Effect Of Catalyst Preparation Research Articles

Recent Progress on the Application of the Polyaniline-Pd Catalysts for C-C Cross-coupling Bond Forming Reactions: Trend and Future Analysis

Abstract: In this review recent progress on the application of the polyaniline supported palladium catalysts in different organic transformations focusing on different C-C bond forming reactions such as Suzuki coupling, Heck reactions, oxidative Heck coupling, Ullmann coupling, Sonogashira and related chemistry. Effect of catalyst preparation, characteristic of the support and supported palladium species on the outcome of the catalyst efficiency are also highlighted. Finally, the emerging trend is summarized for the future of this unique modular catalytic system.

Effect of catalyst preparation and storage on chemical looping epoxidation of ethylene

Chemical looping epoxidation (CLE) of ethylene to ethylene oxide (EO) presents an exciting alternative to the incumbent technology of direct epoxidation of ethylene with O2(g). In CLE, the reaction is still catalysed by Ag but oxygen is provided as Olattice from a solid metal oxide, eliminating the need and limitations of using O2(g). Here, the influence of catalyst preparation in CLE is investigated. The Ag catalyst was impregnated on a solid oxide, SrFeO3, which was used as the donor of Olattice in CLE. Temperature programmed reduction in H2 indicated that O-species participating in CLE can be attributed to the removal of the first monolayer of oxygen in SrFeO3. By changing the temperature of calcination in Ag-SrFeO3 preparation, the size of Ag particles was varied, resulting in a simultaneous increase of selectivity for EO (up to 60%) and conversion of C2H4 (up to 10%). Then, an assessment of the effects of impurities (carbonates, hydroxides), which deposit over time on the Ag-SrFeO3 surface, was performed, showing that impurities deteriorate the catalyst performance in CLE. Finally, the doping of the SrFeO3 with Ce to the A-site of the perovskite was carried out, and a substantial improvement of the conversion of C2H4 was achieved, reaching 15%, while maintaining the 60% selectivity for EO.

Synthesis and characterization of AgCoO2 catalyst for oxidation of CO at a low temperature

In this research work, we have discussed about the effect of catalyst preparation and their calcination strategy on the characterization property and activity of the final catalyst. The AgCoO2 catalyst was prepared by the co-precipitation method gave the highest activities for the preferred reactions. The recent study was carried out in the laboratory shows that the calcination strategies of the AgCoO2 precursor highly affect on the activity of resulting catalysts for CO oxidation. The AgCoO2 catalyst obtained by calcination of the precursors in the presence of chemically reactive (CO + air) mixture exhibits the best catalytic activity as compared to the traditional method of calcination. The reactive calcination of the AgCoO2 catalyst produces partially reduced phase of the catalyst causing the highest activity in the reaction. The remarkable activity of the novel catalyst over conventional ones (obtained by calcination of the precursors in reactive calcination) in CO oxidation was associated with the presence of AgCoO2 and its unusual morphology as evidenced by XRD, SEM-EDX, TEM, XPS and FTIR characterization. Further, the activity order of the AgCoO2 catalysts obtained by different calcination conditions was as follows: RC > flowing-air > stagnant-air.

Co-Production of Ethanol and 1,2-Propanediol via Glycerol Hydrogenolysis Using Ni/Ce–Mg Catalysts: Effects of Catalyst Preparation and Reaction Conditions

