Catalyst Attrition Research Articles

Catalyst attrition in cyclones

The mechanism of catalyst attrition in cyclones has been investigated both theoretically and experimentally for various types of catalysts. A model is suggested that considers cyclone attrition under steady-state conditions as a comminution process. It considers the efficiency of such a process by relating the surface energy created by comminution to the kinetic energy, which has been spent to create this surface area. The attrition rate, defined as the mass of attrition-produced fines per unit mass entering the cyclone, is found to be proportional to the surface mean diameter of the material and to the square of the cyclone inlet velocity, and inversely proportional to the square root of the solids-to-gas loading ratio.

The effect of pretreatment on the attrition resistance of spray-dried alumina

Spray-dried alumina is useful as a support for metal catalysts used in fluidized bed and slurry phase reactors. Catalyst attrition resistance, which can be affected by catalyst preparation and pretreatment, is a key characteristic determining successful use of a particular catalyst. In this study, the effects of calcination temperature and pH of an impregnating solution on the attrition resistance of spray-dried Vista-B alumina have been investigated. BET, X-ray diffraction (XRD), scanning electron microscopy (SEM), and particle size distribution (PSD) were used to characterize the pretreated and attrited alumina. The results indicate that the attrition resistance of the boehmite/γ-Al 2O 3 passes through a maximum for a calcination temperature of around 300°C. The impregnation of γ-Al 2O 3 to incipient wetness using different pH-value solutions followed by drying does not itself cause much change in the PSD. However, this treatment changes significantly the attrition resistance of the γ-Al 2O 3 that decreases with increasing pH value of the impregnation solution. The possible causes of the changes in attrition resistance are discussed.

Comparison of Attrition Test Methods: ASTM Standard Fluidized Bed vs Jet Cup

Attrition resistance is one of the key design parameters for catalysts used in fluidized-bed and slurry phase types of reactors. The ASTM fluidized-bed test has been one of the most commonly used attrition resistance evaluation methods; however, it requires the use of 50 g samplesa large amount for catalyst development studies. Recently a test using the jet cup requiring only 5 g samples has been proposed. In the present study, two series of spray-dried iron catalysts were evaluated using both the ASTM fluidized-bed test and a test based on the jet cup to determine this comparability. It is shown that the two tests give comparable results. This paper, by reporting a comparison of the jet-cup test with the ASTM standard, provides a basis for utilizing the more efficient jet cup with confidence in catalyst attrition studies.

Attrition assessment for slurry bubble column reactor catalysts

Significant interest in three-phase slurry bubble column reactors (SBCRs) has come about in recent years due to their excellent heat removal capabilities during reaction. However, no evaluation test for catalyst attrition resistance is available in the literature yet for SBCR catalysts, although severe attrition of catalyst particles has actually been encountered in SBCRs. In this paper, fluidized bed catalyst attrition tests (fluidized bed and jet cup) and other tests (collision and ultrasound) are evaluated for the first time for their suitability in predicting catalyst attrition in an SBCR. Based on comparisons of particle morphology and size distribution (PSD) of a silica supported cobalt catalyst before and after use in an SBCR with the results from the various attrition assessment tests, it is suggested that the fluidized bed, jet cup and ultrasound tests all provide reasonable and efficient predictions of catalyst attrition. Although the dominant attrition mechanism appeared to be fracture in both SBCR run and collision test, the latter showed too little attrition efficiency to be suitable as an attrition test. Despite the fact that abrasion occurs to a greater degree during the fluidized bed, jet cup, and ultrasound tests compared to during an SBCR run, all these three tests cause particle breakage similar to that in the SBCR, but in relatively short periods of time. Therefore, all three, especially the jet cup test, are suitable tests for predicting catalyst attrition resistance in an SBCR environment.

