Surface Micropore Research Articles

Hydrocarbons and residual oil recovery with ultrasonic-assisted waves and co-solvents

In this work, the physicochemical characteristics of the recovered organic fractions and the correlation between organic-makers existence and recovered hydrocarbons are studied on two shale samples from the Kubang Pasu (KP) Formation, Kedah, Malaysia formation. Improving the extractability of organic matter is the key to evaluate the source or reservoir rock petroleum characteristic, this study is an attempt to estimate the optimist extraction technique and conditions for shale rocks. In this work, the physic-chemical characteristics of two moderately organic-rich shale samples from the North-Western Peninsula Malaysia are studied. The recovered organic matter using Soxhlet and ultrasonic extraction processes of the shale samples with toluene is inspected. Samples characteristics in terms of micro-porous surface area and volume analysis, elemental compositions, total organic compounds, surface morphology with elemental mapping, and elemental cations with the active functional groups are analyzed. The solutes of the extraction process are evaluated utilizing gas chromatography and mass spectroscopy (GCMS), and Fourier transforms infrared (FTIR) techniques. The extraction measurements showed a wider range of organic matter recovered from KPK-13 compared to KPK-14 shale. Hence, the total organic content (TOC) of both samples are almost identical (i.e.: ≈ 1.5) which might refer to the higher carbon mineralogy as quantified by EDX mapping, lower surface area according to N2 adsorption analysis, the thermal maturity, or kerogen type of the KPK-14 shale samples. The Soxhlet and ultra-sonication extraction process showed feasible extraction of organic fractions with up to C20. Various configurations of alkanes, alkenes, amines and esters are indicated in the post-sonication solutes with higher weight ratios on the KPK-14 shale sample. The study provides an insightful relation between the organic matter existence and their characteristics, with the possible extractable fractions using the ultrasonic technique as cost and time effective approach.

Quantitative Gas‐in‐place Comparison of Original and Bitumen‐free Lacustrine Shale

AbstractResidual bitumen in organic‐rich shale of oil windows exists widely, and its effect on the gas storage capacity of shale could be two‐fold. Bitumen could occupy and block the nanopores of shale, thereby reducing the gas storage capacity. On the other hand, gas could be dissolved in bitumen in shale gas reservoirs, leading to enhanced gas storage capacity. To quantify the effect of bitumen on the gas‐in‐place (GIP) estimation of lacustrine organic‐rich shale, the micropore characteristics and methane sorption capacity of original and bitumen‐free shale from the Triassic Yangchang Formation of the Ordos Basin, combined with the methane dissolution capacity for the isolated bitumen, were analyzed and compared. GIP for the original and bitumen‐free shale in the depth range of 500–2500 m was evaluated. The results show that micropores in the shale samples were mainly related to organic matter. Clay mineral‐hosted pores contributed slightly to microporosity. Bitumen significantly reduced the micropore surface area and volume of the original shale, with average percentages of 28.09% and 51.26%, respectively. The methane sorption capacity decreased after bitumen removal. When normalized to the original shale mass, the sum of the methane sorption capacity for bitumen‐free shale and the methane dissolution capacity for isolated bitumen was similar to the methane sorption capacity of the original shale, indicating that the lack of methane absorbed on bitumen is the main reason for the decrease in methane sorption capacity after bitumen removal. The contribution of absorbed methane on bitumen to sorbed methane in shale could be higher than 36.23%. Dual effects of bitumen on shale GIP were observed. A high content of bitumen (1.12%) increased the GIP of the shale samples, with an average percentage of 23.5% in the depth range of 500–2500 m, while a low content of bitumen (0.06%) decreased the GIP, with an average percentage of 13.6%.

