447
Ind. Eng. Chem. Prod. Res. Dev. 1905, 24, 447-451 39.3
--
(2) monitoring and assessing service life left in used lubricants; and (3) differentiation and characterization of oils according to their crude source and refining severity.
h
Acknowledgment The authors are indebted to C. Wolfe and G . D. Mendenhall for helpful discussions and assistance in designing and constructing the CL apparatus.
Literature Cited
roo
ooo
IOO
WAVELENOTH
40
'
roo
sso 30
'
080
20
o w reo
'
060
10
660
100
'
OM 0
TIYE IN MINUTES FROM THE BEQlNNlNQ OF OXIDATION TO START OF THE SCAN 1380-800m)
Figure 13. Changes in CL spectrum with time for tetracosane at 202 O C during the first 50 min of oxidation; O2flow, 130 cm3/min.
cations in the petroleum laboratory and in industry. In certain areas of application, it will be especially attractive because of the very short test time and the relatively low cost of analysis. The principal areas of application of CL which are shown in this work are the following: (1)determinations of relative oxidative stabilities of base oils and lubricants;
Clark, D. 6.; Weeks, S. J.; Hsu, S. M. ASLE Preprlnt, No. 82-AM5A-1, Cinclnnati, OH, 1982. Goldenbera. V. I.: Shmulovlch. V. G. Pet. Chem. USSR 1977, 79. 42. Kellogg, R:E. J. Am. Chem. Soc.lWa, 97, 5433. Mendenhall, G. D. Angew. Chem. 1977, 89(4), 220. Reich. L.; Stivala. S. S. "Autoxidation of Hydrocarbons and Polyoleflns"; Marcel Dekker, Inc.: New York, 1969; p 9. Spilners, I.J.; Hedenbug, J. F. "Chemiluminescence Measurements in LiquM Phase Autoxidation of Hydrocarbon Materlals"; Abstracts, The Pittsburgh Conference on Analytical Chemlstry, 1984. Vasilev, R. F.; Karpukchin, 0. N.; Shlyapintokh, V. Ya. Do&/. Akad. Nauk SSR 1959, 725(1), 106. Vasilev, R. F.; Vichutinski, A. A. Do&/. Akad. Nauk SSSR 19628, 742(3), 615. Vasilev, R. F.; Vichutinski, A. A. Do&/. Akad. N a k SSSR 1962b, 145(6), 1301.
Received for review September 6 , 1983 Revised manuscript received January 16, 1985 Accepted M a r c h 13, 1985
Process and Reactor for Dimethyl Phosphite Manufacture Constantln I. Manolache,' Ollvlu V. Popa, D h l B I. Socaclu, and Ioana C. Alexandru Chemical Works of Craiove, Craiova 7 700, Roman&
A new process and a new reactor type to be used in the chemical industry for the manufacture of dimethyl phosphite or other dialkyl phosphites have been developed. Phosphorous trichloride vapor and liquld methanol are brought into reaction in backward flow, and the reaction temperature is maintained by controlling the flow of the methanol introduced. The reactor is an absorptiokcolumn type with packing and has a reaction chamber with an inner spacer f i e d under the phosphorous trichloride feeding nozzle. Above the reaction chamber there is a reaction-perfecting and gas-absorption zone, a methanol feeding nozzle, and a reflux condenser. The reactor low side is provided with a shock cooler to cool the product. Dissipation of the reaction heat takes place without the use of a solvent. The reactor has small dimensions and can be completely automatized. Due to the small volume of the reaction space, the undesirable secondary reactions are diminished, and an output of over 90% is achieved.
