Thiết kế qui trình công nghệ sản xuất vinyl axetat

ĐỒ ÁN CHUYÊN NGÀNH
ĐỀ TÀI 1: Thiết kế qui trình Công nghệ sản xuất Nitrobenzen.
HỌ TÊN SINH VIÊN:
1:…………………………………….
2:……………………………………
ĐỒ ÁN CHUYÊN NGÀNH
ĐỀ TÀI 2: Thiết kế qui trình Công nghệ sản xuấn Ankyl benzensunfonic.
HỌ TÊN SINH VIÊN:
1:…………………………………….
2:……………………………………
ĐỒ ÁN CHUYÊN NGÀNH
ĐỀ TÀI 3: Thiết kế qui trình Công nghệ sản xuất Axetanilit.
HỌ TÊN SINH VIÊN:
1:…………………………………….
2:……………………………………
ĐỒ ÁN CHUYÊN NGÀNH
ĐỀ TÀI 4: Thiết kế qui trình Công nghệ sản xuất Etyl axetat.
HỌ TÊN SINH VIÊN:
1:TRẦN MINH THIỆN
2:VŨ THỊ VƯƠNG
ĐỒ ÁN CHUYÊN NGÀNH
ĐỀ TÀI 5: Thiết kế qui trình Công nghệ sản xuất Vinyl axetat.
HỌ TÊN SINH VIÊN:
1:NGÔ THANH TRÍ…………………………………….
2:NGUYỄN MINH TRUNG……………………………………
ĐỒ ÁN CHUYÊN NGÀNH
ĐỀ TÀI 6: Thiết kế qui trình Công nghệ sản xuất Formandehit từ metanol.
HỌ TÊN SINH VIÊN:
1:…………………………………….
2:…………………………………….
ĐỒ ÁN CHUYÊN NGÀNH

ĐỀ TÀI 7: Thiết kế qui trình Công nghệ sản xuất Axit axetic.
HỌ TÊN SINH VIÊN:
1:VÕ PHƯỚC TUYỂN…………………………………….
2:NGUYỄN HỮU VƯƠNG…………………………………….
ĐỒ ÁN CHUYÊN NGÀNH
ĐỀ TÀI 8: Thiết kế qui trình Công nghệ sản xuất Anilin.
HỌ TÊN SINH VIÊN:
1:…………………………………….
2:…………………………………….
ĐỒ ÁN CHUYÊN NGÀNH
ĐỀ TÀI 9: Thiết kế qui trình Công nghệ sản xuất Phenol.
HỌ TÊN SINH VIÊN:
1. NGUYỄN VĂN VIỆT
2. LÊ TRÍ
ĐỒ ÁN CHUYÊN NGÀNH
ĐỀ TÀI 10: Thiết kế qui trình Công nghệ sản xuất Etyl benzen.
HỌ TÊN SINH VIÊN:
1:ĐOÀN DUY TÙNG
2:TRỊNH ĐÌNH TUYỀN
ĐỒ ÁN CHUYÊN NGÀNH
ĐỀ TÀI 11: Thiết kế qui trình Công nghệ sản xuất Etyl Acrylat.
HỌ TÊN SINH VIÊN:
1:…………………………………….
2:…………………………………….
ĐỒ ÁN CHUYÊN NGÀNH
ĐỀ TÀI 12: Thiết kế qui trình Công nghệ sản xuất MTBE.
HỌ TÊN SINH VIÊN:
1:PAHN VĂN TRUNG
2:NGUYỄN VĂN TRƯỜNG
ĐỒ ÁN CHUYÊN NGÀNH

ĐỀ TÀI 13: Thiết kế qui trình Công nghệ sản xuất ETBE.
HỌ TÊN SINH VIÊN:
1:HUỲNH KIM Ý
2:PHẠM THANH TÙNG
ĐỒ ÁN CHUYÊN NGÀNH
ĐỀ TÀI 14: Thiết kế qui trình Công nghệ tách Hydrocacbon thơm.
HỌ TÊN SINH VIÊN:
1:…………………………………….
2:…………………………………….
ĐỒ ÁN CHUYÊN NGÀNH
ĐỀ TÀI 15: Thiết kế qui trình Công nghệ tách n-parafin.
HỌ TÊN SINH VIÊN:
1:…………………………………….
2:…………………………………….
ĐỒ ÁN CHUYÊN NGÀNH
ĐỀ TÀI 16: Thiết kế qui trình Công nghệ sản xuất Dicloetan.
HỌ TÊN SINH VIÊN:
1:LÂN QUỐC VIỆT
2:ĐẶNG MINH VƯƠNG
ĐỒ ÁN CHUYÊN NGÀNH
ĐỀ TÀI 17: Tìm hiểu Công nghệ tái sinh dầu nhờn.
HỌ TÊN SINH VIÊN:
1:NGÔ BÁ THÙY TRANG
2:LÊ THỊ MỸ VÂN
ĐỒ ÁN CHUYÊN NGÀNH
ĐỀ TÀI 18: Công nghệ thu hồi và xử lý dầu loang.
HỌ TÊN SINH VIÊN:
1:HÀ ANH TUẤN
2:NGUYỄN ĐÌNH VŨ
ĐỒ ÁN CHUYÊN NGÀNH