Ferrocene-based hypercrosslinked polymers derived from phenolic polycondensation with unexpected H2 adsorption capacity

Metal-doped porous organic polymers often display unique properties for applications in gas uptake owing to the incorporation of the metal elements in the polymer networks. In this study, a series of novel ferrocene-based hypercrosslinked polymers were prepared by phenolic polycondensation (Fc-PR-HCPs). To generate the hypercrosslinked polymers, 1,1′-ferrocenedicarboxaldehyde (Fc(CHO)2) and bisphenol A (BPA) were used as the building blocks. The maximum value of BET and micropore surface area is determined to be 1111.4 and 487.4 m2/g for Fc-PR-HCP3. A significant H2 adsorption capacity of 3.11 wt% was achieved for Fc-PR-HCP3 at 77 K/1.0 bar, which was noted to be higher than the porous organic polymers with even higher BET surface area value. The high micropore surface area value and the adsorption sites (aromatic rings and metal ion-active sites) provided by two building blocks were used to explain the significant H2 adsorption capacity successfully. Overall, the findings from this study indicate that Fc-PR-HCPs highlighted prospective applications in the field of H2 capture.

Revisiting the Effect of Pyrolysis Temperature and Type of Activation on the Performance of Carbon Electrodes in an Electrochemical Capacitor.

Hierarchical porous carbons are known to enhance the electrochemical features of electrodes in electrochemical capacitors. However, the contribution of surface oxygen and the resulting functionalities and wettability, along with the role of electrical conductivity and degree of amorphous or crystalline nature in the micro-mesoporous carbons, are not yet clear. This article considers the effect of carbonisation temperature (500–900 °C) and the type of activation (CO2, KOH) on the properties mentioned above in case of carbon xerogels (CXs) to understand the resulting electrochemical performances. Depending on the carbonisation temperature, CX materials differ in micropore surface area (722–1078 m2 g−1) while retaining a mesopore surface area ~300 m2 g−1, oxygen content (3–15%, surface oxygen 0–7%), surface functionalities, electrical conductivity (7 × 10−6–8 S m−1), and degree of amorphous or crystalline nature. Based on the results, electrochemical performances depend primarily on electrical conductivity, followed by surface oxygen content and meso-micropore connectivity. The way of activation using a varied extent of CO2 exposure and KOH concentrations played differently in CX in terms of pore connectivity from meso- to micropores and their contributions and degree of oxidation, and resulted in different electrochemical behaviours. Such performances of activated CXs depend solely on micro-mesopore features.

Dynamic adsorption behavior of benzene, toluene, and xylene VOCs in single- and multi-component systems by activated carbon derived from defatted black cumin (Nigella sativa L.) biowaste

In the current study, activated carbon (AC) was produced from defatted black cumin (Nigella sativa L.) biowaste (DBCB) with ZnCl2 activation by means of the response surface methodology. The optimum process conditions for the production of DBCB-AC with a high iodine number of 1055.02 mg/g were predicted as an activation time of 57 min, activation temperature of 550 °C, and impregnation ratio of 105%. The surface and textural properties of the optimal DBCB-AC were characterized by SEM, FTIR, and BET analysis techniques. The DBCB-AC exhibited a highly porous structure with a specific surface area of 1213.32 m2/g, total pore volume of 0.89 cm3/g, and micropore surface area of 787.65 m2/g. Exploring the comparative and competitive adsorption behavior of volatile organic compounds (VOCs) is of both practical and scientific interest. Therefore, the competitive adsorption of multi-component benzene, toluene, and xylene (BTX) vapors by the DBCB-AC was elucidated. In the single-component system, the adsorption capacities of the BTX vapors at inlet concentrations of 20 mg/L were determined as 495, 580, and 674 mg/g, respectively. In contrast, in the binary-component system, the adsorption capacity of the B-vapor at 20 mg/L B + 10 mg/L T and 20 mg/L B + 10 mg/L X decreased by approximately 42% and 56%, respectively. Similarly, the adsorption capacity of the T-vapor at 20 mg/L T + 10 mg/L X decreased by approximately 47%. In the ternary-component system, the adsorption capacity of the X-vapor remained consistent. The adsorption mechanism of the BTX was explained by adsorption kinetic and isotherm models. The reuse efficiency of the DBCB-AC for the BTX was assessed through five cycles of adsorption-desorption tests and was found to be 89.45%, 88.02%, and 87.25%, respectively. The DBCB-AC, which had high-performance in terms of both reuse efficiency and adsorption capacity, can be recommended as a promising adsorbent for removal of VOC pollutants.

