Catalyst management

Depending on the design of a cat cracker, the circulating inventory can contain 30-1,200 tons of catalyst. Fresh catalyst is added to the unit continually to replace the catalyst lost by attrition and to maintain 

The amount of fresh catalyst added is usually a balance between catalyst cost and desired activity. Most refiners monitor the MAT data from the catalyst vendor s equilibrium data sheet to adjust the fresh catalyst addition rate. It should be noted that MAT numbers are based on a fixed-bed reactor system and, therefore, do not truly reflect the dynamics of an FCC unit. A catalyst with a high MAT number may or may not produce the desired yields. An alternate method of measuring catalyst performance is dynamic activity. Dynamic activity is calculated as shown below  

For example, a catalyst with a MAT number of 70 vol% and a 3.0 wt% coke yield will have a dynamic activity of 0.78. However, another catalyst with a MAT conversion of 68 vol% and 2.5 wt% coke yield will have a dynamic activity of 0.85. This could indicate that in a commercial unit the 68 MAT catalyst could outperform the 70 MAT catalyst, due to its higher dynamic activity. Some catalyst vendors ha% c begun reporting dynamic activity data as part of their E-cat inspection reports. The reported dynamic activity data can vary significantly from one test to another, mainly due to the differences in feedstock quality between MAT and actual commercial application. In addition, the coke yield, as calculated by the MAT procedure, is not very accurate and small changes in this calculation can affect the dynamic activity appreciably. 

The most widely accepted model to predict E-cat activity is based on a first-order decay type [7]  

A jj = Catalyst microactivity at anytime Aq = Catalyst inicroactivity at starting time t = Time after changing catalyst or makeup rate S = Daily fractional replacement rate = addition rate/inventory K = Deactivation constant = fn(A, - A )/-t 

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Eijsbouts, S., Life Cycle of Hydroprocessing Catalysts and Total Catalyst Management, In Hydrotreatment and Hydrocracking of Oil Fractions. 1999, Elsevier Science B. V New York, NY. pp. 21-36. 

Discussed is how this model calculates ZSM-5 activity, gasoline research and motor octane increases and catalyst management policies. Also discussed are ways to utilize ZSM-5 and how its use permits reoptimization of not only the FCC unit but the entire refinery. 

Recent developments in Claus converter efficiency can be divided into two categories improvements in process operating technique and improvements in catalyst management. 

This decrease in residence time led to a smaller catalyst inventory in the reactor-regenerator system, and consequently much lower catalyst deactivation rates due to hydrothermal effects. A lower catalyst inventory has also the additional operational advantage that the FCCU can respond more quickly to changes in catalyst management, allowing the refiner to restore the desired catalyst activity level more promptly following an upset. 

Square metal monoliths, as shown in Figure 13, are used in SCR reactors. Catalyst lives of up to more than 10 years are possible, and with proper catalyst management... 

The processes by which the catalyst manages coke precursors on the Pt crystallites are as follows ... 

The implications of this definition have also been frequently explored. By increasing the rate of a reaction at some fixed temperature, a catalyst can also have the effect of lowering the temperature at which a given rate is achieved (Figure 5.1), and for many practical purposes this is its chief advantage. It can only assist reactions that are thermodynamically favourable, and the position of the equilibrium has to be the same as that which would have resulted, albeit in a much longer time, without it. This also implies that rates of forward and reverse reactions must be helped by the same factor if the equilibrium constant is to remain unaltered. Just how a catalyst manages to exert its influence will be considered in the next section. 

Sufficiently stable catalyst managed to be received sedimentation ammonium paiamolybdate on Amberlyst resin (70 h works) and polyvinyl alcohol (100 h works). Immobilization of hexacarbonyl molybdenum on ion exchange resin the authors [28] have presented by the following (Scheme 4) ... 

When a one-pot reaction is chosen, both reactions can be mediated by two catalysts under the same condition or under different reaction conditions. In the best case, the requirements for an auto tandem reaction are fulfilled, where a single catalyst manages both reactions under the same reaction regime. 

Ewell RB, Gadmer G, Turk WJ. FCC catalyst management. Hydrocarbon Processing 60 103-112, 1981. 

Model pollutants (2-propanol, tert-butanol, acetic acid) were tested with a cement-supported CuO-ZnO catalyst. All these compounds were stable in the absence of a catalyst, but the catalyst managed to convert them almost completely at 380-390 C and 230-235 bar (X = 87-98%). In particular, the alcohols react with CO2 selectivities close to 100%. The same group investigated the performance of a CuO-ZnO-Co203 catalyst (Siid-Chemie AG, also tested in phenol destruction) in... 

Biological catalysts — enzymes — are usually proteins. The development of new protein syntheses is nowadays dominated by genetic protein engineering (see section 4.1.2.6). Bio-organic approaches towards novel catalytically active structures and replicating systems try to manage without biopolymers. 

