Molecular Structure of Conjunct Polymers.

Isobutane Alkylation Catalyzed by H2SO4: Effect of H2SO4 Acid Impurities on Alkylate Distribution

“…The single most characteristic property of ASO is the UV absorption spectra . UV absorption spectra could provide some basic information on the compounds present in ASO by providing some finer details of structures.…”

“…On the basis of the UV absorption spectra of lines 1–3, we concluded that the structures of the typical molecules of ASO are five-membered-ring or six-membered-ring hydrocarbons with two conjugated double bonds. They may simultaneously have concurrent complicated structures including conjugated dienes, homoannular dienes, exocyclic double bonds, and substituents such as alkyl, acyl, and ring residue. ,− As is visible from the UV absorption spectra of lines 4–6 for the ASO + H 2 SO 4 sample, use of H 2 SO 4 as solvent obviously shifted the absorption maximum in the direction of longer wavelengths (called a bathochromic shift) and increased the absorbance (called a hyperchromic effect). Such phenomena may also be due to the reactions between ASO and H 2 SO 4 (the reactions have been observed between ASO and trifluoromethanesulfonic acid) …”

“…At a certain stage of alkylation, the used catalyst phase was recovered as a dark brown viscous liquid. The extraction technique for separation of ASO was similar to that reported earlier 31 and is briefly described as follows. Ice−water was slowly added to the used acid in a dilution proportion under an ice bath.…”

“…They are the main cause of side reactions and high consumption of the catalyst. Many excellent reports are available for the effects of ASO on alkylation and for the relevant reaction mechanisms. ,,− However, the detailed chemical composition of ASO is not completely known . Also, the reaction mechanisms of alkylation have not been fully understood.…”

“…33 Therefore, in this study systematic efforts were made to determine the compositions of used acids. Because a full understanding of the structures of major components of ASO is needed in defining and understanding their roles, 31 ultraviolet (UV) absorption spectra and gas chromatography−mass spectrometry (GC− MS) were used to determine the principal components of ASO. Considerable new data on the distribution, selectivity, RON, and trimethylpentane/dimethylhexane (TMP/DMH) ratio of alkylates during the cycled alkylation reactions are reported.…”