Patent Grant
4927521
This application is related to, Ser. No. 238,677, filed concurrently, entitled CATALYTIC REFORMING WITH IMPROVED ZEOLITE CATALYSTS. This invention relates to an improved method of pretreating a naphtha prior to catalytically reforming same. Catalytic reforming is well known and refers to the treatment of naphtha fractions to improve the octane rating by the production of aromatics. A number of other reactions also occur during reforming, however, hydrocracking reactions are to be particularly minimized because they decrease the yield of gasoline boiling products. However, both C.sub.4.sup.+ and C.sub.5.sup.+ gasolines are maximized by the process of the present invention. There is a high demand for high octane gasoline for use as motor fuels and the like. Accordingly, much research is dedicated to the development of improved reforming catalyst and catalytic reforming processes to produce higher yields of C.sub.4.sup.+ and C.sub.5.sup.+ gasolines. Zeolite Beta has been found to be suited for use in a catalyst for hydrocracking naphtha under mild conditions, (U.S. Pat. No. 3,923,641). However, it is desirous to further treat such catalysts to improve their activity and their stability in acid catalyzed reactions by steaming. The catalyst used in hydrocracking/reforming processes generally contain platinum and high acidity zeolites but have poor C.sub.4.sup.+ and C.sub.5.sup.+ selectivity (U.S. Pat. No. 4,276,151). An example of platinum-containing reforming catalysts is described in U.S. Pat. No. 4,456,527 which relates to a reforming process having "superior" selectivity for dehydrocyclization. It has now been found that higher C.sub.4.sup.+ and C.sub.5.sup.+ gasoline yields can be obtained by pretreating the raw naphtha with a suitable zeolite catalyst prior to reforming. It is therefore, an object of this method to provide an improved process wherein pretreatment of a naphtha using zeolitic catalysts provides significantly higher C.sub.4.sup.+ and C.sub.5.sup.+ gasoline yields than conventional hydrotreating and reforming catalysts. This invention is directed to a process of pretreating a naphtha with a zeolite catalyst containing at least one noble metal and one alkali metal useful for catalytic reforming. Zeolites useful include high silica/alumina zeolite beta, ZSM-23, and other similar ZSM-5 type zeolites. The noble metal loading should be in range of 0.1-1 wt. %, and the alkali metal loading should exceed the cationic exchange capacity of the zeolite component if the improved process results are to be attained. The naphtha may be then more advantageously processed as a reformate. Higher C.sub.4.sup.+ and C.sub.5.sup.+ gasoline yields are obtained. The catalysts described herein are different from U.S. Pat. Nos. 3,783,123 and 4,478,706 which use alkali metal containing zeolite catalysts wherein the zeolites must be specially treated and have exchangeable cations/A10.sub.2.sup.- .ltoreq.1. Furthermore, unlike alkaline earth metal zeolite catalysts which are sensitive to sulfur (U.S. Pat. No. 4,456,527), the present catalysts are stable toward sulfur containing feeds. Further the catalysts in accordance with the invention are sulfur resistant and eliminate the need for careful environmental (Chloride, H.sub.2 O) control. The invention therefore, is also more particularly directed to pretreating naphthas with zeolite catalysts containing a noble metal and having acidity and thereafter catalytically reforming with the same or a different catalyst. Pretreatment results in a reformate feed that produces higher yields of C.sub.4.sup.+ and C.sub.5.sup.+ gasolines.
| Number | Name | Date | Kind |
|---|---|---|---|
| RE31919 | Butter et al. | Jun 1985 | |
| 4076842 | Plank et al. | Feb 1978 | |
| 4623632 | Lambert et al. | Nov 1986 | |
| 4652689 | Lambert et al. | Mar 1987 | |
| 4694114 | Chu et al. | Sep 1987 | |
| 4699708 | Dessau | Oct 1987 |
