Gas To Liquid Research Articles

A Stable Layered Microporous MOF Assembled with Y-O Chains for Separation of MTO Products.

Benefiting from highly tunable pore environments, some metal-organic frameworks (MOFs) have recently shown promising prospects in the separation of methanol-to-olefin (MTO) products (mainly C3H6 and C2H4). However, the "trade-off" between gas storage capacity and selectivity always results in inefficient separation. In addition, poor stability of MOFs also limits practical separation applications. Herein, we have successfully assembled a layered Y-MOF (FJI-W9) with bent diisophthalate ligands (H4L), Y-O chains, and 2-fluorobenzoic acids. As expected, FJI-W9 not only exhibits good chemical stability but also shows significant potential for C3H6/C2H4 separation. For FJI-W9, the C3H6 uptake at 298 K and 10 kPa is 63 cm3/g, and the IAST selectivity of FJI-W9 for C3H6/C2H4 (V/V = 50/50) is calculated to be 20.5. To the best of our knowledge, both C3H6 uptake and selectivity of FJI-W9 surpass most porous materials. GCMC simulation indicates that the special supramolecular binding sites in FJI-W9 have much stronger interactions with C3H6 than C2H4 molecules. More importantly, practical breakthrough experiments demonstrate that FJI-W9 can effectively separate C3H6/C2H4 (50/50) mixtures, thus obtaining high-purity C2H4 and C3H6, respectively.

Assessing the lightning performance of sustainable GTL type dielectric liquids versus mineral oils and synthetic ester in a non-uniform electric field

This paper presents for the first time the results of complex comparative tests on the lightning performance of a wide range of sustainable electrical insulating liquids made in GTL (Gas-to-Liquids) technology. Three different GTLs are compared with conventional mineral oils (inhibited and uninhibited) as well as biodegradable synthetic ester. Tests are aimed to determine Lightning Impulse Breakdown Voltage (LIBV) and Acceleration Voltage (Va) at standard lightning impulse voltage of both polarities. Those are performed at 25 mm gap distance of point-sphere electrode setup representing non-uniform electric field distribution. In addition, light emission is studied as well. Results show that for the conditions of experiment LIBV values tend to be similar for all tested dielectric liquids with a slight advantage of mineral oils at negative polarity and GTL-I oil at positive polarity. In turn, in terms of Va, it was found that at negative polarity the GTL oils are, in general, fully comparable with a high grade inhibited mineral oil. The Va of GTLs is in the range 260–275 kV versus 255–260 kV that characterizes mineral oils. When considering positive polarity the GTL-I is slightly inferior to other hydrocarbons with Va equal to 195 kV versus 230–255 kV characterizing other GTLs and mineral oils. For both polarities tested synthetic ester has much lower acceleration voltage in relation to hydrocarbon liquids including GTLs, which constitutes a huge disadvantage of the ester. Although the studies are limited to only one gap distance and non-uniform electric field distribution, it can be stated that the GTLs are worth to be examined as alternative to mineral oil when considering LIBV and Va as the analysed quantities. In addition, a special added value of the performed measurements should be mentioned that the measurements confirmed that Va parameter may be a good dielectric indicator of a dielectric liquid performance, especially when examining new product introduced to the market.

Experimental Study of Turbulent Premixed Flames of Gas-to-Liquids (GTL) Fuel in a Fan-Stirred Combustion Bomb

