Kinetics of nickel catalyst poisoning

Drozdowski, B.; Zajac, M.

doi:10.1007/bf02673106

Cited by 9 publications

(2 citation statements)

References 5 publications

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“…A quick review of the literature reveals that pioneering kinetic models describing VOs/FAMEs hydrogenation processes were proposed by the mid 20 th century ). Power-law models were used due to their simplicity, and reaction rates were found to be pseudo-first-order with respect to the VOs/FAMEs (Bailey (1949); Swicklik et al (1954); Boelhouwer et al (1956); Vandenheuvel (1956); Eldib and Albright (1957); Coenen (1960); Cousins and Feuge (1960); Nielsen et al (1960); Wisniak (1960); Wisniak and Albright (1961); Scholfield et al (1962); Albright (1965); Mounts and Dutton (1967); Stefanovic and Albright (1969); Albright (1970); Bern et al (1975aBern et al ( , 1975b; Bern (1977); Marangozis (1977); Allen (1978); Snyder et al (1978); Drozdowksi and Zajac (1980); ; Chen et al (1981); Stenberg and Schöön (1985); Colen et al (1988); Jovanović et al (2002); Plourde et al (2004)). However, this type of model does not allow representing any adsorption and surface reaction mechanism, or describing experimental data covering a wide range of conversion due to its limited applications to complex reaction networks.…”

Section: Introductionmentioning

confidence: 99%

Advanced Concepts for the Kinetic Modeling of Fatty Acid Methyl Esters Hydrogenation

Cabrera¹,

Grau²

2008

International Journal of Chemical Reactor Engineering

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Kinetic studies of the catalytic hydrogenation of vegetable oils and fatty acid methyl esters in liquid-phase are commonly performed in the framework of the Langmuir-Hinshelwood-Hougen-Watson (LHHW) formalism using the competitive and non-competitive adsorption models, which are certainly extreme. Based on the advanced concepts of multicentered adsorption and semi-competitive adsorption, mechanistic kinetic models including a distinction between occupied-sites and covered-sites by the large molecules of FAMEs were formulated without expressing an opinion a priori on whether the adsorption regime is competitive or non-competitive. The theoretical basis of the advanced kinetic modeling is described and successfully applied to three application examples of increasing complexity, including: (a) the hydrogenation of methyl oleate without cis-trans isomerization distinction, (b) the cis-trans isomerization and hydrogenation of the methyl oleate, and (c) the methyl linoleate hydrogenation including the cis-trans isomerization of the methyl oleate. The kinetic studies were carried out using a Ni/?-Al2O3, at 398, 413, 428 and 443 K, under isobaric conditions at hydrogen pressures of 370, 510, and 650 kPa, in the absence of mass-transport limitation. After model discrimination based on statistical analysis and taking into account the physical meaning of the estimated parameters, semi-competitive adsorption models were found to be more realistic than the classical LHHW competitive and non-competitive ones, mainly because they give additional information indicating that the adsorbed molecules of methyl linoleate and methyl oleate could cover up to 12 and 7 surface sites, respectively. These values are in adequate agreement with those expected from a rough computational simulation and seem to be the most interesting result, since they are factual and unattainable from the classical LHHW approaches.

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Section: Introductionmentioning

confidence: 99%

Advanced Concepts for the Kinetic Modeling of Fatty Acid Methyl Esters Hydrogenation

Cabrera¹,

Grau²

2008

International Journal of Chemical Reactor Engineering

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“…Phospholipids (PL) are one of the inhibitors of nickel catalysts used in the hydrogenation of oils [1][2][3][4]. PL are natural components of oilseeds which are passed to the oil during the subsequent manufacturing processes.…”

Section: Introductionmentioning

confidence: 99%

Effect of phospholipid structure on kinetics and chemistry of soybean oil hydrogenation with nickel catalysts

Szukalska

2000

Eur. J. Lipid Sci. Technol.

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Phospholipids (PL) are one of the compounds which poison nickel catalysts during the hydrogenation process. It was affirmed that even trace amounts of PL (5—10 ppm P) cause a decrease in catalyst activity. Quantities over 50 ppm P almost totally inhibit the reaction. In bleached oils used for hydrogenation, PL exist as native compounds as well as products of their transformation. In the present work, the effect of native phospholipids, lysophospholipids (LPL) and phosphatidic acids (PA) on the kinetics and chemistry of soybean oil hydrogenation was investigated. It was found that PA were more toxic to nickel catalysts than LPL and native PL. Fine‐grained catalyst was more active and resistant to the poisoning effect of phospholipids than moderate‐grained catalyst. No changes in the oil hydrogenation chemistry were observed in the presence or absence of PL; thus, linoleic and linolenic selectivity and specific isomerization did not undergo any change.

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Sulfur Promotion in Conjugated Isomerization of Safflower Oil over Bifunctional Structured Rh/SBA‐15 Catalysts

et al. 2013

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The sulfur effect on conjugated linoleic acid isomer (CLA) formation during the combined hydrogenation/directed isomerization of safflower oil over a bifunctional (hydrogenation and isomerization) highly structured rhodium‐based catalyst (Rh/SBA‐15) was investigated either by direct addition of increased concentrations of 3‐mercapto‐1,2‐propanediol to the reaction medium or by doping Rh/SBA‐15 with the same sulfur‐based compound yielding the sulfur‐doped Rh‐catalyst (S–Rh/SBA‐15). These catalysts exhibited interesting activity, stability, and recyclability. The maximum CLA contents obtained during the combined reactions with 0, 0.2, 1, 2, 5, and 10 ppm sulfur additions were 73, 99, 131, 110, 105, and 68 mgCLA goil−1, respectively, whereas the amount of harmful trans monoenes remained below 8 %. The safflower oil after partially hydrogenation under the same conditions over S–Rh/SBA‐15 catalyst contained up to 110 mgCLA goil−1. These results showed clear evidence of the sulfur promotion effect on CLA formation during the dual hydrogenation/directed isomerization of safflower oil. A mechanism for the sulfur promotion of the heterogeneous catalyst Rh/SBA‐15 for the conjugated isomerization activity during hydrogenation/directed isomerization of safflower oil was determined by solid‐state 1H NMR analysis of the fresh and spent catalysts. This was also confirmed by liquid‐state 2H NMR analysis of deuterium‐labeled product aliquots withdrawn throughout the reaction. The sulfur promotion towards the double bond conjugation of linoleic acid to form CLA isomers could be explained mechanistically through the preferable formation of the more nucleophilic rhodium sulfide (RhSH) over that of the hydride (RhH). However, both types of Rh clusters constituted distinct catalytic sites leading to the formation of hydrogenation as well as conjugated and geometric isomerization products. The lumped kinetics model described the experimental data well and complied simply with the proposed mechanism.

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Kinetics of nickel catalyst poisoning

Cited by 9 publications

References 5 publications

Advanced Concepts for the Kinetic Modeling of Fatty Acid Methyl Esters Hydrogenation

Advanced Concepts for the Kinetic Modeling of Fatty Acid Methyl Esters Hydrogenation

Effect of phospholipid structure on kinetics and chemistry of soybean oil hydrogenation with nickel catalysts

Sulfur Promotion in Conjugated Isomerization of Safflower Oil over Bifunctional Structured Rh/SBA‐15 Catalysts

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