Production of polychlorinated pyridine mixtures by liquid phase chlorination of beta-picoline or beta-picoline hydrochloride

Preparation of high yields of mixtures rich in polychlorinated pyridines by maintaining a chlorine to beta-picoline weight ratio of greater than about 5:1 when reacting chlorine and beta-picoline or beta-picolie hydrochloride non-catalytically in the liquid phase at temperatures of at least about 190.degree. C., the reactants being contained in a well mixed diluent producing less than one mole of hydrogen chlorine per mole of diluent by reaction with the chlorine in the indicated temperature range. Chlorination of the beta-picoline or beta-picoline hydrochloride in a primary reactor is followed by selective further chlorination thereof in finishing reactor means at a temperature of at least about 190.degree. C. to obtain high yields of desired final products useful as intermediates in the formation of herbicides and the like. Like further chlorination to obtain such final products is also applicable to mixtures rich in monochloro-, dichloro-, and trichloro-3-trichloromethyl pyridines produced by other processes.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to preparation of polychlorinated pyridine 
mixtures by direct liquid phase chlorination of beta-picoline or 
beta-picoline hydrochloride. Typical of the products produced are 
2,3,6-trichloro- and 2,3,5,6-tetrachloro pyridine; and 3-chloro-, 
5-chloro-, 6-chloro-, 2,6-dichloro-, 5,6-dichloro- and 
2,5,6-trichloro-3-trichloromethyl pyridine. These products have utility, 
for example, as intermediates for herbicides and insecticides. A further 
aspect of the present invention relates to further non-catalytic 
chlorination of mixtures rich in 2-chloro-and 6-chloro-3-trichloromethyl 
pyridine to form 2,6-dichloro-3-trichloromethyl pyridine and/or 
2,3,6-trichloro pyridine, and the further non-catalytic chlorination of 
mixtures rich in 5-chloro-3-trichloromethyl pyridine and 
5,6-dichloro-3-trichloromethyl pyridine to form 
2,5,6-trichloro-3-trichloromethyl pyridine and/or 2,3,5,6-tetrachloro 
pyridine. 
Yet another aspect of the invention relates to catalytically chlorinating 
mixtures rich in 6-chloro- and mixtures rich in 
2,6-dichloro-3-trichloromethyl pyridine to form mixtures rich in 
5,6-dichloro- and 2,5,6-trichloro-3-trichloromethyl pyridine. The mixtures 
rich in 5,6-dichloro- and 2,5,6-trichloro-3-trichloromethyl pyridine may 
then be non-catalytically chlorinated to form mixtures rich in 
2,3,5,6-tetrachloro pyridine. 
Still another aspect relates to the formation of 2,3,5,6-tetrachloro 
pyridine from both catalytic and non-catalytic chlorination of 
2,3,6-trichloro pyridine. 
DESCRIPTION OF THE PRIOR ART 
The utility of 2,3,5,6-tetrachloropyridine as an intermediate to 
insecticidal compositions is set forth in Dietsche et al U.S. Pat. No. 
4,256,894. The conversion of 2,3,6-trichloro pyridine to the more 
desirable 2,3,5,6-tetrachloro pyridine by liquid phase ferric 
chloride-catalyzed chlorination is also taught by Dietsche et al U.S. Pat. 
No. 4,256,894. 
To the best of applicants' knowledge, there is no known process for liquid 
phase chlorination of beta-picoline or beta-picoline hydrochloride to 
yield the valuable chlorinated intermediates 2-chloro-, 5-chloro-, 
6-chloro-, 5,6-dichloro-, 2,6-dichloro- and 
2,5,6-trichloro-3-trichloromethyl pyridine and 2,3,6-trichloro- and 
2,3,5,6-tetrachloro pyridine. 
Vapor phase processes for chlorination of beta-picoline or beta-picoline 
hydrochloride, all operating in the temperature range of from about 
300.degree. C. to about 500.degree. C., are known. Clark U.S. Pat. No. 
3,412,095 describes a vapor phase beta-picoline chlorination process 
yielding 3-monochloromethyl pyridine. Bowden et al in U.S. Pat. No. 
4,205,175 describes a vapor phase chlorination process which yields a 
mixture of 2-chloro-and 6-chloro-3-trichloromethyl pyridine. Utility of 
these intermediates to produce herbicidal compositions is also described. 
Nishiyama et al U.S. Pat. No. 4,241,213 also describes a vapor phase 
chlorination process to yield mixtures rich in 6-chloro-3-trichloromethyl 
pyridine. This compound is particularly useful as an intermediate for 
herbicidal compositions. 
Nishiyama U.S. Pat. No. 4,184,041 describes the utility of 
5,6-dichloro-3-trichloromethyl pyridine in the production of herbicidal 
compositions. 
SUMMARY OF THE INVENTION 
It has been discovered that high yields of mixtures rich in chlorinated 
picolines/pyridines may be achieved by non-catalytically chlorinating 
beta-picoline or beta-picoline hydrocholoride in a diluent in the liquid 
phase at temperatures of at least about 190.degree. C. while maintaining 
strong agitation and a feed ratio of chlorine to beta-picoline of at least 
about 5:1 by weight while feeding the chlorine and beta-picoline or 
beta-picoline hydrochloride to the reaction mass in a primary reactor. The 
beta-picoline can be dissolved in carbon tetrachloride or fed full 
strength into the reactor. It s desirable to have a supply of carbon 
tetrachloride available for flushing the feed line in the event of a 
shutdown because stagnant beta-picoline would otherwise tend to degrade in 
and plug the feed line. If beta-picoline hydrochloride is the desired feed 
form, it is fed directly through a sparger into the bottom of the primary 
reactor. After the beta-picoline or beta-picoline hydrochloride has been 
partially chlorinated in the primary reactor, the polychloro picoline is 
subjected to further chlorination in one or more secondary reactors for 
such times and temperatures as appropriate to maximize the yield of the 
desired end product or products. 
The percent of volatiles realized by liquid phase chlorination according to 
the present invention is dependent upon the diluent composition, the 
extent of mixing of the reactants and diluent, the picoline feed rate to 
reaction mass volume, the weight ratio of chlorine-to-picoline being fed, 
and the chlorine partial pressure, which influences chlorine solubility. 
The composition of the diluent media in which the reaction proceeds is 
important in practice of this invention, to secure good yields of the 
desired volatile chlorinated beta-picolines. Its function in this 
invention is quite different from the initiator charge described in Taplin 
U.S. Pat. No. 3,424,754, which deals with alpha-picoline liquid phase 
chlorination. In U.S. Pat. No. 3,424,754, the initiator charge has the 
function of evolving HCl when contacted with chlorine at the reaction 
temperature in order to react with alpha-picoline to form picoline 
hydrochloride. In the present invention, the diluent's function is to be 
reactively less competitive for the chlorine dissolved in it and to help 
remove the heat of reaction evolved by the chlorination of the 
beta-picoline. 
Examples of some compounds usable as diluents in the practice of the 
present invention, in that they generate one mole or less of HCl per mole 
of compound when contacted with chlorine under the reaction conditions of 
the present invention, are: 3-chloro-, 5-chloro-, 6-chloro-, 
5,6-dichloro-, 3,5-dichloro-, 3,6-dichloro-, 3,4,5-trichloro- and 
3,5,6-trichloro-2-trichloromethyl pyridine, 2-chloro-, 6-chloro-, 
2,6-dichloro-3-trichloromethyl pyridine, and 2,3,6-trichloro-, 
2,3,5,6-tetrachloro-, and 2,3,4,5,6-pentachloro pyridine, and mixtures 
thereof. This list is not meant to be exhaustive of all possible diluent 
constituents but is illustrative of compounds useful for the purpose. The 
diluent may be the chlorinated pyridine/picoline products from a previous 
reaction which meet the above criteria and is high in volatiles content. 
