Effect Of Support Properties Research Articles

Selective hydrogenation of dimethyl toluene-2,4-dicarbamate over supported Rh-based catalysts: Effect of support properties

Selective hydrogenation of dimethyl toluene-2,4-dicarbamate over supported Rh-based catalysts: Effect of support properties

Novel synthesis strategy of SAPO-11 molecular sieve with superior performance for hydroisomerization of long-chain n-alkanes: Supergravity-cyclone assisted hydrothermal crystallization method

In this work, we successfully synthesized high performance SAPO-11 molecular sieve via the novel supergravity-cyclone assisted hydrothermal crystallization method for the first time. The initial gel was subjected to cyclone treatment and supergravity shearing treatment to obtain the secondary molecular sieve precursor mixture with high viscosity and micro-bubble distribution. The effects of supergravity shear-cyclone operation on the physicochemical properties of SAPO-11 molecular sieve were investigated. The supergravity-cyclone treatment improved the textural properties and acidity of SAPO-11 molecular sieve. The effects of support properties on the properties of active phase of NiWS-support catalyst and its catalytic performance for hydroisomerization of n-hexadecane were further investigated. NiW/SAPO-11-B showed more active phase with hydroisomerization kinetics advantage and nearly doubled yield of i-hexadecane compared with conventional SAPO-11-based catalyst. The process and mechanism of synthesizing high performance SAPO-11 molecular sieve via the supergravity-cyclone technology were explored. It was found that the supergravity-cyclone assisted crystallization method shortened the crystallization time of SAPO-11 and improved the crystallization efficiency. In addition, the hydroisomerization kinetics of n-hexadecane on SAPO-11-based NiWS supported catalyst was studied. The structure–activity relationship between the structure of active phase and the formation of CUS was investigated, and the influence of support properties on the properties of NiWS active phase and their synergistic mechanism in the hydroisomerization of n-hexadecane were revealed. This is expected to provide a new strategy for the synthesis of high performance SAPO-11 molecular sieve and the preparation of non-noble metal supported catalyst with superior hydroisomerization performance for long-chain alkanes.

Acid site introduced by Al3+penta and boron in Pt/Al2O3 catalyst for dehydrogenation of methylcyclohexane

A series of catalysts with different acid strengths were obtained by constructing unsaturated pentacoordinate (Al3+penta) sites in Al2O3 and loading with boron. The effects of support properties and the addition of boron on the strength and type of catalyst acid were investigated, and their influence on the dehydrogenation performance of methylcyclohexane (MCH) was discussed. In Pt-B/Al2O3-600 catalysts containing Al3+penta sites, the strongly acidic L acid sites gradually decreased and the weakly acidic [L + B] acid sites gradually increased with increasing boron loading, indicating coverage of the Al3+penta site by boron. In Pt-B/Al2O3-750 catalysts without Al3+penta sites, strongly acidic L acid sites gradually decrease with increasing boron loading and weakly acidic [L + B] acid sites remains essentially unchanged. For Pt-B/Al2O3-600 catalysts, the effect of boron on the interaction of Pt with Al2O3 is minimized when the loading of boron is between 0 and 1 wt% and the MCH dehydrogenation performance increases with the number of weak acid sites. At a boron loading of 1 wt%, the abundance of weak acid sites maintains the dispersion of Pt and allows a suitable interaction between Pt and Al2O3, thus enhancing the dehydrogenation performance of MCH.

CO2 hydrogenation to olefins on supported iron catalysts: Effects of support properties on carbon-containing species and product distribution

