Process for the chlorination and sulfochlorination of organic compounds

An improvement in the process for chlorination and sulfochlorination of liquid or dissolved organic components, wherein the gases are intensively mixed with the liquid organics until substantially no gases remain unmixed, and the mixture is then reacted.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an improved process for reacting chlorine and 
mixtures of chlorine and sulfur dioxide with liquid or dissolved organic 
components. The process is particularly advantageous when the liquid phase 
to be treated shows or assumes an increased viscosity under reaction 
conditions. The process according to the invention is particularly 
suitable for the chlorination and sulfochlorination of fatty raw materials 
particularly fatty acids and/or esters thereof with monohydric and/or 
polyhydric alcohols. In the context of the invention, chlorination is 
understood to be both the addition of chlorine onto olefinic double bonds 
of the starting material and also the HCl-forming substitution reaction 
optionally activated by UV-light. Sulfochlorination is understood in the 
usual way to be the optionally UV-activated reaction of SO.sub.2 /Cl.sub.2 
-mixtures with aliphatic chain constituents to form the SO.sub.2 Cl-group, 
the reaction being accompanied by the elimination of HCl. 
2. Statement of the Related Art 
The chlorination and sulfochlorination of fatty raw materials, particularly 
fatty acids and/or fatty acid esters, is known to lead to interesting 
fat-liquoring agents for leather and skins. Thus U.S. Pat. No. 3,988,247 
and corresponding German patent 2,245,077 describe fat-liquoring agents 
such as these based on sulfonated chlorination products of natural or 
synthetic higher fatty acids or fatty acid esters in the form of their 
alkali, ammonium or amine salts, which are characterized in that they 
consist of sulfonated chlorination products which have been obtained by 
the chlorination of higher fatty acids or of esters of higher fatty acids 
having C.sub.8-24 chain lengths up to a chlorine content of from 20 to 45% 
by weight, the chlorination products containing virtually no more double 
bonds and the subsequent sulfonation step with SO.sub.3 having been 
carried out up to a content of from 40 to 100 mol % of SO.sub.3, based on 
chlorination product. 
Corresponding fat-liquoring agents are also described in published German 
patent application 30 18 176 and are characterized in that they comprise 
sulfonated chlorination products which have been obtained by the 
sulfochlorination at 20 to 90.degree. C. of higher fatty acids or of 
esters of higher fatty acids having C.sub.8-24 chain lengths with chlorine 
and SO.sub.2, optionally under UV-light, up to a content of bound chlorine 
of from 5 to 30% by weight and a content of SO.sub.2 Cl-groups of from 1 
to 20% by weight, the ratio of chlorine atoms to SO.sub.2 Cl-groups 
amounting to about 0.7-70:1, preferably 2-20:1, most preferably 2-7:1, 
followed by hydrolysis of those groups (saponification). An improvement is 
described in U.S. Pat. No. 4,451,261 (and corresponding German patent 
application 32 38 741). In this case, the starting materials used for 
producing the sulfonated chlorination products are higher fatty acid or 
fatty acid ester mixtures containing unsaturated fractions. In this 
process, chlorination is initially carried out up to saturation of the 
double bonds and is followed by sulfochlorination with chlorine and 
SO.sub.2. The subsequent hydrolysis step gives the required fat-liquoring 
agents. 
Chlorine and SO.sub.2 are gaseous under the conditions of the 
chlorination/sulfochlorination reaction. In order to be able to react with 
the organic reactant, these gaseous components have to be dissolved in the 
liquid phase. To this end, the gases are normally passed upwards through 
gas distributors into a liquid column or gaseous and liquid reactants are 
passed in countercurrent to one another through exchange units, for 
example packed columns. However, it has been found that the viscosity of 
the organic liquid phase increases within increasing reaction time. At the 
same time, mass transfer between the liquid phase and the gas phase is 
increasingly inhibited. For example, in a column of the liquid reactant 
into which the gaseous reactants are introduced from below, increasingly 
larger bubbles which ascend very rapidly are observed with increasing 
viscosity of the liquid phase indicating a failure to react. The gaseous 
components delivered to the reactor leave the reactor unreacted to an 
increasing extent. The reaction velocity falls, influenced by the rate of 
transfer of the gases into the liquid phase. In the event of simultaneous 
absorption and reaction of several gases, the different solubility of the 
gases in the liquid phase affects the course of the reaction. 
