Can I use a 240 volt, 4500 watt heating element in place of a 120v,1500 watt element?
My appliance is a water distiller with a 10 in. square boiling tank that is on automatic fill (as a little is distilled out, more water comes in to keep it full) My wiring is 110. My breakers are 20amp. The 240v elements are more available in the low density that I need for hard water.

No, you must use the components required by the manufacturer.

Also, electrically speaking the 240v, 20 Amp load will not work on a 120V, 15 Amp circuit .