Range Of Pore Size Distribution Research Articles

Improving konjac glucomannan-based aerogels filtration properties by combining aerogel pieces in series with different pore size distributions

The pore size distribution of konjac glucomannan (KGM)-based aerogels seriously impacted the air filtration efficiency and filtration resistance. This study aimed to investigate the pore size distribution control of KGM-based aerogels through total solid concentration of the sol and to improve the filtration performance by preparing aerogel stacks, which were made by combining KGM-based aerogels with different pore size distribution (range: 0–180 μm). Results indicated that with increased total solid concentration from 50% to 100% of the origin formulae, aerogel pore size became smaller and the porosity was decreased for all the three sample formulae. Meanwhile, the aerogel mechanical property and filtration efficiency were both strengthened with increased total solid concentration, but the air resistance became significantly higher. The changing extent and rule were influenced by the sample components (KGM, starch, gelatin, wheat straw). The aerogel stacks prepared by in series combining the aerogel pieces with different pore size distribution (from large size to small size) was found to improve filtration efficiency (e.g. from 70% to 80% for K1G2S4WS2) and significantly lower the air resistance (e.g. from 270 Pa to 190 Pa for K1G2S4WS2). This study could guide the filtration performance improvement of aerogels.

Impact of chloride intrusion on the pore structure of recycled aggregate concrete based on the recycled aggregate porous interface

This study presents the experimental results of pore structure change in recycled aggregate concrete (RAC) with a 100% replacement ratio subjected to chloride intrusion, comprehensively considered with dry-wet cycles, flexural loading, and temperature. The pore structure of the mortar was determined by mercury intrusion porosimetry, and the scanning electron microscope used to observe the apparent morphology of old and new mortar. The changes in the chemical composition of specimens after chloride intrusion were measured by X-ray diffraction. The results showed that Cl- intrusion led to the formation of a large number of new pores in the original pores that were smaller than the original pore size. The range of the original pore size distribution was also reduced. The increase in temperature increased the rate of dissolution and migration of products between the pores and promoted changes in the pore structure. A large number of connected micro-cracks were generated between the pores under flexural load conditions, which provided additional space for product recrystallization and reshaped the original crack space. The changes in the characteristics of pore structure of old mortar were generally more extensive than those of new mortar after Cl− intrusion. Based on the experimental results, a model for RA dual partition-interface pore network is proposed by considering the old mortar, new mortar, old-new mortar interface, and old aggregate-old mortar interface to analyze the mechanism of change of pore structure.

Connectivity of pores in shale reservoirs and its implications for the development of shale gas: A case study of the Lower Silurian Longmaxi Formation in the southern Sichuan Basin

The unconnected gas-bearing pores in shale gas reservoirs may be transformed into “potential recoverable pores” after large scale hydraulic fracturing. However, the mainstream pore classification methods of shale gas reservoirs, do not take the unconnected pores into account, which impacts the evaluation accuracy of reservoir pore effectiveness. To solve this problem, this paper took the shale of Lower Silurian Longmaxi Formation in the southern Sichuan Basin as the research object to carry out experiments on core porosity, centrifugal + gradual drying NMR after saturated with brine and NMR freeze–thaw using plunger samples and crushed samples to analyze the volume, main development location and main pore size distribution range of unconnected pores. Then, the pore systems were classified, and the lower limit of effective pore size of connected gas-bearing pores was determined. Finally, the total pore effectiveness of shale gas reservoirs was evaluated, and the influence of unconnected pores on the development of shale gas was discussed. And the following research results were obtained. First, there are a large number of unconnected pores in the shale gas reservoirs of the study area, accounting for 30.23%. Most of them are mainly developed in organic matters and a few are developed in clay minerals. The distribution of pore size ranges from 5 nm to 30 nm. Second, T2 cut-off value of clay bound water in the shale gas reservoirs of the study area is 0.26 ms, whose corresponding pore size is 5.35 nm, which is the lower limit of the effective pore size. Third, large-scale hydraulic fracturing can improve the unconnected pores with the size more than 5.35 nm, so effective development of shale gas will be realized. Fourth, after hydraulic fracturing stimulation, the unconnected pores can increase the storage space of fracturing fluid in the matrix, absorb the fracturing fluid in the fractures, replace the shale gas in the pores and promote the automatic alleviation of water lock in shale gas reservoirs, so the single-well shale gas production will be increased. In conclusion, fluid occurrence and pore system in shale pores can be quantitatively divided by means of centrifugal + gradual temperature drying method combined with NMR experiments, mobile water and capillary bound water can be determined by the high speed centrifugal + NMR experiments, and capillary bound water and clay bound water can be determined by the gradual drying + NMR experiments.

