Microactivity

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... 

The decreases in microactivity and surface area are strong functions of thermal deactivation in the regenerator and the presence of metal in the feed. 

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

Except for the results reported in Table III, all catalytic activity and selectivity results were obtained using a microactivity test (MAT), ASTM D-3907-80. 

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. 

When rare earth Y-zeolite (REY) was added to the PILC or to the parent clay, the dried PILC or "as received" clay was reslurried in water and the calcined REY added to the 10 wt % level. This slurry was then mixed, filtered, dried, and calcined at 500 C for 2 hours in air. The calcined REY was obtained from Union Carbide and contained 14.1 wt % rare earth elements, primarily lanthanum and cerium. Portions of the PILC were pretreated by one of the methods listed below prior to the microactivity testing. 

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. ...

This ability is measured throughout the petroleum industry by a tool referred to as the microactivity test. 

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 4. Yearly increase in microactivity (MA) and decrease in recycle caused...

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

Each constituent suffers actions of three kinds the prescribed actions at a distance, represented by the densities of body force bi, microforce 7., and heating A the contact actions, represented by the stress 7), the microstress St and the heating flux q% the internal microactions... 

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... 

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