Henrique S. Cerqueira

The influence of experimental errors during laboratory evaluation of FCC catalysts

The well-known microactivity test (MAT) ASTM D 3907-92, has been used worldwide in laboratory scale testing to determine the activity and selectivity of fluid catalytic cracking (FCC) catalysts. To assess catalytic selectivities by interpolation, either a kinetic model or functional (empirical) relationships between product yields and conversion should be used. Experimental errors may significantly affect analysis and erroneous conclusions might arise, justifying application of statistical methods. Although these methods are well established, they are frequently neglected or oversimplified in catalysis. The aim of the present work is to evaluate the influence of typical experimental errors from MAT units on interpolated yields, based on previously tested empirical functions and data from the literature, and from FCC catalyst samples from PETROBRAS Research Center, with and without a vanadium trap additive. Statistical criteria to identify possible outliers and the confidence intervals for predicted values are discussed. It is shown that the experimental errors on the independent variable, sometimes disregarded, drastically decrease the discrimination capacity of the MAT test concerning iso-conversion and iso-coke evaluations. Concentrating experiments near the conversion region of interest and improvement of MAT repeatability could mitigate this unavoidable problem. These conclusions can be generalized to selectivity analyses related to the reaction systems other than catalytic cracking.

The influence of covariances during laboratory evaluation of FCC catalysts

One problem of practical interest is the evaluation of catalyst activity and selectivity of commercial fluid catalytic cracking (FCC) catalysts. Although different statistical methods may be used for this purpose, these methods are usually neglected or oversimplified in catalysis. In a previous study [1], it was shown that experimental errors of independent variables may exert a significant impact upon the discrimination of catalyst performance in FCC processes and should not be disregarded. In this work it is shown that actual experimental measurements can present strong correlation and that the existence of covariance among experimental measurements can also influence the catalyst discrimination procedure. The influence of covariance among variables on parameter estimation and on the confidence interval (CI) of predicted values is discussed. It is shown that considering the covariances may have either a positive or a negative effect on the CI for predicted values. Practical examples regarding the microactivity test (MAT) of FCC catalyst characterization are used to illustrate the discussion, although the conclusions can be extended to systems other than catalytic cracking.

Performance of FCC catalysts prepared with sub-micron Y zeolite

Abstract A sub-micron sample of Y zeolite was synthesized without template with a Si/Al ratio equal to 2.75. This sub-micron zeolite was embedded in a FCC catalyst formulation at two different contents: 10 and 20wt%. The catalysts were hydrothermally deactivated and evaluated in a fixed bed reactor at various catalyst-to-oil ratios and the results compared to the performance of a regular HUSY containing deactivated catalyst. Although the activity of the samples containing sub-micron zeolites in the cracking of gas oil was reduced when compared to a regular HUSY containing catalyst, the selectivity was affected with a reduction in the coke and an increase in both light cycle oil (LCO) yield and the LCO/bottoms ratio. Accordingly to that, those catalysts may be suitable for resid FCC applications.

New supports for co-based fischer-tropsch catalyst

Publisher Summary The gas-to-liquids (GTL) technology is an attractive route to produce high-quality liquid fuels from natural gas; this technology involves the chemical transformation of natural gas that requires three steps: syngas generation, Fischer–Tropsch synthesis (FTS), and product upgrade. The critical step is the FT synthesis that received significant improvements during the past decades both on the reactor and catalyst technologies. Cobalt-based catalysts are typically used at reaction temperatures in the range of 210–250oC, and after the upgrading step (hydrocracking and hydrodewaxing), the main products are premium diesel, food grade paraffin, and specialty lubricants. The desire to enhance the participation of natural gas in the energy matrix gives momentum to the GTL technology, thus motivating the continuous development of new catalysts for the FT synthesis. Reduction promoters, new supports, and support promoters are the focus of various research activities. In this chapter, the effect of ITQ-6 zeolite and mesoporous material SBA-15 as supports for Co-based Fischer–Tropsch catalyst is investigated and compared with a conventional amorphous SiO 2 support.

Feedstock effect on FCC catalyst stripping

The effect of feedstock on FCC catalyst stripping was investigated based on prototype FCC unit data from three different feedstocks: blend of heavy gas oil from vacuum distillation and delayed coking units, and two different atmospheric residues (paraffinic and with high carbon residue). The higher the feedstock crackability, the higher is the amount of strippable hydrocarbons. The average hydrogen-to-carbon ratio depends on the feedstock and is lower for the paraffinic ATR. The coke on spent catalyst samples was characterized for all feedstocks, indicating a much lower amount of CH 2 Cl 2 insoluble coke for the heavy atmospheric residue feedstock. The insoluble coke of the heavy ATR was also more alkylated and/or naphthenic than in the other feedstocks.

Transformation of methylcyclohexane on an FCC catalyst

The transformation of methylcyclohexane at 723 K over on a USHY sample and on an FCC catalyst composed of 30% USHY and 70% matrix containing 25% Al2O3 was studied. With both samples, C2-C7 alkenes and alkanes, cyclopentane and methylcyclopentane (cracking products), dimethylcyclopentanes and ethylcyclopentane (isomers) and aromatics appeared as primary products. The activity and selectivity of fresh samples as well as the influence of coke deposits on porosity and selectivity are discussed.

Chapter 11 Equilibrium FCC catalyst performance simulation based on mixtures of hydrothermal deactivated samples

Abstract This paper proposes a simple methodology for simulation of equilibrium FCC catalyst (e-cat) performance, employing techniques such as metal impregnation followed by hydrothermal deactivation and laboratory catalyst evaluation. The laboratory evaluation of samples deactivated under different conditions including the e-cat were used in an optimization algorithm, to determine the mixture that best mi overall e-cat performance in terms of activity and main product yields. The proposed methodology may be used in order to establish a specific deactivation protocol for any particular FCC unit.

Methylcyclohexane transformation over HBEA and hmor zeolites: Reaction and deactivation

Abstract Methylcyclohexane transformation was carried out at 450°C over HBEA and HMOR zeolites with similar acidities. Whereas the initial activities of fresh zeolites were very close, the product distributions, extrapoled at zero conversion, were different: 65wt% of C 3 -C 7 alkenes and alkanes with both zeolites but 12 and 23wt% of isomers and aromatics on HBEA against 25 and 10wt% on HMOR; the non desorbed products (“coke”) which appeared as primary products on HMOR and as secondary products on HBEA had very different compositions. HMOR deactivation was also faster than HBEA deactivation. Most of these observations can be related to the different modes of diffusion of reactant and product molecules: monodirectional with HMOR and tridirectional with HBEA.