Jorge, 2 C. Rojas 1. Empleando la tecnica de cronoamperometria y un bano de sulfato de amonio ferroso, se electrodeposito una pelicula de hierro sobre un electrodo de plata. El analisis EPMA indico que la pelicula de hierro presentaba islas de plata de diferentes tamanos, en toda el area. Using chronoamperometry technique and a ferrous ammonium sulphate bath, an iron film was electroplated on a silver electrode. Analysis EPMA indicated that the iron film presented islands of silver of different sizes in all the area.
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V and Ni electrochemical deposition from asphaltenes in heavy oils. William H. Heavy metals are present in porphyrins in oil asphaltenes. High content of V and Ni could be attractive to produce high value metal oxides. These metals are undesirable due to corrosion issues and catalyst contamination in cracking processes. High resolution analytics before and after the deposition was done: elemental analysis, FT-IR, and atomic absorption.
The variables as work potential, reaction time and electrode materials during the electro-reduction was evaluated by cyclic voltammetry and chronoamperommeter in two solutions: I Tetrahydrofuran and LiClO 4 at 0. Results are discussed compared with traditional method of demetallization by acid digestion.
Keywords : Asphaltenes, clectrochemical cell, cyclicvoltametrics, heavy oils, V and Ni metals. Light Oil reserves are depleting and needs for transportation fuel liquids poses new problems to Refineries in order to meet the growing demand.
Research and development in heavy oils has dramatically raised in last years Campetrol, specially focus on resin-asphaltene concentrates CRA. For example one of these basins Llanos Orientales, counts on 6, MMbbl to , MMbbl probable reserves and actually participate with Refining the heavy oils in the near future will help to solve production of fuel liquids for transportation.
Nature and structure of both resins and asphaltenes strongly depend on the origin of the oil Nomura et al. Heavy oil from same reservoirs can show different properties Tharanivasan, D are the most used methods for separation and characterization of asphaltenes and resins.
Usually research laboratories use the precipitation of these components with aliphatic solvents and extraction with toluene in a Soxhlet reflux system, allowing a good separation of resins from asphaltenes Aske, Citations on different models of the asphaltene structure are found, being one of them a model that considers a pillared layers of aromatic structures array Leyva et al. Resins and asphaltenes content in a concentrate type CRA generate industrial and environmental issues because they are highly viscous, high sulfur content, and contains more than 28 metals in form of traces of Pb, V, Ni, Cr, TI, Fe and Al Welter et al.
Metal concentration depends on origin of oil. Some authors reports vanadium content 1. Demetallization by electrolysis is a new route that might be used at moderated conditions of temperature in an convenient mix of solvents in a electrolytic solution.
Vanadium and nickel that deactivate hydrocracking catalyst are present in two forms: heterocyclic porphyrins reported by Treibs A. Al laboratory level the most common method for determination of V and Ni is the acid digestion with strong organic acids at high temperature generating corrosive vapors. Clean alternatives of demetallization are electrochemical processes as the one proposed by Welter et al.
With oil porphyrins extractions rates were The factors that affect this method: electrolytic solution, electrode material, time of reaction and reduction potential.
In this research the electrodeposition was carried out in two solutions evaluating the effect of electrochemical variables by voltammetric determination in the extraction of V and Ni from Castilla heavy crude oil on different electrode materials.
Acid wet digestion for metal extraction. Probes of CRA and asphaltenes weight 3. Quantification of metals was done in a Spectrometer Perkin Elmer , at working conditions shown in Table 1. An electrochemical cell was designed for experiments previous to electrolysis. A second cell with three compartments as seen in figure 2 with a volume probe capacity of ml and a heating jacket with thermostat was built.
Working electrode was a graphite bar with a O content 5. A SEM analysis was also taken as shown in figure 3. Conterelectrode was built with a Pt wire 0. A silver wire 2 cm length immersed in a 0. Experiments on a potentiostat Autolab M were done to evaluate the effect of electrochemical variables potential screen, reaction time and electrode materials for the electrodeposition in the two mentioned electrolytic solution by voltamperommetry.
