Study on the phase transformation mechanism and influencing factors of inorganic condensable particulate matter from coal-fired power plants.

In this study, the concentration of inorganic ions (SO42-, NH4+, NO3- and NO2-) and morphological characteristics of condensable particulate matter (CPM) were investigated to elucidate the formation mechanism of inorganic CPM from ultra-low emission coal-fired power plants. The concentration of inorganic ions increased with the increase of H2O content and concentration of inorganic gaseous contaminants (SO2, NOX and NH3), and decrease of condensation temperature, indicating the enhancement of heterogenous reaction in the saturated flue gas. Furthermore, NOX and SO2 could undergo redox reactions, leading to an elevation in the concentration of SO42- and NO3-. Additionally, the introduction of NH3 resulted in increased concentrations of SO42-, NO3-, and NO2-, highlighting the significant role of NH3 neutralization in CPM nucleation. The condensation of SO3/sulfuric acid aerosols was enhanced under saturation conditions, and SO2 and SO3/sulfuric acid aerosols could contribute synergistically to the formation of SO42-. Moreover, morphological analysis revealed the presence of both well-aggregated solid CPM and dispersed liquid CPM, confirming the formation of inorganic CPM during fast condensation. Furthermore, the detected CPM were composed of S and O, which identified the significant role of sulfates in the inorganic CPM. These findings provide valuable insights for the control of inorganic CPM in flue gas systems.

Different morphologies on Cu-Ce/TiO2 catalysts for the selective catalytic reduction of NOx with NH3 and DRIFTS study on sol-gel nanoparticles.

The copper-cerium binary oxide catalysts supported by titanium dioxide with nanosphere core-shell structures, nanotube (TNT) core-shell structures, impregnation (imp) nanoparticles and sol-gel nanoparticles were prepared for NH3-SCR of NOx under medium-low temperature conditions. The effect of different morphologies on the Cu-Ce/TiO2 catalysts was comprehensively studied through physicochemical characterization. The results showed that the sol-gel nanoparticles exhibited 100% NOx reduction efficiency in the temperature range of 180-400 °C. Compared with the other catalysts, the sol-gel nanoparticle catalyst had the highest dispersion and lowest crystallinity, indicating that morphology played an important role in the NH3-SCR of the catalyst. The in situ DRIFTS study on the sol-gel nanoparticle catalyst shows that cerium could promote Cu2+ to produce abundant Lewis acid sites, which would significantly increase the adsorption reaction of ammonia on the catalyst surface, thereby promoting the occurrence of the Eley-Rideal (E-R) mechanism. With the Ce-Ti interaction on the atomic scale, the Ce-O-Ti structure enhanced the redox properties at a medium temperature. In addition, cerium oxide enhances the strong interaction between the catalyst matrix and CuO particles. Therefore, the reducibility of the CuO species was enhanced.

N2O inhibition by toluene over Mn-Fe spinel SCR catalyst.

Co-removal of toluene in NH3-SCR unit over Mn based catalysts is desirable but still faces the big challenge of byproduct greenhouse gas N2O. In this work, the impacts of toluene on N2O formation mechanism was studied. The main N2O formation pathways in NH3-SCR over Mn-Fe spinel were NH3 oxidation and non-catalytic selective reduction (NSCR), in which NSCR dominated below 250 °C. The N2O from NSCR through both Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanisms was confirmed. And the E-R mechanism was dominant at 200 °C. Toluene was effectively co-removed with NOx with the advantage of N2O inhibition. Toluene suppressed N2O generation from both NH3 oxidation and NSCR. NH3 oxidation by gaseous O2 and catalyst surface oxygen was all limited by toluene, resulting in less adsorbed NH that was further proved by the larger energy barriers of NH3*→NH2* and NH2*→NH* on toluene pre-adsorbed catalyst surface. NO oxidation was also limited, suppressing the generation of adsorbed NO3-. Due to the inhibition of NH3 and NO activation to key intermediates NH and NO3-, respectively, the N2O generation from E-R route was slightly decreased in the presence of toluene, while that from L-H route was completely prohibited at 200 °C.

Correction: Mechanistic study on NO reduction by sludge reburning in a pilot scale cement precalciner with different CO2 concentrations.

[This corrects the article DOI: 10.1039/C9RA04065J.].

Data on species and concentration of the main gaseous products during sludge combustion to support the feasibility of using sludge as a flue gas denitration agent for the cement industry.

The dataset presented in this article is the supplementary data for the research article Fang et al., 2019 [1] and provided detailed data profile to support that sludge is an effective NOX reducing agent, as reductive gas components produce during sludge combustion. The instantaneous concentrations of the main gaseous products during sludge combustion were detected by using Fourier transform infrared spectroscopy (FTIR, DX-4000, Gasmet Technologies). The results showed the distribution and concentration level of gaseous products during sludge combustion and evidenced the feasibility of using sludge as a deNOX agent in cement industry.

Mechanistic study on NO reduction by sludge reburning in a pilot scale cement precalciner with different CO2 concentrations.

