Metal-Modified Active Coke for Simultaneous Removal of SO₂ and NO_<i>x</i> from Sintering Flue Gas

A series of active coke (AC)-based adsorbents modified by different metal combinations (Na/Ba/Cu, Na&Cu/Na&Ba, and Na&Ba&La/Na&Ba&Ce), supporting different contents of metal and calcined at different temperatures, was investigated for simultaneous removal of SO₂ and NO_<i>x</i>. The activity test results showed that supporting 8% NaCO₃, 7% Ba­(NO₃)₂ & 8% NaCO₃, and 10% Ce­(NO₃)₂ & 7% Ba­(NO₃)₂ & 8% NaCO₃ on the AC was best in unitary, bibasic, and ternary metal modifications, respectively. Supporting 10% Ce­(NO₃)₂ & 7% Ba­(NO₃)₂ & 8% NaCO₃ was the best of all. The Fourier transform infrared spectroscopy result showed that the sodium modification made some unsaturated groups and metal chelate complexes form on the AC, so that the removal performance improved. Barium added to 8% Na–AC augmented the amount of unsaturated groups to improve the performance further. The addition of cerium to 7% Ba–8% Na–AC made more unsaturated groups and metal chelate complexes form, thus raising the performance again. The Brunauer–Emmett–Teller (BET) result showed that the unmodified (AC) and modified (10% Ce–7% Ba–8% Na–AC) ACs were predominantly microporous materials, and the pore size distribution and pore width of the modified AC was more extensive and multiple, which were beneficial for the removal of SO₂ and NO_<i>x</i>. Moreover, the removal performance improved significantly as the calcination temperature increased from 200 to 600 °C, whereas it slumped as the calcination temperature increased from 600 to 800 °C. It was explained by the results of X-ray diffraction and BET that CeO₂, which was one of the active ingredients on the AC, increased with the increase of the calcination temperature and the higher the sample calcined at a temperature, the worse the pore structure of the carrier

Studies on the Dual-Templating Function of TBA for the Formation of ZSM-11 Intergrowth Morphology

Hierarchically structured ZSM-11 microspheres with an intergrowth morphology have been hydrothermally synthesized using only one organic templating molecule (TBABr). An investigation of the effects of the structure-directing agent on the zeolite particle morphology and textural properties was performed. It was found that the template tetraalkylammonium ions TBA⁺ (or TPA⁺) not only were located in the channel intersections of ZSM-11 (or ZSM-5), but were also attached to the external surface of the precursors, which prevented these precursors from further condensation. Finally, a morphology of numerous nanocrystals inserting into each other was formed, and the voids among these intergrowth crystals endowed these materials with mesoporosity

NOx Removal over Modified Carbon Molecular Sieve Catalysts Using a Combined Adsorption-Discharge Plasma Catalytic Process

Carbon molecular sieves (CMS), 13X zeolite, and γ-Al₂O₃ were selected as catalyst support to investigate the NOx adsorption capacity, and a series of Cu modified CMS-based catalysts were used to investigate the NOx adsorption and discharge plasma catalytic removal capacity. Results showed that CMS has a larger NOx adsorption amount and lower desorption temperature in NOx temperature programmed desorption (TPD) process. The addition of Cu benefits the NOx adsorption and nonthermal plasmas (NTP) removal capacity, and the NOx removal capacity and the ratio of NTP/(NTP + TPD) achieved 96.2% and 68.39% over 15%Cu-CMS in 30 min. Water vapor has an obvious effect on the NOx adsorption and discharge plasma catalytic process. In cyclic operation, 15%Cu-CMS has a better NOx adsorption-discharge property. The Brunauer–Emmett–Teller (BET) method showed the average pore width, surface area, and pore volume of the sample after cyclic operation has no significant change. X-ray photoelectron spectroscopy (XPS) showed a new lattice oxygen peak appeared in O 1s spectra, and the Cu₂O peak disappeared in Cu 2p spectra after cyclic operation

Interactive Effect for Simultaneous Removal of SO₂, NO, and CO₂ in Flue Gas on Ion Exchanged Zeolites

A purification system for simultaneous removal of SO₂, NO, and CO₂ in flue gas was considered in this study. For improving the purification performance of candidate adsorbent NaX zeolite, ion exchange experiments were conducted with cation K⁺, Ca²⁺, Mn²⁺, and Co²⁺, respectively. The texture properties of series zeolites were examined by N₂ porosimetry, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses. Among the sorbents investigated, K–NaX zeolite exhibited the best result to remove SO₂, NO, and CO₂ all together. XPS results revealed that SO₂ has been oxidized to form SO₄^2– on the solid surface; however, species N and C have not been observed. In order to understand the coadsorption effects, pure component, binary, ternary components, and mimic flue gas breakthrough experiments were designed and carried out. It suggested that SO₂ and NO was bonded on the adsorbent surface with degradation of NO. A little competitive effect of CO₂ on SO₂ and NO adsorption system were found. Finally, monitoring of coadsorption venting gas, thermodynamic equilibrium species simulation, TPD experiment, and quantum chemical calculation technology were used to examine the interactive effect

Adsorption Separation of CO₂/CH₄ Gas Mixture on Carbon Molecular Sieves Modified by Potassium Carbonate

In order to improve the separation performance of CO₂/CH₄ on carbon molecular sieves (CMS), CMS was modified by metal in this study. The surface of CMS had −OH, which could provide a great support for the chemical modification. In this paper, different metal ions, precursors of potassium, loading concentration of potassium carbonate (K₂CO₃), and calcination temperature were investigated for CO₂/CH₄ separation. Results showed that CMS loaded with K₂CO₃ and calcined at 773–873 K was the best for CO₂/CH₄ separation. Compared with the untreated CMS, the adsorption capacity of CO₂ for the best adsorbent increased from 1.15 to 1.72 mmol·g^–1 and the value of separation factor increased from 1.9 to 2.75 mmol·g^–1. The K₂CO₃ treatment was effective in generating metal oxide K₂O and KO₂, which could facilitate the adsorption of CO₂ after K₂CO₃/CMS being calcined. However, the reaction between CH₄ and metal was weak. In summary, K₂CO₃/CMS was proved to be one of the candidates for CO₂/CH₄ separation