Adsorption Of Crotonaldehyde Research Articles

Crotonaldehyde Adsorption on Cu-Pt Surface Alloys: A Quantum Mechanics Study

The adsorption of crotonaldehyde on Cu-Pt alloy surfaces was characterized by density functional theory (DFT). Two surfaces were considered: Cu2Pt/Cu(111) and Cu3Pt/Cu(111). It was determined that the presence of Pt on the surface, even when isolated as single atoms fully surrounded by Cu, provides additional stability for the adsorbates, increasing the magnitude of the adsorption energy by as much as 40 kJ/mol. The preferred bonding on both surfaces is via multiple coordination, with the most stable configuration being a cis arrangement with di-σ bonding of the C=O bond across a Cu–Cu bridge and an additional π bonding to a Pt atom. The fact that Pt significantly affects the adsorption of unsaturated aldehydes such as crotonaldehyde explains why the kinetics of their hydrogenation using single-atom alloy (SAA) catalysts vary with alloy composition, as we previously reported, and brings into question the simple model in which the role of Pt is only to promote the dissociation of H2.

RETRACTED: Investigation of crotonaldehyde adsorption on pure and Pd-decorated GaN nanotubes: A density functional theory study

The effect of Pd-decoration on the performance of a GaN nanotube (GaNNT) was investigated in detecting crotonaldehyde (CA) via density functional theory method. The interaction of the pure GaNNT with CA was weak, and the sensing response (SR) was approximately 4.2. The adsorption energy (E ad ) of CA changed from −5.4 to −23.2 kcal/mol when a Pd atom was decorated onto the surface of the GaNNT and the SR increased to 94.3 as well. At 298 K, the recovery time for the desorption of CA from the Pd-decorated GaNNT surface was 8.0 s. Finally, the Pd-decorated GaNNT was found to be a promising sensor for CA with high sensitivity. • Pd-decorated GaN nanotube may be highly sensitive crotonaldehyde molecule sensor. • The sensing response significantly rises from 4.2 to 94.3 by Pd-decoration. • A short recovery time of 8.0 s is found for the crotonaldehyde desorption.

The roles of metal-promoter interface on liquid phase selective hydrogenation of crotonaldehyde over Ir-MoOx/BN catalysts

A series of MoOx-promoted Ir/BN catalysts were tested for liquid phase selective hydrogenation of crotonaldehyde. The MoOx-promotion could significantly improve the reactivity up to 5-fold. Such improvement was mainly due to the formation of Ir-MoOx interfacial sites in the promoted catalyst, which accelerated the adsorption and activation of crotonaldehyde molecule as evidenced by a much lower activation energy (18.9 kJ mol−1 on the 0.3Mo-3Ir/BN versus 38.4 kJ mol−1 on the 3Ir/BN). The kinetic results revealed negative reaction order of crotonaldehyde (up to -1.1) and high reaction order of H2 (up to 2.2), indicating the high coverage of crotonaldehyde on the catalyst surface suppressed the adsorption of H2 due to its low solubility in the liquid phase. Therefore, the adsorption and activation of H2 on the catalyst might be the rate determining step. However, the preferred adsorption of crotonaldehyde on the Ir-MoOx interface alleviated the suppression of H2 adsorption, which was another reason for the higher activity.

Mechanistic Insights into the Selective Electroreduction of Crotonaldehyde to Crotyl Alcohol and 1-Butanol.

