1 -butanol dehydration

The acid strength of aluminum phosphorous oxide is enhanced by the addition of SO4 up to 3 wt% Enhancement of acid strength is suggested by high catalytic activities for 1-butanol dehydration and cyclohexene skeletal isomerization. However, addition of excess S04 ions reduces the activity for the reactions. The catalytic activity of the oxide prepared from aluminum sulfate is different from those prepared from chloride and nitrate for 1-butanol dehydration equilibrium mixture of butene isomers is produced over the oxide from sulfate whereas the ratios of l-butene/2-butenes and cis/trans art larger than the equilibrium ratios over the oxides from chloride and nitrate. The catalytic behavior of the oxide from sulfate different from the other oxides is caused by the presence of a small amount of SO4 ions generating strong acid sites. 

Dehydration of alcohols proceeds over aluminum phosphorous oxides. Correlation between 1-butanol dehydration activity and amount of acid sites stronger than Ho - 1.5 has been reported. The dehydration of cis- and phosphorous oxides of different Al/P ratios. While the cis isomer is converted more extensively than the irans with all compositions, the relative amount of the two olefinic products (l-/3-methylcyclohexene) increases markedly on increase in the amount of P. The formation of 3-methylcyclohexene from either alcohol takes place on strong acid sites by the 1 process in which carbenium intermediates are involved. On the other hand, the formation of 1-mediylcydohexene takes place on pairs of acid and base sites by the 2 process. The aluminum atoms and aluminum atoms with hydroxy] groups attached function as Lewis add sites and Bransted acid sites, respectively. 

Fig. 19. Linearized initial rate plots for sec-butanol dehydration, Eqs. (80) and (81).

In this research Initiative, we have examined the potential of reactive distillation (9) for terb a/j-butanol dehydration to isobutylene using solid acid catalysis. Advantages to employing reactive distillation for reaction (1) include a) the mild operating conditions required (<120°C), b) quantitative tBA conversions per pass, and c) the option to use lower purity/lower cost, tBA feedstocks. 

Selective lertiarj-Butanol Dehydration to Isobutylene via Reactive Distillation and Solid Acid Catalysis... 

Spectra of ZrC>2-supported WOx species were recorded by Baertsch et al. (2002) after 1 h under 2-butanol dehydration conditions (0.5 kPa reactant, 323 K). The relative abundance of reduced centers was estimated from the Kubelka-Munk function in the range 1.5-3.2 eV (824—388 nm). Dehydration rates were obtained in a separate quartz reactor at 373 K. UV-vis band area and rate increased with the tungsten density up to a particular loading. Equivalent experiments with WOx/ A1203 were performed by Macht et al. (2004). A parallel increase of the initial dehydration rate at 373 K and the relative abundance of reduced centers at 423 K were pointed out. 

The condensate has two liquid phases. It runs from the condenser to a separator or decanter where the water layer is removed for discard and the solvent layer is returned, usually as reflux to the column. This reflux of all or part (the solvent layer) of the condensate after decantation, rather than part of all, was developed in 1927 (2) for acetic acid dehydration with an added solvent as entrainer and for butanol dehydration using butanol itself as the entrainer. 

Knifton, J.F. Sanderson, J.R. Stockton, M.E. Tert-butanol dehydration to isobutylene via reactive distillation. Catal. Lett. 2001, 73 (1), 55-57. 

The relative rates of olefin production and etherification have been shown to vary with reaction conditions (99-101), including temperature and contact time, and with the geometry of the catalyst pore system (99). Bryant (99) has demonstrated kinetic effects in ethanol and n-butanol dehydration that greatly favor olefin formation using a series... 

Ter-butanol dehydration and n-hexane cracking were studied on samples in H form, isobutane dehydrogenation was studied on dried samples activated in situ. Reactions were carried out on st.steel or pyrex integral, fixed bed, plug flow reactors at atmospheric pressure. Catalyst (1-2 cc) was crushed to 20-40 mesh size. On-line chromatographic analyses were carried out. Experimental conditions are outlined in Table 1. Kinetic constants were evaluated by applying eq.(1). 

The type of by-products formed depends on the alcohol and the catalyst. 1-Butanol and 2-butanol dehydration overall the catalysts produces 1-butene, 2-butene, isobutene, and dibutylether. The ether formation is favoured at the lowest temperatures, thus the selectivity towards butenes decreases with decreasing temperature. An exception is found in the dehydration of /-butanol, as selectivity is higher at higher temperatures. This is due to the great numbers of by-products formed during the first stages of the reaction at temperatures as low as 55 C, this being especially true for the Dawson-type acid. 

Characteristic features of base-catalyzed dehydration are typically observed for 2-butanol dehydration. The products consist mainly of 1-butene over rare earth oxides[20], Th02[21], and Zr02[22], This is in contrast to the preferential formation of... 

Figure PI2.8-1 contains plots of the data obtained in n-butanol dehydration trials conducted with each of these batches of catalyst at 600°F and 1 atm. Figure PI2.8-2 contains cross plots of the smoothed data in Figure P12.8-1 that indicate the dependence of the observed rate on the diameter of the catalyst beads at conversions of 7, 14, and 21%. The experimental conditions are such that the catalyst beads are at the same temperature throughout and that there are no significant temperature gradients within the fixed bed.

A survey of catalysis literature reveals that for the majority of transition metal oxide catalyzed reactions, maximum TOFs most frequently correlate with maxima in polymeric surface species content. A limited subset of examples includes WO /ZrOj for o-xylene isomerization [33], n-pentane isomerization [29], and 2-butanol dehydration [34] MoO /AljOj and VO /AljOj for dimethyl ether oxidation [35] MoO /AljOj for propane oxidative dehydrogenation [36] andMoO, supported on TiOj, ZrOj, AljOj, and NbjOs for methanol oxidation [37]. 

FIGURE 11.12 Initial 2-butanol dehydration rates over WO /ZrOj [34],... 

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