Physicochemical characteristics and desulphurization activity of pyrolusite-blended activated coke

<p>In this study, a novel activated coke (AC-P) was prepared by the blending method using bituminous coal as the raw material and pyrolusite as the catalyst. The physicochemical properties of prepared activated coke (AC) were characterized by BET, Fourier-Transform Infrared Spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The results indicated that the blended pyrolusite had a slight effect on the structural properties of AC, while the oxygenated functional groups on AC were increased and MnO₂ and Fe₂O₃ in pyrolusite were reduced to MnO and Fe on the AC-P samples, respectively. All the AC-P samples significantly improved the removal of SO₂, with the highest sulphur capacity (153 mg/g) for the AC blended with 8 wt% pyrolusite, which was 57.7% higher than that of the blank activated cock. This could be mainly attributed to the change in surface chemical properties of the AC-P samples and the active catalytic components in pyrolusite for the catalytic oxidation of SO₂ in desulphurization process.</p

Desulphurization performance of TiO₂-modified activated carbon by a one-step carbonization-activation method

<p>In this study, TiO₂ powder was used as the additive to directly blend with raw bituminous coal and coking coal for preparing modified activated carbon (Ti/AC) by one-step carbonization-activation method. The Ti/AC samples were prepared through blending with different ratios of TiO₂ (0–12 wt%) and their desulphurization performance was evaluated. The results show that the desulphurization activity of all Ti/AC samples was higher than that of the blank one, and the highest breakthrough sulphur capacity was obtained at 200.55 mg/g C when the blending ratio of TiO₂ was 6 wt%. The Brunauer-Emmett-Temer results show that the micropores were dominant in the Ti/AC samples, and their textual properties did not change evidently compared with the blank one. The X-ray photoelectron spectroscopy results show that the loaded TiO₂ could influence the relative content of surface functional groups, with slightly higher content of π–π* transitions groups on the Ti/AC samples, and the relative contents of C=O and π–π* transitions groups decreased evidently after the desulphurization process. The X-ray diffraction results show that the anatase TiO₂ and rutile TiO₂ co-existed on the surface of the Ti/AC samples. After the desulphurization process, TiO₂ phases did not change and Ti(SO₄)₂ was not observed on the Ti/AC samples, while sulphate was the main desulphurization product. It can be assumed that SO₂ could be catalytically oxidized into SO₃ by TiO₂ indirectly, rather than TiO₂ directly reacted with SO₂ to Ti(SO₄)₂.</p

Evolution of Sulfur Species on Titanium Ore Modified Activated Coke during Flue Gas Desulfurization

This study aimed to investigate the evolution of sulfur species on titanium ore, Fe₂O₃, and TiO₂ modified activated coke (i.e., TOAC, FeAC, and TiAC) during the flue gas desulfurization process. The results showed that TOAC, FeAC, and TiAC displayed better desulfurization performance than a blank sample, with the highest sulfur capacity for TOAC at 209.4 mg g^–1. With desulfurization time, the ratios of the adsorbed-S and other-S on activated coke decreased gradually, while those of the water-soluble sulfate increased significantly. The water-soluble sulfate was the main desulfurization product, which accounted for 66.1%, 78.4%, and 76.6% of total removed SO₂ for FeAC, TiAC, and TOAC at breakthrough time, respectively. The production of water-soluble sulfate could be related to the decrease of CO groups and the increase of C–O groups. Meanwhile, the produced water-soluble sulfate covered the active sites (i.e., functional groups, TiO₂, and Fe₂O₃) on activated coke, resulting in the decrease of the adsorption and oxidation of SO₂. Higher sulfur capacity of TOAC could be attributed to the synergistic effects between Fe₂O₃ and TiO₂ on TOAC. TiO₂ can serve as an oxygen carrier and promote the transfer of oxygen molecules to oxidize SO₂, while Fe₂O₃ was transformed into Fe₂(SO₄)₃