Aromatization, using zeolites

Palkhiwala, A.G., lin, Y.H., Perlmutter, D.D., and Olson, D.H. (1999) Liquid phase separation of polar hydrocarbons from light aromatics using zeolites. Adsorption, 5, 399 07. 

Nitration of Fluorinated Aromatics Using Zeolite Beta as a Catalyst General Procedure ... 

Spagnol, M., Gilbert, L., Alby, D. Friedel-Crafts acylation of aromatics using zeolites, ind. Chem. Library 1996, 8, 29-38. 

FRIEDEL-CRAFTS ACYLATION OF AROMATICS USING ZEOLITES... 

Most of the industrial chlorinations of organic compounds are, at present, performed by free CI2 either in the absence of catalysts or in the presence of Lewis acid catalysts such as the halides of aluminium and iron. The major handicap of the Lewis acid catalysts like FeCb or AICI3, is the difficulty of their disposal, after use in the chlorination reaction, in an environmentally friendly manner. The use of zeolite catalysts in the chlorination processes will avoid corrosion and disposal problems. Work-up procedures to isolate and recover the desired product will also be easier leading to simpler and cleeiner process routes. In addition, if zeolites are used as solid catalysts, one may anticipate that desired changes in selectivity (enhanced para-selectivity in nuclear chlorination of aromatics, for example) may be achieved. Zeolite catalysts are well known to catalyze various synthetic transformations, however, relatively a few reports are available on the selective chlorination of aromatics using zeolite catalysts [1-4],... 

Benzoxazoles are produced in high yield from a-acylphenol oximes by a Beckmann rearrangement using zeolite catalysts <95SC3315>. The reaction of the o-benzoquinone 40 with aromatic aldehyde oximes produces the benzoxazoles 41 <95ZOR1060>. The fused oxazolium salts 43 (R = Me, Et, Pr , or Ph R2 = Me or Pr ) are formed from tropone and nitrilium hexachloroantimonates 42 <96JPR598>. 

Smith and coworkers have screened the solid catalysts for aromatic nitration, and found that zeolite (3 gives the best result. Simple aromatic compounds such as benzene, alkylbenzenes, halogenobenzenes, and certain disubstituted benzenes are nitrated in excellent yields with high regioselectivity under mild conditions using zeolite (3 as a catalyst and a stoichiometric quantity of nitric acid and acetic anhydride.11 For example, nitration of toluene gives a quantitative yield of mononitrotoluenes, of which 79% is 4-nitrotoluene. Nitration of fluorobenzene under the same conditions gives p-fluoronitrobenzene exclusively (Eqs. 2.1 and 2.2)... 

Zeolites have an enormous impact on our daily lives, both directly and indirectly. For example, upstream hydrocarbons such as aromatics and olefins are produced using zeolite catalysts. The aromatics or olefins are then separated from the reaction mixtures using zeolite adsorbents. The purified components produced by these zeolite-based methods are then used in downstream processes to produce products that we use daily, such as clothes, furniture, foods, construchon materials and materials to build roads, automobile parts, fuels, gasoline, etc. In addihon to the indirect impacts mentioned above, zeolites also have a direct impact on our daily lives. For example, zeolites are used as builders in detergent formulations. 

In contrast, there are relatively few publications on the conversion of polynuclear aromatics in zeolite catalysts. Lee et al. [16] found unusually high selectivities for 4,4 -diisopropylbiphenyl when dealuminated mordenite was used as catalyst for the alkylation of biphenyl with propene. The reactions of 1- and 2-methylnaphthalene on acid forms of zeolite X, Y, Omega, mordenite and ZSM-5 were studied byDimitrov etal. [17], S o 1 i n a s et... 

A completely new approach for BTX production has emerged in recent years. It converts C2 to C6 paraffins into aromatics using a modified ZSM-5 zeolite catalyst which contains gallium (19). An example of this approach, the Cydar process, has been in commercial operation by British Petroleum at Grangemouth, Scodand since August 1990 (20). It uses C3 C4 feed and employs UOP s CCR technology to compensate for rapid catalyst coking. 

