Zeolite Molecular Sieves Research Articles

Effects of zeolite molecular sieve on the hydrocarbon adsorbent and diffusion performance of gasoline engine during cold start

In this work, adsorption characteristic of the MOR, MFI, and CON zeolites used in hydrocarbon catcher and diffusion properties of hydrocarbon (HC) molecules on them were studied for hydrocarbon emission control during cold start. To find adsorbents with promising adsorption performance for hydrocarbon catcher, the numerical simulation was carried out by using Material studio software with benzene (C6H6) and ethylene (C2H4) as the probes, the Grand Canonical Monte Carlo (MC) method was used in the adsorption simulation, and Molecular Dynamics (MD) method was used to simulate the diffusion of hydrocarbon molecules. The isotherms, adsorption sites, heats of adsorption, and interaction energy distribution of hydrocarbon single-component and multi-component molecules on three different zeolites were studied at various low temperatures and pressures. Based on the simulation results, the most suitable type of molecular sieve was found from the three molecular sieves when the type and quantity of components were different. Results of adsorption simulation show that CON molecular sieve has batter adsorption performance for benzene component. The adsorption amount is 65/unitecell (UC) benzene molecules per cell, which is about twice of MFI molecular sieve. MFI molecular sieve has batter adsorption performance for ethylene component. The adsorption amount is 130/UC ethylene molecules per cell, which is about 2 and 1.5 times of MOR and CON, respectively of MOR molecular sieve. The adsorption simulation results of mixed hydrocarbon components show that the adsorption capacity of each component on the three molecular sieves was ranked as follows: C6H6 > C3H6 > C2H4 > C3H8 > H2O > CH4, collectively. The results of diffusion simulation show that the single component of ethylene molecule has relatively small diffusion coefficient on MFI molecular sieve about 2.2×10−10m/s and good adsorption performance at low temperature, and the largest diffusion coefficient on CON molecular sieve about 3.4×10 −10m/s. The single component of benzene molecules has the smallest diffusion coefficient on the CON molecular sieve 5.9×10−11m/s about and the largest diffusion coefficient on the MOR molecular sieve about 1.76×10−10m/s. In multicomponent diffusion. In multicomponent diffusion. The diffusion degree of each component molecule in the MFI and CON molecular sieve from strong to weak is about: H2O, CH4, C2H4, C3H8, C3H6 and C6H6. The diffusion pattern within the MOR molecular sieve from strong to weak approximately: C3H8, C6H6, C3H6, C2H4, CH4 and H2O. The results show that the high temperature had an obvious effect on the adsorption capacity of zeolite. As temperature rises the molecular diffusion coefficient increases and the molecular motion becomes more intense. After about 500 K, the adsorption capacity is at a very low level.

Design and fabrication of multi-functional equipment to produce gaseous nitrogen/oxygen and water from ambient air

Mother earth provides all the necessary resources for the existence of life. Despite the rich resources of water on our planet, majority of world’s total population experiences water shortage annually. Studies have shown that with the increase of global warming, the average humidity of ambient air is rising annually. Due to the decrease of water table on land, alternative sources of acquiring potable water can be of great utility. Out of the several methods available to tap potable water, this paper aims to achieve an alternate source of receiving fresh water directly from ambient air. This process is completely different from distillation. The ambient air also comprises a majority of Nitrogen, and this N2 is used for the purpose of creating an inert environment in packaging industries and for the purpose of extinguishing fire, a multi-functional equipment has been fabricated in order to extract water, along with pure Nitrogen gas from the residual dry air. A Pressure Swing Adsorption (PSA) system is used to separate the Nitrogen from remaining air molecules based on their relative molecular size. In the current industrial sectors, the valves required to actuate the flow of air in PSA system are controlled by PLC circuits and Cam followers. These electro-mechanical components are overpriced. In this work electronic timers are used to actuate the valve timing, which resulted in economical. The system fabricated is simple in construction and it is easy to replace the Carbon Molecular Sieves (CMS) with Zeolite Molecular Sieves in order to obtain Oxygen gas as the pure product that can be used to help Covid-19 patients using medical grade filters. The system can be scaled up with larger mass of CMS, bigger PSA towers and greater compressor power in order to increase productivity.

Sorption of HCl from an Aromatic Hydrocarbon Mixture Using Modified Molecular Sieve Zeolite 13X.

