Adsorption sulfur dioxide

Wetting properties. A clean carbon surface is hydrophobic. Surface oxides provide sites of adsorption for water and other polar compounds. The more surface oxides there are, the more distinct is the hydrophilic behavior of the carbon. This was confirmed by Healey et al. (39) for graphitized carbon black, and by Kraus (40) and A. V. Kiselev and his group (41) for carbon black. Beebe and Dell (42) measured the sulfur dioxide adsorption on channel black and found an increase after oxidation at 600°. Further evidence for selective adsorption of polar compounds was provided by Gasser and Kipling (43). 

Microcalorimetry of ammonia and sulfur dioxide adsorption and the catalytic reachon of 2-propanol conversion have been used to study the effects on the acid-base properhes of adding small amounts of various ions (Ca, Li, Nd, Ni, Zn, SO ) to y-alumina, silica or magnesia surfaces [51]. 

Figure 9.14 Differential heats of sulfur dioxide adsorption versus coverage on NiCuMgAI mixed oxides.

The acid-base properties of V2O5/7-AI2O3 catalysts prepared by the impregnation method have been characterized by ammonia, pyridine and sulfur dioxide adsorption microcalorimetry. Sulfur dioxide adsorption made it possible to differentiate a vanadate layer from free alumina. 

Figure 9.20 Differential heat of sulfur dioxide adsorption at 353 K as a function of the probe uptake on V205/y-Al203 catalysts with different wt% ofV205 as indicated in the figure.

The prepared materials were studied in subsequent order as hydrogen sulfide and sulfur dioxide adsorbents in the dynamic tests described below. After exhaustion of its adsorbent capacity, each sample is identified by adding the letter H or S referring to hydrogen sulfide or sulfur dioxide adsorption, respectively. The order of the letters reflects the order of the experiments. For instance, SC-IHS is an exhausted sample on which first the hydrogen sulfide breakthrough test was carried out. After exhaustion, the SOj breakthrough test was performed on the same sample. 

Another interesting observation is almost identical behavior of samples exposed for SOj adsorption. Regardless the carbonization temperature the same amounts of SO, are adsorbed on the samples exhausted in the HjS breakthrough test. This suggests that after exhaustion of all active centers responsible for HjS adsorption the differences in surface chemistry, which play a role in sulfur dioxide adsorption/oxidation on fresh surfaces, seem to be somehow screened by HjS adsorption products. Nevertheless, it is interesting that still some capacity exists. 

Alemozafar AR, Guo XC, Madix RJ (2003) Topographic nano-restructuring Sulfur dioxide adsorption on Cu(llO). Surf Sci 524 L84... 

Outka DA, Madix RJ (1984) Sulfur-dioxide adsorption and reaction with atomic oxygen on the Ag(llO) surface. Surf Sci 137 242... 

The acid-base properties of the samples were investigated using adsorption of appropriate probe molecules, namely ammonia and sulfur dioxide, monitored by microcalorimetry. The microcalorimetric studies were performed at 353 K for sulfur dioxide adsorption and at 423 K for ammonia adsorption in a heat flow calorimeter of Tian-Calvet type (Setaram C80), linked to a conventional volumetric apparatus. Before each experiment the samples were outgassed overnight at 673 K. 

The sulfur dioxide adsorption on the other hand showed sharp breakthrough for both catalysts. For the 3.9% sodium hydroxide on Chromo-... 

Sulfur Dioxide Adsorption. This may take place on basic sites, and considerable irreversible adsorption has been reported (2, 18). Further,... 

Sulfur dioxide adsorption at 250°C (2 torr sulfur dioxide) on Chromosorb-A containing 3.9% sodium hydroxide amounted to 0.02 mmole/g compared with 0.06 mmole/g basic sites by benzoic acid titration. This suggests that sulfur dioxide is adsorbed on the basic sites. The sulfur dioxide adsorption corresponded to 6% coverage of the total surface of the catalyst. 

Mechanism of Adsorption. The mechanism of the sulfur dioxide adsorption and oxidation on carbon shows that the sulfur dioxide pick-up can be divided into three subsequent phases in which phase change is a function of time. In phase one, the adsorption rate is controlled by the rate of sulfur dioxide diffusion into the inner surface of the adsorbent. As the adsorption proceeds, the number of locations available for adsorp-... 

Since the bulk of the adsorption is accomplished in the second phase under stationary conditions, the adsorbent was developed to obtain high sulfur dioxide-to-sulfuric acid conversion rates for a large portion of its inner surface. The relationship between pore structure and sulfur dioxide adsorption is shown in Figure 1. The ordinate is the time, in hours, after which 10% of the inlet sulfur dioxide will pass through the carbon without being adsorbed. The mean pore diameter of adsorption pores was selected for the abscissa as the parameter to characterize the adsorbent structure (3). Adsorbents produced from bituminous coal with and without catalyst impregnation were tested. In both cases, the sulfur... 

Cerium-zirconium mixed metal oxides are used in conjunction with platinum group metals to reduce and eliminate pollutants in automotive emissions control catalyst systems. The ceria-zirconia promoter materials regulate the partial pressure of oxygen near the catalyst surface, thereby facilitating catalytic oxidation and reduction of gas phase pollutants. However, ceria-zirconia is particularly susceptible to chemical and physical deactivation through sulfur dioxide adsorption. The interaction of sulfur dioxide with ceria-zirconia model catalysts has been studied with Auger spectroscopy to develop fundamental information regarding the sulfur dioxide deactivation mechanism. 

Figure 6.29. Thermodesorption spectrum obtained with nickel oxide after sulfur dioxide adsorption at 250°C samples 2 to 5...

HIDY The filter media used in this study was a teflon-coated glass fiber substrate, manufactured for us under very strict specifications. It was used uniformly for all aerosol sampling in the SURE. The filter medium is not subject to a sulfur dioxide adsorption artifact, but it is subject to adsorption of nitric acid. It does not adsorb NO or NO2, however. 

Lee, J.K., et al.. Sulfur dioxide adsorption over activated lignite char prepared from fluidized bed pyrolysis, Chem. Eng. Sci., 49(24A), 4483-4490 (1994). 

Fig. 8.9 Sulfur dioxide adsorption (left) and ammonia adsorption right) on some supported group III oxides (AI2O3, Al/Nb, GaiOs, Ga/Nb, andIn203, In/Nb) on niobia. Bulkniobia does not show any basicity [84]...

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