Crude glycerol from biodiesel production is a biobased material capable of co-producing biofuels and chemicals. This study aimed to develop a line of Ni catalysts supported on cerium–magnesium (Ce–Mg) to improve the process efficiency of glycerol hydrogenolysis for ethanol and 1,2-propanediol (1,2-PDO). Results showed that catalytic activity was greatly improved by changing the preparation method from impregnation to deposition precipitation (DP), and by adjusting calcination temperatures. Prepared via DP, the catalysts of 25 wt % Ni supported on Ce–Mg (9:1 mol/mol) greatly improved the effectiveness in glycerol conversion while maintaining the selectivities to ethanol and 1,2-PDO. Calcination at 350 °C provided the catalysts better selectivities of 15.61% to ethanol and 67.93% to 1,2-PDO. Increases in reaction temperature and time improved the conversion of glycerol and the selectivity to ethanol, but reduced the selectivity to 1,2-PDO. A lower initial water content led to a higher conversion of glycerol, but lower selectivities to ethanol and 1,2-PDO. Higher hydrogen application affected the glycerol conversion rate positively, but the selectivities to ethanol and 1,2-PDO negatively. A comparison to the commercial Raney® Ni catalyst showed that the Ni/Ce–Mg catalyst developed in this study showed a better potential for the selective co-production of ethanol and 1,2-PDO from glycerol hydrogenolysis.

Effect of Catalyst Preparation on Hydroisomerization of n-Heptane over Pt/Silicalite-1

The isomerization of n-heptane was comparatively investigated over Pt catalysts prepared by deposition (Pt/S-1-DP) and impregnation precipitation (Pt/S-1-IMP) method with a low loading, separately. It was found that Pt/S-1-DP catalyst produced a much higher catalytic conversion compared with the counterpart catalyst prepared by impregnation. Combined with various characterization techniques, the better performance over Pt/S-1-DP was attributed to not only the well improved dispersity and the smaller size of Pt particles but also the faster transfer of reactive species between Pt sites and acid sites. The activity could be improved by increasing the reduction temperature. Moreover, the (de)hydrogenation of Pt over Pt/S-1 catalyst was verified by in situ infrared spectroscopy through H/D isotope exchange experiment.

Desulfurization and tar reforming of biogenous syngas over Ni/olivine in a decoupled dual loop gasifier

For the production of bio-SNG (substitute natural gas) from syngas of biomass steam gasification, trace amounts of sulfur and tar compounds in raw syngas must be removed. In present work, biomass gasification and in-bed raw gas upgrading have been performed in a decoupled dual loop gasifier (DDLG), with aggregation-resistant nickel supported on calcined olivine (Ni/olivine) as the upgrading catalyst for simultaneous desulfurization and tar elimination of biogenous syngas. The effects of catalyst preparation, upgrading temperature and steam content of raw syngas on sulfur removal were investigated and the catalytic tar reforming at different temperatures was evaluated as well. It was found that 850 °C calcined Ni/olivine was efficient for both inorganic-sulfur (H2S) and organic-sulfur (thiophene) removal at 600–680 °C and the excellent desulfurization performance was maintained with wide range H2O content (27.0–40.7%). Meanwhile, tar was mostly eliminated and H2 content increased much in the same temperature range. The favorable results indicate that biomass gasification in DDLG with Ni/olivine as the upgrading bed material could be a promising approach to produce qualified biogenous syngas for bio-SNG production and other syngas-derived applications in electric power, heat or fuels.

FT-IR study of NO adsorption on MoS2/Al2O3 hydrodesulfurization catalysts: Effect of catalyst preparation

The effect of catalyst preparation on structure and performance of MoS2/Al2O3 hydrodesulfurization (HDS) catalysts was studied by NO adsorption, monitored by infrared spectroscopy (NO-IR) and complemented with EXAFS. The main bands at 1785cm−1 and 1690cm−1 were assigned to the ν(NO) stretching vibrations of coupled mono- or dinitrosyl surface complexes. NO adsorption on sulfided catalysts prepared with nitrilotriacetic acid (NTA) or citric acid (CA) gave rise to additional bands in the IR spectra at 1655cm−1, 1630cm−1 and 1615cm−1, assigned to mononitrosyl adsorption modes. Catalysts prepared with NTA and CA were more active in thiophene HDS than calcined or dried catalysts, despite comparable NO uptake (0.10-0.12 NO/Mo). This was attributed to a changed MoS2 edge structure as suggested by the NO-IR data, as well as to an improved degree of sulfidation as observed by EXAFS. Correlating NO uptake with MoS2 dispersion shows that not more than 30–40% of edge and corner sites were probed with NO. This implies that only a small portion of edge sites may act as active sites in HDS catalysis.

