Toluene unconverted

Ethyltoluene is manufactured by aluminum chloride-cataly2ed alkylation similar to that used for ethylbenzene production. All three isomers are formed. A typical analysis of the reactor effluent is shown in Table 9. After the unconverted toluene and light by-products are removed, the mixture of ethyltoluene isomers and polyethyltoluenes is fractionated to recover the meta and para isomers (bp 161.3 and 162.0°C, respectively) as the overhead product, which typically contains 0.2% or less ortho isomer (bp 165.1°C). This isomer separation is difficult but essential because (9-ethyltoluene undergoes ring closure to form indan and indene in the subsequent dehydrogenation process. These compounds are even more difficult to remove from vinyltoluene, and their presence in the monomer results in inferior polymers. The o-ethyltoluene and polyethyltoluenes are recovered and recycled to the reactor for isomerization and transalkylation to produce more ethyltoluenes. Fina uses a zeoHte-catalyzed vapor-phase alkylation process to produce ethyltoluenes. 

The process consists of a reactor section, continuous catalyst regeneration unit (CCR), and product recovery section. Stacked radial-flow reactors are used to minimize pressure drop and to facilitate catalyst recirculation to and from the CCR. The reactor feed consists solely of LPG plus the recycle of unconverted feed components no hydrogen is recycled. The liquid product contains about 92 wt% benzene, toluene, and xylenes (BTX) (Figure 6-7), with a balance of Cg aromatics and a low nonaromatic content. Therefore, the product could be used directly for the recovery of benzene by fractional distillation (without the extraction step needed in catalytic reforming). 

Methyl-dibenzo[b,f]azepine (4.1 g), N-diethylaminoborane (1.7 g) and freshly distilled toluene (150 cc) are introduced into a 500 cc three-neck flask equipped with a dropping funnel and a condenser, and protected against moisture by a calcium chloride guard tube. The solution is heated under reflux (110°C) for 22 hours under a nitrogen atmosphere and then cooled. A 2 N aqueous sodium hydroxide solution (33 cc) is then run in followed by an 0.316 N aqueous methylchloramine solution (190 cc), the addition of which takes 9 minutes. The mixture is stirred for 1 hour and then decanted. The organic layer is washed with water until it has a pH of 6 and is then extracted with 2 N hydrochloric acid (5 times 50 cc), dried over sodium sulfate, filtered and evaporated. Recrystallization of the residue from petroleum ether yields some unconverted 5-methyl-dibenzo[b,f]azepine (2.17 g). 

The EB dehydrogenation can be done with various commercially available styrene catalysts. The fractionation train separates high-purity styrene, unconverted EB, and minor reaction byproducts such as toluene. 

Description Feed and hydrogen are heated and passed over the catalyst (1). Benzene and unconverted toluene and/or xylene and heavier aromatics are condensed (2) and stabilized (3). 

Unconverted toluene and/or xylenes and heavier aromatics are recycled. 

In the fractionation section, stripper bottoms are fed to a benzene column, where the benzene product is recovered and the unconverted toluene is fractionated for recycle. The toluene column bottoms are sent to a rerun column where the paraxylene concentrated fraction is taken overhead. 

A fractionation train (3,4) separates high-purity styrene product, unconverted EB, which is recycled, and the relatively minor byproduct tar, which is used as fuel. Toluene is produced (5,6) as a minor byproduct and benzene (6) is normally recycled to the upstream EB process. 

The distillation train first separates the benzene/toluene byproduct from main crude styrene stream (8). Unconverted EB is separated from styrene (9) and recycled to the reaction section. Various heat recovery schemes are used to conserve energy from the EB/SM column system. In the final purification step (10), trace C9 components and heavies are separated from the finished SM. To minimize polymerization in distillation equipment, a dinitrophenolic type inhibitor is co-fed with the crude feed from the reaction section. Typical SM purity ranges between 99.90% and 99.95%. 

Description Toluene and air are fed to the reactor (1) in which the oxidation to benzoic acid is carried out at 160°C and 10 atm. The reaction product is a 30% solution of benzoic acid in toluene plus a small quantity of byproducts. Fractionation (2) separates unconverted toluene for recycle, pure benzoic and a bottom fraction of heavy byproducts. 

