High-Temperature Gaseous H2S Removal by ZnâMn-based Sorbent

Article pubs.acs.org/IECR

High-Temperature Gaseous H2S Removal by Zn−Mn-based Sorbent Li Feng Guo,† Kuan Lun Pan,† How Ming Lee,‡ and Moo Been Chang*,† †

Graduate Institute of Environmental Engineering, National Central University, Taoyuan 32001, Taiwan Physics Division, Institute of Nuclear Energy Research, Taoyuan32546, Taiwan

‡

ABSTRACT: Zn−Mn oxides supported on γ-Al2O3 are experimentally evaluated as an adsorbent for removing H2S from gas streams in the temperature range of 350−600 °C. Experimental results indicate that zinc and manganese oxide can be integrated to form a good solid solution for effective adsorption of H2S. With an operating temperature of 600 °C and 200 ppm of H2S on the gas stream, the adsorption capacity of H2S achieved with 10 wt % Zn−Mn/γ-Al2O3 (ZMA) reaches 52 mg S/g at a gas hourly space velocity (GHSV) of 20 000 h−1. Additionally, kinetic study is conducted to evaluate the activation energy. Results indicate that the activation energy of ZMA is 51 kJ/mol and that the reaction rate constant increases with increasing temperature. In addition, the H2S adsorption capacity of ZMA would be significantly increased as CO2, H2, and CO are added into the gas stream individually. In the regeneration process, the activity of ZMA can be completely recovered with air at the low regeneration temperature of 300 °C. Furthermore, the durability test results indicate that the sulfur adsorption capacity achieved with ZMA is maintained at about 52 mg S/g at 600 °C for at least 6 cycles. Overall, the Zn−Mn-based adsorbent shows good performance and stability for H2S removal.

1. INTRODUCTION Biomass is considered as the world’s fourth major energy only next to oil, coal, and natural gas.1 The International Energy Agency (IEA) indicates that biomass is one of the major sources for global primary energy, and oil, coal, and natural gas consumption can be effectively reduced if biomass is properly utilized.1 It is also believed that biomass has good potential to replace the dwindling supplies of oil, coal, and natural gas. Among biomass utilization technologies, thermochemical methods including pyrolysis and gasification are commonly used.2−4 The gas stream generated from gasification mainly comprises of carbon monoxide (CO), hydrogen (H2), and methane (CH4) and is generally called syngas which is of great value for chemical production. However, syngas generated from biomass gasification consists of sulfur-containing gases such as hydrogen sulfide (H2S) and carbonyl sulfide (COS), while H2S mainly dominates with the typical concentration of a few hundred parts per million.5 H2S may cause the corrosion of the absorber, distillation column, heat exchanger, and pipelines. Also, its use leads to poisoning of catalyst as a post-treatment process for the synthesis of dimethyl ether (DME)6 and reduces the efficiency of molten carbonate fuel cells (MCFC) and solid oxide fuel cells (SOFC) if the concentration is above 10 ppm.5,7,8 H2S is highly toxic for humans. Exposure to lowconcentration H2S may damage eyes and the respiratory and central nervous systems9 and even causes death within a short period of time if exposed to a concentration level of 200 ppm or above.10 Additionally, H2S is an important odor-causing substance, with a relatively low odor threshold (0.5−130 ppb).11 H2S removal technologies can be generally divided into wet desulfurization, dry adsorption, and nonthermal plasma technology. The wet absorption method has drawbacks such as a large space for installation, corrosion of facilities, and secondary water pollution, while high energy consumption remains a big concern for nonthermal plasma technology. © 2015 American Chemical Society

Among dry desulfurization means, adsorption with metal oxidebased sorbents is considered as one of the most effective methods. The reaction mechanism is generally described as reactions 1 and 2.12 Metal oxides (MO) react with H2S to form metal sulfide (MS), and MO is regenerated by reacting with O2. MO(s) + H 2S(g) ↔ MS(s) + H 2O(g)

(1)

MS(s) + 1.5O2(g) ↔ MO(s) + SO2(g)

(2)