Effects of Catalyst Preparation on Hydrocarbon Product Distribution in Hydrocracking of the Fischer-Tropsch Product with Low Pt-Loaded Catalysts

For the effective production of hydrocarbon liquid fuel in the hydrocracking of the Fischer-Tropsch (FT) product, the catalytic performance of Pt-loaded catalysts with low Pt content was investigated using an autoclave at 250 °C, an initial H2 pressure of 0.5 MPa, and a reaction time of 1 h. A screening study using Pt-loaded catalysts with a Pt content of 0.1 wt. % indicated that zeolite supports were more favorable for jet fuel (carbon numbers 9–15) production than amorphous oxide supports. The small particle size of the supported Pt particles and the high amount of medium acid sites for the supports led to higher performance of the Pt-loaded zeolite catalysts. In the hydrocracking reaction over Pt catalysts using the zeolite support with the high amount of medium acid sites, the yields of the corresponding jet fuel at 0.02 and 0.1 wt. % were almost the same. Pt-loaded catalysts with a Pt content of 0.02 wt. % were prepared using water-in-oil (w/o) microemulsions and their particle size was controlled between 1.0 and 2.6 nm. While the yield of the corresponding jet fuel was independent of Pt particle size, smaller Pt particles typically promoted the production of lighter hydrocarbons.

Effect of Catalyst Preparation on the Selective Hydrogenation of Vegetable Oil Over Low Percentage Pd/Diatomite Catalysts

Hydrogenated vegetable oils contain high contents of <em>trans</em>-fatty acids. Because of the increased health concern about <em>trans</em>-fatty acids, new hydrogenations have been studied to seek ways for substantial reduction of the <em>trans</em>-fatty acids in the hydrogenated products. In this research, activated diatomite has distinctive properties as a support for hydrogenation catalysts. Investigation of textural properties of raw and purified diatomite samples reveals that during acid activation surface area increases significantly. Although, acid activation of diatomite is a commonly chemical modification to enhance its adsorption capacity. We are preparing adsorption method to synthesize low percentage 0.2% of Pd/Diatomite catalyst. The activated diatomite and the obtained catalyst was characterized by using thermogravimetric analysis (TGA), Brunauer-Emmett-Teller surface area analysis (BET), scanning electron microscopy (SEMEDAX), transmission electron microscopy (TEM). It was utilized for hydrogenation of sunflower oil using the Parr reactor in laboratory testing a variety of temperature (70, 90, 110 ºC) and canola oil in industrial testing, at temperature 90 ºC and 0.5 MPa pressure and compared to commercial nickel catalyst (Pricat-9910) at 150 ºC, 0.5 MPa pressure agitation of 800 rpm for 160 min. The changes in iodine value, fatty acid composition, <em>trans</em>-fatty acids, melting point and solid fat content were investigated on partial hydrogenated sunflower oil and canola oil. The experimentally obtained results show that the palladium catalyst is the most active compared to the commercial catalyst. Lower hydrogenation temperature used 0.2% Pd/Diatomite catalyst, significant reducing the formation of <em>trans</em>-content by 13% in fat.

Ru/TiO2 for the preferential oxidation of CO in H2-rich stream: Effects of catalyst pre-treatments and reconstruction of Ru sites

The preferential oxidation (PROX) of CO is a promising strategy for trace CO clean up in H2-rich stream to fuel cells. In the present study, a series of TiO2 supported clusters were prepared and studied for the PROX of CO. Amongst, Ru/TiO2 catalyst exhibited remarkably high PROX activity in the operation temperature range of fuel cells. The effects of catalyst preparation and pre-treatment on the catalytic performance of Ru/TiO2 were investigated in detail. Ru/TiO2 catalyst prepared by photo-deposition and pre-treated under H2–CO atmosphere was found to be the most promising one and complete CO oxidation could be achieved at >373K. Ru/TiO2 pre-treated under different reducing atmospheres were characterized by high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) of CO adsorption. The surface reconstruction of Ru sites during catalyst pre-treatment was observed and isolated metallic Ru species was identified as preferred active sites for PROX reaction. Based on the catalytic and characterization results, the possible mechanism for PROX of CO over Ru/TiO2 was proposed.

