Cumene conversion

On heating deactivated parent H-mordenite (80 to 33% cumene conversion), quantities of desorbate are so low (30.6 g/gram catalyst) that the desorbable deactivants, and hence the catalyst activity, must be at the pore mouth in the deactivated material. Non-desorbable polynuclear aromatics fill the mordenite tube. On the other hand, aluminum-deficient H-mordenite did not deactivate significantly for the same cumene treatment. Activity of this catalyst could be throughout the tube, but because of the disperse nature of the alumina sites, the high activity of parent H-mordenite, only active at its mouth, is not approached. 

Special care has to be taken, however, that the quinoline titer truly represents the minimum amount of catalyst poison. In most cases this type of base is adsorbed by inactive as well as active sites. Demonstration of indiscriminate adsorption is furnished by the titration results of Roman-ovskii et al. (52). These authors (Fig. 13) showed that introduction of a given dose of quinoline at 430°C in a stream of carrier gas caused the activity of Y-zeolite catalyst (as measured by cumene conversion) to drop with time, reach a minimum value, then slowly rise as quinoline was desorbed. The decrease in catalytic activity with time is direct evidence for the redistribution of initially adsorbed quinoline from inactive to active centers. We have observed similar behavior in carrying out catalytic titrations of amorphous and crystalline aluminosilicates with pyridine, quinoline, and lutidine isomers. In most cases, we found that the poisoning effectiveness of a given amine can be increased either by lengthening the time interval between pulse additions or by raising the sample temperature for a few minutes after each pulse addition. 

Despite the presence of sites that strongly chemisorb a variety of molecules, pure silica gel is catalytically inactive for skeletal transformations of hydrocarbons. However, as has recently been emphasized by West et al. (79), only trace amounts of acid-producing impurities such as aluminum need be present in pure silica gel to provide catalytic activity— especially when a facile reaction such as olefin isomerization is used as a test reaction. They found that addition of 0.012% Al to silica gel resulted in a 10,000-fold increase in the rate of hexene-1 isomerization at 100°C over the pure gel. An earlier study by Tamele et al. (22) showed that introduction of 0.01% wt Al in silica gel produces a 40-fold increase in cumene conversion when this hydrocarbon is cracked at 500°C. The more highly acidic solids that are formed when substantial concentrations of metal oxides are incorporated with silica are discussed in following sections. 

Figure 2. Dependence of catalytic activity for cumene conversion at 290°C on framework aluminum content ( O ) DY550 series, ( ) DY-(Si/Al) series, ( ) SDY, ( A ) HY.

The results can be divided into studies of the coke deposition rate as a function of the amount and type of reactants injected, and studies of the activity (cumene conversion) vs. the cumulative coke level Because of space considerations, only the former is discussed. 

Activity. We concentrate on the conversion of the "actual" feed reactant, cumene, as the measure of activity. We note how the conversion changes when different amounts of different coking additives (decane, naphthalene) are mixed with the feed, and pulsed over a catalyst of different coke levels. We also report data on the conversions of the additives decane or naphthalene under the same conditions. As mentioned earlier, cumene conversion is obtained by carrying out a benzene-ring balance on the contents of the sample collector after each pulse procedure, while conversions of naphthalene or decane are obtained by comparing peak areas with and without catalyst. 

Figure 7. Activity of catalyst for cumene conversion (by benzene-ring balance) in cumene - naphthalene mixtures as a function of coke on the catalyst.

Cumene conversion was determined from an overall mass balance over the cracking reaction system from both the normal and blank runs. 

The cumene conversion at 3 levels catalyst to feed ratio, Cp 5, 50 and 100 1 are shown in Figure 3 in which the conversions are plotted against the time on stream. The general characteristics of catalytic activity (conversion) are exhibited in which a very rapid decline in activity occurs initially and then it is followed by a more graduated loss in activity. 

To effectively utilize the information obtained from the experimental work, it is advantageous to re-evaluate the same data based on the normalized benzene selectivity as described by Equation (5). A more useful trends can be seen as given in Table 1, in which the benzene production and normalized benzene selectivity are listed with respect to the cumene conversion for the same two values of Cp as in the Figure 6. From columns 2 and 4, the maximum benzene production are clearly shown for Cp = 5 and 50 respectively. The best production at low Cp is when the cumene conversion is at 60%, while at high Cp, this is at 75% conversion. These conversion levels are typical in the FCC unit operation. 

On its face value, the cumene conversion and benzene selectivity seem to be better at Cp = 50 than 5. This is only because more catalyst has been used. In fact, it is 10 times more. The normalized benzene selectivities given in columns 3 and 5 with respect to Cp = 5 and 50 provide clearer indication. The physical structures of the catalyst pores and zeolites obtmned from electronic scanning microscope analysis are also important. However, they are not reported here since this is out of the scope of the present contribution and can be found elsewhere[ 15]. To achieve the optimal catalyst effectiveness and obtain the maximum product selectivity, the preferable operation conditions, in the present case, are at a catalyst to feed ratio of 5 while the conversion level is at 60%. 

