Note: Descriptions are shown in the official language in which they were submitted.
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,I FIELD OF INVENTION
.. ~
The field o~ the invention relates to the production
¦iof aromatic carboxylic acids from aromatic materials, such as
I coal, petroleum residium, shale oil, and tar sands. The
invention is particularly useful ~or the production of tereph-
- thalic acid from bituminous coal.
;~ 10 1PRIOR ART
~. I
U.S. Patent 2,785,198 discloses a process for producing
jpolycarboxylic acids from bituminous coal, lignites, peat and
llthe like or their carbonization products such a~ coal, tar, or
pitch by thermal treatment with oxidizing agents such as nitric
! ` I . .
~-~ 15 lacid, chromic acid, permanganate, or oxygen or air under
super-atmospheric pressure in an alkaline medium.
¦ The crude oxidation product is subject to an extraction
.,.
1~ ¦ treatment with a polar organic solvent for both the monocyclic
~ .~ ,. ,
¦ aromatic and high molecular weight polycarboxylic acids, and
~ 20 treating the thusly formed solution with water to extract the
;~ ¦monocyclic aromatic polycarboxylic acids from the rèmainder of
; ¦Ithe mixture.
~ ~ I The alkaline medium disclosed by Grosskinsky et al is
:,',. i~
~ ' sodium hydroxide.
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I U.S. Patent 2,193,337 discloses a process for producing
organic acids by heating carbonaceous material such as sawdust,
, wood chips, peat, or coal with oxygen-containing gases at
elevated pressures and temperatures in the presence of at
; 5, least 10 times the weight of the carbonaceous material of
water and preferably an oxide or hydroxide of an alkali or
¦ alkaline earth metal. Oxalic acid and other organic acids
which are formed, such as mellitic and benzoic acid or acetic
acid, may be isolated from the resulting reaction mixture as
loil salts of the alkali or alkaline earth metals. The caustic
- ¦i material disclosed is an oxide or hydroxide of an alkali metal
`l i
'l or an alkaline earth metal and specifically lime, quick-lime,
'l and caustic soda.
.. ,~ 1
l U.S. Patent 2,786,074 discloses a process for making
15 1! organic acids by oxidizing carbonaceous materials at elevated
` Il temperatures and pressures with gaseous oxygen in the presence
of an alkaline solution. Alkalis which are suitable for use in
: li
¦ a high pressure reactor are specified as sodium hydroxide,
! potassium hydroxide, and mixtures thereof.
,. , .
20 1 U.S. Patent 2,461,740 discloses a process for oxidizing
carbonaceous material to aromatic acids using a two-stage
oxidation process.
. 1 1
' In the first stage, the carbonaceous ma~erial is oxidized
I to a state where it is soluble in aqueous alkali such, for
25 , example, as a solution of sodium hydroxide, potassium hydroxide,
sodium carbonate, or potassium carbonate, especially at elevated
, ll temperatures.
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; Any acid or acid anhydride with suitable oxidizing pro-
perties which can be regenerated by air and recycled in the
process can be employed, for example sulfur trioxide~ oxides of
ll nitrogen, or the acids formed by reaction of these compounds
5,l with water. Specifically disclosed are sulfur trioxide,
! N2O3~ and N2O5.
~, In the second stage, U.S. ~atent 2,461,740 discloses the
use of a high pressure elevated temperature reaction of oxygen
¦I gas in aqueous alkali. The aqueous alkali employed is a
10¦ solution of sodium hydroxide, potassium hydroxide, sodium
¦l carbonate, or potassium carbonate.
i
¦1 U.S. Patent 3,023,217 discloses a process for introducing
I! carboxyl groups into aromatic compounds free from carboxyl
; ll groups, such as aromatic carbocyclic hydrocarbons and aromatic
l5l1heterocyclic hydrocarbons. The patent discloses a process for
introducing into aromatic carbocyclic or aromatic heterocyclic
jl compounds free from carboxyl groups by reacting such materials
¦ in the absence of substantial amounts of oxygen, such as a
non-oxidative atmosphere and under anhydrous conditions, with
~; 20,lalkali metal salts of aliphatic carboxylic acids at elevated
temperatures and pressures in the presence of catalysts.
. i! As disclosed in the process, it is necessary to exclude the
presence of substantial quantities of oxygen. Examples of
! aliphatic carboxylic acids which are used in the form of their
.: i1
25,,lalkali metal salts, especlally their potassium salts, are
oxalic acid, malonic acid, maleic acid, and trichloroacetic
acid.
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Examples o~ suitable compounds free from carboxyl grouDs
; which may be used as starting materials for the process are
aromatic carbocyclic compounds free from carboxyl groups such
Il as monoeyclie aromatie hydroearbons such as benzene or its
s~l derivatives having saturated alkyl or cyeloalkyl substitutes
attached thereto, and dicyelic aromatie hydroearbons such as
naphthalenes, diphenyl, and other polyeyelie aromatie hydro-
earbon eompounds. Similarly, aromatic heteroeyelie compounds
; free from earboxyl groups whieh may be used as starting mate-
~; 10 I rials are heteroeyelie eompounds whieh contain one or more ~;
heteroatoms in the ring and whieh are designated as having an
ll aromatie eharaeter beeause of their ehemieal behavior.
; I U.S. Patent 2,948,750 diseloses a process for earboxylating
aromatie hydrocarbons by direct introduetioh of earbon dioxide
15j to produee polyearboxylie aeids.
, I
Suitable starting materials which are disclosed are
;j aromatie hydroearbons, especially benzene but also toluene,
xylene, eumene and diisopropyl benzene and other benzenes
¦ substituted with saturated or unsaturated alkyl or eyeloalXyl
20ll radieals, naphthalene, diphenyl, diphenylmethane and other
aromatic compounds which may also be substituted with hydro-
I earbon radicals.
Seleetive earboxylation is aeeomplished by heating the
starting materials in the presence of an aeid-binding agent,
251 and earbon dioxide under anhydrous conditions. Examples of the
1 aeid-binding agent are earbonates of alkali metals, espeeially
. . .
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potassium carbonate, the salts of other weak acids such as
bicarbonates, formates, or oxalates. Similarly, the corres-
; Il ponding compounds of other metals are suitable; for example,
the earbonates o the alkali earth metals.
, ,1
S l U.S. Patent 3,023,216 discloses a method of introdueinq
~ I earboxyl groups into aromatic carbocyclie compounds free from
; ~ i!
earboxyl groups by reacting these eompounds in a non-oxidative
atmosphere with alkali metal salts of aromatie carboeyclie or
' I aromatie heteroeyelie earboxylie aeids.
10 I Suitable compounds which are free from carboxyl groups
whieh may be used as starting compounds in this patent are
¦I similar to the starting compounds in U.S. Patent 2,948,750.
U.S. Patent 3,023,216 discloses reacting aromatic ear-
llboxylic eompounds free from earboxyl groups with aromatic
15l;carboxylic aeids in the form of their alkali metal salts.
Both U.S. Patents 3,023,216 and 2,948,750 require specifie
! I
¦ehemieal eompounds as starting materials.
U.S. Patent 2,833,816 diseloses a process for oxidizing
~;~ aromatie eompounds using a eatalyst comprising a lower aliphatic
20 ~earboxylate salt of a heavy metal and bromine. Examples of a
heavy metal are manganese, cobalt, nickel, chromlum, vanadium,
molybdenum, tungsten, tin, and cerium.