A new process and a new reactor type to be used in the chemical industry for the manufacture of dimethyl phosphite or other dialkyl phosphites has been developed. These are important intermediary compounds used for obtaining insecticides, fireproof materials, and other products. In the dimethyl phosphite manufacturing process, the phosphorous trichloride vapors and liquid methanol are brought into reaction in backward flow. The reaction temperature is maintained by evaporating the methanol excess, and the methanol vapors, carried along with methyl chloride, are separated through condensation and recirculated by refluxing. In reactor is an absorption-column type with packing and has a reaction chamber and an inner spacer mounted under the phosphorous trichloride feeding nozzle. There is a reaction-perfecting and gas-absorption zone, a meth-
an01 feeding nozzle, and a reflux condenser above the reaction chamber. The reactor low side is provided with a shock cooler to cool the product. The dimethyl phosphite is obtained from the phosphorous trichloride reaction with methyl alcohol. [(CH,O),P + 3HC11 3CH30H + PCl, (CH30)ZPHO + CH&l+ 2HC1 (1) This is a fast and exothermic reaction generating approximately 50 kcal/mol. Dimethyl phosphite is not the only reaction product, as the hydrochloric acid present reacts with dimethyl phosphite, resulting in monomethyl phosphite and phosphorous acid, respectively, as additional products.
-
(DH,0)2PHO
-
HCl
HCl
CH,Cl+ CH,O(HO)PHO CH3C1 + (H0)zPHO (2)
0196-4321/85/1224-0447~07.5O/O 0 1985 American Chemical Society
448
Ind. Eng. Chem. Prod. Res. Dev., Vol. 24, No. 3, 1985
There are well-known dimethyl phosphite continuous synthesis processes and reactors that generally use a low boiling point solvent in order to dissipate the reaction heat and to partially degas the hydrochloric acid dissolved in the synthesis product. Using one of these processes, we obtain secondary phosphites with low molecular weight radical alkyls (more liable to acid scission). In this process, 3 mol of alcohol and 1 mol of phosphorous trichloride syrupy mixture in a low boiling point solvent are expanded in an adequate jet into an atmospheric pressure chamber. The solvent is maintained under pressure at low temperature. A solvent-significant evaporation takes place, carrying along, to a great extent, the hydrochloric acid formed (Chadwick, 1952). Another method of continuous production of high-purity dihydrocarbon phosphites with improved yields includes continuously bringing together and reacting separate flowing streams of phosphorous trihalide and a member selected from the group consisting of a monohydric hydrocarbon alcohol. The internal chemical reaction temperature is 30-100 "C (Campbell, 1957). There is also an industrial process that uses a taperedbottom reaction vessel in which the methanol and phosphorous trichloride are introduced through the reaction vessel low side distribution rings. The dissipation of the reaction heat and the preliminary hydrochloric acid degassing are achieved by introducing methyl chloride, which evaporates, under adiabatic conditions, in the vicinity of the reaction vessel. The reactor operates at 20 "C and 350-400-mmHg residual pressure. Another process uses a reactor consisting of one coil pipe with a water-cooling shell in which the reactantsmethanol and phosphorous trichloride-are dosed at a constant pressure. The optimum pressure at the reaction product outlet of the reactor is 48-50 "C (Sauli et al., 1973). We present here a new process and reactor for the manufacture of dimethyl phosphite (Manolache et al., 1981). In this process, phosphorous trichloride vapors and liquid methanol are brought into reaction in backward flow in a 3:4 methanokphosphorus ratio. The reaction temperature is maintained by evaporating the methanol excess, and the methanol vapors carried along with the methyl chloride are separated through condensation and recirculated by refluxing. The reactor used for this process, absorption-column type with packing, has a reaction chamber inside which is a coil spacer mounted under the phosphorous trichloride feeding nozzle. Above the reaction chamber there are a reaction-perfecting and gas-absorption zone, a methanol feeding nozzle, and a reflux condenser cooler. On the reactor low side there is a shock cooler to cool the raw product. Figures 1-3 present an example of achieving the process and the reactor. The synthesis reactor, Figure 1,has a reaction chamber (I), a reaction-perfecting zone (2), a phosphorous trichloride feeding nozzle (3), a spacer (4,mounted under 3 inside the reaction chamber), a methanol feeding nozzle (5), a shock cooler (6, mounted under l), and a reflux cooler-condenser (7, mounted at the vapor outlet of 2). On the outer side of the spacer, built as a coil, a methanol film is formed, preventing the degradation of the dimethyl phosphite formed by protecting it against direct contact of the dimethyl phosphite vapors. The optimum reaction temperature experimentally determined is achieved with excess methanol by vaporizing it inside the reaction chamber. The methanol vaporized
A-
L
L
5
Figure 1. Synthesis reactor: (1)reaction chamber; (2) perfecting zone; (3) PCI, feeding nozzle; (4)spacer; (5)CH30H feeding nozzle; (6) shock cooler; (7) reflux condenser-cooler.
