Catalytic cracking definition

Zeolites are crystalline aluminosilicates that have exhibited catalytic activities ranging from one to four orders of magnitude greater than amorphous aluminosilicates for reactions involving carbonium ion mechanisms such as catalytic cracking (144). As a result extensive efforts have been undertaken to understand the nature of the catalytic sites that are responsible for the observed high activity. The crystalline nature of zeolites permits more definite characterization of the catalyst than is possible for amorphous acidic supports such as alumina and silica-alumina. Spectral techniques, in conjunction with structural information derived from X-ray diffraction studies, have led to at least a partial understanding of the nature of the acidic sites in the zeolite framework. 

Hydrotreating processes have two definite roles (1) desulfurization to supply low-sulfur fuel oils and (2) pretreatment of feed residua for residuum fluid catalytic cracking processes. The main goal is to remove sulfur, metal, and asphaltene contents from residua and other heavy feedstocks to a desired level. 

Figures 1 and 2 show that there are five major products obtained from a catalytic cracking operation. These products are 1) light products 2) gasoline 3) light cycle oil 4) slurry or decant oil and 5) coke. The light products are those which have a boiling point below 170°F, gasoline has a boiling point of 170°F-430°F, light cycle oil has by definition here a boiling point of 430°F-630°F, slurry or...

Alumina-promoted fluid catalytic cracking catalysts, commercial viability, 414 Analysis of testing responses definition of sensitivity of result to given variable, 94 problems, 95... 

Before we look at the mechanism of catalytic cracking on catalysts, it is appropriate to give a definition of a catalyst. Catalysis is derived from the Greek word katalysis meaning destruction or weakening. A catalyst is a substance that changes the rate of a chemical reaction but remains chemically unchanged at the end of the reaction. 

At very high velocities, all particles fed to the reactor are carried up with the gas, and this mode of operation is sometimes called fast fluidization. However, since there is no definite bed level, a better term for this system is a transport-line reactor or, as it is called in catalytic cracking, a riser reactor. These are discussed in Chapter 10, on novel types of reactors. 

Heavy aromatic solvent naphtha Heavy aromatic solvent naphtha (petroleum) Petroleum distillates, intermediate catalytic cracked (Polyethyl) benzenes Solvent naphtha, heavy aromatic Solvent naphtha (petroleum), heavy aromatic Classification Petroleum hydrocarbon Definition Complex combination of hydrocarbons obtained from distillation of aromatic streams consists of predominantly C9-16 aromatic hydrocarbons... 

It is hard to find out the most appropriate equipment/method and performance index to measure and assess the quality of catalysts, which is difficult in unified definition and standardization of methods. So far, some methods for evaluating the activities of a few catalysts such as those for catalytic ammonia synthesis and catalytic cracking have been standardized. The evaluation methods are different due to the varieties of catalysts and the experiences of researchers. Sometimes, the technical details of evaluation methods are a part of patent, such as formula and preparation process is confidential. Even then, some basic conceptions and methods for the evaluation and testing of catalysts are still worthy being introduced, which is the main focus of this chapter. 

Sendoda and Ono studied the dependence of catalytic activity of ZSM-5 for alkane conversion on its pretreatment temperature. The activity maximum for propane conversion was observed at the pretreatment temperature of 853 K (Fig. 3.72). This is much higher than the temperature where NH4 —ZSM-5 is transformed into H-ZSM-5, suggesting that ordinary OH groups are not active centers for propane conversion. In the case of hexane cracking, double maxima were observed at 673 K and 853 K (Fig. 3.72). The double maxima pattern was observed also for cracking of pentane and heptane, and for isomerization of o-xylene. These results show definitively the existence of two types of active centers. The one g iving a maximum activity at 673... 

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