Hydrocracking, complex catalytic

Complex process units such as catalytic crackers, hydrocrackers, ethylene units, hydrotreaters, or large crude distilling units typically containing high fire potential equipment. 

In order to obtain quantitative measurements of hydrogenation activity and acidity, various schemes are employed. For example, metal surface area has been related to hydrogenation activity and the adsorption of bases such as pyridine and ammonia have been correlated with acidity ((3). Some authors have used certain key reactions involving pure compounds as an indication of catalytic properties (16). Each of these methods is useful however, because of the complex interdependence of the catalytic functions of the hydrocracking catalysts and changes in these functions with catalyst aging, results from each method must be interpreted with caution. 

Cracking reactions are carried out in order to reduce the molecular size and to produce more valuable transport fuel fractions (gasoline and diesel). Fluid catalytic cracking is acid catalyzed (zeolites) and a complex network of carbe-nium ion reactions occur leading to size reduction and isomerization (see Chapter 4, Section 4.4). Hydrogenation also takes place in hydrocracking, as well as cracking. 

Several of the commercial simulation programs offer preconfigured complex column rigorous models for petroleum fractionation. These models include charge heaters, several side strippers, and one or two pump-around loops. These fractionation column models can be used to model refinery distillation operations such as crude oil distillation, vacuum distillation of atmospheric residue oil, fluidized catalytic cracking (FCC) process main columns, and hydrocracker or coker main columns. Aspen Plus also has a shortcut fractionation model, SCFrac, which can be used to configure fractionation columns in the same way that shortcut distillation models are used to initialize multicomponent rigorous distillation models. 

Froment, G.F. Kinetic modeling of complex processes. Thermal cracking and catalytic hydrocracking. In Chemical Reactor Technology for Environmentally Safe Reactors and Products, de Lasa, H.I, Dogu, G., Ravella, A., Eds. Kluwer Academic Publishers Dordrecht, 1992 409-424. 

Hydrogen is an important feedstock for many essential chemical and petroleum industries such as ammonia, methanol, hydrocracking, hydrogenation of edible oil, hydrodesulphurization, reduction of iron ores and fuel cells. The catalytic steam reforming of natural gas is the most economical process for the production of hydrogen and syngas. Steam reforming of natural gas (mainly methane) is a complex... 

The chemistry that occurs within a hydrocracking reactor or severe hydrotreater is complex due to the variety of chemical structures that make up the feed and the number of different types of catalytic reactions that occur. As in many instances, simplifications have, of necessity, been introduced to develop an understanding of the processes and these in turn have been studied using model compounds to develop or confirm hypotheses. 

The first examples of molecular shape-selective catalysis in zeolites were given by Weisz and Frilette in 1960 [1]. In those early days of zeolite catalysis, the applications were limited by the availability of 8-N and 12-MR zeolites only. An example of reactant selectivity on an 8-MR zeolite is the hydrocracking of a mixture of linear and branched alkanes on erionite [4]. n-Alkanes can diffuse through the 8-MR windows and are cracked inside the erionite cages, while isoalkanes have no access to the intracrystalline catalytic sites. A boom in molecular shape-selective catalysis occurred in the early eighties, with the application of medium-pore zeolites, especially of ZSM-5, in hydrocarbon conversion reactions involving alkylaromatics [5-7]. A typical example of product selectivity is found in the toluene all lation reaction with methanol on H-ZSM-5. Meta-, para- and ortho-xylene are made inside the ZSM-5 chaimels, but the product is enriched in para-xylene since this isomer has the smallest kinetic diameter and diffuses out most rapidly. Xylene isomerisation in H-ZSM-5 is an often cited example of tranSition-state shape selectivity. The diaryl type transition state complexes leading to trimethylbenzenes and coke cannot be accommodated in the pores of the ZSM-5 structure. 

A hydrocarbon is a chemical compound that contains hydrocarbon and carbon. Crude oil is a mixture of hydrocarbons that vary in size and structure from simple to complex. Much modern manufacturing is based on separating the various components in crude oil by their individual boiling points. Important applied concepts of chemical processing include distillation, catalytic cracking, hydrocracking, and alkylation. 

Russell, C.L., Alolecular Modeling of the Catalytic Hydrocracking of Complex Mixtures Reactions of Alkyl Aromatic and Alkyl Polynuclear Aromatic Hydrocarbons, Ph.D. Dissertation, University of Delaware, 1996. 

KINETIC MODELING OF COMPLEX PROCESSES. THERMAL CRACKING AND CATALYTIC HYDROCRACKING... 

ABSTRACT. A fundamental approach is outlined for the kinetic modeling of complex processes like thermal cracking or catalytic hydrocracking of mixtures of hydrocarbons. The reaction networks are written in terms of radical mechanisms in the first case and of carbenium ion mechanisms in the second case. Since the elementary steps of the networks pertain to a relatively small number of classes, the number of rate coefficients is kept within tractable limits. The reaction networks are generated by computer through Boolean relation matrices. The number of continuity equations is limited by the elimination of radicals or carbenium ions through the pseudo-steady-state approximation. 

Hydroisomerization reactions are generally intimately associated with hydrocracking reactions. The overall scheme is rather complex. It involves the independent action of both types of catalytic sites and the existence of a transport mechanism for olefins between these sites. Therefore, the catalyst must be designed according to this bifunctional mechanism. The relative strength of the hydro-dehydrogenation and acidic components must be adjusted for the desired operation. 

Kinetic Modelling of Complex Processes. Thermal Cracking and Catalytic Hydrocracking P. Trambouze 409... 

Thus, one might design a saturates gas plant to process the total naphtha from a crude unit plus light ends from all other sources of saturated hydrocarbons within the complex. This could include hydrotreaters, hydrocrackers, isomerizers and catalytic reformers. The unsaturates gas plant would be designed to process total light ends from all sources of unsaturated hydrocarbons. This could include... 

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