A solid-state NMR, FT-IR and TPD study on acid properties of sulfated and metal-promoted zirconia: Influence of promoter and sulfation treatment

Highly Active Mesoporous Nb–W Oxide Solid‐Acid Catalyst

“…[12] Mesoporous Nb 3 W 7 had three peaks indicating acid strength: a main peak at d = 75 ppm indicating acid strength comparable to that of H-Beta zeolite (d = 78 ppm), [13] another peak at d = 63 ppm indicating comparable strength to HY zeolite, (d = 65 ppm), [12] and a distinct small sharp peak at d = 86 ppm indicating acid strength greater that than that of ion-exchange resin (d = 81 ppm for Amberlyst-15) and comparable in strength to those of strongly acidic zeolites (d = 86 ppm for HZSM-5 [14] and HMOR [13] ) and sulfated zirconia. [15] The 31 P MAS NMR results show an enhancement of acid strength in mesoporous Nb x W (10Àx) oxides, with shifts of the main peaks from d = 67 ppm (x = 7) to d = 70 ppm (x = 5) or d = 75 ppm (x = 3). The acid strength of HY zeolite (d = 65 ppm) was be evaluated to H 0 = À6.6.…”

SO42−/Sn-MMT Solid Acid Catalyst for Xylose and Xylan Conversion into Furfural in the Biphasic System

“…The adsorbed pyridine probe molecules tend to couple with aprotic (Lewis) and/or protonic (Brønsted) catalytic centers through the nitrogen lone-pair electrons to form coordinative bonded pyridine complexes and/or pyridium ions, and hence can be detected by monitoring their ring vibrations [27]. Figure 4 illustrates Py-FTIR spectra of Sn-MMT and SO4 2− /Sn-MMT, in which these The acid properties of this catalyst were examined by NH 3 -TPD ( Figure 3).…”

“…The adsorbed pyridine probe molecules tend to couple with aprotic (Lewis) and/or protonic (Brønsted) catalytic centers through the nitrogen lone-pair electrons to form coordinative bonded pyridine complexes and/or pyridium ions, and hence can be detected by monitoring their ring vibrations [27]. Figure 4 illustrates Py-FTIR spectra of Sn-MMT and SO 4 2− /Sn-MMT, in which these characteristic Elemental analysis by inductively coupled plasma (ICP) ( Table 2) showed that the content of Sn in Sn-MMT was 15.32 wt %, indicating that tin ions were successfully intercalated into the MMT framework by replacing calcium and sodium ions.…”

Comparative Study of Regioselective Synthesis of β-Aminoalcohols under Solventless Conditions Catalyzed by Sulfated Zirconia and SZ/MCM-41

“…[3] Some authors mention that the strong acidity of sulfated zirconia is due to a combination of Lewis and Brønsted acid sites. Sulfated species with covalent bonds as S=O on the surface of SZ are needed for acidity.…”

“…The classical approach for the synthesis of β-aminoalcohols, involving nucleophilic opening of epoxides by amines requires heat treatment and requires an excess of amine. Several catalysts have been utilized in these reactions: montmorillonite [16], Ti(o-i-Pr) 4 [17], SmI 2 , [18] basic metal amides, [19] SmCl 3 [20], metal triflates such as Sn(OTf) 2 , Cu(OTf) 2 , LiOTf and Yb(OTf) 3 [21], ammonium decatungstocerate (IV) [22], RuCl 3 [23], zirconium (IV) chloride [24], cyclodextrins [25] and also CeCl 3 [26], silica-gel [27], alumina [28], ionic liquids [29], water [30] We have successfully used sulfated zirconia for Biginelli condensation reactions, [35] for the Paal Knorr reaction in the synthesis of tetrahydroindolone derivatives [36] and for the acylal protection and deprotection reactions [37]. In this paper we have synthesized, characterized and evaluated sulfated zirconia and SZ/MCM-41 in the oxirane opening with amines to obtain β-aminoalcohols under mild, solventless conditions.…”