The invention provides an energy-saving and environment-friendly method for preparing
ethylbenzene from
dry gas. The method is mainly used for gas-liquid separation and
tail gas debenzolization of a
reaction product of preparing
ethylbenzene from
dry gas. The method is characterized in that gas-liquid separation and
tail gas absorption of a
reaction product of
ethylbenzene preparation from dry gasare carried out in a same
tower, an absorption and separation
tower is divided into four sections, a
tower upper section is a packing section, a tower middle section is a tube
nest cooling section, atower lower section is a plate type tower, and a tower bottom section is a tower kettle. The
reaction product enters from the upper part of the tower kettle and an absorbent enters from the top of the packing section; after the
tail gas is absorbed and separated by the absorption and separation tower, the tail gas enters a
fuel gas pipe network from the tower top, and rich absorption liquid is mixed with condensed liquid in the reaction product and flows out from the bottom of the tower kettle to enter a
benzene tower. Non-condensable gas at the top of the
benzene tower returns to the absorption and separation tower, circulating
benzene 1 is extracted from the upper section of the benzene tower and enters an
alkylation reactor, circulating benzene 2 at the bottom of a benzene tower refluxtank enters an
alkyl transfer reactor, materials at the bottom of the benzene tower enter an ethylbenzene tower to obtain a product ethylbenzene at the top of the ethylbenzene tower, and tower bottomliquid of the ethylbenzene tower is divided into three parts, one
stream returns to the absorption and separation tower as an absorbent, one
stream is sent to the
transalkylation reactor, and the other
stream is
aromatic hydrocarbon oil. The
separation process is simple and reliable, tower equipment is reduced while reaction heat is fully utilized, equipment investment and subsequent operation cost are saved, and
energy consumption of the device is reduced. According to the
separation method, the
recovery rate of benzene carried by the tail gas is greater than 99.9%, and the purity of an ethylbenzene product is greater than 99.8%.