Paul Sabatier was the most outstanding chemist in the history of France. He won a noteworthy place in the history of French science because of the outstanding value of his scientific work, which is universally recognized. Sabatier was a French genius who worked hard to reach a superior degree of human perfection. He was defined by high standards of honor. Sabatier is known for his outstanding contributions to the field of catalysis, which had a profound impact on industrial and economic advancements and garnered considerable attention during the twentieth century. Sabatier identified anomalies in Faraday's physical theory and, in response, formulated his own chemical theory, which postulated the formation of unstable intermediaries. His subsequent painstaking work and discovery of the use of finely divided metal hydrogenation catalysts subsequently formed the basis for the margarine, oil hydrogenation, and synthetic methanol industries. He demonstrated the selectivity of catalytic action and the selectivity of catalysts to poisons as well as he introduced the use of supports and demonstrated the resultant enhancement in activity. He also made a close study of catalytic hydration and dehydration, carefully examining the feasibility of specific reactions and the general activity of various catalysts. In 1912, Paul Sabatier won the Nobel Prize in Chemistry for his work on heterogeneous catalysis, specifically his method of hydrogenating organic compounds in the presence of finely disintegrated metals, by which progress in organic chemistry was greatly advanced.

The celebration of the 350th anniversary of the French Academy of Science in 2016 provides the possibility to remember the central life and work of Sabatier, a universal scientist and ubiquitous chemist who gained his fame through patience, sacrifice, hard work, and only by merit of his own strengths.

1 Life of Sabatier or one hope of happiness…

Paul Sabatier was born on 5 November 1854 in Carcassonne, a small medieval town with an impressive fortress near Toulouse in southwestern France. He was the youngest of the seven children of Alexis Sabatier and Pauline Guilhem. He attended primary school in Carcassonne before moving to the “Lycée” in Toulouse in 1868. After one year, he joined the Collège Saint-Marie. He finished his secondary studies at Sainte-Marie, a Catholic high school. In June 1872, after receiving his diplomas as a ‘bachelier ès sciences’ (bachelor of sciences) and ‘bachelier ès lettres’ (bachelor of humanities), he departed for Paris to prepare for the entrance examinations to the ‘Grandes Écoles’ (‘École polytechnique’ and ‘École normale supérieure’). He placed highly in the entrance competitions for both schools; however, he chose the ‘École normale supérieure’, where Louis Pasteur was teaching chemistry, which he entered in 1874. At the ‘École normale’, he took courses given by Charles Friedel, Jean Gaston Darboux, Henry Sainte-Claire Deville, and Pierre Auguste Bertin. In 1877, Sabatier graduated first in his class in the competitive national physics ‘agrégation’ examination (the ‘aggregation’ is a competitive examination for teaching in high schools), and received his ‘license de physique’ and ‘license de mathématiques’ from the ‘École normale’. For one year, he taught in Nîmes as a professor of physics at the local school. Mutatis, mutandis…. Afterward, Louis Pasteur and Marcelin Berthelot each offered him a position as an assistant in their laboratories. In 1878, he chose to become an assistant in the laboratory of Marcelin Berthelot, then at the Collège de France. It is curious that he chose Berthelot, a man who was philosophically opposed to Sabatier's opinions, instead of Pasteur, a practicing Catholic with a philosophy closer to Sabatier's. However, this choice served as the first small step propelling him toward his ultimate accomplishments. In 1880, he received his Doctor of Science (‘docteur ès sciences’) degree for his work on The Thermochemistry of Sulfides, supervised by Berthelot. Sabatier took over responsibility for courses in physics offered by the Faculty of Sciences at Bordeaux until January 1882, when he accepted a similar post at the University of Toulouse. He additionally became responsible for courses in chemistry in 1883 and was elected Professor of Chemistry in 1884, a post which he retained until his retirement in 1930. He became Dean of the Faculty of Science in 1905, a post which he occupied until 1929. He subsequently remained faithful to Toulouse throughout his entire life, turning down many offers of attractive positions elsewhere, notably including offers to succeed Moissan at the Sorbonne in 1908 and Berthelot at the Collège de France. He retired from his professorship in 1930, after nearly fifty years of uninterrupted service to the Faculty of Science. After his retirement, he continued to lecture until his death in 1941.