The Impact of Microstructure of Filtration Materials on Its Auto-Activation for Manganese Removal from Groundwater

The study investigates the impact of pore structure parameters of three chemically non-active filtration materials on the auto-activation time and the height of the filtration zone for manganese removal from groundwater. At a technical scale, the activation is a long process which may require a period of up to three months. The process can be shortened by the use of porous filtration materials. In this study, three filtration materials (silica sand, chalcedonite sand, GAC—granulated activated carbon) were investigated using subcritical nitrogen adsorption and mercury injection capillary pressure measurements. These methods provide a comprehensive evaluation of pore structure parameters, including specific surface area (SSA), micro- and mesopore volumes, and an extended range of pore size distribution (PSD). The studied materials provided a wide range of micro- and mesopore volumes as well as SSA. In order to investigate the auto-activation time of filtration material—the time required to achieve the requested quality of the filtrate—and the height of the filtration zone, a pilot experiment was conducted for 1950 h. The pilot installation consisted of three-meters-high (10 cm diameter) filtration columns filled with the tested filtration materials. The results indicate that the internal pore structure and the investigated auto-activation parameters are correlated. Both auto-activation time and the size of the filtration zone were influenced by the mesopore volume and the associated SSA of the tested materials. The micropore volume was less effective in improving the autoactivation parameters. The research results indicated the importance of pore structure characteristics which should be considered prior to time-consuming pilot and technological tests.

The beauty inhabited inside the modified Graphene for moisture detection at different frequencies

The present paper details on the synthesis and characterization of the modified Graphene and its moisture sensing application. The characterization tools as Brunauer–Emmett–Teller (BET), Scanning Electron Microscopy (SEM), Electron Dispersive X -rays (EDX), Particle size distribution, Fourier-Transform Infrared (FTIR), UV–Vis spectrophotometry and Raman are employed for characterizing the synthesized material. The BET demonstrations of the synthesized material have a specific surface area as 10.55 m2/g together with pore size distribution range from 10.34 to 97.44 nm, confirming the mesoporous material. The SEM, EDX, FTIR, UV–Vis spectroscopy and Raman analysis of the synthesized material confirmed that it is the modified Graphene (m-Graphene). Presence of the ID/IG = 1.55 confirms more defects along with many dangling bonds which are more beneficial for the humidity detection. The humidity sensing characteristics of m-Graphene based sensor have been observed from 100 Hz to 10 kHz frequencies and the best sensitivity was found at 100 Hz. The sensor shows high sensitivity of 2.51 MΩ/%RH along with the calculated repeatability, response and recovery time of 96.05%, 24 and 13 s, respectively, at room temperature.

Effect of old mortar pore structure on relative humidity response of recycled aggregate concrete

In this paper, based on the pore structure characteristics of old mortar attached to recycled concrete aggregate (RCA) surface, recycled aggregate concrete (RAC) internal relative humidity (RH) response process and mechanism were investigated, considering different temperatures, RCA replacement ratios and load condition. The RH was determined by the embedded probe, pore structure was measured by mercury intrusion porosimetry (MIP), and micro-cracks of the old and new mortar were observed through scan electron microscope (SEM). The experimental results indicated that: (1) The range of critical pore size distribution and the proportion of large capillary pores volume in the old mortar was larger than in new mortar, resulting in RH response rate in RAC being faster than natural aggregate concrete (NAC). The obstruction of saturated small pores (pore neck) on the diffusion of gaseous water in the connected large pores causes the RH response hysteresis. (2) The RH response rate in the pores increases with the increasing temperature, especially in RAC. (3) Under the bending load, the pore network of old mortar creates more micro-cracks than the new mortar which provided additional channels for the diffusion of gaseous water. These conclusions will be helpful for further understanding to the durability of RAC.

