Preparation of N-hydrocarbylthiophosphoric triamides

Continuously fed to and mixed in a first reactor are (i) a preformed mixture of primary hydrocarbyl monoamine, tertiary amine and liquid inert organic solvent, and (ii) thiophosphoryl chloride while removing heat of reaction to maintain the reaction temperature in the range of about -20.degree. C. to about +50.degree. C. A reaction mixture containing N-hydrocarbylaminothiophosphoryl dichloride is formed. Ammonia and an effluent stream from the first reactor are continuously fed to and mixed in a second reactor in proportions of at least about 16 moles, of ammonia per mole of N-hydrocarbylaminothiophosphoryl dichloride that produce a reaction mixture containing N-hydrocarbylthiophosphoric triamide, and that keep in solution ammonium chloride co-product formed in the reaction. Heat of reaction is removed so that the temperature is high enough to keep ammonium chloride-ammonia complex from forming a solid phase in this reaction mixture, but low enough to avoid significant reduction in yield of N-hydrocarbylthiophosphoric triamide being formed. Effluent is withdrawn from the second reactor so as to maintain a substantially constant volume of reaction mixture in the second reactor. The process eliminates a difficult filtration of the co-product ammonium chloride formed in the second reaction. Also, it possible to accomplish this in a continuous process, with improved efficiency in large scale production of the N-hydrocarbylthiophosphoric triamides. Moreover, the ammonium chloride can be readily converted in the process to an industrially useful liquid co-product mixture.

BACKGROUND 
N-hydrocarbylthiophosphoric triamides are known to be effective urease 
inhibitors for use with urea-based fertilizer compositions. See, for 
example, U.S. Pat. No. 4,530,714 to J. F. Kole, et al. 
Known procedures for preparing N-hydrocarbylthiophosphoric triamides 
involve batch operations in which N-hydrocarbylaminothiophosphoryl 
dichloride (also known as N-hydrocarbylthiophoramidic dichloride) is 
formed in a first reaction, recovered, and often purified. In a second 
reaction, the N-hydrocarbylaminothiophosphoryl dichloride is reacted with 
ammonia to produce a slurry from which co-product ammonium chloride is 
separated by filtration. See for example, U.S. Pat. No. 4,530,714, 
especially Examples IX, XVII, XVIII, and XX thereof. A desirable addition 
to the art would be a process which makes it possible to efficiently 
produce large scale commercial quantities of N-hydrocarbythiophosphoric at 
high yields, especially if this could be accomplished by means of a 
continuous process. 
Filtration of the co-product ammonium chloride from the reaction product 
mixture can be a difficult and time-consuming operation, especially if the 
process is being conducted on a large scale in commercial-type production 
facilities. A desirable contribution to the art would be a process wherein 
the filtration of co-product ammonium chloride formed in the production of 
N-hydrocarbylthiophosphoric triamides can be eliminated. An additional 
desirable contribution would be to enable formation of a useful liquid 
co-product mixture containing the ammonium chloride formed in the process. 
The NH.sub.4 Cl and NH.sub.3 binary system has been discussed in the 
literature. See, for example, Hideki Yamamoto, Seiji Sanga, and Junji 
Tokunaga, The Canadian Journal of Chemical Engineering, Vol. 66, February 
1988, pp 127-130 ("Measurement of Heat of Mixing for Ammonium 
Chloride+Ammonia at 25 C"); James Kendall and J. G. Davidson, J. Am. Chem. 
Soc. 1920, Vol. 42, pp 1141-1145 ("Addition Compounds of Ammonia with the 
Ammonium Halides"); and Sueyoshi Abe, Kyozo Watanabe, and Tatsusaburo 
Hara, J. Soc. Chem. Ind. Japan, 1935, Vol, 38, pp 1402-1406 ("Solubilities 
and Vapor Pressures of NH.sub.4 Cl+NH.sub.3 System"). 
THE INVENTION 
In accordance with this invention, novel process technology is provided 
which eliminates the need for filtration of the co-product ammonium 
chloride formed in the production of N-hydrocarbylthiophosphoric 
triamides. In addition, this invention makes it possible to achieve this 
beneficial result in a continuous process, which thus contributes 
substantially to the efficiency with which N-hydrocarbylthiophosphoric 
triamides can be produced on a large scale. Moreover, this invention makes 
it possible, pursuant to a preferred embodiment, to form a useful liquid 
co-product mixture containing the ammonium chloride formed in the process. 
