DESCRIPTION
METHOD FOR PREPARING ALLYL ALCOHOL
Technical Field
[0001] The present invention relates to a method for preparing allyl alcohol and, more
particularly, to a novel method for preparing allyl alcohol, wherein glycerol and formic
acid are reacted under specific synthesis conditions so as to drastically increase the
concentration of allyl alcohol in liquid reaction products and minimize an allyl formate
byproduct and the production of unreacted formic acid. This application claims the
benefit of Korean Patent Application Nos. KR 10-2013-0074507, filed June 27, 2013,
KR 10-201 4-0061369, filed May 22, 2014, and KR 10-201 4-0079572, filed June 27,
2014, which are hereby incorporated by reference in their entirety into this application.
Background Art
[0002] Ally1 alcohol is the simplest unsaturated alcohol represented by
CM2=CHCH20H, and is employed as a pesticide or is importantly utilized as a feed
material or an intermediate in the course of producing many compounds. Furthermore, it
may be used as an antiseptic, or applied in a variety of fields, including preparation of
phthalic acid ester useful as a polymer plasticizer, preparation of butane-1,4-diol as a
monomer of polyester (PBT), or production of acrylic acid.
[0003] Thorough research is ongoing into preparation of allyl alcohol, including reacting
propj.lene, acetic acid and oxygen to give allyl acetate that is then hydrolyzed into allyl
alcohol based on petrochemical processes. Also, as for eco-friendly preparation
processes of allyl alcohol using bio materials compared to conventional petrochemical
processes, when glycerol is reacted with formic acid, allyl alcohol may be obtained at
high yield even in the absence of a catalyst, which is disclosed in U.S. Patent No.
8273926. IJseful as the material for allyl alcohol in such a registered patent, glycerol is a
byproduct mainly resulting from preparation of biodiesel, and is currently utilized as a
material for medical or cosmetic products, a solvent or lubricant. Since the supply of a
glycerol byproduct is expected to increase in proportion to an increase in production of
biodiesel, new applications, in addition to conventional glycerol uses, are under study.
However, in order to maximize the yield of allyl alcohol in the above patent, formic acid
has to be excessively added (e.g. 1.45 equivalents) relative to glycerol. In this case, the
present inventors expect that the drawbacks such as long reaction time and complicated
processing steps may occur, despite high allyl alcohol yield. As illustrated in FIG. I, due
to excessive use of formic acid and low product selectivity of allyl alcohol, gas phase
products obtained via (a) according to a conventional technique include COz, IizO (W,
bp 100 "C), allyl formate (AF, bp 80 - 83 "C), and allyl alcohol (AA, bp 97 "C), with a
large amount of unreacted formic acid (FA, bp 100.8 "C). Also, allyl alcohol in the
liquid reaction products obtained from (b) through a gas separator has a low
concentration, undesirably increasing energy and cost required for the separation process
thereof. Since the difference of boiling points of W, AA and FA as the gas phase
products is very small, it is impossible to separate such products via typical distillation.
Furthermore, due to the azeotropes of formic acid-water (FA-W) and allyl alcoholformic
acid-water (AA-FA-W), it is very difficult to separate formic acid from these
products. Hence, in order to prepare allyl alcohol on a commercial scale, the liquid
reaction products should contain allyl alcohol in a large amount and also the production
of allyl formate byproduct and the production of unreacted formic acid should be
minimized. and thereby it is possible to easily perform the subsequent separation
process. Accordingly, there is a need for a novel synthesis method able to drastically
increase the concentration of allyl alcohol from glycerol under specific synthesis
conditions.
Disclosure
Technical Problem
[0004] The present invention has been made keeping in mind the above problems in the
related art, and an object of the present invention is to provide a novel method for
preparing allyl alcohol, wherein specific synthesis conditions are applied so that the
concentration of allyl alcohol in the liquid reaction products may be drastically increased
and the production of allyl formate byproduct and the production of unreacted formic
acid may be minimized.
Technical Solution
[0005] In order to accomplish the above object, the present invention provides a method
for preparing allyl alcohol, comprising: a) adding glycerol with formic acid in an amount
of 0.4 - 1.2 equivalents relative to 1 equivalent of glycerol and then increasing a reaction
temperature to 220 - 240 "C from room temperature at a heating rate of at least 2.0
"Clmin in an inert gas atmosphere so that glycerol and formic acid are reacted; and b)
condensing gas reaction products obtained in a), thus separating liquid reaction products
including allyl alcohol therefrom.
