Effect of the calcination temperature on the performance of a CeMoOx catalyst in the selective catalytic reduction of NOx with ammonia

The Effect of Calcination Temperature on Various Sources of ZrO2 Supported Ni Catalyst for Dry Reforming of Methane

Dry reforming of methane (DRM) over an Ni-based catalyst is an innovative research area due to the growing environmental awareness about mitigating global warming gases (CH4 and CO2) and creating a greener route of synthesis. Herein, 5% Ni supported on ZrO2 obtained from various sources was prepared by the impregnation method. The catalysts were calcined at 600, 700, and 800 °C. Furthermore, Ni-RC stabilized with MgO, SiO2, TiO2, and Y2O3 were tested. Characterization techniques employed comprise the N2 physisorption, infrared spectroscopy, Raman, thermogravimetric analysis, XRD, and TEM. The results of the present study indicated that the ZrO2 support source had a profound effect on the overall performance of the process. The best catalyst Ni-RC gave an average conversion of CH4 and CO2 of 61.5% and 63.6% and the least deactivation of 10.3%. The calcination pretreatment differently influenced the catalyst performance. When the average methane conversion was higher than 40%, increasing the calcination temperature decreased the activity. While for the low activity catalysts with an average methane conversion of less than 40% the impact of the calcination temperature did not constantly decrease with the temperature rise. The stabilization of Ni-RC denoted the preference Y2O3 stabilized catalyst with average values of CH4 and CO2 conversion of about 67% and 72%, respectively. The thorough study and fine correlation will be advantageous for technologically suitable Ni-15Y-RC catalysts for DRM.

Ceria–tungsten–tin oxide catalysts with superior regeneration capacity after sulfur poisoning for NH3-SCR process

A combined study on the anti-sintering ability, SO2-poisoning mechanism and thermal regeneration property of CeWSnOx catalysts for NH3-SCR reaction.

The Deactivation Mechanism of the Mo-Ce/Zr-PILC Catalyst Induced by Pb for the Selective Catalytic Reduction of NO with NH3

As a heavy metal, Pb is one component in coal-fired flue gas and is widely considered to have a strong negative effect on catalyst activity in the selective catalytic reduction of NOx by NH3 (NH3-SCR). In this paper, we investigated the deactivation mechanism of the Mo-Ce/Zr-PILC catalyst induced by Pb in detail. We found that NO conversion over the 3Mo4Ce/Zr-PILC catalyst decreased greatly after the addition of Pb. The more severe deactivation induced by Pb was attributed to low surface area, lower amounts of chemisorbed oxygen species and surface Ce3+, and lower redox ability and surface acidity (especially a low number of Brønsted acid sites). Furthermore, the addition of Pb inhibited the formation of highly active intermediate nitrate species generated on the surface of the catalyst, hence decreasing the NH3-SCR activity.

CeZrOx Promoted Water-Gas Shift Reaction under Steam–Methane Reforming Conditions on Ni-HTASO5

Ni-based catalysts (Ni-γ-Al2O3, Ni-HTASO5 and Ni-CeZrOx) were prepared by impregnation method and characterized by BET, AAS, XRD, H2-TPR, CO-TPD, NH3-TPD, XPS, TG-DSC-MS and Raman spectroscopies. Using CeZrOx-modified Al2O3 (HTASO5) as support, the catalyst exhibited good catalytic performance (TOFCH4 = 8.0 × 10−2 s−1, TOFH2 = 10.5 × 10−2 s−1) and carbon resistance for steam-methane reforming (SMR) reaction. Moreover, CeZrOx was able to enhance water-gas shift (WGS) reaction for more hydrogen production. It was found that the addition of CeZrOx could increase the content of active nickel precursor on the surface of the catalyst, which was beneficial to the decomposition of water and methane on Ni-HTASO5. Furthermore, Ni-HTASO5 could decrease the strong acid sites of the catalyst, which would not only contribute to the formation of low graphited carbon, but also decrease the amount of carbon deposition.

