This Review documents some examples of recent innovations in the field of catalytic selective oxidation from an industrial point of view. The use of alkanes as building blocks for the synthesis of bulk chemicals and intermediates is discussed, along with the main properties that catalysts should possess in order to efficiently catalyse the selective oxidation of these hydrocarbons. The currently developed processes for propene oxide and new processes under investigation for the synthesis of adipic acid are also described, highlighting innovative aspects for a better sustainability of the chemical industry.

Sustainability in Catalytic Oxidation: An Alternative Approach or a Structural Evolution?

Selective oxidation of light alkanes: interaction between the catalyst and the gas phase on different classes of catalytic materials

Heterogeneous catalysis plays a key role in the manufacture of essential products in key areas of agriculture and pharmaceuticals, but also in the production of polymers and numerous essential materials. Our understanding of heterogeneous catalysts is advancing rapidly, especially by using the latest characterisation methods on these relatively complex effect materials. At the heart of these catalytic processes, both selective oxidation and hydrogenation play a key role. Both oxidation and hydrogenation exhibit similar requirements since often a partial reaction product is required, rather than the products of total hydrogenation or oxidation, in the latter case this being typically carbon dioxide and water. This Feature Article considers the approaches available for catalyst discovery and design for heterogeneous catalysts. Three catalysts are considered in detail, two exemplifying oxidation and the other selective hydrogenation. The design of vanadium phosphates for the selective oxidation of butane to maleic anhydride is described in terms of the search for advanced materials with superior activity. This is achieved through the synthesis of wholly amorphous vanadium phosphates. The design of supported gold and gold palladium alloy catalysts for the oxidation of carbon monoxide and the direct hydrogenation of oxygen to form hydrogen peroxide is described and the problems concerning selectivity control are discussed.

/pdf/heterogeneous-catalysts-discovery-and-design-3uc0nk55a9.pdf

Heterogeneous catalysts—discovery and design

Vanadium phosphate catalysts have been extensively studied since the 1960s, when it was discovered that they are effective catalysts for the oxidation of butane to maleic anhydride. They represent the sole example of a commercialised material for the catalytic oxidation of an alkane. To date several hundred papers have been devoted to their study. Yet, virtually all studies have concentrated on two specific phases, namely the vanadyl hemihydrate precursor, VOHPO4·0.5H2O, which is converted into vanadyl pyrophosphate, (VO)2P2O7, which most researchers consider to be the active component of vanadium phosphate catalysts. In this feature article the nature of the active catalyst components is revisited and new approaches being pioneered in the synthesis of vanadium phosphates are described. In particular, detailed comments are made concerning the method of preparation and the role of crystalline and amorphous vanadium phosphate catalysts.

Vanadium phosphate: a new look at the active components of catalysts for the oxidation of butane to maleic anhydride

The development of a descriptor or descriptors that can relate the activity of catalysts to their physical properties is a major objective of catalysis research. In this study, we have found that the apparent activation energy for propene oxidation to acrolein over scheelite-structured, multicomponent, mixed metal oxides (Bi3FeMo2O12, Bi2Mo2.5W0.5O12, and Bi1–x/3V1–xMoxO4, where 0 ≤ x ≤ 1) correlates with the band gap of the catalyst measured at reaction temperature. We show through theoretical analysis of the energy components comprising the activation energy why the band-gap energy is the primary component dependent on catalyst composition and, hence, why one should expect the activation energy for propene oxidation to correlate with the band-gap energy. We also demonstrate that the change in band-gap energy with composition arises from the interplay between the sizes and energies of the V 3d, Fe 3d, Mo 4d, and W 5d orbitals, which give rise to the lowest unoccupied crystal orbitals. Both the utility of...

/pdf/band-gap-energy-as-a-descriptor-of-catalytic-activity-for-55n3kgdi31.pdf

Band-Gap Energy as a Descriptor of Catalytic Activity for Propene Oxidation over Mixed Metal Oxide Catalysts

A Comparison of the Reactivity of “Nonequilibrated” and “Equilibrated” V–P–O Catalysts: Structural Evolution, Surface Characterization, and Reactivity in the Selective Oxidation ofn-Butane andn-Pentane

G. Calestani

Papers

A Comparison of the Reactivity of “Nonequilibrated” and “Equilibrated” V–P–O Catalysts: Structural Evolution, Surface Characterization, and Reactivity in the Selective Oxidation ofn-Butane andn-Pentane