Temperature-programmed Desorption Of Ammonia Research Articles

Enhanced catalytic performance of ethyl-levulinate to γ-valerolactone: Effect of copper loading on Ni/KIT-5 catalyst

A facile wet impregnation method was employed to prepare a bimetallic Ni–Cu catalyst on a mesoporous KIT-5 support, keeping the nickel loading constant (5 wt%) while varying the copper wt.% (xCu, where x = 8, 10, 12, 14). Several physico-chemical techniques, including X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), temperature-programmed desorption of ammonia (NH3-TPD), temperature-programmed reduction of hydrogen (H2-TPR), and X-ray photoelectron spectroscopy (XPS), were utilized for catalyst characterization. An environmentally friendly NiCu bimetallic-supported catalyst system was developed in response to many problems, including metal leaching, sintering, and cost. A mesoporous KIT-5 silica support with a large surface area was used. The hydrogenation of ethyl levulinate to gamma-valerolactone was studied utilizing a high-pressure stirred reactor and a range of reaction temperatures (120–160 °C), hydrogen pressures (10–30 bar), and reaction periods. Various catalysts were used in the investigation. Among all tested catalysts, the 12Cu–5Ni/KIT-5 one shows excellent activity. The best GVL yield is 84% at a conversion of 100% after 8 h of treatment at 150 °C and 25 bar H2 pressure; the promotion is also 76.1%. Optimization of reaction conditions was shown to correlate the physicochemical parameters of the catalyst with its activity.

Furfural production from xylan using a Pueraria Residues carbon-based solid-acid catalyst.

The conversion of biomass into high value-added platform compounds is an important method of biomass utilization. The conversion of hemicellulose represented by xylan into furfural can not only reduce the consumption of fossil fuels, but also promotes the development and utilization of non-edible biomass resources. In this study, a bifunctional solid-acid catalyst prepared from agricultural and forestry waste Pueraria (P. eduli) Residues was used to convert xylan into furfural in a biphasic system. In this study, P. eduli Residues was used as raw material to prepare a P. eduli Residues-based carbon solid-acid catalyst (PR/C-SO3H-Fe) by one-step sulfonation carbonization and impregnation. The catalyst catalyzes the conversion of xylan to furfural in a biphasic system (2-methyltetrahydrofuran/water). The physicochemical properties of the catalysts were characterized by X-ray powder diffraction, scanning electron microscopy, differential thermogravimetric analysis, Brunauer-Emmett-Teller surface area, Fourier transform infrared spectroscopy and ammonia temperature-programmed desorption. Subsequently, the experimental conditions were studied and optimized, such as metal species, iron ion concentration, reaction time and temperature, volume ratio of organic phase to water phase and ratio of substrate to catalyst. The results showed that under conditions of 160 °C, 50 mg catalyst, 100 mg xylan and 7 mL reaction solvent, the yield of furfural could reach 78.94% after 3 h of reaction. This study provides an effective research method for the conversion of xylan into furfural, and provides a reference for the catalytic conversion and utilization of hemicellulose in agricultural and forestry biomass. It also provides a feasible method for the resource utilization of agricultural and forestry waste. © 2024 Society of Chemical Industry.

Bifunctional Catalytic Performance of Zn/ZSM-5 in the Aromatization of LPG and the Conversion of Pyrolytic Gases from Recycled Polypropylene

Zn-modified ZSM-5 zeolites with different zinc contents were successfully prepared by the impregnation method and compared with unmodified ZSM-5. Their potential for LPG (liquefied petroleum gas) aromatization and the conversion of pyrolysis gases obtained from recycled polypropylene was subsequently evaluated. In this process, various characterization tests were performed on the prepared catalysts, including SEM-EDS (scanning electron microscopy with energy-dispersive spectroscopy), TPD-NH₃ (temperature-programmed desorption of ammonia), and FTIR (Fourier-transform infrared spectroscopy). Under optimized conditions, the best results were obtained with 2% Zn/ZSM-5, which generated a higher production of BTX (benzene, toluene, and xylene) isomers, which are major components of gasoline. Likewise, in catalytic pyrolysis of recycled polypropylene, this catalyst generated a higher production of aromatic compounds. Therefore, this catalyst showed excellent performance in generating valuable hydrocarbons of great industrial interest, particularly aromatics.

