Industrial & Engineering Chemistry Research最新文献

This study probes the effectiveness of using a Ag/CeO₂–Al₂O₃ mixed metal oxide support compared to Ag-modified single supports (Ag/CeO₂ and Ag/Al₂O₃) on acetone removal under VUV irradiation at room temperature. It is shown that under VUV light, the type of support can affect acetone oxidation at the microscopic and macroscopic levels. At the microscopic level, the findings from X-ray photoemission spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) analyses showed that the nature of the support can influence the oxidation state of silver. At the macroscopic level, it was demonstrated that the support can control the dominance of the oxidation mechanism. While Ag/Al₂O₃, compared to Ag/CeO₂, can boost acetone and ozone conversion, the selectivity of Ag/Al₂O₃ (88%) was lower than that of Ag/CeO₂ (96%). However, not only can Ag/CeO₂–Al₂O₃ with an optimized 1:1 ratio of CeO₂/Al₂O₃ oxidize 96 and 98% of the inlet acetone and ozone, respectively, but also the reaction selectivity was above 97%. Moreover, the influence of relative humidity (RH) on Ag/CeO₂–Al₂O₃ activity under VUV light was investigated, and it proved the dual character of RH. Although RH improved the VUV photolysis performance in the gaseous state, it poisoned the gas–catalyst interface, leading to an inhibition role in the catalytic reactions. The high and sustainable performance of the Ag/CeO₂–Al₂O₃ catalyst at room temperature, achieved through engineering of the mixed metal oxide support and maintained even under humid conditions, offers a promising solution for indoor air quality control in diverse settings. These include residential, commercial, and industrial spaces and potential applications in reducing volatile organic compounds (VOCs) from automotive emissions.

This study utilized a synthetic gas test bench (SGB) and two engine test benches (ETBs) to evaluate the periodic operation of an industrially relevant three-way catalyst formulation. The goal was to bridge the gap between laboratory-scale testing and real-world applications, ensuring the reliability of catalysts in engine environments under periodic conditions. SGB testing showed significant increases in NO, CO, and hydrocarbon conversion and N₂ selectivity under dynamic operation compared to stoichiometric steady-state conditions. Despite differences in ETB testing due to the realistic conditions, notable improvements in pollutant conversion were achieved. Challenges included inaccurate control of the mean air–fuel equivalence ratio (AFR) by the engine control unit and the AFR sensor. The findings underscore the importance of harmonizing engine operation with formulation-governed catalyst properties to minimize tailpipe emissions. Periodic operation emerges as a promising technique for enhancing catalyst efficiency in varying engine conditions.

Although the synthesis of low-molecular-weight poly(2,6-dimethyl-1,4-phenylene oxide) (LMW-PPO) has been widely studied, preparing metal-free LMW-PPO with high thermal stability and satisfactory dielectric properties is still challenging. In this study, a new method for synthesizing metal-free LMW-PPO by nonmetal catalysts has been developed. In the absence of Cu(II) catalysts, amines can catalyze benzoyl peroxide (BPO) to produce metal-free LMW-PPO in CH₃CN (M_n in the range of 4.0 × 10³–6.0 × 10³), and N,N-dimethyl-p-toluidine (DMT) exhibits high reactivity in the yield of PPO (68.4%) with a low 3,3′,5,5′-tetramethyl-4,4’diphenoquinone (DPQ) yield (2.6 × 10^–2%) and PDI (1.50). The low dielectric constant (D_k = 1.96) and low dielectric loss factor (D_f = 1.57 × 10^–3) of the obtained PPO indicate that amines are more appropriate for the synthesis of metal-free LMW-PPO with superior dielectric properties. Meanwhile, the M_n values of PPO can be successfully mediated by regulating the contents of the catalyst or mixing appropriate contents of toluene in CH₃CN, and the decreased T_g values from 209.3 to 170.8 °C with decreasing M_n values from 1.7 × 10⁴ to 4.1 × 10³ indicate the improved processability of the LMW-PPO while maintaining high thermal stability (T_d5% = 420.8–434.2 °C). Density functional theory (DFT) calculations further reveal the formation of oxidizing radicals from BPO by DMT, which then initiate H-abstraction from DMP to form the DMP radical. The produced DMP radicals then polymerize to LMW-PPO. This study provides new insight into synthesizing highly qualified LMW-PPO by metal-free catalysts.