Pore structure evolution during lean-oxygen combustion of pyrolyzed residual from low-rank coal and its effect on internal oxygen diffusion mechanism

The lean-oxygen combustion of incompletely pyrolyzed char dominates at the combustion front of coalfield fires. Using non-local-density functional theory (NLDFT) and Barrette-Joynere-Halenda (BJH) analysis based on N2 and CO2 composited adsorption isotherms, the pore (0.4–300 nm) structure characteristics of pyrolyzed char during lean-oxygen combustion were obtained. The results indicate that the main pore morphology changes from irregular ink-bottle shape of raw coal to cylindrical shape of pyrolyzed char, then to slit-shaped and wedge-shaped pores under the effect of oxidative expansion, and finally coalesce into amorphous macropores during combustion. For the weak-caking coal, softened colloids diffuse and block the mesopores, leading to the reverse development of mesopores into smaller-sized pores. The pore development changes from the generation of secondary micropores in pyrolysis stage to the progressive expansion mode of mesopores in initial combustion stage, then to the free coalescence mode of macropores in late combustion stage. The dominant internal oxygen diffusion mechanism transforms from Knudsen diffusion to transition diffusion at 650 °C, and the carbon-oxygen reaction interfaces shift from the inner surface of deep micropores to the shallow mesopores and macropores. Finally, 650 °C is determined as the early-warning temperature for the accelerating spread of coalfield fires.

Synthesis of Hierarchical Porous SAPO-34 and Its Catalytic Activity for 4,6-Dimethyldibenzothiophene.

Zeolite SAPO-34 has been widely used in the industry because of its special pore structure and wide distribution of acid sites in the pore channel. However, traditional SAPO-34 with a small pore size suffers from carbon deposition and deactivation in catalytic reactions, and its inability to catalytically convert bulky organic molecules limits its industrial application. Meanwhile, impurities of SAPO-5, which have weak acidity leading to rapid catalyst deactivation, appear in SAPO-34 zeolite. Therefore, it is of great significance to synthesize SAPO-34 zeolite with a mesoporous pore structure, which can significantly improve the transfer of molecules in zeolites. In this paper, SAPO-34 zeolite with a hierarchical pore structure was synthesized, and its hydrodesulfurization performance for 4,6-dimethyldibenzothiophene (4,6-DMDBT) was studied in a fixed bed reactor. The characteristic results show that BET-specific surface area, micropore volume, and mesoporous volume of synthesized SAPO-34 are 754 m2 g−1, 0.25, and 0.23 cm3 g−1 respectively, and the pore size is mainly concentrated at 4 nm. The catalytic conversion of 4,6-DMDMT with Co- and Mo-supported SAPO-34 is about 83%, which is much higher than the catalytic performance of Al2O3.

Biochar-Mediated Degradation of Roxarsone by Shewanella oneidensis MR-1.

It is widely believed that biochar plays an essential role in sequestrating pollutants. The impacts of biochar on microbial growth, and consequently on the environmental fate of pollutants, however, remains poorly understood. In this study, wheat-straw-derived biochar was used to investigate how biochar amendment affected Shewanella oneidensis MR-1 growth and roxarsone transformation in water under anaerobic conditions. Three biochar with different physicochemical properties were used to mediate the roxarsone degradation. The results showed that the degradation rate of roxarsone could be accelerated by the increase of biochar pyrolysis temperature. From the characterization of biochar, the total specific surface area, micropore surface area and micropore volume of biochar increase, but the average pore diameter decreases as the pyrolysis temperature increases. Through infrared spectroscopy analysis, it was found that as the pyrolysis temperature increases, the degree of condensation of biochar increases, thereby increasing the pollutant removal rate. From the changes of the relative concentration of MR-1 and its secreted extracellular polymer content, the growth promotion ability of biochar also increases as the pyrolysis temperature increases. These results suggest that wheat-straw-derived biochar may be an important agent for activating microbial growth and can be used to accelerate the transformation of roxarsone, which could be a novel strategy for roxarsone remediation.

