Ozonization of A5-steroids


To finish building propanal you need to add two carbons and an oxygen Start by adding another sp C (it should still be selected) and continue by adding an sp C and an sp O Atoms are added by clicking on unfilled valences m the model (the valences turn into bonds)  [c.1259]

If a compact film growing at a parabolic rate breaks down in some way, which results in a non-protective oxide layer, then the rate of reaction dramatically increases to one which is linear. This combination of parabolic and linear oxidation can be tenned paralinear oxidation. If a non-protective, e.g. porous oxide, is fonned from the start of oxidation, then the rate of oxidation will again be linear, as rapid transport of oxygen tlirough the porous oxide layer to the metal surface occurs. Figure C2.8.7 shows the various growth laws. Parabolic behaviour is desirable whereas linear or breakaway oxidation is often catastrophic for high-temperature materials.  [c.2729]

Phenylpyridine. The first stage is the preparation of a solution of phenyl-lithium in dry ether. Equip a 1-litre three-necked flask with a dropping funnel, a mercury-sealed mechanical stirrer, and an efficient reflux condenser provide the last-named with a drying tube filled with calcium chloride or cotton wool (1). Flush the apparatus with dry, oxygen-free nitrogen gas. Place 7 -35 g. of hthium shavings or wire (2) in the flask, and introduce a solution of 78-5 g. (52-5 ml.) of dry, redistilled bromobenzene in 250 ml. of anhydrous ether into the dropping funnel. Start the stirrer. Run in about 2 ml. of the solution when the reaction starts, as indicated by an initial cloudiness (3), add the remainder at such a rate that the solvent refluxes gently (about 45 minutes). Finally, add 50 ml. of anhydrous ether through the dropping funnel. Continue the stirring until all or most of the hthium disappears (1-1 5 hours) (4).  [c.931]

Ostensibly, a gas chromatograph (GC) apparatus should be ideal as an inlet for a plasma torch because the effluents from the chromatographic column are already in the gas phase and can be pas,sed straight into the plasma flame. However, most analyses carried out by GC involve carbon compounds, with oxygen, nitrogen, and halogens as commonly occurring constituents. The gas flow from the capillary GC column is normally increased by mixing in more argon gas with the effluent before it reaches the flame. Introduction of a sample into a GC column as a solution means there is usually a large solvent peak at the start of any gas chromatogram. Because the eluting solvent contains a large amount of material, it must be diverted from the flame otherwise, it would make the plasma very unstable or even extinguish it. Therefore, all GC connections to an ICP/MS instrument contain a diverter to switch the gas flow from the flame during the few seconds required for the solvent to elute from the end of the GC column.  [c.101]

When the oxygen demand is low, eg, at the start of a batch fermentation when the amount of biomass is small, the oxygen uptake rate at the bioreaction site is the limiting step and the level of dissolved oxygen is high (near saturation). When the oxygen demand becomes high, however, the rate-limiting step is that associated with transfer across the bubble—Hquid interface and this rate of transfer is critically dependent on the fluid flow at the gas—Hquid interface as weU as the concentration of oxygen in both the gas and the Hquid phases. The Hquid-phase oxygen concentration is now low, but it should not be allowed to fall below the critical value. It is when this gas-—Hquid mass transfer step is rate-limiting that the biggest demands are made on the bioreactor. Then there is the greatest difficulty in getting enough oxygen into the suspending fluid (broth) to satisfy the oxygen demand of the biological species.  [c.332]

Applications. Small and medium sized foundries producing castings for automotive and other similar appHcations often utilize iron melting channel melting furnaces. They allow melting off shift at lower power demands and make their total working batch available at the start of the pouring shift. Power consumption under these operation conditions ranges from 600 to 880 kW h/t. More continuous operation can reduce this figure. Furnaces have been designed to superheat Hquid iron deHvered in 90 t batches prior to its introduction into a basic oxygen furnace (BOF) for conversion to steel. Similar furnaces are utilized for duplexing in conjunction with cupolas in large foundries.  [c.131]