2 Scientific work or labor omnia vincit improbus

During his doctoral thesis work, Sabatier prepared anhydrous sodium monosulfide and hydrosulfides in the pure state. He established the formula for a hydrated potassium hydrosulfide and showed that a number of alkaline polysulfides that had been described as distinct chemical species were actually mixtures containing free sulfur.

He developed an original method for the preparation of sulfides of calcium, barium, and strontium in the pure state based on passing a stream of hydrogen over the corresponding carbonates heated to live red (approximately 500 °C). He was the first to describe a method for the preparation of pure and crystallized aluminum sulfide by reacting hydrogen sulfide with alumina heated to red heat in a carbon boat. He prepared ‘persulphure d'hydrogène’ (hydrogen persulfide) and studied its properties, particularly its ability to decompose violently under the influence of light or in the presence of substances that react with it to form unstable combinations. He found that in the presence of water, it formed a rather unstable form of amorphous sulfur, which was insoluble in carbon disulfide, whereas the influence of ether led to the formation of a crystalline variety of sulfur known as ‘soufre nacre’ (pearl sulfur) or ‘soufre de Gerne 3’. He developed a new preparation method for silicon disulfide.

He studied the selenides and was the first to isolate a silicon selenide. He discovered the formation of a non-volatile subselenide of boron.

From 1881 onward, he studied various hydrates of metallic chlorides, determining their heats of hydration, their stability, the possibility of their dehydration under cold conditions, and their reactions with cold concentrated hydrogen chloride. He showed that the absorption of hydrogen chloride into a solution of cupric chloride decreased the solubility of this salt, yielding crystals of hydrated cupric chloride that dissolved in the presence of an additional amount of hydrogen chloride, leading to the formation of complex hydrochlorides. Sabatier was one of the first to use absorption spectroscopy to study hydrates, particularly those of cupric bromide. He observed in 1896 that the reactions of all copper compounds with a nitrosulfuric solution (nitrosulfuric acid), obtained by dissolving nitric acid in sulfuric acid, yielded an intense blue-purple solution because of the reduction of the nitric acid into a new acid, which he named nitrosodisulfonic acid (also known today as nitrosisulfonic acid). He developed a method for the direct synthesis of dark blue nitrosisulfonic acid. He proved that nitrosisulfonic acid could produce several metallic salts. After Berthelot and Mond in 1891, he also independently succeeded in producing iron carbonyl. Sabatier and his doctoral student Senderens speculated that other unsaturated gaseous molecules, such as nitric oxide, nitrous oxide, nitrogen peroxide, acetylene, and ethylene, could also be fixed on nickel or on reduced iron, yielding well-defined, stable, and volatile products comparable to nickel carbonyl. Sabatier studied the reactions of “incompleted” or “unsaturated” molecules on various metals. Between 1893 and 1894, Sabatier and Senderens succeeded in fixing nitrogen peroxide on copper (Cu₂NO₂), nickel and iron; they named these compounds “Nitro Metals.” They also found that they could produce the major types of natural petroleum by modifying the conditions of the hydrogenation of ethylene, and they achieved the synthesis of methane by hydrogenating carbon dioxide or carbon monoxide.

Sabatier then formulated a chemical theory of catalysis involving intermediate stages consisting of the formation of unstable chemical compounds, which determined the direction and rate of the reaction. He assumed that various nickel hydrides were involved in hydrogenation, whose compositions depended on the activity of the nickel. He found that carefully prepared nickel resulted in very active NiH₂, which would act on benzene, whereas impure nickel or nickel prepared at too high a temperature resulted in an impoverished hydride, Ni₂H₂, which was inactive for benzene but acted on ethylenic carbides or nitrate derivatives. Having made certain that Moissan was not thinking of continuing to study the reaction, Sabatier and Senderens repeated the experiment using ethylene instead of acetylene. When a stream of ethylene was applied to nickel, cobalt, or iron that had been freshly reduced, they observed the same results as Moissan and Moureu. However, the gas that exited the apparatus was not hydrogen, but instead consisted mainly of ethane, a saturated molecule. Ethane could arise only from the hydrogenation of ethylene, and this hydrogenation had been induced by the metal. In fact, they found that if a mixture of ethylene and hydrogen was applied to reduced nickel, then ethylene would be hydrogenated into ethane and the same metal could be used indefinitely (June 1897).

