Although most of the metallic constituents of crude oil are concentrated in the residues, some of the organometallic compounds are actually volatilized at refinery distillation temperatures and appear in the feed to the FCC cracking units. Metal contents in the feedstock be likely to deposit on the matrix of FCC catalysts where they catalyze the burning of carbon in to carbon monoxide. In general, only a part of the total (25-30%) deposited metal is active. Nickel in FCC feed and iron scale are leading sources of such contaminants. Iron scale can be a cause of afterburning problems in the flue gas lines, cyclones, and dilute phase of the regenerator. Other metal contents for example lead, sodium, and vanadium will be active as poisons to the active precious metal contained in CO oxidation promoters. major raises in contents level will boost the severity and consumption rates for CO promoters. since the compounds of these metals cannot, overall, be removed from the cracking unit as volatile compounds the common approach has been to passivate them or render them harmless under the conditions that are come acrossed during the cracking process. Incorporation of additives into the cracking catalyst or separate particles that merge with the metals and therefore perform as "traps" or "sinks" in order that the active zeolite component is protected is one of the passivation method. The metal contents with some portion of catalyst are removed together from the system during its normal operation and added fresh metal trap together with makeup catalyst so as to affect a continuous pulling out of the deleterious metal contaminants throughout operation. Depending upon the level of the undesired metals in the feed to the unit, the quantity of additive may be varied relative to the makeup catalyst in order to attain the desired degree of metals passivation.
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The on hand metal passivator are divided or clasified into two categories in terms of function and role, i.e. the single-function metal passivator like nickel passivator or vanadium passivator composed of single effective metal for example Sb, Sn or Bi; and difunction metal passivator composed of more then metals like Sb--Sn, Sb--Bi, Sb--Re, etc which can at the same time passivate nickel and vanadium. Metal passivators can be added in to two ways: one is to insert it to the reactor with the catalytic cracking feedstock and this method is typically applied for the liquid metal passivator. The other is to combine it to the reactor with the catalyst and this method is generally applied for solid metal passivator for example vanadium trapping agent. Many patents described the additives proposed for this reason include the alkaline earth metals and rare earths such as lanthanum and cerium compounds [1-8]. These materials which are typically in the oxide form at the temperatures encountered in the regenerator most probably exhibit a high reaction rate with vanadium to yield a stable, complex vanadate species which effectively binds the vanadium and stops degradation of the active cracking component in the catalyst.
To passivate the activity of vanadium and nickel on FCC catalyst, antimony and tin are used. The reason of their use is to reduce the making of gas caused by the metals catalyzed dehydrogenation. Their result on CO promotion catalysts is to decrease their activity as well. Thus, the severity of the promotion application and the possibility of after burn problems will be increased as the increased use of passivators. .
In biochemical method a biocatalyst consisting enzyme which degrags porphyrine molecule is used by contacting it in an aquas medium. Embodiments of the biocatalyst can be cytochrome C reductase and heme oxygenase, for example cytochrome C reductase from Bacillus megaterium, Escherichia coli, catharanthus roseuse, plant cells, animal cells or yest cells.
Hossein Salehizadeh et. al. achieved 55% microbial degradation of vanadium oxide octaethyl porphyrin (VOOEP) by mircroorganism Aspergillus sp.MS-100, when the temperature was 30 ï‚°C, pH was 7.0, and the concentration of VOOEP was 20 mg/l for 7 days. Mircroorganism Aspergillus sp.MS-100 were isolated from polluted soil at the Isfahan refinery, Isfahan, Iran .
In an US patent metals were removed from fossil fuel by contacting it (aquas medium) with a biocatalyst chosen from the group consisting of an enzyme which degragds the molecule of porphyrine. Embodiments of the biocatalyst are heme oxygenase and cytochrome C reductase, such as cytochrome C reductase from Bacillus megaterium, catharanthus roseuse, Escherichia coli, animal cells, plant cells or yest cells .