Galich el al. 136) showed that, within an alkali metal-exchanged X series (Table XIX), as cationic radius increased, cumene conversion decreased. Also, the products contained larger amounts of l-methyl-3-ethylbenzene and less toluene, ethylbenzene, and propenylbenzene. The dealkylation of lower temperature (260°) over REX catalyst than did other related dealkylations. The major liquid product was benzene, with small amounts of toluene, ethylbenzene, and cumene. Isobutane was the major gaseous product, and no olefins were observed. 

A plot of different feed rates versus cumene conversion is shown in Fig 3. The conversion decreases with increase in feedrate, while the overall selectivity to cumene and DIPB remains... 

In the present work, Si/Al ratios varied from 6 to 600. Neither initial activity levels nor sustained operation showed an activity advantage for A1203 removal. Rather, activity appeared to decrease with increasing Si/Al at the 1% cumene conversion level, both with H2 and with helium. 

Cumene conversion under excess of benzene was studied over H-ZSM-11 in the adsorbed phase at 473 K by in situ C MASNMR. To follow the fate of different carbon atoms during the reaction, cumenes labelled with C-isotopes either on a-or on p-positions of the alkyl chain or in the aromatic ring have been synthesized. The primary product of cumene conversion over H-ZSM-11 was found to be n-propylbenzene. It is formed via intermolecular reaction of cumene and benzene. At long reaction times, the formation of n-propylbenzene is accompanied by complete scrambling of both cumene and n-propylbenzene alkyl chain carbon atoms and formation of toluene, ethylbenzene and butylbenzene. The rate of isomerization is higher than the rate of scrambling and fragmentation. 

The ability of 13C MASNMR to distinguish unambiguously between the different carbon atoms in the alkyl chain and the aromatic ring of cumene and NPB motivated our choice of this method to trace the label during the reaction. Table 2 lists the chemical shifts of the carbon atoms of cumene, NPB and some other byproducts which might be formed in the course of cumene conversion. 

In experiment A, cumene labelled in the ring as well as In the alkyl chain was used to follow the fate of the aromatic ring atoms and to simultaneously follow the cumene conversion to NPB and other products. Aromatic regions of the MASNMR spectra taken from sample A before and after treatments at 486 K for 60 and 540 min are shown on Figure la. The spectrum of initial unheated sample contains 3 lines at 149 ppm, corresponding to i c-i in cumene, at 128.5 ppm, ascribed to i3C-3,5 in cumene, and in benzene and at 126.5 ppm - to i3C-2,4,6 in cumene. After heating for 60 min, the conversion of cumene to NPB estimated from the aliphatic part of the spectrum, was more than 50% meanwhile the line at... 

In the presence of an excess of benzene, the primary product of cumene conversion over H-ZSM-11 is n-propylbenzene. NPB is formed via intermolecular reaction of cumene with benzene. 

Isopropylbenzene. See also Cumene conversion to phenol, 947, 969 nitration, 878... 

A method is described for the preparation of zinc-containing zeolite by direct synthesis from hydrogels. The synthesis of Zn-MFI type zeolite materials and the post synthesis introduction of Cu are discussed. The samples are characterized by XRD, AAS, thermal analysis, SEM and Si-NMR spectroscopy. The catalytic results on the cumene conversion are discussed. 

Find whether tetraline will act as an inhibitor or accelerator when added in small amounts to cumene. Conversely, find the effect on the rate of a small addition of cumene to tetraline. Other things being equal, which pure compound oxidizes faster, cumene or tetraline ... 

The use of variable-valence metal compounds as catalysts, as a rule, is accompanied by a decrease in the selectivity of the oxidation of cumene to the hydroperoxide, mainly due to the formation of cumyl alcohol upon the decomposition of CH [35, 36], An increase in the reaction rate witii retention of high selectivity up to cumene conversion of 35-40% is observed at oxidation of cumene when zinc and cadmium complexes of N-heterocyclic bases are used as catalysts [37],... 

Cumene conversion was developed to the production stage by BP Chemicals and Hercules in the early 1950 s, and modified further by Phenolchemie,... 

The addition of Co and Mn acetates to the reaction mixture changes the general features of the products formation kinetics (1.19). Thus increases and acetophenone has been identified (AcP). The sum of the products exceeds by 7.3-fold that at cumene ozonolysis. OZ is obtained at the interaction of ozone with the benzene ring, and AcP is provided by the monomolecular decomposition reaction of RO"-radicals. Most likely the main role of Mn is in accelerating of these two reactions. The catalytic properties of the metal salts studied are confirmed by the ratio of the amount of the products formed in the catalyzed and noncatalysed processes per unit of absorbed ozone. At Co Mn=5 l this ratio becomes equal to 7.3 and is greater by about 6% than that in the absence of Mn. The cumene conversion is increased but the selectivity of the process is reduced. The contribution of OZ and ApC to the total sum of the products formed is 27%. The synergism of the simultaneous action of the both salts (Fig. 19) can be associated with the occurrence of the following reaction ... 

Ethylation of cumene proceeds at 313 K A very high selectivity (99.6%) is obtained at a cumene conversion of 99.6% over K/KOH/AI2O3, prepared in a similar manner to Na/Na0H/Al203. The higher basicity of the former is confirmed from the binding energy of Ois by XPS. 

Figure 5. Dependence of cumene conversion in Al-Si catalysts synthesized at pH = 10.7 from sols (1 ) and gels (2 ) at 723 K (1) and 773 K (2).

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