Literature Cited AGFA, DP 202 170 (1908). Fiat Final Report No. 1313, 231 (1948). Gordon, M..Miller, J. G., Day, A. R.. J. Am. Chem. SOC., 71, 1245 (1949). Groggins, P. H., "Unit Process in Organic Synthesis", McGraw-Hill, 5th ed, p 400, New York. N.Y., 1958. Groggins. P. H.. in Kirk-Othmer, "Encyclopedia of Chemical Technology", Vol. I, pp 698-701, New York, N.Y.. 1947. Inventa. GB-PS 829 25 1 (1 960). Jansen. R., 2.farbenind., 12 (14), 197 (1913). Kappler, E.,Liebusch, W., Kleinke. H., DDR 77 985 (1969).
Quick, A. J., J. Am. Chern. SOC., 42, 1033 (1920). Richmond, H. H., U S . Patent 2 708 680 (1955). Zengel, H.G., Bergfeld, M. J., DTAS 2 216 116 (1972a). Zengel, H. G., Bergfeld, M. J., DTOS 2 216 028 (1972b). Zengel, H. G., Bergfeld, M.J., DTAS 2 313 548 (1973a). Zengel, H. G., Bergfeld, M. J., Belgian Patent 812 358 (1973b). Zengel, H. G., Bergfeld, M. J., DTOS 2 437 470 (1974). Zengel, H. G., Bergfeld, M.J., Patent 2 437 370.7/42 (1975).
Received for review January 12,1976 Accepted May 5 , 1976
The Thermal Condensation of Isobutylene with Formaldehyde Paul R. Stapp Phillips Petroleum Company, Bartlesville, Oklahoma 74004
Isobutylene was condensed thermally with formaldehyde to give 3-methyl-3-buten-1-01 in good yield in either a batch reactor or a continuous stirred tank reactor. In the continuous reactor, temperatures of 275 to 300 OC at 2000 psig at residence times of 20 to 35 min appear optimum using isobutylene/formaldehyde mole ratios of 1O:l or higher. Formaldehyde conversions of 80 to 85% are observed under these conditions with ultimate yields of approximately 80%. The use of methanolic solutions of formaldehyde provides a convenient method of pumping formaldehyde in a continuous process. The thermal condensation of trans- and cis-2-butene with formaldehyde gives 2-methyl-3-buten-1-01 which, in common with 3-methyl-3-buten-1-01, should be capable of dehydration to isoprene. 1-Butene gives a cis/trans mixture of 3-penten-1-01.
Introduction Thermal condensation of isobutylene with formaldehyde has been carried out in a mixture of acetic acidlacetic anhydride (Blomquist and Verdol, 1955), in acetic anhydride alone (Watanabe and Suga, 1963), and in the absence of solvent (Brace, 1955). In each instance, low yields of 3-methyl-3buten-1-01 derivatives were obtained. Because 3-methyl-3buten-1-01 is a potentially useful chemical intermediate, i.e., for dehydration to isoprene (Steubinger and Mueller, 1972; Friedlin et al., 1964), our earlier studies of formaldehydeolefin reactions (Stapp, 1971) were extended to include the thermal reaction of isobutylene with formaldehyde. If proper operating conditions are chosen, high yields of unsaturated alcohol may be obtained.
Experimental Section Apparatus. All temperatures cited are in "C. Batch condensations were conducted in a 1-1. stainless steel "Magnedrive" autoclave (Autoclave Engineers, Inc.). Solvent (if any) and paraformaldehyde were charged, the autoclave was sealed and flushed with nitrogen, and isobutylene was charged liquid phase from tared cylinders. For the continuous studies, a system was assembled using a Whitey Micro Regulating Laboratory Feed Pump to pump liquid isobutylene and a LS-30 Lapp Pulsafeeder to pump formaldehyde solution to a mixing tee. After vaporization in a preheater constructed of 20 f t of 3/s-in. stainless steel tubing wound in a coil and heated by steam to ca. 170 "C the feed was introduced through the top opening of the autoclave. Product was removed continuously from a dip tube extending to the bottom of the autoclave. Pressure was controlled by a Taylor Fulscope and product was collected, after reduction to atmospheric pressure
with a pressure control valve, in 1.7-1. bombs cooled in dry ice. Materials. The olefins used were Phillips Pure Grade materials and powdered paraformaldehyde (usually assaying 94-95%) was obtained from Mallinckrodt. Solvents, when used, were reagent grade commercial materials. Analysis. In the batch runs excess isobutylene was vented through a wet test meter and the product was removed from the autoclave and purified by distillation at atmospheric pressure, GLC analyses of product purity were carried out on a 10 f t X ji4-in. column of Carbowax 20M operated isothermally at 125 "C. Product analyses from 1-h samples in the continuous runs were analyzed as follows: excess isobutylene was distilled a t room temperature into an evacuated tared bomb. An aliquot was removed from the residual liquid and analyzed for formaldehyde to determine formaldehyde conversion. A second aliquot was analyzed by GLC using n-propyl alcohol as an internal standard. Periodically, samples were also analyzed by distillation as a check on the internal standard technique; results were in good agreement. GLC analyses were also carried out on the unreacted liquid isobutylene in order to correct for a small amount of 3-methyl-3-buten-1-01carried over in the isobutylene distillation.
