Yiwei Sun,Xiaoli Wei,Fangcao Liu,Bing Liu,Jiaming Zhao,Yubao Bi,Wenfeng Han
Developing effective techniques to produce and stabilize highly active metastable F-Al-O species in HFCs dehydrofluorination system without being over-fluorinated to Al-F is a major challenge. Herein, we report a new strategy for the formation and stabilization of metastable species. Using NaH 2 PO 4 as a P source, phosphoric acid groups are modified to the surface of Al 2 O 3 leading to the fabrication of AlPO 4 /Al 2 O 3 interface. P and Al 2 O 3 bond to form Al-O-P structure at the interface and stabilize F-Al-O in the dehydrofluorination system. Further studies show that AlPO 4 /Al 2 O 3 interface increase the oxygen vacancy content of catalyst and accelerate the conversion of HFC-152a on the catalyst surface. Meanwhile, AlPO 4 /Al 2 O 3 interface improves the surface acidity of Al 2 O 3 , endue a large number of Lewis weak acid sites, reducing the carbon accumulation of catalyst, and improving the stability of catalyst. The activity test showed that AlPO 4 /Al 2 O 3 interface shows high catalytic performance (74.2 %) and excellent stability (50 h) for 1,1-difluoroethane dehydrogenation compared with Al 2 O 3 (30 % and low stability) without P modification.
Jiangtao Li,Yunjia Xue,Xueying Zhang,Fan Zhang,Wenhao Hu,Jiachen Liu
The SiC-ZrO 2 coating was prepared on the surface of aluminosilicate ceramic fiber fabric (ASFF) to enhance the radiation heat dissipation. However, the Si-sol in the SiC-ZrO 2 coating caused the fiber to adhere together at high temperatures. The brittle fracture of the ASFF led to a deterioration in its temperature resistance. In this paper, an Al 2 O 3 interface was prepared on the surface of ASFF by spraying alumina precursor. The Al 2 O 3 interface prepared by 3.0 wt% alumina precursor was uniformly covered on the fiber surface. The flexibility of ASFF/Al 2 O 3 /SiC-ZrO 2 was maintained after static oxidation at 1300 °C for 1 h. The tensile strength of ASFF/Al 2 O 3 /SiC-ZrO 2 at 1200 °C were increased from 5 to 7 MPa to 21.35 ± 2.58 MPa. The Al 2 O 3 interface not only limited the direct contact between Si-gel and fiber, but also reacted with Si-gel to produce mullite at high temperature. The problem of fiber adhesion caused by Si-sol in ASFF matrix was solved. Additionally, the SiC-ZrO 2 coating reduced the surface temperature of ASFF rom 1700 °C–1300 °C. Combining the radiation performance of SiC-ZrO 2 coating and the isolation effect of the Al 2 O 3 interface, ASFF/Al 2 O 3 /SiC-ZrO 2 was able to operate continuously for 300 s under the 1700 °C butane-oxygen flame heating condition.
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