Chemical Characterization of Catalysts. I. Poisoning of Cracking Catalysts by Nitrogen Compounds and Potassium Ion<sup>*</sup>

Mills, Gregory; Boedeker, E. R.; Oblad, A.G.

doi:10.1021/ja01160a035

Cited by 150 publications

(68 citation statements)

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“…Irreversible adsorption of ammonia [470], pyridine or quinoline [471] has been taken as a measure of strong acid sites. The heat of desorption has also been used as indicator of acid strength [472].…”

Section: Acidic and Basic Groupsmentioning

confidence: 99%

Nature and Estimation of Functional Groups on Solid Surfaces

1983

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Section: Acidic and Basic Groupsmentioning

confidence: 99%

Nature and Estimation of Functional Groups on Solid Surfaces

1983

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Section: Introductionmentioning

confidence: 99%

“…have a poisoning influence on the cracking activity of catalys ts. Mills, Boedeker, and Oblad [16] assume that the "active hydrogen ions" are eliminated from the catalyst during cracking, and as a resu lt the cracking activity is decr eased .Water contained in bentonites also plays a very important role in their adsorben t properties in nonaqueous media. This water , generally determined 1 'rhis in vestigation was sponsored as a joi nt resea rch project un dertaken b y t he Bone Char Research P roject, Inc. and t he Nationa l Burea u of Sta.nd3rds.…”

mentioning

confidence: 99%

Surface changes in an original and activated bentonite

López-González¹,

Deitz²

1952

J. RES. NATL. BUR. STAN.

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The p h ys ical adsorption of ni trogen was used to st ud y a bentoni te activated by a t reatm en t with h ydrochloric acid. The Brunauer-E mmett-Teller equation , t he Huttig equation , and a so-call ed "summation " eq uatio n were used in t he calculation of th e surface ar ea s available to ni trogen . Th e cha nges in surface area at different te mperat ures ha ve bee n related to t he q uan t ity of ad sor bed water and t he amount of con s ti t ut ional h ydro xyl grou ps. The surface area is a measure of on ly th e external boundary (nons welli ng surface) of th e bentonite, and this is in crea sed signifi cantly by t he activation pro cess. The ratio of surface areas (a ctivated to ori ginal) is about four. A max imum in t he s urface area was found tJ exist when a ll of t he adsorbed watel' was eliminated. However, t he surface area d ecreased wit h t he removal of water formed by d ecomposit ion of t he constitutional h ydroxyl gro ups. Chemical analyses, d eh ydrat ion curves, t hermal d iffere ntial analyses, X-ray patterns, and elec tron mi crographs were employed to cha racteri ze the materials. [6,8,9] . I . IntroductionAcid treatments of bentonites significan tly change some of the specific proper ties of interest in industrial processes. If th e acid is at relatively low concentration (abou t 0.1 to 0.01 N), the exchangeable cations are replaced by h ydrogen ions. If the acid concentration is increased, there is a partial chemical solution of the crystal structure. The extent of the dissolving action d ep ends upon the concen tration and nature of the acid, temp erature, r eaction time, and the ra tio of the two r eactants.The decolorizing action and the efficien cy of many clay-cracking catalysts, which generally have very specific properties, increase in general with the amount of hydrogen ions present on the surface [14] . R ecent studies [15] have shown that the catalytic action of silica-alumina gels can also be r elated to th e hydrogen ions present on the surface. Small amounts of basic compounds (calcium, potassium, nitrogen , etc.) have a poisoning influence on the cracking activity of catalys ts. Mills, Boedeker, and Oblad [16] assume that the "active hydrogen ions" are eliminated from the catalyst during cracking, and as a resu lt the cracking activity is decr eased .Water contained in bentonites also plays a very important role in their adsorben t properties in nonaqueous media. This water , generally determined 1 'rhis in vestigation was sponsored as a joi nt resea rch project un dertaken b y t he Bone Char Research P roject, Inc. and t he Nationa l Burea u of Sta.nd3rds., Guest worker holding a fellowship of t he Consejo Superior de In ... est i ga.cionp~ Cientificas, Spain.3 F i~ure s in brackets ind icate the literat ure references at the end of this p aper.by loss of weigh t after h eat tr eatments, is in part adsorbed ' water and in pa rt clue to the decomposition of the co nstitu tional hydroxyl groups [18,19] . Both forms, when r etained in the bento ni te, play an importan...

