Cracking catalysts composition

Cracking Catalyst Composition. Several workers (20-21) have reported differences among cracking catalysts to remove SOx which correlated qualitatively with alumina content. Our work confirmed these reports as shown on Figure 2. Plotted are %S02 removal... 

Independence from cracking catalyst composition has been shown by adding cerium and alumina to cracking catalyst (25). The data on Table I demonstrate this. 

For cracking catalyst composition, we showed that alumina content is important by showing how catalysts synthesized to contain various amounts of alumina removed SO2. Although for years alumina content has been considered important by the industry, it was difficult to find a conclusive reference showing that fact. 

The main objective in FCC catalyst design is to prepare cracking catalyst compositions which are active and selective for the conversion of gas-oil into high octane gasoline fraction. From the point of view of the zeolitic component, most of the present advances in octane enhancement have been achieved by introducing low unit cell size ultrastable zeolites (1) and by inclusion of about 1-2 of ZSM-5 zeolite in the final catalyst formulation (2). With these formulations, it is possible to increase the Research Octane Number (RON) of the gasoline, while only a minor increase in the Motor Octane Number (MON) has been obtained. Other materials such as mixed oxides and PILCS (3,4) have been studied as possible components, but there are selectivity limitations which must be overcome. 

A mixture of monolauryl phosphate sodium salt and triethylamine in H20 was treated with glycidol at 80°C for 8 h to give 98% lauryl 2,3-dihydro-xypropyl phosphate sodium salt [304]. Dyeing aids for polyester fibers exist of triethanolamine salts of ethoxylated phenol-styrene adduct phosphate esters [294], Fatty ethanolamide phosphate surfactant are obtained from the reaction of fatty alcohols and fatty ethanolamides with phosphorus pentoxide and neutralization of the product [295]. A double bond in the alkyl group of phosphoric acid esters alter the properties of the molecule. Diethylethanolamine salt of oleyl phosphate is effectively used as a dispersant for antimony oxide in a mixture of xylene-type solvent and water. The composition is useful as an additive for preventing functional deterioration of fluid catalytic cracking catalysts for heavy petroleum fractions. When it was allowed to stand at room temperature for 1 month it shows almost no precipitation [241]. 

The desire to have catalysts that were uniform in composition and catalytic performance led to the development of synthetic catalysts. The first synthetic cracking catalyst, consisting of 87% silica (Si02) and 13% alumina (AI2O3), was used in pellet form and used in fixed-bed units in 1940. Catalysts of this composition were ground and sized for use in fluid catalytic cracking units. In 1944, catalysts in the form of beads about 2.5 to 5.0 mm in diameter were introduced and comprised about 90% silica and 10% alumina and were extremely durable. One version of these catalysts contained a minor amount of chromia (Cr203) to act as an oxidation promoter. 

Introduction of zeolites into catalytic cracking improved the quality of the product and the efficiency of the process. It was estimated that this modification in catalyst composition in the United States alone saved over 200 million barrels of crude oil in 1977. The use of bimetallic catalysts in reforming of naphthas, a basic process for the production of high-octane gasoline and petrochemicals, resulted in great improvement in the catalytic performance of the process, and in considerable extension of catalyst life. New catalytic approaches to the development of synthetic fuels are being unveiled. 

Steam pre-treatment of fluid cracking catalysts has been conventionally employed to represent the deactivation occurring in a commercial FCC unit. Appropriate steam pre-treatment methods have been developed so that the activity and selectivity of the steam pre-treated catalyst is equivalent to a commercially deactivated catalyst (12). However, a unique steaming method may not be suitable for catalysts of varying compositions (12). Two steaming methods designed to simulate deactivation in a commercial unit of the two types of catalysts used in this work were employed. Super-D was treated for 8 hours at 732 C with a steam pressure of 2 atmospheres. The catalysts containing ZSM-5 were treated for 12 hours at 827°C with a steam partial pressure of 0.2 atmosphere. 