In this study, the removal of chlorides, especially HCl, from an aromatic hydrocarbon mixture composed of benzene, toluene, xylenes, and ethylbenzene has been studied. Molecular sieve zeolite 13X as such and exchanged with different amounts of alkali and alkaline earth metal ions has been used as an adsorbent. Different techniques like inductively coupled plasma-optical emission spectroscopy, X-ray powder diffraction, N2 adsorption–desorption for Brunauer–Emmett–Teller surface area and pore volume, and scanning electron microscopy were utilized to analyze all of the adsorbents. The effect of varying concentrations of alkali and alkaline earth metal cations and process parameters like temperature and flow rate on the removal of HCl has been studied by performing the adsorption breakthrough experiment. The main objective of this study is to determine the precise concentration of exchangeable ions and the optimum temperature, pressure, and feed flow rate at which the adsorbent exhibits the highest capacity toward the sorption of chloride species from an aromatic hydrocarbon stream. The maximum chloride sorption capacity was observed at T = 100 °C, P = 35 kg/cm2, and a liquid hourly space velocity (flow rate) of 2 h–1 when the molecular sieve zeolite 13X (NaX) exchanged with 0.6 wt % Ca2+ and 1 wt % Mg2+ cations was used as an adsorbent.

Fabrication of KDF-loaded chitosan-oligosaccharide-encapsulated konjac glucomannan/sodium alginate/zeolite P microspheres with sustained-release antimicrobial activity

Potassium diformate(KDF) is a non-antibiotic growth promoter. To improve the utilization of KDF in the intestinal tract, P-type zeolite molecular sieve (zeolite P) was used as the drug-binding effector of KDF and was encapsulated in sodium alginate (ALG)/konjac glucomannan (KGM)/chitosan oligosaccharide (COS) composite hydrogel microspheres to prepare environment friendly, intelligent and pH-sensitive composite hydrogel microspheres for controlling the release of KDF. The composite hydrogel microspheres were characterized using XRD, FT-IR, TGA, and SEM. In addition, the swelling behavior of the composite hydrogel microspheres in three buffered media was determined. Thus, the phase composition, structural characteristics, thermal stability, apparent morphology and swelling properties were determined. Results indicated that the composite hydrogel microspheres possessed pH sensitivity, compatibility and porous 3D network structure. Furthermore, ALG formed polyelectrolyte complexes with COS, providing the composite hydrogel microspheres a complete three-dimensional network structure. The embedded network structure of zeolite P, which limited the size of the inner capsule, assisted in improving the thermal stability, and allowed expansion and controlled release of KDF. Under a simulated gastrointestinal environment, the in vitro release conformed to a good pH-sensitive drug release pattern and prevented premature release of KDF in the gastric juice. In the in vitro antibacterial test, the maximum inhibition rate of the antibacterial agent against Escherichia coli, Staphylococcus aureus and Bacillus subtilis were 96.63%, 93.81% and 93.31%, respectively, indicating its considerable potential as an intestinal antibacterial.

Effect of Oxide Content of Graphene Oxide Membrane on Remarkable Adsorption for Calcium IonsSupported by the National Natural Science Foundation of China (Grant No. 11675246).

Graphene oxide membranes (GOMs), as one of the most promising novel materials, have gained great interest in the field of adsorption. However, the oxygen content of graphene oxide is directly related to its adsorption properties, such as suspension stability, adsorption capacity, and reusability of GOMs. Here, a series of reduced GOMs with oxygen content from 28% to 12% were conveniently prepared by the thermally reduced and the corresponding interlayer spacing of these membranes changed from 8.0 Å to 3.7 Å. These prepared GOMs have remarkable Ca2+ adsorption capacity, which increases with the oxygen content or interlayer spacing of GOMs. Importantly, the max adsorption capacity of the mass ratio between adsorbed Ca2+ and pristine GOMs can reach up to 0.481 g/g, which is about one order of magnitude higher than the adsorption capacity of activated sludge, magnetic Fe3O4, functionalized silica, zeolite molecular sieve, and other reported previously. Moreover, GOMs show excellent stability and the Ca2+ can be easily desorbed by water, so that the GOMs can be reused. Our previous theoretical analysis suggests that this remarkable adsorption is attributable to the strong interactions between Ca2+ and GO sheets, including the ion-π interactions between Ca2+ and aromatic graphitic rings as well as the electrostatic interaction between Ca2+ and oxygen-containing groups.

