Molecular Dynamics Investigation of the Potentiality of Zeolite NaY for Trimethylbenzene Isomer Separation: An Insight in Terms of Structure, Energetics, and Dynamics

Isomers of trimethylbenzene (TMB) are the important constituent chemicals used in a variety of industrial applications, including the production of synthetic resins, insecticides, dyes, pigments, and pharmaceuticals. However, these applications require them in their purest form, mandating them to separate from their mixtures. Due to the similar physicochemical properties of the TMB isomers, traditional methods such as cryogenic distillation are very energy-expensive. Thus, adsorption-based separation methods using nanoporous adsorbents such as zeolite are a cost-effective alternate. Such adsorption-based separation methods, however, require the isomers to exhibit significant differences in their adsorption and diffusion properties. In the present report, we carried out a thorough investigation of the structural, energetic, and dynamical properties of the three isomers of TMB in a faujasite-type zeolite NaY containing cage-like pores. Our results indicate that 1,2,4-TMB exhibits the most facile translational and out-of-plane rotational motions in contrast to the other two isomers. However, the in-plane rotational motions are seen to be more facile in 1,2,3-TMB compared with the other two isomers. It is evident from our analysis that the dynamics are dominantly driven by entropy. These results highlight the importance of the porous material in the case of the separation of a given hydrocarbon mixture.

2-step lignin-first catalytic fractionation with bifunctional Pd/ß-zeolite catalyst in a flow-through reactor

This work demonstrates an additive and hydrogen-free 2-step lignin-first fractionation in flow-through. First, solvolytic delignification renders lignin liquors with its native chemical structure largely intact; and second, ß-zeolite catalytic depolymerization of these liquors leads to similar monomer yields as the corresponding 1-step fractionation process. Higher delignification temperatures lead to slightly lower ß-O-4 content in the solvated lignin, but does not affect significantly the monomer yield, so a higher temperature was overall preferred as it promotes faster delignification. Deposition of Pd on ß-zeolite resulted in a bifunctional hydrogenation/dehydration catalyst, tested during the catalytic depolymerization of solvated lignin with and without hydrogen addition. Pd/ß-zeolite displays synergistic effects (compared to the Pd/γ-Al2 O3 and ß-zeolite tested individually and as a mixed bed), resulting in higher monomer yield. This is likely caused by increased acidity and the proximity between the metallic and acid active sites. Furthermore, different ß-zeolite with varying SAR and textural properties were studied to shed light onto the effect of acidity and porosity in the stabilization of lignin monomers. While some of the catalysts showed stable performance, characterization of the spent catalyst reveals Al leaching (causing acidity loss and changes in textural properties), and some degree of coking and Pd sintering.

Crystal Engineering of TiO2 for Enhanced Catalytic Oxidation of 1,2-Dichloroethane on a Pt/TiO2 Catalyst

Crystal engineering of metal oxide supports represents an emerging strategy to improve the catalytic performance of noble metal catalysts in catalytic oxidation of chlorinated volatile organic compounds (CVOCs). Herein, Pt catalysts on a TiO₂ support with different crystal phases (rutile, anatase, and mixed phase (P25)) were prepared for catalytic oxidation of 1,2-dichloroethane (DCE). The Pt catalyst on P25-TiO₂ (Pt/TiO₂-P) showed optimal activity, selectivity, and stability, even under high-space velocity and humidity conditions. Due to the strong interaction between Pt and P25-TiO₂ originating from the more lattice defects of TiO₂, the Pt/TiO₂-P catalyst possessed stable Pt⁰ and Pt²⁺ species during DCE oxidation and superior redox property, resulting in high activity and stability. Furthermore, the Pt/TiO₂-P catalyst possessed abundant hydroxyl groups, which prompted the removal of chlorine species in the form of HCl and significantly decreased the selectivity of vinyl chloride (VC) as the main byproduct. On the other hand, the Pt/TiO₂-P catalyst exhibited a different reaction path, in which the hydroxyl groups on its surface activated DCE to form VC and enolic species, besides the lattice oxygen of TiO₂ for the Pt catalysts on rutile and anatase TiO₂. This work provides guidance for the rational design of catalysts for CVOCs.