ĐỀ TÀI 19: Tổng quan về phụ gia cho xăng Etanol.
HỌ TÊN SINH VIÊN:
1:NGUYỄN HỮU VƯƠNG
2:VÕ PHƯỚC TUYỂN
ĐỒ ÁN CHUYÊN NGÀNH
ĐỀ TÀI 20: Tìm hiểu qui trình tổng hợp nhiên liệu sạch từ nguồn nguyên liệu
biomass Việt Nam bằng công nghệ tổng hợp F -T ở áp suất thường.
HỌ TÊN SINH VIÊN:
1:NGUYỄN MINH TRUNG
2NGÔ THANH TRÍ
ĐỒ ÁN CHUYÊN NGÀNH
ĐỀ TÀI 21: Tìm hiểu công nghệ sản xuất ethanol từ xenlulo.
HỌ TÊN SINH VIÊN:
1:NGUYỄN CHÍ TRUNG
2:NGUYỄN NHẬT TRƯỜNG
ĐỒ ÁN CHUYÊN NGÀNH
ĐỀ TÀI 22: Thiết kế qui trình công nghệ tổng hợp etanol bằng phần mền mô
phỏng Hysys.
HỌ TÊN SINH VIÊN:
1:PHAN THANH TÚ
2:LÊ MINH TUẤN
ĐỒ ÁN CHUYÊN NGÀNH
ĐỀ TÀI 23: Tìm hiểu qui trình công nghệ tổng hợp mỡ nhờn canxi.
HỌ TÊN SINH VIÊN:
1:…………………………………….
2:…………………………………….
ĐỒ ÁN CHUYÊN NGÀNH
ĐỀ TÀI 23: Chưng cất dầu thô bằng phần mền hysys.
HỌ TÊN SINH VIÊN:
1:NGUYỄN THỊ KIM YẾN

2:ĐINH VĂN YÊN
2. Vinyl Acetate
2.1. Properties
Physical Properties. Vinyl acetate [108-05-4], CH
3
CO
2
CH=CH
2
, M
r
86.09, is a colorless,
flammable liquid with a characteristic, slightly pungent odor, bp 72.8 °C, density at 20 °C
0.932 g/mL, mp – 93.2 °C, viscosity 0.43 mPA · s, vapor pressure 12 kPa at 20 °C, 42.6 kPa
at 50 °C, coefficient of cubic expansion 0.0014 K
–1
, flashpoint – 8 °C, ignition temperature
385 °C. Lower/upper flammability limits in air 2.3/13.4 vol %, ignition group (VDE 0165)
G 2, specific heat 1.926 kJ/kg; heat of evaporation 379.3 kJ/kg at 72.7 °C, heat of combustion
2082.0 kJ/mol, refractive index 1.3956, heat of polymerization 1035.8 kJ/kg, solubility of
water in vinyl acetate 0.9 wt % at 20 °C, solubility of vinyl acetate in water 2.3 wt % at
20 °C, azeotrope with water bp 66 °C/100 kPa, water content 7.3 wt %.
Chemical Properties. The chemical property which is exploited almost exclusively is the
capacity to polymerize (see Section Use, Economic Importance).
Other reactions of vinyl acetate: halogens give 1,2-dihaloethyl acetates [6], hydrogen halides
give 1-haloethyl acetates [7], acetic acid gives ethylidene diacetate (see Section Production),
hydrogen cyanide gives 2-acetoxypropionitrile [8], hydrogen peroxide gives
hydroxyacetaldehyde [9], and dienes, such as butadiene or cyclopentadiene, give
Diels – Alder products [10].
Transesterification with carboxylic acids produces the corresponding vinyl carboxylate and

acetic acid [11] (see also Section Quality Specifications, Analysis,Storage, Transport, and
Toxicology) and with alcohols gives the corresponding acetate and acetaldehyde. Thermal
cleavage gives ketene and acetaldehyde [12]. Acid-catalyzed [13] or thermal [14] hydrolysis
produces acetaldehyde and acetic acid. Vinyl acetate can be epoxidized with peracetic acid
(84 % yield) [15]. It undergoes addition of H-active compounds, e.g., dimethyl phosphite
gives dimethyl acetoxyethylphosphonate [16].
2.2. Production
There are various possible routes for vinyl acetate production:
1.Addition of acetic acid to acetylene:
a.in the liquid phase in the presence of homogeneous mercury salt catalysts
b.in the gas phase in the presence of heterogeneous catalysts containing zinc salts
2.Addition of acetic anhydride to acetaldehyde giving ethylidene diacetate, and subsequent
cleavage of the latter to form vinyl acetate and acetic acid
3.Reaction of ethylene with acetic acid and oxygen
a.in the liquid phase in the presence of palladium/copper salts as homogeneous catalysts
b.in the gas phase on heterogeneous catalysts containing palladium
4.Reaction of methyl acetate or dimethyl ether with carbon monoxide and hydrogen in the
liquid phase in the presence of homogeneous catalysts, e.g., rhodium salts or noble metals
of the platinum group, giving ethylidene diacetate; cleavage of the latter giving acetic acid
and vinyl acetate
Acetylene, which is expensive, has mostly been replaced by the cheaper alternative, ethylene;
ca. 80 % of the available capacity is used for process 3 b and ca. 20 % for process 1 b.
Processes 1 a, 2, and 3 a are no longer used, while process 4, although allegedly developed to
an industrial level, has not yet been used industrially. It may become more important because
the starting materials can readily be produced from coal or naphtha.
2.2.1. Addition of Acetic Acid to Acetylene
Liquid-Phase Process The addition of carboxylic acids to acetylene using mercury salts as the
catalyst [17] is now of historical interest only. For more details see [18], [19].