In the practice of the present invention, an excess of chlorine is fed 
relative to that needed for the beta-picoline and beta-picoline 
hydrochloride chlorination, which excess provides additional agitation and 
hence better mixing, and also a higher chlorine partial pressure which 
increases the chlorine solubility in the reaction media. A chlorine to 
beta-picoline weight ratio of at least about 5:1 is needed. As the 
temperature increases in excess of 200.degree. C., the weight ratio of 
chlorine to beta-picoline fed needs to be higher in order to achieve the 
high yields of the desired volatile chloro-picolines. This is necessary 
because chlorine reacts more rapidly with the beta-picoline or 
beta-picoline hydrochloride as the temperature increases and therefore the 
chlorine dissolved in the reaction medium must be more rapidly replaced. 
This is accomplished by increasing the rate of chlorine addition relative 
to the beta-picoline flow rate which increases the chlorine partial 
pressure and hence its mole fraction in the liquid reaction medium. Gas 
solubilities tend to decrease with rising temperature, but an increase in 
system pressure increases the chlorine solubility. 
The beta-picoline or beta-picoline hydrochloride feed is to be controlled 
relative to the reaction volume so no more than about 10% by volume of 
light phase accumulates relative to the chlorinated picoline phase at 
temperatures in excess of about 190.degree. C. Potential decomposition 
products can result above this temperature in the absence of cooling and 
excess chlorine. Since beta-picoline hydrochloride and the diluent are 
somewhat immiscible and of different densities, good mixing is necessary 
in order to achieve dispersion of chlorine and beta-picoline or 
beta-picoline hydrochloride into the diluent. 
Controlling these variables results in the high yields of volatile 
polychlorinated beta-picolines in the liquid phase at temperatures in 
excess of 190.degree. C. 
Care must be taken to ensure that metallic impurities, such as iron, 
copper, aluminum and other Lewis Acid type metals, are excluded from the 
reaction mass, as they will cause different reactions in the chlorination 
that may not be desirable. 
We have also discovered that the chloro-picolines can be further 
chlorinated non-catalytically, at predictable functions of time vs. 
temperature, to give other useful intermediates. For example, when 
subjected to further non-catalytic chlorination in liquid phase at high 
temperature, 5-chloro-3-trichloromethyl pyridine goes to 
5,6-dichloro-3-trichloromethyl pyridine. Similarly 
6-chloro-3-trichloromethyl pyridine non-catalytically chlorinates to 
2,6-dichloro-3-trichloromethyl pyridine as does 2-chloro-3-trichloromethyl 
pyridine. The process can be interrupted at this stage and these two main 
components, namely, 5,6-dichloro-3-trichloromethyl pyridine and 
2,6-dichloro-3-trichloromethyl pyridine, may be separated out, or, if 
chlorination is continued, 5,6-dichloro-3-trichloromethyl pyridine goes to 
2,5,6-trichloro-3-trichloromethyl pyridine and on still further 
chlorination to 2,3,5,6-tetrachloro pyridine, which has great utility as 
an intermediate in insecticidal compositions. 
2,6-Dichloro-3-trichloromethyl pyridine can be chlorinated 
non-catalytically further to 2,3,6-trichloro pyridine. 2,3,6-Trichloro 
pyridine also can be chlorinated with or without ferric chloride catalyst 
to 2,3,5,6-tetrachloro pyridine. The process can be selectively controlled 
to realize a very high yield of 2,3,5,6-tetrachloro pyridine, or the yield 
of 5,6-dichloro-3-trichloromethyl pyridine and 6-chloro-3-trichloromethyl 
pyridine, both of which have utility as intermediates for herbicides, can 
be maximized by not chlorinating as long. 
Mixtures rich in 6-chloro-3-trichloromethyl pyridine can be chlorinated 
catalytically to mixtures rich in 2,5,6-trichloro-3-trichloromethyl 
pyridine. Mixtures rich in 2,6-dichloro-3-trichloromethyl pyridine can be 
chlorinated catalytically to mixtures rich in 
2,5,6-trichloro-3-trichloromethyl pyridine. Mixtures rich in 
2,5,6-trichloro-3-trichloromethyl pyridine can be chlorinated 
non-catalytically to mixtures rich in 2,3,5,6-tetrachloro pyridine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
EXAMPLE 1 
FIG. 1 schematically illustrates a continuous batch type reaction system 
for producing mixtures rich in polychlorinated pyridine/picolines 
according to the present invention. Primary reactor R1, secondary reactor 
R2, and absorber C2 are suitably glass of cylindrical configuration, 
electrically heated and each about 1 liter in volume, and with an inside 
diameter of 4 inches and an inside height of 7 inches. Finishing reactors 
R3A and R3B are glass, spherical, electrically heated and about 1 liter in 
volume. Water cooled scrubber column C1 is suitably of cylindrical design, 
11/2 inches in diameter, containing as packing some 18 inches of 1/4 inch 
glass rings. 
Scrubber column C1 includes a holding tank or reservoir T1 and the overhead 
vapor from column C1 is delivered through vent line 10 to disengaging tank 
T2 in which the carbon tetrachloride collects, with the chlorine and 
hydrogen chloride evolving from column C1 being delivered by vent line 12 
and sparged into hydrochlorination tank T3. For startup, beta-picoline 
hydrochloride, suitably previously prepared conventionally, as by sparging 
anhydrous HCl into a pool of beta-picoline maintained between 80.degree. 
C. and 100.degree. C. until saturated with HCl, is charged to 
hydrochlorination tank T3 and beta-picoline hydrochloride is withdrawn 
from tank T3 and delivered to bottom discharging sparger 14 in reactor R1 
through line 16. An alternate startup mode involves feeding beta-picoline 
dissolved in carbon tetrachloride through lines 68 and 70 thence into line 
14, generating hydrogen chloride which is vented to hydrochlorination tank 
T3. For startup, also, primary reactor R1 was charged through charge line 
18 with 1000 grams of diluent, consisting of chlorinated pyridine from a 
previous reaction (suitably comprising about 22.4% 6-chloro-, 48.9% 
5,6-dichloro-, 27.3% 3,6-dichloro-, and 4.1% 
4,6-dichloro-2-trichloromethyl pyridine by weight). 406 grams of like 
diluent material was also charged to secondary reactor R2 through charge 
line 20. 453 grams of a suitable absorbent was charged through charge line 
64 to absorber C2, the composition of the absorbent selected for this 
example being 66.7% 6-chloro-, 15.2% 5,6-dichloro-, 1.8% 
3,6-dichloro-2-trichloromethyl pyridine, and 4.9% 2,6-dichloro-, 4.9% 
2,3,5,6-tetrachloro-, and 1.1% 2,3,4,5,6-pentachloropyridine, and 2.7% 
5,6-dichloro-, 1.8% 2,6-dichloro-3-trichloromethyl pyridine, by weight. 
The absorbent charged to C2 needs to have a melting point of less than 
80.degree. C. and substantial solubility with carbon tetrachloride. Its 
purpose is to absorb higher melting chlorinated pyridines, e.g. those with 
melting points greater than 90.degree. C., namely, 2,3,5,6-tetra- and 
2,3,4,5,6-pentachloro pyridine. If these higher melting point 
chloropyridines were allowed to enter the scrubber column C1 in 
substantial quantity, they would tend to plug the column packing. The 
refluxing carbon tetrachloride in scrubber column C1 tends to concentrate 
the entrained chloropyridines that enter it in the bottom tank T1 thereof, 
and keep the overhead vapors substantially free of chlorinated pyridines 
which would otherwise plug the vapor outlet 10. Some typical examples 
which meet the criteria of suitable absorbent materials for absorber C2 
are 6-chloro-, 5,6-dichloro-, 3,6-dichloro-, 
3,5-dichloro-2-trichloromethyl pyridine, and mixtures thereof. 