Greenly synthesized zeolites as sustainable materials for corrosion protection: Design, technology and application

The progress and use of effective and economic anticorrosive resources are in high mandate due to huge safety and economic concerns about corrosion. Significant advancements have already been achieved that help in minimizing corrosion costs up to US $375 to US $875 billion annually. The use of zeolites in anticorrosive and self-healing coatings is well-studied and documented in many reports. The self-healing property of zeolite-based coatings is attributed to their ability to provide anticorrosive protection in the defected areas through forming protective oxide films i.e. passivation. The synthesis of zeolites from the traditional hydrothermal method is associated with several drawbacks including their high cost and discharge of harmful gases such as oxides of nitrogen (NO_x) and greenhouse gases (CO₂ and CO). In view of this, some green approaches such as solvent-free, organotemplate-free, use of safer organic templates, green solvents (e.g. ILs) and energy efficient (MW and US) heating, one-step reactions (OSRs) etc. are adopted in the green synthesis of zeolites. Recently, the self-healing properties of greenly synthesized zeolites are documented along with their mechanism of corrosion inhibition.

Transformation of CO2 with Glycerol to Glycerol Carbonate over ETS-10 Zeolite-Based Catalyst

Catalytic conversion of CO₂ with the surplus glycerol (GL) produced from biodiesel manufacturing has attracted much academic and industrial attention, which proves the urgent requirement for developing high-performance catalysts to afford significant environmental benefits. Herein, titanosilicate ETS-10 zeolite-based catalysts with active metal species introduced by impregnation were employed for coupling CO₂ with GL to efficiently synthesize glycerol carbonate (GC). The catalytic GL conversion at 170 °C miraculously reached 35.0% and a 12.7% yield of GC was obtained on Co/ETS-10 with CH₃CN as a dehydrating agent. For comparison, Zn/ETS- Cu/ETS-10, Ni/ETS-10, Zr/ETS-10, Ce/ETS-10, and Fe/ETS-10 were also prepared, which showed inferior coordination between GL conversion and GC selectivity. Comprehensive analysis revealed that the presence of moderate basic sites for CO₂ adsorption-activation played a crucial role in regulating catalytic activity. Moreover, the appropriate interaction between cobalt species and ETS-10 zeolite was also of great significance for improving the glycerol activation capacity. A plausible mechanism was proposed for the synthesis of GC from GL and CO₂ in the presence of CH₃CN solvent over Co/ETS-10 catalyst. Moreover, the recyclability of Co/ETS-10 was also measured and it proved to be recycled at least eight times with less than 3% decline in GL conversion and GC yield after a simple regeneration process through calcination at 450 °C for 5 h in air.

Laboratory Study of the Effect of Zeolite and Cement Compound on the Unconfined Compressive Strength of a Stabilized Base Layer of Road Pavement

Soil stabilization using cement is regarded as one of the conventional methods to improve the engineering properties of soil used in infrastructure and road bodies. Considering the environmental problems caused by the production and consumption of cement, finding a suitable replacement for cement is necessary. The present study aims to experimentally evaluate the effect of using zeolite instead of cement in the stabilization of pavement layers. In this research, only 5% of cement was used in the control sample, while zeolite was used instead of cement in other samples by 20, 30, 40, and 60 wt.% of cement. According to the analysis, the highest unconfined compressive strength was obtained in the sample containing 30% (wt.% of cement) of zeolite instead of cement (equivalent to 1.5% of the total stabilizing materials) after 28 days of treatment, which was 29% more than that of the sample without zeolite. Evaluating the fracture strains reveals that using zeolite instead of cement increases the fracture strain by 33%, and in other words, changes the behavior of the sample from brittle mode to soft mode.

