Partial oxidation of naphthalene

An alternative route to phthalic anhydride is the partial oxidation of naphthalene. The heat of reaction is — 430 kcal/mol. This reaction can be performed using a promoted V2O5 catalyst on silica, much like that considered in Example 9.1. Suppose In(fik) = 31.6800—19,100/T for the naphthalene oxidation reaction and that the subsequent, complete oxidation of phthalic anhydride follows the kinetics of Problem 9.3. Suppose it is desired to use the same reactor as in Example 9.1 but with a,>, = 53g/ m. Determine values for and T aii that maximize the output of phthalic anhydride from naphthalene. 

Fluidized bed reactors were first employed on a large scale for the catalytic cracking of petroleum fractions, but in recent years they have been employed for an increasingly large variety of reactions, both catalytic and non-catalytic. The catalytic reactions include the partial oxidation of naphthalene to phthalic anhydride and the formation of acrylonitrile from propylene, ammonia, and air. The noncatalytic applications include the roasting of ores and Tie fluorination of uranium oxide. 

There were 820 million pounds of phthalic anhydride produced in the United States in 1995. One of the end uses of phthalic anhydride is in the fiberglass of sailboat hulls. Phthalic anhydride can be produced by the partial oxidation of naphthalene in either a fixed or a fluidized catalytic bed. A flowsheet for die commercial process is shown in Figure P3-11. Here the reaction is carried out in a flxed-bed reactor with a vanadium pentoxide catalyst packed in 25 -mm-diameter tubes. A production rate of 31,000 tons pet year would require 15,000 tubes. 

The production of phthalic anhydride by partial oxidation of naphthalene was carried out in fluid-bed reactors for many years, and performance... 

As an example of selective molecular recognition with the imprinted silica 2, a Knoevenagel C-C bond-forming reaction was performed with a bifunctional reactant (Fig. 9). This type of a sequential reaction system is important in numerous industrial applications such as the dehydrogenation of butylene to butadiene or the partial oxidation of naphthalene or o-xylene to phthalic anhydride [44]. The ability to suppress the B to C reaction avoids production of undesired products in these cases. 

Problem 8-4 (Level 3) A pilot plant is being operated to test a new catalyst for the partial oxidation of naphthalene to phthalic anhydride. The chemistry of this process can be approximated as two first-order reactions in series ... 

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). 

Either naphthalene or ortho-xylene is an acceptable starting material for partial oxidation to phthalic anhydride, but current raw materials costs favor the former as a starting material. Both fixed and fluidized bed processes have been used on a commercial scale, but you are to focus your attention on the former. Figure 13.5 is a schematic flow diagram of the proposed process. Most research groups that have studied the catalytic oxidation of naphthalene over vanadium pentoxide agree that the principal reactions are... 

Pulping additives such as quinoid compounds increase the yield of the pulp mass up to 4% [128]. For commercial application the most promising additives are anthraquinone (AQ) or the more convenient soluble salt of tetrahydroan-thraquinone (THAQ). If AQ or THAQ could be obtained at a price below 2/kg it would find a substantial market as a pulping additive [129], Commercial production of THAQ is now based on the partial thermochemical oxidation of naphthalene. In recent years, however, the lure of the pulp market has promoted several attempts to develop a process for the electrosynthesis of THAQ based on the indirect electrooxidation of naphthalene to naphthaquinone (NQ) with Ce4+, according to the stoichiometry of the reactions 1, 2 and 3. 

Fluidised catalysts are also used in the synthesis of high-grade fuels from mixtures of carbon monoxide and hydrogen, obtained either by coal carbonisation or by partial oxidation of methane. An important application in the chemical industry is the oxidation of naphthalene to phthalic anhydride, as discussed by Riley(131). The kinetics of this reaction are much slower than those of catalytic cracking, and considerable difficulties have been experienced in correctly designing the system. 

The oxidation of aromatic hydrocarbons originating from coal is one of the first organic gas phase oxidation processes carried out on an industrial scale. The development of these processes was initiated by the discovery that the V2Os catalyst used for the oxidation of sulphur dioxide was also applicable to the partial oxidation of benzene to maleic anhydride and naphthalene to phthalic anhydride. Remarkably, V2Os-based catalysts are still used in these processes today as they appear superior to any other type of catalyst. 

The gas phase oxidation of naphthalene to phthalic anhydride over V2Os-based catalysts is one of the oldest successful partial oxidation processes and is still of industrial importance today. Common commercial catalysts are modified silica-supported V—K—S—O catalysts and catalysts similar to those used for benzene or o-xylene oxidation. Maximum phthalic anhydride yields of 80—85 mol. % (92—98 wt. %) at 350—400°C are reported. By-products are naphthoquinone (2—5%), maleic anhydride (2— 5%) and carbon oxides. 