The metals may be supplied in the form of metal salts;
for example such as manganese aeetate. The bromine may be
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supplied as ionic bromine, or other bromine compounds solu~le
in the reaction medium such as potassium bromate.
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` Thus, the process requires the conjoint presence of
` bromine and a heavy metal oxidation catalyst.
The starting material required is an aromatic compound
` containing one or more aliphatic substituents to produce
I corresponding aromatic carboxylic acids.
:, ,
;; U~S. Patent 3,Q64,043 discloses a process for oxidizing
para-toluic acid or para-formyl toluene to produce terephthalic
10,, acid.
, ,'
U.S. Patent 3,064,046 discloses a process for oxidizing
toluic acid or formyl toluene to produce orthophthalic acid or
isophthalic acid.
I . .
l Both U.S. Patents 3,064,043 and 3,064,046 require specific
15'~ starting materials to be oxidized.
I ,i U.S. Patent 3,558,458 discloses a process for preparing
': ~ '! . !
aromatic acids by treating an alkyl aryl ketone ~ith water at
an elevated temperature in the presence of a reaction promoting
agent. The reaction promoting agent may comprise an alkaline
~` 20l catalyst, a transition metal salt, or actinic light. Examples
¦l of an alkaline catalyst include potassium acetate, lithium
acetate, rubidium acetate, and cesium acetate. The process is
- l . i
,! conducted in water at a temperature of about 200C to 400C.
' 1 ~
I ~l The art discloses processes for the alkaline oxidation of
coal employing large amounts of chemicals relative to the
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amount of water soluble coal acids produced, see Uni~ed States
Patent 2,786,074 and a report entitled "Production of Chemicals
by Oxidation of Coal", Battelle Laboratory, Columbus, Ohio of
March 31, 1975. The report also suggests the use of potassium
` ; acetate and acetic acid in a cyclic process for the Henkel
reaction at page 19.
Recovery of caustic soda and sodium carbonate was dis-
closed by Industrial and Engineering Chemistry, Volume 44 (1952),
at page 2791 in an article entitled "Water-Soluble Polycarboxylic
~ , ,
Acids by Oxidation of Coal" beginning at page 2784.
Japanese Patent 18,365 discloses the reclamation of alkali
by recrystallization and requires the consumption of one part
by weight of the alkali and 1.5 parts of sulfurlc acid for each
:;
two parts of coal consumed.
Non-alkaline oxidation of coal generally yields about
10 parts by weight of water soluble coal acids based on 100
parts of coal carbon consumed. Alkaline oxidation yields have
::
been about 30 to about 42 parts per 100 parts of coal carbon
consumed. Therefore, alkaline oxidation processes are favored
because of the higher yield possible.
In systems like HCI/KCl, H2S04/K2S04, and HN03/KN03 the
salts do not produce an alkali solution by hydrolysis because
., ~ s
~ the acids involved are too strong. These systems over oxidize
,.. ,........................................................................ ~
~ the coal and therefore result in much lower yield of coal
-:
` acids.
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Another disadvantage of treatment of coals with strong acids is
the production of unwanted by-products by chlorination, sulfation, or nitra-
tion of the aromatic nuclei of the coal.
` Coal acids have been prepared by nitric acid oxidation, United
States Patents 3,~68,9~3; 3,709,931; 2,555,~10; in the presence of nitrogen
catalyst, United States Patent 3,702,340; and oxidation in a non-alkaline
aqueous medium, United States Patent 3,259,650.
The caustic-oxygen treatment of coal has been described in United
States Bureau of Mines Information Circular No. 8234 at pages 74 to 98.
In another process, United States Patent 3,259,650 discloses the
use of a non-alkaline medium and produces lower yields of water soluble coal
acids.
United States Patent 2,927,130 discloses a process for the recovery
of alkalis and terephthalic acid from aqueous solutions containing alkali
~ ~ salts of terephthalic acid. Alkalis of interest are sodium, potassium and
; ammonium. The patent discloses that dialkali salts of terephthalic acid in
,..
aqueous solution can easily be divided into difficultly soluble monoalkali
.. . . .
salts and alkali bicarbonate by introducing carbon dloxlde lnto the solu-
" tion, and that the difficultly soluble monoalkali salts of terephthalic acid
;;:
~ 20 can be hydrolyzed with water into free terephthalic acid and dialkali salts
... ..
; ~ of terephthalic acid. The free terephthalic acid separates out as a solid,
while the dialkali terephthalate remains in solution.
. Although oxidation can be carried out in reclaimable acidic media,
~ these processes are not as desirable because of lower yields and unwanted
-~ by-products due to chlorination, sulfation, and nitration.
The use of the applicant's invention allows reclamation of the re-
..;.,
' agent, higher yields, and less production of undesirable by-products. In
the applicant's invention, the material principally consumed in the process
;: ~
~:~ is the aromatic material. Almost all other reagents are almost fully re-
coverable and completely reusable. In one embodiment of the applicant's
invention, the applicant has found that 92 to 95 percent by weight of potas-
;,~ sium could be recovered as potassium acetate.
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SUMMARY OF THE INVENTION
This invention provides an improved process for che
production of carboxylic acids from carbonaceous materials.
According to the present invention; there is provided a
process for producing carboxylic acid from carbonaceous material
comprisiny:
a. treating a mixture of
i. a carbonaceous material, ii. water, and iii. a water
soluble reagent comprising a Group Ia or IIa metal formate,
10 acetate, or propionate, said reagent producing an alkaline
solution by hydrolysis, with oxygen, under conditions sufficient
to convert at least a portion of said carbonaceous material to a
carboxylic acid salt of said reagent;
b. removing water from said mixture from step (a);
d C. treating the mixture from step (b) with an acid of said
-; reagent to convert at least a portion of said carboxylic salt to
carboxylic acid and said reagent and to precipitate said carboxy-
lic acid; and -
d. separating said carboxylic acid formed in step (c) from said
20 reagent.
Furthermore, the invention provides a process for produc-
ing isomerized aromatic carboxylic acid from aromatic materials `
comprising:
a. treating a mixture of an aromatic material, water, and a
water soluble reagent comprising a Group Ia or IIa metal, said
reagent producing an alkaline solution by hydrolysis, with oxygen
-
under conditions sufficient to convert at least a portion of said
aromatic material to an aromatic carboxylic acid sal-t of said
Group Ia or IIa metal of said reagent;
30 b. isomerizing said aromatic carboxylic acid salt by heating to
produce an isomerized aromatic carboxylic acid salt without
10 -
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:
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-P converting said aromatic carboxylic acid salt to an aromatic
carboxylic acid salt of a different Group Ia or IIa metal prior
to isomerizing said aromatic carboxylic acid salt;
c. converting said isomerized aromatic carboxylic acid salt to
isomerized aromatic carboxylic acid, and regenerating said reagent
comprising said Group Ia or IIa metali
d. recovering said isomerized aromatic carboxylic acid; and
e. recycling said reagent comprising said Group Ia or IIa metal
thusly regenerated to step (a) to supply a portion of said reagent
required for producing said aromatic carboxylic acid salt.
- Thus mixture of carbonaceous material, water, and a water
soluble reagent comprising a Group Ia or IIa metal formate,
acetate, or propionate is first formed. The Group Ia or IIa
metal formate, acetate, or propionate is such that it will produce
~' an alkaline solution by hydrolysis. Thus, hydrogen is excluded
~ from the group comprising Group Ia or IIa metals.
