Enhancing CO and H2 Production in Propane Dry Reforming in Excess of CO2

This study focuses on addressing the challenges in the dry reforming of propane, a process historically marked by low syngas yields and only moderate conversions of CO2 and propane. The primary objective was to enhance CO2 utilization and boost the selectivity of syngas (CO and H2) production using titania-based catalysts. For synthesizing these catalysts, an impregnation method was employed with subsequent characterization through X-ray diffraction (XRD), N2 adsorption-desorption, ammonia temperature-programmed desorption (TPD), and hydrogen temperature-programmed reduction (TPR). The titania-based catalysts generally possess weak acidic strength, with each catalyst displaying a unique reduction profile. The dry reforming process using these catalysts resulted in varying levels of propane conversion, with V/Ti, Ir/Ti, Al/Ti, and Zr/Ti catalysts showing distinct efficiencies. Notably, the Ir/Ti and V/Ti oxide catalysts achieved the lowest selectivity for generating intermediate byproducts such as methane, ethane, ethylene, and propylene while successfully promoting higher syngas CO and H2 production alongside stable propane conversion. When exposed to excess CO2, each catalyst consumed differing amounts of CO2 molecules. Particularly, the Ir/Ti and V/Ti oxide catalysts demonstrated enhanced activity in promoting CO2 reactions with intermediate radical species, facilitating carbon-carbon (C-C) bond dissociation and leading to increased syngas production. This study offers valuable insights into the potential of titania-based catalysts in improving the efficiency and selectivity of propane dry reforming processes for blue hydrogen.

Low-temperature CeCoMnOx spinel-type catalysts prepared by oxalate co-precipitation for selective catalytic reduction of NO using NH3: A structure-activity relationship study

CeCoMnOx spinel-type catalysts for the selective catalytic reduction of NO using NH3 (NH3-SCR) are usually prepared by alkaline co-precipitation. In this paper, a series of CeCoMnOx spinel-type catalysts with different calcination temperatures were prepared by acidic oxalate co-precipitation. The physicochemical structures and NH3-SCR activities of the CeCoMnOx spinel-type catalysts prepared by oxalate co-precipitation and conventional ammonia co-precipitation were systematically compared. The results show that the CeCoMnOx spinel-type catalysts prepared by the oxalate precipitation method (CeCoMnOx-C) have larger specific surface area, more mesopores and surface active sites, stronger redox properties and adsorption activation properties than those prepared by the traditional ammonia co-precipitation method at 400 °C (CeCoMnOx-N-400), and thus CeCoMnOx-C have better low-temperature NH3-SCR performance. At the same calcination temperature of 400 °C, the NO conversion of CeCoMnOx-C-400 exceeds 89 % and approaches 100 % within the reaction temperature of 100-125 °C, which is 14.8 %-2.5 % higher than that of CeCoMnOx-N-400 at 100-125 °C. In addition, the enhanced redox and acid cycle matching mechanisms on the CeCoMnOx-C surface, as well as the enhanced monoadsorption Eley-Rideal (E-R) and double adsorption Langmuir-Hinshelwood (L-H) reaction mechanisms, are also derived from XPS and in situ DRIFTS characterization.

Recent Progress on Improving Low-Temperature Activity of Vanadia-Based Catalysts for the Selective Catalytic Reduction of NOx with Ammonia

Selective catalytic reduction of NOx with NH3 (NH3-SCR) has been successfully applied to abate NOx from diesel engines and coal-fired industries on a large scale. Although V2O5-WO3(MoO3)/TiO2 catalysts have been utilized in commercial applications, novel vanadia-based catalysts have been recently developed to meet the increasing requirements for low-temperature catalytic activity. In this article, recent progress on the improvement of the low-temperature activity of vanadia-based catalysts is reviewed, including modification with metal oxides and nonmetal elements and the use of novel supports, different synthesis methods, metal vanadates and specific structures. Investigation of the NH3-SCR reaction mechanism, especially at low temperatures, is also emphasized. Finally, for low-temperature NH3-SCR, some suggestions are given regarding the opportunities and challenges of vanadia-based catalysts in future research.

