High Temperature H2S Removal Research Articles

Medium and high temperature H2S removal via phosphazene polyoxometalate ionic liquids: Performance evaluation and mechanism exploration

The development of non-aqueous solvent desulfurizer is crucial to addressing the challenges associated with traditional liquid-phase wet desulfurization technologies. Based on this, we prepared a series of phosphazene polyoxometalate ionic liquids (PPILs) based of 1-butyl-3-methylimidazolium chloride using different kinds of phosphazenes (PNs) combined with polyoxometalate (POM), and used for hydrogen sulfide (H2S) dynamic absorption experiments. The effects of PN type and ratio, temperature and desulfurizer concentration on the desulfurization performance of different PPILs were explored. Among them, PPILs@IBuPN-9 as the optimal desulfurizer could keep almost 100 % desulfurization efficiency in the medium and high temperature range (100–200 °C). The results showed that the combination of PNs with POM significantly improved and widened the H2S removal performance and the operational temperature window of the desulfurizer. Besides, PPILs@IBuPN-9 required only air regeneration to maintain relatively stable cycle performance for at least four times and the sulfur capacity could be efficiently increased during multiple regenerations. It was found that the hydrogen bonding sites on IBuPN network formed significantly enhanced the H2S capture ability of PPILs and the sulfur capacity was substantially improved by S2− substitution of oxygen atoms in the POM according to the characterization results and density functional theory calculations. This study promotes the deep integration of polyoxometalate chemistry with ionic liquids in the field of gas purification and promotes the development of non-aqueous phase desulfurization process.

Kinetics of H2S removal using alkaline residue as in-bed sorbent in fluidized bed gasification of biomass and wastes

The use of alkaline residue from the acetylene industry (carbide slag, CS) as in-bed sorbent to remove H2S from syngas from biomass/waste fluidized bed (FB) gasification was investigated. Measurements were conducted in a laboratory FB applying differential conversion technique, tracking the reaction using both gas measurements and solid analysis. Apparent reaction kinetics was obtained, without external mass transfer limitations, for different gas mixtures containing CO2, H2O, CO, H2 and CH4, having relatively low H2S concentration (500–1000 ppm). The addition of CO2 and H2O to an N2-H2-H2S mixture showed that the reaction rate was reduced in the presence of these species. Varying the H2 concentration between 7 and 14% in simple (N2-H2-H2S) reactive gas mixtures did not affect the results, while both CO and H2 potentially affected the reaction rate if also CO2 was present in the gas. Other operating parameters, such as sorbent particle size, sulfidation- and calcination temperature also affected the CaO sulfidation rate, which increased with temperature between 800 and 900 °C and was enhanced by higher calcination temperature. Specific surface area and pore size distribution of the calcined CS was measured before and after the sulfidation reaction, showing that CS maintained a large fraction of its original pore volume even after most of the CaO had been converted into CaS. The sulfidation rate of calcined limestone was also measured for comparison showing that the reaction rate using CS was slightly lower, but similar to that using limestone, showing that CS is a promising alternative to conventional calcium-based sorbents for high temperature H2S removal, contributing to promote the circular economy, while avoiding the current stacking of CS at the acetylene production sites.

Kinetic Study on High-Temperature H2S Removal over Mn-Based Regenerable Sorbent Using Deactivation Model.

The kinetics of high-temperature H2S removal over Mn/Al sorbents prepared by co-precipitation method was investigated in a fixed-bed reactor using a deactivation model. The initial sorption rate constant (k0), deactivation rate constant (kd), apparent activation energy (Ea), and deactivation energy (Ed) were obtained. The k0 and kd values of Mn/Al sorbents are much higher than those of pure Mn2O3. This indicates that Mn/Al sorbents have higher reactivity on the removal of H2S and less diffusion resistance caused by the formation of the sulfided product. The Ea and Ed values for the sorbent with the Mn content (wt %) of 35.4% are 38.18 and 31.05 kJ/mol, respectively. The deactivation model gives excellent predictions for the H2S breakthrough curves in the sulfidation–regeneration process.

