Page 386 - Chemical process engineering design and economics

366 Chapter 7

cal, plasma, and sonochemical. Table 7.1 gives an example of each reaction type.
Since thermochemical reactions are the most common, we will consider them in
detail in this chapter.
Mixtures of alkyl halides and chlorinated aromatic side chains are produced
industrially in photochemical reactors. For example, reacting methane with chlo-
rine, using mercury arc lamps, produces a mixture of the four isomers of chloro-
methane [1].
Samdani and Gilges [2] list a number of commercial processes for electro-
chemically synthesizing organic compounds. An example is the conversion of
glucose to gluconic acid. Gluconic acid, sold as a 50% aqueous solution, is used
in metal pickling and as a protein coagulant in the production of tofu (soy bean
curd), as well as in many other applications [3].
A sonochemical reaction is an indirect way of conducting a thermochemical
reaction. Ultrasound causes cavitation in liquids, elevating the temperature in mi-
croscopic cavities in the liquid, which promotes chemical reaction. There appears
to be no commercial application of ultrasonic energy to conduct chemical reac-
tions. Pandit and Moholkar [4] list several organic reactions conducted in the
laboratory. A possible future application is the destruction of chlorinated hydro-
carbons in wastewater or ground water [5].
A plant operated by Huls in Marl, Germany, uses an electric-arc plasma
reactor to produced acetylene [6]. A plasma is an electrically conductive but
electrically neutral gas. In this process, a hydrocarbon and hydrogen mixture
flows into a reaction chamber where the hydrocarbon is cracked into acetylene,
ethylene, hydrogen, and soot.

Table 7.1 Energy Sources for Chemical Reaction

Energy Source Product Example

Thermochemical Ammonia
Biochemical Ethanol
Electrochemical Gluconic Acid
Photochemical Chloromethanes
Plasma Acetylene
Sonochemical Fumaric Acid
(Laboratory Scale)

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