The effect of catalyst preparation on the activity of MoO3-SiO2 catalyst in transesterification of diethyl oxalate

Transesterification of diethyl oxalate (DEO) with phenol over MoO3-SiO2 catalysts prepared by the sol-gel technique (MoO3-SiO2 (SG)) and the impregnation method (MoO3-SiO2 (I)) was conducted to produce diphenyl oxalate (DPO), which can be used as a precursor for manufacturing diphenyl carbonate (DPC). The sample MoO3-SiO2 (SG) containing 12 wt % of MoO3 showed the best performance with 71.0% conversion of DEO and 32.0% selectivity to DPO. Compared to MoO3-SiO2 (I), improvements in the DEO conversion and DPO selectivity with MoO3-SiO2 (SG) were 16.1 and 7%, respectively. Crystal structure and phase composition of MoO3-SiO2 (I) and MoO3-SiO2 (SG) catalysts with varying MoO3 contents were investigated. The sample MoO3-SiO2 (SG) with a similar chemical composition to MoO3-SiO2 (I) has a larger specific surface area, indicating that the active component is well dispersed on the surface of the MoO3-SiO2 (SG) catalysts. Results of XRD and XPS measurements suggest a high degree of dispersion of MoO3-SiO2 (SG) catalysts that can account for an increase in DEO conversion and DPO selectivity. Coordinately unsaturated MoO3 species play a significant role in the catalytic performance of MoO3-SiO2 (SG) catalysts in transesterification of DEO with phenol. In addition, IR measurements of pyridine adsorption and NH3-TPD data indicate that the amount of acid sites on the surface of MoO3-SiO2 (SG) exceeds that found for the surface of MoO3-SiO2 (I). An enhanced concentration of surface MoO3 species in tetrahedral coordination coupled with the presence of weak Lewis acid sites appear to be the main reason why MoO3-SiO2 (SG) catalysts are superior to the MoO3-SiO2 (I) system.

Effect of Catalyst Preparation on the Performance of CaO-ZnO Catalysts for Transesterification

Effect of Catalyst Preparation on the Performance of CaO-ZnO Catalysts for Transesterification

Effect of catalyst preparation on Au/Ce1−xZrxO2 and Au–Cu/Ce1−xZrxO2 for steam reforming of methanol

We tested 3 wt% gold (Au) catalysts on CeO2–ZrO2 mixed oxides, prepared by co-precipitation (CP) and the sol–gel (SG) technique, for steam reforming of methanol (SRM). Uniform Ce1−xZrxO2 solid solution was dependent on the Zr/Ce ratio, where the incorporation of Zr4+ into the Ce4+ lattice with a ratio of 0.25 resulted in smaller ceria crystallites and better reducibility, and was found to be efficient for SRM activity. The catalytic activity was suppressed when the ratio was ≥0.5, which led to the segregation of Zr from solid solution and sintering of Au nanoparticles. It was found that the CP technique produced better catalysts than SG in this case. For the bimetallic catalysts, the co-operation of Au–Cu supported on Ce0.75Zr0.25O2 (CP) exhibited superior activities with complete methanol conversion and low CO concentration at 350 °C. Furthermore, the size of the alloy particle was strongly dependent on the pH level during preparation.

