Design, synthesis, and nanoengineered modification of spherical graphene surface by layered double hydroxide (LDH) for removal of As (Ⅲ) from aqueous solutions

In this study, new nano spherical graphene modified with LDH(Layered Double Hydroxide) was prepared and used to remove As(Ⅲ) ion from aqueous solutions. At first, graphene oxide was synthesized from graphite using a well-known Hammer method. The obtained graphene oxide solution was sprayed in octanol solution under different temperatures and sprayed speed as influenced variables. The structure and physical characterization of synthesized spherical graphene oxide were determined by various techniques,including FT-IR, N_(2) adsorption–desorption, SEM, TEM, and EDX. In the next step, the hydrothermal method was applied to deposition LDH on the spherical graphene oxide. The synthesized spherical graphene modified by LDH was used to remove As(Ⅲ) as a toxic heavy metal ion. The effect of influenced variables including p H, contact time, amount of sorbent, and type eluent studied and the optimum values were as 8, 30, 50, and HCl(0.5 mol·L^(-1)), respectively. After optimization, the studied sorbent was shown a high adsorption capacity(149.3 mg·g^(-1)). The adsorption mechanism and kinetic models exhibited good agreement with the Langmuir isotherm and pseudo-second-order trends, respectively. Besides, the synthesized product was tested for seven times without significant loss in its sorption efficiency.

Comparison of performance of Ni-Mo/γ-alumina catalyst in HDS and HDN reactions of main distillate fractions

A bimetallic nickel-molybdenum catalyst supported on γ-alumina was synthesized by the two-step incipient wetness impregnation technique.The activity of the prepared Ni-Mo/γ-alumina catalyst was evaluated in a down flow fixed-bed microreactor.In this way,hydrodesulfurization(HDS)and hydrodenitrogenation(HDN)reactions of the main distillate fractions of crude oil were assessed.XRD,SEM,TPR,ICP-OES,BET-BJH and nitrogen adsorption/desorption methods were used for characterizing the synthesized Ni-Mo/γ-alumina catalyst.The active metals with Ni/Mo mass ratio of 0.23 and total metal of 13.7 wt% were loaded on the support,similar to the commercial industrial catalyst.The performance tests were conducted at 3.0 MPa(for light naphtha and heavy naphtha)and at 4.5 MPa(for kerosene and gas oil).The results revealed that the total sulfur conversion of the light naphtha,heavy naphtha,kerosene and gas oil fractions was 98.3%,95%,91.7% and 90.1%(after 24 h),respectively.

Comparing the deactivation behaviour of Co/CNT and Co/γ-Al_2O_3 nano catalysts in Fischer-Tropsch synthesis

An extensive study of Fischer-Tropsch （FT） synthesis on cobalt nano particles supported on γ-alumina and carbon nanotubes （CNTs） catalysts is reported.20 wt% of cobalt is loaded on the supports by impregnation method.The deactivation of the two catalysts was studied at 220 C,2 MPa and 2.7 L/h feed flow rate using a fixed bed micro-reactor.The calcined fresh and used catalysts were characterized extensively and different sources of catalyst deactivation were identified.Formation of cobalt-support mixed oxides in the form of xCoO yAl2O3 and cobalt aluminates formation were the main sources of the Co/γ-Al2O3 catalyst deactivation.However sintering and cluster growth of cobalt nano particles are the main sources of the Co/CNTs catalyst deactivation.In the case of the Co/γ-Al2O3 catalyst,after 720 h on stream of continuous FT synthesis the average cobalt nano particles diameter increased from 15.9 to 18.4 nm,whereas,under the same reaction conditions the average cobalt nano particles diameter of the Co/CNTs increased from 11.2 to 17.8 nm.Although,the initial FT activity of the Co/CNTs was 26% higher than that of the Co/γ-Al2O3,the FT activity over the Co/CNTs after 720 h on stream decreased by 49% and that over the Co/γ-Al2O3 by 32%.For the Co/γ-Al2O3 catalyst 6.7% of total activity loss and for the Co/CNTs catalyst 11.6% of total activity loss cannot be recovered after regeneration of the catalyst at the same conditions of the first regeneration step.It is concluded that using CNTs as cobalt catalyst support is beneficial in carbon utilization as compared to γ-Al2O3 support,but the Co/CNTs catalyst is more susceptible for deactivation.

