Next Issue
Volume 5, June
Previous Issue
Volume 4, December
 
 

Chemistry, Volume 5, Issue 1 (March 2023) – 48 articles

Cover Story (view full-size image): Biodiesel made from renewable triglycerides (TGs) is a low-emission fuel alternative to diesel. Compared to homogeneous bases, solid base catalysts are more attractive due to their lower environmental impact and simpler purification processes. However, improving the stability and activity of solid base catalysts is challenging. Basic zeolites, particularly two-dimensional zeolites, are promising solid base catalysts for the transesterification of TGs due to their high surface area, superior stability, and tunable basicity. This review presents recent advancements in the synthesis, characterization, and catalytic performance of basic zeolites for TG transesterification. It highlights challenges and prospects for developing basic zeolites for biodiesel production via transesterification. View this paper
  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Reader to open them.
Order results
Result details
Section
Select all
Export citation of selected articles as:
12 pages, 3309 KiB  
Article
Stimuli-Responsive Designer Supramolecular Polymer Gel
by M. Douzapau, Srayoshi Roy Chowdhury, Surajit Singh, Olamilekan Joseph Ibukun and Debasish Haldar
Chemistry 2023, 5(1), 691-702; https://doi.org/10.3390/chemistry5010048 - 22 Mar 2023
Cited by 2 | Viewed by 1979
Abstract
This paper reports a stimuli-responsive designer supramolecular polymer gel in dimethylsulphoxide (DMSO)/water (1:2) based on a dipeptide amphiphile and β-cyclodextrin (β-CD) The dipeptide amphiphile contains caproic acid at the N terminus and methyl ester at the C terminus. From X-ray single crystal diffraction, [...] Read more.
This paper reports a stimuli-responsive designer supramolecular polymer gel in dimethylsulphoxide (DMSO)/water (1:2) based on a dipeptide amphiphile and β-cyclodextrin (β-CD) The dipeptide amphiphile contains caproic acid at the N terminus and methyl ester at the C terminus. From X-ray single crystal diffraction, the amphiphile adopts a kink-like conformation. The amphiphile self-assembled to form a parallel sheet-like structure stabilized by multiple intermolecular hydrogen bonds. Moreover, the parallel sheet-like structure is also stabilized by edge-to-edge ππ stacking interactions. In higher-order packing, it forms a corrugated sheet-like structure stabilized by hydrophobic interactions. The dipeptide amphiphile interacts with β-cyclodextrin and forms gel through supramolecular polymer formation in (DMSO)/water (1:2) by a simple heating-cooling cycle. The sol-to-gel transformation is because of a host–guest complex between compound 1 and β-CD and the formation of supramolecular polymer accompanied by microstructure changes from nanofibers to microrods. The gel is temperature responsive with a Tgel of 70 °C. The supramolecular polymer gel is also responsive to stimuli such aspicric acid and HCl. The extensive spectroscopic studies show that the aromatic hydrophobic side chain of compound 1 forms a host–guest complex with β-CD. These results will be helpful for the design of advanced programable eco-friendly functional materials. Full article
(This article belongs to the Special Issue Programmable and Stimulus-Responsive Supramolecular Assemblies)
Show Figures

Figure 1

29 pages, 15587 KiB  
Review
Cesium Heteropolyacid Salts: Synthesis, Characterization and Activity of the Solid and Versatile Heterogeneous Catalysts
by Marcio Jose da Silva, Alana Alves Rodrigues and Neide Paloma Gonçalves Lopes
Chemistry 2023, 5(1), 662-690; https://doi.org/10.3390/chemistry5010047 - 21 Mar 2023
Cited by 4 | Viewed by 2263
Abstract
Keggin-type heteropolyacid cesium salts have been regarded as potential candidates for heterogeneous catalytic reactions. This review describes the success of Keggin-type heteropolyacids cesium salts (Cs-HPA salts) as efficient catalysts in various synthesis processes. The Cs-HPA catalysts can be synthesized as solid salts through [...] Read more.
Keggin-type heteropolyacid cesium salts have been regarded as potential candidates for heterogeneous catalytic reactions. This review describes the success of Keggin-type heteropolyacids cesium salts (Cs-HPA salts) as efficient catalysts in various synthesis processes. The Cs-HPA catalysts can be synthesized as solid salts through the metathesis of a solution containing precursor HPA and another solution containing soluble Cs salt, which will give Cs-HPA salt as a solid precipitate. Alternatively, they can be also obtained from the commercial precursor HPA. In this review, all the routes to prepare the different cesium salts (i.e., saturated, lacunar, metal-doped) were described. These salts can be used in acid-catalyzed reactions (i.e., esterification, etherification, acetalization, dehydration) or oxidative transformations (oxidative esterification, oxidation, epoxidation). All of these reactions were addressed herein. Aspects related to the synthesis and characterization of these catalyst salts were discussed. This review aims to discuss the most pertinent heterogeneous catalytic systems based on Keggin HPA Cs salts. The focus was to correlate the physicochemical properties of these salts with their catalytic activity. Ultimately, the most recent advances achieved in the applications of these Cs-HPA salts as catalysts in the synthesis of industrial interest compounds were discussed. Cesium heteropoly salts are an alternative to the traditional soluble mineral acids as well as to solid-supported catalysts. Full article
Show Figures

Graphical abstract

16 pages, 4051 KiB  
Review
Perspectives on the Structural Design and Luminescent Behavior of Liquid Crystalline Materials Based on Copper(I) Complexes
by Muhammed Alkali and Viorel Cîrcu
Chemistry 2023, 5(1), 646-661; https://doi.org/10.3390/chemistry5010046 - 15 Mar 2023
Cited by 1 | Viewed by 1735
Abstract
This paper provides insight into the various studies that have been carried out to date on liquid crystalline materials based on copper(I) complexes. Although the study of copper(I) complexes with respect to their liquid crystalline property is quite limited, metallomesogens prepared with different [...] Read more.
This paper provides insight into the various studies that have been carried out to date on liquid crystalline materials based on copper(I) complexes. Although the study of copper(I) complexes with respect to their liquid crystalline property is quite limited, metallomesogens prepared with different structural components and ligands from groups such as azamacrocycles, alkythiolates, ethers, isocyanides, phenanthroline, Schiff bases, pyrazolates, phosphines, biquinolines, and benzoylthioureas are reported and summarized in this review. A special section is dedicated to the discussion of emission properties of copper(I) metallomesogens. Full article
(This article belongs to the Section Crystallography)
Show Figures

Figure 1

13 pages, 6768 KiB  
Article
MgAl-NO3 LDH: Adsorption Isotherms and Multivariate Optimization for Cr(VI) Removal
by Anna Maria Cardinale, Cristina Carbone, Simone Molinari, Gabriella Salviulo and Francisco Ardini
Chemistry 2023, 5(1), 633-645; https://doi.org/10.3390/chemistry5010045 - 14 Mar 2023
Cited by 1 | Viewed by 1551
Abstract
Within the framework of the various strategies studied for the abatement of polluting agents in water, both from anthropogenic and natural origins, adsorption processes are among the most widespread techniques. In this context, Layered Double Hydroxides (LDHs) play a fundamental role. In this [...] Read more.
Within the framework of the various strategies studied for the abatement of polluting agents in water, both from anthropogenic and natural origins, adsorption processes are among the most widespread techniques. In this context, Layered Double Hydroxides (LDHs) play a fundamental role. In this study, a Mg–Al LDH (nitrate intercalated, Mg/Al = 2) was prepared to be used as an anion exchanger for Cr(VI)-removal purposes from water. The LDH was synthesized through a coprecipitation reaction, followed by an aging process under heating. The compound was characterized by means of inductively coupled plasma–atomic emission spectroscopy (ICP-AES), X-ray powder diffraction (XRPD), field-emission scanning electron microscopy (FE-SEM) and Fourier-transform infrared spectroscopy (FT-IR). Regarding LDH adsorption capacity, with respect to Cr(VI), the adsorption isotherms and reaction kinetic were studied, and the adsorption process was well described by the Langmuir model. A central composite design was used for the multivariate optimization of the working parameters. The maximum adsorption capacity was estimated to be 30 mg/g. Full article
(This article belongs to the Special Issue Low-Cost Water Treatment - New Materials and New Approaches)
Show Figures

