Process for the production and purification of N-butyl acrylate

Details Process for the production and purification of N-butyl acrylate Process for the production and purification of N-butyl acrylate

1999-09-14

2001-01-30

Kumar, Shailendra (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Carboxylic acid esters

C560S205000

Reexamination Certificate

active

06180820

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an improved process for the production and purification of nbutyl acrylate.
2. Background Information and Description of Related Art
n-Butyl acrylate (BuAcA) is a commodity chemical useful for the production of acrylic resins and polymers and copolymers for paint formulations, solvent coatings, textile and leather finishes and adhesives and binders. One method of synthesizing BuAcA is to react n-butanol (BuOH) with acrylic acid (HAcA) in the presence of an acid catalyst, e.g., a sulfonic acid, in at least one reaction zone to produce a mixture of BuAcA, water and several by-product impurities, and subjecting the product mixture to purification in at least one distillation zone, together with any of various schemes of reflux and recycle streams among the reaction zone(s) and distillation zone(s) to obtain a BuAcA of relatively high purity. When any of these processes are operated, low boiling impurities produced in the reaction zone, i.e., those having boiling points near or below BuAcA, such as butyl acetate and dibutyl ether and characterized as “light ends,” or “lights” must be systematically disposed of to prevent them from interfering with the described reaction and compromising the purity of the BuAcA. However, this is often difficult to accomplish, e.g. by purging an appropriate stream, without also losing an unduly large amount of BuAcA product and unreacted BuOH, and/or incurring an unfavorably large cost in energy consumption or purification equipment to prevent such loss. Thus, any improved process, which accomplishes an adequate disposal of light ends while keeping the loss of BuAcA and unreacted BuOH and/or the incremental cost of energy and equipment to a minimum, is very desirable.
U.S. Pat. No. 4,012,439, issued Mar. 15, 1977 to Erpenbach et al., discloses a process for producing n-butyl acrylate by reacting acrylic acid with n-butanol in liquid phase and in contact with an acid cation exchanger as a catalyst. The process utilizes a single reaction zone and three distillation zones.
U.S. Pat. No. 4,280,010, issued Jul. 21, 1981 to Erpenbach et al., discloses a continuous process for making alkyl acrylates free from ether by reacting a C
1
-C
4
-alkanol in a molar ratio of 1:1 to 1:2 in liquid phase at 80° to 130° C. under 100-760 mmHg in the presence of a catalyst. The process employs a single reaction zone and two distillation zones for separating the alkyl acrylate from unreacted alkanol and ether by-product.
U.S. Pat. No. 4,814,493, issued Mar. 21, 1989 to Dougherty et al., teaches a process for the production of a n-butyl acrylate by reaction of n-butanol with acrylic acid in the presence of an esterification catalyst and soluble manganese or cerium. The system for carrying out the process includes a reactor from which a butyl acrylate reaction product is sent to a finishing tower wherein the reaction product is separated into a pure butyl acrylate stream, a volatile stream a portion of which is sent to a butanol recovery tower, and a residue stream which is recycled to the reactor. A butanol stream from the butanol recovery tower is recycled to the reactor, and a residue stream from such tower is removed from the system.
South African Patent No. 9704628 issued Mar. 25, 1998, discloses a process wherein acrylic acid (HAcA) and n-butanol (BuOH) are reacted in two reactors in series, and the product separated in two distillation columns to produce a stream comprising butyl acrylate (BuAcA), dibutyl ether (DBE), butyl acetate (BuAc), and BuOH. Such stream is further separated in a splitter distillation column to provide an overhead fraction containing DBE, BuAc, and BuOH, and a bottoms fraction containing BuAcA and heavy end components (“heavies”), e.g., low molecular weight polymers of HAcA and/or BuAcA and Michael addition products. The overhead fraction from the splitter column is subjected to further distillation in the presence of water to separate BuOH and BuAcA from lights containing DBE and BuAc, with the BuOH and BuAcA being recycled to either or both reactors and the lights being sent to waste treatment, while the bottoms fraction from the splitter distillation is rectified in a butyl acrylate distillation column to separate BuAcA product from heavies which are recycled to either or both reactors.
BRIEF SUMMARY OF THE INVENTION
In accordance with this invention, n-butyl acrylate (BuAcA) is produced by a process comprising reacting generally, amounts of n-butanol (BuOH) with acrylic acid (HAcA) in a reaction zone from which an overhead vapor mixture is withdrawn comprising BuAcA, BuOH, water and light ends which are organic by-product impurities having boiling points near or somewhat below that of BuAcA, and composed mainly of n-butyl acetate (BuAc) and di-n-butyl ether (DBE). BuAcA, BuOH and water are removed in the overhead vapor mixutre by a combination of binary and ternary azeotropes. The vapor mixture is condensed to form a substantially organic liquid phase comprising a major proportion of BuAcA and minor proportions of BuOH, water and light ends, and a substantially aqueous liquid phase comprising mainly water and a minor proportion of BuOH. The organic phase is fed to a finishing fractionation zone, from which a side stream of BuAcA product is withdrawn. Most of the overhead stream of the finishing fractionation zone composed of a portion of the total of BuAcA and BuOH present and minor portions of water and light ends, is recycled to the reaction zone. However, to prevent an undesirable buildup of light ends in the system, a minor proportion of such overhead stream is purged and sent to a purge recovery fractionation zone together with a quantity of makeup water such that the formation of low boiling azeotropes of water with components of the light ends is increased thus facilitating separation of the light ends from the valuable BuAcA and BuOH in the purge stream.
The overhead vapors from the purge recovery fractionation zone are condensed to form separate organic and aqueous liquid phases, with each phase containing a portion of the light ends produced in the system. The majority of light end impurities remain in the organic phase compared to the aqueous phase. A portion of the organic phase and optionally, a portion of the aqueous phase, are discarded such that the total amount of light ends in such discarded portions is comparable to the amount of light ends produced in the reaction. By “discard” what is meant is to remove the stream or portion thereof from the process. The stream may be further processed for proper disposal or further treated for recovery and reuse. The remainder of the organic phase is recycled as reflux to the purge recovery zone and at least a portion of the aqueous phase is recycled as feed to the purge recovery zone.
The residue from the purge recovery zone, containing the bulk of the BuAcA and BuOH in the purged portion of the organic phase of the condensed overhead from the finishing zone, and having a reduced light ends content is recycled to the reaction zone.
The process of the invention accomplishes the prevention of a buildup of light ends in the system while minimizing the loss of BuAcA and unreacted BuOH, while keeping the cost of energy and new equipment to accomplish this purpose, at a relatively low level.


REFERENCES:
patent: 5877345 (1999-03-01), Bauer et al.

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