The operational startup sequence is that of introducing the diluent to the 
primary and secondary reactors, then initiating chlorine flow, then 
heating the reactors to desired reaction temperature, then initiating the 
beta-picoline or beta-picoline hydrochloride flow. By this procedure, the 
beta-picoline or beta-picoline hydrochloride only sees excess chlorine in 
the reactors and degradation thereof to nonvolatiles is avoided. Once 
reactors R1 and R2 were charged, external heat was applied and the 
temperature of primary reactor R1 thereof was maintained at 230.degree. 
C., with secondary reactor R2 being maintained at 150.degree. C. and 
absorber C2 maintained at 140.degree. C. Chlorine gas from a suitable 
pressurized source was delivered to the reactor R1 through feed line 22 
and bottom placed sparger 24 at a flow rate of 440 grams per hour. The 
flow rate of beta-picoline hydrochloride sparged into reactor R1 through 
bottom placed sparger 14, the discharge stream of which is closely 
adjacent (with about 1/2 inch spacing) to the discharge stream of chlorine 
sparger 24, was maintained at a rate equivalent to 29 grams beta-picoline 
per hour, amounting to a chlorine to picoline feed ratio of about 15:1. 
As will be understood, the beta-picoline hydrochloride fed to primary 
reactor R1 releases hydrogen chloride from both the reaction with the 
chlorine and the decomposition of the hydrochloride salt. This hydrogen 
chloride along with excess chlorine is vented from reactor R1 through vent 
line 26 and sparged into the charge in secondary reactor R2 through bottom 
discharging sparger 28, the overhead vapor including hydrogen chloride and 
excess chlorine being vented from reactor R2 and delivered through line 30 
to absorber C2, thence through line 62 to scrubbing column C1, thence 
through line 10 and line 12 to hydrochlorinating tank T3, the vapor flow 
from which passes through line 32 to hydrogen chloride and chlorine gas 
recovery means, known per se, for recycling of the chlorine gas to the 
process and recovery of the hydrogen chloride, as desired. Once hydrogen 
chloride gas is being generated and is passing through the system to 
hydrochlorination tank T3, the beta-picoline feed into tank T3 through 
line 15 can be started if that is the desired feed mode. 
Secondary reactor R2 is only partially charged with diluent at startup. 
This is for the reason that, as the volume of the reaction mass in reactor 
R1 increases in the course of the reaction, a portion of the reaction mass 
is moved from reactor R1 to reactor R2 (by volatilization and entrainment) 
through line 26 and through discharge line 34 for further chlorination in 
reactor R2. The temperature in secondary reactor R2 influences the degree 
of continued chlorination. In this example the relatively low temperature 
of 150.degree. C. serves to quench the reaction occurring in primary 
reactor R1 and to slow the rate of chlorination. A higher temperature in 
secondary reactor R3, such as a temperature greater than 200.degree. C., 
would continue the chlorination process at a higher rate than occurs at 
150.degree. C. In this example, reactors R3A and R3B were chosen to take 
the reaction to the desired degree of chlorination by operating at 
210.degree. C. for 12 hours. 
When the liquid volume in secondary reactor R2 increases to the point where 
the reactor R2 is filled to its operating level, further increase in 
liquid volume is taken care of by progressively discharging the excess 
through line 36 to either finishing reactor R3A through line 38, or to 
finishing reactor R3B through line 40, depending on the setting of valve 
42. 
Chlorination to process end point is completed in either reactor R3A or 
reactor R3B by continued introduction of chlorine gas through bottom 
discharging sparger 44 or 46, with continued heating of the reactors R3A 
or R3B to a desired temperature for a desired time to yield the desired 
product distribution, e.g. a temperature of 210.degree. C. and a time of 
twelve hours, in this selected example. Chlorine and hydrogen chloride 
vapor takeoff from reactors R3A and R3B is delivered through vent lines 
48, 50 to absorber C2 through sparge line 74, thence to scrubber column 
C1. 
Chlorinated reaction product is withdrawn from the reactors R3A and R3B 
through respective discharge lines 52, 54, with the product going to 
product purification means known per se, such as a vacuum fractional 
distillation column. Liquid discharge from holding tank T2 is delivered to 
scrubber column C1 through line 56 to return carbon tetrachloride to the 
column C1, with makeup of carbon tetrachloride from an appropriate supply 
if necessary, as indicated at 58. The liquid phase fraction collecting in 
bottem tank T1 of the scrubber column C1 is returned to absorber C2, as 
indicated at line 60. 
Finishing reactors R3A and R3B can be smaller or larger than reactors R1 
and R2, depending on the desired residence time to complete the 
chlorination reaction. For example, with a reaction temperature of 
230.degree. C. and a residence time of 12 hours in the primary reactor R1 
and a reactor temperature of 150.degree. C. and a residence time of 12 
hours in the secondary reactor R2, the time required to complete the 
reaction in reactor R3A or in reactor R3B is about 12 hours at 210.degree. 
C. temperature. The controlling factor determining reaction time in 
reactor R3A or reactor R3B is the maximum concentration of the desired 
product. If the principal desired product is 5,6 
dichloro-3-trichloromethyl pyridine, additional chlorination in R3A or R3B 
would be required for maximum recovery. If the principal desired product 
is 6-chloro-3-trichloromethyl pyridine, less time would be required in R3A 
or R3B. Correspondingly, additional time would be required to maximize the 
concentration of 2,3,6-trichloro pyridine in R3A or R3B. In this first 
example, it has been assumed that a mixture of end product compounds, with 
each compound present in substantial proportion, was desired, and to this 
end the composition of the end product obtained in R3A and R3B comprised 
11.7% 2,3,6-trichloro pyridine, 24.4% 6-chloro-3-trichloromethyl pyridine, 
and 16.1% 5,6-dichloro-3-trichloromethyl pyridine, by weight. Further, 
product purification and recycle to R3A or R3B for further chlorination, 
as indicated at 76, can convert the 5-chloro-3-trichloromethyl pyridine to 
5,6-dichloro-3-trichloromethyl pyridine and 2-chloro- and 
2,6-dichloro-3-trichloromethyl pyridine to 2,3,5-trichloro pyridine. 
Excess chlorine, hydrogen chloride, and some volatile corrosive 
chloro-picoline hydrochlorides and entrained chlorinated pyridines, some 
of which have melting points in excess of 100.degree. C., are transferred 
to secondary reactor R2 from primary reactor R1 by heated vent line 26 and 
bottom discharging sparger 28, with the volatile hydrochlorides being 
absorbed and reacted further in secondary reactor R2. These hydrochlorides 
are very corrosive and tend to form solids on condenser surfaces that are 
in the 30.degree. C. to 100.degree. C. temperature range, the operating 
temperature range of scrubber column C1 and, along with the high melting 
chloropyridines, would cause a plugging problem in column C1 if passed 
directly from primary reactor R1 to the scrubber column C1. Their 
absorption and further reaction in secondary reactor R2 help eliminate 
such plugging problems and absorber C2 completely eliminates the high 
melting chloropyridines in the vent line 62 to column C1. The excess 
chlorine, hydrogen chloride, and entrained products passing to column C1 
through absorber C2 vent line 62 are there scrubbed with carbon 
tetrachloride discharged to column C1 through line 56. The entrained 
chlorinated pyridine products buildup in tank T1 and the liquid level 
therein is controlled by recycling the excess liquid back to absorber C2 
through discharge line 60. When the level in absorber C2 reaches the 
operating level, processing of the excess material is begun through line 
66 for removal of the high melting chloropyridine reaction products from 
the absorber material. These chlorinated pyridine products are removed 
from the absorbent material by vacuum distillation. Process absorbent is 
then recycled back to C2 through line 64. 
As will be apparent, finishing reactors R3A and R3B are operated in a batch 
manner, permitting one to be on line while the other is having the 
chlorinated product removed or is being filled from secondary reactor R2. 
