Clay Catalysts Research Articles

Household Infrared Technology as an Energy-Efficient Approach to Achieve C-Cπ Bond Construction Reactions

We examined the ability of short-wave infrared (IR) light in the λ1.5-3.0 µm region of the infrared emission spectrum to accomplish C−Cπ bond construction reaction between π-excessive azaheteroaromatic and different carbonyl substrates supported on a bentonitic clay catalyst in solventless condition via a three-component condensation reaction. Preliminary studies show that the implementation of a domestic Flavor-Wave® oven fitted with a halogen heater lamp as a chemical reactor was as effective as the use of near IR light (λ1.1 µm) in fostering batch-wise organic reactions. Overall, this approach reveals its potential exploitation as an energy-efficient source to assemble biologically engaging (hetero)arenebisindolylmethanes framework, in the same way, that assure its sustainable development as for efficient generation of small libraries of molecules comparable to high-tech instrumentations performances.

Catalytic depolymerization of kraft lignin for liquid fuels and phenolic monomers over molybdenum-based catalysts: The effect of supports

Catalytic lignin depolymerization (CCLD) for liquid fuels and phenolic monomers was investigated over various supports including clays (e.g., sepiolite (SEP), attapulgite (ATP), and montmorillonite (MTM)), and oxides (e.g., Al2O3 and SiO2) as well as their supported Mo-based catalysts under supercritical ethanol. The characterization results demonstrated that different supports with diverse structural properties could affect the textural structures, surface Mo5+ content, and acid sites distribution. Clay-based supports had more strong acid sites as compared with Al2O3 and SiO2, which went against the production of lignin oil (LO) and led to form more solid products during CLD experiments. Meanwhile, the obtained petroleum ether-soluble product (PEsp) in LO catalyzed by sole supports was mainly alkyl/alkoxy substituted phenols. Additionally, Mo species (especially Mo5+) significantly increased the yields of LO and PEsp. Mo/SiO2 had the highest surface Mo5+ species, showing the highest LO yield of 85.2%, in which the produced alkyl/alkoxy substituted phenols reached 450.3 mg/glignin. Among the clay-supported Mo catalysts, Mo/SEP presented superior LO (82.3%) and PEsp (70.8%) yields and the generated substituted phenols reached 398.8 mg/glignin. This paper systematically reported the application of green and environmentally friendly clay-based materials in lignin conversion, which provides some key information for the development of clay catalysts for biomass conversion.

Orbital asymmetric hybridization enhances surface Lewis acid-base reactions of charged clay catalysts

A strong electric field of 108–10 V/m could be produced from the surface charges of clay. In this study, the asymmetric hybridization of atomic orbitals in the electric field at the clay surface substantially enhances the Lewis acid-base reactions between the surface O and Cu2+/Ca2+/Mg2+/H2O. This has been confirmed by cationic adsorption kinetics, energies, critical coagulation concentrations (CCCs) and infrared spectral analyses of –OH and Si-O stretches for H2O and clay crystal respectively. The enhanced Lewis acid-base reaction energy for Cu2+, Ca2+ and Mg2+ at charged clay surface is found in an order of Cu2+(−27.21 kJ/mol) > Ca2+(−15.51 kJ/mol) > Mg2+(−6.061 kJ/mol). For surface H2O, a new blueshift adsorption peak (3612 cm−1) is observed in the infrared spectral analyses which indicate a strong Lewis acid-base reaction for H2O at charged clay surface. This study indicates that, for the catalytic activities of charged clay catalysts, the background cation types and concentrations, the electric field intensity and the orbital asymmetric hybridization effect at charged clay surface would be coupled and intertwined. Importantly, in those factors/effects the electric field and its initiated orbital asymmetric hybridization of surface atoms/cations should play the critical roles, and thus these two key factors should be emphasized in clay catalyst design.

