Abstract

Petrochemicals are derived from natural gas or petroleum and can be broadly classified as olefins or aromatics. The choice of feedstock for a given operator is primarily an economic issue, but may be constrained by technical considerations or local availability of indigenous hydrocarbons. Feedstock economics are influenced by fuels products markets and the seasonal effects in fuels prices. Olefins are produced primarily by the thermal cracking of hydrocarbon feedstocks such as ethane, propane, naphtha, or gas oil. In the United States, the most important olefin feedstocks are ethane and propane, which are recovered from natural gas, whereas in most of the rest of the world naphthas are the dominant feedstocks. Lesser quantities of olefins, primarily propylene, are produced from refinery gas streams. Aromatics are recovered from refinery catalytic reformer operations and pyrolysis gasoline from olefin plants based on naphtha or gas oil feedstock. In the United States, reformer operations are the most important source; in the rest of the world, pyrolysis gasoline is the dominant feedstock. Although alternative feedstocks have been the subject of much research, only minimal usage can be expected over the coming decades.