Learn Portuguese (Portugal): O embarcar dos passageiros demorou mais tempo do que a viagem. - The boarding of the passengers took more time than the journey.

The current lesson teaches that mais de is used before numbers (like mais de duas horas). Because this sentence compares two things (the time the boarding took versus the journey itself) rather than stating a numerical amount, it requires the standard comparative form mais do que.

Why is a verb used as a noun here with O embarcar? Couldn't we just use the noun o embarque?

You absolutely can use o embarque, which means the exact same thing. However, placing the masculine singular article o before an infinitive verb is a common way to turn the verb into a noun. Doing this emphasizes the continuous action or process of boarding, rather than just the concept.

To say it took more time, could I translate literally and say tomou mais tempo?

No, Portuguese does not use the verb tomar for consuming time. When talking about an action taking time, you must use demorar (to take time) or the verb levar (to take), as in levou mais tempo.

Is the word do in mais tempo do que optional?