Gas Phase Process

The first process was developed in Munich by Consortium f. Elektrochemische Industrie
[20]. It was further developed and used industrially by Wacker Chemie in Burghausen. Until
1965, almost all vinyl acetate was produced by the acetylene gas-phase process. Only two
smaller plants used the ethylidene diacetate process [21]. Zinc salts on activated charcoal
have proved to be effective catalysts. The development of suitable types of activated charcoal
has improved the process [22].
Most of the industrial development work was concerned with carrying out the reaction. In the
shaft furnaces used initially as reactors, controlling the heat of reaction was difficult. An
occasional runaway of the reaction led to baking of the catalyst. Exothermic
autodecomposition of the acetylene could not always be avoided. For better heat removal,
other types of reactor employing a cooling medium were used. At Hoechst, Fischer furnaces
were initially used, and at Wacker-Chemie tube furnaces.
As far as is known, all producers using the solid bed catalysts have started to use tube
reactors because of the defined gas flow, the easier charging and discharging of the catalyst,
and the good temperature control. Only at Kurashiki in Japan, Du Pont in the United States,
and in some plants in the former Soviet Union have fluidized-bed reactors been used. Solid
bed and fluidized bed processes are considered of equal value.
Process Description. The modes of operation of individual producers no longer differ
significantly [23]. The process used by Hoechst until 1975 is described as an example
(Fig. 1). Process data are given later in this section.
Figure 1.
Acetylene gas
phase process for
vinyl acetate
production
a) Acetic acid
evaporator; b)
Reactor; c) Heat
transfer oil,

cooling loop; d)
Quenching tower;
e) Recycle gas
blower; f) Liquid
ring pump; g)
Washing column;
h) Regenerating
column; i)
Lightends
column; j) Pure
vinyl acetate
column; k)
Crotonaldehyde
column; l) Acetic
acid column; m)
Residue column;
n) Degassing
column; o)
Acetaldehyde
column; p)
Acetone column;
q) Water removal
[Full View]
The circulated acetylene is preheated at the exit of the reactor in a countercurrent, and is then
mixed with acetic acid vapor. The circulating gas can also be fed directly through the acetic
acid evaporator (a). The gas, heated to the reaction temperature, enters the tube reactor (b).
The heat of reaction is removed by heat transfer oil in the cooling loop (c).
The mixture leaving the reactor is cooled in stages. The last cooling stage takes place in the
quenching tower (d). In this packed column, the gas mixture is cooled to 0 °C. The
condensate itself is used for cooling. It is circulated from the bottom to the top of the

quenching tower via a brine – cooled condenser. The liquid product stream is removed;
excess acetylene is recycled via a circulating gas blower (e).
The crude vinyl acetate produced at the bottom of the quenching tower is distilled giving
acetic acid, which is recycled, and pure vinyl acetate. Some 90 % of the circulating gas is
acetylene; the remainder is CO
2
, CO, and methane formed from thermal decomposition,
acetaldehyde, N
2
, and other inert substances. To prevent enrichment of the impurities in the
circulating gas, a small portion is removed behind the quenching tower (d) and then purified.
The acetylene from the gas stream, which has been brought to ca. 100 kPa overpressure by
means of a liquid ring pump (f), is extensively absorbed in a washing column (g) containing
brine-cooled vinyl acetate. The inert substances are led as waste-gas to flare. The sump
product from (g) is freed from dissolved acetylene in a regeneration column (h) by boiling.
The acetylene is recycled. The crude vinyl acetate formed in the bottom of the quenching
tower (d) contains ca. 62 – 63 wt % vinyl acetate and 30 –35 % acetic acid. It also contains
dissolved acetylene, acetaldehyde, crotonaldehyde, acetone, methyl acetate, ethylidene
diacetate, and acetic anhydride.
In the lightends column (i) acetaldehyde, acetone, methyl acetate, dissolved acetylene, some
vinyl acetate, and water (originating from the starting materials) are first distilled overhead.
The sump product is fractionated in distillation columns ( j – m). Pure vinyl acetate is
removed as the top product of the column ( j). In (k) crotonaldehyde distills at the head as an
azeotrope after addition of water. The bottom of the acetic acid column (l) also contains,
besides acetic acid, the high-boiling ethylidene diacetate and acetic anhydride (unless they
have already been hydrolyzed in the crotonaldehyde column), and very small quantities of
polymers. Column (m) is operated under vacuum, and to some extent batchwise; the residual
acetic acid distills so extensively that the liquid sump product which remains can
subsequently be incinerated. The distillate from the lightends column (i) contains mainly
acetaldehyde, acetone, methyl acetate, vinyl acetate, and water. It is purified in distillation

