Butene Selectivity Research Articles

Understanding the Deactivation of Ag−ZrO2/SiO2 Catalysts for the Single‐step Conversion of Ethanol to Butenes

AbstractAg−ZrO2/SBA‐16 has recently been found to be efficient for catalyzing the single‐step conversion of ethanol to butene (1‐ and 2‐butene mixtures) in the presence of H2. The reaction proceeds via a cascading sequence of reactions over mixed metal and Lewis sites, with the catalyst composition tuned to selectively favor butene formation. However, the catalyst slowly deactivates when evaluated over long reaction times. In this work, we evaluated the lifetime of the Ag−ZrO2/SBA‐16 catalyst system for ethanol‐to‐butene conversion at 325 °C for up to 800 hours on stream. Several characterization techniques were used to elucidate the mechanism(s) by which catalyst deactivation occurs. Coke deposition, Ag particle sintering, and Ag0‐to‐Ag+ oxidation state change were identified to be the major causes of catalyst deactivation. Coke deposits cover primarily Lewis acid sites which are responsible for aldol condensation, Meerwein‐Ponndorf‐Verley (MPV) reduction, and dehydration reactions. Ag particle sintering and Ag oxidation state change leads to a reduction in the number of metallic Ag sites responsible for the dehydrogenation/hydrogenation steps. The fresh catalyst likely experiences hydrothermal sintering in the early stage of reaction and permanently loses some active Lewis acid sites before reaching a new structural steady state. The deactivation of Lewis acid sites leads to a decrease in overall ethanol conversion, whereas the deactivation of the metallic Ag sites decreases the butene selectivity. For catalyst regeneration, oxidative calcination (at 500 °C) followed by reduction (at 325 °C) successfully removes all the coke species on the catalyst surface and restores the metallic Ag particles of the 4Ag−4ZrO2/SBA‐16 catalysts.

Enhanced performance of supported Pd-Pt bimetallic catalysts prepared by modified electroless deposition for butane dehydrogenation

The alumina supported Pd-Pt based bimetallic catalysts were prepared by modified electroless deposition and evaluated for butane dehydrogenation. The bimetallic Pd-Pt catalysts exhibited superior performance compared to that of monometallic catalysts. The superior performance may be attributed to strong synergistic interaction between metals, stronger metal-support interaction and lower acidity. The higher activity of alloyed Pd-Pt metal resulted in higher conversion for bimetallic catalysts. The lower acidity resulted in higher butene selectivity and stability for bimetallic catalysts by minimizing cracking and secondary reactions. The co-deposited catalyst with more uniform distribution of Pd and Pt metals showed better performance than bimetallic catalysts prepared by sequential deposition. Co-deposited Pd-Pt/Al catalyst showed the highest butane conversion (50 %), butene yield (42 %) and stability. The reported yield is much higher than many reported values for Pt or Pd based catalysts. The co-deposited Pd-Pt/Al catalyst also exhibited better dehydrogenation performance in comparison to corresponding co-impregnated bimetallic catalyst.

Modification of a phase-inhomogeneous alumina support of a palladium catalyst. Part II: the effect of palladium dispersion on the formation of hydride forms, electronic state, and catalytic performance in the reaction of partial hydrogenation of unsaturated hydrocarbons

It was shown for the first time that amorphous phase in an alumina support promotes the formation of palladium particles in a wide size range. This catalyst has a low selectivity to butenes in the 1,3-butadiene hydrogenation. It was suggested that surface palladium aluminates contribute to an increase in butene selectivity up to 99.5% at a hydrogenation temperature of not more than 65 °C. At higher reaction temperatures, the catalyst based on phase-homogeneous γ-Al2O3 has the highest activity and butene selectivity. This catalyst was obtained by the traditional impregnation method and contains highly dispersed palladium particles with a sufficiently high electron density. It was shown that the formation of hydride forms on palladium particles with a size of less than 1 nm was detected by temperature-programmed reduction with hydrogen.

Gas Separation Membranes Based on Germanium Containing Polyalkylenesiloxane

An original method for the synthesis of monomer for the preparation of a new membrane polymer, 2,2,4,4,6,6-hexamethyl-1-oxa-2,6-disyl-4-germanocyclohexane, is proposed, which allows increasing the yield of the target substance. By polycondensation polymerization, a membrane-forming germanium-containing polycarbosiloxane was synthesized. Based on it, new highly permeable membranes with high selectivity of butane / methane were first obtained and studied. When comparing the transport properties of silicon and germanium-containing polymers, it was found that polycarbosiloxane containing germanium atoms in the main chain shows higher values of butane selectivity and permeability.