A variety of metal oxides have been developed for desulfurization purposes. Westmoreland and Harrison (1976) evaluated the feasibility of metal oxides for desulfurization based on thermodynamic calculation and indicate that oxides of Fe, Zn, Mn, Mo, V, Ca, Sr, Ba, Co, Cu, and W are of good potential.13 Among them, zinc oxide and manganese oxide are primarily considered owing to their excellent performance for H2S adsorption. Kim et al. (2007) indicated that ZnO could react with H2S rapidly due to favorable sulfidation thermodynamics and good affinity to H2S.14 However, the reaction temperature should not be higher than 550 °C, otherwise zinc oxide might be reduced to elemental zinc and vaporize.15,16 Compared to zinc oxide, manganese oxide is relatively stable at elevated temperatures. Ben-Slimane and Hepworth (1994) indicated that manganese oxide is stable at high temperatures (>973 °C).17 The reaction rate of Mn-based sorbents with H2S is shown to be faster than that of Zn- or Fe-based sorbents.18 Complex metal oxides have been developed to improve physical and chemical properties of adsorbents and the adsorption capacity of H2S. Previous study indicates that zinc and manganese match pretty well for solving the zinc oxide Received: Revised: Accepted: Published: 11040

June 9, 2015 October 19, 2015 October 23, 2015 October 23, 2015 DOI: 10.1021/acs.iecr.5b02078 Ind. Eng. Chem. Res. 2015, 54, 11040−11047

Article

Industrial & Engineering Chemistry Research

Figure 1. Experimental setup.

pretreatment prior to measurement. The crystal structure of the impregnation-prepared adsorbents was identified by X-ray diffraction (XRD) (Bruker, D8AXRD) with Cu−Kα radiation at 40 kV and 40 mA and the diffraction patterns in the range of 10° ≤ 2θ ≤ 80° at a scanning rate of 6°/min. Temperature-programmed oxidation (TPO) of H2S-saturated ZMA sorbent was applied in regeneration process with the temperature varying from 100 to 600 °C at a heating rate of 5 °C/min. The air flow rate was controlled at 200 mL/min, and the SO2 outlet concentration was measured by an online analyzer (Testo 350,Testo). 2.3. H2S Adsorption and Regeneration Tests. H2S adsorption tests are divided into two parts including adsorption and regeneration. The experimental system is schematically shown in Figure 1. The experiment was performed in a fixedbed quartz reactor with the diameter of 20 mm and 4 g adsorbent was applied. The gas stream contains H2S with N2 as balance gas, and the gas hourly space velocity (GHSV) is fixed at 20 000 h−1 unless specified otherwise. The effect of temperature on H2S adsorption capacity (mg H2S/g) is investigated at a temperature range of 350−600 °C. The H2S concentration is adjusted from 200 to 1000 ppm to evaluate its effect. In addition to adsorption test, desorption (or regeneration) test is also performed in this study. After adsorption process, the experimental system is first purged with N2 to sweep H2S away. Then, hot air (300 °C) is injected into the system for regeneration when the adsorbent bed reaches 300 °C, and 1.2 L/m of air is applied as the working gas. The adsorption process continues until no SO2 is detected, and the outlet SO2 concentration was measured by Testo 350. Highgrade H2S, N2, and air were supplied from gas cylinders. A set of mass flow controllers (MFC) were used to adjust and control the gas flow rate, and gas was well mixed upstream the reactor. The experimental data were taken as reactions reached steady state. The performance is calculated on the basis of adsorption capacity as shown in eq 3.

problem at high temperatures, and it is expected that Zn−Mnbased adsorbent can effectively adsorb H2S.19 In this study, Zn−Mn based adsorbents are prepared and γAl2O3 is selected as a support for removing H2S from hightemperature gas streams, because γ-Al2O3 can effectively promote H2S adsorption performance.20 Previous studies mainly focused on the stability of the adsorbent. Important characteristics such as excellent sulfur removal capacity, fast adsorption kinetics, chemical and physical stability, and ability to regenerate are required to be a good adsorbent for H2S removal. Therefore, various operating parameters including space velocity, temperature, regeneration, inlet H2S concentration, and effect of gas composition on H2S adsorption are extensively evaluated via a lab-scale experimental setup.

