Hydrogenation Of Crotonaldehyde Research Articles

Mechanistic insights on the promoting roles of IrFe alloy in selective hydrogenation of crotonaldehyde

IrFe alloy nanoparticles with different Ir/Fe molar ratios were synthesized and exhibited good performance in the gas phase selective hydrogenation of crotonaldehyde (CRAL). The IrFe alloy with an Ir/Fe ratio of 19/1 gave a turnover frequency (TOF) of 0.022 s−1 at 80 °C and a crotyl alcohol (CROL) selectivity of 91 %, while the bare Ir/BN catalyst gave a TOF of 0.0014 s−1 and a CROL selectivity of 74 %. Detailed characterizations, kinetic investigation, and in situ spectroscopic study revealed that the altered electronic structure of the IrFe alloy with transfer from Fe to Ir species was essential for its improved performance. Also, density functional theory calculations indicated that such an electronic structure resulted in strong CRAL interaction with the Ir-Fe entity, thus higher adsorption capacity and lower reaction barrier than that on the Ir-Ir counterpart, which accounted for the higher activity. Moreover, the hydrogenation of C = O bond required lower barrier on the Ir-Fe site than that on the Ir-Ir, which well explained the higher selectivity to CROL.

Synthesis of n-butanol from ethanol over Pt-Y/beta catalyst: Synergistic catalysis of yttrium and platinum site

Conversion of ethanol to high-value alcohols is an attractive approach for developing renewable biofuels, the key is to develop stable and high-efficient catalysts. In this work, based on the preparation strategy of heteroatomic Beta zeolites, a bifunctional Pt-Y/Beta catalyst was prepared by solid-state ion exchange and impregnation. Through characterization techniques such as TEM, NMR and XAS, it was confirmed that the Y species were incorporated into the framework of Beta zeolite by interacting with the silanol groups located at the defect sites, while the Pt species were confirmed to be present on the surface of the zeolite in the form of dispersed nanoparticles. The unique structure form and the favorable spatial proximity of the two metallic active sites lead to a synergistic catalysis, which enable a one-step conversion of ethanol to n-butanol with exceptionally high selectivity of 68 %. In situ DRIFT characterization, ethanol-TPD and relay experiment results show that in the ethanol to n-butanol reaction, the Pt species in Pt-Y/Beta catalyst serves as the active center for the dehydrogenation of ethanol and the hydrogenation of crotonaldehyde and crotyl alcohol, while the Y species is responsible for catalyzing the condensation reaction of acetaldehyde.

Selective Hydrogenation of Croton Aldehyde on Pt Nanoparticles Controlled by Tailoring Fraction of Well-Ordered Facets Under Different Pretreatment Conditions

Selective Hydrogenation of Croton Aldehyde on Pt Nanoparticles Controlled by Tailoring Fraction of Well-Ordered Facets Under Different Pretreatment Conditions

Electron synergy effect in the PtCo/CNTs bimetallic catalysts for promoting highly selective and stable hydrogenation of crotonaldehyde

Herein, we synthesized PtCo/CNTs, Pt/CNTs, and Co/CNTs nanocatalysts at room temperature by chemical reduction method. The synergistic effect in PtCo/CNTs for crotonaldehyde (CAL) hydrogenation is investigated. The nanostructures, morphologies, electronic property, Pt–Co interaction, surface characteristic and composition of the catalysts are examined by XRD, BET, SEM, XPS, HRTEM, STEM, STEM-EDX elemental maps and line profiles and H2-TPD. It is found that Pt and Co forms PtCo bimetallic nanoparticles in the PtCo/CNTs catalyst and the PtCo bimetallic nanoparticles are coated on multi-walled carbon nanotubes. And PtCo/CNTs achieves 83.5% CAL conversion, 91.3% crotyl alcohol (COL) selectivity, and 647.4 h−1 turnover frequency (TOF) at 60 °C within 2 h under 3 MPa hydrogen, and its catalytic performance remains basically unchanged after five recycles. According to the analysis, the presence of PtCo bimetallic particles lead to electron transferring from Co to Pt (synergy effect), which improves their activation ability of hydrogen and desorption of CC in COL and thus enhances its selectivity to COL.

