Processes demetalation

The University of Osaka is the holder of two patents regarding the least studied biorefining processes, demetallization, and bioconversion. The metals are removed from the fossil fuel, under mild conditions (room temperature and atmospheric pressure) by the microbial oxidation action and a UV-photochemical reaction [166], The bioconversion refers to conversion of high molecular weight alkanes by the action of B. thermoleovorans B23 and B. thermoleovorans H41 strains to lower molecular weight molecules [167],... 

Most mordant dyes are monoazo stmctures. The most important feature of this class of dyes is excellent fastness to light and washing. Mordant dyes are available ia aU shades of the spectmm with the exceptioa of bright violets, blues, and greens. To be useful, the metal complexes must be stable, ie, must not demetallize when subjected to dyebath conditions and aU aftertreatment processes, especially repeated washings. Chromium forms stable chelate rings with mordant dyes which are not affected by treatment with either weak acid or alkaU (see Coordination compounds). 

Consider the oil-recycling plant shown in Fig. 3.16. In this plant, two types of waste oil are handled gas oil and lube oil. The two streams are first deashed and demetallized. Next, atmospheric distillation is used to obtain light gases, gas oil, and a heavy product. The heavy product is distilled under vacuum to yield lube oil. Both the gas oil and the lube oil should be further processed to attain desired properties. The gas oil is steam stripped to remove light and sulfur impurities, then hydrotreated. The lube oil is dewaxed/deasphalted using solvent extraction followed by steam stripping. 

Residues containing high levels of heavy metals are not suitable for catalytic cracking units. These feedstocks may be subjected to a demetallization process to reduce their metal contents. For example, the metal content of vacuum residues could be substantially reduced by using a selective organic solvent such as pentane or hexane, which separates the residue into an oil (with a low metal and asphaltene content) and asphalt (with high metal content). Demetallized oils could be processed by direct hydrocatalysis. 

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. 

The largest investment has been in desulfurization, and in most instances it has been proven that the sulfur compounds have been transformed into oxidized moieties, but the actual cleavage of the last C—S bond in most cases does not take place to the extent desired or to levels needed for implementing BDS. Other processes such as demetallization and upgrading are just starting to be studied. Collateral technologies, for gas treatment and reducing viscosity by emulsification ( in well treatments) are commercially available. 

In contrast, electrocatalysis in a nonaqueous solvent like dichloromethane with soluble palla-dium(II) and silver(II) porphyrins produces mainly oxalate.145 However, demetallation rapidly deactivates the catalysts. In these cases the catalytic processes are interpreted in terms of reduced forms of the macrocyclic ligand, rather than by formation of Pd1 or Ag1 species following metal-centered reduction. 

Based on studies showing that the close proximity between the porphyrin and the Cm is essential for the observation of an electron transfer process, Fukuzumi and co-workers have prepared the porphyrin-C6o diad 41, in which the C6o-pyrrolidinyl moiety is directly connected to the meso position of the porphyrin macrocycle (Scheme 12) <03JPC(A)8834>. The strategy adopted for the synthesis of the starting porphyrin involved the 2+2 condensation of a maso-unsubstituted dipyrrylmethane with 3,5-di-tert-butylphenyl-substituted dipyrrylmethane and 3,5-di-tert-butylbenzaldehyde, to give 39, in 11.5% yield. Subsequent Ni(II) metallation, followed by Vilsmeier-Haack formylation and demetallation, gave rise to 40 which was used as the 1,3-dipole precursor this dipole in the presence of N-methylglycine and C6o, yielded the expected diad 41. 

DEMET (2) A process for removing metal contaminants from spent FCC catalysts by a series of pyrometallurgical and hydrometallurgical procedures. These typicaly include calcination, chlorination, and sulfiding. The demetallized catalyst can be re-used. Developed by ChemCat Corporation, LA, in 1988 first operated commercially in New Jersey in 1989. Now operated by Coastal Catalyst Technology. 

Demex [Demetallization by extraction] A process for removing metal compounds from heavy petroleum fractions, after vacuum distillation, by solvent extraction and supercritical solvent recovery. The solvent is typically a mixture of octanes and pentanes. Developed jointly by UOP and the Institute Mexicano del Petroleo seven units were operating in 1988. Hydrocarbon Process., 1988, 67(9), 66. 

Using a one-pot process of oxidative cyclization in air, the arylamine 780a was transformed to the tricarbonyl(ri -4b,8a-dihydro-9H-carbazole)iron complex 792. Finally, demetalation of 792 and subsequent aromatization gave carbazomycin A (260). This synthesis provided carbazomycin A (260) in three steps and 65% overall yield based on 602 (previous route four steps and 35% yield based on 602) (610) (Scheme 5.88). 

The formation of sandwich-type POMs from solutions of metal cations and triva-cant heteropolytungstate species may alternatively be viewed as means to sequester cations from solution [116]. The question then arises if reversible dissociation of the metal cations from the multidentate ligands is possible as well. The sequestration and subsequent release of metal cations under appropriate conditions is of considerable interest in waste decontamination technology as well as in medicine [124]. Following these ideas, the demetallation process of ten multi-iron Wells-Dawson polyoxometalates is studied by cyclic... 

Specifically, Fig. 20 shows representative slow potential scan rate cyclic voltam-mograms of Fe4P4 and Fe4As4 in a pH = 3 solution and also as a function of ionic strength for this last complex. A demetallation process of the reduced POMs was detected as appears on this figure. Detailed study of the whole process... 

In this work, a chemical demetallization agent was used to convert entrained non-filterable metals into a form which could be effectively removed by filteration or sedimentation. Waste oils were demetallized by diammonium phosphate (DAP). A detailed parametric study was undertaken to map out the process variables so as to identify the most efficient demetallization conditions. 

Equipment. A three-neck distillation flask was used as a reactor. In a typical run, the flask was charged with waste oil and demetallizing reagents. The content was agitated and heated by a mechanical stirrer and heating mantle respectively. The reaction was carried out at atmospheric pressure, and water vapor and light ends were condensed and collected during the process. Oil was filtered immediately after the reaction by means of a vacuum filteration system, or allowed to settle down at constant temperature for a sedimentation study. 

The demetalation process was followed by absorption spectrophotometry (measurement of the decay, as a function of time and cyanide concentration, of the di-copper(I) complexes characteristic metal-to-ligand-charge-transfer (MLCT) bands in the visible region [111]) which gave access to the kinetic parameters, in particular to the second-order dissociation rate constants CN given in Table 1. 

Figure 26. Schematic representation of the demetalation process which occurs (a) in two consecutive distinct steps for the face-to-face complexes (b) in an apparent single step for the trefoil knots complexes. 5 F r...

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