As the concentration of oxygen in the ascending bubbles falls, a point is reached where the mass transfer of oxygen from the bubble becomes rate limiting. Above this transition region (assumed to be negligible), if the partial pressure of oxygen in equiHbrium with the dissolved oxygen is negligible compared to the partial pressure of oxygen in the bubble and if the bubbles are of constant size and rise at a uniform rate, the deHvery of oxygen to the solution is approximately first order, in both time and distance, with respect to the oxygen in the bubble. The system therefore has a characteristic transfer height. As the bubbles rise through this distance, they deHver ca 63.2% (100 x (1 — 1/e)) of the oxygen they contained at the start. The transfer characteristics of a mixed zone system can be approximated with a relatively simple equation (177).  [c.342]

Tubular Reactor. The tubular reactor is essentially along double-pipe heat exchanger. The process side tube s internal diameter maybe as wide as 6.4 cm, its length as long as 1800 m (4). A cooling jacket is utilized to remove a portion of the reaction heat, which in turn results in operation at a conversion per pass of 35% or lower. Most commercial reactors control reaction pressure with a cycle valve that opens periodically. This type of pressure control not only creates pressure pulses and surges in process side velocity that can reduce reactor wall polymer contamination, but also optimizes heat transfer to the jacket. In tubular reactors, the tubes are operated either with a single front feed entry or in combination with one or more side entries. Peroxide-type initiators and/or oxygen are used to start reaction at one or more points along the reactor. Thus, the tubular reactor resembles a series of alternating polymerization and cooling zones.  [c.373]

Uses. A primary early use was the iacorporation of a small cast candle ia a quick-start canister, which was filled with potassium superoxide [12030-88-5] and used ia a portable breathing apparatus. The candle rapidly produced an initial supply of oxygen until the superoxide became fully activated, particularly at lower temperatures. Large candles, deUveting 3—4 m (120 fT) oxygen ia 45 minutes, are used ia long-duration submergence submarine operation. A furnace holds a stack of two candles the upper one is ignited, which subsequently ignites the lower one. Together these furnish enough oxygen for 120 people for 1.5 hours.  [c.486]

Perchloric Acid and Perchlorates" under "Chlorine Compounds, Inorganic" in ECT 1st ed., VoL 3, pp. 716—729, by H. L. Robson, Mathieson Chemical Corp., and J. C. Schumacher, Western Electrochemical Co. under "Chlorine Oxygen Acids and Salts" in ECT 2nd ed., VoL 5, pp. 61—84, byj. C. Schumacher and R. D. Stewart, American Potash Chemical Corp. in ECT 3rd ed., Vol. 5, pp. 646—667, by R. C. Rhees, Pacific Engineering Production Co.  [c.69]

Miscellaneous Radioprotective Agents. Steroid hormones have been extensively studied for their abihty to protect against infertility in males receiving XRT (see Hormones). A variety of results have been reported (249). Pretreatment using a GnRH antagonist protects spermatogonia stem cell function from single doses of x-rays. Pretreatment using testosterone also protects spermatogonia stem cells from four daily x-ray fractions, whereas sub-q medroxyprogesterone and testosterone pretreatments protect against a single 3-Gy (300-tad) dose of x-rays. Similatly, 1.5—2.2 fold protection of spermatogonia stem cells has been reported in rats implanted with encapsulated testosterone and estradiol six weeks prior to irradiation. Such protection perhaps involves alterations in oxygen levels, GSH levels, and DNA repair activity in the stem cells. In contrast, no protection against damage to spermatogenesis by pretreatment using either testosterone or estrogen is observed after single y- or x-ray doses.  [c.499]

This process was improved and expanded (133) to provide starting materials for the C19-sex hormones that include estrogens and androgens (see Fig. 10). Oxidative cleavage of enol ether (79) with chromium trioxide followed by elimination of the Cl6-acyl-oxygen in hot acetic acid affords pregnenolone acetate (81) in over 80% yield. Pregnenolone acetate (81) can be converted to progesterone by methods similar to the Marker process. The cleavage of the C17 side chain begins with the treatment of (81) with hydroxjlamine to afford the C20 oxime (82). Beckman rearrangement of (82) affords the ene-amide (83). Mild acid hydrolysis of (83) results in dehydroepiandrosterone acetate [853-23-6] (84) (133). The same processes have been appHed to the stmcturaHy similar steroid alkaloids solasodine (44) and tomatidine (43).  [c.428]

