Density-functional theory calculations and microkinetic analysis are used to investigate the efficacy of Ga-modified γ-Al 2 O 3 (110) surfaces for the catalytic dehydrogenation of ethane and elucidate the synergy between Ga and Al sites. The model surfaces are modified by either Ga grafting or doping. We consider and analyze numerous active sites and rank them using microkinetic analysis. The kinetic parameters obtained from microkinetic modeling are compared with experimental values for ethane dehydrogenation over Ga 2 O 3 −Al 2 O 3 mixed oxides prepared by coprecipitation. The dominant reaction pathway proceeds via heterolytic C−H bond dissociation to a surface proton and a metalcarbanion intermediate that undergoes β-hydride elimination. We find that grafted Ga sites are catalytically inactive. In contrast, Ga-doped sites exhibit 5-fold enhancement in catalytic activity when compared to the sites on pristine Al 2 O 3 , owed to the synergy between neighboring Al III and Ga IV sites. Furthermore, we model and investigate the effect of surface hydroxylation, demonstrate how surface water interferes with the aforementioned synergy between Al III and Ga IV sites and discuss the implications for the catalytic activity of the modified surfaces. Increase in the partial pressure of H 2 O significantly increases the apparent activation energies of dehydrogenation and interestingly changes the most active site.

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We present a perspective for accelerating biomass manufacturing via digitalization. We summarize the challenges for manufacturing and identify areas where digitalization can help. A profound potential in using lignocellulosic biomass...

Due to the feasibility of an electrically rechargeable zinc/air cell made of a zinc foil as active material, an aqueous choline acetate (ChAcO) mixture as an electrolyte and a spinel MnCo2O4 (MCO) and NiCo2O4 (NCO) as a bi-functional oxygen catalyst was investigated in this work. The 30 wt.% water-containing aqueous ChAcO solution showed high contact angles close to those of KOH favoring triple-phase boundary formation in the gas diffusion electrode. Conductivity and pH value of 30 wt.% H2O/ChAcO amounted to 5.9 mS cm−1 and 10.8, respectively. Best results in terms of reversible capacity and longevity of zinc/air cell were yielded during 100 h charge/discharge with the MnCo2O4 (MCO) air electrode polarization procedure at 100 µA cm−2 (2.8 mA g−1zinc). The corresponding reversible capacity amounted to 25.4 mAh (28% depth of discharge (DOD)) and the energy efficiency ranged from 29–54% during the first and seventh cycle within a 1500 h polarization period. Maximum active material utilization of zinc foil at 100 µA cm−2 was determined to 38.1 mAh (42% DOD) whereas a further charging step was not possible due to irreversible passivation of the zinc foil surface. A special side-by-side optical cell was used to identify reaction products of the zinc/air system during a single discharge step in aqueous ChAcO that were identified as Zn(OH)2 and ZnO by Raman analysis while no carbonate was detected.

Production of butadiene from biomass-based tetrahydrofuran (THF) is explored as an alternative to the existing petroleum-based processes. Metal oxide catalysts have been shown to exhibit varying product selectivities when reacted with THF. Among those oxides, ZrO2 showed the highest selectivity for butadiene. In contrast, Al2O3 showed the highest selectivity for the competing retro-Prins products, C3H6 and HCHO. The reasons behind the varying selectivity across oxides are unclear. In this work, we employ periodic density functional theory and mean-field microkinetic modeling to investigate the mechanism of the reaction of THF to butadiene and retro-Prins products on t-ZrO2 (101) (dry and hydrous) and on γ-Al2O3 (110). Our simulations reproduce the experimental selectivity trends. High selectivity for butadiene is promoted by the presence of neighboring Lewis acid metal sites that facilitate E1cB hydroxyl elimination from a 3-butenoxide intermediate; on hydrous Al2O3; where such neighboring Lewis acid centers are not available, the butenoxide undergoes E2 elimination and retro-Prins products ensue. The THF ring opening is rate-determining on ZrO2, whereas the γ-proton elimination that yields the 3-butenoxide intermediate is rate controlling on hydroxylated Al2O3. We conclude that the local topology around the active site greatly influences the mechanism and selectivity.