Nitrogen Adsorption Tests Research Articles

Ni[sbnd]Y2O3[sbnd]Al2O3 aerogel catalysts with high coke deposition resistance for syngas production by biogas reforming

The control of coke deposition is one of the most important challenges during reforming processes using Ni/Al2O3 catalysts. To minimize the effects of coke deactivation and increase the catalytic performance, NiY2O3Al2O3 aerogel catalysts were synthesized by the epoxide-initiated gelation method and dried with supercritical CO2. The catalysts with yttria added were evaluated in terms of syngas production and coke formation in biogas reforming reactions in the temperature range of 500–800 °C. The techniques used to characterize the catalysts were nitrogen adsorption tests, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, inductively coupled plasma optical emission spectroscopy, thermogravimetric analysis, scanning and transmission electron microscopy. Nanoscale and mesoporous catalysts with high specific surface area were obtained. The catalysts maintained an amorphous structure with high metal dispersion and homogeneous distribution. Yttria insertion promoted higher interaction between the active phase and the support in the catalysts. For the first time, profiles for the coke deposition and syngas production were determined simultaneously during reforming reactions. Hydrogen production increased with yttria addition on the catalysts. The syngas production was highest at 800 °C. However, the hydrogen production was highest at 600 and 700 °C. The coke-resistance of the catalysts decreased in the following order: NiY2.5Al > NiY5Al > NiAl > NiY10Al. The yttria promoter showed a decrease in the coke formation of 58 wt% compared to NiAl at 700 °C. NiY2O3Al2O3 aerogel catalysts are a promising alternative in the search for high-coke-resistance catalysts and for increasing the syngas production in biogas reforming reactions.

Impact of Brine/CO2 exposure on the transport and mechanical properties of the Mt Simon sandstone

Abstract When sandstone rocks are exposed to CO2-saturated brine, their transport and mechanical properties can change due to brine/CO2-induced chemical reactions. The present study investigates the change in the flow-through characteristics, porosity, and the mechanical behavior of Mt. Simon Sandstone samples caused by exposure to brine/CO2. The cores, extracted from a depth interval of 2110.4–2111.4 m (6924–6927 ft) in the Mt. Simon formation, were first characterized for their mechanical and transport properties, and then aged in CO2-saturated brine at pressures of 17.24 MPa (2500 psi) and temperature of 50 °C for one to two weeks. Following that, the changes in the transport and mechanical properties of the samples were analyzed using He pycnometry, flow perporometry and triaxial testing. Our experiments show that the porosity of the Mt. Simon samples slightly increases after exposure to CO2/brine, while the permeability increases more substantially depending on the stress state. Measurements of the flow-through pore size distribution (PSD) are indicative of the changes occurring and are consistent with the observed increases in permeability. Nitrogen adsorption tests (BET), before and after incubation, show a significant loss of pore volume in the mesoporous range that is indicative of clay dissolution. Weakening of the materials was observed based on the mechanical properties studied, a result that is consistent with the observed dissolution of clays that play a central role in the cementation of the quartz grains. Finally, the analysis of the brine compositions reveals an increase in concentration of most cations after incubation with the Mt. Simon cores. This is also consistent with mineral/clay dissolution, confirmed by the porosity, transport, and mechanical property measurements as well as electron microscopy analysis of the same samples.

Preparation and Properties of SiBCO Aerogel and Its Composites.

To obtain new high-temperature resistant composites that can meet the requirements of aircraft development for thermal insulation and mechanical properties, SiBCO aerogel composites were prepared by sol-gel, supercritical drying and high-temperature pyrolysis with trimethyl borate (TMB) or phenylboronic acid (PBA) as the boron source and mullite fiber as reinforcement. The structure and composition of the SiBCO aerogel and its composites were characterized with SEM, FT-IR, ICP and nitrogen adsorption tests. The specific surface area of the SiBCO aerogel is 293.22 m2/g, and the pore size is concentrated in the range of 10–150 nm. The mechanical properties, the thermal insulation properties and the temperature resistance were also studied. Due to the introduction of boron, the temperature resistance of SiBCO aerogel composites is improved greatly, and the service temperature of composites reached 1773 K. When n (TMB)/n (TEOS) = 1/1, the temperature resistance of the composites is the best. After heating in air at 1773 K for 30 min, the shrinkage of SiBCO aerogel composites is only 2.45%, and the thermal conductivity of the composites is 0.138 W/(m·K) at 1773 K. In addition, the type and amount of catalyst also have certain effects on the mechanical properties and temperature resistance of the composites.

