4 FUNDAMENTALS OF INDUSTRIAL CATALYTIC PROCESSES

“Chemistry without catalysis would be a sword without a handle, a light without brilliance, a bell without sound.” - A . Mittasch

1.1 Emergence of Catalyst Technology, A Brief History

1.1.1 Basic Variables for Control of Chemical Reactions Since the beginning of time, man has been concerned about the control of chemical reactions. There are

presently four basic variables available to us to control chemical reactions: (1) temperature, (2) pressure, (3) concentration, and (4) contact time.

In the 19‘h and early 20th centuries most industrial reactions were run at high temperatures and pressures in order to achieve reasonable rates of production. This is the dedgehamrner approach. Unfortunately, these severe conditions are ( I ) energy intensive, (2) corrosive or otherwise damaging to equipment and materials, and (3) nonselective-that is, they result in undesirable side reactions and side products.

However, in the last 4-5 decades, two important technological developments have enabled us to run most chemical reactions under less severe conditions:

1. First, extensive use of catalysts, substances which speed up reaction rate, has enabled us to operate at lower pressures and temperatures. We call this thefeather approach.

2. Second, improved methods of contacting, such as packed and fluidized catalyst beds, have enabled us to operate under continuous flow conditions at much higher efficiencies.

1.1.2 A Brief History of Catalyst Technology Development Let’s briefly trace the historical developments leading to the present extensive use of catalytic

processes.’ Catalyst technology was practiced on a small scale for centuries in inorganic form to make soap and in the form of enzymes to produce wines, cheeses, and other foods and beverages (Heinemann, 1981). The word ‘catalysis’ was coined by Berzelius in 1836; moreover, catalysts were identified and studied by Berzelius, Davy, Faraday, and other scientists in the early 1800s. However, industrial catalyst technology had its real beginning about 1875 with large-scale production of sulfuric acid on platinum catalysts, although sadly the inventor of this catalyst, Peregrin Philips (British Patent No. 6096, 1831), did not live to see the first contact sulfuric acid plant constructed (Burwell, 1983).

I n the ensuing 100 years, catalyst technology expanded exponentially, although the timeline can be highlighted with several major breakthroughs (summarized in Table 1.1). The first of these was ammonia oxidation on Pt gauze developed by Ostwald and leading to the production of nitric acid in 1903. The discovery of promoted iron for ammonia synthesis by Mittasch, and the subsequent development of the ammonia synthesis process by Bosch and Haber occurred in the period of about 1908 to 1914; however, this important advance was no accident, since Mittasch, with typical German thoroughness, investigated over 2500 catalyst compositions in his search for the optimum. Ninety years later, it is still the most widely used catalyst for this reaction. Consider what impact this single discovery has had on agriculture and our ability to feed the masses of the world.

In the early 1900s (1920-1940), catalytic processes for hydrogenation of CO to methanol or liquid hydrocarbons paved the way for using synthesis gas from natural gas or coal to produce liquid fuels and chemicals.

’ The history of catalytic technology has been reviewed by Heinemann (l98l), while Davis and Hettinger (1983) have edited a volume that reviews selected histories of developments in heterogeneous catalysis with emphasis on those in the United States. Laidler’s text on kinetics ( I 987) includes biographical sketches of important contributors to the fields of kinetics and catalysis research and technology.