2. EXPERIMENTAL SECTION 2.1. Adsorbent Preparation. Ten weight percent Zn− Mn/γ-Al2O3 (ZMA) was prepared by the incipient wetness impregnation method. First, the support material (γ-Al2O3) was pulverized to appropriate size (48−100 mesh). The corresponding metal nitrates including Zn(NO3)2·6H2O and Mn(NO3)2·4H2O were used as precursors to prepare aqueous solution with appropriate stoichiometry. The ratio of Zn and Mn is controlled at 1. Subsequently, the treated support material was soaked in the nitrate solutions prepared (the weight (%) ratio of Zn−Mn:γ-Al2O3 = 10:90), heated, and continuously stirred to evaporate the water at 80 °C. The mixed material was dried at 120 °C for 24 h, and then calcined at 600 °C for 6 h in air to obtain 10 wt % Zn−Mn/γ-Al2O3 and used as such. 2.2. Characterization of Adsorbent. The morphology of the adsorbent prepared was observed by using scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS) (JEOL, JSM-6700F), with the specimen being sputtered with gold for better analysis. The specific surface area (BET) was measured with Micromeritics ASAP 2010, and the samples were placed at 110 °C under vacuum overnight as 11041

DOI: 10.1021/acs.iecr.5b02078 Ind. Eng. Chem. Res. 2015, 54, 11040−11047

Article

Industrial & Engineering Chemistry Research adsorption capacity (mg H 2S/g) =

P(MW)Q mRT

∫0

t

{H 2Sin − H 2Sout } dt

(3)

Where P denotes pressure, (MW) is the molecular weight of H2S, Q is total gas flow rate, and t is the time of adsorption, while m, R, T, H2Sin, and H2Sout stand for adsorbent mass, ideal gas constant, gas temperature, inlet H2S concentration, and outlet H2S concentration, respectively.

3. RESULTS AND DISCUSSION 3.1. Effect of Temperature on Adsorption Capacity. Figure 2 shows the adsorption capacity of ZMA for H2S with

Figure 4. Arrhenius plot of H2S adsorption on ZMA.

Figure 5. Effect of space velocity on H2S adsorption capacity with ZMA (T = 400 °C, [H2S] = 200 ppm, N2 as balance gas). Figure 2. Effect of temperature on H2S adsorption capacity with ZMA ([H2S] = 200 ppm, GHSV = 20 000 h−1, and N2 as balance gas).

Figure 6. H2S adsorption capacity on ZMA with various H2S concentrations (T = 400 °C, GHSV = 23 000 h−1, N2 as balance gas).

Figure 3. ln(ln C0/C) vs time for ZMA at different reaction temperatures. (C0 = [H2S]0 = 1000 ppm).

Table 1. Rate Parameters Obtained with ZMA at Different Reaction Temperatures temperature (K) kd ln(k0W/Q) k0

723 K 0.0542 5.1251 148

773 K 0.0520 5.2866 187

798 K 0.543 5.8160 327

823 K 0.0543 6.1705 481

the operating condition of T = 350−600 °C, [H2S] = 200 ppm, and GHSV = 20 000 h−1. Experimental results indicate that adsorption capacity (expressed as mg H2S/g) increases with increasing temperature. H2S adsorption capacities are 15.4, 41.9, and 52.8 mg H2S/g at T = 350, 500, and 600 °C, respectively. Since H2S adsorption with ZMA involves chemisorption, H2S adsorption capacity generally increases with increasing temperature.

873 K 0.0390 6.2430 548

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Figure 9. Thermal programming desorption (TPD) profile of H2Ssaturated ZMA sorbent.

Figure 7. Effects of temperature and space velocity on H2S adsorption with ZMA ([H2S] = 1000 ppm, N2 as balance gas).

Figure 10. Durability test of ZMA for H2S adsorption ([H2S] = 200 ppm, GHSV = 20 000 h−1, and Tregeneration = 300 °C). Figure 8. Effect of gas composition on H2S adsorption for ZMA ([H2S] = 200 ppm, N2 as balance gas, and T = 400 °C).

at high temperatures, forming good solid solution. Physical and chemical properties of ZMA will be discussed later. Kinetic study for the reaction between H2S and ZMA is conducted by using a deactivation model. As reported in previous studies,19,23,24 the deactivation model can be applied for gas−solid reactions. This model has several assumptions to be made in order to simulate H2S adsorption, the assumptions can be summarized as (1) the H2S adsorption is operated at isothermal conditions, (2) external mass transfer limitations can be ignored, (3) the adsorption system is in pseudosteady state, and (4) the adsorption is a first-order reaction. Mathematical models are described as eqs 4−8:

