Fluoride complexes with

Perchloric acid (HCIO4 Ho —13.0), fluorosulfuric acid (HSO3F Ho — 15.1), and trifluoromethanesulfonic acid (CF3SO3H Ho —14.1) are considered to be superacids, as is truly anhydrous hydrogen fluoride. Complexing with Lewis acidic metal fluorides of higher valence, such as antimony, tantalum, or niobium pentafluoride, greatly enhances the acidity of all these acids. 

UOP in a joint venture with ChevronTexaco developed an additive technology named Alkad . The additive is based on HF salts of amines, which form liquid onium polyhydrogen fluoride complexes with HF, reducing the vapor pressure of the catalyst 65% to more than 80% aerosol reduction is claimed with this additive. As in the ReVap technology, additional separation columns have to be installed. Both additives are claimed to increase the product octane number, especially when propene, isobutylene, and pentenes are employed in the feedstock. 

A CE determination of fluoride in rain water was compared with IC and ISE potentiometry the IC response was related to the total concentration, whereas CE and ISE responded to free fluoride [50]. The fluoride concentrations obtained by CE and ISE were systematically lower than those obtained by IC due to the fluoride complexation with aluminium. The detection limits for IC and ISE were similar (0.2 and 0.3 pmol/l) and somewhat lower than those for CE (0.6 xmol/l). CE was evaluated as an alternative method to the EPA ion chromatographic method for the determination of anions in water and a better resolution and a shorter analysis time were found for CE [51]. 

Pyridinium poly(hydrogen fluoride) (PPHF), which serves as an HF equivalent catalyst with decreased volatility,159 showed similar characteristics in liquid CO2.158 Other liquid amine poly (hydrogen fluoride) complexes with high (22 1) HF/amine ratios are also effective catalysts in the alkylation of isobutane with butenes and, at the same time, also act as ionic liquid solvents.160 Likewise the solid poly(ethyleneimine)/ HF and poly(4-vinylpyridinium)/HF (1 24) complexes have proved to be efficient catalysts affording excellent yields of high-octane alkylates with research octane numbers up to 94. 

Paushkin and Topchiev also used H3P()4-BF3 at room temperature to alkylate benzene with olefins (287,402). For alkylation of benzene with alcohols, temperatures of 90-97° and a feed mole ratio of 0.5 alcohol 1.0 benzene 0.5 catalyst were recommended (394). In a recent study (400a) these authors supplemented their previously published views (396) concerning the properties of boron fluoride complexes with phosphoric acid, alcohols, and sulfuric acid as catalysts. Data on the electroconductivity of these catalysts was correlated with their activity in alkylation of isobutane and it was concluded (400a) that the acid ion concentration did not affect the alkylation or polymerization reactions over these catalysts, and therefore the carbonium ion mechanism was not applicable. 

Roberson, C. E., and Barnes, R. B. Stability of fluoride complex with silica and its distribution in natural water systems. Chem. Geol. 21, 239-256 (1978). 

Fluoride ion (F ) from ammonium fluoride complex with aluminium (AP +) and ferric (Fe+++) in acid solution in the form of double fluoride with consequent release of phosphorus held in the soil by these trivalent ions... 

The complexing of zirconium and hafnium ions by fluoride ions is quite extensive compared to chloro complexing, while complex ion formation w ith bromide and iodide ions is negligible. Formation constants for fluoride complexing with zirconium(IV) and hafnium(IV) calculated from the data of Connick (126), Buslaev (94), and Hume (574), have been summarized graphically by Goldstein (213). Slightly different values have been published by Bukhsh (92). Noren (15a, 401-403) has redetermined the equilibrium constants for the reaction. 

Further procedures are based on a discoloration of organic dyes with zir-conium(IV) salts (zirconium-eriochromcyanine R), leading to the formation of a blue fluoride complex with trivalent lanthane and alizarine complexone, or they depend on the measurement with a fluoride ion selective electrode based on lanthanum fluoride [18]. 

Fig. 11. The molar refractivity and cell volume of lithium fluoride complexes with the smaller lanthanide trifluorides. Courtesy of the Am. Chem. Soc.

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