Modification of Cs-X for styrene production by side-chain alkylation of toluene with methanol

Elucidating the Distribution and Speciation of Boron and Cesium in BCsX Zeolite Catalysts for Styrene Production

“…Consistent with the findings of XRD, no evidence of the formation of cesium clusters or oxide species was detected by TEM. If present, these species may play a role in directing the selectivity during the reaction because strong basicity is associated with an increased transfer hydrogenation of styrene to ethylbenzene …”

“…Such identification is a prerequisite for understanding their mechanistic role; however, prominent knowledge gaps persist in the literature. It is widely accepted that cesium is present in the cationic form and is located in accessible charge‐balancing positions within the faujasite‐type framework . However, few attempts have been made to characterize the identity and location of boron species, which are normally assumed to be present as boric oxide/acid particles.…”

“…If present, these species may play ar olei nd irectingt he selectivity during the reaction because strong basicity is associated with an increased transfer hydrogenation of styrene to ethylbenzene. [30] Complementary analyses by TOF-SIMS ( Figure 3a)p rovided evidenceo fh igh chemical homogeneity within each crystal, as seen by the homogenous intensity,a lthough ac areful comparison revealed slight variations in the concentration of Cs detected in different crystals. Additionally,t he correspondence between theE DX and TOF-SIMS resultss uggests, in turn, that chemicald istributions are not significantly altered upon exposure to the incident electron and ion beam, respectively.L astly, from ac omparison of the maps obtained from BCsX and CsX ( Figure S2 in the Supporting Information), it can be concluded Representative elementalm aps of the boron distribution obtained from cross sections of BCsX are shown in Figure 4.…”

“…It is widely acceptedt hat cesium is presenti nt he cationic form and is located in accessible charge-balancing positions within the faujasite-type framework. [30,32,33] However,f ew attempts have been made to characterizet he identitya nd location of boron species, which are normally assumed to be presenta sb oric oxide/acid particles.…”

“…[23,34,35] Because boric acid (frequently used as the source) dehydrates into boric oxide at about 363 K, which, in turn, melts at temperatures from 573 to 723 K, [36] boric oxide is expected to be the predominant species in the dried, fresh catalyst. Nonetheless, prior to the reaction, the catalyst is typicallyt reated in situ at temperatures between 723 and 773 K, [10,11,23,24,30,37] at which boric oxide should be al iquid.W ith this in mind, the chemical state of boron species close to the surfaceofBCsX was studied by XPS prior to and after calcination (7738K, N 2 ,2h). Importantly,r eports in the literature instruct on how binding energies for framework Si 2p, Al 2p, and O1sc ore levels are highly dependento nt he Si/Al value for Xz eolites.…”