Au–Pt bimetallic nanoparticle catalysts supported on UiO-67 for selective 1,3-butadiene hydrogenation

Bimetallic nanoparticle (NP)-supported catalysts for use in the hydrogenation reaction has received growing attention on account their excellent catalytic performance. In the present work, bimetallic Au–Pt and monometallic Pt/Au NPs were supported on the Zr-based metal–organic framework UiO-67 via a simple impregnation–reduction method. The catalytic performance of the catalysts for selective 1,3-butadiene (1,3-BD) hydrogenation was influenced by the space velocity, reaction temperature and Au/Pt molar ratio. Whilst bimetallic AuPt/UiO-67-3 displayed catalytic activity similar to that of Pt/UiO-67 for selective 1,3-BD hydrogenation, the former also exhibited much higher selectivity toward total butenes than the latter. The AuPt/UiO-67-3 catalyst with a 1.1:1.0 Au/Pt molar ratio exhibited the best catalytic activity and butene selectivity for selective 1,3-BD hydrogenation at 100 °C with a space velocity of 117 L/(h gcat).This work provides a practical example of novel and efficient bimetallic supported catalysts.

Enhanced stability of highly-dispersed copper catalyst supported by hierarchically porous carbon for long term selective hydrogenation

Copper based catalysts have high potential for the substituent of noble-metal based catalysts as their high selectivity and moderate activity for selective hydrogenation reaction; however, achieving further high catalytic stability is very difficult. In this work, the carbonization process of Cu-based organic frameworks was explored for the synthesis of highly-dispersed Cu supported by hierarchically porous carbon with high catalytic performance for selective hydrogenation of 1,3-butadiene. The porous hierarchy of carbon support and the dispersion of copper nanoparticles can be precisely tuned by controlling the carbonization process. The resultant catalyst carbonized at 600 °C exhibits a rather low reaction temperature at 75 °C for 100% butadiene conversion with 100% selectivity to butenes, due to its reasonable porous hierarchy and highly-dispersed copper sites. More importantly, unprecedentedly stability of the corresponding Cu catalyst was firstly observed for selective 1,3-butadiene hydrogenation, with both 100% butadiene conversion and 100% butenes selectivity over 120 h of reaction at 75 °C. This study verifies that a simply control the carbonization process of metal organic frameworks can be an effective way to obtain Cu-based catalysts with superior catalytic performance for selective hydrogenation reaction.

Supported palladium nanoclusters: morphological modification towards enhancement of catalytic performance using surfactant-assisted metal deposition

In the present study, alumina-supported palladium catalysts were prepared by modified electroless deposition (ED) method in presence of surfactants and their performance was significantly improved compared to that prepared in absence of surfactants. Depending on the type and concentration of surfactant, loading and morphology of deposited palladium varied. Both anionic (sodium dodecyl sulphate) and non-ionic (Tween 20) surfactants were observed to be the most effective in dispersing the metals in the precursor solution. Average metal cluster sizes obtained for catalysts prepared by wetness impregnation, modified electroless deposition and surfactant-assisted deposition method were 11.89, 4.6 and 1.18 nm, respectively. The conversion of butane and selectivity to butene was observed to be function of size of deposited Pd cluster. The conversion and selectivity towards butenes increased with the decreasing particle size. The SDS surfactant-assisted prepared catalyst, having the lowest metal cluster size (1.18 nm), showed the highest activity (33% conversion at 600 °C) and over 99% selectivity for butenes.

Bimetallic Au-Pd alloy nanoparticles supported on MIL-101(Cr) as highly efficient catalysts for selective hydrogenation of 1,3-butadiene.

