Properties, catalyst

For all experiments, a commercial NiMo-supported y-alumina catalyst was used. Its properties are specific surface area of 175 m /g, mean average pore volume of 0.56 cmVg, mean average pore diameter of 127 A, molybdenum content of 10.66 wt%, and nickel content of 2.88 wt%. The tetralobular commercial catalyst had a diameter of 2.54 mm. 

Fig[iire 10 2 (a) Framework sintciiires and (b) pore cross sections of two types of zeolites, (a) Faiijasiie-type zeolite has a three-dimensional channel system with pores at iea.si 7.4 A in diameter. A pore is formed by 12 oxygen atoms in a ring. 

Oegnan. Chem. Eng. Prog.. 34(2. 33 (1988). Reproduced by permission of the American Institute of Chemical Engineers. Copyright 1988 AIChE. All rights reserved. I 

Ortho- and meia- to para-xylene. Hence we have a very high selectivity to form para-xylene. 

In some cases a catalyst consists of minute panicles of an active material dispersed ova a less active substance called a support. The active material is frequently a pure metal or metal alloy. Such catalysts are called supported catalysts, as distinguished from un.supported cataly.m. Catalysts can also have small amounts of active ingredients added called promoters, which increase their activity. Examples of supported catalysts are the packed-bed catalytic converter in an automobile, (he platinum-on-alumina catalyst used in petroleum reforming, and the vanadium pentoxide on silica used to oxidize sulfur dioxide in manufacturing sulfuric acid. On the other hand, platinum gauze for ammonia oxidation, promoted iron for ammonia synthesis, and silica-alumina dehydrogenation catalyst used in butadiene manufacture typify unsupported catalysts. 

Chemisorption on active sites is what catalyzes the reaction. 

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The most important factors affecting performance are operating temperature, surface velocity, contaminant concentration and composition, catalyst properties, and the presence or absence of poisons or inhibitors. 

The product distrihution is influenced hy the catalyst properties as well as the various reaction parameters. The catalyst activity and selectivity are functions of acidity, crystalline size, silica/alumina ratio, and even the synthetic procedure. Since the discovery of the MTG process. 

With each shipment of fresh catalyst, the catalyst suppliers typically mail refiners an inspection report that contains data on the catalyst s physical and chemical properties. This data is valuable and should be monitored closely to ensure that the catalyst received meets the agreed specifications. A number of refiners independently analyze random samples of the fresh catalyst to confirm the reported properties. In addition, quarterly review of the fresh catalyst properties with the catalyst vendor will ensure that the control targets are being achieved. 

Catalyst circulation is largely influenced by the physical layout of the unit and the fluidization properties of the catalyst. Some cat crackers circulate with ease regardless of the catalyst s physical properties. However, in other designs, the unit can experience circulation difficulties with minor changes in catalyst properties. 

Changing catalyst properties. This can be due to changes in the fresh catalyst s physical properties and/or malfunctioning of the cyclones. 

Verify that the fresh catalyst properties have not changed... 

Plot the physical properties of the equilibrium catalyst. The plotted properties will include particle size distribution and apparent bulk density. The graph confirms any changes in catalyst properties. 

Certain catalyst properties appear to increase coke formation. Catalysts with high rare earth content tend to promote hydrogen transfer reactions. Hydrogen transfer reactions are bimolecular reactions that can produce multi-ring aromatics. 

Changes in Operating Conditions Changes in Catalyst Properties Changes in feedstock Properties Changes in Mechanical Conditions of the Equipment... 

The performance of the unit is a function of feed quality, catalyst properties, operating variables, and the mechanical condition of the unit. The indicators used to measure the unit s performance are ... 

Huid Catalytic Cracking Handbook Catalyst Properties... 

The fresh catalyst properties that increase gasoline yield are ... 

Plot the catalyst s unit cell size, rare earth, and activity. Check if there is any fluctuation in catalyst properties. 

Evaluation of the interaction among feed quality, catalyst properties, and operating conditions... 

Vehicle data represents the complex interaction of many variables, including vehicle performance, reactor design and location, as well as catalyst properties. For a catalyst that has failed, one must ponder whether the converter design used in the vehicle is suitable for the catalyst, the quantity of the catalyst used is correct, the distance of the converter from the exhaust manifold is suitable, the catalyst has been inadvertantly overheated to above 2000°F or poisoned by lead and sulfur, or whether the catalyst can be modified to produce a far superior product. 

The single-event microkinetic concept ensures the feedstock independence of the kinetic parameters [8]. Present challenges in microkinetic modelling are the identification of catalyst descriptors accounting for catalyst properties such as acidity [10,11] and shape selectivity [12,13]. 

Many experiments were performed to answer the question of catalyst property changes due to repeated reaction Interruption. Every time the reaction Is stopped in the mlnlreactor to analyze the sample. It Is necessary to stop the reaction In the pilot plant as well to assure that the catalyst In pilot plant and mlnlreactor maintain Identical histories in reaction time. 

Selectivity is determined by a number of factors, such as intrinsic properties of the catalyst complex (metal and ligands), reaction conditions (concentration, temperature, pressure), and reactor configuration (solvent, reactor, process). Here, we will focus on the catalyst properties. 

Typical products distribution, and selectivity profiles were similar to what was reported in the earlier publication (1). The reaction network is shown in Scheme 1. The catalyst properties and test data are given in Table 1. 

The Knudsen diffusion coefficient may be evaluated from equation 12.2.4 if the catalyst property values are used to estimate the average pore radius. From equation C of Illustration 6.2,... 

Temperature, 705 °K Pressure, 1.480 MPa H2 feed rate, 8 moles/ksec Cyclohexane feed rate, 2 moles/ksec Conversion of cyclohexane, 15.5% Quantity of catalyst, 10.4 g Catalyst Properties ... 

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