Feed Molar Ratio Research Articles

Resolution of trans-1,2-cyclohexanedicarboxylic acid containing two carboxylic groups by forming diastereomeric salts based on feeding molar ratio control.

To investigate the thermodynamic and molecular self-assembly mechanism of trans-1,2-cyclohexane dicarboxylic acid containing two carboxylic acid groups in the chiral resolution process, (S)-phenylethylamine was used as the chiral resolving agent. Two stoichiometric salts were formed when the raw materials were fed at different molar ratios: cyclohexane dicarboxylate monophenylethylamine salt and cyclohexane dicarboxylate diphenylethylamine salt. When the molar ratio of the (S)-phenylethylamine to trans-1,2-cyclohexane dicarboxylic acid was less than 3:1, trans-(1S,2S)-cyclohexane dicarboxylic acid was obtained with 97 e.e% purity. But when the molar ratio exceeded 3:1, the product was the racemic trans-(1,2)-cyclohexane dicarboxylic acid. In addition, single crystal structures of more soluble mono-salt, less soluble mono-salt, and less soluble di-salt were obtained. The weak intermolecular interactions and the way of the molecules packing in the crystals were analyzed. The hydrogen bond was stronger in the less soluble salt than that in the more soluble salt. And a "lock-and-key" structure in the hydrophobic layers makes it more tightly packed through the van der Waals interaction, which is responsible for the stability of less soluble salts.

Cobalt oxide-alumina catalysts for the methane-assisted selective catalytic reduction of SO2 to sulfur

Preventing emission of pollutants in any kind, is a way to protect global environment. The objective of this study is to develop cobalt catalysts supported on alumina for the conversion of the toxic gas SO2 into elemental sulfur using methane. Although several useful catalysts have been proposed, there is still a need to synthesize a catalyst with a high sulfur yield that is also persistent during on-stream stability. To this end, four different catalysts were prepared using the wet impregnation technique, with Co3O4 content ranging from 0 to 15 wt%. Catalytic activity tests were carried out at atmospheric pressure and temperatures ranging from 550 to 800 °C. The Al2O3–Co (15 %) catalyst exhibited superior performance, with a sulfur yield of 98.1 % at 750 °C. The catalytic stability of the best catalyst was examined using a 20 h on-stream stability test under the optimized conditions including an SO2/CH4 molar feed ratio of 2 at 750 °C. The structural changes of the used catalyst after the stability test were investigated using XRD and TPO analyses. It was revealed that sulfidation of Co3O4 after a short while, results in decreasing the sulfur yield from 98.1 % to 89.8 %.

Fischer–Tropsch synthesis over the Co–Ni/Al2O3 nanocatalyst: influence of process variables, modeling and optimization using response surface methodology

AbstractBACKGROUNDLight olefins production greatly influenced by the process conditions. In the present work Al2O3 supported Co‐Ni nanocatalysts were evaluated for production of light olefins. Incipient wetness impregnation procedure was used for catalyst synthesis. Catalysts were characterized for determining the physicochemical properties using various techniques of XRD, SEM, EDS, H2‐TPR, TPD, TEM, XPS, TGA, DSC, FT‐IR, and BET. The influence of process conditions (Pressure, Temperature and H2/CO inlet feed molar ratio) was investigated on the catalytic performance of Co‐Ni/γAl2O3 nanocatalyst toward lower olefins. Temperature, pressure, and feed ratio factors were changed in wide ranges of 250–450 °C, 1–12 bar, and 1–4 respectively. The Response Surface Methodology (RSM) method was employed for modeling and optimization.RESULTSThe optimum process conditions were obtained using the RSM method (T = 383 °C, P = 4 bar, and H2/CO = 1.92). The highest selectivity of light olefinic products and conversion of carbon monoxide and the lowest selectivity toward methane were obtained concurrently under the optimized conditions with desirability of 0.896.CONCLUSIONThe impact of inlet feed ratio, temperature, and pressure factors was investigated and it was found that the performance of the catalyst greatly depends on the operational parameters. © 2023 Society of Chemical Industry.

