Performance and Recovering of a Zn-Doped Manganese Oxide as a Regenerable Sorbent for Hot Coal Gas Desulfurization

Abstract

The performance of a ZnO-doped manganese oxide MZ(1:0.1) as a regenerable sorbent for hot coal gas desulfurization in 70-cycles tests in a fixed bed reactor has been studied. Sulfidation has been carried out at 700 °C using a simulated RKW coal gas, while regeneration of the sulfided sorbent has been conducted at 800 °C using pure air. The performance was very good as deduced from low pre-breakthrough H2S concentration in the outlet gas, high sorbent efficiency, and long durability. Despite that, a slight efficiency decay was observed that will make the sorbent become inactive after a certain number of successive cycles in use. Simple methods of preparation, similar to those used in the manufacture of the original fresh sorbents, are shown to be effective in recovering the activity of this sorbent. Additionally, because manganese sulfate plays an important role in the long durability exhibited by manganese based sorbents, the evolution of this compound in the reactor bed in a typical regeneration test has been studied by FTIR spectroscopy. It is formed during the first stages of regeneration but it decomposes then, although not completely, in the last stages of the process, acting as a por-forming additive, like graphite, in every cycle.

Removal of Hydrogen Sulfide with Metal Oxides in Packed Bed Reactors—A Review from a Modeling Perspective with Practical Implications

“…Doping with chromium oxide [92] and manganese [93][94][95][96]. Also addition of molybdenum [97], vanadium [96][97][98][99] Doping other metal ions into manganese oxide such as Zn [104][105][106], Fe [106] and Al [107][108][109]. Desulfurization at temperatures higher than 700 • reduces the chances of sulfate formation [96].…”

Highly stable and regenerable Mn-based/SBA-15 sorbents for desulfurization of hot coal gas

“…Similarly, Slimane and Hepworth [14,15] also found that manganese-based sorbents presented high initial sorption rate, high sulfur capacity and good regenerative ability during hot coal gas desulfurization at 700-1000 • C but with high H 2 S equilibrium concentration (around 150 ppmv). Therefore, a variety of oxides, such as zinc oxide [16][17][18][19], iron oxides [18,[20][21][22], copper oxides [19,21,23,24], and vanadium oxides [25,26] were incorporated into manganese oxides in order to increase the H 2 S removal efficiency. However, the application of zinc and ferric oxides is limited to a maximum temperature of 600 • C due to zinc evaporation and the reduction of ferric oxides at reductive atmosphere.…”

Deactivation of MnO_x-CeO_x/ACF Catalysts for Low-Temperature NH₃-SCR in the Presence of SO₂

“…Thehighertheoxidationstateofmanganeseis,themoreeasily S 6+ mightformduringlow鄄temperatureSCRprocess.Somuch moreS 4+ isfoundforMnO x 鄄CeO x /ACF T andmuchmoreS 6+ is foundforM鄄MnO x 鄄CeO x /ACF T (M=Fe,Cu,orV). FT鄄IRspectraofthedeactivatedcatalystsafterthermal treatmentareshowninFig.8.ThespectraofMnO x 鄄CeO x /ACFT exhibitadsorptionpeakscorrespondingtothestretchingvibration ofMn-O [25] (605cm -1 )andC -O(1392cm -1 )whichindicate theoxygenatedgroupsonthesurfaceofthecatalysts.The adsorptionpeakcenteredat837cm -1 isassignedtothestretching vibrationofS-O.M鄄MnO x 鄄CeO x /ACF T (M=Fe,Cu,orV)shows almostthesamespectraofMnO x 鄄CeO x /ACF T .Theadsorption peakcenteredat500cm -1 isassignedtooutplaneblendingvib鄄 rationofSO 2-3 whichindicatessulfitesinthedeactivatedcatalysts afterthermaltreatment.Thecharacteristicadsorptionsinthe frequencyrange1000-1420cm -1 havebeenreportedtobethe infraredactivenormalmodeofSO [2][3][4] groupsinthecatalysts.The bandcenteredat1115cm -1 canbeassignedtomanganesesulfates andthebroadbandin1000-1200cm -1 havealsobeenreported tocorrespondtoCe(SO 4 ) 2 formation [26] .Itisverifiedthatthereac鄄 tionsbetweenmetalsandSO 2 takeplaceunderlow鄄temperature SCRconditions.…”