The electroreduction of crotonaldehyde, which can be derived from the aldol condensation of acetaldehyde (sustainably produced from CO2 reduction or from biomass ethanol), is potentially a carbon-neutral route for generating high-value C4 chemicals such as crotyl alcohol and 1-butanol. Developing functional catalysts is necessary toward this end. Herein, the electrocatalytic conversion of crotonaldehyde to crotyl alcohol and 1-butanol was achieved in 0.1 m potassium phosphate buffer electrolyte (pH=7). More importantly, the mechanisms and structure-activity relationships of these transformations were elucidated. Crotyl alcohol was formed on oxide-derived Ag at -0.75 V versus the reversible hydrogen electrode (RHE) with a faradaic efficiency (FE) of 84.3 % (reactant conversion after 75 min electrolysis=9.8 %), which is 1.6 times higher than that on polished Ag foils. The coordinatively-unsaturated sites on oxide-derived Ag surfaces were proposed to facilitate crotonaldehyde adsorption via its oxygen atom in order to promote crotyl alcohol formation. On electrodeposited Fe nanoflakes, crotonaldehyde could be reduced to 1-butanol with an outstanding FE of 60.6 % (reactant conversion after 75 min electrolysis=9.4 %) at -0.70 V vs. RHE. This is nearly 3 times higher than the FE of 1-butanol observed on polished Fe foils at the same potential. More strikingly, the corresponding partial current density of 1-butanol was -9.19 mA cm-2 , which is 43 times higher than that on Fe foils. The presence of tensile strains and grain boundaries on the Fe nanoflakes were elucidated and suggested to activate a concerted reduction of the C=O and C=C bonds in crotonaldehyde to produce 1-butanol selectively.

Atmospheric ozonolysis of crotonaldehyde in the absence and presence of hydroxylated silica oligomer cluster adsorption

As one of the main components of combustion of tobacco products occurs (CARB), crotonaldehyde has an acute toxicity and widely exists in the atmosphere, which is harmful to human health. The removal efficiency of VOCs by ozonation can reach 80–90%. Based on the theory of quantum chemistry, the degradation mechanism, kinetics and toxicity of crotonaldehyde by ozonation in gas phase and heterogeneous phase were studied. Ozone was added to the olefins unsaturated double bond to form a five-membered ring primary ozonide, which was further fractured due to its unstable structure to form a Criegee intermediate and an aldehyde compound. The reaction rate constant of crotonaldehyde with ozone was 1.24 × 10−17 cm3 molecule−1 s−1 at 298 K and 1 atm, which was an order of magnitude higher than the experimental value. From toxicity assessment, it was found that the ozonation of crotonaldehyde is beneficial to the removal of toxicity. Mineral dust aerosol exists in the atmosphere in large quantities, and SiO2 is the most abundant component. VOCs are transformed into particle state on their surface through homogeneous nucleation and heterogeneous nucleation. Referring to the crystal structure of SiO2, five hydroxylated silica oligomer cluster structures were simulated and the adsorption configurations of crotonaldehyde on their surface were simulated. The adsorption of crotonaldehyde on the surface of the clusters was achieved by forming hydrogen bonds and had good adsorption effects. The adsorption of hydroxylated silica oligomer clusters didn't change the ozonation mechanism of crotonldehyde, but had a certain effect on the reaction rate.

Adsorption of crotonaldehyde on metal surfaces: Cu vs Pt.

The thermal chemistry of crotonaldehyde on the surface of a polished polycrystalline copper disk was characterized by temperature-programmed desorption (TPD) and reflection-absorption infrared spectroscopy (RAIRS) and contrasted with previous data obtained on a Pt(111) single crystal substrate. A clear difference in the adsorption mode was identified between the two surfaces, highlighted by the prevalence of RAIRS peaks for the C=C bond on Cu vs for C=O on Pt. Adsorption was also determined to be much weaker on Cu vs Pt, with an adsorption energy on the former ranging from -50 kJ/mol to -65 kJ/mol depending on the surface coverage. The experimental data were complemented by extensive quantum mechanics calculations using density functional theory (DFT) to determine the most stable adsorption configurations on both metals. It was established that crotonaldehyde adsorption on Cu occurs via the oxygen atom in the carbonyl group, in a mono-coordinated fashion, whereas on Pt multi-coordination is preferred, centered around the C=C bond. The contrasting surface adsorption modes seen on these two metals are discussed in terms of the possible relevance to selectivity in single-atom alloy hydrogenation catalysis.