Analysis of the reaction mass in the on line reactor R3A or R3B for 
maximum concentration of the desired chloropyridine(s) indicates when the 
reaction is finished. When this occurs the contents of the on line reactor 
R3A or R3B are pumped through the respective discharge lines 52 or 54 to 
the purification section of the system, conventional per se. 
The residence time in each reactor R1, R2 and R3A or R3B typically varies 
from about 5 to about 40 hours, and the total cycle time in the reactors 
is about 10 to 120 hours. From the previously described feed and reaction 
conditions set forth in Example 1, 75 grams per hour of product was 
obtained that contained about 14.1% 5-chloro-, 24.4% 6-chloro-, 6.3% 
2-chloro-, 16.1% 5,6-dichloro-, and 9.8% 2,6-dichloro-3-trichloromethyl 
pyridine, by weight. In addition, 11.7% 2,3,6-trichloro pyridine was 
present. The volatiles content of the reaction mass was greater than 96%. 
As known per se, 2,3,6-trichloro pyridine can be separated and processed 
further through ferric chloride catalyzed liquid phase chlorination to 
2,3,5,6-tetrachloro pyridine, such as described in Dietsche et al U.S. 
Pat. No. 4,256,894. In this example, also, the total residence time was 
about 21 hours. In practice of the invention appropriate variation in 
residence time is determinable on a predictable basis, taking into 
consideration the product composition desired, and the reactor pressure 
and reactor temperature. In addition, the quantity of diluent recycled to 
the reactors may also be varied to vary the residence time. In any event, 
as earlier indicated, the feed rate of beta-picoline or beta-picoline 
hydrochloride relative to the reaction volume is to be controlled so that 
no greater than about 10% by volume of lighter phase (undiluted picoline 
hydrochloride) exists in the reaction mass. 
The gases in vent line 32 from hydrochlorination tank T3 are predominantly 
excess chlorine and hydrogen chloride, which stream can be separated or 
purified by a number of conventional techniques such as absorption of the 
hydrogen chloride in water, or drying the chlorine and compressing the 
chlorine gas for recycle, or fractional distillation. 
EXAMPLE 2 
Utilizing the same reaction system shown in FIG. 1 and described in Example 
1, reactors R1 and R2 were respectively charged with 928 grams and 635 
grams of chlorinated picoline diluent from a previous reaction. Absorber 
C2 was charged with 585 grams of the same material. The composition of the 
diluent was 4% pentachloropyridine, 54% 6-chloro-, 15% 6-dichloro-, and 2% 
4,6-dichloro-2-trichloromethyl pyridine, and 6.3% 6-chloro-, 2% 2-chloro-, 
1.5% 5,6-dichloro- and 1.5% 2,6-dichloro-3-trichloromethyl pyridine, by 
weight. Chlorine at a flow rate of 440 grams per hour was sparged into 
reactor R1 and reactors R1 and R2 were heated to temperatures of 
210.degree. C. and 150.degree. C. respectively. Absorber C2 was maintained 
at 140.degree. C. Beta-picoline was then sparged into reactor R1 through 
sparger 14 after being premixed with about an equal volume of carbon 
tetrachloride. The beta-picoline feed was at a rate equivalent to about 20 
grams beta-picoline per hour. The average residence time of the reaction 
mass in each of the reactors R1 and R2 was about 12 hours. Chlorination of 
the effluent from reactor R2 was continued in reactor R3A for 9 hours at 
160.degree. C. and then for 5 hours at 190.degree. C. The resulting 
reaction product contained about 21% 5,6-dichloro-3-trichloromethyl 
pyridine by weight, and the volatile content of the reaction mass was 
greater than 98%. 
The analyses of the reaction products obtained in Examples 1 and 2 are 
given in the following Table ONE. 
TABLE ONE 
______________________________________ 
Compound Example 1 Example 2 
______________________________________ 
##STR1## 11.7% by wt. 
##STR2## 3.4 
##STR3## 14.1 
##STR4## 24.4 3.0% by wt. 
##STR5## 6.3 3.6 
##STR6## 16.1 21.4 
##STR7## 9.8 12.5 
##STR8## 29.1 
##STR9## 25.4 
______________________________________ 
EXAMPLES 3 through 7 
Examples 3 through 7 serve to illustrate some of the process variables 
which can occur in practice of the present invention, and for such purpose 
were conducted as simplified batch processes. A chlorination reactor 
comprising a 1000 ml spherical glass reactor, heated by an electric 
heating mantle, was equipped with two sparge tubes and a line which was 
vented through a 5000 ml glass knockout pot to a caustic scrubber. The 
spargers were bottom placed and closely spaced (2 centimeters apart) and 
the respective feed lines to the spargers were fed through rotometers and 
flow controlled through respective needle valves, one being supplied from 
the source of chlorine gas, and the other supplied from a source of 
beta-picoline (Examples 3 and 4) or beta-picoline hydrochloride (Examples 
5-7). In each run, the procedure followed was the same except for the 
variables investigated, namely, diluent composition, temperature, 
chlorine-to-picoline feed ratio, residence time, and picoline flow rate 
relative to reaction mass volume. In Example 3, which is illustrative, the 
reactor was charged with 715 grams of diluent, the composition of which is 
given in the following TABLE TWO, and chlorine feed was initiated through 
the chlorine sparger at the rate of 380 grams per hour and the charge 
heated to a temperature of 235.degree. C. Beta-picoline dissolved in an 
equal volume of carbon tetrachloride was then sparged into the reactor at 
the rate of about 28 grams per hour for a period of 5 hours. The weight 
ratio of chlorine to the beta-picoline being fed during the reaction was 
about 13.5:1. Chlorine feed was continued at the rate of 380 grams per 
hour for 9 more hours at a temperature of 210.degree. C. after the 
picoline feed was discontinued. The reaction process parameters are 
tabulated in the following TABLE THREE. The gross weight of the resulting 
reaction product was 1065 grams, indicating a net production of 350 grams 
of product. The product was a clear tractable fluid, with a volatiles 
proportion of greater than 98%, as measured by internal standard gas 
chromatography. The constituency of the product was as tabulated in TABLE 
THREE. 
As indicated, additional runs, designated Examples 4, 5, 6 and 7 involved 
the diluents set forth in TABLE TWO, the parameters set forth in TABLE 
THREE and produced reaction products comprising the compounds set forth in 
TABLE FOUR. 
TABLE TWO 
__________________________________________________________________________ 
DILUENT COMPOSITION 
Compound Examples 3 & 4 
Example 5 
Example 6 
Example 7 
__________________________________________________________________________ 
##STR10## 2.2% 
by wt. 
2.5% 
by wt. 
##STR11## 1.7 1.0 
##STR12## 
3.0% 
by wt. 
2.1 2.1 
##STR13## 
73.0 61.1 77.0 17.4% 
by wt. 
##STR14## 
17.0 9.2 10.7 51.6 
##STR15## 
2.3 0.6 1.0 22.3 
##STR16## 
2.0 0.6 1.0 1.4 
##STR17## 
1.0 1.0 
##STR18## 1.8 1.6 
##STR19## 7.3 
##STR20## 2.9 
##STR21## 7.4 
__________________________________________________________________________ 
TABLE THREE 
______________________________________ 
Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 
______________________________________ 
Initial 235.degree. C. 
245.degree. C. 
250.degree. C. 
235.degree. C. 
195.degree. C. 
