Autoclave experiments, methods

From a computerized study, optimized reactor designs have been proposed. One point that may profitably be considered, even in laboratory autoclave experiments, is the proposal that the most convenient method of maintaining a constant polymerization temperature consists of heating the reaction system rapidly to initiate the polymerization, then applying cooling as soon as the reaction has been initiated. Presumably, toward the end of the process, additional heating may be needed to complete the conversion [96]. 

Methods and procedures employed with in-pile tests. In-pile investigations were carried out with autoclaves and loops (described in Article 5-2.2). A majority of the autoclave experiments and all the loop experiments were conducted in the Low Intensity Test Reactor at ORXL. The maximum thermal-neutron flux available for these experiments was about 2 X 10 neutrons/(cm )(sec). 

The British Pharmacopoeia (1993) recognizes five methods for the sterilization of pharmaceutical products. These are (i) dry heat (ii) heating in an autoclave (steam sterilization) (iii) filtration (iv) ethylene oxide gas and (v) gamma or electron radiation. In addition, other approaches involving steam and formaldehyde and ultraviolet (UV) light have evolved for use in certain situations. For each method, the possible permutations of exposure conditions are numerous, but experience and product stability... 

When drug solutions and containers can withstand autoclaving conditions, this method is preferred to other sterilization methods because moist heat sterilizes quickly and inexpensively. However, judgment must be exercised and experiments run to ensure that the solution and container are permeable to steam. Oils and tightly closed containers, for example, are not normally sterilizable by steam. 

With autoclave syntheses a high yield of clusters is achieved, and it is possible for researchers to follow the reaction path in solution by gradually changing (from experiment to experiment) the working parameters of the synthesis (temperature, pressure, exposure at working temperatures, etc). All these advantages of the autoclave technique have resulted in an abundance of new forms of technetium clusters (particularly, polynuclear ones) because it has been possible to develop and improve the method of obtaining these compounds. 

It was found [9,49] that all the postulates enumerated above are satisfied by the autoclave method for the reduction of technetious acid in concentrated hydrogen halide solutions by molecular hydrogen under a pressure of 3-5 MPa at 140-220 °C. A series of experiments showed that the final product of the reduction of H [TcOJ under these conditions is a mixture of outwardly similar crystalline substances with similar physico-chemical properties. The composition of the mixture can be described by the general overall formula [TcXi,s o.3 m(H20, OH , H30+)] , where X = I or Br and n > 2.8... 

Experiments were performed in a 125 ml stainless steel rocking autoclave. Co2(CO)8 (12), (S)-(+)-PMePrPh (13, 14) and (S)-(-)-PMePh(CH2Ph) (13, 14) were prepared according to published methods, all other reagents were laboratory grade chemicals. 

The reaction is carried out in vapour phase (250°C) using a flow system (see methods section). This procedure turned out to be essential in order to mantain the hydrogen transfer as the main reaction pathway. A batch experiment carried out in an autoclave actually showed a wide range of condensation products besides some saturated ketone [6]. Reactions of ketones over oxide catalysts can lead to a variety of products due inter alia to aldol condensation, intramolecular dehydration and intermolecular disproportionation [16]. However, the presence of a good hydrogen donor such as a secondary alcohol and vapour phase conditions favour the transfer hydrogenation as the major reaction [16,17]. In our reaction conditions, products attributable to crotonic condensations and subsequent 1,4 Michael addition [18] were observed by g.l.c.-m.s. (Table 1). 

Experiments were performed in Teflon-lined titanium autoclaves, submerged in a thermostated oil bath. The supernatant liquors were analyzed using atomic absorption spectrometry. Solid residues were washed with water, dried and examined by the following surface analytical methods ... 

In our present work we performed the experiments with a static method similar to Jay et al. [17, 18]. The main part of our apparatus is a high-pressure autoclave with two sapphire windows and magnetic stirring [6-10, 14], A detailed description has already been published [9],... 

Basic experiments were carried out with an extractor in analytical scale (SFE-703, DIONEX). For a typical experiment the extraction cells (10 ml internal volume) were fully filled with a homogeneous mixture of the flame retardent and the inert MgS04 and placed into the oven chamber of the extractor. After reaching the desired extraction conditions (pressures of 250 to 500 bar and temperatures of 60, 80 or 100 °C) the samples were extracted for 45 min. The extracted components were analysed by gravimetric, spectroscopic and/or chromatographic methods (IR, GC-MSD). Further experiments were made with realistic brominated ABS composites (granulated composites) in analytical scale and also with an extraction autoclave in laboratary scale (500 ml internal volume). 

The experimental program for the kinetic study comprised only 17 experiments altogether, but the formal program was not started until the ability to obtain quality data had been established. This meant that we had fine-tuned analytical methods and experimental procedures so that good material balances could be obtained routinely at any desired reaction conditions. Also, by the time the formal program was started, the catalyst activity in the autoclave had declined to a relatively constant level from the hyperactivity characteristic of new hydrogenation catalysts. 

In this report we will describe the use of variable temperature MASNMR spectroscopy to follow the crystallization of the aluminophosphate, VPI-5. The results of the in-situ experiments are compared to those obtained for VPI-5 S3mthesized in autoclaves by traditional methods. 

If secondary and tertiary amines are desired, only 2 to 3 moles of ammonia are used. Aqueous ammonia does not react to any extent at room temperature, owing to the immiscibility of halide and water. Industrially, aqueous ammonia is used and heated in an autoclave under pressure. Tertiary halides, as, for example, tert-butyl and tert- m.y bromides, do not yield amines, but yield olefines almost exclusively. The object of the present experiment is to illustrate the ammonolysis of alkyl halides. The ammonolysis of aryl halides cannot be easily accomplished in the laboratory, as it involves the use of high pressure, and temperatures of about 200°. Industrially the method is practical. 

Applying modification of substances having different chemical nature and different methods to deposit their pyrolysis products one can obtain adsorbents with differentiated surface properties and thus showing different chromatographic resolution abilities. The data in Table 7 and Figs. 17 20 confirm this statement. Figs. 17-20 show adsorption isotherms while Table 7 lists characteristic data of n-heptane and chloroform adsorption on Adsorbent Y as well as on the same adsorbent but modified with n-heptanol in an autoclave and in a rotary reactor. Similarly to the experiments described in papers... 

All reactions were carried out in a thermostated, magnetically stirred 50 ml autoclave (baffles, two thermocouples, X-shaped stirrer, 1=25 mm, max. 900 rpm). A reservoir and a pressure regulator allowed experiments to be carried out under isobaric conditions, p and T in the autoclave and in the reservoir were recorded every 10 s. Usually, the reactions were stopped after 10 min corresponding to conversions of 10 - 50%. Conversion and e.e. were determined by GLC-analysis of the crude reaction mixture (30 m capillary 3-Dex 100, 75°C). In all experiments with HCd modifier, the R-enantiomer was the major enantiomer. The initial rates of hydrogenation were calculated with a linear least square method from the pressure drop in the reservoir, accounting for the compressibility of hydrogen. In all series, one experiment was carried out without modifier to determine k (see below). 

In a standard experiment 100 mg catalyst (5wt% Pt salen USY modified with salen according to methods a or b 5wt% salen AI2O3), 4 ml n-hexane and 2 ml substrate (methylpyruvate or methylacetoacetate) were introduced into a 75 ml autoclave. This mixture was heated at 60 °C with a pressure of 70 bar for 17hrs. 

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