Catalytic utilizing of CO2 into valuable olefins on Fe-based catalysts is a feasible way to mitigate the pressure of carbon neutrality. Herein, by investigating the effects of support (SiO2, Al2O3, CNT, and ZrO2) on the structure and catalytic performance of iron catalysts, we have found that ZrO2 supported catalysts are more beneficial to olefin selectivity and chain growth. The optimization catalytic performance of FeNa/ZrO2 displays C2-C7 olefin selectivity of 68.2% (O/P = 8.0) with a space time yields (111.4 g Kgcat-1h−1) at XCO2 = 32.7%, 320 ⁰C, 2.0 MPa, CO2/H2/Ar = 1:3:3, and 9000 mL g-1h−1. Characterizations show that the support regulates the composition of the iron oxide phase and the iron carbide phase and induces to form the highest content of Fe5C2 on the spent FeNa/ZrO2, which is probably caused by the carbon rich surface and lower disorder of carbon species. Besides, the higher intensity of CO2 and CO adsorption and lower intensity of H2 adsorption is confirmed on the surface of the FeNa/ZrO2 catalysts, leading to a higher ratio of C/H on the surface of the spent catalysts and consequently inhibiting the hydrogenation of olefins. Therefore, the O/P is 8 times as many as that on the FeNa/SiO2 and FeNa/Al2O3. Understanding the effect of support on CO2 hydrogenation to olefins over iron-based catalysts would be significant for precisely designing new catalysts.

Iron(II) phthalocyanine (FePc) over carbon support for oxygen reduction reaction electrocatalysts operating in alkaline electrolyte

In this work, we initially report a detailed advancement in the utilization of metal-N4 chelate macrocycles in the oxygen reduction reaction (ORR). Then, iron(II) phthalocyanines supported on two different carbon-based supports specifically carbon nanotube and black pearl (carbon spheres) were synthesized and their activities toward ORR in alkaline media were studied. With the help of physical and surface characterization like Raman, BET, XRD, XPS, and electron microscopy analysis, the similarity in surface chemistry and surface area of the materials and the differences in the structure and morphology of the supports were established. This work also brings forth the effect of support properties on the electrocatalytic activity of the materials by a detailed electrochemical analysis using rotating disk electrode in oxygen saturated 0.1 M KOH. Comparison with existing literature on Fe-phthalocyanine supported on diverse carbon support is presented.

The effect of support properties on n-octanol oxidation performed on gold – silver catalysts supported on MgO, ZnO and Nb2O5

Catalytic behaviour of supported nanometal catalysts for alcohols selective oxidation depends on the nature of the support and its surface. To identify the main feature that could explain these effects, supported mono- (Au) and bimetallic (AuAg) catalysts were prepared by using pure MgO, ZnO and Nb2O5, representative of three different types of oxides (basic, amphoteric and acidic, respectively), to get homogeneous metal-support interaction for each catalyst. The catalysts were characterized by XRD, N2 physisorption, TEM, UV–vis, XPS and 2-propanol decomposition as test reaction. It was found that the catalytic activity is influenced by the electron mobility between the gold nanoparticles and the support, which in turns depends on the intermediate electronegativity of the support. Selectivity in n-octanol oxidation was determined by redox properties of the gold species, the acid-base properties of the supports and the catalyst pretreatment. Silver addition modified the acid-base properties of the catalytic system, thus influencing the selectivity in n-octanol oxidation. Pretreatment of the catalyst (drying in air or thermal treatment in hydrogen flow) had a significant impact on its activity and selectivity.

Effect of support properties on preparation process and adsorption performances of solvent impregnated resins

The effect of support properties on preparation process and adsorption performances of solvent impregnated resins (SIRs) has been studied. Five SIRs were prepared by impregnating di(2-ethylhexyl)phosphoric acid (D2EHPA) in five macroporous absorbent resins (MARs), respectively and used to extract V(IV) from aqueous solutions. The impregnation equilibrium can be fast achieved for the MARs with smaller pore size and bigger specific surface area, where D2EHPA is preferentially adsorbed in the micropores approximately as wall-spreading to form monolayer films, resulting in the relatively high utilization efficiency of extractant and stability of the SIRs. However, the extractant is more likely to accumulate in the macropores and/or mesopores than in the micropores, which leads to the higher mass ratio of extractant and pore-filling percentage in the SIRs with abundant macropores and/or mesopores. D2EHPA can be adsorbed on XAD-7HP fabricated with poly(methyl methacrylate) by virtue of relatively strong Hydrogen-bond, thus it can exist not only inside the pores but also on the surface of the resin, which causes the high mass ratio of extractant and extremely high pore-filling percentage although it contains the minimum pore volume. The relatively strong hydrogen-bond between XAD-7HP and D2EHPA is also believed to be responsible for its high adsorption capacity for V(IV) and utilization efficiency of the impregnated extractant.