Reactor 
Temp 
Diluent 715 gms 470 gms 934 gms 
825 gms 
677 gms 
charge 
Feed beta beta beta beta beta 
Form picoline/ 
picoline/ 
picoline/ 
picoline/ 
picoline/ 
CCl.sub.4 
CCl.sub.4 
hydro- hydro- hydro- 
chloride 
chloride 
chloride 
Cl.sub.2 
380 380 440 440 440 
Flow gms/hr gms/hr gms/hr gms/hr gms/hr 
Rate 
Beta- 28 29 25 9 4.9 
Picoline 
gms/hr gms/hr gms/hr gms/hr gms/hr 
flow rate 
(as beta- 
picoline) 
Cl.sub.2 : 
13.5:1 13:1 17:1 49:1 9:1 
beta- 
picoline 
ratio 
(by weight) 
Reaction 
5 hrs 5 hrs 1.50 hrs 
6 hrs 5 hrs 
Time 
with both 
Cl.sub.2 and 
beta- 
picoline 
feeds 
Additional 
9 hrs 9 hrs 2 hrs 6 hrs 
reaction 
@ @ @ @ 
time and 
210.degree. C. 160.degree. C. 
190.degree. C. 
210.degree. C. 
temp. + 5 hrs 
with Cl.sub.2 @ 
feed only 190.degree. C. 
Amt. of 350 gms 355 gms 93 gms 133 gms 
602 gms 
product 
produced 
Volatility 
&gt;98% 92% 99% 99% 99% 
of 
produced 
product 
______________________________________ 
TABLE FOUR 
__________________________________________________________________________ 
Compound Example 3 
Example 4 
Example 5 
Example 6 
Example 7 
__________________________________________________________________________ 
##STR22## 
25% by wt. 3.5% 
by wt. 
##STR23## 3.0 
##STR24## 
7.5 7.1% 
by wt. 15.8% 
by wt. 
##STR25## 
5.4 45.7 20.0% 
by wt. 
55.3 7.6 
##STR26## 15.0 21.0 14.4 9.5 
##STR27## 
6.8 6.4 10.0 2.0 23.9 
##STR28## 
42.7 4.7 49.0 38.9 12.1 
##STR29## 
10.5 
##STR30## 
2.0 2.0 
##STR31## 31.1 
__________________________________________________________________________ 
An important aspect of the present invention is the discovery that further 
liquid phase chlorination of certain monochloro and 
dichloro-3-trichloromethyl pyridines, in liquid phase and at a temperature 
of at least about 190.degree. C., can be effected in a chlorinating 
reactor, such as finishing reactors R3A and R3B, to realize valuable 
dichloro- and trichloro-3-trichloromethyl pyridines and trichloro and 
tetrachloro pyridines. As will be apparent, this aspect of the invention 
is applicable to effluent mixtures from reactor R2 in the foregoing 
examples, and also to monochloro and dichloro-3-trichloromethyl pyridines 
and mixtures thereof prepared by other processes, such as the chlorinated 
beta-picolines produced by the vapor phase processes disclosed in Bowden 
et al U.S. Pat. No. 4,205,175 (2-chloro- and 6-chloro-3-trichloromethyl 
pyridine), as well as Nishiyama U.S. Pat. No. 4,241,213 
(6-chloro-3-trichloromethyl pyridine). 
The following Examples 8 through 17 are presented to illustrate batch-type 
chlorination products obtained by continued liquid phase chlorination of 
mixtures rich in monochloro, dichloro-, and trichloro-3-trichloromethyl 
pyridines, such as those obtained in the effluent mixtures from reactor R2 
by the process of the present invention, or which may be otherwise 
obtained or available from other chlorination processes. 
In Examples 8-11, sixty grams per hour of chlorine were sparged into the 
bottom of a heated 250 cc spherical glass reactor. 
EXAMPLE 8 
In Example 8 shown in TABLE FIVE, 100 grams of a mixture rich in 6-chloro- 
and 2-chloro-3-trichloromethyl pyridine were chlorinated in the liquid 
phase at 190.degree. C. After two hours, the reactor was sampled and a 
significant decrease in the concentrations of the 6-chloro- and 
2-chloro-3-trichloromethyl pyridine was noted, i.e. 15.6% decreased to 
9.6% and 7.8% decreased to 2.8% respectively. A corresponding increase in 
the concentration of 2,6-dichloro-3-trichloromethyl pyridine was noted, 
i.e. 5.3% to 13.0%. The following reactions were therefore occurring at 
this stage of process: 
##STR32## 
TABLE FIVE 
______________________________________ 
Initial Molar Concentration 
Molar at 2 hrs of Chlori- 
Compound Concentration 
nation at 190.degree. C. 
______________________________________ 
15.6% 9.6% 
##STR33## 7.8% 2.8% 
##STR34## 5.3% 13.0% 
______________________________________ 
EXAMPLE 9 
Example 9 shown in TABLE SIX illustrates an additional chlorination 
reaction occuring in this liquid phase system, namely: 
##STR35## 
One hundred grams of a mixture rich in 6-chloro- and 
2,6-dichloro-3-trichloromethyl pyridine were chlorinated for 4 hours in 
the liquid phase at 210.degree. C. The 6-chloro-3-trichloromethyl pyridine 
concentration decreased from 6.9% to 2.1% during this time, while the 
2,6-dichloro-3-trichloromethyl pyridine concentration increased only 
slightly from 12.9% to 14.3%. Concentration of 2,3,6-trichloro pyridine 
increased from 2.3% to 6.3%. 
TABLE SIX 
______________________________________ 
Initial Molar Concentration 
Molar at 4 hrs at Chlori- 
Compound Concentration 
nation at 210.degree. C. 
______________________________________ 
##STR36## 6.9% 2.1% 
##STR37## 0.9% 
##STR38## 12.9% 14.3% 
##STR39## 2.3% 6.3% 
______________________________________ 
EXAMPLE 10 
Liquid chlorination of a mixture rich in 2,3,6-trichloro pyridine catalyzed 
with four weight percent ferric chloride is illustrated in TABLE SEVEN and 
Example 10. Fifty grams of a mixture rich in 2,3,6-trichloro pyridine was 
chlorinated at 195.degree. C. for 4 1/4 hours. The concentration of 
2,3,6-trichloro pyridine decreased from 89.4% to 1.7% while the 
concentration of 2,3,5,6-tetrachloro pyridine increased from 4.5% to 
97.6%. 
##STR40## 
TABLE SEVEN 
______________________________________ 
Initial Molar Concentration 
Molar after 9.25 hrs at 
Compound Concentration 
195.degree. C. + 4% FeCl.sub.3 
______________________________________ 
89.4% 1.7% 
##STR41## 4.5 97.6 
##STR42## 0.6 
______________________________________ 
It has been demonstrated by Examples 8-10 that various liquid phase, 
uncatalyzed and catalyzed chlorinations result in a method of producing 
mixtures rich in 2,3,5,6-tetrachloro pyridine, if desired. Useful 
chlorinated pyridines such as 6-chloro-3-trichloromethyl pyridine, may be 
separated out by vacuum distillation prior to being further chlorination, 
if desired. 
EXAMPLE 11 
This example illustrates the conversion of 5-chloro-3-trichloromethyl 
pyridine to 5,6-dichloro-3-trichloromethyl pyridine by liquid phase 
chlorination. 
One hundred grams of a mixture rich in 5-chloro- and 
5,6-dichloro-3-trichloromethyl pyridine was chlorinated in the liquid 
phase to a mixture richer in 5,6-dichloro-3-trichloromethyl pyridine and 
in 2,5,6-trichloro-3-trichloromethyl pyridine. TABLE EIGHT illustrates the 
results. 
TABLE EIGHT 
______________________________________ 
Molar Concentration 
Initial after 3 hrs liquid 
Molar phase chlorination 
Compound Concentration 
@ 190.degree. C. 
______________________________________ 
##STR43## 4.7% 
##STR44## 4.6 7.6% 
##STR45## 0.7 1.9 
##STR46## 
##STR47## 
______________________________________ 
EXAMPLE 12 
970 grams of a mixture rich in 5,6-dichloro- and 
2,5,6-trichloro-3-trichloromethyl pyridine were charged to a chlorinator. 
