A study of desulfurization ability and activation energy for CuO-AgO sorbents

In this study, we investigated desulfurization abilities and activation energy using TGA for CuO-AgO sorbents calcined at 700 °C. CuO was used as a main active material and AgO was used as an additive material and 25 wt% SiO₂ was used as a support material. The desulfurization reaction temperatures were 450 °C, 500 °C, and 550 °C and the regeneration reaction temperature was 700 °C. From the TGA experiments, the best sulfur loading of CAS1 sorbent containing 1 wt% AgO was about 14.95 g sulfur/100 g sorbent at 550 °C. The activation energy was calculated by the Chatterjee-Conrad method based on the TGA experiment. Desulfurization ability and activation energy of sorbent were decreased as the content of AgO increased.     

Modified Semi‐Coke‐Supported Cerium Oxide‐Doped Zinc Ferrites for the Removal of H2S from Coal Gas

Cerium oxide‐doped ZnFe₂O₄ sorbents supported on modified semi‐coke (MSC) were prepared to improve the desulfurization efficiency of zinc ferrites. The sulfidation tests of the ZnFe₂O₄/MSC sorbents with and without Ce were carried out using a fixed‐bed reactor at 450 °C. The effect of the CeO₂/ZnFe₂O₄ molar ratio of the sorbents on the sulfur capacity was studied. The characteristics of the sorbents were analyzed by X‐ray diffraction, N₂ adsorption, scanning electron microscopy and X‐ray photoelectron spectroscopy. The results showed that cerium oxide could greatly improve the desulfurization reactivity of the ZnFe₂O₄/MSC sorbents. The molar ratio of Ce to Zn and Fe influences the desulfurization reactivity, and a good sulfur capacity of the sorbent can be obtained with a Ce/Zn/Fe ratio of 4:4:1. It was also found that the addition of CeO₂ could enlarge the surface area and the pore volume, thus improving the dispersion of active components. Ce doping results in an increment of the oxygen adsorbed on the sorbent surface, which facilitates the adsorption of H₂S. The Ce ions could act as carriers of the oxidation and reduction reactions and the oxygen transfer could be accelerated during the desulfurization process of coal gas.     

Sulfidation and regeneration of iron-based sorbents supported on activated-chars prepared by pressurized impregnation for coke oven gas desulfurization

The sulfidation and regeneration properties of lignite char-supported iron-based sorbent for coke oven gas (COG) desulfurization prepared by mechanical stirring (MS), ultrasonic assisted impregnation (UAI), and high pressure impregnation (HPI) were investigated in a fixed-bed reactor. During desulfurization, the effects of process parameters on sulfidation properties were studied systematically. The physical and chemical properties of the sorbents were analyzed by X-ray diffraction (XRD), scanning electron microscope coupled with energy dispersive spectroscopy (SEM-EDS), Fourier transform infrared (FTIR) and BET surface area analysis. The results of desulfurization experiments showed that high pressure impregnation (HPI) enhanced the sulfidation properties of the sorbents at the breakthrough time for char-supported iron sorbents. HPI method also increased the surface area and pore volume of sorbents. Sulfur capacity of sorbents was enhanced with increasing sulfidation temperatures and reached its maximum value at 400 °C. It was observed that the presence of steam in coke oven gas can inhibit the desulfurization performance of sorbent. SO₂ regeneration of sorbent resulted in formation of elemental sulfur. HPIF10 sorbent showed good stability during sulfide-regeneration cycles without changing its performance significantly.     

锰系可再生高温脱硫剂的制备及其性能测试

煤气的高温脱硫净化是 IGCC 和 DRI 生产的瓶颈,直接影响整个过程的热效率。在50℃、pH值约为9的条件下采用硝酸锰、硝酸铝混合溶液与氨水进行共沉淀,制备了锰含量不同的脱硫剂,在固定床反应器中考察了脱硫剂的硫化及再生性能,并利用XRD、SEM、BET等手段表征了脱硫剂在硫化/再生过程中的物相和结构变化。共沉淀法制备的脱硫剂Mn/Al分散性好,在850℃高温下进行脱硫反应可以定量快速进行。脱硫硫容与脱硫剂锰含量呈正比,Mn-S/Mn-O交换原子比在0.90~0.95之间,改变空速和进口H₂S含量并不改变脱硫硫容。采用O₂浓度为3%的稀释空气在850℃下再生,再生后的硫容稳定,说明所制备的脱硫剂可用于高温可再生脱硫。     