Gold–palladium (Au–Pd) bimetallic nanoparticle (NP) catalysts supported on MIL-101(Cr) with Au : Pd mole ratios ranging from 1 : 3 to 3 : 1 were prepared through coimpregnation and H2 reduction. Au–Pd NPs were homogeneously distributed on the MIL-101(Cr) with mean particle sizes of 5.6 nm. EDS and XPS analyses showed that bimetallic Au–Pd alloys were formed in the Au(2)Pd(1)/MIL-101(Cr). The catalytic performance of the catalysts was explored in the selective 1,3-butadiene hydrogenation at 30–80 °C on a continuous fixed bed flow quartz reactor. The bimetallic Au–Pd alloy particles stabilized by MIL-101(Cr) presented improved catalytic performance. The as-synthesized bimetallic Au(2)Pd(1)/MIL-101(Cr) with 2 : 1 Au : Pd mole ratio showed the best balance between the activity and butene selectivity in the selective 1,3-butadiene hydrogenation. The Au–Pd bimetallic-supported catalysts can be reused in at least three runs. The work affords a reference on the utilization of a MOF and alloy nanoparticles to develop high-efficiency catalysts.

Correlating Oxygen Species with Product Selectivity for Dehydrogenation of Butane over Titanium Mixed Oxide Catalysts

This study investigated the dehydrogenation of butane over TiO2-based catalysts prepared by a co-precipitation method. The catalysts were characterized in detail using various surface techniques, such as XRD, XPS, SEM, and pyridine-FTIR. Their performances towards butane dehydrogenation showed that the product distribution was considerably affected by reaction temperature, as well as the composition of the catalysts. Two different selectivity regions were observed for most of the catalysts. Higher butenes selectivity over butadiene was obtained at relatively low temperatures, while an opposite trend was observed at high temperatures. In-situ DRIFT measurements did not find obvious change of the reaction pathway for butane dehydrogenation over the TiO2-based catalysts. The variation in selectivity with temperature can be well correlated with the different types of oxygen species on the catalysts.

Thermodynamic Separation of 1-Butene from 2-Butene in Metal-Organic Frameworks with Open Metal Sites.

Most C4 hydrocarbons are obtained as byproducts of ethylene production or oil refining, and complex and energy-intensive separation schemes are required for their isolation. Substantial industrial and academic effort has been expended to develop more cost-effective adsorbent- or membrane-based approaches to purify commodity chemicals such as 1,3-butadiene, isobutene, and 1-butene, but the very similar physical properties of these C4 hydrocarbons make this a challenging task. Here, we examine the adsorption behavior of 1-butene, cis-2-butene, and trans-2-butene in the metal-organic frameworks M2(dobdc) (M = Mn, Fe, Co, Ni; dobdc4- = 2,5-dioxidobenzene-1,4-dicarboxylate) and M2(m-dobdc) (m-dobdc4- = 4,6-dioxidobenzene-1,3-dicarboxylate), which all contain a high density of coordinatively unsaturated M2+ sites. We find that both Co2(m-dobdc) and Ni2(m-dobdc) are able to separate 1-butene from the 2-butene isomers, a critical industrial process that relies largely on energetically demanding cryogenic distillation. The origin of 1-butene selectivity is traced to the high charge density retained by the M2+ metal centers exposed within the M2(m-dobdc) structures, which results in a reversal of the cis-2-butene selectivity typically observed at framework open metal sites. Selectivity for 1-butene adsorption under multicomponent conditions is demonstrated for Ni2(m-dobdc) in both the gaseous and the liquid phases via breakthrough and batch adsorption experiments.

Identification of amorphous and crystalline phases in alumina entity and their contribution to the properties of the palladium catalyst

The purpose of this paper is to identify the phase inhomogeneity, undetectable by X-ray method, and the reason for its occurrence in the composition of aluminum oxide. It is shown that even a trace amount of carbon (0.23 wt%) in the precursor of aluminum oxide can cause a high content of amorphous phase (38%). Carbon is present due to the products of incomplete hydrolysis of the aluminum alkoxides (alumoxanes) in the commercial sample of boehmite. The fact that the amorphous and crystalline phases in the composition of aluminum oxide differ in reactivity under hydrothermal treatment is first described. It is shown in a split endothermic peak on the differential scanning calorimetry curve. It is investigated that the brief hydrothermal treatment of the phase-inhomogeneous aluminum oxide and its subsequent calcination lead to formation of a defective structure with greater acidity in the composition of the aluminum oxide. This aluminum oxide was used as a support of the palladium catalyst in the 1,3-butadiene hydrogenation. This catalyst showed higher selectivity to 1-butene and low selectivity to butane, compared to the catalyst on alumina with amorphous phase.