`- Examples of such soluble reagents are potassium acetate,
potassium formate, potassium propionate, sodium acetate, sodium
formate, sodium propionate, lithium acetate, lithium formate,
:,:
~ lithium propionate, magnesium acetate, calcium acetate, barium
-~ acetate, beryllium acetate, etc.
The carbonaceous material may be coal, lignite, peat,
, coke, char, and other materials containing, or capable of evolving,
or producing, a hydrocarbon material, either liquid or solid.
`~ Pure water is not required and in fact process water may
- be used over and over at least in part.
,. ... . .
~ The mixture can be formed in any manner in a mlxlng zone
;~ using mixers suitable for handling slurries containing solids if
a solid or solid-like carbonaceous material is to be converted,
or mixers suitable for handling liquids if liquid aromatic
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materials are to be converted.
The mixture is removed from the mixing zone and fed to
a reaction zone wherein the mixture is reacted with oxygen,
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or an oxygen-containing gas such as air. The reaction zone and
the mi~ing zone can be, if desired, in the same vessel as in
some batch-type processes r or they may be separate vessels as
~ in some continuous processes.
5, More particularly, this invention provides an improved
i process for the production of aromatic carboxylic acids from
,1 aromatic materials.
.. I
A mixture of an aromatic materialr water, and a water
I soluble reagent comprising a Group Ia or IIa metal formate,
10~ acetate, or propionate is first formed. As described above,
the Group Ia or IIa metal formate, acetate, or propionate is
such that it will produce an alkaline solution by hydrolysis.
Thus, hydrogen is excluded from the group comprising Group Ia
or IIa metals.
; 151 Examples of such soluble reagents are potassium acetate,
, 1 potassium formate, potassium propionate, sodium acetate, sodium
I '` formate, sodium propionate, lithium acetate, lithium formate,
-~ ! lithium propionate, magnesium acetate, calcium acetate, barium
i ~1 acetate, beryllium acetate, etc.
201~ The aromatic material may be coal, especially bituminous
coal, petroleum residium, lignite, peat, pitch, tar, coke,
char, oil shale, oil from oil shale, and any other material
containing or capable of evolving or producing aromatic material
; , either liquid or solid.
25', Any kind of coal, including lignite, anthracite, or coke
or char can be used, but bituminous coals give the best yields.
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Yields of benzene carboxylic acid from anthracite coal are low
because anthracite is too aromatized. Anthracitic coals
produce a product having a high percentage of polynuclear
aromatic acids.
;"
Sll Yields from lignites are low because lignite produces
little aromatic material, thus the yield of aromatic carboxylic
acids will be low.
¦ The mixture is treated with oxygen under conditions
sufficient to convert the aromatic material to an aromatic
lOI,carboxylic acid salt of the reagent. In general, a temperature
I llof about 200C to about 350C is required. The pressure in the
reaction zone should be sufficient to maintain a liquid state
in the reaction zone. Generally this requires a pressure of at
¦least about 250 psig. Preferred reaction zone conditions are
15i`about 270C and about 900 psig.
¦ Reaction times in the reaction zone depend upon the ;~
' lltemperature, degree of agitation, the proportion of aromatic
material, water, and water soluble reagent, the solid-to-liquid
ratio, and the particle size of the solid material. Generally,
20¦~reaction times of from about ten minutes to about three hours
are required.
During oxidation carboxylic acids are formed which react
I!with the reagent to form carboxylic acid salts, and the volatile
- ,lacid of the reagent, the latter of which can be reclaimed by
~ 25'lventing vapor from the reactor.
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After treating the mixture with oxygen or an oxygen-
containing gas such as air to convert the aromatic material
into aromatic carboxylic acid, water is removed from the
mixture in a dewatering zone. In the dewatering zone, an
5l amount of water is removed which is sufficient that upon the
addition of "an acid of said reagent" that at least a ~ortion
of the aromatic carboxylic acid salt will be converted to an
aromatic carboxylic acid precipitate. The solution will
¦ contain the regenerated reagent which can be recycled for
10¦l further use.
As used herein and claimed herein, the expression "an
acid of the reagent" means an acid which is formed by the
~ Il replacement of the Group Ia or IIa metal atom of the water
; ¦I soluble reagent with hydrogen. The acid, therefore, will
1S fl either be formic, acetic, or propionic acid, or mixtures
;I thereof.
¦ Thus the invention can be seen to comprise the use of
Il an alkaline-acid-system. Examples of alkaline-acid-systems
: l!
', which may be used in the invention are potassium acetate-acetic
20 il acid, or potassium forma~e-formic acid, or potassium propionate-
.~ j,
propionic acid. Any alkaline-acid buffer system can be used
!
l from which a component is volatile or extractable. Since
,.; l -
; ¦ potassium acetate is the most soluble, it is therefore preferred.
i As mentioned earlier, systems liXe HCl/KCl, H2S04/K2S04,
2s il and HN03/KN03 are unsuitable because the salts do not produce
an alkali solution by hydrolysis since the acids involved are
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, too strong. Equally important is the fact that unwanted
by-products are formed by chlorination, sulfation, or nitration
o aromatic nuclei.
The dewatering zone can be in the same vessel as the
,1
reaction zone as in some batch processes, or it can be in a
separate vessel as in some continuous processes.
The water from the dewatering zone can be used in the
~, mixing zone to supply at least part of the water reqùirements
~i in the mixing zone.
10l The dewatered mixture, i.e., the mixture from the de-
i watering zone, is then treated in an acidification zone with an
1l acid of the reagent to convert the aromatic carboxylic acid
; I salt to an aromatic carboxylic acid precipitate and the reagent~
i 1I For example, potassium phthalate treated with acetic acid is
15 11 converted to phthalic acid and potassium acetate. In the case
I where no aromatic carboxylic acid precipitate is formed separa-
!
,I tion can be achieved by solvent extraction or other suitable
; ~, means.
~ The acidification zone may be in the same vessel as the ; ~;
- 20~l~ dewatering zone as in some batch processes, or it can be in a
i separate acidification vessel as in some continuous processes.
Sufficient acid must be added to the mixture to effect the
conversion of the aromatic carboxylate to the aromatic carboxy-
lic acid and to cause precipitation.
.. : i
25, The conditions in the acidification zone must be such
that the s~ecies of aromatic carboxylic acid desired to preci-
- 14 -
11 .
i
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pitate will in fact precipitate. These conditions, especialiy
temperature, will vary depending upon the species or species of
aromatic carboxylic acids which are desired to form precipitates.
j After forming the aromatic carboxylic acid precipitate,
the precipitate is separated rom the mixture in a separation
zone. Any apparatus capable of separating solids from liquids
may be used such as a filter. The separated solid comprises
the aromatic carboxylic acid precipitate.
The separated liquid from the separation zone is treated
10l, in a regeneration zone to recover the reagent from the liquid.
' The liquid stream from the acidification zone contains
~ l both the reagent and an acid of the reagent. The reagent and
,. ,
the acid of the reagent are separated in a separation zone.
The separated reagent can be used for additional treatment of
fresh aromatic material in the mixing zone whether the process
`~ ; is batch or continuous.
The separated acid of the reagent can be used to acidify
, !
additional material in the acidification zone whether the
~process is batch or continuous.
~ !
