<i>n</i>‐Butane, <i>iso</i>‐Butane and 1‐Butene Adsorption on Imidazolium‐Based Ionic Liquids Studied with Molecular Beam Techniques

Winter, Leonhard; Bhuin, Radha Gobinda; Maier, Florian; Steinrück, Hans‐Peter

doi:10.1002/chem.202102492

Cited by 3 publications

(1 citation statement)

References 88 publications

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“…This behavior is interpreted as the blocking of 1-butene adsorption sites by the IL, until at θ IL = 0.55 ML the Pt(111) surface is completely covered by ILs. This finding is in line with previous studies from our group, which showed that (1) 1-butene adsorption is not expected at 180 K on pure IL surfaces 56 and (2) ∼0.5 ML of IL is needed to wet a metal surface completely. 31 For 1,3-butadiene, a similar linear decrease of θ butadiene,SAT is observed for increasing θ IL (see Figure 3b, full squares).…”

Section: ■ Results and Discussionsupporting

confidence: 93%

Tailoring the Selectivity of 1,3-Butadiene versus 1-Butene Adsorption on Pt(111) by Ultrathin Ionic Liquid Films

et al. 2023

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The solid catalyst with ionic liquid layer (SCILL) concept is a promising approach to enhance the selectivity of hydrogenation reactions, like the selective hydrogenation of 1,3-butadiene to 1-butene using transition-metal catalysts. In this context, the adsorption dynamics of 1,3-butadiene and 1-butene were studied on Pt(111) modified with ultrathin layers of the ionic liquid (IL) 1,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide ([C1C1Im][Tf2N]). The sticking coefficients of the two hydrocarbons are measured using the direct method of King and Wells. Both olefins show pronounced precursor-mediated dynamics on clean Pt(111) and on the IL-modified surface. Increasing the IL coverage leads to an increased blocking of adsorption sites for the incoming olefins. Coadsorbed hydrogen does not significantly affect the precursor and site-blocking effects for 1,3-butadiene. Interestingly, a smaller IL amount is needed to prevent 1-butene adsorption compared to 1,3-butadiene adsorption, which is proposed to be directly related to the IL’s influence on selective hydrogenation in SCILL catalysis. Indeed, molecular dynamics simulations show IL film densification/relaxation as the key mechanism to allowing/excluding olefin adsorption on the metal. Being a function of IL coverage, the energy of film penetration is used to control the effective olefin adsorption energy and thus creates an operation regime for suppressing 1-butene while permitting 1,3-butadiene adsorption.

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Section: ■ Results and Discussionsupporting

confidence: 93%

Tailoring the Selectivity of 1,3-Butadiene versus 1-Butene Adsorption on Pt(111) by Ultrathin Ionic Liquid Films

et al. 2023

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n‐Butane, iso‐Butane and 1‐Butene Adsorption on Imidazolium‐Based Ionic Liquids Studied with Molecular Beam Techniques

Winter

Bhuin

Maier

et al. 2021

Chemistry A European J

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The interaction of molecules, especially hydrocarbons, at the gas/ionic liquid (IL) surface plays a crucial role in supported IL catalysis. The dynamics of this process is investigated by measuring the trapping probabilities of nbutane, iso-butane and 1-butene on a set of frozen 1-alkyl-3methylimidazolium-based ILs [C n C 1 Im]X, where n = 4, 8 and X À =Cl À , Br À , [PF 6 ] À and [Tf 2 N] À . The decrease of the initial trapping probability with increasing surface temperature is used to determine the desorption energy of the hydrocarbons at the IL surfaces. It increases with increasing alkyl chain length n and decreasing anion size for the ILs studied. We attribute these effects to different degrees of alkyl chain surface enrichment, while interactions between the adsorbate and the anion do not play a significant role. The adsorption energy also depends on the adsorbing molecule: It decreases in the order n-butane > 1-butene > iso-butane, which can be explained by different dispersion interactions.

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Understanding the Buoy Effect of Surface‐Enriched Pt Complexes in Ionic Liquids: A Combined ARXPS and Pendant Drop Study**

Hemmeter,

Paap,

Wellnhofer

et al. 2023

ChemPhysChem

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Recently, we demonstrated that Pt catalyst complexes dissolved in the ionic liquid (IL) [C4C1Im][PF6] can be deliberately enriched at the IL surface by introducing perfluorinated substituents, which act like buoys dragging the metal complex towards the surface. Herein, we extend our angle‐resolved X‐ray photoelectron spectroscopy (ARXPS) studies at complex concentrations between 30 and 5%mol down to 1%mol and present complementary surface tension pendant drop (PD) measurements under ultra clean vacuum conditions. This combination allows for connecting the microscopic information on the IL/gas interface from ARXPS with the macroscopic property surface tension. The surface enrichment of the Pt complexes is found to be most pronounced at 1%mol. It also displays a strong temperature dependence, which was not observed for 5%mol and above, where the surface is already saturated with the complex. The surface enrichment deduced from ARXPS is also reflected by the pronounced decrease in surface tension with increasing concentration of the catalyst. We furthermore observe by ARXPS and PD a much stronger surface affinity of the buoy‐complex as compared to the free ligands in solution. Our results are highly interesting for an optimum design of ionic catalyst solutions contact areas with a surrounding reactant/product phase, such as in SILP catalysis.

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n‐Butane, iso‐Butane and 1‐Butene Adsorption on Imidazolium‐Based Ionic Liquids Studied with Molecular Beam Techniques

Cited by 3 publications

References 88 publications

Tailoring the Selectivity of 1,3-Butadiene versus 1-Butene Adsorption on Pt(111) by Ultrathin Ionic Liquid Films

Tailoring the Selectivity of 1,3-Butadiene versus 1-Butene Adsorption on Pt(111) by Ultrathin Ionic Liquid Films

n‐Butane, iso‐Butane and 1‐Butene Adsorption on Imidazolium‐Based Ionic Liquids Studied with Molecular Beam Techniques

Understanding the Buoy Effect of Surface‐Enriched Pt Complexes in Ionic Liquids: A Combined ARXPS and Pendant Drop Study**

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