Post-Synthesis Functionalization Enables Fine-Tuning the Molecular-Sieving Properties of Zeolites for Light Olefin/Paraffin Separations.

Zeolite molecular sieves are widely used in gas separation and shape-selective catalysis, but these applications often require discriminating differences as little as 0.1 Å. Molecular sieving with such size selectivity demands zeolites with highly tunable pore diameters and adsorption properties, which are technically challenging to prepare. Nevertheless, it is shown that a wide range of organic functional groups can be covalently functionalized onto the interior pore walls of the zeolites, MOR, LTL, FAU, and MFI, to systematically "tune" their effective pore diameters with respect to the size of organic groups. For organic functionalization, small and aggressive organic electrophiles are used (e.g., organo-halide and -diazonium) as grafting agents, which are accessible to the intracrystalline void space, forming a C-Ozeolite bond in a reaction with a bridging oxygen as proved by multiple analysis data. It is demonstrated that the post-functionalization can be used to tailor the molecular sieving action of a parent zeolite to give size-selective adsorbents for light olefin/paraffin separations. 4-Methoxybenzene-functionalized MOR separates ethylene from ethane with an ideal-adsorbed-solution-theory selectivity of ≈5873, whereas toluene-grafted MOR completely separates propylene/propane mixtures. Therefore, tailoring the molecular-sieving properties of zeolites by organic functionalization broadens their applications to challenging separations.

Heat storage performance analysis of ZMS-Porous media/CaCl2/MgSO4 composite thermochemical heat storage materials

A new composite thermochemical heat storage (TcHS) material was proposed herein with good heat storage performance and desirable stability, which was prepared by using solid-state cold pressing with a zeolite molecular sieve (ZMS) and two salts (CaCl2 and MgSO4). First, the optimized mass content (CaCl2:MgSO4 = 6:4) denoted Smix was obtained, which represents an equilibrium between the adsorption capacity and deliquescence. Then, two types of ZMS porous media: 13X and NaY were added to Smix to further prevent deliquescence and improve stability, respectively. An orthogonal experiment with four factors (mass fraction, pressure, temperature, and humidity) and three levels was used to test the optimal preparation conditions, and the optimal configurations were obtained for Xopt (13X-ZMS: CaCl2: MgSO4 = 10: 54: 36) and Yopt (NaY-ZMS: CaCl2: MgSO4 = 20: 48: 32). The optimized samples were measured by SEM, XRD and thermal conductivity tests, and the adsorption capacities for Smix, Xopt, and Yopt were found to follow the order of Xopt (0.449 g/g) > Smix (0.374 g/g) > Yopt (0.335 g/g). The accumulated void formation for the porous media can promote heat and mass transfer and can significantly improve the adsorption capacity and avoid deliquescence. Differential scanning calorimetry (DSC) results showed that the heat storage density (HSD) for Xopt (1414.49 J/g) is higher than that for Yopt (1097.02 J/g). Finally, 20 cycles showed that Xopt has good cycle stability based on the normalized ad/desorption mass (>1) and normalized desorption heat (>0.8). The results showed that Xopt shows application potential as a TcHS composite material in medium- and low-temperature thermochemical adsorption heat storage systems.

One-pot synthesis of TMOS from SiO2-enriched minerals and supercritical MeOH in a flow reactor

An original method for direct synthesis of tetramethyl orthosilicate from SiO2 raw minerals and supercritical methanol was developed for the first time in a flow mode. The process promoted by KOH was performed at 270 °C and 100 atm using 3 Å zeolite molecular sieves to shift the reversible reaction toward TMOS formation by removing released water. The equilibrium constant Keq of the reaction was determined as 0.839E-08. Silica gel (100 wt% SiO2), quartz sand (97 wt% SiO2), expanded perlite (73 wt% SiO2) and vermiculite (38 wt% SiO2) were tested as SiO2 minerals. The highest equilibrium concentration of TMOS equal to 20.4 g/L was achieved for silica gel that can be increased using larger amount of water adsorbent.