A submerged-culture oxidizer with instmmentation to control the oxygen concentration of the mash accurately and with a heat-transfer system that efftcientiy controls the temperature is described in Reference 40. Clear vinegar may be withdrawn from the oxidizer by use of tangential filters which retain the bacteria in the system. Blinding of the filter is precluded by the rapid flow of Hquid across the filter surface (53,54). The clear vinegar is removed from the system and the bacterial cells are retained to continue their work. Glycerol catalyzes the production of vinegar from the alcohoHc solution obtained from malt wort (55), and its degradation pathways have been elucidated. Certain strains of Saccharomjces cerevisiae produce enough SO2 to slow the start of oxidation Jicetobacter (56). A scmbber has been patented which greatly increases the efficiency of vinegar production by recycling ethanol and acetic acid vapors normally lost with the exhaust air stream (57).  [c.410]

Wet air oxidation is based on a Hquid-phase oxidation between the organic material in the wastewater and oxygen suppHed by compressed air. The reaction takes place flamelessly in an enclosed vessel which is pressurized and at a high temperature, typically 13.79 x 10 Pa and 575°C. The system temperature, initiated by a start-up boiler, is maintained through auto thermal combustion of organics once the reaction starts.  [c.192]

Liquid Fuels and Chemicals from Gasification of Coal. Gasification of coal using steam and oxygen in different gasifiers provides varying proportions of carbon monoxide and hydrogen. Operations at increasing pressures increases the formation of methane. Because mixtures of CO and H2 are used as the start of chemical synthesis and methane is not wanted or needed for chemical processes, the conditions favoring its formation are avoided. The product gases may then be passed over catalysts to obtain specific products. Iron-based catalysts are used to produce hydrocarbons in the Eischer-Tropsch process, or zinc or copper catalysts are used to make methyl alcohol.  [c.236]

EGR can seriously degrade engine performance, especially at idle, under load at low speed, and during cold start. Control of the amount of EGR during these phases can be accompHshed by the same electronic computer controller used in the closed loop oxygen sensor TWC system. Thus the desired NO reduction is achieved while at the same time retaining good driveabiUty.  [c.492]

Process Conditions. To effectively design a catalytic control system, the Manufacturers of Emissions Controls Association recommends the following data be obtained (5) Hst of all VOCs present and range of concentration of each, flow rate of exhaust and expected variabiUty, oxygen concentration in exhaust and expected variabiUty, temperature of exhaust and expected variabiUty, static pressure, potential uses for heat recovery, particular performance criteria and/or regulations to be met, capture efficiency, ie, fraction of all organic vapors generated by the processes that are directed to the control device, presence of hydrocarbon aerosols in the effluent exhaust, identity and quantity of all inorganic and organic particulate, amount of noncombustibles, presence of possible catalyst deactivators, and anticipated start-up/shutdown frequency of the system.  [c.506]

Use oxygen to start a diesel engine.  [c.302]

Catalytic cracking in the Houdry process was originally performed in fixed beds. Temperature control in these reactors was achieved using a molten salt heat removal scheme as the catalyst was regenerated. The heat of reaction and some of the required feed preheat were supplied by circulating the molten salt through vertical tubes distributed through the reactor bed. A typical reaction cycle for an individual reactor was about ten minutes. At the end of this cycle, feed was automatically switched to another reactor that had been regenerated. The spent reactor was steam purged for several minutes and then isolated by an automatic cycle timer. Regeneration air was then introduced and the carbon was burned off at a rate at which the bed temperature could be controlled by the recirculating of the molten salt stream. The regenerated bed had to be purged of oxygen before being returned into cracking service. A typical operation consisted of three to six reactors. The main difficulty with the fixed-bed catalytic cracker was that equilibrium was never achieved. The gas oil conversion (i.e., the amount of feed converted to lighter components) was initially high at the start of the reaction and gradually diminished as carbon deposited onto the catalyst until regeneration was needed. To minimize this effect multiple parallel reactors were employed however, true steady-state operation was never actually achieved. Reaction-bed temperatures during reaction and regeneration cycles fluctuated considerably.  [c.206]