Figure 1

17 pages, 1954 KiB  
Article
Impact of Di- and Poly-Radical Characters on the Relative Energy of the Doubly Excited and La States of Linear Acenes and Cyclacenes
by Yasi Dai, Juan-Carlos Sancho-García and Fabrizia Negri
Chemistry 2023, 5(1), 616-632; https://doi.org/10.3390/chemistry5010044 - 11 Mar 2023
Cited by 2 | Viewed by 1733
Abstract
Linear and cyclic acenes are polycyclic aromatic hydrocarbons that can be viewed as building blocks of graphene nanoribbons and carbon nanotubes, respectively. While short linear acenes demonstrated remarkable efficiency in several optoelectronic applications, the longer members are unstable and difficult to synthesize as [...] Read more.
Linear and cyclic acenes are polycyclic aromatic hydrocarbons that can be viewed as building blocks of graphene nanoribbons and carbon nanotubes, respectively. While short linear acenes demonstrated remarkable efficiency in several optoelectronic applications, the longer members are unstable and difficult to synthesize as their cyclic counterparts. Recent progress in on-surface synthesis, a powerful tool to prepare highly reactive species, opens promising perspectives and motivates the computational investigations of these potentially functional molecules. Owing to their di- and poly-radical character, low-lying excited states dominated by doubly excited configurations are expected to become more important for longer members of both linear and cyclic molecules. In this work, we investigate the lowest-lying La and the doubly excited (DE) state of linear acenes and cyclacenes, with different computational approaches, to assess the influence of the di-/poly-radical characters (increasing with the molecular dimensions) on their relative order. We show that DFT/MRCI calculations correctly reproduce the crossing of the two states for longer linear acenes, while TDUDFT calculations fail to predict the correct excitation energy trend of the DE state. The study suggests a similarity in the excited electronic state pattern of long linear and cyclic acenes leading ultimately to a lowest lying dark DE state for both. Full article
(This article belongs to the Section Theoretical and Computational Chemistry)
Show Figures

Figure 1

14 pages, 3086 KiB  
Article
Comparison of Cu-CHA-Zeolites in the Hybrid NSR-SCR Catalytic System for NOx Abatement in Mobile Sources
by Sergio Molina-Ramírez, Marina Cortés-Reyes, Concepción Herrera, María Ángeles Larrubia and Luis José Alemany
Chemistry 2023, 5(1), 602-615; https://doi.org/10.3390/chemistry5010043 - 10 Mar 2023
Viewed by 1564
Abstract
DeNOx activity in a NSR–SCR hybrid system of two copper-containing chabazite-type zeolitic catalysts was addressed. A Pt-Ba-K/Al2O3 model catalyst was used as the NSR (NOx storage and reduction) catalyst. For the SCR (selective catalytic reduction) system, two Cu-CHA [...] Read more.
DeNOx activity in a NSR–SCR hybrid system of two copper-containing chabazite-type zeolitic catalysts was addressed. A Pt-Ba-K/Al2O3 model catalyst was used as the NSR (NOx storage and reduction) catalyst. For the SCR (selective catalytic reduction) system, two Cu-CHA zeolites were synthesized employing a single hydrothermal synthesis method assisted with ultrasound and incorporating Cu in a 2 wt.%, 2Cu-SAPO-34 and 2Cu-SSZ-13. The prepared catalysts were characterized, and the crystallinity, surface area, pore size, HR-TEM and EDX mapping, coordination of Cu ions and acidity were compared. The NH3 storage capacity of the SCR catalysts was 1890 and 837 μmol NH3·gcat1 for 2Cu-SAPO-34 and 2Cu-SSZ-13, respectively. DeNOx activity was evaluated for the single NSR system and the double-bed NSR–SCR by employing alternating lean (3%O2) and rich (1%H2) cycles, maintaining a concentration of 600 ppm NO, 1.5% H2O and 0.3% CO2 between 200 and 350 °C. The addition of the SCR system downstream of the NSR catalyst significantly improved NOx conversion mainly at low temperature, maintaining the selectivity to N2 above 80% and reaching values above 90% at 250 °C when the 2Cu-SSZ-13 catalyst was located. The total reduction in the production of NH3 and ~2% of N2O was observed when comparing the NSR–SCR configuration with the single NSR catalyst. Full article
Show Figures

Figure 1

13 pages, 2525 KiB  
Article
Selective Styrene Oxidation Catalyzed by Phosphate Modified Mesoporous Titanium Silicate
by Rupak Chatterjee, Avik Chowdhury, Sudip Bhattacharjee, Rajaram Bal and Asim Bhaumik
Chemistry 2023, 5(1), 589-601; https://doi.org/10.3390/chemistry5010042 - 10 Mar 2023
Cited by 2 | Viewed by 1638
Abstract
Selective oxidation of organics over an efficient heterogeneous catalyst under mild liquid phase conditions is a very demanding chemical reaction. Herein, we first report the modification of the surface of mesoporous silica MCM-41 material by phosphate for the efficient incorporation of Ti(IV) in [...] Read more.
Selective oxidation of organics over an efficient heterogeneous catalyst under mild liquid phase conditions is a very demanding chemical reaction. Herein, we first report the modification of the surface of mesoporous silica MCM-41 material by phosphate for the efficient incorporation of Ti(IV) in the silica framework to obtain highly ordered 2D hexagonal mesoporous material STP-1. STP-1 has been synthesized by using tetraethyl orthosilicate, triethyl phosphate, and titanium isopropoxide as Si, P, and Ti precursors, respectively, in the presence of cationic surfactant cetyltrimethylammonium bromide (CTAB) under hydrothermal conditions. The observed specific surface area and pore volume of STP-1 were 878 m2g−1 and 0.75 ccg−1, respectively. Mesoporous STP-1 has been thoroughly characterized by XRD, FT-IR, Raman spectroscopy, SEM, and TEM analyses. Titanium incorporation (Ti/Si = 0.006) was confirmed from the EDX analysis. This mesoporous STP-1 was used as a heterogeneous catalyst for the selective oxidation of styrene into benzaldehye in the presence of dilute aqueous H2O2 as an oxidizing agent. Various reaction parameters such as the reaction time, the reaction temperature, and the styrene/H2O2 molar ratio were systematically studied in this article. Under optimized reaction conditions, the selectivity of benzaldehyde could reach up to 93.8% from styrene over STP-1. Further, the importance of both titanium and phosphate in the synthesis of STP-1 for selective styrene oxidation was examined by comparing the catalytic result with only a phosphate-modified mesoporous silica material, and it suggests that both titanium and phosphate synergistically play an important role in the high selectivity of benzaldehyde in the liquid phase oxidation of styrene. Full article
Show Figures

