Pentadienes serve as key building blocks for the chemical and polymer industries and are widely used as monomers in the production of adhesives, plastics, and resins. However, state-of-the-art processes to produce pentadienes are based on steam cracking of naphtha (typically at 850ºC) and rely on fossil fuels with the attendant environmental impacts. Therefore, the sustainable production of pentadienes from renewable resources, such as biomass-derived materials, is a vitally important and urgent task.Â
Methyltetrahydrofuran (2-MTHF) can be produced readily from lignocellulose-derived furfural via low-cost, high-yield processes and has been identified as a sustainable resource for making pentadienes via ring-opening, hydrogen transfer and dehydration processes. Leading catalysts for this reaction include amorphous SiO2/Al2O3, and Al or B- zeolites. However, these microporous catalysts often suffer from deactivation due to the formation of cokes. Furthermore, achieving effective selectivity control towards pentadienes in this reaction is still a significant challenge.
MCM-41 is a mesoporous silica-based material used as a catalyst or catalyst support for a wide range of reactions; emerging niobium-based catalysts have shown exceptional performance for the hydrodeoxygenation of biomass under mild conditions.
An international team of researchers studied whether MCM-41 materials containing weak acid sites and active niobium sites effectively address the challenges of pentadiene production. The reaction mechanism of conversion of 2-MTHF is complex, involving multiple reaction intermediates and products. The ring-opening of 2-MTHF is the rate-limiting step in this conversion. The research team aimed to determine the full molecular details of the catalytic mechanism through the use of operando X-ray Absorption Spectroscopy (XAS), combined with Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and in situ high-field solid-state Nuclear Magnetic Resonance spectroscopy.
On Diamond’s I20-EDE beamline, they used the spectroscopy group’s recently commissioned high-temperature synchronous gas/vapour phase XAS/DRIFTS set-up coupled to the mass spectrometer and in-house developed gas dosing rig. This combination enabled them to propose a detailed reaction mechanism via temperature programmed spectroscopy.
Read more on Diamond website
Image: The highly selective conversion of biomass-derived 2-methyltetrahydrofuran (2-MTHF) into pentadienes has been achieved over an aluminium and niobium bimetallic atomically doped on MCM-41. The Nb(V) sites enhance the catalytic performance by binding 2-MTHF.