Advantageous Effects
[0006] According to the present invention, a method for preparing allyl alcohol employs
specifyc synthesis conditions so that the concentration of allyl alcohol in liquid reaction
products can be drastically increased and an allyl formate byproduct and the production
of unreacted formic acid can be minimized, making it possible to produce allyl alcohol
on a commercial scale.
Description of Drawings
[0007] FIG. 1 illustrates a conceptual design for the preparation of allyl alcohol;
[0008] FIG. 2 illustrates a two-step reaction pathway for synthesizing allyl alcohol from
glycerol; and
(0009j FIG. 3 illustrates a mechanism for esterification of glyceryl formate and formic
acid.
Best Mode
[0010] Hereinafter, a detailed description will be given of a method for preparing allyl
alcohol and allyl alcohol prepared thereby, according to the present invention.
[OOll] The present invention addresses a method of mainly producing allyl alcohol,
wherein specific synthesis conditions are applied so that the concentration of allyl
alcohol in liquid reaction products may be remarkably increased and an allyl formate
byproduct and the production of unreacted formic acid may be minimized. Therefore,
allyl alcohol may be produced in a quite high concentration, compared to conventional
methods.
(00121 To this end, the method for preparing allyl alcohol according to the present
invention comprises: a) adding glycerol with formic acid in an amount of 0.4 - 1.2
equivalents relative to 1 equivalent of glycerol and then increasing a reaction
temperature to 220 - 240 "C from room temperature at a heating rate of at least 2.0
"C/min in an inert gas atmosphere so that glycerol and formic acid are reacted; and b)
condensing a gas reaction products obtained in a), thus separating a liquid reaction
products including allyl alcohol therefrom.
[0013] Since glycerol and formic acid are reacted at 1: 1, the equivalent ratio is defined
as the same concept as a molar ratio in the present invention.
[0014] Specifically, a two-step reaction for synthesizing allyl alcohol from glycerol is
illustrated in FIG. 2. This reaction produces 1 mol allyl alcohol by seqcentially
eliminating 2 rnol water from 1 rnol glycerol. The first reaction step occurs by reacting 1
mol formic acid with 1 rnol glycerol at low temperature, and the second reaction step
takes place at high temperature in the presence of formic acid, converting 1 rnol glyceryl
formate, the allyl alcohol precursor, which is produced by the first reaction step. More
specifically, in the first reaction step, 1 mol formic acid reacts with 1 rnol glycerol, to
produce 1 mol glyceryl formate, an allyl alcohol precursor, and 1 mol water. In the
second reaction step, 1 rnol glyceryl formate converts to 1 rnol allyl alcohol at high
temperature in the presence of formic acid, also producing 1 mol water and 1 rnol carbon
dioxide. In the second reaction step, the formic acid acts as a catalyst, rather than
directly participating in the reaction.
[0015] In the first reaction step, when the heating time is increased or an excess of
formic acid is added, a side reaction, No. a in FIG. 2, may occur. The side reaction may
become dominant, and ultimately the production of an allyl formate byproduct may be
increased.
[0016] The glyceryl formate, the first reaction step products, produced via reacting
glycerol with formic acid, may undergo additional esterification. As illustrated in FIG. 3,
when glyceryl formate reacts with formic acid, glyceryl diformate may be produced.
This reaction is reversible.
[0017] In order to minimize the esterification producing glyceryl diformate from
glyceryl formate obtained in the first reaction step, it is essential to prevent the reaction
of glyceryl formate with an excess of formic acid and to maximally increase the heating
rate to the temperature at which the second reaction step occurs. Specifically, when the
production of glyceryl diformate, which is a side-reaction product, is reduced in the first
reaction step, the selectivity of allyl alcohol may increase, thus ensuring the favorable
effects for the subsequent separation process. The method for preparing allyl alcohol
according to the present invention has the following features to drastically increase the
concentration of allyl alcohol and to minimize the ally formate byproduct and the
production of unreacted formic acid.
[0018] In the method for preparing allyl alcohol according to the present invention, any
commercially available glycerol may be used without particular limitation so long as it is
useful in preparation of allyl alcohol. Preferably useful is glycerol with a purity of 60 -
99.5%.
