Breakthrough Sulfur Capacity Research Articles

Fabrication and Performance of xMnyCe/Hexagonal Mesoporous Silica Sorbents with Wormhole-Like Framework for Hot Coal Gas Desulfurization

A series of xMnyCe/hexagonal mesoporous silica (HMS) sorbents with wormhole-like structure was prepared by a sol–gel method, and their performance for hot coal gas desulfurization was investigated at 600 °C. All xMnyCe/HMS sorbents exhibited high breakthrough sulfur capacity, and the utilization of these sorbents was much higher than that of 10Mn/HMS. The breakthrough sulfur capacity over 4Mn1Ce/HMS sorbents was 121.7 mg of S/g of sorbent with the utilization of 82.4%. Such a behavior was maintained in eight consecutive desulfurization–regeneration cycles. The effects of the desulfurization temperature, H2 concentration, and 7% steam on the performance of 4Mn1Ce/HMS were examined. The fresh, used, and regenerated samples were characterized by means of X-ray diffraction, N2 adsorption, Fourier transform infrared absorption spectroscopy, and high-resolution transmission electron microscopy techniques. The results confirmed that the manganese oxide was dispersed highly on the HMS support because of the syner...

Desulfurization activity of metal oxides blended into walnut shell based activated carbons

AbstractBACKGROUNDWalnut shell, a nutshell waste, was used to prepare activated carbons (AC) for desulfurization. Titanium ore (TO), TiO2 or Fe2O3 was blended into the resulting carbonized powders, which were extruded into cylinders and activated under CO2 atmosphere. The desulfurization activity of samples was evaluated in a fixed bed under a simulated gaseous mixture from coal combustion.RESULTSWalnut shell can be used to prepare activated carbons (AC) for desulfurization, giving an AC surface area of 401.2 m2 g−1. When TO, TiO2 or Fe2O3 were added into the AC, the surface area of ACTO2, ACT2 and ACF2 increased to 937.1, 661.8 and 791.0 m2 g−1. Ti and Fe in TO are changed into anatase TiO2 and Fe2O3 in ACTOx, and TiO2 and Fe2O3 exist in ACTx and ACFx, respectively. The optimum additive dosage of ACTOx, ACTx and ACFx is 2%. The breakthrough sulfur capacity of ACT2 is higher than that of ACTO2 and ACF2, but other ACTOx is better than ACTx and ACFx, indicating that TiO2 and Fe2O3 have synergistic effects in ACTOx.CONCLUSIONPore structure and metal oxides are the main factors which influence the desulfurization performance of catalysts. © 2013 Society of Chemical Industry

Nanocrystalline ZnCO3—A novel sorbent for low-temperature removal of H2S

The reactivity of a nanocrystalline ZnCO3 toward H2S (0.2vol% in N2/H2 mixture) at 140–180°C was characterized by thermal gravimetric analysis and by breakthrough curves measurements. We have found that under used conditions transformation of ZnCO3 into ZnS is complete and the rate determining step of the sulfidation is the surface reaction. Such behavior is in strike contrast with that of ZnO whose sulfidation is severely limited by diffusion. The higher reactivity of ZnCO3 in comparison with ZnO is attributed to the different microstructure of ZnS layer formed in these materials after a partial sulfidation. As in ZnO–ZnS transformation the molar volume increases (from 14.5 to 23.8cm3/mol), a continuous protective ZnS layer is formed hampering the access of H2S to the non reacted ZnO core. By contrast, in ZnCO3–ZnS transformation the molar volume decreases (from 27.9 to 23.8cm3/mol), which produces a discontinuous non-protective ZnS layer enabling a complete transformation of ZnCO3 even at 140°C. The higher reactivity of ZnCO3 results in a considerable increase of the breakthrough sulfur capacity of the carbonate in comparison with oxide. The material has therefore a good potential for being used as a disposable sorbent for H2S capture at low temperature.

Adsorptive removal of sulfur compounds using IRMOF-3 at ambient temperature

Zinc-based metal–organic framework (IRMOF-3) was used as adsorbent for removal of dimethyl sulfide, ethyl mercaptan and hydrogen sulfide in fixed bed reactor at ambient temperature. These samples before and after exposure to sulfur compounds were characterized by Fourier transform infrared (FTIR), and X-ray diffraction (XRD), and thermo gravimetric (TG), and X-ray photoelectron spectroscopy (XPS). The results show that IRMOF-3 exhibit the best performance for hydrogen sulfide removal with the highest breakthrough sulfur capacity, followed by ethyl mercaptan and dimethyl sulfide. This is in consistent with the interaction strength between IRMOF-3 and sulfur compounds. In the case of dimethyl sulfide and ethyl mercaptan, the interaction comes from the weak interaction between the amino group in the MOFs and the sulfur atom of the adsorbate. This can also be considered as a hydrogen bond complex in which the amino group in the MOFs and the S atom of the sulfur compounds play the role of H-donor and H-acceptor, respectively. In the case of hydrogen sulfide, the interaction with sulfur atom originates from the amino group and zinc site in the MOFs. The former is more like an acid–base interaction, whereas the latter results in new products of ZnS and H2O and serious destruction of the MOFs.

