Catalyst Preparation Method Research Articles

Synthesis of bimetallic NiMo/MgO catalyst for catalytic conversion of waste plastics (polypropylene) to carbon nanotubes (CNTs) via chemical vapour deposition method

Non-biodegradable waste plastics constitute huge environmental problem and their effective disposal or beneficiation to value-added products such as carbon nanotubes (CNTs) is imperative for environmental sustainability. However, methods employ in the preparation of the catalysts employed in the catalytic conversion of waste plastics to CNTs play a key role in providing the desired nanoparticle morphology and stability towards increasing the catalytic (active) sites for nucleation and growth of carbon nanotubes (CNTs). It also determines the diameter, nature and alignment of the produced CNTs. In this study, bimetallic NiMo supported on MgO catalyst was prepared by two different synthesis methods: sol–gel and incipient wet impregnation (IWI) methods. Physico-chemical property and catalytic activity of the catalysts obtained from these catalyst preparation methods were evaluated and compared during the synthesis of CNTs from waste polypropylene under similar conditions using a one-step chemical vapour deposition technique (CVD). The physico-chemical properties of the prepared catalysts and those of the produced CNTs were obtained via X-ray diffraction (XRD) and Scanning electron microscopy (SEM) and compared. Results reveal that all prepared catalysts are porous and exhibited catalytic activity, but the catalyst obtained via IWI method is more porous and displayed higher catalytic activity when compared to the one obtained via sol–gel. Furthermore, bulk deposition of multi-walled CNTs (MWCNTs) of different diameters was also observed.

Highly efficient and green approach of synthesizing carboxylic acids from aldehydes using sodium hexametaphosphate

Oxidation of aldehydes is considered as one of the important organic reactions and is a common reaction employed in the manufacturing of cosmetic products, dyestuff, plasticisers and fibres. Various literature and methods have been generated that are capable of oxidising aldehydes to carboxylic acids efficiently. However, there are some limitations in these catalytic systems including waste formation, use of expensive and toxic oxidants, use of metals, sophisticated method of catalyst preparation and some of these reactions required to be performed under a pressurised condition. For the first time, an environmentally benign and highly efficient method for the preparation of carboxylic acids from aldehydes using the Sodium Hexametaphosphate (SHMP) and aqueous hydrogen peroxide is described. After the completion of reaction, the aqueous SHMP was separated from the organic layer. After being recharged with hydrogen peroxide, the aqueous SHMP was reused for five consecutive times without any significant loss of catalytic activity. Under the improved protocol, the yields of the desired products were recorded to be excellent (80–97%). Furthermore, the desired products were yielded by precipitation method, with no column purification needed. The current protocol avoids the utilisation of hazardous reagents which is scientifically important, especially in achieving a more sustainable world.

Alkali Lignin Catalytic Hydrogenolysis with Biofuel Production

AbstractIn this paper synthesized palladium (Pd)-containing catalysts were used in the hydrogenolysis of lignin in the presence of a hydrogen donor solvent, i-propanol, to obtain liquid fuel components. A study of the influence of the catalyst support nature, catalyst preparation method and supercritical solvent nature on the lignin depolymerization was completed. It was found that the use of Pd-containing catalysts results in the formation of aromatic compounds (mainly benzene and toluene) for both supercritical solvents used (i-propanol and CO2). The maximum conversion of lignin (50 %) was achieved when the supercritical i-propanol was used and maximum selectivity to aromatics (over 70 %) was observed in the presence of the Pd-containing catalyst synthesized by hydrothermal deposition on the polymeric matrix of hyper-crosslinked polystyrene.