Diesel engine performance evaluation on transesterified gmelina seed oil catalysed by thermally modified Iyi-Nsukka kaolin clay catalyst compared to fossil diesel and blends

The thermally modified Iyi-Nsukka kaolinite clay catalyst (TMIKCCat800) was prepared and characterised by X-ray Diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and Atomic abrasion spectrophotometry (AAS) to verify catalyst properties.

One pot synthesis of aluminum pillared intercalated layered clay supported silicotungstic acid (STA/Al-PILC) catalysts

One pot synthesis of silicotungstic acid (STA) containing aluminum pillared intercalated layered clay (STA/Al-PILC) catalysts is carried out by addition of STA to aluminum pillared clay synthesis media. STA-Al Keggin type pillar agents which are formed by charge interaction among them are inserted between clay layers. Effect of parameters on catalyst structure such as pH of clay suspension, STA quantity, addition step and its isolation in buffer solution are investigated. STA addition step has a crucial role on properties of catalysts. Conservation of the layered structure of Al-PILC support in the presence of STA is seen from X-ray powder diffraction (XRD) patterns and transmission electron microscopy (TEM) images. Basal spacing values do not show much difference with respect to that of Al-PILC support which is measured as 1.85 nm. The catalyst which owes the best structural properties has 217 m2/g surface area, 0.20 cm3/g pore volume, 0.44 nm average micropore size and 3.90 nm average mesopore size with high STA loading success. Lewis acidity is dominant acid character in all catalysts. Preservation of Keggin structure of STA in PILC structures is seen by X-ray photo electron spectroscopy (XPS) with a clear W4f7/2 and W4f5/2 spin orbital doublet. The increase in STA amount leads no additional increase in STA loading. Agglomeration, which is seen clearly in TEM images, occurs when STA is added either as its powder form to Al-pillar agent media or after isolating it within the buffer solution to Al-pillar agent-clay suspension. The proposed model which assumes the placement of pillar agents between clay layers, either after coupling with each other or alone, explains effects of STA addition steps on structural properties.

Performance evaluation of unmodified and thermally modified Iyi-Nsukka kaolinite clay as heterogeneous catalyst for biodiesel production

The unmodified Iyi-Nsukka kaolinite clay catalyst (UMIKKCat) and thermally modified Iyi-Nsukka kaolinite clay catalyst (TMIKCCat800) were prepared and characterised using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and Atomic abrasion spectrophotometry (AAS) to verify catalyst properties.

Sulfated ordinary clay for acid-catalyzed conversion of biomass derivatives: Impacts of abundance and types of acidic sites on catalytic performance

Ordinary clay is an abundantly available material for use as catalyst support. In this study, sulfuric acid was used as sulfonating agent to prepare sulfated clay-based super-acid catalyst. The effects of sulfuric acid concentration and calcination temperature on physiochemical properties, interaction of sulfur species with the oxides in clay, distribution of Brønsted acid sites and Lewis acid sites were characterized with XRD, pore structure analysis, FT-IR, elemental analysis, NH3-temperature programmed desorption (NH3-TPD) and Pyridine-DRIFTS etc. The catalytic performance of different catalysts was evaluated by conversion of furfuryl alcohol (FA) to ethyl levulinate (EL). The results showed that sulfuric acid reacted with alumina in clay to form Al2(SO4)3, thus changing structure and crystal phase of the catalyst. Increasing calcination temperature enhanced the interaction between sulfate species and clay, the retaining of sulfur on clay surface and the formation of more Brønsted acid sites while less Lewis acid sites. In addition, balanced distribution of the acidic sites was crucial for selective conversion of FA to EL. Over the clay catalyst impregnated with 4 ​M ​H2SO4 and calcined at 300 ​°C, the yield of EL could reach 90%. The catalyst was not stable in polar solvent like ethanol due to leaching of sulfur species, while in aprotic solvent like dimethyl sulfoxide, the catalyst maintained a good catalytic stability.