Crystal-plane effects of anatase TiO2 on the selective hydrogenation of crotonaldehyde over Ir/TiO2 catalysts

Supported Ir/TiO2 catalysts with the anatase TiO2 nanocrystals exposing {101}, {100} and {001} planes were tested for selective hydrogenation of crotonaldehyde. The Ir/TiO2-{101} catalyst dominantly exposing {101} plane gave a initial reaction rate of 166.1 μmol gIr-1 s−1 at 80 °C and a turnover frequency of crotyl alcohol formation of 0.022 s−1, which is 5 and 7 times respectively higher than those obtained on the Ir/TiO2-{001} catalyst dominantly exposing {001} plane even though they have similar Ir particle sizes (ca. 1.3 nm). The reaction behaviors were related to the surface oxygen vacancy, which served as surface acid sites and provide adsorption sites for CO bond in the CRAL molecule. Therefore, the higher concentration of oxygen vacancy in the Ir/TiO2-{101} accounted for the improved performance compared to the Ir/TiO2-{001}. However, strong adsorption of crotonaldehyde and/or products on the catalyst surface, as well as the CO poisoning via decarbonylation of crotonaldehyde, were the main reasons for the catalyst deactivation.

The effects of MoOx decoration on the selective hydrogenation of crotonaldehyde over MoOx-promoted Ir/TUD-1 catalysts

A series of MoOx-promoted Ir/TUD-1 catalysts were tested for liquid phase selective hydrogenation of crotonaldehyde. The promoted catalysts showed higher activity and selectivity than the unpromoted one, with the best performance being obtained on an Ir-0.1Mo/TUD-1 (with a crotyl alcohol yield of 86.7% and a turnover number of 325.7 h−1). The large pore sizes of the TUD-1 is beneficial to the diffusion of the reactant and thus the supported catalyst is more active than that supported on the commercial SiO2. The characterization results revealed decoration of Ir particles by MoOx, which altered the morphologies and electronic properties of the catalysts. Such decoration resulted in the generation of Ir-MoOx interfacial sites, which altered the adsorption and activation of crotonaldehyde molecule and brought up enhanced activity and selectivity. However, at high MoOx content, the Ir surface was fully covered by MoOx, which results in strong adsorption of crotonaldehyde and fewer surface Ir atoms for H2 dissociation and thus declined activity.

Investigation on the Hydrocarbon and Oxygen-Containing Hydrocarbon Intermediates Leading to Crotonaldehyde Formation on TiO2

Aldol condensation of CH3CHO, forming crotonaldehyde (2-butenal, CH3CH═CHCHO), readily occurs on TiO2 at 35 °C. At a higher coverage or at an elevated temperature, the crotonaldehyde can be oxidized to crotonate. Adsorption and thermal reactions of CH3CHBr2, BrCH2CH2Br, BrCH2CH2OH, and ClCH2CH2OH on TiO2 can produce crotonaldehyde, in contrast to CH2═CHBr. CH3CHBr2 has the highest reactivity toward the crotonaldehyde formation among the halogenated compounds studied. The pathways of CH3CHBr2 + Ti–O–Ti → CH3CHO + 2Ti–Br and BrCH2CH2Br + Ti–O–Ti → Ti–O–CH2CH2Br + Ti–Br → CH3CHO +2 Ti–Br are proposed for the reactions of CH3CHBr2 and BrCH2CH2Br. The crotonaldehyde generated from the reactions of the four halogenated compounds on TiO2 has lower C═O and C═C stretching frequencies as compared to those of the crotonaldehyde directly from its adsorption on TiO2. This result is attributed to the presence of Br or Cl atoms near the crotonaldehyde adsorption sites and the change in the Ti ionic bonding environment. ...

