Morten Bjørgen

Conversion of Methanol to Hydrocarbons: How Zeolite Cavity and Pore Size Controls Product Selectivity

Liquid hydrocarbon fuels play an essential part in the global energy chain, owing to their high energy density and easy transportability. Olefins play a similar role in the production of consumer goods. In a post-oil society, fuel and olefin production will rely on alternative carbon sources, such as biomass, coal, natural gas, and CO(2). The methanol-to-hydrocarbons (MTH) process is a key step in such routes, and can be tuned into production of gasoline-rich (methanol to gasoline; MTG) or olefin-rich (methanol to olefins; MTO) product mixtures by proper choice of catalyst and reaction conditions. This Review presents several commercial MTH projects that have recently been realized, and also fundamental research into the synthesis of microporous materials for the targeted variation of selectivity and lifetime of the catalysts.

Electronic and vibrational properties of a MOF-5 metal–organic framework: ZnO quantum dot behaviour

UV-Vis DRS and photoluminescence (PL) spectroscopy, combined with excitation selective Raman spectroscopy, allow us to understand the main optical and vibrational properties of a metal-organic MOF-5 framework. A O(2-)Zn(2+)[rightward arrow] O(-)Zn(+) ligand to metal charge transfer transition (LMCT) at 350 nm, testifies that the Zn(4)O(13) cluster behaves as a ZnO quantum dot (QD). The organic part acts as a photon antenna able to efficiently transfer the energy to the inorganic ZnO-like QD part, where an intense emission at 525 nm occurs.

In Situ Infrared Spectroscopic and Gravimetric Characterisation of the Solvent Removal and Dehydroxylation of the Metal Organic Frameworks UiO-66 and UiO-67

Herein, the desolvation, dehydroxylation and rehydroxylation of the metal organic frameworks UiO-66 and -67 are followed by in situ DRIFTS and TG–DSC. The spectra recorded on UiO-66 feature multiple bands corresponding to chemically inequivalent isolated hydroxyl groups, whereas UiO-67 has the expected single μ3-OH band from the Zr6O4(OH)4 cornerstone. Complete rehydration is demonstrated on both materials. Based on further experimental insights, hypotheses are given to explain the observed differences between UiO-66 and -67. Quantum chemical calculations are employed in order to deduce the feasibility of one possible explanation for the observed behaviour on UiO-66.

The conversion of methanol to hydrocarbons over dealuminated zeolite H-beta

Conversion of methanol-to-hydrocarbons has been studied over beta-zeolites with varying contents of aluminum, obtained by dealumination of the parent sample with oxalic acid. It was found that the dealumination leads to catalysts which are more resistant to deactivation. The total amount of methanol which might be converted to hydrocarbons before the catalyst becomes completely deactivated increased. The conversion capacity is higher at high reactant feed rates.

Mechanistic Proposal for the Zeolite Catalyzed Methylation of Aromatic Compounds

Alkylation and methylation reactions are important reactions in petrochemical production and form part of the reaction mechanism of many hydrocarbon transformation processes. Here, a new reaction mechanism is explored for the zeolite catalyzed methylation of arenes using quantum chemical calculations. It is proposed that the most substituted methylbenzenes, which will reside predominantly on the protonated form when adsorbed in a zeolite, can react directly with a neutral methanol molecule in the vicinity, thereby initiating the methylation reaction without having to return a proton to the zeolite surface. The calculated barriers are quite low, indicating that the suggested mechanism is plausible. This route might explain how the most substituted methylbenzenes can function as efficient reaction intermediates in the methanol to hydrocarbons reaction without themselves acting as catalyst poisons as a consequence of their high proton affinities.

Conversion of methanol to hydrocarbons: Hints to rational catalyst design from fundamental mechanistic studies on H-ZSM-5

In this study, the mechanism of the methanol-to-hydrocarbons (MTH) reaction over H-ZSM-5, which is the archetype MTH catalyst, has been pursued. From isotopic labeling experiments, it is demonstrated that the reaction scheme for alkene formation from methanol over H-ZSM-5 is essentially different from those previously drawn for H-beta and H-SAPO-34. In addition to a modified hydrocarbon pool mechanism, wherein ethene is formed from the lower methylbenzenes, a parallel C 3+ alkene methylation/cracking cycle is operative. The results showing that ethene and propene are formed through different catalytic cycles, are of utmost importance for understanding and possibly controlling the ethene/propene selectivity in methanol-to-propene catalysis.