The key role of catalysis in the phase-out of chlorofluorocarbons (CFCs)

Synthesis of microporous fluorinated chromia with a sharp pore distribution

“…For example, it is difficult to use the fluorinated chromia as an inorganic membrane material for the combination of catalysis and separation processes because this reaction membrane needs one kind of material with a sharp pore distribution. 14 According to our design, we would like to prepare a kind of porous metal fluoride with a sharp pore distribution to satisfy the above-mentioned purpose. As we know, urea CO(NH 2 ) 2 in solution will gradually decompose to release NH 3 with increasing temperature.…”

Recent developments in the preparation of high surface area metal fluorides

“…Decomposition is however more complex as shown by reaction (2) and includes also a partial oxidation of Cr 3+ to Cr >3+ and formation of Cr-oxofluorides, mainly in the form of a volatile chromium dioxide difluoride, CrO 2 F 2 . Final decomposition products are therefore relatively pure amorphous CrF 3 with very high surface areas ranging from 200 to 300 m 2 g À1 .…”

“…For these reactions, aluminium-or chromiumbased catalysts were most frequently used [1]. In the last three decades, heterogeneous catalysis on these catalysts played a decisive role in the phase-out of ozone-depleting chlorofluorocarbons (CFCs) [2]. Related catalytic processes included syntheses of hydrochlorofluorocarbons (HCFCs) or hydrofluorocarbons (HFCs) as alternatives for CFCs, environmentally safe destruction of CFCs and conversion of CFCs into environmentally more acceptable products, mainly HFCs.…”

Catalytic Dehalogenation

“…Chlorofluorocarbons in the aqueous environment 2003 [1] Catalysis for CFC replacements 2001 [2] Metal-mediated reductive hydrodehalogenation of organic halides 2002 [3] Chlorocarbon and chlorofluorocarbon dehalogenation over supported metal catalysts.…”

“…The approach was then demonstrated with 20 kg of catalyst in a pilot-scale water treatment plant. VOCs are linked to photochemical smog [2], stratosphereic ozone depletion [3,4], and the formation of tropospheric ozone [5]. In this system also, hydrogen sulfide must be avoided, and the system was flushed every 42 h with H 2 O 2 for 10 min to inhibit sulfate-reducing bacterial growth (the occasional spikes in system performance seen in Fig.…”