Graphical abstract

18 pages, 5995 KiB  
Article
Ni-Mg/Al Mixed Oxides Prepared from Layered Double Hydroxides as Catalysts for the Conversion of Furfural to Tetrahydrofurfuryl Alcohol
by Abdulaziz Aldureid, Daniel Montané, Jordi Llorca and Francesc Medina
Chemistry 2023, 5(1), 571-588; https://doi.org/10.3390/chemistry5010041 - 09 Mar 2023
Cited by 1 | Viewed by 1459
Abstract
Ni-Mg/Al mixed oxide catalysts (Ni2Al, Ni2Mg1Al, and Ni1Mg1Al) obtained from layered double hydroxides (LDHs) were tested on the one-pot production of tetrahydrofurfuryl alcohol (TFA) from furfural (FF). Upon calcination at 400 [...] Read more.
Ni-Mg/Al mixed oxide catalysts (Ni2Al, Ni2Mg1Al, and Ni1Mg1Al) obtained from layered double hydroxides (LDHs) were tested on the one-pot production of tetrahydrofurfuryl alcohol (TFA) from furfural (FF). Upon calcination at 400 °C and reduction at 500 °C, the LDHs gave catalysts containing small nickel crystallites (<4 nm) dispersed on mixtures of metal oxides and spinel structures. Complete conversion of FF (>99.5%) was achieved on all the catalysts after 4 h at 190 °C and 5.0 MPa of H2 using 5 wt.% FF in ethanol and a furfural-to-catalyst mass ratio of 7.44 g/g. TFA evolved from the sequential hydrogenation of FF to furfuryl alcohol (FA) to TFA. Competing reaction routes involved decarbonylation of FF to furan (FUR) followed by hydrogenation to tetrahydrofuran (THF) or hydrogenolysis to n-butane (BU) and the hydrogenation of the carbonyl group in FF to form 2-methyl furan (mFUR) and its hydrogenation to 2-methyltetrahydrofuran (mTHF). A third competing route consisted of the nucleophilic addition of FF with ethanol and with FA to form acetals (such as 2-(diethoxymethyl)furan, FDA), which were later converted to difurfuryl ether (DFE) and tetrahydrofurfuryl ethyl ether (TFEE) as final products. Hydrogen pressure favored the production of TFA and diminished the formation of acetals, while temperature reduced the capacity of the catalyst to hydrogenate the furan ring, thus reducing TFA and increasing FA and FUR. An 80% yield to TFA was achieved with the Ni2Mg1Al catalysts after 6 h at 190 °C and 50 bar H2, but a variety of coproducts were present at low concentration. Testing of the catalysts in gas-phase hydrogenation conditions at atmospheric pressure revealed a poorer performance, with FA as the main product. Full article
Show Figures

Figure 1

12 pages, 3944 KiB  
Article
Degradation of Epoxy–Particles Composites Exposed to UV and Gamma Radiation
by Mauricio Torres, Louise Burdin, A. Victoria Rentería-Rodríguez and Edgar A. Franco-Urquiza
Chemistry 2023, 5(1), 559-570; https://doi.org/10.3390/chemistry5010040 - 08 Mar 2023
Cited by 2 | Viewed by 1997
Abstract
In the design and fabrication of any structural system for space application, balance between mass, stiffness and strength is crucial. Structures in space environments are exposed to high radiation levels and thermal shock, due to the sun irradiance and rotation around Earth. Therefore, [...] Read more.
In the design and fabrication of any structural system for space application, balance between mass, stiffness and strength is crucial. Structures in space environments are exposed to high radiation levels and thermal shock, due to the sun irradiance and rotation around Earth. Therefore, accurate determination of the thermal and radiation properties is a key issue for the materials used in such applications. This study reports the thermal and mechanical performance of particle composites (epoxy resin and ZnO particles) after gamma and UV radiation. Composites are exposed to gamma and UV radiation at rates of 1 kGy and 10 kGy and characterized after exposure. For the evaluation, DMA, TGA and three-point bending mechanical test are performed to determine thermal properties and possible material degradation after radiation exposure. The incorporation of the filler in the thermal, radiation and mechanical response of the epoxy system improves as a function of its concentration. Then, epoxy resin reinforced with ZnO particles can be a potential candidate as a polymeric matrix for fiber-reinforced composites for nanosatellites. Full article
(This article belongs to the Section Chemistry of Materials)
Show Figures

Graphical abstract

15 pages, 3864 KiB  
Article
Conversion of Ethanol to Butadiene over Binary MgO-SiO2 Mixed Oxides Prepared by the Ammonia Evaporation Method
by Ismail Bin Samsudin, Stephan Jaenicke and Gaik-Khuan Chuah
Chemistry 2023, 5(1), 544-558; https://doi.org/10.3390/chemistry5010039 - 07 Mar 2023
Viewed by 1560
Abstract
The ammonia evaporation method, originally applied for the preparation of highly dispersed silica-supported copper catalysts, was used to synthesize magnesia-silica for the one-step conversion of ethanol to 1,3-butadiene. The MgO-SiO2 catalysts obtained by this method contained a high fraction of magnesium silicate [...] Read more.
The ammonia evaporation method, originally applied for the preparation of highly dispersed silica-supported copper catalysts, was used to synthesize magnesia-silica for the one-step conversion of ethanol to 1,3-butadiene. The MgO-SiO2 catalysts obtained by this method contained a high fraction of magnesium silicate hydrates, which are associated with enhanced butadiene selectivity. These catalysts were benchmarked against those prepared by a conventional wet-kneading method. A Mg/Si molar ratio of 4 was optimal, forming butadiene with 37% yield, which is far superior to the 15% yield obtained with MgO-SiO2 formed by wet-kneading. At 475 °C and a WHSV of 3.2 h−1, a productivity of 0.612 gBD gcat−1 h−1 was measured without the catalyst suffering from deactivation, even after 52 h TOS. The catalysts were characterized by spectroscopic and thermal techniques to elucidate their physicochemical properties and explain the differences in the catalytic performance. The presence of magnesium silicate hydrates gave a balance of surface acidity and basicity, which greatly improved butadiene formation. The open morphology of MgO-SiO2 with vertically arranged platelets and the presence of large pores are proposed to contribute to the stability of the catalyst. Full article
Show Figures

Graphical abstract

18 pages, 4009 KiB  
Article
Gold Clusters Immobilized by Post-Synthesis Methods on Thiol-Containing SBA-15 Mesoporous Materials for the Aerobic Oxidation of Cyclohexene: Influence of Light and Hydroperoxide
by Rafael Delgado, Carlos Márquez-Álvarez, Álvaro Mayoral, Ramón de la Serna, Javier Agúndez and Joaquín Pérez-Pariente
Chemistry 2023, 5(1), 526-543; https://doi.org/10.3390/chemistry5010038 - 07 Mar 2023
Viewed by 1404
Abstract
Gold nanospecies produced by a historically inspired two-liquid phase system were immobilized on plate-like mesoporous silica, SBA-15, functionalized with mercaptopropyl groups by a post-synthesis method, and the resulting materials were tested in the oxidation of cyclohexene with molecular oxygen at atmospheric pressure. The [...] Read more.
Gold nanospecies produced by a historically inspired two-liquid phase system were immobilized on plate-like mesoporous silica, SBA-15, functionalized with mercaptopropyl groups by a post-synthesis method, and the resulting materials were tested in the oxidation of cyclohexene with molecular oxygen at atmospheric pressure. The main purpose of this approach was to compare the physicochemical properties and catalytic performance of these materials with those of previously reported related materials functionalized by in situ methods during synthesis. In addition, catalytic tests under ambient lighting and darkness and also in the presence and absence of the initiator tert-butyl hydroperoxide (TBHP) were carried out. The samples were characterized by chemical analysis, N2 adsorption/desorption, TGA, SEM, HRTEM, UV-vis spectroscopy and XPS. Gold nanoclusters and isolated gold atoms but no AuNPs were found in the catalysts (0.31–2.69 wt.% of gold). The XPS shows that nearly 60% of the -SH groups (1.33 wt.% of S) were oxidized to sulphonic groups upon gold immobilization. The AuNCs and isolated gold atoms evolved in the the reaction medium to form AuNPs. The activity of the samples was lower than that of the catalysts supported on related S-bearing SBA-15 functionalized in situ, which was attributed to their different Au/S ratios, which in turn regulated the evolutionary process of the gold species during the reaction. The catalysts turned out to be inactive in darkness, which evidences that the cyclohexene oxidation carried out at ambient illumination is actually photocatalyzed by the AuNPs formed in situ during the reaction. The TBHP initiator is required to obtain the activity in order to counteract the inhibitors of cyclohexene auto-oxidation present in the commercial reagent. On the other hand, no major differences in the selectivity among the different catalysts and reactions were observed, with 2-cyclohexen-1-one and 2-cyclohexen-1-ol resulting from the allylic oxidation as main products (selectivity of (one + ol) ~80% at a conversion ≥ 35%; one/ol~2). Full article
Show Figures