A pilot study for enhanced transformation of a metabolite 3,5-dichloroaniline derived from dicarboximide fungicides through immobilized laccase mediator system.

This pilot investigation aimed to evaluate the removal efficiency and the underlying biocatalytic pathways of immobilized fungal laccase during the oxidative biotransformation of a non-phenolic metabolite, 3,5-dichloroaniline (3,5-DCA) derived from dicarboximide fungicides. The maximum loading of laccase on the microporous support surfaces could reach 36.4mg/g. The immobilized laccase on the microporous support surfaces exhibited excellent thermal stability, pH adaptability, storage stability, and reusability compared to free laccase. The ILMS assay indicated that the immobilized laccase efficiently removed studied 3,5-DCA (99-100%) in the aqueous medium, within 72h in the presence of catechol. In this study, we identified three coupling reaction products during the removal of 3,5-DCA through an ILMS assay. Based on the identified coupling reaction products, we proposed the reaction pathway for the biotransformation of 3,5-DCA by immobilized laccase, which was shown to be potentially useful in the sustainable environmental remediation of aniline metabolite (i.e., 3,5-DCA) derived from dicarboximide fungicides.

Pyrolytic gas exfoliation and template mediation inducing defective mesoporous carbon network from industrial lignin for advanced lithium-ion storage

Enzymatic hydrolysis lignin (EHL) from the biorefinery industry has been considered an ideal carbon source to prepare high-performance carbonaceous electrodes due to its high aromaticity and abundance. However, the severe agglomeration of the directly carbonized EHL results in insufficient lithium storage sites and inferior transfer kinetics. Herein, a delicate strategy of pyrolytic gas exfoliation and template mediation through ZnCO3 and ZnC2O4 decomposition was developed to engineer the microstructure of EHL-derived carbonaceous material (ECM) at 650 °C for robust lithium storage. The mesoporous ECM with an interconnected grape-like (200 nm) network is prepared by single CO2 exfoliation and ZnO templating. Surface micropores are engineered by temporary ZnO activation at 500–650 °C. The blocky ECM with coexisting micro/mesopores is prepared by dual CO/CO2 exfoliation and ZnO templating. The tempestuous release of CO2 produces deep micropores. The developed mesoporous structure boosts fast Li-ion transportation and accessibility for defects. In addition, the nanostructured grape-like (200 nm) network exposes active surface defects and shortens the charge-diffusion distance. Thus, the mesoporous ECM displays a robust capacity (534.1 mAh·g−1 at 0.2 A·g−1), superior rate capability (323.4 mAh·g−1 at 1 A·g−1) and excellent cycling stability. The blocky ECM with coexisting micro/mesopores shows better lithium storage performance than the microporous blocky ECM prepared by ZnCl2 activation.

Determination of Microporous and Mesoporous Surface Areas and Volumes of Mesoporous Zeolites by Corrected t‐Plot Analysis

AbstractZeolites are well‐known microporous catalysts involved in many industrial applications. Their microporosity yet impedes diffusion of bulky molecules. To overcome this drawback, zeolites with hierarchical bimodal porosity, e. g. micropores and mesopores, are developed. In this context, it is important to develop/use methods able to evaluate accurately the textural properties of mesoporous zeolites. t‐Plot can be in theory used for determining the micro‐ and mesopore surface areas and pore volumes. However, classical t‐plot analysis overestimates the mesopore surface areas and underestimates the micropore volumes for hierarchical micro‐/mesoporous materials. Measurements performed with mechanical mixtures of FAU‐Y and MCM‐41 allows to provide corrections, which are up to date limited to mesoporous FAU‐Y. The present work describes specific corrections of the t‐plot for a broader series of zeolites including MFI, *BEA and MOR, based on a set of mechanical mixtures of zeolites and MCM‐41. Minor correction factors are required for MOR, whilst for MFI and *BEA similar corrections as for the FAU‐Y are inferred for the micropore volume. As far as the surface area is concerned higher correction factors are required for MFI compared to *BEA. This corrected t‐plot analysis is applied to characterize a great variety of mesoporous zeolites prepared by micelle‐templating.

