Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Patent
1991-10-24
1993-01-19
Evans, Joseph E.
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
568864, C07C 29149, C07C 3104, C07C 31125
Patent
active
051808587
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a process for the catalytic hydrogenation of liquid saturated and unsaturated C.sub.6-24 fatty acid methyl esters for the production of saturated fatty alcohols and methanol in the presence of gaseous hydrogen and hydrogenation catalysts under pressures of 50 to 300 bar and at temperatures in the range from 160.degree. to 250.degree. C.
Hitherto, trickle bed reactors, which are essentially shaft reactors up to 2 m in diameter and between 5 m and 10 m in length, have been used for processes of the type in question carried out in industrial plants. The catalyst required for the hydrogenation is distributed as a random packing in the reactor (Ullmann's Enzyklopadie der Technischen Chemie, 4th Edition, Vol. 11, pages 433 and 434). In these reactors, the reaction is carried out adiabatically, i.e. in the mostly exothermic reactions, the temperature increases along the catalyst packing. However, since the selectivity of most types of catalyst is largely dependent on temperature, changes in the reaction mechanism can occur as a result of temperature changes in the reactor so that mostly unwanted secondary or consecutive reactions can therefore take place. Moreover, excessive temperatures can lead to irreversible catalyst damage.
In addition, there is an unfavorably broad residence time distribution in known shaft reactors despite the uniform distribution of liquid over the cross-section This reduces the degree of utilization of the reactor.
Although it is known that, to limit the increase in temperature, the gas phase may be passed through the reactor in a large excess or several reactors arranged in series with intermediate cooling may be used, this method of temperature control is unsuitable for the hydrogenation of fatty acid methyl ester because the unwanted consecutive reactions cannot be ruled out in this way and, if certain temperatures are increased, the catalysts can suffer losses of activity through recrystallization and structural changes.
It is also known that catalytic reactions can be carried out in an isothermally operated tube bundle reactor (cf. Chemie-Technik, Vol. 4 (1975), No. 12, pages 439 to 441). In the so-called Bayer cold hydrogenation process, catalytic hydrogenations are carried out substantially isothermally at low temperatures so that the catalyst is not subjected to any temperature variations and there is no danger of overheating. However, the reaction described in this literature reference is by no means a critical hydrogenation reaction because the reaction product is not subjected to the further reaction to this extent, if at all, so that--if necessary--unreacted fractions can be recycled; even an extended residence time under hydrogenation conditions does not damage the product.
The problem addressed by the present invention was to provide a process of the type mentioned at the beginning in which considerably higher throughputs by comparison with conventional processes can be achieved, particularly in the hydrogenation of unsaturated fatty acid methyl esters and short-chain fatty acid methyl esters having chain lengths of 6 to 10 carbon atoms.
According to the invention, this problem is solved by the process mentioned at the beginning in that the hydrogenation reaction is carried out in a tube bundle reactor in which isothermal conditions are established by a cooling or heating fluid, the liquid phase and gas phase being passed together as a co-current trickle phase over catalyst packings in the individual tubes of the reactor without any back-mixing, and in that the load per unit volume of the reactor is between 0.2 and 2.5 liters starting material per liter reactor volume per hour and the load per unit area of each individual tube of the reactor is between 1.5 and 24 m.sup.3 starting material per m.sup.2 reactor cross-section per hour and the reaction parameters of temperature and pressure are correspondingly adapted to the particular activity of the catalyst. In the process according to the invention, throughputs up to 3 times higher than in processes
REFERENCES:
patent: 3341610 (1967-09-01), Dunlop et al.
patent: 4960960 (1990-10-01), Harrison et al.
patent: 5043485 (1991-08-01), Fleckenstein et al.
Carduck Franz-Josef
Demmering Guenther
Fleckenstein Theo
Goebel Gerd
Kubersky Hans-Peter
Evans Joseph E.
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Millson Jr. Henry E.
Szoke Ernest G.
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