In one embodiment of this invention N-hydrocarbylthiophosphoric triamide is 
produced by a process which comprises: 
a) continuously feeding to and mixing in a first reaction chamber (i) a 
preformed mixture of hydrocarbyl primary amine, tertiary amine and at 
least one liquid inert organic solvent, and (ii) thiophosphoryl chloride 
and maintaining the temperature of the reaction mixture in the range of 
about -20.degree. to about +50.degree. C., to produce a reaction mixture 
containing N-hydrocarbylaminothiophosphoryl dichloride; 
b) continuously feeding and mixing in a second reaction chamber (i) an 
effluent stream of reaction mixture formed in the first reaction chamber, 
and (ii) ammonia in proportions (1) that are at least about 16 moles of 
ammonia per mole of N-hydrocarbylaminothiophosphoryl dichloride, (2) that 
produce a reaction mixture containing N-hydrocarbylthiophosphoric 
triamide, and (3) that keep in solution substantially all of the ammonium 
chloride co-product formed in the reaction, and maintaining the 
temperature of the reaction mixture high enough to keep ammonium 
chloride-ammonia complex from forming an appreciable amount of solid phase 
in said reaction mixture, but low enough to avoid significant reduction in 
yield of N-hydrocarbylthiophosphoric triamide; and 
c) withdrawing effluent from the second reaction chamber at a rate 
sufficient to maintain a substantially constant volume of reaction mixture 
in the second reaction chamber. 
The reactions of a) and of b) are both exothermic reactions. Thus to 
maintain the desired temperature in the reaction of a) it is preferred to 
remove heat of reaction at a rate sufficient to keep the temperature 
within the desired range. If desired, the reactants and/or solvent can be 
precooled and thereby serve as a means of assisting in controlling the 
temperature. Likewise to maintain the temperature in the reaction of b) 
above, it is preferred to remove heat of reaction from the mixture formed 
in b) at a rate of removal such that the temperature remains within the 
limits specified above. Again it is also possible to precool either or 
both of the feeds going to the above second reaction chamber. 
Unless a portion of the N-hydrocarbylaminothiophosphoryl dichloride 
produced in the first reaction chamber is to be used for other purposes, 
such as for the synthesis of one or more flame retardants or lubricant 
additives, it is preferable to withdraw the effluent from the first 
reaction chamber and feed this effluent to the second reaction chamber at 
a rate that maintains a substantially constant volume of reaction mixture 
in the first reaction chamber. 
In another preferred embodiment, the effluent from c) above is 
caused/allowed to separate into an inorganic phase comprising 
predominately ammonia, ammonium chloride and co-product thiophosphoric 
triamide, and an organic phase comprising predominately 
N-hydrocarbylthiophosphoric triamide, tertiary amine, solvent and 
dissolved ammonia, and the resultant phases are separated from each other. 
Such a separation is readily conducted, even on a large scale. 
The above and other embodiments of this invention will be apparent from the 
ensuing description, accompanying drawings, and appended claims.

FURTHER DETAILED DESCRIPTION 
Reactants 
The principal reactants in the process are primary hydrocarbyl monoamine, 
thiophosphoryl chloride (PSCl.sub.3), and ammonia. The hydrocarbyl group 
of the primary amine reactant can be any hydrocarbyl group such as alkyl, 
cycloalkyl, alkenyl, cycloalkenyl, alkynyl, aryl, aralkyl, or 
cycloalkylalkyl group. Typically the hydrocarbyl group will contain up to 
about 20 carbon atoms, and preferably up to about 10 carbon atoms. Of such 
compounds monoalkyl amines, monocycloalkylamines and monoarylamines are 
preferred, and of these, monoalkyl amines having 2 to 6 carbon atoms in 
the molecule are especially preferred. Most preferred as the amine 
reactant is n-butylamine. 
The ammonia is preferably stored and handled in its liquid form. However, 
gaseous ammonia, or mixtures of gaseous and liquid ammonia, can also be 
used, if desired. 
Solvent 
As noted above, at least one liquid inert organic solvent is employed in 
the process. While any solvent meeting these criteria can be used, it is 
preferred to use a solvent that boils at one or more temperatures in the 
range of about 40.degree. to about 120.degree. C. and preferably in the 
range of about 55.degree. to about 90.degree. C. at ordinary atmospheric 
pressures. Thus use can be made of liquid paraffinic, cycloparaffinic, 
and/or aromatic hydrocarbons, liquid halocarbons and halohydrocarbons, 
ethers, esters, and other organic liquids which do not interfere with the 
desired reactions. Ethers, especially cyclic ethers such as 1,4-dioxane, 
1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, and 
tetrahydropyran, are preferred. Preferably the solvent is recovered, most 
preferably by one or more flash distillations, and is used as recycle in 
the process. 
