Heterogeneous Catalysis with Cultural Connections - ChemPRIME

Heterogeneous Catalysis with Cultural Connections

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The speeding up of a reaction in which the catalyst is in a different phase than the reactants is termed as heterogeneous catalysis. In this form of catalysis, the reactants are most commonly found in the gas phase with some solid substance acting as the catalyst. By the nature of this combination, the rate-limiting step occurs at the gas-solid interface, or the solid's surface. Heterogeneous catalysis is for this reason often referred to as surface catalysis.

Although the exact mechanisms of heterogeneous catalysis for reactions have yet to be fully understood, it is known that the catalyst's surface contains active sites that are capable of weakening or breaking bonds in the reactant molecule's structure. This manipulation results in a decreasing of the activation energy for the reaction and an increase in the rate of reaction.

Diagram of the industrialized Haber process

Heterogeneous catalysis is used extensively to facilitate numerous processes fundamental to many important industries. The Haber process for synthesis of NH3 from N2 and H2 is one such example of how essential surface catalysis is to industry. This process of nitrogen fixation makes use of an enriched iron catalyst in order to produce ammonia on an industrial scale.[1] A method by which the abundant atmospheric nitrogen might be efficiently transformed into nitrates had been avidly searched for throughout history, for this compound is necessary for the production of potent fertilizer and munitions.

It wasn't until the twentieth century, however, that the German chemist Fritz Haber succeeded in developing a process by which ammonia could be produced from air in a reasonably efficient manner. The German company BASF immediately recognized the potential of such a process. They purchased it and delegated the task of scaling the process to industrial-level production to Carl Bosch. Success was soon attained, and BASF was producing ammonia on the industrial scale by 1913.[2]

Influence on WWI

The Haber Process had broad implications for Germany, a country on the verge of waging a war of unprecedented scale. The use of nitrates as an agricultural fertilizer was rapidly supplanted by their use to produce explosives. Ammonia can be converted into a synthetic form of Chile saltpeter, which was used at the time as a fundamental ingredient in gunpowder and highly effective explosives. Whereas the allies had access to natural forms of saltpeter in large and easily accessible quantities, Germany had no such alternatives. If Germany didn't have the option of producing its own synthetic nitrates through the Haber process, its only option would have been importing saltpeter from Chile. This would have been highly unrealistic, as the British Navy was capable of blocking the supply with relative ease.[3]

Munitions factory worker

For these reasons, it is arguable that the Germans would have ever attempted to conduct such an immense war without the aid of the Haber Process. The German army would have had no means of producing gunpowder and explosives, two components essential to the success of an army during the twentieth century. Furthermore, the effect of the Haber Process on the production of fertilizers was also highly influential on the decision of waging war. By 1915, the dependence of industrialized countries on nitrogen-based fertilizers was undeniable. Without food and an efficient means by which it might be produced, an army cannot function. Thus, by providing a source of fertilizer, the Haber Process further increased Germany's chances of realistically contending in a large-scale war.

The use of the Haber process by Germany during World War I is just one example of how a single concept in chemistry can shift the entire course of history. Fritz Haber's contribution to science, a small but ingenious process, could arguably have precipitated the largest war up to that point in history. The purpose of this statement is not to denigrate chemistry. In fact, much good has been brought about by the Haber process. Its contribution to the agricultural industry is immense even to this day, and the increased food production brought about by greater access to potent fertilizers has allowed for the sustenance of greater populations and better lifestyles. The purpose is rather to point out the powerful impact that a simple concept such as heterogeneous catalysis can have on the course of history.

References

  1. http://www.chemguide.co.uk/physical/equilibria/haber.html
  2. http://en.wikipedia.org/wiki/Haber_process
  3. http://query.nytimes.com/mem/archive-free/pdf?_r=1&res=9807EEDA133BEE32A25750C0A9649C946195D6CF&oref=slogin
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