Toluene Hydroealkylation Process

TOLUENE HYDRODEALKYLATION PROCESS

Toluene hydrodealkylation or hydrodealkylation of toluene (HDA) is a process that used to produce benzene. The reaction occurs as:

Toluene + H2 Benzene + CH4

The process need toluene and hydrogen as a main reactor. Then, toluene and hydrogen are converted in a reactor packed with catalyst to produce benzene and methane. This reaction is exothermic and the operating conditions are 500 0C to 660 0C, and 20 to 60 bar of pressure. This process begins with mixing fresh toluene with a stream of recycle unreacted toluene, and the mixing is achieved in a storage tank. Then, the toluene is pumped to combine it with a stream of mixed hydrogen and fresh hydrogen gas. The mixture of toluene and hydrogen is preheated before it is introduce to the heater or furnace. In the furnace, the stream is heated to 600 0C, then introduced into the reactor. Basically, the main reactions occurs in the reactor.

C7H8 + H2 C6H6 + CH4

Toluene hydrodealkylation process is irreversible process and requires catalyst. The catalyst used in this process consist of molybdenum oxides or chromium, platinum oxides or platinum, silica or alumina. Minor reversible side reaction is:

2 Benzene Diphenyl + H2

The catalytic process occurs at lower temperature anf offers higher selectivity but requires frequent regeneration of the catalyst. Then, the products are cooled and introduced into a pair of separators which separate the unreacted hydrogen. The unreacted hydrogen is compressed and recycle back to the feed and reactor. The products that leaving the separators are heated before introduced into a distillation column which the toluene is separated from the stream and recycle back to the...

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... temperature of 112 0C also and a pressure 2.5 bar. Cooling water is used to condense the vapor exiting column. Remaining methane and hydrogen are separated in reflux drum where the vapor stream is combined with other gases streams. The overhead of first and second separator are combined to form fuel gas. The liquid stream exiting in the bottoms of the reflux drum is pumped at pressure of 3.3 bar for discharging pressure. The pump stream is separated in two streams. One stream is to feed to tray one of the column and the other one stream is cooled down to 38 0C in heat exchanger. Then, the cooled product stream is sent to storage.

Advantages of this process are:

 Higher reaction efficiencies

 Lower hydrogen consumption

 Higher conversions

 Lower operating temperature

 Higher liquid yield

 Open to advances in catalysis

 Clean operations

 Good selectivity