Dry-box process

The iron oxide suspension family of processes is of historical interest because they constitute transitional processes that evolved from the traditional iron-oxide dry-box processes and were forerunners of the chelated-iron based processes that currently share the U.S. market for liquid redox processes together with the vanadium based Stretford process. 

This process was disclosed in Germany in 1934 and widely used for the removal of organic sulfur compounds from synthesis gas. It represents an extension of the classical iron oxide dry box process. Ils basis is the oxidation of organic sulfur compounds to oxides of sulfur at elevated temperatures over a catalyst consisting of hydrated iron oxide and. sodium carbonate. The oxides of sulfur react with the sodium carbonate and are retained in the bed as sodium sulfate. The required oxygen is provided by adding a small amount of air to the gas ahead of the catalytic converters. The process, as it was practiced at a German installation, has been described in detail by Sands et al. (1948). 

Historiad Background. The first installations utilized a simple form of the iron oxide (or dry-box) process. In this form of the process, hydrogen sulfide was removed completely by reaction with hydrated ferric oxide, resulting in the formation of ferric sulfide. After removal from the box and exposure to atmospheric oxygen, the ferric sulfide oxidized to elemental sulfur and ferric oxide. The oxidized mixture was reloaded into the box and used to react with additional hydrogen sulfide. The cycle could be repeated several times before the material lost activity due to the presence of excessive amounts of elemental sulfur. 

Two forms of iron oxide were used in the early dry box processes unmixcd oxides and mixed oxides. Unmixed oxides included modified iron ores containing up to 75% iron oxide and residue from the purification of bauxite, called Lux in Europe, which contained 23 to 50% iron oxide. Natural bog ore found in Denmaik and Holland was also widely used. 

For the copper/aluminum catalyst analyses later described, the sample mount was transfered from the XPS system following treatment and analysis to an inert atmosphere dry box without air exposure. From there individual pellets were transferred to the SAM for subsequent analysis without air exposure. The reverse process was employed for the next reaction cycle. 

Because of these precursor modification reactions, the process chemistry of chelate processes is as complex, or more so, than that involved in sol-gel processes.78 However, it is typical for chelate processes that some control of process chemistry is sacrificed in return for more expedient solution preparation. For example, the hour-long (or longer) reflux processes that have been historically used in 2-methoxyethanol based sol-gel processing of ferroelectric films are not used. Rather, the entire solution preparation procedure is generally completed within one hour, with only the initial phase of the procedure being carried out under dry box and inert atmosphere conditions. Once the chelation reaction(s) has occurred, the hydrolysis sensitivity of the precursor solution is reduced to the point where the remaining process chemistry may be carried out under ambient conditions.46... 

Iron Sponge Also called Dry box. An obsolete process for removing hydrogen sulfide from gas streams by reaction with iron oxide monohydrate. The ferric sulfide that is formed is periodically re-oxidized to regenerate ferric oxide and elemental sulfur. When this process becomes inefficient because of pore-blockage, the sulfur is either oxidized to sulfur dioxide for conversion to sulfuric acid, or is extracted with carbon disulfide. 

Two observationally constrained box-models, based on the Master Chemical Mechanism and with different levels of chemical complexity, have been used to study the HOx radical chemistry during the SOAPEX-2 campaign, which took place during the austral summer of 1999 (January-February) at the Cape Grim Baseline Air Pollution Station in northwestern Tasmania, Australia. The box-models were constrained to the measured values of long lived species and photolysis rates and physical parameters (NO, NO2, O3, HCHO, j(01D), j(N02), H2O and temperature). In addition the detailed model was constrained to the measured concentration of CO, CH4 and 17 NMHCs, while the simple model was additionally constrained only to CO and CH4. The models were updated to the latest available kinetic data and completed with a simple description of the heterogeneous uptake and dry deposition processes. 

The whole procedure can be done on a vacuum line, but is certainly easier and swifter in the open if done on the bench , one must take precautions against the acid (or indeed any other liquid) picking up atmospheric moisture during the processing. (Inert gas blanket or dry-box, p. 5)... 

Fig. 9.10. Apparatus for the determination of molecular weights of air-sensitive compounds by the isothermal distillation technique. Temperature fluctuations of the two solvents are minimized in this illustration by a Dewar filled with water. This apparatus is used in the following manner. In a dry box the sample is placed in a tared tube through sidearm A, the sidearm is then sealed off, the tube and remnant of the sidearm are weighed, and the tube is attached to the apparatus by glassblowing at B. A weighed portion of a standard is introduced into the other bulb, and the filling tube is sealed off. After evacuation, opening of the break-seal, and reevacuation, a measured portion of solvent is distilled into both arms of the apparatus. The process of equilibration is followed by periodic removal and measurement of the solvent from one arm. The solvent may be measured volumetricly in the liquid or gas stales, or by weight.

If desired, the preparation process can be carried out in an inert atmosphere by enclosing the equipment in a dry box, a plastic glove bag or simply in a plastic bag with slits for the hands. An inert atmosphere may be desirable for cementing the coal to the slide -- especially if temperatures above about 100°C are used for melting the thermoplastic. For other parts of the preparation an inert atmosphere is not as important since oxidation at room temperature is much slower. 

USE In manuf of ammonia, nitric acid, nitrates, cyanides, etc. in manuf explosives in filling high-temp thermometers, incandescent bulbs to form an inert atm for preservation of materials, for use in dry boxes or glove bags. Liquid nitrogen in food-freezing processes iu the laboratory as a coolant. Pharmaceutic aid (air displacement). Caution In high concns it is a simple asphyxiant. 

Cruser and Bard, 1969) and RRDE (Maloy et al., 1971) methods have been presented, so that the emission intensity and electrolysis current can be used to obtain information about the efficiency and pathway of the process. Finally, the electrochemical cells make small scale experiments possible and are especially amenable to vacuum line and dry box techniques. 

In a carbon dioxide-free dry-box, 200.0 g. (8.35 mols) of anhydrous lithium hydroxide is placed in a nickel trough, 12 in. long, in. in diameter, in. thick, lined with silver foil 16 in. long, 6 in. wide, and 0.002 in. thick. The trough is placed in a tube furnace (Fig. 2). The furnace is heated to 675° 10° and maintained at this temperature by a temperature controller. The open end of the furnace is closed with a rubber stopper connected with a glass tube and rubber tubing to a Dry Ice-acetone trap, which is directed to a vacuum pump. The pressure is maintained at about 0.5 in. The process is allowed to proceed for half an hour at the temperature indicated, after which... 

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