Hydrofluoric acid-Boron trifluoride

Acid mixtures containing nitric acid and a strong acid, eg, sulfuric acid, perchloric acid, selenic acid, hydrofluoric acid, boron trifluoride, or an ion-exchange resin containing sulfonic acid groups, can be used as the nitrating feedstock for ionic nitrations. These strong acids are catalysts that result in the formation of nitronium ions, NO" 2- Sulfuric acid is almost always used industrially since it is both effective and relatively inexpensive. 

Important aviation and motor alkylate gasoline processes are the jet-type sulfuric acid process, the Kellogg sulfuric acid autoref rigeration process, the UOP hydrofluoric acid process, and the Stratford effluent refrigeration process. Petrochemical alkylation includes various processes using as catalysts solid phosphoric acid, aluminum chloride, hydrofluoric acid, boron trifluoride, and phenol and ether complexes of boron trifluoride (1). 

The addition takes place according to Markownikoff s rule. The addition of carbo lic acida to the double bonds of isobutylene and trimethyl-ethylene gives tertiary esters. A true equilibrium independent of sulfuric acid concentrations is established in the exothermic reaction. The addition does not go well with ethylene, but goes well with many of the higher alkenes, particularly with some of the terpenes. To avoid the polymerizing effects of sulfuric acid, various other catalysts, such as sulfonic acids, triethylamine, hydrofluoric acid, boron trifluoride, and cuprous chloride have been used. The addition may take place at room temperature or higher and is aided by pressure. The vapors of the acid and hydrocarbon may be passed over catalysts, such as activated carbon, heteropoly acids, or metal phosphates. ... 

Hydrofluoric Acid (Boron Trifluoride Catalyst) — 6 68 176 248 -21 20 80 120 - G B B B - - plus liquid aromatic hydrocarbons (ortho-, para. and metaxylene plus ethyl benzene)... 

Also obtained by reaction of EKONOL ), an aromatic polyester as Friedel-Crafts reagent, with chlorobenzene in triflic acid solution at 25° for 18 h (28%) [922]. Similar resnlts can be obtained using hydrofluoric acid/boron trifluoride or aluminium chloride in place of triflic acid [922]. 

Preparation by reaction of m-hydroxybenzoic acid with fluorobenzene in the presence of a hydrofluoric acid/boron trifluoride mixture at r.L for 6 h into an autoclave under 30 psig of boron trifluoride (61%) [350],... 

Boron forms strong bonds to fluorine (644kJmol ), usually combining with three or four fluorides in its compounds or salts. Several binary fluorides of boron are known including boron trifluoride, BF3, a stable gas of great industrial importance as a Lewis acid. Boron trifluoride is synthesized industrially by reaction of hydrofluoric acid with borates or boric oxides (equation 42). ... 

Nitronium tetrafluoroborate was first prepared by adding a mixture of anhydrous hydrofluoric acid and boron trifluoride to a solution of dinitrogen pentoxide in nitromethane. Nitric acid can be used in place of dinitrogen pentoxide, and by replacing boron trifluoride by other Lewis-acid fluorides Olah and his co-workers prepared an extensive series of stable nitronium salts. ... 

Benzene and phthaUc anhydride may be condensed to o-benzoylbenzoic acid using hydrofluoric acid and boron trifluoride instead of anhydrous aluminum chloride (37). 

Licensors offer a variety of catalysts to promote the isomerization— silica alumina by itself or enhanced with a noble metal like platinum or a non-noble metal like chromium. Another uses hydrofluoric acid with boron trifluoride In the case of the noble metal catalytic process, the feed enters a vessel with a fixed catalyst bed at 850°F and 14.5 psi. As is often the case, a small amount of hydrogen is present to reduce the amount of coke laying down on the catalyst. The effluent is processed in a standard fashion to separate the hydrogen, the para- and ortho-xylene, and any unreacted or miscellaneous compounds. Yields of para-xylene are in the 70% range. 

Ethereal fluoboric acid can be prepared as follows 19 ml. (19 g., 0.95 mole) of anhydrous hydrofluoric acid, b.p. 19.4° (760 mm.) [Caution Hydrofluoric acid in contact with the skin produces extremely painful hums. It is therefore necessary to use eoery precaution to protect exposed parts of the body, especially the hands and eyes. Cf. Org. Syntheses, Coll. Vol. 2, 295 1943), Note 3 Org. Syntheses, 46, 10 1966), Note 1 is added in small portions with shaking or stirring to 126 ml. (142 g., 1.00 mole) of distilled boron trifluoride etherate, b.p. 126° (760 mm.), contained in a 500-ml. polyethylene flask that is cooled in an ice bath to 0°. The concentration of the resulting yellowish solution of fluoboric acid in ether is about 52% by weight ca. 6.6 moles per 1.). 

Reaction with hydrofluoric acid produces boron trifluoride, BF3. 

Reaction with hydrofluoric acid produces boron trifluoride B2O3+ 6HF —> 2BF3 -I- 3H2O... 

Boron trifluoride is prepared by treating borax with hydrofluoric acid or boric acid with ammonium bifluoride. The complex intermediate product is then treated with cold fuming sulfuric acid. 

Bartlett prepared xenon difluoride by the reaction of xenon with silver fluoride in hydrofluoric acid in the presence of boron trifluoride ... 

In carrying out the alkylation of benzene the propylene tetramer is reacted with an excess of benzene in the presence of a Friedel-Crafts catalyst such as aluminum chloride, boron trifluoride, or hydrofluoric acid. With careful control of this reaction, yields of alkylate boiling from 500° to 650° F. are of the order of 80% of theory with the losses due to slight olefin degradation and dialkylation. Inspection of commercial aromatic products, believed to be typical of this process, indicates the composition to be that shown in... 

In their studies of conductance of the methylbenzenes in anhydrous hydrofluoric acid, Kilpatrick and Luborsky (96) found that the specific conductance of solutions of prehnitene and durene changed with time, and additional experiments indicated this was due to rearrangement toward isodurene. It should be noted that the symmetrical configuration 1,2,4,5- is the strongest base of the three tetramethylbenzenes. The concentration and stability of the ArH+ ions are the important factors in the isomerization. With the xylenes and trimethylbenzenes in anhydrous hydrofluoric acid, no reaction was observed at 20°, but isomerization did take place upon addition of boron trifluoride. This is interpreted to be due to an increase in the concentration of ArH+ by the reaction... 

By adjusting the amount of boron trifluoride, introduced in gaseous form in hydrofluoric acid in contact with the organic phase, it is therefore possible to extract the m-xylene from an aromatic Cs cut after agitation. The HF — BF3 solvent is also an isomerization catalyst whose activity is related to the operating conditions, so that the combination of extraction and isomerization (see Section 4.4.22) offers a number of economic advantages. 

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