200 grams per hour of chlorine were sparged into the bottom of the 
chlorinator for 8 hours at a reaction temperature of 260.degree. C. and 
for 3 hours at a reactor temperature of 230.degree. C. The 
5,6-dichloro-3-trichloromethyl pyridine content decreased from 10.6 mole 
percent to 4.3 mole percent, while 2,5,6-trichloro-3-trichloromethyl 
pyridine content decreased from 19.1 mole percent to 9.2 mole percent. The 
2,3,5,6-tetrachloro pyridine content of the mass increased from 28.5 mole 
percent to 44.2 mole percent. 
In summary: 
__________________________________________________________________________ 
##STR48## 
##STR49## 
##STR50## 
total moles 
__________________________________________________________________________ 
Start 
10.6% 19.1 28.5 58.2 
Finish 
4.3 9.2 44.2 57.7 
__________________________________________________________________________ 
The above reactions occur during the production of 
2,3,5,6-tetrachloro pyridine from 
5,6-dichloro-3-trichloromethyl pyridine via 
2,5,6-trichloro-3-trichloromethyl pyridine. 
Examples 13 through 15 are presented to illustrate the fact that 
2,5,6-trichloro-3-trichloromethyl pyridine can be prepared from 
6-chloro-3-trichloromethyl pyridine or from 2,6-dichloro-3-trichloromethyl 
pyridine as well as from 5,6-dichloro-3-trichloromethyl pyridine (as 
described in Examples 11 and 12). Regardless of the method of preparation 
of 2,5,6-trichloro-3-trichloromethyl pyridine, non-catalytic liquid phase 
chlorination thereof at temperatures in excess of 190.degree. C. yields 
mixtures rich in 2,3,5,6-tetrachloro pyridine. 
EXAMPLE 13 
Seventy-five grams of a chlorinated pyridine mixture containing 79.2 mole 
percent 6-chloro-3-trichloromethyl pyridine was chlorinated catalytically 
as suggested by Ishihara Sangyo Kaisha Ltd. in Japan Kokai Tokkyo Koho 
82,183,760 (Chem. Abs., 98:143281b (1983)). 
Thus, two grams of ferric chloride were added to the above mentioned 
chlorinated pyridine mixture and chlorine was fed (sparged) into the 
liquid at 70 grams per hour and at temperatures from 200.degree. C. to 
215.degree. C. The reaction temperature can be as low as 160.degree. C. 
The catalyst can be a halide of Fe, W, Mo, Ti, or Sb. 
The data in TABLE NINE illustrate that 2,5,6-trichloro-3-trichloromethyl 
pyridine can be made from 6-chloro-3-trichloromethyl pyridine by way of 
5,6-dichloro- or 2,6-dichloro-3-trichloromethyl pyridine. 
TABLE NINE 
__________________________________________________________________________ 
Molar Concentration 
Molar Molar after 12 hrs of 
Concentration 
Concentration 
chlorination at 
Initial after 6 hrs of 
after 12 hrs of 
200.degree. C. and 15 hrs 
Molar chlorination 
chlorination 
of chlorination 
Compound Concentration 
at 200.degree. C. 
at 200.degree. C. 
at 215.degree. C. 
__________________________________________________________________________ 
##STR51## 2.2% 2.7% 1.0% 
##STR52## 
18.6% 17.6 18.4 24.8 
##STR53## 
79.2 38.8 25.4 3.1 
##STR54## 
0.6 2.3 3.2 5.5 
##STR55## 12.0 15.3 20.4 
##STR56## 19.0 18.7 4.1 
##STR57## 5.6 13.5 36.8 
__________________________________________________________________________ 
EXAMPLE 14 
Continued chlorination of 5,6-dichloro- and 2,5,6-trichloromethyl pyridine 
using a catalyst does not give optimum results. Therefore, the chlorinated 
pyridine product made in Example 13 (after chlorination for 12 hours at 
200.degree. C. and 15 hours at 215.degree. C.) was water washed four times 
with two volumes of fresh water per volume of chlorinated pyridine product 
in order to remove the catalyst ferric chloride. (Distillation is another 
method that can be used to separate the chloropyridine from the ferric 
chloride.) 
The resulting ferric chloride-free product was then non-catalytically 
chlorinated in liquid phase at 260.degree. C. for 6 hours in a 
mechanically agitated reactor with a chlorine flow of 7 grams per hour. 
The reaction temperature can be as low as 190.degree. C. The bulk of the 
2,5,6-trichloro-3-trichloromethyl pyridine was converted to 
2,3,5,6-tetrachloro pyridine as can be seen in TABLE TEN. 
TABLE TEN 
______________________________________ 
Molar 
Concentration 
Initial After 6 hrs 
Molar Clorination 
Compound Concentration 
at 260.degree. C. 
______________________________________ 
##STR58## 1.0% 5.7% 
##STR59## 24.8 56.0 
##STR60## 3.1 -- 
##STR61## 5.5 7.8 
##STR62## 20.4 8.5 
##STR63## 4.1 2.9 
##STR64## 36.8 19.0 
______________________________________ 
EXAMPLE 15 
Seventy-five grams of a chloropyridine mixture containing 88.1 mole percent 
2,6-dichloro-3-trichloromethyl pyridine were chlorinated in a mechanically 
agitated chlorinator with a chlorine flow of 10 grams per hour at 
220.degree. C. after 3 grams of ferric chloride were added to the mixture. 
The reaction temperature can be as low as 160.degree. C. TABLE ELEVEN 
shows that after 31/2 hours of chlorination, the 
2,6-dichloro-3-trichloromethy pyridine had essentially been completely 
converted to 2,5,6-trichloro-3-trichloromethyl pyridine at 72.5 percent 
molar concentration or its further chlorinated product 2,3,5,6-tetrachloro 
pyridine at 22.0 percent molar concentration. This is added proof that 
2,5,6-trichloro-3-trichloromethyl pyridine can be made from 
2,6-dichloro-3-trichloromethyl pyridine. 
At this point, the chlorinated pyridine product made in Example 15 may be 
treated according to the first step in Example 14 to remove the catalyst 
ferric chloride. The catalyst-free product may then be non-catalytically 
chlorinated according to the second step in Example 14 to convert the bulk 
of the 2,5,6-trichloro-3-trichloromethyl pyridine to 2,3,5,6-tetrachloro 
pyridine. 
When the batch is further chlorinated for 4 additional hours at 220.degree. 
C. without removing the ferric chloride catalyst, the results are shown in 
TABLE ELEVEN. The concentration of 2,3,4,5,6-pentachloro pyridine 
increased to 24.2 mole percent and the concentration of 
2,5,6-trichloro-3-trichloromethyl pyridine decreased to 35.4 mole percent. 
Therefore the bulk of the 2,5,6-trichloro-3-trichloromethyl pyridine does 
not go exclusively to 2,3,5,6-tetrachloro pyridine, but also makes 
significant quantities of 2,3,4,5,6-pentachloro pyridine. This is 
undesirable from an efficient yield standpoint. 
TABLE ELEVEN 
______________________________________ 
Initial Molar Molar 
Molar Concentration 
Concentration 
Concen- after 31/2 after 71/2 hrs 
Compound tration hrs @ 220.degree. C. 
total @ 220.degree. C. 