A superior Fe-V-Ti catalyst with high activity and SO2 resistance for the selective catalytic reduction of NOx with NH3

A series of Fe-V-Ti oxide catalysts were prepared by a co-precipitation method, among which the Fe_0.1V_0.1TiO_x catalyst showed the optimal NH₃-SCR performance and excellent SO₂ resistance. Fe_0.1V_0.1TiO_x achieved > 90% NO_x conversion at 225-450 °C under a GHSV of 200,000 h^-1. When introducing SO₂ and H₂O to the SCR reaction for 24 h, the NO_x conversion maintained a level above 93% at 250 °C. The Raman and Mössbauer spectra showed that FeVO₄ and Fe₂O₃ coexisted on the surface of TiO₂. In Fe-V-Ti catalysts, the charge interaction between Fe₂O₃ and FeVO₄ as well as the electronic inductive effect between Fe and V species resulted in the improvement of SCR activity and N₂ selectivity at high temperatures. The NH₃-SCR process on the Fe_0.1V_0.1TiO_x catalyst mainly followed the Eley-Rideal (E-R) reaction mechanism with gaseous NO reacting with adsorbed NH₃ adsorbed species.

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.

NH3-SCR performance and the resistance to SO2 for Nb doped vanadium based catalyst at low temperatures

Niobium oxide as the promoter was doped in the V/WTi catalyst for the selective catalytic reduction (SCR) of NO. The results showed that the addition of Nb₂O₅ could improve the SCR activity at low temperatures and the 6wt.% additive was an appropriate dosage. The enhanced reaction activity of adsorbed ammonia species and the improved dispersion of vanadium oxide might be the reasons for the elevation of SCR activity at low temperatures. The resistances to SO₂ of 3V6Nb/WTi catalyst at different temperatures were investigated. FTIR spectrum and TG-FTIR result indicated that the deposition of ammonium sulfate species was the main deactivation reason at low temperatures, which still exhibited the reactivity with NO above 200°C on the catalyst surface. There was a synergistic effect among NH₃, H₂O and SO₂ that NH₃ and H₂O both accelerated the catalyst deactivation in the presence of SO₂ at 175°C. The thermal treatment at 400°C could regenerate the deactivated catalyst and get SCR activity recovered. The particle and monolith catalysts both kept stable NO_x conversion at 225°C with high concentration of H₂O and SO₂ during the long time tests.

Catalytic oxidation of nitric oxide (NO) over different catalysts: an overview

Nitrogen oxides (mainly NO) are one of the major air pollutants that lead to a number of environmental problems such as photochemical smog, acid rain and haze.

Effect of Ni doping in NixMn1−xTi10 (x = 0.1–0.5) on activity and SO2 resistance for NH3-SCR of NO studied with in situ DRIFTS

The Ni_0.4Mn_0.6Ti₁₀ catalyst exhibits excellent SO₂ resistance, high NO conversion and N₂ selectivity in the range of 190–360 °C even in the presence of 100 ppm SO₂ and 15% H₂O under a GHSV of 40 000 h⁻¹ due to the interaction among Mn, Ni and Ti oxides.

Performance optimization of a MnO2/carbon nanotube substrate for efficient catalytic oxidation of low-concentration NO at room temperature

Performance optimization of a MnO₂ NS/CNT series of catalysts could be realized via doping methods or acid treatment.

Mechanistic study of selective catalytic reduction of NO with NH3 over highly dispersed Fe2O3 loaded on Fe-ZSM-5

Highly dispersed Fe_xO_y clusters loaded on Fe-ZSM-5 with a Fe³⁺ concentration up to 22 wt% promoted the de-NO_X activity with an efficiency of 91%. The reaction route was temperature dependent.

Simultaneous removal of elemental mercury and NO from simulated flue gas using a CeO2 modified V2O5–WO3/TiO2 catalyst

The redox cycle (V⁴⁺ + Ce⁴⁺ ↔ V⁵⁺ + Ce³⁺) over V₂O₅–WO₃/TiO₂–CeO₂ plays a key role in Hg⁰ oxidation and NO conversion.

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.

Promoting effect of Nd on the reduction of NO with NH3 over CeO2 supported by activated semi-coke: an in situ DRIFTS study

The morphology and NH₃-SCR performance of CeO₂-Nd/ASC catalysts.

Cerium promotion on the hydrocarbon resistance of a Cu-SAPO-34 NH3-SCR monolith catalyst

Ce was introduced to promote the HC resistance of Cu-SAPO-34, and a series of CuCe-xcatalysts with various content of Ce were prepared by a wet co-impregnation method.

Nb-doped VOx/CeO2 catalyst for NH3-SCR of NOx at low temperatures

The Nb-1VO_x/CeO₂ catalyst exhibited higher NH₃-SCR activity than 3V₂O₅–10WO₃/TiO₂ and also showed excellent SO₂/H₂O resistance.