Adsorption of volatile organic compounds by industrial porous materials: Impact of relative humidity

Abstract In this study, the adsorption of several classes of volatile organic compounds by materials with a range of pore size distributions and chemistries were assessed gravimetrically in both dry and wet carrier gas conditions. Measurements carried out at room temperature, and a range of relative humidity values (RH) from 0 to 70%, reflected real-world conditions similar to those of indoor air. Dry removal performance appeared to be dependent on the surface area of adsorbents and, for polar compounds, the relative hydrophobicity of the material. Performance of sorbents with hydrophilic surface chemistry, such as silica gel and molecular sieve 13X, decreased drastically with small increases in pre-exposed humidity. Activated charcoal and high-silica faujasite Y retained their capacities for toluene in relative humidities up to 50% and 70% respectively, with their selectivity for non-polar species credited to hydrophobic pore structure and low water vapour uptake. These conclusions help to emphasise the importance of process humidity as a key parameter when designing or selecting adsorbents in realistic process conditions. Additionally, the methods used in this study provide a simple and reproducible way of testing porous materials for applications requiring or involving high levels of relative humidity.

Long-term impacts of topsoil depth and amendments on soil physical and hydrological properties of an Alfisol in central Ohio, USA

Soil hydrological properties and aggregate stability are strongly impacted by erosion and management practices. However, magnitudes of the erosion-induced changes in topsoil depth and the attendant alterations in soil properties are not well understood. Therefore, the present study was conducted on a long term (20 years) simulated study of topsoil depth and use of soil amendments to monitor changes in soil hydrological properties, and aggregate stability of an Alfisol at the Waterman Farm of The Ohio State University, Columbus, Ohio. The aim of the study was to compare long-term effects of soil amendments (synthetic fertilizer and organic compost) on soil physical and hydrological properties at varying soil depth. The experimental plots, comprising of five treatments, were laid out in Randomized Block Design and replicated thrice. Treatments were: (1) topsoil removed (20 cm deep), (2) undisturbed topsoil (intact topsoil); with two soil amendments: (a) synthetic fertilizer 150 kg nitrogen (N) ha−1 yr−1, (b) organic compost at 20 Mg ha−1 yr−1, and (3) a permanent grass field (as a benchmark plot). Soil properties, measured for 0–10 cm and 10–20 cm depth, were: texture, aggregate stability, geometric mean diameter (GMD) of aggregates, water retention properties, hydraulic conductivity (Ks), pore size distribution, and plant available water capacity (PAWC). Aggregate stability was the highest (87.9 and 84.7%) in the permanent grass at 0–10 cm and 10–20 cm depths, respectively. Among the cultivated treatments, compost- amended undisturbed plots (87.6 and86.9%) had the highest proportion of water stable aggregates (WSA) at 0–10 cm and 10–20 cm depths, respectively. However, the GMD of aggregates was the highest 4.1 mm (0–10 cm) and 3.5 mm (10–20 cm) for the topsoil removed and compost-amended treatment. Soil texture was silty clay loam in topsoil removed treatments, clay loam in the undisturbed treatment, and loam in permanent grass treatment, probably due to artificial removal of topsoil. Plant available water content was more in the disturbed and undisturbed compost-amended plots for both the 0–10 and 10–20 cm depths, respectively. The highest soil water volumetric content ranged from 0.37 to 0.25 m3 m−3 in the topsoil removed fertilizer added compared with 0.34 to 0.24 m3 m−3 in undisturbed compost added plots, respectively. However, the pore size distribution was not affected by treatments at the 0–10 cm depth. For the10-20 cm depth, an overall greater pore size distribution range of 0.04 to 0.33 m3 m−3 was observed in the permanent grass, and undisturbed compost amended treatments. Soil Ks (cm day−1) for 0–10 cm depth did not differ significantly across treatments. The data obtained enhances the understanding of the impacts of long-term use of amendments on soil water retention and aggregate stability of simulated topsoil removed and undisturbed field under no-till (NT) in corn (Zea mays)–soybean (Glycine max L. Merr.) rotation in the Eastern Corn Belt of the U.S.

