Thermal cracking of hydrocarbons

partial aromatization of hydrocarbons occurs, but to a lesser extent than in high-temperature pyrolysis. 

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Although ethylene is produced by various methods as follows, only a few are commercially proven thermal cracking of hydrocarbons, catalytic pyrolysis, membrane dehydrogenation of ethane, oxydehydrogenation of ethane, oxidative coupling of methane, methanol to ethylene, dehydration of ethanol, ethylene from coal, disproportionation of propylene, and ethylene as a by-product. 

Mechanism. The thermal cracking of hydrocarbons proceeds via a free-radical mechanism (20). Siace that discovery, many reaction schemes have been proposed for various hydrocarbon feeds (21—24). Siace radicals are neutral species with a short life, their concentrations under reaction conditions are extremely small. Therefore, the iategration of continuity equations involving radical and molecular species requires special iategration algorithms (25). An approximate method known as pseudo steady-state approximation has been used ia chemical kinetics for many years (26,27). The errors associated with various approximations ia predicting the product distribution have been given (28). 

H2, hydrogen, is a colorless, odorless, tasteless, nonpolar, diamagnetic, diatomic gas with the lowest atomic weight and density of any known substance. It has low solubility in water and is very flammable. Hydrogen is prepared by reactions of metals with water, steam or various acids, electrolysis of water, the water gas reaction and thermal cracking of hydrocarbons. It combines with metals and nonmetals to form hydrides. 

Willems, P, A., and Froment, G. F., Kinetic modeling of the thermal cracking of hydrocarbons. 

Carbon formation can occur by thermal cracking of hydrocarbons according... 

The major industrial source of ethylene and propylene is the pyrolysis (thermal cracking) of hydrocarbons.137-139 Since there is an increase in the number of moles during cracking, low partial pressure favors alkene formation. Pyrolysis, therefore, is carried out in the presence of steam (steam cracking), which also reduces coke formation. Cracking temperature and residence time are used to control product distribution. 

The usual temperature of flue gas entering the shield section is 1300-1650°F and should be 200-300°F above the process temperature at this point. The proportions of heat transferred in the radiant and convection zones can be regulated by recirculation of hot flue gases into the radiant zone, as sketched on Figure 8.19(b). Such an operation is desirable in the thermal cracking of hydrocarbons, for instance, to maintain a proper temperature profile a negative gradient may cause condensation of polymeric products that make coke on the tubes. Multiple chambers as in... 

The term carbon black includes furnace black, colloidal black, thermal black, channel black, and acetylene black. Carbon black is mostly derived from petroleum and involves partial combustion or a combination of combustion and thermal cracking of hydrocarbons, and to a lesser extent natural gas, at 1200 tol400°C. 

Gas phase free radical reactions are used in industry for pyrolysis, halogenation and combustion reactions. Nowadays, and probably for a long time to come, the thermal cracking of hydrocarbons constitutes the main production route for olefins, which are the basic feedstocks of the chemical industry around the world. Hydrocarbon pyrolysis is thus of considerable economic interest, as is shown by the very large amount of effort dedicated both to fundamental and applied research in this field (see, for example, refs. 35—37). 

Application To produce polymer-grade ethylene and propylene by thermal cracking of hydrocarbon fractions—from ethane through naphtha up to hydrocracker residue. Byproducts are a butadiene-rich C4 stream, a Cg— Cg gasoline stream rich in aromatics and fuel oil. 

Technip Ethylene/cracking furnaces Ethane to HVGO Thermal cracking of hydrocarbons in the presence of steam by highly selective GK and SMK cracking furnaces 500 2001... 

A key technical difference between the two approaches is that thermal cracking of hydrocarbons to ethylene is usually performed at temperatures in excess of 800 C, whereas catalytic processes occur generally below 550°C. 

Reaction of Steam on Hydrocarbons. The catalytic interaction of steam and hydrocarbons has been used commercially on a large scale. The thermal cracking of hydrocarbons is an important part of petroleum refining and produces a large amount of hydrogen. The reaction of steam on methane from natural gas at about 1100 °C is... 

Acetylene is currently produced by the thermal cracking of hydrocarbon feeds. This thermal cracking requires considerable quantities of energy since the reactions are strongly endoth mic. Further dissociation into carbon and hydrogen of all hydrocarbons begins at relatively low temperatures. Thus, the reactions must be allowed to proceed very rapidly and quenched very quickly to stable temperatures. 

Cracking of hydrocarbons is known to occur at relative high temperatures even in the absence of any catalyst. Moreover, thermal cracking of hydrocarbons for a-olefin producrion is carried out in different reactors [12,13. The reactor design can be optimised in order to obtain a favourable product distribution. However, the transfer of heat into the hydrocarbon may be accomplished in a catalytic reactor with constant... 

Derivation (1) Thermal cracking of hydrocarbon gases (800-900C), (2) dehydration of ethanol, (3) from synthesis gas with Ru as catalyst. 

The overall reaction in a partial oxidation reactor is highly exothermic. The desired reactions may be accompanied by thermal cracking of hydrocarbons or oxidative dehydrogenation into nonsaturated compounds including olefins, polyaromatics, and soot. The control of the heat balance and the formation of by-products are important considerations in the design of partial oxidation reactors. 

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