Effects analysis on hydrocarbon reduction efficiency of a beta zeolite catcher in gasoline engine during cold start

In this work, a new post-processing device-HC catcher was designed. The device used the same carrier as TWC, and was coated with HC adsorption material, that is, beta zeolite molecular sieve used in this study. The cold start test was conducted on the gasoline engine test bench. The HC catcher was installed at the exhaust manifold outlet. The difference between the HC amount in the exhaust before and after the installation of the HC catcher was compared. It was found that at the beginning of the cold start of the gasoline engine, the effect of the HC catcher was obvious, and there was almost no HC emission. With the increase of exhaust temperature, the trapping effect of the HC catcher decreased. The adsorption capacity of the HC trapping material was limited, and it was also affected by the temperature. Then the Material studio software was used to carry out the molecular simulation for studying the adsorption of the HC simulated molecule (propene) on the beta zeolite at different temperatures. The high temperature had an obvious effect on the adsorption capacity of beta. After about 300 °C, the adsorption capacity was at a very low level.

Reducing Water Activity by Zeolite Molecular Sieve Membrane for Long-Life Rechargeable Zinc Battery.

Aqueous electrolytes offer major advantages in safe battery operation, green economy, and low production cost for advanced battery technology. However, strong water activity in aqueous electrolytes provokes a hydrogen evolution reaction and parasitic passivation on electrodes, leaving poor ion-transport in the electrolyte/electrode interface. Herein, a zeolite molecular sieve-modified (zeolite-modified) aqueous electrolyte is proposed to reduce water activity and its side-reaction. First, Raman spectroscopy reveals a highly aggressive solvation configuration and significantly suppressed water activity toward single water molecule. Then less hydrogen evolution and anti-corrosion ability of zeolite-modified electrolyte by simulation and electrochemical characterizations are identified. Consequently, a zinc (Zn) anode involves less side-reaction, and develops into a compact deposition morphology, as proved by space-resolution characterizations. Moreover, zeolite-modified electrolyte favors cyclic life of symmetric Zn||Zn cells to 4765 h at 0.8mA cm-2 , zinc-VO2 coin cell to 3000 cycles, and pouch cell to 100 cycles. Finally, the mature production technique and low-cost of zeolite molecular sieve would tremendously favor the future scale-up application in engineering aspect.

Effects of the heating source on the regeneration performance of different adsorbents under post-combustion carbon capture cyclic operations. A comparative analysis

This work presents a comparative study of microwave and conventional (conductive) heating for adsorbent regeneration. A binary gas mixture representative of pre-dried flue gas from coal-fired power plants (15% v/v CO2 in N2) was passed through a rotatory fixed-bed adsorption column filled with a zeolite molecular sieve (13X) and an activated carbon (NoritR2030CO2). The impact of the two regeneration methods on both the textural properties and the carbon capture performance (CO2 uptake capacity, regeneration efficiency, and rate of regeneration) were assessed and compared after consecutive adsorption/desorption cycles. Overall, NoritR2030CO2 maintained stable adsorption capacity and regeneration efficiency with both conventional and microwave heating but slightly better with the latter. Additionally, power consumption per adsorbent unit mass and per adsorbate removed were reduced with microwave regeneration by 18.69 and 17.76% respectively compared to conventional regeneration. In the case of 13X, adsorption capacity and regeneration efficiency were found to be relatively stable after a drop in the first cycle in both heating modes, whereas power requirement was found higher in microwave regeneration than in conventional regeneration.NoritR2030CO2 showed a slightly higher maximum desorption rate when regenerated with microwave heating compared to conductive heating. Contrarily, the maximum desorption rate for the molecular sieve is higher with conductive heating as opposed to microwave heating. However, the data indicated a bigger desorption rate with the microwave regeneration in both adsorbents in later stages of the heating process (i.e. from min 16th for NoritR2030CO2 and from min 18th for 13X until process completion). The breakthrough time (tb) of NoritR2030CO2 was unaffected by cyclic operation or the heating methods, whereas in 13X this value varied over the cycles. The latter observation indicates that 13X requires either longer times or higher temperatures to achieve full regeneration compared to NoritR2030CO2.It can be concluded that microwave-assisted regeneration presented slight advantages over regeneration with conductive heating in delivering more steady capture capacity and regeneration efficiency for NoritR2030CO2 under the test conditions employed here whereas 13X exhibited indifference.