In vitro and in vivo study of magnesium containing bioactive glass nanoparticles modified gelatin scaffolds for bone repair

Magnesium containing bioactive glass nanoparticles modified gelatin scaffolds (MBGNs/Gel scaffolds) have shown recently the potential for bone regeneration due to its good biocompatibility, bioresorbability and bioactivity. Nevertheless, its use is limited by its complicated manufacturing process and a relatively expensive price. In this study, MBGNs were prepared by sol–gel process. The MBGNs/Gel was synthesized by a simple immersion method. SEM, transmission electron microscopy and dynamic light scattering analysis showed that the particles had spherical morphology with mean particle size of 100 nm. The MBGNs/Gel scaffolds were observed by SEM. The scaffolds showed connected pore structure with pore size ranging from 100 to 300 μm. SEM images with high magnification showed the existence of MBGNs on the surface of micro-pores. The ion release results revealed the release of Mg, Ca and Si elements from the MBGNs. MTT assay and cytotoxicity studies indicated that, the scaffolds provide a suitable ion related micro-environment for cell attachment and spreading. The Reverse Transcription-Polymerase Chain Reaction (RT-PCR) results showed the scaffolds could promote the osteogenesis of MC3T3-E1. The in vivo study also showed higher amount of new bone and trabecular bone which indicated excellent bone induction and conduction property of modified scaffolds. So, the developed MBGNs/Gel scaffolds are a potential candidate for bone regeneration applications.

Carbon Aerogel Based Thin Electrodes for Zero‐Gap all Vanadium Redox Flow Batteries – Quantifying the Factors Leading to Optimum Performance

AbstractDirect growth of resorcinol−formaldehyde carbon aerogels (CAGs) on carbon paper electrodes was achieved using a new approach. Materials with variations in density, mesoporosity and microporosity were prepared. Microstructural properties of the resultant thin electrodes are shown to directly influence performance in zero‐gap redox flow battery (RFB). BET analysis shows a total surface area between 643 to 931 m2 g−1. Deposition of only ≈15 wt.% CAG on the carbon electrode leads to a 320‐fold increase in electrochemical surface area. Analysis of the results saw a strong positive correlation of RFB performance with surface area. The best performing electrodes had a good balance between microporous and external surface area, and on the macroscopic scale had sufficiently large pores to allow efficient electrolyte permeation. The poorest performing electrodes which had the highest surface area, also had poor macroscopic porosity leading to large mass transport and solution resistance losses. The best performing electrodes were tested in a zero‐gap setup using polarization curves, showing a 25 % increase in power density at 100 mA cm−2 and a peak power density of 706 mW cm−2 at 1 V using thin electrodes.

Structural control of a novel hierarchical porous carbon material and its adsorption properties

Novel hierarchical porous carbon materials (HPCs) were fabricated via a reactive template-induced in situ hypercrosslinking procedure. The effects of carbonization conditions on the microstructure and morphology of HPCs were investigated, and the adsorption of methylene blue (MB) on HPCs was explored. The as-prepared HPCs has a hierarchical micro-, meso- and macropore structure, which results from the overlap of hollow nanospheres possessing microporous shells and macroporous cavities. The carbonization temperature, carbonization time and carbonization heating rate played important roles in tailoring the nanostructures of HPCs. The BET specific surface area and micropore specific surface area can reach 2388 m2 g−1 and 1892 m2 g−1, respectively. Benefitting from the well-developed pore structure, the MB removal efficiency can exceed 99% under optimized conditions. The adsorption kinetics and thermodynamics can be well described by a pseudo-second-order model and Langmuir model, respectively. Furthermore, such adsorption was characterized by a spontaneous endothermic process.

