Hydrocracking in the Oil Industry

Introduction

Petroleum refining is done today by using a platinum-based catalyst in conjunction with hydrogen, a process known as Hydrocracking. Operating at very high pressures (1,000-3,000 psi), hydrocrackers convert petroleum into gasoline, jet fuel, heating oil, and feedstock's for the petrochemical industry (Speight p.14).

Discussion

The production of transportation fuels is the primary business of most refineries, but other products are also important. This entry provides an overview of the processes by which refineries convert petroleum into an array of products.

Fuels, of course, are created in order to be destroyed by burning. As gasoline, diesel, and jet fuels are burned, they produce heat and a complex mixture of products that are vented into the atmosphere. The production of heat is the sole purpose for which the fuels are created; everything else is a byproduct. As researchers have become more knowledgeable about controlling the combustion process, they have had more success controlling the chemical composition of the products of combustion. Better control enables engineers to further reduce the effects that the combustion gases have on the environment. The other goal of this entry is to provide an overview of the combustion process.

The solution to the refiners dilemma was the development of cracking technology. The chemical conversion of less desirable is heavier in hydrocarbon molecules than the more desirable lighter ones. The idea behind cracking technology was understood by late 19th-century engineers and scientists, but as an industrial-scale process, cracking technology did not become widespread until the 1920s. Cracking technologies enabled refiners to increase the quantity of the lighter fractions that they obtained from each barrel of oil by converting some of the heavier hydrocarbons into lighter ones.

Not surprisingly, various different cracking technologies developed since the 1920s. Fluid catalytic cracking, for example, is a process that occurs at intense temperatures and low pressures. The heavier fractions of the petroleum mixed with a catalyst, a material that, while it is not consumed in the resulting chemical reaction, facilitates the conversion of heavier hydrocarbons into lighter ones. By contrast, a more expensive process, called Hydrocracking, uses intense temperatures and intense pressures (greater than 130 atmospheres) to break the larger hydrocarbons into smaller, lighter molecules. In Hydrocracking, hydrogen gas is introduced together with a catalyst. The hydrogen gas is produced in site; refineries are some of the most important producers and consumers of hydrogen gas (Copp & Zanella p. 65).

Cracking technologies operate on a rich mixture of hydrocarbons. They reduce the average size of the hydrocarbon molecules on which they operate but even after processing, the resulting mixture still contains some considerable hydrocarbons. In addition, some of the hydrocarbons produced by the cracking processes are too light materials consisting of these molecules have the boiling points that are too low to have any value as gasoline. These lighter hydrocarbons are recovered and subjected to yet another process, called polymerization, by which they combined to form larger gasoline-type hydrocarbons.

The cracking processes to which crude oil subjected also has the effect of decreasing the density of the ...