Biomass hydrodeoxygenation catalysts innovation from atomistic activity predictors

Abstract

Circular economy emphasizes the idea of transforming products involving economic growth and improving the ecological system to reduce the negative consequences caused by the excessive use of raw materials. This can be achieved with the use of second-generation biomass that converts industrial and agricultural wastes into bulk chemicals. The use of catalytic processes is essential to achieve a viable upgrade of biofuels from the lignocellulosic biomass. We carried out density functional theory calculations to explore the relationship between 13 transition metals (TMs) properties, as catalysts, and their affinity for hydrogen and oxygen, as key species in the valourization of biomass. The relation of these parameters will define the trends of the hydrodeoxygenation (HDO) process on biomass-derived compounds. We found the hydrogen and oxygen adsorption energies in the most stable site have a linear relation with electronic properties of these metals that will rationalize the surface's ability to bind the biomass-derived compounds and break the C–O bonds. This will accelerate the catalyst innovation for low temperature and efficient HDO processes on biomass derivates, e.g. guaiacol and anisole, among others. Among the monometallic catalysts explored, the scaling relationship pointed out that Ni has a promising balance between hydrogen and oxygen affinities according to the d -band centre and d -band width models. The comparison of the calculated descriptors to the adsorption strength of guaiacol on the investigated surfaces indicates that the d -band properties alone are not best suited to describe the trend. Instead, we found that a linear combination of work function and d -band properties gives significantly better correlation. This article is part of a discussion meeting issue ‘Science to enable the circular economy’.

Hydrodeoxygenation of guaiacol over orthorhombic molybdenum carbide: a DFT and microkinetic study

“…Such direct relation between the catalytic performance and the d-band position of the transition metal is due to the bonding and anti-bonding states formed when the adsorbate approaches the surface, where hybridization between the frontier orbitals of the adsorbate and s and d-orbital of the metal occurs; the adsorption strength is therefore dependent on the relative position of the metal states with respect to the Fermi level. The dband theory has been quite successful in explaining, for instance, the trends observed in the oxygen reduction reactions (ORR) [10][11][12][13] , and the d-band center of catalytic materials has also been used as a descriptor for property prediction in transition-metal catalysed HDO studies [14][15][16][17] . The transferability of the d-band approach is now of consideration for alternative composite catalysts, such as carbides and nitrides.…”

Decomposition of Formic Acid over Orthorhombic Molybdenum Carbide

“…For the considered surface facets, the lowest surface energy is calculated for γ110 (4.22 J m -2 ) and the highest surface energy is calculated for γ001 (4.94 J m -2 , Figure 1S), with a total range of 0.72 J m -2 . Whilst not the most energetically favourable [37], the Mo-terminated (100) facet is relatively stable and, therefore, investigated in the continuation of this study. To determine a chemically accurate thickness for the (100) slab model, γ100 was calculated as a function of slab thickness; γ100 differs by 0.47 J m -2 between two and four layers, and by less than 0.13 J m -2 , when comparing four, six and eight layers; thus, for a balance of computational efficiency and accuracy, subsequent calculations are performed with a four-layer model.…”

“…Therefore, only the metal terminations for the facets are considered herein. Furthermore, recent experimental and computational studies report that the (100) facet is highly active for hydrodeoxygenation (HDO) reactions [34,35]; the same surface has a high affinity towards hydrogen adsorption [36], which is a favourable characteristic for an HDO catalyst [37].…”

The Effect of Pristine and Hydroxylated Oxide Surfaces on the Guaiacol HDO Process: A DFT Study

“…Different catalytic materials have been studied to improve the HDO efficiency. Supported transition metals like Ni and Pt nanoparticles have received substantial attention due to their oxyphilic characteristics, helping to absorb oxygen compounds and easy desorption of deoxygenated products [13] . These metal nanoparticles are commonly supported on oxides due to their easy preparation, stability, and accessible cost [14] .…”