Phrasal prepositions

The English language as many phrasal verbs; e.g. "give up" does not mean to donate in an ascending direction, "He set out to write a novel" does not mean he put something in an exterior position, etc.

There are phrases like "ahead of" or "equal to" that can plausibly be considered phrasal prepositions, but one could just say there is an adjective or an adverb followed by a preposition.

Is there a standard concept of "phrasal prepositions"? Would such a concept be useful?