Benzene Production from Naphtha

The process under analysis comprises four major sections: (1) Naphta Hydrotreatment & Reforming; (2) Aromatics Separation; (3) Toluene Disproportionation; (4) Paraxylene Recovery

Naphta Hydrotreatment & Reforming. Initially, the naphtha feedstock is treated with hydrogen under high temperature and pressure conditions to remove impurities that act as poison for the catalysts downstream. The treated naphtha is then sent to catalytic reforming, where paraffins and naphthenes are converted to aromatics. The product from reforming is then sent to the aromatics separation section.

Aromatics Separation. The reformate is fed to a reformate splitter, where a C7- fraction is obtained as the top product and a C8+ heavier fraction as the bottom product. The C7- fraction is fed to a sulfolane extraction unit for aromatics recovery. The aromatic extract is sent to a column to recover the Benzene as the top product. The bottom of this column is fed to a second column where toluene is separated as distillate, while the bottom stream is fed to the xylene splitter, where xylenes are separated as the top product from C9+ aromatics, that exit from the bottom. These heavy aromatics are fed to a fourth column, where a C9 fraction is produced as overhead and then mixed with the toluene stream to be sent to the toluene disproportionation section.

Toluene Disproportionation. The toluene and C9 aromatics mix is then fed to a reactor to be converted into xylenes and benzene via disproportionation reaction. The product from the disproportionation unit is then recycled to the benzene column.

Paraxylene Recovery. The mixed xylenes produced as the top product of the xylene splitter are fed to an adsorption unit, where paraxylene is separated and purified. The separated raffinate stream is fed to an isomerization step, where ortho- and metaxylene, as well as ethylbenzene, are isomerized into paraxylene. The reactors effluent is sent to the deheptanizer, where C7 and lighter components are removed as the overhead product, while a mixed xylenes stream exits from the bottom and returns to the xylene splitter.