Previous studies indicate that zinc oxide might be reduced at T > 550 °C although it has a good H2S adsorption efficiency.15,16 Vaporization of zinc oxide could be improved by adding either Fe or Ti;19 however, obstacles such as spalling and cracking appear at high temperatures. This study is motivated to evaluate the effectiveness of applying manganese oxide as a promoter to improve the properties of zinc-based sorbent for H2S adsorption. Indeed, ZMA shows good performance for H2S adsorption at a high temperature (600 °C). Previous study indicates that manganese-based sorbents are promising for H2S adsorption, but they are difficult to regenerate.21 However, vaporization and low activities of using zinc oxide and manganese oxide individually could be improved as they are combined to prepare the adsorbent. Similar results were reported in previous study.22 Possibly, mobilities of Zn and Mn atoms are increased during calcination

da = kdC man → a = a0exp( −kdt ) dt

(m = 0, n = 1) (4)

With the pseudosteady state assumption, the H2S mass balance is expressed as follows: −Q 0 11043

dC − k 0Ca = 0 dW

(5) DOI: 10.1021/acs.iecr.5b02078 Ind. Eng. Chem. Res. 2015, 54, 11040−11047

Article


Figure 11. X-ray diffraction patterns of 10 wt % Zn−Mn/γ-Al2O3: (a) fresh adsorbent, (b) adsorbent after one regeneration, (c) saturated adsorbent, (d) adsorbent after nine regeneration cycles.

Equation 5 can be integrated to obtain eq 6

∫C

C 0

ka dC =− 0 C Q0

∫0

W

⎛k a⎞ ⎛C⎞ dW → ln⎜ ⎟ = −⎜⎜ 0 ⎟⎟W ⎝ C0 ⎠ ⎝Q0 ⎠

Combining eqs 4 and 6 results in eq 7 ⎡ kW ⎤ C = C0exp⎢ − 0 exp( −kdt )⎥ ⎢⎣ Q 0 ⎥⎦

(6) 11044

(7)


Article


Figure 12. SEM patterns of 10 wt % Zn−Mn/γ-Al2O3: (a) fresh and (b) saturated.

presented in Figure 6. Results indicate that H2S adsorption capacities are 31.2 and 30.7 mg H2S/g, respectively, with the inlet H2S concentration of 200 and 400 ppm. As H2S concentration is further increased to 1000 ppm, the H2S adsorption capacity decreases to 27.4 mg H2S/g. Clearly, H2S adsorption capacity decreases with increasing H2S concentration. Collisions between pollutant molecules and adsorbent increase at a higher concentration and should result in a higher adsorption capacity. However, high inlet H2S concentration may cause partial saturation of the active zone, resulting in the reduction of H2S adsorption. Namely, ZMA has better performance for H2S adsorption at a lower H2S concentration. As presented previously, the adsorption capacity of H2S achieved with ZMA is 31.2 mg H2S/g for the gas stream containing 200 ppm. To understand the effects of temperature and space velocity on H2S adsorption, experimental tests were conducted at various temperatures with specific space velocity (Figure 7). Results indicate that H2S adsorption capacity achieved with ZMA reach and maintain 52 mg S/g with the GHSV of 10 000−23 000 h−1 at 600 °C. On the other hand, the H2S adsorption capacity greatly decreases to 38−29.7 mg H2S/g as space velocity is increased from 10 000 to 30 000 h−1 at 400 °C. Obviously, ZMA has excellent performance at high temperatures. This indicates that temperature is a critical parameter affecting H2S adsorption capacity. In this study, ZMA reveals a high H2S adsorption capacity at a high temperature (600 °C). From the kinetic viewpoint, increasing temperature can effectively increase H2S adsorption capacity. As mentioned previously, ZMA possesses low activation energy, namely, ZMA can react with H2S readily. Furthermore, the kinetic analysis indicates that the reaction rate constant increases with increasing temperature (see Figure 4). The experimental results are consistent with the kinetic analysis. 3.4. Effect of Gas Composition on H2S Adsorption. In addition to H2S, syngas generated from biomass gasification may contain CO2, H2, and CO, and their effects should be evaluated for real applications. Figure 8 shows the effects of CO2, H2, and CO, on H2S adsorption with ZMA individually. Results indicate that H2S adsorption capacity with ZMA can be significantly increased as CO2, H2, and CO are introduced to the gas stream individually ([CO2] = 1%, [H2] = 1%, and [CO] = 1%). In the presence of CO2, H2, and CO, H2S adsorption capacity increases from 32 to 54, 58, and 62 mg S/g. This result