Results and Discussion In our initial studies it was found that condensation of 3.0 mol of formaldehyde with 4.82 mol of isobutylene occurred smoothly in diphenyl ether solvent in a stirred autoclave a t 300 "C to give substantially complete formaldehyde conversion. Two major products were found in addition to considerable methanol and methyl formate. These were separated by preparative GLC and identified as 3-methyl-3-buten-1-01 and 3-methyl-3-butenyl formate in yields of 40% and 18%, respectively. Ind. Eng. Chem., Prod. Res. Dev., Vol. 15, No. 3, 1976
189
CHB
I
+ CH,O
CH,=C-CH,
Table I. Dependence of Yield on Mole Ratio a
I
+
CH2=C-CH2CH20H i-
CH i
0
I
CH,=~-CH,CH,OCH
II
It has been established that formaldehyde thermally decomposes to carbon monoxide and methanol or carbon monoxide and hydrogen in competitive reactions dependent on the decomposition temperature (Calvert and Steacie, 1951). It has also been demonstrated that formaldehyde can be catalytically disproportionated to methyl formate under mild conditions (Stapp, 1973). 2CH,O CH,O 2CH10
--
-
Mol of CHzO
Mol of i-C1Hs
Mole ratio
% Yield ofb 3-Methyl-3buten-1-01
+
Table 11. Dependence of Yield on Temperature
i-C4H&HzO
In the present system it appears that the major product, 3methyl-3-buten-1-01, is formed via the well established cyclic "ene" mechanism (Hoffman, 1969;Keung and Alper, 1974).
of ester
4.0 4.48 1.12 31.8 15.3 0.98 4.13 4.20 51.2 11.3 0.70 5.09 7.27 71.7 9.3 0.49 5.23 10.63 84.6 5.7 a These results were obtained using 250 ml of benzene solvent and powdered paraformaldehyde assaying 94-95% at 200 "C for 6 h. Based on charged formaldehyde.
+
CO CH,OH CO H? HCO,CH,
% Yieldb
7.05 7.00 7.21
Temp, "C 200 250 275
Time, h
% Yield of 3-methyl-3-buten-l01
6 2 0.5
63 71 74
Table 111. Dependence of Yield on Mole Ratio at 275 "C
Hzc
C ' H,
P
Methyl formate and methanol are formed from formaldehyde by the reactions shown above although it is not yet clear why methyl formate tends to predominate. I t may be that traces of formic acid present in the charged formaldehyde catalyze this disproportionation. Small amounts of carbon monoxide and traces of hydrogen (normally found in appreciable quantities only in very high temperature decompositions) were subsequently found in the off-gas. The ester, 3-methyl-3butenyl formate, is probably formed by thermal transesterification of the unsaturated alcohol with methyl formate. CH,
I
CH,=CCH,CH,OH
+ HCO,CH, CH,,
-+
0
I II CH,=C-CH,CH,OCH + CHiOH
A number of similar thermal condensations of isobutylene with paraformaldehyde at mole ratios ranging from 1.07 to 1.47 in toluene, sulfolane, pyridine, benzene, and cyclohexane at temperatures of 200 to 300 "C for 3-6 h all gave substantially the same results. Yields of unsaturated alcohol ranged from 22 to 40% and yields of unsaturated ester varied between 11 and 24%. In the experiment conducted at 300 OC complete formaldehyde conversion was observed very quickly; at 200 "C 6 h was required. One run at 150 "C for 6 h gave only traces of unsaturated alcohol and ester but did give a nearly 20% yield of methyl formate. Trioxane did not react with isobutylene in benzene solution a t 200 "C. In these condensations of formaldehyde with isobutylene, competitive formation of methyl formate and methanol is apparently catalyzed to a certain extent by the autoclave walls since, under comparable conditions, the rate of methyl formate production was halved on heating paraformaldehyde in benzene in a Carius Tube. In order to more fully define the effect of reaction variables 190
lnd. Eng. Chem., Prod. Res. Dev., Vol. 15, No. 3, 1976
Mole ratio
Temp, "C
Time, h
Yield, %
2.06 4.11 7.21 10.89 11.29 7.66 7.50
275 275 275 275 275 275 325
0.5 0.5 0.5 0.5 0.5 2.0 0.5
39 62 74 79 80 67 42