Catalytic benzylation of arenes using metal-ion modified HY zeolites for sustainable synthesis

Microporous zeolites are commonly employed as catalysts for the benzylation of arenes and benzyl alcohol. However, their catalytic efficiency is often compromised by diffusion limitations, particularly in reactions involving larger arenes. In this study, we developed metal-ion modified HY zeolites using Zn, Mg, and Ni as dopants and investigated their catalytic performance in the benzylation of a range of arenes, including toluene, benzene, mesitylene, p-xylene and with benzyl alcohol (BzOH). The structural and acidic properties of the modified HY zeolites were characterized using a combination of techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), N₂ adsorption–desorption isotherms, Fourier-transform infrared (FTIR) spectroscopy, ammonia temperature-programmed desorption (NH₃-TPD), and proton magic angle spinning nuclear magnetic resonance (1H MAS NMR) spectroscopy. The presence of catalytically active Brønsted acid sites (BAS) was detected by 1H MAS NMR spectroscopy and it was demonstrated that the HY zeolite's acidity is considerably modulated by the addition of metal ions. The catalytic evaluations indicated that the metal-ion modified HY zeolites exhibited superior activity compared to unmodified HY zeolite, with the catalytic performance following the order Zn/HY > Ni/HY > Mg/HY > HY for the benzylation of benzyl alcohol with mesitylene. Further investigation into the mechanism revealed that the synergistic effect of metal ions and acidity plays a crucial role in enhancing the accessibility of arenes to the surface catalytic sites and thereby improving catalytic performance. These findings underscore the importance of the metal-acidity synergy in optimizing the catalytic efficacy of modified HY zeolites for selective benzylation reactions.

Effects of adding metals to Beta zeolite on ethanol conversion to hydrocarbons

This study investigated the effects of Beta zeolite ion exchange with Fe, Zn, and Co on ethanol conversion to hydrocarbons. Various characterization techniques such as X-ray fluorescence (XRF), inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray diffraction (XRD), magic angle rotation nuclear magnetic resonance spectrometry (MAS NMR) of 29Si and 27Al, scanning electron microscopy (SEM), nitrogen physisorption, ammonia temperature-programmed desorption (NH3-TPD) and Fourier transform infrared spectroscopy (FTIR) were employed. Catalytic tests were performed at temperatures from 475 to 550 °C under ambient pressure. The metal addition to Beta zeolite reduced micropore area and volume, decreased the concentration of the extra-framework aluminum, and increased total acid site density and Lewis acid sites, except for Fe. For all catalysts, ethylene was identified as the primary product. However, catalysts containing Zn and Co displayed the formation of propylene and C1 to C3 paraffins. The catalyst with Fe exhibited the highest deactivation and a significant decrease in acidity, attributed to the formation of extra-framework aluminum, resulting in exclusive ethylene production.

Value-added bioproducts by bioethanol dehydrogenation to acetaldehyde through Cu and Zn modified biochar catalysts

ABSTRACT In this study, the efficiency of a series of biochar-supported Cu catalysts, biochar-supported Zn catalysts, and biochar-supported Cu-Zn catalysts was determined through bioethanol dehydrogenation to the high-value chemical, acetaldehyde. Each metal, with weight percentages of 10, 20, and 30, and the combination of Cu-Zn, including 10 wt% of Cu and Zn, 15 wt% of Cu – 5 wt% of Zn, and 15 wt% of Cu and Zn, were fully loaded onto biochar using an incipient wetness impregnation technique. Subsequently, all biocatalysts were subjected to bioethanol dehydrogenation reactions in a temperature range of 200–400 °C. The optimum metal loading for the catalyst was found to be the combination of 15 wt% Cu and 15 wt% Zn. This catalyst resulted in a reasonable acetaldehyde yield of 56.2%, an initial bioethanol conversion of 57.3%, and a very high acetaldehyde selectivity of 98.1% at a mild reaction temperature of 300 °C and ambient pressure. These results were attributed to the optimal concentration of weak-medium acid and medium base sites. Active acid and base sites were identified through temperature-programmed desorption of ammonia (NH3-TPD) and temperature-programmed desorption of carbon dioxide (CO2-TPD), respectively. Furthermore, the reaction stability test of the best biocatalyst (15Cu-15Zn/BB) was proven by maintaining this reaction at the same temperature (300 °C) for 10 h. However, the catalytic performance slightly decreased due to the coke formation of Cu species.

