Decrease In Surface Area Research Articles

Influence of Structural Characterization of C3S-C3A Paste under Sulfate Attack

The durability of C3S-C3A paste with varied C3A content (0%, 5%, 10%, and 20%) against sulfate attack at various attack ages (3 d, 7 d, 28 d, and 180 d) was investigated in this study through the examinations of corrosion product composition, Ca/Si and Al/Si of calcium-(aluminum)-silicate-hydrate (C-(A)-S-H) gel, formation and evolution of microstructure, migration and transformation of Al containing phase products, and pore structure. The results indicated that sulfate attack can promote the hydration reaction in C3S-C3A paste, thus accelerating the production of C-(A)-S-H gel in the paste. With the increase of C3A content, the acceleration effect becomes more significant. In addition, sulfate attack led to the dealumination and decalcification of C-(A)-S-H gel, resulting in the reduction of the gelling power of C-(A)-S-H gel. The degree of dealumination and decalcification of C-(A)-S-H gel increases with the increase of C3A content. At the same time, free Al and Ca promote the formation of expansive products such as ettringite and gypsum. Finally, under the action of sulfate, the pore characterization of C3S-C3A paste deteriorated, showing a decrease in specific surface area, cumulative pore volume and average pore diameter.

Aerobic epoxidation of α-pinene using Mn/SAPO-34 catalyst: Optimization via Response Surface Methodology (RSM)

Aerobic epoxidation of bio-based olefins is an important topic in green and sustainable chemistry. In this work, an Mn/SAPO-34 catalyst was prepared by ion-exchange method for the epoxidation of α-pinene in presence of molecular oxygen and iso-butyraldehyde. The factors influencing α-pinene epoxidation were determined and the conditions were optimized by response surface methodology (RSM). The result showed that the sensitive conditions were co-reductant amount, Mn loading amount and catalyst amount. After optimization, α-pinene was completely converted and a 90.47% yield of 2,3-epoxy-pinane was obtained. The result showed that the catalyst was reusable for six cycles. In addition, the support and catalysts were characterized by XRD, BET, ICP-OES, SEM-EDS, TEM and XPS, and it was confirmed the reasons for the degradation of the catalyst activity were the damage of crystal particles, the decrease in specific surface area of catalyst, the loss of active components and the irreversible oxidation of Mn2+

Development and Characterization of Zinc Glutarate (ZNGA) and Double Metal Cyanide (DMC) Catalyst for Bio-Based Polycarbonate Application

Heterogeneous metal complex catalyst such as Zinc glutarate (ZnGA) and Zinc-Ferum Double Metal Cyanide (Zn-Fe DMC) have been shown to improve reactivity for alternating copolymerization using CO2 and epoxides. However, there are not lot of studies that have been done to study the effect of different parameter such as time and temperature on the catalytic activities of ZnGA and Zn-Fe DMC. ZnGA was treated with toluene while Zn-Fe DMC catalyst was treated with (complexing agent) tert-butanol. The main focus of this study is to synthesize ZnGA and Zn-Fe DMC at different parameter where the catalysts were produced at a variety of temperatures (50,60,70 °C) and reaction times (3h & 9h). Three different zinc-ferum ratios (1:4, 1:6, and 1:8) were developed for the Zn-Fe DMC catalyst to compare the effect of iron as metal and zinc on the active site. The catalyst was characterized using Fourier-transform infrared spectroscopy (FTIR) to determine their functional elements and Brunauer–Emmett–Teller analysis (BET) for surface characterization and pore size. The effects of reaction parameters such as time and reaction temperature were investigated using this catalyst in an auxiliary-batch reactor. FTIR result shows that GA was successful incorporation into ZnO and the production of ZnGA catalysts. The presence of typical functional groups in the Zn–Fe DMC catalysts was also confirmed. The surface area and pore volume of ZnGA increases as the temperature and reaction time increases while Zn-Fe DMC the surface area and pore volume decrease as the ratio increases. These surface-modified catalysts can generate high-molecular-weight polymers, which benefits both the environment and industry.

