The invention discloses a technique for producing
styrene by alkylating
toluene and
methanol side chains. The method comprises the steps of mixing and heating
methanol vapor and air to obtain a mixture, enabling the mixture to enter a reactor producing
formaldehyde by using
methanol, and generating
formaldehyde under the action of a catalyst; condensing a product, enabling the condensed product to enter a rectifying
tower so as to remove water generated in the reaction, pressurizing a product at the
tower top, enabling the pressurized product to enter a high-pressure separator, discharging noncondensable gas containing
hydrogen from the top of the high-pressure separator, mixing and heating and a product at the bottom and
toluene, enabling the mixture to enter a
side chain alkylation reactor, enabling a gaseous product to return to therectifying
tower after a product obtained in the reaction is subjected to separation by a gas-liquid separator, enabling a
liquid product to enter a
toluene tower, an
ethylbenzene tower and a
styrene tower sequentially, enabling toluene to return to the
side chain alkylation reactor, and discharging
ethylbenzene,
styrene and C9<+>heavy aromatics. The technique is of a two-
step method for toluene and methanol
side chain alkylation, not only can the generation degree of a
side reaction between styrene and
hydrogen be effectively inhibited, but also the hydrothermal deactivation of the catalyst for side chain alkylation can be alleviated.