Performance of Date Palm Ash as a Cementitious Material by Evaluating Strength, Durability, and Characterization

Cement manufacturing is indeed a major contributor to global warming that involves energy-intensive production processes along with emitting huge greenhouse gasses into the atmosphere. To adopt sustainable construction practices, agro-industrial waste materials as supplementary cementitious materials (SCMs) have been used by numerous researchers to partially replace conventional ordinary Portland cement (OPC) with SCMs by evaluating its optimum replacement dosage. This study aims to: (1) highlight the background of the date palm tree and the application of date palm waste as a construction material; (2) optimizing the dosage of date palm ash (DPA) as a cementitious material, at the replacement level of 10%, 20%, and 30%; and (3) understand the reaction kinetics by way of characterization techniques. DPA-based binary mixes were compared with each other and with the control (100% OPC mix) through fresh, mechanical, durability, and microstructural properties. The mechanism of reaction at early- and long-term period of curing was studied by characterization tests on paste, including nitrogen adsorption test (BET), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR). The outcome revealed 10% DPA as a strong and durable substitute to OPC, by formation of more Calcium Silicate Hydrate (C-S-H) and Calcium Aluminosilicate Hydrate (C-A-S-H) gel, whereas up to 30% DPA replacement can further maximize clinker replacement with reasonable performance, together with enhanced sustainability and reduced construction cost.

Synthesis of low shrinkage monolith alumina aerogels by surface modification and ambient pressure drying

The authors have synthesised a kind of low shrinkage alumina (Al2O3) aerogel using an inexpensive salt of aluminium (AlCl3 ·6H2 O) via tetraethoxysilane modification and an ambient pressure drying process. The morphology, pore structure, surface group, crystal phase and thermal properties of the Al2O3 aerogel are analysed by X-ray diffractometer, scanning electron microscopy, Fourier transform infrared spectra and nitrogen adsorption test. Further improvement in thermal stability and thermal shrinkage are obtained by incorporation of silicon (Si) atoms during the aerogel preparation. The specific surface area of modified aerogel is 480 m2/g and the diameter shrinkage is 8% after drying, and reach 304 m2/g and 16.5% after heating at 1000°C. The approach, which is straightforward, inexpensive and safe, can be employed to prepare a monolithic mesoporous material with low shrinkage and high-temperature resistance. This will further promote the potential application of packaging and thermal insulation materials.

Auto-Crosslinked Rigid Foams Derived from Biorefinery Byproducts.

A new macroporous foam‐like material is presented based on autocross‐linking humins, an industrial biorefinery byproduct. Humins foams are obtained by a simple heating process, without any pretreatment and with high control of morphology, porosity, and carbon content. Untreated humins have been characterized by GC, ultra‐performance liquid chromatography (UPLC), elemental analysis, and FTIR, whereas the mechanism of foaming was elucidated by a combination of thermal and rheological analyses. A preliminary screening of conditions was conducted to identify the parameters controlling this foaming process. A foam was produced in a controlled way with open and/or closed cells with cell diameters between 0.2 and 3.5 mm. Humins foams were characterized by Raman spectroscopy, FTIR, SEM, nitrogen adsorption, pycnometry, and mechanical tests. The results show that, based on humins, it is possible to obtain porous materials with controlled architectures and a range of parameters that can be tailored, depending on the foreseen applications.

