Reaction energy categorization

Hazards associated with chemical reactions depend on the energy that can evolve in the course of reaction. The chemical reaction energy is categorized in Table 5.4-32 (based on data of Hoffman, 1985, and Rogers, 1997). 

In cases where the aromatic C—C bonds were attacked and various water-soluble substances capable of extraction from oil were formed, a reduction in the total heating value of the fuel was consequently observed [137], Hence, such reaction was categorized as an industrially unacceptable reaction, since that pathway not only destroyed the carbon skeleton reducing the energy content of fuel but also converted DBT to 3-hydroxy-2-formylbenzothiophene without actually desulfurizing it to HBP. 

Metabolic reactions are categorized into two types, anabolic and catabolic. Anabolic reactions construct complex molecules from simple molecules, usually while using up energy that becomes stored in chemical bonds. Catabolic reactions break down complex molecules into multiple simple molecules, usually while releasing energy. 

Different strategies have evolved for thermochemical hydrogen production to effectively utilize the potentials of, in particular, nuclear and solar thermal energy sources. These strategies, which we discuss below, can be categorized depending upon the number of process steps involved and whether electrolysis is employed in a reaction. 

Luminescence processes may be categorized by the excitation method used with any particular luminescent molecule. Photoluminescence is the excitation process that involves the interaction of electromagnetic radiation with photons. The process is termed chemiluminescence when the exciting energy results from a chemical reaction. Any luminescence arising from an organism is referred to as bioluminescence. 

The term explosion is best defined as a process that involves a sudden release of energy resulting in a rapid and significant buildup of overpressure. Explosions can be categorized into physical/mechanical and chemical explosions. For example, an explosion caused by a sudden release of compressed gas is a physical explosion. A chemical explosion is caused by a chemical reaction(s), which could be combustion, exothermic decomposition or exothermic reaction. Chemical explosions can occur in gas, liquid or solid phase. Chemical explosions that occur in liquid and solid phases are sometimes called condensed phase explosions. Explosive explosions fall in this category. 

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