The demonstrated performance of ZSM-5 in over 35 cracking units is reviewed. The main features of ZSM-5 are its high activity and stability, favorable selectivity, metals tolerance and flexibility, particularly when used as an additive catalyst. ZSM-5 cracks and isomerizes low octane components in the naphtha produced by the faujasite cracking catalyst. As a result and olefins are produced and gasoline compositional changes occur which explain its increased research and motor octanes. A model was developed which predicts ZSM-5 performance in an FCC unit. 

There are three different kinds of octane catalysts in current use. Some are based in part on an active non-zeolite matrix composed of a porous silica/alumina component. Others are based on low cell size (2.425-2.428 nm) ultra stable faujasite (USY), a catalyst composition developed in 1975 (2) for the purpose of octane enhancement. A third catalyst system makes use of a small amount (1-2%) of ZSM-5 as an additive. While the net effect in all cases is an increase in the measured octane number, each of the three catalytic systems have different characteristic effects on the composition and yield of the gasoline. The effects of the ZSM-5 component on cracking is described in other papers of this symposium and will not be discussed here. 

The rates of hydrolysis of siliceous materials will be affected by several factors. For instance, the rate will be directly related to surface area, explaining the low rates observed for silica deposition from the Vycor apparatus. Also, the composition of the siliceous material will Influence the rate of hydrolysis, explaining the differing amounts of silica transferred from pure silica, silica alumina, zeolite, and the high alumina cracking catalyst. 

To show the effect of having zeolite present in the contaminated particles, a REY commercial cracking catalyst with a matrix surface area of ca. 85 m /g was also contaminated with nickel and vanadium, and steamed (1450 F, 4 hrs, 90% steam, 10% air) to age the metals. Its select vities were compared to the non-zeolitic additive having the same surface area and chemical composition blended with sufficient metals-free active cracking component to give the same conversion. 

At very low surface areas (about 5 m /g) and constant conversion (70%), the contaminant selectivities are dominated by the matrix composition (Table I). Rare earth and magnesium-containing microspheres were prepared to examine the effects of these metal oxides on catalyst selectivities in the presence of nickel and vanadium. These oxides were chosen because the literature (3,5,10-15) has shown them to be effective at reducing the deleterious effects of vanadium in cracking catalysts. 

The low H/C-ratio of FCC feed derived from liquefied biomass led to low conversion and poor gasoline selectivity. Addition of alumina to the matrix resulted in a catalyst more active for heavy oil cracking but with a poor selectivity. Alumina-montmorillonite catalysts showed activities for heavy oil cracking comparable to that of a conventional, zeolite based, cracking catalyst. Effects of matrix composition and zeolite type on the heavy oil cracking performance are discussed. 

Of the many factors which influence product yields in a fluid catalytic cracker, the feed stock quality and the catalyst composition are of particular interest as they can be controlled only to a limited extent by the refiner. In the past decade there has been a trend towards using heavier feedstocks in the FCC-unit. This trend is expected to continue in the foreseeable future. It is therefore important to study how molecular types, characteristic not only of heavy petroleum oil but also of e.g. coal liquid, shale oil and biomass oil, respond to cracking over catalysts of different compositions. 

Because of the ease of experimentation batch-solids devices are much preferred however, they can only be used when deactivation is slow enough (in the order of minutes or longer) so that sufficient data on the changing fluid composition can be obtained before exhaustion of the catalyst. When deactivation is very rapid (in the order of seconds or less) then a flowing-solids system must be used. Cracking catalysts whose activity half-lives can be as short as 0.1 second fall into this class. 

Van Broekhoven, E., Cracking process employing a catalyst composition and absorbent which contain an anionic clay, U.S. Patent 4,946,581, 1990. 

The catalytic cracking of four major classes of hydrocarbons is surveyed in terms of gas composition to provide a basic pattern of mode of decomposition. This pattern is correlated with the acid-catalyzed low temperature reverse reactions of olefin polymerization and aromatic alkylation. The Whitmore carbonium ion mechanism is introduced and supported by thermochemical data, and is then applied to provide a common basis for the primary and secondary reactions encountered in catalytic cracking and for acid-catalyzed polymerization and alkylation reactions. Experimental work on the acidity of the cracking catalyst and the nature of carbonium ions is cited. The formation of liquid products in catalytic cracking is reviewed briefly and the properties of the gasoline are correlated with the over-all reaction mechanics. 

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