Heteropoly acid supported on hierarchical Y zeolite decorated SiC foam as the structured catalytic packing for reactive distillation synthesis of ethyl lactate

Rational design of catalytic packing is crucial in developing reactive distillation (RD) processes as efficient in-situ coupling of reaction and separation is required. Structured catalytic packings are advantageous than the conventional packings (e.g., inert packing + catalyst ‘tea bags’), due to the integration of the catalysis and separation function in one unit, mitigating mass/heat transfer limits. Herein, we present one of the latest developments in the field of structured catalytic packings, which was applied to a pilot-scale RD process of ethyl lactate (EL) synthesis via acid-catalyzed esterification and showed the advantages. The tungstophosphoric acid and hierarchical Y zeolite were uniformly decorated on corrugated silicon carbide (SiC) foam sheets via new preparation method (of ultrasound-assisted impregnation and microwave-assisted drying). The activity of the resulting materials was first assessed in a batch reactor, then the best candidate was employed by the pilot process. Findings from the pilot-scale RD experiments show that the developed structured SiC foam catalytic packing (SSFCP) exhibited an excellent performance (with the normalized conversion of 0.155 mol/gcatalyst), outperforming the conventional seepage catalytic packing internal (0.002 mol/gcatalyst). The influence of various variables (including molar feed ratio, feed position and reflux ratio) on the process performance of the pilot RD rig was also investigated and optimized, achieving a lactic acid conversion of 46.9 % and EL purity of 44.9 % (bottom). The good performance was attributed to the improved mass transfer thanks to SiC foam corrugated sheet (which encourage the vortex formation), thereby enabling more efficient coupling with the reaction. The SSFCP demonstrated reasonable stability, making it a promising candidate for relevant practical RD applications.

Surface Morphologies and Wettability Studies of pH‐Sensitive Nanofibrillated Membranes

AbstractThe pH‐sensitive membranes have been extensively used in various fields. Through the incorporation of specific functional groups on pH‐sensitive molecules, diverse surface energies and degrees of wettability can be achieved at different pH values. In this study, we transformed pH‐sensitive copolymers into nanofibrillated membranes to increase their sensitivity to pH in terms of the contact angle formed by liquid droplets on their surface. Because N,N‐dimethylaminoethyl methacrylate (DMAEMA) contains an amino group, it is sensitive to acidic and alkaline environments. Moreover, to enhance the functionality, we selected styrene and methyl methacrylate (MMA) for random copolymerization with DMAEMA. We then used anodized aluminum oxide (AAO) templates to process the two copolymers into biomimetic fibrillated membranes. The contact angles between various‐pH aqueous droplets and different membranes were measured. Our results indicated that when the droplets were alkaline, the contact angle on the nanofibrillated membranes was large. When the pH of the droplets was decreased, the contact angle also decreased. In addition, the membranes were found to be reusable after being tested, washed, and dried. The surface free energy of nanofibrillated membranes with different molar feed ratios was also investigated in this study by using the model of Owens, Wendt, Rabel and Kaelble.

Cyanogel-Based Preparation of Amorphous NiFe Nanoaggregates with Enhanced Activity and Stability for OER

The development of cost-efficient electrocatalysts for oxygen evolution reaction (OER) with high efficiency is crucial to widespread applications of water splitting for hydrogen production. In this work, porous three-dimensional (3D) amorphous NiFe nanoaggregates composed of interconnected nanograins were synthesized by a cyanogel-based wet chemical reduction method using the NiCl2/Na4Fe(CN)6 cyanogel as the precursor and NaBH4 as the reducing agent. The influence of the incorporated Fe amount was carefully studied by slightly changing the feeding molar ratios of the Ni/Fe atoms in the precursors. The intrinsic 3D backbone structure of the cyanogel resulted in crystal nuclei tending to generate along with the backbones, which is key to the formation of NiFe nanoaggregates with a porous 3D interconnected structure. The synthesized NiFe nanoaggregates with a 3D interconnected structure and high porosity, as well as the incorporation of Fe, are in favor of high surface area, more active sites, and abundant oxygen vacancies, leading to superior activity and stability of OER in alkaline electrolytes with a low overpotential of 0.35 V at 10 mA cm−2, a high current density of 24.8 mA cm−2 at 1.65 V, a small Tafel slope of 76.9 mV dec−1, and attractive durability in 1 M KOH solution.