Supported silver adsorbents for selective removal of sulfur species from hydrocarbon fuels

Dispersed silver oxides on supports such as TiO₂, γ-Al₂O₃ and SiO₂ were observed to be effective desulfurizing agents for refined fuels at ambient conditions. TiO₂ was determined to be the most stable support for silver oxide. Ag (4 wt%)/TiO₂ demonstrated a saturation sulfur capacity of 6.3 mgS/g for JP5 fuel containing 1172 ppmw sulfur. This high affinity for sulfur translated to one sulfur heterocycle associated with every two surface Ag atoms in the sorbent even in the presence of a 160-fold excess of other aromatics found in the fuel. A unique attribute of these sorbents was that they were thermally regenerable at 450 °C using air as a stripping medium over multiple cycles. Desulfurization characteristics also varied with fuel composition. Variation in desulfurization performance between JP5, JP8 and a light fraction JP5 were established and associated with the differences in sulfur composition of these fuels. The effects of surface area, porosity and crystal structure of the sorbent on sulfur capacity are also presented.     

New development of zinc-based sorbents for hot gas desulfurization

This paper introduced two new zinc-based sorbents for hot gas desulfurization, G-201 and G-202. Evaluation tests proved that both G-201 and G-202 sorbents had good performance in desulfurization. They could reduce H₂S concentration from about 10 g/m³ in coal gas to less than 20 mg/m³. In addition, the sulfur capacity of both sorbents increased with temperature rising. No decrease in sulfur capacity of G-201 occurred during 20-desulfurization/regeneration cycle tests, whose calculated value was 19.43–24.23 g/100 g sorbent. G-201 sorbent passed a 1500 h real hot gas desulfurization test in a fixed-bed PDU. No occurence of striping, attrition and sintering on the surface of used sorbents was found after the long-time test. The reactivity was stable and the sulfur capacity is 21.19 g/100 g sorbent after the 1500 h test.     

Reactivity of copper oxide-based sorbent in coal gas desulfurization

Various CuO-based sorbents were prepared to investigate effects of sorbent ingredients such as SiO₂, MnO₂, and MoO₃ on desulfurization reactivity. Several candidate sorbents chosen from a TGA screening test were further tested in a microreactor system. The amount of SiO₂ support to minimize sintering of sorbents was 25 wt%. Sulfur loading was seriously affected by the amount of additives (MnO₂, MoO₃) in a multi-cycle test. Improvement of sulfur loading by the additives was observed in the multi-cycle test. Effects of support materials on sulfur loading were also investigated by using SiO₂, g-alumina and zeolite. SiO₂ showed the best performance among the support candidates. The sorbent showing the best sulfur loading ability was CMS6 (CuO :MoO₃ : MnO₂ : SiO₂=61 : 11 : 3 : 25). Its sulfur loading reached up to 13.8 g sulfur/100 g sorbent in a multi-cycle test.     

The effect of HCl and H<Subscript>2</Subscript>O on the H<Subscript>2</Subscript>S removing capacities of Zn-Ti-based desulfurization sorbents promoted by cobalt and nickel oxide

The sulfur removing capacities of various Zn-Ti-based sorbents were investigated in the presence of H₂O and HCl at high-(sulfidation, 650 °C; regeneration, 800 °C) and medium-(sulfidation, 480 °C; regeneration, 580 °C) temperature conditions. The H₂O effect of all sorbents was not observed at high-temperature conditions. At mediumtemperature conditions, the reaction rate of ZT (Zn/Ti : 1.5) sorbent decreased with the level of H₂O concentration, while modified (ZTC, ZTN) sorbents were not affected by the water vapor. HCl vapor resulted in the deactivation of ZT sorbent with a cycle number at high-temperature due to the production of ZnCl₂ while the sulfur removing capacities of ZTC and ZTN sorbents were maintained during 4–5 cyclic tests. In the case of medium-temperature conditions, ZT sorbent was poisoned by HCl vapor while cobalt and nickel added to ZT sorbent played an important catalytic role to prevent from being poisoned by HCl due to providing heat, emitted when these additives quickly react with H₂S even at medium-temperature conditions, to the sorbents     