Low-temperature selective catalytic reduction of NO with NH3 over Mn–Ce–Ox/TiO2: a comparison between catalyst preparation methods

Three Mn–Ce–Ox/TiO2 mixed oxides (MCT) were prepared by sol–gel (SG), citric acid complexing (CA), and co-precipitation (CP) methods and used as catalysts for selective catalytic reduction of NO with NH3 (NH3-SCR) at low temperatures (75–200 °C). The physicochemical properties of the prepared catalysts were investigated by N2 adsorption, X-ray diffraction (XRD), temperature-programmed reduction by H2 (H2-TPR), adsorption of NH3 and NO followed by temperature-programmed desorption (NH3/NO-TPD), X-ray photoelectron spectroscopy (XPS), and in situ diffuse-reflectance infrared Fourier transform (DRIFT) spectroscopy. The results show that both the low-temperature de-NOx activity and the resistance to SO2 poisoning of the Mn–Ce–Ox/TiO2 catalyst decrease in the order of MCT-CP > MCT-SG > MCT-CA. These disparities can be mainly attributed to the difference in specific surface area, fractions of Mn4+ (Mn4+/(Mn2++Mn3++Mn4+)) and surface adsorbed oxygen (surface adsorbed oxygen/(surface adsorbed oxygen + lattice oxygen)) species, and the adsorption capacity for NH3 and NO of the different catalysts.

Aerobic oxidation of benzyl alcohol: Influence from catalysts basicity, acidity, and preparation methods

The effect of catalyst preparation method and metal precursors on the catalyst basicity were studied in Pd catalysts supported on magnetic SBA-15 for benzyl alcohol oxidation (BzOH) to benzaldehyde (BzH). The reaction was carried out in an environmentally friendly condition, i.e, in the absence of additive and solvent, at low temperature (95 °C) in the presence of oxygen. Various techniques such as ball milling and impregnation as well as different precursors such as nitrate and chloride of palladium were applied for catalyst preparation. Among them, MPM-2 catalyst which was prepared by nitrate precursor and physical hand mixing, exhibited the most optimized basicity. The intensity of 2.9 × 10−10 of total basicity was measured by CO2-TPD experiment. The catalysts showed 50 % of BzOH conversion and 95 % of selectivity towards BzH after 3.5 h. The activation energy of the reaction was significantly decreased and reached 17.6 kJ.mol-1.

One-step synthesis of magnetically recyclable palladium loaded magnesium ferrite nanoparticles: application in synthesis of anticancer drug PCI-32765

Novel Palladium nanoparticles supported nano Magnesium ferrite catalyst (Pd/MgFe2O4) was synthesized by one-step ultrasound assisted coprecipitation. In-situ formed by-products assisted salt cage calcination approach was employed to control the particle size by minimizing the risk of nanoparticle aggregation during calcination. Palladium nanoparticles were grafted on the surface of nanocrystalline MgFe2O4 without using any reducing agents, capping agents and surface modifiers. The catalyst preparation method was having minimum process operations and can be used for synthesis of various potential nanocatalytic systems. The catalyst was extensively characterized by using various techniques SEM-EDS, TEM, FT-IR, XPS, XRD, VSM, BET, and ICP-AES. Pd/MgFe2O4 was magnetically separable and shown its potential utility for ligand less Suzuki-Miyaura coupling reaction using green solvent system Water and Ethanol. The nanocatalyst shows consistent activity and excellent reusability in the synthesis of Biaryls with excellent yields. In addition, the prepared catalytic nanoparticles were successfully applied in the synthesis of 5-(4-phenoxyphenyl)-7H-pyrrolo[2,3-d]pyrimidin-4-ylamine an intermediate for preparing the marketed anticancer drug PCI-32765 under the name IMBRUVICA® (Ibrutinib-BTK inhibitor).

Coke-free methane dry reforming over nano-sized NiO-CeO2 solid solution after exsolution

Exsolution as a method for catalyst preparation is generally only studied in perovskites or similar systems, which puts a constraint on the catalyst support composition, owing to size and charge balance effects. We show that Ni nanoparticle growth occurs via the exsolution mechanism from a NiO-CeO2 solid solution with the fluorite structure to form the supported Ni/CeO2 catalyst. This supported catalyst showed high methane dry reforming activity and coke-free performance at 800 °C and using 50 vol% CH4/50 vol% CO2 feed gas composition and 5000 Lkgcat−1 h−1. The use of solid-solutions such as these can therefore expand the variety of catalyst supports which could provide coke-free performance under dry reforming reaction conditions.

