A Fourier transform mass spectrometry study of ethene oligomers in HMFI zeolite

Jeong, Sejin; Fisher, Karen R.; Howe, Russell F.; Willett, Gary D.

doi:10.1016/s1387-1811(98)00130-9

Cited by 6 publications

(4 citation statements)

References 16 publications

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“…Finally, previous reports may help us understand the actual formation process of Au-cationized species, including the small cationized fragments observed in both SIMS and LAMS experiments. In their study of polyethylene, Jeong et al demonstrated that bare Au + ions do not react with hydrocarbons to generate Au-cationized species . Instead, the association of excited neutral gold atoms with organic fragments could, after the emission of a thermal electron, generate organometallic ions, as was proposed by Wojciechowski et al In LAMS, the higher sample absorbance induced by the gold clusters and its subsequent heating also lead to an increased gas-phase density, which should favor such collision-induced processes.…”

Section: Resultsmentioning

confidence: 95%

Sample Metallization for Performance Improvement in Desorption/Ionization of Kilodalton Molecules: Quantitative Evaluation, Imaging Secondary Ion MS, and Laser Ablation

et al. 2003

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The metallization procedure, proposed recently for signal improvement in organic secondary ion mass spectrometry (SIMS) (Delcorte, A.; Médard, N.; Bertrand, P. Anal.Chem. 2002, 74, 4955)., has been thoroughly tested for a set of kilodalton molecules bearing various functional groups: Irganox 1010, polystyrene, polyalanine, and copper phthalocyanine. In addition to gold, we evaluate the effect of silver evaporation as a sample treatment prior to static SIMS analysis. Ion yields, damage cross sections, and emission efficiencies are compared for Ag- and Au-metallized molecular films, pristine coatings on silicon, and submonolayers of the same molecules adsorbed on silver and gold. The results are sample-dependent but as an example, the yield enhancement calculated for metallized Irganox films with respect to untreated coatings is larger than 2 orders of magnitude for the quasimolecular ion and a factor of 1-10 for characteristic fragments. Insights into the emission processes of quasimolecular ions from metallized surfaces are deduced from kinetic energy distribution measurements. The advantage of the method for imaging SIMS applications is illustrated by the study of a nonuniform coating of polystyrene oligomers on a 100-microm polypropylene film. The evaporated metal eliminates sample charging and allows us to obtain enhanced quality images of characteristic fragment ions as well as reasonably contrasted chemical mappings for cationized PS oligomers and large PP chain segments. Finally, we report on the benefit of using metal evaporation as a sample preparation procedure for laser ablation mass spectrometry. Our results show that the fingerprint spectra of Au-covered polystyrene, polypropylene, and Irganox films can be readily obtained under 337-nm irradiation, a wavelength for which the absorption of polyolefins is low. This is probably because the gold clusters embedded in the sample surface absorb and transfer the photon energy to the surrounding organic medium.

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Section: Resultsmentioning

confidence: 95%

Sample Metallization for Performance Improvement in Desorption/Ionization of Kilodalton Molecules: Quantitative Evaluation, Imaging Secondary Ion MS, and Laser Ablation

et al. 2003

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“…Moreover, many reactions catalyzed by zeolites have gained benefits from size and shape selectivity of the nanosized pores of the zeolites. Linear alkenes are produced by oligomerization of light alkenes in zeolite pores [3][4][5] due to the constraints of the zeolite pore systems. Therefore, understanding the interactions of alkenes with acidic zeolites and dimerization and oligomerization in zeolite pore systems is of fundamental importance, because they are key steps in many important reactions catalyzed by zeolites, [6] for example, alkene oligomerization, alkylation of benzene with alkenes, and methanol-to-gasoline conversion.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Ethylene Dimerization over Faujasite Zeolite by the ONIOM Method

2005

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Ethylene dimerization was investigated by using an 84T cluster of faujasite zeolite modeled by the ONIOM3(MP2/6-311++G(d,p):HF/6-31G(d):UFF) method. Concerted and stepwise mechanisms were evaluated. In the stepwise mechanism, the reaction proceeds by protonation of ethylene to form the surface ethoxide and then C--C bond formation between the ethoxide and the second ethylene molecule to give the butoxide product. The first step is rate-determining and has an activation barrier of 30.06 kcal mol(-1). The ethoxide intermediate is rather reactive and readily reacts with another ethylene molecule with a smaller activation energy of 28.87 kcal mol(-1). In the concerted mechanism, the reaction occurs in one step of simultaneous protonation and C--C bond formation. The activation barrier is calculated to be 38.08 kcal mol(-1). Therefore, the stepwise mechanism should dominate in ethylene dimerization.

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“…12 In this manner, the mechanism of ethene dimerization has been controvertibly discussed by theoretical methods with much less information from experimental results. [13][14][15] The formation of ethoxy species from ethene has not been observed so far due to the rapid oligomerization of ethene, while ethoxy species were observed from the dehydration of ethanol over acidic OH groups by using IR spectroscopy and NMR. [16][17][18] Accordingly, a simple question arises: whether ethoxy species act as intermediates in ethene dimerization and oligomerization.…”

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confidence: 99%

“…First, the oligomerization of ethene was observed at 303 K by IR spectroscopy for confirmation. [13][14][15] The time course of spectra measured after introduction of ethene to H-ZSM-5 zeolite at 303 K is arrayed in Fig. 1.…”

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confidence: 99%