[0019] In the method for preparing allyl alcohol according to the present invention, any
coinmercially available formic acid may be used without particular limitation so long as
it is useful for the reaction with glycerol. In the present invention, formic acid may be
added in an amount of 0.4 - 1.2 equivalents relative to 1 equivalent of glycerol. If the
amount of formic acid is less than 0.4 equivalents, the amount of formic acid that may
participate in the reaction is too small, and thus economic benefits may be negated. In
contrast, if the amount thereof exceeds 1.2 equivalents, the amount of unreacted formic
acid may increase and the production of allyl formate is increased due to side reactions,
undesirably lowering the concentration of allyl alcohol in the liquid reaction products.
[0020] In the method for preparing allyl alcohol according to the present invention,
glycerol and formic acid may be reacted by increasing the reaction temperature to 220 -
240 "C from room temperature at a heating rate of at least 2.0 "Clmin.
[0021) If the reaction temperature is lower than 220 "C, the reaction of the glyceryl
formate does not proceed to the next step. In contrast, if the reaction temperature is
higher than 240°C, the production of allyl formate may be increased.
[0022] The heating rate from room temperature after addition of formic acid to glycerol
in a) is set to at least 2.0 "Clmin, preferably 2.0 - 7.0 "Clmin, and more preferably 4.0 -
7.0 "Clmin. If the heating rate is less than 2.0 "Clmin, the production of glyceryl
diforinate becomes dominant in the first reaction step as shown in FIG. 2, undesirably
increasing the production of allyl formate in the second reaction step.
[0023] In the method for preparing allyl alcohol according to the present invention, the
total reaction time including the heating time may be set to 7 h or less. If the total
reaction time exceeds 7 h, the concentration of allyl alcohol in the liquid reaction
products may be remarkably decreased. Furthermore, the separation of the liquid
reaction products in b) may be carried out using a gas separator, as shown in the concept
design for preparation of allyl alcohol in FIG. 1.
[0024] The inert gas may be any one selected from the group consisting of nitrogen,
argon and helium, and the gas reaction products may include at least one selected from
the group consisting of carbon dioxide, water vapor, allyl formate, allyl alcohol, and
unreacted formic acid. The liquid reaction products may include at least one selected
from the group consisting of allyl alcohol, allyl formate, unreacted formic acid, and
water.
[0025] The concentration of allyl alcohol in b) is 40 wt% or more, and preferably 45
wt% or more, based on the total weight of the liquid reaction products, and thus
economic benefits may be obtained and the production of allyl formate byproduct and
the unreacted formic acid may be minimized, making it possible to prepare allyl alcohol
on a commercial scale.
Mode for Invention
[0026] The following examples of the present invention are disclosed for illustrative
purposes, but those skilled in the art will appreciate that various modifications, additions
and substitutions are possible, without departing from the scope and spirit of the
invention as disclosed in the accompanying claims.
[0027] Example 1
[0028] A 3-neck round-bottom flask was connected with a separation device having a
gas separator and a 1-neck round-bottom flask. To measure the inner temperature of the
reactor, one of the necks of the 3-neck round-bottom flask was provided with a
thermocouple 1. In the 3-neck round-bottom flask, 202.6 g of glycerol and formic acid in
an amount corresponding to 0.6 equivalents based on the molar ratio were placed, and
the temperature of the reactants were increased to 230 "C at a heating rate of 4.2 "Clmin
using a sand bath in a nitrogen atmosphere. As the reaction progressed, gas reaction
products were generated from the liquid reactants, and then passed through the gas
separator connected to the reactor, after which only the liquid reaction products were
collected in the 1-neck round-bottom flask provided to the end of the gas separator. The
reaction was not terminated until it passed 4.2 h after the reaction temperature was
reached, and the reactor was cooled, after which the liquid reaction products collected in
the flask was quantitatively analyzed using gas chromatography. Furthermore,
quantitative analysis of unreacted glycerol remaining in the reactor was carried out using
gas chromatography. The concentration of allyl alcohol in the liquid reaction products
was measured to be 50.9 wt%.