GENERAL DESCRIPTION OF THE INVENTION 
The present invention is based on the surprising observation that, despite 
the increasingly poor miscibility of the gas and liquid phases during the 
reaction, homogenization of the reaction mixture can be obtained by the 
additional application of mechanical forces, particularly at those stages 
of the reaction in which, basically, the appearance of the mixture of 
reactants is not indicative of good miscibility. 
Accordingly, the present invention relates to a process for the 
chlorination and sulfochlorination of fatty raw materials which are liquid 
under reaction conditions, particularly fatty acids and/or esters thereof, 
by reaction with chlorine and SO.sub.2, in which the liquid starting 
material is circulated through a reaction zone where it is reacted with 
chlorine and SO.sub.2 which are introduced into the circuit, the new 
process being particularly characterized in that the chlorine and SO.sub.2 
are introduced in parallel current with the liquid starting materials (as 
contrasted with countercurrent) and, together with the liquid starting 
material, are passed through an intensive mixer during or before entry 
into the reaction zone. The quantity of chlorine and SO.sub.2 introduced 
is measured in such a way that the reaction mixture passes through the 
reaction zone as a substantially homogeneous liquid phase.

DETAILED DESCRIPTION OF THE INVENTION 
The principle on which the process according to the invention is based is 
illustrated in the flow chart in FIG. 1. The liquid to be 
chlorinated/sulfochlorinated is delivered to the mixer R from the 
container B by the pump P. Shortly before, or during, entry into R, the 
gaseous reactant or the corresponding mixture of reactants is introduced 
into the circulating liquid, preferably through a coaxial pipe. Static 
and/or active mixing elements introduced into the liquid circuit may be 
used as the mixing zone, preference being attributed to static mixing 
elements which, by means of intersecting baffle elements in the mixing 
zone, produce a highly turbulent zig-zag flow of the gas-liquid mixture. 
Under the effect of the intensive mechanical mixing of the gas-liquid phase 
in the mixer R, the gas phase is completely or substantially completely 
dissolved in the increasingly viscous liquid phase, despite the short 
residence time of the reaction mixture in the mixer R. Since the (a) rate 
of flow of the reactants (b) time of mixing and (c) mixer capability are 
all variables, among others, it is impractical to set definite mechanical 
parameters for the mixer or definite process parameters for the mixing 
step. However, the mixer mechanical capability and mixing process 
parameters should be such that the gas phase is at least substantially 
(preferably completely) dissolved in the liquid phase. The preferred 
embodiment of the invention, the liquid leaving the mixing zone R contains 
hardly any visible gas bubbles. The gas liquid mixture then passes through 
the reaction zone G and then through a heat exchanger after which it is 
returned to the container B and removed as desired. Any HCl formed is 
given off in the container and may be delivered to a scrubber. 
The described procedure enables the reaction to take place in a 
single-phase, homogeneous medium, affording inter alia the following 
advantages: 
The reaction velocity cannot be limited by the gas-liquid transfer so that 
the different solubilities of chlorine and SO.sub.2 in the liquid phase 
have no effect upon the course of the reaction. The chlorine and SO.sub.2 
have the same residence time in the reaction zone, i.e. a narrow residence 
time spectrum. The residence time of chlorine and SO.sub.2 in the reaction 
zone is determined solely by the liquid circuit. Unreacted gas is unable 
to penetrate and escape. It is possible to use liquid phases of high 
viscosity which, hitherto, it has not been possible to deliver 
economically to the reaction because of the high tendency of the gas phase 
to escape from the liquid phase. The reaction itself may be carried out at 
lower temperatures and, thus at correspondingly higher viscosities of the 
liquid phase which is of advantage, for example in regard to the 
selectivity of sulfochlorination. Accordingly, viscosity no longer has any 
bearing upon the choice of the reaction temperature. The sulfochlorination 
reaction may thus be carried out without difficulty using a mol ratio of 
chlorine to SO.sub.2 of 1:1 without chain chlorination occurring at the 
same time or significant losses of SO.sub.2 being incurred. This is of 
interest in cases where inexpensive fats having relatively high iodine 
values are used. With fats such as these, it is possible first to add 
chlorine onto the olefinic double bond and then to carry out 
sulfochlorination without chain chlorination. It is known that, for the 
same chain chlorine content, only half as much chlorine is consumed in the 
addition reaction as in the substitution reaction. 
