TOLUENE HYDRODEALKYLATION PROCESSToluene hydrodealkylation or toluene hydrodealkylation (HDA) is a process used to produce benzene. The reaction occurs as: Toluene + H2 Benzene + CH4 The process requires toluene and hydrogen as the main reactor. Then, the toluene and hydrogen are converted in a catalyst-filled reactor to produce benzene and methane. This reaction is exothermic and the operating conditions range from 500 0C to 660 0C and from 20 to 60 bar pressure. This process begins with mixing fresh toluene with a stream of recycled unreacted toluene and mixing is achieved in a storage tank. Then, the toluene is pumped to combine with a stream of mixed hydrogen and fresh hydrogen gas. The mixture of toluene and hydrogen is preheated before being introduced into the heater or oven. In the oven the stream is heated to 600°C and then introduced into the reactor. Basically, the main reactions take place in the reactor. The hydrodealkylation process of toluene C7H8 + H2 C6H6 + CH4 is irreversible and requires a catalyst. The catalyst used in this process consists of molybdenum or chromium oxides, platinum or platinum oxides, silica or alumina. The minor reversible secondary reaction is:2 Benzene diphenyl + H2The catalytic process occurs at a lower temperature and offers higher selectivity but requires frequent regeneration of the catalyst. Next, the products are cooled and introduced into a pair of separators that separate the unreacted hydrogen. The unreacted hydrogen is compressed and recycled into the feed and reactor. The products leaving the separators are heated before being introduced into a distillation column from which the toluene is separated from the stream and recycled back to... the center of the paper... also at a temperature of 112 0C and a pressure of 2 .5 bar. The cooling water is used to condense the vapor exiting the column. The remaining methane and hydrogen are separated in the reflux drum where the steam stream is combined with other gas streams. The overheads of the first and second separators are combined to form fuel gas. The liquid stream exiting the bottom of the reflux drum is pumped to a pressure of 3.3 bar for the discharge pressure. The pump flow is separated into two flows. One stream is to be fed to the tray of one of the column and the other stream is cooled to 38 0C in the heat exchanger. Then, the cooled product stream is sent to storage. The 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