Production of hydrogen and syngas via pyrolysis of bagasse in a dual bed reactor

Pyrolysis of bagasse followed by thermal cracking of tar was carded out at atmospheric pressure using a dual bed reactor. The first bed was used for the pyrolysis and the second bed was used for thermal cracking of tar. Iron fillings were used as the packed bed material in the second bed. The effects of reaction time （20 to 40 rain）, reactor temperature （600 to 900 ℃） and packed bed height （40-100 mm） on the product （char, tar and gas） yield and gas （H2, CO, CO2, CH4, CnHm） composition were studied. Over the ranges of the experimental conditions used, the operating conditions were optimized for pyrolysis temperature around 850 ℃, a reaction time of 30 min and packed bed height of 100 mm, thus we could obtain a gas richer in hydrogen and carbon monoxide and poorer in carbon dioxide and hydrocarbons. It was observed that compared with single bed process, dual bed process increased the gas yield from 0.397 to 0.750 m3/kg and decreased the tar yield from 0.445 to 0.268 g/g while the heating value of the product gas remained almost constant （10-11 M J/m3）.

Enhancement of bimetallic Fe-Mn/CNTs nano catalyst activity and product selectivity using microemulsion technique

Bimetallic Fe-Mn nano catalysts supported on carbon nanotubes(CNTs) were prepared using microemulsion technique with water-to-surfactant ratios of 0.4-1.6. The nano catalysts were extensively characterized by different methods and their activity and selectivity in Fischer-Tropsch synthesis(FTS) have been assessed in a fixed-bed microreactor. The physicochemical properties and performance of the nanocatalysts were compared with the catalyst prepared by impregnation method. Very narrow particle size distribution has been produced by the microemulsion technique at relatively high loading of active metal. TEM images showed that small metal nano particles in the range of 3–7 nm were not only confined inside the CNTs but also located on the outer surface of the CNTs. Using microemulsion technique with water to surfactant ratio of0.4 decreased the average iron particle sizes to 5.1 nm. The reduction percentage and dispersion percentage were almost doubled. Activity and selectivity were found to be dependent on the catalyst preparation method and average iron particle size. CO conversion and FTS rate increased from 49.1% to 71.0% and 0.144 to 0.289 gHC/(gcat h), respectively. While the WGS rate decreased from 0.097 to 0.056 gCO2/(gcat h). C5+liquid hydrocarbons selectivity decreased slightly and olefins selectivity almost doubled.

Performance enhancement of bimetallic Co-Ru/CNTs nano catalysts using microemulsion technique

Bimetallic cobalt-ruthenium nano catalysts supported on carbon nanotubes(CNTs)are prepared using microemultion technique with water-to-surfactant ratios of 0.5—1.5.The nano catalysts were extensively characterized by different methods and their activity and selectivity in Fischer-Tropsch synthesis(FTS)have been assessed in a fixed-bed microreactor.The physicochemical properties and performance of the nanocatalysts were compared with the catalyst prepared by impregnation method.Very narrow particle size distribution has been produced by the microemulsion technique at relatively high loadings of active metals(15 wt%Co and 1 wt%Ru).According to TEM images,small Co particles(2—7 nm)were mostly confined inside the CNTs.Comparing with the catalyst prepared by impregnation,the use of microemulsion technique with water to surfactant ratio of 0.5 decreased the average cobalt oxide particle size to 4.8 nm,the dispersion was almost doubled and the reduction increased by 28%.Activity and selectivity were found to be dependent on the catalyst preparation method and water-to-surfactant ratio(as well as cobalt particle sizes).CO conversion increased from 59.1%to 75.1%and the FTS rate increased from 0.291 to0.372 gHC/(gcath).C5+liquid hydrocarbons selectivity decreased from 92.4%to 87.6%.

Effect of elemental molar ratio on the synthesis of higher alcohols over Co-promoted alkali-modified Mo_2C catalysts supported on CNTs

A series of molybdenum carbide catalysts promoted by potassium and cobalt,supported on carbon nanotubes（CNTs） were prepared by carbothermal hydrogen reduction method using CNTs as a carbon precursor.Firstly,molybdenum and cobalt were loaded by co-precipitation method,and then potassium and additional molybdenum were impregnated to previous resultant.Different Mo/Co and K/Co molar ratio were used in catalyst synthesis.All the catalysts were characterized by ICP,BET,TEM,TPR,XRD and XPS,and the catalysts performances for higher alcohols synthesis（HAS） were investigated in a fixed-bed micro-reactor.The maximum selectivity to higher alcohols（C2＋OH） was obtained at Mo/Co and K/Mo molar ratios of 1.66 and 0.6,respectively.XRD results confirmed the formation of K-Mo-C site and Co3Mo3 C phase that might play important role in producing C2＋OH.

