Toluene hydrodealkylation

In catalytic toluene hydrodealkylation, toluene is mixed with a hydrogen stream and passed through a vessel packed with a catalyst, usually supported chromium or molybdenum oxides, platinum or platinum oxides, on siHca or alumina (50). The operating temperatures range from 500—595°C... 

Toluene hydrodealkylation to benzene and methane Phthalic anhydride by air oxidation of naphthalene Trickle bed reactor for hydrodesulfurizatiou... 

THD [Toluene hydrodealkylation] A process for converting toluene to benzene, developed by the Gulf Oil Corporation. 

Since toluene is nothing more than benzene with a methyl group attached, creating one from another is relatively easy. Benzene, toluene, and for that matter, xylenes too, are coproduced in the processes just described—coke making, cat reforming, and olefin plants operations. The ratio of benzene to the other aromatics production is rarely equal to the chemical feedstock requirements.. fo.r the three. One method for balancing supply and demand is toluene hydrodealkylation (HDA). This process accounts for 10—15% of the supply of benzene in the United States and is a good example of what can be done when one or more coproducts are produced in proportions out of balance with the marketplace. 

Toluene Hydrodealkylation. Benzene is produced from the hydrodemethylation of toluene under catalytic or thermal conditions. The main catalytic hydrodealkylation processes are Hydeal (UOP) and DETOL (Houdry) (49). Two widely used thermal processes are HDA (Arco and Hydrocarbon Research Institute) and THD (Gulf). These processes contribute 25—30% of the world s total benzene supply. 

Figure 2.11 Input/output structure by toluene hydrodealkylation process.

Figure 2.12 Structure of separations for the toluene hydrodealkylation (HDA) process.

In the HDA process, benzene is produced by toluene hydrodealkylation, a mildly exothermic reaction (ArH950 K = -50450J/mol) with moderate activation energy ( a = 217 600 J/mol) ... 

Figure 4.9 Toluene hydrodealkylation reactor/separation/recycle structure of the plant.

EB-poor C8 aromatics cuts are produced which favors further pX separation Low-value toluene and C9+ aromatics (that are generally sent to the gasoline pool because of their high octane number) are transformed into high value pX Toluene hydrodealkylation units can be easily revamped into TDP or transalkylation units... 

The main undesired reactions, which occur essentially with normal TDP, are toluene hydrodealkylation, toluene-xylenes transalkylation and ring cracking. 

Toluene is the most abundant and lowest cost aromatic material. This is a reason to be the valuable raw material for the production of various chemical products. The main chemical use for toluene Is, in fact, production of benzene by dealkylation. The reaction can be carried out either thermally or catalytically using variety of catalysts including supported metals or metal oxides [1-6], amorphous silica-alumina [7] and zeolites [8-19]. The simplest toluene hydrodealkylation reaction is the reaction in which the methyl group is removed in the presence of the forming mainly methane CeHsCHs + H2 —> CeH0 + CH4... 

Other refinery applications in which PRISM separators have been successfully used are naphtha hydrotreaters, middle distillate hydrotreaters, cat crackers, and toluene hydrodealkylation.56,57... 

---