The Impact of Mineral Dissolution on Drainage Relative Permeability and Residual Trapping in Two Carbonate Rocks

Carbon dioxide injection into deep saline aquifers is governed by a number of physico-chemical processes including mineral dissolution and precipitation, multiphase fluid flow, and capillary trapping. These processes can be coupled; however, the impact of fluid–rock reaction on the multiphase flow properties is difficult to study and is not simply correlated with variations in porosity. We observed the impact of rock mineral dissolution on multiphase flow properties in two carbonate rocks with distinct pore structures. Observations of steady-state hbox {N}_2–water relative permeability and residual trapping were obtained, along with mercury injection capillary pressure characteristics. These tests alternated with eight stages in which 0.5% of the mineral volume was uniformly dissolved into solution from the rock cores using an aqueous solution with a temperature-controlled acid. Variations in the multiphase flow properties did not relate simply to changes in porosity, but corresponded to the changes in the underlying pore structure. In the Ketton carbonate, dissolution resulted in an increase in the fraction of pore volume made up by the smallest pores and a decrease in the fraction made up by the largest pores. This resulted in an increase in the relative permeability to the nonwetting phase, a decrease in the relative permeability to the wetting phase, and a modest, but systematic decrease in residual trapping. In the Estaillades carbonate, dissolution resulted in an increase in the fraction of pore volume made up by pores in the central range of the initial pore size distribution, and a corresponding decrease in the fraction made up by both the smallest and largest pores. This resulted in a decrease in the relative permeability to both the wetting and nonwetting fluid phases and no discernible impact on the residual trapping. In summary, the impact of rock matrix dissolution will be strongly dependent on the impact of that dissolution on the underlying pore structure of the rock. However, if the variation in pore structure can be observed or estimated with modelling, then it should be possible to estimate the impacts on multiphase flow properties.

Study on Preparation of an Oil Sludge-Based Carbon Material and Its Adsorption of CO2: Effect of the Blending Ratio of Oil Sludge Pyrolysis Char to KOH and Urea

How to prepare a low-cost carbon material with a high carbon dioxide (CO2) adsorption performance has attracted much attention worldwide. Oil sludge, a hazardous solid waste, needs to be disposed off properly. Oil sludge pyrolysis has been proven to be an effective method for waste treatment with the production of pyrolysis oil, gas, and char. In this study, nitrogen-doped carbon (NC) was prepared and characterized based on oil sludge pyrolysis char (OSC). Specifically, NCs were generated by mixing OSC with potassium hydroxide and urea under different blending ratios of 1:3:2, 1:3:3, and 1:3:4 at 700 °C. NCs showed good surface morphology and pore structures with large specific surface areas (1056.45–1138.15 m2·g–1), pore volumes (1.54–1.63 cm3·g–1), and a wide range of pore size distribution. The best CO2 adsorption capacity of NCs at room temperature and pressure is 3.3 mmol·g–1 under a blending ratio of 1:3:2. In addition, the CO2/N2 selectivity of NCs is as high as 8.434. The adsorbent synthesized from oil sludge by a simple and low-cost method is a promising material for carbon dioxide adsorption.

Study on a nitrogen-doped porous carbon from oil sludge for CO2 adsorption

As an adsorbent material, porous carbon (PC) with high specific surface area, renewability and excellent thermal stability has been certified to be a potential candidate for carbon dioxide (CO2) adsorption. However, its high manufacturing cost and insufficient CO2 adsorption capacity are still significant problems to be solved urgently. The present work reported a nitrogen-doped porous carbon (NPC) synthesized from hazardous waste oil sludge (OS) via a facile and low-cost approach. The NPC possessed favorable features for excellent adsorbent, such as outstanding specific surface area (1224 m2·g−1), large pore volume (1.738 cm3·g−1) as well as tunable and large range of pore size distribution, among which the specific surface area and pore volume of porous carbon (PC) were just 632 m2·g−1 and 0.826 cm3·g−1, respectively. The carbon material NPC prepared by mixing oil sludge pyrolysis char with KOH and urea at 700 °C achieved the formation of nitrogen-containing functional groups, with CO2 adsorption capacity as high as 3 mmol·g−1. Furthermore, NPC possessed excellent reproducibility and thermal stability. It is demonstrated that the NPC synthesized from OS via a facile and low-cost approach was a promising adsorbent material for CO2 capture. This work provides a new strategy for synergetic processing of hazardous industrial waste and greenhouse gas.