Synthesis of CuAl-LDHs by Co-Precipitation and Mechanochemical Methods and Selective Hydrogenation Catalysts Based on Them

The paper presents the results of the synthesis and study of CuAl layered double hydroxides (LDHs) as well as their application as catalysts for the selective hydrogenation of crotonaldehyde. Phase-homogeneous LDHs were obtained by co-precipitation and mechanochemical methods, and critical parameters ensuring the formation of the target product were identified. In the case of coprecipitation, the formation of LDH is most affected by the pH of the reaction medium and the CO32−/Al3+ ratio. The optimal CO32−/Al3+ ratio is ca. 0.5–0.8 and pH 9.5–10.0. When mechanochemical synthesis is used, at 500 m·s−2 and 60 min, it is possible to obtain a single-phase CuAl LDH, whereas at higher energies, LDH is destroyed. The mechanochemical method makes it possible not only to reduce the synthesis time and the amount of alkaline wash water but also to obtain more dispersed copper particles with a higher hydrogenating activity. The conversion of 2-butenal (T = 80 °C, P = 0.5 MPa, 180 min, ethanol) for this sample was 99.9%, in contrast to 50.5% for the catalyst obtained by co-precipitation. It is important that, regardless of the conversion, both catalysts showed high selectivity (S = 90–95%) for the double bond hydrogenation.

Selective hydrogenation of crotonaldehyde over Ir/TiO2 catalysts: Unraveling the metal-support interface related reaction mechanism

For the supported catalysts for the selective hydrogenation of α, β - unsaturated aldehyde with H2, tailoring of metal - support interfacial effect to improve reaction performance is a significant but challenging subject. In this work, we regulated both the size regimes of the Ir deposits (single atom, nanocluster and nanoparticle) and the crystal plane of anatase TiO2 (TiO2(101), TiO2(100) and TiO2(001)) so as to alter the Ir-TiOx interfacial properties, in order to unravel reaction mechanism of selective hydrogenation of crotonaldehyde over the Ir/TiO2 catalysts. Both the activity and selectivity to crotyl alcohol increased as the Ir size grew from single atom to nanoparticle, ascribed to high Ir0 content, high concentration of surface defects and prominent H-spillover effect on the Ir nanoparticles. Moreover, the in situ Fourier transform infrared spectroscopy (FTIR) and density functional theory (DFT) calculations demonstrated that an end-on CO adsorption mode for crotonaldehyde molecule was favored at the Ir-TiOx interface particularly at high H coverage, which thus facilitated the hydrogenation of CO bond to form crotyl alcohol. Moreover, the highest reactivity of the Ir nanoparticles was evidenced by the lowest reaction barrier. These results explicitly demonstrate that larger metal nanoparticles and adsorption geometry of the reactant at the metal - support interface are vital for improved catalytic performance, which would shed light on the ingenious catalyst design.

The Hydrogenation of Crotonaldehyde on PdCu Single Atom Alloy Catalysts.

Recyclable PdCu single atom alloys supported on Al2O3 were applied to the selective hydrogenation of crotonaldehyde to elucidate the minimum number of Pd atoms required to facilitate the sustainable transformation of an α,β-unsaturated carbonyl molecule. It was found that, by diluting the Pd content of the alloy, the reaction activity of Cu nanoparticles can be accelerated, enabling more time for the cascade conversion of butanal to butanol. In addition, a significant increase in the conversion rate was observed, compared to bulk Cu/Al2O3 and Pd/Al2O3 catalysts when normalising for Cu and Pd content, respectively. The reaction selectivity over the single atom alloy catalysts was found to be primarily controlled by the Cu host surface, mainly leading to the formation of butanal but at a significantly higher rate than the monometallic Cu catalyst. Low quantities of crotyl alcohol were observed over all Cu-based catalysts but not for the Pd monometallic catalyst, suggesting that it may be a transient species converted immediately to butanol and or isomerized to butanal. These results demonstrate that fine-tuning the dilution of PdCu single atom alloy catalysts can leverage the activity and selectivity enhancement, and lead to cost-effective, sustainable, and atom-efficient alternatives to monometallic catalysts.

