High adsorption selectivity of activated carbon and carbon molecular sieve boosting CO_(2)/N_(2) and CH_(4)/N_(2) separation

Flue gas and coal bed methane are two important sources of greenhouse gases.Pressure swing adsorption process has a wide range of application in the field of gas separation,and the selection of adsorbent is crucial.In this regard,in order to assess the better adsorbent for separating CO_(2) from flue gas and CH_(4) from coal bed methane,adsorption isotherms of CO_(2),CH_(4) and N_(2) on activated carbon and carbon molecular sieve are measured at 303.15,318.15 and 333.15 K,and up to 250 kPa.The experimental data fit better with Langmuir 2 compared to Langmuir 3 and Langmuir-Freundlich models,and Clausius-Clapeyron equation was used to calculate the isosteric heat.Both the order of the adsorbed amount and the adsorption heat on the two adsorbents are CO_(2)>CH_(4)>N_(2).The adsorption kinetics are calculated by the pseudo-first kinetic model,and the order of adsorption rates on activated carbon is N_(2)-CH_(4)>CO_(2),while on carbon molecular sieve,it is CO_(2)-N_(2)>CH_(4).It is shown that relative molecular mass and adsorption heat are the primary effect on kinetics for activated carbon,while kinetic diameter is the main resistance factor for carbon molecular sieve.Moreover,the adsorption selectivity of CH_(4)/N_(2) and CO_(2)/N_(2) were estimated with the ideal adsorption solution theory,and carbon molecular sieve performed best at 318.15 K for both CO_(2) and CH_(4) separation.The study suggested that activated carbon is a better choice for separating flue gas and carbon molecular sieve can be a strong candidate for separating coal bed methane.

Preparation and Characterization of Stellera Chamaejasme-Based Carbon Molecular Sieves

The activation effect of boric acid as an activator is good,and we investigate the best activation conditions for the boric acid impregnation method.To represent the structural characteristics and adsorption performance of the Stellera Chamaejasme based carbon molecular sieves,we use Brunner-Emmet-Teller(BET)measurements,scan-ning electron microscope(SEM),Raman spectra(Raman),X-ray diffraction(XRD),and adsorption property measurement.When the loading ratio was 0.68:1,the specific surface area was 532.21 m^(2)/g,the total pore volume was 0.24 cm 3/g,the average pore size was 1.81 nm,the adsorption value of methylene blue was 145.28 mg/g,and the adsorption value of iodine was 713.33 mg/g,the results showed that boric acid had better activation effect.The carbon molecular sieves made from Stellera Chamaejasme and activated with boric acid produce two peaks on the aperture distribution graph that are densely distributed in the micropore range.This indicates that boric acid’s pore-forming tendency is primarily micropore.

Synthesis of ZSM-22/SAPO-11 composite molecular sieve-based catalysts with small crystallites and superior n-alkane hydroisomerization performance

To improve oil quality,ZSM-22/SAPO-11 composite molecular sieves were synthesized by adding ZSM-22 into a synthetic gel of SAPO-11 for n-decane hydroisomerization.The mass ratios of ZSM-22/(ZSM-22+SAPO-11)in the composite molecular sieves were optimized and the optimal ZSM-22/SAPO-11 composite(ZS-9)was obtained.The electrostatic repulsions between the ZSM-22 precursors and the SAPO-11 crystalline nuclei produced small ZSM-22 and SAPO-11 crystallites in ZS-9,which increased the specific surface area and mesopore volume and thereby exposed more acid sites.In comparison with conventional SAPO-11,ZSM-22 and their mechanical mixture,ZS-9 with smaller crystallites and the optimal medium and strong Brønsted acid centers(MSBAC)content displayed a higher yield of branched C_(10) isomers(81.6%),lower cracking selectivity(11.9%)and excellent stability.The correlation between the i-C_(10) selectivity and the MSBAC density of molecular sieves indicated that the selectivity for branched C_(10) isomers first increased and then decreased with increasing MSBAC density on the molecular sieves,and the maximum selectivity(87.7%)occurred with a density of 9.6×10^(−2)μmol m^(−2).