Graphical abstract

15 pages, 4126 KiB  
Article
Kinetic and Spectroscopic Studies of Methyl Ester Promoted Methanol Dehydration to Dimethyl Ether on ZSM-5 Zeolite
by Zhiqiang Yang, Benjamin J. Dennis-Smither, Zhuoran Xu, Zhenchao Zhao, Meiling Guo, Neil Sainty, Guangjin Hou, Xuebin Liu and Glenn J. Sunley
Chemistry 2023, 5(1), 511-525; https://doi.org/10.3390/chemistry5010037 - 06 Mar 2023
Viewed by 1595
Abstract
Methyl carboxylate esters have been shown to be potent promoters of low-temperature methanol dehydration to dimethyl ether (DME) using various zeolite catalysts. In the present work, catalytic kinetic studies, in-situ Fourier-transform infrared spectroscopy (FT-IR) and solid-state nuclear magnetic resonance spectroscopy (NMR) techniques were [...] Read more.
Methyl carboxylate esters have been shown to be potent promoters of low-temperature methanol dehydration to dimethyl ether (DME) using various zeolite catalysts. In the present work, catalytic kinetic studies, in-situ Fourier-transform infrared spectroscopy (FT-IR) and solid-state nuclear magnetic resonance spectroscopy (NMR) techniques were used to elucidate the promotional mechanism of methyl carboxylate esters on methanol dehydration to DME, using the medium pore zeolite H-ZSM-5 (MFI) as the catalyst. Kinetic studies were performed using the very potent methyl n-hexanoate promoter. The DME yield was dependent on both the methanol and methyl n-hexanoate partial pressures across the temperature ranges used in this study (110 to 130 °C). This is consistent with the promoted reaction being a bimolecular reaction between methanol and ester species adsorbed at the catalyst active sites, via an SN2 type reaction, as previously postulated. The in-situ FT-IR studies reveal that the Brønsted acid (BA) sites on H-ZSM-5 were very rapidly titrated by ester carbonyl group adsorption and bonded more strongly with esters than with methanol. Upon methanol addition, an even lower DME formation temperature (30 °C) was observed with methyl n-hexanoate pretreated H-ZSM-5 samples in the in-situ NMR studies, further confirming the strong promotion of this methyl ester on methanol dehydration to DME. The adsorption and reactivity of different methyl esters on H-ZSM-5 indicates that while methyl formate more easily dissociates into a surface methoxy species, [Si(OMe)Al], and carboxylic acid, it is a less potent promoter than alkyl-chain-containing methyl esters in methanol dehydration to DME, which in turn did not show this dissociative behavior in the low-temperature NMR studies. This indicates that methyl alkyl carboxylates do not need to be dissociated to a surface methoxy species to promote the methanol dehydration reaction and that a bimolecular associative mechanism plays an important role in promoting DME formation. Full article
Show Figures

Figure 1

19 pages, 3864 KiB  
Review
Niche Applications of MXene Materials in Photothermal Catalysis
by Zhiyi Wu, Jiahui Shen, Chaoran Li, Chengcheng Zhang, Chunpeng Wu, Zimu Li, Xingda An and Le He
Chemistry 2023, 5(1), 492-510; https://doi.org/10.3390/chemistry5010036 - 06 Mar 2023
Cited by 7 | Viewed by 2978
Abstract
MXene materials have found emerging applications as catalysts for chemical reactions due to their intriguing physical and chemical applications. In particular, their broad light response and strong photothermal conversion capabilities are likely to render MXenes promising candidates for photothermal catalysis, which is drawing [...] Read more.
MXene materials have found emerging applications as catalysts for chemical reactions due to their intriguing physical and chemical applications. In particular, their broad light response and strong photothermal conversion capabilities are likely to render MXenes promising candidates for photothermal catalysis, which is drawing increasing attention in both academic research and industrial applications. MXenes are likely to satisfy all three criteria of a desirable photothermal catalyst: strong light absorption, effective heat management, and versatile surface reactivity. However, their specific functionalities are largely dependent on their structure and composition, which makes understandings of the structure–function relationship of crucial significance. In this review, we mainly focus on the recent progress of MXene–based photothermal catalysts, emphasizing the functionalities and potential applications of MXene materials in fields of photothermal catalysis, and provide insights on design principles of highly efficient MXene–based photothermal catalysts from the atomic scale. This review provides a relatively thorough understanding of MXene–based materials for photothermal catalysis, as well as an in–depth investigation of emerging high-prospect applications in photothermal catalysis. Full article
Show Figures

Figure 1

13 pages, 997 KiB  
Article
Conversion of Sugar Di-Ketals to Bio-Hydrocarbons through Catalytic Cracking over Beta Catalysts in Fixed and Fluidized Catalytic Beds
by Cristiane Cardoso, Yiu L. Lam, Marlon B. B. de Almeida and Marcelo Maciel Pereira
Chemistry 2023, 5(1), 479-491; https://doi.org/10.3390/chemistry5010035 - 04 Mar 2023
Cited by 1 | Viewed by 1340
Abstract
Second-generation biomass (BM) can be produced in amounts that meet worldwide fuel demands. However, BM favors parallel and undesirable reactions in its transformation chain. We circumvent this problem by first modifying BM by ketalization, giving a user-friendly liquid we named BP (bio-petroleum). This [...] Read more.
Second-generation biomass (BM) can be produced in amounts that meet worldwide fuel demands. However, BM favors parallel and undesirable reactions in its transformation chain. We circumvent this problem by first modifying BM by ketalization, giving a user-friendly liquid we named BP (bio-petroleum). This study converted a representative compound of BP, DX (1,2:3,5-di-O-isopropylidene-α-D-xylofuranose), mixed with n-hexane by beta zeolites and catalysts containing beta zeolite. Beta zeolite showed low coke and high liquid product yields in converting this mixture (having 30 wt. % DX) into hydrocarbons in a fixed-bed reactor at 500 °C with a space velocity of 16 h−1 (0.3 catalyst/feed). Its performance was further improved by steam treatment (lowering the coke yield by lowering the acid site density) or incorporation into a catalyst (improving DX participation due to the active sites in the matrix). Further, by changing the conversion process from a fixed bed to a fluidized cracking unit, a much larger amount of the deactivated catalyst could be used (catalyst/feed = 3), remarkably reducing oxygenates and fully converting DX. Additionally, the green hydrocarbon efficiency (olefin, aromatics, furans, and cyclo-alkanes) of DX was approximately 77%. Hence, beta catalysts were shown to have a great potential to provide green fuels for future bio-refineries. Full article
Show Figures