The effect of support properties in the preparation of Pd size-controlled catalysts by “water-in-oil” microemulsion method

Abstract The palladium particles pre-formed by “water-in-oil” microemulsion method were deposited onto carbon, silica and cellulose supports which differed in hydrophobic and textural properties. Microemulsions with anionic bis(2-ethylhexyl)sulfosuccinate (AOT) and non-ionic polyoxyethylene(7-8)octylphenyl ether (Triton-X 114) surfactants were used. Palladium particles of size with narrow range but various average sizes (ca. 8–9 and ca. 4 nm) were obtained using hydrazine hydrate or NaH 2 PO 2 as reducing agents. The results obtained by a number of techniques (XPS, XRD, SEM, TEM) showed that porosity of support and polarity of its surface determined the migration of Pd particles inside the pore structure as well as their aggregation in the final catalysts. Increased polarity of silica surface due to pre-treatment with water produced the most extensively aggregated particles. Pre-treatment of silica with non-polar cyclohexane, the solvent of bulk microemulsion, exhibited a very advantageous role because both processes migration and aggregation of primary Pd particles were almost completely inhibited. In the obtained 1%Pd/SiO 2 catalyst no aggregated particles appeared and it exhibited very high activity in liquid phase hydrogenation of styrene.

Effect of Alumina Support on the Formation of the Active Phase of Selective Hydrodesulfurization Catalysts Co-Mo/Al2O3

Two different commercial alumina supports were used for the preparation of selective hydrodesulfurization (HDS) catalysts Co-Mo/Al 2 O 3 . The effect of support properties on the HDS activity and selectivity of the corresponding Co-Mo catalysts were studied by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, scanning transmission electron microscopy-energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The HDS activity and selectivity were measured using a continuous flow fixed-bed microreactor. The Al 2 O 3 support with higher crystallinity and fewer hydroxyl groups had a moderate metal-support interaction, which resulted in an increase of the average slab length and stacking number of MoS 2 . This gave more formation of the active CoMoS phase and an increase in HDS activity and selectivity. ：以两种商用 Al 2 O 3 为载体, 制备了汽油选择性加氢脱硫催化剂 Co-Mo/Al 2 O 3 , 并采用红外光谱、X 射线衍射、N 2 吸附-脱附、透射电镜、扫描透射-能谱和 X 射线光电子能谱等手段系统研究了载体物化性质对催化剂活性相形成的影响. 结果表明, 表面羟基数量少和结晶程度高的载体与活性金属间相互作用减弱, 促进了 Mo 物种的硫化还原, 使 MoS 2 片晶的尺寸和层数增加, 且其硫化态催化剂上 CoMoS 活性位更多, CoMoS/MoS 2 比更大, 因而显著提高了相应 Co-Mo 催化剂加氢脱硫活性和选择性. An Al 2 O 3 support with higher crystallinity and fewer hydroxyl groups has a moderate metal-support interaction that increased the slab length and stacking number of MoS 2 , which gave more formation of the active CoMoS phase and an increase in Hydrodesulfurization activity and selectivity.

Effect of support properties on the performance of silica-supported bis(oxazoline)–copper chiral complexes

Mesoporous silica materials with different textural properties have been prepared by sol–gel synthesis under mild acidic conditions, and used as supports for chiral IndaBox ligand. After complexation with copper, these solids are catalysts for cyclopropanation reactions. Enantioselectivities in the range of 52–57% e.e. for cis cyclopropanes and 42–48% e.e. for trans cyclopropanes are obtained without any effect of the textural properties. However, these properties show an important effect on the activity and mainly on the recyclability of the catalyst. In contrast with the expected effect, solids with very large pores but low surface area lead to a significant deactivation upon recovery, whereas solids with highly developed surface area lead to the best overall results.

