Alumina-Supported Copper Chloride

Leofanti, G.; Marsella, A.; Cremaschi, B.; Garilli, M.; Zecchina, Adriano; Spoto, Giuseppe; Bordiga, Silvia; Fisicaro, P.; Berlier, Gloria; Prestipino, Carmelo; Casali, G.; Lamberti, Carlo

doi:10.1006/jcat.2001.3304

Cited by 77 publications

(106 citation statements)

References 63 publications

Supporting

Mentioning

106

Contrasting

Order By: Relevance

“…The fact that the n-CO of Cu + ◊ ◊ ◊ CO adducts formed by Family I catalysts are P CO dependent, is well known in surface science and is due to the mutual perturbation of adjacent carbonyls 57 that, in turns, testifies of Cu(I) adsorbing sites are adjacent each-other. 24 Conversely, for both K3.1Cu5.0 and Cs10.4Cu5.0 samples the n-CO value is almost pressure independent, suggesting that Cu(I) adsorbing sites are sufficiently isolated from each other and that the interaction between two Cu + ◊ ◊ ◊ CO adducts is negligible. Note again that the non complete reduction of K3.1Cu5.0 and Cs10.4Cu5.0 catalysts may be also responsible for this behaviour.…”

Section: Ir Spectroscopy Of Adsorbed Comentioning

confidence: 92%

“…In the same set of works by Leofanti et al it has been shown that the surface Cu-aluminate phase is totally inactive 23 and that the overall ethylene oxychlorination reaction (3) is catalyzed only by the CuCl 2 phase following a three steps redox mechanism: chlorination of ethylene by reduction of CuCl 2 to CuCl (4); oxidation of CuCl to an oxychloride (5) and re-chlorination with HCl (6), closure of the catalytic cycle: 24,25 2CuCl 2 + C 2 H 4 → C 2 H 4 Cl 2 + 2CuCl (4) 2CuCl + 1/2O 2 → Cu 2 OCl 2 (5)…”

Section: Introductionmentioning

confidence: 98%

See 1 more Smart Citation

Quantification of copper phases, their reducibility and dispersion in doped-CuCl2/Al2O3 catalysts for ethylene oxychlorination

Muddada

Olsbye

Leofanti³

et al. 2010

Dalton Trans.

View full text Add to dashboard Cite

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...

show abstract

Section: Ir Spectroscopy Of Adsorbed Comentioning

confidence: 92%

Section: Introductionmentioning

confidence: 98%

Quantification of copper phases, their reducibility and dispersion in doped-CuCl2/Al2O3 catalysts for ethylene oxychlorination

Muddada

Olsbye

Leofanti³

et al. 2010

Dalton Trans.

View full text Add to dashboard Cite

show abstract

“…[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). (3)], and c) re-chlorination of this oxychloride with HCl [closure of the catalytic cycle, [7,8] Eq. The mixture was stirred at 23 8C for 30 min and extracted with diethyl ether (3 Â 20 mL).…”

mentioning

confidence: 98%

“…The formation of the mixed chloride, although not detectable by XRD owing to too small crystal size, [6] is suggested by IR spectroscopy of adsorbed CO on samples previously reduced in ethylene ( Figure 3). [7,17] The difference in n Ä(CO) (2139 cm À1 for Cu5.0 and 2117 cm À1 for K3.6Cu5.0) implies that the Cu I ions on the two catalysts belong to different compounds: a totally reduced CuCl salt for sample Cu5.0 [7,17,18] and a mixed, partially reduced potassium ± copper chloride for sample K3.6Cu5.0. [7,17] The difference in n Ä(CO) (2139 cm À1 for Cu5.0 and 2117 cm À1 for K3.6Cu5.0) implies that the Cu I ions on the two catalysts belong to different compounds: a totally reduced CuCl salt for sample Cu5.0 [7,17,18] and a mixed, partially reduced potassium ± copper chloride for sample K3.6Cu5.0.…”

mentioning

confidence: 99%

The Chemistry of the Oxychlorination Catalyst: an In Situ, Time-Resolved XANES Study

et al. 2002

View full text Add to dashboard Cite

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

show abstract

“…EXAFS measurements on the high loading samples show that Cu 2+ is reduced in the presence of the ethene reagent. 13 It was also suggested that KCl can act to stabilise Cu(II)Cl 2 , making the reduction processes more challenging and switching the rate determining step for dichloroethane production from Cu(I)Cl oxidation to Cu(II)Cl 2 reduction by ethene.…”

Section: 11mentioning

confidence: 99%

Structural behaviour of copper chloride catalysts during the chlorination of CO to phosgene

et al. 2018

View full text Add to dashboard Cite

The interaction of CO with an attapulgite-supported Cu(II)Cl 2 catalyst has been examined in a micro-reactor arrangement. CO exposure to the dried, as-received catalyst at elevated temperatures leads to the formation of CO 2 as the only identifiable product.However, phosgene production can be induced by using a catalyst pre-treatment where the supported Cu(II)Cl 2 sample is exposed to a diluted stream of chlorine.Subsequent CO exposure at $370 C then leads to phosgene production. In order to investigate the origins of this atypical set of reaction characteristics, a series of X-ray absorption experiments were performed that were supplemented by DFT calculations. XANES measurements establish that at the elevated temperatures connected with phosgene formation, the catalyst is comprised of Cu + and a small amount of Cu 2+.Moreover, the data show that unique to the chlorine pre-treated sample, CO exposure at elevated temperature results in a short-lived oxidation of the copper. On the basis of calculated CO adsorption energies, DFT calculations indicate that a mixed Cu + /Cu 2+ catalyst is required to support CO chemisorption.

show abstract

Alumina-Supported Copper Chloride

Cited by 77 publications

References 63 publications

Quantification of copper phases, their reducibility and dispersion in doped-CuCl2/Al2O3 catalysts for ethylene oxychlorination

Quantification of copper phases, their reducibility and dispersion in doped-CuCl2/Al2O3 catalysts for ethylene oxychlorination

The Chemistry of the Oxychlorination Catalyst: an In Situ, Time-Resolved XANES Study

Structural behaviour of copper chloride catalysts during the chlorination of CO to phosgene

Contact Info

Product

Resources

About