Desulfurization of Transportation Fuels by Adsorption

Abstract

This paper is a review on sorbents for desulfurization of transportation fuels (gasoline, diesel, and jet fuel). Since the π‐complexation sorbents are the most promising, they are the focus of the discussion. During π‐complexation, the thiophenic compounds can bind selectively to the sorbents, especially the substituted ones. The later remain highly unreacted in hydrodesulfurization (HDS) (i.e., “refractory” sulfur). Molecular orbital (MO) calculations and experiments have shown that these refractory compounds [(e.g., 4‐methyldibenzothiophene and 4,6‐dimethyldibenzothiophene (DMDBT)] bind strongly with the π‐complexation sorbents because of a better electron donation/back‐donation ability. The sorbents reviewed include Ag‐Y, Cu(I)‐Y, Ni(II)‐Y, and Ni(II)‐X zeolites prepared using various ion‐exchange techniques. The techniques included vapor and solid‐state ion exchanges, which are suitable for obtaining high loadings of transition metals. The best sorbent, Cu(I)‐Y [vapor‐phase ion‐exchanged (VPIE)], is capable of producing almost 38 cm³ of desulfurized fuel per g of sorbent with a sulfur concentration of less than 0.2 ppmw. Using these π‐complexation sorbents in layered bed matrices further increases the desulfurization capacity.     

Regeneration of Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-based high-temperature coal gas desulfurization sorbent in atmosphere with sulfur dioxide

Regeneration of a high-temperature coal gas desulfurization sorbent is a key technology in its industrial applications. A Fe₂O₃-based high-temperature coal gas desulfurizer was prepared using red mud from steel factory. The influences of regeneration temperature, space velocity and regeneration gas concentration in SO₂ atmosphere on regeneration performances of the desulfurization sorbent were tested in a fixed bed reactor. The changes of phase and the composition of the Fe₂O₃-based high-temperature coal gas desulfurization sorbent before and after regeneration were examined by X-ray diffraction (XRD) and X-ray Photoelectron spectroscopy(XPS), and the changes of pore structure were characterized by the mercury intrusion method. The results show that the major products are Fe₃O₄ and elemental sulfur; the influences of regeneration temperature, space velocity and SO₂ concentration in inlet on regeneration performances and the changes of pore structure of the desulfurization sorbent before and after regeneration are visible. The desulfurization sorbent cannot be regenerated at 500°C in SO₂ atmosphere. Within the range of 600°C–800°C, the time of regeneration becomes shorter, and the regeneration conversion increases as the temperature rises. The time of regeneration also becomes shorter, and the elemental sulfur content of tail gas increases as the SO₂ concentration in inlet is increased. The increase in space velocity enhances the reactive course; the best VSP is 6000 h^?1 for regeneration conversion. At 800°C, 20 vol-% SO₂ and 6000 h^?1, the regeneration conversion can reach nearly to 90%.     

Regeneration of Fe2O3-based high-temperature coal gas desulfurization sorbent in atmosphere with sulfur dioxide

Regeneration of a high-temperature coal gas desulfurization sorbent is a key technology in its industrial applications. A Fe₂O₃-based high-temperature coal gas desulfurizer was prepared using red mud from steel factory. The influences of regeneration temperature, space velocity and regeneration gas concentration in SO₂ atmosphere on regeneration performances of the desulfurization sorbent were tested in a fixed bed reactor. The changes of phase and the composition of the Fe₂O₃-based high-temperature coal gas desulfurization sorbent before and after regeneration were examined by X-ray diffraction (XRD) and X-ray Photoelectron spectroscopy(XPS), and the changes of pore structure were characterized by the mercury intrusion method. The results show that the major products are Fe₃O₄ and elemental sulfur; the influences of regeneration temperature, space velocity and SO₂ concentration in inlet on regeneration performances and the changes of pore structure of the desulfurization sorbent before and after regeneration are visible. The desulfurization sorbent cannot be regenerated at 500°C in SO₂ atmosphere. Within the range of 600°C–800°C, the time of regeneration becomes shorter, and the regeneration conversion increases as the temperature rises. The time of regeneration also becomes shorter, and the elemental sulfur content of tail gas increases as the SO₂ concentration in inlet is increased. The increase in space velocity enhances the reactive course; the best VSP is 6000 h⁻¹ for regeneration conversion. At 800°C, 20 vol-% SO₂ and 6000 h⁻¹, the regeneration conversion can reach nearly to 90%.     

