Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Solid hydrocarbon polymer
Reexamination Certificate
1994-06-14
2001-06-12
Reamer, James H. (Department: 1614)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Solid hydrocarbon polymer
Reexamination Certificate
active
06245727
ABSTRACT:
This invention relates to a discontinuous process for conducting a heterogeneously catalyzed reaction taking place at elevated temperature, in which heat-sensitive products are formed.
In discontinuous processes for conducting heterogeneously catalyzed reactions, solid catalysts directly introduced into the reactor are size-reduced by stirring elements and have to be filtered after the reaction. This often gives rise to considerable losses of catalyst and product. Another problem arises where it is intended to take the measures described in German patent applications P 38 13 612.0 and P 38 26 320.3 to shorten the batch time and, optionally, the reaction time. In this case, problems arise during circulation of the solids-laden reaction mixture, particularly at the liquid distributor of the film evaporator.
The problem addressed by the present invention on the one hand is to avoid the losses of catalyst and product in a process of the type mentioned at the beginning and, on the other hand, to shorten the batch time and, optionally, the reaction time in accordance with the earlier applications cited above.
According to the invention, this problem is solved in a process of the type mentioned at the beginning by the fact that a heat transfer unit different from the reactor is used for heating and the heterogeneous catalyst is used in a fixed bed and in that the reaction mixture is continuously circulated in succession through the catalyst and then through the heat transfer unit.
In one particular embodiment of the invention, the heat transfer unit is a film evaporator, more especially a falling film evaporator or thin layer evaporator, in which the more readily volatile reaction products are separated. In this embodiment of the process, the reaction mixture after passing through the fixed-bed catalyst flows through the evaporator in which more readily volatile components are evaporated, so that the reaction equilibrium is shifted towards the product side. Thus, in an esterification reaction for example, the water of reaction formed may be removed directly after contact with the catalyst, i.e. immediately after its formation.
If the reaction is an esterification reaction catalyzed by ion exchangers containing sulfonic acid groups, possible hydrolysis of the sulfonic acid, i.e. elimination of the catalytically active acidic groups, is reduced or prevented in this way. Basically, however, any solid catalysts are suitable for the purposes of the invention. Thus, suitable catalysts are basic or acidic, organic or inorganic anion or cation exchangers or acidic aluminas or zeolite or specially prepared bleaching earths.
The coarse-particle catalyst material initially introduced into the fixed-bed catalyst is retained by suitable elements, for example by wedge-wire screens, and does not enter the stirred tank. The catalyst material may thus be reused for subsequent batches. Accordingly, there is no need to filter off a solid catalyst or to wash out a homogeneous catalyst.
To enhance the separation of the more readily volatile reaction product formed, the film evaporator is if necessary operated under reduced pressure.
In addition, the pressure in the film evaporator may advantageously be lowered during the production process, more especially beginning at normal pressure. Thus, the reaction equilibrium may be kept in a desired position in accordance with the progress of the reaction.
To obtain a better separating effect than that obtained with a film evaporator alone, educts and secondary products are not separated simply by distillation, instead a rectification column connected to the reactor, in which the more readily volatile reaction products are separated, is additionally used. In many cases, not only is the reaction product removed, at least one component of the starting product is also separated, so that the starting product has to be replenished accordingly. To avoid excessive replenishment, the more readily volatile components of the reaction mixture are rectified before their separation. This process is used, for example, in esterification reactions where an educt, for example a short-chain alcohol, is separated from a secondary product, for example water, by rectification to avoid the need to replenish the low-boiling educt, namely alcohol.
To prevent the reaction equilibrium from shifting, the starting products removed during separation of the more readily volatile reaction products are replenished.
It is particularly avantageous to use the process according to the invention for esterification and/or transesterification reactions. It is also particularly advantageous to use the process according to the invention for transacetalization and/or acetal-forming reactions, above all in the production of formaldehyde ethyl cyclododecyl acetal. This compound is known under the name of Boisambrene Forte® which is a registered trade mark. Where the process according to the invention is used for esterification or transesterification reactions, the production of wax esters or fragrances is particularly advantageous.
In reactions involving a pressure-dependent azeotrope between an educt and a reaction product, it is of advantage to carry out the reaction under the pressure at which maximum recycling of the educt can be guaranteed. In addition, it is proposed, particularly for the production of Boisambrene Forte® , that the reaction be carried out under an elevated pressure of up to 6 bar absolute and more especially up to 4 bar absolute. This is because the increase in pressure results in a reduction in the quantity of ethylal to be replenished in view of the dependence on pressure of the ethylal/ethanol azeotrope.
The invention also relates to a plant for the discontinuous heterogeneously catalyzed production of heat-sensitive products at elevated temperature comprising a reactor. To shorten the batch time and, optionally, the reaction time without creating additional problems during circulation of the reaction mixture, it is proposed that this plant be provided with a heat transfer unit arranged outside and connected to the reactor, a fixed-bed catalyst preceding the heat transfer unit and a pump for continuously circulating the reaction mixture in succession through the catalyst and then through the heat transfer unit.
The heat transfer unit is advantageously a film evaporator, more especially a falling film evaporator, which is designed to separate the more readily volatile reaction products in vacuo.
In addition, it is proposed that the catalyst container comprise elements for retaining catalyst material.
Further advantages mentioned above are obtained when the plant is designed to carry out the reaction under elevated pressure.
REFERENCES:
patent: 5110508 (1992-05-01), Buettgen et al.
patent: 3813612 (1989-11-01), None
patent: 3826320 (1990-02-01), None
patent: 0178669 (1986-04-01), None
patent: 0342357 (1989-11-01), None
patent: 2185613 (1974-01-01), None
patent: 2293238 (1976-08-01), None
patent: 1526977 (1978-10-01), None
Adrian Kurt
Bollweg Heinz
Gutsche Bernhard
Jeromin Lutz
Peukert Eberhard
Drach John E.
Henkel Kommanditgesellschaft auf Aktien
Millson, Jr. Henry E.
Reamer James H.
LandOfFree
Discontinuous process for conducting a heterogeneously... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Discontinuous process for conducting a heterogeneously..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Discontinuous process for conducting a heterogeneously... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2480622