Sorption of Nitrogen Bases and XPS Study of Mesoporous Solid Acid SBA-15

Abstract

contains a high concentration of tSi(CH 2 ) 3 SO 3 H functionalities accessible to ion exchange and adsorption of nitrogen bases. High-resolution XPS was used to determine stoichiometric equivalences between the -SO 3groups and NH 4 + cations exchanged for the -SO 3 H protons as well as between the -SO 3 H groups and adsorbed pyridine and ethylenediamine. XPS core-level shifts (CLS) of S2p photoemission to lower BEs identify the -SO 3 H groups as sites for cation exchange and donor hydrogen bonding to the adsorbed nitrogen bases. The N1s CLS to higher BEs identify the nitrogen atoms of pyridine and one of the two N atoms of ethylenediamine as acceptors of the hydrogen bond. The CLS are smaller than those previously observed in Nafion-H and sulfated zirconia (SZ) (Johansson, M.; Klier, K. Topics Catal. 1997, 4, 99). An all-electron, nonrelativistic DFT theory yields core-level orbital energies where shifts correlate well with the observed XPS CLS. As a result of this combined study, the propylsulfonic groups of the SBA-15 material are identified as weaker acids than those of Nafion-H and SZ, albeit ones with high surface concentration and excellent ion-exchange capacity.

Efficient and facile tuning of Vulcan XC72 with ultra-small Pt nanoparticles for electrocatalytic applications

“…Carbon Functionalization and Pt anchoring groups corresponding to BEs of 399.5 eV 13 and a minimal contribution at 401.7 eV previously reported for EDA 14 and tentatively assigned to protonated amine groups (-NH 3 + ) 15 . Furthermore, the C1s spectrum also confirms the functionalization of carbon with C-O and C-N species at 286.7 80 eV and an excess of carboxylic groups at 288.9 eV from the preliminary oxidation step that did not react with EDA to render the amide bonding (Figure 2).…”

Catalytic Synthesis of Oxygenates: Mechanisms, Catalysts and Controlling Characteristics

“…The SBA-15 catalyst was synthesized at 313K from tetraethoxysilane (TEOS, Aldrich) and 3-mercaptopropyltrimethoxysilane (MPTMS, Aldrich) with Pluronic 123 EO 20 PO 70 EO 20 triblock copolymer (MW = 5800, Aldrich) as the templating agent using the one-step direct synthesis procedure of Margolese et al [31] and as described previously [37]. Following prehydrolysis of TEOS and Pluronic 123, MPTMS and H 2 O 2 (30%, Aldrich) were added and the mixture was equilibrated for 20 h. After further aging at 373K for 24 h, the white precipitate was filtered, air-dried at ambient temperature, and then refluxed in 95% ethanol for 24 h (200 ml of ethanol/1.5 g of dried solid) to extract any remaining Pluronic template.…”

“…High resolution X-ray photoelectron spectroscopy (XPS) analysis was carried out using the Scienta ESCA-300 instrument, as described in detail elsewhere [37]. Based on estimates by Hunsicker et al [39], XPS analysis of very porous materials of uniform composition provides a bulk analysis because of the large escape depths.…”

“…By X-ray photoelectron spectroscopy (XPS), we have shown that oxidation of the thiol (-SH) groups to sulfonic acid (-SO 3 H) groups is not always complete and can be quantitatively analyzed from photoemissions of the two species [36,37]. The -SO 3 H groups on SBA-15 can be utilized for Brønsted acid-catalyzed synthesis reactions at vapor-solid interfaces, e.g.…”

“…In the present research, we investigate the catalytic properties and stability of a large pore SBA-15 catalyst, prepared in this laboratory and characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), BET surface area, and sorption of nitrogen bases [37], for the dehydrocondensation/dehydration of mixtures of alcohols to form ethers and olefins and probe the mechanistic pathway and reaction intermediates involved in these reactions. The advantages of large-pore silica-based materials are in applicability to reactions of large molecules and non-swelling properties.…”