1723 357241 2 Graphical abstract Research Highlights All main nitrogen fixation methods were overviewed  Energy consumption of the methods were compared  The Haber-Bosch and non-thermal plasma processes are industrially promising  Metallocomplex nitrogen fixation is more energy intensive than the HaberBosch 3 AbstractThe conversion of atmospheric nitrogen into valuable substances such as fertilisers and fine chemicals is essential for agriculture and many other processes that sustain life on the planet. Although the Haber-Bosch process is the most important method of nitrogen fixation, the process is associated with major environmental concerns because it is very energy intensive and requires non-renewable feedstock to generate hydrogen. Hence, alternative ways of nitrogen fixation are being studied, from plasma synthesis and biological processes to metallocomplex catalysis, while existing methods are being improved using novel catalysts. This review covers all of the major areas of nitrogen fixation, discusses the industrial feasibility of each process, the reaction mechanisms, and provides a comparative evaluation of the various nitrogen fixation processes in terms of energy efficiency. Considering energy efficiency, the Haber-Bosch process and non-thermal plasma nitrogen fixation are promising methods for green industrial nitrogen fixation. Although metallocomplex nitrogen fixation takes place at ambient pressures, energy estimations show that this method does not provide higher energy efficiency than biological nitrogen fixation or the Haber-Bosch process. Biological nitrogen fixation on the other hand, has energy efficiency comparable to that of the Haber-Bosch process.

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The desorption of methanol and dimethyl ether has been studied over fresh and hydrocarbon-occluded ZSM-5 catalysts with Si/Al ratios of 25, 36 and 135 using a temporal analysis of products reactor. The catalysts were characterized by XRD, SEM, N 2 physisorption and pyridine FT-IR. The crystal size increases with Si/Al ratio from 0.10 to 0.78 µm. The kinetic parameters were obtained using the Redhead method and a plug flow reactor model with coupled convection, adsorption and desorption steps. ZSM-5 catalysts with Si/Al ratios of 25 and 36 exhibit three adsorption sites (low, medium, and high temperature sites), while there is no difference between medium and high temperature sites at a Si/Al ratio of 135. Molecular adsorption on the low temperature site and dissociative adsorption on the medium and high temperature sites give a good match between experiment and the plug flow reactor model. The DME desorption activation energy was systematically higher than that of methanol. Adsorption stoichiometry shows that methanol and DME form clusters onto the binding sites. When non-activated re-adsorption is accounted for, a local equilibrium is reached only on the low and medium temperature binding sites. No differences were observed, other than in site densities, when extracting the kinetic parameters for fresh and activated ZSM-5 catalysts at full coverage. Graphical AbstractElectronic supplementary material The online version of this article (https://doi

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Highlights• Pd-Bi catalysts were studied in the 2-methyl-3-butyn-3-ol semi-hydrogenation • Poisoning with Bi increases alkene selectivity, but decreases activity • Poisoning with Bi hinders the formation of Pd beta-hydride phase • Kinetic modelling suggets significant ligand effects at high Bi content

The unique feature of the zeolite catalysts is the presence of catalytically active acidic hydroxyls, also known as Brønsted acid sites (BAS), in the zeolite micropores of molecular dimensions. The accessibility and catalytic properties of BAS depend on their local environment, and it is therefore important to know the exact locations of BAS and the number of BAS in these locations. This paper reports a detailed FT-IR investigation into BAS present in the acidic and partially Na-exchanged samples of industrially important mordenite (MOR) zeolite. Our results demonstrate the existence of (at least) six distinct BAS that can be visualized by six single bands in Fourier self-deconvolution traces of the IR spectra. The quantitative estimates for the amounts of these distinct BAS were obtained using the six-band deconvolution method developed in this work. These estimates show that in the purely acidic H-MOR sample about 25% of BAS are located in eight-membered ring (8-MR) channels (O1−H and O9−H hydroxyls), ∼13% of BAS are at the intersections between the side pockets and 12-MR channels (O5−H hydroxyls), and ∼62% of BAS are located in 12-MR channels (∼39% correspond to O2−H and/or O10−H hydroxyls and the remaining 23% to O3−H and O7−H hydroxyls). These quantitative data demonstrate that the acid sites are distributed quite evenly between oxygen atoms in different crystallographic positions, thus revealing the complexity of the experimental identification of distinct BAS in mordenites and explaining the variety of the earlier suggestions regarding their positions in these zeolites.