Research of Zeolite and Zeolite Water from Rhodope Mountains, Bulgaria

The physicochemical composition and antibacterial effect of aqueous zeolite infusion (spring zeolite water Sevtopolis with zeolite from deposit Beli plast, Bulgaria) obtained for 12 and 36 hours was tested. Ordinance No. 9/2001, Official State Gazette, issue 30, and Decree No.178/23.07.2004 regarding the quality of water intended for drinking and household purposes were applied to study the physicochemical composition. Staphylococcus aureus-ATCC and TSA-MRSA and Escherichia coli ATCC were used in the studies. Both tested zeolite waters reduced the amount of viable E. coli and S. aureus cells even when they were in high concentrations (106 cells/ml). The effect of the 36-hour infusion was better, under the influence of which after 60 minutes the number of live bacteria of both tested species decreases by almost half compared to the initial amounts. Slightly higher sensitivity to two zeolite waters was shown by E. coli, whose cells were reduced to about 35% after two hours of exposure zeolite water tested. However, about 20% of the cells of the tested bacteria survived even after 96 hours of exposure to these waters. Only in E. coli no growth was found after 96 hours of exposure to 12 hours zeolite water. These results show the effectiveness of zeolite for water purification from Gram-positive and Gram-negative bacteria, as well as prospects for the use of zeolite water as a prophylactic and auxiliary treatment for bacterial infections.

Recent advances in zeolite-encapsulated metal catalysts: A suitable catalyst design for catalytic biomass conversion

Metal clusters and nanoparticles, which have been used to tune the acidity of zeolite support, are beneficial for promoting the catalytic performance of various reaction processes, including biomass conversion. However, catalytic instabilities resulting from metal coalescence, sintering and leaching are major problems that need to be resolved. Therefore, metal encapsulation within the zeolite structure has been proposed as a feasible solution for this issue, particularly for biomass conversions that require high temperatures. In this current review, recent developments in metal confinement techniques are described along with experimental examples of biomass upgrading reactions. The present and future perspectives of zeolite-encapsulated metal catalysts in biomass conversions are also given.

Progress of Catalytic Valorization of Bio-Glycerol with Urea into Glycerol Carbonate as a Monomer for Polymeric Materials

Versatile polymers with highly adjustable characteristics and a broad range of applications are possibly developed owing to the contemporary industrial polymerization techniques. However, industrial production of large amounts of chemicals and polymers heavily depends on petroleum resources which are dwindling and unsustainable. Of particular interest is to utilize sustainable and green resources for the manufacture of polymeric materials. The efficient transformation of bio-glycerol to the relevant functional derivatives are being widely investigated owing to the increasing demand for enhancing the value of glycerol manufactured by biodiesel and oleochemical industries. With respect to glycerol-based polymer chemistry and technology, considering the economy and environmental benefits, using effective catalysts for the selective transformation of bio-glycerol and urea into glycerol carbonate (GC) as a polymer monomer is of great significance. In this review, recent studies on GC synthesis involving the catalysts such as zinc, magnesium, tungsten, ionic liquid-based catalysts, reaction conditions, and possible pathways are primarily described. Some critical issues and challenges with respect to the rational development of heterogeneous catalytic materials like well-balanced acid-base sites are also illustrated.

M[B2(SO4)4] (M = Mn, Zn)—Syntheses and Crystal Structures of Two New Phyllosilicate Analogue Borosulfates

Borosulfates are a rapidly expanding class of silicate analogue materials, where the structural diversity is expected to be at least as large as known for silicates. However, borosulfates with cross-linking of the anionic network into two or even three dimensions are still very rare. Herein, we present two new representatives with phyllosilicate analogue topology. Through solvothermal reactions of ZnO and MnCl2∙4H2O with boric acid in oleum (65% SO3), we obtained single-crystals of Mn[B2(SO4)4] (monoclinic, P21/n, Z = 2, a = 8.0435(4), b = 7.9174(4), c = 9.3082(4) Å, β = 110.94(1)°, V = 553.63(5) Å3) and Zn[B2(SO4)4] (monoclinic, P21/n, Z = 2, a = 7.8338(4), b = 8.0967(4), c = 9.0399(4) Å, β = 111.26(1)°, V = 534.36(5) Å3). The crystal structures reveal layer-like anionic networks with alternating vierer- and zwölfer-rings formed exclusively by corner-linked (SO4)- and (BO4)-tetrahedra.