Effects of plasma-treated rock asphalt on the mechanical properties and microstructure of oil-well cement

In this study, natural rock asphalt with a high softening point was selected as an oil-well cement admixture. The effects of the asphalt, which was subjected to a low-temperature plasma treatment, on the mechanical properties and microstructure of the cement paste were investigated. The results show that the hydrophilicity of the surface of the rock asphalt, and the interfacial bonding between the asphalt and cement matrix were improved with the use of the low-temperature plasma technology. The addition of the treated rock asphalt reduced the compressive strength of the cement paste but improved its tensile strength. Triaxial stress-strain curves, obtained under static and multicycle loads, showed that the rock asphalt improved the toughness of the oil-well cement paste. The addition of the 3% rock asphalt obviously enhanced the mechanical deformability of the cement paste. The results of the scanning electron microscopy analysis showed that the rock asphalt can deflect cracks and prevent crack propagation. The ability to restrain crack propagation improved as the adhesion between the treated hydrophilic asphalt and matrix cement improved. The results of the nitrogen-adsorption tests and mercury-intrusion porosimetry tests showed that the incorporation of the rock asphalt reduced the number of harmful pores present within the cement composite. The results of the X-ray diffraction (XRD) and thermogravimetric (TG) analyses performed on the asphalt-cement composites showed that the asphalt slightly retards cement hydration.

Characterizing Pores and Pore-Scale Flow Properties in Middle Bakken Cores

Summary To understand the flow and transport mechanisms in shale reservoirs, we needed reliable core-measured data that were not available to us. Thus, in 2014, we conducted a series of diverse experiments to characterize pores and determine the flow properties of 12 Middle Bakken cores that served as representatives for unconventional low-permeability reservoirs. The experiments included centrifuge, mercury-intrusion capillary pressure (MICP), nitrogen adsorption, nuclear magnetic resonance (NMR), and resistivity. From the centrifuge measurements, we determined the mobile-fluid-saturation range for water displacing oil and gas displacing oil in addition to irreducible fluid saturations. From MICP and nitrogen adsorption, we determined pore-size distribution (PSD). Finally, from resistivity measurements, we determined tortuosity. In addition to flow characterization, these data provided key parameters that shed light on the mechanisms involved in primary production and the enhanced-oil-recovery (EOR) technique. The cores were in three conditions: clean, preserved, and uncleaned. The hydrocarbon included Bakken dead oil and decane, and the brine included Bakken produced water and synthetic brine. After saturating the cores with brine or oil, a set of drainage and imbibition experiments was performed. NMR measurements were conducted before and after each saturation/desaturation step. After cleaning, PSD was determined for four cores using MICP and nitrogen-adsorption tests. Finally, resistivity was measured for five of the brine-saturated cores. The most significant results include the following: Centrifuge capillary pressure in Bakken cores was on the order of hundreds of psi, both in positive and negative range. Mobile-oil-saturation range for water displacing oil was very narrow [approximately 12% pore volume (PV)] and much wider (approximately 40% PV) for gas displacing oil. In Bakken cores, oil production by spontaneous imbibition of high-salinity brine was small unless low-salinity brine was used for spontaneous imbibition. Resistivity measurements yielded unexpectedly large tortuosity values (12 to 19), indicating that molecules and bulk fluids have great difficulty to travel from one point to another in shale reservoirs.

Contribution of single coal property to the changes of structure and reactivity of chars from blending coking

This study investigates the contribution of single coal in blends on the properties of the char produced. Three kinds of coals with varying rank and caking ability were used for the preparation of the chars at 1150 °C in muffle furnace. Char reactivity towards carbon dioxide (CRI) and char strength after reaction (CSR) were tested through the fixed-bed reactor in a laboratory scale and the tumbler, respectively. X-ray diffraction (XRD), scanning electron microscope (SEM), and nitrogen adsorption test were applied to obtain the information for the chemical and physical structures of the char. The study results show that the CRI of char increases with the increase of subbituminous coal content in blends for its role in increasing the surface area and decreasing the crystallite height (Lc) of the chars; the increase of fat coal content in coal blends causes the decrease of the CRI of chars for its contribution to the more ordered crystallite structure and less surface area. The contribution of single coal property in blends to the CSR of chars is just contrary compared to its contribution to the CRI of the chars. Coal blends with high volatile yield and low GR.I value would cause higher surface area and lower crystallite height of char. The CRI of the char can be well predicted by GR.I value and volatile yield of the coal blends quantitatively: CRI(%)=-0.029GR.I+1.995Vdaf−57.937, which is of certain theoretical guiding significance for gasification of char from coal blends.