Physical and Chemical Properties - Physical State at 15 XI and I atm Liquid Molecular Weight 43.07 Boiling Point at I atm 133, 56, 329 Freezing Point -108, -78, 195 Critical Temperature Not pertinent Critical Pressure Not pertinent Specific Gravity 0,832 at 20°C (liquid) Vapor (Gas) Specific Gravity 1.5 Ratio of Specific Heats of Vapor (Gas) 1.192 Latent Heat of Vaporization 333, 185, 7.75 Heat of Combustion -15,930, -8,850, -370.5 Heat of Decomposition Not pertinent. Health Hazards Information - Personal Protective Equipment If exposure is possible, wear full clothing (neoprene slicker suit, rubber boots, rubber gloves, chemical goggles). If vapors may be present, wear all purpose canister or gas mask if vapors are known to be present, use self-contained breathing apparatus. Symptoms Following Exposure Material gives inadequate warning of overexposure by respiration or skin contact. May cause vomiting and possibly death when inhaled, ingested, or absorbed through skin. Severe blistering agent can produce third-degree chemical burns of skin. Has corrosive effect on mucous membranes and may cause scaring of esophagus if swallowed. Corrosive to eye tissue may cause permanent corneal opacity and conjunctival scarring. Effects on eye tissue, and skin may be delayed. Treatment for Exposure INHALATION remove victim from exposure and administer oxygen steroid therapy (by physician) is recommended. SKIN OR EYES prompt and adequate irrigation with water (within 60 seconds of exposure) can prevent serious injury. Toxicity by Inhalation (Threshold Limit Value) Data not available rt-Term Inhalation Limits 5 ppm for 30 min Toxicity by Ingestion Grade 4 LD below 50 mg/kg (rat) Late Toxicity Causes cancer in mice. Effects on man unknown. Vapor (Gas) Irritant Characteristics Vapor is moderately irritating such that personnel will not usually tolerate moderate or high concentrations.  [c.175]

When simulating large molecular systems, it is often advantageous to use a group-based cutoff (sometimes called a residue-based cutoff). Here, the large molecules are divided into groups, each of which contains a relatively small number of connected atoms. If the calculation involves small solvent molecules then each solvent molecule is also conveniently regarded as a single unconnected group. Why are groups useful Fet us consider the electrostatic interaction between two water molecules. In the popular TIP3P model there is a charge of -0.834e on the oxygen and 0.417e on each hydrogen. The electrostatic interaction between two water molecules is calculated as the sum of nine distinct site-site interactions. If we start from the minimum energy arrangement for the water dimer shown in Figure 6.13 and  [c.341]

The reagent Is expensive and poisonous, consequently the hydroxylation procedure is employed only for the conversion of rare or expensive alkenes (e.g., in the steroid field) into the glycols. Another method for hydroxylation utilises catalytic amounts of osmium tetroxide rather than the stoichiometric quantity the reagent is hydrogen peroxide in tert.-butyl alcohol This reagent converts, for example, cyc/ohexene into cis 1 2- t/ohexanedlol.  [c.894]

Anyway, all that pure oxygen has infiltrated every part of the enclosed system and the solution in the reaction flask is allowed to stir, exposed to all that oxygen for 1 hour. At first the solution is brownish black, but as it absorbs the oxygen over that hour s time it will turn an olive green. After 1 hr it s time for the chemist to add the safrole slowly over a 30min period. As the safrole is being added it will start to take up all that oxygen causing the palladium to turn black again (shows that things are working) but after the addition is complete and the safrole has been converted to MD-P2P the palladium will again start to soak up the remaining oxygen and turn green once again. The solution remains stirring at room temperature for 16-24 hours. If the balloon loses significant volume during the reaction, one just fills it up again. Nothing bad will happen.  [c.63]

To illustrate let s start with the hydrogen of nitric acid As shown m Figure 1 5 hydrogen is associated with only two electrons those m its covalent bond to oxygen It shares those two electrons with oxygen and so we say that the electron count of each hydrogen is (2) = 1 Because this is the same as the number of electrons m a neutral hydrogen atom the hydrogen m nitnc acid has no formal charge  [c.18]

