Sludge-forming reaction

Treatment with aluminum chloride is one of the few chemical methods applied commercially to lubricants in the past 25 years. Aluminum chloride reacts with the undesirable sludge-forming hydrocarbons the complex reaction product is removed by settling. 

Vigorous stirring helps to break up the thick sludge formed on addition of the reaction mixture to the acid and also serves to remove soluble inorganic salts. 

If 14 or more carbons are present, the product may be diamantane or a substituted diamantane. " These reactions are successful because of the high thermodynamic stability of adamantane, diamantane, and similar diamond-like molecules. The most stable of a set of C H isomers (called the stabilomer) will be the end product if the reaction reaches equilibrium. Best yields are obtained by the use of sludge catalysts (i.e., a mixture of AIX3 and ferf-butyl bromide or iec-butyl bromide).Though it is certain that these adamantane-forming reactions take place by nucleophilic 1,2-shifts, the exact pathways are not easy to unravel... 

The phosphate-hydroxide or conventional treatment method is commonly used. It involves the addition of phosphate and caustic to boiler. The caustic is added to maintain a pH in the range 10.5-11.2. This practice is used in high-pressure boilers. In this process, calcium and magnesium salts are precipitated in a sludge form. The following reaction leads to the formation of sludge. 

The precipitated hydroxyapatite or other form of calcium phosphate is incorporated in the sludge floe. Reaction 13.9.3 is strongly hydrogen ion-dependent, and an increase in the hydrogen ion concentration drives the equilibrium back to the left. Thus, under anaerobic conditions when the sludge medium becomes more acidic due to higher CO2 levels, the calcium returns to solution. 

Stability. Diesel fuel can undergo unwanted oxidation reactions leading to insoluble gums and also to highly colored by-products. Discoloration is beheved to be caused by oxidation of pyrroles, phenols, and thiophenols to form quiaoid stmctures (75). Eventually, these colored bodies may increase in molecular weight to form insoluble sludge. 

Iron Reduction. The reduction of nitrophenols with iron filings or turnings takes place in weakly acidic solution or suspension (30). The aminophenol formed is converted to the water soluble sodium aminopheno1 ate by adding sodium hydroxide before the iron-iron oxide sludge is separated from the reaction mixture (31). Adjustment of the solution pH leads to the precipitation of aminophenols, a procedure performed in the absence of air because the salts are very susceptible to oxidation in aqueous solution. 

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