Effect of Stirring Rate and Functionalization Method on the Synthesis of Spherical Silica Particles Encapsulated Amine Moieties

Silica nanocapsules (SiNC) utilization as adsorbent in pollution control have gained much attraction as SiNC are highly porous, have high surface area, excellent thermal and mechanical stability and a tuneable physicochemical property. In this study, microemulsion technique was used to synthesized SiNC. Effect of stirring rate as well as the effect of different method of amine functionalization i.e. grafting, wet impregnation, co-condensation, on the physicochemical properties of SiNC were studied. The stirring rate have significant effect on the physical properties of the SiNC. As the stirring speed increased from 200 rpm to 600 rpm, the particle diameter and the surface area decreases, 695 to 600 nm and 773 to 654 m2/g, respectively. The SEM and TEM analysis shows higher stirring rate produced surface with extensive damage while lower stirring rate produced a smoother surface. Different functionalization method affected the amount of amine groups incorporated into the SiNC. The FTIR spectra shows that the impregnation method incorporates higher amount of amine as indicated by the higher peak transmissions in the region 3450 – 3250 cm-1. However, amine functionalization of SiNC resulted in decrease of surface area as surface pore of the SiNC were occupied by the amine moieties’ molecules. The optimum condition for synthesizing amine functionalized SiNC were determined to be at stirring rate of 450 rpm through wet impregnation method as the SiNC produced were of spherical shape with smooth surface, and a relatively high surface area of 695 m2/g and pore diameter of 601 nm. These physicochemical characteristics shows the synthesized amine functionalized SiNC have promising qualities for application as adsorbents.

Management of a rare case of pediatric deep sternal wound infection with vacuum-assisted closure (VAC)

Background: Deep sternal wound infection (DSWI) or mediastinitis is a severe and life-threatening infection with high morbidity and mortality rates. Vacuum-assisted closure (VAC) provides good results and is very useful in wound closure. VAC therapy is a safe and affordable method for managing complex sternal and thoracic injuries. The use of VAC has been shown to increase parasternal blood flow by dilating arterioles, reducing bacterial load, and accelerating granulation tissue formation. It also helps with facilitating wound edge closure. Case and Operation Technique: A 6-month-old baby presented with an ulcer 2 cm deep in the thorax region. The wound had an exposed bone surrounded by slough and hyperemic edges. Bone destruction was seen to have reached the costochondral joint with a gross visible appearance of the pleura. Management of this patient included debridement, sternotomy, internal fixation of the sternum using the Robiscek technique, and application of the Water Shield Drainage (WSD) and VAC. The tobacco-sack technique was used to close the open wound. The Robiscek technique was used in this patient because of the bone destruction to the costochondral joints causing the sternum to become unstable. The VAC dressing was then connected to a suction with an intermittent negative pressure of 75mmHg. After a significant decrease in the wound surface area, a local rotational flap was used to close the wound. Conclusion: The use of modified VAC for deep sternal wound infection (DSWI) is effective, simple, and affordable with minimal complications.

Structural studies and selected physical investigations of LiCoO2 obtained by combustion synthesis.

Nanocrystalline powders of LiCoO2 were synthesized using a modified solution combustion method, and the effects of the annealing temperature (450-900 °C) on structure and composition were investigated using various methods, including XRD, SEM, EPR, and electrical studies. It was found that, as the process temperature increases, the value of the specific surface area decreases, and, hence, the size of the crystallites increases. XRD analysis showed that phase-pure LiCoO2 material was maintained without additional phases. EPR studies revealed the presence of two Ni3+ complexes resulting from Ni impurities. The electrical properties of the studied LiCoO2 samples were investigated by using impedance spectroscopy. Comparison of the effect of annealing temperature on electrical conductivity shows a very interesting behavior. As the annealing temperature increases, the DC conductivity value increases, reaching a maximum at a temperature of 500 °C. However, further increase in the annealing temperature causes a steady decrease in the DC conductivity.

Adsorption and Release Properties of Drug Delivery System Naproxen-SBA-15: Effect of Surface Polarity, Sodium/Acid Drug Form and pH.

