The role of the compositions of HZSM-5 zeolites modified with nanosized anatase in propane and ethanol conversion

Design of MFI Type Aluminum- and Titanium-Containing Zeolites

“…The objects of the study are HZSM-5 zeolites (H (4-n)x )[T n+ x Si 4+ 12−x O 24 ] × wH 2 O (hereinafter as HZSM) with Si/Al and Si/Ti silicate modules, nanocomposites in the systems of HZSM (Si/Al = 12, 25, 40, 300)-nanoscale anatase (NA/HZSM) and HZSM (Si/Al = 40, 300)-nanoscale anatase doped with transition metals (NA:M/HZSM, M = Ag, Ni, V). Methods of HZSM zeolites, NA/HZSM, and NA:M/HZSM nanocomposites synthesis and characterization are systematized based on works [16,33,34,54,[65][66][67][68][69][70][71][72][73][74][75][76] and presented in Supplementary Materials.…”

“…Analysis of the stretching vibrations intensity in the regions of ~3650 to 3680 cm −1 and ~3720 to 3740 cm −1 allows us to judge Brønsted acid sites (Figure 6a) [16]. The content of bridging hydroxyls Si 4+ -OH-Al 3+ (~3650 to 3680 cm −1 [133]) in HZSM structure large cavities as well as weak terminal silanol groups Si-OH (~3720 cm −1 and ~3740 cm −1 , respectively, in the inner framework for HZSM (12) and in the outer frame for all HZSM [136]) is greater in HZSM (25) than in HZSM (12).…”

“…These groups are practically absent in HZSM (40), although there is a shoulder at ~3670 cm −1 (Figure 6a). The high content of bridging hydroxyls in HZSM( 25) is probably caused by the presence in it of a higher impurity Fe 3+ ions content (Si 4+ -OH-Fe 3+ ) (Table S1), which together with Al 3+ ions (Si 4+ -OH-Al 3+ ) are responsible for the formation of OH-groups in zeolite framework [16].…”

“…In the FTIR spectra of the NA/HZSM-1 (Figure 7a) and NA/HZSM-2 (Figure 7b) nanocomposites, the bands responsible for Ti-O-Ti and Ti-O natural fundamental vibrations of NA (~400 to 700 cm −1 ), as well as for the bending (~3420 cm −1 ) and stretching (~3200 cm −1 ) vibrations of the Ti-OH groups [16,137], are superimposed on the corresponding bands of the initial zeolites (Figure 6), which can be judged by the appearance of additional shoulders in the range of 400-550 cm −1 vibrations, most noticeable in the NA/HZSM-2 spectra (Figure 7b). At that, the nanocomposites exhibit a decrease in the content of Brønsted acid sites in NA/HZSM-1 (marked with an oval in Figure 7a) compared to the initial zeolites (Figure 6a) and almost their absence in NA/HZSM-2 (marked with an oval in Figure 7b).…”

“…Aluminosilicalites (H 1+ x )[Al 3+ x Si 4+ 12−x O 24 ] × wH 2 O are used in acid-catalyzed reactions such as isomerization and alkylation of hydrocarbons [13], acylation of anisole (C 7 H 8 O) with a propionic anhydride (C 6 H 10 O 3 ) to obtain p-methoxypropiophenone (C 10 H 12 O 2 ) [14], transformation of ethanol (C 2 H 5 OH) into diethyl ether ((C 2 H 5 ) 2 O) [15,16] or ethylene (C 2 H 4 ) [16,17], propane (C 3 H 8 ) conversion with the formation of the main products propylene (C 3 H 6 ) and ethylene (C 2 H 4 ) [16], etc., and as adsorbents for recovery of methanol (CH 3 OH) [18], hydrocarbons (propane C 3 H 8 , propene C 3 H 6 , and n-butane C 4 H 10 ) [19] from carbon monoxide (CO) [20] from the gas phase; and dyes (for example, methyl green [21]), which are used in the staining process (in textile industry) and contaminate wastewater [22]-from an aqueous medium.…”