This study experimentally investigates the turbulent flame speeds (St) of Gas-to-Liquids (GTL) fuel and a 50/50 blend with diesel across turbulence intensities (u') ranging from 0.5 to 3.0 m/s and equivalence ratios (Φ) from 0.7 to 1.3. Experiments were conducted using a cylindrical fan-stirred combustion bomb at an initial temperature (Ti) of 463 K and atmospheric pressure under near homogeneous and isotropic turbulence (HIT) conditions. A pressure transducer measured the St of the propagating GTL flame. High-speed imaging reveals that changes in flame brightness are associated with variations in flame temperature and soot incandescence. Compared to diesel, stoichiometric GTL and the 50/50 diesel-GTL blend showed peak combustion pressure reductions of 8.9% and 4.9%, respectively. Rich diesel fuel and lean GTL exhibited higher pressure rise rates, flame propagation, and St due to their Lewis numbers (Le) being less than one, enhancing flame-turbulence interaction. At u` of 0.5, 1.5, and 3.0 m/s, St for GTL increased by approximately 3.6%, 5.3%, and 2.8%, respectively, when compared to diesel, with these increases observed at Φ < 1.1. Transition from wrinkled to corrugated flamelets with increasing u` supports models predicting flame stability and potential industrial combustion efficiency improvements. Comparisons with numerical St results using the Zimont Turbulent Flame Speed Closure (Zimont TFC) model showed good agreement at lower (u' = 0.5 m/s) and mid-range (u' = 2.0 m/s) turbulence intensities but discrepancies at higher intensities (u' = 3.0 m/s), highlighting the need to refine numerical models for more accurate predictions across all turbulence levels.

Evaluation of activated carbon fiber packed-bed for the treatment of gas-to-liquid wastewater: experimental, modeling and ASPEN Adsorption simulation

AbstractThis study investigates the continuous adsorption treatment of gas-to-liquid (GTL) wastewater from the Fischer-Tropsch process using activated carbon fiber (ACF) as the adsorbent. ACF, characterized by a high surface area of 1232 m²/g, was utilized to treat actual GTL wastewater, which contains long and short-chain alcohols, fatty acids, and other hydrocarbons. Experimental analysis, packed-bed modeling and simulation using ASPEN Adsorption were employed to understand the dynamics of the adsorption process. The experimental setup involved a bench-scale column packed with specified masses of ACF, with GTL wastewater pumped upward through the column at varying flow rates. Breakthrough curves were constructed to assess column performance, with parameters, such as feed flow rate (5 and 10 mL/min) and packing mass (5 and 10 g) systematically varied. The results demonstrate a significant influence of these parameters on column performance, with higher flow rates initially accelerating adsorption kinetics. Conversely, increasing packing mass extends the duration of column saturation, improving efficiency. Empirical models, including the Yoon-Nelson and El-Naas et al. models were applied to fit the experimental data, with the latter showing superior performance in representing the adsorption mechanism within the column. Quantitative analysis of model fitting using Akaike Information Criteria (AIC) identified the Yoon-Nelson and El-Naas et al. model as the most suitable for describing the GTL wastewater/ACF system, with an AIC weight parameter of 0.33 and R2 averaging 86.5%. Furthermore, simulation results from ASPEN Adsorption exhibited strong agreement with experimental data, validating its efficacy for simulating liquid adsorption processes. The study provides valuable insights into the design and optimization of large-scale wastewater treatment systems, offering practical solutions to address global water challenges.

Applications of in-situ solid-state nuclear magnetic resonance (ssNMR) in methanol to olefins (MTO) reaction

Applications of in-situ solid-state nuclear magnetic resonance (ssNMR) in methanol to olefins (MTO) reaction

A mixed polynuclear clusters-based Y-MOF with an unprecedented (12, 12, 18)-c topology: highly efficient propylene/ethylene separation and iodine adsorption

The design and synthesis of highly stable metal–organic frameworks (MOFs) bearing unpredictable polynuclear clusters and new topologies are important for the development of novel and complicated MOFs. Herein, the polynuclear rare-earth (RE) clusters with more coordination modes and the small V-shaped ligand (2,5-thiophenedicarboxylic acid) were chosen, and subsequently JLU-MOF132 with three different yttrium clusters (two independent Y6 and one Y9 clusters) and a novel (12, 12, 18)-connected topology was successfully synthesized. Notably, JLU-MOF132 exhibits high porosity, excellent thermal, acid-base, and solvent stabilities. JLU-MOF132 shows considerable potential in methanol-to-olefins (MTO) products (C3H6 and C2H4) separation. The high ideal adsorbed solution theory C3H6/C2H4 selectivities (9.2, 10.6, and 15.1) and the breakthrough experiments results, including the high C2H4 purity (>99.9 %) and productivities (26.1, 73.1, and 101.0 L·kg-1), demonstrate its practical purification capability. Semi-empirical tight binding (xTB) quantum chemical calculations explain the mechanisms that differentiate C2H4 and C3H6 adsorption in JLU-MOF132. In addition, JLU-MOF132 also displays outstanding radioactive iodine adsorption performance, with an iodine uptake of 750 mg·g-1 in vapor and 153 mg·g-1 in cyclohexane solutions. Briefly, this work not only demonstrates the viability of employing the V-shaped ligand to increase the structural diversity of highly stable MOFs, but also enhances the application potential of MOFs in the fields of the MTO products separation and radioactive iodine adsorption.

