Octane-boosting catalysts

The increase in octane number required to replace lead can be achieved in a number of ways (Ref. 16), all of which increase the manufacturing costs some require substantial additional investment. At the current state of the art and prices the average cost of an octane-ton is about 1.8. The most attractive but limited octane enhancement is obtained by the use of octane boosting catalysts in the cat cracker. 

The concentration of the ZSM-5 additive should be greater than 1% of the catalyst inventory to see a noticeable increase in the octane. An octane boost of one research octane number (RON) will typically require a 2% to 5% ZSM-5 additive in the inventory. It should be noted that the proper way of quoting percentage should be by ZSM-5 concentration rather than the total additive because the activity and attrition rate can vary from one supplier to another. There are new generations of ZSM-5 additives that have nearly twice the activity of the earlier additives. 

A model which is consistent with the chemistry described previously has been developed to predict the performance of ZSM-5 in an FGG unit. Application of this model allows the user to take full advantage of ZSM-5 s flexibility for specific applications. The model has been used in many commercial applications to determine the catalyst makeup rate required to achieve a given octane boost. It has also been used to tailor the catalyst makeup strategy to obtain a desired octane boost in a given period of time. 

As discussed above, the potential octane boost which can be achieved from ZSM-5 addition is a function of five parameters the regenerator temperature and steam partial pressure (which determine the activity maintenance) the base and ZSM-5 catalyst makeup rates (which determine the catalyst age) and the base gasoline octane. The sensitivity of the model to these parameters is discussed below. 

One of the main applications of the ZSM-5 performance model is to determine the optimal catalyst makeup strategy to achieve a desired octane boost in a required period of time. Since ZSM-5 is used primarily as an additive, the catalyst makeup policy can be tailored to fit the refiner s needs. 

Aluminophosphate-based catalysts are used for the catalytic cracking of heavy boiling hydrocarbons and for the selective reaction with low-octane hydrocarbons resulting in octane boost in catalytic cracking. The aluminophosphate catalyst is applied by itself or in mixture with other types of cracking catalysts. ... 

In the early 1950s, reforming processes that jdelded more octane-boosting aromatics were introduced by Standard of Indiana and Exxon. This was achieved at the expense of increased catalyst deactivation at the lower operating pressures. A regeneration cycle had to be added, which required adding one reactor to the normal set of three used in the platforming process. 

Adding ZSM-5 catalyst additive is another process available to tlie refiner to boost production of light olefins. ZSM-5 at a typical concentration of 0.5 to 3.0 wt% is used in a number of FCC units to increase the gasoline octane and light olefins. As part of the cracking of low octane components in the gasoline, ZSM-5 also makes C. C4, and Cj olefins (see Figure 6-2). Paraffinic feedstocks respond the most to ZSM 5 catalyst additive.. 

MTBE is used on a large scale as an octane number boosting additive in unleaded gasoline. Sulfonic acid resins are applied as efficient catalysts for the industrial production of MTBE from methanol and isobutylene (222). Since 1987, investigations of the synthesis of MTBE with reactants in the gas phase have been performed with zeolites HY (223-225), H-Beta (226), HZSM-5 (224,225), and H-BZSM-5 (227) as catalysts. 

Besides faujasite (Y) zeolites, today s catalysts contain several additional functional materials, such as metal traps, nickel-resistant matrices, bottoms-cracking matrices, and small pore zeolites, such as, for instance, ZSM-5. These zeolites are often added as separate (additive) particles with the intention of boosting the gasoline octanes and/or the production of light olefins (propylene). 

Here, first olefinic intermediates are generated over platinum. These intermediates are either cracked to form lighter olefins or cyclized and isomerized over the acidic chlorided alumina. The olefins and naphthenes thus formed are finally dehydrogenated over the platinum to form paraffins and aromatics. Zeolitic acids such as mordenite(20) and ZSM-5(21) have been substituted for the chlorided alumina as acid catalyst components. All of these acid components have been reported to boost reformed product octane. However, much of the enhanced octane observed with these materials is accompanied by enhanced cracking activity and by reduced yields. 

The MBR process reduces the benzene content of light reformate, FCC gasoline, or pyrolysis gasoline to below 1 vol% while boosting pool octane up to one point. The zeolite catalyst alkylates benzene with light... 

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