Synthesis of UiO-66-Pyca-CuO by a Simple and Novel Method: MOF-based Metal Thin Film as Heterogeneous Catalysts for the Synthesis of α-Aminonitriles.

Metal-organic frameworks (MOFs), particularly UiO-66-NH2, are employed as catalysts in many industrial catalyst applications. As converting catalysts into thin film significantly increases their catalytic properties, we report a general approach to synthesizing MOF thin films (UiO-66-Pyca-CuO). First, functionalization of UiO-66-NH2 was done with 3-pyridine carboxaldehyde by the postsynthesis method, and then, UiO-66-Pyca was entangled on the surface of copper oxide nanoparticles with a modern strategy (MOF thin film). The morphology and structure of the synthesized UiO-66-Pyca-CuO were determined by using X-ray diffraction, Fourier transform infrared, field-emission scanning electron microscopy, energy-dispersive analysis of X-ray, inductively coupled plasma-mass spectrometry, elemental analyses of CHNOS, temperature-programmed desorption of ammonia, Brunauer-Emmett-Teller, and X-ray photoelectron spectroscopy. We studied the catalytic action of the UiO-66-Pyca-CuO thin film in the synthesis of α-aminonitriles via Strecker reaction. Our studies show that this catalysis can be a suitable catalyst in the synthesis of α-aminonitriles because of having advantages such as using the solvent being environmentally friendly, easy separation of the catalyst (only by picking up the MOF thin film from inside the solution), the reaction at room temperature, high yield, and reusability.

The Role of The Ni/HZSM-5 Ratio on The Anisole Hydrodeoxygenation Reaction

ABSTRACT. Bio-oil is a renewable energy source with high oxygen levels, and anisole is a chemical widely employed in research to represent it. Catalytic hydrodeoxygenation (HDO) reduces the oxygen content. A catalyst known as nickel-modified HZSM-5 has shown promising results for HDO. Meanwhile, catalyst efficiency depends on the Ni/HZSM-5 ratio. So, this study aims to determine how the Ni/HZSM-5 ratio influences the catalyst's properties, activity, and selectivity in anisole HDO. The Ni/HZSM-5 catalyst was made using the wet impregnation method with various ratios of Ni/HZSM-5. The catalysts were analyzed for their morphology using scanning electron microscopy-energy-dispersive X-ray (SEM-EDX). The diffraction patterns were studied using X-ray diffraction (XRD). Surface area and porosity were determined through gas sorption analysis (GSA). Then, the acidity strength was evaluated via temperature-programmed ammonia desorption (NH3-TPD). The characterization results show Ni was successfully impregnated and distributed evenly in HZSM-5 without changing the primary structure. Adding Ni metal to HZSM-5 increases the surface area of the catalyst but reduces its acid strength. The catalytic performance of the catalysts was then evaluated in a flow reactor at 400 °C, using 15 mL/min H2 gas. The liquid products of the reaction were analyzed using gas chromatography-mass spectroscopy (GC-MS). The results of the catalytic performance show that Ni4.5/HZSM-5 has the highest catalytic activity in anisole conversion. At the same time, Ni6.4/HZSM-5 shows the highest selectivity towards benzene-toluene-xylene (BTX). Keywords: Hydrodeoxygenation, nickel, anisole, heterogeneous catalyst, acidity.

Catalytic activity of Zr/CeO2-Al2O3 catalyst for diesel soot oxidation: synthesis, characterization, and performance evaluation.