Sabatier and Senderens studied the hydrogenation of unsaturated hydrocarbons in depth and then turned to their next challenging problem: the hydrogenation of benzene. Using the same experimental method, they obtained nearly pure cyclohexane in 1901. After these successes, Sabatier was absolutely confident of the general nature of the experimental method they were using, stating its principle as follows: “Vapor of the substance, together with an excess of hydrogen, is directed on to freshly reduced nickel held at a suitable temperature (between 150° and 200 °C).”

After 1901, Sabatier proceeded from one type of reaction to another, transforming unsaturated or functionalized compounds into saturated or newly functionalized ones. Among these reactions, two were of particular interest: the transformation of water gas, the domestic gas used at that time, which contained small quantities of toxic carbon monoxide, into a completely nontoxic gas and the production of the major types of natural petroleum (Pennsylvanian, Romanian, Galician, and Baku) by modifying the conditions for the hydrogenation of acetylene. In addition to studying hydrogenation and other catalytic reactions, Sabatier demonstrated the reversibility of the catalytic process, namely, that the same catalyst can be used for both the direct and reverse reactions (hydrogenation and dehydrogenation). One of his most important contributions to the development of catalysis was his hypothesis regarding this phenomenon: “Powdered nickel is comparable in every way with a ferment and, as in the case of the living organism which constitutes ferments, infinitesimal doses of certain substances are sufficient to attenuate and even suppress altogether their functional activities.”

Sabatier was the father of the chemical theory of catalysis. According to his theory, during catalysis, a temporary unstable intermediate between the catalyst and one of the reactants forms on the surface of the catalyst. Since nickel is absolutely necessary for combining acetylene and hydrogen, it can be assumed that the nickel begins by attracting the hydrogen, but the capricious hydrogen soon breaks from the metal to join with the acetylene.

In 1912, Sabatier was awarded the Nobel Prize in Chemistry for his method of hydrogenating organic compounds in the presence of finely divided metals, which led to great progress in organic chemistry.

Sabatier's discoveries lie at the root of most of the largest chemical industries of today: almost all commercially produced chemicals involve catalysis at some stage of the process of their manufacture (e.g., petroleum treatment, petrochemicals, chemical synthesis, synthetic fuels, fat hydrogenation). The same principles outlined by Sabatier also apply in the ubiquitous automotive catalytic converter, which breaks down some of the more harmful byproducts of automotive exhaust. Nanotechnology and nanoparticles represent a new frontier in catalysis because the total surface area of a solid has an important effect on its catalytic reaction rate. An example is the synthesis of fuels from carbon dioxide and hydrogen. At the beginning of the twentieth century, Sabatier developed a process using a catalyst that reacts with carbon dioxide and hydrogen to produce methane and water. This reaction provides a means of producing water from the byproducts of the current life-support systems onboard the International Space Station and, thus, a way to produce water without the need to transport it from Earth. A system based on this principle was integrated into the station's water recovery system in October 2011. The six-astronaut crew aboard the ISS now uses water synthesized via this reaction. The hydrogen used is a waste product of the oxygen generation system; carbon dioxide is generated by the crew's metabolisms and released through respiration. The generated water is retained, whereas methane is vented outside of the space station. This “Sabatier Reaction System” can produce as much as 2500 liters of water per year.

Sabatier and Espil made the interesting discovery that after being used to hydrogenate nitrobenzene, nickel poisoned by chlorine recovers its ability to hydrogenate benzene. With Mailhe, another of his doctoral students, Sabatier found that certain metal oxides were catalysts not for hydrogenation and dehydrogenation, but instead for hydration and dehydration. They also observed that amorphous oxides were more active catalysts for dehydrogenation or dehydration than crystalline oxides, with the calcination of the latter at temperatures higher than 500 °C leading to marked agglomeration. This was the first observed example of sintering effects, which were later exploited to graduate the activity of catalysts.