一种Sieve极大似然估计的渐近性质

该文针对部分线性模型，在响应变量的观测值为Ⅰ型区间删失数据的情形下，讨论Ｓｉｅｖｅ极大似然估计的渐近性质．用三角级数来构造Ｓｉｅｖｅ空间，在一定条件下证明了该估计具有强相合性；得到了该估计的弱收敛速度，并且非参数部分的估计达到了最优收敛速度；还算出了参数部分的信息界．

Mineralogical Characterization of Sieved and Un-Sieved Samples

Mineralogical characterization applied to mineral processing is now widespread. The first step for a mineralogi- cal characterization study is usually size fractionation. Preparation of polished sections is done on size fractions to reduce complications in making representative cross sections of particles with large size differences. A sample is commonly fractionated into five or six size intervals. The drawback of this procedure is that it makes liberation studies more expensive, because one sample actually produces five or six sub-samples that need to be studied, i.e. one from each size interval. Thus to reduce cost of liberation studies, it would be desirable to study the un-sized sample. This paper provides a comparative liberation study of a set of samples both using size fractions and using the un-sized samples. The samples studied are the feed, the concentrate and the tails of a lead rougher flotation circuit. The results consistently show significant differences between the sized and the un-sized samples. Nevertheless, the results indicate that un-corrected liberation data from un-sized samples can be used for comparative studies that involve several related samples. Thus, it is possible to improve (or further understand) a concentrator circuit by using mineralogical data from un-sized samples around such circuit.

基于Sieve Bootstrap方法的长记忆过程均值变点的检验

本文提出一个新的统计量来检测长记忆时间序列中可能存在的均值变点,在原假设下推导出了检验统计量的极限分布在备择假设下证明了检验方法的一致性.为便于实际应用还提出了一种Sieve Bootstrap方法来近似统计量的临界值.模拟结果表明本文方法不仅可以很好的控制经验水平,而且相比已有均值变点检验的方法经验势也有了一定幅度的提高.

用Sieve实现邮件过滤

Sieve是一种用来产生电子邮件过滤器的语言。为便于广大用户的使用 ,它设计得相当简单 ,但同时又内涵丰富 ,应用广泛。介绍了一种应用Sieve语言的电子邮件过滤系统。

Malus sieversii: the origin, flavonoid synthesis mechanism, and breeding of red-skinned and red-fleshed apples

Flavonoids play essential roles in human health.Apple(Malus domestica Borkh.),one of the most widely produced and economically important fruit crops in temperate regions,is a significant source of flavonoids in the human diet and is among the top nutritionally rated and most widely consumed fruits worldwide.Epidemiological studies have shown that the consumption of apples,which are rich in a variety of free and easily absorbable flavonoids,is associated with a decreased risk of various diseases.However,apple production is challenged by serious inbreeding problems.The narrowing of the hereditary base has resulted in apples with poor nutritional quality and low flavonoid contents.Recently,there have been advances in our understanding of the roles that Malus sieversii(Ledeb.)M.Roem has played in the process of apple domestication and breeding.In this study,we review the origin of cultivated apples and red-fleshed apples,and discuss the genetic diversity and construction of the core collections of M.sieversii.We also discuss current research progress and breeding programs on red-skinned and red-fleshed apples and summarize the exploitation and utilization of M.sieversii in the breeding of high-flavonoid,and red-fleshed apples.This study highlights a valuable pattern of horticultural crop breeding using wild germplasm resources.The future challenges and directions of research on the molecular mechanisms of flavonoid accumulation and high-flavonoid apple breeding are discussed.

