A method for synthesizing N-methylmorpholine with granular
solid superacid as a catalyst comprises the following steps: loading an SO4<2-> / MxOy super acidic catalyst into a
fixed bed; heating the
fixed bed to the temperature of 260-360 DEG C; pumping
nitrogen into the
fixed bed to ensure the catalysts under the protection of the
nitrogen; introducing N-methyldiethanolamine
aqueous solution into the fixed
bed; dehydrating the N-methyldiethanolamine
aqueous solution in the presence of the catalyst to generate the N-methylmorpholine; collecting
mixed gas of the N-methylmorpholine and water, whichis discharged from the
discharge hole of the fixed
bed and passes through a condensing unit, into a flask, then adding
solid NaOH for alkaline separation to separate supernatant;
drying the supernatant with NaOH, removing the
drying agent and carrying out rectification to collect distillates at a temperature of 104-106 DEG C to obtain the product of N-methylmorpholine. The invention has the effect as follows: the invention is fixed
bed catalysis under normal pressure; the catalyst has stability and resistance to
carbon deposition, and the method has the advantages of simple catalytic process,high product yield and purity, low cost and the like.