Effect of Ce modification on desulfurization performance of regenerated sorbent for high temperature H2S removal from coal gas

Ce modified MnxOy/Al2O3-La have been prepared to investigate the effect of Ce loadings on pre-breakthrough H2S removal efficiency, breakthrough sulfur capacity (BSC) and BSC durability of the sorbents during desulfurization-regeneration cycles. The results showed Ce modification could improve the pre-breakthrough H2S removal efficiency of regenerated sorbents during desulfurization-regeneration cycles. The XPS characterization showed that the Ce can promote the binding energy of Mn ion to shift to lower energy, which enhanced H2S adsorption on the regenerated sorbent. However, the Ce loading sequence had effect on BSC durability of sorbent during desulfurization-regeneration cycles. The Ce-MnxOy/Al2O3-La with co-impregnation of Mn and Ce oxides had higher BSC than MnxOy/Al2O3-La, while the Ce/MnxOy/Al2O3-La with Ce loading on the surface of MnxOy/Al2O3-La had lower BSC and worse BSC durability than MnxOy/Al2O3-La. The characterization results showed Ce-MnxOy/Al2O3-La obtained better surface area and pore structure than MnxOy/Al2O3-La, and Ce ion can promote the increasing of the around electron density of Mn ion, which was beneficial for H2S adsorption of Ce-MnxOy/Al2O3-La. The poor surface area and pore structure would cause the low BSC of Ce/MnxOy/Al2O3-La, and less stability of pore structure might lead to poorer BSC durability of Ce/MnxOy/Al2O3-La than MnxOy/Al2O3-La during desulfurization-regeneration cycles.

Metal oxide/TiO2 nanocomposites as efficient adsorbents for relatively high temperature H2S removal

Hydrogen sulfide is a highly toxic and corrosive gas that is present in different environments such as hot coal gases. In order to have a clean atmosphere and prolong the life of industrial equipment and metallic catalysts, it is necessary to remove or decrease the concentration of this gas in feedstocks to sub parts per million before their use. To accomplish this task, various nanocomposite sorbents were studied for H2S removal at relatively high temperature. To this end, the NiO/TiO2, CuO/TiO2, and CoO/TiO2 nanocomposites were prepared through wet impregnation. X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) equipped with Energy-dispersive X-ray spectroscopy (EDS) and N2 adsorption/desorption were used for characterizing the prepared nano sorbents. The H2S adsorption reaction experiments were performed at relatively high temperature and effects of the promoter to TiO2 ratio, sorbent mass and desulfurization temperature were studied. The results showed that at 480 °C, the CoO promoted TiO2 shows longer breakthrough time followed by NiO/TiO2 and CuO/TiO2 sorbents. The best results were obtained by using the promoter to TiO2 ratio of 2.5/5 among the ratios used. By decreasing the temperature and performing the experiments at 400 °C, the nickel oxide promoted TiO2 showed better results than the CoO/TiO2 suggesting the lower sulfidation activity of CoO promoter at this temperature.

High-temperature H2S removal performance over ordered mesoporous La-Mn-supported Al2O3-CaO sorbents

A series of La-Mn supported on ordered mesoporous Al2O3-CaO (OMA-2Ca) sorbents with various Mn/La molar ratio were first designed and synthesized for removal of H2S at 650–850°C. 40% 98Mn2La/OMA-2Ca exhibited satisfactory desulfurization performance at 800°C with a breakthrough sulfur capacity (BSC) of 16.15gS/100g sorbent. Elemental sulfur was formed during desulfurization as a result of synergistic catalysis of γ-Al2O3 and lanthanum oxysulfide at high temperature. The existence of high content steam in hot coal gas obviously reduced the sulfur capacity because of the formation of MnAl2O4. After five successive sulfidation-regeneration cycles, high BSC (about 90% of the initial BSC) was maintained. In addition, the characterization results indicated that the mesostructure of OMA-2Ca remained intact during sulfidation and regeneration except that the amorphous wall was converted to γ-Al2O3 phase, and active species were still well dispersed on support, which indicated the stability of Mn-La/OMA-2Ca sorbent.