A design kinetic and hydrodynamic study of a coupled dual fluidized bed MTO reactor-regenerator system

The methanol-to-olefin (MTO) process, employing a dual-fluidized bed system, has introduced a new and reliable route for producing light olefins. This study intends to employ a comprehensive approach to simultaneously design and evaluate the reactor and regenerator performance. Namely, an inclusive design for a pilot-scale MTO system, encompassing the reactor, regenerator, interconnected catalyst transfer pipelines, and other critical operational aspects, is presented. The computational fluid dynamics (CFD) method using the Eulerian-Eulerian model was used to evaluate hydrodynamics, while the coupled reactor-regenerator kinetic model was developed by combining reaction kinetics with the two-phase model. The models were validated against experimental data and demonstrated a promising agreement. More importantly, an innovative procedure was devised to apply these modelling techniques to design this dual-fluidized bed system—the final design for the 10 kg catalyst inventory in the reactor at the pilot scale. The system achieves methanol conversion of 98.87 %, with ethylene and propylene product mass fractions of 45.51 % and 37.79 %, respectively.

Mechanism of methanol-to-olefin (MTO) reaction

The full name of MTO is methanol to olefin, which is a new chemical reaction process to gain an important chemistry industry raw material. In this paper, we mainly talk about several general reaction process as well as the mechanism of the reaction. The use of molecular sieve catalytic process is a key point where the new MTO process different form the original simple petroleum cracking in order to again olefin. In this work we mainly discuss how the MTO process could happen with the assist of the molecular sieve catalyst. There are direct mechanism Carbene mechanism and Methane-formaldehyde mechanism. The effect of the direct mechanism is to gain some simple and short Carbon-Carbon product. And then the indirect mechanism will take on to control the rate of the reacting process and the ration of different products. By studying on the mechanism of the MTO reaction, we can figure out how a powerful catalyst, molecular sieve catalyst, works in the reaction. Also, the MTO process is a meaningful way to take place of the origin cracking process to gain olefin, as the storage of petroleum is decreasing fast recently.

Mechanistic investigation of methanol-to-olefins conversion catalyzed by H-ZSM-5 zeolite: a DFT study.

The mechanisms for the formation of the first C - C bond and lower olefins on methanol to olefins (MTO) conversion on H-ZSM-5 had been focused in dispute. In this paper, density functional theory has been used to study the reaction mechanisms of methanol to olefins on ZSM-5. The configurations of reactants, intermediates, products and transition state of the numerous reactions involved in such a process have been optimized, as well as the elementary reactions related to these configurations were determined by the calculation of corresponding activation energy barriers and reaction heats. Here, two different kinds of the mechanisms were proposed for the formation of dimethylether (DME), one involving an associative interaction of two methanol molecules with the zeolite Brønsted acid sites and the other occurring via a surface methoxy species and a methanol molecule. A critical intermediate of the methoxy methyl cation was theoretically verified by the reaction of the methoxy species and dimethylether. Besides, it was found that the first intermediates containing a C - C bond were 1,2-dimethoxyethane and 2-methoxy-ethanolare, in which the former was formed from methoxy species with dimethyl ether and the latter was formed from methanol by onium ions((CH3)2O+CH2CH2OCH3), respectively. For the whole reaction mechanism, the results in this paper indicated that the ethene formation is more favorable than propylene formation due to the low activation energy barrier for ethene formation (123.49 vs. 162.09kJ.mol-1). From these calculations, it would be concluded that ethene is the first alkene product that induces the occurrence of the hydrocarbon pool mechanism. All the periodic density function theory (DFT) calculations were performed by the Vienna Ab Initio Simulation package (VASP). The interaction between nucleus and valence electron was described using the pseudopotentials found in the projector augmented wave (PAW) method. PBE-D3 was used in the whole DFT calculations and CI-NEB was used to locate transition state.