Ultraselective carbon molecular sieve membrane for hydrogen purification

Hydrogen is a green clean fuel and chemical feedstock. Its separation and purification from hydrogencontaining mixtures is the key step in the production of hydrogen with high purity(>99.99%). In this work, carbon molecular sieve(CMS) membranes with ultrahigh permselectivity for hydrogen purification were fabricated by high-temperature(700–900 ℃) pyrolysis of polymeric precursor of phenolphthaleinbased cardo poly(arylene ether ketone)(PEK-C). The evolution of the microstructural texture and ultramicroporous structure and gas separation performance of the CMS membrane were characterized via TG-MS, FT-IR, XRD, TEM, CO2 sorption analysis and gas permeation measurements. CMS membranes prepared at 700 ℃ exhibited amorphous turbostratic carbon structures and high H2 permeability of 5260 Barrer with H2/CH4, H2/N2 and H2/CO selectivities of 311, 142, 75, respectively. When carbonized at900 ℃, the CMS membrane with ultrahigh H2/CH4 selectivity of 1859 was derived owing to the formation of the dense and ordered carbon structure. CMS membranes with ultrahigh permselectivity exhibit an attractive application prospect in hydrogen purification.

CH4/N2 separation on methane molecules grade diameter channel molecular sieves with a CHA-type structure

Samples of methane molecules grade diameter channel CHA-type molecular sieves(Chabazite-K, SAPO-34 and SSZ-13) were investigated using the adsorption separation of CH4/N2 mixtures. The isotherms recorded for CH4 and N2 follow a typical type-Ι behavior, which were fitted well with the Sips model(R2>0.999) and the selectivity was calculated using IAST theory. The results reveal that Chabazite-K has the highest selectivity(SCH4/N= 5.5).2 SSZ-13 has the largest capacity, which can adsorb up to a maximum of 30.957 cm3·g-1(STP) of CH4, due to it having the largest pore volume and surface area, but the lowest selectivity(SCH4/N2= 2.5). From the breakthrough test, we can conclude that SSZ-13 may be a suitable candidate for the recovery of CH4 from low concentration methane(CH4<20%) based on its larger pore volume and higher CH4 capacity. Chabazite-K is more suited to the separation of high concentration methane(CH4>50%) due to its higher selectivity.

Kinetics and Mechanism of the Photo-oxidation of Thiophene by O_2 Adsorbed on Molecular Sieves

Photochemical oxidation of thiophene in n-octane/water extraction system using O2 as oxidant was studied. The reaction mechanism ofthiophene oxidation was proposed. Results obtained here can be used as the reference for the oxidative desulfurization of gasoline because thiophene is one of the main components containing sulfur in fluid catalytic cracking gasoline. Thiophene dissolved in n-octane was photodecomposed and removed into the water phase at ambient temperature and atmospheric pressure. A 500 W high-pressure mercury lamp （main wave length 365 nm, 0.22 kW/m） was used as light source for irradiation, and air was introduced by a gas pump to supply O2. Thiophene can be photo-oxidized to sulfone, oxalic acid, SO4^2-, and CO2. The desulfurization yield of thiophene in n-octane is 58.9% under photo-irradiation for 5 h under the conditions of air flow at 150 mL/min and V（water）：V（n-octane）=1：1. It can be improved to 92.3% by adding 0.15 g zeoliteartificial into 100 mL reaction system, which is the adsorbent for O2 and thiophene. And under such conditions, the photo-oxidation kinetics of thiophene with O2/zeoliteartificial is first-order with an apparent rate constant of 0.5047 h^-1 and a half-time of 1.37 h. The sulfur content can be depressed from 800 μL/L to less than 62 μL/L.

Preparation and evaluation of α-Al2O3 supported lithium ion sieve membranes for Li^+ extraction

