Polyol-Mediated Synthesis of V2O5–WO3/TiO2 Catalysts for Low-Temperature Selective Catalytic Reduction with Ammonia

Abstract

We demonstrated highly efficient selective catalytic reduction catalysts by adopting the polyol process, and the prepared catalysts exhibited a high nitrogen oxide (NOX) removal efficiency of 96% at 250 °C. The V2O5 and WO3 catalyst nanoparticles prepared using the polyol process were smaller (~10 nm) than those prepared using the impregnation method (~20 nm), and the small catalyst size enabled an increase in surface area and catalytic acid sites. The NOX removal efficiencies at temperatures between 200 and 250 °C were enhanced by approximately 30% compared to those of the catalysts prepared using the conventional impregnation method. The NH3-temperature-programmed desorption and H2-temperature-programmed reduction results confirmed that the polyol process produced more surface acid sites at low temperatures and enhanced the redox ability. The in situ Fourier-transform infrared spectra further elucidated the fast absorption of NH3 and its reduction with NO and O2 on the prepared catalyst surfaces. This study provides an effective approach to synthesizing efficient low-temperature SCR catalysts and may contribute to further studies related to other catalytic systems.

Polyol Synthesis of Nanoparticles: A Decade of Advancements and Insights

“…(v) Temperature control: The distinctive advantage of polyol synthesis lies in its capacity to be carried out at comparatively low temperatures, effectively mitigating concerns of particle agglomeration or undesired side reactions [98][99][100]. This controlled and milder temperature environment safeguards the formation of nanoparticles from undesirable interactions, ensuring the production of homogeneous and well-dispersed nanoparticles.…”

Phase Equilibria and Phase Diagram of the Quaternary NaOH–Na3VO4–Na2WO4–H2O System at 278.15 K to 353.15 K

“…The use of a selective catalytic reduction (SCR) catalyst has become the most effective means of reducing nitrogen oxide (NO x ) emissions from stationary segments around the world because of strengthened regulatory trends and emerging environmental issues. − The most widely used SCR catalyst, the V 2 O 5 –WO 3 /TiO 2 system, , contains a considerable amount of valuable metals (7–10 wt % of WO 3 , 0.5–1.5 wt % V 2 O 5 , and 70–80 wt % TiO 2 ) . This system shows excellent catalytic properties, such as a wide operating temperature window and high denitration rate …”

Nitration-Promoted Vanadate Catalysts for Low-Temperature Selective Catalytic Reduction of NOX with NH3

“…9−11 This technology can reduce up to 60−90% of NO X in exhaust gas, contain secondary pollutant emission, and can operate at a relatively low temperature (∼350 °C). 12 Many transition-metal catalysts have been used for SCR reactions, such as vanadium, tungsten, copper, iron, and manganese oxides. Among these, V-based catalysts (V 2 O 5 -WO 3 or MoO 3 /TiO 2 ) have been commercially adopted due to their lower ability to oxidize SO 2 to SO 3 ; additionally, these catalysts exhibit greater catalytic activity, compared to other transition-metal catalysts.…”

“…Thus, many nations and governments have strengthened their emission regulation policies to control nitrogen oxide emissions . Several processes have been proposed to either eliminate or control nitrogen oxide emissions: for example, selective catalytic reduction (SCR), selective noncatalytic reduction, and non-selective catalytic reduction. − Among these technologies, SCR is the most advanced and efficient; it works by converting NO X in exhaust gas into N 2 and H 2 O, using ammonia (NH 3 ) as a reducing agent. − This technology can reduce up to 60–90% of NO X in exhaust gas, contain secondary pollutant emission, and can operate at a relatively low temperature (∼350 °C) . Many transition-metal catalysts have been used for SCR reactions, such as vanadium, tungsten, copper, iron, and manganese oxides.…”