Highly-dispersed Ni on BEA catalyst prepared by ion-exchange-deposition-precipitation for improved hydrodeoxygenation activity

BEA zeolite-supported nickel is a promising catalyst for the hydrodeoxygenation reaction. In this study, highly dispersed Ni/BEA catalysts prepared via ion-exchange-deposition-precipitation (IDP) utilising careful pH control were investigated in the hydrodeoxygenation of guaiacol. In comparison, catalysts prepared by incipient wetness impregnation (IWI) and deposition-precipitation (DP) methods were also studied and IDP catalysts were shown to have higher dispersion. Over these carefully prepared catalysts significantly increased selectivity toward hydrocarbons was observed. The presence of nickel hydrides was confirmed by H2-TPD and H2-FTIR. IDP catalyst displays a higher metal dispersion and higher concentration of nickel hydrides than impregnated and DP catalysts, while bigger Ni nanoparticles formed in impregnated catalysts exhibit a higher concentration of nickel hydrides per surface Ni. The guaiacol conversion was not significantly affected by the catalyst preparation method, while the product selectivity was altered. Higher cyclohexane formation rate was detected over IDP catalysts compared to DP and impregnated catalysts. Besides, cyclohexane formation rate displays a positive linear correlation with the concentration of nickel hydrides, suggesting nickel hydrides play a crucial role in the hydrodeoxygenation reaction.

Carbon-Based Catalysts for Biodiesel Production—A Review

In recent years, a new class of superior heterogeneous acid catalyst for biodiesel production has emerged. These catalysts offer advantages over their predecessors such as high surface area, elevated acid site density, enhanced catalyst activity, good operation stability and relevant economic affordability in an environmentally friendly frame. This review was concerned with carbon-based solid acid (CBAS) catalysts derived from both carbohydrate and pyrolysis products. A series of CBASs with various origins such as D-glucose, sucrose, starch, cellulose and vegetable oil asphalt, converted to char and sulphonated, have been explored as potential heterogeneous catalysts. Catalyst preparation and synthesis methods were briefly summarized. Catalyst characterization and performance for biofuels related reactions were elucidated, identifying potential research applications. Three catalysts in particular were identified as having potential for industrial application and requiring further research.

The Catalyzed Conversion of Methane to Value‐Added Products

The progress of direct, selective conversion of methane (CH4) to organic oxygenates utilizing heterogeneous and homogeneous processes conducted in the gaseous or liquid phase is reviewed. The most active catalytic systems are examined in terms of rates, longevity, and reaction mechanisms. Despite significant effort, the successful heterogeneous mimicking of selective CH4 oxidation performed in an enzymatic system (methane monooxygenase) is still elusive. Under mild reaction conditions, the reaction is too slow, and under harsh conditions, total oxidation prevails. Thus, of particular interest herein is the assessment of oxidation at intermediate temperatures to 1) reduce total oxidation and 2) obtain sufficient concentration of activated oxygen and CH4 species. Important operational parameters such as reaction conditions, catalyst preparation methods, and cofeeding of chemicals, which significantly affect the yield of desired products, are discussed. One particular system that is successful is the catalytic conversion of CH4 to methanol under mild conditions using nitrous oxide (N2O) with Fe‐based catalysts or oxygen (O2) with Cu‐based catalysts. Special attention is paid to the controversy related to the identification of active sites, where the oxygen species suitable for CH4 oxidation are purportedly formed.

