Kinetics of hydroprocessing

Heck, R. H., Stein, T. R., "Kinetics of Hydroprocessing Distillate Coal Liquids, Symposium on Refining of Synthetic Crudes, Chicago, (1977). 

Fukuyama and Terai used a lumped model to study the kinetics of hydroprocessing of VR (7 to 10 MPa 700K). A total of seven lumps comprising hydrocarbon groups was determined by SARA analysis, as well as different fractions of products and a residue. The kinetics parameters were used to identify the most active Fe/AC catalyst. The same catalyst was the most resistant to deactivation. 

Kinetics of hydroprocessing reactions, as well as kinetics of deactivation over carbon supported catalysts have been investigated under a wide range of... 

Callejas, M. A., and Martmez, M. T., Hydroprocessing of a Maya Residue. 1. Intrinsic Kinetics of Asphaltene Removal Reactions. Energy Fuels, 2000. 14 pp. 1304—1308. 

In Section IV, the kinetics and mechanisms of catalytic HDM reactions are presented. Reaction pathways and the interplay of kinetic rate processes and molecular diffusion processes are discussed and compared for demetallation of nickel and vanadium species. Model compound HDM studies are reviewed first to provide fundamental insight into the complex processes occurring with petroleum residua. The effects of feed composition, competitive reactions, and reaction conditions are discussed. Since development of an understanding of the kinetics of metal removal is important from the standpoint of catalyst lifetime, the effect of catalyst properties on reaction kinetics and on the resulting metal deposition profiles in hydroprocessing catalysts are discussed. 

Kinetics and Mechanism of Hydroprocessing Reactions over Carbon and Carbon-Supported Catalysts... 

Eccles (1993) modeled the kinetics of residue hydroprocessing in an EBR by using the power-law model. The reactor was assumed to behave as a liquid phase back-mixed tank. The model consists of a single equation for estimation of frequency factor and includes residue conversion and all the reactor-independent variables. 

Callejas, M.A., Martinez, M.T. 1999. Hydroprocessing of a Maya residue Intrinsic kinetics of sulfur-, nitrogen-, nickel-, and vanadium-removal reactions. Energy Fuels 13 629-636. 

Trasobares, S., Callejas, M.A., Benito, A.M., Martinez, M.T., Severin, D., Brouwer, L. 1998. Kinetics of conradson carbon residue conversion in the catalytic hydroprocessing of a maya residue. Ind. Eng. Chem. Res. 37 11-17. 

Mathur, K. N. Sarbak, Z. Islam, N., Kwart, H., and Katzer, J. R., Kinetics and Mechanism of Catalytic Hydroprocessing of Components of Coal-Derived Liquids, DOE, Office of Fossil Energy. Washington, DC. X and XI Quarterly 1982 August 16, 1981 to February 15, 1982. 

The new specifications not only limit the concentration of sulfur to 0.05% but also specify that the fuel should have the combustion properties of a 10% or lower aromatics-containing fuel and have a minimum cetane number of 40. Fuels that have more than 10% aromatics are now able to meet these specifications through additives (22). However, as smoke emission standards become more restrictive, the aromatics content of diesel fuels may have to be lowered to a true value of 10% or less. A very thorough review of the consequences of this potential problem has recently been written by Stanislaus and Cooper, which covers in detail aromatic hydrocarbon hydroprocessing kinetics, thermodynamics, catalyst compositions, and mechanisms (109). There is little need to repeat the details of that report... 

Hydrodemetallation reactions require the diffusion of multiringed aromatic molecules into the pore structure of the catalyst prior to initiation of the sequential conversion mechanism. The observed diffusion rate may be influenced by adsorption interactions with the surface and a contribution from surface diffusion. Experiments with nickel and vanadyl porphyrins at typical hydroprocessing conditions have shown that the reaction rates are independent of particle diameter only for catalysts on the order of 100 /im and smaller (R < 50/im). Thus the kinetic-controlled regime, that is, where the diffusion rate DeU/R2 is larger than the intrinsic reaction rate k, is limited to small particles. This necessitates an understanding of the molecular diffusion process in porous material to interpret the diffusion-disguised kinetics observed with full-size (i -in.) commercial catalysts. 

The use of model compounds in reaction kinetic studies has provided valuable insight into the fundamental processes occurring in residuum hydroprocessing. The reaction of Ni and V porphyrins under commercial... 

Prins summarizes advances in understanding of the reactions in catalytic hydrodenitrogenation (HDN), which is important in hydroprocessing of fossil fuels. Hydroprocessing is the largest application in industrial catalysis based on the amount of material processed. The chapter addresses the structures of the oxide precursors and the active sulfided forms of catalysts such as Ni-promoted Mo or W on alumina as well as the catalytically active sites. Reaction networks, kinetics, and mechanisms (particularly of C-N bond rupture) in HDN of aliphatic, aromatic, and polycyclic compounds are considered, with an evaluation of the effects of competitive adsorption in mixtures. Phosphate and fluorine promotion enhance the HDN activity of catalysts explanations for the effect of phosphate are summarized, but the function of fluorine remains to be understood. An account of HDN on various metal sulfides and on metals, metal carbides, and metal nitrides concludes this chapter. 

Girgis, M. J., Reaction Networks, Kinetics, and Inhibition in the Hydroprocessing of Simulated Heavy Coal Liquids, Ph.D. Dissertation, Univ. of Delaware, 1988. 

The objective of this book is to serve as a practical reference work on testing for the main hydrocarbon-conversion processes applied in oil refineries catalytic cracking, hydroprocessing, and reforming. These fields were combined because of the clear analogies and congruence between the areas, such as deactivation of active sites by coke, mass-transfer phenomena of hydrocarbons into solid catalysts, hydrocarbon chemistry and reaction kinetics, and downscaling of commercial conditions to realistic small-scale tests. 

The oxidation reactions of carbon and sulfur on hydroprocessing catalysts seem to be kinetically controlled by oxygen diffusion inside the catalyst porosity. Figure 3 shows the carbon and sulfur removal for Cat C which contains a very high amount of nickel and molybdenum, and an appreciable load of carbon. It is clear that the sulfur elimination occurs at higher temperatures than for the other catalysts and is simultaneous to carbon combustion. A tentative explanation of this phenomenon would be that the diffusion of oxygen in the microporosity is limited by coke deposit which needs to be at least partly removed to allow complete sulfur oxidation. 

S. J. Khang and J. F. Mosby (personal communication) have presented process models to describe the removal of sulfur, vanadium, and nickel in residuum hydroprocessing. The kinetic models are given below in Eq. (16) ... 

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