Hydrocarbon conversion processes

Innumerable reactions occur in acid catalyzed hydrocarbon conversion processes. These reactions can be classified into a limited number of reaction families such as (de)-protonation, alkyl shift, P-scission,... Within such a reaction family, the rate coefficient is assumed to depend on the type, n or m cfr. Eq. (1), of the carbenium ions involved as reactant and/or product, secondary or tertiary. The only other structural feature of the reactive moiety which needs to be accounted for is the symmetry number. The ratio of the symmetry number of the... 

Zones, S.I., Zhang, G., Krishna, K.R., Biscardi, J.A., Marcantononoi, P., and Vittoratos, E. (2005) Preparing small crystal SSZ-32 and its use in a hydrocarbon conversion process. United States Patent Application Publication US 0092651 Al. 

The fundamental step in acid-catalyzed hydrocarbon conversion processes is the formation of the intermediate carbocations. Whereas all studies involving isomerization, cracking, and alkylation reactions under acidic conditions (Scheme 5.1) agree that a trivalent carbocation (carbenium ion) is the key intermediate, the mode of their formation of this reactive species from the neutral hydrocarbon remained controversial for many years. 

Reactions (1) - (4) pass on the catalyst in a warmed pipe in a recuperative mode. The main disadvantage of considered process is the necessity to use the surplus of H20 [1], The surplus is defined with molar ratio (mol H20)/C = N. Depending on operation conditions, tubular furnaces designs and the used catalyst 2 power consumption of hydrocarbons conversion process as a whole. Necessity of increase N is connected with allocation of carbon on the catalyst (the mechanism of carbon allocation is... 

Thus, in ammonia synthesis, mixed oxide base catalysts allowed new progress towards operating conditions (lower pressure) approaching optimal thermodynamic conditions. Catalytic systems of the same type, with high weight productivity, achieved a decrease of up to 35 per cent in the size of the reactor for the synthesis of acrylonitrile by ammoxidation. Also worth mentioning is the vast development enjoyed as catalysis by artificial zeolites (molecular sieves). Their use as a precious metal support, or as a substitute for conventional silico-aluminaies. led to catalytic systems with much higher activity and selectivity in aromatic hydrocarbon conversion processes (xylene isomerization, toluene dismutation), in benzene alkylation, and even in the oxychlorination of ethane to vinyl chloride. 

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. 

Hydrocarbon conversion processes as potential candidates for using zeolite membranes... 

Beck et oL 5370785 06.12.94 Hydrocarbon Conversion Process Employing a Porous Material... 

Supported metal catalysis are employed in a variety of commercially important hydrocarbon conversion processes. Such catalysts consist, in general, of small metal crystallites (0.S to 5 nm diameter) dispersed on non-metallic oxide supports. One of the major ways in which a catalyst becomes deactivated is due to accumulation of carbonaceous deposits on its surface. Catalyst regeneration, or decoking, is normally achieved by gasification of the deposit in air at about 500°C. However, during this process a further problem is frequently encountered, which contributes to catalyst deactivation, namely particle sintering. Other factors which can contribute to catalyst deactivation include the influence of poisons such as sulfur, phosphorus, arsenic and... 

A series of related events in the late 1940 s and early 1950 s led to the need for a new hydrocarbon conversion process. Reduced overseas shipments as a result of the end of... 

Recent surface science discoveries, however, demonstrate that step edges and defect sites display markedly lower activation barriers than terrace sites, and thus promote the Taylorian view of catalysis. The selectivity can be strongly influenced by the specific poisoning of these step edge sites. For a number of hydrocarbon conversion processes, these steps will be the most active and lead to potential C-H and C-C bond breaking steps which can ultimately result in deactivation via the formation of surface graphene overlayers. 

Traditional hydrocarbon conversion process models have implemented lumped kinetics schemes, where the molecules are aggregated into lumps defined by global properties, such as boiling point or solubility. Molecular information is obscured due to the multi-component nature of each lump. However, increasing environmental concerns and the desire for better control and manipulation of the process chemistry have focused attention on the molecular composition of both the feedstocks and their refined products. Modeling approaches that account for the molecular fundamentals underlying reaction of complex feeds and the subsequent prediction of molecular properties require an unprecedented level of molecular detail. 

While the first commercial installation of a unit employing the t5q)e of technology in use today was started up in Chevron s Richmond, California refinery in 1960, hydrocracking is one of the oldest hydrocarbon conversion processes. Its origin is the work done by Sabatier and Senderens, who in 1897 published the discovery that unsaturated hydrocarbons could be hydrogenated in the vapor phase over a nickel catalyst. In 1904, Ipatieff extended the range of feasible hydrogenation reactions by the introduction of... 

Mazurek, H. (1987) Hydrocarbon Conversion Process Using a Molten Salt , US Patent 4,665,261. 

This chapter provides a few examples of the many opportunities that exist to reduce carbon emission in hydrocarbon conversion processes. Potentially substantial reduction could be achieved by new, iimovative catalytic systems. In addition to improving selectivity in chemical reactions, new processes that match the number of carbon and hydrogen atoms in the reactants with those in the products should... 

Many of the hydrocarbon-conversion processes are still in the development stage, and this is particularly true of the higher-molecular-weight materials, which constitute the bulk of petroleum. For these reasons, it is of primary importance to be able to judge the feasibility of proposed reactions or processes and to compute (or estimate) other thermal factors such as the heat of reaction. These factors can be evaluated by means of thermodynamics, and in time it may be possible to develop processes by which whole series of hydrocarbons can be converted into other series of hydrocarbons in a selective manner or by a number of consecutive processes to convert one series of hydrocarbons after another, until the entire mixture is converted into a single type of material. 

Although pillared clays could generate low cost fluidized cracking catalysts (FCC) with unique selectivity properties, they have not yet been accepted by the petroleum industry. In fact, refiners (to date) have been reluctant to field test these new catalysts because, in addition to a high tendency for coke generation, they exhibit hydrothermal stability inferior to that of those zeolites used in hydrocarbon conversion processes. The physicochemical properties of pillared clays have been reviewed elsewhere (1,2). 

Petroleum feedstocks are complex hydrocarbon mixtures characterized by their intricate structural nature and composition at the molecular level. For modeling purposes, this implies a gigantic interconnected reaction network. Modeling of hydrocarbon conversion processes therefore has an inherent high level of complexity. 

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