Catalyst attrition in fluidized‐bed systems

AbstractCatalyst attrition has often been a major obstacle in the development of new fluidized‐bed processes and it is still of concern for existing processes whenever the catalyst is changed. The main consequence of attrition is the generation of fines and the resulting loss of valuable material. In this work the attrition of FCC catalysts in a fluidized‐bed system consisting of a bubbling bed, cyclone gas cleaning, and external solids recirculation is studied. An approach developed describes the attrition‐induced overall solids loss based on the main attrition sources: grid jet attrition, bubble‐induced attrition, and attrition in the cyclone. Their respective contributions to the overall attrition rate are calculated from separately derived model equations that take into account the design of the system, the operating conditions, and the material properties of the catalysts. The solids entrainment from the bed into the cyclone is shown to have a strong effect on the attrition‐induced loss rate and must therefore be taken into account for an a‐priori prediction.

Attrition of precipitated iron Fischer-Tropsch catalysts

A precipitated, doubly promoted, iron oxide catalyst was studied to elucidate phenomena that may lead to catalyst attrition during slurry phase Fischer-Tropsch synthesis. The catalyst was examined by electron microscopy (SEM and TEM), electron and X-ray diffraction, sedigraph particle size analysis and BET surface area measurements. The catalyst undergoes attrition both at the micro- as well as the nano-length scales. On the micro-scale, this involves a breakup of ca. 30 μm spherical agglomerates into ca. 1 μm particles, a process that can be initiated even by the mixing that occurs in the sedigraph analyzer. On the nano-scale, we find that exposure of the catalyst to CO at increasing temperatures transforms single crystals of α-Fe 2O 3 into Fe 3O 4 and ultimately to Fe-carbide, with rounded particles as small as ca. 20 nm. The details of phase transformations and the resulting crystallite morphology and size distribution could play a major role in influencing the overall attrition resistance of precipitated iron oxide catalysts. In this paper, we describe the effects of the CO activation temperature on catalyst structure at the micro- and nano-scales.

Laboratory Testing Procedure for Evaluation of Moving Bed Catalyst Attribution

Abstract A laboratory scale attribution test has been designed to simulate particle-particle and particle-wall attrition forces which are similar to those experienced in commercial moving bed units. The modified drum test uses two concentric rotating drums to induce particle breakage. Using this test, the distribution of particle shapes and sizes produced by catalyst attrition in a moving bed unit have been successfully duplicated.

A novel liquid fluidized bed microreactor for coal liquefaction studies. 2. Hydrotreating results

The novel liquid fluidized bed reactor subject of earlier cold model studies has now been utilized as a laboratory hydrotreater. In the present contribution we demonstrate how reliable hydrotreating kinetics can be obtained despite a small 5-g catalyst charge and the presence of a large exothermic heat effect. The reactor may be treated as perfectly mixed. With our benchmark commercial catalyst (Amocat 1A) no evidence of catalyst attrition has appeared after 30 days of continuous operation

Design of tubing bomb microreactors to minimize mass transfer effects and catalyst attrition in coal liquefaction and model compound reactions

The tubing bomb microreactor (TBMR) is widely used for coal liquefaction and related high pressure model compound reactions. In this work mass transfer and mixing characteristics of the TBMR have been investigated for coal liquefaction and model compound reactions under a variety of reaction conditions by using paraffinic, aromatic, and hydrogen donor solvents, as well as N 2 and H 2 atmospheres. Both horizontal and vertical TBMR orientations, as well as the influence of mixing ball agitators, were investigated. A horizontally oriented TBMR which minimizes mass transfer influences and catalyst attrition was developed.

Butane oxidation to maleic anhydride over vanadium phosphate catalysts

Three aspects of the title reaction are considered: (1) control of catalyst morphology, (2) imparting catalyst attrition resistance, (3) advantages of separating the redox steps. We find that the best catalysts contain (VO) 2P 2O 7 which must be prepared from a (VO) 2H 2O(PO 3OH) 2 precursor. This dehydration reaction is topotactic in nature and controls the morphology of the (VO) 2P 2O 7 catalyst particles. The special feature of the predominant surface obtained in this way is presumably V-V pairs. By itself, (VO) 2P 2O 7 is mechanically too weak to be useful in fluid bed or recirculating solids reactors. We have discovered a novel method of imparting attrition resistance without loss of selectivity to maleic anhydride. The attrition resistance is provided using only small amounts (∼10wt%) of silica. Higher selectivities to maleic anhydride are observed when the two steps of the redox process are separated. The vanadium phosphate is circulated between two reactors. In one, butane is oxidized by vanadium phosphate; in the other, the vanadium phosphate is reoxidized.

