Core–Shell Zeolite Composite with Silicalite-1/NaY Structure for the Adsorption Desulfurization of Dimethyl Disulfide from Methyl tert-Butyl Ether

Abstract

Desulfurization of dimethyl disulfide (DMDS) from methyl tertbutyl ether (MTBE) has been studied on the silicalite-1/NaY core−shell composites. By changing the mass ratio of tetraethyl orthosilicate (TEOS)/ NaY, the silicalite-1 shell synthesis condition was conducted at the mass ratio of TEOS/tetrapropylammonium hydroxide (TPAOH)/ethanol (EtOH)/H 2 O = (10, 15, 20, 25, 30 g):19 g:17 g:87 g ((0.048, 0.072, 0.096, 0.12, 0.144): 0.0234:0.369:4.8293 in molar ratio, where the mass of NaY zeolite was quantified to 5 g) by a hydrothermal synthesis at 180 °C for 24 h. Results showed that when the mass ratio of TEOS/TPAOH/EtOH/H 2 O/NaY = 20 g:19 g:17 g:87 g:5 g, the silicalite-1 coating could be dispersed and covered on the surface of NaY well (the thickness of silicalite-1 shell ranged from 100 to 400 nm) with the best sulfur adsorption capacity as 20.711 mg s /g adsorbent . The shape-selective adsorption mechanism of desulfurizing DMDS from MTBE on these core−shell composites was also elaborated.

Selective Adsorption of Dimethyl Disulfide on Acid-Treated CuYH@Silicalite-1 Core–Shell Structure: Methyl tert-Butyl Ether as a Competition Component

“…Lee et al investigated desulfurizing DMDS in C4 hydrocarbon mixtures with β zeolites and claimed that Cu­(I) ion-exchanged zeolites showed high DMDS capacity of 8.70 mg s /g adsorbents . Nevertheless, when adsorbing DMDS in MTBE, there would be a fierce competition between them on π-complexation adsorbents, which has been detailedly described in the previous studies, − and Yang et al , had claimed that the adsorption capacity of sulfur on π-complexation adsorbents decreased sharply in the presence of MTBE. To solve the competitive adsorption, by using modified ZSM-5 zeolites, Zhao et al had tried to adsorb DMDS from MTBE and acknowledged that the pore structure and acidity both played key roles in the adsorption process and reached a not too optimistic adsorption capacity of 8.24 mg s /g adsorbents .…”

“…15,16,29 Previously, we have applied a core−shell structured composite with NaY whose structure is shown in Scheme 2 with CuY as the core and silicalite-1 as the shell to remove DMDS in MTBE solution and obtained an adsorption capacity of sulfur on NaY@silicalite-1 and CuY@silicalite-1 to be 20.711 and 32.882 mg s /g adsorbent , respectively. 21,22 In the present study, we are trying a new way in synthesizing core−shell composites by the dealuminization of HCl on Y zeolite to obtain a better growth environment for the silicalite-1 shell. Dealuminization is an efficient method to increase the ratio of Si/Al by transferring framework Al into an extra-framework position and then being washed away.…”

“…In consideration of the fact that Y zeolite has been proved a promising material in adsorption extensively owing to its high solid acidity, crystalline microporous properties, and 3D pores (tetrahedral framework structures), − in addition, their activity and stability could be further improved by steaming, ion exchange, and treatment with acid or base. ,, Previously, we have applied a core–shell structured composite with NaY whose structure is shown in Scheme with CuY as the core and silicalite-1 as the shell to remove DMDS in MTBE solution and obtained an adsorption capacity of sulfur on NaY@silicalite-1 and CuY@silicalite-1 to be 20.711 and 32.882 mg s /g adsorbent , respectively. , In the present study, we are trying a new way in synthesizing core–shell composites by the dealuminization of HCl on Y zeolite to obtain a better growth environment for the silicalite-1 shell. Dealuminization is an efficient method to increase the ratio of Si/Al by transferring framework Al into an extra-framework position and then being washed away. ,− Xin-Mei et al modified a USY zeolite with citric acid and obtained improved a Si/Al ratio Y zeolite with smaller unit cell parameters.…”