Experimental study of low-temperature combustion characteristics of shale rocks

Relatively low temperature (500 °C) combustion has been applied to shale rocks collected from Lianmuqing, Xinjiang Province, China, to improve the permeability of shale without pore structure change caused by mineral decomposition. The shale rocks were firstly grinded into small particles, then burned in a furnace at a constant temperature of 500 °C for 5 min, 15 min, and 30 min, respectively. A cylindrical shale sample was also subjected to the combustion experiment. It was found that thermal cracking occurred along the height of the shale as combustion propagated from bottom to top. From the low-temperature nitrogen adsorption test, it was found that the pore diameters of shale samples were in the range of 2–50 nm, which were less than the mean free path of an oxygen molecule. Thus, the diffusion of gas inside the shale was Knudsen diffusion and the Knudsen number (Kn) was between 8 and 25. Moreover, the mean diameter of shale pores and the effective diffusion coefficient increased with increasing oxidization time. Whereas the surface area decreased after combustion, the diameter of the shale particles remained constant. So the density of the shale decreased with increase of combustion time. According to the porous media combustion model, the oxidization of shale particles was considered to be in Regime I, which is under kinetic control at isothermal combustion condition (500 °C). Furthermore, the effective diffusion coefficient was in a range of 3 × 10−6–6 × 10−6 m2/s. It increased with increasing combustion duration, especially during the first five minutes. The experiment results showed that low temperature combustion can effectively improve shale permeability to facilitate gas extraction from shale reservoir.

Effect of Ca(OH)2 on shrinkage characteristics and microstructures of alkali-activated slag concrete

The study presents the shrinkage behaviour of Ca(OH)2-added alkali-activated slag (AAS) concrete. A series of tests were performed to determine the plastic shrinkage, autogenous shrinkage and drying shrinkage. In order to explain shrinkage mechanisms, the moisture loss was monitored; the pore structure was examined by nitrogen adsorption test; hydration process was assessed by isothermal calorimetry; hydration products and microstructure were characterised by XRD, SEM/EDS and TG/DTG. It was found that the use of Ca(OH)2 increased the plastic shrinkage of AAS concrete, but reduced autogenous and drying shrinkage. This is because the addition of Ca(OH)2 accelerated the hydration at very early stage, while non-noticeable impact could be identified after 120 h. The results from nitrogen adsorption test showed a decrease in mesopores by adding Ca(OH)2, which was responsible for the less drying and autogenous shrinkage. Meanwhile, the Ca/Si of C-S-H (I) increased from 0.89 to around 1.40 at 28 d when adding 5% and 10% Ca(OH)2. XRD patterns indicated C2ASH8 and C4AH13 were found in Ca(OH)2-added samples. These changes in hydration products also contribute less drying and autogenous shrinkage in Ca(OH)2-added samples.

Experimental study on thermo-responsive inhibitors inhibiting coal spontaneous combustion

Due to its strong fluidity and easy evaporation characteristic, high water-cut physical inhibitors (HWPIs) cause the decrease in moisture content of coal, so that its inhibitory effect on coal spontaneous combustion weakens or even fails. Aiming at solving the problem, this paper proposes to inhibit coal spontaneous combustion using thermo-responsive inhibitors (TRIs). These inhibitors are sensitive to specific temperatures and can retain their effects as long as the temperatures have not been reached. Besides, when the temperatures are reached, they are able to absorb heat and undergo physical and chemical changes to release H2O and inert gases (defined as gases that are not involved into the coal oxidation reaction in this paper) such as NH3 and CO2, so as to inhibit the low-temperature oxidation of coal. Based on the temperature-programmed experiment of coal spontaneous combustion, this paper analyzed the effects of types and amounts of TRIs on coal spontaneous combustion by using differential scanning calorimetry (DSC), scanning electron microscope (SEM), thermogravimetry-derivative thermogravimetric analysis-differential scanning calorimetry (TG-DTG-DSC) and nitrogen adsorption test methods. The results show that CaCl2•6H2O achieves the most stable inhibitory effect, as its inhibiting rate rises steadily in the heating process to reach a maximum value of 79.9% at 200 °C.