20~ In another embodiment an isomerized aromatic carboxylic
acid is produced by treating a mixture of an aromatic material,
water, and a water soluble reagent comprising a Group Ia or IIa
metal, the reagent is such that it produces an alkaline solution
' by hydrolysis, with oxygen under conditions sufficient to
convert at least a portion of the aromatic material to an
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~aromatic carboxylic acid salt of the Group Ia or IIa metal of
the reagent. The aromatic carboxylic acid salt is isomerized
~by heating to produce an isomerized aromatic carboxylic
l,acid salt without converting the aromatic carboxylic acid salt
l~to an aromatic carboxylic acid salt of a different Group Ia or
IIa metal prior to isomerizing the aromatic carboxylic acid
salt. Thus, for example, a sodium salt of the aromatic carboxylic
acid is not converted to a potassium salt of the aromatic
carboxylic acid. The isomerized aromatic carboxylic acid salt
llis then converted to an isomerized aromatic carboxylic acid, and
; i¦the reagent comprising said Group Ia or IIa metal is regenerated.
The isomerized aromatic carboxylic acid is recovered and the
reagent comprising the Group Ia or IIa metal thusly regenerated
¦is recycled to supply a portion of the reagent required for
,producing the aromatic carboxylic acid salt.
' ,~ The process is particularly valuable where the said
aromatic material is coal and/or the reagent is a potassium
reagent.
i BRIEF DESCRIPTION OF THE DRAWINGS
I! _ .
. 20 ¦i Figure 1 is a schematic flow diagram for my process for
the production of terephthalic acid from bituminous coal.
::~' I
; ¦ Figure 2 is a schematic flow diagram for my process for
! the production of carboxylic acid from coal.
'I DESCRIPTIGN OF PREFERRED EMBODIMENT
l, Referring to Figure 1, a finely divided bituminous coal
; l~through stream 10, water through stream 12 and potassium
- 15a -
'.1 .
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acetate through stream 14 are introduced into mixer 20. About
five parts water by weight and about 1 to 5 parts by weight of
potassium acetate are added to the mixer per part by weight of
coal. Any type of mixer may be used. After mixing, the
` 5 mixture is removed from mixer 20 through stream 22 and intro-
`I duced into autoclave 30. Air or oxygen is introduced into
. .
autoclave 30 through line 24. About two parts by weight of
oxygen per part by weight of coal is charged to autoclave 30.
` Ifi The coal is oxidized in autoclave 30 to produce aromatic
lOII carboxylic acids comprising benzene carboxylic acids, poly-
nuclear aromatic acids, carbon dioxide and water. The potassium
` ¦ acetate reacts with the thusly formed acids to produce potassium
f~ ~I salts thereof and acetic acid.
` il The autoclave is operated at a temperature of about 200
15 ll to about 350C, preferably about 270C, and at a pressure of
about 250 psig to about 2000 psig, preferably about 900 psig.
Temperatures below about 200C are not desirable because the
formation of polynuclear aromatic carboxylic acids are favored
ll and temperatures above about 350C are not desirable because
201l the formation of carbon dioxide is favored. Pressures outside
~ l¦ this range, however, can be used. Lower pressures are not
: I! desirable because kinetic rates are lower. Higher pressures
- l¦ are not desirable because of the cost of high pressure equipment
i and compression costs. Preferably the contents of autoclave 30
25l are agitated to increase product yield and to lower reaction
time.
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Gases comprising carbon dioxide, acetic acid and water
vapor are removed from autoclave 30 through line 31 and fed
,' into condenser 350. In condenser 350 the vaporous acetic acid
, and water vapor are condensed. The condensate and gases are
removed from condenser 350 through line 360 and fed to separator
, 370. The condensate comprising aqueous acetic acid is separated
',from the gas comprising carbon dioxide in separator 370. The
, 'gas is removed from separator 370 through line 380 and the
llcondensate through line 390. Both of streams 380 and 390 are
lO~¦fed to subsequent steps in the process as will be described
" Illater.
~.- I
, j The thusly formed aromatic acid salts are discharged
from autoclave 30 through line 32 to filter 40. , -
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; !¦
Filter 40 is used to separate the liquid product from
15,,residual solids. Filter 40 may be any type Oe filter, such as
a precoated revolving drum filter or a vacuum filter. The
, liquid product containing the dissolved thusly formed potassium
~ ~,acid salts is removed from filter 40'through line 42. The
', llsolids which contain unreacted coal and ash are removed from
20,`filter 40 through line 44 and recycled to mixer 20. The
filtration step is optional and is not needed if the solids in
stream 32 will not interfere with a subsequent isomerization
! step as described later.
i1
Liquid stream 42 from filter 40 is charged to evaporator
, 25 50 where most of the water therein is removed. The damp solids
;,containing the thusly formed potassium acid salts are removed
1. ' ~
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from the evaporator 50 through line 52 and enter dryer 60.
Water from evaporator 50 is removed through line 54 and recycled
to mixer 20.
In dryer 60, the remaining water which contains acetic
5 , acid is removed from the damp solids. The thusly formed dry
solids are removed from dryer 60 through line 62 and charged to
il isomerization reactor 80. It is important to dry the solids
charged to the isomerization reactor sufficiently to prevent
1 ll excessive reaction between water and aromatic carboxylic acids
.'~ 10l~ in the isomerization reactor.
,, I
In an alternate embodiment, potassium benzoate can be
introduced, as through line 66, into isomerization reactor 80
to simultaneously undergo conversion to terephthalic acid.
. .1 .
~ In isomerization reactor 80, the dry acid salts are
.,
catalytically isomerized at a temperature of from about 400C
¦, to about 440C at a pressure of about 10 atmospheres, and for a -
period of time of about 10 to about 100 minutes to cause
isomerization of the dry potassium acid salts to more valuable
'I products such as terephthalate and isomerized polynuclear ~`
20~l aromatic acid salts.
,I Preferably a carbon dioxide environment is maintained
- Il in the isomerization reactor. Especially preferably the carbon
dioxide is produced in the oxidation step as mentioned earlier
' and is fed to the isomerization reactor 80 through line 380.
25l If free oxygen is present in the gas in line 380 then it must
l be removed or converted to carbon dioxide (not shown) before
; - 18 -
. . ~
the gas is fed to isomerization reactor 80. Stream 380 may be
used as a source of carbon dioxide without any subsequent puri-
fication or treatment, if it does not contain free oxygen,
since it is not necessary to use pure carbon dioxide. In still
another embodiment, any inert atmosphere, such as nitrogen, may
be used.
Examples of catalysts useful for promoting the isomeriz-
ation are the oxides, carbonates, or halides of zinc or
cadmium. Organic salts, particularly carboxylates such as
cadmium ben~oate, are particularly good catalysts. Cadmium
iodide is a preferred catalyst, in concentrations varying from
1 to 15 parts by weight per 100 parts by weight of aromatic
carboxylic acid salts. The preferred concentration of cadmium
iodide is about 5 parts by weight per 100 parts by weight of
the aromatic carboxylic acid salt mixture.
The products are removed from isomerization reactor 80
through line 82 and enter cooler 90 where the products are
cooled to a temperature of about 200C to about 100C, pref-
erably about 100 C. It is necessary to cool the products
because decomposition occurs at higher temperatures when
exposed to water or oxygen. For example, exposure to water can
cause potassium tereph~halate to decompose to ben~oic acid and
potassium bicarbonate; and exposure to oxygen can cause potas-
sium terephthalate to decompose to carbon dioxide and potassium
bicarbonate.
The cooled products rcmoved from cooler 90 through line
92, together with water from line 94, are charged to dissolver
.
. - 19 -
,
s
:
100. In dissolver 100 the potassium acid salts are completely
dissolved.