Of the various suitable solvents, tetrahydrofuran is particularly preferred 
because of its good solvency properties, desirable boiling point, ready 
availability and low cost. In a well-designed facility for the process of 
this invention, about 99% of the tetrahydrofuran can be recovered, and 
preferably the recovered tetrahydrofuran is used as recycle in the 
process. 
HCl Acceptor 
A tertiary amine is used as an acid acceptor for the by-product HCl formed 
in the first reaction. It is not consumed by the process, and in the 
preferred embodiments the tertiary amine is recycled in the process. 
Suitable tertiary amines include heterocyclic tertiary amines such as 
3-picoline (bp ca. 143.degree.-144.degree. C.), 4-picoline (bp ca. 
143.degree. C.), 4-chloropyridine (bp ca. 147.degree.-148.degree. C.), 
3-ethylpyridine (bp ca. 165.degree.-166.degree. C.), and 4-ethylpyridine 
(bp ca. 166.degree. C.), and trialkylamines such as tripropylamine (bp ca. 
155.degree.-158.degree. C.), and tri-sec-butylamine (bp ca. 
191.degree.-192.degree. C.). Relatively low boiling tertiary amines such 
as pyridine (bp ca. 115.degree. C.), 2-picoline (bp ca. 128.degree. C.), 
N,N-diethylmethylamine (bp 63.degree.-65.degree. C.), and triethylamine 
(bp ca. 89.degree. C.) are preferred. 
From a cost-effectiveness standpoint, triethylamine is a particularly 
preferred tertiary amine. In a well-designed facility for the process of 
this invention, about 99% of the triethylamine can be recovered, and 
preferably the recovered triethylamine is used as recycle in the process. 
Thus the process is capable of producing suitably high purity product(s) 
while at the same time being both highly efficient and environmentally 
friendly. 
Reaction Conditions 
The first stage reaction involving reaction between thiophosphoryl chloride 
and the primary amine is typically conducted at one or more temperatures 
in the range of about -20.degree. to about 50.degree. C., and preferably 
at one or more temperatures in the range of about 0.degree. to about 
15.degree. C. The pressure conditions for this reaction are not important 
unless evaporative cooling is used to control reactor temperature. If 
using evaporative cooling, the reactor pressure is controlled such that 
the reaction mass will boil at the desired reactor temperature. 
Proportions of reactants in the first stage are essentially equimolar, and 
the mole ratio of primary amine to thiophosphoryl chloride is typically in 
the range of about 0.95 to about 1.1 moles of amine per mole of the 
PSCl.sub.3. For best results, the mole ratio of primary amine to 
thiophosphoryl chloride is in the range of about 1.00 to about 1.05 moles 
of amine per mole of the PSCl.sub.3. 
The desired product of the first stage reaction is an 
N-hydrocarbylaminophosphoryl dichloride. Such compounds have the formula, 
(H)(R)N--P(.dbd.S)Cl.sub.2, where R is a hydrocarbyl group. 
As noted above, primary hydrocarbyl monoamine and tertiary amine are 
charged to the first reaction chamber as a preformed mixture which also 
includes one or more solvents, and the proportions of primary hydrocarbyl 
monoamine and tertiary amine in such preformed mixture are typically in a 
molar ratio range of about 1:1 to about 1:1.5 respectively. Typically, the 
proportions of such preformed mixture and the thiophosphoryl chloride fed 
to the first reaction chamber are such that per mole of thiophosphoryl 
chloride there are in the range of about 0.95 to about 1.1 moles of 
primary hydrocarbyl monoamine and in the range of about 0.95 to about 1.5 
moles of tertiary amine. 
In the second stage reaction between the N-hydrocarbylaminothiophosphoryl 
dichloride and ammonia, one or more temperatures in the range of about 
5.degree. to about 50.degree. C. and one or more pressures in the range of 
about 15 to about 100 psig are typically employed, with the proviso that 
in any given situation, the temperature is high enough to keep the 
co-product ammonium chloride-ammonia complex in solution, yet low enough 
to avoid significant reduction in yield (e.g., a loss of more than 5 wt % 
yield) of N-hydrocarbylthiophosphoric triamide. The 
N-hydrocarbylthiophosphoric triamides have the formula, 
(H)(R)N--P(.dbd.S)(NH.sub.2).sub.2, where R is a hydrocarbyl group. 
Preferred conditions for the second stage reaction, especially when 
producing N-n-butylthiophosphoric triamide involve one or more 
temperatures in the range of about 8.degree. to about 15.degree. C. and 
one or more pressures in the range of about 25 to about 40 psig. In the 
second stage reaction the proportions of ammonia to the 
N-hydrocarbylaminothiophosphoryl dichloride are such that there are at 
least about 16 moles of ammonia, and preferably at least about 20 moles of 
ammonia, per mole of N-hydrocarbylaminothiophosphoryl dichloride. In 
theory there is no upper limit on the amount of ammonia used as the excess 
ammonia does not materially interfere with the desired reactions. Thus the 
amount of excess ammonia above the foregoing minimum amounts is largely a 
matter of common sense and practicality; i.e., the larger the excess, the 
larger the amounts of ammonia that need to be recovered and recycled. 
