Initially attractive because it was cheap and relatively abundant, natural gas also held the advantage of being cleaner burning and far less damaging to the environment, factors that became increasingly important with the passage of the Clean Air Act in the 1970s. Indeed, natural gas has replaced crude oil as the most important source of petrochemical feedstocks.
Petrochemical and automotive engineers had already responded to environmental concerns in a variety of ways. As early as the 1940s German émigré Vladimir Haensel invented a type of reforming refining process called platforming that used very small amounts of platinum as a catalyst and produced high-octane, efficient-burning fuel without the use of lead. Haensel's process, which was eventually recognized as one of the most significant chemical engineering technologies of the past 50 years, made the addition of lead to gasoline no longer necessary. Today, more than 85 percent of the gasoline produced worldwide is derived from platforming.
Also well ahead of the environmental curve was Eugene Houdry, who had developed catalytic cracking; in 1956 he invented the catalytic converter, a device that removed some of the most harmful pollutants from automobile exhaust and that ultimately became standard equipment on every car in the United States. Other engineers also developed methods for removing more impurities, such as sulfur, during refining, making the process itself a cleaner affair. For its part, natural gas was readily adopted as an alternative to home heating oil and has also been used in some cities as the fuel for fleets of buses and taxicabs, reducing urban pollution. Environmental concerns have also affected the other side of the petrochemical business, leading to sophisticated processes for recycling existing plastic products.
Somewhere around the middle of the 20th century, petroleum replaced coal as the dominant fuel in the United States, and petroleum processing technologies allowed petrochemicals to replace environmentally harmful coal tar chemistry. The next half-century saw this dominance continue and even take on new forms, as plastics and synthetic fibers entered the consumer marketplace. Despite increasingly complex challenges, new generations of researchers and engineers have continued to keep the black gold bonanza in full swing.