Techno economic and life cycle assessment of olefin production through CO2 hydrogenation within the power-to-X concept

The paper deals with exhaustive process modelling, techno-economic and life cycle assessment (TEA/LCA) of olefin (ethylene and propylene) production through captured CO2 and electrolytic hydrogen. Olefins are important building block chemicals with several applications and carbon capture and utilisation (CCU) can provide a sustainable production route. The proposed system involves direct air capture (DAC) of CO2; proton exchange membrane (PEM) water electrolysis for hydrogen production, methanol synthesis, methanol to olefins (MTO) upgrade, and power generation from off-shore wind turbines. This study proposes a new integrated process as the first attempt to holistically assess a whole CCU assembly aiming at olefins production. Processing modelling has been implemented using the Aspen plus V12.1 and MATLAB R2022a software to solve the mass and energy balances of each unit operation. The modelling results showed a carbon efficiency of 72.3% to ethylene and propylene. In addition, the process is designed and integrated in such a way that no external heat supply is required. A specific energy consumption (SEC) of 150 MJ/kg olefins (41 kWh/kg) has been estimated. A minimum selling price of £3.67 per kg of olefins is required for the proposed process to break-even. The sensitivity analysis has revealed that the major cost driver is the cost of electricity. In addition, the life cycle assessment (LCA) has exposed that the proposed synthesis route of olefins has the potential to reduce the global warming potential (GWP) by 47% compared to fossil - based production. The outcomes of this study can be beneficial to engineering conceptual studies, policy makers and contribute new information to the CCU academic community.

Measurements of ignition delay time of gas-to-liquid (GTL) fuel blends

The ignition delay time (IDT) is a fundamental combustion parameter of any fuel, which has a direct impact on its combustion and exhaust emissions in diesel engines. In this research, a thorough experimental study was conducted to investigate the ignition delay of Gas-to-Liquid (GTL) fuel and its 50%–50 % blends with diesel under a wide range of operating conditions using a conventional shock tube apparatus. Simultaneously, a comprehensive chemical kinetic model, based on the well-established POLIMI mechanism, was developed to simulate the complex combustion chemistry of diesel, GTL, and their blends. Several loading pressures in the driver section ranging from 6 to 14 bar that results in reflected pressure of 8–16 bar, and equivalence ratios ranging from 0.5 to 1.3 as well as different initial temperatures have been examined. Calibration of the shock tube indicated that a driver gas tailoring technique was necessary to be used, which was conducted by adding a small ratio of either argon or nitrogen to helium to get an extended test time by 32 % with a good rapture pressure. IDT measurements showed that GTL has the shorter ignition delay time than that of diesel fuel for all conditions. The findings show that IDT measurements for GTL fuel has a shorter ignition delay time than that of diesel fuel for all conditions. Under stoichiometric conditions (ɸ = 1.0), IDT of the blended fuel was about 3 ms, very close to that of GTL at 975 K. However, at a temperature above 1000 K, the IDT of the three fuels were almost identical and ranging between 1 and 2 ms. At a temperature of 1100 K, the IDT of the blended fuel was 5.5 ms, almost a middle value between those of the pure diesel, 0.522 ms, and GTL fuel, 0.495 ms. The shortest IDT of the blended fuel was about 0.4 ms with the highest value of the reflected pressure of 14 bar, while the longest IDT was around 10 ms with the rich mixture at ɸ = 1.3. The study can add to the existing literature illustrating the behavior of GTL-diesel blend can affect IDT.

Two-Step Hydrothermal Synthesis of Submicrometric and Hierarchical Hollow SAPO-34 with Superior Catalytic Performance in Methanol to Olefin (MTO) Reaction.

