Characterization of CrOx/Al2O3 catalysts for dichloromethane oxidation

This paper studies ethyl-dimethyl-2-methoxyethylammonium tris(pentafluoroethyl)trifluorophosphate ionic liquid [(NEMM)MOE][FAP] as 1 wt% additive to a polyalphaolefin (PAO 6) in the lubrication of CrN PVD coating. The tribological behavior of this mixture has also been compared with a traditional oil additive, such as zinc dialkyldithiophosphate (ZDDP). Friction and wear tests were performed by means of a ball-on-plate reciprocating tribometer, and XPS was used to analyze wear surfaces. The experimental results showed that both additives substantially improve the anti-friction and anti-wear performance of the base oil. However, the tribological behavior of the ionic liquid as oil additive does not reach that of ZDDP. The interactions of each additive with the surface and tribofilm formation contributed to improve the tribological behavior of the lubricants.

Lubrication of CrN Coating With Ethyl-Dimethyl-2-Methoxyethylammonium Tris(pentafluoroethyl)Trifluorophosphate Ionic Liquid as Additive to PAO 6

Chromium oxides dispersed on various supports by precipitation method were tested for the catalytic fluorination of HCFC-133a to HFC-134a. Catalytic activity decreased in the order of MgO>Al2O3>MgF2>TiO2>ZrO2. The most active Cr/MgO, when properly activated and pre-fluorinated before the reaction, shows superior activity to other catalysts that have been reported so far. Isolated (monomeric) Cr(VI) species that was formed during an optimized thermal activation were changed into fluoride (CrxFy) and oxyfluoride (CrxOyFz) form of monomeric and oligomeric Cr species during the pre-fluorination with HF, the latter of which are believed to be active sites for the reaction. High pre-fluorination temperature accelerates the formation of crystalline Cr2O3 due to the formation of crystalline MgF2 from MgO which anchors the isolated Cr(VI).

Preparation and characterization of magnesia-supported chromium catalysts for the fluorination of 1,1,1-trifluoro-2-chloroethane (HCFC-133a)

The catalytic gas phase reaction between CF3 CCl CH2 with HF yielding CF3 CF CH2 was investigated regarding the reaction pathways involved. Different from the reaction under liquid phase (homogenous) conditions, in heterogeneous phase CF3 CCl CH2 does not add HF forming the saturated intermediate CF3 CFCl CH3 but undergoes direct Cl/F exchange at the starting olefin molecule resulting directly in the formation of CF3 CF CH2. This might be caused mainly by the fact that under heterogeneous gas phase conditions higher temperatures are needed as compared to liquid phase conditions thus suppressing the formation of kinetically less stable CF3 CFCl CH3 under these conditions. Since for all the reaction steps involved in this complex reaction system the Gibbs free reaction enthalpy values are close to zero [1] , the selectivity towards several reaction products is strongly dependent on the reaction parameters, e.g. temperature, pressure and molar ratio of the reactants. Based on the catalytic data obtained for fluorinated chromia as catalyst, a reaction path distinguishing direct chlorine against fluorine exchange versus hydrofluorination/dehydrochlorination is proposed.

Catalytic formation of 2,3,3,3-tetrafluoropropene from 2-chloro-3,3,3-trifluoropropene at fluorinated chromia: A study of reaction pathways

Catalytic decomposition of dichlorodifluoromethane (CFC-12) in the presence of water vapor was investigated over a series of pure and WO 3 -promoted metal oxides. Although pure TiO 2 , SnO 2 and Fe 2 O 3 showed less activity for the decomposition of CFC-12, obvious enhancement in activity was actualized by supporting WO 3 on them using Ti(OH) 4 , Sn(OH) 4 and Fe(OH) 3 as support precursors. The decomposition activity depended on the calcination temperature obviously and attained to a maximum as the content of WO 3 reached its utmost dispersion capacity on different supports. The 95% conversion temperature of WTi, WSn and WFe catalysts prepared by optimum conditions were 260°C, 315°C and 345°C, respectively. CO 2 was the main-product and no CO was detected as by-product. The selectivity to by-product CFC-13 on WO 3 -modified metal oxides was much lower than on unmodified metal oxides and it also exhibited a coverage-dependent effect. The catalytic activity of WO 3 /TiO 2 , WO 3 /SnO 2 and WO 3 /Fe 2 O 3 all remained steady for 120 h on stream.

Catalytic decomposition of CFC-12 over solid acids WO3/MxOy (M=Ti, Sn, Fe)

The transformation of CF3CH2Cl over bulk chromium(III) oxide, fluorinated or not, leads mainly to the fluorination product CF3CH2F and to the alkene CF2=CHCl. In the presence of HF, CF3CH2F is the main product. In absence of HF this product is also obtained with HF formed in the elimination reaction of CF3CH2Cl to CF2=CHCl. At the same time a part of HF is used for the fluorination of chromium oxide. The XPS analysis of fluorinated catalysts with HF gives surface fluorine atomic contents which correspond to a F/Cr ratio of 0.36. A survey of the effect of partial pressures of HF and of CF3CH2Cl shows a zero order for HF and a 0.6 order for CF3CH2Cl. The fluorination reaction could occur on a partially fluorinated chromium(III) oxide involving HF oligomer species previously postulated by Rowley et al. [L. Rowley, J. Thomson, G. Webb and J.M. Winfield, Appl. Catal. A, 79 (1991) 89–103].

E. Colnay

Papers

Catalytic gas-phase fluorination of 1,1,1-trifluoro-2-chloroethane over chromium (III) oxide: Preparation of hydrofluoroalkanes