Naphthalene products

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. 

Total nameplace capacity for all U.S. naphthalene producers in 1993 was 124 petroleum. Naphthalene production from 1968 to 1993 is Hsted in Table 7. 

The decline in naphthalene production in 1973 primarily resulted from competition with o-xylene as the feedstock for phthaHc anhydride. Periods of feedstock shortages and the loss of one principal producer also affected petroleum naphthalene output. 

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-... 

Aryl acetylenes undergo dimerization to give 1-aryl naphthalenes at 180 °C in the presence of ruthenium and rhodium porphyrin complexes. The reaction proceeds via a metal vinylidene intermediate, which undergoes [4 + 2]-cycloaddition vdth the same terminal alkyne or another internal alkyne, and then H migration and aromatization furnish naphthalene products [28] (Scheme 6.29). 

Experimental observations support these views. Photolysis of 1-naphthylazide in the presence of diethylamine and tetramethylethylenediamine (TMEDA) yields azirine, but no ketenimine-derived adducts at ambient temperature. " In the presence of diethylamine but in the absence of TMEDA, good yields of 1-amino-naphthalene and 1,1 -azo-naphthalene, products attributable to the triplet nitrene are observed. Good yields of 46 are also achieved when the photolysis of 1-naphthylazide and diethylamine is performed at —60 °C in the absence of TMEDA. Presumably, lowering the temperature extends the hfetime of azirine 43 by reducing its rate of reversion to singlet 1-naphthylnitrene more than it retards the rate of its reaction with diethylamine. 

Naphthalene is produced from coal tar or petroleum. It is made from petroleum by dealkylation of methylnaphthalenes in the presence of hydrogen at high temperature and pressure. Petroleum was a major source of naphthalene until the 1980s, but now most naphthalene is produced from coal tar. The pyrolysis of bituminous coal produces coke and coke oven gases. Naphthalene is condensed by cooling the coke gas and then separated from the gas. Naphthalene production in the United States is slightly greater than 100,000 tons annually. 

Two sources of naphthalene exist in the U.S. coal tar and petroleum. Coal tar was the traditional source until the late 1950s, when it was in short supply. In 1960, the first petroleum-naphthalene plant accounted for over 40% of total naphthalene production. The availability of large quantities of o-xylene at competitive prices during the 1970s affected the position of naphthalene as the prime raw material for phthalic anhydride. Production for 1992 was less than 50% of Ihe levels in the early 1980s. The last dehydroalkylation plant for petroleum naphthalene was shut down late in 1991. Coal tar has stabilized at around 85 x 103 t/yr, and petroleum-naphthalene production is around 6—8 x 103 t/yr. The reduction of petroleum production has opened the door for imported naphthalene, mainly from Canada. 

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... 

The naphthalene-rich bottoms from the solvent column then are fed to the naphthalene column where a naphthalene product (95% naphthalene) is produced. The naphthalene column is operated at near atmospheric pressure to avoid difficulties that are inherent to vacuum distillation of this... 

Alkylates made specifically as feedstocks for synthetic petroleum sulphonates are typically long chain (average C chain > 16) and may use propylene oligomers which result in branched chains. Naphthalene products use the same propylene technology but tend to shorter chains (di-isopropylnaphthalene, di-nonylnaphthalene). 

Unsymmetrically en -substituted 1,8-diborylnaphthalenes have also been prepared and investigated as bidentate Lewis acids. The synthesis of such derivatives is non-trivial because it necessitates the sequential introduction of boryl moieties at the / en-positions of the naphthalene backbone. Thus far, this strategy has only been applied successfully on few occasions. The reaction of 1,8-dilithionaphthalene-tmeda with one equivalent of dimesitylboronfluoride results in the formation of dimesityl-1,8-naphthalenediylborate 26 as a monoborylated naphthalene product (Scheme ll).32 This derivative is the only example of an anionic 1,8-boron-bridged naphthalene derivative. However, it is important to note that Siebert has reported the synthesis and structure of a neutral 1,8-boron-bridged naphthalene derivative which features a (di-Ao-propylamino)boron moiety bridging the two naphthalene peri-carbon atoms.33 A single-crystal analysis carried out on 26-Li(py)4 confirmed... 

As shown in Equation (132), dihydrofurans having a 3-acetyl group underwent benzannulation via photoinduced cleavage of the dihydrofuran ring to give naphthalene products <2001TL3351>. Helicene-type compounds and benzo[/(/]xanthenes were also produced by this method <2005TL7303>. 

The alpha dinitrotoluene will form addition products mth naphthalene and anthracene just as the alpha trinitrotoluene will do. The naphthalene product has the following formula. (12)... 

The pyrolytic studies on meteorites are commonly done at different temperatures. A preheating step is utilized to insure that any possible adsorbed gases on the surface of the meteorite from the terrestrial environment are eliminated. Several organic compounds are monitored in pyrolysates such as polycyclic aromatic compounds. As an example, the results on naphthalene production upon pyrolysis from several carbonaceous chondrites, normalized by the total carbon content before pyrolysis, are shown in Figure 17.2.1 [76],... 

Figure 17.2.1. Naphthalene production upon pyrolysis from several carbonaceous chondrites [76] reported to total carbon.

Two examples of a 1,2-diarylethylene photocyclisation have been reported in which one or both of the arenas is a naphthalene. The major product obtained by photocyclisation of (203) was (204) which results from cyclisation of the unsubstituted ortho position of (203) onto the 1-position of the naphthalene. Products of the alternative modes of cyclisation, which would yield (205), (206), or (207), were formed in little or no quantity. A study of the photocyclisation the dinaphthylethylenes (208)-(211) concludes that no dibenzo-dihydrophenanthrenes are formed which derive from cyclisation onto a ring position possessing a fluorine substituent. ... 

Diphenylmanganese (or its mesityl analog) fails to react with but-2-yne in THF, but the less basic diethyl ether allows incorporation of acetylene in the complex and the subsequent reaction. No naphthalenic product is detected, suggesting that they form only when arylchromium(II or III) is used as the condensation reagent. 

The catalyst Pd(PPh3)4 favors phenanthrene formation, while Pd2(dba)3 generates primarily the naphthalene product. 

As noted in Section 3, the lifetimes of arylalkene radical cations in the absence of added nucleophiles or alkenes are frequently determined by their reaction with excess neutral alkene in solution to generate an adduct radical cation that ultimately gives the 1,2-diarylcyclobutane or substituted naphthalene products described above. Rate constants for the addition of the radical cation to its neutral precursor have been measured recently for both styrene and diarylethylene radical cations using either flash photolysis or pulse radiolysis methods. - ... 

Figure 9.3 shows the flow-sheet for the hydrogenation of coal tar-derived naphthalene (Unionfining) the naphthalene product can be further purified by crystallization or distillation. 

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. 

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