Activation and deactivation phenomena commonly observed in the case of slurry or gas phase ethylene polymerization kinetics are associated to molecular aspects of the formation and inhibition of active centers. As a preliminary study of the problem, we have to identify what step during the formation or action of the active centers is concerned by the well-known activating agents: temperature, ethylene pressure and a-olefins addition. They all lead to an irreversible increase in the polymerization rate, which can be attributed to the creation of new active centers. Hydrogen was also considered, since it is an activator for propene polymerization, but it deactivates ethylene polymerization. This deactivation is often partially reversible. Different explanations of this complex behaviour are presented. 0 1993, Hiithig & Wepf Verlag, Basel CCC 0025-1 16X/93/$05.00

SUMMARY: The catalytic system Ti(OBu) 4 in combination with methylaluminoxane (MAO) was tested for the syndiospecific polymerization of styrene. A comparison was established between this homogeneous catalytic system and the same one supported on silica or alumina. An attempt was made to introduce a "tether" between the support and the active species to enhance both productivity and syndiospecificity. These tethers consisted of diols with different lengths. At last, the catalytic system Zr(OBu) 4 was supported on silica or alumina with MAO as a cocatalyst and was tested under the same conditions as other catalysts. This study reveals that Ti(OBu) 4 supported on silica enhances the productivity and leads to higher molecular weights, while the addition of a diol does not result in any enhancement compared to the silica-supported catalyst. On the contrary, alumina alone does not seem to be a good support for Ti(OBu) 4 , while introducing a short diol such as ethylene glycol leads to a great enhancement of both productivity and syndiospecificity. As reported in the literature, Zr(OBu) 4 always leads to much lower productivities than Ti(OBu) 4 .

To optimize yields, the study of reaction kinetics related to the synthesis of 2-hydroxyethylhydrazine (HEH) obtained from the alkylation of N 2 H 4 by 2-chloroethanol (CletOH) was carried out with and without sodium hydroxide. In both cases, the main reaction of HEH formation was followed by a consecutive, parallel reaction of HEH alkylation (or dialkylation of N 2 H 4 ), leading to the formation of two isomers: 1,1-di(hydroxyethyl)hydrazine and 1,2-di(hydroxyethyl)hydrazine. In this study, hydrazine and hydroxyalkylhydrazine alkylations followed S N 2 reactions triggered directly by CletOH or indirectly in the presence of a strong base by ethylene oxide, an intermediate compound. The kinetics was studied in diluted mediums by quantifying HEH and CletOH by gas chromatography and gas chromatography coupled with mass spectrometry (GC-MS). The activation parameters of each reaction and the influence of a strong base present in the medium on the reaction mechanisms were established. A global mathematical treatment was applied for each alternative. It allowed modeling the reactions as a function of reagent concentrations and temperature. In the case of direct alkylation by CletOH, simulation was established for semi-batch and batch syntheses and was confirmed in experiments for concentrated mediums (1.0 M ≤ [CletOH] 0 ≤ 3.2 M and 15.7 M ≤ [N 2 H 4 ] 0 ≤ 18.8 M). Simulation therefore permits the prediction of the instantaneous concentration of reagents and products, in particular ethylene oxide concentration in the case of indirect alkylation, which must be as weak as possible.

EXPERIMENTAL PARTReagents Water was passed through an ion exchange resin. All the salts used (NaOH, Na 2 SO 4 , Na 2 SO 4 ⋅ 10H 2 O, BaCl 2 , Na 2 HPO 4 and KH 2 PO 4 ) were products of reagent grade (99%) purity (Chimie plus, Merck and Acros).Samples of Hydroxylamine O Sulfonique Acid (HOSA) were of reagent (97%) grade purity supplied by ISOCHEM and Aldrich. Piperidine (PP) and N aminopiperidine (NAPP) were supplied by Aldrich, with reagent grade purities of 99 and 97% respectively. Azopiperidine (TTZ) was produced by oxidation of NAPP by HOSA. It was prepared at 20°C with a pH 13.7 ([NaOH] = 0.5 mol/l) by mixing two 100 mL aqueous solutions of HOSA and NAPP. A white prod uct precipitated, which was filtered, washed with cold water (5°C), and then dried under low pressure. AnalysesNaOH and piperidine concentrations were deter mined, by using an automatic titration apparatus, Metrohm Titrino 702 SM, with a glass electrode (ref erence: calomel electrode, KCl saturated solution).Abstract-A new route to synthesize N aminopiperidine (NAPP) from hydroxylamine O sulfonique acid (HOSA) and piperidine was described. Kinetics of the reaction was investigated to optimize the conditions of the synthesis. Since the reaction is fast, this study was carried out in a diluted medium (10 -3 to 10 -2 mol/l).To determine the concentration of the reaction product, NAPP was allowed to react with formaldehyde and the product was analysed by UV and HPLC techniques. The formation of NAPP is consistent with the first order reaction to two reagents, governed by the nucleophilic substitution via SN2 mechanism. Oxidation of NAPP by HOSA was identified as the main secondary reaction which consistently reduced the yield of NAPP. A number of differential equations were elaborated and solution of these equations serves to predict the behavior of the system as a function of the reagent concentrations, pH and temperature. From the corre sponding mathematical treatment a unique implicit expression was derived that characterizes the reaction medium. It was found that the [PP] 0 /[HOSA] 0 molar ratio (p), the initial concentrations of [PP] 0 and [HOSA] 0 , the ratio of rate constants k 2 /k 1 and temperature are the only parameters that affect the yield of NAPP from HOSA. The results calculated from this model are in good agreement with the experimental data and they can be used to determine the optimal conditions of the reaction.