Hydrogen fluoride, liquid alkylation

The alkylation of paraSins with olefins to yield higher molecular weight branched-chain paraffins may be carried out thermally or catalyt-ically. The catalysts for the reaction fall into two principal classes, both of which may be referred to as acid-acting catalysts (1) anhydrous halides of the Friedel-Crafts type and (2) acids. Representatives of the first type are aluminum chloride, aluminum bromide, zirconium chloride, and boron fluoride gaseous hydrogen halides serve as promoters for these catalysts. The chief acid catalysts are concentrated sulfuric acid and liquid hydrogen fluoride. Catalytic alkylations are carried out under sufficient pressure to keep at least part of the reactants in the liquid phase. 

The determination of fluorine in various liquid and gaseous hydrocarbons is vital at many points in the refining process primarily in any blend component that has been sourced fiom the hydrogen fluoride (HF) Alkylation Unit. Fluorinated compounds poison process catalysts therefore, it is essential that process feeds be as free of fluorine as possible. As an example, butane is used to produce methyl tertiary-butyl ether (MTBE). The butane must be fluorine free prior to butane isomerization to prevent the poisoning of the process catalyst, fri addition, any HF acid or its combustion products may be extremely destructive in any environment. Therefore, any finished hydrocarbon product or synthesized material that is utilized in the presence of sufficient heat (i.e., car engine), such as frel and lubricating oils, must be free of fluoride. 

Detal [Detergent alkylation] A process for making detergent alkylate, i.e., alkyl aromatic hydrocarbons such as linear alkyl benzenes, as intermediates for the manufacture of detergents, by reacting C10-C13 olefins with benzene in a fixed bed of an acid catalyst. Developed by UOP and CEPSA as a replacement for their Detergent Alkylate process, which uses liquid hydrogen fluoride as the catalyst. Demonstrated in a pilot plant in 1991 and first commercialized in Canada in 1996. Offered by UOP. 

Aromatic Compounds with Sulfides and Mercaptans. Alkyl sulfides and mercaptans function very similarly to ethers and alcohols. Hydrogen sulfide is produced and it escapes as a gas not being significantly soluble in liquid hydrogen fluoride. In this respect the technique of procedure is similar to that used for alkyl halides. 

The oxidative fluorination of C-H bonds of the side chain in toluene l43 and ethylbenzene derivatives 4 has been reported.45 4fi These alkyl aromatics bearing electronegative substituents are cleanly fluorinated on the alkyl group in liquid hydrogen fluoride in the presence of lead(IV) oxide,45 nickel(IV) oxide,45 silver(II) fluoride,46 cobalt(III) fluoride,46 or cobalt(III) acetate.46... 

Concentrated sulfuric acid and hydrogen fluoride are still mainly used in commercial isoalkane-alkene alkylation processes.353 Because of the difficulties associated with these liquid acid catalysts (see Section 5.1.1), considerable research efforts are still devoted to find suitable solid acid catalysts for replacement.354-356 Various large-pore zeolites, mainly X and Y, and more recently zeolite Beta were studied in this reaction. Considering the reaction scheme [(Eqs (5.3)—(5.5) and Scheme 5.1)] it is obvious that the large-pore zeolitic structure is a prerequisite, since many of the reaction steps involve bimolecular bulky intermediates. In addition, the fast and easy desorption of highly branched bulky products, such as trimethylpentanes, also requires sufficient and adequate pore size. Experiments showed that even with large-pore zeolite Y, alkylation is severely diffusion limited under liquid-phase conditions.357... 

Pyridinium polyhydrogen fluoride and related polyhydrogen fluorides were developed as a modified liquid complex of anhydrous hydrogen fluoride for fluor-ination reactions.39 These complexes are ionic liquids. It was subsequently found40 that such ionic liquids with higher complexed HF content are advantageous reactions media for alkylation and other reactions. 

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. 

Two reports demonstrate that Bronsted (Olah et al., 1999) or Lewis acids (Oakes et al., 1999) may be more reactive in sc C02 than in organic solvents. The isobutane-isobutylene alkylation (eq. 2.2), which is used commercially to increase the octane numbers in automotive fuels, has been demonstrated to occur in sc C02 with several liquid acid catalysts (Olah et al., 1999). Increased selectivity for Cg-alkylates is observed in sc C02 relative to neat acid media when anhydrous HF, pyridine poly(hydrogen fluoride) (PPHF),... 

Alkylation is accomplished by using either of two catalysts (1) hydrogen fluoride and (2) sulfuric acid. In the alkylation process using liquid hydrogen fluoride (Fig. 1), the acid can be used repeatedly, and there is virtually no acid-disposal problem. The acid/hydrocarbon ratio in the contactor is 2 1 and temperature ranges from 15 to 35°C can be maintained since no refrigeration is necessary. The anhydrous hydrofluoric acid is regenerated by distillation with sufficient pressure to maintain the reactants in the liquid phase. 

CAS 55-91-4. [(CH3)2CHO]2POF. Oily liquid, forms hydrogen fluoride in the presence of moisture. One member of a series of compounds, the fluorophosphate alkyl esters, characterized by extremely high toxicity, marked mitotic effects noted even in concentrations that are chemically undetectable. 

Olah GA, Mathew T, Goeppert A et al (2005) Ionic liquid and solid HF equivalent amine-poly(hydrogen fluoride) complexes effecting efficient environmentally friendly isobutane-isobutylene alkylation. J Am Chem Soc 127 5964—5969... 

This chapter continues the discussion of the use of solid reagents to minimize exposure to hazardous reagents, to make workups easier, and to minimize waste. Liquid acids are also corrosive, may be difficult to recycle for repeated use, and may show low activity or selectivity in some reactions.1 Large amounts of sulfuric acid and hydrogen fluoride are used in petroleum refining for the alkylation of isobutane with olefins to produce high-octane gasoline.2 A typical reaction of this type (6.1) is shown. 

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