Propellants are mixtures of chemical compounds that produce large volumes of high temperature gas at controlled, predetermined rates, and can sustaia combustion without requiring atmospheric oxygen for the purpose. Principal applications are ia launching projectiles from guns, rockets, and missile systems. Propellant-actuated devices are used to drive turbiaes, move pistons, operate rocket vanes, start aircraft engines, eject pilots, jettison stores from jet aircraft, pump fluids, shear bolts and wires, and act as sources of heat ia special devices. Propellants are appHcable wherever a weU-controUed force must be generated for a relatively short period of time. SoHd propellants are compact, have a long storage life, and may be handled and used without exceptional precautions.  [c.32]

Although ASTM D381 measures the gum existing in gasoline at a particular point in time, it does not indicate how much more might be formed during storage at the refinery, during various modes of transportation, in service station tanks, or in vehicle tanks. The oxidative stabihty test (ASTM D525) was developed to provide a rapid means of predicting future gum formation. This method consists of placing a sample of the gasoline in a bomb, pressurizing it to 690 kPa (100 psi) with oxygen, and maintaining it at a temperature of 100°C. The pressure inside the bomb is monitored continuously. The oxygen reacts with the gasoline slowly at first, but eventually the pressure drops sharply, 14 kPa (2 psi) or more within a 15 minute interval, indicating a breakpoint. The time from the start of the test to the breakpoint is the induction period and is a measure of the oxidative stabihty of the gasoline. ASTM D4814 Specifies that gasoline induction period must exceed 240 minutes, although most good gasolines have induction periods in excess of 960 minutes, the duration of the test.  [c.183]

Adsorptive Separation. A noncryogenic air separation process, which is increasingly employed for small- to moderate-scale oxygen production units, is based on the adsorption of nitrogen (but not oxygen) onto 2eohtes (see Adsorption, gas separation) (19). This batch process, known as vacuum swiag adsorption (VSA), typically uses two identical switching beds, each containing two strata. The first stratum removes water and carbon dioxide the second adsorbs nitrogen from the flowing air. In the two-bed system, while unit one is on-stream adsorbiag first water and carbon dioxide and then nitrogen from the air, unit two is being evacuated to remove the previously adsorbed nitrogen. The product oxygen is substantially unaffected. After a certain period, the second bed is brought iato sequential use, while the first is evacuated, etc. Depending on the operating cycle chosen, the product may be up to about 93% oxygen. The balance is nitrogen and argon. Moisture and carbon dioxide residuals are ia the low ppm range. The oxygen is produced at about 24 kPa (3.5 psig) and must be compressed if the oxygen is required at higher pressures. The flow of the oxygen is unsteady but the use of a surge tank or a compressor can even out the oxygen flow.  [c.478]

Portable breathing apparatus are used by fire departments, damage-control teams, and workers in unbreathable atmospheres (21). The wearer uses a canister containing the chemical, a breathing bag, and a mask. The chemical is packaged as 4.8—9.5-mm (2—4-mesh) granules with glass fiber filters which trap any dust. Approximately three breaths are required to start the chemical reaction and deUver oxygen. Alternatively, a smaH chlorate candle can be used to dehver oxygen immediately.  [c.487]

Petroleum is thought to be derived from a variety of living organisms buried with sediments in previous geological eras. A small fraction of these organisms were trapped in oxygen-deficient (or reducing) environments where they escaped complete oxidation to carbon dioxide. Over tens or hundreds of millions of years, the residual organic material was subjected to a complex series of chemical changes known as diagenesis and catagenesis (2,3). In diagenesis, which occurs below 50°C, the organics undergo microbial action and some chemical reactions, resulting in dehydration, condensation, cyclization, and polymerisation. During catagenesis, which occurs under a thermal stress of 50—200°C, the organics react with the surroundings by a combination of thermocatalytic cracking, decarboxylation, and hydrogen disproportionation to form petroleum in the sedimentary rocks. In the vast majority of cases the petroleum is not found where the precursors were laid down, but in reservoirs where accumulation occurs after migration from the source rocks through geologic strata (3,4) (see Petroleum, origin of petroleum).  [c.164]

