n-butyraldehyde

n-butyraldehyde (boiling point: 74.8oC, density: 0.8016) is made by the reaction of propylene (propene-1, CH3CH=CH2), carbon monoxide, and hydrogen (synthesis gas) at 130 to 175oC and 3675 psi (25.3 MPa) over a rhodium carbonyl, cobalt carbonyl, or ruthenium carbonyl catalyst (Fig. 1).

CH3CH=CH2 + CO + H2 → CH3CH2CH2CH=O

The reaction is referred to as the oxo process, and a second product of the reaction is iso-butyraldehyde (boiling point: 64.1oC, density: 0.7891).

CH3CH=CH2 + CO + H2 → CH3CH(CH3)CH=O

The ratio of the normal to the iso product is approximately 4:1. Other catalysts produce different normal-to-iso product ratios under different conditions. For example, a rhodium catalyst can be used at lower temperatures and pressures and gives a normal-to-iso product ratio of approximately 16:1.

Butyraldehyde is used for the production of n-butyl alcohol.

CH3CH2CH2CH=O + H2 → CH3CH2CH2CH2OH

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t-Butyl alcohol

t-Butyl alcohol (melting point: 25.8oC, boiling point: 82.4oC, density: 0.7866, flash point: 11.1oC) is a low-melting solid that, after melting,exists as a colorless liquid. t-Butyl alcohol is produced by the hydration of iso-butene. The favored tertiary carbocation intermediate limits the possible alcohols produced to only this one.

(CH3)2C=CH2 → (CH3)3COH

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Titanium Dioxide

The production of titanium dioxide pigments involves reaction between sulfuric acid and the ore which contains iron, titanium sulfate and other compounds. After pretreatment, which includes the crystallization of iron as ferrous sulfate, the liquor is heated and hydrolyzed to precipitate Titanium dioxide. Prior to this operation, the concentration of liquor has to be adjusted by the evaporation of water. It is essential that this process takes place in an evaporator with short heat contact times in order to avoid the premature hydrolysis that occurs with prolonged heating, which subsequently causes fouling of the heat surface and blockage of the tubes. Although the liquor contains a high proportion of sulfuric acid, the presence of other ions in solution may inhibit corrosion, so that copper often can be used for heat transfer surfaces. Titanium is another material used for this application. Generally, single or multiple effect rising film evaporators are used for this duty, the number of effects being determined by throughput and by assessing the cost of operation against the increase in capital required for additional equipment. In some cases, it is economically attractive to operate the evaporator as a single effect unit at atmospheric pressure using the vapor given off for preheating. The liquor is discharged at a temperature in excess of 212°F (100°C), reducing the subsequent thermal load at the hydrolysis stage.

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Acetaminophen

Acetaminophen, sold under the trade name Tylenol, is a widely used anal- gesic and antipyretic that is an over-the-counter drug. Combined with codeine it is one of the top five prescription drugs. Acetaminophen is pre- pared by treating p-aminophenol with a mixture of glacial acetic acid and acetic anhydride.

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Aluminum sulfate

Aluminum sulfate [Al2(SO4)3, alum, filter alum, papermaker’s alum] is manufactured from aluminum oxide (Al2O3, alumina, bauxite). A mixture of the crude ore and sulfuric acid is heated at 105 to 110 degree C for 15 to 20 hours.

Al2O3.2H2O + 3H2SO4 → Al2(SO4)3 + 5H2O

Filtration of the aqueous solution is followed by evaporation of the water to give the product, which is processed into a white powder. Alum has two prime uses. It is bought by the pulp and paper industry for coagulating and coating pulp fibers into a hard paper surface by reacting with small amounts of sodium carboxylates (soap) present. Aluminum salts of carboxylic acids are very gelatinous. In water purification it serves as a coagulant, pH conditioner, and phosphate and bacteria remover. It reacts with alkali to give an aluminum hydroxide floc that drags down such impurities in the water. For this reason it also helps the taste of water.

6RCO2–Na+ + Al2(SO4)3 → 2(RCO2–)3Al3+ + 3Na2SO4
Al2(SO4)3 + 6NaOH → 2Al(OH)3 + 3Na2SO4

Pharmaceutically, aluminum sulfate is employed in dilute solution as a mild astringent and antiseptic for the skin. The most important single application of aluminum sulfate is in clarifying water; sodium aluminate, which is basic, is sometimes used with aluminum sulfate, which is acid, to produce the aluminum hydroxide. Aluminum sulfate is also used in sizing of paper, as a mordant in the dye industry, chemical manufacturing, concrete modification, soaps, greases, fire extinguishing solutions, tanning, cellulosic insulation, and in some baking powders.

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Aluminum chloride

Aluminum chloride (AlCl3) is a white solid when pure that sublimes on heating and, in the presence of moisture, decomposes with the evolution of hydrogen chloride. Anhydrous aluminum chloride is manufactured primarily by the reaction of chlorine vapor on molten aluminum.

2Al + 3Cl2 → 2AlCl3

In the process, chlorine is fed in below the surface of the aluminum, and the product sublimes and is collected by condensing. These air-cooled condensers are thin-walled, vertical steel cylinders with conical bottoms. Aluminum chloride crystals form on the condenser walls and are periodically removed, crushed, screened, and packaged in steel containers. Aluminum chloride is used in the petroleum industries and various aspects of organic chemistry technology. For example, aluminum chloride is a catalyst in the alkylation of paraffins and aromatic hydrocarbons by olefins and also in the formation of complex ketones, aldehydes, and carboxylic acid derivatives.

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Aluminum

Aluminum (melting point: 660 C, boiling point: 2494o C) is the most abundant metal in the world and makes up 7 to 10% by weight of the earth’s crust. Aluminum is manufactured by the electrolytic reduction of pure alumina(Al2O3) in a bath of fused cryolite (Na3AlF6). It is not possible to reduce alumina with carbon because aluminum carbide (A14C3) is formed and a back-reaction between aluminum vapor and carbon dioxide in the condenser quickly reforms the original aluminum oxide again. The electrolytic cells are large containers (usually steel), and each is a cathode compartment lined with either a mixture of pitch and anthracite coal or coke baked in place by the passage of electric current or prebaked cathode blocks cemented together. Two types of cells are used in the Hall-Heroult process: those with multiple prebaked anodes (Fig. 1), and those with a self-baking, or Soderberg, anode. In both types of cell, the anodes are suspended from above and are connected to a movable anode bus so that their vertical position can be adjusted. The prebaked anode blocks are manufactured from a mixture of low-ash calcined petroleum coke and pitch or tar formed in hydraulic presses, and baked at up to C.

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