Naphthalene removal

Reposition the test-tube clamp so that the test tube containing the solid naphthalene is again partially submerged in the boiling water bath. Heat the test tube until the naphthalene is melted and you can remove the thermometer and stirrer as a unit. CAUTION The thermometer, stirring wire, and test tube may be hot. Do not discard the naphthalene. Remove all the naphthalene from the stopper, thermometer, and stirrer by washing them with acetone. 

Formation of 247 may be favored by steric factors, as the 3-and 4-positions of benzo[6]thiophene are analogous to the peri positions of naphthalene. Removal of the 4-substituent from the plane of the ring would be expected to relieve steric strain. 

Into a suitable flask equipped with motorized stirrer, thermometer and powder funnel, add 185 milliliters of 70% nitric acid, followed by carefully adding 350 milliliters of 98% sulfuric acid. Thereafter, place this flask into a water bath at room temperature, and then slowly add in small portions, 450 grams of dry powdered naphthalene over a period of 6 hours while rapidly stirring the acid mixture and maintaining its temperature below 30 Celsius. After the addition of the naphthalene, remove the powder funnel and replace it with a condenser and then reflux the entire reaction mixture for 2 hours at 60 Celsius with constant stirring. After refluxing for 2 hours, remove the heat source, and allow the reaction mixture to cool to room temperature. Thereafter, drown the entire reaction mixture into 1000 milliliters of ice water, and then filter-off the precipitated crystals. Then wash these crystals with three 250-milliliter portions of cold water, and then vacuum dry or air-dry the crystals. The dry solid product will be a mixture of para, ortho, and meta isomers. 

Light Oil Removal from Coal Gas, 1359 Naphthalene Removal from Coal Gas, 1366... 

A closed system for removing naphthalene from coke-oven gas in the final cooler is described by Kroll and Barry (1991). In this system, recycled water and fresh water are sprayed into the process gas at high flow rates to cool and saturate the gas with water. Naphthalene is condensed and collected with the water. The naphthalene is removed from the water by contact with liquid tar in a liquid-liquid extraction step at the bottom of the spray contactor. After naphthalene removal the water is pumped through an indirect heat exchanger (cooler) and recycled with fresh water makeup to the spray nozzles. 

Naphthalene is adequately removed in the oil-washing operation for benzol recovery, and a separate naphthalene removal step is not required if benzol is recovered. This type of operation is shown in the overall coke byproduct recovery flow diagram (Figure 16-25) where residual naphthalene in the gas from the final cooler is removed by the light oil scrubber. However, in some cases it is advantageous to remove naphthalene in a separate step before the gas is processed for the removal of benzol and other impurities. This is usually accomplished hy oil washing. 

The types of oils used for light-oil absorption are also suitable for naphthalene removal. Petroleum oils which are free of naphthalene are preferable from the standpoint of maximum naphthalene removal. However, coal-tar oils have a somewhat higher absorptive capacity. 

Students should carry out the purification by steam distillation of (a) crude nitrobenzene or chlorobenzene, or of (b) crude naphthalene, o-nitrophenol (p. 170) or />-tolunitrile (p. 194) as examples of solid compounds which may also be purified in this way. When the distillation is complete, disconnect the tubing (Fig. 15) between C and D before removing the flame from under D, otherwise the contents of C will be sucked back into D as the latter cools. 

The. more tightly held an electron is. the more difficult it is to remove, hence the higher the electrode potential necessary to remove it. Make the reasonable hypothesis that the electron removed in a one-electron oxidation comes from the highest occupied orbital. HOMO. Using SHMO. determine the HOMO for ben7 ene, biphenyl, and naphthalene. 

The sulphonation of toluene at 100-120° results in the formation of p-toluene-sulphonic acid as the chief product, accompanied by small amounts of the ortho and meta isomers these are easily removed by crystallisation in the presence of sodium chloride. Sulphonation of naphthalene at about 160° 3uelds largely the p-sulphonic acid at lower temperatures (0-60°) the a-siil-phonic acid is produced almost exclusively. 

Approximately 50—55% of the product from a coal-tar refinery is pitch and another 30% is creosote. The remaining 15—20% is the chemical oil, about half of which is naphthalene. Creosote is used as a feedstock for production of carbon black and as a wood preservative. Because of modifications to modem coking processes, tar acids such as phenol and cresyUc acids are contained in coal tar in lower quantity than in the past. To achieve economies of scale, these tar acids are removed from cmde coal tar with a caustic wash and sent to a central processing plant where materials from a number of refiners are combined for recovery. 

The BASF process uses /V-methy1pyrro1idinone as the solvent to purify acetylene in the cracked gas effluent. Alow pressure prescmbbing is used to remove naphthalenes and higher acetylenes. The cracked gas is then compressed to 1 MPa (10 atm) and fed to the main absorption tower for acetylene removal. Light gases are removed from the top of this tower. 

