Our Gemara on Amud Beis describes the difference between objects utilized FOR a mitzvah versus objects that are utilized in service of something that has an intrinsic holiness. For example, a Lulav or a Succah is an object used for a mitzvah, however a mantle for a Sefer Torah, Aron Kodesh, or a tefilin bag is an object of the holy, Tashmishe Kedusha.  That is, it serves an object that has Kedusha or holiness. The objects of the holy cannot he disposed of, and instead must be buried, unlike an object of a mitzvah which technically can be disposed of.

Nefesh HaChayyim (4:30) uses this Gemara to highlight the difference between the holiness of mitzvos versus the holiness of Torah.  A mitzvah is holy when one is engaged in it, however after that the holiness dissipates.  This is why an object used for a mitzvah, tashmishe mitzvah can be disposed of. However, Torah has an intrinsic independent holiness, and thus the objects that serve them, remain imbued with holiness.  This is why in one respect Torah study is superior to other mitzvos.  We are holy when we perform a mitzvah, but then that holiness dissipates.  But the study of Torah imbues a holiness that endures.  In essence, when doing a mitzvah, we are tashmishe mitzvah, like a lulav.  When we study Torah though, we are Tashmishe Kedusha such as an aron kodesh.