The invention discloses a method for preparing
ethylbenzene by reaction of dilute
ethylene and
benzene, which uses the dilute
ethylene in
dry gas of
oil refinery as
raw material,
water washing and selective removal of propylene are conducted for the
dry gas before the
dry gas enters an
alkylation reactor in sections,
alkylation reaction of the dilute
ethylene in dry gas and the
benzene proceeds under the circumstances that
zeolite catalyst exists, the dry gas and / or low-temperature gas-phase
benzene are utilized for taking heat during the
alkylation reaction, and the
reaction temperature rising is reduced; after the vapor-liquid separation of the alkylation
reaction product,
tail gas is discharged from the device through low-temperature absorption, and cycle benzene,
ethylbenzene, propyl benzene, diethylbenzene and heavy component are sequentially separated from the
liquid product through a
separation system; the diethylbenzene and the benzene are mixed and enter an anti-alkylation reactor and anti-alkylation reaction proceeds on
molecular sieve catalyst for further converting to the
ethylbenzene. The invention effectively reduces the benzene consumption and the
energy consumption during the course of preparing ethylbenzene by dilute ethylene, the ethylene conversion rate is more than or equal to 99%, the total selectivity of generating ethylbenzene is more than or equal to 99%, the
recovery rate of benzene carried by the
tail gas is more than or equal to 99.5%, and the
xylene content in the ethylbenzene is less than 800 ppm.