Catalytic Hydrothermal Liquefaction of Penicillin Residue for the Production of Bio-Oil over Different Homogeneous/Heterogeneous Catalysts

In this study, penicillin residue (PR) was used to prepare bio-oil by hydrothermal liquefaction. The effects of homogeneous (organic acid and alkaline catalysts) and heterogeneous catalysts (zeolite molecular sieve) on the yield and properties of bio-oil were investigated. The results show that there are significant differences in the catalytic performance of the catalysts. The effect of homogeneous catalysts on the bio-oil yield was not significant, which only increased from 26.09 (no catalysts) to 31.44 wt.% (Na2CO3, 8 wt.%). In contrast, heterogeneous catalysts had a more obvious effect, and the oil yield reached 36.44 wt.% after adding 5 wt.% MCM-48. Increasing the amount of catalyst enhanced the yield of bio-oil, but excessive amounts of catalyst led to a secondary cracking reaction, resulting in a reduction in bio-oil. Catalytic hydrothermal liquefaction reduced the contents of heteroatoms (oxygen, mainly), slightly increased the contents of C and H in the bio-oil and increased the higher heating value (HHV) and energy recovery (ER) of bio-oil. FTIR and GC-MS analyses showed that the addition of catalysts was beneficial in increasing hydrocarbons and oxygen-containing hydrocarbons in bio-oil and reducing the proportion of nitrogen-containing substances. Comprehensive analyses of the distribution of aromatic, nitrogen-containing and oxygen-containing components in bio-oil were also performed. This work is beneficial for further research on the preparation of bio-oil by hydrothermal liquefaction of antibiotic fermentation residue.

Preparation of a Gangue-Based X-type Zeolite Molecular Sieve as a Multiphase Fenton Catalyst and Its Catalytic Performance.

In this study, a series of X-type zeolite molecular sieve catalysts, modified with copper (Cu-X), were prepared by an alkali fusion–hydrothermal synthesis using coal gangue from Inner Mongolia. These catalysts were used in the degradation of the methylene blue dye by a Fenton-like reaction. Characterization results showed that Cu is considered to be present in the surface structure of the zeolite in the form of doped Cu ions and metal oxide. It is believed that Cu2+ is the main active site involved in the Fenton reaction. The X-ray photoelectron spectroscopy (XPS) spectra indicated that Cu2+ and Cu+ coexist in the catalysts and participate together in the Fenton reaction. The degradation of methylene blue by the Cu-X catalysts was investigated to determine the optimal catalytic conditions in terms of six aspects: catalyst dosage, initial solution concentration, initial pH of the solution, H2O2 dosage, copper loading, and reaction temperature. The experimental results showed that CX-1.0 had excellent activity and stability for the degradation and decolorization of the methylene blue dye, which could completely degrade the dye within 90 min, and the total organic carbon removal rate reached as high as 97.8%. Electron spin resonance (ESR) and radical capture experiments showed that •OH played a dominant role in the Fenton-like reaction. Combined with XPS, ESR, and catalytic tests, the redox cycle of Cu+/Cu2+ was found to be accelerating the generation of reactive radicals in the Fenton system.

A HIGHLY PORTABLE AND INEXPENSIVE FIELD SAMPLING KIT FOR RADIOCARBON ANALYSIS OF CARBON DIOXIDE

AbstractRadiocarbon (14C) analysis of carbon dioxide (CO2) can be extremely useful in carbon cycle studies because it provides unique information that can infer the age and source of this greenhouse gas. Cartridges containing the CO2-adsorbing zeolite molecular sieve are small and highly portable, which makes them more suitable for field campaigns in remote locations compared to some other CO2 collection methods. However, sampling with molecular sieve cartridges usually requires additional equipment, such as an infrared gas analyser, which can reduce portability and pose limitations due to power demands. In addition, 14C analysis of CO2 is increasingly being used in field experiments which require high numbers of replicate CO2 collections, placing extra pressure on an expensive and cumbersome collection apparatus. We therefore designed and built a molecular sieve CO2 sampling kit that utilizes a small, low power CO2 sensor. We demonstrate the reliability of the new kit for the collection of CO2 samples for 14C analysis in a series of laboratory and field tests. This inexpensive sampling kit is small, light-weight, highly portable, and has low power demands, making it particularly useful for field campaigns in remote and inaccessible locations.

ZSM-5 Zeolite Nanosheet-Based Membranes on Porous Polyvinylidene Fluoride for High-Flux Desalination

A submicrometer-thick molecular sieve zeolite nanosheet laminated (ZNL) membrane has been synthesized on macroporous polyvinylidene fluoride (PVDF) substrate via the simplistic vacuum filtration-co...