columns (o – q).
Stabilizers. To avoid polymerization during the distillative work-up of the crude vinyl
acetate, polymerization inhibitors are added. The preferred stabilizer is hydroquinone. Copper
resinate, phenothiazine, or methylene blue are also used.
Materials and Environmental Aspects. The plant is made from mild steel in the hot area of the
reaction section and in places where no liquid acetic acid is present. These areas include the
reactor, the gas – gas heat exchanger, and the circulating gas blower. For the distillation
section and the equipment in the reaction section which comes into contact with liquid
product, stainless steel 316 L is used. The process has almost no polluting waste streams. All
gaseous or liquid byproducts (high-boiling, crotonaldehyde, and acetone – methyl acetate
fractions) can be incinerated. Waste circulating gas is passed to the excess gas burner.
Process Data. The catalyst consists of zinc acetate on activated charcoal (particle size 3 –
4 mm) as the carrier material. The zinc content is 10 – 15 wt %. The catalyst is produced by
dipping. As the activated charcoal can contain traces of copper, small quantities of other
components are added to the catalyst to prevent the formation of cuprene, which can block
the tubes.
The operating time is ca. 5000 – 7000 h, depending on the type of activated charcoal used. It
also depends on the purity of the acetylene and the circulating acetic acid. When using
acetylene produced from carbide, the type of carbide is important. Because of the varying
contents of phosphorus hydrides, hydrogen sulfide, arsine, and ammonia in the acetylene, it
sometimes has to be further purified before being used in vinyl acetate production. This
involves several steps.
Acetylene produced from petrochemicals does not contain these components. The decrease in
catalyst activity is caused to a small extent by migration of zinc acetate out of the catalyst, but
to a greater extent by formation of byproducts or by foreign components, which either act as
catalyst poisons or adhere to the catalyst surface and pores [24], [25]. Vinyl acetate itself
does not appear to contribute to the deactivation of the catalyst under the reaction conditions.
The space – time yield for the vinyl acetate is normally 60 – 70 g per liter catalyst per hour.
The reaction temperature is 160 – 170 °C, depending on the type of activated charcoal used
as catalyst, but increases to 205 – 210 °C as the catalyst activity decreases. At the elevated

temperature in the reactor, more byproducts are formed.
The pressure can increase a little during the operating time of a catalyst charge. This is
caused by a slight increase in the flow resistance of the catalyst. The maximum pressure is ca.
40 kPa overpressure. Plants are protected against overpressures greater than 40 – 50 kPa
because acetylene can undergo exothermic autodecomposition at high pressures and
temperatures:

The acetylene pipes leading to the plant therefore contain barriers which inhibit the acetylene
autodecomposition. The plants are also provided with equipment for automatic flushing with
inert gas. The molar ratio acetic acid : acetylene is normally between ca. 1 : 4 and 1 : 4.5. The
load per m
3
catalyst is ca. 135 m
3
(STP) recycle gas per hour and 76 kg acetic acid per hour.
The recycle gas consists of ca. 90 % acetylene. Acetylene conversion is ca. 15 % and acetic
acid conversion ca. 55 %. The yields based on acetic acid can reach 99 %, or 98 % based on
acetylene, if the acetaldehyde formed (2 – 3 kg per 100 kg vinyl acetate) is included in the
yield.
2.2.2. Ethylidene Diacetate Process


The process was developed by Celanese Corporation of America [26] and was operated
industrially in the United States from 1953 to 1970, and then replaced by the ethylene gas-
phase process. A small plant (Celmex) operated in Mexico until 1991. Acetic anhydride is
converted to ethylidene diacetate with acetaldehyde in the liquid phase using catalysts such as
iron(III) chloride. The ethylidene diacetate is then cleaved thermally to vinyl acetate and
acetic acid, using catalysts such as toluenesulfonic acid. Some of the ethylidene diacetate is
converted back to acetic anhydride and acetaldehyde.
2.2.3. Reaction of Acetic Acid with Ethylene and Oxygen

Liquid-Phase Process. The formation of vinyl acetate from ethylene and acetic acid in the
presence of palladium chloride and alkali acetate in glacial acetic acid was first described by
MOISEEW [27]:

Addition of benzoquinone to the reaction mixture was said to reoxidize the palladium to
palladium chloride. The reaction corresponds to the Wacker – Hoechst process, in which
acetaldehyde is obtained from ethylene and water in the presence of palladium chloride:

The palladium formed is reoxidized to Pd
2+
with copper(II) chloride. The copper(I) chloride
formed is reoxidized with oxygen (→ Acetaldehyde). Production of vinyl acetate by a similar
route has been widely investigated [28-30]. Corresponding production plants were
commissioned by ICI in England, Celanese in the United States, and Tokuyama
Petrochemical in Japan [31], but later shut down. Now only the ethylene gas-phase process
uses ethylene as the starting material (see below).
In the liquid-phase process, a recycle ethylene gas stream is passed through a reaction
solution containing acetic acid, water, high-boiling byproducts analogous to those of the
acetaldehyde process, PdCl
2
, and CuCl
2
. Oxygen is passed into the reaction solution at the
same time to reoxidize the palladium and the CuCl. The reaction and regeneration of the
catalyst take place in one step:



Water is formed in the reoxidation of CuCl; part of the vinyl acetate formed is hydrolyzed to
acetaldehyde and acetic acid. Part of the acetaldehyde is also formed directly from ethylene,

as in the acetaldehyde process.
A certain ratio of palladium ions to copper ions and of copper ions to chloride ions is
necessary for reoxidation of the palladium. Chlorine, which is lost through formation of
chlorinated byproducts, is replaced by hydrochloric acid. To maintain the necessary quantity
of chloride ions in solution, alkali metal chloride must be added. A typical reaction solution
contains ca. 30 – 50 mg/L palladium ions and 3 – 6 g/L copper ions.
Byproducts include CO
2
, formic acid, oxalic acid, oxalic acid esters, chlorinated compounds,
and butenes. The pressure is 3 – 4 MPa, and the reaction temperature 110 – 130 °C. The ratio
of acetaldehyde to vinyl acetate can be controlled by adjusting the water concentration and
the residence time [32].
Gas-Phase Reaction. The process was developed to an industrial scale only slightly later than
the ethylene liquid-phase process, and has been used in industry since 1968. Currently, 80 %
of world vinyl acetate capacity uses the ethylene gas-phase process. There are two variants:
one developed by National Distillers Products (United States) [49], and the other
independently by Bayer in cooperation with Knapsack and Hoechst (Germany) [33-35]. Most
plants employ the Bayer – Hoechst variant, of which there are several versions. The original
process has been further developed by various operators.
In the ethylene gas-phase process, ethylene reacts exothermically with acetic acid and oxygen
on solid bed catalysts, giving vinyl acetate and water:


