Factors that could influence the activity of a WO3/SiO2 catalyst: Part III

Schalkwyk, C. van; Spamer, A.; Moodley, D.J.; Dubé, Tiffany; Reynhardt, Jan P. K.; Botha, J.M.; Vosloo, Hermanus C.M.

doi:10.1016/s0926-860x(03)00536-2

Cited by 28 publications

(23 citation statements)

References 9 publications

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“…Although it has been a common practice in the petrochemical industry to isomerize straight chain hydrocarbons to branched ones for octane number improvement, the task of converting straight chain fatty acids or corresponding alkyl esters to branched ones has turned out to be much more challenging. This observation is not surprising because carboxylic acids have been recognized as a poison in the isomerization of hydrocarbons [14]. Therefore, published work on the skeletal isomerization of linear fatty acids and esters has so far appeared only in a few patent literature [15,16].…”

Section: Introductionmentioning

confidence: 99%

Skeletal isomerization of unsaturated fatty acids: the role of mesopores in HBeta zeolites

Zhang

2007

Catal Lett

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Fatty acids are an important class of feedstock for the production of many chemicals, such as surfactants, lubricants, biodiesel, etc. Fatty acids derived from vegetable oils and animal fats typically have linear aliphatic chain, and are therefore called linear fatty acids. Products based on branched fatty acids offer many attractive properties over those based on linear ones, e.g. low melting points and low viscosity. Catalytic skeletal isomerization of linear fatty acids to branched ones is particularly important for industrial production of branched fatty acids. This paper for the first time reveals the key properties of the most active zeolite catalysts for this reaction. Among many solid acid catalysts studied, acidic Beta zeolites were found to stand out in their performance for the reaction. In this work, several acidic Beta zeolites (HBeta) from commercial sources were evaluated for their performance in fatty acid skeletal isomerization. The activities of these zeolites under identical test conditions were found to vary in a wide range, even with similar silica to alumina molar ratios (SAR). A combination of characterization techniques was used to systematically investigate the most critical property of the zeolites responsible for the observed superior activity. All the HBeta zeolites in this study have high crystallinity. Pore size distribution of the zeolites was identified to be the most important factor that unambiguously correlates the catalyst activity to the amount of mesopores in the HBeta zeolites.

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Section: Introductionmentioning

confidence: 99%

Skeletal isomerization of unsaturated fatty acids: the role of mesopores in HBeta zeolites

Zhang

2007

Catal Lett

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“…It is reported that the effect of substitution on the ease of the metathesis reaction is CH 2 )RCH 2 CH) R 2 CHCH)R 2 C= [7]. It was also observed in a recent literature report that WO 3 /SiO 2 system can tolerate up to 400 ppm butanol and 2-methyl-1-hexene (vinylidene) [6]. A slight decline in conversion from 16 and 24 h is observed with 2-pentanone and 2-methyl-1,5 hexadiene, respectively as depicted in Fig.…”

Section: Influence Of Feed Composition On the Catalyst Activity And Smentioning

confidence: 98%

“…2-Pentanone is a Lewis base consisting of a carbonyl group. It was proposed in the literature report that the Lewis base slows the metathesis reaction by reacting with metal carbene to form a metal oxide [6]. 2-Methyl-1,5-hexadiene is a non-conjugated diene that contains two alkene sites available for metathesis, of which one site is sterically hindered.…”

Section: Influence Of Feed Composition On the Catalyst Activity And Smentioning

confidence: 99%

“…Typical heterogeneous catalysts for the metathesis reaction are WO 3 /SiO 2 , CoO/MoO 3 /Al 2 O 3 , MoO 3 /Al 2 O 3 and Re 2 O 7 / Al 2 O 3 . Silica-based catalysts for example WO 3 /SiO 2 , when deactivated by feed impurities can regain their original activity when the impurity is removed from the feed [4,6]. This is due to the high operating reaction temperature of between 300 and 500 8C for WO 3 /SiO 2 catalyst system and inherent slow reductive elimination of metal carbene species with tungsten systems.…”

Section: Introductionmentioning

confidence: 99%

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Influence of feed components on the activity and stability of cobalt molybdenum alumina metathesis catalyst

Kwini

Botha

2005

Applied Catalysis A: General

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“…The most often used catalyst is WO 3 /SiO 2 , due to the following reasons: (i) it is resistant to poisoning by oxygenated and sulided compounds due to the high reaction temperature (more than 350°C) [41,42]; (ii) even if the coke formation is important at high temperature, the catalyst can be regenerated easily by calcination in air [42], without decomposition of the active sites, in A lot of studies were made on the WO 3 /SiO 2 system, before and after activation by propene, by using various spectroscopic methods such as Raman, UV-visible, EPR, XANES, and EXAFS. The irst studies were made by Raman and led to the conclusion that the active site was an isolated surface complex of tungsten but of unknown structure [43].…”

Section: Solids Containing Group VI (Mo W) Metal Ions Used In Heteromentioning

confidence: 99%

Olefin Metathesis by Group VI (Mo, W) Metal Compounds

Lefèbvre¹,

Bouhoute²,

Szeto³

et al. 2018

Alkenes

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Olein metathesis is an important reaction not only in petroleum chemistry but also in ine chemistry. Professors Grubbs, Schrock, and Chauvin obtained the Nobel Prize in 2005 for the development of this reaction (determination of the mechanism and synthesis of homogeneous catalysts). This reaction can be described as the redistribution of carbon chains of oleins via a breaking of their C═C double bonds. It is catalyzed by metal carbenes and the catalytic cycle passes through a metallacyclobutane. The purpose of this chapter is to give an overview of catalysts based on tungsten or molybdenum active for this reaction. Numerous tungsten and molybdenum organometallic complexes displaying a carbene functionality were synthesized. Some of them are highly active in olein metathesis. Industrially, tungsten oxide on silica is used as a precursor of the propene production by olein metathesis of but-2-ene and ethylene. However, the active sites are not well known but they can be modeled by grafting, via surface organometallic chemistry, perhydrocarbyl complexes of molybdenum or tungsten on oxide surfaces. After a review of the complexes used in homogeneous catalysis, a review of the industrial catalysts and their models will be given.

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Factors that could influence the activity of a WO3/SiO2 catalyst: Part III

Cited by 28 publications

References 9 publications

Skeletal isomerization of unsaturated fatty acids: the role of mesopores in HBeta zeolites

Skeletal isomerization of unsaturated fatty acids: the role of mesopores in HBeta zeolites

Influence of feed components on the activity and stability of cobalt molybdenum alumina metathesis catalyst

Olefin Metathesis by Group VI (Mo, W) Metal Compounds

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