New Way of Removing Hydrogen Sulfide at a High Temperature: Microwave Desulfurization Using an Iron-Based Sorbent Supported on Active Coke

Microwave was applied to the high-temperature removal of H2S by a Fe-based sorbent supported on active coke (Fe2O3/AC). The influence of the loading content, adsorption temperature, and desulfurization way on the sulfidation properties of sorbents was investigated. N2 adsorption, X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy techniques were used to characterize the structure of sorbents before and after desulfurization. The results reveal that the microwave sulfidation performs best at 600 °C, while a further increase of the temperature leads to a lower sulfur capacity and utilization rate of Fe2O3 as a result of the pore structure deteriorating sorbents. The Boltzmann function is suitable for describing the H2S evolution behavior of the Fe2O3/AC sorbent bed. Several advantages of microwave sulfidation over the conventional way are as follows: much better performance of Fe2O3/AC sorbents, less decline in surface area and pore volume per unit sulfur capacity when rem...

La2CuO4/ZSM-5 sorbents for high-temperature desulphurization

The high-temperature H2S removal was conducted over xLayCu/ZSM-5 sorbents prepared via citric acid method. The sorbents showed good desulphurization performance, the maximal sulfur capacity of 2240.5μmolS/g over 5La5Cu/ZSM-5 was achieved at 700°C. The presence of H2 obviously shortened the breakthrough time and reduced the sulfur capacity. However, the presence of CO had little influence on the desulphurization behavior. The sulfidation activity of La2O3 can be significantly enhanced by introduction of Cu due to the intimate mixing of La2O3 and CuO, the formation of La2CuO4 compound.

Performance of Zn–Fe–Mn/MCM-48 sorbents for high temperature H2S removal and analysis of regeneration process

MCM-48 was synthesized using a rapid and facile process at room temperature. A series of 50%Zn–Fe–Mn/MCM-48 sorbents were prepared and their performance of hot coal gas desulfurization was investigated. High breakthrough sulfur capacity (13.2g-S/100g sorbent) and utilization (66.1%) of 50%1Zn2Fe2Mn/MCM-48 sorbent at 550°C was achieved. The characterization results of XRD, BET, TPR and FT-IR revealed that MCM-48 had excellent thermal stability at less than 700°C, ZnMn2O4 and (Mn, Zn)Fe2O4 were mainly active particles in fresh sorbents which were highly dispersed on support. The MCM-48 mesoporous structure remained intact after eight successive desulfurization/regeneration cycles. The regeneration process of 50%1Zn2Fe2Mn/MCM-48 sorbent was analyzed, it indicated that the breakthrough sulfur capacity decline of sorbent was due to the migration of Zn onto the sorbent surface and Zn accumulated on the surface and vaporized to the exterior from the surface. In the TPO test, the oxidation of Zn was different for 50%Zn/MCM-48 at 700°C. It revealed that the temperature of regeneration for ZnO sorbent should be higher than 700°C.

Desulfurization Behavior of Fe–Mn-Based Regenerable Sorbents for High-Temperature H2S Removal

A series of Fe–Mn-based sorbents with different Fe/Mn mole ratios was prepared via coprecipitation for the high-temperature removal of H2S. Performance tests were carried out at 1123 K in a fixed-bed reactor, indicating that metallic Fe and MnO were the active components of the Fe–Mn-based sorbents in the hot gas. Single Fe-based sorbents exhibited a low desulfurization efficiency and effective sulfur capacity. The addition of manganese (Fe/Mn mole ratios less than 8:2) considerably improved the desulfurization efficiency and effective sulfur capacity of the Fe-based sorbents. In the first sulfidation test, effective sulfur capacities of 20.71, 20.72, and 20.14 g S/(100 g sorbent) were obtained for Mn7Fe3, Mn5Fe5, and Mn3Fe7, respectively. During five sulfidation–regeneration cycles, Mn7Fe3, Mn5Fe5, and Mn3Fe7 were stable, maintaining high activities and sulfur capacities, and reduced the amount of H2S to a few ppmv. After sulfidation, the sulfided sorbents could easily be regenerated with 2% O2 in N2 at ...