Regenerable potassium-based alumina sorbents prepared by CO<Subscript>2</Subscript> thermal treatment for post-combustion carbon dioxide capture

Potassium carbonate supported on alumina is used as a solid sorbent for CO₂ capture at low temperatures. However, its CO₂ capture capacity decreases immediately after the first cycle. This regeneration problem is due to the formation of the by-product [KAl(CO₃)(OH)₂] during CO₂ sorption. To overcome this problem, a new regenerable potassium-based sorbent was fabricated by CO₂ thermal treatment of sorbents prepared by the impregnation of δ-alumina with K₂CO₃ in the presence of 10 vol% CO₂ and 10 vol% H₂O. The CO₂ capture capacities of the new regenerable sorbents were maintained over multiple CO₂ sorption tests. These results can be explained by the fact that the sorbent prepared by CO₂ thermal treatment did not form any by-product during CO₂ sorption. Based on these results, we suggest that the regeneration properties of potassium-based sorbents using δ-alumina could be significantly improved by the use of the CO₂ thermal treatment developed in this study.     

Experimental study on ZnO-TiO<Subscript>2</Subscript> sorbents for the removal of elemental mercury

ZnO-TiO₂ sorbents synthesized by an impregnation method were characterized through XRD (X-ray diffraction), XPS (X-ray photoelectron spectroscopy) and EDS (Energy dispersive spectrometer) analyses. An experiment concerning the adsorption of Hg⁰ by ZnO-TiO₂ under a simulated fuel gas atmosphere was then conducted in a bench-scale fixed-bed reactor. The effects of ZnO loading amounts and reaction temperatures on Hg⁰ removal performance were analyzed. The results showed that ZnO-TiO₂ sorbents exhibited excellent Hg⁰ removal capacity in the presence of H₂S at 150 °C and 200 °C; 95.2% and 91.2% of Hg⁰ was removed, respectively, under the experimental conditions. There are two possible causes for the H₂S reacting on the surface of ZnO-TiO₂: (1) H₂S directly reacted with ZnO to form ZnS, (2) H₂S was oxidized to elemental sulfur (S _ad ) by means of active oxygen on the sorbent surface, and then S _ad provided active absorption sites for Hg⁰ to form HgS. This study identifies three reasons why higher temperatures limit mercury removal. First, the reaction between Hg⁰ and H₂S is inhibited at high temperatures. Second, HgS, as the resulting product in the reaction of mercury removal, becomes unstable at high temperatures. Third, the desulfurization reaction strengthens at higher temperatures, and it is likely that H₂S directly reacts with ZnO, thus decreasing the S _ad on the sorbent surfaces.     

Regenerable Sorbents for High-Temperature Desulfurization of Syngas from Biomass Gasification

Single-metal high-temperature solid sorbents for syngas cleaning using Mn, Ca, Fe, Cu, or Mo supported on γ-Al₂O₃ were synthesized, characterized, and tested in a fixed-bed reactor. H₂S and SO₂ concentrations in the gas after treatment at T = 400 to 700 °C were compared with thermodynamic calculations. The Mn-based sorbent showed the best ability to achieve a low sulfur residual in the gas, especially at temperatures above 600 °C. Sorbents with Fe, Cu, and Mo gave SO₂ formation in the initial phase, but this could be avoided by a pre-reduction treatment of the sorbent material.     

Sorbent development for continuous regenerative H2S removal in a rotating monolith reactor

A high capacity and regenerable manganese based sorbent for desulfurization of hot dry fuel gas from coal gasification has been developed. Pure γ-Al₂O₃ and washcoated cordierite monoliths impregnated with manganese acetate and calcined at 973 K resulted in highly dispersed Mn₃O₄ on γ-Al₂O₃. MnS was formed during sulfidation and MnAl₂O₄ during subsequent regeneration with steam. The optimal operation temperature was found to be between 1123 and 1223 K. The maximum capacity of the acceptor was 17 mass% sulfur which was obtained for a 32 mass% manganese loading. A deactivation test of 65 subsequent sulfidation and regeneration cycles showed minor deactivation during the first cycles followed by a stable performance. This sorbent will be used in a rotating monolith reactor in which absorption and regeneration takes place simultaneously in separate sections, which enables a continuous operation.     