Oxygen levels in the VGO parallel the nitrogen content. Thus, the most identified oxygen compounds are phenols and carboxyUc acids, frequendy called naphthenic acids. These may account for from ppm to neady 3% of a VGO. The presence of numerous complex naphthenic and naphtheno aromatic acid stmctures in cmde oils, especially immature forms, has been shown (34). Among the different stmctures a number of specific steroid carboxyUc acids have been identified.  [c.172]

Constmction of underwater (submatine) pipelines does not take place under water. Pipelines are welded onshore and dragged iato position by powerful wiaches on ships floating on the water surface (for short lines), welded on a specially constmcted lay barge, and lowered to the ocean floor by a stinger from one end of the barge or welded onshore, floated on pontoons, and towed to the offshore area where they are lowered iato position. For smaller size pipelines, the lines can be welded onshore and spooled onto large reels, placed on special ships, and spooled iato the offshore trench. In shallow water, or where endangered by anchors or wave action, submatine pipelines are laid ia trenches ia the sea bottom (35). Underwater pipelines are concrete-coated or weighted to overcome the buoyancy effect concrete coatings appHed over the primary coating provide additional protection against damage duting laying and against corrosion. Submatine pipelines are being used regularly to transport oil, natural gas, and other commodities to shore from offshore locations, such as the Gulf of Mexico, the North Sea, and the Arabian Gulf One of the longest and technically challenging submatine pipeline systems is a 2599-km, 1200-mm dia pipeline for transporting natural gas across the Mediterranean Sea and the Strait of Messiaa from gas fields ia Algeria to Italy pipes are laid ia water depths to 610 m. Offshore and onshore pipelines require different design factors (36).  [c.50]

At the start of the nineteenth century, platinum was refined in a scientific manner by William Hyde WoUaston, resulting in the successful production of malleable platinum on a commercial scale. During the course of the analytical work, WoUaston discovered paUadium, rhodium, indium, and osmium. Ruthenium was not discovered until 1844, when work was conducted on the composition of platinum ores from the Ural Mountains.  [c.162]

The final polymerization stage is usually done in an autoclave fitted with a powerful mechanical stirrer to handle the viscous melt under high vacuum at a temperature above the melting point of the final polymer. During this critical stage it is important to eliminate oxygen and the process is blanketed with inert gas (nitrogen or argon). During the polycondensation stage, the linear oligomers and the bishydroxyalkyl terephthalate esters undergo a succession of El reactions, eliminating the diol which is removed under high vacuum, and thus molecular weight increases steadily. A polymerization catalyst is needed tin and titanium compounds are suitable for both El and polymerization, but for PET, antimony trioxide is the usual polymerization catalyst (77). It only becomes active at high temperatures and thus can be added at the start of the El stage along with the other catalysts. There has been a move away from heavy metals (eg, antimony), particularly in Europe, where they are viewed with increasing disfavor on environmental grounds. Even in the United States problems can arise with heavy-metal contaminants (including antimony) in waste glycolysis stiH-bottoms. These caimot be landfilled for environmental reasons and their safe disposal causes added expense. A less toxic metal is clearly advantageous. However, alternatives are not universally satisfactory. Titanium alkoxides cause unacceptable yeUowing of PET, apparently due to reaction with vinyl ends. This does not occur with PBT. Germanium compounds, either as the dioxide, tetraalkoxide, or glycol oxide, are good catalysts, nontoxic, and give very white polymers. However, they are considered too expensive due to the scarcity of the metal. Germanium or germanium—titanium mixtures have been disclosed in a patent relating to PET bottles (78). Antimony trioxide is a robust polymerization catalyst however, in PET it is susceptible to reduction to metallic antimony, which can cause a grayish blue color in the final polymer.  [c.294]

A more compHcated system is found in the Ruhrstahl-Heraeus (RH) process (Eig. 9), which has two hoUow legs as compared to only one in the DH. By bubbling argon into one leg, a pressure difference is created circulating steel though the vacuum chamber and back into the vessel. Oxygen and carbon dissolved in the steel react to form CO, which escapes. Reduction of carbon from 0.08 to 0.03% and oxygen from 400 to 50 ppm occurs, at which point the steel can be economically killed with aluminum. The higher carbon contents at entry improve the yield of iron in the BOE vessel. In the Ruhrstahl-Heraeus oxygen blowing (RH-OB) process, even higher carbon contents (0.10%) can be treated, with oxygen blown into the degasser, thus further improving yield. Eor interstitial-free steels, the start carbon, which may be 0.03%, is reduced to <20 ppm. Oxygen and nitrogen are also held at levels near 20 ppm. A very high quaHty sheet steel is produced with exceptional deep-drawing properties.  [c.380]