Catalytic acetalization of biomass glycerol with acetone over TiO2–SiO2 mixed oxides

TiO2–SiO2 catalysts for glycerol acetalization with acetone are synthesized by the sol–gel method and characterized by N2 adsorption–desorption, X-ray diffraction, NH3-temperature programmed desorption, Fourier transform infrared spectroscopy and ultraviolet–visible diffuse reflectance spectroscopy techniques in the present work. The effects of catalyst preparation and acetalization parameters such as reaction time, acetone/glycerol ratio, catalyst amount and reaction temperature on acetalization are investigated simultaneously. Pyridine adsorption results indicate that Ti–Si mixed oxides naturally only consist of Lewis acidic sites. The results of catalyst preparation and characterization show that Bronsted acidic sites can be produced after Ti–Si mixed oxides adsorb water molecules, and TiO2–SiO2 (Si/Ti = 1) calcined at 550 °C exhibits the most total acidic density leading to the highest catalytic property in glycerol acetalization. The glycerol catalytic acetalization mainly occurs on the Bronsted acidic sites. The effects of acetalization parameters indicate that the formation of the main product 5-membered ring ketal 2,2-dimethyl-1,3-dioxolane-4-yl methanol (about 90 %) is governed by kinetics. About 95 % glycerol conversion in acetalization is obtained under the optimum conditions.

Photodecolorization of methyl orange over α-Fe2O3-supported HY catalysts: The effects of catalyst preparation and dealumination

An α-Fe2O3-supported HY zeolite (α-Fe2O3/HY) was prepared by introducing nanosized α-Fe2O3 into an HY zeolite support through in situ (α-Fe2O3/HYIS) and ion-exchange (α-Fe2O3/HYIE) methods. The effect of the preparation methods on the physicochemical properties of the catalyst were studied via XRD, FESEM-EDX, TEM, UV–vis DRS, FTIR, XPS, 29Si and 27Al MAS NMR, ESR and BET surface area analysis. In this study, dealumination was accomplished by using a facile electrolysis system without any strong acids, reactive compounds and/or hydrothermal treatment. Dealumination accompanied by ion exchange of Al with Fe3+ ions in the HY zeolite framework resulted in the formation of an active species that had a higher photoactivity towards the decolorization of methyl orange (MO). A 5wt% α-Fe2O3/HYIS was found to produce an 80% photodecolorization of 30mgL−1 of MO at pH 2 with 0.375gL−1 catalyst, while 5wt% α-Fe2O3/HYIE only produced 23% photodecolorization under similar conditions (2h reaction time). This study showed that the kinetics follow a pseudo-first order Langmuir–Hinshelwood model with an activation energy (Ea) calculated for both 5wt% α-Fe2O3/HYIS and 5wt% α-Fe2O3/HYIE to be 45.8kJmol−1 and 70.2kJmol−1, respectively. Measurements of the mineralization of MO by COD, BOD5 and TOC analysis were 27.0%, 69.6% and 16.9%, respectively, after 2h of contact time. The Fe dissolution from the catalyst showed insignificant leaching of Fe (<1%) when subjected to AAS. A reusability study demonstrated that α-Fe2O3/HYIS could be a promising photocatalyst for the degradation of various dyes in wastewater.

Factors Influencing the Activity, Selectivity, and Stability of Rh-Based Supported Ionic Liquid Phase (SILP) Catalysts for Hydroformylation of Propene

An investigation has been carried out on the effects of catalyst preparation on the activity and stability of supported ionic liquid phase (SILP) catalysts for propene hydroformylation. Catalyst activity and stability were found to be strongly influenced by ligand and ionic liquid composition, ligand-to-rhodium ratio, and the surface density of silanol groups on the silica support. Highest activity was achieved using rhodium sulfoxantphos (SX) complexes in the presence of [bmim][OctSO4]. In situ FT-IR and solid-state 31P and 29Si MAS NMR characterization suggest that active Rh centers are not present as homogeneous complexes dissolved in an ionic liquid film, instead are present as HRh(CO)2SX complexes bound to the support by interactions of the sulfonate groups of SX with silanol groups of the support. The function of the ionic liquid is to inhibit undesired interactions of SX ligands, since such interactions render the phosphine groups unavailable for interaction with the Rh+ cations. Catalyst deactivation is attributed mainly to the formation of catalytically inactive [Rh(CO)(μ-CO)SX]2 or HRh(SX)2 complexes when the SX/Rh ratio is too low or high, respectively.

