First add hexamine, then water and HCl and boil the shit.
look here for the procedure:
Patent US4321412
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EXAMPLE
1,050.1 g of chlorinated p-xylene, consisting of 47.61% of p-xylyl chloride, 43.76% of p-xylene, 3.6% of nuclear-chlorinated p-xylene and 5.03% of polychlorinated p-xylenes, the mixture containing exactly 500 g (3.55 moles) of p-xylyl chloride, are stirred with 546.7 g (3.9 moles) of urotropin for 15 minutes, under nitrogen, in a 4 liter three-necked flask equipped with a reflux condenser and stirrer.
1,000 g of water are then added and the mixture is refluxed for 3 hours. It is then allowed to cool, brought to a pH of 3-4 at room temperature with 170 ml of concentrated HCl, and then refluxed for a further 15 minutes.
Thereafter, the mixture is allowed to cool again and the aqueous phase is separated off. The organic phase is distilled after addition of 0.01 g of hydroquinone.
You can steamdistill the benzaldehyde out of the reaction flask first, separate water and organic layer consisting of benzaldehyde and toluene and separate those by usual separation preferable under reduced pressure.
The nitrogen atmosphere is not necessary but unavoidably some benzylalcohol will be formed when oxygen is present.