Pore structure characteristics of China sapropelic coal and their development influence factors

Sapropelic coal is similar to humic coal in organic matter content, and to shale in kerogen type. Research on the sapropelic coal pore structure can help to understand the differences between humic coal and shale in pore development. In this paper, the pore structures of 21 sapropelic coal samples from Shaanxi, Shanxi, Gansu and Shandong provinces were determined, coupled with proximate analysis, reflectance (Ro), maceral and fractal analysis, scanning electron microscopy (SEM), mercury porosimetry (MIP), and low-temperature nitrogen adsorption tests. The results indicate that Late Paleozoic and later age sapropelic coals are low rank with Ro values ranging from 0.31% to 0.82%, and Early Paleozoic sapropelic coals are high rank with Ro values ranging from 2.64% to 5.89%. The low-rank coals are mainly of Types IIa and IIb kerogen containing humic detritus. The high-rank coals are of Type I kerogen composed by bitumen matrix and minerals. According to the normalized pore size distribution (PSD) curves of MIP and low-temperature N2 adsorption, three pore types (Type IM, Type IIM, and Type IIIM) for seepage pores and three pore types (Type IN, Type IIN, and Type IIIN) for adsorption pores are divided, respectively. For seepage pores, all the low-rank sapropelic coals have the Type IM PSD, while the high-rank coals contain Type IM, Type IIM and Type IIIM PSDs. From Type IM via Type IIM, to Type IIIM, the content of mesopores and macropores increases; meanwhile, the fractal dimensions (Dt, derived from the thermodynamics model) also increase. For adsorption pores, from type IN via type IIN to type IIIN, the BET specific surface area (SSA), density function theory (DFT) volume and Frenkele-Halseye-Hill (FHH) fractal dimension (Df) successively increase, and the medium pore diameters successively decrease. It was found that the development of the saproplelic coal pore structure was controlled by the integrated effects of coal rank and composition. Generally, the seepage pores of sapropelic coals studied in this work are mainly primary or intergranular pores with weak correlation with the coal composition. However, the development of the adsorption pores has obvious correlations with organic matter content, ash yield rate (Aad) and moisture content (Mad).

The effects of supercritical CO2 on mesopore and macropore structure in bituminous and anthracite coal

The effects of supercritical CO2 (scCO2) on coal pores play a critical role in CO2 geological storage-enhanced coalbed methane recovery (CO2-ECBM). To investigate the effects of scCO2 on the pore structure and connectivity in coals of different ranks, CO2 sequestration processes were replicated using a scCO2 geochemical reactor. Four coal samples with different ranks were exposed to scCO2 and water for 240 h under 80 °C and 20 MPa. Mercury intrusion porosimetry, nitrogen adsorption tests, and scanning electron microscopy analysis were used to identify the pore volume, pore size distribution, pore connectivity, and pore morphology of the coal samples before and after scCO2-H2O treatment. The increase in the macropore volume caused by the scCO2 is mainly controlled by the pores >30 μm, resulted from the dissolution of carbonate minerals with large grain size in organic matter. The coal rank has a positive influence on the volume and specific surface area of the pores >30 μm, whereas coal rank is more significant for macropore specific surface area in the high-volatile bituminous coal and macropore volume in the low-volatile bituminous, semi-anthracite, and anthracite coal. With an increase in the coal rank, the volume and specific surface area of the mesopores increase. The changes in the mesopore volume in the high-volatile bituminous coal are caused by changes in the pores 20–50 nm in diameter, while these changes in the low-volatile bituminous coal, semi-anthracite, and anthracite are caused by changes in the pores <20 nm, due to the formation of dissolution-created pores in minerals; additionally, many pores <3 nm are generated by the scCO2. At the macropore scale, the scCO2 increases the volume of the non-effectively interconnected pores more than that of the effectively interconnected pores, indicating that the scCO2 has a weak effect on the increase in macropore connectivity. The volume of the effectively interconnected pores increases more at the mesopore scale than at the macropore scale, and the scCO2 treatment increases the connectivity of the mesopores.

