Processing, naphthalene production

The quahty of naphthalene required for phthaUc anhydride manufacture is generally 95% minimum purity. The fixed plants do not require the high (>98%) purity naphthalene product and low (<50 ppm) sulfur. The typical commercial coal-tar naphthalene having a purity ca 95% (freezing point, 77.5°C), a sulfur content of ca 0.5%, and other miscellaneous impurities, is acceptable feedstock for the fixed-bed catalyst process based on naphthalene. 

The use of computers has made it possible to characterise models with large numbers of individual steps. Andersson and Lamb [25] used an analogue computer to estimate parameters in a model with 15 reactions which described naphthalene production by hydrodealkylation. Also, they were able to predict temperature distributions and effluent concentrations for a commercial reactor. Kurtz [26] took 200 simultaneous reactions into account in an experimental study of the gas-phase chlorination of methyl chloride. Model discrimination and parameter estimation for catalytic processes are discussed in a comprehensive review by Froment [27]. 

Finn et al. reported the first instance of a metal-catalyzed aromatization of enediynes via vinylidene intermediates [7]. Aromatization of unstrained enediynes is knovm as Bergman cyclization and occurs at 200-250 °C via diradical intermediates [8]. Ruthenium-vinylidene complex 7 was formed when 1,2-benzodiyne 6 was treated with RuCp(PMe3)2Cl and NH4PF6 at 100 °C, ultimately giving good naphthalene product 8 ingood yields (Scheme 6.4). This process mimics Myers-Saitocyclizationof5-allene-3-... 

Coal-Tar Process. The largest quantities of naphthalene are obtained from the coal tar that is separated from the coke-oven gases. The coal tar first is processed through a tar-distillation step where ca the first 20 wt% of distillate, i.e., chemical oil, is removed. The chemical oil contains practically all the naphthalene present in the tar. It 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 sulfunc acid. Principal U.S. producers obtain their crude naphthalene product by fractional distillation of the tar acid-free chemical oiL... 

Electron-transfer Initiation. Initiation of carboanionic growth by aromatic radical anions involves a direct electron transfer to monomer, though in the case of aromatic components with electron affinities greater than naphthalene the process is slow. Perhaps more importantly these can allow a subsequent side-reaction with the growing carboanion (Scheme 13). While the product (15)... 

The Sulzer-MWB and the Brodie crystallization processes are most commonly used to recover naphthalene by crystallization. Figure 9.5 shows the Sulzer-MWB flow sheet, which is operated in a modified form in plants with a naphthalene production of up to 60,000 tpa. 

Naphthalene is fed to a phthalic anhydride production process. The feed is available at 208°C and 79 2q kPa. The flowrate is 18,500 kg/h in 1.5 in Schedule 40 pipe. A punp with NPSH characteristics as plotted in Figure 18.9 is used. Will this punp be suitable for the desired duty If not, what modifications would be necessary in order to use the existing punp Be quantitative. 

From this stage, each diradical species can follow two reactions pathways. Firstly a termination process, by intramolecular cyclization, followed by an irreversible aromatization giving naphthalenic species secon y a propagation process by reacting either with carbon-1 or carbon-2 of a new molecule of monomer to form trimer diradicals ii, l2 t3 etc... These two possibilities are explicited on diradical 4 in scheme 3. Such a mechanism explains the formation of naphthalenic products 6 and Z (from Qi and ds respectively) but also the 2,6-disubstituted isomer one, which was not found experimentally. 

For substances with a moderate triple point pressure e.g., benzoic acid, 6 mm., m.p. 122° naphthalene, 7 mm., m.p. 80° ), the simple process described above for camphor will not give a satisfactory yield of a sublimed product. Thus, for example, if naphthalene is heated it will melt at T (80°), and will boil when the vapour pressure is 760 mm. (218°) ... 

The theory of sublimation, t.e. the direct conversion from the vapour to the sohd state without the intermediate formation of the liquid state, has been discussed in Section 1,19. The number of compounds which can be purified by sublimation under normal pressure is comparatively small (these include naphthalene, anthracene, benzoic acid, hexachloroethane, camphor, and the quinones). The process does, in general, yield products of high purity, but considerable loss of product may occur. 

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 unit Kureha operated at Nakoso to process 120,000 metric tons per year of naphtha produces a mix of acetylene and ethylene at a 1 1 ratio. Kureha s development work was directed toward producing ethylene from cmde oil. Their work showed that at extreme operating conditions, 2000°C and short residence time, appreciable acetylene production was possible. In the process, cmde oil or naphtha is sprayed with superheated steam into the specially designed reactor. The steam is superheated to 2000°C in refractory lined, pebble bed regenerative-type heaters. A pair of the heaters are used with countercurrent flows of combustion gas and steam to alternately heat the refractory and produce the superheated steam. In addition to the acetylene and ethylene products, the process produces a variety of by-products including pitch, tars, and oils rich in naphthalene. One of the important attributes of this type of reactor is its abiUty to produce variable quantities of ethylene as a coproduct by dropping the reaction temperature (20—22). 

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. 

Naphthalene derivatives are of diverse importance as intermediates for agricultural, constmction, pharmaceutical, photographic, mbber, tanning, and textile chemicals. In this article production figures, economics, and processes are discussed for most commercially important compounds. Sources for a more comprehensive study of naphthalene derivatives are available (1 8). 

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. 

