Patent Application
20080000807
In accordance with the present invention, the sulfur content of a FCC gasoline is reduced to lower levels by the use of an additive-containing catalyst composition. The FCC catalyst is preferably made of powder and generally possesses an average particle size in the range of 50-100 microns and a bulk density in the range of 0.5-1.0 kg/L. It is preferred that the particle size, density and mechanical strength of the catalyst composition of the present invention is the same as a conventional FCC catalyst in which the composition is to be physically mixed.
The cracking catalyst particles preferably contain at least one cracking catalyst component which is catalytically active for the cracking of hydrocarbons in the absence of added hydrogen. The cracking catalyst component preferably comprises a zeolite, a non-zeolite molecular sieve, a catalytically active amorphous silica alumina species, or a combination thereof. The cracking catalyst component is most preferably a Y-type zeolite selected from the group consisting of Y, USY, (described in U.S. Pat. No. 3,293,192, which is incorporated herein by reference), REY and RE-USY (described in U.S. Pat. Nos. 3,607,368 and 3,676,368, both of which are incorporated herein by reference) and mixtures thereof. The cracking catalyst particles may also contain one or more matrix components such as clays, modified clays, alumina, etc. The cracking catalyst particles may also contain a binder such as an inorganic oxide sol or gel. Preferably, the cracking catalyst particles contain at least 5 wt. %, more preferably about 5 to 50 wt. %, of cracking catalyst component.
The support material of the claimed composition is preferably a montmorillonite clay which possesses a surface area in the range of 150-350 m2/g. The clay has been calcined in air at 550° C. to remove physically adsorbed water. Calcinations at 550° C. did not result in much increase in the surface area.
Clay material itself possesses considerable capacity to reduce sulfur in gasoline fraction. However, the reduction in the benzothiophene fraction is minimal. It was observed that the impregnation of a Lewis acid component onto the clay did not significantly increase either overall sulfur reduction capacity or the reduction of benzotiophene.
Incorporating zirconium, the preferred Group IV metal, into the pores of the subject clay increased the surface area by about 15 to about 25%. It was observed that impregnation of the zirconium incorporated clay material with a Lewis acid significantly reduced the sulfur content of the gasoline fraction which is catalytically cracked. It is most preferable to use a Lewis acid including compounds of Group II metals, preferably zinc, to effect a reduction in the sulfur content of gasoline.
In order to further illustrate the present invention and the advantages thereof, the following specific examples are presented. The examples are presented as specific description of the claimed invention. It should be understood, however, that the invention is not limited to the specific details set forth in the examples. The examples illustrate the preparation and catalytic evaluation of specific compositions for reducing sulfur content of a catalytically cracked gasoline fraction.
Micro activity test (MAT) evaluation of FCC catalyst/additive mixtures were carried out according to ASTM method D-3907, at a reaction temperature of 510° C. and a injection time of 30 seconds for a catalyst to oil ratio between 3 to 5, to obtain conversion of 55 to 75%. The feed used was a vacuum gas oil of Arabian light crude origin. Sulfur content of this feed was 2.5 weight percent. Other properties of this feed are shown in Table 1. The sulfur content of the gasoline fraction was measured by GC-SCD. For comparison purposes, sulfur content of gasoline fraction was calculated at 71% conversion level.
Sulfur Content of Gasoline Fraction Obtained with Use of a Conventional FCC Catalyst.
A steamed, conventional, commercial FCC zeolite catalyst, a typical low RE-USY type available from any FCC catalyst supplier, was evaluated in MAT according to ASTM D 3907.
Sulfur Reduction with a Commercially Available Additive Composition.
A commercial sulfur reduction additive generally available from a typical catalyst supplier, for example, Albemarle, CClC, Englehard, Grace Davison, or Intercat, labeled as comparative additive in the tables were added (10 wt. %) to the same steamed conventional FCC catalyst, namely, low RE-USY, as in Example 1 and was tested in MAT under the same conditions as in Example 1. The sulfur content of the gasoline fraction in this Example is compared with the reference sulfur content in
Base Material of the Claimed Novel Composition has Considerable Capacity to Reduce Sulfur Content of FCC Naphtha.
To measure the sulfur reduction ability of the support material, Montmorillonite clay itself was mixed with a conventional catalyst, a typical RE-USY type available from any FCC catalyst supplier, and evaluated in MAT. The results obtained, which are shown in
Results Obtained by Use of a Zinc-Impregnated Clay.
A composition was prepared by impregnating 2% Zn on the clay described in Example 3 by the incipient wetness method. 10%, by weight, of this composition was mixed with the same commercial catalyst, a typical low RE-USY type, available from any FCC catalyst supplier, as in Example 1 and tested in MAT.
Effect of Incorporating Zirconium into the Pores of Clay
A composition of Zr-Clay was prepared by incorporating zirconium into the pores of montmorillonite clay by ion exchange. About 2 weight percent zirconium was incorporated. This composition was mixed with a commercial FCC zeolite catalyst, a typical low RE-USY type, available from any FCC catalyst supplier, in a ratio of 1:10.
Results Employing Zinc Impregnated on Zirconium Incorporated Montmorillonite Clay.
A composition was prepared by impregnating 2 wt. % zinc on the composition described in Example 5 (Zr incorporated clay), by the incipient wetness method. 10 wt. % of this material was mixed with a typical low RE-USY type, available from any FCC catalyst supplier, and tested in MAT at the same conditions as described in Example 1.
Composition Consisting of Zinc Impregnated on Zirconium Incorporated Montmorillonite Clay (Sulfur Compound Distribution)
Catalytically cracked gasoline contains different sulfur compounds, such as mercaptans, saturates, thiophenes and benzothiophenes. Sulfur compound distribution in the product gasoline fraction obtained in Example 6 was determined by the use of GC-SCD. It is shown in Table 3. The composition of the present invention possesses a different reducing effect with respect to the various types of sulfur compounds. With the composition of the present invention, sulfur reduction is most effective for saturates and C2-C4 thiophenes.
Gasoline Yield is not Affected by the Use of Novel Additive
Table 4 lists the product yields of gasoline, gas, LCO, HCO and coke obtained with a conventional catalyst, i.e., low RE-USY®, a comparative additive, and the additive compositions of the present invention, at 71% conversion. Gasoline yield and coke yield is not affected by the use of the additive composition of the present invention, which is 50% and 3.1%, respectively.
Various modifications of the present invention are possible in light of the foregoing teachings. However, it is to be understood that other modifications may be made without departing from the scope thereof, which is to be determined solely by the claims which follow.
