R. A. Aitken

With Sulfuric Acid

Sulfuric acid is believed to be the worlds largest-volume industrial chemical. The production of phosphate fertilizer materials, especially wet-process phosphoric acid, is the major end-use market for sulfuric acid, accounting for nearly 60% of total world consumption. The balance is consumed in a wide variety of industrial and technical applications. Apparent world sulfuric acid consumption increased by about 7% between 1985 and 1997 in spite of a 20% decline between 1988 and 1993. A moderate increase of about 10% is forecast for the 1999-2002 period, assuming a reasonably rapid recovery from the present global economic crisis. The United States is the major market, accounting for 30% of world consumption in 1997. Socialist Asia, Western Europe and Africa are also large consumers, each accounting for more than 10% of world consumption. Major declines have occurred in the former USSR, Western Europe and Eastern Europe since the late 1980s. A further decline is projected for Western Europe, while a partial recovery is forecast for the former USSR and Eastern Europe. Major increases occurred in Socialist Asia, the United States and Latin America between 1985 and 1997. World sulfuric acid consumption in 1997 was about 157 million metric tons with an estimated fob value of about

With Acid Halides

8 billion. Many phosphate fertilizer companies produce sulfuric acid from elemental sulfur. The process generates heat, which can be recovered and used in the plant or to operate cogeneration facilities. Periodically, phosphate fertilizer companies also participate in the merchant sulfuric acid market, selling excess acid at the gate or supplementing their requirements with purchased acid, typically by-product acid. About 65% of world sulfuric acid in 1997 was produced from elemental sulfur. Approximately 13% was produced from pyrites and the balance from other sources (mainly smelter gases). Over the years, the volume produced from elemental sulfur and other sources has increased at the expense of pyrites. International trade involved approximately 5% of world sulfuric acid production in 1997, up from 2.5% in 1985. The percentage and the total volume may decline somewhat during the forecast period. In 1997, Western Europe and the United States combined accounted for almost 60% of world sulfuric acid imports. Japan accounted for 15%. Increased recovery of by-product sulfuric acid at smelters has had a significant impact on the industry, leading to increased trade in sulfuric acid (since byproduct producers are not necessarily located near acid markets) and forcing some sulfur-burning plants to close. One portion of the sulfuric acid business that has grown as a result of environmental restrictions is the portion that regenerates sulfuric acid. The primary environmental issue that has affected the sulfuric acid industry is restrictions on sulfur dioxide emissions in other industries, such as copper smelting. Smelters have been required to recover increasing percentages of the sulfur dioxide that is emitted during the smelting process. In many cases, smelters have chosen to recover the by-product sulfur dioxide in the form of sulfuric acid. Other industries such as power plants are also coming under increased pressure to reduce their sulfur dioxide emissions. At the present time, these industries have generally chosen to limit sulfur dioxide emissions by burning low-sulfur coal or using limestone scrubbing systems. However, several companies are recovering the sulfur dioxide as sulfuric acid.

One-Electron Oxidation

An acid halide (also known as an acyl halide) is an organic compound derived from an carboxylic acids by replacing a hydroxyl group with a halide group.