All synthesis other than Upgrading Synthesis will abide by the rule of random synthesis.
The types of synthetic item and main item are the same. In other words, the synthetic result will be the same type as the main item, regardless of what catalyst you used. Therefore, please make sure to check the type of main item before synthesizing.
The grade of final product is influenced by the grade of main item and catalyst. Higher quality and rarity of item and catalyst indicates higher synthetic grade of the final product, and vise versa.