By arranging eq 7, the following equation can be obtained: ⎛k W ⎞ ⎡ ⎛ C ⎞⎤ ln⎢ln⎜ 0 ⎟⎥ = ln⎜⎜ 0 ⎟⎟ − kdt ⎣ ⎝ C ⎠⎦ ⎝ Q0 ⎠

(8)

Where a, Q0, C, C0, kd, K0, t, and W are activity of the solid reactant, gas flow rate, outlet concentration of H2S, inlet concentration of H2S, deactivation rate constant, initial sorption rate constant, time, and active species mass, respectively. A straight line can be obtained by plotting ln(ln C0/C) versus time, and the slope and intercept obtained are equal to − kd and ln[k0W/Q0], respectively. Figure 3 shows the plots of ln(ln C0/C) versus time at temperatures ranging from 450 to 600 °C, and detailed results of the regression analysis of the data obtained are presented in Table 1. The initial sorption rate constants k0 can be calculated for the temperature ranging from 450 to 600 °C. Figure 4 shows the plots of ln k0 versus 1/T, and activation energy (Ea) of 51 kJ/mol is calculated by Arrhenius equation. Also, the same deactivation model has been used to calculate activation energy of Zn−Mn/SiO2, and the results indicate that that activation energy of Zn−Mn/SiO2 for H2S adsorption is 98.8 kJ/mol.19 Obviously, the activation energy of H2S adsorption on ZMA obtained in this study is relatively lower if compared with literature. A low activation energy indicates that adsorption reaction may occur at a low temperature, namely, ZMA is a good H2S adsorbent from kinetic perspective. 3.2. Effect of Space Velocity on H2S Adsorption. The effect of space velocity on H2S adsorption is shown in Figure 5. The reaction temperature is controlled at 400 °C while the initial H2S concentration is fixed at 200 ppm. Results indicate that H2S adsorption capacity reaches and keeps at the maximum value of 33 mg H2S/g, with the GHSV varying from 10 000 to 23 000 h−1. As space velocity is further increased to 26 000 h−1, the H2S adsorption capacity is significantly reduced to 23.3 mg S/g adsorbent. With the GHSV of 30 000 h−1, H2S adsorption capacity is further reduced to 20.1 mg S/g adsorbent, which is about 60% of the maximum value. Reduction of H2S adsorption capacity at a high GHSV might result from the limitation of diffusion. 3.3. Effect of Operating Parameters on H2S Adsorption. Gas streams containing various H2S concentrations ranging from 200 to 1000 ppm are fed into the reactor to investigate its effect on H2S adsorption and the results are 11045


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transforms to Mn2O3. This reveals that part of the zinc oxides is volatilized, resulting in deactivation.

may be attributed to the water-shift reaction. According to reaction 1, H2O(g) can be formed during sulfidation reaction and H2O(g) produced may adsorb on ZMA surface to decrease H2S adsorption capacity. However, production of H2O(g) can be inhibited as CO2 or H2 is introduced into gas stream, thereby increasing H2S adsorption capacity. In addition, H2O(g) can be consumed in the presence of CO. Consumption of H2O(g) by CO can be explained by reaction 9. Overall, the H2S adsorption capacity achieved with ZMA can be increased in the presence of CO2, H2, or CO. H 2O(g) + CO → H 2 + CO2

ZnMn2O4 → ZnO + Mn2O3

(10)

ZnO + H 2S → ZnS + H 2O

(11)

1.5Mn2O3 + 3H 2S → 3MnS + 3H 2O + 0.75O2

(12)

Figure 12a and b displays the SEM images of fresh and saturated ZMA, respectively. The results indicate that fresh adsorbent presents as pellets with slight agglomeration. For saturated adsorbent, metal sulfides can be observed over the surface and within the pores of absorbent, which may block the pores, resulting in low adsorption capacity.