The process according to the invention is particularly suitable for the 
chlorination/sulfochlorination of fats such as triglycerides, fatty acids 
and/or esters thereof, in any mixture. Examples include tallow, tallow 
fatty acid methyl ester, coconut oil fatty acid last runnings methyl 
ester, LT last runnings ester, and mixtures thereof. 
The invention preferably starts out with higher fatty acids or with higher 
fatty acid esters, having chain lengths of from C.sub.8 to C.sub.24 and 
more especially from C.sub.10 to C.sub.20, and iodine numbers of from 10 
to 120. Mixtures of fatty acids or naturally occurring fats or oils with a 
proportion of mono- or polyunsaturated fatty acids are preferred. Examples 
of these fatty acid mixtures are the fatty acid mixtures (or esters 
thereof) obtained from coconut oil, soya oil, palm kernel oil, cottonseed 
oil, rape oil, linseed oil, castor oil, sunflower oil, olive oil, neat's 
foot oil, peanut oil, herring oil, cod-liver oil, shark-liver oil, whale 
oil, tallow fats or lard. The corresponding naturally occurring fats or 
oils and naturally occuring wax esters may also be used as starting 
material for the process of this invention. The crucial factor is that 
chlorination and sulfochlorination are now no longer hindered by the high 
viscosity of the corresponding liquid phases or reaction products formed 
therefrom. 
Particularly preferred starting materials are synthetically produced esters 
of mixtures of saturated and unsaturated fatty acids having chain lengths 
of from C.sub.8 to C.sub.24 and preferably from C.sub.10 to C.sub.20 and 
iodine numbers of from 10 to 120, for example decane carboxylic acid, 
palmitic acid, stearic acid, behenic acid, dodecene carboxylic acid, oleic 
acid, linoleic acid or carboxylic acids produced by the oxidation of 
paraffin and esters thereof with monohydric C.sub.1-4 -aliphatic alcohols. 
By virtue of their ready availability, it can also be of advantage to use 
fatty acid esters which are transesterification products produced from 
natural, animal or vegetable fats, oils or waxes reacted with the lower 
monohydric aliphatic alcohols, particularly methanol. Other alcohols 
suitable for ester formation are polyhydric C.sub.2-6 -aliphatic alcohols, 
such as ethylene glycol, 1,2-propylene glycol, glycerol, pentaerythritol 
or sorbitol, or even higher C.sub.8-24 -alcohols, such as decyl or oleyl. 
In one preferred embodiment of the invention, the reaction is carried out 
in the absence of viscosity-reducing diluents. To solve the problem of 
viscosity in this field, it had already been proposed to obtain improved 
mass transfer between the gas and liquid phases by using inert 
viscosity-reducing diluents. 
Suitable mixing elements (see R in FIG. 1) are, typically, commercially 
available rotor-stator machines. In these machines, high speed rotors 
produce a mechanical shearing effect between rotor and stator. Under this 
shearing effect, the gas is completely dissolved during its short 
residence time in the machine. The homogeneous or substantially 
homogeneous liquid phase leaving the rotor-stator machine is delivered to 
the reaction zone G which is usually irradiated with a UV-lamp. 
In one preferred embodiment of the invention, static mixing elements are 
used. Static mixing elements are also commercially available. Suitable 
static mixing elements are, for example, built-in elements of corrugated, 
multiple-bend intersecting expanded metal blades. A system of intersecting 
channels such as this imposes a highly turbulent zig-zag flow on the 
mixture of liquid phase and gaseous reactants. This ensures intensive 
mixing and, ultimately, homogenization of the reaction phase. For 
literature on this subject, see W. Tauscher, "Das breite 
Anwendungsspektrum des statischen Mischers", Chemische Produktion 10:10-14 
(1977). Suitable static mixing elements are, for example, those made by 
Gebrueder Sulzer AG, Winterthur, Switzerland, which are marketed under the 
trademark "SMV". 