Diesel soot is a significant contributor to air pollution. Soot particles present in diesel engine exhaust have a negative impact on the environment and human health. Diesel oxidation catalysts (DOCs) and diesel particulate filters (DPFs) currently use noble metal-based catalysts for soot oxidation. Due to the use of noble metals in the catalyst, the cost of diesel after-treatment systems is steadily rising. As a result, diesel vehicles have become commercially less viable than gasoline vehicles and electronic vehicles. The study focuses on an alternative diesel oxidation catalyst with efficiency similar to that of a noble metal catalyst but with a much lower cost. CeO2-Al2O3 catalysts are known for their oxygen storage capacity and high redox activity, making them suitable for soot oxidation. Adding Zr to these catalysts has been shown to influence their structural and chemical properties, significantly affecting their catalytic behavior. Therefore, the current study is focused on using Zr/CeO2-Al2O3 as a substitute for noble metal-based catalysts to enhance its performance for diesel soot oxidation in automotive exhaust. Evaporation-induced self-assembly (EISA) was used to prepare 1, 3, and 5 weight (wt) % Zr supported mesoporous CeO2-Al2O3 catalysts. Morphological, structural, and physicochemical properties of the synthesized catalysts were examined using Brunauer-Emmett-Teller (BET) absolute isotherm, Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Temperature programmed reduction (TPR), and Temperature-programmed desorption of ammonia (NH3-TPD). XRD, BET, and SEM data confirmed that the catalysts were mesoporous and low-crystalline with a high surface area. The soot oxidation activity of the catalysts was evaluated using a thermogravimetric analysis (TGA) technique. The loose contacts soot oxidation activity test suggested that 50% oxidation of soot occurred at 390°C in the absence of a catalyst. T50 of CeO2-Al2O3 catalyzed soot oxidation was 296°C. Adding Zr to the catalyst significantly improved catalytic activity for diesel soot oxidation. We observed a further drastic change in T50 of soot over 1, 3, and 5% Zr/CeO2-Al2O3, which were 220°C, 210°C, and 193°C, respectively. According to these results, incorporating Zr into the CeO2-Al2O3 catalyst significantly improved the oxidation process of soot.

Sub-ppm short-chain fatty acids detection with La(III) modified SnO2 gas sensors

La(III) modified nanocrystalline SnO2 with lanthanum content [La]/([Sn] +[La]) = 0; 0.5; 1 and 2 mol. % were prepared by flame spray pyrolysis and characterized by X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Identification of surface segregation of La(III) containing phases was performed via Raman spectroscopy. Acidic properties of pure and La(III) modified SnO2 were characterized by temperature-programmed desorption of ammonia (TPD-NH3) with mass spectral determination of desorption products. It was demonstrated that decrease in the Lewis acidity of the SnO2 surface leads to the specific increase in sensor response when detecting gases with acidic properties like short-chain fatty acids (SCFAs) and H2S. The obtained materials are capable to detect SCFAs at ppb concentration level, including high air humidity conditions (RH = 80 %).

Performance of sulfided NiMo catalyst supported on pillared bentonite Al and Ti under hydrodeoxygenation reaction of guaiacol

Bio-crude oil is known to be sustainable, eco-environmentally, and an alternative energy source produced by biomass pyrolysis. However, its quality remains relatively low due to a higher oxygen concentration compared to liquid fuels from fossils. Therefore, an upgrading process is necessary through the catalytic hydrodeoxygenation (HDO) process. This work synthesized pillared bentonite using Al and Ti metals as the pillaring agent to produce Al-PILC and Ti-PILC as catalyst support for sulfided NiMo. Their catalytic activity in HDO reaction using guaiacol as a model compound of bio-crude oil were also evaluated. Characterization of the bentonite-pillared materials, including Al-PILC, Mo/Al-PILC, NiMo/Al-PILC, Ti-PILC, Mo/Ti-PILC, and NiMo/Ti-PILC, was performed using Surface Area Analyzer, X-ray Diffractometer (XRD), Temperature-Programmed Desorption of ammonia (NH3-TPD), X-Ray Fluorescence (XRF), and Scanning Electron Microscope (SEM) techniques. The characterization results confirm the pillarization process of bentonite using Al and Ti metals as the pillaring agent, and the preparation of the NiMo catalyst using the stepwise impregnation method was successfully prepared. The NiMo/Ti-PILC catalyst performs a superior conversion value on the HDO guaiacol reaction than other catalysts. A well dispersion of Mo and Ni metals on the surface support (NiMo/Ti-PILC), thus creating numerous active sites of the catalyst after the sulfidation. Variations in time and temperature during the HDO guaiacol reaction significantly affected the conversion.