Reactor effluent is diluted with water (5), and unconverted cyclohexane carboxylic acid is recycled to the process, while the ladam solution flows to the crystallization plant (6) where it is neutralized with ammonia. Ammonium sulfate crystallizes at bottom and the top organic layer of caproladam is recovered and purified through a two-solvent (toluene and water) extraction (7) and a continuous fractionation (8). 

In the fractionation section the SM unit, unconverted EB is separated from SM product in the EB/SM splitter (7). SM product is recovered as overhead from the SM column (8). Typical SM product purity is in the range of 99.9 to 99.95 wt-%. Recycle EB is taken from the bottom of the EB recovery column (9). A benzene-toluene splitter (10) is often used to recycle benzene to the EBOne unit and export toluene as a minor co-product. 

The liquid product is seat to a stabilization column to eliminate light products and then to a column to separate unconverted toluene. The benzene distillate undergoes clay treating before being upgraded. 

Consider, for instance, ethylbenzene dehydrogenation to styrene. The traditional plant used in the process industry [32] is based on an fixed-bed catalytic reactor to which a preheated mixture of ethylbenzene and steam, which prevents coke formation, is fed. The reaction products then normally undergo a rather complex separation scheme, mostly based on distillation columns, aimed at recovering styrene (the desired product), benzene, toluene and H2 (by products), and a certain amount of unconverted ethylbenzene, which has to be recycled. The overall conversion per pass is typically around 60%, whereas selectivity is close to 90%. 

The Fina/Badger distillation section consists of three distillation columns. All the columns are designed to operate under vacuum to minimize temperature and polymer formation. The first column in the sequence splits the benzene and toluene byproducts from the unconverted EB and styrene product. The benzene and toluene mixture is typically sent to an integrated EB plant where it is further fractionated. In this case, the benzene by-product is ultimately consumed in the EB unit and the toluene becomes a by-product stream from the EB plant. 

Caprolactam is obtained at atmospheric pressure, in the presence of a solvent (cyclohexane) in a multistage reactor. Hexahydrobenzoic add and oleum, previously mixed at 35 C, are introduced into the reactor. Nitrosyl sulfuric acid (prepared by the absorption of NO—NO in oleum) is injected at each stage in predetermined quantities. Once-through conversion of hexahydrobenzoic add is limited to 50 per cent The temperature is kept at 80 C by the evaporation of cyclohexane. The reactor effluent is then diluted with water at low temperature. The cyclohexane evaporated is recondensed and used to extract unconverted hexahydrobenzoic add and allow its recycle, while the caprolactam formed goes into the aqueous solution. This phase is neutralized by ammonia. Ammonium sulfate, formed at the rate of 4.2 t/t of product, is recovered by centrifuging. The lactam is extracted with the toluene, reextracted with water and dehydrated. The final yield of the operation is 72 per cent weight in relation to toluene. 

The toluic aldehyde/HBF complex is then decomposed by heating between 130 and 180 C in the presence of a solvent (benzene). The BF3. HF and unconverted toluene are recovered and recycled. The o- and p-tohiic aldehydes are separated by crystallization. Purified p-toluic aldehyde is air-oxidized (in solution m acetic add) in the presence of manganese acetate, cobalt acetate and sodium bromide, by the technique employed for p-xylene. This takes place around 200°C, at 2.10 Pa absolute ... 

Zeolites are unique as shape-selective catalysts. Mass transport shape selectivity is a consequence of transport restrictions allowing some species to diffuse more rapidly than others in zeolite pores. Small molecules enter the pores and are catalytically converted, but larger molecules may pass through a flow reactor unconverted because they do not fit into the pores, where almost all the catalytic sites are located. Similarly, product molecules formed inside a zeolite may be so large that their diffusion out of the pores may be so slow that they are largely converted into other products before escaping into the product stream. Mass transport selectivity is illustrated by toluene disproportionation catalysed by HZSM-5 13 (figure C2.7.13). The desired product is industrially valuable/ -xylene. 

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