inside the reaction chamber is condensed and introduced again into the reactor. Here, together with the feeding methanol, it produces the hydrochloric acid and dimethyl phosphite absorption (carried along with the methyl chloride and methanol vapors) and the dissipation of the reaction heat. The synthesis raw product from the reaction chamber, with cooled raw product level, enters the shock cooler where it is instantly cooled. The dimethyl phosphite has been prepared, via a continuous process, in an installation shown in Figure 2. The raw materials-phosphorous trichloride and methyl alcohol-are introduced into some proportioning funnels (8 and 9). The heating agent (glycerin) is introduced into the thermostat (lo), the ice-salt mixture into the cooling vessel (ll),and the sol into the cooler (6) and cooler-condenser (7). The phosphorous trichloride from the proportioning funnel (8) is introduced into the evaporator (12) until 7040% capacity is reached. The nitrogen is introduced into the reactor by a collecting flask (13) with 10-15 L/h flow. The thermostat (10) is adjusted to 99 "C with the contact thermometer (14). The evaporator (12) is heated by starting the thermostat (10). Low-flow methanol is introduced into the reactor from the proportioning funnel (9) when 83-85 "C thermostat temperature is reached. When 93-95 "C thermostat temperature is reached, the reaction temperature (RT) rises quickly. The reaction temperature is prevented from rising by measuring the methanol flow. The nitrogen admission into the reactor is stopped. The dosing of the phosphorous trichloride from the proportioning funnel (8) into the evaporator (12) to maintain 70-80 % levels in the evaporator is started. When the thermostat temperature reaches 99 "C, the installation runs at the set loading and parameters.
Ind. Eng. Chem. Prod. Res. Dev., Vol. 24, No. 3, 1985 449
II
13
Figure 2. Laboratory installationfor the continuous synthesis of the dimethyl phosphite: (1) reaction chamber; (2) perfecting zone; (3) PC13feeding nozzle; (4) spacer; (5) CH30H feeding nozzle; (6) shock cooler; (7) reflux condenser-cooler; (8) PC13 dosing funnel; (9) CH30H dosing funnel; (10) thermostat; (11) cooling vessel; (12) evaporator; (13) collecting flask; (14) contact thermometer; (15) manometer; (16-20) thermometers.
The cooler is cooled. The product from the reaction chamber is collected in the flask and kept at -5 to +5 "C by using the ice-salt mixture from the cooling vessel. The methanol vapors carried along with the methyl chloride from the reaction chamber enter the cooler-condenser. The condensed methanol is introduced into the reactor as reflux; the methyl chloride leaves the coolercondenser and enters the atmosphere. The reactor pressure is read at the gauge (15) and the installation temperatures at the thermometers (16-20). The thermostat thermic-agent feeding ends when the installation is stopped, and low-flow methanol continues to be introduced into the reactor until the reaction temperature decreases to 40-50 OC. The results achieved after 10 experiments at optimum determined parameters are given in Table I. The dimethyl phosphite has been prepared by the continuous process in the pilot installation shown in Figure 3. The synthesis reactor is a column having a 150-mm diameter and a 3.400-mm packing height (8 X 8 X 1mm glass rings). The reaction chamber (1, the column low side on a 1.000-mm height) has inside a coil spacer (4) having a 530-mm height, a 44-mm i.d., a 6-mm coil diameter, and a 7-mm pitch, which is fitted under the phosphorous trichloride vapor feeding nozzle. Measuring flasks (21 and 22) are fed with raw materials, i.e., phosphorous trichloride and methyl alcohol, and a buffer tank (23) is fed with heating agent (eutectic mixture
dl
I
450
Ind. Eng. Chem. Prod. Res. Dev., Vol. 24, No. 3, 1985
m
fQ1 4
f
Y
aY
e
M
B
a8
Q
2
gz
2 3
r0
8
co
b
+
i E
L
e
E: c
t;il C
C
c 0
c
0 c Q
cC c
C
c
6 a 5 E
ce C
.L
a
i C Q c
s
1
p: .e C Q
a
1
c
b
d
$ 3
e *
a
:1 i I* I F4
Ind. Eng. Chem. Prod. Res. Dev., Vol. 24, No. 3, 1985 451
Figure 3. Pilot unit for the continuous synthesis of the dimethyl phosphite (1)reaction chamber; (2) perfecting zone; (3) PC13feeding nozzle; (4) spacer; (5) CHBOHfeeding nozzle; (6) shock cooler; (7) reflux condenser-cooler; (8) PC13 dosing funnel; (9) CH,OH dosing funnel; (10) thermostat; (11)cooling vessel; (12) evaporator; (13) collecting flask; (14) contact thermometer; (15) manometer; (16-20) thermometers; (21) PC13 measuring vessel; (22) CHBOHmeasuring vessel; (23) buffer vessel for heating agent; (24) dosing pump; (25) thermic-agent pump; (26) preheater.
