Complex sentence: Weak acids, such as propionic acid, have been used to catalyze this reaction and often requires high temperatures (100 to 200 ° C) and long reaction times (10 to 120 h).
Split into simpler sentences: Weak acids, such as propionic acid, have been used to catalyze this reaction. THIS... and often requires high temperatures (100 to 200 ° C) and long reaction times (10 to 120 h).