A submicrometric and hierarchical hollow SAPO-34 molecular sieve was synthesized by an easy and low-cost two-step hydrothermal method. First, the crystallized mixture was obtained by direct drying after a first-step hydrothermal reaction. Then, the SAPO-34 product was obtained by adding the crystallized mixture to silicon-free gel and using cheap and common template agents. Compared to conventional SAPO-34, the submicrometric and hierarchical hollow SAPO-34 exhibits superior catalytic activity in the MTO reaction.

High-Yield Synthesis of Hierarchical SAPO-34 by Recrystallization Method for Efficient Methanol-to-Olefin Reactions.

Prolonging the lifetime of SAPO-34 catalysts and enhancing their olefin selectivity in methanol-to-olefin (MTO) reactions are critical yet challenging objectives. Here, a series of hierarchical SAPO-34 catalysts were synthesized using a straightforward recrystallization method. The incorporation of triethylamine into the recrystallization mother liquor facilitated the formation of mesopores, achieving a high solid yield of up to 90%. Notably, the addition of phosphoric acid and ammonium polyvinyl phosphate alcohol during the recrystallization process significantly enhanced the crystallinity and regularity of the hierarchical SAPO-34 crystals, consequently increasing the mesopore size. Due to the substantially improved mass transfer efficiency and moderated acidity, the SP34-0.14P-0.06R catalysts exhibited a prolonged lifetime of 344 min and 80.3% selectivity for ethylene and propylene at a weight hourly space velocity (WHSV) of 2 h-1. This performance markedly surpasses that of the parent SP34 catalyst, which demonstrated a lifetime of 136 min and a selectivity of 78.0%. Remarkably, the SP34-0.14P-0.06R maintained a lifetime of 166 min even at a high WHSV of 10 h-1, which is more than 5-fold greater than that of the original microporous SP34. This research offers valuable insights into the design and development of hierarchically porous zeolites with high yields, enhancing the efficiency of MTO reactions and other applications.

Kinetic Modeling and Techno-Economic Analysis of a Methanol-to-Gasoline Production Repurposed Refinery Equipment.

Methanol-to-gasoline (MtG) is an alternative process for the production of liquid fuel that involves the conversion of methanol into light and heavy hydrocarbons. The attractiveness of this option relies on multiple feedstocks that can be used to produce methanol, which can impact the greenhouse gases emitted into the atmosphere in comparison to petroleum-based feedstocks. However, one of the challenges of this alternative gasoline production is its high investment cost. This study presents a solution to increase affordability by using repurposed equipment from petrochemical industries. The study employs three modeling techniques, i.e., kinetic modeling, process modeling, and techno-economic analysis. First, a lumped MtG kinetic mechanism using an hierarchical zeolite socony mobil-5 (HZSM-5) catalyst was developed and validated against the literature data to enable high-accuracy process modeling and optimization. Then, the kinetics were implemented in Aspen Plus V12 for process simulations of the fixed-bed MtG, optimization of the operating conditions, and heat integration to increase energy efficiency. Lastly, a techno-economic analysis (TEA) gives the levelized cost of the e-gasoline along with the sensitivity analysis to demonstrate the variables that mainly affect the cost. The TEA showed a price for the e-gasoline with a gray methanol feedstock of 1.82 USD/L, which is comparable with the current average retail gasoline price (1.29 USD/L). Additionally, increasing the capacity by 161 times can reduce the levelized price of e-gasoline to 0.761 USD/L.