Microstructure and Tensile Behavior of a Novel Monocrystalline Co‐Based Superalloy at Different Temperatures

Microstructures and tensile properties of a novel monocrystalline Co‐based superalloy are investigated by experiments and finite element simulation. Microstructures of heat‐treated alloys are composed of γ and cubical γ' precipitates without the presence of the secondary phase, and the fraction of γ' phase is about 86%. The experimental results show that tensile properties of the novel monocrystalline Co‐based superalloy have abnormal yield behavior. In low and medium temperature ranges (R.T. 850 °C), the yield stress increases gradually with temperature increase and the tensile fracture surface is characterized by cleavage rupture. At 850 °C, fracture mechanism is composite of cleavage and microporous. While above 850 °C, the yield stress decreases rapidly, and fracture surface is constituted of mixed fracture surface of dimples and micropores. The simulation results show that the tensile stress‐–strain curves are well fitted to the experimental data at different temperatures.

Synthesis of a Zn/Fe–N–C electrocatalyst towards efficient oxygen reduction reaction via a facile one-pot method

The high price and unsatisfactory stability of Pt-based catalysts for the sluggish oxygen reduction reaction (ORR) severely limit the development of fuel cells and metal-air batteries. Therefore, developing Pt-free electrocatalysts with excellent activities and stabilities is significant. Herein, an efficient Zn/Fe–N–C electrocatalyst is synthesized via a facile one-pot method. Owing to its curved nanosheet structure, appropriate microporous and mesoporous specific surface areas, abundant defects and high Fe–Nx content, Zn/Fe–N–C exhibits remarkable ORR activity and stability in alkaline electrolyte. Its half-wave potential is 0.843 V, which is 10 mV higher than that of Pt/C. Moreover, Zn/Fe–N–C also manifests satisfactory performance in a practical Zn-air battery. Its maximum output power density is 108.5 mW cm−2, which is equivalent to that of Pt/C. In this work, a simple synthesis method for highly active ORR electrocatalyst is provided, which can be implemented for the future design and synthesis of electrocatalysts used in fuel cells and metal-air batteries.

Biomimetic modification on the microporous surface of cardiovascular materials to accelerate endothelialization and regulate intimal regeneration

Vascular stents are widely used in the clinical treatment of coronary heart disease, but the long-term safety still needs to be improved. Surface biological functional modification is an effective way to improve the biocompatibility and clinical performance of cardiovascular materials, but how to achieve long-term effective and precise regulation of in situ vascular intimal repair through the reasonable construction of the surface physical and chemical structure is still an important task in the current surface modification research. In this study, ECM-derived components, including laminin, heparin, and SDF-1, were incorporated into the titanium surface with a microporous structure. It was found that the modified surface could effectively control the continuous release of biomolecules. In vitro biocompatibility evaluation results showed that the constructed functional layer could effectively inhibit the activation of platelet adhesion and excessive proliferation of smooth muscle cells. In addition, the modified surface also showed the potential to induce rapid regeneration of vascular endothelium. In vivo animal tests further proved that the modified sample may contribute to inhibiting vascular intimal hyperplasia. This study provided a new approach for the surface biological function modification of Ti-based vascular stents.

3D-printed porous PEEK scaffold combined with CSMA/POSS bioactive surface: A strategy for enhancing osseointegration of PEEK implants