As reported in the literature, the acylation of aromatic hydrocarbons can be carried out by using zeolites as catalysts and carboxylic acids or acyl chlorides as acylating agents. Thus toluene can be acylated by carboxylic acids in the liquid phase in the presence of cation exchanged Y-zeolites (ref. 1). The acylation of phenol or phenol derivatives is also reported. The acylation of anisole by carboxylic acids and acyl chlorides was obtained in the presence of various zeolites in the liquid phase (ref. 2). The acylation of phenol by acetic acid was also carried out with silicalite (ref. 3) or HZSM5 (ref. 4). The para isomer has been generally favoured except in the latter case in which ortho-hydroxyacetophenone was obtained preferentially. One possible explanation for the high ortho-selectivity in the case of the acylation of phenol by acetic acid is that phenylacetate could be an intermediate from which ortho-hydroxyacetophenone would be formed intramolecularly. 

In 1993, UOP commercialized an improved Pt-based catalyst, 1-210. This catalyst is based on a molecular sieve, but not an aluminosilicate zeolite. UOP claims that yields are about 10% better than those for 1-9 catalyst. EB to xylenes conversion is about 22—25% with a Cg aromatics per pass loss of about 1.2—1.5%. As discussed below, UOP s Isomar process can also use zeolite catalysts which convert EB to benzene rather than to xylenes. UOP has licensed over 40 Isomar units. 

Nitration of aromatic compounds using zeolites as catalysts. 107... 

NITRATION OF AROMATIC COMPOUNDS USING ZEOLITES AS CATALYSTS... 

Nitration of monosubstituted aromatics, toluene in particular, has been extensively studied using zeolites in order to direct the reaction towards the formation of the desired para-isomer. Toluene has been nitrated para-selectively with benzoyl nitrate over zeolite catalysts.[14,15] For example, when mordenite is used as a catalyst, MNTs are formed in almost quantitative yields, giving 67 % of the para-isomer in 10 min, but tetrachloromethane is required as solvent. However, the main problems associated with the use of benzoyl nitrate are handling difficulties due to its sensitivity toward decomposition, and the tendency toward detonation upon contact with rough surfaces. Nagy et a/.[19 21] reported the nitration of benzene, chlorobenzene, toluene and o-xylene with benzoyl nitrate in the presence of an amorphous aluminosilicate, as well as with zeolites HY and ZSM-11, in hexane as a... 

Using Menke s conditions, Smith et al.[29,30] have described a method for the nitration of benzene, alkylbenzenes and halogenobenzenes using zeolites with different topologies (HBeta, HY, HZSM-5 and HMordenite) as catalysts and a stoichiometric amount of nitric acid and acetic anhydride. The reactions were carried out without solvent at temperatures between -50 °C and 20 °C. For the nitration of toluene, tridirectional zeolites HBeta and HY were the most active catalysts achieving >99 % conversion in 5 min reaction time. However, HY exhibited selectivity to the p-nitrotoluene very similar to the homogeneous phase, while with HBeta, selectivities to p-nitrotoluene higher than 70% could be achieved. HBeta zeolite exhibited excellent para-selectivity for the nitration of the different monosubstituted aromatics (Table 5.1). The catalyst can be recycled and the only by-product, acetic acid, can be separated by vacuum distillation. 

We then carried out similar reactions in which various zeolites were used as catalysts instead of Fe(acac)3 in an attempt to determine which zeolite, if any, would be most applicable to para-selective aromatic nitration. Zeolites HB and NaB produced the greatest selectivity for para-chloronitrobenzene (85 %) and the highest yields (90 and 96 %). Therefore, zeolite HB was tested with a range of other substrates (Scheme 4). The results are shown in Table 1. 

This paper is focused on commercially important syntheses of aromatic ketones and ethers with application in pharmaceuticals, agrochemicals, perfumery, etc. It will be demonstrated using several examples that clean processes using zeolite catalysts can be substituted economically for existing polluting processes. Limitations in the use of zeolite catalysts will also be emphasized, other solid catalysts leading, in certain cases, to much better results in terms of selectivity and stability. 

The reformation of lower paraffins to aromatics has been studied for about 20 yr by using zeolite catalysts. Recently, an excellent review was published of lower alkane transformation to aromatics on ZSM-5 zeolites [2]. From the studies of the mechanism of this reaction, it has been suggested that the bifunctional catalysts, having solid acidity and dehydrogenation activity, can effectively promote the aromatization of lower paraffins[3-6]. It has been reported that ZSM-5 and ZSM-11 are excellent solid acid catalysts [7] and the transition metals [8], Ga [9] and Zn [9] show high dehydrogenation activity in this reaction. In the case of bifunctional... 

Friedel-Crafts Acylation of Aromatic Ethers Using Zeolites... 

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