The mixture is removed from dissolver 100 through line 102
and enters filter 110 where any undissolved solids are separated
from the liquid portion of the mixture. The thusly separated
liquid portion is removed from filter 110 through line 112 and
charged to precipitator 120. Treatment of the solution with
activated charcoal to remove any impurities which impart a
color to the terephthalic acid solution can be performed
, 10 prior to the precipitation step if desired.
The thusly separated solids, which consist essentially
of char and ash, are removed from filter 110 through line 114
and a portion thereof lS recycled to mixer 20 by way of line
116, or alternately the solids are recycled to autoclave 30
(not shown), to undergo further oxidation to produce additional
carboxylic acids. In order to prevent buildup of solids,
principally ash, in the system, another portion of the solids
is removed from the system through line 118.
In still another embodiment ~not shown), solids from
filter 110 are mechanically treated or floated to separate the
ash material from the carbonaceous material. The carbonaceous -
material can be returned to mixer 20, or alternately to auto-
clave 30, while the separated ash fractlon is removed from the
system.
Returning to dryer 60, the vapor stream, removed from the
dryer through line 64, is fed to condenser 70 wh~re~pon water
.~
''
:
- 20 -
~"
. ~,,
'
t5S
vapor containing acetic acid vapors is condensed to produce
a~ueous acetic acid. The condensate and any gases are removed
from condenser 70 through line 72 and fed to separator 75 which
separates the aqueous acetic acid from the gases. The separated
5` aqueous acetic acid is removed from separator 75 through line
, 76 and then charged to precipitator 120. Make-up acetic acid
' ' is fed to precipitator 120 through line 124. An excess of
acetic acid is maintained in the precipitator to effect preci-
~ ¦I pitation of terephthalic acid. A pH of about 3 to about 7,
10,, preferably about 4.7 to about 5.5, is maintained in preci-
pitator 120 to cause conversion of the potassium terephthalate
¦ to the terephthalic acid. By controlling the pH in the preci-
pitator in this range, i.e. about 3 to about 7, terephthalic
Il acid will be formed from the potassium acid salt and will be
15¦ caused to precipitate. Other aromatic carboxylic acids are
¦ more soluble than terephthalic acid and will remain in solution.
' A low pH, for example below about 3, in the precipitator is
~i undesirable because this will cause impurities to co-precipitate
¦¦ with terephthalic acid,while a high pH, for example over about
20i' 7, is undesirable because insu~ricient precipitation o tereph-
thalic acid will result, thereby reducing the yield.
¦I The temperature in the precipitator must be controlled
below the temperature at which significant product begins to
dissolve. This temperature is about 5C to about 25C when the
25l principal product is terephthalic acid. Precipitator 120 may
be any type, such as a continuous stirred tank reactor.
!
- 21 -
i
; 1, ' .
!i
S
` Gases removed ~rom separator 75 through line 77, which
; I comprise carbon dioxide, can be used to maintain at least part
of carbon dioxide atmosphere in the isomerization reactor 80.
These gases are fed to reactor 80 through line 78 or vented
5` through line 79. If gases from separator 75 contain free
oxygen then the free oxygen must be removed or converted
Ij
I ~ to carbon dioxide (not shown) before the gases are fed to
¦ isomerization reactor 80.
,, i . '.
l All of the products are removed from precipitator 120
lOI~through line 122 and enter filter 130. Filter 130 may be any
jltype, such as a precoated revvlving drum filter. -
The solid product, terephthalic acid, is removed from
filter 130 through line 131 and stored in s~orage vessel
135,
15l, The liquids are separated from the solid terephthalic
¦acid in filter 130 and the liquid is removed from the filter
-through line 132. If it is desired to remove more soluble
carboxylic acids from the acid solution, then liquids in line
132 are fed to separator 140.
. ,!
20l Separator 140 may be a liquid-liquid extraction apparatus.
The separated carboxylic acids are removed from the separator
140 through line 152 and are fed to purifier 160. Purification
of the carboxylic acid in purifier 160 may be by conventional
Imeans. The purified carboxylic acids are removed from the
: ,
; 25 purifiér 160 through line 162 and sent to storage vessel 170.
~ The impurities, consisting principally of potassium salts and
: I, ' i
~ - 22
,
. 1'1 ,
1:~2Q~55
;
water soluble aromatic acids, are removed from purifier 160
through line 164. These impurities may be recycled to the
autoclave.
. !`
In an alternate embodiment (not shown), if it is not
5 desirable to remGve the more soluble carboxylic acids from
liquid stream 132, then stream 132 is fed directly to separator
~ll90 instead of stream 142 for separation of acetic acid from
¦¦potassium acetate. In this embodiment, elements 140, 142, 152,
1 160, 162, 164, and 170 are omitted.
10 ~I Returning to separator 140, stream 142, which does not
¦contain the separated aromatic carboxylic acid but which
contains potassium acetate and acetic acid, is fed to separator
l90 for separation of acetic acid from potassium acetate.
IlAcetic acid may be separated from potassium acetate in separator
15 lll9o by distillation or by steam distillation, or by solvent
extraction or by other standard procedures.
- I The separated acetic acid is removed from separator 190
through line 194 and is recycled to precipitator 120 through
'line 126. Make-up acetic acid may be added to precipitator 120
~ 1
20 Ithrough line 124.
Il Potassium acetate is removed rom separator 190 through
¦lline 192 and enters reactor 200 whereupon it is treated with
lime which is introduced to reactor 200 through line 196. The
ilpurpose of the lime treatment is to prevent buildup of sulfate
25 lin the recycle stream and thereby liberate potassium for
; lirecycle. Reactor 200 can be a con~inuous stirred tank reactor.
- 23
,~
s5
!
",`'' "
The product from reactor 200 is removed therefrom through
~j line 202 and enters filter 210 whereupon calcium sulphate is
: ` separated as a solid from the liquid stream containing the
, dissolved potassium acetate. Filter 210 may be any type, such
as a vacuum filter. Calcium sulphate is removed from filter
210 by line 212. The calcium sulphate may be used in the
; making of portland cement, gypsum or pool acid or disposed of
by landfill. The potassium acetate stream is removed from
~Ifilter 210 through line 214 and is recycled to mixer 20.
''Make-up potassium acetate may be added to mixer 20 through
¦lline 14.
Alternately, if there is no desire to produce isomerized
carboxylic acids, stream 32 can be fed directly to filter 110
. ,1 . j .
~and the steps involving elements 40 through 102 are omitted.
IlThe alternate process is shown in Figure 2. This process,
l although similar, still has considerable value because of the
Ilregeneration and recycling of potassium acetate, line 214, to
mixer 20 or, alternately, to autoclave 30 (not shown). ~owever,
by eliminating the isomerization step, an aromatic carboxylic
,iacid of different constituents is produced and the yield of
'~terephthalic acid will be reduced. This carboxylic acid
I Ilmixture is useful in detergent manufacturing.
In another embodiment, the product from the isomerization
~Ireactor 80, preferably having been cooled in cooler 90, dissolved
l in dissolver 100 and filtered in filter 110 to remove undissolved
:; 1l . .
solids is sent to a precipitator for treatment with carbon
dioxide. In this embodiment, the precipitator is used to
.. .
~ , - 24 -
" ','
- ,i . .
.
.
precipitate the monopotassium salt of terephthalic acid by
treatment with carbon dioxide. Thus, the aqueous solution
containing dipotassium terephthalate in stream 112 is treated
in the precipitator with carbon dioxide to produce the mono~
potassium salt of terephthalic acid and potassium bicarbonate.
jIn this embodiment, which is not shown in either Figure 1 or 2,
acetic acid is not charged to the precipitator. The precipitator
is maintained at a temperature below about 50C, preferably
llbelow 30C, and especially preferably at about 0C to enhance
,the dissolving of carbon dioxide in the solution.