Single-step conversion of ethanol into n-butene-rich olefins over metal catalysts supported on ZrO2-SiO2 mixed oxides

With airlines committed to drastically reduce their carbon footprint by 2050, producing jet fuel from renewable ethanol is of particular interest. Recently, we reported on an Ag/ZrO2/SBA-16 catalyst that is very effective for directly converting ethanol into to n-butene-rich olefins jet fuel precursors (i.e., 88% at full conversion). Here, we report on a Cu/ZrO2/SBA-16 catalyst that presents remarkable olefins selectivity (i.e., 89% at 96% conversion) and enhanced stability as compared to Ag/ZrO2/SBA-16 catalyst. Under severe operating conditions a conversion loss < 10% was observed with the Cu/ZrO2/SBA-16 catalyst as compared to a 50% loss of conversion with the Ag/ZrO2/SBA-16 catalyst. Combined experimental and computational tools revealed that replacing Ag with Cu shifts the reaction pathway of crotonaldehyde hydrogenation from 1,3-butadiene (i.e., coke precursor) production to butyraldehyde formation. Experiments conducted with 4%Cu/4%ZrO2 supported on SBA-16, dealuminated zeolite Beta, and aluminum silicate revealed the performance and stability advantage of the SBA-16-supported catalyst.

Hydrogenation of crotonaldehyde over ligand-capped Ir catalysts: Metal-organic interface boosts both activity and selectivity

Hydrogenation of crotonaldehyde over ligand-capped Ir catalysts: Metal-organic interface boosts both activity and selectivity

Efficient Ni[sbnd]Ir alloy catalyst for selective hydrogenation of benzonitrile, crotonaldehyde and benzylideneacetone

SiO2-supported NiIr alloy acted as an effective heterogeneous catalyst for the hydrogenation of benzonitrile, crotonaldehyde and benzylideneacetone, showing much higher activity than monometallic Ni/SiO2 and Ir/SiO2 catalysts and superior selectivity to benzyl-benzylidene-amine, butanal and 4-Phenyl-butan-2-one at high conversion. Furthermore, the main active sites were investigated on the basis of the relationship of TOFs and the alloy composition for the hydrogenation of crotonaldehyde, benzonitrile and benzylideneacetone, and the active site was the isolated Ni atom surrounded by Ir atoms for the hydrogenation of crotonaldehyde and related to the structure of substrate in selective hydrogenation.

Conversion of by-products of alcohol production to produce isobutanol

Intensive research is underway in all developed countries to create an economical process for the production of butanol and its derivatives from biomass, which reduces the cost of the product compared to existing processes for producing synthetic butanol based on fossil raw materials. This is primarily due to the prospects of using butanol and its derivatives as an alternative fuel. The paper proposes a technology for the production of isobutyl alcohol, which provides for the processing of by-products of alcohol production by hydrogenation of crotonaldehyde. A concentrate of ethyl alcohol head fractions (KGF) and a concentrate of ethyl alcohol head fractions (KGF) were used as objects of research. In the process of work, a technology for processing by-products of alcohol production is proposed, which includes a number of stages with the production of isobutyl alcohol as a finished product, which can be used in the production of plastics, rubber, coatings, medicine and the production of special solvents, as well as as an additive to fuel. Experimental studies were conducted to obtain isobutanol and study its physicochemical properties: color, density; mass fraction of isobutyl alcohol, mass fraction of acids in terms of acetic acid, bromine number, mass fraction of carbonyl compounds in terms of oil aldehyde, mass fraction of non-volatile residue. The technological process at the isobutanol production plant is differentiated by stages, which are carried out sequentially in separate reactors with the treatment of intermediates with catalysts. As a result of the developed technology, butyl alcohol with a mass fraction of isobutyl alcohol of at least 99.3% was obtained.