Effective NbOx-Modified Ir/SiO2 Catalyst for Selective Gas-Phase Hydrogenation of Crotonaldehyde to Crotyl Alcohol

NbOx-modified Ir/SiO2 catalyst (Ir-NbOx/SiO2) showed high activity and selectivity for gas-phase hydrogenation of crotonaldehyde, and Ir-NbOx/SiO2 with Nb/Ir molar ratio of 0.5 (Ir-NbOx/SiO2 (Nb/Ir = 0.5)) provided high crotyl alcohol yield of 87%. This is the highest crotyl alcohol yield among those in gas-phase over reported heterogeneous catalysts. The activities (TOF per surface Ir atom) at low conversion level (40%, W/F = 0.37 gcat·h·mol–1) and high conversion level (97%, W/F = 2.2 gcat·h·mol–1) were calculated to be 0.21 and 0.08 s–1, which are more than 3 times higher than those over reported heterogeneous catalysts. High activity and high yield are derived from the combination of Ir metal with NbOx species. Based on the spectroscopic and kinetic studies, the high activity and high selectivity are attributed to strong adsorption of crotonaldehyde on NbOx species by the high Lewis acidity, and suppression of over-hydrogenation of the produced crotyl alcohol at high conversion level. It is suggested ...

Metal–support interaction effects on chemo–regioselectivity: Hydrogenation of crotonaldehyde on Pt13/CeO2(1 1 1)

The metal–support interaction on the chemical reactivity is illustrated here by density functional theory calculations for the hydrogenation of crotonaldehyde on Pt13 clusters deposited on CeO2(111). Adsorption of crotonaldehyde on the supported cluster is globally strengthened, compared to Pt(111), both on top of the cluster and at the interface with ceria. The activation barriers of the first and the second hydrogenation steps at both CC and CO bonds are consequently increased, but particularly at CO on top of the cluster, with respect to Pt(111). In contrast, the hydrogenation at CO is far easier at the interface with ceria, which underlines the key role of the support. The considered model shows a preferential route toward the formation of the saturated aldehyde, in contrast to the measurements. This study paves the way to advanced theoretical models with larger nanoparticles supported on reduced ceria in realistic conditions of environment.

Crotonaldehyde adsorption on Ir(1 1 1), an interesting trans- and cis-configuration transformation

Trans- and cis-crotonaldehyde (CAL) adsorption behaviors on Ir(111) were systematically investigated using density functional theory (DFT) method. Our results indicate that the interaction between CC bond of CAL and Ir(111) is stronger than that between CO and surface; and the configurations with both CO and CC bonds simultaneously adsorbed at Ir(111) are more stable than those with an individual CO or CC one at surface. It is very interesting to find that the stability of trans- and cis-CAL on Ir(111) reverses compared with that in gas phase. On the basis of the potential energy surface (PES) of CAL isomerization, CAL mainly exists as trans-structure in gas phase; while trans- and cis-CAL might coexist on Ir(111). The electronic interactions between CAL and Ir(111) are well explained by charge density difference. Different coverages of CAL on Ir(111) indicates that the interactions between CAL and Ir(111) decrease with coverage. This work provides important information for the further study of the selective hydrogenation mechanism of CAL.

Impact of co-adsorbed oxygen on crotonaldehyde adsorption over gold nanoclusters: a computational study