Robust preparation and multiple pore structure design of poly (tetrafluoroethylene-co-hexafluoropropylene) hollow fiber membrane by melt spinning and post-treatment

Abstract In this work, poly (tetrafluoroethylene-co-hexafluoropropylene) (FEP) hollow fiber membranes were fabricated by melt-spinning method with solvent-free condition, while no coagulation bath was involved. The robust and solvent-free method for preparation of FEP hollow fiber greatly reduced environmental pollution for no solvent recovery problem. Calcium carbonate (CaCO3) as pore-forming agent, and dioctyl phthalate (DOP) as plasticizer as well as dispersant were used in this study. Meanwhile, the formation mechanism of multi-microporous structure with stretching pores, interface microvoids and dissolved micropores was studied, that the addition of CaCO3 brought about interfacial microvoids during the hot stretching-setting treatment and a dissolved pore structure after soaking and washing with hydrochloric acid bath. Furthermore, the effects of hot stretching-setting and hydrochloric acid solution treatment on the membranes’ structure and performance were characterized. The morphology exhibited that the prepared FEP hollow fiber membrane presented a kind of homogeneous membrane and the pore size distribution range remained relatively stable and narrow. Moreover, FEP membrane revealed excellent stability and solvent resistance with the mechanical strength retention rate up to 90%. These findings suggest that the FEP hollow fiber membrane prepared by this method will be great potential in the field of separation and purification in harsh conditions.

Pressure pulse-decay tests in a dual-continuum medium: An improved technique to estimate flow parameters

The pressure pulse-decay permeability (PDP) measurement is a well-established technique to measure the permeability of tight rock samples such as shale. The conventional applications of the PDP measurement almost exclusively treat shale samples as a single-continuum system, even though the gas flow in some shale samples may be more accurately characterized by a dual-continuum, which is due to the large range of pore size distribution and chemical/mineralogical difference between organic and inorganic matters. However, studies about measurements of flow parameters for dual-continuum shale rock samples are very limited in literature. Liu et al. (2016) proposed a new analytical technique to characterize the dual-continuum behavior of a test sample using the PDP measurement with the same upstream and downstream reservoir volumes. In this study, a more general analytical technique is proposed and allows for using different upstream and downstream reservoir volumes in the PDP setup. With this new technique, all the existing PDP systems in laboratories can be conducted to characterize the dual-continuum behavior of a test sample without the need of modifying the upstream and downstream reservoir volumes, and the measured flow parameters of samples can be used as input parameters in the reservoir simulation of the dual-continuum system. The validity and practical usefulness of the new technique is demonstrated by the successful identification and characterization of the dual continuum behavior of test samples in laboratory.

Effect of on-line stretching treatment on the structure and performance of polyvinyl chloride hollow fiber membranes.

In this work, polyvinyl chloride (PVC) hollow fiber membranes were prepared via a melt-spinning method and on-line stretching treatment. Gamma-butyrolactone (GBL) and epoxidized soybean oil (ESO) were selected as the solvent and the thermal stabilizer, respectively. The effects of on-line stretching treatment on the membrane structure and performance were characterized by means of morphology, surface roughness, pore size distribution, permeation performance and so on. The morphology showed that the prepared PVC hollow fiber membrane belonged to a homogeneous membrane. The on-line stretching treatment decreased the roughness of the inner surface and the outer surface, but it increased the water contact angle, mean pore size, porosity and pure water flux. Meanwhile, the pore size distribution range remained stable and narrow. The rejection of Direct Black 19 particles was higher than 90% when it approached a steady value. This type of membrane filtration was a deep intercept. Furthermore, the tensile strength increased with the increment of stretching ratio, and the elongation at break showed the opposite trend. The biggest tensile strength could be obtained as the stretching ratio reached 3.0 and was 23.89 MPa.

