on the type of ore. However, the extraction processes are simdar to those of other nohle metals (see Platinum, Rhodium and Iridium). Ruthenium, like Rhodium, may he obtained from accumulated anode sludges in electrolytic refining of nickel or copper from certain types of ores. Also, residues from refining nickel by Mond carbonyl process contain ruthenium and other precious metals at very low concentrations. The extraction processes are very lengthy, involving smelting with suitable fluxes and acid treatments. 

Of great interest to the molecular biologist is the relationship of protein form to function. Recent years have shown that although structural information is necessary, some appreciation of the molecular flexibility and dynamics is essential. Classically this information has been derived from the crystallographic atomic thermal parameters and more recently from molecular dynamics simulations (see for example McCammon 1984) which yield independent atomic trajectories. A diaracteristic feature of protein crystals, however, is that their diffraction patterns extend to quite limited resolution even employing SR. This lack of resolution is especially apparent in medium to large proteins where diffraction data may extend to only 2 A or worse, thus limiting any analysis of the protein conformational flexibility from refined atomic thermal parameters. It is precisely these crystals where flexibility is likely to be important in the protein function. 

TABLE 2-6. Common Fuel Contaminants Resulting from Refining Processes... 

Copper can be present in fuel systems in the form of heating coils, cooling coils, brass fittings, or bronze parts. Copper is quite resistant to corrosion by water but can be attacked by ammonia and sulfur compounds. Finished fuels usually do not contain ammonia unless the ammonia somehow carries over from refining process operations. Sulfur compounds such as hydrogen sulfide and possibly elemental sulfur are more frequently the cause of copper corrosion problems in fuel systems. 

Meanwhile, extensive investigation of other of the many reactions by which tetraethyllead can be synthesized, such as the substitution of magnesium and other alkylating metals for sodium and of other ethyl esters for ethyl chloride, has led to the conclusion that none of these is likely to replace the lead-sodium-ethyl chloride method in the foreseeable future. Further reduction in cost would appear most likely to come from refinements in the existing process, and further reduction in operating hazards. One important factor in the cost is not susceptible to improvement by research—the cost of pig lead, which today represents about 18% of the selling price of tetraethyllead as motor fluid. The present price of pig lead is about three times that during most of the past 25 years. 

C- Can be prepd from refin ery gases resulting from the cracking of petroleum. 

Gerd Jacob Bensen.—Hot air passed through the sugar to dry it. Crystallized sugar placed in a vacuum pan. Crystals thus gat are mixed with a clear sirup produced from refined sugar the mixture put into moulds and stoned. 

Up to this point, the picture we have presented is quite clear and, aside from refined numerical details, accepted without reservations. It is in the search for the detailed mechanism for the NO + O chemiluminescent reaction that serious problems arise. As this field has been extensively reviewed recently by Schiff370 and by Spindler,396 we shall concentrate on the more significant aspects of the controversy. 

---