As an attractive biomaterial for orthopedic implants , polyetheretherketone (PEEK) has many prominent characteristics such as good biocompatibility and biomechanical properties , as well as natural radiolucency. However, the potential clinical application is limited due to its biologically inert surface and poor osseointegration . To solve this problem, we fabricate a macroporous PEEK scaffold modified with methacrylated chitosan/polyhedral oligomeric silsesquioxane (CSMA/POSS) nanocomposite through 3D printing , sulfonation and UV-induced graft polymerization. The water contact angle, protein adsorption ability and biomineralization study of the sulfonation-treated PEEK (SPEEK)-CSMA/POSS scaffolds were measured in order to evaluate the surface properties. The results indicated that CSMA/POSS as a bioactive microporous surface integrated with nanoparticles promoted the protein adsorption and apatite formation . For the in vitro and in vivo evaluation of the osteogenicity, rat bone marrow mesenchymal stem cells (rBMSCs) and rat calvaria defect repair model were used. Biological results showed that the 3D porous structure and bioactive surface of modified PEEK scaffolds provided a suitable condition for cell adhesion and proliferation, enhanced the osteogenic differentiation of rBMSCs and promoted osteogenesis in vivo compared to the untreated PEEK scaffold. Therefore, 3D-printed macroporous PEEK scaffold modified with CSMA/POSS bioactive microporous surface represents a promising modification strategy for enhancing osseointegration of PEEK implants.

Impact of Pore Structure on Two-Electron Oxygen Reduction Reaction in Nitrogen-Doped Carbon Materials: Rotating Ring-Disk Electrode vs. Flow Cell.

The impact of pore structure on the two-electron oxygen reduction reaction (ORR) in nitrogen-doped carbon materials is currently under debate, and previous studies are mainly limited to the rotating ring-disk electrode (RRDE) rather than the practical flow cell (FC) system. In this study, assisted by a group of reliable pore models, the impact of two pore structure parameters, that is, Brunauer-Emmett-Teller surface area (SBET ) and micropore surface fraction (fmicro ), on ORR activity and selectivity are investigated in both RRDE and FC. The ORR mass activity correlates positively to the SBET in the RRDE and FC because a higher SBET can host more active sites. The H2 O2 selectivity is independent of fmicro in the RRDE but correlates negatively to fmicro in the FC. The inconsistency results from different states of the electrode in the RRDE and the FC. These insights will guide the design of carbon materials for H2 O2 synthesis.

Hierarchical MFI Zeolite Catalysts: How to Determine Their Textural Properties?-A Comparative Study

It is important to elucidate the role of the surface areas and pore volumes of hierarchical zeolites to understand their behavior as catalysts. Micro-and mesopore surface areas and volumes of the hierarchical MFI (Mobil Five zeolites) were assessed following several methods: (i) N2 adsorption at 77 K using classical and corrected t-plot analyses methods, (ii) pre-adsorption of n-nonane was followed by the study of the N2 adsorption at 77 K, and (iii) non-local-density functional theory (NLDFT) analysis using either the N2 adsorption method at 77 K or the Ar adsorption method at 87 K. In order to assess the viability of each method, a set of hierarchical MFI-type zeolites was prepared by different approaches: alkaline treatment (desilication), synthesis in clear solution (nanocrystals), synthesis in the presence of bifunctional organic surfactant (nanosheets), and micelle-templating assisted alkaline treatment. NLDFT methods could not be used to accurately determine the micro-and mesopore surface areas, as larger surface areas compared to those obtained using the BET equation were obtained. This overestimation is even more pronounced with Ar at 87 K. Results from the classical t-plot analysis performed under conditions of N2 adsorption at 77 K for mechanical mixtures of MFI and MCM-41 revealed the underestimation of the micropore volumes and the overestimation of the mesopore surface areas. Corrections were provided for t-plot analysis. The results obtained using the corrected t-plot method were in good agreement with the results obtained using the NLDFT method in the presence of Ar at 87 K during the calculation of the micro-and mesopore volumes of hierarchical MFI-type zeolites. Micropore and mesopore surface areas calculated by the corrected t-plot method were in good agreement with those calculated using the n-nonane pre-adsorption method for the hierarchical MFI-type zeolites characterized by the presence of large zeolite domains. The NLDFT method, in the presence of Ar, can be used to assess the micro-and mesopore volumes of the hierarchical zeolites at 87 K. However, it cannot be used to determine the surface areas. The corrected t-plot method can be used to efficiently calculate both the volumes and surface areas.