Study on Toughening Phenolic Foams in Phosphorus-Containing Tung Oil-Based Derivatives

Phenolic foams (PFs) as thermal insulation material with outstanding flame retardancy are required to match society’s ever expanding safety expectations; however, a trade off exists between flame retardancy and toughness. Here, for the first time, we synthesized a novel reactive phosphorus containing tung oil based derivative and used it to toughen PF, resulting in PFs with a combination of excellent mechanical properties and flame retardancy. Compared with pure PF, the modified PFs exhibit enhanced mechanical properties, with specific compressive and flexural strengths as high as 5.67 MPa and 12.46 MPa, which represent increases of 90.67% and 178.7% over those of pure PF, respectively. Meanwhile, the limiting oxygen index (LOI) values of the modified PFs are improved as much as 40.83%. Scanning electron microscopy micrographs show that the microstructure of the modified PFs is better than that of pure PF, with a more uniform cell morphology, a narrower pore size distribution range, and a smaller average pore size, all of which are beneficial to the foam’s mechanical properties. This study provides a scientific paradigm for the development of advanced PFs based on renewable biological resources.

Evolution of pore structure during microwave freeze-drying of Chinese yam

In order to reduce the energy consumption of freeze drying (FD), microwave freeze drying (MFD) can be used to dry Chinese yam. Porosity is a critical factor influencing transport mechanism, and can be considered as an important index to reflect the changes of structure of MFD foods. In this study, the changes of pore structure during the process of MFD Chinese yam were investigated by SEM and mercury porosimetry. The results showed that some closed pores could transform to open pores in drying process, and the open porosity showed a rising trend throughout the drying process. The pore size distribution range was about 10 nm to 106 nm throughout the drying process. In the early stage of drying, the pore size was mainly in the range of 10-104 nm, and then the pore size and the number of pores reduced. In the middle and late drying stages, the size of large pores increased again. Keywords: microstructure, microwave freeze drying, porosity DOI: 10.25165/j.ijabe.20181106.4250 Citation: Duan L L, Duan X, Ren G Y. Evolution of pore structure during microwave freeze-drying of Chinese yam. Int J Agric & Biol Eng, 2018; 11(6): 208–212.

A criterion for evaluating the effect of shale-matrix dual-continuum flow on gas production

Because of the large range of pore size distribution and the chemical/mineralogical heterogeneity within shale matrix, gas flow in it may exhibit dual-continuum flow behavior even though rock matrix is not fractured. The relative importance of dual-continuum flow has considerable implications to the shale reservoir characterization and gas production. A matrix-dominant gas flow model is developed to evaluate the impacts of dual-continuum gas flow on gas production. The simulation results reveal three regimes with regard to the relative importance of the dual-continuum flow. When the mass transfer coefficient between the mobile and immobile continua is relatively high, the dual-continuum behavior becomes insignificant within the context of production rate prediction. When the mass transfer coefficient is very small, the dual continuum gas flow behavior also becomes insignificant because gas flow between the two continua is essentially negligible. Thus, the dual-continuum gas flow behavior becomes important to the long-term gas production rate only for the intermediate range of mass transfer coefficient that is shown to depend on porosity and gas adsorption properties. Based on the physical reasoning and numerical simulation results, we propose a criterion to determine the relative importance of the dual-continuum gas flow. The criterion is expressed with a dimensionless parameter that combines several parameters including the mass transfer coefficient, gas viscosity and densities and matrix porosity. The numerical simulation results show that when the dimensionless parameter is less than a critical value, the dual-continuum gas flow becomes important under a variety of different conditions.

