## 1 Introduction  
The emission of nitrogen oxides (NO\({}_{\text{x}}\)) from stationary sources and lean-burn engines remains one of the major challenges in environmental pollution control due to the negative effect of NOx on air quality and human health. Selective catalytic reduction (SCR) of NOx with NH\({}_{3}\) (NH\({}_{3}\)-SCR) over TiO\({}_{2}\) supported V\({}_{2}\)O\({}_{5}\)-WO\({}_{3}\) or V\({}_{2}\)O\({}_{5}\)-MoO\({}_{3}\) catalysts have been extensively investigated due to the high activity of these catalysts in NO reduction [1; 2; 3; 4]. However, the toxicity of active vanadium species and the narrow operation temperature window (300-420 \({}^{\circ}\)C) limit the use of these catalysts on a commercial scale to meet the stringent NOx emission legislations, especially when the boilers are operated at low loads and the temperatures are far below the operation temperature window of the vanadium-based catalysts [5; 6].  
In recent years, significant efforts have been devoted to the development of an environmentally-benign catalyst with a wide operation temperature window and high deNO\({}_{\text{x}}\) activity [7; 8]. Various types of transition and rare earth metals based catalysts have shown an excellent reactivity in NH\({}_{3}\)-SCR reaction over a wide temperature range [9; 10; 11]. Among the non-vanadium NH\({}_{3}\)-SCR catalysts, cerium-based catalysts have been intensively investigated considering their unique properties of high oxygen-storage capacity and facilitated redox cycles between Ce\({}^{4+}\) and Ce\({}^{3+}\), e.g., Ce-Ti, Ce-Zr, Ce-Cu-Ti and Ce-Mn, etc. [12; 13; 14; 15; 16; 17].  
Recently, tungsten, a typical promoter and stabilizer in vanadium-based catalysts, has been used as a dopant to improve the performance of Ce-based catalysts [18; 19; 20]. [PERSON] et al. reported that the doping of W into CeO\({}_{2}\)/TiO\({}_{2}\) catalysts significantly enhanced the SCR of NH\({}_{3}\) in the temperature range of 150-300 \({}^{\circ}\)C, compared to the catalysts without W doping. The catalyst sample with 6 wt.% W exhibited the best performance [21]. [PERSON] et al. found Ce\({}_{20}\)W\({}_{10}\)Ti catalysts prepared by a single step sol-gel method exhibited a NO conversion of 90% at 275 \({}^{\circ}\)C at a gas hourly space velocity (GHSV) of 90,000 h\({}^{-1}\)[22]. They also developed a Ce-W-Ti catalyst prepared by sol-gel method, which exhibited 95% NO conversion rate (250 \({}^{\circ}\)C) at the same GHSV [23]. [PERSON] et al. reported that Ce\({}_{0.2}\)W\({}_{0.1}\)Ti catalysts synthesized by a facile homogeneous precipitation method showed 100% NO conversion and N\({}_{2}\) selectivity in a wide temperature range of 250 \({}^{\circ}\)C to 400 \({}^{\circ}\)C at a high gas hourly space velocity (GHSV) of 250,000 h\({}^{-1}\), which was significantly higher than that using Ce-Ti catalysts without W doping [24; 25]. Currently, Ce-W-Ti catalysts were assumed to be one of the potential candidates for the commercial vanadium-based catalysts [26]. The performance of the Ce-W-Ti catalysts were closely related to the redox properties between the active metals.  
To further improve the activity of the Ce-W-Ti catalysts in low temperature NH\({}_{3}\)-SCR, a novel solution combustion method has been used to prepare a series of Ce-W-Ti catalysts with different Ce/W ratios and tested over a wide temperature range. The effect of these catalysts on the conversion of NO and N\({}_{2}\) selectivity has been investigated. A range of catalyst characterization techniques including N\({}_{2}\) adsorption-desorption, X-ray diffraction (XRD), X-ray photoelectron spectrometry (XPS), temperature programmed desorption of NH\({}_{3}\) (NH\({}_{3}\)-TPD) has been used to better understand the properties of the Ce-W-Ti catalysts and their effects on the SCR of NO with NH\({}_{3}\).