The removal of the acetonitrile using activated carbon-based sorbent impregnated with sodium carbonate

To remove acetonitrile, various activated carbon (AC)-based sorbents impregnated with alkali or alkaline earth metal were tested in a fixed-bed quartz reactor at 30 °C. The AC-based sorbents impregnated with sodium (NaAC) showed more enhanced acetonitrile removal capacities than that of the pure AC sorbent despite a notable decrease in their surface areas and pore volumes. The NaAC-10 sorbent (with 10 wt% sodium carbonate) especially showed an excellent acetonitrile removal capacity (15mg CH₃CN/g sorbent) and regeneration ability, which indicates that the alkali metal was the adsorption site of the acetonitrile.     

π‐Complexation Studied by Fluorescence Technique: Application in Desulfurization of Petroleum Product using Magnetic π‐Complexation Sorbents

Abstract

Magnetic π‐complexation sorbents were studied for petroleum product desulfurization by fluorescent technique. The ability of metal cation to form π‐complexation decreases in the order following: Cu⁺>Ni²⁺>Co²⁺>Al³⁺. The order is consistent with that of desulfurization performance of their corresponding magnetic sorbents (γ‐Al₂O₃‐Cu(I)>γ‐Al₂O₃‐Ni(II)>γ‐Al₂O₃‐Co(II)>γ‐Al₂O₃). Both π‐complexation strength and desulfurization performance of the sorbents increase with temperature. The adsorptive performances of magnetic γ‐Al₂O₃‐Cu(I) sorbent to different compounds have the following orders: DBT>fluorene, and pyrene>naphthalene>benzene, respectively. In this study, dibenzothiophene (DBT) was used as a model sulphur‐containing compound for desulfurization. The maximal adsorption amount of magnetic γ‐Al₂O₃‐Cu(I), was 0.362 mmol DBT g^?1.     

Simultaneous experiments of sulfidation and regeneration in two pressurized fluidized-bed reactors for hot gas desulfurization of IGCC

Hot Gas Desulfurizarion for IGCC is a new method to efficiently remove H2S in fuel gas with regenerable sorbents at high temperature and high-pressure conditions. The Korea Institute of Energy Research did operation of sulfidation in a desulfurizer and regeneration in a regenerator simultaneously at high pressure and high temperature conditions. The H₂S concentration at exit was maintained continuously below 50ppmv at 11,000 ppmv of inlet H₂S concentration. The sorbent had little effect on the reducing power in the inlet gas in the range from 11% to 33% of H₂. As inlet H₂S concentration was increased, H₂S concentration in the product gas was also increased linearly. The sorbent was maintained at low sulfur level by the continuous regeneration and the continuous solid circulation at the rate of 1.58× 10⁻³ kg/s with little mean particle size change.     

Reactivity of Metal Oxide Sorbents for Removal of Sulfur Compounds from Coal Gases at High Temperature and Pressure

Abstract

Hot-gas desulfurization for the integrated gasification combined cycle (IGCC) process has been investigated to effectively remove hydrogen sulfide with various metal oxide sorbents at high temperatures and pressures. Metal oxide sorbents such as zinc titanate oxide, zinc ferrite oxide, copper oxide, manganese oxide, and calcium oxide were found to be promising sorbents in comparison with other removal methods such as membrane separation and reactive membrane separation. The removal reaction of H₂S from coal gas mixtures with zinc titanate oxide sorbents was conducted in a batch reactor. The main objectives of this research are to formulate promising metal oxide sorbents for removal of hydrogen sulfide from coal gas mixtures, to compare reactivity of a formulated sorbent with a sorbent supplied by the Research Triangle Institute at high temperatures and pressures, and to determine effects of concentrations of moisture contained in coal gas mixtures, and to determine effects of concentrations of moisture contained in coal gas mixtures on equilibrium absorption of H₂S into metal oxide sorbents. Promising durable metal oxide sorbents with high-sulfur-absorbing capacity were formulated by mixing active metal oxide powders with inert metal oxide powders and calcining these powder mixtures.     

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.