H2S removal: Correlation between performance and loading species of Zn‐Fe/attapulgite

Three kinds of sorbents, Zn/attapulgite (ATP), Fe/attapulgite, and Zn‐Fe/attapulgite with different amounts of Fe and Zn were prepared and used for H2S removal at room temperature. The stirring time and final pH were selected. According to the breakthrough time, desulfurization efficiency and sulfur capacity, the order of desulfurization performance was Zn‐Fe/ATP > Zn/ATP > Fe/ATP. The results of X‐ray diffraction (XRD), Ultraviolet–visible diffuse reflectance spectroscopy (UV–vis‐DRS), ammonia‐dissolving tests and transmission electron microscope (TEM) indicated that for the Fe sorbents, a stronger interaction between the loadings and supports (ILS) led to a poorer desulfurizing capability, even with increasing loading amounts. The oligomeric Fe species which were the main active substance for H2S removal among the three kinds of Fe species in the sorbents, affected the desulfurization performance. The performance of Zn sorbents depended on the loading amount and ILS rather than dispersity. Due to the interaction between Zn and Fe, Zn‐Fe/ATP has the best ILS and the greatest amount of oligomeric Fe species, and hence has the best performance. However, an increase in loading amount leads to a decline in the proportion of the oligomeric Fe species and an increase in large particle Fe species, and hence the reaction rate of loading was reduced. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 378–384, 2014

Reactive adsorption desulfurization over a Ni/ZnO adsorbent prepared by homogeneous precipitation

A high-performance Ni/ZnO adsorbent was prepared by homogeneous precipitation using urea hydrolysis and characterized by N2 adsorption-desorption, X-ray diffraction (XRD), and scanning electron microscope (SEM). The adsorbent was applied to the deep desulfurization of gasoline and showed a high breakthrough sulfur capacity and a remarkably high volume hourly space velocity. The effects of coexisting olefins in gasoline as well as adsorptive conditions on the adsorptive performance were examined. It was found that olefins in gasoline had a slightly inhibiting effect on the desulfurization performance of the adsorbent. The optimum conditions were 673 K, 1.0 Mpa with a volume hourly space velocity of 60 h−1. Under the optimum conditions, ultralow sulfur gasoline could be produced and the breakthrough sulfur capacity of the adsorbent was 360 mg-s/g-sorb for the model gasoline.

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

A series of mesoporous xCuyMn/SBA-15 sorbents with different Cu/Mn atomic ratios were prepared by wet impregnation method and their desulfurization performance in hot coal gas was investigated in a fixed-bed quartz reactor in the range of 700–850°C. The successive nine desulfurization–regeneration cycles at 800°C revealed that 1Cu9Mn/SBA-15 presented high performance with durable regeneration ability due to the high dispersion of Mn2O3 particles incorporated with a certain amount of copper oxides. The breakthrough sulfur capacity of 1Cu9Mn/SBA-15 observed 800°C is 13.8g S/100g sorbents, which is remarkably higher than these of 40wt%LaFeO3/SBA-15 (4.8g S/100g sorbents) and 50wt%LaFe2Ox/MCM-41 (5.58g S/100g sorbents) used only at 500–550°C. This suggested that the loading of Mn2O3 active species with high thermal stability to SBA-15 support significantly increased sulfur capacity at relatively higher sulfidation temperature. The fresh and used xCuyMn/SBA-15 sorbents were characterized by means of BET, XRD, XPS, XAES, TG/DSC and HRTEM techniques, confirmed that the structure of the sorbents remained intact before and after hot coal gas desulfurization.

Desulfurization of hot coal gas over high-surface-area LaMeOx/MCM-41 sorbents

We prepared LaMeOx/MCM-41 (Me=Co, Zn, Fe) sorbents of high specific surface area by means of sol–gel method. For comparison purposes, the unsupported composite metal oxides were also synthesized. Breakthrough and total sulfur capacity over LaFeO3/M41 were 3.24 and 3.70g, respectively, significantly higher than the former (0.35g) over unsupported LaFeO3. The materials were characterized using Brunauer, Emmett and Teller (BET), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (H2-TPR), temperature-programmed reduction and sulfidation (TPRS), and high-resolution transmission electron spectroscopy (HRTEM) techniques. Their ability for H2S removal was evaluated over a fixed-bed reactor, and the effects of reaction temperature, feed composition, and support on desulfurization were studied. The results of successive sulfidation/regeneration cycles (×10) revealed that the LaFeO3/M41 sorbent was stable enough for desulfurization of hot coal gas in chemical industry.

