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We present a methodology that allows us to extract quantitative information from EXAFS data collected on complex samples where the absorbing species is present in more than one phase. We have chosen as our case study the CuCl2/Al2O3 material, which represents the basic catalyst for the ethylene oxychlorination reaction (a fundamental intermediate step in PVC production). In previous studies [J. Catal. 2000, 189, 91, and J. Catal. 2000, 189, 105], it has been shown that three different copper species are present on CuCl2/Al2O3a Cu-aluminate phase, a highly dispersed copper chloride phase, and an aggregated paratacamite (Cu2(OH)3Cl) phase, whose relative fraction depends on copper loading, sample aging, and heating conditions. In this work, we extract from the EXAFS spectra the fraction of the three phases on a quantitative ground. A study of the corresponding XANES spectra allows us to qualitatively support the EXAFS results. This methodology represents a generalization of the standard EXAFS procedure that can be of general interest in all cases where more than one phase is present on the sample.

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Almost all of the world production of vinyl chloride today is based on cracking of 1,2-dichloroethane. For many decades, this compound has been produced by catalytic oxychlorination of ethylene with hydrochloric acid and oxygen [Eq. (1)]. The reaction is performed at 490 ± 530 K and 5 ± 6 atm (1 atm % 1.01 Â 10 5 Pa) using both air and oxygen in fluid-or fixed-bed reactors. [1] C 2 H 4 2 HCl 1 ³2O 2 3 C 2 H 4 Cl 2 H 2 O(1) 24 h, then cooled to 0 8C, and quenched with aqueous hydrochloric acid (3 m, 5 mL). The resulting mixture was warmed to 23 8C and stirred for 30 min, at which point aqueous sodium hydroxide (3 m, 10 mL) was added. The mixture was stirred at 23 8C for 30 min and extracted with diethyl ether (3 Â 20 mL). The combined organic layers were dried over anhydrous sodium sulfate, filtered, and concentrated in vacuo. Column chromatography on silica gel eluting with 30 % diethyl ether in pentane afforded (R)-2-ethyl-2-methyl-2,3-dihydrocinnamyl alcohol 5 a (239 mg, 1.34 mmol, 96 %) as a colorless oil. 1 H NMR (CDCl 3 ): d 7.19 ± 7.31 (m, 5 H), 3.33 (s, 2 H), 2.61 (AB, 2 H, J 24.6 Hz), 1.58 (bs, 1 H), 1.27 ± 1.40 (m, 2 H), 0.93 (t, 3 H, J 7.5 Hz), 0.82 ppm (s, 3 H); 13 C NMR (CDCl 3 ): d 139.0, 130.8, 128.1, 126.2, 68.4, 42.8, 39.1, 29.1, 21.0, 8.3 ppm. High-resolution FAB-MS: m/z (MH): 179.14359 (C 12 H 19 O requires 179.14359).[a] 25 D À 5.9 (c 14.2, CH 2 Cl 2 ). The product was determined to have 94 % ee by HPLC (Chiralcel OD column, eluting with 1 % 2-propanol in hexanes at 0.7 mL min À1 ; R t 20.5 min (major enantiomer), 22.8 min (minor enantiomer)).[21] Greater than two equivalents of electrophile must be added, as the Sand C-alkylations occur at similar rates.[22] The reasons for this dichotomous behavior are unclear. We have been unable to detect significant E/Z isomerization under the reaction conditions. Other effects such as aggregation state and/or different reactive conformations of the E and Z enolates cannot be ruled out.[23] Alkylation of amide enolates with unactivated electrophiles often requires the addition of HMPA or LiCl for useful reaction rates to be observed. For examples see ref.[19] and a

Alumina supported CuCl2, the basic catalyst for ethylene oxychlorination, has been investigated by UV-Vis spectroscopy, EPR, EXAFS and XANES in a wide range (0.25-9.0 wt%) of Cu concentration. We have evidenced that, at low Cu content, the formation of a surface aluminate species takes place. The formation of this surface copper aluminate stops at 0.95 wt% Cu / 100 m2; at higher Cu concentrations excess copper chloride precipitates directly from solution during the drying step forming an highly dispersed CuCl2.H2O, phase, overlapping progressively the surface aluminate. Depletion tests and IR spectroscopy of adsorbed NO have demonstrated that the latter is the only active phase. A complete catalytic cycle has then been performed on CuCl2/Al2O3 catalyst. EPR, XANES and EXAFS, have been used to demonstrate that the ethylene oxychlorination reaction: C2H4 + 2HCl + ½ O2 --> C2H4Cl2 + H2O follows a three steps mechanism: (i) reduction of CuCl2 to CuCl (2CuCl2 + C2H4 --> C2H4Cl2 + 2CuCl), (ii) oxidation of CuCl to give an oxychloride (2CuCl + ½ O2 --> Cu2OCl2) and (iii) closure of the catalytic circle by rechlorination with HCl, restoring the original CuCl2 (Cu2OCl2 + 2HCl --> 2CuCl2 + H2O). Finally, we have shown that time resolved, in situ, spectroscopy is a very promising technique to investigate the interplay between catalyst activity and oxidation state of copper

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