Ni can be used as a catalyst for dry reforming of methane (DRM), replacing more expensive and less abundant noble metal catalysts (Pt, Pd, and Rh) with little sacrifice in activity. Ni catalysts deactivate quickly under realistic DRM conditions. Rare earth oxides such as CeO₂, or as CeO₂-ZrO₂-Al₂O₃ (CZA), are supports that improve both the activity and stability of Ni DRM systems due to their redox activity. However, redox-active supports can also enhance the undesired reverse water gas shift (RWGS) reaction, reducing the hydrogen selectivity. In this work, Ni on CZA was coated with an ultrathin Al₂O₃ overlayer using atomic layer deposition (ALD) to study the effects of the overlayer on catalyst activity, stability, and H₂/CO ratio. A low-conversion screening method revealed improved DRM activity and lower coking rate upon the addition of the Al₂O₃ ALD overcoat, and improvements were subsequently confirmed in a high-conversion reactor at long times onstream. The overcoated samples gave an H₂/CO ratio of ∼1 at high conversion, much greater than uncoated catalysts, and no evidence of deactivation. Characterization of used (but still active) catalysts using several techniques suggests that active Ni is in formal oxidation state >0, Ni-Ce-Al is most likely present as a mixed oxide at the surface, and a nominal thickness of 0.5 nm for the Al₂O₃ overcoat is optimal.

Besides being a renewable energy source, the catalytic conversion of bio-alcohols can serve as a sustainable means of producing high-value chemicals. Butenes produced by dehydration of 1-butanol could serve as building blocks for several essential compounds such as fuels and polymers. This study provides theoretical insights into the competing pathways for the formation of butene isomers (1-butene, cis/trans 2-butenes and iso-butene) during catalytic dehydration of 1-butanol in H-ZSM-5. As di-1-butyl ether (DBE) is one of the key products during low temperature dehydration of 1-butanol, a new mechanism for direct formation of trans-2-butene from DBE via E1 elimination is also envisaged along with the direct dehydration of 1-butanol to trans-2-butene. A 2-butoxide mediated stepwise mechanism and a concerted mechanism involving simultaneous protonation of the double bond by the Brønsted acid site and abstraction of the H_γ by the zeolite oxygen are considered for the double bond isomerization in H-ZSM-5. A monomolecular 2-butoxide and iso-butoxide mediated mechanism is considered for the skeletal isomerization. The transformation of 2-butoxide to iso-butoxide occurs via a π-bonded propene–methyl carbocationic transition state. DFT based microkinetic simulations show that, except for very low conversion levels where 2-butenes are produced via E1 elimination of 1-butanol from the protonated di-1-butyl ether (DBE*), the formation of 2-butenes occurs essentially via double bond isomerization mechanisms with comparable contributions of both concerted and 2-butoxide mediated stepwise mechanisms. Owing to the higher activation barrier for the skeletal isomerization, isobutene is not observed in the simulated temperature range of 450–500 K. Simulation results indicate that low reaction temperature, low site time and high butanol pressure favor production of 1-butene and DBE, while high temperature and site time and low butanol pressure favor the consecutive reactions leading to production of butene isomers.

Ab initio based microkinetic modelling of 1-butanol dehydration to butene isomers is used to obtain mechanistic insights into the effect of a zeolite framework. A detailed microkinetic model including double bond isomerization, skeletal isomerization and mechanisms for the direct formation of 2t-butene from 1-butanol dimer and di-1-butyl ether (DBE) is considered for the dehydration in H-ZSM-5, H-ZSM-22 and H-FER. H-FER favors the production of 2t-butene and H-ZSM-22 achieves thermodynamic equilibrium composition for linear butenes even at low conversion levels, while H-ZSM-5 maximizes 1-butene selectivity. Significant differences are observed in the reaction mechanism leading to formation of 2t-butene. For H-ZSM-5 and H-ZSM-22, the formation of 2-butenes occurs via double bond isomerization of 1-butene produced from butanol dehydration. For the double bond isomerization of 1-butene to 2t-butene, both concerted and 2-butoxide mediated stepwise mechanisms contribute significantly in H-ZSM-5, while only the concerted mechanism is operative in H-ZSM-22. On the other hand, for H-FER, 2t-butene is mainly produced from the butanol dimer via an E1 elimination accompanied by a 1,2-hydride shift. This in turn can be attributed to an increase in enthalpic stabilization of the E1 elimination transition state for the direct formation of 2t-butene from 1-butanol dimer when moving from H-ZSM-5 to H-FER. Isobutene formation is not observed in all three zeolites at the investigated temperature range of 450–500 K.

Multi-response maps show that atomically dispersed iron on alumina provides relatively high activity and good stability in low temperature CO oxidation.