On the initial deactivation of MnxOy–Al2O3 sorbents for high temperature removal of H2S from producer gas

MnxOy−Al2O3 sorbents with Mn loadings of 15 and 30wt.% were prepared by wet impregnation using Mn(NO3)2.4H2O precursor and γ-alumina. After calcination at 600°C in air and reduction in H2/N2, the solids were tested for the removal of H2S from a model, dry producer gas with a composition of 0.4vol.% of H2S in 40vol.% of H2, the balance being inert gas (N2 and Ar). Regeneration was performed with 10vol.% O2 in N2 at 450°C, which was the same temperature as that used for the H2S uptake measurements. 13 sorption/regeneration cycles were performed. The initial sorption capacity adjusted for the Mn content was similar for the two samples, which is in agreement with comparable chemisorption values obtained from O2 pulse chemisorption measurements. The fresh and the tested samples were characterized by N2 sorption, XRD, Raman spectroscopy and TPR. During the testing, an overall deactivation was observed which was more pronounced for the sample with 30wt.% of Mn. The main reasons for the initial sorbent decay are proposed to be related to an alumina phase transition, transformation of the Mn oxides as well as an incomplete regeneration.

Kinetic Study on the Sulfidation and Regeneration of Manganese-Based Regenerable Sorbent for High Temperature H2S Removal

This paper describes a kinetic study on the sulfidation and regeneration of Mn/Al2O3 sorbent for high temperature H2S removal. The influence of the reactant gas compositions and temperatures on the sulfidation and regeneration behavior was systematically investigated in a thermogravimetric apparatus. The results show that the shrinking core model can be used to correlate with the experimental data. The sulfidation is mainly dominated by diffusion. Through the regressions of the initial sulfidation reaction data, the chemical reaction order, activation energy, and pre-exponential factor are 1, 37.42 kJ/mol, and 4.16 × 10–2 m/s, respectively, and the diffusion activation energy and pre-exponential factor are 57.23 kJ/mol and 6.41 × 10–5 m2/s, respectively. O2 regeneration has the same situation as sulfidation; the chemical reaction order, activation energy, and pre-exponential factor are 1, 24.62 kJ/mol, and 0.17 m/s, respectively, and the diffusion activation energy and pre-exponential factor are 122.44 kJ...

Manganese-based regenerable sorbents for high temperature H2S removal

A series of sorbents with different manganese contents have been prepared by co-precipitation method for 850°C regenerative H2S removal. The sulfur capacity increased linearly with the increase of manganese content. The performance of sorbents prepared by co-precipitation of Mn nitrate and Al nitrate appears to be stable over five sulfidation–regeneration cycles. Al2O3 plays an important role in the performance of sorbents and the recovery of elemental sulfur in O2 regeneration. With increasing Mn content in the sorbent, increasing O2 concentration in the regeneration gas or increasing total regeneration gas flow rate, the recovery of elemental sulfur decreased. Elemental sulfur is the only product with SO2 regeneration. The sorbents cannot be completely regenerated with SO2 under the conditions used. The sorbents, however, can be completely regenerated by steam. The main product for steam regeneration is H2S. Steam regeneration results in less sintering than O2 regeneration.

Synthesis and Activity Comparison of Copper-Incorporated MCM-41-Type Sorbents Prepared by One-Pot and Impregnation Procedures for H2S Removal

In the present study, novel copper-incorporated MCM-41-type high-surface-area mesoporous materials were synthesized following a direct hydrothermal synthesis method and also by the impregnation of copper into the mesopores of the pre-synthesized MCM-41 structure. XRD results indicated the formation of a CuO phase within the MCM-41 structure. Sharp H2S breakthrough curves, quite high sorption rate parameters, and high sulfur retention capacities were obtained in high-temperature removal of H2S using these copper-incorporated mesoporous materials. XRD patterns of the sulfided products indicated the formation of a Cu1.81S phase within the MCM-41 structure. A deactivation model gave good predictions of the experimental H2S breakthrough data.

Mn−Cu and Mn−Cu−V Mixed-Oxide Regenerable Sorbents for Hot Gas Desulfurization

Porous Mn−Cu and Mn−Cu−V mixed-oxide sorbents prepared by the complexation technique were tested for high-temperature removal of H2S in the presence of hydrogen gas. Sorption experiments carried out at 627 °C in a fixed-bed reactor showed higher reactivity and also higher sulfur retention capacity (over 0.15 g of S/g of sorbent) for the Mn−Cu mixed oxide than for the Mn−Cu−V mixed oxide. Successive sulfidation−regeneration cycles demonstrated that the Mn−Cu mixed oxide was also more stable than Mn−Cu−V, maintaining its activity and about 90% of its sulfur retention capacity at the end of five cycles. Although formation of some MnSO4 was observed during regeneration at 700 °C with a gas mixture containing 6% oxygen in nitrogen, this did not cause significant reduction in the activity of this mixed-oxide sorbent. It was also shown that a previously proposed deactivation model gave good predictions of the experimental breakthrough curves obtained with these sorbents.

