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The comprehensive understanding of the composition, behaviour and reactivity of a catalyst used inside industrial plants is an extremely hard task that is rarely achieved. It requires the use of different spectroscopic techniques, applied under in situ or in operando conditions, and combined with the investigation of the catalyst activity. Often the operating experimental conditions are different from technique to technique and the different results must be compared with care. In the present contribution, we combined in situ XANES/EXAFS, IR spectroscopy of adsorbed CO, CO chemisorption and catalytic tests performed using a pulse reactor in depletive mode. This multitechnical approach resulted in the understanding of the role that dopants (LiCl, KCl, CsCl, MgCl(2) LaCl(3)) have in the nature, relative fraction, reducibility and dispersion of Cu-phases on CuCl(2)/gamma-Al(2)O(3) catalysts for oxychlorination reaction, a key step of the PVC chemistry. In the undoped catalyst two Cu phases coexist: Cu-aluminate and supported CuCl(2), being the latter the only active one [J. Catal., 2000, 189, 91]. EXAFS and XANES highlighted that all dopants contribute more or less efficiently in increasing the fraction of the active copper species, that reaches a value of almost 100% in the case of MgCl(2) or LaCl(3). EXAFS directly, and IR indirectly, proved that the addition of KCl or CsCl (and less efficiently of LiCl) results in the formation of mixed CuK(x)Cl(2+x) or CuCs(x)Cl(2+x) phases, so altering the chemical nature of the active phase. XANES spectroscopy indicates that addition of MgCl(2) or LaCl(3) does not affect the reducibility by ethylene (under static conditions) of the active CuCl(2) phase and that the reducibilility of the new copper-dopant mixed chloride are in the order CuCl(2)> CuLi(x)Cl(2+x) > CuK(x)Cl(2+x) > CuCs(x)Cl(2+x). However, when reduction is done inside a pulse reactor, a more informative picture comes out. The last technique is able to differentiate all samples, and their ability to be reduced by ethylene resulted in the order: La- > Mg- > Li-doped > undoped > K- > Cs-doped catalyst. To understand this apparent discrepancy the dispersion of the active phase, measured by CO chemisorption, was needed: it has been found that addition of LiCl increases enormously the dispersion of the active phase, LaCl(3) significantly and MgCl(2) barely, while addition of both KCl and CsCl results in a decrease of the surface area of the active phase. The mechanism of the enhancing effect of La and Mg on catalytic activity is still not clear, but it could be associated to the modification that they induce to the support surface: the Cu is so highly dispersed that almost all is in direct contact with support surface. It is finally worth noticing that the previous EXAFS and XANES study allowed us to refer the chemisorption data to the active phase only, while the IR study allowed us to fix the Cu(+)/CO surface stoichiometry. Summarizing the use of a multidisciplinary approach has been the conditio sine qua non (mandator...

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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

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