Reactions at elevated pressures

To our knowledge, the first published report of a photocatal-ytic reaction at elevated pressure was W. Strohmeyer1s hydrogenation of 1,3-cyclohexadiene under hydrogen at 10 atm /22/. On photolysis, the iridium complex 8 formed a very active catalyst, probably by dissociation of a phosphine ligand (Equation 17). At 70 C, with hydrogen at 10 atm, and a catalyst/substrate ratio of 1/100,000, the activity was 196 per minute and the turnover number was 96,000 mol of product/mol catalyst. 

Fig. 1. An ultrahigh vacuum apparatus for studying single crystal catalysts before and after reaction at elevated pressures.

General Motivations for Studies of Ionic Reactions at Elevated Pressures. . . 221... 

II. GENERAL MOTIVATIONS FOR STUDIES OF IONIC REACTIONS AT ELEVATED PRESSURES... 

In the foregoing examples of reactions that occur at approximately 1 bar, the reactants and products are for practical purposes in their standard states. For reactions at elevated pressures, this is not the case, and additional calculations are required to take into account the effect of pressure on the heat effects of reaction. The method of doing this is considered in Chap. 6. Suffice it to say at this point that the effect of pressure on the heat of reaction is usually small compared with the effect of temperature. 

Htittinger, K.J. Merdes, W.F. (1992). The carbon-steam reaction at elevated pressure formations of product gases and hydrogen inhibitions, Carbon, Vol. 30, No. 6, pp. 883-894. 

J. H. Futrell, T. O. Tiernan, F. P. Abramson, and C D. Miller, Modification of a time-of-flight mass spectrometer for investigation of ion-molecule reactions at elevated pressures. Rev. Sci. Instr. 39, 340-345 (1968). 

This chapter deals with ion clusters, clustering reactions, and equilibria studied by mass spectrometric detection of ions escaping from ion sources at pressures above 1 Torn Many of the phenomena encountered in this pressure range have significance beyond the study of ion clusters. Some such features of general importance to ion-molecule reactions at elevated pressures are also included in the discussion. 

It is found that the undesired dissociation process is suppressed by carrying out the reaction at elevated pressure (up to 6.08x 10 Pa) along with the enhancement of the rate of desired reaction [7]. In selected cases enantiomeric efficiencies approaching 100% are achieved. Acetophenone is reduced in 3 days with 100% ee at 2.03x10 Pa (Table 26.3) [8] and in less than 24 h at 6.08x10 Pa. 

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