Synthesis of an NaY zeolite molecular sieve from a kaolin/dimethyl sulfoxide intercalation composite

AbstractNaY zeolite was synthesized from kaolin/dimethyl sulfoxide (DMSO) intercalation composites using an in situ crystallization technique. The effects of the intercalation ratios and the amounts of the kaolin/DMSO intercalation composite on the synthesis of an NaY zeolite molecular sieve were studied. The samples were characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, differential thermal analysis, N2 adsorption–desorption and scanning electron microscopy. In the in situ synthesis system, when the kaolin/DMSO intercalation composite was added, pure NaY zeolite was formed. By increasing the amount of kaolin/DMSO intercalation composite added, the crystallinity of the samples increased, and after reaching the maximum amount of kaolin/DMSO intercalation composite added, the crystallinity decreased with further increases of the amount of kaolin/DMSO intercalation composite added. To higher intercalation ratio, the crystallinity can be greatly improved at the lower addition content. At an intercalation ratio of 84%, the added amount of kaolin/DMSO intercalation composite was 2.5% and the crystallinity of the NaY zeolite molecular sieve reached a maximum value of 45%. At intercalation ratios of 55% and 22%, the amount of kaolin/DMSO intercalation composite added was 15% and the crystallinities of the NaY zeolite molecular sieves were 44% and 47%, respectively. The NaY zeolite has good thermal stability and a particle diameter of ~0.5 μm. The Brunauer–Emmett–Teller (BET) specific surface area and pore volume of the sample were 519 m2 g–1 and 0.355 cm3 g–1, respectively.

Molecular simulation for adsorption and separation of CH<sub>4</sub>/H<sub>2</sub> in zeolites

Based on the high-throughput calculation method of molecular simulation, except the structures with zero surface area and less than zero adsorption capacity, four geometric descriptors (largest cavity diameter, specific surface area, pore volume and porosity), an energy descriptor (heat of adsorption), adsorption capacity, and adsorption selectivity coefficient of 199 zeolites are obtained. By studying the correlation between structural characteristics and adsorption separation performance, the result shows that when the largest cavity diameter is 6 Å, the surface area is 1400–2100 m<sup>2</sup>·g<sup>–1</sup>, and the pore volume is in a range of 0.2–0.3 cm<sup>3</sup>·g<sup>–1</sup>, the zeolite has the greatest influence on the adsorption capacity and adsorption selectivity for methane molecules. At the same time, it is found that the largest cavity diameter and porosity of zeolite molecular sieves have a positive correlation, and there is also an obvious linear relationship between the CH<sub>4</sub> adsorption selectivity coefficient of the equimolar CH<sub>4</sub>/H<sub>2</sub> mixed component and the single-component CH<sub>4</sub> adsorption capacity. By using the grand canonical Monte Carlo simulation method, physical quantities such as adsorption isotherms and isosteric heats of adsorption for CH<sub>4</sub> and H<sub>2</sub> of three channel-shaped zeolites are obtained. The result shows that the pore structure (surface area and pore volume) of the channel-shaped zeolite has a greater influence on the CH<sub>4</sub> adsorption capacity than the energy effect (heat of adsorption), under the same external environment. Combining with the industrial background of steam methane reforming hydrogen production, the separation and selectivity performance of the CH<sub>4</sub>/H<sub>2</sub> mixed system under different components are further studied. The result reveals that there is no correlation between adsorption selectivity of ultra-microporous zeolite material for CH<sub>4</sub> and bulk pressure or feed ratio. According to the centroid distribution density of gas molecules, it is found that CH<sub>4</sub> preferentially occupies the space of smaller pore windows in the channel-shaped zeolite, while the distribution range of H<sub>2</sub> is larger but there is no unambiguous preferential adsorption site.