All catalysts used in industry contain palladium and alkali metal salts on carrier materials,
e.g., silicic acid, aluminum oxide, lithium spinel, or activated charcoal. Additional activators
can include gold, rhodium, platinum, and cadmium.
The reaction mechanism is assumed to involve either pure metal catalysis [36] or a reaction
sequence according to the following equations:

The finely divided palladium on the catalyst is thought to be oxidized to divalent palladium.
For reoxidation of the palladium, a redox reaction analogous to the liquid-phase process is
assumed. Copper, manganese, and iron are cited as redox elements [37].
In the process, which operates above 140 °C and at overpressure 0.5 – 1.2 MPa, practically
no acetaldehyde is formed, even if the acetic acid used as starting material contains water.
Byproducts are water, CO
2
and small quantities of ethyl acetate, ethylidene diacetate, and
glycol acetates.
Process Description: Reaction Section (Fig. 2). The recycle gas stream, which consists
mainly of ethylene, is saturated with acetic acid in the evaporator (a) and is then heated to the
reaction temperature. The gas stream is then mixed with oxygen in a special unit.
Figure 2.
Ethylene gas
phase process for
vinyl acetate
production;
reaction section
a) Acetic acid
evaporator; b)
Reactor; c) Steam
drum; d)
Countercurrent
heat exchanger;
e) Water cooler;
f) Recycle gas
washing column;
g) Recycle gas
compressor; h)
Water wash; i)

Potash wash; j)
Potash
regeneration; k)
Crude vinyl
acetate collector;
l) Predehydration
column; m) Phase
separator
[Full View]
The allowed oxygen concentration is determined by the flammability limits of the
ethylene – oxygen mixture. The flammability limit depends on temperature, pressure, and
composition. It is shifted by additional components, such as acetic acid, nitrogen, and argon,
which are brought in with the oxygen, or by CO
2
. In general, the oxygen concentration at the
entry to the reactor is ≤8 vol %, based on the acetic-acid-free mixture. It is essential to avoid
gas mixtures capable of igniting; great care is taken in mixing in oxygen and measuring the
oxygen concentration. If the oxygen stream is switched off, the inlet line must be flushed
with nitrogen immediately to avoid back-diffusion of the circulating gas. The mixing
chamber is usually installed behind concrete walls. The heat of reaction is removed in the
form of steam via (c) from the tube reactor (b) by evaporative cooling in the shell side of the
reactor.
The reaction temperature is adjusted by the pressure of the boiling water. The steam formed
can be used within the plant itself in the work-up section. The heat of reaction is ca.
250 kJ/mol based on vinyl acetate, because of the simultaneous formation of CO
2
.
Pressurized water in a circulation loop is used for cooling in some plants.
Ethylene conversion is 8 – 10 %, and that of acetic acid 15 – 35 %. Oxygen conversion can
be up to 90 %. As small quantities of alkali metal salt on the catalyst migrate under the

reaction conditions, traces of alkali metal salt are mixed with the gas at the entry to the
reactor [38].
The gas mixture leaving the reactor is first cooled in (d) in countercurrent with the cold
recycle gas, which is thus warmed. There is virtually no condensation of the acetic acid, vinyl
acetate, or water. The dew point is generally not reached. The gas mixture is then led into the
predehydration column (l) and then cooled to about room temperature in (e). The liquid
product consists of an acetic-acid-free mixture of vinyl acetate and water. The mixture is
separated in a phase separator (m) into an aqueous phase, which is removed, and an organic
vinyl acetate phase, which is recycled to the head of the predehydration column.
Between 40 and 50 % of the water formed in the reaction is removed in this way without the
need to supply extra energy; this quantity of water does not need to be removed in the
subsequent distillation of the crude vinyl acetate. Most of the energy consumed in the
distillation is used for water removal. Crude vinyl acetate, which is low in water, collects in
the sump of the predehydration column. Older plants do not have this column [39]. The
noncondensed vinyl acetate fraction is washed out of the circulating gas with acetic acid in
column (f) [40]. The remaining gas is recycled via compressor (g), after addition of fresh
ethylene.
To remove the CO
2
formed in the reaction, a partial stream of recycle gas is first washed with
water in column (h) to remove the remaining acetic acid. The CO
2
is then absorbed with
potash solution in column (i). The potash solution is regenerated by depressurizing to normal
pressure and boiling ( j). Depending on the quantity of CO
2
formed in the reactor, the desired
CO
2
content of the circulating gas can be adjusted by altering the quantity of circulating gas

present in the circulating gas wash, and the degree of absorption in the potash wash. The CO
2

concentration is generally 10 – 30 vol % [41], [42]. It is also possible to perform water and
CO
2
washes in the main gas stream [43].
To remove inert gases (nitrogen, argon) mainly brought in with the oxygen, a small quantity
of waste-gas is removed before the CO
2
absorption column (i) and then incinerated. In some
plants, part of the ethylene contained in this waste-gas is recovered by additional purification
to reduce ethylene loss.
The liquid products formed, i.e., the condensate from the sump of the predehydration column
(l) and the sump of the circulating gas wash, are depressurized to almost normal pressure and
drained off into a collector for crude vinyl acetate (k). The circulating gas portions dissolved
under the pressure of the circulating gas system are degassed and recycled to the circulating
gas system after compression.
Process Description: Distillation Section. Distillative work-up of the liquid products to give
acetic acid (which is recycled) and pure vinyl acetate is carried out in various ways,
depending on the location of the plant and on the relative importance of energy consumption
and investment costs. Besides the systems shown in Figures 3 and 4, combinations of both
versions are used.
Figure 3.
Ethylene gas-
phase process for
vinyl acetate
production; work-
up of crude vinyl
acetate

