In cement kiln flue gas emissions, high concentrations of alkali and alkaline earth metals cause the deactivation of the NbCe/Ti catalysts, significantly reducing their operational lifespan under industrial conditions. Here, the NbCe-loaded titanium nanotubes (NbCe/TiNTs) catalyst has been synthesized via hydrothermal and impregnation methods. The NbCe/TiNTs catalyst exhibits superior resistance to potassium (K) and calcium (Ca) poisoning. Notably, NbCe/TiNTs catalyst maintains high NOx conversion across a wide temperature range (192–350 °C). The 5Ca-NbCe/TiNTs and 3K-NbCe/TiNTs catalysts achieve a 90% NOx conversion at 235 and 242 °C, respectively, demonstrating remarkable resistance to K and Ca poisoning. The results indicate that TiNTs supports enhance both the specific surface area and surface acid sites of the catalyst, synergistically improving its resistance to K and Ca poisoning. Furthermore, an in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) study elucidates selective catalytic reduction with the NH3 (NH3-SCR) reaction mechanism, revealing dual contributions from both the Eley–Rideal (E–R) and Langmuir–Hinshelwood (L–H) mechanisms on the catalyst. This work provides a research direction for enhancing the alkali poisoning resistance of NOx removal catalysts.
Metabolic alkalosis, the most common acid–base disorder, is related to significantly increased mortality in hospitalized patients. Hunting for pH sensors lying in the neutral to alkaline pH range still remains challenging and in demand. Herein, we engineered a colorimetric/fluorescent method for monitoring alkalic pH based on a phenylboronic acid-containing probe (DDPB). In this approach, the dicyanoisophorone group of DDPB acted as an optical signal moiety, while the boronic acid acted as the latent pH response site. It was exactly deciphered that the reversible pH monitoring principle is based on the deprotonation/protonation mechanism and intramolecular charge transfer (ICT) strategy via1H NMR and DFT calculations. This approach presented a pH-sensitive response over pH values ranging from 7.00 to 10.23 (pKa = 9.33) with excellent reversibility. We further explored its application in sensing pH on a paper substrate for visual and rapid detection. In addition, it was successfully applied to measure pH variations in HK-2 cells when the cells underwent alkalosis. This work extends the application of optical probes based on boronic acid under alkaline pH conditions, and provides a new strategy for the design of alkaline pH probes.
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