Mesoporous silica SBA-15 was prepared via sol-gel synthesis and functionalized with different types of organosilanes containing various organic functional groups: (3-aminopropyl)triethoxysilane (SBA-15-NH2), (3-mercaptopropyl)triethoxysilane (SBA-15-SH), triethoxymethylsilane (SBA-15-CH3), triethoxyphenylsilane (SBA-15-Ph), and (3-isocynatopropyl)triethoxysilane (SBA-15-NCO). The prepared materials were investigated as drug delivery systems for naproxen. As model drugs, naproxen acid (HNAP) and its sodium salt (NaNAP) were used. Mentioned medicaments belong to the group of non-steroidal anti-inflammatory drugs (NSAIDs). The prepared materials were characterized by different analytical methods such as transmission electron microscopy (TEM), infrared spectroscopy (IR), nitrogen adsorption/desorption analysis (N2), thermogravimetric analysis (TG), 1H, 13C and 23Na solid-state nuclear magnetic resonance spectroscopy (1H, 13C and 23Na ss-NMR). The abovementioned analytical techniques confirmed the successful grafting of functional groups to the SBA-15 surface and the adsorption of drugs after the impregnation process. The BET area values decreased from 927 m2 g-1 for SBA-15 to 408 m2 g-1 for SBA-15-NCO. After drug encapsulation, a more significant decrease in surface area was observed due to the filling of pores with drug molecules, while the most significant decrease was observed for the SBA-15-NH2 material (115 m2 g-1 for NaNAP and 101 m2 g-1 for HNAP). By combining TG and nitrogen adsorption results, the occurrence of functional groups and the affinity of drugs to the carriers' surface were calculated. The dominant factor was the volume of functional groups and intermolecular interactions. The highest drug affinity values were observed for phenyl and amine-modified materials (SBA-15-Ph = 1.379 μmol m-2 mmol-1 for NaNAP, 1.761 μmol m-2 mmol-1 for HNAP and SBA-15-NH2 = 1.343 μmol m-2 mmol-1 for NaNAP, 1.302 μmol m-2 mmol-1 for HNAP) due to the formation of hydrogen bonds and π-π interactions, respectively. Drug release properties and kinetic studies were performed at t = 37 °C (normal human body temperature) in different media with pH = 2 as simulated human gastric fluid and pH = 7.4, which simulated a physiological environment. Determination of drug release quantity was performed with UV-VIS spectroscopy. The surface polarity, pH and naproxen form influenced the total released amount of drug. In general, naproxen sodium salt has a higher solubility than its acid form, thus significantly affecting drug release from surface-modified SBA-15 materials. Different pH conditions involved surface protonation and formation/disruption of intermolecular interactions, influencing both the release rate and the total released amount of naproxen. Different kinetic models, zero-order, first-order, Higuchi and Hixson-Crowell models, were used to fit the drug release data. According to the obtained experimental results, the drug release rates and mechanisms were determined.

Effect of attaching hydrophilic oligopeptides to the C-terminus of organic solvent-tolerant metal-free bromoperoxidase BPO-A1 from Streptomyces aureofaciens on organic solvent-stability

Metal-free bromoperoxidase BPO-A1 from Streptomyces aureofacience was selected among several similar enzymes exhibiting brominating activity as the most stable haloperoxidase against 70%(v/v) methanol. A comparison of the BPO-A1 and octahistidine-tagged BPO-A1 at the C-terminus (BPO-A1-His8) revealed that the His-tag enhanced the organic solvent-stability of BPO-A1 with pH- and heat-stabilities. Additionally, the contribution of the hydrophilicity at the C-terminal of BPO-A1 to the organic solvent-stability was confirmed employing several mutants bearing hydrophilic oligopeptides. Fortunately, two excellent mutants, BPO-A1-Lys8 and BPO-A1-Arg8, with high stabilities against various water-miscible organic solvents were obtained. In conclusion, the enhancing effect of the hydrophilic oligopeptides on the organic solvent-stability was associated with a decrease in the hydrophobic surface area near the C-terminus.