Simple Fabrication of Hydrophobicity-Controlled Fe-ZSM-5 for Aqueous-Phase Partial Oxidation of Methane with Hydrogen Peroxide

Surface hydrophobicity is an important factor in controlling the catalytic activity of heterogeneous catalysts in various reactions, particularly liquid-phase reactions using water as the (co)solvent. In this study, the surface hydrophobicity of Fe-ZSM-5 was successfully controlled using a simple coating method in which furfuryl alcohol was used as the carbon precursor. Various techniques, such as N2 physisorption, temperature-programmed desorption of ammonia, and contact angle measurements of water droplets, were used to characterize the catalysts. Fe-ZSM-5 catalysts with different degrees of hydrophobicity were used for the aqueous-phase selective oxidation of methane with H2O2. The positive effect of the surface carbon coating on the catalytic performance was confirmed when the carbon content was not sufficiently high to block the pores.

Biodiesel Production via Transesterification Reaction over Mono- and Bimetallic Copper-Noble Metal (Pt, Ru) Catalysts Supported on BEA Zeolite

This work focuses on the study of biodiesel production from commercial rapeseed oil and methanol via transesterification reactions on monometallic copper and bimetallic copper–noble metal (platinum, ruthenium) catalysts supported on BEA zeolite. The catalysts were prepared by wet impregnation method on the hydrogen form of BEA zeolite. As part of the study, the physicochemical and catalytic properties of the prepared catalytic materials were determined. The catalytic activity tests were carried out in the transesterification reaction over prepared catalysts at 220 °C for 2 h in an autoclave. The physicochemical properties of the obtained catalysts were investigated by X-ray diffraction (XRD), specific surface area and porosity (BET), a scanning electron microscope equipped with an energy dispersive spectrometer (SEM–EDS) and temperature-programmed desorption of ammonia (TPD-NH3) method. The results of the catalytic activity showed the promotional effect of the noble metal on the TG conversion and FAME efficiency of copper catalysts in the biodiesel production process. The most active catalyst turned out to be the calcined 5%Cu–1%Ru/BEA catalyst, which showed the highest TG conversion of 85.7% and the second highest FAME efficiency of 58.4%. The high activity of this system is explained by its surface acidity and large specific surface area.

Effect of Bimetallic Co-Cu/Dolomite Catalyst on Glycerol Conversion to 1,2-Propanediol

This present study examines the efficacy of using dolomite (Dol, CaMg(CO3)2)-supported copper (Cu) and cobalt (Co) bimetallic and monometallic catalysts for the hydrogenolysis of glycerol to propylene glycol (PG; 1,2-PDO). The proposed catalysts were generated using the impregnation process before they were calcined at 500°C and reduced at 600°C. Advanced analytical techniques namely Brunauer, Emmett, and Teller (BET) method; the Barrett, Joyner, and Halenda (BJH) method; temperature-programmed desorption of ammonia (NH3–TPD), hydrogen-temperature programmed reduction (H2-TPR), X-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM) were then used to characterise the synthesised catalysts, whose performance was then tested in the hydrogenolysis of glycerol. Of all the synthesised catalysts tested in the hydrogenolysis process, the Co-Cu/Dol bimetallic catalyst performed best, with an 80.3% glycerol conversion and 85.9% PG selectivity at a pressure of 4 MPa, a temperature of 200°C, and a reaction time of 10 hours. Its high catalytic performance was attributed to effective interactions between its Co-Cu-Dol species, which resulted in acceptable acidity, good reducibility of metal oxide species at low temperatures, larger surface area (15.3 m2 g-1), large-sized particles, fewer pores (0.032 cm3 g-1), and smaller pore diameter (0.615 nm).

Enhancing CO and H2 Production in Propane Dry Reforming in Excess of CO2.