Effects of Carrier Materials on Anaerobic Hydrogen Production by Continuous Mixed Immobilized Sludge Reactors

To enhance hydrogen production rate and increase substrate utilization efficiency of anaerobic fermentation, three carrier materials, Granular Activated Carbon (GAC), Zeolite Molecular Sieve (ZMS) and Biological Ceramic Ring (BCR), were used as carrier materials in Continuous Mixed Immobilized Sludge Reactors (CMISRs). The effects of carrier materials and substrate organic loading rate (OLR, OLR = 12, 24, 36, 48 kg/m3/d) on biohydrogen production were investigate, respectively. The highest HPRs of ZMS, GAC and BCR were achieved under the OLR of 36 kg COD/m3/d, and were 2.01, 1.81, and 2.86 L/L/d, respectively. The highest COD removal efficiencies of ZMS, GAC and BCR were 38.95 % (OLR = 24 kg COD/m3/d), 36.47 % (OLR = 36 kg COD/m3/d), and 41.03 % (OLR = 36 kg COD/m3/d), respectively. The best substrate degradation rate of ZMS, GAC and BCR were 40.33 % (OLR = 24 kg COD/m3/d), 38.30 % (OLR = 24 kg COD/m3/d) and 45.60 % (OLR = 12 kg COD/m3/d). The results indicated that biological ceramic ring get better hydrogen production and wastewater treatment performance as sludge carrier material for hydrogen production in immobilized bioprocesses.

Upgrading of Biogas to Methane Based on Adsorption

Upgrading raw biogas to methane (CH4) is a vital prerequisite for the utilization of biogas as a vehicle fuel or the similar field as well. In this work, biogas yield from the anaerobic fermentation of food waste containing methane (CH4, 60.4%), carbon dioxide (CO2, 29.1%), hydrogen sulfide (H2S, 1.5%), nitrogen (N2, 7.35%) and oxygen (O2, 1.6%) was upgraded by dynamic adsorption. The hydrogen sulfide was removed from the biogas in advance by iron oxide (Fe2O3) because of its corrosion of the equipment. Commercial 13X zeolite and carbon molecular sieve (CMS) were used to remove the other impurity gases from wet or dry biogas. It was found that neither 13X zeolite nor CMS could effectively remove each of the impurities in the wet biogas for the effect of water vapor. However, 13X zeolite could effectively remove CO2 after the biogas was dried with silica and showed a CO2 adsorption capacity of 78 mg/g at the condition of 0.2 MPa and 25 °C. Additionally, 13X zeolite almost did not adsorb nitrogen (N2), so the CH4 was merely boosted to ac. 91% after the desulfurated dry biogas passed through 13X zeolite, nitrogen remaining in the biogas. CMS would exhibit superior N2 adsorption capacity and low CO2 adsorption capacity if some N2 was present in biogas, so CMS was able to remove all the nitrogen and fractional carbon dioxide from the desulfurated dry biogas in a period of time. Finally, when the desulfurated dry biogas passed through CMS and 13X zeolite in turn, the N2 and CO2 were sequentially removed, and then followed the high purity CH4 (≥96%).

A simple cryogenic method for efficient analysis of triple oxygen isotopes in silicates.

Oxygen isotopic ratios of silicates are excellent tools to reconstruct paleotemperature and isotopic composition of the precipitating fluid. However, the measurement of 17 O/16 O is difficult due to the low abundance of 17 O. The present study reports a simplified high-precision analytical technique for measuring the two oxygen isotope ratios, 17 O/16 O and 18 O/16 O, in silicates. Silicate samples were ablated by a CO2 laser in a BrF5 environment. The released oxygen (O2 ) was then cryogenically trapped in a molecular sieve zeolite (MSZ). Associated contaminants such as BrF5 , F2 , NF3 etc. were cleaned by passing the gas through a NaCl trap followed by a cooled (-25°C) MSZ-packed U-tube trap. The purified O2 was analysed in a MAT 253 isotope ratio mass spectrometer for oxygen isotope ratios. The δδ17 O and δ18 O values of the working gas were calibrated by NBS-28 and crosschecked by inter-laboratory references UWG-2, SCO and IMAU-O2 . The average analytical precisions (using aliquots of NBS-28, UWG-2, SCO, and laboratory internal standards IIT-KGP-SQ quartz and IIT-KGP-NQ quartz) of the δ17 O, δ18 O and ∆'17 O values were 0.04‰, 0.08‰ and 4 per meg, respectively. A new cryogenic cleaning technique was developed that does not require GC but efficiently removes NF3 -contaminants from oxygen gas produced by laser fluorination of silicates. The technique is simple, quick and cost-effective and provides highly precise and accurate δ17 O, δ18 O and ∆'17 O values.