FX ChemStruct will always try to make "chemical sense" out of what you have typed. This can lead to problems. For example, if you type catalyst into an structure, FX ChemStruct will try to interpret it as elements and will format it this way.
Calcium, Tantalum, an "l" that it cannot convert to an element, Yttrium, Sulphur and a renegade "t". Probably not what you intended!
You can force FX ChemStruct to leave this text alone by surrounding it in quotes. By typing "catalyst" with the quotes, you will get what you intended.