A naphthalene sulfonation product that is rich in the 2,6-isomer and low in sulfuric acid is formed by the reaction of naphthalene with excess sulfuric acid at 125°C and by passing the resultant solution through a continuous wiped-film evaporator at 245°C at 400 Pa (3 mm Hg) (26). The separation in high yield of 99% pure 2,6-naphthalenedisulfonate, as its anilinium salt from a cmde sulfonation product, has been claimed (27). A process has been patented for the separation of 2,6-naphthalenedisulfonic acid from its isomers by treatment with phenylenediarnine (28). 

H-acid, l-hydroxy-3,6,8-ttisulfonic acid, which is one of the most important letter acids, is prepared as naphthalene is sulfonated with sulfuric acid to ttisulfonic acid. The product is then nitrated and neutralized with lime to produce the calcium salt of l-nitronaphthalene-3,6,8-ttisulfonic acid, which is then reduced to T-acid (Koch acid) with Fe and HCl modem processes use continuous catalytical hydrogenation with Ni catalyst. Hydrogenation has been performed in aqueous medium in the presence of Raney nickel or Raney Ni—Fe catalyst with a low catalyst consumption and better yield (51). Fusion of the T-acid with sodium hydroxide and neutralization with sulfuric acid yields H-acid. Azo dyes such as Direct Blue 15 [2429-74-5] (17) and Acid... 

NaOH solution is added dropwise to an aqueous suspension of this ester at 40—70°C over 1 h and the reaction mixture kept for 2 h to give 86.6% DHNA of 98.7% purity (74), which is then esterified with (CgH O) to obtain PDNA. The esterification process is dramatically improved by adding a small amount of inorganic or organic acid, preferably methanesulfonic acid, benzene sulfonic acid, or naphthalene sulfonic acid subsequent isolation and crystallisation gives a pure product (75). 

Approximately 45% of the world s phthaUc anhydride production is by partial oxidation of 0-xylene or naphthalene ia tubular fixed-bed reactors. Approximately 15,000 tubes of 25-mm dia would be used ia a 31,000 t/yr reactor. Nitrate salts at 375—410°C are circulated from steam generators to maintain reaction temperatures. The resultant steam can be used for gas compression and distillation as one step ia reduciag process energy requirements (100). 

A typical primary distillation product pattern at a coke-oven tar-processing plant is given in Table 1. At some coke-oven distilleries, only one fraction, designated naphthalene oil, is taken between 180 and 240°C. Two fractions, light creosote or middle oil (230—300°C) and heavy creosote or heavy oil (above 300°C), are taken between the naphthalene oil and pitch. 

The carbonization by-products are usually refined, within the coke plant, into commodity chemicals such as elemental sulfur (qv), ammonium sulfate, benzene, toluene, xylene, and naphthalene (qv) (see also Ammonium compounds BTX processing). Subsequent processing of these chemicals produces a host of other chemicals and materials. The COG is a valuable heating fuel used mainly within steel (qv) plants for such purposes as firing blast furnace stoves, soaking furnaces for semifinished steel, annealing furnaces, and lime kilns as well as heating the coke ovens themselves. 

Arylalkylsulfones ate important intermediates obtained by alkylation of arylsulfinic acids. The latter ate obtained by reduction of the corresponding sulfonyl chloride. This reduction process is simple and of general appHcation involving the addition of the isolated sulfonyl chloride paste to excess aqueous sodium sulfite followed by salting-out the product and isolation. With mote rigorous reduction conditions, such as zinc/acid, sulfonyl chlorides ate reduced through to aryknercaptans, eg, 2-mercaptonaphthalene is manufactured from naphthalene-2-sulfonyl chloride. 

The process of anionic polymerisation was first used some 60 or more years ago in the sodium-catalysed production of polybutadiene (Buna Rubbers). Typical catalysts include alkali metals, alkali metal alkyls and sodium naphthalene, and these may be used for opening either a double bond or a ring structure to bring about polymerisation. Although the process is not of major importance with the production of plastics materials, it is very important in the production of synthetic rubbers. In addition the method has certain special features that make it of particular interest. 

This type of addition process is particularly likely to be observed when the electrophile attacks a position that is already substituted, since facile rearomatization by deprotonation is then blocked. Reaction at a substituted position is called ipso attack. Addition products have also been isolated, however, when initial electrophilic attack has occurred at an unsubstituted position. The extent of addition in competition with substitution tends to increase on going to naphthalene and the larger polycyclic aromatic ring systems. ... 

The raw material has to be washed to remove impurities. Diluted sodium hydroxide allows the removal of phenols and benzonitrile, and diluted sulphuric acid reacts with pyridine bases. The resulting material is distilled to concentrate the unsaturated compounds (raw feedstock for coumarone-indene resin production), and separate and recover interesting non-polymerizable compounds (naphthalene, benzene, toluene, xylenes). Once the unsaturated compounds are distilled, they are treated with small amounts of sulphuric acid to improve their colour activated carbons or clays can be also used. The resulting material is subjected to polymerization. It is important to avoid long storage time of the feedstock because oxidation processes can easily occur, affecting the polymerization reaction and the colour of the coumarone-indene resins. 

An electrostatic precipitator is used to remove more tar from coke oven gas. The tar is then sent to storage. Ammonia liquor is also separated from the tar decanter and sent to wastewater treatment after ammonia recovery. Coke oven gas is further cooled in a final cooler. Naphthalene is removed in a separator on the final cooler. Light oil is then removed from the coke oven gas and is fractionated to recover benzene, toluene, and xylene. Some facilities may include an onsite tar distillation unit. The Claus process is normally used to recover sulfur from coke oven gas. During the coke quenching, handling, and screening operation, coke breeze is produced. The breeze is either reused on site (e.g., in the sinter plant) or sold offsite as a by-product. 

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