The amount of solvent used in the process is an amount sufficient to 
provide a suitably fluid reaction medium, and thus is largely a matter of 
choice, common sense, and practicality. Thus unduly excessive amounts of 
solvent should be avoided as the larger the amount used, the larger the 
amount that needs to be recovered and recycled. 
The first stage and the second stage reactions are both exothermic 
reactions and thus suitable equipment should be provided to ensure that 
adequate cooling capacity is available for each of the two stages. In a 
preferred embodiment, the heat of reaction from the first stage reaction 
mixture is removed by continuously circulating a portion of that reaction 
mixture from the first stage reaction chamber into a heat exchanger where 
heat is removed by a cooling medium, and thence back to the first reaction 
chamber. In a particularly preferred embodiment the heat of reaction from 
the first stage reaction mixture is removed by controlling the pressure 
such that the reaction mixture boils and the vapors from the boiling 
mixture are condensed in a dephlegmator heat exchanger and refluxed back 
to the first reaction chamber. 
In another preferred embodiment the reaction mixture in the first reaction 
chamber is continuously stirred or agitated by a mechanical stirrer or 
agitator, and the preformed mixture and the thiophosphoryl chloride are 
both fed into such reaction mixture below the surface thereof and in close 
proximity to the stirrer/agitator to ensure prompt and rapid mixing of 
these feeds. 
In still another preferred embodiment, the heat of reaction from the second 
stage reaction mixture is removed by continuously circulating a portion of 
that mixture through a heat exchanger and thence back to the second 
reaction chamber. 
Alternatively, the first and the second reaction chambers are both heat 
exchangers that provide a residence time in the range of 1 to about 10 
minutes and that provide sufficient heat exchange surface in contact with 
the reaction mixture therein to enable removal of the heat of reaction 
generated within such residence time. 
Effluent from the second reaction chamber is withdrawn at a rate sufficient 
to maintain a substantially constant volume of reaction mixture in the 
second reaction chamber, and preferably, the effluent from the first 
reaction chamber is withdrawn therefrom and fed to the second reaction 
chamber at a rate that maintains a substantially constant volume of 
reaction mixture in the first reaction chamber. 
Preferably, the effluent from the second reaction chamber is caused/allowed 
to separate into (A) an inorganic phase comprising predominately ammonia, 
ammonium chloride and co-product thiophosphoric triamide, and (B) an 
organic phase comprising predominately N-hydrocarbylthiophosphoric 
triamide, tertiary amine, solvent and dissolved ammonia, and the resultant 
phases are separated from each other. This is preferably accomplished by 
allowing the effluent to stand in a quiescent state for a suitable period 
of time for the distinct separate phases to form and then draining off the 
lower layer. Other separation techniques such as siphoning off the top 
layer, use of emulsion breakers, and like procedures can be used whenever 
deemed necessary or desirable. After effecting this separation, it is 
preferred to separate ammonia along with a portion of the solvent from the 
isolated organic phase, and compress and cool this ammonia-solvent mixture 
to form a recycle mixture of liquid ammonia and solvent. This separation 
also provides as the residual mixture, a concentrated product mixture 
comprising predominately N-hydrocarbylthiophosphoric triamide, and 
residual solvent and tertiary amine. The recycle mixture of ammonia and 
the solvent remaining therewith is recycled for use as a portion of the 
ammonia feed to the second reaction chamber. 
The concentrated product mixture is then processed so as to separate and 
recover tertiary amine and solvent therefrom, and the tertiary amine and 
solvent collected therewith are recycled for use as a portion of the feed 
for making the preformed mixture to be fed to the first reaction chamber. 
The residual portion of the organic phase remaining after this separation 
comprises N-hydrocarbylthiophosphoric triamide, and only small residual 
amounts of solvent and tertiary amine. Thereupon the 
N-hydrocarbylthiophosphoric triamide and the small residual amounts of 
solvent and tertiary amine are separated from each other to yield a 
purified N-hydrocarbylthiophosphoric triamide product. Either or both of 
this separated residual solvent and tertiary amine is/are recycled for use 
as a portion of the feed for making the preformed mixture fed to the first 
reaction chamber. 
