Hydrogenations hexene

Figure 20.1. Relationship between stirring rate and the initial rate of 1-hexene hydrogenation over Wilk/STA at 36°C and two hydrogen pressures.

Figure 1 Hydrogen uptake curves for 1-hexene hydrogenations run at 35°C and 50 psig of hydrogen in 10% toluene/EtOH with a stirring rate of 1700 rpm. a) AHC-Wilk catalyst b) Homogeneous Wilkinson s catalyst.

Pasadena October 23, 1989 Ethylene, isobutane, hexene, hydrogen 33 tons escaped 23 dead, 130-300 injured... 

Hydrogenation was a zero order reaction in the olefin over each catalyst up to more than 60% conversion in complete agreement with the observation of Boudart et al [11,12]. For 1-hexene hydrogenation no turnover frequency data were found over any of the transition metal catalysts and under comparable conditions. For 1-hexene initial rates were determined, because isomerization occurs over Pd [13] and the non-terminal olefins hydrogenate slower. Indeed, deuterium uptake decreased appreciably after a short initial period. A similar effect was found for Rh as well, but over Ft, no decrease in rate was observed in complete accordance what was expected [13]. The hydrogenation of both olefins showed mild structure sensitivity over Pd catalysts, with an apparent maximum in hydrogenation rate at 65% dispersion. 

A number of early transition metal compounds, e.g., Ti111 hydrides, have long been known as hydrogenation catalysts. Similarly, metallocene compounds of lanthanides and actinides can be extremely active, as a comparison of the turnover numbers of 1-hexene hydrogenations at 25°C (1 bar H2) show CpfLuH, 120,000 [Ir(COD)-(py)(PCy3)]PF6, 6400 [Rh(COD)(PPh3)2]PF6, 4000 RuHCl(PPh3)3, 3000 ... 

This result shows impressively that small changes at the ligand molecules may cause drastic effects in selectivity. The reason for the deactivation of the catalyst towards cw-2-hexene hydrogenation is still not completely understood. 

In run 270, on the crystalline catalyst of runs 267 and 271, L was 4500 the olefin ratio, 1.6 and the alkane yield, 9.2%. Here, 2-hexene hydrogenated 0.2 times as fast as methylpentene. In comparison with run 271, the yield of 4-methyl-2-pentene was slightly reduced but that of 2-methyl-2-pentene was cut nearly to 0.1 of its value in run 271. The degree of isomerization of 2-hexene was close to that in run 272 on a new sample of chromia activated at 400° in hydrogen. 

The cationic metallocene complex [Cp 2ThMe][(/x-H)(/x-CHCH2But) B(C6F5)2 ] (Scheme 62) has been reported to be a highly active catalyst for 1-hexene hydrogenation.131... 

In the presence of carbon monoxide and catalysts such as Co2(CO)s, [Co(CO)3PPh3]2 and Rh6(CO)i6, hydroformylation of alkenes was observed (Scheme 14.10). The hydrogen required for this reaction was produced from carbon monoxide via the water-gas shift reaction. This reaction seems to be catalyzed by the same catalytic species as the hydroformylation reaction. Up to 55 % hydro-forraylated products are formed from cyclohexene and 1-hexene. Hydrogenation is the main side reaction. 

The same calorimeter was used to determine the enthalpy of hydrogenation of phenylalkynes. In this case the calorimetric standard was allylbenzene, used in order to minimize the difference in reaction medium interactions for the reactant and for the standard. The kinetics of hexene hydrogenation was progressively slowed by the presence of accumulated aromatic product in the calorimeter. When allylbenzene was used as the thermochemical standard this kinetic effect did not occur. 

Table 6.4 1-Hexene hydrogenation by Pt(0) NPs isolated from BMI.BF4 (J.4nm) and re-dispersed in BMI.PF4 and those isolated from BMI.PFe (2.3 nm) and re-dispersed in BMI.BF4 at 75 °C under 6 atm of hydrogen (constant pressure) and 1-hexene/Pt = 250.

---