Fluidized-bed reaction systems are not normally shut down for changing catalyst. Fresh catalyst is periodically added to manage catalyst activity and particle size distribution. The ALMA process includes faciUties for adding back both catalyst fines and fresh catalyst to the reactor. 

Polymerization and depolymerization of sihcate anions and their interactions with other ions and complexing agents are of great interest in sol—gel and catalyst manufacture, detergency, oil and gas production, waste management, and limnology (45—50). The complex silanol condensation process may be represented empirically by... 

Mineral acids are used as catalysts, usually in a concentration of 20— 40 wt % and temperatures of 30—60°C. An efficient surfactant, preferably one that is soluble in the acid-phase upon completion of the reaction, is needed to emulsify the a-pinene and acid. The surfactant can then be recycled with the acid. Phosphoric acid is the acid commonly used in the pine oil process. Its mild corrosion characteristics and its moderate strength make it more manageable, especially because the acid concentration is constandy changing in the process by the consumption of water. Phosphoric acid is also mild enough to prevent any significant dehydration of the alcohols formed in the process. Optimization of a process usually involves considerations of acid type and concentration, temperature, surfactant type and amount, and reaction time. The optimum process usually gives a maximum of alcohols with the minimum amount of hydrocarbons and cineoles. 

Applied Sciences, Inc. has, in the past few years, used the fixed catalyst fiber to fabricate and analyze VGCF-reinforced composites which could be candidate materials for thermal management substrates in high density, high power electronic devices and space power system radiator fins and high performance applications such as plasma facing components in experimental nuclear fusion reactors. These composites include carbon/carbon (CC) composites, polymer matrix composites, and metal matrix composites (MMC). Measurements have been made of thermal conductivity, coefficient of thermal expansion (CTE), tensile strength, and tensile modulus. Representative results are described below. 

For reactions which progress slowly at room temperature it may be necessary to heat the mixture or add a catalyst for the reaction to occur at an economically-viable rate. For very fast reactions the mixture may need to be cooled or solvent added to dilute the reactants and hence reduce the speed of reaction to manageable proportions. In general the speed of reaction... 

What needs to be understood is that the role of managers changes in quality management systems. The day-to-day process is driven by the staff involved in the process, rather than the manger, and these staff are likely to be in every department in the company. The role of the manager is to monitor performance, be a catalyst for improve-... 

In this book we have decided to concentrate on purely synthetic applications of ionic liquids, just to keep the amount of material to a manageable level. FFowever, we think that synthetic and non-synthetic applications (and the people doing research in these areas) should not be treated separately for a number of reasons. Each area can profit from developments made in the other field, especially concerning the availability of physicochemical data and practical experience of development of technical processes using ionic liquids. In fact, in all production-scale chemical reactions some typically non-synthetic aspects (such as the heat capacity of the ionic liquid or product extraction from the ionic catalyst layer) have to be considered anyway. The most important reason for close collaboration by synthetic and non-synthetic scientists in the field of ionic liquid research is, however, the fact that in both areas an increase in the understanding of the ionic liquid material is the key factor for successful future development. 

Reflux overhead vapor recompression, staged crude pre-heat, mechanical vacuum pumps Fluid coking to gasification, turbine power recovery train at the FCC, hydraulic turbine power recovery, membrane hydrogen purification, unit to hydrocracker recycle loop Improved catalysts (reforming), and hydraulic turbine power recovery Process management and integration... 

A small amount of nickel in the FCC feed has a significant influence on the unit operation. In a clean gas oil operation, the hydrogen yield is about 40 standard cubic feet (scf) per barrel of feed (0.07 wi /r ). This is a manageable rate that most units can handle. If the nickel level increases to 1.5 ppm, the hydrogen yield increases up to 100 scf per barrel (0.17 wt%). Note that in a 50,000 barrel/day unit, this corresponds to a mere 16 pounds per day of nickel. Unless the catalyst addition rate is increased or the nickel in the feed is passivated (see Chapter 3), the feed rate or conversion may need to be reduced. The wet gas will become lean and may limit the pumping capacity of the wet gas compressor. 

We have included in this volume two chapters specifically related to society s kinetic system. We have asked James Wei of the University of Delaware, recent Chairman of the consultant panel on Catalyst Systems for the National Academy of Sciences Committee on Motor Vehicle Emissions, to illustrate key problems and bridges between the catalytic science and the practical objectives of minimizing automobile exhaust emissions. We have also asked for a portrayal of the hard economic facts that constrain and guide what properties in a catalyst are useful to the catalytic practitioner. For this we have turned to Duncan S. Davies, General Manager of Research and Development, and John Dewing, Research Specialist in Heterogeneous Catalysts, both from Imperial Chemical Industries Limited. 

Fig. 1. Schematic of the pilot unit used for catalyst life and heat management testing.

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