The specific techniques used for effecting the foregoing separations will 
depend to some extent upon the identities of the materials making up the 
mixtures being processed. Usually distillations or flash distillations 
will be employed whenever this is feasible. However, in any case where 
such distillation procedures are not feasible because of the properties of 
the materials being processed, recourse may be had to other separation 
techniques such as solvent extraction procedures, chromatographic 
separation procedures, or the like. 
The following Example is given to illustrate a preferred embodiment of the 
process of this invention and is not intended to limit the scope of this 
invention. Unless otherwise specified all quantities and percentages are 
by weight. 
EXAMPLE 
First Stage Reaction 
Referring now to the embodiment depicted in FIGS. 1 and 2, triethylamine 
(TEA) and tetrahydrofuran (THF) are fed to the first reactor 10 as a 
mixture from a recycle solvent tank 12. Make-up THF and TEA stored in 
tanks 14 and 16, respectively, are added to recycle tank 12 as needed to 
maintain a constant solvent composition going to reactor 10. The feed rate 
is determined by maintaining a constant feed ratio of TEA to PSCl.sub.3, 
based on periodic analyses of TEA in the TEA/THF mixture. This analysis 
should have .+-.400 ppm (or better) resolution to allow control of the 
TEA/PSCl.sub.3 mole ratio within 1-2% of target (1.10.+-.0.02). TEA is 
consumed in this first reaction step and regenerated in the second 
reaction, while THF acts only as a solvent. 
In first reactor 10, PSCl.sub.3 (mass flow controlled) is reacted with 
n-butylamine (NBA) to form N-n-butylaminothiophosphoryl dichloride (BATPD) 
intermediate. The NBA is stored in tank 20 under nitrogen. Two different 
streams are fed to the reactor: 1) neat PSCl.sub.3 from tank 18; and 2) 
mixed feeds of recycle THF/TEA and NBA from static mixer 22. The NBA feed 
rate is proportioned to the PSCl.sub.3 feed rate to maintain a mole ratio 
of approximately 1.01 moles of NBA per mole of PSCl.sub.3 and the THF/TEA 
feed rate is proportioned to the PSCl.sub.3 feed rate to maintain a mole 
ratio of approximately 1.10 moles of TEA per mole PSCl.sub.3. 
Mixing is considered highly important for achieving very high efficiency in 
this reaction, and thus the NBA and THF/TEA are combined in static mixer 
22 upstream of the reactor, and introduced to the reactor through a dip 
leg just above the agitator. The PSCl.sub.3 is fed neat through a separate 
dip leg into the same area of the reactor. The HCl formed as co-product 
reacts with the TEA to form a TEA.cndot.HCl salt which precipitates from 
the reaction mass. 
The reaction to form this intermediate BATPD is very exothermic, and most 
of this heat of reaction is removed by refluxing the THF solvent in a 
dephlegmator 24. Recommended reaction conditions in reactor 10 are 
0.degree.-15.degree. C. and, to allow solvent reflux, about 40-70 mm Hg 
(0.8-1.4 psia) pressure. Feed rates are adjusted to provide a three hour 
residence time in reactor 10. Since this reaction is very fast (1-2 
minutes maximum) and irreversible, holdup in this reactor simply provides 
surge capacity for the process. Additional cooling for the reaction is 
provided by the reactor jacket and a pump-around loop through heat 
exchanger 26. The reaction mass discharge is fed continuously to the 
second reactor 30 via level control on first reactor 10. 
Second Stage Reaction 
In the second reactor 30, the intermediate BATPD from reactor 10 reacts 
with ammonia to give the final product, N-(n-butyl)thiophosphoric triamide 
(BTPT). The HCl generated by the reaction also reacts with ammonia to form 
ammonium chloride, and the TEA.cndot.HCl also reacts with ammonia to 
liberate the TEA and form additional ammonium chloride. A total of 5 moles 
of ammonia per mole BATPD is consumed in this step. This reaction is very 
exothermic, and the heat of reaction is removed via a pump-around loop 
through heat exchanger 32. Reaction conditions for reactor 30 are 
8.degree.-15.degree. C. and 25-38 psig, and the residence time is about 90 
minutes. 
Ammonia is fed by pressure control to reactor 30, and the ammonia feed 
consists of the recycle stream from product phase column 33 and fresh 
ammonia from storage vessel 34. A total of about 23-25 moles of ammonia 
per mole of BATPD is fed to reactor 30. Of this, about 14 moles is fresh 
ammonia. In order to keep the ammonium chloride co-product in solution, 
this amount of excess ammonia is used so that the ammonium chloride and 
the ammonia form a separate liquid phase containing about three moles of 
ammonia per mole of ammonium chloride. At lower ammonia levels, the 
ammonium chloride precipitates from the solution, forming a slurry which 
tends to cause pluggage problems. If the temperature in reactor 30 is 
allowed to go below about 5.degree.-6.degree. C., the ammonium 
chloride/ammonia complex (NH.sub.4 Cl.cndot.3NH.sub.3) will precipitate, 
which can also cause pluggage problems. Effluent discharge from this 
reactor is controlled to maintain constant level in reactor 30, and is 
sent to phase separator 36. 