In-Situ Catalytic Fast Pyrolysis of Pinecone over HY Catalysts

The in-situ catalytic fast pyrolysis of pinecone over HY catalysts, HY(30; SiO2/Al2O3), HY(60), and 1% Ni/HY(30), was studied by TGA and Py-GC/MS. Thermal and catalytic TGA indicated that the main decomposition temperature region of pinecone, from 200 to 400 °C, was not changed using HY catalysts. On the other hand, the DTG peak heights were differentiated by the additional use of HY catalysts. Py-GC/MS analysis showed that the efficient conversion of phenols and other oxygenates formed from the pyrolysis of pinecone to aromatic hydrocarbons could be achieved using HY catalysts. Of the HY catalysts assessed, HY(30), showed higher efficiency in the production of aromatic hydrocarbons than HY(60) because of its higher acidity. The aromatic hydrocarbon production was increased further by increasing the pyrolysis temperature from 500 to 600 °C and increasing the amount of catalyst due to the enhanced cracking ability and overall acidity. The use of 1% Ni/HY(30) also increased the amount of monoaromatic hydrocarbons compared to the use of HY(30) due to the additional role of Ni in enhancing the deoxygenation and aromatization of reaction intermediates.

Comprehensive Analysis of the Copper Exchange Implemented in Ammonia and Protonated Forms of Mordenite Using Microwave and Conventional Methods

This article presents the results of a comprehensive study of copper-exchanged mordenite samples prepared from its ammonia and protonated forms (Si/Al = 10) using two different ion exchange methods: conventional and microwave (MW)-assisted. The protonated H-MOR-10 sample was obtained by calcination of commercial NH₄MOR-10; in this case, a slight degradation of the mordenite framework was observed, but the resulting defects were partially restored after the first ion-exchange procedure of protons for copper ions. The level of copper exchange in the studied materials was found to be limited to 70%. Regardless of the exchange procedure, the replacement of ammonium or proton ions with copper led to a linear increase in the a/b ratio of cell parameters in accordance with an increase in the level of copper exchange, which means that all Cu²⁺ cations are ion-exchangeable and enter the main mordenite channel. Thermal analysis indicated a correlation between the replacement of various ammonium and hydroxyl groups by copper ions during the exchange treatment and their dehydroxylation energy during thermal decomposition. As a conclusion: MW-assisted treatment proved itself as an efficacious method for the synthesis of copper-exchanged mordenites, which not only significantly reduces preparation time but leads to a systematically higher copper exchange level.

Trends in Solid Adsorbent Materials Development for CO2 Capture

A recent report from the United Nations has warned about the excessive CO₂ emissions and the necessity of making efforts to keep the increase in global temperature below 2 °C. Current CO₂ capture technologies are inadequate for reaching that goal, and effective mitigation strategies must be pursued. In this work, we summarize trends in materials development for CO₂ adsorption with focus on recent studies. We put adsorbent materials into four main groups: (I) carbon-based materials, (II) silica/alumina/zeolites, (III) porous crystalline solids, and (IV) metal oxides. Trends in computational investigations along with experimental findings are covered to find promising candidates in light of practical challenges imposed by process economics.