a) Azeotrope
column; b)
Wastewater
column; c)
Drying/lightends
column; d) Pure
vinyl acetate
column
[Full View]
Figure 4.
Ethylene gas-
phase process for
vinyl acetate
production;
variant for work-
up of crude vinyl
acetate
a) Dehydration
column; b) Pure
vinyl acetate
column; c)
Wastewater
column
[Full View]
The liquid products contain 20 – 40 wt % vinyl acetate and ca. 6 – 10 vol % water. The rest
consists of acetic acid and small quantities of byproducts, e.g., ethylidene diacetate and ethyl
acetate. To work up the liquid products (Fig. 3) a vinyl acetate – water mixture can be
distilled at the head in a first distillation (a). This mixture separates into two phases. The
dissolved vinyl acetate is distilled from the water phase in wastewater column (b). The
remaining water is wastewater. The organic vinyl acetate phase is freed as the top product in

a second distillation (c) from dissolved water, other volatile products, and acetaldehyde,
formed by vinyl acetate hydrolysis. The sump product is dry vinyl acetate, which is distilled
in a third distillation column (d) to give pure vinyl acetate as the top product.
To remove polymers, a small partial stream is removed from the sump of the third distillation
column and fed back to the first column. Thus all nonvolatiles and polymers produced in the
distillative work-up are contained in the sump of the first column, together with the recycled
acetic acid. To remove the polymers and nonvolatiles, a partial stream is removed from the
acetic acid evaporator in the reaction section of the plant. From this, the acetic acid for
recycling is distilled so that the residue, which is still flowable, can be incinerated.
The small quantities of ethyl acetate formed are removed through a side exit in the first
column (a) as a mixture with acetic acid, water, and vinyl acetate [44].
If an additional column is used for the work-up, only the dissolved water is distilled over in
the second distillation, in the third the light ends, and in the fourth the pure vinyl acetate [45].
In another version (Fig. 4) the water contained in the crude vinyl acetate is removed as an
azeotrope with the vinyl acetate together with volatile products, e.g., acetaldehyde, in a first
distillation column (a), which operates at increased pressure. The dry bottom product, which
contains vinyl acetate, acetic acid, polymers, and nonvolatiles, is fractionated in a second
column (b) into pure vinyl acetate as the top product, and acetic acid and nonvolatiles. The
last two are recycled. Ethyl acetate is removed through a side exit in the second distillation
column as a mixture with acetic acid and vinyl acetate [46], [47].
To avoid polymer formation during the distillative workup of the crude mixture,
polymerization inhibitors, e.g., hydroquinone, benzoquinone, or tert-butylcatechol, must be
added. Passing in oxygen-containing gases is also said to inhibit polymerization [48].
Process Data. The catalysts used always contain palladium as the metal or a salt, alkali metal
salts, and additional activators, e.g., metallic gold or alkali acetoaurate, cadmium acetate, or
noble metals of the platinum group. Silicic acid of various structures, aluminum oxide, spinel,
or activated charcoal are mainly used as the carrier material [49-54], [55].
The space – time yield for vinyl acetate is 200 g L
–1
h

–1
, in older plants up to more than
1000 g L
–1
h
–1
, depending on the catalyst and the plant layout. The life time of the catalyst is
≤ 4 a.
The reaction pressure is 0.5 – 1.2 MPa overpressure. The space – time yield for vinyl acetate
increases with the reaction pressure and with the oxygen concentration in the reaction gas.
However, an increase in pressure shifts the flammability limits of ethylene – oxygen to lower
oxygen concentrations, reducing the quantity of oxygen available, and consequently the
quantity of vinyl acetate formed, so pressure limits are set; higher pressures also raise
equipment costs.
The reaction temperature is generally > 140 °C. It increases to > 180 °C towards the end of
the catalyst life. A lower reaction temperature results in the formation of less CO
2
, but then
the heat produced in the reactor can no longer be used in the plant.
The gas loading of the catalyst is 2 – 4 m
3
(STP) per liter catalyst per hour. The gas mixture
contains 10 – 20 mol % acetic acid, 10 – 30 % CO
2
, and ca. 50 % ethylene. The maximum
oxygen content is ca. 1.5 % below the flammability limit, which varies with the composition
of the gas mixture and the reaction conditions. The nitrogen and argon contents are adjusted
according to the quantity of waste gas. They are generally ca. 10 %, but depend on the purity
of the oxygen used.
For old plants, energy consumption is ca. 3 t of heating steam per tonne of vinyl acetate

