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Publications (4) View all
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Article: Hydrotreatment of Vegetable Oils to Produce Bio-Hydrogenated Diesel and Liquefied Petroleum Gas Fuel over Catalysts Containing Sulfided Ni–Mo and Solid Acids
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ABSTRACT: Biohydrogenated diesel (BHD) and liquefied petroleum gas (LPG) fuel were produced by the hydrotreatment of vegetable oils over Ni–Mo-based catalysts in a high-pressure fixed-bed flow reaction system at 350 °C under 4 MPa of hydrogen. Because triglycerides and free fatty acids underwent the hydrogenation and deoxidization at the same time during the reaction, various vegetable oils (jatropha oil, palm oil, and canola oil) were converted to mixed paraffins by the one-step hydrotreatment process although they contained quite different amounts of free fatty acids. Ni-Mo/SiO2 formed n-C18H38, n-C17H36, n-C16H34, and n-C15H32 as predominant products in the hydrotreatment of jatropha oil. These long normal hydrocarbons had high melting points and thus gave the liquid hydrocarbon product over Ni-Mo/SiO2 a high pour point of 20 °C. Either Ni-Mo/H-Y or Ni-Mo/H-ZSM-5 was not suitable for producing BHD from jatropha oil because a large amount of gasoline-ranged hydrocarbons was formed on the strong acid sites of zeolites. When SiO2-Al2O3 was used as a support for the Ni-Mo catalyst, the pour point of the liquid hydrocarbon product decreased to −10 °C by converting some C15–C18n-paraffins to iso-paraffins and light paraffins on SiO2-Al2O3. Because SiO2-Al2O3 had a proper solid acidic strength, both the chemical composition and the pour point of liquid hydrocarbon product over Ni-Mo/SiO2-Al2O3 were similar to those of a normal diesel bought from a petrol station. Meanwhile, the glycerin groups in the vegetable oils were converted to propane over Ni-Mo/SiO2-Al2O3 by the hydrogenation and deoxidization. Therefore, the liquid hydrocarbon product can be directly used as a BHD fuel for the current diesel engines, and the gas hydrocarbon product can be used as a liquefied petroleum gas (LPG) fuel in the hydrotreatment of vegetable oils over Ni-Mo/SiO2-Al2O3.08/2011; -
Article: Kinetic modeling of vacuum gas oil catalytic cracking
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ABSTRACT: A new kinetic model for catalytic cracking of vacuum gas oil is presented. The proposed model is based on lumping technique and considers the most important products in the FCC process: (1) gasoline (C5-493 K), (2) C4¿s (butane, i-butane and butenes), (3) C3¿s (propane and propylene), (4) dry gas (H2, C1-C2), (5) coke and (6) unconverted VGO (decanted and light cycle oils). A vacuum gas oil and an equilibrium catalyst recovered from a commercial FCC unit were employed to evaluate the kinetic and deactivation constants by using experimental information obtained in a microactivity plant. Good predictions of product yields with average absolute deviation less than 5 % with respect to experimental information were obtained.Revista de la Sociedad Química de México. 01/2002; -
Article: Estimation of Kinetic Constants of a Five-Lump Model for Fluid Catalytic Cracking Process Using Simpler Sub-models
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ABSTRACT: A new sequential method to estimate rate constants in complex kinetic models is proposed. This method reduces the number of parameters to be estimated simultaneously. A five-lump kinetic model for the catalytic cracking process was selected in order to apply the proposed methodology. The kinetic parameters of this model were determined by using successively non linear estimation with various three- and four-lump kinetic models. Experimental data obtained in a MAT reactor using three gas oils and a commercial equilibrium catalyst were utilized to evaluate the rate constants. The effects of reaction temperature and space velocity were studied in the range of 480−500 °C and 6−48 h-1, respectively. Good predictions of gas oil, gasoline, LPG, dry gas, and coke yields were obtained from the kinetic model, with average absolute deviation less than 2% with respect to experimental information.10/2000; -
Article: Fundamental kinetic modeling of the catalytic reforming process
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ABSTRACT: In this work, a fundamental kinetic model for the catalytic reforming process has been developed. The complex network of elementary steps and molecular reactions occurring in catalytic reforming has been generated through a computer algorithm characterizing the various species by vectors and Boolean relation matrices. The algorithm is based on the fundamental chemistry occurring on both acid and metal sites of the catalyst. Rates are expressed for each of the elementary steps involved in the transformation of the intermediates. The Hougen-Watson approach is used to express the rates of the molecular reactions occurring on the metal sites of the catalyst. The single event approach is used to account for the effect of structure of reactant and activated complex on the rate coefficients of the elementary steps occurring on the acid sites. This approach recognizes that even if the number of elementary steps is very large they belong to a very limited number of types, and therefore it is possible to express the kinetics of elementary steps by a reduced number of parameters. In addition, the single event approach leads to rate coefficients that are independent of the feedstock, due to their fundamental chemical nature. The total number of parameters at isothermal conditions is 45. To estimate these parameters, an objective function based upon the sum of squares of the residuals was minimized through the Marquardt algorithm. Intraparticle mass transport limitations and deactivation of the catalyst by coke formation are considered in the model. Both the Wilke and the Stefan-Maxwell approaches were used to calculate the concentration gradients inside of the particle. The heterogeneous kinetic model was applied in the simulation of the process for typical industrial conditions for both axial and radial flow fixed bed reactors. The influence of the main process variables on the octane number and reformate volume was investigated and optimal conditions were obtained. Additional aspects studied with the kinetic model are the reduction of aromatics, mainly benzene. The results from the simulations agree with the typical performance found in the industrial process.
