Organic compounds -- part of the class 532-570 series – Organic compounds – Nitriles
Reexamination Certificate
1996-02-21
2001-06-12
Higel, Floyd D. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Nitriles
Reexamination Certificate
active
06245931
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for producing acrylonitrile from propylene, or methacrylonitrile from isobutylene, by ammoxidation. More particularly, the present invention is concerned with a process for producing acrylonitrile or methacrylonitrile by reacting propylene with, or reacting isobutylene with ammonia and molecular oxygen in-the gaseous phase in the presence of an improved ammoxidation catalyst composition comprising a novel oxide catalyst and a silica carrier having the oxide catalyst supported thereon, the oxide catalyst comprising, in specific ratios, oxides of molybdenum, bismuth, iron, nickel, a mixture of chromium and indium, at least one element selected from potassium, rubidium and cesium and optionally at least one element selected from manganese, magnesium, zinc, cerium, sodium, and phosphorous.
2. Discussion of Prior Art
There has been well known a process for producing acrylonitrile from propylene, or methacrylonitrile from isobutylene, by ammoxidation in the gaseous phase, which comprises reacting propylene with, or reacting isobutylene with ammonia and molecular oxygen. This process, which has been widely known as an ammoxidation process, has been practiced on a commercial scale. With respect to catalysts for use in this ammoxidation process, a number of proposals have been made, wherein the catalysts have compositions containing molybdenum, bismuth and iron as essential components.
For example, in Unexamined Japanese Patent Application Laid-Open Specification No. 2-59046, U.S. Pat. No. 5,071,814, Examined Japanese Patent Application Publication No. 40-2532, GB Patent No. 1,434,581, Examined Japanese Patent Application Publication No. 51-6649, GB Patent No. 1,436,475, U.S. Pat. No. 4,190,556, U.S. Pat. No. 4,162,234, U.S. Pat. No. 4,167,494 and U.S. Pat. No. 5,093,299, the so-called multi-component oxide catalysts containing molybdenum, bismuth and iron are disclosed.
The catalysts disclosed in the above-mentioned patent documents have shown various advantageous characteristics. But, in the ammoxidation using these catalysts, the occurrence of side reactions is not effectively suppressed, so that the yield of acrylonitrile or methacrylonitrile is not satisfactorily high.
SUMMARY OF THE INVENTION
With respect to a process for producing acrylonitrile from propylene, or methacrylonitrile from isobutylene by using a multi-component oxide catalyst system comprised of oxides of molybdenum, bismuth and iron, the present inventors have made extensive and intensive studies with a view toward improving the yield of acrylonitrile or methacrylonitrile. As a result, it has unexpectedly been found that by use of a catalyst composition comprising an oxide catalyst, which contains, in addition to molybdenum, bismuth and iron, a mixture of chromium and indium, at least one element selected from potassium, rubidium and cesium and, optionally, at least one element selected from manganese, magnesium, zinc, cerium and phosphorous, in specific ratios, and a silica carrier having the oxide catalyst supported thereon, the desired acrylonitrile or methacrylonitrile can be produced with high selectivity and in high yield. The present invention has been completed, based on this novel finding.
Accordingly, it is a primary object of the present invention to provide a process for producing acrylonitrile from propylene, or methacrylonitrile from isobutylene, by ammoxidation, using an ammoxidation catalyst composition, which enables the desired acrylonitrile or methacrylonitrile to be produced with high selectivity and in high yield.
The foregoing and other objects, features and advantages of the present invention will be apparent from the following detailed description and appended claims.
DETAILED DESCRIPTION OF THE INVENTION
According to the present invention, there is provided a process for producing acrylonitrile or methacrylonitrile, which comprises reacting propylene with, or reacting isobutylene with ammonia and molecular oxygen in the gaseous phase in the presence of an oxide catalyst composition comprising:
(a) an oxide catalyst represented by the following formula:
Mo
m
Bi
b
Fe
f
Ni
n
Q
q
A
a
E
e
O
x
(I)
wherein:
Q is a mixture of chromium and indium,
A is at least one element selected from the group consisting of potassium, rubidium and cesium,
E is at least one element selected from the group consisting of manganese, magnesium, zinc, cerium, sodium and phosphorus, and
m, b, f, n, q, a, e and x are the relative atomic ratios of molybdenum, bismuth, iron, nickel, Q, A, E and oxygen, respectively,
wherein
m is a number of from 10 to 14,
b is a number of from 0.1 to 3,
f is a number of from 0.1 to 3,
n is a number of from 4 to 10,
q is a number of from 0.1 to 2,
a is a number of from 0.01 to 0.5,
e is a number of from 0 to 3, and
x is determined by the valence requirements of the other elements present; and
(b) a silica carrier having the oxide catalyst supported thereon, wherein the silica carrier is present in an amount of from 40 to 60% by weight, based on the total weight of the oxide catalyst and the silica carrier.
In the formula (I), m is preferably from 11 to 13,
b is preferably from 0.3 to 2, f is preferably from 0.5 to 2.5,
n is preferably from 5 to 9, q is preferably from 0.2 to 1.5 and
a is preferably from 0.1 to 0.4.
The characteristic feature of the oxide catalyst to be used in the process of the present invention resides in that it contains, as an essential component, component Q consisting of chromium and indium which is effective for achieving not only high selectivity for acrylonitrile or methacrylonitrile but also high reactivity of propylene or isobutylene. In other words, the use of chromium and indium in the form of a mixture thereof (component Q) is extremely effective for producing acrylonitrile or methacrylonitrile in high yield, as compared to the use of chromium alone or indium alone. In component Q, the ratio of chromium to the sum of chromium and-indium is preferably from 0.1 to 0.9, more preferably from 0.3 to 0.7. With respect to the amount (q) of the component Q relative to the amount (f) of iron, it is preferred the ratio of q to the sum of q and f be from 0.1 to 0.7.
Component A is also essential to the catalyst composition to be used in the process of the present invention although the content thereof is very small. Component A is effective for improving the selectivity for acrylonitrile from propylene or for methacrylonitrile from isobutylene. When rubidium, cesium or potassium is used alone as component A, rubidium and cesium are more effective for improving the above-mentioned selectivity than potassium, so that the necessary amount of component A can be reduced by use of rubidium or cesium. When component A is used in an amount exceeding the range as defined herein, the reactivity of propylene or isobutylene is lowered.
The above-mentioned ranges of m, b, f and n representing the relative atomic ratios of the other essential components of the oxide catalyst to be used in the process of the present invention are also important from the viewpoint of providing not only high selectivity but also high reactivity in the ammoxidation conducted by the process of the present invention. If an oxide catalyst having a composition falling outside of the ranges as defined herein is employed for the ammoxidation, the selectivity and/or the conversion will be lowered, leading to a lowering of the yield of the desired acrylonitrile or methacrylonitrile.
Component E which is optionally contained in the oxide catalyst may be used for further improving the reactivity of propylene or isobutylene, or for adjusting the properties of the resultant catalyst composition (such as surface area, pore distribution, particle morphology and density). Phosphorus occasionally imparts an improved abrasion resistance to the catalyst composition to be used in the process of the present invention.
As mentioned above, the oxide catalyst composition to be used in the process of the present inventio
Aoki Kunitoshi
Komada Satoru
Asahi Kasei Kabushiki Kaisha
Higel Floyd D.
Pennie & Edmonds LLP
Sackey Ebenezer
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