produced. As a result of process improvements, modern plants have a heating steam
consumption of 1.2 t per tonne of vinyl acetate.
The yields are up to 99 % based on acetic acid, and up to 94 % based on ethylene, if the
acetaldehyde, formed in small quantities by hydrolysis of vinyl acetate during the distillative
work-up, is included in the yield.
The process has not yet posed any environmental problems. Volatile and nonvolatile liquid
products are incinerated. The water produced in the reaction can contain traces of acetic acid
formed by hydrolysis of vinyl acetate in the wastewater column. It is subjected to biological
wastewater treatment. To remove inert gases brought in with the oxygen, some of the waste-
gas containing nitrogen and argon is burned after partial recovery of the ethylene it contains.
There are small quantities of residual ethylene in the CO
2
, formed in the regeneration column
of the potash absorber. Removal of ethylene, e.g., by subsequent catalytic incineration, is
now necessary in Germany because of more stringent regulations. In addition, special
measures are required for waste-gas incineration.
Plants are generally made from stainless steel 316 L, apart from the potash washer, which is
made from normal steel or stainless steel 321.
Proposals for Process Improvement. Since the first plants for the ethylene gas-phase process
were commissioned, numerous suggestions have been made for improving the process; some
of these are now being introduced industrially. Proposals regarding the catalyst include:
simplification of production methods [56]; activity improvement (increase in vinyl acetate
space – time yield [57-60], [55], [61]; improvement in selectivity (less CO
2
formation) [62],
[63]; increase in life span [64-66]; reduction in flow resistance in the reactor (form of carrier
material) [67]; better utilization of the noble metal content (distribution on the carrier) [68];
regeneration of spent catalysts [69-74].
Proposals regarding the mode of operation include: increasing the vinyl acetate space – time
yield by raising the oxygen concentration in the gas at the entry to the reactor by adding

desensitizers [75]; facilitating separation of ethyl acetate from vinyl acetate [76-79];
increasing the selectivity of the reaction by adding other components to the reaction gas [80];
carrying out the reaction on a fluidized bed [81]; lowering the energy consumption, e.g., by
making use of the heat of condensation of the gas coming out of the reactor for removal of
the water formed (see Section Production) [39]; simplified work-up of the polymer-
containing residue [82].
2.2.4. Reaction of Methyl Acetate with CO and H
2
.
Several companies have attempted to develop a reaction which, in principle, has been known
for a long time. It involves the conversion of methanol, acetic anhydride, dimethyl ether, or
preferably methyl acetate to ethylidene diacetate with carbon monoxide and hydrogen [83-
95], [96-98]:

The reaction takes place in the liquid phase at ca. 7 MPa and ca. 150 °C. Rhodium salts
together with methyl iodide and amines can be used as catalyst. The ethylidene diacetate
formed can be cleaved to vinyl acetate and acetic acid, using the process previously
employed by Celanese (see Section Production). As the acetic acid formed in the process can
be reesterified to methyl acetate using methanol, the process essentially involves production
of vinyl acetate from methanol and synthesis gas:



Dimethyl ether can also be used to prepare methyl acetate:

It is said to be possible to produce dimethyl ether by partial oxidation of natural gas:

Byproducts are formed in all the steps; recovering them in pure form is expensive [99-102].
The process has not yet been used in industry. It could become more important, depending on
the further development of raw material prices.

2.3. Quality Specifications, Analysis,Storage, Transport, and Toxicology
Quality. The specifications of individual producers often differ only slightly with regard to
the content of impurities. One specification requires: vinyl acetate ≥ 99.9 wt %, acid (as
acetic acid) ≤ 0.005 wt %; carbonyl (as acetaldehyde) ≤ 0.02 wt %, water ≤0.04 wt %;
distillation range 95 % at 72 – 73 °C within 0.5 °C; peroxide free; polymer free; capacity for
polymerization (see Section Use, Economic Importance)
Analysis. The following methods are used for quality testing:
Carbonyl groups: titration of the hydrochloric acid formed after conversion to the oxime
using hydroxylamine hydrochloride solution
Water content: titration with Karl-Fischer solution
Acid content: neutral to litmus
Peroxide: test with potassium iodide solution
Polymer content: mixtures with petroleum ether must not produce turbidity or precipitation
of solids
Polymerization test: carried out differently by individual producers; the time taken for the
onset of polymerization following the addition of a defined quantity of dibenzoyl peroxide
and warming to a defined temperature
Storage. As a flammable liquid, vinyl acetate is assigned to VbF, group A, class 1, and
ignition group T 2 according to VDE 0165. It can be stored in steel, aluminum, or stainless
steel containers under nitrogen. It is not necessary to add stabilizers at lower temperatures. If
the vinyl acetate is to be warmed, stabilizers, such as hydroquinone, hydroquinone
monomethyl ether, or diphenylamine are added. The quantity of stabilizer used is small, e.g.,
3 – 20 ppm hydroquinone, so that it does not generally need to be removed during the later
polymerization.
Transport. Vinyl acetate is transported in practically all quantities: small containers, drums,
tankers, tank cars, and ships. Stabilizers are usually added for transportation.
Safety Data
Toxicological Data
Protection at Work
Compatibility with water

2.4. Use, Economic Importance
Vinyl acetate is used mainly for the production of polymers and copolymers, e.g., for paints
(mainly dispersions), adhesives, textile and paper processing, chewing gum [→ Poly(Vinyl
Esters), and for the production of poly(vinyl alcohol) (→ Paints and Coatings – Poly(Vinyl
Alcohol)) and polyvinylbutyral (→ Paints and Coatings – Poly(Vinyl Acetals)).
Vinyl acetate – ethylene copolymers (→ Poly(Vinyl Esters) – Properties) are processed to
give resins, paints (→ Paints and Coatings – Poly(Vinyl Esters)), and sheeting. Floor
coverings and gramophone records are made from vinyl acetate – vinyl chloride copolymers.
Vinyl acetate is also used in small quantities as a comonomer in polyacrylic fiber production.
Uses differ according to the region. In Japan, ca. 70 % of vinyl acetate is used in the
production of poly(vinyl alcohol), while in the United States and Europe more than half is
processed to give poly(vinyl acetate).
The total capacity for vinyl acetate production was < 10
6
t/a in 1965. In 1994 it was ca.
3.8×10
6
t/a. The rapid increase has been promoted significantly by the development of the
ethylene gas-phase process. After ethylene had become one of the cheapest raw materials in
the chemical industry, it was obvious that vinyl acetate should be produced from ethylene
instead of acetylene. The vinyl acetate capacities of individual countries are listed in Table 1.