composed of 73.5% diphenyl and 26.5% diphenyl oxide (diphyl). The evaporator (12) is fed up to 7040% capacity with phosphorous trichloride from the measuring flask (21) by using a metering pump (24). Nitrogen is introduced into the reactor with 14*160 L/h flow through the collecting vessel (13). Sol is introduced into the cooler-condenser (7), the cooler (6), and the collecting-vessel cooler (13). The heating agent is introduced in the heating cycle of the buffer tank (23) via the pump (25) through the preheater (26) and the evaporator bypass (12). A controlled-flow steam is introduced into the preheater and the heating agent is heated. When the diphyl temperature reaches 98-102 "C,pass the controlled-flow diphyl through the evaporator (12). Low-flow methanol is introduced into the reactor from the measuring vessel (22). When the reaction temperature (RT-1) rises, the methanol flow rises too, so the temperature can be maintained at about 70-80 "C. The introduction of nitrogen into the reactor is stopped, at 65-70 O C reaction temperature. The dosing pump (24) is started and the evaporator (12) is continuously fed from the measuring flask (21) with a phosphorous trichloride controlled flow. A 7040% capacity is maintained in the evaporator. All the operations are done to keep the installation running continuously. The product from the reaction chamber is cooled in the cooler (6) and collected into the collecting vessel (13). While the reactor is running continuously, the dimethyl phosphite concentration in the synthesis product is a minimum of 23-25 gf 100 g. The methanol vapors carried along by the methyl chloride from the reaction chamber enter the cooler-con-
denser (7), from where the condensed methanol goes back
to the reactor as reflux and the methyl chloride exits into the atmosphere. The evaporator thermic-agent feeding is ended when the installation is stopped, and low-flow methanol continues to be introduced into the reactor until the reaction temperature (RT-1) decreases to 40-50 "C. The parameters and the results achieved after two experiments are given in Tables I1 and 111. Conclusions The process and the reactor solve the problem of the dissipation of the reaction heat without the use of a solvent, and in this way it is possible to erect high-capacity plants at low purchasing and operation costs. The excess methanol used to dissipate the reaction heat is recovered and returned to the synthesis by the simple purification process of the raw dimethyl phosphite. The plants could be completely automatized and present a high reliability of operation. Due to the small volume of the reaction space, the undesirable second reactions are much diminished, and output of more than 90% is achieved. Registry NO.PC13,7719-12-2;CHSOH, 67-56-1; (CH,O),PHO, 868-85-9.
Literature Cited Campbell, C. H. U.S. Patent 2794820, 1957. Chadwick, 0. H. US. Patent 2582817, 1952. Manolache, C.; Popa, 0.;Socaciu, D.: Alexandru, I. Socialist Republic of Romania Brevet 72512, 1981. Sauli, V.; Skalsky, I.; Dostal, I. Czechoslovaklan Patent 148 569, 1973. Received for review August 24, 1983 Revised manuscript received October 17, 1984 Accepted March 25, 1985
