Emergence of Catalyst Technology, A Brief History

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^th and early 20^th centuries most industrial reactions were run at high temperatures and pressures in order to achieve reasonable rates of production. This is the sledgehammer approach. Unfortunately, these severe conditions are (1) 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 the feather 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.

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).

In 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.

Germany used this technology during World War I1 to provide synthetic fuels for operating their war machinery when petroleum supplies had been cut off. The development of efficient Ni catalysts for hydrogenation of organic compounds provided new synthesis routes to chemicals and foodstuffs, including low cholesterol vegetable oils. Catalytic cracking, which began between 1935 and 1940, was the first significant use of solid catalysts in the petroleum industry-a very important development, which allowed refiners to increase gasoline yield and thereby use petroleum crude feedstock more efficiently. This was followed in 1950 by the development of catalytic naphtha reforming involving dehydrogenation of cyclohexane to benzene and isomerization of straight chain alkanes to increase gasoline octane rating. Around 1960 marked the beginning of hydrotreating catalyst technology at refineries to remove sulfur, nitrogen, and metals from petroleum feedstocks, a technology, which has continued to expand as petroleum feedstocks have become increasingly ‘sour’ with organic sulfur and nitrogen compounds.

Around 1955, Ziegler-Natta discovered that AIC13 catalysts could be used for production of polypropylene at low pressures. This and later discoveries of catalysts for making important monomer building blocks such as acrylonitrile and acrolein (beginning around 1963) revolutionized the chemical and polymer industries.

One of the first large-scale industrial processes to utilize a homogeneous catalyst was the Wacker Process for making acetaldehyde from ethylene. The use of this ‘feather approach’ (around 1960) enabled reduction of the temperature and pressure from 375-500°C and ten’s of atmospheres to 100°C and 7 atm. Since then more than a dozen large-scale commercial processes (exceeding 100,000 metric tons per year) have been developed based on homogeneous catalysis, including olefin hydrogenation and disproportionation,c arbonylation, oxidation, and polymerization (Heinemann, 198 1).

Several decades ago, Weisz and Frilette (I 960) coined the word ‘shape-selective catalysis’ to describe the unique selectivity properties of crystalline molecular sieves or zeolites in cracking n-alkanes to exclusively straight chain products. The ‘shape-selectivity’ of zeolites is based on their unique ability to selectively admit or reject molecules of a characteristic size and/or shape at the entrance to molecular-size pores containing active sites. Aluminosilicate zeolites are further characterized by a high density of strong acid sites. Because of their high activities and selectivities for acid-catalyzed reactions, zeolites quickly (1964-8) found application to catalytic cracking and hydrocracking of petroleum feedstocks. In the subsequent three decades, zeolites have found numerous applications to shape-selective petroleum processing and production of chemicals and fuels (Chen et al., 1989; Bhatia, 1990; Chon et al., 1996; Guisnet and Gilson, 2002; Auerbach et al., 2003), e.g. catalytic reforming to produce octane boosters, dewaxing of distillate fuels and lubebase feedstocks, oligomerization of light olefins to distillates, xylene synthesis and isomerization, ethylbenzene and paraethyltoluene synthesis, and gasoline or light olefin production from methanol.

During the late 1970s and early 1980s, noble metal catalysts were developed for control of CO, hydrocarbon and NO emissions from automobiles. Increased emphasis on environmental control in the United States and Europe during the 1980s and 1990s led to the development of vanadium titania and zeolite catalysts for selective reduction of nitrogen oxides with ammonia. Catalysts for removal of volatile organic hydrocarbons (VOCs) and hazardous organics such as chlorohydrocarbons were also developed during this period. Developments since 1990 will be addressed later in the chapter.