MoO₃ on zeolites MCM-22, MCM-56 and 2D-MFI as catalysts for 1-octene metathesis

Abstract

Highly active olefin metathesis catalysts were prepared by thermal spreading MoO3 and/or MoO2(acac)2 on MWW zeolites (MCM-22, delaminated MCM-56) and on two-dimensional MFI (all in NH4 + form). The catalysts‘ activities were tested in the metathesis of neat 1-octene (as an example of a longer chain olefin) at 40 °C. Catalysts with 6 wt % or 5 wt % of Mo were used. The acidic character of the supports had an important effect on both the catalyst activity and selectivity. The catalyst activity increases in the order 6MoO3/HZSM-5(25) (Si/Al = 25) << 6MoO2(acac)2/MCM-22(70) < 6MoO3/2D-MFI(26) < 6MoO3/MCM-56(13) < 6MoO3/MCM-22(28) reflecting both the enhancing effect of the supports‘ acidity and accessibility of the catalytic species on the surface. On the other hand the supports‘ acidity decreases the selectivity to the main metathesis product C14 due to an acid-catalyzed double bond isomerization (followed by cross metathesis) and oligomerization. 6MoO3/2D-MFI(26) with a lower concentration of the acidic centres resulting in catalysts of moderate activity but with the highest selectivity.

Total Oxidation of Toluene and Propane over Supported Co3O4 Catalysts: Effect of Structure/Acidity of MWW Zeolite and Cobalt Loading

“…Thus, based on their structural and textural characteristics, synthesized materials were qualified as a representative set of MWW zeolites with different acidities and architecture of crystalline layers 28,43 to be used for further study.…”

SBA-15 as a Support for Effective Olefin Metathesis Catalysts

“…With the discovery of new advanced supports, such as zeolites and mesoporous molecular sieves, molybdenum and tungsten oxides particularly attracted the attention of many research groups in their efforts to increase the effectiveness of commercially important catalysts [9,63]. Several studies showed that various mesoporous siliceous materials (MCM-41 [15,64,65], KIT-6 [66]), or MWW-zeolites [65,67], and MFI-zeolites [65,67,68] were substantially more active than ordinary silica or silica-alumina. However, the most commonly used support was SBA-15 for its large pores and high BET areas.…”

“…The beneficial effect of Al modification of the SBA-15 (Table 2, entry 8) was ascribed to the formation of Brønsted acid sites, which improve Mo dispersion. Conversely, acidity induces double bond isomerization and alkene oligomerization [67]. (ii) The dependence of activity on metal loading has a maximum: at high metal concentrations, the dispersion is imperfect, and a part of the metal forms metal oxide microcrystals, which do not contribute to the catalytic activity.…”

Quantum chemical simulation of MoO3 dispergation on hydroxylated SiO2 surface

“…800 K is required for dispergation of MoO3 over supports surface. Special attention was given to molybdate species resulted from MoO3 loading on aluminosilicate molecular sieves MCM-22, MCM-56 and 2D-MFI [23] and on siliceous molecular sieves MCM-41, MCM-48 and SBA-15 [24,25] which are active in olefins metathesis.…”