Boosted regeneration of coked SAPO-34 catalyst in MTO fluidized bed reactor by diluted air at elevated temperatures

SAPO-34 zeolite as an excellent catalyst for methanol-to-olefins (MTO) reaction suffers rapid deactivation by prevalent coking. Herein, regeneration of coked-SAPO-34 in a fluidized-bed reactor was successfully intensified by altering temperature (550–650 °C) and oxygen content (7–21 vol.%). Fresh, used, and regenerated catalysts were characterized by different methods to understand the correlation between regeneration conditions, coke content, and catalyst performance. The minor residual coke over the regenerated catalyst comprised active hydrocarbon pool intermediates (like naphthalene, benzaldehyde, phenol, and derivatives), which increased by decreasing regeneration temperature and promoted the selectivity to light olefins at earlier reaction times. The restored microporosity and lifetime of regenerated catalyst were superior by increasing temperature. However, higher attrition at 650 °C, as confirmed by SEM images, caused a partial weight loss of the catalyst and a slight decline in relative crystallinity, hence 600 °C was preferred with additional advantage of less energy consumption. Meanwhile, introducing lower oxygen not only moderated the coke oxidation rate but also enhanced the recovery of beneficial catalytic features for the MTO conversion. Consequently, considering an excellent regeneration as well as lower emission of CO2 detected in the flue gas, diluted air containing 14 vol.% O2 at 600 °C was suggested as the most promising method.

Spatial-temporal self-attention network based on bayesian optimization for light olefins yields prediction in methanol-to-olefins process

Methanol-to-olefins (MTO), as an alternative pathway for the synthesis of light olefins (ethylene and propylene), has gained extensive attention. Accurate prediction of light olefins yields can effectively facilitate process monitoring and optimization, as they are significant economic indexes and stable operation indicators of the industrial MTO process. However, the nonlinearity and dynamic interactions among process variables pose challenges for the prediction using traditional statistical methods. Additionally, physical-based methods relying on first-principle theory are always limited by an insufficient understanding of reaction mechanisms. In contrast, data-driven methods offer a viable solution for the prediction based solely on process data without requiring extensive process knowledge. Therefore, in this work, a data-driven approach that integrates spatial and temporal self-attention modules is proposed to capture complex interactions. Furthermore, Bayesian optimization is employed to determine the optimum hyperparameters and enhance the accuracy of the model. Studies on an actual MTO process demonstrate the superior prediction performance of the proposed model compared to baseline models. Specifically, 24 process variables are selected as the high-dimensional inputs, and yields of ethylene and propylene, as the low-dimensional outputs, are successfully predicted at various prediction horizons ranging from 2 to 8 h.

Investigating the Sole Olefin-Based Cycle in Small-Cage MCM-35-Catalyzed Methanol-to-Olefins Reactions.

Small-pore zeolites catalyze the methanol-to-olefins (MTO) reaction via a dual-cycle mechanism, encompassing both olefin- and aromatic-based cycles. Zeolite topology is crucial in determining both the catalytic pathway and the product selectivity of the MTO reaction. Herein, we investigate the mechanistic influence of MCM-35 zeolite on the MTO process. The structural properties of the as-synthesized MCM-35 catalyst, including its confined cages (6.19 Å), were characterized, confirming them as the catalytic centers. Then, the MTO reactions were systematically performed and investigated over a MCM-35 catalyst. Feeding pure methanol to the reactor yielded minimal MTO activity despite the formation of some aromatic species within the zeolite. The results suggest that the aromatic-based cycle is entirely suppressed in MCM-35, preventing the simultaneous occurrence of the olefin-based cycle. However, cofeeding a small amount of propene in methanol can obviously enhance the methanol conversion under the same studied reaction conditions. Thus, the exclusive operation of the olefin-based cycle in the MTO reaction, independent of the aromatic-based cycle, was demonstrated in MCM-35 zeolite.

Simultaneous Integration of the Methanol-to-Olefin Separation Process and Heat Exchanger Network Based on Bi-Level Optimization

The separation section of the methanol-to-olefin (MTO) process is energy-intensive, and the optimization and heat integration can enhance energy efficiency and reduce costs. A bi-level optimization model framework is proposed to optimize the separation process and simultaneously integrate the heat exchanger network (HEN). The upper level employs a data-driven BP neural network proxy model instead of the mechanism model for the separation process, while the lower level adopts a stage-wise superstructure for the HEN without stream splits. The interaction between the two systems is realized effectively through information exchange. A bi-level particle swarm algorithm is employed to optimize complex problems and determine the optimal operational parameters for the distillation system and HEN. Compared with the typical sequential synthesis method, the optimization by the proposed approach reduces the total annual cost by 1.4293×106 USD/y, accounting for 4.76%.

