Sealed autoclave

This reaction [65-67] is only rarely encountered in the benzene series but is extremely useful for appropriate derivatives of naphthalene, where the mechanism of the reaction has been investigated extensively. The reaction allows a hydroxy group to be exchanged for an amino group or vice versa. When a hydroxy group is to be converted into an amino group, the naphthol is heated under pressure with ammonium bisulphite (often produced in situ by introduction of ammonia liquor and sulphur dioxide into a sealed autoclave) at a temperature of 100-150 °C the naphthol is thereby converted into the corresponding naphthylamine. The mechanism of the reaction is outlined in Scheme 4.22. 

Figure 2. The effect of dissolved Si concentration on etch pit density on quartz surfaces etched a) in sealed autoclaves for 6.5 hours, b) in a flow reactor for 6.5 hours (R5), 31.5 hours (R5SK), and 25-28 hours (R9). Reproduced with permission from Ref. 16. Copyright 1986 Pergamon Press.

Diverse biomass compounds were heated in sealed autoclaves in the presence of acids as catalyst at 200 °C for 16 h, and essentially two kinds of reaction scenarios were found. For soft biomass, nontextured biomass, hydrophilic and water-dispersible carbonaceous nanoparticles in the size range of 20-200 nm were obtained. The occurrence as spherical particles indicates that the soft biomass was first liquefied, and then carbonized, which offers possibilities to chemically interfere with this complex process as discussed above. 

Under batch conditions, methylations with DMC must necessarily be run in sealed autoclaves, given its boiling point (90°C) and the reaction temperature (>160°C). Batch methylations with DMC can be performed on a number of different substrates and, under such conditions, the reaction mechanism can be conveniently investigated in fact, the sampling of the reaction mixture at different conversions, and the identihcation of possible intermediates (see later) is easier with respect to CF-processes. For compounds that are susceptible to multiple methylation, the results are of special interest, since methylation with DMC totally inhibits multiple substimtion in both N- and C-alkylation, for primary aromatic amines and for CH2-active compounds, respectively. 

In our development studies, Endeavor (5 mL) and Buchi (IL) reactor systems were used to screen catalysts and to evaluate the impurity profile under various process conditions. Elydrogenation kinetic studies were carried out using a 100 mL EZ-seal autoclave with an automatic data acquisition system to monitor the hydrogen uptake and to collect samples for HPLC analysis. Standard conditions of 5 g of aldehyde in 25 mL ethyl acetate and 25 mL methanol with 0.5 g of 5%Pd/C Engelhard Escat 142 were used in this investigation. For the Schiff s base formation and subsequent hydrogenation, inline FTTR was used to follow the kinetics of the Schiff s base formation under different conditions. Tables 1 and 2 show the changes in the substrate concentration under different conditions. Both experiments were carried without any limitations of gas-liquid mass transfer. 

Flow reactors offer considerable advantages over sealed autoclaves for supercritical reactions. Not only do flow-reactors require a much lower volume than a batch reactor for a given throughput of material (with obvious safety advantages) but also it is much easier to optimise reaction conditions in a flow reactor. We have already reported [4,5] the use of a miniature flow-reactor for the photochemical preparation of unstable metal complexes. We are now extending these techniques to the study of thermal and catalytic reactions. As an initial stage we... 

Experiments with gaseous reactants (propane and isobutane. Table III) were carried out by charging the liquefied gas from a weighed stainless-steel sampling cylinder into the sealed autoclave containing hydrochloric acid and, when used, a liquid alkane after which ethylene was charged and the autoclave was rotated and heated. 

Laboratory experiments below 800 K and 100 MPa can be conducted with sealed autoclaves developed initially by Morey etal Figure 1(a) shows this type of vessel, which is to be wholly put into a furnace. The liner and the seal disk are made of an inactive metal such as silver or gold. Since the pressure caimot be measured directly, one should calculate it from the degree of fill and the pressure-volume-temperature PVT) data of water. 

The sealed autoclave is carefully placed in the shaking assembly and initially pressurized to 5300 psi of CP grade carbon monoxide. (The autoclave i not... 