Figure 1

16 pages, 4394 KiB  
Article
Crotonaldehyde Adsorption on Cu-Pt Surface Alloys: A Quantum Mechanics Study
by Ricardo Ruvalcaba, Jonathan Guerrero-Sanchez, Noboru Takeuchi and Francisco Zaera
Chemistry 2023, 5(1), 463-478; https://doi.org/10.3390/chemistry5010034 - 03 Mar 2023
Cited by 2 | Viewed by 1657
Abstract
The adsorption of crotonaldehyde on Cu-Pt alloy surfaces was characterized by density functional theory (DFT). Two surfaces were considered: Cu2Pt/Cu(111) and Cu3Pt/Cu(111). It was determined that the presence of Pt on the surface, even when isolated as single atoms [...] Read more.
The adsorption of crotonaldehyde on Cu-Pt alloy surfaces was characterized by density functional theory (DFT). Two surfaces were considered: Cu2Pt/Cu(111) and Cu3Pt/Cu(111). It was determined that the presence of Pt on the surface, even when isolated as single atoms fully surrounded by Cu, provides additional stability for the adsorbates, increasing the magnitude of the adsorption energy by as much as 40 kJ/mol. The preferred bonding on both surfaces is via multiple coordination, with the most stable configuration being a cis arrangement with di-σ bonding of the C=O bond across a Cu–Cu bridge and an additional π bonding to a Pt atom. The fact that Pt significantly affects the adsorption of unsaturated aldehydes such as crotonaldehyde explains why the kinetics of their hydrogenation using single-atom alloy (SAA) catalysts vary with alloy composition, as we previously reported, and brings into question the simple model in which the role of Pt is only to promote the dissociation of H2. Full article
Show Figures

Graphical abstract

11 pages, 1589 KiB  
Communication
Aluminum-Catalyzed Cross Selective C3–N1′ Coupling Reactions of N-Methoxyindoles with Indoles
by Keisuke Tokushige, Toshiki Yamashiro, Seiya Hirao and Takumi Abe
Chemistry 2023, 5(1), 452-462; https://doi.org/10.3390/chemistry5010033 - 03 Mar 2023
Cited by 2 | Viewed by 4136
Abstract
C3–N1′ bond formation of bisindoles has been a great challenge due to the intrinsic reactivity of indoles as both C3 and N1-nucleophilic character. Herein, we demonstrate an C3–N1′ cross-coupling reaction of indoles using N-methoxyindoles as N-electrophilic indole reagents in the presence of [...] Read more.
C3–N1′ bond formation of bisindoles has been a great challenge due to the intrinsic reactivity of indoles as both C3 and N1-nucleophilic character. Herein, we demonstrate an C3–N1′ cross-coupling reaction of indoles using N-methoxyindoles as N-electrophilic indole reagents in the presence of Lewis acid. The bisindoles generated in this transformation are latent C3-nucleophile, allowing them to be used as strategic intermediates in sequential C3–N1′–C3′–N1″ triindole formations. The potential synthetic usefulness of this sequential transformation was highlighted upon application to the construction of C3–N1 looped polyindoles. Full article
(This article belongs to the Section Molecular Organics)
Show Figures

Graphical abstract

14 pages, 1728 KiB  
Review
Advancements in Basic Zeolites for Biodiesel Production via Transesterification
by Guoju Yang and Jihong Yu
Chemistry 2023, 5(1), 438-451; https://doi.org/10.3390/chemistry5010032 - 03 Mar 2023
Cited by 4 | Viewed by 2101
Abstract
The excessive utilization of petroleum diesel has led to the depletion of fossil resources and severe environmental pollution. Biodiesel produced from renewable triglycerides (TGs) or waste lipids is a low-emission fuel substitute for diesel. Biodiesel is mainly produced by transesterification reactions over homogeneous [...] Read more.
The excessive utilization of petroleum diesel has led to the depletion of fossil resources and severe environmental pollution. Biodiesel produced from renewable triglycerides (TGs) or waste lipids is a low-emission fuel substitute for diesel. Biodiesel is mainly produced by transesterification reactions over homogeneous base catalysts with excellent activity and low cost. In comparison, solid base catalysts are more attractive due to their lower environmental impact and simpler production and purification processes. It remains a challenge to further improve the stability and activity of solid base catalysts. Because of the high surface area, superior stability, and tunable basicity, basic zeolites, especially two-dimensional zeolites, have emerged as promising solid basic catalysts for the transesterification of TGs. In this review, we present recent advancements in the synthesis, characterization, and catalytic performance of basic zeolites for the transesterification of TGs. Challenges and development prospects of basic zeolites for biodiesel production via transesterification are also pointed out. We expect that this review will inspire the more efficient and rational design of zeolites for sustainable fuel production. Full article
Show Figures

Graphical abstract

16 pages, 4109 KiB  
Article
How Topological Differences between Two Oxide Surfaces Determine Selectivity—The Case of the Dehydra-Decyclization of Tetrahydrofuran
by Sai Praneet Batchu, Stavros Caratzoulas and Dionisios G. Vlachos
Chemistry 2023, 5(1), 422-437; https://doi.org/10.3390/chemistry5010031 - 01 Mar 2023
Cited by 1 | Viewed by 1364
Abstract
Production of butadiene from biomass-based tetrahydrofuran (THF) is explored as an alternative to the existing petroleum-based processes. Metal oxide catalysts have been shown to exhibit varying product selectivities when reacted with THF. Among those oxides, ZrO2 showed the highest selectivity for butadiene. [...] Read more.
Production of butadiene from biomass-based tetrahydrofuran (THF) is explored as an alternative to the existing petroleum-based processes. Metal oxide catalysts have been shown to exhibit varying product selectivities when reacted with THF. Among those oxides, ZrO2 showed the highest selectivity for butadiene. In contrast, Al2O3 showed the highest selectivity for the competing retro-Prins products, C3H6 and HCHO. The reasons behind the varying selectivity across oxides are unclear. In this work, we employ periodic density functional theory and mean-field microkinetic modeling to investigate the mechanism of the reaction of THF to butadiene and retro-Prins products on t-ZrO2 (101) (dry and hydrous) and on γ-Al2O3 (110). Our simulations reproduce the experimental selectivity trends. High selectivity for butadiene is promoted by the presence of neighboring Lewis acid metal sites that facilitate E1cB hydroxyl elimination from a 3-butenoxide intermediate; on hydrous Al2O3; where such neighboring Lewis acid centers are not available, the butenoxide undergoes E2 elimination and retro-Prins products ensue. The THF ring opening is rate-determining on ZrO2, whereas the γ-proton elimination that yields the 3-butenoxide intermediate is rate controlling on hydroxylated Al2O3. We conclude that the local topology around the active site greatly influences the mechanism and selectivity. Full article
Show Figures

