Mineral oils: processes and products – Chemical conversion of hydrocarbons – Cracking
Reexamination Certificate
2002-11-12
2004-09-14
Griffin, Walter D. (Department: 1764)
Mineral oils: processes and products
Chemical conversion of hydrocarbons
Cracking
C208S120010, C208S120100, C208S120150, C208S120200, C208S120300
Reexamination Certificate
active
06790343
ABSTRACT:
The present invention relates to a sulfur transfer additive for catalytic cracking of hydrocarbons and a catalytic cracking process of hydrocarbons. More particularly, the present invention relates to a liquid sulfur transfer additive for catalytic cracking of hydrocarbons comprising at least two metal elements, and a catalytic cracking process using said sulfur transfer additive.
The hydrocarbon feed processed in the commercial fluidized catalytic cracker (FCC) usually contains 0.3 to 3.0% by weight of sulfur. Based on the total amount of the sulfur contained in the hydrocarbon feed, about 20 to 60% by weight of the sulfur is transferred to the cracked gas in form of H
2
S, which can be recovered by converting it into elemental sulfur, about 20 to 70% by weight to the light oil products as organic sulfur compounds, which must be removed from the oil products by means of hydrotreating or hydrofining, and the remaining about 5 to 30% by weight to the coke deposited on the catalyst particles. However, when the amount of sulfur contained in the hydrocarbon feed is higher, the light oil products will contain too much of sulfur to meet the standard specifications for the products. Although the sulfur content in the light oil products can be reduced to meet the specifications by lowering the initial boiling point (IBP) or by means of other more severe post-treatment, this will increase the costs and decrease the profits. In the catalyst regenerator of the FCC system, the sulfur contained in the coke is burned off, forming sulfur dioxide and sulfur trioxide (collectively called SO
x
hereinafter), which are emitted to the atmosphere with the flue gas, resulting in environmental pollution. In addition, the higher amount of SO
x
in the regenerator flue gas leads to corrosion of the regenerator equipment.
The solution most widely used nowadays to reduce the SO
x
content in regenerator flue gas and the sulfur content in light oil products of FCC system is the use of solid sulfur transfer additives. The solid sulfur transfer additives can be divided into two categories. One is the additives dedicated to reduce the SO
x
concentration in regenerator flue gas, and the other is the additives dedicated to reduce the sulfur content in light oil products, especially gasoline. The sulfur transfer additives described in U.S. Pat. Nos. 4,589,978 and 5,021,228 fall into the first category, while the sulfur transfer additive described in U.S. Pat. No. 5,376,608 falls into the second category. The sulfur transfer additive disclosed in U.S. Pat. No. 4, 589, 978 contains 1~20% of lanthanum (La), cerium (Ce) and a support, wherein the weigh ratio of lanthanum to cerium is 1:10 to 10:1, and the support can be alumina, silica, kieselguhr or zeolite, etc. This sulfur transfer additive is used as separate particles and mixed with the catalytic cracking catalyst. With this sulfur transfer additive, it is required to operate the regenerator at a full CO combustion mode, 0-2% (vol.) excess of O
2
. When 0.5~4.8% of the sulfur transfer additive based on the catalyst inventory of the FCC system is added, SO
x
can be reduced by 30~80%. U.S. Pat. No. 5,021,228 disclosed a sulfur transfer additive which is a composition containing (1) porous alumina support, (2) as a first component the metals of actinium series such as the thorium and uranium in amount of 0.5~10 wt. %, (3) as a second component the alkali metal such as potassium and sodium in amount of 1~5% wt. %. This composition is used as one component of the catalytic cracking catalyst and 60% of SO
x
can be transferred to H
2
S. U.S. Pat. No. 5,376,608 disclosed a catalytic cracking catalyst composition comprising a zeolite dispersed in an inorganic oxide matrix and, as a separate component, a Lewis acid supported on alumina, wherein the separate component comprises 1~50 wt. % of elements and compounds Ni, Cu, Zn, Ag, Cd, Ti, Bi, B and Al. Other components of the composition are 5~50 wt. % of synthetic faujasite, 10~60 wt. % of clay, and 10~30 wt. % of inorganic binder selected from silica, alumina and silica-alumina. It was reported that the sulfur content in gasoline was markedly reduced without any negative effect on the gasoline yield using the composition.
The prior art sulfur transfer additives such as those disclosed in the above-mentioned patents are of only single-function, i.e. the additives which can reduce the SO
x
concentration in regenerator flue gas can not reduce the sulfur content in the light oil products, and the additives which can reduce the sulfur content in the light oil products can not reduce the SO
x
concentration in regenerator flue gas. Furthermore, these sulfur transfer additives have no catalytic activity, and will dilute the catalyst if added into the cracking catalyst. As a result, the activity of the catalyst in the FCC system is reduced and the selectivity becomes deteriorated. For instance, when 5.0% of sulfur transfer additive is added to an equilibrium catalyst with a microactivity of 60, the microactivity will be lowered by about 3 unit and the selectivity is significantly affected. Additionally, the prior art sulfur transfer additives are all solid, thus requires that the particle distribution, mechanical strength and sphericity of the sulfur transfer additives be matched well with those of the catalyst. When the solid particles are added to the FCC system, the ratio of the su transfer additive to the catalyst inventory in the system can not be flexibly adjusted, thus, can not accommodate to the operation for frequent variations in the sulfur content in the hydrocarbon feed. Furthermore, the preparation of the solid sulfur transfer additives need complex equipment.
It is an object of the present invention to provide a liquid sulfur transfer additive and a catalytic cracking process using the same, which can reduce the SO
x
content in the regenerator flue gas and the sulfur content in the light oil products at the same time, and has no negative effect on the activity and selectivity of the catalyst in FCC system, so as to overcome the defects of the prior art solid sulfur transfer additives i.e. the solid sulfur transfer additives in the prior art can only reduce the SO
x
content in the regenerator flue gas or can only reduce the sulfur content in the light oil products, and to obviate the negative effect of the prior art sulfur transfer additives on the cracking catalyst activity and selectivity, After extensive and profound research, the present inventors find the following sulfur transfer additive and catalytic cracking process, and achieve the object as stated above.
In the first aspect, the present invention provides a sulfur transfer additive for catalytic cracking of hydrocarbons, characterized in that it is a liquid product comprising at least two metal elements selected from the following three classes:
a). alkali earth metals,
b). transition metals and P zone metals, and
c). rare earth metals,
and wherein there are at least two metal elements from the different classes.
In the second aspect, the present invention provides a process for catalytic cracking of hydrocarbons, characterized in that the sulfur transfer additive as stated in the first aspect of the present invention is used.
In yet another aspect, the present invention provides an application process of the sulfur transfer additive of the present invention as stated above.
These and other aspects of the present invention are apparent to the ordinary skilled in the art with reference to the following detailed description of the present invention.
The sulfur transfer additive of the present invention comprises at least two metal elements selected from the following three classes: a) alkali earth metals, b) transition metals and P zone metals, and c) rare earth metals, and wherein there are at least two metal elements from the different classes. That is to say, the present sulfur transfer additive comprises at least one metal element selected from alkali earth metals and at least one metal element selected from transition metals and P zone metals,
Deng Xianliang
Guo Haiqing
Liu Jinlong
Liu Shufang
Qi Wenyi
China Petro-chemical Corporation
Christie Parker and Hale, LLP
Griffin Walter D.
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