Tetrahydronaphthalene [119-64-2] (Tetralin) is a water-white Hquid that is insoluble in water, slightly soluble in methyl alcohol, and completely soluble in other monohydric alcohols, ethyl ether, and most other organic solvents. It is a powerhil solvent for oils, resins, waxes, mbber, asphalt, and aromatic hydrocarbons, eg, naphthalene and anthracene. Its high flash point and low vapor pressure make it usehil in the manufacture of paints, lacquers, and varnishes for cleaning printing ink from rollers and type in the manufacture of shoe creams and floor waxes as a solvent in the textile industry and for the removal of naphthalene deposits in gas-distribution systems (25). The commercial product typically has a tetrahydronaphthalene content of >97 wt%, with some decahydronaphthalene and naphthalene as the principal impurities. 

Tetrahydronaphthalene is produced by the catalytic treatment of naphthalene with hydrogen. Various processes have been used, eg, vapor-phase reactions at 101.3 kPa (1 atm) as well as higher pressure Hquid-phase hydrogenation where the conditions are dependent upon the particular catalyst used. Nickel or modified nickel catalysts generally are used commercially however, they are sensitive to sulfur, and only naphthalene that has very low sulfur levels can be used. Thus many naphthalene producers purify their product to remove the thionaphthene, which is the principal sulfur compound present. Sodium treatment and catalytic hydrodesulfuri2ation processes have been used for the removal of sulfur from naphthalene the latter treatment is preferred because of the ha2ardous nature of sodium treatment. 

The coal tar first is processed through a tar-distillation step where ca the first 20 wt % of distillate, ie, chemical oil, is removed. The chemical oil, which contains practically all the naphthalene present in the tar, is reserved for further processing, and the remainder of the tar is distilled further to remove additional creosote oil fractions until a coal-tar pitch of desirable consistency and properties is obtained. 

The chemical oil contains ca 50 wt % naphthalene, 6 wt % tar acids, 3 wt % tar bases, and numerous other aromatic compounds. The chemical oil is processed to remove the tar acids by contacting with dilute sodium hydroxide and, in a few cases, is next treated to remove tar bases by washing with sulfuric acid. 

Naphthalenesulfonic Acid. The sulfonation of naphthalene with excess 96 wt % sulfuric acid at < 80°C gives > 85 wt % 1-naphthalenesulfonic acid (a-acid) the balance is mainly the 2-isomer (P-acid). An older German commercial process is based on the reaction of naphthalene with 96 wt % sulfuric acid at 20—50°C (13). The product can be used unpurifted to make dyestuff intermediates by nitration or can be sulfonated further. The sodium salt of 1-naphthalenesulfonic acid is required, for example, for the conversion of 1-naphthalenol (1-naphthol) by caustic fusion. In this case, the excess sulfuric acid first is separated by the addition of lime and is filtered to remove the insoluble calcium sulfate the filtrate is treated with sodium carbonate to precipitate calcium carbonate and leave the sodium l-naphthalenesulfonate/7J(9-/4-J7 in solution. The dry salt then is recovered, typically, by spray-drying the solution. 

Naphthalene sodium prepared in dimethyl ether or another appropriate solvent, or metallic sodium dissolved in Hquid ammonia or dimethyl sulfoxide, is used to treat polyfluorocarbon and other resins to promote adhesion (138—140). Sodium, usually in dispersed form, is used to desulfurize a variety of hydrocarbon stocks (141). The process is most useful for removal of small amounts of sulfur remaining after hydrodesulfurization. 

In the Sulser-MWB process the naphthalene fractions produced by the crystallisation process are stored in tanks and fed alternately into the crystalliser. The crystalliser contains around 1100 cooling tubes of 25-mm diameter, through which the naphthalene fraction passes downward in turbulent flow and pardy crystallises out on the tube walls. The residual melt is recycled and pumped into a storage tank at the end of the crystallisation process. The crystals that have been deposited on the tube walls are then pardy melted for further purification. Following the removal of the drained Hquid, the purified naphthalene is melted. Four to six crystallisation stages are required to obtain refined naphthalene with a crystallisation point of 80°C, depending on the quaHty of the feedstock. The yield is typically between 88 and 94%, depending on the concentration of the feedstock fraction. 

Both Watts and sulfamate baths are used for engineering appHcation. The principal difference in the deposits is in the much lower internal stress obtained, without additives, from the sulfamate solution. Tensile stress can be reduced through zero to a high compressive stress with the addition of proprietary sulfur-bearing organic chemicals which may also contain saccharin or the sodium salt of naphthalene-1,3,6-trisulfonic acid. These materials can be very effective in small amounts, and difficult to remove if overadded, eg, about 100 mg/L of saccharin reduced stress of a Watts bath from 240 MPa (34,800 psi) tensile to about 10 MPa (1450 psi) compressive. Internal stress value vary with many factors (22,71) and numbers should only be compared when derived under the same conditions. 

Phthalic anhydride. Naphthalene is oxidized by air to phthalic anhydride in a Bubbling flmdized reaclor. Even though the naphthalene feed is in liquid form, the reaction is highly exothermic. Temperature control is achieved by removing heat through vertical tubes in the bed to raise steam [Graham and Way, Chem. Eng. Prog., 58, 96 (Januaiy 1962)]. 

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