Isopropylation, benzene, rate

The column used was a Pecosphere 3 mm in diameter and 3 cm long carrying a Cl8 stationary phase. The mobile phase was a mixture of methanol (75%) and water (25%) at a flow rate of 2 ml/min. The solutes were 1 benzene, 2 toluene, 3 ethyl benzene, 4 isopropyl benzene, 5 t-butylbenzene, 6 anthracene, and 7 sodium chloride. 

Excess benzene is always used in the reactors, also for two reasons. First, the benzene acts like a heat sponge, mitigating the rate at which the temperature increases due to the exothermic reaction. Second, excess benzene helps eliminate some of the undesirable side reactions that can take place, mainly the formation of di- or tri-isopropyl benzene (benzene hooking up with two or three propylenes) or other miscellaneous compounds. 

A sieve-tray distillation column with a partial reboiler and a total condenser is to be designed to separate a mixture of benzene, toluene, and cumene (a common name for isopropyl benzene). The feed flows at the rate of 40 mol/s benzene, 30 mol/s toluene, and 30 mol/s cumene. It enters the column at a pressure of 1.05 atm and 50 mol% vaporized. We desire at least 98.5% recovery of the toluene in the distillate, and at least 98.5% recovery of the cumene in the bottoms. Design the column for a reflux ratio of 2.0. 

Cumene (isopropyl benzene) was used as oxidizing hydrocarbon and azo-bis-isobutyronitrile as initiator, which forms ffee-radicals upon thermal decay. Initiating rate was determined from the following formula ... 

The functionalization of EPDM with MA is carried out in a Berstorff 25 mm corotating twin screw extruder. EPDM (Keltan 740 DSM), Perkadox 14 (bis(tert. butyl peroxy isopropyl) benzene AKZO half life times 5 min at 175 °C 10 sec at 210 °C [4]) and Nourymix(50/50 wt% masterbatch of MA on polyethylene AKZO) were mixed and starved fed to the first section of the extruder. A nitrogen atmosphere was maintained over the reaction mixture throughout the extruder. In the last sections free maleic anhydride and other volatile components were removed by applying vacuum on the last vent. Standard extrusion conditions were throughput rate 1 kg/h residence time 5 minutes rotor speed 150 rpm Mass temperatures in the die 220-260 OC. The MA-content in the rubber was determined with potentiometric titration and infrared analysis. 

Effects other than those of purely viscometric origin were seen to be significant in a schematic study by McHugh and co-workers of the free radical decomposition of cumene hydroperoxide [48], and subsequent oxidation of cumene (isopropyl benzene) [49, 50] in a range of supercritical and liquid solvents. The effective non-catalysed rate coefficients for cumene hydroperoxide decomposition in non-polarisable supercritical fluids (krypton, xenon) were greater than that for non-polar liquid cyclohexane, as expected a priori on the basis of viscosities. Yet, liquid 1-octene and 1-hexanol gave similar... 

Low substrate selectivity accompanying high positional selectivity was also found in isopropylation of a range of alkyl and halogenobenzenes by /-propyl bromide or propene in nitromethane, tetramethylene sulphone, sulphur dioxide, or carbon disulphide, as indicated by the relative rates in Table 86. The toluene benzene reactivity ratio was measured under a wide range of conditions, and varied with /-propyl bromide (at 25 °C) from 1.41 (aluminium chloride-sulphur... 

Since there is inherent in reactions which give low selectivities, the possibility that non-competitive conditions are responsible, Olah and Overchuck359 have measured directly the rates of benzylation, isopropylation, and fer/.-butylation of benzene and toluene with aluminium and stannic chlorides in nitromethane at 25 °C. Apparent second-order rate coefficients were obtained (assuming that the concentration of catalyst remains constant), but it must be admitted that the kinetic plots showed considerable departure from second-order behaviour. The observed rate coefficients and kreh values determined by the competition method are given in Table 88, which seems to clearly indicate that the competitive ex-... 

Furfuryl acetate. Reflux a mixture of 39 2 g. (34 8 ml.) of redistilled furfuryl alcohol, 48 g. of glacial acetic acid, 150 ml. of benzene and 20 g. of Zeo-Karb 225/H in a 500 ml. bolt-head flask, using the apparatus described under isoPropyl Lactate. After 3 hours, when the rate of collection of water in the water separator is extremely slow, allow to cool, separate the resin by suction filtration, and wash it with three 15 ml. portions of benzene. Remove the benzene, etc., from the combined filtrate and washings under reduced pressure (water pump) and then collect the crude ester at 74-90°/10 mm. a small sohd residue remains in the flask. Redistil the crude ester from a Claisen flask with fractionating side arm pure furfuryl acetate passes over at 79-80717 mm. The yield is 14-5 g. 