Carbon dioxide conversion via reverse water-gas shift reaction: Reactor design

The reverse water gas shift (RWGS) reaction converts carbon dioxide (CO2) and hydrogen (H2) to syngas, which is used to produce various high-added-value chemicals. This process has attracted great interest from researchers as a way of mitigating the potential environmental impacts of this greenhouse gas, with emphasis on global warming. This work aims to model and simulate an industrial catalytic reactor using kinetic data for the RWGS reaction. The simulation was carried out in Aspen Plus® v10. The thermodynamic analysis showed that the appropriate conditions for the reaction are feed molar ratio (H2/CO2) of 0.8:1, 750 °C, and 20 bar. The RWGS process proceeds in a multi-tubular fixed bed reactor with 36.26% CO2 conversion and 96.41% CO selectivity, at residence times in the order of 2.7 s. These results are at near-equilibrium CO2 conversion with higher CO selectivity.

Two-Stage Conversion of Used Cooking Oil to Biodiesel Using Ion Exchange Resins as Catalysts

This study focuses on the development of a novel two-stage (esterification–transesterification) synthesis of biodiesel from used cooking oil (UCO) using ion exchange resins as catalysts. Esterification of the UCO has been conducted using various types of ion exchange resin catalysts. Purolite D5081, a hyper cross-linked resin, showed the best catalytic performance among all the catalysts investigated, with 92% of free fatty acid (FFA) conversion. The transesterification of pre-treated used cooking oil (P-UCO) was carried out sequentially using several acidic and basic ion exchange resin catalysts. In the screening process, the Diaion PA306s catalyst showed the best catalytic performance and was selected for the optimisation study. A triglyceride conversion of ca. 75% was recorded at the optimum reaction conditions (9% (w/w) catalyst loading, 328 K reaction temperature, 18:1 methanol to P-UCO feed mole ratio, and 350 rpm stirring speed). Furthermore, the reusability study of the Diaion PA306s catalyst gave a similar triglyceride conversion after a couple of cycles without losing its catalytic activity. A dry purification technique was found to give the lowest percentage of glycerides and glycerine content and, therefore, was chosen as the best biodiesel purification route.

Modelling and experimentation of a continuous nutrient recovery reactor – an assessment of mixing on reactor operation

Phosphorus recovery from human waste will help assure global food security, reduce environmental impact, and ensure effective stewardship of this limited and valuable resource. This can be accomplished by the precipitation of struvite (MgNH4PO4·6H2O) in a two-zone reactor, continuously fed with nutrient-rich hydrolysed urine and a magnesium solution. The solid struvite crystals are periodically “harvested”, removing accumulated crystal mass – and therefore recovered nutrients – from the process, and the operating campaign can, in principle, be continuously operated in a batch-continuous operating mode. A previously developed process model is augmented, incorporating two well-mixed volumes (upper zone and lower zone) that are coupled by intermixing forward and back flows. The intermixing back flow is parametrised and, therefore, adjusted for analysis. Crystal linear growth rate is modelled by a simple power-law kinetic, driven by the nutrient solution's saturation index (SI) of struvite. The instantaneous mass transfer rate of struvite constituents from liquid to solid phase is predicted, using the total interfacial area of the crystal population exposed to the well-mixed solution. This model describes a 12-L, laboratory reactor operated in the hybrid batch-continuous mode, although larger reactors could easily be accommodated, subject to their mixing behaviours. Experiments were performed at a 10-hour hydraulic residence time (HRT), which, importantly, is based on the volume of the well-mixed lower zone, since this is the volume of liquid that actively interacts with the suspended struvite crystals. The Mg/P feed molar ratio was varied (0.34, 0.64 and 1.29) to assess Mg feed rate-limiting behaviour. The concentration profiles of elemental P and Mg agree with experimentation, while P and Mg composition in the solid and X-ray diffraction support the production of struvite.