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“…Mills et al (1950). They studied a number of silica and silica-alumina cracking catalysts for activity in cumene cracking in a portion of their work, correlating loss of activity vs. uptake of various basic nitrogen compounds on the catalyst.…”

Section: Chemical Titrotion Methods For Acidic Oxide Surfacesmentioning

confidence: 99%

“…The exponential portion of the curve is not so uniquely interpreted; it could indicate heterogeneity of the weaker acidic sites which, incidentally, do not contribute substantially to total dehydration activity, or it could be the result of interaction between poison molecules on adsorption at high surface coverage. As in the case of Mills et al (1950), the amount of base required to effect a given loss of activity differs from case to case.…”

Section: Titration Of -Oxide Surfacesmentioning

confidence: 99%

Progress toward the a priori determination of catalytic properties

Butt

1976

AIChE Journal

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SCOPEThe ultimate achievement in catalysis would be the ability to determine without experimentation the optimum catalyst for a given chemical reaction. Fortunately, we are assured of a certain degree of job security, for this feat is certainly not possible at present, nor does it seem likely for at least some time to come. What we can do, however, is to make use of the accumulated wisdom and experience resulting from decades of research in catalysis through development of correlations which can provide some norms for catalytic behavior.The present review considers a number of these correlations, both old and new, with concern as to the progress which has been made over the years towards the ultimate achievement. In general, the concepts of the active site and surface complexes are viewed as ingredients more or less common to all correlations. Questions which should be addressed are the nature (chemical, geometric) of the active site and its relationship to surface structure, the density of active sites, chemistry of surface reactions at active sites, and the influence of electronic factors on the nature of active sites. Many correlations have an extensive history, as will become apparent, so the review presents an interesting combination of old and new in representative, if not comprehensive, form. CONCLUSIONS AND SIGNIFICANCEThere is a wide variation in the degree of understanding of different types of catalysts. This depends on both the catalytic system and who is trying to understand it. -*-rice this review ranges all the way from quantum ..echanical calculations of chemisorption on metals to ex post facto correlations of coke deposition on silica-alumina. And one general observation can be made concerning the correlations considered here: they all work, sort of.Chemisorption/titration methods have provided a significant amount of information regarding the nature of acid oxide and supported metal surfaces. In the latter case, it is found that rather simple geometric concepts may provide quite effective means of activity correlation, particularly for very highly dispersed metals with accompanying small crystallite dimension. Electronic theories, in and out of favor over the past 30 years return with deeper insight due to recently developed capabilities in quantum chemical calculations. The relationship between strength of chemisorption and activity seems firmly established on both metals and oxides, at least for the few systems for which sufficient experimental information exists.Correlations in catalysts seem to remain an experiment first, theory second matter; however, there appears to be some progress in the understanding of relationships once thought to be strictly empirical. Examples in this review deal with the compensation effect, catalyst deactivation, and alloy catalysts.To those readers actively engaged in catalysis research, apologies are offered for the presumption implied by the title of this review. Perhaps it should be "Has There Been Progress Toward the a Priori Deteimination oE Catalytic Prope...

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Chemical Characterization of Catalysts. I. Poisoning of Cracking Catalysts by Nitrogen Compounds and Potassium Ion^*

Cited by 150 publications

References 1 publication

Nature and Estimation of Functional Groups on Solid Surfaces

Nature and Estimation of Functional Groups on Solid Surfaces

Surface changes in an original and activated bentonite

Progress toward the a priori determination of catalytic properties

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Chemical Characterization of Catalysts. I. Poisoning of Cracking Catalysts by Nitrogen Compounds and Potassium Ion*

Cited by 150 publications

References 1 publication

Nature and Estimation of Functional Groups on Solid Surfaces

Nature and Estimation of Functional Groups on Solid Surfaces

Surface changes in an original and activated bentonite

Progress toward the a priori determination of catalytic properties

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Product

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About

Chemical Characterization of Catalysts. I. Poisoning of Cracking Catalysts by Nitrogen Compounds and Potassium Ion^*