Using Numerical Analysis to Develop a Retort Process to Enhance Antioxidant Activity and Physicochemical Properties of White Radish (Raphanus sativus L.) in Different-Sized Packages

Thermal processing of white radish using retort sterilization at different temperatures was investigated according to the dimension of the package. Four different samples with the same weight and volume were placed in packages with different dimensions. The degree of sterilization (i.e., F0-value) at the cold point targeted at 6 min was determined based on experimental data and heat transfer simulation. The sterilization time was considerably increased with a decrease in surface area to unit volume ratio (φ) at each temperature. The sterilization time for the sample with the highest φ (155.56) was approximately five times faster than the sample with the lowest φ (72.22) at all heating temperatures. Numerical simulation conducted with a proper heat transfer coefficient (h) showed mostly good agreement with the experimental data (RMSE < 2 °C). Changes in color and total phenolic content were higher for samples heated at higher temperatures. Hardness values of white radish samples measured for center and edge parts separately were more uniform for samples with a high φ. Results in this study suggest that optimizing heating conditions of root vegetables must consider their package dimensions to satisfy quality attributes after sterilization. Numerical simulation can be utilized as a useful tool to design the sterilization process.

Photocatalytic Activity and Electron Storage Capability of TiO2 Aerogels with an Adjustable Surface Area

Mesoporous TiO2 aerogels with a surface area larger than 600 m2 g–1 have been prepared via acid-catalyzed sol–gel synthesis and supercritical drying. Varying temperature treatments in air result in changes in the morphology of the aerogels and their specific surface area. Interestingly, the ability to store photogenerated electrons in the surface states of the aerogels upon illumination of dispersions in water–methanol mixtures increases at lower calcination temperatures. Additionally, the extent of electron storage capability also depends on hole scavenger concentration. Increasing the calcination temperature to 500 °C results in a decreased surface area and electron storage capability but increased hydrogen evolution rates. Finally, nitrogen reduction to ammonia in the dark is performed with photogenerated stored electrons in TiO2 aerogels, separating the charge carrier photogeneration from the dark reduction reaction.

Tuning of Microenvironment in Covalent Organic Framework via Fluorination Strategy promotes Selective CO2 Capture.

Herein, we have designed and synthesized two heteroatom (N, O) rich covalent organic frameworks (COF), PD-COF and TF-COF, respectively, to demonstrate their relative effect on CO2 adsorption capacity and also CO2 /N2 selectivity. Compared to the non-fluorinated PD-COF (BET surface area 805 m2 g-1 , total pore volume 0.3647 ccg-1 ), a decrease in BET surface area and also pore volume have been observed for fluorinated TF-COF due to the incorporation of fluorine to the porous framework (BET surface area 451 m2 g-1 , total pore volume 0.2978 ccg-1 ). This fact leads to an enormous decrease in the CO2 adsorption capacity and CO2 /N2 selectivity of TF-COF, though it shows stronger affinity towards CO2 with a Qst of 37.76 KJ/mol. The more CO2 adsorption capacity by PD-COF can be attributed to the large specific surface area with considerable amount of micropore volume compared to the TF-COF. Further, PD-COF exhibited CO2 /N2 selectivity of 16.8, higher than that of TF-COF (CO2 /N2 selectivity 13.4).

Preparation of Ni/SiO2 using silicon-rich-biomass as source for acetic acid steam reforming

In this paper, four kinds of silicon-rich biomass (rice husk, rice straw, peanut shell, corncob) were used as raw materials for SiO2 extraction by heat treatment method. And the extracted SiO2 was applied to prepare Ni/SiO2 catalyst for acetic acid (AcOH) steam reforming. Various characterization methods were used to analyze the purity, structure and specific surface area characteristics of SiO2 extracted from different sources. It was found that the silica prepared by acid washing and calcination (AWC) had larger specific surface area, abundant pore channels and larger pore volume. By water washing and calcination (WWC), K2O impurity would be remained in SiO2, which might dissolve SiO2 during the calcination process, generating an increase in the pore size and a decrease in the specific surface area. While the CaO impurity in SiO2 promoted the dispersion of the active components and enhanced the interaction between the active component and the carrier. A series of reforming catalysts were prepared by using the obtained SiO2 as carriers. It was found that the lifetime of catalyst from low to high was Ni/RS-SiO2 <Ni/PS-SiO2 <Ni/RH-SiO2, which was in the opposite order of K2O content. Acid washing was beneficial for the enhancement of Ni/RH-AC-SiO2 activity, and the increase of Ni/RS-AC-SiO2 stability. Among the four catalysts, the Ni/RH-AC-SiO2 catalyst exhibited the highest carbon conversion (100%) and hydrogen yield at 600 °C, which may be because that the acid washing removed the metal oxide impurity K2O. And its large specific surface area, the concentrated pore size distribution, and the suitable interactions between the support and carrier may also contribute to its high catalyst activity.

