Water autogenous pressure

In the first step of the polymerization process, a prepolymer is prepared as a slurry in water. Excess diamine is added to control the degree of polymerization, eg, degree of polymerization = 6-14 (158). This prepolymerization step is conducted at approximately 200°C under autogenous pressure for less than 90 min. 

Waste nylon-6,6 was washed in a diluted commercial detergent solution at 100°C for 0.5 h and then rinsed twice with water to remove any finishes present. The washed nylon-6,6 was then reacted with molten adipic acid for 1.5 h or more at a temperature of 175°C with a weight ratio of nylon-to-adipic acid of 0.15 1. The molten product was then exposed to steam at a temperature of 230-233°C to remove any stabilizers present. The acidolysis product was then hydrolyzed with water at a temperature of 204°C under autogenous pressure for 0.5 h or longer with a ratio of water to acidolysis product of 0.50 1 (w/w). The hot solution was then filtered at 100°C to remove any titanium dioxide present. The filtered product was then mixed with HMDA to neutralize any excess acid present. The solution was then filtered to remove any solids. A 50% by weight aqueous solution of HMDA was added to the filtrate, and under standard polymerization conditions, polyhexamethylene adipamide (nylon-6,6) was produced. 

This process is carried out at a temp, from about 200C up to the critical temperature of water at autogenous pressure. PAN is degraded without the production of toxic hydrogen cyanide as a by-product. 

The cross aldol condensation of citral (Millennium Chemicals, 40 % cis-isomer + 55 % trans-isomer) with acetone (Merck, PA) was carried out at 353 K in N2 atmosphere under autogenous pressure ( 250 kPa) in a batch PARR reactor, using an acetone/citral = 49 (molar ratio) and a catalyst/(citral+acetone) = 1 wt.% ratio. Catalysts were pre-treated ex-situ in flowing N2 at 773 K for 2 h to remove adsorbed water and carbon dioxide and then quickly transferred to the reactor without exposing them to air. Reaction products were analyzed by gas chromatography. Selectivities (Sj, mol of producty /mol of citral reacted) were calculated as (%) = Cj X 100/ TCj where Cj is the concentration of product j. Product yields rjj, mol of product y/mol of citral fed) were calculated as Tfj = SjXat- Thirteen samples of the reaction mixture were extracted and analyzed during the 6-hour reaction. The main reaction product of citral conversion was pseudoionone, PS (cis- and trans- isomers). 

Synthesis of MCM-41 with Additives. The hydrothermal crystallization procedure as described earlier [10] was modified by adding additional salts like tetraalkylammonium (TAA+) bromide or alkali bromides to the synthesis gel [11]. Sodium silicate solution ( 14% NaOH, 27% Si02) was used as the silicon source. Cetyltrimethylammonium (CTA) bromide was used as the surfactant (Cl6). Other surfactants like octadecylltrimethylammonium (ODA) bromide (C,8), myristyltrimethylammonium (MTA) bromide (C,4) were also used to get MCM-41 structures with different pore diameter. Different tetralkylammonium or alkali halide salts were dissolved in little water and added to the gel before addition of the silica source. The final gel mixture was stirred for 2 h at room temperature and then transferred into polypropylene bottles and statically heated at 100°C for 4 days under autogeneous pressure. The final solid material obtained was washed with plenty of water, dried and calcined (heating rate l°C/min) at 560°C for 6 h. 

The supported Cu/Ce02 catalyst (denoted here as Cu/Ce-CTAB) was hydrother-mally prepared using Ce and Cu nitrates as precursors with a surfactant, CTAB [90], In a typical synthesis method, Ce(N03)3 6H20 was dissolved in hot distilled water, to which Cu(N03)2 3H20 in H20 was added dropwise. Then, CTAB was dissolved in a mixture of H20 and ethanol, and the obtained solution was added to the Cu + Ce solution. The typical molar composition is Cu/CTAB/H20 = 1.0 0.55 325. The homogeneous slurry mixture was hydrothermally treated at 175 °C for 24h in a Teflon-lined autoclave vessel under an autogeneous pressure. The resultant product was washed with distilled H20 and EtOH, and dried at ambient temperature for 10 h and then at 100 °C for 8h, followed by heating at 500°C for 6h under a He flow. The Cu contents of the obtained solid catalysts were determined by XRF. 

