What is the mechanism of catalyst-induced arsenic poisoning?
Thread Content
Arsenic poisoning often occurs in catalysts during use; this is the case with cobalt-molybdenum-based catalysts, for example. What is the mechanism behind arsenic poisoning? What reactions take place when arsenic adsorbs onto the catalyst, leading to its deactivation?
During combustion, coal releases arsenic (As) due to high temperatures and intense oxidation, which causes catalyst poisoning. Arsenic poisoning of SCR catalysts is caused by gaseous arsenic compounds (As2O3) diffusing into the catalyst surface and accumulating in its pores, where they then react with O2 at the active sites of the catalyst to form As2O5. At the same time, As2O3 diffuses into the catalyst and solidifies in both active and inactive regions, restricting the diffusion of reaction gases within the catalyst and damaging the capillaries, thereby forming a saturated layer of arsenic. The arsenic-saturated layer has almost no activity; this saturated layer prevents reactants from diffusing into the interior of the catalyst. The extent of this inhibition is proportional to the thickness of the arsenic-saturated layer, as a result of which the surface activity of the catalyst is impaired, while the catalyst inside retains its initial activity. Studies have also shown that As2O3 concentrates within the catalyst pores, physically blocking the catalyst and causing its deactivation. This article is excerpted from China Thesis Network; the original address is: http://www.xzbu.com/8/view-3858094.htm
This post was last edited by 654262293 on 2025-4-24 14:55