Novel highly efficient Ni-based mesoporous alumina-silica supported catalysts for methane dry reforming: Influence of nickel loading

In this study, the dry reforming of methane (DRM) was examined over the Ni/Al2O3-SiO2 catalysts with various nickel contents for the syngas production. The mesoporous nanocrystalline aluminosilicate with a high surface area (180.87 m2. g−1) was utilized as support for preparing the nickel-based catalysts by the wet impregnation method. The XRD, BET, H2-TPR, TPO, and FESEM analyses were performed to characterized the calcined catalysts. The obtained results indicated that the catalyst efficiency was enhanced by increasing the nickel loading values from 5 to 15 wt%, while the sample with 20 wt% Ni showed a lower efficiency compared to the 15 wt% Ni catalyst. The catalyst with 15 wt% Ni loading showed the best activity (XCO2 = 79%, XCH4 = 74.5%) and stability (activity drop for CH4 ≈ 2.7% and CO2 ≈ 0.3%) at 700 °C for 5 h. Also, the effects of the operational conditions, such as GHSV, CH4/CO2 ratio, long-term stability, reduction and calcination temperatures were studied. As GHSV changed from 12000 to 30000 ml/h.gcat, both conversions were declined. Also, the CO2 conversion was increased and the CH4 conversion was decreased by increasing the feed molar ratio (CH4: CO2) from 0.5 to 2. A constant syngas generation was obtained in long-term stability test of the reduced catalyst, which had no variation in activity during 10 h of reaction. In addition, there was no significant difference in results when the calcination (550, 650, and 750 °C) and reduction temperatures (600, 700, and 800 °C) were varied.

FABRICATION OF TERNARY SILICA-CALCIUM-MAGNESIUM AEROGELS: EFFECT OF FEEDING RATE AND MOLAR RATIO ON PROPERTIES

The silica-calcium-magnesium ternary aerogels were prepared by a solvent exchange method and a subsequent ambient pressure drying process. The effect of process parameters such as feeding rate (9-70 mL.min-1) and molar ratio (Si/(Ca:Mg) = 1:1 - 3:1) on the material characteristics including density, elemental content, surface area, pore size, pore volume, and morphology of powders were investigated. Aerogels were characterized by Fourier transform infrared spectroscopy (FTIR), inductively coupled plasma optical emission spectroscopy (ICP-OES), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), Barrett–Joiner–Halenda (BJH) and tapping density analysis. It was found that the molar ratio of Si/(Ca:Mg) could remarkably affect the surface area and density of aerogels, while the feeding rate had slight effect. The resultant aerogels exhibited high specific surface areas. The results showed that the aerogel has a Si/(Ca:3Mg) molar composition obtained with 9 mL.min-1 had the highest surface area (524 m2.g−1). The increase of Ca to Mg molar ratio caused a decrease in the surface area and density of samples. The resultant aerogels are promising candidates as adsorbents to remove various contaminants.

One‐Pot Polyol Synthesis and Scalable Production of Rh−Pd Alloy Nanorods with Tunable Compositions

AbstractCombining different precious metals to generate alloy nanocrystals with desirable shapes and compositions remains a challenge because of the low miscibility between these metals and/or the different reduction potentials of their salt precursors. Specifically, Rh and Pd are considered to be immiscible in the bulk solid over the entire composition range. Here we demonstrate that Rh−Pd alloy nanorods with well‐distributed and tunable compositions can be synthesized using a one‐pot polyol method. The success of our synthesis relies on the introduction of bromide as a coordination ligand to tune the redox potentials of Rh(III) and Pd(II) ions for the achievement of co‐reduction. The atomic ratio of the Rh−Pd alloy nanorods can be facilely tuned by changing the molar feeding ratio between the two precursors. We also systematically investigate the effects of water on the morphology of the Rh−Pd alloy nanocrystals. In an attempt to promote future use of these alloy nanorods, we successfully scale up their synthesis in a continuous‐flow reactor with no degradation to the product quality.

