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Патент USA US2408178

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Patented Sept. 24, 1946
2,408,177 ,
William P. Ratchford, Willow Grove, and Charles
r -H. Fisher, Abington, Pa., assignors to Claude R.
Wickard, as Secretary of Agriculture of the
United States of America, and his successors in
No Drawing. Application May 4, 1943,
Serial No. 485,618
1 Claim.
(Cl. 260-486)
(Granted under the act of March 3, 1883, as
amended April 30, 1928; 3'70 0. G. 757)
This application is made under the act ‘of
March 3, 1883, as amended by the act of April 30,
1928, and the invention herein described, if pat
ented, may be manufactured and used by or for
the Government of the United States vof America
for governmental purposes without the payment
to us of any royalty thereon.
Our invention relates to ‘the manufacture of
unsaturated organic compounds and more par
ity, can be increased enormously by conducting
‘the pyrolysis under pressure. ‘In addition, the
use of superatmospheric pressures as herein de
scribed hasthe following advantages over oper
ation at essentially atmospheric pressure: (1)
Better heat transfer is afforded, and (2) the boil
ing points of the products are raised and hence
condensation of the products is facilitated.
The pyrolysis chamber, may be empty or may
' ticularly to the manufacture of acrylic esters by 10 contain packing materials such as quartz chips,
passing vapors of lactic acid derivatives through
pyrolysis tubes or chambers maintained at ele
vated temperatures.
Acrylic esters are formed when certain lactic
Raschig'rings, lumps of coke, metal shavings,
and so forth. Vapors of the carboXylic acid es
ters may be passed in at the bottom of the cham
her and out at the top, or in at the top and out
acid derivatives, such as methyl alpha-aoetoxy 15 at the bottom, or if desired, the pyrolysis tube
propionate, are passed at essentially atmospheric
may be mounted in a horizontal position.
In the examples set forth below, illustrating
pressure through tubes maintained at temper
atures ranging from 400° to 600° C. (Ritchie,
our invention, the reagent, methyl alpha-acetoxy
propionate, was allowed to flow by gravity from
Jones and Burns, U. S. 2,265,814, Dec. 9, 1941;
Smith and coworkers, Ind. Eng. Chem. 34, 473 20 a calibrated cylinder into a constant-feed pump
capable of operating under high pressures. The
(1942)). ' Also, esters of carboXylic acids on pyro—
lysis generally yield the carboxylic acid and an '
reagent was pumped under pressure into heated
unsaturated compound (Pelt and Wibaut, Rec.
stainless-steel tubing 1/4" inside diameter which
trav. chem. 60, 55-64 (1941)) ; Hurd, “Pyrolysis 0f '
was heated over a length of approximately 12
Carbon Compounds,” Reinhold Publishing Corp., 25 feet. The temperature was essentially uniform
over a considerable length‘ of the heated 12-foot
section, although some of the forward end of
the tubing served as a preheater. After passing
through the heated reaction zone, the vapors
compounds, suchas acrylic esters, by passing cer
tain esters of carboxylic acids through a hot tube 30 passed through a cooled condenser and into a
or chamber.
high-pressure receiver. Gases were released
through a throttling valve from the top of this
A further object is to provide improved condi
tions for pyrolysis which will increase the rate of
receiver at such a rate that the desired pressure
was maintained in the system- The liquid prod
conversion, increase the capacity of a pyrolysis
unit of any given size, and decrease production 35 ucts were collected at the bottom of the receiver
costs and capital investment.
-by manipulation of a suitable Valve.
Other objects of our invention will be apparent
New York city (1929).
An object of our invention is to provide a com
mercial process for manufacturing unsaturated
Example I
from the following description.
We have found that esters of carboxylic acids
can be transformed into unsaturated compounds
by pyrolysis under pressures much higher than
atmospheric pressure and that certain lactic acid
derivatives can be converted into acrylic esters
by pyrolysis of lactic acid derivatives under in
creased pressures. Moreover, we have found that
methyl alpha-acetoirypropionate, which is pre
pared conveniently by acetylating the methyl
ester of lactic acid, can be pyrolyzed satisfactorily
at high pressures and that methyl acrylate is pro
duced in good yield by this operation. We have
Methyl alpha-acetoxypropionate (315.5 grams)
was pumped into the pyrolysis chamber at the
rate of 1.12 moles per hour. The reaction tem
perature and pressure were 550° C. and 45 pounds
per square inch, respectively. The liquid prod
ucts were 85.4 percent of the charge.
High con
versions into methyl acrylate and acetic acid
were obtained.
Example I1
Methyl alpha-acetoxypropionate (858 grams)
methyl lactate and acetic anhydride under super
was pumped at 135 pounds per square inch‘ into
the pyrolysis chamber at 550° C. The rate of
atmospheric pressures yields methyl acrylate.
pumping was 3.18 moles per hour. High con
' also found that the pyrolysis of mixtures of
versions into methyl acrylate and acetic acid
Further, we have found that the throughput
of any given pyrolysis unit, and hence its capac 55 were obtained.
Example III
Methyl alpha-acetoxypropionate (1580 grams)
pyrolysis of esters of organic alcohols and car
boxylic acids.
Having thus described our invention, we claim:
The process of manufacturing methyl acrylate
was pumped at 900 pounds per square inch into
the pyrolysis chamber at 488° C. at a pumping
rate of 23 moles per hour. The reagent was sat
which comprises thermally decomposing methyl
isfactorily converted into methyl acrylate and
about 400° to 600° C. and a pressure of about 3
alpha-acetoxypropionate at a temperature of
to 60 atmospheres.
acetic acid.
Our invention is not limited to the examples
given above, but is applicable generally to‘ the 10
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