Mechanism of thermally activated sodium persulfate–biochar skeleton treatment to improve the dewaterability of waste activated sludge

Sludge dewatering is a necessary process in the disposal of waste activated sludge (WAS). In this study, thermally activated sodium persulfate–biochar skeleton pretreatment was performed to improve the dewaterability of sludge, and its internal mechanism was systematically elucidated. The experimental results showed that, under optimal operating conditions, the water content of WAS could be reduced from 89.7% to 61.3% of the raw sludge. Under these conditions, the capillary suction time and specific resistance to filtration were roughly 23.23% and 59.57% of those in the raw sludge, respectively. This study proposes a relationship between organic matter migration and sludge physical structure that explains the dewaterability improvement mechanism. Separate thermal treatment caused organic matter such as proteins, polysaccharides, and humic substances to dissolve, releasing their bound water. Simultaneously, changes in the surface structure (pore size reductions and BET surface area increases) deteriorated the dewaterability of WAS. The reactive oxygen species generated by the thermally activated sodium persulfate further mineralized the organic matter, simplifying the floc surface structure (pore size increases and BET surface area decreases) and finally improving the dewaterability. Under these conditions, the addition of biochar increased the pore size, and further improved sludge dewaterability.

Structural properties and reactivity variations of wheat straw char catalysts in volatile reforming

Abstract In this study, wheat straw char was prepared at 500°C and used as a catalyst (at 500–700°C) to reform the wheat straw volatiles. The char samples before and after reforming were characterized in terms of N2 adsorption (BET area), Raman spectroscopy, Fourier transform infrared spectroscopy, proximate analysis, ultimate analysis, and inductively coupled plasma measurements. The surface morphology of the used char was analyzed by a scanning electron microscope. The results have revealed that following the reforming process, the carbon content increased from 69.2% to 71.7% (at 500°C), 73.9% (at 600°C), and 74.3% (at 700°C) and the fixed carbon content increased from 64.6% to 68.7% (at 500°C), 71.4% (at 600°C), and 72.4% (at 700°C). In contrast, the higher heating value of the used char remained unchanged. We observed a decrease in specific surface area (from 112.67 to 7.93 m2·g−1), but an increase in char defects and functional groups following the reforming process (at 600°C) served to maintain catalytic activity, as shown in a second reforming test. Our results suggest that surface defects and functional groups are the main factors contributing to char reactivity.

Enhanced hydrogen adsorption properties of mesoporous nano-TiO2@SnO2

Today, hydrogen as being one of the most advantageous energy supplies for various applications and specifically not with carbon emissions, alluring strategies are made possible for its production and storage. Since the metal oxides (MOs) semiconductors give rise to the development of new technologies related to renewable energy and environmental issues, this work is envisioned to study the hydrogen adsorption properties of TiO2@SnO2 catalyst synthesized via novel approach by integrating sol–gel and thermal decomposition methods. The synthesized TiO2 and its composite have been analyzed by sophisticated instruments to reveal the drastic enhancement of hydrogen adsorption. In this work, hydrogen measurements were accomplished by quartz crystal (QC) microbalance method. The Raman scattering experiment of the composite revealed the lower peak intensity compared with pure TiO2, which demonstrated the surface defects that created oxygen vacancies with reduced oxidation states of the metal centers. Meanwhile, the mesoporous nanostructure of TiO2@SnO2 could be confirmed via High resolution transmission electron (HR-TEM) microscopic analysis. Besides, the intermediate states of the composite were analyzed through Photoluminescence (PL) spectra which demonstrated the delay in recombining charges. The Barrett-Joyner- Halenda (BJH) method illustrated the larger pore size and pore volume with decreased surface area of the composite. The addition of SnO2 into TiO2 has reported 4 times greater the adsorption of pristine TiO2 particles, because of the capacity of SnO2 to hinder pores. Moreover, the titania oxidation states play a predominant role in the procurement of larger H2 adsorption. Also, the Ti4+ and Sn4+ reveal fragile Kubas type of adsorption that facilitated the hydrogen storage.

