Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
2000-04-07
2001-06-05
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C564S416000, C564S420000, C564S423000
Reexamination Certificate
active
06242649
ABSTRACT:
A continuous process for the preparation of aromatic amines The invention relates to a continuous process for the preparation of aromatic di- and polyamines by catalytic hydrogenation of the di- and polynitro compounds corresponding to the amines at high temperatures and optionally with simultaneous removal of heat from the reaction mixture in order to generate steam with a pressure above atmospheric of >1.5 bar abs. on a fixed bed.
Processes for the preparation of aromatic amines by catalytic hydrogenation of the nitro compounds on which they are based are known in large number (DE-A-2 135 155, DE-A-2 106 644, DE-A-4 435 839, EP-A-0 696 573 and WO 97/20 804).
Generally speaking, the industrial-scale catalytic hydrogenation of aromatic polynitro compounds in suspensions is carried out at low temperatures because there is a risk of uncontrolled secondary reactions during the hydrogenation of aromatic polynitro compounds at high temperatures. These secondary reactions may lead to the formation of unwanted by-products and hence to reductions in yield. Reactions involving hydrogenation of the nucleus, hydrogenolytic cleavage or the formation of high molecular weight, tar-like products may be mentioned by way of example in this connection. Explosive secondary reactions may also take place which are due to the highly exothermic course of the nitro group reaction and its high rate of reaction at relatively high temperatures.
When aromatic polynitro compounds are reacted with hydrogen, a considerable amount of heat is released. Advantageous hydrogenation processes are those in which the increased reaction energy does not have to be destroyed with an expenditure of energy but in which the reaction energy can be utilised economically in the form of steam production.
Fouling and deposits of catalysts are observed time and again in the catalytic suspension processes. Product impurities, relatively poor hydrogenation yields and high catalyst consumptions are often associated with this. The expenditure on cleaning and maintenance is considerable.
Thelen et al. (DE-A-2 135 154 and DE-A-2 135 155) have circumvented these disadvantages by the description of catalytic hydrogenation on a fixed bed. In spite of the advantageous arrangement of the catalyst in a fixed bed, the disadvantages are that the quantity of heat is removed in the reactor, the dimensions and structure of the reactor and the deposition of the catalyst in spinel form onto the cooling tubes are very expensive. The throughput of aromatic polynitro compounds is small. The removal of heat is problematic and the reaction must be carried out only at low temperatures.
The catalytic hydrogenation of aromatic nitro compounds on a fixed bed in a combination of two fixed bed reactors is described in WO 97/20 804 (Chambost et al.). The division of the product quantities after the first reactor with simultaneous gas separation is problematic and expensive. Disadvantages of the process described here are the use of two reactors and the low reaction temperatures of up to 120° C. Moreover, large quantities of solvents such as alcohols or ethers are used in some cases, the solvent having to be separated from the aromatic diamine after the reaction and optionally worked up.
REFERENCES:
patent: 5563296 (1996-10-01), Zarnack et al.
patent: 5779995 (1998-07-01), Witt et al.
patent: 2106644 (1972-08-01), None
patent: 2135154 (1973-02-01), None
patent: 9720804 (1997-06-01), None
Beckhaus Heiko
Langer Reinhard
Barts Samuel
Bayer Aktiengesellschaft
Gil Joseph C.
Whalen Lyndanne M.
LandOfFree
Continuous method for producing aromatic amines does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Continuous method for producing aromatic amines, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Continuous method for producing aromatic amines will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2484236