Selective Ethylene Dimerization by Palladium(II) Complexes Bearing a Phosphinoferrocene Sulfonate Ligand

Palladium(II) complexes featuring the hybrid anionic ligand 1′-(diphenylphosphino)ferrocene-1-sulfonate (L–), viz., trans-(Et3NH)2[Pd(μ-Cl)Me(L-κP)]2 (1), [Pd(Me)(dmap-κN1)(L-κ2O,P)](2; dmap = 4-(dimethylamino)pyridine), and [Pd(η3-allyl)(L-κ2O,P)] (6), were synthesized and together with the previously reported compounds trans-(Et3NH)2[PdCl2(L-κP)2] and [Pd(LCY)(L-κ2O,P)] (LCY = 2-[(dimethylamino-κN)methyl]phenyl-κC1 and 2-[(methylthio-κS)methyl]phenyl-κC1) tested as precatalysts for Pd-catalyzed ethylene dimerization. Only compound 1 gave rise to an active catalyst after activation by sequential halogen removal with Tl[PF6] and Na[BAr′4] (Ar′ = 3,5-bis(trifluoromethyl)phenyl) in chloroform. Thus, the formed catalyst efficiently mediated the dimerization of ethylene showing both good activity (TOF ≈ 95 h–1) and high selectivity for 1-butene (95%) at 21 °C and 30 bar of ethylene pressure. DFT calculations have shown that the dimerization reaction is thermodynamically preferred over the formation of higher oligomers and that O,P-chelate coordination of the phosphinosulfonate ligand in all Pd(II) reaction intermediates is vital for the catalytic process. In particular, the O,P-chelating phosphinoferrocene sulfonate ligand stabilizes and electronically differentiates the reaction intermediates and favors concerted ethyl migration to coordinated ethylene giving rise to 1-butene.

Hydrogenation of acetylenic contaminants over Ni-Based catalyst: Enhanced performance by addition of silver

The hydrogenation of acetylenic contaminates into valuable chemicals is a clean and promising process for minimizing the waste and improving economic benefits. In this work, the enhancement of Ag on Ni/Al2O3 catalyst for acetylenic stream hydrogenation was studied by multiple characterization techniques and DFT calculations. The addition of Ag shows negligible effect on the particle size of Ni nanoparticles, but modifies the electronic and geometric structures of Ni active sites by electron transfer and site isolation, respectively, which weaken the adsorption strength of Ni sites for reactants and intermediates and thus suppress their polymerization. Due to the enhancement of Ag, Ni-Ag/Al2O3 catalyst exhibited excellent performance for the hydrogenation of acetylenic contaminates for a 700-h evaluation: ∼99.8% of total conversion and ∼98% of butane selectivity. Moreover, besides the high-quality products of butane, the results of simulation by Aspen Plus simulator indicates that 98% of benzene in acetylenic contaminates can be recovered as a chemical product with 99% of purity. This Ni-Ag/Al2O3 catalyzed hydrogenation process for acetylenic contaminates exhibits a potential of substantial economic and green benefits for the industrial production.

Efficient Catalytic Dehydration of High-Concentration 1-Butanol with Zn-Mn-Co Modified γ-Al2O3 in Jet Fuel Production

It is important to develop full-performance bio-jet fuel based on alternative feedstocks. The compound 1-butanol can be transformed into jet fuel through dehydration, oligomerization, and hydrogenation. In this study, a new catalyst consisting of Zn-Mn-Co modified γ-Al2O3 was used for the dehydration of high-concentration 1-butanol to butenes. The interactive effects of reaction temperature and butanol weight-hourly space velocity (WHSV) on butene yield were investigated with response surface methodology (RSM). Butene yield was enhanced when the temperature increased from 350 °C to 450 °C but it was reduced as WHSV increased from 1 h−1 to 4 h−1. Under the optimized conditions of 1.67 h−1 WHSV and 375 °C reaction temperature, the selectivity of butenes achieved 90%, and the conversion rate of 1-butanol reached 100%, which were 10% and 6% higher, respectively, than when using unmodified γ-Al2O3. The Zn-Mn-Co modified γ-Al2O3 exhibited high stability and a long lifetime of 180 h, while the unmodified γ-Al2O3 began to deactivate after 60 h. Characterization with X-ray diffraction (XRD), nitrogen adsorption-desorption, pyridine temperature-programmed desorption (Py-TPD), pyridine adsorption IR spectra, and inductively coupled plasma atomic emission spectrometry (ICP-AES), showed that the crystallinity and acid content of γ-Al2O3 were obviously enhanced by the modification with Zn-Mn-Co, and the loading amounts of zinc, manganese, and cobalt were 0.54%, 0.44%, and 0.23%, respectively. This study provides a new catalyst, and the results will be helpful for the further optimization of bio-jet fuel production with a high concentration of 1-butanol.