Advances in the use of CO2 as a renewable feedstock for the synthesis of polymers

Carbon dioxide offers an accessible, cheap and renewable carbon feedstock for synthesis. Current interest in the area of carbon dioxide valorisation aims at new, emerging technologies that are able to provide new opportunities to turn a waste into value. Polymers are among the most widely produced chemicals in the world greatly affecting the quality of life. However, there are growing concerns about the lack of reuse of the majority of the consumer plastics and their after-life disposal resulting in an increasing demand for sustainable alternatives. New monomers and polymers that can address these issues are therefore warranted, and merging polymer synthesis with the recycling of carbon dioxide offers a tangible route to transition towards a circular economy. Here, an overview of the most relevant and recent approaches to CO2-based monomers and polymers are highlighted with particular emphasis on the transformation routes used and their involved manifolds.

Microwave-Assisted Catalytic Solvolysis of Lignin to Phenols: Kinetics and Product Characterization

Lignin, a major component of lignocellulosic biomass, is a valuable source of phenolic and aromatic compounds. It is, therefore, vital to develop strategies to selectively deconstruct lignin to valuable chemicals. This study focuses on the kinetics of depolymerization of lignin and the production of phenols via a microwave-assisted catalytic process at mild conditions of 80 °C in dimethyl sulfoxide/water medium. Four different catalysts used in this study, viz., Fe2O3, LaFeO3, ZrO2, and zeolite-Y hydrogen (ZYH), were characterized for structure, specific surface area, and surface morphology. The molecular weight reduction of lignin and the evolution of phenolic monomers and oligomers were monitored using various techniques, and the rate constants of lignin degradation in the presence of different catalysts were determined using a continuous distribution kinetics model, assuming scission of the lignin macromolecule at any random position. The rate constants (min-1) followed the trend: ZYH (26 × 10-4) ≈ LaFeO3 (25 × 10-4) > ZrO2 (22 × 10-4) > Fe2O3 ≈ no catalyst (16 × 10-4). Vanillic acid (15 mg g-1) and methyl phenol (17 mg g-1) were the major phenolics obtained with LaFeO3, whereas coniferaldehyde (13 mg g-1) was the major phenolic compound with Fe2O3. Vanillin was produced at ca. 11 mg g-1 with both Fe2O3 and ZYH. LaFeO3 is shown to be a promising catalyst for both molecular weight reduction of lignin and the production of monomeric phenols, whereas the use of Fe2O3 results in the formation of only phenols, possibly via specific end-chain depolymerization. The selectivities of the monomeric phenols were higher with these two catalysts, whereas with ZYH and ZrO2, the selectivities of the oligomers were better. The reusability of the catalysts and the effect of catalyst loading on kinetics of lignin depolymerization were also evaluated.

Carbonic anhydrase inspired poly(N-vinylimidazole)/zeolite Zn-β hybrid membranes for CO2 capture

Hydrophobic channels of ion-exchanged zeolite β imitate the function of the hydrophobic pocket in carbonic anhydrase.

Cu–Mn composite oxides: highly efficient and reusable acid–base catalysts for the carbonylation reaction of glycerol with urea

A series of Cu–Mn composite oxides were prepared by co-precipitation and used as catalysts for the carbonylation of glycerol.

3D-printed zeolite monoliths with hierarchical porosity for selective methanol to light olefin reaction

Herein, we report the rapid synthesis of customized zeolite monoliths with various compositions and hierarchical porosity (macro–meso–micro) using a 3D printing technique.

Potential and challenges of zeolite chemistry in the catalytic conversion of biomass

This review emphasizes the progress, potential and future challenges in zeolite catalysed biomass conversions and relates these to concepts established in existing petrochemical processes.

Volume accessibility of acid sites in modified montmorillonite and triacetin selectivity in acetylation of glycerol

Generated space around acid centers by dealumination termed as ‘volume accessibility’ which helps glycerol to interact with acylium ions formed on the acid sites more effectively leading to the product triacetin.

Superior performance of mesoporous tin oxide over nano and bulk forms in the activation of a carbonyl group: conversion of bio-renewable feedstock

The efficiency of mesoporous tin oxide as an acid catalyst in the activation of a carbonyl group through selected organic transformations involving the conversion of biomass derived molecules to value-added chemicals is reported.