Structural transformation of porous and disordered carbon during ball-milling

Mechanical ball-milling is a commonly used method to shattering crystals or introducing defects in carbon materials. But herein, we observe that the highly porous and disordered carbon lattice of activated carbon is converted to graphitic structure during ball-milling, along with the introduction of oxygen in the bulk phase. The well-developed pores are gradually eliminated, leading to obviously decreased surface area from 1364 to 156 m2 g-1 and improved compaction density from 0.573 to 1.423 g cm-3. Due to the continuous particle cleavage, re-assembly, and cold-welding, the as-formed carbon blocks show 2 times larger in size and 4 times higher bulk oxygen content. This simultaneous crystallinity enhancement and oxygen functionalization is barely observed in other methods. The mechanism is that highly reactive carbon radicals generated by mechanical cleavage of carbon skeleton enable atom rearrangement to form large graphitic domains or being terminated by oxygenated groups. Interestingly, the capacitive energy storage performance of the ball-milled activated carbon is changed from electric-double-layer to pseudo-capacitance in aqueous electrolyte, showing significantly improved volumetric capacitances and high-rate performance. Our work provides a theoretical guidance for mechanochemistry of porous and disordered carbon materials.

Nano-structured porous carbon-silica composite aerogel derived from low-cost kapok fibers and TEOS

This study proposes an ambient-temperature synthesis of highly porous carbon–silica composite aerogels (C-Si aerogel) made using kapok fibers. Effects of the fiber's volume in the C-Si composite and the pyrolysis temperature on the properties of the obtained C-Si aerogel was determined. Initially, tetraethyl orthosilicate (TEOS) in methanol was mixed with 3–20 % v/v of pretreated kapok fibers. After that, the gel underwent incubation, a solvent change, and at-pressure drying. Then, the dried fiber-silica composite aerogels (F-Si) were pyrolyzed under an inert N2 atmosphere at temperatures of 300 °C to 800 °C for 15 min. Analysis of the resulting materials indicated that the highest surface area of 753 m2/g with 5.5 nm pore size was found in the C-Si5400 aerogel sample. Further increases of kapok fiber content above 5 % v/v decrease both surface area and pore volume of the C-Si aerogels. This is because the high volume of kapok fibers has probably blocked the pores or voids of the C-Si aerogel. In comparison, the C-Si5400 aerogel sample had a surface area 21 % higher than a conventional silica aerogel. Notably, carbon–silica composite aerogel can be obtained by pyrolyzing dried fiber-silica composite aerogels in the temperature range from 400 °C to 600 °C. In addition, pyrolysis of C-Si composite at temperatures above 800 °C can remove kapok fibers and yield a pure silica aerogel. However, as the pyrolysis temperatures rise from 500 °C to 800 °C, carbon–silica composite aerogels' pore volume and surface area decrease. All adsorption and desorption isotherms obtained from N2 adsorption experiments on C-Si aerogel composite at −196 °C are type IV isotherms. The mean pore size of these carbon–silica composite aerogels is in the range of 4.2 to 7.8 nm. This study's results show that the degree of the kapok filling volume and pyrolysis temperature play essential roles in the microstructure properties of the obtained C-Si composite materials.

Intensification of CO2 hydrogenation by in-situ water removal using hybrid catalyst-adsorbent materials: Effect of preparation method and operating conditions on the RWGS reaction as a case study

