Patent DE-102005056377-A1 (DE)
Title: Preparation of acrolein and/or acrylic acid useful for e.g. preparing polymers involves dehydrogenating propane to hydrogen and product gas comprising propylene; and oxidizing molecular hydrogen to steam and product gas to target products
Inventor: MACHHAMMER OTTO
IPC: C07C47/22
Filed: 2005-11-24
Abstract: Preparation of acrolein and/or acrylic acid (target product) involves: in reaction zone (A): partially dehydrogenating propane catalytically from a mixture of fresh propane and recycled mixture forming molecular hydrogen and propylene; oxidizing molecular hydrogen to steam and forming product gas (A); in reaction zone (B): partially oxidizing product gas (A) to product gas (B) comprising target product; in separation zones: removing target product from product gas (B), scrubbing of carbon dioxide present in the residual gas (I); and recycling residual gas (I) into reaction zone (A). Preparing acrolein and/or acrylic acid (target product) from propane involves: (i) in reaction zone (A): feeding gaseous streams of fresh propane, and recycled mixture to a first reaction zone (A) to form a reaction gas (A), passing the reaction gas A through at least one catalyst bed in which partial heterogeneously catalyzed dehydrogenation of the propane forms molecular hydrogen and propylene; oxidizing molecular hydrogen by molecular oxygen to steam; and feeding the resulting product gas (A) comprising molecular hydrogen, steam, propylene and propane is withdrawn from reaction zone (A) to reaction zone (B); (ii) in reaction zone (B), the product gas A from reaction zone A, with feeding of molecular oxygen, forming a reaction gas (B) comprising molecular hydrogen, steam, propane, propylene and molecular oxygen, and the propylene is subjected to a heterogeneously catalyzed partial gas phase oxidation to give a product gas (B) comprising target product, unconverted propane, molecular hydrogen, steam, carbon dioxide as a by-product, and also other secondary components having lower and higher boiling points than water; (iii) in a first separation zone: removing target product, water and secondary components having a higher boiling point than water present from the product gas (B) to leave a residual gas (I) comprising unconverted propane, carbon dioxide, molecular hydrogen, the secondary components and any unconverted propylene and any unconverted molecular oxygen; (iv) in second separation zone: as an aftertreatment measure (1), scrubbing out carbon dioxide present in residual gas (I) and condensing out water present if any; as an aftertreatment measure (2), discharging a remaining portion of residual gas (I); as aftertreatment treatment measure (3), removing molecular hydrogen by a separating membrane in a third separation zone (III); and as an aftertreatment measure (4), chemically reducing any molecular oxygen present in residual gas (I), where the sequence of use of aftertreatment measures 1 - 4 is as desired; and (v): recycling aftertreated residual gas (I) which comprises unconverted propane into reaction zone (A) as at least one of the two feed streams comprising propane. The amount of molecular hydrogen (M), which is at least 5 - 95 mol % of the total amount of molecular hydrogen produced in reaction zone (A) and that fed to reaction zone (A), is oxidized to steam in reaction zone (A).