Metal-zeolite formulations

Although initially promising, the catalytic decomposition of NO has proven to be difficult to realize. A large number of metal-zeolites formulations has been tested... 

The success of ZSM5 in Isomerisation,165 Methanol to Gasoline166 and Cyclar167 has prompted the investigation of the potential of metal-zeolite formulations in conventional, bifunctional reforming. To date this approach has had little success, possibly because the acidity in H-zeolites is too strong, permanent and inflexible for the conventional reforming case.168... 

Full catalyst formulations consist of zeolite, metal and a binder, which provides a matrix to contain the metal and zeolite, as well as allowing the composite to be shaped and have strength for handling. The catalyst particle shape, size and porosity can impact the diffusion properties. These can be important in facile reactions such as xylene isomerization, where diffusion of reactants and products may become rate-limiting. The binder properties and chemistry are also key features, as the binder may supply sites for metal clusters and affect coke formation during the process. The binders often used for these catalysts include alumina, silica and mixtures of other refractory oxides. 

The first part of the book documents the history, structure, chemistry, formulation and characterizations of zeolites in Chapters 1-4. The past 60 years have seen a progression in molecular sieve materials from aluminosilicate zeolites to micro-porous silica polymorphs, microporous aluminophosphate-based polymorphs, metallosihcate and metallophosphate compositions, octahedral-tetrahedral frameworks, mesoporous molecular sieves and, most recently, hybrid metal organic frameworks (MOFs). 

Generally speaking, resid FCC (RFCC) catalysts should be very effective in bottoms cracking, be metals tolerant, and coke and dry gas selective. Based on many years of fundamental research and industrial experiences, a series of RFCC catalysts, such as Orbit, DVR, and MLC, have been developed by the SINOPEC Research Institute of Petroleum Processing (RIPP) and successfully commercialized [1]. These catalysts are very effective in paraffinic residue cracking. However, in recent years more and more intermediate-based residue has been introduced into FCC units, and the performances of conventional RFCC catalysts are now unsatisfactory. Therefore, novel zeolites and matrices have been developed to formulate a new generation of RFCC catalysts with improved bottoms cracking activity and coke selectivity. 

The specifically formulated CGP-1 catalyst plays a vital role in the MIP-CGP process. Unique catalyst design, such as metal promoted MFl zeolite, phosphorus modified Y zeolite, and a novel matrix with excellent capability to accommodate coke [12] were involved to ensure the primary cracking and secondary reactions to proceed within a defined path. The commercial trial results of the MIP-CGP process in SINOPEC Jiujiang Company showed that, in combination with CGP-1 catalyst, the propylene yield was 8.96 wt%, which increased by more than 2.6% as compared with FCC process. The light ends yield and slurry yield are basically equal. The olefin content of the gasoline produced by MIP-CGP process was 15.0 v%, which was 26.1% lower than that of FCC gasoline. The sulfur content of gasoline was decreased from 400 to 270 pg/g. 

Concerns about the effect of TPP on eutrophication have led many states, cities, and regional governments to ban the use of the compound in syndets. Such bans have caused serious problems for detergent manufacturers, however, because no entirely satisfactory substitute for TPP has yet been found. Two promising candidates are the sodium salt of nitrilotriacetic acid, 3Na, N(CH2C02)3 , or NTA and ethylenediaminetetraacetic acid (EDTA). Both of these compounds act in much the same way as TPP, that is, by sequestering metal ions. Other builders that have been incorporated into syndet formulations include sodium carbonate, synthetic zeolites, borates, and organic polymers known as polycarboxylates. 

Tn the course of experimentation with formulations of silica, alumina, and A various alkali metal oxides in attempts to prepare new synthetic zeolites, a formulation containing cesium replacing some of the sodium in a typical faujasite preparation yielded a new crystalline zeolitic product which showed a typically cubic powder diagram having a body-centered pattern of... 

The actual technology involves the formulation of multifunctional cracking catalysts which are composed of different amorphous and crystalline acid functions, and a series of additives for metal passivation, SOx removal, promotors for total combustion, and octane enhancing additives. Among them, zeolite Y is the main component controlling the activity and selectivity of the cracking catalysts. 

Catalytic reactions of hydrocarbons over zeolites are reviewed. The historical development of various mechanistic proposals, particularly of the carbonium ion type, is traced. In spite of numerous catalytic, spectroscopic, and structural studies which have been reported concerning the possible roles of Bronsted acid, Lewis acid, and cationic sites, it still is not possible to formulate a comprehensive mechanistic picture. New activity and product data for cumene cracking and isotope redistribution in deuterated benzenes over Ca-and La-exchanged Y zeolites is presented. Cracking of the isomeric hexanes over alkali metal-exchanged Y and L zeolites has been studied. This cracking is clearly radical rather than carbonium-ion in nature but certain distinct differences from thermal cracking are described. 

When considering as yet unexploited zeolite characteristics, we may need to consider recent electronic technology, particularly the formulation of computer chip sur ce structures, which approaches the atomic scale. Although zeolites do not possess electronic properties, their surfaces have a great variety of repeated pores that can be doped with metals or oxides. Such treatments may also introduce desired electronic characteristics. 

Additional information about the catalytic performance of the catalysts can be obtained from the analysis of the product distribution, which is affected by the metallic and acid functionalities. Tables 4 and 5 compare the product distributions obtained in the DBT and 4,6-DMDBT reactions with the NiMo/Al203, NiMo/HNaY and NiMo catalysts with 20% of HNaY in their formulation. In the case of DBT, zeolite incorporation into the catalyst changes the contributions of the direct desulfurization (DDS) pathway, which yields biphenyl-type compounds, and of the desulfurization through hydrogenation (HYD) pathway, which gives cyclohexylbenzene-type compounds. Also, the proportion of CHB in the reaction products and the liquid yield decrease with the number of accessible zeolite acid sites in the catalyst. This effect is due to the cracking of CHB on the zeolite acid sites. On the other hand, the formation of DCH is enhanced on the catalysts where Mo precursor phase is more polymerized (NiMo/HNaY-Al203(P) and NiMo/HNaY formulations). 

The results obtained in the present work indicate that the method used for the catalyst preparation leads to some changes in the characteristics and performance of the obtained catalytic formulations. These changes are due to differences in the characteristics of both the deposited metallic species (their coordination state, location and dispersion) and the contribution of the acidic component of the catalyst (number of accessible acid sites and partial destruction of zeolite structure). Therefore, the importance of the method used for the preparation of zeolite-containing catalysts is clearly observed. 

Composition of the inorganic framework can be varied just like the surfactant use has been expanded beyond the original cationic species. The number of explored element combinations has been enormous and often driven by specific catalytic needs and prior experience with amorphous or crystalline compositions [37]. One of the leading approaches was doping of silica formulation with appropriate activating clement, such as aluminum (lo impart acidity) and titanium or vanadium for redox potential. Based on analogy of AlPO s and SAPO s to zeolites these compositions were also synthesized in the mesoporous form as were other non-silica inorganic oxides and their combinations [38]. Pure metal mesoporous product was obtained via the pre-formed liquid crystal route 1391. 

Finally, new types of NOx and SOx abatement catalysts use rare earths in their formulations, helping to increase the activity and stability of transition-metal-containing zeolites. 

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