The monopotassium salt of terephthalic acid, a precipitate,
is separated from the aqueous solution of potassium bicarbonate
in a separation zone which may be a filter. The separated
I,monopotassium salt of terephthalic acid is then charged to a
lS ~hydrolyzer where it is treated with water to form dipotassium
terephthalate and terephthalic acid. The dipotassium tereph-
,thalate remains in solution while the terephthalic acid precipi-
tates. The terephthalic acid may then be separated from the
'dipotassium terephthalate solution and the dipotassium tereph-
Ithalate solution recycled to the precipitator above, or treatedin another zone. In either case, the dipotassium terephthalate
~,is treated with carbon dioxide to convert the dipotassium
¦terephthalate to monopotassium salt of terephthalic acid and
additional potassium bicarbonate.
~ The monopotassium salt of terephthalic acid can be neu-
ltralized by other means, if desired, such as treatment with
,carbon dioxide or an acid such as acetic acid in an aqueous
solution.
- 25 -
, 1,
,1
!! .,
--- \
~z0~ss
The potassium bicarbonate solution after separation from
ithe monopotassium solid terephthalic acid can be recycled to
~mixer 20, or alternately to autoclave 30, as the water soluble
reagent comprising a Group Ia or IIa metal. Preferably the
S potassium bicarbonate is converted to potassium carbonate by
heating, and the potassium carbonate is recycled to mixer 20,
~or alternately to autoclave 30, as the water soluble reagent
'comprising a Group Ia or IIa metal. In this embodiment, the
liwater soluble reagent comprising a Group Ia or IIa metal does
"not require the use of a formate, acetate or propionate of such
metal.
Furthermore, in this embodiment the alkali metal reagent,
which is potassium in the above description, is recovered and
lrecycled in the process. As can be seen, nd conversion of the
l~potassium aromatic carboxylic acid salt prior to isomerization
is required in the process. That is to say, it is not necessary
to convert the potassium acid salt to a sodium acid salt, or ~ -
vice versa, prior to isomerization. -
~ The process of this invention has the advantage over prior
lart for producing terephthalic acid in that it is not necessary
,to prepare the salts of the aromatic carboxylic acids, then to
separate the benzene carboxylic acids from the remaining
polynuclear carboxylic acids; and then to convert the benzene
~Icarbox~lic acids to the potassium salt of the a,_ids prior to
25 isomerization. ~-
- 26 -
.
, . ~ , .
~Z~1~55
Anothe~ advantage of this invention is that it is not
necessary to prepare the salts in a separate zone apart from
` the o~idation zone since in this invention the salts are
prepared directly in the oxidation zone.
1 Another advantage of this invention is that it is not
necessary to treat the aromatic carboxylic acid salts or
convert the aromatic carboxylic acid salts to their aromatic
,¦carboxylic acids and then treat, with a compound which contains
'la Group Ia or IIa metal prior to isomerization.
I Similarly, another advantage of this invention is that it
is not necessary to convert the aromatic carboxylic acid salts
ito their aromatic carboxylic acids and to treat the aromatic
! carboxylic acids with a Group Ia or IIa metal prior to
lisomerization.
15 ll Still another advantage of this invention is that after
,the aromatic material is oxidized in the presence of a first
compound comprising a Group Ia or IIa metal to form an aromatic
carboxylic acid salt of the Group Ia or IIa metal, it is not
necessary to convert the aromatic carboxylic acid salt of the
,IGroup Ia or IIa metal to another aromatic carboxylic acid salt
of another Group Ia or IIa metal prior to isomerization.
Another advantage is that the reagent is regenerated by
the process.
.,
- 27 -
. .
EXA;1PLE I
Regeneration of Reagent
The following is an example of the conversion of an
aromatic carboxylic acid with a metal acetate to a metal
S aromatic carboxylate followed by the conversion of the metal
aromatic carboxylate by treating with an excess acetic acid to
convert the metal aromatic carboxylate to aromatic carboxylic ~ -
acid. ~This corresponds to Step Nos. 30, 40, 50, 60, 120, 130,
` and l90 in Figure l.)
18.82 gr of dry reagent grade trimesic acid (l, 3, 5
~benzene-tricarboxylic acid) was added to a flask together with
39.50 gr of potassium acetate and 300 gr of water. This mixture
~was boiled until all of the trimesic acid was dissolved.
~ (This corresponds to the state found in autoclave 30 of
15~~igure l.)
., .
The mixture was then evaporated to dryness. It is
estimated that at least 80% of the acid was converted to its
potassium salt. (This corresponds to the state found in dryer
~ 60 of Figure l.) The condensate consisted of acetic acid and
water.
Three extractions of the acid salt took place using 80 cm3
~ i
,of a mixture containing 90% glacial acetic acid and 10% by weight
,of water for each extraction. Each extraction took place at
i 60C with stirring for 15 minutes. Each time the acetic acid
- 28 -
., . i
I
~Z~I~S5
water mixture containing newly formed potassium acetate was
passed through a 50-60 ASTt~ sintered glass filter, with the
newly formed trimesic acid remaining behind. (This corresponds
to steps 120 and 130 in Figure 1.)
The extract was evaporated to dryness by heating to
200C under vacuum. 37.53 gr of extract or 95~ by weight of
the original potassium acetate was recovered. The weight of
the remaining dry trimesic acid was 20.22 gr. It thus con-
tained the remaining potassium. (This corresponds to step 190
in Figure 1.)
The fact that the reclaimed potassium acetate may contain
some potassium trimesate and trimesic acid in this experiment
is of no consequence to the process of this invention because
it is intended that the reclaimed potassium acetate be recycledO
However, should a higher reclamation factor be desired, the
extraction with the acetic acid water mixture can be repeated
with the results being predicted by a fractionation curve as
used in distiilation.
EXAMPLE II
Oxidation of Coal
i
About 28 gr of coal, 170 gr of potassium acetate, and
400 gr of water were charged to a stirred autoclave.
The mixture was treated with oxygen at a total pressure
of 1700 psig at a temperature of 500F for 30 minutes with
continuous stirring taking place.
.
- 29 -
., ,
:, , i
'~
~ \
~L~L2~5S
The autoclave contents were analyzed and 12.8 gr of coal
acids were found to be present. About 6.4 gr of this was
benzene-carboxylic acids, which represents a 28~ yield on a dry
ash free coal basis.
EXAMPLE III
:
Regeneration of Reagent, Specifically Potassium Acetate
To demonstrate the regeneration of potassium acetate, the
, following experiment was carried out.
Pyromellitic acid, a typical constituent of coal acids, I -
, I ~
10 ~ was used. I --
18.82 gr of pyromellitic acid were reacted with 39.5 gr of
potassium acetate to give 30.4 gr of tetrapotassium pyromellate
and an unmeasured amount of acetic acid. The acetic acid is
' recoverable by distillation. The salt was extracted with a ', -
15 I water/acetic acid mixture, and 37O5 gr of potassium acetate
, was recovered. 1-
The salt was converted back to pyromellitic acid. Thus,
95~ potassium acetate was reclaimed after forming the potassium
, salt of pyromellitic acid.
- 20 ~XAMPL~ IV
:
Precipitation of Aromatic Carboxylic Ac d, Specifically
, Terephthalic Acid
A prepared solution of potassium terephthalate consisting
of 10 gr of potassium terephthalate in 100 gr of water was
treated with 100 ml of 6~ acetic acid solution and immediately
i produced 6.7 gr of a white precipitate of terephthalic acid.