Oxidative study of Acid Yellow 23 using K10-Montmorillonite chemically modified

Catalytic ozonation of the azo dye Acid Yellow 23 was investigated in the presence of Montmorillonite K10 and its chemically modified counterpart with Cobalt and Nickel (Co-Ni-K10). The material thus obtained were characterized by BET, XRD and TGA analysis. The effects of different variables were studied, such as: catalyst dose, ozone dose, ozonation time and pH. Clay-catalysed reactions are strongly dependent on the adsorption of the reactant, which in turn should depend on acid-base, electrostatic and hydrophilic-organophilic interactions. The basicity of the clay catalyst surface is expected to favour the interactions with the acidic groups of the studied organic molecule. The interactions involved in adsorption are determined by the pKa values of each group in each organic molecule.

Visible-Light Enhanced Catalytic Wet Peroxide Oxidation of Natural Organic Matter in the Presence of Al/Fe-Pillared Clay

An Al/Fe-pillared clay catalyst (Al/Fe-PILC) prepared from low cost technical-grade reagents has been investigated in the photocatalytic Wet Peroxide Oxidation (photo-CWPO) of dissolved Natural Organic Matter (NOM) under circumneutral pH. The successful pillaring of the layered clay material was confirmed by X-ray diffraction (XRD), N2 adsorption at −196 °C, cation exchange capacity (CEC) and simultaneous thermal analysis (TGA/DSC). High levels of mineralization of the dissolved organic carbon and color removal of a synthetic NOM surrogate solution were achieved even under natural lab’s lighting and ambient temperature and pressure, whereas the absence of radiation (in dark) was found to strongly affect the performance of the degradation. The photo-CWPO of NOM activated by the Al/Fe-PILC clay catalyst under visible light irradiation (LED lamp, 450 and 550 nm peaks) displayed a DOC mineralization of 72% and color removal of 73% in just 210 min of irradiation at neutral pH, whereas both responses decayed under ultraviolet lightning (λ: 365 nm) to 41% and 58%, respectively. This behavior is ascribed to formation of triplet states of natural organic matter (3NOM*) by absorption of visible light, which seems to synergistically improve the rate-determining step of the heterogeneous Fenton process, namely reduction of Fe3+ into Fe2+ on the surface of the clay catalyst. Interestingly, experiments performed at neutral and pH 3.0 showed very similar efficiencies under visible light irradiation; these findings may really facilitate the application of the photo-CWPO process to assist conventional drinking water treatment plants in the removal of NOM before the typical disinfection by chlorine to produce safer drinking water.

Effect of Ni/Co vermiculite as catalysts for Catalytic pyrolysis of plastic wastes

In this study, the modified vermiculite adjusted with Ni and Co for pyrolysis of plastic is characterized by X-ray diffraction (XRD) and Brunauer Emmett Teller (BET). These results indicate that the ratio of Ni and Co can affect the surface area and pore diameter of catalyst. In addition, the results of GC show that Ni and Co not only have a good selectivity of C3, the main gaseous hydrocarbons of pyrolysis products, but also play an important role in dealing with low quality of oil products of plastic pyrolysis by controlling the concentration of metal oxide particles in the vermiculite layer. The adjustment of the molar ratio of Co and Ni can optimize the hydrogenation/dehydrogenation of metal active sites. It means that the greatly catalytic activity of supported Ni and Co catalysts is caused by moderate total acidity, relatively high surface area, and uniformly dispersed oxide particles on vermiculite support. Therefore, it suggests that adopting the clay catalyst is an efficient and environmentally friendly way to produce valuable products in pyrolysis of plastic waste.