Effect of graphene functionalizing on the performance of NiMo/graphene in HDS and HDN reactions

In this research,to remove sulfur and nitrogen compounds from heavy naphtha,various nanocatalysts were prepared through supporting NiMo over nanoporous graphene and evaluated in hydrodesulfurization and hydrodenitrogenation reactions.The nanoporous graphene was initially functionalized in order to facilitate the metal being loaded on it.Three different methods were used to functionalize the nanoporous graphene.The NiMo/nanoporous graphene nanocatalysts were characterized by field emission scanning electron microscopy,Fourier transform infrared spectroscopy,X-ray diffraction,inductively coupled plasma optical emission spectrometry,temperature-programmed reduction,nitrogen adsorption-desorption isotherms and transmission electron microscopy techniques.Catalyst performance was evaluated in terms of conversions of sulfur,mercaptans(R-SH)and nitrogen compounds.It was found that the functionalized nanoporous graphene support could significantly enhance the catalytic performance in comparison with the industrial NiMo/alumina catalyst.Among the functionalized graphene supports,amine-functionalized graphene exhibited the best results.By using NiMo supported over amine-functionalized graphene,the conversions of total sulfur and R-SH reached 97.8%and 98.1%,respectively.

Studies on accelerated deactivation of ruthenium-promoted alumina-supported alkalized cobalt Fischer-Tropsch synthesis catalyst

Accelerated deactivation of ruthenium-promoted alumina-supported alkalized cobalt （K-Ru-Co/γ-Al 2 O 3 ） Fischer-Tropsch （FT） synthesis catalyst along the catalytic bed over 120 h of time-on-stream （TOS） was investigated. Catalytic bed was divided into three parts and structural changes of the spent catalysts collected from each catalytic bed after FT synthesis were studied using different techniques. Rapid deactivation was observed during the reaction due to high reaction temperature and low feed flow rates. The physico-chemical properties of the catalyst charged in the Bed #1 of the reactor did not change significantly. Interaction of cobalt with alumina and the formation of CoAl 2 O 4 increased along the catalytic bed. Reducibility percentage decreased by 4.5%, 7.5% and 12.9% for the catalysts in the Beds #1, #2 and #3, respectively. Dispersion decreased by 8.8%, 14.4% and 26.6% for the catalysts in the Beds #1, #2 and #3, respectively. Particle diameter increased by 0.6%, 2.4% and 10.4% for the catalysts in the Beds #1, #2 and #3, respectively, suggesting higher rate of sintering at the last catalytic bed. The amount of coke at the last catalytic bed was significantly higher than those of Beds #1 and #2.

Study of Physical, Chemical and Morphological Alterations of Smectite Clay upon Activation and Functionalization via the Acid Treatment

The present study was carried out on the effect of acid leaching on the modification and structure alteration of montmorillonite. A nanostructured, activated material was prepared by selective leaching of pure smectite clay with different concentrations of sulfuric acid (1 - 10 N/L) at 85°C for 120 min using a solid/liquid ratio of 1:20 and a reflux system. The Fourier transform infrared (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-Ray diffraction (XRD) techniques were used for the characterization and study of the acid-treated montmorillonite clay. Chemical structure of specimens was distinguished by FTIR. The results showed that the formation of Si-OH bonds and leaching of Al3+ ions increased progressively with severity of the acid treatment. As the FTIR studies indicated, acid treatment led to the removal of the octahedral Al3+ cations and an increase in the Si-OH bonds. The morphological alteration of the untreated and treated montmorillonite was investigated by using TEM and SEM. X-ray fluorescence (XRF) analysis revealed a considerable decrease in the relative content of Al by increasing the acid strength. Moreover, the XRD results showed that the treatment using highly concentrated acid resulted in the formation of an amorphous silica phase.