This study focuses on addressing the challenges in the dry reforming of propane, a process historically marked by low syngas yields and only moderate conversions of CO2 and propane. The primary objective was to enhance CO2 utilization and boost the selectivity of syngas (CO and H2) production using titania-based catalysts. For synthesizing these catalysts, an impregnation method was employed with subsequent characterization through X-ray diffraction (XRD), N2 adsorption-desorption, ammonia temperature-programmed desorption (TPD), and hydrogen temperature-programmed reduction (TPR). The titania-based catalysts generally possess weak acidic strength, with each catalyst displaying a unique reduction profile. The dry reforming process using these catalysts resulted in varying levels of propane conversion, with V/Ti, Ir/Ti, Al/Ti, and Zr/Ti catalysts showing distinct efficiencies. Notably, the Ir/Ti and V/Ti oxide catalysts achieved the lowest selectivity for generating intermediate byproducts such as methane, ethane, ethylene, and propylene while successfully promoting higher syngas CO and H2 production alongside stable propane conversion. When exposed to excess CO2, each catalyst consumed differing amounts of CO2 molecules. Particularly, the Ir/Ti and V/Ti oxide catalysts demonstrated enhanced activity in promoting CO2 reactions with intermediate radical species, facilitating carbon-carbon (C-C) bond dissociation and leading to increased syngas production. This study offers valuable insights into the potential of titania-based catalysts in improving the efficiency and selectivity of propane dry reforming processes for blue hydrogen.

Role of the surface layer of epoxy resin

Water pollution threatens human health, and the safe supply of drinking water has been recognized as a problem worldwide. The increasing accumulation of heavy metals in water from various sources has led to the search for effective and environmentally friendly treatment methods and materials for their removal. To impart the necessary characteristics to minerals, in particular to improve sorption properties, one of the methods is modification. Modern technologies using sorbents require qualitatively new sorption materials with increased capacity and high selectivity of action. Epoxy resins are widely used as a base material in the coating field due to their advantages including adsorption properties. In this work, shungite from the Koksu deposit and Shankhanai zeolite were used as natural sorbents for modification. The purpose of this work is to study the interaction of epoxy resin ED-20 with the surface of a natural sorbent through a layer of polyethylene polyamine. Methodology. To study the surface of the prepared samples, methods such as infrared spectroscopy, gravimetry and the temperatureprogrammed desorption method were used. Results and discussion. This article presents the results of IR spectroscopic analysis of natural sorbents shungite and zeolite modified with epoxy resin ED-20 and polyethylene polyamine. The obtained surface epoxy layers were studied for resistance to aqueous environments of varying acidity for 90 days. The acid-base properties of the surface layers of modified sorbents were studied by the method of temperature-programmed ammonia desorption. Conclusion. By modifying shungites and zeolites with polyethylene polyamine, followed by cross-linking them on the surface of a natural mineral with ED-20 epoxy resin, a durable layer of epoxy resin was obtained.

Preparation of Solid Superacid SO42-/ZrO2 and SO42-/ZrO2-MxOy (M=Ce, Co, Mn, and Zn) and Its Application in Toluene Nitration.

The nitration reaction of aromatic compounds is one of the extensively studied chemical reactions that result in the manufacturing of various industrial products applied in pharmaceuticals, dyes, perfumes, and explosives. A series of modified sulfated zirconia (SZ) catalysts SO42-/ZrO2-MxOy (M=Ce, Co, Mn, Zn, and M/SZ) doped with different metal elements by a coprecipitation method were investigated in the toluene nitration reaction. Various characterization techniques (X-ray diffraction, Brunauer-Emmett-Teller, thermogravimetric analysis, X-ray photoelectron spectroscopy, and temperature-programmed desorption of ammonia) indicated that doping metal elements in SZ led to excellent catalytic properties, increasing the specific surface area of the catalyst and facilitating the formation of a stable tetragonal zirconia phase. Doping zinc and cobalt in SZ enhanced the acidity of the catalyst and formed stronger acidic sites, promoting the generation of nitronium ions and providing more active sites for the toluene nitration reaction. Additionally, it reduced the loss of sulfate ions in the catalytic system that helped in improving the stability of the catalyst. Under the same conditions, the catalytic activity of toluene nitration reaction demonstrated the following order: Zn/SZ > Ce/SZ > Co/SZ > Mn/SZ > SZ, with the zinc-doped SZ catalyst exhibiting the best catalytic performance, achieving a toluene conversion rate of 78.58% and a para/ortho nitrotoluene ratio of 0.67.