Chemical upcycling of waste polyolefinic plastics to low-carbon synthetic naphtha for closing the plastic use loop

Designing an effective pathway to remove waste plastics from landfill and incineration plants and create a circular economy requires a more appropriate technology beyond the conventional mechanical recycling by melting and re-molding. This study aims to convert waste plastic into low-carbon synthetic naphtha which can be used as a feedstock for new plastic production, via a new and simple technical approach. To be specific, waste plastics are decomposed and reformed into naphtha fractions via a one-step catalytic pyrolysis over Al2O3 pillared montmorillonite clay catalyst. Experimental results show that Al2O3 pillared montmorillonite clay produces up to 60.3% C5-C12 alkanes, while ZSM-5 gives high contents of aromatics (46%) and olefins (35%). The promising results of Al2O3 pillared M-clay may be due to the special features of this material, including the large pore size and Al2O3-induced active sites (more Brønsted acid sites). The further batch experiments confirm the feasibility of scaling up and processing the polyolefinic plastic mixture.

Synthesis and characterization of a novel nickel pillared–clay catalyst: In-situ carbon nanotube–clay hybrid nanofiller from Ni-PILC

This work presents a novel synthesis of a nickel complex to fabricate Ni-pillared clay (Ni-PILC) as the supporting catalyst for the synthesis of carbon nanotubes (CNTs). To identify the synthesized complex structure, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), elemental analysis, and X-ray photoelectron spectroscopy (XPS) were applied to propose the hexanuclear acetato-ammonia nickel(II) acetate complex, with the chemical formula of [Ni6(OOCCH3)11(NH3)·7H2O]+(OOCCH3)−. Various concentrations of the nickel complex (0.5, 1, 2, 3, 4, 5, 6, 7, and 8 CECs) were used to instigate the ion exchange reaction with the montmorillonite (Mt) surface. Chemical vapor deposition was used to synthesize CNTs. XRD, TGA, Raman, SEM, and TEM characterizations were performed on the CNTs to investigate the influence of the catalyst concentration on the properties of CNTs. Depending on the catalyst concentration, the mass loss of CNTs varied from 28% at 0.5 CEC of the Ni catalyst to ~70% at 8 CEC of the Ni complex. XRD indicated that Na+Mt. layers were intercalated with nickel species during the ion-exchange processes, and then delaminated due to the growth of CNTs. The introduction of higher concentrations of the nickel salt into Mt. improved the quality and the synthesis yield.

Catalytic wet peroxide oxidation of a real textile azo dye Cibacron Red P-4B over Al/Fe pillared bentonite catalysts: kinetic and thermodynamic studies

In the present work, Al/Fe pillared clay catalysts (Al/Fe-PILCs) with different active metal ratios (Fe/(Fe + Al) molar ratio in the intercalating solution) were prepared by using bentonite clay from Ordu (Fatsa) area in Turkey. Batch experiments were performed to study the catalytic wet peroxide oxidation of Cibacron Red P-4B azo dye on the obtained heterogeneous catalysts. The raw bentonite and catalyst samples were characterized by means of XRD (X-ray diffraction), XRF (X-ray fluorescence), DTA (differential thermal analysis), TG (thermogravimetric analysis), BET (Brunauer–Emmett–Teller), SEM (scanning electron microscopy), EDS (energy dispersive spectrometry) and FTIR (Fourier transform infrared) techniques. The basal spacing (d001) of Al/Fe-PILCs increased with the increase in active metal ratio up to 17.2 A for the catalyst with 12% active metal ratio (NaBAlFe12). The BET specific surface area and the micropore volume of NaBAlFe12 showed a decrease compared to raw bentonite. The color removal ratio increased with increasing active metal ratio and reached to 99.24% after 4 h reaction for the NaBAlFe12 catalyst. The pseudo-first order kinetic model was well obeyed the experimental data (k = 0.0075 min−1 at 25 °C). The activation energy (Ea) was calculated as 12.26 ± 0.78 kJ mol−1. It was also found that the catalytic oxidation process was endothermic (ΔH = 9.64 ± 0.76 kJ mol−1) and nonspontaneous (ΔG = 95.35 ± 1.46 kJ mol−1). The catalysts were chemically stable and reusable with low release of iron.