Developing Machine Learning Models for Catalysts in Oxidative Dehydrogenation of n‐butane

Abstract1,3‐butadiene is widely used as a raw material in the synthesis of rubber and automobile tires. In this study, machine learning models were utilized to predict the performance of catalysts in the oxidative dehydrogenation of n‐butane to 1,3‐butadiene., The datasets consisted of 304 data points generated from experiments conducted in a fixed‐bed reactor in the temperature range of 400– 500 °C and O2/C4 molar feed ratio of 1–4 mol/mol, using metal oxides of Nickel (Ni), Iron (Fe), Cobalt (Co), Bismuth (Bi), Molybdenum (Mo), Manganese (Mn) and Tungsten (W) supported on gamma alumina catalysts. Repeated 10‐fold cross‐validation was used, with 70 % of the datasets randomly selected for training and optimizing the models, whereas the remaining 30 % were used for testing the models. Among the various models examined, support vector machine with radial basis function (SVMR) model had the best coefficient of determination (R2) performance for the n‐butane conversion (training set: 98.3 % vs. test set: 88.3 %) and 1,3‐butadiene selectivity (training set: 94.0 % vs. test set: 88.6 %). In addition, the models had the lowest training and test mean absolute errors (MAE) and root mean square errors (RMSE). This study highlights the notable role of machine learning algorithms in enhancing the prediction of n‐butane oxidative dehydrogenation catalyst performance, thus promoting the development of more effective catalyst designs that exhibit high activity and selectivity, contributing positively to the field of heterogeneous catalysis. Notably, a user‐friendly application incorporating the developed machine learning models was developed, providing an invaluable tool for the real‐time on‐site prediction of catalyst performance in the oxidative dehydrogenation of n‐butane to 1,3‐butadiene. This application is a significant advancement, facilitating swift and accurate catalyst performance prediction, fostering more efficient catalyst design, streamlining, and revolutionizing the rubber and automobile tire synthesis industries.

Kinetics of acetic acid and isoamyl alcohol liquid esterification over Amberlyst-70

This work is a kinetic study on liquid phase esterification between acetic acid and isoamyl alcohol using Amberlyst-70 as catalyst. There are not scientific papers with fitted kinetic models for this esterification system using this catalyst. Experiments were carried out in a laboratory batch reactor at controlled temperature conditions. Molar feed ratio (between 2 and 0.5), temperature (between 353.15 K and 383.15 K) and catalyst load (between 0.5 wt% and 2.0 wt%) were the manipulated experimental conditions. Measured composition profiles were used to fit the parameters for three versions of the pseudohomogeneous model (PHM) that differ in their activity model. At the end, a PHM model based on molar fractions is recommended to explain composition changes due to the esterification reaction. Calculated values for activation energy and chemical equilibrium constant are E = 43 kJ/mol and KE = 5.22, respectively. In accordance with the Weisz-Prater criterion, intraparticle mass transport effects were appreciable in experimental kinetic tests due mainly to the particle size used (0.363 mm). In order to take into account diffusional effects, the effectiveness factor was calculated using the Maxwell-Stephan equations. Therefore, adjusted models are the intrinsic kinetics and they can be used to simulate and design reactors and reactive distillation operations.

Strategies for preventing gelation in preparation of hyperbranched benzoxazines with high performance

The gelation of linear oligomeric benzoxazine precursors (OBPs) and high-molecular-weight benzoxazine precursors (HMWBPs) have been noticed and addressed by various effective actions, while no similar reports on hyperbranched benzoxazoles have been available. A series of hyperbranched benzoxazines were synthesized by A2 + B3 method using 1,3-bis(3-aminopropyl)tetramethyldisiloxane (BATSi) and 1,1,1-tris(4-hydroxyphenyl)ethane (THPE) and paraformaldehyde, namely HB-TSis, to examine the conditions for preventing gelation. We found that in most cases, increasing the feeding molar ratio of -OH to NH2 group, prolonging the reaction time and increasing the reactant concentration were all favorable for the formation of soluble HB-TSis. Except when the molar ratio of -OH to NH2 was 2:3, a lower reactant concentration was more likely to avoid gel formation. A sufficiently high vacuum degree during drying was reported for the first time as a factor affecting the gelation of polybenzoxazine precursors. In addition, gelation-free HB-TSis exhibited high degrees of branching (DBs) and weight-average molecular weight (Mw) in the range of 0.58–0.69 and 6100–10,100 Da, respectively. Their cured resins, poly(HB-TSi)s, both perform well in terms of thermal stability with high char yield (Yc) varying from 37.9 to 56.2%, and flame retardancy with low the heat release capacity (HRC) varying from 49.9 to 81.9 J/(g K), which are capable of being applied as nonignitable materials.

