A large-cavity zeolite with wide pore windows and potential as an oil refining catalyst

Abstract

Crude oil is an important feedstock for the petrochemical industry and the dominant energy source driving the world economy, but known oil reserves will cover demand for no more than 50 years at the current rate of consumption. This situation calls for more efficient strategies for converting crude oil into fuel and petrochemical products. At present, more than 40% of oil conversion is achieved using catalysts based on faujasite; this zeolite requires extensive post-synthesis treatment to produce an ultrastable form, and has a large cavity accessible through four 0.74-nm-wide windows and thus limits the access of oil molecules to the catalytically active sites. The use of zeolites with better accessibility to their active sites should result in improved catalyst efficiency. To date, two zeolites with effective pore diameters exceeding that of faujasite have been reported, but their one-dimensional pore topology excludes use in oil refining. Similarly, zeolites with large pores and a three-dimensional pore topology have been reported, but in all these materials the pore openings are smaller than in faujasite. Here we report the synthesis of ITQ-21, a zeolite with a three-dimensional pore network containing 1.18-nm-wide cavities, each of which is accessible through six circular and 0.74-nm-wide windows. As expected for a zeolite with this structure, ITQ-21 exhibits high catalytic activity and selectivity for valuable products in preliminary oil refining tests.

Binder Effects in SiO2‐ and Al2O3‐Bound Zeolite ZSM‐5‐Based Extrudates as Studied by Microspectroscopy

“…Zeolite‐based catalyst bodies are employed on a global scale in important chemical processes, such as the synthesis of many bulk chemicals1, 2 as well as crude‐oil refining 3. 4 Particular examples include xylene isomerisation,5, 6 benzene alkylation7, 8 and methanol conversion to hydrocarbons 9.…”

Predictive design of engineered multifunctional solid catalysts

“…[34][35][36] However, due to the interconnecting micropores, diffusion can be hindered for larger organic molecules and this can have a detrimental effect of lower reaction rates and, consequently reduced versatility, for the range of substrates that can access the active sites. Therefore there is a significant interest 37 into the synthesis of larger-pore zeolites and zeotypes. As a direct consequence, numerous large pore materials have been synthesized, for example, AlPO-8, 38 VPI-5 39 and cloverite, 40 which possess pore diameters in the range of 8-13 Å (see Figure 3).…”

Mesostructured Zeolites: Bridging the Gap Between Zeolites and MCM-41

“…In addition, there have been efforts to alleviate the diffusion limitations through a synthesis of extra-large-pore molecular sieves (e.g., ITQ-21, ITQ-37 and ITQ-40) View Article Online using organic structure directing agents (SDAs). 24,69,70 Corma et al exhibited that the synthesized materials can contain large pore openings (i.e., up to 16-member rings) or large cavities (i.e., 1.8 nm-wide). The results from catalytic cracking of a vacuum gas oil show that the activity of ITQ-21 is higher than that of the USY zeolite, but it produces a lower gasoline yield.…”