Facile Fabrication of Ce/V-Modified Multi-Channel TiO2 Nanotubes and Their Enhanced Selective Catalytic Reduction Performance

To optimize one-dimensional (1D) TiO₂ nanofibers, tailor-made multi-channel TiO₂ nanotubes have been successfully fabricated by electrospinning technology. After loading with Ce and V, the CeVTi-tube catalyst exhibited a broad working temperature window and acceptable resistance to H₂ O and SO₂ for elimination of NO_x . The corresponding analysis revealed that the multi-channel structure provided more surface adsorbed oxygen species and that the wall of nanotubes anchored active components efficiently, which was beneficial to improve the stability as well as dispersion of the active components. Besides, a synergistic effect between Ce and V easily occurred at the CeVTi-tube catalyst, and its reducibility was significantly improved since the electron transformation between Ce and V was dramatically enhanced. Consequently, the tailor-made multi-channel CeVTi-tube catalyst exhibited satisfied de-NO_x efficiency at the temperature range of 220-460 °C. It seemed that the multi-channel TiO₂ nanotubes hold great potential as an excellent carrier for SCR catalysts.

The balance of acidity and redox capability over modified CeO2 catalyst for the selective catalytic reduction of NO with NH3

The effect of acidity and redox capability over sulfuric acid-modified CeO₂ catalysts were studied for the selective catalytic reduction of NO_x with NH₃ (NH₃-SCR). The deposition of sulfate significantly enhanced the catalytic performance over CeO₂. NO_x conversion over 4H₂SO₄/CeO₂ at 230-440 °C was higher than 90%. The strong redox capability of CeO₂ could result in unselective NH₃ oxidation and decrease high temperatures catalytic activity and N₂ selectivity. The deposition of sulfate increased the acidity and weakened the redox capability, and then increased the high temperature NO_x conversion and N₂ selectivity. An appropriate level of acidity also promoted the activity at 190-250 °C over ceria-based catalysts, and with further increase in the acidity, the SCR activity decreased slightly. Weak redox capability lowered the low-temperature catalytic activity. Excellent SCR activity requires a balance of acidity and redox capability on the catalysts.

Comprehensive study of the promotional mechanism of F on Ce–Mo/TiO2 catalysts for wide temperature NH3-SCR performance: the activation of surface Ti–F bonds

The CeFMoTiO_x catalyst was prepared via a solvothermal method. It confirmed that O_α was not only generated during the transformation between Ce⁴⁺ and Ce³⁺ but was also released from F⁻ species of the surface Ti–F bonds.

Natural manganese ore catalyst for low-temperature selective catalytic reduction of NO with NH3 in coke-oven flue gas

Different types of manganese ore raw materials were prepared for use as catalysts, and the effects of different manganese ore raw materials and calcination temperature on the NO conversion were analyzed. The catalysts were characterized by XRF, XRD, BET, XPS, H₂-TPR, NH₃-TPD, and SEM techniques. The results showed that the NO conversion of calcined manganese ore with a Mn:Fe:Al:Si ratio of 1.51:1.26:0.34:1 at 450 °C reached 80% at 120 °C and 98% at 180~240 °C. The suitable proportions and better dispersibility of active ingredients, larger BET surface area, good reductibility, a lot of acid sites, contents of Mn⁴⁺ and Fe³⁺, and surface-adsorbed oxygen played important roles in improving the NO conversion.

Promotional Effects of Ti on a CeO2-MoO3 Catalyst for the Selective Catalytic Reduction of NOx with NH3

In this study, Ti was doped to CeO₂-MoO₃ to promote the catalytic performance for the selective catalytic reduction of NO_x with NH₃ (NH₃-SCR). The preparation method for CeMo_0.5Ti_aO_x (a = 0, 1, 2, 5, 10) catalysts was a stepwise precipitation method. When Ti was doped, all of the Ce-Mo-Ti catalysts exhibited remarkably improved NO_x conversion and N₂ selectivity than the CeMo_0.5O_x without Ti. The CeMo_0.5Ti₅O_x with excellent activity in a broad temperature range was selected as an optimal catalyst to investigate the effects of Ti addition. The formation process analysis of the CeMo_0.5Ti₅O_x showed that, the Mo and Ti species first precipitated together from the mixed solution with the increase of pH, and then Ce species precipitated onto the Mo-Ti precipitates. The obtained catalyst exhibited remarkably facilitated NO_x and NH₃ adsorption, enhanced charge imbalance, promoted redox property, and improved surface acidity, which are all important reasons for the excellent catalytic performance of an NH₃-SCR catalyst.

Ceria-based catalysts for low-temperature selective catalytic reduction of NO with NH3

Low-temperature NH₃-SCR has attracted considerable attention owing to the vast demand in industrial furnaces and its energy-conserving feature. This review summarizes the recent advances in the application of ceria-based catalysts for low-temperature NH₃-SCR.