Crotonaldehyde (2-butenal) adsorption over gold sub-nanometer particles, and the influence of co-adsorbed oxygen, has been systematically investigated by computational methods. Using density functional theory, the adsorption energetics of crotonaldehyde on bare and oxidised gold clusters (Au13, d = 0.8 nm) were determined as a function of oxygen coverage and coordination geometry. At low oxygen coverage, sites are available for which crotonaldehyde adsorption is enhanced relative to bare Au clusters by 10 kJ mol(-1). At higher oxygen coverage, crotonaldehyde is forced to adsorb in close proximity to oxygen weakening adsorption by up to 60 kJ mol(-1) relative to bare Au. Bonding geometries, density of states plots and Bader analysis, are used to elucidate crotonaldehyde bonding to gold nanoparticles in terms of partial electron transfer from Au to crotonaldehyde, and note that donation to gold from crotonaldehyde also becomes significant following metal oxidation. At high oxygen coverage we find that all molecular adsorption sites have a neighbouring, destabilising, oxygen adatom so that despite enhanced donation, crotonaldehyde adsorption is always weakened by steric interactions. For a larger cluster (Au38, d = 1.1 nm) crotonaldehyde adsorption is destabilized in this way even at a low oxygen coverage. These findings provide a quantitative framework to underpin the experimentally observed influence of oxygen on the selective oxidation of crotyl alcohol to crotonaldehyde over gold and gold-palladium alloys.

Adsorption and hydrogenation mechanism of crotonaldehyde on a Pd(111) surface by periodic DFT calculations

The parallel adsorption of crotonaldehyde to the Pd(111) surface at the fcc–hcp site through the CC and CO is the most stable. The full hydrogenation mechanism follows the steps O → C2 → C3 → C1 to generate the product of n-butane. For the partial hydrogenation, the 1,4-addition is identified as a primary mechanism.

Selective oxidation of crotyl alcohol and crotonaldehyde on V2O5/MgO: In situ FTIR study

The adsorption of crotyl alcohol, crotonaldehyde and crotonic acid on MgO, V2O5 and V2O5/MgO mixed oxide was studied under oxidizing conditions by in situ FTIR spectroscopy. The results were further analyzed in order to investigate the surface intermediates of crotonaldehyde oxidative dehydrogenation to maleic anhydride. A stable surface compound, alkoxide, was found during the crotyl alcohol adsorption for all oxides at room temperature (RT). The reaction between the adsorbed crotonaldehyde and the oxygen atom of the catalyst resulted in the formation of carboxylate at higher temperatures (T>373 K). The formation of two different reaction products (furane and maleic anhydride) was detected from IR spectra following the crotonaldehyde adsorption at various oxygen pressures. It can be deduced that crotonic acid easily dissociates to form the surface carboxylate-crotonate, which is further oxidized to maleate and consequently to maleic anhydride at 573 K.

FTIR study of the interaction of crotonaldehyde and maleic anhydride with V 2O 5 and MoO 3

The adsorption of crotonaldehyde and maleic anhydride on MoO 3, respectively, V 2O 5 has been studied by FTIR spectroscopy. Crotonaldehyde was adsorbed mainly in molecular form due to hydrogen bonds with Brönsted acid sites of these oxides (physical adsorption) at room temperature (RT). Stable surface complexes (coordinatively bonded crotonaldehyde, carbonyl compounds and carboxylates) were found during the adsorption of crotonaldehyde on MoO 3, respectively, V 2O 5 at 298–573 K. Carboxylates and consecutively maleic anhydride were products of reaction between crotonaldehyde and active sites of V 2O 5 surface at high temperatures in the atmosphere of reaction gas. Maleic anhydride was physically adsorbed on MoO 3, respectively, V 2O 5 via hydrogen bonds with surface hydroxyls.

FTIR study of the interaction of crotonaldehyde and maleic anhydride with V2O5 and MoO3

The adsorption of crotonaldehyde and maleic anhydride on MoO 3 , respectively, V 2 O 5 has been studied by FTIR spectroscopy. Crotonaldehyde was adsorbed mainly in molecular form due to hydrogen bonds with Brönsted acid sites of these oxides (physical adsorption) at room temperature (RT). Stable surface complexes (coordinatively bonded crotonaldehyde, carbonyl compounds and carboxylates) were found during the adsorption of crotonaldehyde on MoO 3 , respectively, V 2 O 5 at 298–573 K. Carboxylates and consecutively maleic anhydride were products of reaction between crotonaldehyde and active sites of V 2 O 5 surface at high temperatures in the atmosphere of reaction gas. Maleic anhydride was physically adsorbed on MoO 3 , respectively, V 2 O 5 via hydrogen bonds with surface hydroxyls.

