Stoichiometry ethylene oxide production

Figure 9.3 shows the system and an effective control structure. Ethylene oxide is very volatile, and ethylene glycol is very heavy. Thus, the product is removed from the bottom of the column. The ethylene oxide concentrates in the top of the column. No distillate product is removed. The water feed is introduced to hold the liquid level in the reflux dmm. This level loop achieves the necessary balancing of the reaction stoichiometry by adjusting the makeup water flow rate to exactly match the water consumption by reaction with ethylene oxide. Production rate is set by flow controlling the ethylene oxide. 

Silver is unique in its ability to catalyze the reaction forming a molecular O2 adsorbed species which reacts with ethylene to form ethylene oxide (Scheme 1). Absorbed atomic oxygen [Ag(0)ads], a by-product of this process, is responsible for waste formation. From the stoichiometry of the mechanism, the maximum yield of selective product (ethylene oxide) is 80%. ... 

To demonstrate the principles of plant-wide control for a recycle system, consider the ethylene glycol plant shown in Figure 10.4. Equivalent amounts of water and ethylene oxide are fed to a reactor, as dictated by the reaction stoichiometry, to produce ethylene glycol. The liquid product stream is sent to a distillation column to separate unreacted water and ethylene oxide from the ethylene glycol. The unreacted feed is sent back through a recycle loop to the reactor. 

The overall oxidation is first-order in Fe(ri), and the main product is tetrachlor-ethylene, indicating a stoichiometry... 

A detailed study of the oxidation of alkenes by O on MgO at 300 K indicated a stoichiometry of one alkene reacted for each O ion (114). With all three alkenes, the initial reaction appears to be the abstraction of a hydrogen atom by the O ion in line with the gas-phase data (100). The reaction of ethylene and propylene with O" gave no gaseous products at 25°C, but heating the sample above 450°C gave mainly methane. Reaction of 1-butene with O gives butadiene as the main product on thermal desorption, and the formation of alkoxide ions was proposed as the intermediate step. The reaction of ethylene is assumed to go through the intermediate H2C=C HO which reacts further with surface oxide ions to form carboxylate ions in Eq. (23),... 

The oxygen required for the one-step process is calculated based on the reaction stoichiometry and catalyst selectivity. For simplification, it is assumed that the ethylene that does not form acetaldehyde is oxidized to carbon dioxide and water. Actually, several hydrocarbon by-products are also formed but the quantities are small and this simplification does not introduce appreciable error. 

Another potential source of processlble precursors Is the citric acid/ethylene glycol system which has been esiployed previously in the preparation of highly dispersed perovskite, spinel and related complex oxides. This method provides soluble, metal-organic, polymer precursors which have been used for the fabrication of oxide thin films as well as for the production of oxide powders with excellent homogeneity, good stoichiometry control and uniform sizes at relatively low temperatures(13,14). 

---