Effect of Sodium on the Adsorption of SO2 on Al2O3 and on Its Reaction with H2S

Abstract

The adsorption of SO2 on A1203 and on 3% sodium on A1203 preactivated at 350 and 600 "C has been studied by gravimetry, thermodesorption, infrared spectroscopy, and Raman spectroscopy. The quantity of SOz adsorbed is greater on NdA1203. A comparison of the results showed that physical adsorption occurs on weak basic 0,or OH-sites. Chemisorption mainly arises from adsorption on basic sites through the formation of sulfite species (AlOS02) which are characterized by an infrared band near 1060 cm-'. Other minor species such as disulfite or hydrogen sulfite were postulated in order to account for (1) a perturbation of surface OH groups and (2) the constant quantity of chemisorbed species which form as a function of the temperature of activation. The sulfite species were more stable on NdAlzO3 than on Al2O3, and they were less reactive toward HzS. This is attributed to the greater basicity of the 3% sodium-doped catalyst and accounts for the lower reactivity of NdAl2O3 relative to pure A1203. On either A1203 or NdAlzO3, no sulfur was produced if gaseous SO2 was added to preadsorbed H2S. However, in the reverse sequence, 2HzS(g) + S02(ads) -(3/n)S, + 2H20, sulfur was detected via Raman spectroscopy.

Mass and electron-transfer conditions for the electrochemical oxidation of hydrogen sulfide at vanadium pentoxide film modified electrode

“…Metal oxide catalysts, such as the oxides of aluminum, vanadium, titanium, iron, alkaline earth and rare earth elements [17][18][19][20], have shown a great industrial importance particularly in the catalytic oxidation of H 2 S. Vanadium pentoxide (V 2 O 5 ) among other metal oxides exhibited a greater reactivity and selectivity towards the oxidation of H 2 S into elemental sulfur [21,22]. In the previous study [23], it was reported that the overpotential of sulfide oxidation at V 2 O 5 film modified electrode (V 2 O 5 -ME) decreased substantially by 500 mV compared with that of the unmodified electrode of similar base material.…”

Development of a Transient Kinetic Model for the Simultaneous Adsorption of SO2−NOx over Na/γ-Al2O3 Sorbent

“…The above step is analogous to the adsorption of SO 2 on O 2-sites formed with Al as Al-O-SO 2 and sulfite or disulfite of Na, i.e., Na 2 S 2 O 5 , which was also observed in the IR spectra by Saad et al (1995).…”

“…The adsorption of SO 2 on γ-Al 2 O 3 and Na/γ-Al 2 O 3 has been studied earlier by many researchers (Saad et al, 1995;Mitchell, 1996). For example, Saad et al (1995) reported the positive effect of Na on the SO 2 adsorption onto γ-Al 2 O 3 and concluded that the Al-O-Na group is primarily responsible for the chemisorption of SO 2 . As reported by Zotin and Faro (1989), the presence of Na increases the SO 2 adsorption capacity from 1.5 mol/nm 2 to 2.6 mol/nm 2 at 373 K. Mitchell et al (1996) reported that, at low Na loading up to 1 wt %, Na acts as a promoter for the formation of an adsorbed sulfite or sulfate that has a structure similar to that of aluminum sulfite or sulfate.…”

“…The site capacity C t could be measured by either SO 2 or NO 2 chemisorption as these components can independently adsorb on the surface. The SO 2 sorption capacity is reported to be 2.8 molecule nm -2 at 300 K (Saad et al, 1995) and 2.6 molecule nm -2 at 373 K (Zotin and Faro, 1985) for Na/γ-Al 2 O 3 sorbent, values that are equivalent to about 0.5 mol kg -1 of sorbent capacity. Hence, the estimated C t values in the present work are reasonable.…”

Determination of adsorbed species in the surface hydrolysis of SOF/sub 2/ on activated alumina

“…Figure 3 shows the FTLR spcctra of sample A and B in the adsorbed S-0 stretching mode (vso) region (1000-1250 cm-I). The virgin alumina (sample A) shows two vibration bands at 1080 and 1160 cm" which can be undoubtedly attributed to the presence of sulfite (SO3) [12] which is usual contaminant in alumina. For the sample containing small amounts of adsorbed sulfur from SOF2 (curte labelled after), in addition to the intrinsic presence of the two peaks already described, we observe thc presence of a broad band which contains several species.…”