Catalytic performance of desilicated HZSM-12 for benzylation reaction of benzene with benzyl alcohol

The catalytic production of diphenylmethane from the reaction of benzene with benzyl alcohol was investigated using HZSM-12 and desilicated HZSM-12 that was obtained by treating ZSM-12 with 0.2M NaOH solution at 85 ?C for 60 min. The untreated and alkaline treated ZSM-12 zeolites were characterized by X-ray diffraction, nitrogen adsorption/desorption isotherms, scanning electron microscopy, inductively coupled plasma optical emission spectrometry, and temperature-programmed desorption of ammonia. The desilicated HZSM-12 showed promising catalytic performance with benzyl alcohol conversion of 100% and the selectivity to diphenylmethane of 74% and 87% in 4 h and 8 h reaction time, respectively. The reaction parameters affecting benzyl alcohol conversion and product distribution were also presented. The activities of fresh and regenerated catalysts were compared, and characterization results indicated that the occluded organic molecules decreased the number of acidic sites of the catalyst after the reaction and regeneration.

IMPROVED ACIDITY OF MESOPOROUS ZrO2-WO3 THROUGH NH3-AIR SUBSECTION-CALCINATION TREATMENT

ZrO2-WO3 mixed metal oxides are important solid acid catalysts, and typically, ammonia gas calcination reduces their acidity. However, in this study, we introduce an updated NH3 calcination technique that can increase the acidity of mesoporous ZrO2-WO3 solid acids. Their structures and acid properties were thoroughly characterized through X-ray diffraction (XRD), N2 adsorption measurement, pyridine-adsorbed infrared spectroscopy (Py-IR), temperature-programmed desorption of ammonia (NH3-TPD), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM) and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis-DRS) analysis. The resulting materials exhibit remarkable activity in the Friedel-Crafts (F-C) reaction of anisole and benzyl alcohol. Our investigations showed that the subnanometer WOx clusters act as the most active sites for the F-C reaction, and NH3-air calcination is essential for the formation of WOx clusters. This treatment not only enhances acidity but also provides a novel method of obtaining acidic ZrO2-WO3 mixed metal oxides. Most importantly, it presents a fresh approach for regulating the formation of WO3 clusters and catalytic activity.

Enhancing the catalytic properties of silicalite-1 through ammonium fluoride modification for waste glycerol acetalization.

Silicalite-1 is a silica with a zeolitic MFI (Mobil Five) structure devoid of noticeable catalytically active (e.g., acid) sites. In this study, we present its modification with NH4F solutions of varying concentrations (0.5-3 M), which generates efficient and selective acid sites for the acetalization of glycerol with acetone towards solketal (2,2-dimethyl-1,3-dioxolane-4-methanol). The creation of acid sites is attributed to the partial elimination of external silanol groups in silicalite-1 and the generation of some framework defects, resulting also in increased porosity. The characterization of the modified materials was performed using various techniques, i.e. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), temperature-programmed desorption of ammonia (TPD-NH3), and Fourier-transform infrared spectroscopy (FTIR). The results demonstrate that the newly created acidic sites of Brønsted and Lewis nature exhibit significantly higher acidic strength and enhanced accessibility for reagents compared to the pristine one, resulting in exceptional glycerol conversion in the acetalization of glycerol with acetone and notable selectivity towards solketal. Glycerol conversion over modified silicalite-1 reached nearly 70%, with the selectivity to solketal exceeding 98% at 70° C after 1 hour of reaction time, using a mixture of glycerol and acetone in a 1 : 1 ratio. The proposed reaction mechanism takes into account a combination of Brønsted and Lewis acid sites. The obtained results indicated that Brønsted acid sites, especially those of higher strength, are the most beneficial in this process. The remarkable catalytic performance and stability of modified silicalite-1 make it a promising candidate for potential industrial applications in the utilization of waste glycerol formed in the biofuel industry.