Resins obtained as products from mixtures in which the ratio of urea to glycol was greater than 3.5 to 1 could not be steam-distilled readily because their viscosities were too high. However, it was found that any of the intermediate resins could be cleaved if they were heated with approximately an equal weight of water to about 270° under autogenous pressures for twenty minutes to one hour. If water treatment was carried out at 300° or higher, ethyleneurea itself was hydrolyzed quite extensively and ethylenediamine was obtained. 

This liquid (370 g.) was hydrolyzed by heating it with an equal weight of water to 250° for 2 hrs. in an agitated 800-cc. silver-lined bomb under an autogenous pressure of 925 atm. The resulting product was distilled. Ethylenediamine in 10% yield, based upon ethanolamine, was obtained in the first fraction. The pressure was reduced and 155 g. of ethyleneurea, m.p. 126—129°, distilling at 170—180°/4 mm. was obtained crude yield, 55%, based upon ethanolamine. 

Exploratory syntheses were accomplished in 15 ml Teflon-lined autoclaves which were statically heated at autogenous pressure in forced convection ovens. Larger autoclaves (300 ml, 600 ml, and above) have also been successfully employed. At specified times, the autoclaves were removed from the oven, quenched in cold water, and the pH of the contents measured. Product VPI-5 was recovered by slurrying the autoclave contents in water, decanting the supernatant liquid, filtering the white solid, and drying the crystals in ambient air. 

Compounds 1, 2, 3, 4 and 5 were synthesized hydrothermally or solvothermally using H3BO3 as the boron source. All reagents were of analytical grade. The syntheses were carried out in 20 mL Teflon-lined stainless steel vessels under autogeneous pressure with a filling capacity of approximately 70%. The sole resulting crystals were collected by filtration, washed with distilled water for 1, 2 and 3 but with ethanol for 4 and 5, and dried in air at ambient temperature. 

Hydrothermal bombs containing aqueous mixtures of a metal compound and phosphoric acid are typically heated to temperatures of 100-350 °C, generating autogenous pressures up to 300 bar. The pressure rises more rapidly above the critical temperature of water, 373 °C, and hydrothermal pressures of 3000bar are typically generated at 600-1000 °C in sealed metal tubes surrounded by a supporting pressure of an inert gas. 

The tetracyano species K4[Cr(CN)4(CO)2] forms by heating KCN and Cr(CO)2(bipy)2 in liq NHj under autogenous pressure at 120°C. This yellow-green salt is not decomposed by atmospheric oxygen and is soluble without decomposition in water. ... 

For the preparation of RE-POM complexes, traditional aqueous solution synthesis and hydrothermal synthesis [2] are the two main synthetic methods. In traditional aqueous solution synthesis, reactions are carried out in the temperature range from room temperature to the boiling point of water, and in general start from plenary or lacunary POMs and simple RE salts. Hydrothermal reactions typically proceed in the temperature range 120-200 C under autogenous pressure, and usually use simple metal salts of all the required elements as the starting materials. As different solubility problems are minimized under hydrothermal conditions, the... 

The H-ZSM-5 (Si/Al=25, PQ Corp.) and Silicalite (S-1) zeolites were used to prepare the microporous copper-containing catalysts, Cu-ZSM-5 and Cu-S-1. ( We recall that S-1 has the same framework topology of ZSM-5, but without AP+ ions in the framework, and therefore S-1 is an all silica materials as MCM-41.) S-1 was prepared using TEOS and a 20% aqueous solution of tetrapropylammonium hydroxide (TPA-OH) (Fluka-purum). TEOS was poured in the TPA-OH solution. The resulting mixture was kept at 333 K for 3 h and then heated under autogenous pressure in a 350 mL stainless autoclave in an oven at 448 K for 24 h, without stirring. The solid was washed with water, dried 2 h at 383 K and finally treated in air at 823 K for 5 h. Further details were reported in Ref 4. 

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