Evidence of heterogeneous catalytic activity of ZSM-5 in supercritical water for dodecane cracking

Chemicals from heavy oils by ZSM‐5 catalysis in supercritical water: Model compound and reaction engineering

“…For all other product categories, the relationships between selectivity and conversion are qualitatively (aromatic Figure 1b and gas Figure 1c) and/or quantitatively (coke, Figure 1d) different in the presence and absence of SCW. In particular, selectivity plots shown in Figure 1e,f confirm the observation previously made by Zaker et al 42 that water suppresses aromatic formation as the amount of coke formed in the presence of SCW is always an order of magnitude less than observed in the absence, even when the observations are made at the same conversion.…”

“…We considered whether all of the observations made here were the consequence of SCW degradation of ZSM‐5—as descrbied by Zaker et al 42 and Maag et al 41 To test this explanation, we prepared two versions of ZSM‐5 by subjecting it to a mild and a severe SCW treatment. Table S3 provides more details on the BAS of SCW‐treated ZSM‐5 samples.…”

“…Previous work suggests an opportunity to engineer the reaction network to exploit the coke suppression effect of SCW, while minimizing the disadvantage of reduced alkane cracking. Accomplishing this requires understanding the effect of water on reaction rates and mechanisms, which goes beyond the observations of conversion and yield previously made by Zaker et al 42 Because of the complexity of the reaction mixture, we adopt a group‐type modeling approach to capture the effects of water on broad kinetic phenomena. Gudiyella et al 2 used a similar approach to quantify the role of SCW on the rates of atmospheric residue upgrading, motivating its application to catalytic systems.…”

“…Motivated by the work of Maag et al, 41 Zaker et al 42 quantifed ZSM‐5 catalytic activity for alkane cracking and aromatization in the presence of SCW at 400°C and 24 MPa to understand the effect of SCW on the catalyst acidity and activity. Since zeolite degradation products have shown catalytic activity in some former studies, Zaker et al 42 evaluated the catalytic activity of ZSM‐5 degradation products under SCW conditions. Their results indicated that the catalytic activity of degraded ZSM‐5 must be attributed to its retained heterogeneous acid sites and cannot be ascribed to its degradation products.…”

Understanding initial zeolite oligomerization steps with first principles calculations

“…Zeolites can be synthesized with detailed control of their physiochemical properties which makes them excellent materials for applications in fields such as separations, 1,2 ion exchange, 3 and catalysis. 4,5 The ability to control the structural and chemical functionalities of a given zeolite is extremely important for its end application. For example, ZSM-5 (MFI type) is one of the most commonly used industrial catalysts in the cracking of long hydrocarbon chains to produce light olefins due to its acidic properties and (hydro)thermal stability.…”