Pyrolysis or Cracking

Paraffins react with nitric acid at high temperatures to form a mixture of nitroparaffins which find use as solvents. 

Oxidation by reaction with oxygen in the air is a major use of paraffins. Paraffins are converted to more reactive compounds called olehns by cracking under pressure at high temperature. 

An important reaction in the manufacture of gasoline is isomerization of straight-chain paraffins to more highly branched compounds, which have better fuel properties (higher octane rating). 

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Ethylene Dichloride Pyrolysis to Vinyl Chloride. Thermal pyrolysis or cracking of EDC to vinyl chloride and HCl occurs as a homogenous, first-order, free-radical chain reaction. The accepted general mechanism involves the four steps shown in equations 10—13 ... 

Olefin plants all have two main parts the pyrolysis or cracking section and the purification or distillation section. The ethane cracker in Figure 5—2 has a pyrolysis (from the Greek, pyros, fire) section that consists of a gas-fired furnace where the cracking takes place. The newer individual furnaces can each handle more than 400 million pounds per year of ethane feed. 

Propane s greatest use is not as a fuel but in the petrochemical industry as a feedstock. As an alkane, it undergoes typical alkane reactions of combustion, halogenation, pyrolysis, and oxidation. Pyrolysis or cracking of propane at several hundred degrees Celsius and elevated pressure in combination with metal catalysts result in dehydrogenation. Dehydrogenation is a primary source of ethylene and propylene ... 

The raw materials of the polymer industry are obtained by pyrolysis (or cracking ) of oil. In earlier times, they were similarly obtained by pyrolysis of coal, which leads to the formation of coke, tars and town gas . Waste hydrocarbon polymers are similar in chemical structure to mineral oil and on heating to high temperatures they crack to give a mixture of lower molecular weight hydrocarbons (see, for example. Table 4,4), some of which have utility both as chemical feedstocks e.g. the olefins) and the rest as fuels. Pyrolysis can be carried out successfully... 

Endothermic processes By way of example the following penalties are assigned calcination (0.40), electrolysis (0.20), pyrolysis or cracking (0.4). 

The feedstock is passed through the pyrolysis or cracking section using a very short residence time of 0.1 to 0.6 seconds, with the relatively longer residence times required for a heavy feedstock such as naphtha. However,... 

Combustion is the rapid exothermic oxidation of combustible elements in fuel. Incineration is complete combustion. Classical pyrolysis is the destructive distillation, reduction, or thermal cracking and condensation of organic matter under heat and/or pressure in the absence of oxygen. Partial pyrolysis, or starved-air combustion, is incomplete combustion and occurs when insufficient oxygen is provided to satisfy the combustion requirements. The basic elements of each process are shown on Figure 27. Combustion of wastewater solids, a two-step process, involves drying followed by burning. 

Asphalt samples (SR-125 and AB-25) were 100% volatile under conditions of analysis, and asphaltene samples (asphaltenes SR-125 and asphaltenes AB-25) were 92% and 83% volatile, respectively. No cracking, pyrolysis or other form of molecular decomposition was observed. 

This review focuses on some technical and practical aspects of the pyrolysis or thermal cracking of waste plastics, to yield liquid fuels and monomers as a main product. It... 

Pyrolysis involves the thermal decomposition, degradation, or cracking of a large molecule into smaller fragments. Pyrolysis GC is an excellent technique for identifying certain types of compounds which cannot be analyzed by derivatization, e.g., polymers. The pyrolysis temperamre is typically between 400°C and 1000°C. A number of analytical pyrolyzers have been introduced and are commercially available. The devices consist of platinum resistively heated and Curie point pyrolyzers. The carrier gas is directed through the system, and the platinum wire is heated to a certain temperature. The material decomposes, and the fragmentation products are analyzed. ... 

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