Towards greener chemical processes with a new catalyst for ethylene hydroformylation

A research led by ITQ (UPV-CSIC) has demonstrated the possibility to replace molecular catalysts in solution for all-solid catalysts based on isolated metal atoms for selective gas-phase ethylene hydroformylation, an important industrial chemical reaction. The discovery paves the way for greener chemical processes, with greater energy efficiency and lower carbon footprint, for the valorization of unconventional raw materials, alternative to crude oil. To test the designed catalyst, synchrotron light techniques have been used, among others, at the ALBA Synchrotron.

The hydroformylation of ethylene is a chemical process of remarkable industrial significance. In particular, this chemical reaction entails the net addition of a formyl group (-CHO carbon, hydrogen and oxygen) and a hydrogen atom to the ethylene carbon-carbon double bond. This process enables valorizing raw materials such as refinery off-gases as well as unconventional feedstocks such as shale-gas (a kind of natural gas) into oxygenated platform chemicals. Moreover, hydroformylation is also considered a reactive separation alternative to current cryogenic distillations, which are applied to recover ethylene, a valuable commodity chemical, from mixtures with less valuable gases such as ethane. Such cryogenic distillation separations count among the most energy demanding operations in the chemical industry and are therefore associated to high carbon footprints.

Catalysts are materials that are central to steering essentially all chemical transformations of the current chemical industry. A major class of industrially applied catalysts consists of molecular organometallic compounds that operate in a liquid solvent. These catalysts have proven to be highly active and exceedingly selective for a wide range of important transformations. However, they also face significant challenges. First, their limited thermal and chemical stability, which shortens their functional lifetime. On the other hand, the technical complexity associated with their recovery from liquid mixtures with products and solvents of the process, to prevent losses of the precious metals these catalysts are typically made of.

Now, scientists from the Instituto de Tecnología Química (ITQ, UPV-CSIC), the ALBA Synchrotron, the Institute for Nanoscience & Materials of Aragón (INMA, CSIC-UZ) and the Karlsruhe Institute for Technology have designed a new catalyst for selective gas-phase ethylene hydroformylation. Their research shows that a material bearing isolated atoms of rhodium (Rh) stabilized within the surface of stannic oxide (SnO2) is an all-inorganic solid catalyst which delivers an exceptional performance for the gas-phase hydroformylation of ethylene, in par with those thus far exclusive for conventional molecular catalysts in liquid media.

Read more on the ALBA website

Image: From left to right: Giovanni Agostini (former beamline responsible at NOTOS, ALBA), Gonzalo Prieto (ITQ), Juan José Cortés (ITQ), Wilson Henao (ITQ), Carlos Escudero (beamline scientist at NOTOS, ALBA) and Carlo Marini (beamline responsible of NOTOS, ALBA).

Efficient production technique for a novel ‘green’ fertiliser

Advanced milling technique produces slow-release soil nutrient crystals

A purely mechanical method can produce a novel, more sustainable fertiliser in a less polluting way. That is the result of a method optimised at DESY’s light source PETRA III. An international team used PETRA III to optimise the production method that is an adaptation of an ancient technique: by milling two common ingredients, urea and gypsum, the scientists produce a new solid compound that slowly releases two chemical elements critical to soil fertilisation, nitrogen, and calcium. The milling method is rapid, efficient, and clean—as is the fertiliser product, which has the potential to reduce the nitrogen pollution that fouls water systems and contributes to climate change. The scientists also found that their process is scalable; therefore, it could be potentially implemented industrially. The results by scientists from DESY; the Ruđer Bošković Institute (IRB) in Zagreb, Croatia; and Lehigh University in the USA have been published in the journal Green Chemistry. The new fertiliser still needs to be tested in the field.

For several years, scientists from DESY and IRB, have been collaborating to explore the fundamentals of mechanical methods for initiating chemical reactions. This method of processing, called mechanochemistry, uses various mechanical inputs, such as compressing, vibrating, or, in this case, milling, to achieve the chemical transformation. “Mechanochemistry is quite an old technique,” says Martin Etter, beamline scientist at the P02.1 beamline at PETRA III. “For thousands of years, we’ve been milling things, for example, grain for bread. It’s only now that we’re starting to look at these mechanochemical processes more intensively using X-rays and seeing how we can use those processes to initiate chemical reactions.”

Etter’s beamline is one of the few in the world where mechanochemistry can be routinely performed and analysed using X-rays from a synchrotron. Etter has spent years developing the beamline and working with users to fine-tune methods for analysing and optimising mechanochemical reactions. The result has been a globally renowned experiment setup that has been used in studying many types of reactions important to materials science, industrial catalysis, and green chemistry.

Read more on the DESY website

Image: The co-crystals of the novel fertiliser (symbolised here with gypsum) release their nutrients much more slowly

Credit: DESY, Gesine Born