on the yield of 3-methyl-3-buten-1-01, a survey of the effect of variation in the isobutylene/formaldehyde mole ratio was conducted. These results are summarized in Table I. It is immediately obvious that going to higher olefin/CHzO ratios improves the yield markedly; in these experiments the crude reaction products were nearly water-white and only traces of unreacted formaldehyde remained. In the high mole ratio runs only traces of methanol and methyl formate were found and, after isolation of the products by distillation, 5 to 10% of heavier products remained. These heavies were mobile liquids which, by GLC analysis, were complex mixtures of 15 to 20 components and were not further investigated. The use of higher temperatures (and shorter residence times) and the elimination of solvent was also tested as is shown in Table 11. For convenience, this series was arbitrarily run at approximately 7:l mole ratio since this gives lower pressures (ca. 1900 psi) and larger quantities of product for analysis. The runs made in the absence of solvent gave somewhat lower yield than comparable runs made in benzene at 200 "C, but part of this may be due to a loss of product while venting the excess isobutylene; GLC analyses of condensed off-gas did show the presence of small amounts of 3-methyl3-buten-1-01. However,'the experiments at 250 and 275 "C gave yields equivalent to those observed in benzene at 200 "C. In the run at 250 "C the reactor was at constant pressure after 50 min and in the run a t 275 "C the reactor was a t constant pressure after 10 min. Once more essentially complete formaldehyde conversion was observed and the crude reaction products were nearly water white. The effect of mole ratio on product yield at 275 "C with no solvent was also tested. Table I11 summarizes the results. Again, the dependence of yield on mole ratio is noteworthy. In the runs a t 30 min residence time the crude products were
still water-white but going to longer reaction periods or higher temperatures, as illustrated by the last two experiments in Table 111,gave yellow to brown reaction mixtures with inferior yields. The importance of a large excess of olefin in obtaining high yields is undoubtedly due to a simple mass-law effect. In addition, product 3-methyl-3-buten-1-01 has reasonable thermal stability a t 275 O C in the presence of excess isobutylene, but reacted quite rapidly with formaldehyde in benzene at 275 "C under our normal operating conditions to give a complex mixture of unsaturated polyols, esters, and formals. Although solvent variation among the inert solvents gave little change in either reaction rate or product distribution, some other classes of solvent led to different results. Condensation of isobutylene with 45% aqueous formaldehyde (8.2:l mole ratio) gave a very dark reaction mixture and only 37% yield of 3-methyl-3-buten-1-01 along with 16% of 4,4dimethyl-1,3-dioxane a t complete formaldehyde conversion. The use of benzene cosolvent along with the aqueous formaldehyde gave 63% of 3-methyl-3-buten-1-01, 3% of 3methyl-3-butenyl formate, and 3% of 4,4-dimethyl-1,3-dioxane under similar conditions. Since formaldehyde is known to have a moderate solubility in nonpolar organic solvents (Walker, 1964), it appears that phase-transfer (Dockx, 1973; Starks and Owens, 1973) into, and subsequent reaction in, the organic phase gives comparable results to the normal system. In order to verify the assumption that by-product 3methyl-3-butenyl formate was formed via thermal transesterification of 3-methyl-3-buten-1-01,the utility of esters as solvents was also tested. Reaction in either methyl formate or methyl benzoate did lead to extensive transesterification. (CH,),C=CH2
+ CH20 + RCO,CH, CH,
I
-+
CH,=C-CH,CH,OH R = H, 37% R = C,H,, 42%
0
CH,
I I + CHL=C-CHBCH20CR 45% %%
Surprisingly, diethyl carbonate did not give ester interchange but triethyl orthoformate gave extensive thermal exchange under the same conditions. (CH&=CH,
+ CHBO + HC(OCBH5h
Table IV CHzO Ultimate yield of 3Temp, Press, Residence conversion, methyl-3-buten-1-01, "C psi time,min % %
'
38.3 17.8 22.8 29.2 33.3 68.1
2000 2000 2000 2000 2000 2000
275 285 285 285 285 285
79 78 87 75 87 73
90