Toluene alkylation with isopropyl alcohol was chosen as the test reaction as we can follow in a detail the effect of zeolite structural parameters on the toluene conversion, selectivity to cymenes, selectivity to para-cymene, and isopropyl/n-propyl ratio. It should be stressed that toluene/isopropyl alcohol molar ratio used in the feed was 9.6, which indicates the theoretical toluene conversion around 10.4 %. As you can see from Fig. 2 conversion of toluene over SSZ-33 after 15 min of T-O-S is 21 %, which is almost two times higher than the theoretical toluene conversion for alkylation reaction. The value of toluene conversion over SSZ-33 is influenced by a high rate of toluene disproportionation. About 50 % of toluene converted is transformed into benzene and xylenes. Toluene conversion over zeolites Beta and SSZ-35 is around 12 %, which is due to a much smaller contribution of toluene disproportionation to the overall toluene conversion. A slight increase in toluene conversion over ZSM-5 zeolite is connected with the fact that desorption and transport of products in toluene alkylation with isopropyl alcohol is the rate controlling step of this reaction [9]... 

The LB film depositions were performed using a Joyce-Loebl Langmuir Trough IV equipped with a microbalance for measurement of the surface pressure by the Wilhelmy plate method. Filtered deionized water with a pH of 7 was used for the subphase. For the electron beam lithography study, PMMA was spread on the water surface from a dilute benzene solution ( 10 mg PMMA in 20 ml benzene). The novolac/PAC mixtures were spread from solutions ( 20 mg solids in 10 ml solvent) of isopropyl acetate. For the fluorescence studies, the PMMA/PDA mixture was spread on fee water surface from a dilute benzene solution (1.75 mg PDA and 8.33 mg PMMA in 20 ml benzene). Prior to compression, a 20 min interval was allowed for solvent evaporation. The Langmuir film was compressed to the desired transfer pressure at a rate of 50 cm2/min, followed by a 20 minute equilibration period. The Cr-coated silicon wafers and quartz wafers were immersed into fee subphase before... 

Ethylation, which involves an unstable ethylcarbenium ion as intermediate, is much slower (1500 times over AICI3) than isopropylation. It is also the case in benzene alkylation with propene for the undesired formation of n-propylbenzene, which involves a primary n-propyl carbocation. Furthermore, as alkyl substituents activate the aromatic ring, consecutive alkylation of the primary product occurs with a greater rate than the first alkylation step ( 2 > i)-... 

Figure 5. Dependence of rate decay lime constant on reactant mole ratio for benzene isopropylation over HY...

The coexistence of NH3 is indispensable for selective benzene oxidation. Neither benzene oxidation nor combustion proceeded in the absence of NH3 (Table 2.5). Fe/ZSM-5 has been reported to be active and selective for phenol synthesis from benzene using N20 as an oxidant [97], but selective benzene oxidation did not proceed with N20 instead of 02. The addition of H20 to the system gave no positive effects on the catalytic performance, either. In addition, other amine compounds such as pyridine and isopropyl amine did not produce phenol. The phenol formation rate and selectivity increased with increasing NH3 pressure because the coexisting NH3 produces active Re clusters, as described below, and reached maximum conversion and selectivity at a partial pressure of NH3 of around 35—42kPa. 

A solution of 8.2 g. (0.040 mole) of purified aluminum isopropoxide and 2.75 g. (0.011 mole) of 4-keto-l,2,3,4-tetrahydrochrysene in 25 cc. of dry toluene is refluxed for four hours, in an oil bath. After the solution has cooled slightly, 25 cc. of dry isopropyl alcohol is added to facilitate removal of acetone, the water is removed from the reflux condenser, and a water condenser set for downward distillation is attached to the top by means of a short bent tube (a Hahn partial condenser with a 1-cm. layer of isobutyl alcohol in the inner condensing tube may be used). The mixture is heated at such a rate that slow distillation occurs (2 to 5 drops per minute, the volume of solution should be maintained by further addition of solvent as needed). When the test for acetone is completely negative, f the toluene solution is cooled and the aluminum salt is decomposed with cold 10% sulfuric acid (from 5 cc. of concentrated sulfuric acid and 80 cc. of water). The product is separated with the toluene, and the solution is washed with dilute aqueous ammonia and water, and then evaporated at room temperature under a stream of air (solutions of secondary alcohols which are susceptible to dehydration should be evaporated at room temperature a stream of air should not be used with carbinols boiling below 200°). There is obtained 2.10 g. (76%) of colorless 4-hydroxy-l, 2,3,4-tetrahydrochrysene melting at 156-158°. Two recrystallizations from a mixture of benzene and petroleum ether bring the melting point to 160-162°. 

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