Dioxide Conversion

Using a 0—10% excess of chlorine and 100% excess of sulfur dioxide, conversions of around 50% are obtained. The Hquids in the reaction product are condensed and separated, the sulfur mono- and dichloride are returned for further reaction, and the excess gases are also recycled, producing an ultimate yield near 100% on all reactants. 

Double-Absorption Plants. In the United States, newer sulfuric acid plants ate requited to limit SO2 stack emissions to 2 kg of SO2 per metric ton of 100% acid produced (4 Ib /short ton Ib = pounds mass). This is equivalent to a sulfur dioxide conversion efficiency of 99.7%. Acid plants used as pollution control devices, for example those associated with smelters, have different regulations. This high conversion efficiency is not economically achievable by single absorption plants using available catalysts, but it can be attained in double absorption plants when the catalyst is not seriously degraded. 

Fig. 3 showed the catalyst stability of Ni-Mg/HY, Ni-Mn/HY, and Ni/HY catalysts in the methme reforming with carbon dioxide at 700°C. Nickel and promoter contents were fixed at 13 wt.% and 5 wt.%, respectively. Initial activities over M/HY and metal-promoted Ni/HY catalysts were almost the same. It is noticeable that the addition of Mn and Mg to the Ni/HY catalyst remarkably stabilized the catalyst praformance and retarded the catalyst deactivation. Especially, the Ni-Mg/HY catalyst showed methane and carbon dioxide conversions more thrm ca. 85% and 80%, respectively, without significant deactivation even after the 72 h catalytic reaction. 

R. S., Carbon dioxide conversions in microreactors, in Proceedings of the 4th International Conference on Microreaction Technology, IMRET 4, pp. 187-193 (5-9 March 2000), AIChE Topical Conf. Proc., Atlanta, USA. 

Furthermore, a liquid-phase distributor is used on the top of the bed and the overall gas-phase mass transfer coefficient was experimentally measured as 0.153 s 1 for liquid flow rate equal to 14 X 10 5 m3/s. Under these conditions, the experimental value of sulfur dioxide conversion was approximately 18%. 

Up to 0.5% of sulphur may also initiate the curing effect of lead dioxide. Conversely, the addition of fatty acids and their salts may exert an inhibitory influence upon the curing process of polymer LP. Thus the addition of one part by weight of stearic acid to polymer LP approximately doubles the curing time. 

As with other volatiles, inhalation is viewed as the main route of entry for chloroform. Its absorption and distribution to all organs is rapid. Except for some CO2 production most of it is exhaled unchanged. The carbon dioxide conversion rate appears to vary with both port of entry and species. When human volunteers of both sexes were administered 500 mg of CHClj orally, from 20 to 60% of it continued to be exhaled unchanged for 40 to 120 minutes (ref. 38). 

The capillary plasma reactor consists of a Pyrex glass body and mounted electrodes which are not in direct contact with the gas flow in order to eliminate the influence of the cathode and anode region on CO2 decomposition. Analysis of downscaling effects on the plasma chemistry and discharge characteristics showed that the carbon dioxide conversion rate is mainly determined by electron impact dissociation and gas-phase reverse reactions in the capillary microreactor. The extremely high CO2 conversion rate was attributed to an increased current density rather than to surface reactions or an increased electric field. 

Figure 16.7 shows that an increase of the liquid injection leads to a decrease in gas temperature at the outlet of the fluidized bed, while an improved sulfur dioxide conversion is also documented (see Fig. 16.8). 

Fig. 16.56. Comparison of measured and simulated sulfur dioxide conversions.

For fluidized beds, one essential operating parameter is that of gas throughput this is necessary for fluidization of the bed material, and depends on the diameter and density of the particles and on the density and viscosity of the gas. These studies highlight the fact that sulfur dioxide conversion is decreased at increased gas flow rate, and thus with higher energy input. As a result, a more rapid drying of the liquid contained in the bed occurs with a coupled decrease in the mass transfer surface. 

Figure 3.14 Carbon dioxide conversions in aqueous media.

Yumura T, Amenomori T, Kagawa Y, Yoshizawa K (2002) Mechanism for the formaldehyde to formic add and the formic acid to carbon dioxide conversions mediated by an iron-oxo species. J Phys Chem A 106 621... 

The problem with sulfur dioxide containment is that many smelter processing units produce sulfur dioxide concentrations of 1-2% whereas the minimum economic concentration for sulfur dioxide conversion processes (e.g., for sulfuric acid or sulfur production) is 3.5-4%. Thus, the economic solution to containment requires either modification of the smelter process to obtain higher sulfur dioxide concentrations, or capture of sulfur dioxide at relatively low concentrations followed by some means of regeneration of a high concentration of sulfur dioxide (Chap. 3). Throw-away approaches to sulfur dioxide containment, lime or limestone wet scrubbing, are worthy of consideration by small-scale smelters (e.g., Eqs. 13.35-13.37). 

The expected return of oil price increases over the next decade will again spur investigation into conversion processes for alternative fuel sources such as coal. Coal gasification will produce substantial amounts of carbon dioxide as a by-product. If this carbon dioxide could be converted economically to methanol or methane, established zeolite catalytic processes could convert these intermediates to gasoline. Furthermore, concern about providing a substitute for natural gas to the established gas pipelines has led the Gas Research Institute to sponsor investigation of carbon dioxide conversion selectively to methane (2). 

Figure 1. Effect of water vapor on sulfur dioxide conversion using various iron-containing alumina catalysts...

The preceding test was repeated with 20 g of Jamaican red mud catalyst replacing the red bauxite at 420 °C. The results in Figure 3 indicate that up to 20% water vapor slightly inhibited the sulfur dioxide conversion on this iron-rich catalyst. In absence of water, carbonyl sulfide was formed (curve a), but with water, hydrogen sulfide (curve c) was formed instead. 

The relationship between sulfur dioxide conversion and the water-to-sulfur dioxide ratio is shown in Figure 4. Since the gas residence time, the reaction temperature, and the dry inlet gas composition were held constant, it is evident that the reaction rate increases with the partial... 

Figure 4. Relationship between sulfur dioxide conversion and the water-to-sulfur dioxide ratio...

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