Intensifying CO2 hydrogenation reactions by in-situ water removal via hydrophilic adsorbents alongside the catalyst is an innovative approach that can drastically improve the performance of conventional processes whose yields are restricted by thermodynamics. Here, the sorption-enhanced (SE) reverse water–gas shift (RWGS) reaction was explored as a case study since it represents the starting point of all CO2 hydrogenation processes. Hybrid materials containing both catalyst (Cu/UGSO) and hydrophilic adsorbent (13X zeolite) were conceived to investigate for the first time (i) the effect of preparation method (with major impact on physicochemical properties and performance) and (ii) main operating parameters affecting greatly the yields (temperature and catalyst/adsorbent ratio). A comparison between mechanically mixed catalyst-adsorbent and bifunctional materials (containing active metal, catalytic support, and adsorbent within the same particle) revealed that Cu presence decreased the adsorptive ability of bifunctional materials, due to the decrease of specific surface area and zeolite acidity. In contrast, mechanical mixtures allowed to fully preserve the assets of both adsorbent and catalyst, to significantly intensify the reaction. The catalyst-adsorbent mixture obtained by wet mixing offered the best results by minimizing the average distance between catalytic and adsorption sites. 250 °C was found optimum for a significant reaction rate and a non-negligible water adsorption capacity of 13X zeolite. The reaction thermodynamic barrier was found to be crossed for catalyst/adsorbent mass ratio lower than 1, the intensification leading to a significant increase in CO2 conversion. The findings of this work are crucial for implementing this type of intensified process, which pushes the limits dictated by thermodynamic equilibrium, and provide information of high interest to guide future research on all SE processes of CO2 valorization via catalytic hydrogenation.

Thermodynamic characteristics of high-pressure CH4 adsorption on longmaxi shale subjected to supercritical CO2-water saturation

The shale-CH4 interaction after supercritical CO2 (ScCO2) injection can be well interpreted by adsorption thermodynamics study. Using a gravimetric method, the methane adsorption experiments over wide range of pressure (up to 35 MPa) and temperature (30–90 °C) were conducted on Longmaxi shale before and after ScCO2-water saturation (60days/20Mpa/70°C). In addition, low-temperature CO2 and N2 adsorption experiments were performed to analyze the variations of pore structure of shale. Results indicates that the high-pressure CH4 adsorption curves of shale exhibit obvious excess adsorption characteristics, and the excess adsorption capacity of shale to CH4 decreased after ScCO2-water saturation, which is mainly caused by the decrease of the specific surface area of shale. Comparing to Brunauer-Emmett-Teller, Dubinin-Radushkevich and Ono-Kondo models, the excess adsorption data can be well-fitted by Langmuir model through combining Henry equation. Additionally, the thermodynamic parameters of shale-CH4 adsorption pair, including the isosteric heat of adsorption, enthalpy change, Gibbs free energy change and entropy change, displayed strong dependence on adsorption capacity and temperature, and altered in varying degrees after ScCO2-water saturation, demonstrating that the shale gas recovery can be enhanced by ScCO2-water-shale interaction from the perspective of thermodynamics. This study provides a reference for CO2 enhanced shale gas recovery.

Study on the deactivation of Ni-based catalyst in the hydrotreating process of waste plastic pyrolysis oil

The deactivation mechanism of Ni-based catalyst in the hydrotreating process of waste plastic pyrolysis oil (WPPO) was investigated. The accelerated deactivation experiment of catalyst was performed with model oil containing different impurities, and results indicated that the deactivation of catalyst was related to chlorides, nitrides, and sulfides in WPPO. By changing the concentration of chloride, the interactions between the three impurities were studied. Combined with the characterization results of fresh and spent catalysts, chloride was the direct cause of the deactivation of the catalyst. Chlorine atoms in chlorides were converted into HCl gas in hydrotreating, which reacted with Ni active sites, resulting in the sintering of the average Ni particle size from 52.62 nm to 139.63 nm, and the loss of Ni active components by 3–8 wt%, especially inhibiting the hydrodesulfurization activity of the catalyst. In addition, HCl reacted with NH3 (byproduct of nitride hydrogenation) to generate NH4Cl. The high concentration of HCl in the reaction system increased the crystallization temperature of NH4Cl from 210 °C to 294 °C, which led to the crystallization of ammonium salts in the catalyst bed. NH4Cl crystals adsorbed on the catalyst surface, resulting in a decrease in specific surface area and pore volume, and an increase in the average pore diameter of the catalyst, which was the main reason for the rapid deactivation of the catalyst. Furthermore, based on the deactivation mechanism, several appropriate solutions were proposed.