Phase Separation 
The reaction mass coming from reactor 30 separates into two phases in phase 
separator 36, namely, (A) an inorganic phase containing ammonia, ammonium 
chloride, most of the by-product thiophosphoric triamide (TPT), and small 
amounts (&lt;1%) of BTPT, THF and TEA; and (B) an organic phase containing 
THF, TEA, BTPT, some of the TPT, the other phosphorus by-product 
impurities, and ammonia. These are separated by gravity in separator 36 by 
employing a residence time therein of approximately 45 minutes. The 
separated phases are then stored, respectively, in two vessels, vessel 38 
for the organic phase mixture and vessel 40 for the inorganic phase 
mixture. All three of these vessels (separator 36, and vessels 38 and 40) 
are maintained at the same pressure (40-50 psig) to allow gravity flow, 
and are cooled to hold a constant temperature (and thus constant 
composition and pressure). In the preferred system depicted, make-up 
ammonia can be fed directly to any of these drums from storage vessel 34, 
if the ammonia concentration becomes low enough to cause ammonium chloride 
precipitation. 
Organic Phase Distillation 
The organic phase from vessel 38 is first distilled in product phase column 
33 to remove dissolved ammonia and most of the solvents, i.e., THF and 
TEA. The ammonia stream (which contains about 25% THF) is recycled 
directly to the second stage reaction in reactor 30; the combined THF and 
TEA solvents are taken as a vapor side-stream from the column sump, 
condensed in condenser 35, and transferred via pump 37 to recycle solvent 
tank 12. The concentrated (bottoms) product solution (containing about 50% 
THF) is transferred to feed drum 42. 
Column 33 is operated at about 7-8 psia pressure and 55.degree. C. bottoms 
temperature to minimize thermal decomposition of the product. Built into 
the upper portion of column 33 is column dephlegmator condenser 46 which 
is used to cool the vapor and condense most of the THF as internal reflux. 
Two 2-stage blowers, 48 and 50 compress the ammonia vapor sufficiently 
(about 35 psig) to allow condensation and cooling with refrigerated 
Dowtherm.RTM. J coolant. This liquid ammonia/THF stream is then routed 
directly back to reactor 30. 
Inorganic Phase Dilution 
Typically, the inorganic phase (chiefly composed of ammonia and ammonium 
chloride) is first diluted with water and stored in storage tank 56, 
analyzed, and batch transferred to a railcar 58 prior to shipment. 
Preferably, the water added is proportioned to yield a co-product solution 
containing about 25% water, about 38% dissolved ammonium chloride and 
about 37% ammonia, which is a useful industrial product mixture. In order 
to suit specific industrial uses for the ammonia and ammonium chloride 
co-products, the amount of water added can be varied, and in fact, the 
addition of water can be entirely eliminated if desired. 
Wiped-film Evaporation. Nitrogen Strip and Optional Dilution 
The concentrated BTPT/THF/TEA solution from feed drum 42 is fed (by flow 
control) to wiped-film evaporator 44, to remove most of the remaining THF 
and TEA solvents. Wiped-film evaporator 44 is operated at about 110 mm Hg 
absolute and 95.degree. C., producing a bottoms product containing &lt;2% 
residual solvents. The solvent vapors from wiped-film evaporator 44 are 
condensed in heat exchanger 62, and the condensed solvent is recycled to 
recycle solvent tank 12 via pump 64. The bottoms product (predominately 
BTPT) from wiped-film evaporator 44 is fed (by level control on the 
bottoms receiver pot and pump 66) directly to the upper portion of 
nitrogen stripping column 68, in which hot nitrogen (about 65.degree. C., 
atmospheric pressure) is passed upwardly in countercurrent flow to the 
down-flow product stream to further reduce the small residual solvent 
content of the BTPT to about 0.5% maximum. This neat product stream is 
then gravity fed into storage vessel 70 in which, if desired, it can be 
mixed with one or more solvents for storage and ultimate shipment. 