Effect of preparation method of palygorskite-supported Fe and Ni catalysts on catalytic cracking of biomass tar

In this study, the effect of catalyst preparation and additive precursors on the catalytic decomposition of biomass using palygorskite-supported Fe and Ni catalysts was investigated. The catalysts were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It is concluded that the most active additive precursor was Fe(NO3)3·9H2O. As for the catalyst preparation method, co-precipitation had superiority over incipient wetness impregnation at low Fe loadings.

Investigation of water gas-shift activity of Pt–MO x–CeO 2/Al 2O 3 (M = K, Ni, Co) using modular artificial neural networks

The water gas shift activity of promoted Pt–CeO 2/Al 2O 3 catalysts were investigated in this work. The catalysts were prepared by incipient to wetness impregnation and tested using a microflow reaction system. It was found that K has beneficial effects under product-containing feed compositions while Co and Ni promoters worsen catalyst performance. The reaction temperature and feed H 2O/CO ratio positively affect the catalytic activity, whereas CO 2 and H 2 addition to the feed decreases CO conversion, as expected. The experimental results were also modeled using modular neural networks, at which the catalyst preparation and operational (reaction) variables were used together in the same network because they are interacting but processed differently because they are dissimilar in their form (i.e. categorical versus continuous) and their effects on catalytic activity. It was concluded that the effects of catalyst preparation and operational variables and their relative importance could be comprehended more accurately by using this approach, which may be also employed in other similar systems.

Catalytic dehydroxylation of glycerol to propylene glycol over Cu–ZnO/Al 2O 3 catalysts: Effects of catalyst preparation and deactivation

The dehydroxylation of glycerol to propylene glycol was investigated over Cu–ZnO/Al 2O 3 catalysts prepared by three different methods—incipient wetness impregnation (IWI), co-precipitation (COP), and sol–gel (SG). The prepared catalysts were tested for their catalytic activity and selectivity in a continuous flow fixed-bed reactor at 523 K and 3.2 MPa under hydrogen atmosphere. The fresh and spent catalysts were characterized by several techniques, including BET, XRF, XRD, TPR, and TPO. Among the catalysts tested, the Cu–ZnO/Al 2O 3 catalyst prepared by the IWI method provided the highest catalytic performance, which could be due to its low coke formation. XRD, TPR, and TPO results indicated that possible causes of the catalyst deactivation are the combination of carbon deposit and sintering of active metals. Copper leaching was also found in the catalyst prepared by SG method.

Effect of catalyst preparation on the yield of carbon nanotube growth

Abstract Multi-wall carbon nanotubes (MWCNTs) were synthesized by catalytic chemical vapor deposition (CVD) on catalytic iron nanoparticles dispersed in a silica matrix, prepared by sol gel method. In this contribution, variation of gelation condition on catalyst structure and its influence on the yield of carbon nanotubes growth was studied. The precursor utilized were tetraethyl-orthosilicate and iron nitrate. The sols were dried at two different temperatures in air (25 or 80 °C) and then treated at 450 °C for 10 h. The xerogels were introduced into the chamber and reduced in a hydrogen/nitrogen (10%v/v) atmosphere at 600 °C. MWCNTs were formed by deposition of carbon atoms from decomposition of acetylene at 700 °C. The system gelled at RT shows a yield of 100% respect to initial catalyst mass whereas the yield of that gelled at 80 °C was lower than 10%. Different crystalline phases are observed for both catalysts in each step of the process. Moreover, TPR analysis shows that iron oxide can be efficiently reduced to metallic iron only in the system gelled at room temperature. Carbon nanotubes display a diameter of about 25–40 nm and several micron lengths. The growth mechanism of MWCNTs is base growth mode for both catalysts.