Cumene strong acid catalyst

Because new high-acfivify befa zeolife cafalysfs such as QZ-2000 catalyst are such strong acids, they can be used at lower reaction temperatures than SPA catalyst or other relatively lower-activity zeolites such as MCM-22 catalyst. The lower reaction temperature in turn reduces the olefin oligomerization reaction rate, which is relatively high for SPA catalyst. The result is that beta zeolite catalysts tend to have higher selectivity to cumene and lower selectivity to both nonaromatics that distill with cumene (such as olefins, which are analyzed as Bromine Index, and saturates) and heavy by-products. For example, although butyl-benzene is typically produced from traces of butylene... 

Side Chain Aikyiation ofAikyiaromatiCS. Alkylation of alkylbenzenes with alkenes or alcohols over base catalysts yield the products alkylated at the side chain, while ring-alkylation proceeds over acidic catalysts. To abstract a proton from the alkyl groups, strongly basic catalysts are required. The pKa values of toluene and cumene are 35 and 37, respectively. In the vapor-phase reaction of toluene with methanol, alkali ion-exchanged zeolites, especially, RbX and CsX give ethylbenzene and styrene as products, while acidic zeollites afford xylenes (52). 

As we saw in Section 6.3, treatment of an alkene with a strong acid, most commonly FIX, H2SO4, H3PO4, or HF/BFj, generates a carbocation. Cumene, an intermediate in the industrial synthesis of both acetone and phenol (Problem 16.65), is synthesized industrially by treating benzene with propene in the presence of phosphoric acid as a catalyst. 

Zi et al. [91] measured the acidity of chemically dealuminated Y zeohtes by titration with n-butylamine using various indicators. The strengths of the acid sites were compared to the activity of the catalysts for cumene cracking and n-propanol dehydration. Cumene cracking was only observed on strongly acidic sites (Hammett acidity function Ho < -3), while the dehydration of n-propanol was catalyzed by (nearly) all acid sites on the catalyst surface. 

Akolekar [151] found a linear relation between the number of strong acid sites (determined by adsorption of pyridine at 400 °C) and the conversion of cumene over metal-substituted AlPO-ll with the exception of Mg-AlPO-11. A closer look at the acid site distribution, however, showed that this catalyst has the largest concentration of sites with lower add strength (pyridine desorption between 300 and 400 °C). As described above, the activity of these sites must be included. Tian et al. [152] studied SAPO-11 molecular sieves, which were dealuminated by EDTA to achieve different Al contents. After de-alumination the activity for cumene cracking improved, which was attributed to the formation of strong Bronsted add sites around Si domains and to a reduction of the Lewis acidity. 

As in all alkylation reactions the catalyst used to produce cumene from propylene and benzene is a strong acid and a number of processes have been introduced. The first were developed by Distillers and Hercules in 1953 ... 

The acidic nature of NiCaY after reduction of the metal can be illustrated by using the model reaction of cracking of cumene. Figure 3 shows the catalytic activity at various temperatures and the yields of the products. The catalyst possesses high activity even at 200°C, where the conversion is 20.5 mole %. At 400° C the activity increases and the conversion reaches 97.1 mole %. At 200°C dealkylation is accompanied by disproportionation with formation of diisopropylbenzene. With increasing temperature the disproportionation decreases, while hydrogenolysis of the alkyl chain is strongly increased. 

In Section V it was shown that the Si/AI ratio has a strong influence o the acidic properties of zeolites. Dealumination, as discussed previously, is a widely used means of changing the acid character of zeolite catalysts. Such changes in the acid strength distribution are manifested as changes in catalytic behavior. For example, dealumination of HY zeolites increased the catalytic activity for cumene cracking at 573 K, reaching a maximum at a... 

In the cumene oxidation process, in a first reaction cumene is oxidized to CHP. In a second reaction, CHP is cleaved to phenol and acetone by using a strong mineral acid as catalyst. The reaction heat is 117kJ/mol for the oxidation and 252 kJ/mol for the cleavage. The oxidation is carried out at pressures ranging from atmospheric to approximately 7 bar and temperatures between 80 and 120 C. The cleavage is performed around atmospheric pressure and temperatures in the range between 40 and 80 °C. 

Phenol is the monomer used in higher quantity in the production of phenolic resins. Phenol was initially derived from coal tar, but with the increased commercialization of phenolic resins, the demand for phenol grew significantly. Currently, the peroxidation of cumene is the predominant synthetic route for the production of phenol, accounting for over 90% of world production. In this process, cumene is oxidized with oxygen to produce cumene hydroperoxide. Subsequently, the peroxide is decomposed to phenol and acetone using a strong mineral acid as a catalyst (Fink, 2005 Weber and Weber, 2010). Cumene is in turn produced from the alkylation of benzene with propylene (Weber and Weber, 2010). 

Narayanan et al. [153] compared two ZSM-5 zeoHtes, one synthesized with and the other without a template. Although these catalysts were different in the amounts of Lewis and Bronsted add sites, the conversion of cumene was found to be in the same range, which indicates that Lewis add sites did not strongly influence the cracking of cumene. More conclusions cannot be drawn from this study because of the lack of acid site distributions. 

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