Spinel lithium manganese oxide ion-sieves have been considered the most promising adsorbents to extract Li^+ from brines and sea water.Here,we report a lithium ion-sieve which was successfully loaded onto tubular α-Al2 O3 ceramic substrates by dipping crystallization and post-calcination method.The lithium manganese oxide Li4 Mn5 O(12)was first synthesized onto tubular α-Al2 O3 ceramic substrates as the ion-sieve precursor(i.e.L-AA),and the corresponding lithium ion-sieve(i.e.H-AA) was obtained after acid pickling.The chemical and morphological properties of the ion-sieve were confirmed by X-ray diffraction(XRD) and scanning electron microscopy(SEM).Both L-AA and H-AA showed characteristic peaks of α-Al2 O3 and cubic phase Li4 Mn5 O(12) and the peaks representing cubic phase could still exist after pickling.The lithium manganese oxide Li4 Mn5 O(12) could be uniformly loaded not only on the surface of α-Al2 O3 ubstrates but also inside the pores.Moreover,we found that the equilibrium adsorption capacity of H-AA was 22.9 mg·g^-1.After 12 h adsorption,the adsorption balance was reached.After 5 cycles of adsorption,the adsorption capacity of H-AA was 60.88% of the initial adsorption capacity.The process of H-AA adsorption for Li^+correlated with pseudo-second order kinetic model and Langmuir model.Adsorption thermodynamic parameters regarding enthalpy(△N), Gibbs free energy(△G) and entropy(AS) were calculated.For the dynamic adsorptiondesorption process of H-AA,the H-AA exhibited excellent adsorption performance to Li^+ with the Li^+ dynamic adsorption capacity of 9.74 mg·g^-1 and the Mn^2+dissolution loss rate of 0.99%.After 3 dynamic adsorption-desorption cycles,80% of the initial dynamic adsorption capacity was still kept.

Investigation of ZSM-5/MCM-41 Composite Molecular Sieve for Reducing Olefin Content of FCC Gasoline

ZSM-5/MCM-41 composite molecular sieve was prepared by the nano-assembling method.The ZSM-5 molecular sieve,the MCM-41 molecular sieve,the ZSM-5/MCM-41 mechanical mixture and the ZSM-5/MCM-41 composite molecular sieve were characterized by X-ray powder diffractometry,N2 adsorption isotherms,temperature programmed desorption of ammonia and scanning electron microscopy and their properties were analyzed.Using FCC gasoline as the feed,activities of different molecular sieves for reducing olefin content were investigated in a continuous high-pressure micro-reactor unit under the following conditions:a reaction temperature of 400℃,a reaction time of 2 h,a weight hourly space velocity of 3h-1,and a reaction pressure of 2.0 MPa.The results showed that the HMCM-41 molecular sieve had low reaction performance,and the HZSM-5 molecular sieve demonstrated high aromatization activity,while the ZSM-5/MCM- 41 composite molecular sieve exhibited a best olefin-reducing performance because of its high isomerization activity and moderate aromatization activity.With a largest olefin-reducmg capability and a reasonable distribution of products,the composite molecular sieve was more suitable for FCC gasoline upgrading compared to other three catalysts.

Selective synthesis of triacetin from glycerol catalyzed by HZSM-5/MCM-41 micro/mesoporous molecular sieve

HZSM-5/MCM-41 molecular sieve (H-ZM) catalysts with well-defined micro/mesoporous structures were synthesized and showed high performance for selective synthesis of triacetin via the esterification reaction of glycerol with acetic acid. The conversion of glycerol was demonstrated to be 100% and the triacetin selectivity was over 91%, which can be attributed to the synergistic effect regarding suitable acidic property, excellent diffusion efficiency and good stability derived from the combined advantages of microporous molecular sieve HZSM-5 and mesoporous molecular sieve MCM-41.

Spray-drying assisted layer-structured H_(2)TiO_(3) ion sieve synthesis and lithium adsorption performance

A spray-drying assisted solid-state method to prepare spherical layer-structured H_(2)TiO_(3) ion sieve(LSTIS)particles is reported herein.The effects of synthesis parameters(calcination temperature,calcination time,and the lithium-titanium molar ratio)on adsorption-desorption performance(the delithiation ratio,titanium dissolution loss,and the adsorption capacity)were investigated.The as-prepared LSTIS exhibited an equilibrium adsorption capacity of 30.08 mg·g^(-1)(average of 25.85 mg·g^(-1) over 5 cycles)and ultra-low titanium dissolution loss of less than 0.12%(average of 0.086%over 5 cycles).The LSTIS showed excellent selectivity toward Li^(+) in Na^(+),K^(+),Mg^(2+),and Ca^(2+) coexisting saline solutions where its adsorption capacity reached 27.45 mg·g^(-1) and the separation factors of Li^(+) over the coexisting cations exceeded 100.The data suggests that the LSTIS is promising to competitively enrich Li^(+) from saline solutions.