Table 1. World vinyl acetate capacities
A plant with a capacity of 150 000 t/y is to be commissioned by Hoechst Celanese in South
East Asia in 1997.
The economic optimum of individual process variants depends on location. Investment costs,
material consumption (acetic acid, ethylene, acetylene), and energy consumption need to be
compared. The weighting depends on the prices of energy and starting materials, and on
official regulations specific to a particular country.

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 $%    &
                   !   
Figure 2. Ethylene gas phase process for vinyl acetate production; reaction section
a) Acetic acid evaporator; b) Reactor; c) Steam drum; d) Countercurrent heat exchanger; e) Water cooler; f)
Recycle gas washing column; g) Recycle gas compressor; h) Water wash; i) Potash wash; j) Potash
regeneration; k) Crude vinyl acetate collector; l) Predehydration column; m) Phase separator
Figure 3. Ethylene gas-phase process for vinyl acetate production; work-up of crude vinyl acetate
a) Azeotrope column; b) Wastewater column; c) Drying/lightends column; d) Pure vinyl acetate column
Figure 4. Ethylene gas-phase process for vinyl acetate production; variant for work-up of crude vinyl acetate
a) Dehydration column; b) Pure vinyl acetate column; c) Wastewater column
AXIT AXETIC
1. Introducon
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/
%00M

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3111  2
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(
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= 2 
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2. 2. Physical Properties
Acetic acid is a clear, colorless, corrosive liquid that has a pungent odor and
is a dangerous vesicant. It has a pK
a
of 4.77 [2]. It melts at 16.75 °C [3] and
boils at 117.9 °C [4] under 101.3 kPa [5]. It has a pungent vinegarlike odor.
The detectable odor is as low as 1 ppm. The acid is combustible with a low
flash point of 43 °C. The explosion limits of acetic acid vary from the upper
explosion limit (UEL) of 16 % at 92 °C to the lower explosion limit (LEL)
of 4 % at 59 °C. The liquid is usually available as glacial acetic acid with
less than 1 wt % water and over 98 % purity. Besides water, the acid
contains traces of impurities such as acetaldehyde, oxidized substances, iron,
and chlorides.
Occasionally, the acid may be colored due to the presence of ethyl
acetoacetate [141-97-9]. The acetate is easily mistaken for formic acid
because it reduces mercuric chloride. Traces of mercury may cause
extensive corrosion by reaction with aluminum. Aluminum is a common
material for containers to ship the acid [6].
Glacial acetic acid is very hydroscopic. The presence of 0.1 wt % water
lowers the freezing point significantly [7]. Measuring the freezing point is a
convenient way to evaluate acetic acid purity. This is shown in Table 1 [8].
3.
4. Table 1. Freezing points for various acetic acid – water mixtures
wt %
CH
3
COOH
96.8

96.4
96.0
93.5
80.6
50.6
18.1
5.
Acetic acid forms azeotropes with many common solvents, such as benzene,
pyridine, and dioxane. Acetic acid is miscible with water, ethanol, acetone,
benzene, ether, and carbon tetrachloride. However, it is not soluble in CS
2

[2].
The physical properties of acetic acid are well documented, and their
accuracy is important for commercial production. For instance, design and
operation of distillation processes requires precise data. High-precision
values provide a valuable asset to the chemical industry [9], [10].
The density of mixtures of acetic acid and water [11-13] is listed in Table 2.
The density exhibits a maximum between 67 wt % and 87 wt %,
corresponding to the monohydrate (77 wt % acetic acid). The density of pure
acetic acid as a function of temperature is listed in Table 3 [14], [15].
6.
7. Table 2. Densities of aqueous acetic acid solutions at 15 °C
wt %
CH
3
COOH
60
70
80

90
95
97
99
100
8.
9.
10. Table 3. Dependence of the density of pure acetic acid on temperature
t, °C
130
139
140
145
156
180
220
260
300
320
321
11.
Due to the difficulty in eliminating traces of water from acetic acid, the
value for the boiling point varies from 391 to 392 K [10]. Careful studies
prove that pure acetic acid boils at 391.10 K under 101.325 kPa [16]. The
critical temperature and critical pressure are 594.45 K and 5785.7 kPa [3].
Precise data on vapor pressure of acetic acid are available from a regression
equation (Eq. 1) [10], which covers the range from the normal boiling point
to the critical point.
12.
(1)

13.
14.
where P is vapor pressure in kPa; T
r
is reduced temperature T/T
c
, T is
temperature in K; T
c
is 594.45 K, P
c
is 5785.7 kPa, A is 10.08590, B is
– 10.37932; C is – 3.87306, and D is 0.29342.
The vapor pressure of pure acetic acid is given in Table 4 [17]. The density
of the vapor corresponds to approximately twice the molecular mass because
of vapor-phase hydrogen bonding [8]. Hydrogen-bonded dimers and
tetramers have both been proposed. Reports indicate that in the gas phase,
the acid exists mainly in an equilibrium between monomer and dimer (Eq. 2)
according to vapor density data [18], [19] molecular modeling, IR analysis
[20], and gas-phase electron diffraction [21].
15.
16.
17. Table 4. Vapor pressure of pure acetic acid
t, °C
150.0
160
170
180
190
200

210
220
230
240
250
260
270
280
18.