Ethylene oxide forms explosive mixtures in air at concentrations ranging from. f to 80% by volume. The explosion hazard is eliminated when the gas is mixed with sufUeicnt concentrations of carbon dioxide. Carhoxide is a commercial sterilant containing 10% ethylene oxide and 9()%> carbon dioxide by volume that can be handled and released in air without danger of explosion. Sterilization is aeeompiishcd in a sealed, autoclave-like chamber or in gas-impermeable bags. 

The solution of cis, cis, c/s-N-methyl- hexahydrojulolidinium hydroxide was mixed with NaOH (Wako Pure Chemical), colloidal silica (Shokubai Kasei, Cataloid), sodium aluminate (Wako Pure Chemical) and distilled water in a glass beaker, and stirred overnight at room temperature. The ratios were as follows Si/Al2=40, 100, 500, H2O/Si=50, OH7Si=0.1, SDA/Si=0.2. Afterwards, the mixture was poured into Teflon-lined autoclaves (Parr) and the sealed autoclaves were heated at 170°C for 7 days. The obtained solid of Na-SSZ-35 was filtered, washed with water the dried. Na-SSZ-35 was calcined at 550°C for 6h in air, and converted to H-SSZ-35 by stirring in the solution... 

The aqueous reaction mixture is heated, often (> 100 °C) in a sealed autoclave. 

Figure 4.1-5 Modified Bridgeman seal autoclave showing the temperature gradient crystal growth onto seed crystals [17]. The nutrient is held at a higher temperature than the seed crystals, thus leading to supersaturation conditions in the seed region. The transport is ill a...

Metal oxide nanocrystals are mainly prepared by the solvothermal decomposition of organometallic precursors. Solvothermal conditions afford high autogenous pressures inside the sealed autoclave that enable low-boiling solvents to be heated to temperatures well above their boiling points. Thus, reactions can be carried out at elevated temperatures and the products obtained are generally crystalline compared to those from other solution-based reactions. 

Sealed autoclaves or bombs capable of withstanding pressure greater than 1 atm can also be used. In this case, the reactants, catalyst, and solvent are added to the bomb. The reactor is heated to the desired temperature and the alkylene oxide is metered in to maintain a pressure of approximately 10-15 psig. As the alkylene oxide reacts, the pressure drops and then additional alkylene oxide can be added from a steel cylinder connected by flexible tubing to the bomb with appropriate valving. The bomb can either be heated or cooled as desired and agitation may be provided by either a rocking mechanism or a sealed mechanical stirrer. 

Other technological aspects of carbon nanotube synthesis currently under scrutiny include study of the growth mechanism [67,71], attempts to control the diameter [72-74], processes which yield very long CNTs [70,75], optimization of the catalyst composition [76], and improvements in purity [77]. A major area of focus is the production of CNTs at selected sites on a substrate (micropatterning) [78-81]. Other synthetic methods investigated have been (i) a solvothermal route, in which reactants are heated in solution in a sealed autoclave [82,83] (ii) a solid-state metathesis process [84] (iii) a hydrothermal process which produces MWNTs from amorphous carbon [85] and (iv) low-temperature processes [59]. 

More recently, Hayashi et have observed an efficient rate enhancement in the 3-HQD-catalyzed MBH reaction under high pressure induced by freezing water in a sealed autoclave. In most cases, moderate to good yields were obtained for the MBH reaction between various aldehydes with acrylates under 200 MPa pressure (Scheme 2.31). 

Etherification of Sucrose Chelates by Allyl Halides, and Sodium Bromoacetate, Allyl bromide or chloride was added to a dimethylsulphoxide (DMSO) solution of sucrose chelate in the ratios of sucrose allyl halide 1 1,1, 1 1,3, 1 2,0 and 1 2,5 and kept at 80°C for 16 to 48 h. The allyl bromide reactions were carried out in screw cap, sealed test tubes and most of the allyl chloride reactions in a sealed autoclave. Decomposition of the sucrose was prevented by keeping the ratio of sucrose to allyl halide equal or less than the ratio 1 2,5. The reaction between sucrose chelates and sodium bromoacetate was performed in the following ratios sucrose bromoacetate, 1 2,6, 1 3,8, 1 5,2 and 1 7,0, in DMSO for 72 h at 70°C. 

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