Figure 1

16 pages, 3813 KiB  
Article
Vapor-Phase Oxidant-Free Dehydrogenation of 2,3- and 1,4-Butanediol over Cu/SiO2 Catalyst Prepared by Crown-Ether-Assisted Impregnation
by Enggah Kurniawan, Shuya Hosaka, Masayuki Kobata, Yasuhiro Yamada and Satoshi Sato
Chemistry 2023, 5(1), 406-421; https://doi.org/10.3390/chemistry5010030 - 28 Feb 2023
Cited by 9 | Viewed by 2170 | Correction
Abstract
A silica-supported copper (Cu/SiO2) catalyst containing highly dispersed Cu nanoparticles was prepared via a crown-ether-assisted impregnation method. A 12-crown-4-ether-assisted Cu/SiO2 catalyst outperformed several Cu/SiO2 catalysts prepared with various organic additives in the dehydrogenation of 2,3- and 1,4-butanediol. It was [...] Read more.
A silica-supported copper (Cu/SiO2) catalyst containing highly dispersed Cu nanoparticles was prepared via a crown-ether-assisted impregnation method. A 12-crown-4-ether-assisted Cu/SiO2 catalyst outperformed several Cu/SiO2 catalysts prepared with various organic additives in the dehydrogenation of 2,3- and 1,4-butanediol. It was found that the catalytic activity, i.e., the formation rate of acetoin from 2,3-butanediol and that of γ-butyrolactone from 1,4-butanediol, was proportional to the copper surface area. Full article
Show Figures

Graphical abstract

13 pages, 1755 KiB  
Article
Gold(III) Chloride-Mediated Transformation of Furfural to the trans-N,N-4,5-Diaminocyclopent-2-enones in the Presence of Anilines
by Marina A. Tzani and Ioannis N. Lykakis
Chemistry 2023, 5(1), 393-405; https://doi.org/10.3390/chemistry5010029 - 27 Feb 2023
Viewed by 1639
Abstract
We investigated the efficient approach of a series of trans-N,N-4,5-substituted-diaminocyclopent-2-enones (trans-DACPs) from furfural and anilines mediated by Gold(III) chloride (HAuCl4). The present protocol required a low amount of the catalysts, 1.5 mol%, open air [...] Read more.
We investigated the efficient approach of a series of trans-N,N-4,5-substituted-diaminocyclopent-2-enones (trans-DACPs) from furfural and anilines mediated by Gold(III) chloride (HAuCl4). The present protocol required a low amount of the catalysts, 1.5 mol%, open air conditions, the absence of any additives, and short reaction times. The desired trans-DACPs were isolated in good to high yields. The protocol was also applied to secondary amines, leading to the corresponding 4,5-diamino-cyclopent-2-enones in good yields. To the best of our knowledge, this is the first gold-mediated paradigm as an efficient catalyst for the formation of the cyclopentenones core-bearing C-N bonds under mild reaction conditions. Full article
Show Figures

Graphical abstract

12 pages, 2128 KiB  
Article
Solvent-Assisted Adsorption of Cellulose on a Carbon Catalyst as a Pretreatment Method for Hydrolysis to Glucose
by Abhijit Shrotri, Kiko Eguchi, Lina Mahardiani, Hirokazu Kobayashi, Masakuni Yamashita, Hiroshi Yagita and Atsushi Fukuoka
Chemistry 2023, 5(1), 381-392; https://doi.org/10.3390/chemistry5010028 - 24 Feb 2023
Viewed by 1778
Abstract
Cellulose hydrolysis to glucose using a heterogeneous catalyst is a necessary step in producing bio-based chemicals and polymers. The requirement for energy-intensive pretreatments, such as ball milling, to increase the reactivity of cellulose is one of the major issues in this area. Here, [...] Read more.
Cellulose hydrolysis to glucose using a heterogeneous catalyst is a necessary step in producing bio-based chemicals and polymers. The requirement for energy-intensive pretreatments, such as ball milling, to increase the reactivity of cellulose is one of the major issues in this area. Here, we show that by using solvent-assisted adsorption as a pretreatment step, cellulose can be adsorbed on the surface of a carbon catalyst. For adsorption pretreatment, phosphoric acid (H3PO4) performed better than other solvents such as sulfuric acid (H2SO4), tetrabutylammonium fluoride/dimethyl sulfoxide (TBAF/DMSO) and 1-butyl-3-methylimidazolium chloride ([BMMI]Cl). Hydrolysis after the adsorption of cellulose and the removal of H3PO4 produced a 73% yield of glucose. Partial hydrolysis of cellulose in H3PO4 before adsorption increased the final glucose yield. The glucose yield was proportional to the number of weakly acidic functional groups on the carbon catalyst, indicating the reaction was heterogeneously catalyzed. In a preliminary lab-scale life-cycle analysis (LCA), greenhouse gas (GHG) emissions per kg of glucose produced through the hydrolysis of cellulose were calculated. The H3PO4-assisted adsorption notably reduces GHG emissions compared to the previously reported ball milling pretreatment. Full article
Show Figures

Graphical abstract

16 pages, 2537 KiB  
Article
Application of DFT/TD-DFT Frameworks in the Drug Delivery Mechanism: Investigation of Chelated Bisphosphonate with Transition Metal Cations in Bone Treatment
by Fatemeh Mollaamin and Majid Monajjemi
Chemistry 2023, 5(1), 365-380; https://doi.org/10.3390/chemistry5010027 - 23 Feb 2023
Cited by 5 | Viewed by 1604
Abstract
Carbon nanotubes (CNTs) are applied in a drug delivery system, which can be reacted with different structures such biomolecules. Bones have vital functions and are the locations of biochemical reactions in cells that might be exposed various diseases. As different metal ions are [...] Read more.
Carbon nanotubes (CNTs) are applied in a drug delivery system, which can be reacted with different structures such biomolecules. Bones have vital functions and are the locations of biochemical reactions in cells that might be exposed various diseases. As different metal ions are integral components of bone tissue with different functions in the physiological cellular medium as well as in bone treatment, they can be used differently as a basis or as a supplement for various materials in the field of bone repair. Therefore, this research aims to represent the recent progress in conjugated bisphosphonate (BP)-divalent transition metal ions of Mn2+, Fe2+, and Co2+ with an emphasis on the properties of interaction with a (6, 6) armchair carbon nanotube as a nanocarrier to exhibit the potential biomedical application of drug delivery. In this article, “CNT” linked to “BP“ of alendronic acid, ibandronic acid, neridronic acid, and pamidronic acid, which are chelated to transition metal cations of Mn2+, Fe2+, and Co2+, was investigated based on DFT insights for obtaining the electron charge density. Transition metals chelating with phosphonate groups, which are large with six O atoms with negative charges, are active in generating chelated complexes with the bisphosphonates [BPs- Mn2+/Fe2+/Co2+] through the status of drug design. In this work, B3LYP/6-311+G(d,p)/lanl2dz we have estimated the susceptibility of CNT for conjugating alendronic acid, ibandronic acid, neridronic acid, and pamidronic acid, which are chelated to transition metal cations of Mn2+, Fe2+, and Co2+ through NMR, NQR, IR, UV-VIS spectroscopy, and HOMO-LUMO analysis. Finally, the obtained results have confirmed that the possibility of applying CNT and BPs of alendronic acid, ibandronic acid, neridronic acid, and pamidronic acid becomes suitable in transition metal chelating for delivery application. The calculated HOMO–LUMO energy gaps for BPs of alendronic acid, ibandronic acid, neridronic acid, and pamidronic acid at the B3LYP/6-311+G (d,p) level have revealed that the energy gap reflects the chemical activity of the molecule. Full article
(This article belongs to the Special Issue Theoretical Investigations of Reaction Mechanisms II)
Show Figures