Activation of Nano Kaolin Clay for Bio-Glycerol Conversion to a Valuable Fuel Additive

High production of biodiesel results in a surplus of glycerol as a byproduct that leads to a drastic decline in the glycerol price as well as overall biodiesel production. Alternative methods must be introduced for the economical process for biodiesel production via utilization of crude glycerol into valuable chemicals or fuel additives. This study introduces an ecofriendly process of solketal synthesis from glycerol and acetone in the presence of a novel metakaolin clay catalyst, which is a useful additive in biodiesel or gasoline, in order to enhance the octane number and to control the emissions. Moreover, kaolin clay catalysts are low cost, abundantly available, eco-friendly and one of the more promising applications for solketal synthesis. In this study, raw kaolin clay was activated with an easy acid activation technique, modification in physicochemical and textural properties were determined by using X-ray diffraction (XRD), Fourier Transform Infra-Red (FTIR) spectroscopy, Brunauer–Emmett–Teller (BET) and Field Emission Scanning Electron Microscope. Among all acid-treated catalysts, metakaolin K3 have shown best catalytic properties, high surface area and pore size after acid activation with 3.0 mol/dm3 at 98 °C for 3 h. Acetalization of glycerol with acetone carried out in the presence of an environmentally friendly and inexpensive novel metakaolin K3 catalyst. The maximum yield of solketal obtained was 84% at a temperature of 50 °C, acetone/glycerol molar ratio 6/1 and for 90 min with novel metakaolin clay catalyst. Effect of various parameters (time, temperature, acetone/glycerol molar ratio, catalyst loading) on the solketal yield and glycerol conversion was discussed in detail. This approach offers an effective way to transform glycerol into solketal—a desirable green chemical with future industrial applications.

A practical approach for synthesis of biodiesel via non-edible seeds oils using trimetallic based montmorillonite nano-catalyst

The potential of new trimetallic (Ce, Cu, La) loaded montmorillonite clay catalyst for synthesizing biodiesel using novel non-edible Celastrus paniculatus Willd seed oil via two-step transesterification reaction has been reported along with catalyst characterization. Transesterification reaction was optimized and maximum biodiesel yield of 89.42% achieved under optimal operating reaction states like; 1:12 oil to methanol ratio, 3.5% of catalyst amount, 120 °C of reaction temperature for 3 h. The predicted and experimental biodiesel yields under these reaction conditions were 89.42 and 89.40%, which showing less than 0.05% variation. Additionally, optimum biodiesel yield can be predicted by drawing 3D surface plots and 2D contour plots using MINITAB 17 software. For the characterization of the obtained biodiesel, analysis including the GC/MS, FT-IR, 1H NMR and 13C NMR were applied. The fuel properties of obtained biodiesel agrees well with the different European Union (EU-14214), China (GB/T 20828), and American (ASTM-951, 6751) standards.

Semi-Batch Gasification of Refuse-Derived Fuel (RDF)

Gasification is a promising technology for the conversion of mixed solid waste like refuse-derived fuel (RDF) and municipal solid waste (MSW) into a valuable gas consisting of H2, CO, CH4 and CO2. This work aims to identify the basic challenges of a single-stage batch gasification system related to tar and wax content in the producer gas. RDF was first gasified in a simple semi-batch laboratory-scale gasification reactor. A significant yield of tars and waxes was received in the produced gas. Waxes were analyzed using gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) spectrometry. These analyses indicated the presence of polyethylene and polypropylene chains. The maximum content of H2 and CO was measured 500 sec after the start of the process. In a second series of experiments, a secondary catalytic stage with an Ni-doped clay catalyst was installed. In the two-stage catalytic process, no waxes were captured in isopropanol and the total tar content decreased by approximately 90 %. A single one-stage semi-batch gasification system is not suitable for RDF gasification; a large fraction of tar and waxes can be generated which can cause fouling in downstream processes. A secondary catalytic stage can significantly reduce the tar content in gas.

