Equilibrium catalyst properties

I 4 Predictive Modeling of the Fluid Catalytic Cracking (FCQ Process Table 4.23 Equilibrium catalyst properties. 

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. 

Plot properties of the fresh and equilibrium catalysts ensure that the catalyst vendor is meeting the agreed quality control specifications. Verify that the catalyst vendor has the latest data on feed properties, unit condition, and target products. Verify the fresh makeup rate. Check for recent temperature excursions in the regenerator or afterburning problems. 

Using the catalyst vendor s equilibrium catalyst report, the physical properties of the circulating catalyst may be monitored for any change. Albemarle routinely analyzes a sample of the circulating catalyst inventory among others for physical characteristics, including surface area (SA), metal content, apparent bulk density (ABD), and particle size distribution (PSD). 

Correlation of Equilibrium Catalyst Fraction Properties with Fraction Densitv/Age... 

Coke Deposition. The properties of catalyst fractions separated in coked condition from spent equilibrium catalyst are summarized in Tables III and IV. The distribution of catalyst fractions along with the percent carbon found on each coked fraction is given in Figure 2. The activity for coke deposition falls off sharply with increase in density. Only the three lightest fractions show a coke make that is significantly above the minimum coke make exhibited by the heavier fractions. The fact that the lightest fractions are the most active is consistent with the notion that they are the youngest. The distribution of catalyst... 

The comparison of physical properties of laboratory-steamed catalyst with those of equilibrium catalyst fractions given in Table VII indicates that a wide range of steaming temperatures is necessary to reproduce the equilibrium catalyst deactivation profile for lab steaming times of one day or less. These results indicate that an improved catalyst aging procedure for simulating... 

The experimental data were obtained in a modified MAT [16] which enabled reaction conditions to be easily changed. The feedstock properties and reaction conditions are given in Table 1. The catalysts were a SUPER D and NOVA D equilibrium catalysts from Grace-Davison Co. The initial coke content was built up in previous MAT runs with the same feedstock and reaction conditions. The catalyst was removed from the reactor, mixed, analyzed for coke concentration, and reintroduced to the reactor. 

The properties of a commercial FCC catalyst modified with V and Ni by cyclic deactivation (CD) and impregnation-based laboratory procedures were compared to the properties of equilibrium catalysts tested in a commercial FCC unit. Principle differences were the degree of metal aging and concentration profiles in the catalyst particles. The CD procedure produced properties in the catalyst that were comparatively closer to those exhibited by the equilibrium catalysts. 

Differences in MAT numbers between oxidized and reduced catalysts are proposed to be related to the extent of metal aging. Metals were comparatively more active in the metallated samples than in the equilibrium catalysts. Although this was less evident for the catalyst deactivated by CD, it was observed that the metal aging procedure failed to reproduce completely the state of metals found in equilibrium catalysts. Therefore the aging process of deposited metals still remains a key factor for simulating more closely the properties of FCC equilibrium catalysts. 

Dual particle or separate traps such as RV4+ must have attrition and fluidization properties similar to FCC catalyst. Their advantages are that they do not change the selectivity of the base catalyst and theoretically have a higher capacity for vanadium capture. Performance evaluation of dual particle traps is usually simpler. They can often be isolated from equilibrium catalyst and analyzed for vanadium capture. Confirmation of preferential pick up on integral traps tends to be a bit more qualitative. A disadvantage may be that they are more dependent on vanadium mobility than integral traps. 

The FCC catalyst is the heart and soul of the process. Both chemical and physical properties of the catalyst determine how the FCC unit is designed and operated. Since fresh catalyst is added to the FCC unit regularly, and catalyst is also withdrawn and lost through cyclone systems, the most important catalyst properties to FCC operation are those of the equilibrium catalyst. 

Complexity of the catalytic process itself. The catalytic processes are very complicated. One of the factors that influences catalyst properties includesnon-linearity of surface catalytic reactions which is rarely taken into considerations. The catalyst surface has a feature of fractional-dimension structures where the distributions of the active center on surface show multi-fractional-dimension characteristics. At the same time, there is a non-equilibrium phase change and space-time ordered structures such as the chemical oscillation and chaos during a certain process. 

Steam treatment severity has been varied to match commercial equilibrium catalyst activities and other properties. One measure of a suitably steam-aged catalyst is the surface area which should be in the range of 51 to 200 m /g (Ritter, 1985). Perhaps a more meaningful measure is to use a bulk property of the zeolite, the unit cell size, which is measured by X-ray diffraction. Typically, the unit cell size of USY zeolites are reduced to below 24.26 A whereas RE-USY zeolites equilibrate to 24.26-24.32 A and REY zeolites to 24.5 A in the FCC unit (Scherzer,... 

It is usual to check the properties of equilibrium catalyst (E Cat) to maintain the replacement rate at the optimum level and to review arty potential process problems. The following tests are typical ... 

Equilibrium catalyst attrition index and average particle size distribution (APS) indicate changes in the rate of catalyst attrition. Further analysis of APS for any catalyst that is carried forward into the fractionator, present in the slurry, or which leaves the unit via the regenerator stack can identify problems associated with catalyst quality or cyclone operation. Problems include operation at greater than design feed, catalyst rates or cyclone maloperation. APS is also important in predicting the fluidization properties of the catalyst inventory. 

The ebullated-bed unit consisted of a single reactor loaded with C0-M0/AI2O3 -type catalyst. The feedstock used was vacuum residue of Kuwait export crude diluted with about 10%-15% recycled gas oil (S = 5.2 wt% metals [V + Ni] = 110 ppm N = 4400ppm). Spent catalyst samples were collected from the equilibrium catalyst withdrawn from the reactor, which is a mixture of highly fouled and partially fouled catalysts. The properties of the heavy and light portions of the spent catalyst are presented in Table 10.2. The heavily fouled catalyst contained a substantially higher amount of vanadium (13.83 wt%) than the slightly fouled one (V = 4.37 wt%). Carbon content did not differ appreciably between the two types of spent catalyst particles. 

---