A detailed thermodynamic analysis of CO2 hydrogenation to produce methane at low pressure

Evaluation of CO2, which is harmful to the environment, as an alternative energy source in CH4 production was investigated from a thermodynamic point of view. The methanation of CO2 is exothermic, however it does not occur at low temperatures due to the kinetic barrier. Thermodynamic modeling studies were carried out to determine the appropriate parameters in the reaction using the Gaseq software according to the Gibbs free energy minimization approach. For this purpose, the effects of H2/CO2 molar feed ratio (2, 3, 4 and 5), temperature (100–1100 °C) and pressure (1, 3, 5 and 10 atm) on CO2 conversion (XCO2) and CH4 selectivity (SCH4) were investigated. As a result, 99.87% XCO2 and 99.99% SCH4 were reached using the molar ratio of H2/CO2 = 4 at 1 at m and 100 °C. The CO2 methanation modeling study at low pressure range was studied in detail and low operating pressure proved to be appropriate.

Use of Pd-Ag Membrane Reactors for Low-Temperature Dry Reforming of Biogas-A Simulation Study.

Biogas is a valuable renewable energy source that can help mitigate greenhouse emissions. The dry reforming of methane (DRM) offers an alternative hydrogen production route with the advantage of using two main greenhouse gases, CO2 and CH4. However, its real application is limited mainly due to catalyst deactivation by coke formation and the reverse water gas shift (RWGS) reaction that can occur in parallel. Additionally, the typical dry reforming temperature range is 700-950 °C, often leading to catalyst sintering. A low-temperature DRM process could be in principle achieved using a membrane reactor (MR) to shift the dry reforming equilibrium forward and inhibit the RWGS reaction. In this work, biogas reforming was investigated through the simulation of MRs with thin (3.4 µm) and thick (50 µm) Pd-Ag membranes. The effects of the feed temperature (from 450 to 550 °C), pressure (in the range of 2-20 bar), and biogas composition (CH4/CO2 molar ratios from 1/1 to 7/3) were studied for the thin membrane through the calculation and comparison of several process indicators, namely CH4 and CO2 conversions, H2 yield, H2/CO ratio and H2 recovery. Estimation of the CO-inhibiting effect on the H2 molar flux through the membrane was assessed for a thick membrane. Simulations for a thin Pd-Ag MR show that (i) CO2 and CH4 conversions and H2 yield increase with the feed temperature; (ii) H2 yield and average rate of coke formation increase for higher pressures; and (iii) increasing CH4/CO2 feed molar ratio leads to higher H2/CO ratios, but lower H2 yields. Moreover, simulations for a thick Pd-Ag MR showed that the average H2 molar flux decreases due to the CO inhibiting effect (ca. 15%) in the temperature range considered. In conclusion, this work showed that for the considered simulation conditions, the use of an MR leads to the inhibition of the RWGS reaction and improves H2 yield, but coke formation and CO inhibition on H2 permeation may pose limitations on its practical feasibility, for which proper strategies must be explored.

A novel dynamic coating medium for single stranded DNA separation in capillary electrophoresis: Thermosensitive hydrogel nanoparticles

