The aim of the present work is to establish some correlations between the catalytic activity of several organometallic hydrocarbon‐soluble complex systems and the electric conductivity, as a method which expresses the ionization degree of these catalyst types. The following systems were studied: Al(C2H5)3—VO(C5H7O2)2; Al(C2H5)3—Cr(C5H7O2)3, Al(C2H5)3—Co(C5H7O2)3. The catalytic activity was determined at various molar ratios of AlEt3/M(C5H7O2)n in the stereoregular polymerization reaction of acetylene, where M is a metal. The visible and ultraviolet absorption spectra of the catalysts, as well as the variation of extinctions at various AlEt3/M(C5H7O2)n molar ratios were also determined. The systems with an optimal catalytic activity also show maximum values of electric conductivity and extinctions. The composition, degree of ionization of the catalyst, and the way in which this influences the catalytic activity are also discussed.
The correlation between the catalytic activity of the system Al(C2H5)3–Ti(OC4H9)4 and its electrical conductivity in stereospecific polymerization was investigated. The activity of the catalyst was evaluated for varying molar ratios of Al/Ti (in the range of 0.75–6) and reaction temperatures (in the range of −78 to +70°C.) by means of the velocity of absorption of the acetylene. The ionic state of the catalytic complex may be assessed on the basis of electrical conductivity measurements. The electrical conductivity of the pure state of the two catalyst components is in the range of 10−12 or 10−10 (ohm‐cm.)−1 while that for the catalyst complex is of the order of 10−8 (ohm‐cm.)−1. The experimental data prove the existence of a correlation between the velocity of reaction, the composition of the catalyst complex, and the electrical conductivity. The values obtained for the activation energy of the electrical conductivity correlate with the energy required to break the complex ion aggregate of the catalyst and therefore with the activity of the catalyst.
Pd-Ho/TAlzQ catalysts exhibit higher activity for styrene hydrogenation than Pd/i'AlzQones. The addition of holmiun to Pd catalysts changes the place of the palladiun impregnation front depending on the state of the supported palladiun. As a cunsequence of the interaction between holmiun and Pd/rA1203 suppert, oxidized f m as holmiun aluninate were formed. These forms are catalytically inactive but represent adsorption centers for styrene. On holmiun m ntaining catalysts, hydrogenation takes place between the styrene adsorbed on basic centers and the hvdrogen spilled over fran palladiun particles. EXPER I ENTAL Cata lvsts preparation Ha:miLm containing catalysts were prepared by dry impregnation of either r A1203 (surface sres of 160 &/g('O)) or Pd/rA:203 obtained as previously described( ' I ) , both of them as cviindric extrudates of 3 mn dimter. The aqueous solution of Hcc13 (pH 1.5) was obtained f r m i-bz03 h r c k ) using a Hcl solution (Merck). The catalysts contain 0.1 or 0.5 %wt pa!lsd-un and i %wt holmiun. The s m l e s of Ho/TA1?03 and Pd-m/TA12@ have been dried 6 hrs at 8O'C and then reduced 1. Hicks,R.F., and Bell,A.T., J.Catal. 90, 204-221 (1984).
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