Catalytic thermochemical cracking of polyethylene over nanocomposite bentonite clay

Catalytic thermochemical cracking of polyethylene has been investigated in presence of a series of bentonite clay based nanocomposite with a view toward assessing their suitability in a process for converting plastic waste to fuel. Metal oxides such as manganese oxide (MnO), titanium oxide (TiO2) and zinc oxide (ZnO) were impregnated with sodium montomorillonite bentonite. The clay catalysts were characterized by x-ray diffraction (XRD), scan electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive x-ray (EDX) spectrometers. The effect of different catalysts on the composition and the yield of gaseous was evaluated. ZnO nanocomposite bentonite clay achieved the highest methane gas formation around 93%. The superior catalytic performance of nanocomposites is probably attributed to their uniform dispersed of oxides particles on montmorillonite support.

Michael addition of ethyl anthranilate and phenyl monothioanthranilate to acetylenic esters: experimental and theoretical results

The reaction of ethyl anthranilate with DMAD and with methyl propiolate in dichloromethane in the presence of ethylaluminium dichloride as catalyst at room temperature gives a mixture of the respective E- and Z-intermediate derivatives which do not cyclize even on refluxing for several hours. On carrying out the reaction in refluxing methanol in the absence of the catalyst, only one stereochemical isomer is obtained which is Z-intermediate indicating conversion of less stable isomer into the thermodynamically more stable derivative under these conditions. The resulting product did not cyclize even on refluxing in methanol in the presence of montmorillonite K10 clay catalyst. The reaction of phenyl monothioanthranilate with DMAD and with methyl propiolate gives similar results. A theoretical investigation of the reaction of ethyl anthranilate with methyl propiolate at the B3LYP/6-31 + G(d) level reveals that it occurs in five steps.

Green, cost effective barium loaded montmorillonite catalyst for biodiesel synthesis from waste cooking oil

The development of an alternative fuels is potential study as fossil fuels are rolling out. The large scale consumption of fossil fuels in power generation in various sectors, like agricultural process, commercial use, domestic, transport sectors are continuously rising the fuel cost. The use of waste vegetable oils and their derivatives are found to be feasible and effective solution using catalytic process. Among all the catalysts the montmorillonite clay plays a vital role to provide unique structural properties to leads high yield, catalyst recycling, cost effectiveness and eco-friendliness process. An emphasis is given to highlighting the significance of green processes with justified comparison between Ba loaded clay catalysts with respect to reaction conditions to produce biodiesel through transesterification in present of methanol. The wet impregnated Ba/MT catalysts were characterized by the BET, XRD, SEM and CO2-TPD. The transesterification reaction was carried out using different oil: methanol molar ratios are 3:1, 5:1, 7:1, 9:1, 10:1, 11:1, 12:1, 15:1 and 16:1. The catalyst amount was varied from 1 to 6 wt% to identify the effect of catalyst amount on yield percentage. The reaction time from 1 to 6 h at 30 °C to 100 °C also considered as a parameter to estimate the effect on yield. After the screening of all the catalysts the optimized reaction conditions are drawn for the transesterification reaction of oil are methanol to oil molar ratio is 11:1with 3 wt% catalyst at 60 °C for 3 h of reaction time is optimal. The highest activity of the catalyst was accounted due to high crystallinity, surface area and substantial basicity provided by threshold ratio of Ba and clay.

Fe2O3-modified activated clay as Heterogeneous Catalyst for Fenton-like oxidation of the removal of methylene blue in wastewater

The Fe2O3-modified activated clay catalysts were prepared by precipitation method and were characterized by SEM, and XRD techniques. The catalysts were used a s heterogeneous Fenton catalysts for degradation of simulated methylene blue solution. The effects of initial pH value, H2O2 dosage, and catalyst dosage and reaction temperature on methylene blue removal rate were investigated. The results showed that, under the optimal conditions of initial pH value 3.0, H2O2 dosage 1200 mg/L, catalyst dosage 6.2 g/L and reaction temperature 30°C, 98.3% of decolorization efficiency was achieved within 60 min in a batch process. The results indicated that Fe2O3-modified activate d clay was a promising catalyst for the heterogeneous Fenton system.