[0029] Example 2
[0030] A 3-neck round-bottom flask was connected with a separation device having a
gas separator and a I -neck round-bottom flask. To measure the inner temperatuie of the
reactor, one of the necks of the 3-neck round-bottom flask was provided with a
thermocouple 1. In the 3-neck round-bottom flask, 27.6 g of glycerol and formic acid in
an amount corresponding to 1 equivalent based on the molar ratio were placed, and the
temperature of the reactants was increased to 230 "C at a heating rate of 5 "Clmin using
a sand bath in a nitrogen atmosphere. As the reaction progressed, gas reaction products
were generated formed from the liquid reactants, and then passed through the gas
separator connected to the reactor, after which only the liquid reaction products were
collected in the 1-neck round-bottom flask provided to the end of the gas separator. The
reaction was not terminated until it passed 2.3 h after the reaction temperature was
reached, and the reactor was cooled, after which the liquid reaction products collected in
the flask was quantitatively analyzed using gas chromatography. Furthermore,
quantitative analysis of unreacted glycerol remaining in the reactor was carried out using
gas chromatography. The concentration of allyl alcohol in the liquid reaction products
was measured to be 48.5 wt%.
[0031] Comparative Example 1
[0032] This comparative example was conducted under the same conditions as in
Example 1, with the exception that the heating rate was 1.3 "Clmin. 2.8 h after reached
the reaction temperature, the reaction was terminated, and the reactor was cooled, after
which the liquid reaction products collected in the flask was quantitatively analyzed
using gas chromatography. Furthermore, quantitative analysis of unreacted glycerol
remaining in the reactor was performed using gas chromatography. As such, the
concentration of allyl alcohol in the liquid reaction products was measured to be 38.0
wt%, which is lower than the concentration of allyl alcohol in the examples.
[00331 Comparative Example 2
[0034] This comparative example was conducted under the same conditions as in
Example 1, with the exception that the heating rate was 1.3 "Clmin. To evaluate the
effect of the reaction time at high temperature, 8 h after reached the reaction
temperature, the reaction was terminated, and the reactor was cooled, after which the
liquid reaction products collected in the flask was quantitatively analyzed using gas
chromatography. Furthermore, quantitative analysis of unreacted glycerol remaining in
the reactor was performed using gas chromatography. As such, the concentration of allyl
alcohol in the liquid reaction products was measured to be 37.3 wt%, which is lower
than the concentration of allyl alcohol in the examples.
[0035] The test results depending on the heating rate among the reaction conditions of
Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 1 below.
[Table 11
[0036] As is apparent from Table 1, in both Examples 1 and 2 using the method for
preparing allyl alcohol according to the present invention, the concentration of allyl
alcohol was 40 wt% or more based on the total weight of the liquid reaction products,
and was thus relatively high compared to Comparative Examples 1 and 2. Therefore,
when allyl alcohol was prepared by the preparation method for Examples 1 and 2
according to the present invention, the concentration of allyl alcohol in the liquid
reaction products was high and the allyl formate byproduct and the production of
unreacted formic acid could be minimized.
[0037]
(a) pipeline for transporting vaporized mixture into gas separator from reactor
(b) pipeline for transporting condensed mixture removed from gas separator
(c) pipeline for transporting non-condensed mixture removed from gas separator
(d) pipeline for transporting unreacted material and products from bottom of
reactor

CLAIMS
1. A method for preparing allyl alcohol, comprising:
a) adding glycerol with formic acid in an amount of 0.4 ~ 1.2 equivalents relative
to 1 equivalent of glycerol and then increasing a reaction temperature to 220 ~ 240 °C
from room temperature at a heating rate of at least 2.0 °C/min in an inert gas atmosphere
so that glycerol and formic acid are reacted; and
b) condensing gas reaction products obtained in a), thus separating liquid
reaction products including allyl alcohol therefrom.
2. The method of claim 1, wherein the heating rate in a) is 2.0 ~ 7.0 °C/min.
3. The method of claim 1, wherein the heating rate in a) is 4.0 ~ 7.0 °C/min.
4. The method of claim 1, wherein the inert gas is any one selected from the
group consisting of nitrogen, argon, and helium.
5. The method of claim 1, wherein the gas reaction products comprise at least
one selected from the group consisting of carbon dioxide, water vapor, allyl formate,
allyl alcohol, and unreacted formic acid.
6. The method of claim 1, wherein the liquid reaction products comprise at least
one selected from the group consisting of allyl alcohol, allyl formate, unreacted formic
acid, and water.
7. The method of claim 1, wherein the concentration of allyl alcohol in b) is 40
wt% or more based on a total weight of the liquid reaction products.
8. The method of claim 1, wherein the concentration of allyl alcohol in b) is 45
wt% or more based on a total weight of the liquid reaction products.