As described in commonly-owned co-pending U.S. application Ser. No. Case 
SI-7025!, filed contemporaneously herewith!, all disclosure of which is 
incorporated herein by reference, it is highly advantageous to use a 
wiped-film evaporator operated at a suitable temperature in the range of 
about 60.degree. to about 140.degree. C., and at a suitable pressure 
higher than about 90 torr absolute for separating most of the remaining 
solvents from the BTPT/THF/TEA solution. Use of wiped-film evaporator 
operated under such suitable conditions avoids solids formation on the 
heating surface of the wiped-film evaporator, and successfully overcomes 
problems associated with the recovery of N-alkylthiophosphoric triamides 
from tetrahydrofurantriethylamine solutions, especially thermal 
degradation of the triamide product, while at the same time providing a 
separation process which not only is ideally-suited for large scale 
commercial operation but which, in addition, actually improves the 
efficiency of the product recovery step itself. 
As described in commonly-owned co-pending U.S. application Ser. No. Case 
SI-7026!, filed contemporaneously herewith!, all disclosure of which is 
incorporated herein by reference, the temperature of the mixture in which 
the triamide and ammonium chloride are being co-produced in a suitable 
organic solvent by reaction between N-hydrocarbylaminothiophosphoryl 
dichloride and a suitable amount of initially added and/or incrementally 
added ammonia (i.e., at least 16 and preferably at least 20 moles of 
ammonia per mole of ammonium chloride being formed) should be maintained 
above about 6.degree. C. but below the temperature at which the triamide 
undergoes significant thermal degradation. A separate liquid phase 
containing the ammonium chloride (and ammonia) is formed, and can be 
readily separated, for example by a gravity separation, decantation 
procedures, or the like. At temperatures of about 6.degree. C. and below, 
an ammonia-ammonium chloride complex forms as a solid phase which can 
cause pluggage of reaction equipment and which in any event detracts from 
the efficiency of the overall operation. Thus such low temperatures should 
be avoided. However, if in any special case where chemical or other 
considerations require or involve running the reaction at 
.ltoreq.6.degree. C., the procedure can be modified to conduct the 
reaction at the lower temperature where the solid ammonia/ammonium 
chloride complex forms, and heating the final reaction mass above 
6.degree. C. to melt the complex thus forming the separate liquid 
ammoniate phase to allow phase separation and removal. The thermal 
degradation temperatures of the triamides usually differs at least to some 
extent from compound to compound, and thus the maximum permissible 
temperature may vary from compound to compound. In general, however, 
significant thermal degradation of the triamides is not incurred at 
temperatures of up to about 50.degree. C. and in some cases perhaps not 
until up to still higher temperatures. 
As described in commonly-owned co-pending U.S. application Ser. No. Case 
SI-7028!, filed contemporaneously herewith!, all disclosure of which is 
incorporated herein by reference, it is desirable to inhibit the above 
aqueous solution of ammonia and ammonium chloride stored, in storage tank 
56, against ferrous metal corrosion by dissolving therein a ferrous metal 
corrosion-inhibiting amount of at least one water-soluble salt or oxide of 
zinc, aluminum, arsenic, antimony or bismuth, such as Bi.sub.2 O.sub.3, 
ZnO, ZnCl.sub.2, AlCl.sub.3, and Al.sub.2 O.sub.3. It is believed that 
corrosion by the uninhibited solutions is due to the presence of trace 
amounts of one or more impurities remaining in the solution, which 
impurities are probably, but not necessarily, one or more 
sulfur-containing impurities. Amounts of 1000 ppm (wt/wt) of such 
inhibitors have proven very effective, but any corrosion-inhibiting amount 
consistent with end-product usage and specifications can be employed. 
The following experiments illustrate some of the distinct advantages 
accruing from the practice of this invention as compared to conventional 
process technology for producing N-hydrocarbylthiophosphoric triamides. 
Runs of the Invention: 
BATPD and BTPT reactions were conducted in two, 1-liter reactors in series. 
A solution of PSCl.sub.3 and THF was co-fed with a solution of NBA, TEA, 
and THF into the BATPD reactor at constant flow rates to maintain the 
desired NBA:TEA:PSCl.sub.3 feed ratios. The resulting BATPD reaction 
slurry was co-fed with NH.sub.3 into the BTPT reactor. The BATPD reactor 
effluent rate was adjusted to maintain a constant level therein. The 
NH.sub.3 feed was set to maintain a constant molar ratio of NH.sub.3 to 
phosphorus (as PSCl.sub.3) in the feeds to the BTPT reactor. The residence 
time in each of the reactors was about 5 minutes with reaction 
temperatures of 45.degree.-50.degree. F. (ca. 7.degree.-10.degree. C.) in 
each reactor. BATPD reaction pressure was atmospheric and the BTPT 
reaction pressure was 24-28 psig. The BTPT concentration in the reactor 
product solution was 7-8 wt %. The reactors' flows were maintained until 
the reactors reached steady state. At this point, a sample of the effluent 
from the BTPT reactor was taken. NH.sub.4 Cl was removed for the BTPT 
reactor samples, excess ammonia was vented off, and BTPT was recovered by 
solvent evaporation on a Rotovap.RTM. evaporator at a pressure of 5 mm Hg 
absolute. Table 1 summarizes the results of two runs made in this fashion. 