Crotonaldehyde hydrogenation over alumina- and silica-supported Pt–Sn catalysts of different composition. In situ DRIFT study

Alumina- and silica-supported bimetallic Pt–Sn catalysts with different Pt/Sn atomic ratios have been prepared by using the bimetallic complex cis-[PtCl(SnCl3)(PPh3)2], the monometallic complex cis-[PtCl2(PPh3)2] and SnCl2 as metal precursors. Catalysts have been characterised by X-ray diffraction and transmission electron microscopy techniques, including energy-dispersive X-ray microanalysis, electron diffraction experiments and lattice-fringe microanalysis. The phase composition of the different catalysts has been related to the catalytic behaviour in the vapour phase hydrogenation of crotonaldehyde (but-2-enal). Results show that catalysts containing platinum–tin alloy phases with large particles are more selective towards the hydrogenation of the carbonyl bond to yield crotyl alcohol. The presence of oxidised tin species on the surface of the large alloy particles promotes the hydrogenation of the carbonyl bond. In situ diffuse reflectance infrared spectroscopy studies of crotonaldehyde adsorption under He or H2 reveal differences between bimetallic catalysts and monometallic, and these differences have been related to the different catalytic behaviour of the catalysts.

Crotonaldehyde Hydrogenation on Pt/TiO2and Ni/TiO2SMSI Catalysts

A kinetic and DRIFTS (diffuse reflectance FTIR) investigation of crotonaldehyde adsorption and hydrogenation was conducted over TiO2-supported Pt and Ni with the intent of gaining insight into the adsorption modes of molecules with carbonyl groups on these catalysts in the SMSI and non-SMSI states. Significant enhancement in selectivity toward crotyl alcohol was observed with each catalyst after reduction at 773 K. DRIFT spectra under reaction conditions identified crotonaldehyde species strongly adsorbed through the C=C bond and weakly coordinated through both the C=C and the C=O bonds on these catalysts after reduction at 573 K, which gave a peak at 1693 cm−1. After reduction at 773 K, an additional adsorbed species with a strong band at 1660 cm−1, indicating a significant interaction between the carbonyl group and the surface, was observed, which is presumed to be stabilized at interfacial Pt–TiOxand Ni–TiOxsites. A decrease in the surface coverage of this species paralleled a drop in selectivity to crotyl alcohol with time on stream. After reduction at 573 K, decarbonylation occurred during the initial few minutes on stream to create adsorbed CO on Pt/TiO2in addition to carbon deposition, but these reactions were significantly suppressed after reduction at 773 K, presumably due to a TiOxoverlayer which covers part of the Pt surface and breaks up the ensembles of Pt atoms required for these reactions.

Competition between Acetaldehyde and Crotonaldehyde during Adsorption and Reaction on Anatase and Rutile Titanium Dioxide

The adsorption of acetaldehyde and crotonaldehyde on the anatase and rutile polymorphs of TiO2 has been investigated with Fourier transform infrared spectroscopy (FTIR). Chemisorption of acetaldehyde on TiO2 involves a strong interaction between the surface and the carbonyl oxygen, causing a significant shift in the location of the ν(CO) vibrational mode to lower frequencies; no interaction with surface hydroxyl groups was observed. Capacities for acetaldehyde and crotonaldehyde adsorption under conditions relevant to aldolization reactions were determined in a novel reactor system providing simultaneous mass measurements and mass spectral analysis of gas-phase products. The coverage of acetaldehyde irreversibly adsorbed on TiO2 was similar to values previously reported for the adsorption of alcohols; coverages of crotonaldehyde were approximately 60% of those for acetaldehyde. Both gas-phase and surface analyses indicate that formation of crotonaldehyde by aldol condensation of acetaldehyde occurs on rut...