Figure 1

17 pages, 3017 KiB  
Article
Steering the Metal Precursor Location in Pd/Zeotype Catalysts and Its Implications for Catalysis
by Luc C. J. Smulders, Johan H. van de Minkelis, Johannes D. Meeldijk, Min Tang, Anna Liutkova, Kang Cheng, S. Tegan Roberts, Glenn J. Sunley, Emiel J. M. Hensen, Petra E. de Jongh and Krijn P. de Jong
Chemistry 2023, 5(1), 348-364; https://doi.org/10.3390/chemistry5010026 - 23 Feb 2023
Cited by 2 | Viewed by 2168
Abstract
Bifunctional catalysts containing a dehydrogenation–hydrogenation function and an acidic function are widely applied for the hydroconversion of hydrocarbon feedstocks obtained from both fossil and renewable resources. It is well known that the distance between the two functionalities is important for the performance of [...] Read more.
Bifunctional catalysts containing a dehydrogenation–hydrogenation function and an acidic function are widely applied for the hydroconversion of hydrocarbon feedstocks obtained from both fossil and renewable resources. It is well known that the distance between the two functionalities is important for the performance of the catalyst. In this study, we show that the heat treatment of the catalyst precursor can be used to steer the location of the Pd precursor with respect to the acid sites in SAPO-11 and ZSM-22 zeotype materials when ions are exchanged with Pd(NH3)4(NO3)2. Two sets of catalysts were prepared based on composite materials of alumina with either SAPO-11 or ZSM-22. Pd was placed on/in the zeotype, followed by a calcination-reduction (CR) or direct reduction (DR) treatment. Furthermore, catalysts with Pd on the alumina binder were prepared. CR results in having more Pd nanoparticles inside the zeotype crystals, whereas DR yields more particles on the outer surface of the zeotype crystals as is confirmed using HAADF-STEM and XPS measurements. The catalytic performance in both n-heptane and n-hexadecane hydroconversion of the catalysts shows that having the Pd nanoparticles on the alumina binder is most beneficial for maximizing the isomer yields. Pd-on-zeotype catalysts prepared using the DR approach show intermediate performances, outperforming their Pd-in-zeotype counterparts that were prepared with the CR approach. Full article
Show Figures

Graphical abstract

14 pages, 2644 KiB  
Article
Environmental Applications of Zeolites: Hydrophobic Sn-BEA as a Selective Gas Sensor for Exhaust Fumes
by Martin Jendrlin, Julien Grand, Louwanda Lakiss, Florent Dubray, Philippe Bazin, Jaafar El Fallah, Svetlana Mintova and Vladimir Zholobenko
Chemistry 2023, 5(1), 334-347; https://doi.org/10.3390/chemistry5010025 - 21 Feb 2023
Cited by 3 | Viewed by 1971
Abstract
Environmental monitoring of pollutants, such as NOx and COx, which can be facilitated by a range of gas sensors, is of considerable fundamental and practical importance. This work has been focused on the synthesis and evaluation of zeolite β with [...] Read more.
Environmental monitoring of pollutants, such as NOx and COx, which can be facilitated by a range of gas sensors, is of considerable fundamental and practical importance. This work has been focused on the synthesis and evaluation of zeolite β with tin (Sn-BEA) and dealuminated β (DeAl-BEA) zeolites. The zeolite samples have been extensively investigated by IR, UV-VIS and NMR spectroscopy, XRD, TGA, and N2 adsorption-desorption. The prepared Sn-BEA sample is characterised by the submicron particle size, an almost defect-free structure, and high hydrophobicity. Sensors containing selective microporous layers based on Sn-BEA and DeAl-BEA zeolites have been prepared and extensively tested. Both the Sn-BEA and DeAl-BEA zeolites have been deposited in thin films and evaluated as gas sensors for CO, CO2, NO, and NO2 in the presence of water vapour at room temperature. The Sn-BEA zeolite-based sensor showed high selectivity towards NO2, while the DeAl-BEA is selective towards CO2 and NO2. Full article
Show Figures

Figure 1

20 pages, 4183 KiB  
Article
Environmental Applications of Zeolites: Preparation and Screening of Cu-Modified Zeolites as Potential CO Sensors
by Martin Jendrlin, Julien Grand, Louwanda Lakiss, Philippe Bazin, Svetlana Mintova and Vladimir Zholobenko
Chemistry 2023, 5(1), 314-333; https://doi.org/10.3390/chemistry5010024 - 20 Feb 2023
Cited by 1 | Viewed by 1597
Abstract
This work is focused on the application of Cu-containing zeolites as potential environmental sensors for monitoring carbon monoxide. A number of commercial zeolites with different structural properties (NaX, NaY, MOR, FER, BEA and ZSM-5) were modified using CuSO4, Cu(NO3) [...] Read more.
This work is focused on the application of Cu-containing zeolites as potential environmental sensors for monitoring carbon monoxide. A number of commercial zeolites with different structural properties (NaX, NaY, MOR, FER, BEA and ZSM-5) were modified using CuSO4, Cu(NO3)2 and Cu(OAc)2 solutions as copper sources to prepare Cu+-containing zeolites, since Cu+ forms stable complexes with CO at room temperature that can be monitored by infrared spectroscopy. Zeolite impregnation with Cu(NO3)2 resulted in the highest total Cu-loadings, while the Cu(OAc)2-treated samples had the highest Cu+/Cutotal ratio. Cu(NO3)2-impregnated MOR, which displayed the highest concentration of Cu+, was subjected to a number of tests to evaluate its performance as a potential CO sensor. The working temperature and concentration ranges of the sensor were determined to be from 20 to 300 °C and from 10 to 10,000 ppm, respectively. The stepwise CO desorption experiments indicated that the sensor can be regenerated at 400 °C if required. Additional analyses under realistic flow conditions demonstrated that for hydrophilic zeolites, the co-adsorption of water can compromise the sensor’s performance. Therefore, a hydrophobic Sn-BEA was utilised as a parent material for the preparation of an impregnated Cu-Sn-BEA zeolite, which exhibited superior resistance to interfering water while maintaining its sensing properties. Overall, the prepared Cu-modified zeolites showed promising potential as environmental CO sensors, displaying high sensitivity and selectivity under representative testing conditions. Full article
Show Figures

Figure 1

20 pages, 5604 KiB  
Article
Revisiting the Impact of Tungsten on the Catalytic Properties of Ammonia-SCR V2O5-WO3/TiO2 Catalysts: Geometric vs. Electronic Effects
by Hermann Wilfried Siaka, Christophe Dujardin, Alain Moissette and Pascal Granger
Chemistry 2023, 5(1), 294-313; https://doi.org/10.3390/chemistry5010023 - 20 Feb 2023
Viewed by 1374
Abstract
The SCR performance of V2O5-WO3/TiO2 SCR-catalysts characterized by different surface W density (2.1W/nm2 and 9.5W/nm2) and different surface V density varying in the range 1–8V/nm2 has been investigated in order to clarify [...] Read more.
The SCR performance of V2O5-WO3/TiO2 SCR-catalysts characterized by different surface W density (2.1W/nm2 and 9.5W/nm2) and different surface V density varying in the range 1–8V/nm2 has been investigated in order to clarify existing controversies on the preferential involvement of electronic and geometric effects in the catalytic properties. It was found that tungsten has a weak effect on the VOx cluster size distribution through contraction of dilution effect. In contrast, the optimal interaction between W and V, when both reach their highest composition, appears to be a relevant parameter that can enhance their acidic properties and improve the catalytic efficiency in dry conditions. On the other hand, an absence of significant interaction leads to discontinuity due to deactivation. In the presence of steam, acidic properties are averaged, lowering the impact of the V to W ratio. Finally, the critical importance of acidic properties which outperform redox properties in the definition of active site is pointed out in the light of this study. Full article
Show Figures