An experimental study on the effects of CO2 concentration on the release of reducing gases and the NO reduction efficiency by sludge reburning was carried out in a pilot scale cement precalciner. The results indicate that sludge reburning shows an ideal NO reduction activity. The best NO reduction efficiency of 54% is reached when the CO2 concentration is 25 vol%. Characteristic analysis of the sludge shows that the main types of reducing gases generated by sludge reburning are HCN, NH3, CO and CH4. Among them, CO2 concentration plays a crucial role in the release of HCN, CO and CH4. The mechanistic study indicates that NO reduction is dominated by homogeneous reduction during the sludge reburning process, in particular the reducing gases of CO and NH3 have significant influences on the NO reduction. Meanwhile, the effect of CO2 concentration on NO reduction is mainly due to the difference in CO release. The results of the present study not only provide insight into the mechanism of NO reduction by sludge reburning, but could also contribute to the development of NO X removal technology in the cement industry.

Uniformly active phase loaded selective catalytic reduction catalysts (V2O5/TNTs) with superior alkaline resistance performance.

In this work, protonated titanate nanotubes was performed as a potential useful support and different vanadium precursors (NH4VO3 and VOSO4) were used to synthesize deNOx catalysts. The results showed that VOSO4 exhibited better synergistic effect with titanate nanotubes than NH4VO3, which was caused by the ion-exchange reaction. Then high loading content of vanadium, uniformly active phase distribution, better dispersion of vanadium, more acid sites, better V5+/V4+ redox cycles and superior oxygen mobility were achieved. Besides, VOSO4-based titanate nanotubes catalysts also showed enhanced alkaline resistance than particles (P25) based catalysts. It was strongly associated with its abundant acid sites, large surface area, flexible redox cycles and oxygen transfer ability. For the loading on protonated titanate nanotubes, active metal with cation groups was better precursors than anion ones. V2O5/TNTs catalyst was a promising substitute for the commercial vanadium catalysts and the work conducted herein provided a useful idea to design uniformly active phase loaded catalyst.

Ceria supported on sulfated zirconia as a superacid catalyst for selective catalytic reduction of NO with NH3.

In this paper, ceria supported on sulfated zirconia (CeSZ) as a superacid catalyst was synthesized and the resulted performances for selective catalytic reduction (SCR) of NO with NH(3) were investigated. Experimental results revealed that the sulfation of zirconia supports could greatly improve the SCR activity of the catalysts. Among the tested samples, the CeSZ catalyst with Ce/Zr mole ratio at 0.095 possessed the highest NO conversion (i.e., 98.6% at ca. 420 °C and 180,000 h(-1)). The sulfation had led to a formation of pure tetragonal phase of ZrO(2), a well dispersion of CeO(2), abundant stable superacid sites, increasing surface area and enrichment of Ce(3+) on the surface, all of which were responsible for its excellent performance in SCR of NO with NH(3).

Effect of pH value on the microstructure and deNO(x) catalytic performance of titanate nanotubes loaded CeO2.

The relationship between catalytic performance and pH value of post-treatment of the catalyst supports-titanate materials was investigated and discussed. Three types of titanate nanotubes (TNTs) that are acidic TNTs (TNTs-1.6, pH value at 1.6), neutral TNTs (TNTs-7), and alkaline TNTs (TNTs-12) were synthesized by hydrothermal method with the controlled washing pH value and then were used as the catalyst supports for ceria. These titanate-supported ceria catalysts showed extremely different performance for the selective catalytic reduction in NO. The pH value had a notable effect on the structure and composition of titanate nanotubes and further affected the state and redox property of cerium oxides. The structure of TNTs-1.6, TNTs-7, and TNTs-12 were identified as anatase-like structure, protonated titanate (H(2)Ti(3)O(7)), and Na-containing titanate, respectively. Indeed, the residual sodium (TNTs-12) was harmful to ceria, but the presence of water in the interlayer (TNTs-7) was beneficial to the stability of nanotube structure. Therefore, TNTs-7 doped ceria showed the best SCR activity among these tested samples.

Polyethyleneimine functionalized protonated titanate nanotubes as superior carbon dioxide adsorbents.

In this paper, protonated titanate nanotubes (PTNTs) were modified with polyethyleneimine (PEI) by wet impregnation method for CO(2) adsorption. Their micro-morphology and structural properties were characterized by a range of analytical techniques, including XRD, TEM, SEM, N(2) adsorption etc. Experimental results revealed that the functionalized PTNTs with 50 wt.% PEI loaded exhibited a high CO(2) adsorption capacity of 130.8 mg/g-sorbent at 100°C. Only a minor loss of its capacity was observed after five consecutive adsorption-desorption runs. The PEI was existed both in the internal and external mesoporous pores of PTNTs via chemical combination between amino group and enriched protons, which accounted for their good thermal stability at elevated temperatures. The results present herein imply that the PEI modified PTNTs could be appealing materials for capturing CO(2) from power plant flue gas.