Beyond graphene oxides: Emerging 2D molecular sieve membranes for efficient separation☆

Recent decades witnessed the significant progress made in the research field of 2D molecular sieve membranes.In comparison with their 3D counterparts, 2D molecular sieve membranes possessed several unique advantages like significantly reduced membrane thickness(one atom thick in theory) and diversified molecular sieving mechanisms(in-plane pores within nanosheets & interlayer galleries between nanosheets). M. Tsapatsis first carried out pioneering work on fabrication of lamellar ZSM-5 membrane. Since then, diverse 2D materials typically including graphene oxides(GOs) have been fabricated into membranes showing promising prospects in energy-efficient gas separation, pervaporation, desalination and nanofiltration. In addition to GOs, other emerging 2D materials, including 2D zeolites, 2D metal–organic frameworks(MOFs), 2 D covalent-organic frameworks(COFs), layered double hydroxides(LDHs), transition metal dichalcogenides(TMDCs), MXenes(typically Ti3C2TX), graphitic carbon nitrides(typically g-C3N4), hexagonal boron nitride(h-BN) and montmorillonites(MT) are showing intriguing performance in membrane-based separation process. This article summarized the most recent developments in the field of 2D molecular sieve membranes aside from GOs with particular emphasis on their structure–performance relationship and application prospects in industrial separation.

Phase zone photon sieve

A novel diffractive optical element, named phase zone photon sieve （PZPS）, is presented. There are three kinds of phase plates in PZPSs： PZPS1, PZPS2, and PZPS3. Each of the PZPSs has its own structure and is made on quartz substrate by etching. The three PZPSs have stronger diffraction peak intensity than a photon sieve （PS） when the margin pinhole and zone line width are kept the same. The PZPS3 can produce a smaller central diffractive spot than the ordinary PS with the same number of zones on the Fresnel zone plate. We have given the design method for and the simulation of PZPS and PS. PZPS has potential applications in optical maskless lithography.

Molding of Molecular Sieve Residues and Their Application in Cleaning Oily Wastewater

To deeply clean oily wastewater,molecular sieve residues(MSRs)were sufficiently recycled and utilized due to their high specific surface area,porous structure,and outstanding adsorption property.Molding MSRs(MMSRs)were prepared by adding additives(starch,citric acid,and soluble glass)to MSRs and were then filled into a fixed bed for adsorbing and separating the oil in wastewater.Sodium dodecylbenzenesulfonate was used to modify the MMSRs,and their adsorption property was also investigated.In addition,the MSRs were characterized by scanning electron microscopy,energy-dispersive X-ray spectroscopy,Brunauer–Emmett–Teller analysis,and Fourier transform infrared spectroscopy.The results indicated that MMSRs satisfied the filling requirement of fixed bed,and their dynamic adsorption capacity could reach 0.1854 mg g^?1.Furthermore,the static adsorption capacity of MMSRs achieved 1.7346 mg g^?1 in the optimum conditions,and the oil adsorption performance of modified MMSRs was further enhanced.Therefore,this work suggests that MSRs are promising alternatives in cleaning oily wastewater.

Synthesis and Characterization of CoAPO-11 Molecular Sieve from a Non-aqueous System

ＩｎｔｒｏｄｕｃｔｉｏｎＦｏｌｏｗｉｎｇｔｈｅｓｙｎｔｈｅｓｅｓｏｆａｌｕｍｉｎｏｐｈｏｓｐｈａｔｅｆａｍｉｌｙｏｆｍｏｌｅｃｕｌａｒｓｉｅｖｅｓ（ＡｌＰＯ４－ｎ）ｉｎ１９８２［１］，ａｓｅｒｉｅｓｏｆＭｅＡＰＯ－ｎ（Ｍｅ＝Ｍｇ，Ｍｎ，ＣｏｏｒＦｅ，...