Supported honeycomb monolith catalysts for high-temperature ammonia decomposition and H2S removal

Catalysts that have potential in simultaneous removal of H2S and NH3 decomposition were developed. The monolith supports of high surface area and acceptable mechanical strength based on titania and silica–alumina precursors were prepared and tested. Preparation routine and composition of Mn, Fe and Cu oxides supported honeycomb catalysts have been optimized. Impregnated and washcoated monolith catalysts were tested in ammonia high-temperature decomposition.

Activities of Copper Oxide and Cu−V and Cu−Mo Mixed Oxides for H2S Removal in the Presence and Absence of Hydrogen and Predictions of a Deactivation Model

Considering the importance of high-temperature removal of H2S from industrial gases, sorption studies were carried out on copper oxide and Cu−V and Cu−Mo mixed oxides in the absence and presence of hydrogen in a fixed-bed reactor. Experiments were carried out in a wide temperature range between 300 and 700 °C. A significant amount of SO2 was produced with CuO sorbent in the absence of hydrogen. In the case of mixed oxide sorbents, SO2 formation was detected even in the presence of hydrogen. On the basis of the experimental concentration profiles of H2S, SO2, and H2O measured in the reactor effluent and XRD results for the solid products, reaction sequences were proposed in reducing (in hydrogen) and nonreducing atmospheres. A deactivation model proposed for such noncatalytic gas−solid reactions gave excellent predictions of the H2S breakthrough curves. Sorption rate parameters obtained in the absence of hydrogen were found to be larger than the corresponding values in the presence of hydrogen. Partial red...

High temperature H2Sremoval over high specific surface area [beta ]-SiC supported iron oxide sorbent Part 2Sulfidation and regeneration

Iron oxide sorbent supported on high surface area SiC showed excellent performance for high-temperature H2S removal. This sorbent removed H2S directly with formation of water and with no other products observed in the exit gas. The chemical inertness of the SiC support and the weak interaction between the support and the iron oxide phase, led to rapid sulfidation of the sorbent resulting in a high absorption capacity (90–95% cf. the theoretical value). This was not the case for sorbents supported on alumina and other refractory oxides. The sorbent also exhibits high stability in the sulfidation and regeneration cycle. The sorbent surface area decreased after the first sulfidation and regeneration cycle from 49 to 17 g−1 and then remained unchanged for the subsequent cycles, maintaining its high performance and selectivity.

High temperature H2Sremoval over high specific surface area [beta ]-SiC supported iron oxide sorbent Part 1Preparation and characterization

Iron oxide sorbents supported on high surface area (49 g-1) SiC have been prepared and characterized. The results show that several forms of iron oxide can coexist including γ-Fe2O3, α-Fe2O3 and an amorphous phase, and these phases are homogeneously dispersed on the SiC surface (particle size from 1 to 5 nm). After controlled calcination the sorbent pore size distribution, measured by N2 adsorption, ranged from 2.5 to 50 nm, which allowed a high accessibility of the reactant gas without microdiffusion phenomena.

Effect of sulfidation/oxidative regeneration cycle on the solid structural changes of sorbent for high-temperature removal of H2S

In order to investigate the effects of sulfidation/oxidative regeneration cycle on the change of structural properties and removal capacity of sorbent, sulfidation/regeneration cycle was carried out up to 15 times in a fixed-bed reactor. The effluent gases from the fixed-bed reactor were analyzed by gas chromatography, and XRD, SEM, and liquid nitrogen physisorption method were used to characterize the reacted sorbents. The sorbent treated first sulfidation/regeneration cycle exhibited maximum specific surface area and the highest H2S removal capacity. Hysteresis of adsorption isotherm of the regenerated sorbent reflected the growth of pores of fresh sorbent and pore size distribution confirmed this fact. Furthermore constant H2S removal capacity was maintained up to 15 times of sulfidation/regeneration cycle.