PtMx/SBA-15 (M = Co, Cu, Ni and Zn) bimetallic catalysts for crotonaldehyde selective hydrogenation

Herein, a series of the Pt-based bimetallic catalysts (PtMx/SBA-15) are gained by using ultrasonic incipient wetness impregnation method (M = Co, Cu, Ni or Zn). The experimental results show that the catalytic performance (including catalytic activity (turnover frequency-TOF), selectivity to crotyl alcohol) of PtCox/SBA-15 for catalyzing crotonaldehyde selective hydrogenation is the best among PtMx/SBA-15. Additionally, the ratio of Pt/Co in the PtCox/SBA-15 catalysts is changed to successfully synthesize PtCo/SBA-15, PtCo2/SBA-15, PtCo5/SBA-15. It demonstrates that the selectivity of the PtCox/SBA-15 catalysts for crotonaldehyde selective hydrogenation to crotyl alcohol is significantly improved with the increase of the Co content. The PtCo5/SBA-15 catalyst provides 83.8% conversion of crotonaldehyde, 94.3% selectivity to crotyl alcohol and TOF of 910.5 h−1 under mild reaction conditions (3.0 MPa H2, 80 °C and 2.0 h). And PtCo5/SBA-15 has much better catalytic performance (higher catalytic activity and selectivity to crotyl alcohol) than PtCu5/SBA-15, PtNi5/SBA-15 and PtZn5/SBA-15. The reasons are as follows: (1) PtCo alloy forms, which is conducive to crotonaldehyde adsorption and activation; (2) there is an appropriate synergy effect between Pt and Co, greatly improving the capacity of the catalyst activating hydrogen under mild conditions; (3) the electron transfers from Co to Pt, resulting in the increase of Pt electron density and decrease of Co electron density, then the Co sites are advantageous to CO group adsorption and activation and Pt sites for H2 adsorbing and activating; (4) with the increase of the Co proportion in PtCox/SBA-15, the synergy effect between Pt and Co in PtCo alloy strengthens and thus increases the selectivity of CO group hydrogenation.

Selective Hydrogenation of Crotonaldehyde on SiO2‐Supported Pt Clusters: A DFT Study

AbstractThe selective hydrogenation of crotonaldehyde has gained considerable attention owing to its industrial applications for producing fine chemicals. Understanding the hydrogenation mechanism from density functional theory (DFT) calculations can provide insights for designing catalysts with high selectivities toward the target products. Among contemporary theoretical investigations of the hydrogenation, the calculated selectivities are not in agreement with the experimental results. Herein, a SiO2‐supported Pt nanocluster is developed, and it is used to investigate the selective hydrogenation of crotonaldehyde. The nanocluster model is used to obtain free energy barriers from DFT calculations, and these are used to build a microkinetic model. The theoretical selectivity values for the products are in agreement with the experimental results. According to the density of state analysis, this is directly attributed to the more accurate d‐band width from the Pt cluster. The contribution of each step to the final product is identified and can be used to intensify the process of generating the target product.

Dual Interface Synergistic Catalysis: The Selective Hydrogenation of Crotonaldehyde Over Pt/Co3O4@PDA

Dual Interface Synergistic Catalysis: The Selective Hydrogenation of Crotonaldehyde Over Pt/Co3O4@PDA

Hydrogenation of Crotonaldehyde Over Fe(Oh)X-Pt/Bn Catalysts: Improved Selectivity to Unsaturated Alcohol Via Pt-Fe(Oh)X Interaction

Hydrogenation of Crotonaldehyde Over Fe(Oh)X-Pt/Bn Catalysts: Improved Selectivity to Unsaturated Alcohol Via Pt-Fe(Oh)X Interaction

The structure and electronic effects of ZIF-8 and ZIF-67 supported Pt catalysts for crotonaldehyde selective hydrogenation

The structure and electronic effects of ZIF-8 and ZIF-67 supported Pt catalysts for crotonaldehyde selective hydrogenation.