' ',
. . ~ .
, - 30 - '
,
S5
EXAMPLE V
Isomerization of Coal Acids
Abo~t 9.3 gr of coal acids were converted to their
corresponding potassium salts. 0.5 gr of cadmium oxide was
thoroughly mixed with the salts. The mixture was then dried to
remove moisture.
The mixture was charged to an autoclave which was pres- j
surized to 130 psig with carbon dioxide. It was heated to
,' 400C and maintained at that temperature for four hours while
at 130 psig.
After cooling, the mixture was dissolved in boiling water
~and filtered to remove char containing the cadmium~
., .
Upon acidification of the mixture with 100 ml of 6~
' acetic acid solution, a yield of 3.2 gr of terephthalic acid
15~ was obtained. This corresponds to a 36~ yield from the coal
acids.
EXAMPLE ~I
, . .
` Conversion of Coal to Terephthalic Acid
~!
, 100 gr potassium acetate and 30 gr of bituminous coal
are mixed with 400 gr of water. The mixture is charged to
an oxidation autoclave and heated to 260C. Oxygen is slowly
added to the autoclave until a total pressure of 1500 psig is
achieved. A product gas consisting of carbon dioxide, steam,
, . .
., i
- 31 -
.
! I i
',' . i
,. `, ~:
;
5~
and acetic acid is periodically vented from the autoclave, and
the autoclave is repressurized with oxygen to 1500 psig each
time. After half an hour of treatment with oxygen, the autoclave
contents are cooled to room temperature and discharged from the
autoclave.
The oxidized mixture is dried by boiling until almost dry ~-
l~and the vapors condensed. A total of 407.6 gr of liquid
i~condensate is collected by combining the condensate from the
llproduct gas and the drying operation. The total condensate
Icomprises of 16.6 gr of acetic acid. The moist oxidized
mixture is thoroughly dried under vacuum for three hours. -
Il About 2.0 gr of cadmium iodide, as catalyst, is intimately
¦,mixed with the dried, oxidized mixture. Thq mixture is then
'Icharged to an isomerization autoclave and heated to 150F.
~Remaining moisture is purged from the autoclave using dry
j'lcarbon dioxide. The autoclave is heated to 395C for 2.5 hours
jj ! :
with 600 psig of carbon dioxide pressure.
The autoclave is then cooled to room temperature. The
solid material is removed from the autoclave and dissolved in
I I ~
i~100 gr of hot water. The solution is filtered to remove char
land solids.
. 1, .
, The condensate from the oxidization and drying steps,
'which contains acetic acid, is added to the solution. A
iprecipitate of 10.2 gr of crude terephthalic acid is formed.
,The terephthalic acid precipitate is separa~ed by filtration.
., ,
- 32 -
, ~
,1 . ,
The filtrate, or mother liquor, is evaporated to form
a condensate containing 0.9 gr of acetic acid dissolved in 450
gr of water. 102 gr of solid residue, containing 98.5 gr of
potassium acetate is obtained. The solid residue is recycled
to the next oxidation step.
The 450 gr of water is reduced in weight to 400 gr
and 1.5 gr of makeup potassium carbonate is added, converting
the remaining acetic acid in solution to potassium acetate.
The solution is recycled to the oxidation step. It can be seen
10 llthat nearly all of the origlnal potassium acetate is recovered
and recycled.
The following table summarizes the mass flows in Example
VI.
15 1 Weight of Coal 30.0 gr
Weight of Potassium Acetate100.0 gr
Weight of Recovered Potassium Acetate 38.5 gr
Weight of Unused Acetic Acid0.9 gr
' Weight of Potassium Carbonate Required
to Regenerate Potassium Acetate from
Acetic Ac1d 1.5 gr
i,
, ~,
- 33 -
.~
,i
,1 .
5~
EXAMPLE VII
Conversion of Coal Char to Terephthalic Acid
100 gr potassium acetate and 30 gr of coal char are
mixed with 400 gr of water. The coal char is produced by
pyrolyzing a bituminous coal at 1500F for 20 minutes in a
~fluidized bed reactor. The mixture is charged to an oxidation
autoclave and heated to 260C. Oxygen is slowly added to
the autoclave until a total pressure of 1500 psig is achieved.
~ A product gas consisting of carbon dioxide, steam, and acetic
lacid is periodically vented from the autoclave, and the auto-
`clave is repressurized with oxygen to 1500 psig each time.
After half an hour of treatment with oxygen, the autoclave
contents are cooled to room temperature and discharged from the
'autoclave.
i The oxidized mixture is dried by boiling until almost dry
and the vapors condensed. A total of 407.6 gr of liquid
condensate is collected by combining the condensate from the
product gas and the drying operation. The total condensate
IcomPrises of 16.6 gr of acetic acid. The moist oxidized
20 I mixture is thoroughly dried under vacuum for three hours. -
About 2.0 gr of cadmium iodide, as catalyst, is intimately
jlmixed with the dried, oxidized mixture. The mixture is then
~charged to an iso~erization autoclave and heated to 150F.
~Remaining moisture is purged from the autoclave using dry
l~carbon dioxide. The autoclave is heated to 395C for 2.5 hours
,with 600 psig of carbon dioxide pressure.
.j I
- 34 -
- `~
The autoclave is then cooled to room temperature. The solid
material is removed from the autoclave and dissolved in lO0 gr of
hot water. The solution is filtered to remove char and solids.
The condensate from the oxidization and drying steps, which
contains acetic acid, is added to the solution. A precipitate of
6.3 gr of crude terephthalic acid is formed. The terephthalic acid
~precipitate is separated by filtration.
The filtrate, or mother li~uor, is evaporated to form a
l condensate containing 0.9 gr of acet1c acid dissolved in 450 gr of
l~ water. 102 gr of solid residue~ containing 98.5 gr of potassium
acetate is obtained. The so1id residue is recycled to the next
oxidation step.
Il The 450 gr of water is reduced in weight to 400 gr and l.5 gr
,lof makeup potassium carbonate is added, converting the remaining
~acetic acid in solution to potassium acetate. The solution is
recycled to the oxidation step. It can be seen that nearly all of
the original potassium acetate is recovered and recycled.
The following table summarizes the mass flows in Example
VII.
20 ~ eight of Coal Char 30.0 gr
1 Weight of Potassium Acetate lO0.0 gr
.
~ '~1 Weight of Recovered Potassium Acetate 9~.5 gr
, .
Weight of Unused Acetic Acid 0.9 gr
Weight of Potassium Carbonate Required
to Regenerate Potassium Acetate from
~ Acetic Acid l.5 gr
,, .
,
';
EXA;~PLE VIII
Conversion of Coal Tar to Terephthalic Acid
100 gr potassium acetate and 30 gr of coal tar are mixed
with 400 gr of water. The coal tar is produced by pyrolyzing a
bituminous coal to 1500F for 20 minutes in a fluidized bed,
cooling the product vapors, and recovering the condensed coal
tar. The mixture is charged to an oxidation autoclave and
heated to 260C. Oxygen is slowly added to the autoclave until
a total pressure of 1500 psig is achieved. A product gas
consisting of carbon dioxide, steam, and acetic acid is
periodically vented from the autoclave, and the autoclave is
repressurized with oxygen to 1500 psig each time. After half
an hour of treatment with oxygen, the autoclave contents are
cooled to room temperature and discharged from the autoclave.