______________________________________ 
##STR65## -- -- -- 
##STR66## 1.6% 22.0% 34.9% 
##STR67## 88.1 0.9 0.9 
##STR68## 6.1 72.5 35.4 
##STR69## -- 2.1 24.2 
______________________________________ 
EXAMPLE 16 
Eighty-five grams of a mixture rich in 2,3,6-trichloro pyridine and 
2,6-dichloro-3-trichloromethyl pyridine were chlorinated without catalyst 
for 14 hours at 225.degree. C. using mechanical agitation and a feed rate 
of 15 grams per hour of chlorine. The 2,3,6-trichloro pyridine molar 
concentration initially was 30.6 mole percent. After the 14 hours of 
chlorination, it had increased to 53.4 mole percent. The 
2,6-dichloro-3-trichloromethyl pyridine concentration was initially 61.1 
mole percent. Then, after the 14 hours of chlorination it decreased to 
26.8 mole percent. 2,3,5,6-tetrachloro pyridine was initially present at 
2.5 mole percent. After the 14 hours of chlorination its molar 
concentration had increased to 12.5%. 2,3,5,6-tetrachloro pyridine was, 
therefore, the product of non-catalytic chlorination of 2,3,6-trichloro 
pyridine. The reaction temperature can be as low as 190.degree. C. 
##STR70## 
The 2,3,6-trichloro pyridine can be separated from the mixture by 
distillation and then treated as in Example 10 to form 2,3,5,6-tetrachloro 
pyridine by catalytic chlorination. 
EXAMPLE 17 
Sixty-five grams of a mixture rich in 2,3,6-trichloro pyridine were 
chlorinated without catalyst at a feed rate of 15 grams per hour of 
chlorine using mechanical agitation. The 2,3,6-trichloro pyridine molar 
concentration initially was 96.3 mole percent. The 2,6-dichloro pyridine 
concentration initially was 1.6 mole percent. The 2,3,5,6-tetrachloro 
pyridine concentration initially was 1.5 mole percent. The mixture was 
chlorinated for 5 hours at 200.degree. C., for 5 hours at 210.degree. C., 
for 4 hours at 220.degree. C., and for 4 hours at 230.degree. C. (total: 
18 hours). After the 18 hours of chlorination, the 2,3,6-trichloro 
pyridine concentration decreased to 94.3 mole percent. The 2,6-dichloro 
pyridine concentration decreased to 0.9 mole percent. The 
2,3,5,6-tetrachloro pyridine concentration increased to 4.1 mole percent. 
The reaction temperature can be as low as 190.degree. C., but the rate of 
reaction will be very low unless the chlorination is conducted under high 
pressure conditions, such as 300 pounds of chlorine pressure. 
In composite, the foregoing Examples 8 through 10 demonstrate that liquid 
phase chlorination carried out at a temperature of at least about 
190.degree. C. while feeding chlorine into a reactor charge progressively 
converts 2-chloro-3-trichloromethyl pyridine and/or 
6-chloro-3-trichloromethyl pyridine to 2,6-dichloro-3-trichloromethyl 
pyridine, which then converts to 2,3,6-trichloro pyridine and then in turn 
to 2,3,5,6-tetrachloro pyridine. Such conversion may be selectively 
controlled to be on a substantially quantitative basis, or can produce 
some intermediate mixture, depending on the time the chlorination is 
maintained. 
Similarly, Examples 11 and 12 demonstrate that chlorination under like 
conditions of mixtures rich in 5-chloro-3-trichloromethyl pyridine and 
5,6-dichloro-3-trichloromethyl pyridine forms mixtures richer in 
5,6-dichloro-3-trichloromethyl pyridine, along with further conversion 
thereof to 2,5,6-trichloro-3-trichloromethyl pyridine, the 
2,5,6-trichloro-3-trichloromethyl pyridine being converted in turn to 
2,3,5,6-tetrachloro pyridine. 
Example 13 demonstrates that catalytic liquid phase chlorination carried 
out at a temperature of at least about 160.degree. C. while feeding 
chlorine into a reactor charge converts mixtures rich in 
6-chloro-3-trichloromethyl pyridine to mixtures rich in 5,6-dichloro- and 
2,5,6-trichloro-3-trichloromethyl pyridine. Example 14 demonstrates that 
non-catalytic liquid phase chlorination carried out at a temperature of at 
least about 190.degree. C. while feeding chlorine into a reactor charge 
converts mixtures rich in 5,6-dichloro- and 
2,5,6-trichloro-3-trichloromethyl pyridine to mixtures rich in 
2,3,5,6-tetrachloro pyridine. Example 15 shows that catalytic liquid phase 
chlorination carried out at a temperature of at least about 160.degree. C. 
while feeding chlorine into a reactor charge converts mixtures rich in 
2,6-dichloro-3-trichloromethyl pyridine to mixtures rich in 
2,5,6-trichloro-3-trichloromethyl pyridine. Example 16 shows that 
non-catalytic chlorination of mixtures rich in 2,3,6-trichloro pyridine 
and 2,6-dichloro-3-trichloromethyl pyridine result in mixtures rich in 
2,3,6-trichloro pyridine and 2,3,5,6-tetrachloro pyridine. Example 17 
shows that a mixture rich in 2,3,6-trichloro pyridine can be 
non-catalytically chlorinated to form 2,3,5,6-tetrachloro pyridine. 
Such an extent of conversion of these monochloro and 
dichloro-3-trichloromethyl pyridines to the indicated dichloro-and 
trichloro-3-trichloromethyl pyridines and the indicated trichloro and 
tetrachloro pyridines by direct chlorination is considered unique and 
provides valuable intermediates for subsequent manufacture of herbicides 
and insecticides by a much simpler and more straightforward process than 
heretofore known. 
The reaction mechanism involved in the liquid phase chlorination of 
beta-picoline appears to be such that at temperatures less than about 
190.degree. C. in the primary reactor 2,4,6-trichloro-3-trichloromethyl 
pyridine is formed, by a progression from the monochloro trichloromethyl 
to the dichloro trichloromethyl and then to the trichloromethyl, with the 
final product being 2,4,6-chloro-3-trichloromethyl pyridine, for which 
there is no known utility. Yield averages in the temperature range from 
100.degree. C. to about 180.degree. C. prove to be from 60% to 70%, so 
reaction products at primary reactor temperatures less than 190.degree. C. 
do not appear to have much utility. We have now discovered, however, that 
at primary reactor R1 temperatures from 190.degree. C. up to higher liquid 
phase chlorination temperatures, e.g., 250.degree. C., a whole series of 
useful reaction products is realized, and at temperatures about 
220.degree. C. and above there is very little 
2,4,6-trichloro-3-trichloromethyl pyridine formed. Typical product 
compositions at 220.degree. C. and higher reaction temperatures in the 
primary reactor involve about 10% 5-chloro-3-trichloromethyl pyridine, 40% 
6-chloro-3-trichloromethyl pyridine, 20% 2-chloro-3-trichloromelthyl 
pyridine by weight and smaller amounts on the order of 1 to 2% of the 
5,6-dichloro-3-trichloromethyl pyridine and the 
2,6-dichloro-3-trichloromethyl pyridine. 
As earlier indicated, we have also discovered that these products can be 
further chlorinated non-catalytically, at predictable functions of time 
vs. temperature, to give other useful intermediates. For example, when 
subjected to further non-catalytic chlorination in liquid phase at high 
temperature, 5-chloro-3-trichloromethyl pyridine goes to 
5,6-dichloro-3-trichloromethyl pyridine. Similarly 
6-chloro-3-trichloromethyl pyridine non-catalytically chlorinates to 
2,6-dichloro-3-trichloromethyl pyridine as does 2-chloro-3-trichloromethyl 
pyridine. The process can be interrupted at this stage and these two main 
components, namely, 5,6-dichloro-3-trichloromethyl pyridine and 
2,6-dichloro-3-trichloromethyl pyridine, may be separated out, or, if 
chlorination is continued, 5,6-dichloro-3-trichloromethyl pyridine goes to 
2,5,6-trichloro-3-trichloromethyl pyridine and on still further 
chlorination to 2,3,5,6-tetrachloro pyridine, which has great utility as 
an intermediate in insecticidal compositions. 