Maleic acid and anhydride are recovered as by-products of the oxidation of xylenes and naphthalenes to form phthalic acids, and are also made specifically by the partial oxidation of benzene over a vanadium pentoxide (V205) catalyst. This is a highly exothermic reaction, and several modifications of the basic process exist, including one using butylenes as the starting materials. 

In 1970, Rozhkov and coworkers reported the first example of anodic partial fluorination of aromatic compound [Eq. (3)] [14,15]. They found that anodic oxidation of naphthalene in Et4NF-3HF/MeCN provided 1-fluoronaphthalene mainly, while the use of Et4NF instead of Et4NF-3HF led to the efficient formation of 1,4-difluoronaphthalene solely. 

Partial oxidation of heavier substrates to promote their functionalization (i) fluorene to fluorenone, naphthalene to naphthoquinone or anthracene to anthraquinone,... 

Partial oxidation of hydrocarbons employing mixed metal oxides as catalysts comprises an economically important class of reactions for the upgrading of base feed stocks [3]. An illustrative example of it is the partial oxidation of o-xylene and/or naphthalene to phthalic anhydride (PA) with a world production of 3.2 million metric tons per year, industrially carried out in shell and tube reactors using air as the oxidizing agent [4]. 

Bosetti et al [4.29] have reported the oxidation of naphthalene by Pseudomonas fliioroscens to optically pure cA-1,2-dihydroxy-1,2-dihydronaphtalene. They reported that the MBR, after 25 h of reaction, had a production rate three times that of a batch reactor. Recently Miyano et al [4.30] reported improvement in the rate of vitamin B12 production by Propionibacterium freudenreichi using a hollow-fiber MBR. The strain used produced also propionic and acetic acid, which inhibit its activity. The authors compared the MBR with a batch reactor using a co-culture. For the batch reactor application, a second strain Ralstodia. Eutropha), which was able to metabolize partially the toxic propionic acid, was introduced into the fermentor. The experimental results of Miyano et al [4.30] showed that the MBR was much more efficient than the co-culture batch operation. 

Catalytic partial oxidation of o-xylene and naphthalene is performed mostly in intensively cooled multi-tubular fixed bed reactors, but systems with a fluidized bed were also developed. Typically, V20s/Ti02 catalysts with K2SO4 or A1 phosphates as promoter are used. In fixed bed reactors, the conversion of both feedstocks per pass is around 90%, and the selectivity is in the range 0.86-0.91 mol PA per mol naphthalene and 0.78 mol per mol o-xylene. (Note that the selectivity would be 100%, if only the reactions according to Eqs. (6.13.1) and (6.13.2), respectively, would take place.) The active compounds are distributed on spheres of porcelain, quartz, or silicium carbide (shell catalyst). The thickness of the shell is only around 0.2 mm, and the diffusion paths for the reactants are short. By this means, the influence of pore diffusion is small, and the unwanted oxidation of phthalic acid anhydride to CO2 is suppressed compared to a catalyst with an even distribution of active compounds where the influence of pore diffusion would be much stronger (see Section 4.5.6.3 Influence of Pore Diffusion on the Selectivity of Reactions in Series ). Thus the intrinsic reaction rates are utilized for the modeling of a technical reactor (next Section 6.13.2). 

The strongly exothermic partial oxidation of o-xylene (and also of naphthalene) is carried out in multi-tubular reactors (with about 10000 tubes) cooled by a molten salt. To simulate the multi-tubular reactor, the two-dimensional reactor model is appropriate in order to account for the radial temperature gradient in the catalyst bed. 

Phthalic anhydride is produced by partial oxidation of o-xylene or naphthalene. Recently the path from naphthalene has been dramatically reduced due to a lack of availability of the raw material. Polynt has been producing PA since its foundation in 1955 based on proprietary technology and catalysts. 

Sumimoto introduced a new sebacic acid process including several catalytic hydrogenation reactions.342 The synthesis starts with naphthalene, which is first partially hydrogenated to tetralin over cobalt oxide or molybdenum oxide, then to decalin over ruthenium or iridium on carbon. The selectivity to cw-decalin is better than 90%. In a later phase of the synthesis 5-cyclododecen-l-one is hydrogenated over Raney nickel to obtain a mixture of cyclododecanone and cyclodode-canol in a combined yield of 90%. The selectivity of this step is not crucial since subsequent oxidation of either compound leads to the endproduct sebacic acid. 

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