Over the past 35 years, the chemical industry has largely changed its raw material base from coal to petroleum and natural gas. This has basically meant a shift from acetylene chemistry and coal tar chemistry to olefin chemistry (ethylene, propylene, isobutylene and butadiene) and petroleum-derived benzene, toluene, and xylenes. Methanol, ammonia, and hydrogen are still made from synthesis gas. However, synthesis gas is now made by methane reforming instead of coal gasification. These conversions have involved a vast expenditure of money, time, and effort, but the financial incentives have been huge and a great deal of new chemistry has been uncovered.