Fischer-Tropsch to olefins over CoMn-based catalysts: Effect of preparation methods

The effects of preparation methods for CoMn-based catalysts on the precursor phase of Co species, the morphology of Co2C nanostructures as well as the catalytic performance for Fischer-Tropsch to olefins were investigated. Five catalysts prepared by precipitation and impregnation methods were compared in detail. CoMn spinel oxide was found in the calcined catalysts prepared by co-precipitation or sequential precipitation starting from the Co salt. However, Co3O4 and MnO2 were the major phases for the calcined catalysts prepared by sequential precipitation starting from the Mn salt or impregnation methods. During the syngas conversion process, Co2C nanoprisms with exposed facets of (101) and (020) were generated from CoMn spinel phase, and exhibited high CO conversion, low methane selectivity and high olefins selectivity. In contrast, Co2C nanospheres carburized from metallic Co or CoO were observed for the other samples with poorer FTO catalytic performance.

Metal-Support Synergy of Supported Gold Nanoclusters in Selective Oxidation of Alcohols

Gold catalysts have been reported to exhibit good performance in aerobic oxidation of alcohols, but the intrinsic origin of the catalytic reactivity is still illusive. The catalyst preparation method, the morphology of the gold particles, and even the support might be key factors that determine the activity. Here, we prepared a series of gold catalysts with different supports, i.e., the hydrotalcite (HT), ZnO, MgO, Al2O3, and SiO2, by using the atomically controlled Au25 nanoclusters (NCs) as the gold precursor. The characterization results of the X-ray diffraction (XRD), UV-vis and transmission electron microscopy (TEM) show that the gold particles were mostly uniformly distributed on the supports, with a mean particle size within 3 nm. In aerobic oxidation of benzyl alcohol, the MgAl-HT- and Al2O3-supported Au25 NCs display good performances, with turnover frequency (TOF) values of ~2927 and 2892 h−1, respectively, whereas the SiO2-, MgO-, and ZnO-supported analogues show much inferior activity. The high resolution TEM and X-ray photoelectron spectra (XPS) results suggest that the interactions between gold and the supports in different samples are differing, which influences the morphology and the nature of gold. Our results further point to the importance of acid-base property of the support and the metal-support synergy rather than the gold particle size alone in achieving high-performance in selective alcohol oxidation. Moreover, this work provided a good way to design gold catalysts with controllable sizes that is crucial for understanding the reaction process in aerobic oxidation of alcohol.

Conversion of polyethylene terephthalate plastic waste and phenol steam reforming to hydrogen and valuable liquid fuel: Synthesis effect of Ni–Co/ZrO2 nanostructured catalysts

Ni–Co/ZrO2 (NCZ) nano-structure catalysts prepared by the hydrothermal method (NCZ-hyd) and conventional impregnation (NCZ-imp) method. The comparative catalytic activity and coke resistance for each prepared catalyst were examined in steam reforming of phenol and polyethylene terephthalate (PET) plastic waste. The Physico-chemical catalysts properties were characterized by N2-adsorption, XRD, FTIR, TEM, SEM, EDX, H2-TPR, CO2-TPD, and TGA. The effects of preparation methods of NCZ nano-structure catalyst on the catalytic performances in PET-phenol steam reforming were investigated. The NCZ-hyd nanostructure catalyst exposed more outstanding catalytic activity and more excellent coke resistance in comparison with the NCZ-imp. The experimental findings exhibited that catalyst synthesized by hydrothermal method were uniform with the size of 8.8 nm, while NCZ particles prepared by conventional impregnation method were un-uniform, unshaped, and agglomerated, and the size distribution of its particles was from 25 to 50 nm. PET-Phenol conversion and hydrogen yield of 56.5% and 52.5% for the NCZ-imp while 67.6% and 64.8% for the NCZ-hyd catalyst were achieved, respectively. The kinetic study of steam reforming of PET-phenol was also implemented. The activation energy was found to be 69.03 J/mol for NCZ-imp while 107.3 J/mol for the NCZ-hyd nanostructured catalysts. The PET-phenol steam reforming produced valuable liquid products such as benzene, 2-methyl phenol, and dibenzofuran which is one of the crucial keys to solving the waste plastic recycling problem.

