The preparation of zeolite bound zeolite comprising zeolite core crystals other than MFI structure zeolite which are bound by MFI structure type zeolite and the use of the zeolite bound by MFI structure type zeolite prepared by the process as an adsorbent or as a catalyst for hydrocarbon conversion. The zeolite bound zeolite is produced by including seed crystals of MFI structure type zeolite into the silica bound aggregate forming mixture and then converting the silica binder of the aggregate to the MFI binder crystals. The resulting zeolite bound zeolite has good strength and integrity.