vantage in using rigorously dried solutions (over 3A molecular sieves) was noted, but if the water content became too high, considerable color and a further decrease in yield was observed. As long as the water concentration was less than about 10%of the total solvent weight, crude reaction products were a light straw color and satisfactory yields were obtained. The use of methanolic formaldehyde in a continuous process was studied by equipping a 1-1. stainless steel Magnedrive autoclave to function as a continuous stirred tank reactor. Table IV shows the results from a number of 1-h runs using 46.5% methanolic formaldehyde at a 10.3:l isobutylene/ formaldehyde mole ratio. A 2-h line out period was conducted before the start of each run. Formaldehyde conversion appears to be a direct function of residence time, but, in this series of experiments, ultimate yield was not greatly affected. Although some scatter in ultimate yield data is apparent, the observed results are quite satisfactory. The effects of temperature and pressure a t constant residence time were also investigated. Increasing temperature to 300 OC provided higher formaldehyde conversions with little effect on yield but reducing the pressure in 500pound increments gave a steady decrease in both conversion and yield. The thermal reactions of the isomeric butenes with paraformaldehyde were also investigated. For convenience in product identification each pure isomer was reacted separately.
H
"\C/CH3
-\/ - \
i' I"
-+
I
H
CH,CH=CHCH,CH,OH 68% trans-, 32% cis-3-penten-1-01
I"
\ /"\
f'
CH3
82 76 80 83 82
CH,
I
CH2WHCHCHZOH 2-methvl-3-buten-1-01
H
I
I
(cH~=&-cH,cH,o),~oc,H~ 5%
Because of the difficulty in using solid paraformaldehyde in a continuous process the feasibility of using methanolic formaldehyde solutions in the thermal production of 3methyl-3-buten-1-01was also tested. Parallel experiments to those carried out in hydrocarbon diluents established that, in batch reactions, methanolic formaldehyde (45-5096 CH20) could be used with about a 5% sacrifice in yield. Little ad-
CCH, 0 F/ H CH?
/
Using conditions (275 "C, 30 min, no solvent, 7.2 mole ratio) which gave 74% yield of 3-methyl-3-buten-1-01from isobuInd. Eng. Chem., Prod. Res. Dev., Vol. 15, No. 3, 1976
101
tylene, trans-%butene gave 50%of 2-methyl-3-buten-1-01 and 21% of 2-methyl-3-butenyl formate and cis-2-butene gave the same alcohol and ester in 17%and 10% yields, respectively. A similar condensation with 1-butene produced 29% of cis/ trans-3-penten-1-01mixture and 18%of ester; the isolation of the cis compound was unexpected since Blomquist et al. (1957) had found that only trans-3-octen-1-01was obtained from 1-heptene. In the cis-2-butene and 1-butene condensations considerable unreacted formaldehyde was present and substantial quantities of methanol and methyl formate were also produced. By inspection of the cyclic mechanisms shown above it would be expected that cis-2-butene would react much more slowly (due to steric hindrance) than the other isomers. The reason for the difference in unsaturated alcohol yield between trans-%butene and 1-butene is not clear but it may be purely statistical; i.e., there are three times as many allylic hydrogens in trans-2-butene. It is also possible that product 2-methyl-3-buten-1-01from cis-2-butene may arise from a prior thermal isomerization to tram-2-butene. Because of the apparent difference in reaction rates between isobutylene and 1-butene with formaldehyde, one experiment was conducted in which a 90% isobutylene/l0% 1-butene mixture was heated with paraformaldehyde a t 275 O C for 30 min. A 74% yield of unsaturated alcohols containing 98% of 3methyl-3-buten-1-01 and 2% of 3-penten-1-01 was obtained. In summary, a process has been developed for the thermal condensation of isobutylene with formaldehyde to produce