Conversion of methyl ethyl ketone to butenes over bifunctional catalysts

The direct conversion of methyl ethyl ketone (MEK) to butene over supported copper catalysts was investigated in a fixed bed reactor over Cu-Al2O3, Cu-zeolite Y sodium (Cu-ZYNa) and Cu-zeolite Y hydrogen (Cu-ZYH). In this reaction, MEK is hydrogenated to 2-butanol over metal sites which is further dehydrated on acid sites to produce butene. Experimental results showed that the selectivity of butene was the highest over Cu-ZYNa, and it was improved by finding the optimum reaction temperature, hydrogen pressure and the percentage of copper loaded on ZYNa. The highest selectivity of butene (97.9%) was obtained at 270 °C and 20 wt% Cu-ZYNa. Over Cu-Al2O3, the selectivity of butenes was less than Cu-ZYNa since subsequent hydrogenation of butene occurred to produce butane. It was also observed that with increasing H2/MEK molar ratio, butane selectivity increased. However, when this ratio was decreased, hydrogenation of butene was reduced, but dimerization to C8 alkenes and alkane began to be favored. The main products over 20% Cu-Al2O3 were butene and butane, and a maximum selectivity of butene (87%) was achieved at an H2/MEK molar ratio of five. The lowest selectivity of butene was obtained using Cu-ZYH, reaching ∼40%. All catalysts were characterized by (NH3-TPD), (CO2-TPD), XPS and TPR to probe catalyst acidity, basicity and the reducibility of Cu loaded on the supports. It was found that the amount of acidity in Cu-ZYH is much higher than in Cu-ZYNa. This could have caused the selectivity of butene to decrease as a result of dimerization, oligomerization and cracking reactions.

Bis(Imido) Tungsten Complexes: Efficient Precatalysts for the Homogeneous Dimerization of Ethylene

The ethylene dimerization performance of a range of bis(imido)tungsten precatalysts, after activation with aluminum cocatalysts, has been assessed. The best-performing system achieved an activity of 409 410 (mol C2H4)(mol W)−1h–1 [79.6 wt % 1-butene] with a 1-butene selectivity of 82.4 wt % [290 770 (mol C2H4)(mol W)−1h–1 activity]. In addition to selected previously reported variants, the symmetrical bis(imido)tungsten(VI) complexes [WCl2(NPh)2(tmeda)] (3) and [WCl2(NR)2(dme)] [R = 2,4,6-trifluorophenyl, 7; 2,4,6-triphenylphenyl, 8; 2,4,6-tris(trifluoromethyl)phenyl, 9], were prepared. A series of unsymmetrical bis(imido)tungsten(VI) complexes [WCl2(NDipp)(NR)(dme)] (R = iPr, 11; tBu, 12; 2,4,6-trimethylphenyl, 13; 2,4,6-trichlorophenyl, 14; 2,4,6-trifluorophenyl, 15; 2,6-dinitrophenyl, 16; 2,4,6-triphenylphenyl, 17) were also synthesized using an improved version of a previous preparative route that eases purification. The molecular structures of complexes 5–13 and 15–17 were determined by X-ray crystal...

Ethene Dimerization and Hydrogenation over a Zeolite-Supported Rh(I)-Carbonyl Complex: Mechanistic Insights from DFT Modeling

Using DFT calculations within a quantum mechanical/molecular mechanical scheme, we present a model study on a zeolite-supported Rh(I) complex, [Rh(CO)(C2H4)]+, to rationalize the experimentally observed ethene hydrogenation and dimerization. Our computational results show that the coordination of an ethene to the Rh center of a [Rh(CO)(C2H4)]+ complex is thermodynamically favorable over H2 coordination. The diethyl complex [Rh(CO)(C2H5)2]+ resulting from hydrogenation acts as a branching point of two catalytic cycles of ethene conversion, to hydrogenation or dimerization. The Rh-acyl complex [Rh(COCH2CH3)(C2H5)(C2H4)]+ is the in situ-generated active species initiating the dimerization, as it entails a tremendous lowering of the C–C coupling barrier, by more than 100 kJ mol–1. Overall, free energy barriers of ethene hydrogenation (89–92 kJ mol–1) are calculated 4–7 kJ mol–1 lower than the barrier for dimerization, 96 kJ mol–1, in qualitative agreement with the experimentally observed selectivity. Finally, a side reaction of the Rh-acyl complex yields a qualitative explanation of the experimentally observed steady increase in butene selectivity.