Pore characteristics of the carbonate shoal from fractal perspective

The carbonate shoal is a notable reservoir for the hydrocarbon enrichment. Fractal theory has been proven to be a robust analytical tool to indicate the pore irregularity and surface roughness for permeable medium. With the aim to study the pore structure of carbonate shoal from fractal perspective, a series of parallel experiments including nuclear magnetic resonance (NMR), high pressure mercury intrusion (HPMI) and scanning electron microscopy (SEM) were carried out in this paper to calculate the fractal dimensions and the results given by various techniques were compared. The relationships between the fractal dimensions along with the petrophysical properties including the pore structure parameters were analyzed. Based on the fractal dimensions, the tested samples and the different pore types could effectively be distinguished. Classification methods for pore system including macropores (dp＞1000 nm), mesopores (1000 nm＞dp＞100 nm), Ⅱ-micropores (100 nm＞dp＞25 nm) and Ⅰ-micropores (dp＜25 nm) in the tight carbonate shoal reservoir were verified by the HPMI-based fractal dimensions. Fractal curves obtained from the NMR data could be divided into two different segments, which respectively corresponds to the seepage pores and adsorption pores. The SEM-based fractal curves were presented as a straight line. Results showed that micropores in the carbonate shoal made greater contribution to the total fractal dimension, although macropores and mesopores tended to have a relatively higher fractal dimension. Porosity and permeability of the tested samples were mainly governed by the meso- and macropores. Negative linear correlations were identified on the one hand between the HPMI-based total fractal dimensions (DHPMI) and the maximum mercury saturation (SHgmax), and the other hand the fractal dimensions of the macropores (DHPMI-macropores) and the average pore size (rave), respectively. Due to the different sensitivities, no clear correlations were obtained between the fractal dimensions obtained from the HPMI, NMR and SEM data in the whole range of pore size distribution, but DHPMI-macropores showed a positive correlation with DNMR-seepage pores.

Integrated NMR and FE-SEM methods for pore structure characterization of Shahejie shale from the Dongying Depression, Bohai Bay Basin

Of particular importance for shale reservoirs is the evaluation of pore structure characteristics that significantly influence a reservoir's storage capacity and flow mechanisms. Due to the presence of multiscale pore sizes in shale reservoirs, a series of experiments, including total organic carbon (TOC), Rock-Eval analysis, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and nuclear magnetic resonance (NMR), were conducted on shale samples from the lower submember of the third member (Es3L) and upper submember of the fourth member of the Eocene Shahejie Formation (Es4U) in the Dongying Depression, Bohai Bay Basin. The results indicate that calcite (averaging 30.5%) and clay (averaging 29.1%) are the dominant minerals. Based on analysis of geochemistry data, the organic matter type of LY1 is I and II. Four main types of reservoir spaces are observed in LY1: intercrystalline pores, dissolved pores, intergranular pores, and microfractures. Shale samples in the study area have a wide range of pore size distributions and complex pore structures because of the wide range of transversal relaxation time (T2) distributions and messy T2 curves of the NMR experiment. Per the NMR results, the percentage of micropores, mesopores and macropores (MS1, MS2, and MS3) were calculated, and the relationships between these proportions and pore structure parameters (porosity, permeability, T2 cutoff value, T2 geometric mean value) and structural characteristics were investigated. MS1 increased with a decrease of T2 cutoff values and geometric mean values, suggesting that shale samples with higher MS2 and MS3 have better pore structures and strong percolation potential. Under similar porosity conditions, samples with high permeability have a larger MS3 value. Laminated and layered shale samples have larger values of MS2 and MS3 than massive shale. Therefore, MS1, MS2 and MS3 are useful to indicate the quality of pore structures; the smaller the MS1, the better the pore structure. Finally, taking three representative shale samples as an example, the relationships between MS1, MS2, and MS3 and the effectiveness of the reservoir were discussed using the logging profile of LY1. The research concludes that MS1, MS2, and MS3 are effective NMR parameters for evaluating the effectiveness of the reservoir.

Photocatalytic degradation of azophloxine on porous La2Ti2O7 prepared by sol-gel method

Cetyltrimethyl ammonium bromide (CTAB) was used in a sol-gel route to synthesize porous lanthanum titanate. The materials are composed of perovskite La2Ti2O7 in monoclinic system. The addition of CTAB does not cause phase transformation, but leads to a slight decreasing tendency of La2Ti2O7 crystallite size. Both the pore volume and pore size distribution range are enlarged after using CTAB. The sample obtained with 4 g CTAB has the maximum BET specific surface area of 42.4 m2/g. When the amount of CTAB is less than 4 g, the increase in photocatalytic degradation efficiency is almost in linear relationship to the amount of CTAB. The reaction rate constants are 0.0032, 0.0116 and 0.0237 min−1 on the La2Ti2O7 samples obtained using 0, 2 and 4 g CTAB. The functional groups in azophloxine molecule are decomposed during photocatalytic oxidation with extending irradiation time.