Microactivity catalyst

Suppose you have an FCCU with a catalyst inventory in the reactor-regenerator of 200 tons. Does adding two tons of fresh catalyst (1 %) significantly affect the apparent cracking activity of the circulating catalyst Field observations indicate that the answer is yes. If 45 microactivity catalyst is being circulated, a 1 % addition of fresh, high-activity catalyst can make a big difference—for a little while. 

The microactivity test uses small quantities of catalyst, only 4 grams, and a feed of 1.33 g in 75 seconds, so it is a very fast test, but the test s empirical usefulness is strictly limited to one well-known technology, for an endothermic reaction and one very limited type of catalyst. 

Figure 2.2.1 shows the simplified sketch of the reactor used for the microactivity test. As can be seen, a fluid-bed catalyst is tested in a fixed bed reactor in the laboratory to predict its performance in a commercial fluid bed reactor. This can be done only because enormous empirical experience exists that has accumulated throughout several decades in several hundreds of reactors both in production and in laboratories. The standard states ... 

The microactivity test provides data to assess the relative performance of fluid cracking catalysts. ... 

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... 

Microactivity Test (MAT) is a small, packed-bed catalytic cracking test that measures activity and selectivity of a feedstock-catalyst combination. 

Analysis of two nickel-containing DFCC revealed that neither heating in air or in steam induced intraparticle transfer of nickel at the thermal and hydrothermal conditions used to age the fresh catalysts (11) prior to microactivity testing. 

Catalytic evaluations were conducted using microactivity tests (MAT) ( ) at 910 F initial temperature, 15 WHSV, 6.0 g catalyst, and a 5.0 cat-to-oil ratio. The feedstock was a metals-free mid-continent gas oil. Each data point shown is the average of two MAT runs. Only MAT runs with acceptable mass balance were used (96 to 101%). Additionally, MAT data was normalized to 100% mass balance. Extensive error analysis of conversion, coke, and hydrogen yields indicates the following respective standard deviations 1.62, 0.29, 0.025. The effects of nickel and vanadium on the hydrogen and coke make were calculated by obtaining the difference between the yields obtained with uncontaminated catalysts and that of the contaminated catalyst at the same conversion. 

The catalyst used in this study corresponds to a fresh commercial catalyst used in one FCC unit of ECOPETROL S.A. This solid is hydrothermal deactivated at the laboratory in cycles of oxidation-reduction (air-mixture N2/Propylene) at different temperatures, different times of deactivation, with and without metals (V and Ni), and different steam partial pressures. Spent catalysts (with coke) are obtained by using microactivity test unit (MAT) with different feedstocks, which are described in Table 10.1. 

An advanced cracking evaluation-automatic production (ACE Model AP) fluidized bed microactivity unit was used to study the catalyst and feed interactions. The fluidized bed reactor was operated at 980°F (800 K). Every feed was tested on two different catalysts at three cat-to-oil ratios 4, 6, and 8. Properties of laboratory... 

Catalytic evaluation of the different pillared clays was performed using a microactivity test (MAT) and conditions described in detail elsewhere (5). The weight hourly space velocity (WHSV) was 14-15 the reactor temperature was 510 C. A catalyst-to-oil ratio of 3.5-3.8 was used. The chargestock s slurry oil (S.O., b.p. >354 C), light cycle oil (LCGO, 232 C < b.p. <354 C) and gasoline content were 62.7 vol%, 33.1 vol% and 4.2 vol% respectively. Conversions were on a vol% fresh feed (FF) basis and were defined as [VfVp/V ] x 100, where is the volume of feed... 

Table 2. Microactivity test results for several pillared clay catalysts after calcination in air at 400 C for lOh. The zeolitic cracking catalyst has been aoed for 5 hours at 760 C with 100% steam at 1 atm. ...

A higher catalyst microactivity implies a reduced amount of unconverted material recycled to the catalytic cracker, thus increasing not only first pass feed conversion to desirable products but also permitting higher throughput of fresh feedstocks due to the reduction in recycle material. Consequently, the development of zeolite catalysts proved a major boon to the refining industry. 

Figure 12. Microactivity response of zeloite cracking catalyst to rare earth content...

FIXED-BED AND FLUIDIZED-BED TESTS In the fixed-bed test, a sample of cracking catalyst was contacted with an FCC feed in a manner similar to the standard microactivity test (MAT) prescribed by ASTM (10). One major difference was that the reactor temperature was increased from 900°F to 960°F to better simulate current commercial operations. 

While most catalyst vendors rely on fixed bed microactivity (MAT) tests, fixed fluid bed (FFB) reactor experiments are widely used within Mobil to characterize FCC catalysts. The amount of catalyst used is constant for each test, and products are collected for a known period of time. In MAT experiments, catalyst bed is fixed while in FFB test the catalyst bed is fluidized. As products are collected over the decay cycle of the catalyst, the resulting conversion and coke yields are strongly influenced by catalyst deactivation. Systematic differences exist between the measured conversion or catalyst activity and coke yields for the MAT and FFB tests. The magnitude of these differences varies depending on the type of catalyst being tested (REY or USY). Experimental data in Figure 1 clearly show that FFB conversion is higher than MAT conversion for USY catalysts. On the other hand, FFB conversion is lower than MAT conversion for REY catalysts. Furthermore, the quantitative... 

Fig. 5.9 Effect of a V-trap on a commercial FCC catalyst (Ecat = Equilibrium Catalyst, MA = Microactivity test (7))...

Laboratory evaluation of the catalytic performance of fresh FOC catalysts involves steaming and activity testing. The latter is most often performed using a microactivity test (MAT). While there are other parameters that are important in comparing total performance of catalysts like attrition and fluidization, this paper... 

Catalytic Cracking Test. A standard microactivity test (MAT) was used to evaluate the conversion and selectivity of catalyst samples. The tests were done at the University of Pittsburgh s Applied Research Center (former Gulf Research Laboratory), a qualified laboratory for MAT evaluations. A standard method, developed by Gulf, was used without modification. A Cincinnati gas oil was cracked under the following conditions cat/oil=3, 16 h 1 WHSV, and 516°C. Prior to charging the reactor, all samples underwent a standard thermal pretreatment. Solids were first heat shocked for 1 h at 593°C. Next, selected materials were impregnated with 3000 ppm Ni and 6000 ppm V, as naphthenates. Then all samples were calcined for 10 h at 538°C. Finally, each material was steamed at 732°C for 14 h in a fluidized bed to produce a catalyst in a simulated equilibrium state. 

Through a series of round robin tests conducted by participating laboratories, ASTM Committee D-32 on Catalysts has characterized a variety of catalyst materials using standard test methods. Materials include fluid cracking catalysts, zeolites, silicas, aluminas, supported metals, and a gas oil feedstock. Properties characterized include surface area, crush strength, catalytic microactivity, particle size, unit cell dimensions and metal content. These materials are available from the National Institute of Standards and Technology as reference materials. 

D-3907 Method for Testing Fluid Catalytic Cracking Catalysts by Microactivity Test Activity of FCC catalysts as evaluated by percent conversion of gas oil using a fixed bed reactor... 

Of particular mention and of widespread interest throughout the petrochemical industry has been the Committee s success in obtaining round robin results on testing fluid cracking catalysts. Overcoming a natural desire not to share data or methods, industry representatives developed a standard method to determine the weight percent conversion of gas oil in a fixed bed microactivity unit. 

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