The effect of support properties on the activity of Pd/C catalysts in the liquid-phase hydrodechlorination of chlorobenzene

The activity of palladium catalysts prepared using active carbons (AG-2000, MeKS) and Sibunit type carbon in the liquid-phase hydrodechlorination of chlorobenzene has been studied. The use of AG-2000 activated carbon prepared from coal raw material provided the highest initial activity of the catalyst ( 9.4 mo l C 6 H 5 Cl /mo l Pd min for the catalyst with particle size of 0.08–0.1 mm) which not reduced within next 4 cycles. However, this activity cannot be explained only on the basis of support texture characteristics. From results of chemical analysis as well as X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HR TEM) data the high activity of the Pd/AG-2000 catalyst is explainable by the presence on the surface of the initial activated carbon of oxygen-containing compounds of iron, aluminum, silicon, calcium and magnesium. The overall ash content of the activated carbon was 11.9 wt.%. It can be assumed that the oxide compounds of iron act as anchoring centers for palladium, and that oxide containing impurities may interact with HCl decreasing deactivation. The experimental data of this work has shown that the main contribution to the Pd/AG-2000 catalyst activity is made by the palladium particles with a size of 3 nm and higher which remain stable under the aggressive conditions of the chlorobenzene hydrodechlorination process.

Effects of ZrO 2/Al 2O 3 properties on the catalytic activity of Pd catalysts for methane combustion and CO oxidation

Zirconia supported on alumina was prepared and characterized by BET surface area, X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), temperature programmed desorption (TPD), and pulse reaction. 0.2% Pd/ZrO 2/Al 2O 3 catalyst were prepared by incipient wetness impregnation of supports with aqueous solution of Pd(NO 3) 2. The effects of support properties on catalytic activity for methane combustion and CO oxidation were investigated. The results show that ZrO 2 is highly dispersed on the surface of Al 2O 3 up to 10 wt.% ZrO 2, beyond this value tetragonal ZrO 2 is formed. The presence of a small amount of ZrO 2 can increase the surface area, pore volume and acidity of support. CO–TPD results show that the increase of CO adsorption capacity and the activation of C O bond after the presence of ZrO 2 lead to the increase of catalytic activity of Pd catalyst for CO oxidation. CO pulse reaction results indicate that the lattice oxygen of support can be activated at lower temperature following the presence of ZrO 2, but it does not accelerate the activity of 0.2% Pd/ZrO 2/Al 2O 3 for methane combustion. 0.2% Pd/ZrO 2/Al 2O 3 dried at 120 °C shows highest activity for CH 4 combustion, and the activity can be further enhanced following the repeat run. The increase of treatment temperature and pre-reduction can decrease the activity of catalyst for CH 4 combustion.

Influence of support properties on the sound radiated from the vibrations of rectangular plates

The control of the forced vibration response of structures through the optimal tuning of its supports is desirable in many applications. Tuning may enhance the dissipation of vibration energy within the supports, thereby reducing fatigue and structure-borne noise. Two different models were developed to calculate the optimal support stiffness that minimizes the velocity response of homogeneous plates. The first model, based on the wave propagation at the edge, yields a good first cut approximation of the optimal properties. The optimal viscous and viscoelastic support stiffness for minimal reflection at the edge was calculated. Maximum absorption of the incident waves occurs when the viscous support stiffness matches the characteristic mechanical impedances of the plate. The second model, based on the Rayleigh–Ritz method, yields more accurate estimates of the optimal support stiffness required to minimize the forced velocity response of the finite rectangular plate. The optimal support properties calculated from the two different methods were in good agreement. This suggested that the modal response of the plate is strongly influenced by the wave reflections at the edges. Finally, the effects of support properties on the sound radiated from the plate were investigated. The optimal support stiffness that minimizes the radiated sound power was found to be smaller than the value that minimizes the velocity response. The results show that both the velocity response and sound radiation are strongly influenced by dissipation of vibration energy at the edges, and demonstrate that support tuning can yield significant noise and vibration reduction.

Effect of support properties on the catalytic activity of HDS catalysts

Series of NiMo catalysts prepared on aluminas modified by different ions (F, Cl, SO4, Zn, Mg, Na) were examined from the point of view of three functions: hydrodesulphurization, hydrogenation and isomerization. It was found that the HDS activity of thiophene of almost all catalysts differed only slightly, except for the catalyst containing fluorine, the activity of which was increased. Substantial differences were found in the isomerization of cyclohexene: the basic metals Na and Mg suppressed isomerization whereas F, SO4 and Cl anions increased it substantially. Hydrogenation of cyclohexene was unaffected by the additives used.