The following preferred process parameters apply in particular where static 
mixing elements of this type built into the flow tube are used: Flow rates 
of the liquid phase in the static mixing zone (based on the empty tube) in 
the range from 0.1 to 5 m/s, preferably from 0.25 to 2.5 m/s. Preferred 
length-to-diameter ratio of the mixing zone is in the range 2-20:1. 
Comparatively short mixing zones ranging in length from about 10 to 50 cm 
provide the intensive mixing required for the purposes of the invention. 
The ratio of the quantity of gas introduced to the quantity of liquid in 
circulation for both the reaction gases, chlorine and SO.sub.2, generally 
amounts to between 0.05 and 500, preferably between 0.1 and 100, and most 
preferably between 0.3 and 30, parts by weight of gas to 1,000 parts by 
weight of liquid. 
The chlorine and sulfur dioxide may be introduced either as gaseous 
reactants or under pressure as liquids into the circulating stream of 
liquid reactant, in which case they either evaporate or are dispersed and 
dissolved as liquid, depending on the temperature and pressure prevailing 
at the point of introduction. The pressure prevailing at the point of 
introduction of the chlorine and/or sulfur dioxide is typically from 0.2 
to 80 bars, preferably 0.2 to 25 bars, most preferably 0.5 to 5 bars. 
If a multiple-stage procedure is adopted in accordance with another 
embodiment of the invention, i.e. if the addition of chlorine onto the 
olefinic double bonds present takes place in a first stage, followed in a 
second stage by sulfochlorination, it can be of advantage to carry out the 
addition of chlorine at a temperature of about 50 to 70.degree. C. and the 
sulfochlorination step at a temperature of about 30 to 50.degree. C. 
The reaction generally lasts for about 2 to 10 hours, by which time from 5 
to 30% by weight of chlorine and from 1 to 20% by weight of SO.sub.2 Cl 
groups have been added. The ratio of chlorine atoms to SO.sub.2 Cl groups 
is typically about 0.7-70:1, preferably about 2-20:1, most preferably 
about 3-7:1. 
Subsequent hydrolysis, such as with aqueous, approximately 30% 
sodium-potassium hydroxide solution, at around 70.degree. C. gives liquid 
highly concentrated water-emulsifiable products characterized by excellent 
stability to oxidation, light, and acids which are eminently suitable, for 
example, for the fat liquoring of leather, as described in detail in 
above-mentioned U.S. Pat. No. 4,451,261. 
The following Examples describe both the addition of chlorine to the 
olefinic double bonds present and also sulfochlorination in a mol ratio of 
1:1, optionally followed by substitution by chlorine at relatively high 
viscosities. 
EXAMPLE 1 
841 kg of tallow fatty acid methyl ester (TME) at 20.degree. C., with an 
Iodine Value (IV) of 52 are introduced into the container B shown in FIG. 
1 and circulated by the pump P at a rate of 15 m.sup.3/ h. Without 
switching on a UV-lamp located in the reaction zone G, 54 kg/h of chlorine 
are introduced, the product temperature rising to 61.degree. C. After its 
chlorine content has reached 14% by weight, the product is cooled to 
40.degree. C. and the UV-lamp in the reaction zone G is switched on. 20 
kg/h of chlorine and 18 kg/h of SO.sub.2 are then introduced until the 
SO.sub.2 Cl content of the reaction product amounts to 15% by weight. 
There is no change in the chain chlorine content. The inflow of SO.sub.2 
is then stopped and the product is chlorinated with 20 kg/h of Cl.sub.2 
under the same conditions up to a chain chlorine content of 18%. 1250 kg 
of tallow fatty acid methyl ester sulfochloride are obtained. 