Cardiac Steroids. Cardiac steroids (steroid lactones) and corresponding glycosides are characterized by their abiUty to exert a powerful inotropic (increasing the force of cardiac contraction) effect, and are used both for their inotropic and antiarrhythmic properties. The two most prevalent cardiac aglycones are the cardenoHdes and bufadienoHdes. The cardenoHdes are steroids that have a C17P-substituted five-membered lactone that is generally a,P-unsaturated, an unusual P faced oxygen on C14, and a bile acid-like cis-A—B ring junction. CardenoHdes are exemplified by digitoxigenin [143-62-4] (55) which is an active ingredient in digitaHs. The bufadienoHdes differ in that they are C24 steroids that possess a C17P-substituted six-membered lactone ring that generally has two degrees of unsaturation. BufadienoHdes can be represented by bufalin [465-21-4] (56) which occurs in toad skin secretions.  [c.423]

Fermentation. Lager beer fermentations with the bottom-fermenting S. uvarum are carried out at 10—16°C for 6—10 days. Fermentation is followed by a lager period of up to several months at 2—5°C. Ale fermentations with the top-fermenting S. cerevisiae are carried out at 15—22°C for 3—5 days. The rate of fermentation is highly dependent on temperature. For example, at 25°C, the rate of fermentation is about three to four times faster than at 10°C. The pH drops from about 5.5 to about 4.3—4.5 during the course of fermentation. The rate of maltose fermentation is almost constant at pH 3.5—5.0 (although it drops sharply outside this range) and the optimum pH for maltottiose fermentation is 4.3—5.4. Thus, the rate of wort fermentation is not greatly affected by this drop. Fermentation and yeast growth are inhibited by high concentrations of ethanol and dissolved carbon dioxide. At ethanol concentrations of 5—6% and carbon dioxide levels of 0.4—0.5%, the inhibition is minimal. Since the alcohol content of U.S. lager beers ranges from 3.4—3.8%, and only reaches about 8.7% in British stout, any inhibition is slight. Initially, brewers fermentations contain 5-10 x 10 yeast cells per mL, corresponding to about 0.75 g yeast soflds per Hter. Fermentation results in a four- to eight-fold increase in cell mass. The basic carbon source for this growth is carbohydrate. Some oxygen is available at the start of the fermentation, by aeration of the wort. Very tittle oxygen, however, is requked for fermentative yeast growth. Nitrogen is supplied by the amino acids in the wort. Some amino acids, particularly asparagine, serine, threonine and lysine, are assimilated rapidly, while others are absorbed more slowly. Protine is not absorbed, and the resulting beer contains a relatively high concentration of this amino acid. Brewers worts usually contain sufficient minerals and vitamins to support yeast growth and fermentation.  [c.391]

Ozone. Ozone [10028-15-6] O, bleaching has been the subject of laboratory and pilot plant studies for many years but it remained uncommercialized until the announcement of the 1992 start-up of a full-scale plant at Union Camp s Franklin, Virginia mill. The laboratory studies have shown that ozone rapidly and extensively delignifies chemical pulps over wide ranges of consistency and other conditions (13). The two principal obstacles to commercialization have been selectivity and cost. Because ozone is such a powerful oxidizing agent it tends to be indiscriminate, so its appHcation must be carefully controUed to prevent pulp strength loss. The cost is high because it must be generated on-site by passing pure, dry oxygen or air through a corona discharge, a process that consumes electrical energy and places high demands on the purification system for recycling unconverted oxygen in the spent ozone stream. Nevertheless, the growing demand for chlorine alternatives is likely to result in these problems being at least partially overcome and ozone bleaching will soon be a commercial reaHty. The selectivity and cost problems probably preclude direct replacement of chlorine, as in the ZED ED sequence, and favor combinations with other delignifying agents, as in the sequences OZED and 0(DZ)ED (14). A likely scenario involves the use of ozone charges of less than 1%, high consistency, and ambient conditions.  [c.156]