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The effect of cationic starches on removal of nickel and vanadium from crude oils in the presence of microwaves was investigated. A series of cationic starches with different degrees of substitution (DS), synthesized by a microwave-dry process, were used to remove nickel and vanadium from crude oils. The effects of a number of factors, such as the degree of substitution of cationicstarches, microwave time and cationic starches dose on nickel and vanadium removal rates from the crude oils were investigated. The results indicate that the higher the degree of cation substitution on the cationic starch, the greater the effect of electrostatic adsorption of the heavy metal positive ions. Sample SC4 had the highest degree of substitution in the cationic starch series and had the highest effect on nickel and vanadium removal rates. The optimum conditions for nickel and vanadium removal from crude oils were as follows: (a) amount of SC4 200 mg/L, (b) microwave power 300 W and (c) microwave time 5 min. Under these conditions, the removal rates of nickel from Iranian and Shengli crude oils were 55.33 and 59.64%, respectively, and the removal rates of vanadium were 76.19 and 78.70%, respectively .
The asphaltene fraction [hexane insoluble (HI)] of a vacuum residue (VR) was treated under ultrasonic irradiation at 40Â°C in Tetra hydro furan (THF) or 150Â°C in 1-methylnaphthalene (1-MN) in the presence of an adsorbent composed of modified macro-reticular polystyrene resin. Such a treatment was found effective to convert the asphaltene into the hexane soluble (HS: maltene) without any hydrogen consumption. 61 and 72% of the HI was converted by the adsorption treatment at 40Â°C in THF and 150Â°C in 1-MN, respectively, to HS materials having lower molecular wts. About 65% of the metal contaminants in the original asphaltene remained with the newly formed maltenes after this treatment. Structural analyses of the asphaltene and maltene fractions before and after the treatment suggests decoagulation and/or depolymerisation of the asphaltene into maltene, while the porphyrin moiety becomes soluble, being transformed to the maltene fraction. The roles of polar solvent, ultrasonic irradiation, and adsorbent are discussed based on the above results .
A feasibility study of the decomposition and demetalation of metalloporphyrins by ultrasonic irradiation is presented in a paper by Tu and Yen. Two representative model compounds, NiTPP and VOTPP, were investigated in this ultrasonic process on the laboratory scale. The extent of the decomposition was detected by UV-visible. The metals were measured by ICP/MS. In the initial investigation, the decomposition of metalloporphyrins, which were dissolved in different solvent-water mixtures, was performed under the ultrasonication process. Among these solvents, the chlorinated-type solvents (e.g., chloroform and dichloromethane) achieved a higher efficiency because they generated more oxidizing species under sonication at 20 kHz frequency. Other additives such as surfactant and hydrogen peroxide, which affect the decomposition efficiency, were also investigated. Under optimal condition, the decomposition efficiency reached about 90% in 1 h for both model compounds. An oxidative intermediate existed for both metalloporphyrins under ultrasonication. The decomposition reaction rates of these two compounds followed pseudo-first-order in reactant concentration and were inhibited by initial feed concentration. The dependence of the rate constants on the different initial concentrations could be determined by the Langmuir Hinshelwood equation .
Yasuhiro Shiraishi et. al. studied simultaneous photoreaction and extraction process, employing an oil/water two-phase system. The results for the demetalation, obtained for vanadyl(IV)- and nickel(II)tetraphenylporphyrin dissolved in tetralin, were compared with those obtained for actual atmospheric residue oil. It was found that photochemical reaction was able to demetalize "free"-type metalloporphyrins, but had difficulty in the demetalation of "bound"-type metalloporphyrins, which are associated strongly with the asphaltenic molecules in residue oil. To weaken this association and thus convert the bound type metalloporphyrins to the free-type ones, a hydrogen-donating polar solvent, 2-propanol, was added to the residue oil and photoirradiated. The 2-propanol was then removed by evaporation, and the resulting residue oil was contacted with aqueous HCl solution, into which the resulting vanadium and nickel were successfully removed. According to this latter development of the process, 93% vanadium and 98% nickel were recovered from atmospheric residue and 73% vanadium and 85% nickel from vacuum residue, respectively. The overall demetalation process, involving the recovery of the 2-propanol, has been formulated as an energysaving and safe demetalation process, which is satisfactory for application in the upgrading of heavy residual feedstocks .
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Myers et al. (1997) reported an improved sodium desulphurization and demetalation process that was developed by a consortium of three companies comprising Imperial Oil Resources (Esso), Exxon R&E Company, and AEA Technology. The technology was used for the treatment of high-sulfur bitumen .
Removal of Ni and V from crude oils by cationic starch in the presence of microwave irradiation 
% Removal Rate
With out Microwave
In the presence of Microwave