Ethylene oligomerization promoted by nickel-based catalysts with silicon-bridged diphosphine amine ligands

A series of nickel complexes [Ni(L1)Br2] (C1), [Ni(L2)Br2] (C2) and [Ni(L3)Br2] (C3) (L1 = N-isopropyl-N-(((diphenylphosphanyl)methyl)dimethylsilyl)-1,1-diphenylphosphanamine, L2 = N-cyclopentyl-N-(((diphenylphosphanyl)methyl)dimethylsilyl)-1,1-diphenylphosphanamine, L3 = N-(2,6-diisopropylphenyl)-N-(((diphenylphosphanyl)methyl)dimethylsilyl)-1,1-diphenylphosphanamine) were synthesized and characterized by elemental analysis, mass spectrometry, spectroscopy and single-crystal X-ray diffraction. L1, L2 and L3 each act as bidentate ligands. Upon activation with ethylaluminum dichloride, these complexes produce efficient catalytic systems for selective dimerization of ethylene to 1-butene, with catalytic activities of 3.45 × 107 g/(molNi·h) and 95.6% butene selectivity containing 87.6% 1-butene fraction.

Synergistic Effects of Dual-Metal Catalysts for Selective Butane Detection by SnO2/Graphene Nanocomposite Sensor

Highly sensitive and selective tin dioxide (SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> )-based sensor material was wet-chemically synthesized by sonication-assisted simultaneous precipitation method, and their sensing characteristics for various environmentally important combustible and reducing gases were investigated by resistance measurements on an assembled “Taguchi-type” sensor prototype. Characteristics and morphologies of the synthesized powder were examined by thermal, physico-chemical, spectral, and optical studies and their effect(s) on sensing properties were correlated. Small amount of gold addition along with palladium in the metal-oxide-semiconductor, such as SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , leads to enhanced sensing properties toward environmentally important and combustible gases such as liquefied petroleum gas (mainly butane), compressed natural gas (mostly methane), carbon monoxide, and hydrogen (H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ). A particular composition of SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> with bi-metallic catalysts (Pd and Au) exhibits excellent sensitivity and butane selectivity. Use of graphene on the final sensor prototype is improved durability in terms of prolonged shelf life by forming a semi-exchangeable coating.

Understanding the underlying mechanism of improved selectivity in pd1 single-atom catalyzed hydrogenation reaction

Supported metal single-atom catalysts (SACs) with maximized metal atom efficiency and unique catalytic properties have drawn tremendous attention in the catalysis field. In this work, we reported that in selective hydrogenation of 1,3-butadiene, graphene supported Pd1 single atoms, synthesized by atomic layer deposition, exhibited expressively 100% butenes selectivity at 100% conversion at near ambient temperature, regardless of hydrogen partial pressures. The hydrogen reaction order was found to be about 1.2, indicating that hydrogenation dissociation is the rate-determining step. Combining with other structural characterization techniques, in situ X-ray absorption fine structure spectroscopy suggests that the Pd1 single atom likely bonds to the graphene support through three PdC and one PdOC coordinations. Density functional theory calculations show that 1,3-butadiene adsorbs on Pd1 via a mono-π adsorption mode (−0.98 eV), much stronger than that of H2 (−0.30 eV), which makes Pd1 to be predominantly covered with a 1,3-butadiene molecule during reaction, consistent very well with the results of H-D exchange reaction. Facilitated by the bridging O atom in the PdOC coordination, H2 dissociates at the 1,3-butadiene covered Pd1 atom in the heterolytic way, then hydrogenates the adsorbed 1,3-butadiene molecule by following the pseudo Horiuti-Polanyi mechanism. Distinct from its adsorption on extended Pd surfaces, such mono-π adsorption of 1,3-butadiene on Pd1 favors 1-butene formation, but impedes the secondary hydrogenation to butane owing to intensified steric hindrance, thus yielding the expressively high butenes selectivity over Pd1 SAC. These findings pave a new way to rational design SACs catalyst in selective hydrogenation reactions.