During the reaction, the viscosity of the liquid phase rises to 300 mPas at 
40.degree. C. Nevertheless, the rotor-stator mixer provided in the mixing 
zone R prevents the formation of any gas bubbles in the circulating liquid 
phase behind the mixer when it is in operation. If, however, the 
rotor-stator machine is switched off, the gas ascends rapidly in the form 
of fist-size bubbles without dissolving. The waste gas from the vessel B 
is colored by the penetrating chlorine gas. 
EXAMPLE 2 
A reaction circuit of the type shown in FIG. 1 is again used. On this 
occasion, however, a static mixer is installed as the mixing unit R. The 
static mixer in question is formed by 4 elements of the type marketed 
under the trademark "SMV 8" by Gebrueder Sulzer AG., Winterthur, 
Switzerland. The total length of the mixing zone amounts to 20 cm for a 
diameter of 5 cm, so that the length-to-diameter ratio is 4:1. 
432 kg of tallow fatty acid methyl ester (TME) at 20.degree. C. (IV=52) are 
introduced into the vessel B and pump-recirculated at a rate of 9 m.sup.3/ 
h. 98 kg/h of chlorine are introduced, the temperature of the liquid phase 
rising to 58.degree. C. After its chlorine content has reached 18% by 
weight, the product is cooled to 41.degree. C., the UV-lamp in the 
reaction zone G is switched on and 14.2 kg/h of Cl.sub.2 and 12.8 kg/h of 
SO.sub.2 are introduced until the SO.sub.2 Cl-content amounts to 16.2% by 
weight. There is no change in the chain chlorine content. 652 kg of 
chlorinated tallow fatty acid methyl ester sulfochloride are obtained. 
Under the process conditions, hardly any gaseous reactants can be seen in 
the pump-recirculated liquid phase after it has passed through the mixing 
zone R. 
EXAMPLE 3 
The continuous working of the process is described in the following Example 
with reference to FIG. 2. 
The addition of chlorine onto the olefinic double bonds of the starting 
material used is carried out in the first reaction loop which consists of 
the first loop recirculation pump P 1, the first loop static mixer R 1 and 
the first loop heat exchanger W 1. 5 m.sup.3 /h of liquid phase at 
60.degree. C. are pump-recirculated in the first reaction loop. 260 kg/h 
of tallow fatty acid methyl ester and 36.4 kg/h of chlorine are 
continuously introduced and 296.4 kg/h of chlorinated tallow fatty acid 
methyl ester are removed and delivered to the second reaction loop in 
which sulfochlorination and chlorination take place simultaneously. In the 
second loop, 9 m.sup.3 /h of liquid phase at 40.degree. C. are 
pump-recirculated in the first stage of the sulfochlorination/chlorination 
process which consists of the second loop recirculation pump P 2, the 
second loop static mixer R 2, the second loop reaction zone with UV-lamp G 
1, the second loop heat exchanger W 2 and the second loop separator B 1. 
51.9 kg/h of Cl.sub.2 and 20.8 kg/h of SO.sub.2 are continuously 
introduced and 342.4 kg/h of chlorinated tallow fatty acid methyl ester 
sulfochloride are run off towards the third loop. At the same time, 26.7 
kg/h of HCl gas leave the second loop separator B 1. 
The third reaction loop consists of a recirculation pump P 3, a third loop 
mixer R 3, a third loop reaction zone with UV-lamp G 2, a third loop heat 
exchanger W 3, and a third loop separator B 2, which taken together 
effectuate the second stage of the sulfochlorination/chlorination process. 
The third loop mixer R 3 used in the second stage of the 
sulfochlorination/chlorination process is a rotor-stator machine. 15 
m.sup.3 /h of liquid phase at 40.degree. C. are pump-recirculated and 46.8 
kg/h of Cl.sub.2 and 18.2 kg/h of SO.sub.2 are continuously introduced. 
24.1 kg/h of HCl gas are separated in the third loop separator B 2. 383.3 
kg/h of chlorinated tallow fatty acid methyl ester sulfochloride 
containing 16.7% by weight of chain chlorine and 15.8% by weight of 
SO.sub.2 Cl are obtained.