Figure 1

13 pages, 2289 KiB  
Article
Catalytic Reductive Amination of Aromatic Aldehydes on Co-Containing Composites
by Vladyslav V. Subotin, Vitalii M. Asaula, Yulian L. Lishchenko, Mykyta O. Ivanytsya, Olena O. Pariiska, Sergey V. Ryabukhin, Dmitriy M. Volochnyuk and Sergey V. Kolotilov
Chemistry 2023, 5(1), 281-293; https://doi.org/10.3390/chemistry5010022 - 17 Feb 2023
Cited by 3 | Viewed by 2513
Abstract
The performance of a series of cobalt-based composites in catalytic amination of aromatic aldehydes by amines in the presence of hydrogen as well as hydrogenation of quinoline was studied. The composites were prepared by pyrolysis of CoII acetate, organic precursor (imidazole, 1,10-phenantroline, [...] Read more.
The performance of a series of cobalt-based composites in catalytic amination of aromatic aldehydes by amines in the presence of hydrogen as well as hydrogenation of quinoline was studied. The composites were prepared by pyrolysis of CoII acetate, organic precursor (imidazole, 1,10-phenantroline, 1,2-diaminobenzene or melamine) deposited on aerosil (SiO2). These composites contained nanoparticles of metallic Co together with N-doped carboneous particles. Quantitative yields of the target amine in a reaction of p-methoxybenzaldehyde with n-butylamine were obtained at p(H2) = 150 bar, T = 150 °C for all composites. It was found that amination of p-methoxybenzaldehyde with n-butylamine and benzylamine at p(H2) = 100 bar, T = 100 °C led to the formation of the corresponding amines with the yields of 72–96%. In the case of diisopropylamine, amination did not occur, and p-methoxybenzyl alcohol was the sole or the major reaction product. Reaction of p-chlorobenzaldehyde with n-butylamine on the Co-containing composites at p(H2) = 100 bar, T = 100 °C resulted in the formation of N-butyl-N-p-chlorobenzylamine in 60–89% yields. Among the considered materials, the composite prepared by decomposition of CoII complex with 1,2-diaminobenzene on aerosil showed the highest yields of the target products and the best selectivity in all studied reactions. Full article
(This article belongs to the Topic Catalysis: Homogeneous and Heterogeneous)
Show Figures

Graphical abstract

12 pages, 2280 KiB  
Article
Theoretical Study of Excited-State Dynamics of Hypercoordinated Carbon Molecule
by Probal Nag and Sivaranjana Reddy Vennapusa
Chemistry 2023, 5(1), 269-280; https://doi.org/10.3390/chemistry5010021 - 15 Feb 2023
Viewed by 1381
Abstract
Structural and dynamical aspects of vibronically coupled S1 (dipole-allowed, “bright”) and S2 (dipole-forbidden, “dark”) states of hypercoordinated carbon molecule, 1,8-dimethoxy-9-dimethoxymethylanthracene monocation, are investigated. Potential energy surfaces are modeled within the linear vibronic coupling scheme. Quantum dynamics simulation show that the nuclear [...] Read more.
Structural and dynamical aspects of vibronically coupled S1 (dipole-allowed, “bright”) and S2 (dipole-forbidden, “dark”) states of hypercoordinated carbon molecule, 1,8-dimethoxy-9-dimethoxymethylanthracene monocation, are investigated. Potential energy surfaces are modeled within the linear vibronic coupling scheme. Quantum dynamics simulation show that the nuclear wavepacket initiated on the “bright” S1 state would move to “dark” S2 within a few femtoseconds via an accessible conical intersection. A dynamical equilibrium of wavepacket exchange between S1 and S2 is observed after 50 fs of propagation time. The activity of vibrational motions associated with the hypercoordinated carbon and C−H vibrations is analyzed using the reduced nuclear densities. Our findings illustrate that the excited-state nonadiabatic behavior has to be taken into account while analyzing the optical properties of this hypercoordinated carbon molecule. Full article
(This article belongs to the Special Issue Hypercoordinate Carbon)
Show Figures

Figure 1

14 pages, 1977 KiB  
Article
Crystal Engineering of Conglomerates: Dilution of Racemate-Forming Fe(II) and Ni(II) Congeners into Conglomerate-Forming [Zn(bpy)3](PF6)2
by Ugo Serdan, Lucas Robin, Mathieu Marchivie, Mathieu Gonidec, Patrick Rosa, Elen Duverger-Nédellec, Emilie Pouget, Philippe Sainctavit, Marie-Anne Arrio, Amélie Juhin, Andrei Rogalev, Fabrice Wilhelm and Elizabeth A. Hillard
Chemistry 2023, 5(1), 255-268; https://doi.org/10.3390/chemistry5010020 - 15 Feb 2023
Viewed by 1755
Abstract
Conglomerate formation, where enantiomers within a racemic mixture self-segregate upon crystallization, is an advantageous property for obtaining chirally pure crystals and allows large-scale chiral resolution. However, the prevalence of conglomerates is low and difficult to predict. In this report, we describe our attempts [...] Read more.
Conglomerate formation, where enantiomers within a racemic mixture self-segregate upon crystallization, is an advantageous property for obtaining chirally pure crystals and allows large-scale chiral resolution. However, the prevalence of conglomerates is low and difficult to predict. In this report, we describe our attempts to engineer conglomerates from racemate-forming compounds by integrating them into a conglomerate-forming matrix. In this regard, we found that Ni(II) and Fe(II) form molecular alloys with Zn(II) in [MxZn(1−x)(bpy)3](PF6)2 (where bpy = 2,2′-bipyridyl). Powder X-ray Diffraction (PXRD) and Energy-Dispersive X-ray spectroscopy (EDX) evidenced conglomerate crystallization with Ni(II) concentrations up to about 25%, while it was observed only for much lower concentrations of Fe(II). This can be attributed to the ability of [Ni(bpy)3](PF6)2 to access a metastable conglomerate phase, while no such phase has been detected in [Fe(bpy)3](PF6)2. Furthermore, the chiral phase appears to be favored in fast-growing precipitates, while the racemic phase is favored in slow re-crystallizations for both Ni(II) and Fe(II) molecular alloys. X-ray natural circular dichroism (XNCD) measurements on [Ni0.13Zn0.87(bpy)3](PF6)2 demonstrate the chirality of the nickel molecules within the zinc molecular matrix. Full article
Show Figures

Graphical abstract

13 pages, 4372 KiB  
Review
Anion-Complexation-Induced Emission Based on Aggregation-Induced Emission Fluorophore
by Dongxing Ren, Liangliang Zhang, Hongwei Qian and Tangxin Xiao
Chemistry 2023, 5(1), 242-254; https://doi.org/10.3390/chemistry5010019 - 07 Feb 2023
Cited by 3 | Viewed by 3554
Abstract
Aggregation-induced emission (AIE) materials have attracted increasing research interest in recent years due to their excellent fluorescence properties in an aggregated state. Concurrently, anion coordination interactions have played a key role in the development of supramolecular assemblies and sensors. In the past decade, [...] Read more.
Aggregation-induced emission (AIE) materials have attracted increasing research interest in recent years due to their excellent fluorescence properties in an aggregated state. Concurrently, anion coordination interactions have played a key role in the development of supramolecular assemblies and sensors. In the past decade, investigations towards fluorescent materials or sensors based on AIE and anion coordination interactions are continuously being reported. In this minireview, we briefly summarize the burgeoning progress of AIE-based materials and sensors driven by anion coordination interactions. We believe that an increasing number of achievements in anion-coordination induced emission materials will appear in the near future and will demonstrate potential applications, including bio-imaging and bio-sensors. Full article
(This article belongs to the Special Issue Supramolecular Anion Recognition: Principles and Applications)
Show Figures

Figure 1

Previous Issue
Next Issue
Back to TopTop