~,
l~ '' The oxidized mixture is dried by boiling until almost dry -
and the vapors condensed. A total of ~07.6 gr of liquid ~ ~
condensate is collected by combining the condensate from the
product gas and the drying operation. The total condensate
,comprises of 16.6 gr of acetic acid. The moist oxidized
imixture is thoroughly dried under vacuum for three hours.
¦ About ~.0 gr of cadmium iodide, as catalyst, is intimately
mixed with the dried, oxidized mixture. The mixture is then
charged to an isomerization autoclave and heated to 150Fo
IlRemaining moisture is purged from the autoclave using dry
~lcarbon dioxide. The autoclave is heated to 395C for 2.5 hours
with 600 psig of carbon dioxide pressure.
Il
`~
The autoclave is then cooled to room temperature. The solid
material is removed from the autoclave and dissolved in 100 gr of
~hot water. The solution is filtered to remove char and solids.
The condensate from the oxidization and drying steps, which
contains acetic acid, is added to the solution. A precipitate of
11.8 gr of crude terephthalic acid is formed. The terephthalic
acid precipitate is separated by filtration.
i'
The filtrate, or mother liquor, is evaporated to form a
,Icondensate containing 0.9 gr of acetic acid dissolved in 450 gr of
liwater. 102 gr of solid residue, containing 98.5 gr of potassium
acetate is obtained. The solid residue is recycled to the next
oxidation step.
1. ~
,~ The 450 gr of water is reduced in weight to 400 gr and 1.5 gr
of makeup potassium carbonate is added, converting the remaining
lacetic acid in solution to potassium acetate. The solution is
recycled to the oxidation step. It can be seen that nearly all of
"the original potassium acetate is recovered and recycled~
! The following table summarizes the mass flows in Example
VIII.
,, .
20 iWeight of Coal Tar 30.0 gr
Weight of Potassium Acetate 100.0 gr
Weight of Recovered Potassium Ace~ate 9805 gr
Weight of Unused Acetic Acid 0.9 gr
Weight of Potassium Carbonate Required
25 to Regenerate Potassium Acetate from
Acetic Acid 1.5 gr
- 37 -
.1
~z~s~
EXAMPLE IX
Conversion of Heavy Residual Oil to Terephthalic Acid
100 gr potassium acetate and 30 gr of heavy residual oil
from a naphthenic crude oil are mixed with 400 gr of water.
The mixture is charged to an oxidation autoclave and heated to
260C. Oxygen is slowly added to the autoclave until a total
'pressure of 1500 psig is achieved. A product gas consisting of
,Icarbon dioxide, steam, and acetic acid is periodically vented
Ifrom the autoclave, and the autoclave is repressurized with
loxygen to 1500 psig each time. After half an hour of treatment
with oxygen, the autoclave contents are cooled to room tempera-
ture and discharged from the autoclave.
The oxidized mixture is dried by boiling until almost dry
land the vapors condensed. A total of 407.6 gr of liquid
Icondensate is collected by combining the condensate from the
product gas and the drying operation. The total condensate
comprises of 16.6 gr- of acetic acid. The moist oxidized
mixture is thorouyhly dried under vacuum for three hours.
~ About 2.0 gr of cadmium iodide, as catalyst, is intimately
,jmixed with the dried, oxidized mixture. The mixture is then
ilcharged to an isomerization autoclave and heated to 150F.
- , Remaining moisture is purged from the autoclave using dry
~carbon dioxide. The autoclave is heated to 395C for 2.5 hours
with 600 psig of carbon dioxide pressure.
.'
. .
- 38 -
"
.
i
The autoclave is then cooled to room temperature. The solid
material is removed from the autoclave and dissolved in 100 gr of
~hot water. The solution is filtered to remove char and sol ds.
The condensate from the oxidization and drying steps, which
contains acetic acid, is added to the solution. A precipitate of
~3.8 gr of crude terephthalic acid is formed. The terephthalic acid
precipitate is separated by filtration.
¦; The filtrate, or mother liquor, is evaporated to form a
I,condensate containing 0.9 gr oE acetic acid dissolved in 450 gr of
¦,water. 102 gr of solid residue, containing 98.5 gr of potassium
¦lacetate is obtained. The solid residue is recycled to the next
oxidation step.
¦ The 450 gr of water is reduced in weight to 400 gr and 1.5 gr
i,of makeup potassium carbonate is added, converting the remaining
'acetic acid in solution to potassium acetate. The solution is
recycled to the oxidation step. It can be seen that nearly all of
, the original potassium acetate is recovered and recycled.
The following table summarlzes the mass flows in Example
IX.
20 1¦ Weight of Heavy Residual Oil30.0 gr
¦~ Weight of Potassium Acetate100.0 gr
¦ Weight of Recovered Potassium Acetate 9~.5 gr
'l Weight of Unused Acetic Acid0.9 gr
~ Weight of Potassium Carbonate Required
to Regenerate Potassium Acetate rrom
Il Acetic Acid 1.5 gr
', - 39 -
l l
-
EXAMPLE X
Conversion of Dipotassium Terephthalate to Terephthalic Acid
L ~ c~ ~ D i c ~
29 gr of dipotassium terephthalate were dissolved in 200
S ml of hot deionized water and the solution was filtered to
remove any insoluble solids. Carbon dioxide was bubbled
through the solution as it was cooled in an ice bath. ~hite
crystals immediately began to form. After the suspension of
llcrystals in the solution had cooled to a temperature of less
l~than -2C (28F) and let stand for thirty minutes, it was then
vacuum filtered. The white needles on the filter were washed
with ice water, dried in a vacuum oven, and weighed. Approxi-
Imately 16.2 gr of precipitate were recovered. A sample was
lanalyzed and found to have the composition:
15 ! Element ~ by Wei~ht
C 47.4
H 2.8
',, K 18.1
O 31.7 (by difference)
I Pure potassium hydrogen terephthalate has the following
~composition:
Element ~_~Y~
! . .
C 47.0
I H 2.5
~I K 19.2
O 31.3
Thus, the precipitate is potassium hydrogen terephthalate.
-- ~O --
J
,,
~Z0~15S
The potassium hydrogen terephthalate was then dissolved in
160 ml of water and boiled for 5 minutes. About 6.5 gr of
terephthalic acid were recovered by filtering the solution.
The solution, which contains dipotassium terephthalate, can be
concentrated and recycled to the carbon dioxide precipitation
step.
EXAMPLE XI
Conversion_of Dipotassium Terephthalate to Terephthalic Acid
,,Using Carbon Dioxide
~0l 29 gr of dipotassium terephthalate were dissolved in 200
ml of hot deionized water and the solution was filtered to
remove any insoluble solids. Carbon dioxide was then bubbled
through the solution (cooled to 25C) in a pressure filtration
apparatus at 800 psig. About 20 gr of potassium hydrogen
terephthalate were recovered after filtration. This was then
dissolved in 200 ml of water and boiled for five minutes.
About 8.0 gr of terephthalic acid were recovered by filtration
of the solution.
.
~, ~
- 41 -
. :
, ! -` ~
OS5
. .
The process of the invention has been described generally
,and by example with reference of clarity and illustration only.
! It will be apparent to those skilled in the art from the
foregoing that various modifications of the process and the
S 'Imat,erials disclosed herein can be màde without departure from
l,the spirit of the invention.
Accordingly, the invention is not to be construed or
¦limited to the specific embodiments illustrated, but only
'as defined,in the fo owing claims.