Experiments were done at different scanning velocities from 0 to mV vs. A solution with 90 ml Li Cl O 4 , 0. Electrodeposition was carried at conditions that were previously determined. All the experiments were at room temperature and the time of the reaction was 24 hours under agitation. To obtain the chronoamperommetry for Castilla crude oil 5g were added to a solution with ml LiClO 4 0. Measurements were done with permanent agitation at a constant potential either Purge was done every time with Nitrogen during 10 min.
Concentrate content CRA in Castilla crude oil was determined as Also resin content 2. A less content of C and H in asphaltenes is found due to the resin elimination. Both probes give bands associated to a N-H bond.
Using equation 1 that relates absorbance and metal concentration a content of 4. Effect of electrolytic medium on the metal recuperation by electrochemical way by means of VC was studied. Electrolytic medium on Pt does not show associated peaks with reactions on the catalyst in the interval of potential measurements. On the graphite electrode surface as working electrode figure 8 , no peaks were observed in the voltamperommetric experiments.
That indicates that the chosen potential interval is the adequate. In figure 9a is shown the voltamperogramm of Castilla crude oil in acetonitrile, observing a reduction wave nearby to In figure 9b peak of the radical anion formation appears at With the purpose to find the reaction time the probe stayed in contact with the working electrode for 15 hours, finding that the peak at Chronoamperommetry Castilla crude is shown in figure It can be observed a typical current characteristic, that it means than the species on the electrode surface are slowly diminishing with time.
It is remarkable that under constant and mild agitation concentration on electrode active surface can reach a stationary value current. Respecting to V and Ni concentrations the molar relation mM of V:Ni was calculated and resulted in a value of With this molar relation and the C charge obtained from the chronoamperommetry of Castilla crude the V and Ni mass deposited was calculated as 2,37x10 -5 g.
Concentration of V and Ni metals determined by atomic absorption in this work was greater in an order of magnitude than the concentrations reported by Colombian Oil Institute for the same probes of Castilla crude oil.
With the experimental data obtained by cyclic voltammetry a potential threshold of 0 to -2, V was determined. In this interval the medium does not present reduction peaks or collateral reactions that could affect Castilla crude oil probe.
Besides, it was possible to find the reaction time for the probe in contact with working electrode as 15 hours, finding the peak at It was chosen the best graphite material with less impurities for the elaboration of the working electrode referred to SEM technique.
Electrodeposition reaction is slow and is affected by electrochemical factors as reaction time and the yield of the process. The low deposition of the metals V and Ni by this electrochemical technique is probably due to the quantity of other metals present in crude oil that interfere, because they form different structures of organic and non organic compounds like Cl and S salts that are known to be in crude oil. Ali, M. A review of methods for the demetallization of residual fuel oils.
Fuel Process. Aske, N. Doctoral Thesis, Department of Chemical Engineering. Method A: Determination of nickel, vanadium, Fe and Na in crude oils and residual fuels by flame atomic absorption spectroscopy. Campero, B. Distribution of vanadylporphyrins in a Mexican off shore heavy crude oil.
Crudos pesados un nuevo horizonte , 2. The determination of trace elements in crude oil and its heavy fractions by atomic spectrometry. Part B. Fish, R. Khuhawar, M. Determination of metal ions in crude oil. Leyva, C. Chemical characterization of asphaltenes from various crude oils. Mello, P. Chimica Acta , , Mogollon, L. Fraccionamiento y desmetalizacion biocatalitica de asfaltenos de crudo Castilla. Nomura, M. Advances in characterization and utilization of asphaltenes. Tharanivasan, K.
Welter, K. Electrochemical removal of metals from crude oil samples. Tan, X. Associative p - p interactions of condensed aromatic compounds with vanadyl or nickel porphyrin complexes are not observed in the organic phase.
Services on Demand Article. Spanish pdf Article in xml format Article references How to cite this article Automatic translation Send this article by e-mail. Abstract Heavy metals are present in porphyrins in oil asphaltenes.
V and Ni electrochemical deposition from asphaltenes in heavy oils. William H. Heavy metals are present in porphyrins in oil asphaltenes. High content of V and Ni could be attractive to produce high value metal oxides. These metals are undesirable due to corrosion issues and catalyst contamination in cracking processes.
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