Effect of activated carbon support on CS 2 removal over coupling catalysts

Supported coupling catalysts for CS 2 removal were prepared with different activated carbons originated from wood, coconut shell and coal as supports, and their catalytic activities for CS 2 removal were tested at ambient temperature. The textural and surface properties of the activated carbons were characterized by nitrogen adsorption, temperature-programmed desorption (TPD) and Boehm titration. The activated carbon support with meso- and macropores, and oxygen-functional groups performs higher CS 2 removal ability at ambient temperature. The effects of flow rate, CS2 inlet concentration, temperature and relative humidity on CS2 removal were also investigated. High efficient removal is obtained at temperature of 50 °C, space velocity of 2000 h −1, inlet CS 2 concentration of 500 mg S/m 3 and relative humidity of 20% with the breakthrough sulfur capacity up to 4.3 g S/g Cat and working sulfur capacity up to 7 g S/g Cat.

Characterization and performance of LaxFeyOz/MCM-41 sorbents during hot coal gas desulfurization

Using a sol–gel method, supported and unsupported LaxFeyOz sorbents were prepared. The effects of composition of sorbent, reaction temperature, WHSV, hot coal gas composition, reactor types and support on the breakthrough sulfur capacities were investigated. When the content of H2S is 0.86% (vol.) in the feed gas, the breakthrough sulfur capacity of 50% LaxFeyOz/MCM-41 (La:Fe=1:2) achieved 7.94gS/100g sorbent, and approximately 63.9% of theoretical sulfur capacity was utilized. The results of ten successive desulfurization–regeneration cycles revealed that 50% LaxFeyOz/MCM-41 (La:Fe=1:2) sorbent presented high performance and stability for hot coal gas desulfurization. The sorbents were characterized by means of BET, XRD, XPS techniques.

Desulfurization behavior of zinc oxide based sorbent modified by the combination of Al2O3 and K2CO3

In order to reduce the unfavorable effect of carbon oxide on desulfurization efficiency for zinc oxide based sorbent and decrease the concentration of carbonyl sulfide in effluent gas during desulfurization process, the modification of zinc oxide based sorbent is necessary in the preparation of zinc oxide based desulfurization sorbent. In this paper, the modified ZnO based desulfurization sorbents were obtained by mixing of active zinc oxide with different additives, which include graphite, Al2O3 and K2CO3, then shaping at ambient temperature, drying at 120°C and calcinating at 550°C. The desulfurization performances for the prepared ZnO based desulfurization sorbents were tested in a quartz upflow fixed-bed reactor under the condition of 300°C, 2000h−1 and simulated coal-derived gas. The phases of sorbents before and after desulfurization were characterized by X-ray diffractometer, and their pore structures were measured by N2 adsorption–desorption method. The experimental results show that COS was present in effluent gas for ZnO based sorbent while removing H2S from simulated coal-derived gas at experimental condition. ZnO based desulfurization sorbent modified by the combination of K2CO3 and Al2O3 achieves obvious improvements in the desulfurization performance, and H2S and COS concentrations in exit gas are below 0.1 mgS/m3 before breakthrough point as well as the accumulated breakthrough sulfur capacity reaches 14wt.%. Adding Al2O3 can improve the pore structure of ZnO based desulfurization sorbent, which benefits H2S to diffuse in the pore of sorbent and improves desulfurization performance. Loading K2CO3 can increase the basicity of ZnO based desulfurization sorbent, which raises the COS catalytic hydrolysis rate on sorbent and decreases concentration of COS present in exit gas.

A sulfur removal and disposal process through H 2S adsorption and regeneration: Breakthrough behaviour investigation

The breakthrough behaviours of H 2S adsorption in a fixed-bed reactor of iron oxide based adsorbent under elevated pressures were studied. The effects of variations in superficial gas velocity from 0.09 to 0.26 m/s, H 2S feed concentration from 0.5% to 6% (v/v), the operating pressure from 405 to 5070 kPa absolute, and the height of the fixed-bed from 11.7 to 24.5 cm on the breakthrough curves and sulfur loading capacity were investigated. It was found that the shape of the breakthrough curves depends on the superficial velocity and the inlet H 2S concentration in gas streams. Under both higher superficial velocity and higher inlet H 2S concentration, the shape of the breakthrough curve becomes steeper, and vice versa. The sulfur loading capacity decreases as the superficial velocity and the inlet H 2S concentration increase, but it increases as the bed height increases. The change of operating pressure does not have a significant effect on the shape of the breakthrough curve or sulfur loading of the adsorbent. The pressure drop across the bed follows the Ergun equation. The investigation was also extended to the use of the regenerated adsorbents. An empirical equation of exponential function can be used to describe the breakthrough curves. This work provides useful data for the adsorption tower design and process optimization.