Nowadays, research on single-stranded DNA (ssDNA) requires a quick, effective and easy operation method to separate small ssDNA fragments from the organism and ssDNA production process to realize their application in gene therapy and drug diagnosis. Herein, a novel separation matrix of thermosensitive hydrogel nanoparticles (NPs) was proposed, which has been successfully applied to the isolation of biomacromolecules such as enzymes, peptides and proteins, based on the desirable properties of various monomers and advantages, such as high sieving capacity, tunability of hydrophilic and hydrophobic performance and non-toxicity. The flexible particles were prepared by precipitation polymerization method in aqueous solution while N-isopropylacrylamide (NIPAm), acrylic acid (AAc) and N-t-butyl acrylamide (TBAm) was performed as co-monomer, which were first used as the dynamic coating to separate small fragments of ssDNA in capillary electrophoresis (CE). The synthesized NPs were bound to the inner wall of the capillary through non-covalent interactions forming stable dynamic coating to affect the electroosmotic flow and improve the separation reproducibility of ssDNA fragments. Based on the formulation design of NPs and condition optimization of electrophoresis, the running buffer TG (25 mM Tris, 192 mM glycine, pH 8.3) was modified by 4 mg·mL−1 optimized NPs aqueous suspension addition while its molar feed ratio of NIPAm /AAc /TBAm /BIS was 83/5/10/2 and particle size was about 214 nm. Both the formulation design and temperature sensitivity of hydrogel nanoparticles contributed to the DNA separation efficiency. The designed NPs with low viscosity provide an approach to increase their capability as the separation medium for small fragment DNA with important physiological functions great potential and promise.

Dry reforming of methane using bimetallic Pt–Ni/Ti-SBA-15: Effect of Si/Ti ratio on catalytic activity and stability

A one-pot hydrothermal technique was used to make a series of Ti-incorporated mesoporous SBA-15 with varying Si/Ti ratios. The synthesized mesoporous materials were modified by introducing Ni (9%) as active metal and Pt (0.5%) as promoter using nickel nitrate and chloroplatinic acid, respectively, as metal precursors through incipient wetness impregnation method. All the catalysts and supports were characterized by X-ray diffraction, BET surface area, Fourier Transform–Infrared spectroscopy, UV–Visible diffuse reflectance spectroscopy, H2–temperature-programmed reduction, NH3–temperature-programmed desorption, transmission electron microscopy, and thermogravimetric analysis. The catalysts were subjected to dry reforming of methane using CH4/CO2 (molar feed ratio of 1:1) with a gas hourly space velocity (GHSV) of 36,000 mL. g−1. h−1 at a temperature range of 400–800 °C. The characterization results confirmed the incorporation of titanium ions in the SBA-15 matrix. However, Si/Ti loadings of 10 and 20 exhibited low extra-framework anatase phase titania levels, and high surface acidity. Among the subjected catalysts, Pt–Ni/Ti-SBA-15 (Si/Ti = 10) showed higher catalytic activity (CH4 = 84% and CO2 = 91%) with a H2/CO ratio of 3.6 after an 8 h reaction, and exhibited higher stability and coke tolerance than the bare catalysts and other modified Pt–Ni/Ti-SBA-15 catalysts. The characterization results of spent catalysts also confirmed low coke deposition on titanium-incorporated catalysts. The remarkable performance of the Pt–Ni/Ti-SBA-15 towards CH4 conversion and CO2 conversion may be related to strong metal–support interaction, presence of strong and weak acid sites, well-dispersed active metals and bi-metallic interaction.

Biodegradable polycarbonates from lignocellulose based 4-pentenoic acid and carbon dioxide.

The production of biodegradable polycarbonate by copolymerizing CO2 with epoxides has emerged as an effective method to utilize CO2 in response to growing concerns about CO2 emissions and plastic pollution. Previous studies have mainly focused on the preparation of CO2-based polycarbonates from petrochemical-derived propylene oxide (PO) or cyclohexene oxide (CHO). However, to reduce dependence on fossil fuels, the development of 100% bio-based polymers has gained attention in polymer synthesis. Herein, we reported the synthesis of glycidyl 4-pentenoate (GPA) from lignocellulose based 4-pentenoic acid (4-PA), which was further copolymerized with CO2 using a binary catalyst SalenCoCl/PPNCl to produce bio-based polycarbonates with vinyl side chains and molecular weights up to 17.1kg/mol. Introducing a third monomer, PO, allows for the synthesis of the GPA/PO/CO2 terpolymer, and the glass transition temperature (T g) of the terpolymer can be adjusted from 2°C to 19°C by controlling the molar feeding ratio of GPA to PO from 7:3 to 3:7. Additionally, post-modification of the vinyl side chains enables the production of functional polycarbonates, providing a novel approach to the preparation of bio-based materials with diverse side chains and functions.