Entrained-Flow Gasifier. The entrained-flow gasifier consists of a plug-flow system in which the fine coal particles concurrentiy react with steam and oxygen. Residence time is a few seconds. These systems operate at high temperatures, well above ash slagging conditions, in order to assure good carbon conversion and provide a mechanism for removal of ash as molten slag. Entrained-flow gasifiers are utilized in the Shell coal gasification process, Texaco coal gasification process, Dow coal gasification process by Destec, and Prenflo by Kmpp-Koppers (7). The short residence time required in entrained gasifiers can result in potentially high throughputs at elevated pressures. Entrained gasifiers have high feedstock flexibiUty. The agglomerating tendency and fines content of feed coal that greatiy limit the operation of the moving-bed and fluid-bed gasifiers are not a problem in entrained gasification. Entrained gasifiers, which can use 100% of the mine output, have a small coal inventory that results in rapid start-up, shutdown, and load-foUowing characteristics. Entrained gasifiers have greater turndown capacity than do fluid-bed gasifiers, and the product gases contain no tars and light oils, thus faciUtating heat recovery and requiring less gas cleaning and purification. Also, the product gas contains much lower quantities of other impurities, such as mercaptans, ammonia (qv), carbon disulfide (qv), carbonyl sulfide, and thiophene (qv), than does that of other types of gasifiers. Treatment of the wastewater from the gas cleaning operation is therefore simpler for entrained-flow gasifiers.  [c.269]

For operations producing 30,000 tons or less of copper annuaHy, hydrometaHurgy offers an alternative to smelting that avoids problems associated with sulfur dioxide recovery and environmental controls. Techniques include the Anaconda oxygen—ammonia leaching process, the Lake Shore roast-leach-electrowin process, and ferric chloride leaching processes for the treatment of copper sulfides. AH the facHities that use these techniques encountered serious technical problems and were shut down within a few years of start-up.  [c.205]

The hydrocarbon exclusion by smaU-pore zeolites allows PSA to achieve a 10 to 30 K dewpoint depression in air-brake compressors, even at high discharge air temperatures in the presence of compressor oil [Ausikaitis, in Katzer, Molecular Sieves—ll. Am. Chem. Soc. Symp. Ser, 40, pp. 681-695 (1977)]. The high-purity hydrogen employed in processes such as hydrogenation, hydrocracking, and ammonia and methanol produc tion is produced by PSA cycles with adsorbent beds compounded of activated carbon, zeolites, and carbon moleciilar sieves [Martin, Gotzmann, Notaro, and Stewart, Adv. Cryog. Eng., 31, I07I-I086 (1986)]. The impurities to be removed include ammonia, carbon oxides, nitrogen, oxygen, methane, and heavier hydrocarbons. In order to be able to produce purities as high as 99.9999  [c.1542]

The flammable range in air lies between the lower flammable limit (LFL) and upper flammable limit (UFL) as determined by test for the conditions of interest. Outside this range of compositions the gas or vapor cannot be ignited. Operation at less than the LFL is often considered to be safer than operation at above the UFL, particularly for atmospheric storage tanks. Even if liquid in a tank rapidly generates sufficient vapor for operation above the UFL, flammable mixtures may occur around tank openings such as sampling ports, and the flammable range may be traversed inside the tank during start-up or other operational condition. However, there are many cases where operation above the UFL is essential, such as storage of high vapor pressure liquids, or has other advantages, such as some vent collection header applications [168]. Alternatively, vessel atmospheres can be rendered nonflammable using inert gas as described in NFPA 69. This technique reduces the oxygen concentration below the Limiting Oxygen Concentration (LOC) which is the minimum oxygen concentration required to sustain combustion. Inerting is usually ineffective near tank openings, especially in cases where solids additions occur and entrain air. Also, for  [c.86]


See pages that mention the term Ozonization of A5-steroids : [c.124]    [c.126]    [c.333]    [c.427]    [c.439]    [c.68]    [c.21]    [c.306]    [c.2230]   
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Organic reactions in steroid chemistry Volume 2  -> Ozonization of A5-steroids