Preparation and selection of Fe-Cu sorbent for COS removal in syngas

A series of iron-based sorbents prepared with iron trioxide hydrate, cupric oxide by a novel method was studied in a fixed-bed reactor for COS removal from syngas at moderate temperature. In addition, the sorbents mixed with various additives in different ratios were tested. The effects of additive type and ratio on the breakthrough capacity and desulfurization performance, as well as the influence of operating conditions on sulfidation behavior of the sorbent, were investigated. The simulate gas contained 1% COS, 5% CO2, 20%–30% CO and 60%–70% H2. The outlet gases from the fixed-bed reactor were automatically analyzed by on-line mass spectrometry, and the COS concentration before breakthrough can be kept steady at 1 ppmv. The result shows that the breakthrough sulfur capacity of the sorbent is as high as 25 g-S/100 g. At 700 K and space velocity of 1000 h−1, the efficiency of sulfur removal and breakthrough sulfur capacity of the sorbent increase with the increase of copper oxide with an optimum value. The result shows that the species and content of additives also affect desulfurization performance of the sorbent.

Cu–Zn–Al mixed metal oxides derived from hydroxycarbonate precursors for H 2S removal at low temperature

One series of Cu–Zn and two series of Cu–Zn–Al hydroxycarbonate precursors with varying metal molar ratios were prepared via co-precipitation or multi-precipitation method, and the mixed metal oxides obtained by calcination of the precursor materials were used as adsorbents for H 2S removal in the range of 25–100 °C. The results of H 2S adsorption tests showed that these mixed oxides, especially two series of Cu–Zn–Al mixed metal oxides exhibited markedly high breakthrough sulfur capacities (ranging from 4.4 to 25.7 g S/100 g-sorbent with increase of Cu/Zn molar ratio) at 40 °C. Incorporation Cu and/or Al decreased the mean crystalline sizes of ZnO and CuO species in the Cu–Zn and Cu–Zn–Al mixed metal oxide adsorbents by decreasing of mean crystalline sizes of hydroxycarbanate phases mainly including hydrozincite, aurichalcite and malachite, segregation of Al phase, etc. Higher breakthrough sulfur capacity of each adsorbent in two ternary series than that of the corresponding adsorbent in binary series should be ascribed to the enhancement of the dispersion of ZnO and/or CuO species with incorporation of aluminum, thereby increasing the overall rate of reaction between the adsorbent and H 2S by reducing the thickness of potential sulfide shell on the outer layer of the oxide crystalline grains and increasing the area of the interface for the exchange of HS −/S 2− and O 2−. For each series of adsorbents, the breakthrough sulfur capacity increased with the increase of Cu/Zn molar ratio regardless of changes of the dispersion of CuO and/or ZnO. This phenomenon might be mainly attributed to faster rate of the lattice diffusion of HS −, S 2− and O 2− or exchange of HS −/S 2− and O 2− during the sulfidation of CuO than that during the sulfidation of ZnO due to less rearrangement of the anion lattice.

Characteristics and Reactivities of Solid Wastes Sorbent for Medium-temperature Flue Gas Desulfurization

In this study, sorbent for flue gas desulfurization is prepared using metallurgical dusts (MD) abundant in iron oxides as the main active component, lime as promoter, and amylum as special additive. The reactivity of the sorbent is conducted in a quartz fixed-bed reactor within the medium temperature range of 300°C–750°C under heating and isothermal conditions, while the physical and chemical properties of the sorbent are measured using ICP-AAS, SEM, XRD, and so on. The experimental results indicate that with temperature increasing from 300°C to 750°C, breakthrough sulfur capacity of the sorbent increases from 0.0257 gS/gSorbent at 300°C to 0.1391 gS/gSorbent at 650°C, then decreases to 0.0836 gS/gSorbent at 750°C, and that the removal efficiency of SO2 and breakthrough sulfur capacity of the sorbent depend on the chemical kinetics of Fe2O3 and CaO in the temperature range of lower than 600°C, but on the thermodynamic equilibrium of sulfuration of Fe2O3, the thermal stability of the Fe2(SO4)3 and content of CaO in the range of higher than 650°C. Physical and chemical analyses of the fresh and reacted sorents further verify that the effective and dominating component of the sorbent is Fe2O3 within the temperature range of lower than 650°C, while is CaO in higher than 650°C.