TABLE 1 
______________________________________ 
Experiments Conducted Pursuant to the Invention 
Experi- 
Mole Feed Ratios 
NBPT Purity 
NBPT Yield 
% Product 
ment NBA:TEA:NH.sub.3 :PSCl.sub.3 
wt % on P, % Closure 
______________________________________ 
Run A 1.04:1.06:25.4:1 
92.4 92.4 97.5 
Run B 1.03:1.04:22.0:1 
93.3 90.1 97.2 
______________________________________ 
Runs Not of the Invention: 
Both the BATPD and the BTPT reactions were carried out in a 1-liter high 
pressure glass reactor equipped with a cooling coil. First PSCl.sub.3 was 
charged to the reactor. Some THF was then added in order to raise the 
liquid level above the agitator blades. TEA and NBA were premixed in THF 
in a dropping funnel under a nitrogen atmosphere. The TEA/NBA/THF solution 
was then slowly fed to the PSCl.sub.3 /THF solution while maintaining the 
reactor temperature at approximately 50.degree. F. (ca. 10.degree. C.). 
The BATPD reaction mass was kept at 50.degree. F. (10.degree. C.) until 
the ammonia addition the next day. The ammonia addition normally took 
about 15-20 minutes to complete during which time the reactor was kept at 
approximately 50.degree. F. At the end of the BTPT reaction, the pressure 
was 25-30 psig. The product solution, which contained 7-8 wt % BTPT, was 
separated from co-product ammonium chloride and excess ammonia. The BTPT 
was finally recovered by removing solvent on a Rotavap.RTM. evaporator at 
5 mm Hg absolute. Table 2 summarizes the results of two runs made in this 
fashion. The runs differed primarily in the TEA to PSCl.sub.3 ratio in the 
BATPD reactor and the ammonia-to-phosphorus ratio used in the BTPT 
reactor. 
TABLE 2 
______________________________________ 
Experiments Not Conducted Pursuant to the Invention 
Experi- 
Mole Feed Ratios 
BTPT Purity 
BTPT Yield 
% Product 
ment NBA:TEA:NH.sub.3 :PSCl.sub.3 
wt % on P, % Closure 
______________________________________ 
Run C 1.02:1.20:26.7:1 
86.4 84.6 89.0 
Run D 1.02:1.02:32.6:1 
86.1 85.2 90.4 
______________________________________ 
It can be seen that the purity of the N-hydrocarbylthiophosphoric triamide 
obtained with the use of the present invention was 6-7% higher than that 
obtained using the prior art with the yield improvement coming at the 
expense of unidentifiable phosphorus impurities. 
It is to be understood that the reactants and components referred to by 
chemical name or formula anywhere in the specification or claims hereof, 
whether referred to in the singular or plural, are identified as they 
exist prior to coming into contact with another substance referred to by 
chemical name or chemical type (e.g., another reactant, a solvent, or 
etc.). It matters not what preliminary chemical changes, transformations 
and/or reactions, if any, take place in the resulting mixture or solution 
or reaction medium as such changes, transformations and/or reactions are 
the natural result of bringing the specified reactants and/or components 
together under the conditions called for pursuant to this disclosure. Thus 
the reactants and components are identified as ingredients to be brought 
together in connection with performing a desired chemical reaction or in 
forming a mixture to be used in conducting a desired reaction. 
Accordingly, even though the claims hereinafter may refer to substances, 
components and/or ingredients in the present tense ("comprises", "is", 
etc.), the reference is to the substance, component or ingredient as it 
existed at the time just before it was first contacted, blended or mixed 
with one or more other substances, components and/or ingredients in 
accordance with the present disclosure. Thus the fact that a substance, 
component or ingredient may have lost its original identity through a 
chemical reaction or transformation during the course of contacting, 
blending or mixing operations, if conducted in accordance with this 
disclosure and with the application of common sense and the ordinary skill 
of a chemist, is thus wholly immaterial for an accurate understanding and 
appreciation of the true meaning and substance of this disclosure and the 
claims thereof. 
Each and every patent or other publication referred to in any portion of 
this specification is incorporated in toto into this disclosure by 
reference, as if fully set forth herein. 
This invention is susceptible to considerable variation in its practice. 
Therefore the foregoing description is not intended to limit, and should 
not be construed as limiting, the invention to the particular 
exemplifications presented hereinabove. Rather, what is intended to be 
covered is as set forth in the ensuing claims and the equivalents thereof 
permitted as a matter of law.