2,6-dichloro-3-trichloromethyl pyridine can be chlorinated 
non-catalytically further to 2,3,6-trichloro pyridine. In addition, 
5,6-dichloro-, 2,6-dichloro-, and 2,5,6-trichloro-3-trichloromethyl 
pyridine can be prepared by catalytic chlorination of 
6-chloro-3-trichloromethyl pyridine. Also, 
2,5,6-trichloro-3-trichloromethyl pyridine can be prepared by catalytic 
chlorination of 2,6-dichloro-3-trichloromethyl pyridine. Removal of the 
catalyst from 5,6-dichloro-, 2,6-dichloro-, and/or 
2,5,6-trichloro-3-trichloromethyl pyridine will allow the above mentioned 
non-catalytic chlorination to proceed to the final chlorination products, 
namely, 2,3,6-trichloro pyridine and 2,3,5,6-tetrachloro pyridine. The 
2,3,6-trichloro pyridine also can be chlorinated with or without ferric 
chloride catalyst to 2,3,5,6-tetrachloro pyridine. The ferric chloride 
catalyzed reaction is a much faster and therefore more economical route to 
2,3,5,6-tetrachloro pyridine from 2,3,6-trichloro pyridine. The process 
can be selectively controlled to realize a very high yield of 
2,3,5,6-tetrachloro pyridine, or the yield of 
5,6-dichloro-3-trichloromethyl pyridine and 6-chloro-3-trichloromethyl 
pyridine, both of which have utility as intermediates for herbicides, can 
be maximized by not chlorinating as long. 
In general, the primary reactor R1 is maintained at a temperature of at 
least 190.degree.. Its maximum practical temperature for practice of the 
present invention is that temperature at which it can be safely operated 
in the liquid phase. Retention time in the primary reactor Rl should also 
be such that there is no unreacted beta picoline or beta picoline 
hydrochloride in vent line 26 or in the liquid passed to the secondary 
reactor R2 through line 34. In what is considered the best mode for 
practice of the invention (Example 1), the secondary reactor R2 is 
maintined at 150.degree. C. This relatively low temperature in reactor R2 
serves two purposes. It effectively slows the reaction down so further 
chlorinations are controlled and the desired end point is not overshot. In 
addition, the lower temperature in R2 helps to absorb and quench the very 
hot overhead vapor from reactor R1 and makes it easier for absorber C2 to 
be maintained at its relatively low operating temperature (140.degree. 
C.), so that it will effectively of keep the high melting point pyridines 
from being carried over into scrubbing column C1 and plugging it up. 
Secondary reactor R2, when operated at a temperature substantially lower 
than the primary reactor R1, serves as what might be termed a buffering or 
stabilizer reactor. It need not be cooler than reactor R1, however. It all 
depends on what end products are desired. 
Finishing reactors R3A and R3B are also run at a selected temperature, 
210.degree. C. in the case of Example 1, and a selected time, 12 hours in 
Example 1, to get a maximum composition of the desired products, e.g. in 
Example 1 to get 6-chloro- and 5,6-dichloro-3-trichloromethyl pyridine and 
the derivatives that go to 2,3,6-trichloro pyridines on further 
chlorination. If the reaction objective is to make a product rich in 
2,3,6-trichloro pyridine and 2,3,5,6-trichloro pyridine, secondary reactor 
R2 should be run very hot and the finishing reactors R3A and R3B also 
should be run very hot for a very long period of time, since these final 
products are "at the end of the line", from the point of view of 
progressive chlorination reaction. 
The main criteria for the absorbent charge in absorber C2 is that it is 
nonreactive at the temperature at which the absorber operates (140.degree. 
C.), is a compound or mixture of compounds having a melting point less 
than 80.degree. C., and is mutually soluble in carbon tetrachloride so 
that it doesn't plug up the scrubbing column C1, either through melting or 
freezing or lack of solubilization. The absorber charge, being 
nonreactive, is basically is a one time charge and recycled after removal 
of the absorbed product components, with only slight makeup from time to 
time. Functionally, the absorbent acts and is handled in much the same way 
as the carbon tetrachloride in the scrubbing column C1. 
The chlorination process described in Taplin U.S. Pat. No. 3,424,754 relies 
on chlorine gas sparging into the liquid reaction mass to dissolve the 
chlorine in the reaction mass and to mix alpha-picoline hydrochloride with 
the initiator charge. According to Chemical Engineering Handbook, Perry, 
3d Edition, page 1215 (1950), agitation produced by the degree of gas 
sparging involved in the process of U.S. Pat. No. 3,424,754 (estimated to 
be about 1.5 cubic foot per square foot minute at 200.degree. C.) is 
usually too mild to move immiscible liquids with appreciable density 
differences into good contact with each other. In reactions according to 
the present invention, it is a practical necessity to maintain the 
reaction mass well mixed so that there is good contact and quick 
dispersion of the beta-picoline hydrochloride into the diluent at the 
desired reaction temperatures of greater than 190.degree. C. because the 
polychlorinated pyridine diluent and the beta-picoline hydrochloride are 
immiscible and have substantially different densities (about 1.6 and about 
1.2 grams per cubic centimeter, respectively), and because beta-picoline 
hydrochloride is unstable in this temperature range, i.e. the salt tends 
to break down to its components, namely hydrogen chloride and 
beta-picoline. If there is breakdown into the components, the hydrogen 
chloride is volatile and escapes through the vent system and beta-picoline 
builds up in a lighter liquid phase. Experimentation has shown that 
chlorinating beta-picoline hydrochloride in the absence of a diluent at a 
temperature in excess of 160.degree. C. results in intractable mixtures of 
tars and polymers. Such tendency to form higher molecular weight reaction 
products increases at higher reaction temperatures. 
Yields of volatile chlorinated picolines in excess of 99% and other new 
useful products are obtained when care is taken to ensure a high partial 
pressure of chlorine and sufficient mixing and quick dispersion of the 
beta-picoline or beta-picoline hydrochloride into a chlorine rich diluent 
which does not substantially compete for the available chlorine. This is 
accomplished by sparging chlorine (in excess of that needed for the 
reaction) and beta-picoline or beta-picoline hydrochloride at closely 
spaced locations near the bottom of the reactor means containing the 
polychlorinated pyridine diluent charge. The mixing required to ensure 
adequate contact between the liquids and gas can be achieved by high gas 
flow rate sparging, mechanical agitation, or a combination of both. High 
gas flow rates as described by Braulich, A.J.; Ch. E. Journal, Volume 11, 
No. 1, pp. 73-79, can achieve mixing of a magnitude almost equivalent to 
high power input mechanical mixing. Several disadvantages are inherent in 
the use of high gas flow rates, however. They are: 
(a) high entrainment of the reactor liquids to the scrubber column C1 where 
they are scrubbed with carbon tetrachloride and must be recycled to the 
reaction system. 
(b) a large volume of chlorine gas which must be purified, dried, and 
recycled. 
Another mode of operation to enhance mixing is to combine mechanical 
agitation with chlorine gas and beta-picoline or beta-picoline 
hydrochloride sparging to achieve the desired degree of mixing and excess 
chlorine. High maintenance of mechanical seals and agitators are some of 
the disadvantages of such a mechanical agitation system. 
An increase in reactor back pressure aids in increasing the chlorine 
concentration in the reaction liquid. The stoichiometric amount of 
chlorine reacted per unit of beta-picoline fed is greater than 3:1 by 
weight. Chlorine in excess of the stiochiometric requirement is considered 
essential to ensure that the beta-picoline or beta-picoline hydrochloride 
does not form undesirable tars and polymers. Therefore, weight ratios of 
at least about 5:1 of chlorine to beta-picoline being fed are deemed 
necessary in practice of the present process. 
Care must be taken not to exceed the thermal stability of the diluent 
system. Diluents such as 6-chloro- or 5,6-dichloro-2-trichloromethyl 
pyridine can decompose vigorously at temperatures greater than 260.degree. 
C.