The Roles of Precursor-Induced Metal–Support Interaction on the Selective Hydrogenation of Crotonaldehyde over Ir/TiO2 Catalysts

Various supported Ir/TiO2 catalysts were prepared using different Ir precursors (i.e., H2IrCl6, (NH4)2IrCl6 and Ir(acac)3) and tested for vapor phase selective hydrogenation of crotonaldehyde. The choice of Ir precursor significantly altered the Ir-TiOx interaction in the catalyst, which thus had essential influences on the geometric and electronic properties of the Ir species, reducibility, and surface acidity, and, consequently, their reaction behaviors. The Ir/TiO2-N catalyst using (NH4)2IrCl6 as the precursor gave the highest initial reaction rates and turnover frequencies of crotyl alcohol formation. Such high performance was ascribed to the high Ir dispersion and high surface concentration of Ir0 species, as well as a higher surface acidity, in the Ir/TiO2-N catalyst compared to its counterparts, indicating the synergistic roles of the Ir-TiOx interface in the reaction, as the interfacial sites were responsible for the adsorption/activation of H2 and the C=O bond in the crotonaldehyde molecule.

Three-Factor Kinetic Equation of Catalyst Deactivation.

The three-factor kinetic equation of catalyst deactivation was obtained in terms of apparent kinetic parameters. The three factors correspond to the main cycle with a linear, detailed mechanism regarding the catalytic intermediates, a cycle of reversible deactivation, and a stage of irreversible deactivation (aging), respectively. The rate of the main cycle is obtained for the fresh catalyst under a quasi-steady-state assumption. The phenomena of reversible and irreversible deactivation are presented as special separate factors (hierarchical separation). In this case, the reversible deactivation factor is a function of the kinetic apparent parameters of the reversible deactivation and of those of the main cycle. The irreversible deactivation factor is a function of the apparent kinetic parameters of the main cycle, of the reversible deactivation, and of the irreversible deactivation. The conditions of such separability are found. The obtained equation is applied successfully to describe the literature data on the reversible catalyst deactivation processes in the dehydration of acetaldehyde over anatase and in crotonaldehyde hydrogenation on supported metal catalysts.

The effects of TiO2 crystal-plane-dependent Ir-TiOx interactions on the selective hydrogenation of crotonaldehyde over Ir/TiO2 catalysts

Three supported Ir/TiO2 catalysts, containing anatase TiO2 nanocrystals with predominantly exposed {101}, {100}, and {001} planes, were subjected to various pre-treatments (H2 reduction at different temperatures and O2 re-oxidation) and then tested in the vapor phase selective hydrogenation of crotonaldehyde. The pre-treatments significantly altered the Ir-TiOx interactions, including the morphologies and electronic properties of the Ir species and their surface acidity. These interactions were also closely related to the crystal planes of TiO2, which further supported the observed reaction behaviors of the various Ir/TiO2 catalysts. The best performance was obtained using the Ir/TiO2-{101} catalyst pre-reduced at 300 °C, owing to its higher Ir0 surface concentration and moderate surface acidity compared to the other catalysts. Moreover, these findings indicated the synergistic role of the Ir-TiOx interface in the reaction, as the interfacial sites were responsible for the adsorption/activation of H2 and the C=O bond in the crotonaldehyde molecule. However, pre-reduction at 400 °C resulted in partial encapsulation of the Ir particles by TiOxvia strong metal-support interactions, which is unfavorable for the catalytic reaction owing to the loss of Ir-TiOx interfacial sites.

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.