(9)

3.5. Characteristic of TPO for 10 wt % Zn−Mn/γ-Al2O3. TPO test of H2S-saturated ZMA is conducted at a temperature range of 100−600 °C with air (200 mL/min) as the working gas. The heating rate is controlled at 5 °C/min. As shown in Figure 9, one peak appears at 300 °C representing the regeneration of ZMA. It is well know that regeneration with air is an extremely exothermic reaction; therefore, the temperature of adsorbent bed is significantly higher than that of the furnace. Yasyerli (2005) indicated that the regeneration temperature of Zn−Ce oxide with 6% O2 as working gas is 700 °C.22 The regeneration temperature of ZMA prepared in this study is lower than that of Zn−Ce oxide. This is attributed to the fact that zinc and manganese oxides form a good solid solution, enhancing oxygen mobility. In short, ZMA can be regenerated at a lower temperatures, thus reduces its operating cost. 3.6. Durability Test. The durability of an adsorbent is important in determining its practical usefulness. Durability testing of ZMA was conducted with nine adsorption/ regeneration cycles. Experimental conditions were controlled at [H2S] = 200 ppm, GHSV = 20 000 h−1, Tadsorption = 400 or 600 °C, and Tregeneration = 300 °C, and the results are presented in Figure 10. At Tadsorption = 600 °C, the H2S adsorption capacity remains as 53 mg H2S/g for the first six cycles and at 32 mg H2S/g for the first seven cycles at Tadsorption = 400 °C. This finding reveals that a higher adsorption temperature leads to a higher adsorption capacity but lower durability. Overall, the adsorption capacities of both cases (i.e., Tadsorption = 600 and 400 °C) decreased with cycle times. Deactivation of adsorbent may be partly attributed to the reduction of BET surface area and pore volume after seven cycles of adsorption/desorption. Because regeneration is an extremely exothermic reaction, it may cause partial sintering on the adsorbent surface, resulting in the deactivation of adsorbent. Another possibility, some H2S may be adsorbed on deep pore and cannot be readily desorbed, further reducing the activity of adsorbent 3.7. Characterization of the Adsorbent. The BET surface area and average pore diameter of fresh ZMA are 150.6 m2/g and 112.5 Å, respectively. Figure 11 displays the Xray powder diffraction patterns of the ZMA. As shown in Figure 11a, fresh ZMA has main diffraction peaks at 29.1°, 31.5°, 32.9°, 36.1°, 44.8°, 58.8°, 61.0°, and 64.8° which are assigned to those from ZnMn2O4. Clearly, zinc oxide and manganese oxide are well bonded together. The H2S-saturated ZMA (after adsorption) has diffraction peaks mainly assigned to ZnS and MnS. XRD patterns of ZMA after one cycle and nine cycles are shown in Figure 11b and d, respectively. The crystal structure of ZMA after one cycle is still assigned to ZnMn2O4. The XRD pattern results indicate that the reactions in the cases of ZMA can be described by reactions 10−12.19 However, the crystal structure of ZMA after nine cycles is no longer ZnMn2O4 and

4. CONCLUSIONS With a high BET surface area (150.6 m2/g), ZMA holds excellent structure and good physical and chemical properties for removing H2S from gas streams. The adsorption capacity of ZMA for H2S increases monotonously with increasing temperature (350−600 °C), and the activation energy of H2S adsorption on ZMA is 51 kJ/mol. This result is consistent with kinetic analysis, and it is easy to react with H2S. Additionally, the influence of space velocity on H2S adsorption with ZMA is not significant at a high temperature, because it involves reaction of kinetics and chemisorption. As CO2, H2, and CO is added to the gas stream individually, H2S adsorption capacity of ZMA can be significantly increased. In addition, ZMA can be effectively regenerated by air as working gas at a temperature of 300 °C. Overall, ZMA reveals good property for H2S adsorption and stability of regeneration. It has good potential to serve as an adsorbent for removing H2S from hot gas streams.

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AUTHOR INFORMATION

Corresponding Author

*Mailing address: No. 300, Jhongda Road, Chungli, Taoyuan City 32001, Taiwan. E-mail: [email protected]. Phone: +886-3-4227151-34695. Fax: +886-3-42267. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors acknowledge the financial support from the Ministry of Science and Technology (NSC100-3113-E-042A001 and NSC101-3113-E-042A-001) of ROC.

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REFERENCES

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High-Temperature Gaseous H2S Removal by ZnâMn-based Sorbent

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High-Temperature Gaseous H2S Removal by ZnâMn-based Sorbent