Kainan Xing,Minghe Cao,Qinkai Zhu,Haojie Yin,Meizhen Lu,Jianbing Ji
Vegetable oils and their derivatives are of great interest because of their abundance and renewability. This paper prepares nonanal (N) and methyl 9-oxonanoate (M) from methyl epoxystearate (ME) with WO 3 ∙0.33H 2 O, WO 3 ∙H 2 O, and WO 3 ∙2H 2 O as catalysts and H 2 O 2 as the oxidant without the use of organic solvent. The reaction temperature, catalyst amount, H 2 O 2 amount, and reaction time effects on ME conversion and N/M yield are investigated. The results show that WO 3 ∙H 2 O has the best catalytic performance. The optimal reaction conditions are: reaction temperature 60 °C, reaction time 40 min, ME/H 2 O 2 /WO 3 ∙H 2 O molar ratio 1/1.2/0.4, under which the ME conversion and N/M yield reach 95% and 70%, respectively. WO 3 ∙ n H 2 O reacts with H 2 O 2 to form soluble tungsten anions, resulting in severe tungsten loss. Al-MCM-41 materials with different silicon to aluminum molar ratios are added to the reaction system as adsorbents to recover the catalyst by effective adsorption of tungsten anions. The adsorption performance improves as the Si/Al ratio decreases, however, the ME conversion and N/M yield decrease. Thus, 50 is the most suitable Si/Al ratio. The ME conversion and N/M yield can still reach 90% and 60% after four times of use. Practical applications : The nonanal has a natural fragrance and can be used in the cosmetic industry as well as in the preparation of bio-based surfactants. The methyl 9-oxonanoate can be converted into polymer monomers by hydrogenation or amination. The results show that WO 3 ∙ n H 2 O has good catalytic activity, and a satisfying yield of aldehyde products is obtained under mild reaction conditions.
Chemical bath deposition (CBD) is regarded as an ideal approach for tungsten oxide (WO 3 ) electrochromic films because of its low cost and high efficiency. However, the currently reported WO 3 films prepared by CBD suffer from poor stability, delayed switching speed, and inadequate optical modulation (ΔT) due to undesirable morphology, oxygen vacancies, and crystallinity, which limit their potential application. This study presents WO 3 ·nH 2 O films by CBD assisted with different sulfates (Na 2 SO 4 , (NH 4 ) 2 SO 4 , and K 2 SO 4 ) as capping agents. The K 2 SO 4 -assisted CBD-prepared WO 3 ·nH 2 O films (W-K) possess optimal performance with large optical modulation (ΔT = 87 % at 630 nm), fast switching speed (t c /t b= 7.4/4.2 s), and outstanding cycling stability (5000 cycles). The effect of capping agent on growth mechanism and structural morphology of WO 3 ·nH 2 O is investigated in detail. Benefit from the optimal capping effect of K 2 SO 4 , W-K has the larger specific surface area, rich oxygen vacancies, and amorphous/crystalline structure, which endow W-K with ample redox reaction sites, easier for ions and electrons to migrate, and leading to the release of reaction stress. Besides, the electrochromic devices assembled by W-K demonstrate good electrochromic performance overall. This research offers a fresh perspective on the low-cost and high-efficiency electrochromic WO 3 films and devices, and provides a feasible guide for their implementation of commercial applications.
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