999-65-5

This work reports the production of di-n-butyl ether (DNBE) by means of 1-butanol dehydration in the liquid phase on acidic ion-exchange resins. Dehydration experiments were performed at 150 °C and 40 bar on 13 styrene-codivinylbenzene ion exchangers of different morphology. By comparing 1-butanol conversions to DNBE and initial reaction rates it is concluded that oversulfonated resins are the most active catalysts for 1-butanol dehydration reaction whereas gel-type resins that swell significantly in the reaction medium as well as the macroreticular thermostable resin Amberlyst 70 are the most selective to DNBE. The highest DNBE yield was achieved on Amberlyst 36. The influence of typical 1-butanol impurities on the dehydration reaction were also investigated showing that the presence of 2-methyl-1-propanol (isobutanol) enhances the formation of branched ethers such as 1-(1-methylpropoxy) butane and 1-(2-methylpropoxy) butane, whereas the presence of ethanol and acetone yields ethyl butyl ether and, to a much lesser extent, diethyl ether.

We report a new continuous method for forming ethers, acetals and ketals using solid acid catalysts, DELOXAN ASP or AMBERLYST 15, and supercritical fluid solvents. In the case of ether formation, we observe a high selectivity for linear alkyl ethers with little rearrangement to give branched ethers. Such rearrangement is common in conventional syntheses. Our approach is effective for a range of n-alcohols up to n-octanol and also for the secondary alcohol 2-propanol. In the reaction of phenol with an alkylating agent, the continuous reaction can be tuned to give preferential O- or C- alkylation with up to 49% O-alkylation with supercritical propene. We also investigate the synthesis of a range of cyclic ethers and show an improved method for the synthesis of THF from 1,4-butandiol under very mild conditions.

This study of the catalytic dehydration of n-butanol on zeolite H-ZSM-5 and amorphous aluminosilicate confirms the reaction scheme proposed earlier by the authors for isobutanol dehydration. The rate constant for n-butanol dehydration on H-ZSM-5 (determined from in situ FTIR kinetic studies by monitoring the growth of the water deformation peak at 1640 cm-1) is shown to be the true dehydration rate constant (1.7*10-4 s-1 at 100 deg C). On the other hand, the rate constants determined from GC steady-state kinetic studies (temperature interval 105-185 deg C) are effective ones, giving activation energies of 22+/-2 kcal/mol and 33+/-2 kcal/mol for complete dehydration and dehydration to butene only, respectively. By studying the dehydration reaction under different conditions (flow and static reactors, steady-state and non-steady-state regimes) and on samples with rather similar acid strengths but different porous systems (H-ZSM-5-microporous channels with diameter ca. 5.5 Angstroem, and amorphous aluminosilicate-pores of average diameter ca. 50 Angstroem), it was shown that depending on the concentration of butanol in the immediate vicinity of the active alkoxide intermediate -OC4H9, different reaction paths are utilized. High concentrations of alcohol favor ether formation, whereas low ones favour butene. This also explains the so-called "stop effect" observed in GC experiments, where an increase in the rate of butene formation occurs when the flow of alcohol is stopped and replaced with a flow of pure helium. Here, decreasing the concentration of alcohol in the micropores results in more of the alkoxide intermediate transforming to butene rather than to ether (which was the case at steady state).

Aliphatic primary alcohols, when intercalated in certain ion-exchanged montmorillonites, react preferentially via an intermolecular nucleophilic displacement of water to give high yields of di-(alk-1-yl) ethers, rather than the competitive intramolecular dehydration to alkenes; an essentially similar process yields polymeric material, poly(phenylenemethylene), from benzyl alcohol, but aliphatic secondary and tertiary alcohols, in contrast, yield alkenes almost exclusively.