Kinetic, infrared, and X-ray absorption studies of adsorption, desorption, and reactions of thiophene on H-ZSM5 and Co/H-ZSM5

Abstract

Temperature programmed desorption and infrared and X-ray absorption near-edge spectroscopies were used during adsorption and reactions of thiophene in order to probe adsorbed intermediates and catalytic structures responsible for thiophene reactions with propane or H 2 on H-ZSM5 and Co/H-ZSM5. Infrared spectra showed that thiophene interacts with acidic OH groups in H-ZSM5 via hydrogen bonding at ambient temperature. No additional bands were detected on Co/H-ZSM5, suggesting the absence of specific interactions with Co cations. During adsorption at ambient temperatures, infrared bands assigned to CH 2 groups near C=C bonds or Satoms and to S-H species were detected and H-ZSM5 and Co/H-ZSM5 acquired colors typical of thiophene oligomers. Slightly above ambient temperatures, benzene and H 2 S formed from pre-adsorbed thiophene. These results indicate that hydrogen-bonded thiophene undergoes ring opening or oligomerization near ambient temperature on acidic OH groups in H-ZSM5. Some of the adsorbed thiophene (20-50%) interacts weakly with channel walls or with residual Na cations and desorbs unreacted. The remaining adsorbed thiophene desorbs as H 2 S, aromatic hydrocarbons, and organosulfur compounds, such as methylthiophene and benzothiophene, or forms irreversibly adsorbed unsaturated organic deposits. In situ infrared studies during thiophene and thiophene-propane reactions at 773 K on H-ZSM5 and Co/H-ZSM5 showed that surface coverages of thiophene-derived intermediates were low on acidic OH groups and Co cations. Co K-edge X-ray absorption near-edge spectra measured during these reactions confirmed that Co 2+ cations do not reduce or sulfide; their local environment, however, changes slightly, apparently because of interactions of strongly adsorbed species with Co cations. Sulfur K-edge X-ray absorption spectra detected small amounts of organosulfur species, but no inorganic sulfides, after thiophene, thiophene-H 2 , and thiophene-propane reactions, consistent with the observed stability of exchanged cations against reduction and sulfidation. S : Al ratios were less than 0.04 at. on all samples; these amounts represent less than 1% of the S-atoms removed from thiophene as H 2 S during catalytic propane-thiophene reactions.

Production of low sulfur diesel fuel via adsorption: an equilibrium and kinetic study on the adsorption of dibenzothiophene onto NaY zeolite

“…Therefore, zeolites are potential adsorbents for refractory sulfur-containing compounds and have attracted the most interest in recent years. Many publications have reported that zeolites are very effective for the removal of sulfur compounds (Jiang and Ng 2006;Hernandez-Maldonado et al 2004Hernandez-Maldonado and Yang 2003a, 2003b, 2004a, 2004b, 2004c, 2004dVelu et al 2003;Ng et al 2005;Jiang et al 2005, Yang et al 2001, 2003Yu et al 2002;Wang et al 2009). …”

Label‐Free Chemical Imaging of Catalytic Solids by Coherent Anti‐Stokes Raman Scattering and Synchrotron‐Based Infrared Microscopy

“…[24][25][26] The observed spectral changes in the nonlinear Raman spectra upon the inclusion of 2-chlorothiophene in the zeolite provide clear evidence for the interaction of the reactant with the catalyst framework, for example, by means of hydrogen bonding (Scheme 1, structure A), which is known to occur at room temperature. [20] In Figure 1 b, a microphotograph of an individual H-ZSM-5 crystal is presented, along with a schematic representation illustrating the crystals intergrowth structure and crystallographic orientations. [27,28] Within the H-ZSM-5 crystals, which have a two-dimensional pore network with interconnected straight and sinusoidal pores, the direction of the straight pores is parallel to the crystallographic b axis.…”

Adsorption of sulfur compound utilizing rice husk ash modified with niobium

“…The incorporation of metals such as Cu, Ni, Zn, Ag, Ce and Co [1,2,28,29] oxides such as Al 2 O 3 and TiO 2 [30][31][32][33][34], has received attention in desulfurization by adsorption, because of several possible interactions as much both the aromatic rings as with the heteroatom of sulfur (in the thiophenic derivatives), providing a greater selectivity for the sulfur compounds [35]. For example, the theoretical and experimental study of titanium oxide in the adsorption of thiophene demonstrated relatively weak and selective interactions between thiophene molecules and the metal oxide [36].…”