Abstract: The invention is directed to various alkylaryl phosphite compositions that ideally are suitable for use as secondary antioxidants in polymers. In one aspect, the phosphite composition comprises a tris(monoalkylaryl)phosphite in an amount from 51 to 95 weight percent; and at least one of: a bis(monoalkylaryl)dialkylaryl phosphite; a bis(dialkylaryl)monoalkylaryl phosphite; and a tris(dialkylaryl)phosphite. The inventive phosphite composition is a solid at ambient conditions. The invention also relates to alkylate compositions and processes for forming such alkylate compositions and such phosphite compositions.