Enhance low temperature oxidization of shale gas recovery using hydrogen peroxide

Gas extraction from shale has been challenging due to extremely low permeability in shale formations. Recently, high temperature treatment methods were introduced to remove organic matters from shale to increase shale pore diameter and reservoir permeability. In this study, hydrogen peroxide was used as oxidizer to react with organic matters in shale samples for 6, 12, 24, and 48 h, respectively. X-ray diffraction (XRD) tests were employed to study the mineral compositions. Then, thermal decomposition experiments of shale samples were also conducted by the combined Thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) technique to analyze the weight loss behaviors and gas emission in N2 environment during pyrolysis. Afterwards, the effect of pyrolysis and reaction duration on pore diameter were investigated by liquid nitrogen adsorption and desorption tests. Finally, scanning electron microscopy (SEM) images of the shale samples were analyzed to reveal pore structure change on the surface of shale samples. From the experiments, it was found that the organic matters could react with H2O2 at ambient temperature and pore diameter increased with reaction time. The mean pore diameter increased by 40% when samples were treated with H2O2 for 48 h. More larger pores were observed on the surface of both pyrolyzed and H2O2 treated shale samples from the SEM images. Moreover, the pyrolyzed samples have larger pores compared to the H2O2 treated samples due to the decomposition of minerals at high temperature.

Preparation and thermal properties of polyethylene glycol/expanded graphite as novel form-stable phase change material for indoor energy saving

Phase change material (PCM) is a new kind of material for energy storage; its thermal properties are key factors in determining the application areas and the actual effect. The polyethylene glycol (PEG)/expanded graphite (EG) composite was prepared as a novel form-stable PCM by vacuum impregnation in this study. Nitrogen adsorption test indicated that EG belonged to materials in mesoporous scale with developed porous structure and prodigious adsorbility. The PEG/EG PCM owned excellent sealing performance and remarkable thermal storage capacity. The phase change temperatures and latent heats of the PEG/EG PCM were in range of 18.89–25.93 °C and 97.56–98.59 J·g−1 respectively. TGA and thermal performance manifested that the PEG/EG PCM presented good thermal stability and EG performed favorable conductivity and improved the thermal storage efficiency. The obtained PCMs were suitable for indoor energy saving and thermal comfort improvement.

Micropore Structure and Fractal Characteristics of Low‐Permeability Coal Seams

With the raw coal from a typical low‐permeability coal seam in the coalfield of South Junger Basin in Xinjiang as the research object, this paper examined six kinds of coal samples with different permeabilities using a scanning electron microscope and a low‐temperature nitrogen adsorption test that employed a JSM‐6460LV high‐resolution scanning electron microscope and an ASAP2020 automatic specific surface area micropore analyzer to measure all characteristic micropore structural parameters. According to fractal geometry theory, four fractal dimension calculation models of coal and rock were established, after which the pore structure characteristic parameters were used to calculate the fractal dimensions of the different coal seams. The results show that (1) the low‐permeability coal seam in the coalfield of South Junger Basin in Xinjiang belongs to mesoporous medium, with a certain number of large pores and no micropores. The varying adsorption capacities of the different coal seams were positively correlated with pore volume, surface area, and the mesoporous surface area proportions, from which it was concluded that mesopores were the main contributors to pore adsorption in low‐permeability coal seams. (2) The raw coal pore fractal dimension had a negative linear relationship to average pore size, a positive linear relationship with total pore volume, total surface area, and adsorption capacity, and a positive correlation with the mesoporous surface area proportion; that is, the higher the fractal dimension, the larger the pore volume and surface area of the raw coal. (3) The permeability of the low‐permeability coal seam had a phase correlation with the micropore development degree; that is, the permeability had a phase negative correlation with the pore distribution fractal dimension, and there was a positive correlation between permeability and porosity. These results are of theoretical significance for the clean exploitation of low‐permeability coal seam resources.

