Process for preparing pyromellitic dianhydride

US5387699A · kind A · utility

Assignee

• LP INDUSTRIES LLC · US

Inventors

• Werner Wagner · Bad Nenndorf, DE
• Frank Müller · Birkenfeld, DE
• Hans-Jurgen Eberle · Munich, DE
• Franz Grundei · Ebersberg, DE

Key dates

• Filing date: Dec 22, 1993
• Grant date: Feb 7, 1995
• Expiry date: Dec 22, 2013

Classification

• Technology area (CPC B): Performing Operations; Transporting
• CPC primary: B01J2523/00
• WIPO field: Chemical engineering
• WIPO sector: Chemistry

Abstract

The invention relates to a process for preparing pyromellitic dianhydride (PMDA) by heterogeneously catalyzed oxidation in the gas phase by means of a gas containing molecular oxygen. The process involves oxidizing benzaldehydes which are 2,4,5-trialkylated by C.sub.1 - to C.sub.3 -alkyl groups or mixtures of benzaldehydes which are 2,4,5-trialkylated by C.sub.1 - to C.sub.3 -alkyl groups and benzenes which are 1,2,4,5-tetraalkylated by C.sub.1 - to C.sub.3 -alkyl groups in the presence of a catalyst. The catalyst contains as active components 5% to 95% by weight of one or more transition-metal oxides of sub-group IV of the Periodic Table of the Elements, from 1% to 50% by weight of one or more transition-metal oxides of sub-group V of the Periodic Table of the Elements. The catalyst also contains from 0% to 10% by weight of one or more oxides of elements of main group I of the Periodic Table of the Elements and/or from 0% to 50% by weight of one or more oxides of elements of main groups III, IV and V of the Periodic Table of the Elements and of elements of sub-groups VI and VII of the Periodic Table of the Elements. The indicated percentages by weight are based in each case on the…