Ni–supported palm oil fuel ash catalyst (Ni–POFA) from in situ glycine-nitrate combustion for methane cracking

Metal-supported catalysts synthesized using a conventional impregnation method are usually suffered from non-uniform distribution and agglomeration of catalyst particles. In this work, in situ glycine-nitrate combustion method has been explored to synthesize Ni catalyst supported on palm oil fuel ash (Ni–POFA). The properties and performance of the catalyst were compared with one produced using impregnation method. Effects of pre-treatment and catalyst preparation method have been investigated and characterizations of POFA and Ni–POFA catalysts were performed using XRF, XRD, BET surface area, FESEM and TGA. Catalytic activity of the catalysts was evaluated for methane cracking at 550 °C. Results showed that pre-treatment has improved the composition of SiO2 in POFA from 42.4 to 72.0%. Ni–POFA catalyst synthesized using in situ glycine-nitrate combustion method exhibited a good catalytic performance during the methane cracking with an initial H2 yield of 6.4%. This was attributed to high Ni metal dispersion on POFA support. Nevertheless, the degradation of CH4 conversion for this particular catalyst was more significant than one produced using impregnation method. Catalyst prepared using in situ glycine-nitrate combustion was active towards carbon formation, thus led to an obvious formation of carbon on the catalyst surface. Additionally, catalyst preparation method influenced the type of carbon formed on the spent Ni–POFA catalysts.

Comparison of the effects of the catalyst preparation method and CeO2 morphology on the catalytic activity of Pt/CeO2 catalysts for the water-gas shift reaction

The key factors (Pt0 dispersion & oxygen vacancies) should maintain high values to attain high catalytic activity and they are directly affected by the morphology and the preparation method of the catalyst.

The catalytic oxidation of toluene at low temperature over palladium nanoparticles supported on Alumina sphere catalysts: effects of Palladium precursors and preparation method

Abstract In this study, 1 wt.% Pd/Al2O3 sphere catalysts were prepared using the wet-impregnation (WI) and deposition-precipitation (DP) method using palladium chloride and tetraamminepalladium (II) nitrate as salt precursors. All catalysts were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier-transform infrared (FTIR) spectroscopy. The catalytic activity in toluene oxidation under gas-phase conditions was measured. The obtained results showed that metal dispersion and catalytic activity were strongly dependent on the salt precursor and method of catalyst preparation. The use of tetraamminepalladium (II) nitrate as the precursor presented smaller particle size, an enhanced dispersion and higher specific surface area. Moreover, the catalyst prepared with this precursor also showed higher catalytic activity than that prepared with palladium chloride. At 1 wt.% Pd loading, complete oxidation of toluene was achieved at 250°C. However, there was only approximately 80–90% efficient at the same temperature when the catalyst was prepared with palladium chloride as the precursor.

Effect of Cu/CeO2 catalyst preparation methods on their characteristics for low temperature water−gas shift reaction: A detailed study

• Cu/CeO 2 catalysts were prepared using different impregnation orders for Cu and Ce. • Cu–Ce/CeO 2 (prepared by co-impregnation) exhibited the highest catalytic activity. • Cu dispersion and Cu particle size are important factors in reaction < 280 °C. • Oxygen vacancy concentration and active Cu species are important factors > 360 °C. To investigate the effect of Cu/CeO 2 catalysts preparation methods for low temperature water−gas shift reaction, Cu/CeO 2 catalysts were prepared with various impregnation sequences and applied to the water−gas shift reaction at a high gas hourly space velocity of 36,080 mL/g·h. The catalyst preparation method affected both the Cu−Ce synergistic effect and the physico−chemical properties of the Ce promoted Cu/CeO 2 catalysts, such as specific surface area, Cu particle size, Cu dispersion, amount of active Cu species and oxygen vacancy concentration. Among the prepared catalysts, Cu–Ce/CeO 2 showed the highest CO conversion because of the high contents of active Cu species and high concentration of oxygen vacancies.