3-methyl-3-buten-1-01 in good yield in either a batch reactor or a continuous stirred tank reactbr. Although conditions have not been optimized for the similar condensation of cis- and trans-2-butene, it appears that they can be converted to 2methyl-3-buten-1-01 which should also function as a precursor to isoprene. Small amounts of 1-butene might be tolerated but the boiling point of 3-penten-1-01 does not differ sufficiently from 3-methyl-3-buten-1-01 for sepiuation; upon dehydration 3-penten-1-01 would produce piperylene and require efficient fractionation in the final isoprene purification. Literature Cited Blomquist, A. T., Passer, M., Schollenberger, C. S.. Wollnsky, J., J. Am. Chem. SOC.,70, 4972 (1957). Blomquist, A. T., Verdol, J. A., J. Am. Chem. SOC.,77, 78 (1955). Brace, N. O., J. Am. Chem. Soc., 77, 4666 (1955). Calvert, J. G.. Steacie, E. W. R., J. Chem. Phys., 10, 176 (1951). Dockx, J., Synthesis, 441 (1973). Friedlin, L. K., Sharf, V. Z., Abidov. M. A,, Neftekhimiya, 4, 609 (1964). Hoffman, H. M. R., Angew. Chem. ht. Ed. En@, 8,556 (1969). Keung, E. C.. Alper, H., J. Chem. Educ., 49, 97 (1974). Stapp, P. R., J. Org. Chem., 36,2505 (1971). Stapp, P. R., J. Org. Chem., 38, 1433 (1973). Starks. C. M., Owens, R. M., J. Am. Chem. SOC.,95,3613 (1973). Steubinger, A., Mueller, H., (to BASF), U.S. Patent 3 657 376 (Apr 18, 1972). Walker, J. F., “Formaldehyde”, 3rd ed, p 52, Reinhold, New York, N.Y., 1964. Watanabe. S., Suga, K., Bull. Chem. SOC.Jpn., 36, 1495 (1963).
Received for review January 19,1976 Accepted May 14,1976
Friction Resistance and Stickiness of Polyester Chips Helmut Heinze Zimmer AG, Frankfurt am Main, West Germany
An apparatus is described for determining relative values for friction resistance and stickiness of polyester chips under simulated processing conditions. Tests performed with chips made from polyethyleneterephthalate demonstrate the mode of operation of the unit and the effect of various parameters upon the measuring results.
Introduction Chips made from polyethylene terephthalate (PET) are known for their tendency to stickiness during drying and crystallization at temperatures above the glass transition temperature (Illers, 1971), in particular at temperatures from 95 to 110 “C. In this temperature range, “amorphous” PET chips will be subject to a partial crystallization leading to certain heat effects and a transient softening (Korotaeva et al., 1968). This involves the formation of P E T spherulites of lamellar structure (Roberts, 1969). During progressive heat treatment of the partially crystallized chips, which brings about further Crystallization, the tendency to stickiness is initially comparatively low but rises rapidly in a temperature range from ca. 220 “C up to the melting point of the PET material. These effects must be considered as well for drying and crystallization of P E T chips as, in particular, for their solid-state polycondensation (Maxiori and Foglia, 1969). Depending on the heating conditions, the temperature corresponding to the beginning of the lS2
Ind. Eng. Chem., Prod. Res. Dev.. Vol. 15, No. 3, 1976
melting process can be increased, as has been indicated by DTA measurements (Wiesener and Hoffrichter, 1970). Several approaches are feasible to prevent a tendency to stickiness and consequent operational trodble. Heating programs have been established, €or instance, or precautions have been taken to keep the chips in sufficient relative motion to one another (Jacobs et al., 1967; Gelperin et al., 1967). Another suggestion frequently made is the adding of anticaking agents, i.e., small quantities of fluid or pulverous substances which adhere to the chip surface and are intended to suppress largely or even entirely any tendency to stickiness (Hecht et al., 1966; Maxion, 1969; Okuzumi, 1969; Buxbaum, 1970). In fact, economy of continuous solid state polycondensation to yield high-viscous PET will be determined by the possibility of avoiding stickiness. By comparison with the drying procedure, the temperature level required for solidstate polycondensation is very high and the residence time is long (Jaeger et al., 1968; Hoeltermann et al., 1968). In view of testing the friction and sticking behavior, i.e., flowability, of P E T chips and the suitability of various sub-