New trends in the improvement of cyclones

This article examines the possibilities of reducing catalyst attrition and cyclone wall erosion through optimization of the aerodynamic conditions in the cyclone. It is assumed that the disintegration of catalyst particles and erosion of the cyclone walls take place at exactly the same points (e.g. the seats of erosion in the cyclones can serve as natural indicators in determining the zones of catalyst pulverization). In catalytic cracking units, internal cyclones are used as the primary means of cleanup of the gas for process purposes. Cyclones trap out 99.8-99.95% of the catalyst entrained from the fluidized bed by the contact gas. The retrofitting of standard cyclones with chambers for preliminary aerodynamic stabilization of the flow yielded favorable results. The results of erosion tests on type TsN cyclones with and without a stabilization chamber indicate that the proposed stabilization method can give an approximately fivefold reduction of erosion of the cylindrical part of the cyclone. An important advantage of cyclones with added stabilization is the increased efficiency of dust collection. It is concluded that supplementary aerodynamic stabilization of the dust-laded gas flow and reduction of the angle of attack can give substantial improvements in the operating characteristics of cyclones, both cylindrical and more » spiral-conical. « less

Investigation of dust collection systems in commercial catalytic cracking units

This article reports on a study based on the results of operating tests on catalytic cracking units differing in the design of the reactor sections, in the type of dust collection systems, and in the strength of the catalysts used. Quantitative relationships are established for the determination of the coefficient of formation of fine fractions through attrition and the determination of the coefficients of catalyst entrainment into the separation zone. These relationships are applicable to catalytic cracking units of the 1A/1M, GK, and 43-103 types, using the catalysts KMTsR, MA, and KMTs. The proposed procedure makes it possible to take into account the timewise change in the particle size distribution of the catalyst as a consequence of catalyst attrition and loss of part of the fine fractions through the dust collection system. It is concluded that the model of quasi-equilibrium in fluidized systems with return of the solid phase can be used not only in designing or reconstructing catalytic cracking units, but also in optimizing the catalyst consumption in currently operating units, and also in solving a broad group of problems in application to various processes with fluidized beds.

Oxidation of Methanol in a Fluidized Bed. 1. Catalyst Attrition Resistance and Process Variable Study

Oxidation of Methanol in a Fluidized Bed. 1. Catalyst Attrition Resistance and Process Variable Study

Catalyst attrition and deactivation in fluid catalytic cracking system

A population balance model has been developed for catalyst properties, which is in good agreement with commercial fluid cracking data. The application

Inhalation toxicology of automotive emissions as affected by an oxidation exhaust catalyst.

Preliminary data are given on the acute inhalation toxicology of automotive emissions as affected by an oxidation exhaust catalyst. The catalyst effectively reduced CO and HC in the exhause which apparently had an effect (at least in a closed exposure system) on oxidant and NO2 levels by altering the HC/NOx ratio. There was a resultant reduction in biological effects due to the exposure. The catalyst altered the type of particulate to one which probably contained sulfuric acid as a major component. No evidence was present in these acute exposures to suggest a toxic response due to the higher sulfate emissions or possible catalyst attrition products. The effects of long-term exposure have not yet been investigated.

Diffusion Kinetics and Catalyst Attrition in Cyclic Processes

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDiffusion Kinetics and Catalyst Attrition in Cyclic ProcessesP. S. WeiszCite this: Ind. Eng. Chem. Fundamen. 1969, 8, 2, 325–329Publication Date (Print):May 1, 1969Publication History Published online1 May 2002Published inissue 1 May 1969https://doi.org/10.1021/i160030a023RIGHTS & PERMISSIONSArticle Views66Altmetric-Citations3LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (3 MB) Get e-Alerts