Highly Active Mesoporous Cu−Al2O3 Catalyst for the Hydrodeoxygenation of Furfural to 2‐methylfuran

AbstractWhile furfural has great potential as a platform chemical through diverse conversion pathways, 2‐methylfuran is one of the key components as a fuel additive and a precursor of derived biofuels. However, catalyst design to control reactivity of active species to furfural has been challenging. Herein, we demonstrate that a mesoporous Cu−Al2O3 catalyst prepared by solvent‐deficient precipitation shows the enhancement of furfural hydrodeoxygenation performance. Not only is the unique pore structure provided, but also the synergistic effects of improved Cu accessibility, co‐existence of Cu0/Cu+ states, and strong metal‐support interaction contribute to the superior activity and stability. Additionally, essential parameters for the synthesis and the test reaction are studied to improve the selectivity to 2‐methylfuran. The employed catalyst preparation method opens a new channel for tailoring the bifunctionality of supported Cu catalysts.

Preparation of LaAlO3 perovskite catalysts by simple solid-state method for oxidative coupling of methane

Abstract The preparation of LaAlO3 perovskite catalysts for the oxidative coupling of methane (OCM) using a very simple solid-state method with good reproducibility is described. To obtain high performance LaAlO3 catalysts, preparation conditions such as time, temperature, and oxygen content, which have a strong effect on the catalytic activity, are controlled during the calcination process. As the calcination time and temperature increase, the catalytic activity of LaAlO3 improves due to the good homogeneity and high crystallinity of LaAlO3 perovskite. Especially, the LaAlO3 catalyst calcined at 1350 °C for 24 h shows the highest selectivity and yield of C2 hydrocarbons. LaAlO3 catalysts calcined at various oxygen fractions show a volcano-shaped curve with respect to oxygen content in calcination gas, and the LaAlO3 catalyst prepared with an oxygen content of 5 % exhibits the best catalytic performance in this reaction. The appropriate oxygen fraction provides the LaAlO3 catalyst with a large amount of electrophilic lattice oxygen species and a sufficient amount of adsorption oxygen species, which are known to play key roles in the OCM reaction. This study clearly reveals this simple, highly reproducible, and mass-productive solid-state method as a promising preparation method for high performance LaAlO3 perovskite catalysts for OCM.

Effect of the catalyst preparation method on the performance of Ni-supported catalysts for the synthesis of saturated amines from nitrile hydrogenation

The liquid-phase hydrogenation of butyronitrile to saturated amines was studied on silica-supported Ni catalysts prepared by either incipient-wetness impregnation (Ni/SiO 2 -I) or ammonia (Ni/SiO 2 -A) methods. A Ni/SiO 2 -Al 2 O 3 -I sample was also used. Ni/SiO 2 -I was a non-acidic catalyst containing large Ni 0 particles of low interaction with the support, while Ni/SiO 2 -A was an acidic catalyst due to the presence of Ni 2+ species in Ni phyllosilicates of low reducibility. Ni/SiO 2 -I formed essentially butylamine (80%), and dibutylamine as the only byproduct. In contrast, Ni/SiO 2 -A yielded a mixture of dibutylamine (49%) and tributylamine (45%), being the formation of butylamine almost completely suppressed. The selective formation of secondary and tertiary amines on Ni/SiO 2 -A was explained by considering that butylamine is not release to the liquid phase during the reaction because it is strongly adsorbed on surface acid sites contiguous to Ni 0 atoms, thereby favoring the butylimine/butylamine condensation to higher amines between adsorbed species. Ni/SiO 2 prepared by the ammonia method forms selectively secondary and tertiary amines from butyronitrile hydrogenation. The catalyst contains Ni 0 nanoparticles in close contact with Ni +2 species in Ni phyllosilicates that favor the condensation reactions.