Pore evolution characteristic of shale in the Longmaxi Formation, Sichuan Basin

Through the field emission scanning electronic microscope (FESEM) and the nitrogen adsorption test, pore type and structure of shale reservoir in the Longmaxi Formation in the Sichuan Basin were well studied. Result showed that the pore type includes organic pore, intercrystalline pore, dissolution intracrystalline pore and interparticle pore, and the organic pore was one of major pore types; among the organic pore, the micropore had large pore volume and specific surface area, and was the main storage space of shale gas. Through study on effect of total organic carbon (TOC), organic matter maturity (Ro), diagenesis and tectonism on shale porosity, influence of TOC on porosity could be divided into four stages: the rapid increasing stage (TOC from 0 to 2%), the slow decreasing stage (TOC from 2 to 3%), the rapid increasing stage (TOC from 3 to 4% or 6%) and the rapid decreasing stage (TOC > 4% or 6%); influence of the maturity on porosity of shale could be divided into three stages: the rapid decreasing stage (Ro from 1.5 to 2.2%), the rapid increasing stage (Ro from 2.2 to 2.7%) and the rapid decreasing stage (Ro > 2.7%); during the high thermal evolution stage, the organic diagenesis was stronger than the inorganic diagenesis; the tectonism had a great impact on porosity, and the more intense the tectonism was, the smaller the porosity would be. The evolution of shale porosity of the Longmaxi Formation underwent five stages: the immature rapid compaction stage (Ro<0.7%), the mature hydrocarbon generation and dissolution stage (Ro from 0.7 to 1.3%), the high mature pore closed stage (Ro from 1.3 to 2.2%), the overmature secondary pyrolysis stage (Ro from 2.2 to 2.7%) and the overmature slow compaction stage (Ro>2.7%); among which the mature hydrocarbon generation and dissolution stage and the overmature secondary pyrolysis stage were the most favorable shale pore development stages.

An overview and experimental study on hybrid binders containing date palm ash, fly ash, OPC and activator composites

Global warming due to high greenhouse gasses emission coupled with excessive energy involved in concrete manufacturing process is indeed an alarming threat. To overcome the problem, numerous researches have been carried out to partially replace ordinary Portland cement (OPC) with supplementary cementitious materials (SCMs) that includes agricultural or industrial solid wastes, development of alternative binder known as geopolymer concrete made of one or more pure SCMs using alkaline activators and elevated temperature curing or by development of hybrid cement system that incorporates alkaline activation of OPC-based SCMs. This study aims to: (1) carry out an overview on: CO2 emission by construction industry; alternate cement systems such as partial replacement, geopolymers and most importantly hybrid binders; as well as identification of date palm ash (DPA) as a potential waste material and (2) develop novel hybrid alkali activated binders with a combination of agro-industrial waste to form binary and ternary mortar binders cured under water up to 28-days. The utilized SCMs include fly ash (FA), ground date palm ash (GDPA) i.e. alkali activated or raw DPA i.e. non-activated. These hybrid and non-hybrid binders were compared through physical properties such as strength and workability along with microstructural properties by hydration products and pore volume. X-ray diffraction (XRD) technique was employed to get the mineral composition; phase decomposition of unreacted water, C-S-H/C-A-S-H gel and Ca(OH)2 had been studied by Thermogravimetric analysis (TGA) while nitrogen adsorption test determined surface area of particles as well as pore volume of the paste. The results revealed potential use of DPA as a strong and sustainable material in ternary blend with FA and OPC in conventional non-hybrid binder that can efficiently maximize clinker replacement without energy utilization in alkaline activation.

Hydrogen rich syngas production from biomass gasification using synthesized Fe/CaO active catalysts

Biomass gasification for hydrogen rich syngas production was investigated using the Fe/CaO catalysts in a fluidized bed reactor. The synthesized catalysts were prepared by an impregnation method with different Fe/CaO mass ratios (5%, 10%, 15%, 20%) for enhancing H2 concentration and syngas yields and then characterized using X-ray diffraction (XRD), nitrogen adsorption and desorption isotherms test, scanning electron microscopy (SEM) and CO2 absorption capacity test. The results showed that the Fe load had significant influences on the composition, textural properties and CO2 adsorption capacity. Results of gasification experiments verified that the presence of Fe enhanced the concentration and yield of H2. The highest syngas yield of 38.21 mol/kg biomass, H2 yield of 26.40 mol/kg biomass, LHV values of 8.69 MJ/kg and gasification efficiency of 49.15% were obtained at an optimized mass ratio of Fe/CaO = 5%. In addition, the characterization results indicated that Ca2Fe2O5 phase was formed. The Ca2Fe2O5 had less CO2 absorption capacity and effect on the gasification, but was considered to be a catalyst for tar cracking thus preventing the CaO deactivation.