Influence of acid strength on olefin selectivity of chabazite (CHA) framework zeolite/zeotype during tandem CO2 hydrogenation

The role of Brønsted acid sites (BAS) strength of chabazite (CHA) framework on olefin selectivity during methanol-to-olefin (MTO) and tandem CO2 hydrogenation was investigated over an aluminosilicate, SSZ-13 and a silicoaluminophospate, SAPO-34 and their bifunctional admixtures with In2O3. During MTO, SSZ-13 and SAPO-34 yielded primarily olefins (cumulative selectivity of ∼60 % and ∼90 %, respectively at cumulative turnover number, TON over 500 molC/molH+). Interestingly, an interpellet admixture of In2O3/SSZ-13 (distance between redox sites and BAS of 260–900 µm) predominantly yielded paraffins (cumulative selectivity of ∼93 % at cumulative TON over 40) via the secondary hydrogenation of olefins as seen from the cumulative paraffin-to-olefin (P/O) ratio of ∼21 during CO2 hydrogenation. In comparison, an interpellet In2O3/SAPO-34 admixture yielded majority olefins (cumulative selectivity of ∼67 % at cumulative TON over 60) due to a lesser degree of secondary hydrogenation (cumulative P/O ratio of ∼0.2) on the BAS in SAPO-34, which has a lower acid strength as compared to SSZ-13. Interestingly, both interpellet admixtures of In2O3/SSZ-13 and In2O3/SAPO-34 remained stable during tandem CO2 hydrogenation by favoring the olefin cycle and suppressing the formation of deactivation-inducing-aromatics as probed via occluded hydrocarbon analysis, unlike MTO, where SSZ-13 and SAPO-34 showed fast deactivation. However, in intrapellet admixtures (distance between redox sites and BAS of 270–1500 nm) of In2O3/SSZ-13 and In2O3/SAPO-34, ion exchange of BAS (H+) with Inδ+ (from In2O3) inhibited C–C coupling and predominantly formed CH4. Overall, our study related the product selectivity and deactivation in MTO and tandem CO2 hydrogenation over CHA framework zeolite/zeotype to the aromatic and olefin cycle propagation in the hydrocarbon pool mechanism. These underpinnings will help with rational catalyst design for tandem CO2 hydrogenation.

Waste-derived activated carbons for effective adsorptive removal of strontium, barium, and binary pollutants: A response surface methodology study

A double-pronged approach to pollution management is proposed by sustainably managing solid wastes and converting them to activated carbons that are then utilized for water treatment. In this study, gas-to-liquids (GTL) derived biosolids, carboard and their mixed samples are used to produce the activated carbons. In a laboratory batch study, a Box-Behnken experimental design was used with four factors and three levels to optimize the removal of single component strontium and barium, and the binary system of pollutants from an aqueous solution. The design incorporated response surface modeling (RSM) techniques with a total of 29 different experimental data points collected and analyzed in this study. The study was conducted considering four parameters: the initial pH of the solution (ranging from 4.0 to 8.0), temperature (ranging from 20 to 40 ℃), the percentage of cardboard (fixed at 0 %, 50 %, and 100 %), and the amount of adsorbent (between 0.05 and 0.5 g). These factors were assigned three levels, represented as −1, 0, and 1. A second-order polynomial regression equation was then developed to estimate the responses. The statistical significance of the independent variables and their interactions was assessed using analysis of variance (ANOVA) with a 95 % confidence level (α = 0.05). The results revealed that only temperature and dosage show significant effects on the responses and that optimum values of the selected parameters were obtained by solving the prediction equations, which were validated with less than 4 % error %. In an attempt to optimize the factors, a pH of 5.5, temperature of 40 ℃ and dose of 0.3 g is found for all three samples. Validation results for optimization also proved that varying the percentage cardboard showed little difference in the percentage removal of all the pollutants. The results from this study can be directly applied for any such systems trying to optimize these parameters and the prediction equations can be utilized effectively.