Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
2000-08-18
2002-07-16
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S240000, C502S241000, C502S242000, C502S243000, C502S244000, C502S245000, C502S246000, C502S247000, C502S248000, C502S250000, C502S252000, C502S253000, C502S254000, C502S258000, C502S263000, C502S300000, C502S302000
Reexamination Certificate
active
06420307
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a catalyst for propylene ammoxidation to acrylonitrile. More particularly, the present invention relates to a fluidized-bed catalyst for propylene ammoxidation to acrylonitrile.
BACKGROUND OF THE INVENTION
The acrylonitrile is a basic organic chemical material. It has been widely used in chemical industry. At present, producing acrylonitrile mainly use the process of propylene ammoxidation. In the process, catalyst makes important effect on propylene conversion, acrylonitrile selectivity, and so on. Nowadays, the most popular catalyst used for the propylene ammoxidation is a fluidized-bed catalyst. In order to get high activity and high selectivity. The catalyst have already been made a series of improvements through long-lasting research. Most of these improvements mainly focused on the active component of the catalyst and the mixture ratio of the active component.
It has been well know that the balance between acrylonitrile output and market demand is gradually being formed. Nowadays, acrylonitrile manufacturers are paying more attention to increasing acrylonitrile output and reducing starting material consumption of existing plants rather than setting up new plants. Utilizing a new catalyst with excellent performance replace old one to innovate existing plant can eliminate the so called “bottle neck” in the production process, increase 50-80% production capacity and save lots of cost in comparison with setting up new plant. The economic efficiency is considerable high.
However, two problems will occur in the process of making technical innovation. One is reaction pressure go up, another is catalyst amount is beyond a certain limitation. Therefore, it is required that the new catalyst should have higher capacity for loading propylene and higher capacity for bearing reaction pressure.
The reaction pressure of fluidized-bed reactor comes from a series of equipment resistance from the outlet of reactor to the top of absorbing tower, such as heat exchanger, tower and pipeline. Because of increasing production capacity, it consequently makes the amount of flowing materials apparently increase at reactor outlet and results in the increase of resistance. In addition, it makes further increase of resistance force that more heat exchanging equipment need to be used due to the deficient heat transferring area. In order to meet the requirement of the environmental protection, the waste gas of reaction from the absorbing tower top is not allowed to discharge directly into atmosphere and it will be transferred to waste-gas burning unit to burn. Thus, the pressure of the top of absorbing tower is to be raised if a blowing machine has not been used. Due to the above-mentioned reasons, at present, the running pressure of reactor is higher than the design pressure by 0.5-1.0 times. It is to reach up to above 0.08 Mpa.
Actually, the second problem is a catalyst load, namely WWH. It means the weight of proprlene feed per unit weight of catalyst per hour. With increase of the feedstock entered into the reactor, the fluidizing height of catalyst may exceed the height of cooling water pipe if the catalyst load is unchanged. At the same time, the reaction linear velocity of the reactor also should be outstandingly raised. These two changes may lead the increase of reactor dilute phase temperature, resulting in the increase of the amount of carbon dioxide formed and the decrease of the acrylonitrile selectivity. Accordingly, the catalyst with higher WWH can settle the above-mentioned problem.
Theoretically, the capacity of absorbing propylene should be improved as the increase of the catalyst WWH. However, there is not any theory indicate a certain relationship between the metal elements used in the catalyst and capacity of absorbing propylene.
Various methods were proposed in the prior art for solving the aforementioned problems. For example, Chinese patent CN1021638C disclosed the catalyst, which had a composition represented by following general formula:
A
a
B
b
C
c
Ni
d
Co
e
Na
f
Fe
g
Bi
h
M
i
Mo
j
O
x
Wherein,
A represents K, Rb, Cs, Sm and Tl;
B represents Mn, Mg, Sr, Ca, Ba, La and rare earth element;
C represents P, As, B, Sb and Cr
M represents W, V
The catalyst had a higher yield of acrylonitrile, but lower propylene load. The yield of acrylonitrile of the said catalyst would be considerably decreased under higher reaction pressure. Based upon further research done by the present inventor, it is found that the component B and M have effect on the running load of the catalyst and on its properties under high pressure. Some metal elements of component B will adversely affects on the increase of running load of catalyst as well as the catalyst properties under high pressure, so these metals are not suitable to be used in the catalyst running under higher pressure and higher load. Besides, in the above-mentioned Chinese patent CN1021638C, it was provided that the sum of i and j in the catalyst composition should be 12, namely it was a constant. Under the rule, the component Mo was decreased as the component M was increased. It would result in the adverse effect on the acrylonitrile yield. The catalyst composition of the present invention is not limited by the rule.
DETAILED DESCRIPTION OF THE INVENTION
The object of the present invention is to provide a new fluidized-bed catalyst for propylene ammoxidation to acrylonitrile, which can overcome the problem that the fluidized-bed catalyst for propylene ammoxidation to acrylonitrile is not suitable for higher reaction pressure and higher load. The catalyst of the present invention can achieve higher acrylonitrile even under higher reaction pressure and higher load.
The object of the present invention can be realized by a new fluidized-bed catalyst is used in the process of propylene ammoxidation to crylonitrile. The catalyst comprises silica as carrier and a catalytic composition represented by following general formula:
A
a
B
b
C
c
Ge
d
Na
e
Fe
f
Bi
g
Mo
h
O
x
Wherein
component A represents at least one element selected from the group consisting of Li, K, Rb, Cs, Sm, In and Tl;
component B represents a mixture of Pr plus W or a mixture of Pr plus W and at least one element selected from the group consisting of P, Sb, Cr, Ce, As, B, Te, Ga, Al, Nb, Tb, La and V;
component C represents at least one element selected from the group consisting of Ni, Co, Sr, Mn, Mg, Ca, Zn, Cd, Cu and mixtures thereof;
a is a number of from 0.01 to 1.5;
b is a number of from 0.01 to 3.0;
c is a number of from 0.1 to 12.0; preferably from 2 to 10;
d is a number of from 0.01 to 2.0; preferably from 0.01 to 1.0;
e is a number of from 0.01 to 0.7; preferably from 0.05 to 0.5;
f is a number of from 0.1 to 8; preferably from 1.0 to 3.0;
g is a number of from 0.01 to 6; preferably from 0.1 to 2.0;
h is a number of from 12 to 14.5;
the atom value of Pr is a number of from 0.01 to 0.75;
the atom value of W is a number of from 0.01 to 1.0; and
x is a number of oxygen atoms required to satisfy the valence requirement of the other element in the catalyst;
The content of silica as carrier is 30-70 wt %; preferable 40-60 wt %.
In a preferred embodiment of the invention, the component C is selected from the group consisting of Mg and a mixture of Mg with other metals. In another preferred embodiment of the invention, the component B is selected from the group consisting of a mixture of Pr plus W plus Sb and a mixture of Pr plus W plus Sb with other metals, and component C is selected from the group consisting of Sr and a mixture of Sr with other metals. In another preferred embodiment of the invention, component B is selected from the group consisting of a mixture of Pr plus W plus Ce and a mixture of Pr plus W plus Ce with other metals, and component C is selected from the group consisting of Mg and a mixture of Mg with other metals. In another preferred embodiment of the invention, component B is selected from the group consisting of Pr plus W plus Cr plus La and a mixture of Pr plus W plus Cr plus La with other metals, and
Chen Xin
Wang Guojun
Wu Lianghua
Anderson Kill & Olick P.C.
Bell Mark L.
China Petro-Chemical Corporation
Hailey Patricia L.
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