Non-catalytic conversion of wheat straw,walnut shell and almond shell into hydrogen rich gas in supercritical water media

Agricultural wastes as lignocellulosic biomasses are known as the major resources of bioenergy. These valuable resources can be converted into useful environmental friendly fuels and chemicals. Wheat straw, walnut shell and almond shell are the main agricultural wastes in Kurdistan province, Iran. This study investigates the hydrogen-rich gas production via gasification of these biomasses in supercritical water media. Experiments were performed first, in the base case condition using a stainless steel batch micro reactor system. Then, the effect of reaction time on the total gas yield and yield of hydrogen, were investigated. It was seen that the total gas yields and gasification efficiencies increased by increasing the reaction time to 30 min and then the total gas yield was approximately remained constant. Among three used feed stocks, wheat straw with higher amount of cellulose and lower amount of lignin had the highest total gas and hydrogen yields in shorter reaction times.The maximum hydrogen yields of 7.25, 4.1 and 4.63 mmol per gram of wheat straw, almond shell and walnut shell occurred at 10, 15 and 20 min of reaction time, respectively.

Green and High Efficient Synthesis of 2-Aryl Benzimidazoles: Reaction of Arylidene Malononitrile and 1,2-Phenylenediamine Derivatives in Water or Solvent-Free Conditions

A fast, high efficiency and environmentally friendly procedure for the synthesis of 2-aryl benzim-idazole derivatives has been reported. Reaction between 1,2-phenylenediamine derivatives and arylidene malononitrile under aqueous media and also solvent-free conditions generates 2-aryl benzimidazole derivatives with a high yield.

N-heterocyclic Carbene Catalysed Polymerisation of 2,5-Diformylfuran

The biobased renewable monomer 2,5-diformylfuran is polymerised using various N-heterocyclic carbene(NHC)catalysts in dimethyl sulfoxide(DMSO)affording a low molar mass polymer.It is shown that catalyst structure as well as the temperature and time the polymerization is running have a noticeable effect on its molar mass.The obtained material is charac­terized by nuclear magnetic resonance(NMR),thermogravimetric analysis(TGA),differential scanning calorimetry(DSC)and X-ray diffraction(XRD).An attempt at chain extension with diamine leads to precipitation of the polymer.This new biobased polymer material might be useful as a sustainable resin.

Ultrasensitive Indium Phosphide Nanomembrane Wearable Gas Sensors

Air quality is deteriorating due to continuing urbanization and industrialization.In particular,nitrogen dioxide(NO_(2))is a biologically and environmentally hazardous byproduct from fuel combustion that is ubiquitous in urban life.To address this issue,we report a high-performance flexible indium phosphide nanomembrane NO_(2)sensor for real-time air quality monitoring.An ultralow limit of detection of~200 ppt and a fast response have been achieved with this device by optimizing the film thickness and doping concentration during indium phosphide epitaxy.By varying the film thickness,a dynamic range of values for NO_(2)detection from parts per trillion(ppt)to parts per million(ppm)level have also been demonstrated under low bias voltage and at room temperature without additional light activation.Flexibility measurements show an adequately stable response after repeated bending.On-site testing of the sensor in a residential kitchen shows that NO_(2)concentration from the gas stove emission could exceed the NO_(2)Time Weighted Average limit,i.e.,200 ppb,highlighting the significance of real-time monitoring.Critically,the indium phosphide nanomembrane sensor element cost is estimated at<0.1 US$due to the miniatured size,nanoscale thickness,and ease of fabrication.With these superior performance characteristics,low cost,and real-world applicability,our indium phosphide nanomembrane sensors offer a promising solution for a variety of air quality monitoring applications.

氮掺杂炭材料在锂离子电池负极的研究进展

硬碳、活性炭、碳纳米管(CNTs)、石墨烯、多孔炭和炭纤维等炭材料替代锂离子电池的石墨阳极是目前的研究热点。与石墨相比,这种材料已表现出更好的储锂电化学性能,但仍有待进一步发展空间。其中一种有效的方法是在炭材料结构中加入杂原子(例如氮),提高其作为锂离子负极时的电化学性能。本综述首先描述了氮掺杂如何对锂离子电池的性能产生积极影响,并举例说明了氮掺杂炭材料的优势。然后,比较了不同N掺杂炭材料中的X射线光电子能谱和扫描隧道显微镜的表征结果,通过统计分析了掺氮量对掺氮碳材料比容量的影响。

纳米孔碳负载Fe_3O_4催化剂上苯直接羟基化制苯酚(英文)

Fe3O4/CMK-3 was prepared by impregnation and used as a catalyst for the direct hydroxylation of benzene to phenol with hydro-gen peroxide. The iron species in the prepared catalyst was Fe3O4 because of the partial reduction of iron(III) to iron(II) on the surface of CMK-3. The high catalytic activity of the catalyst arises from the formation of Fe3O4 on the surface of CMK-3 and the high selectivity for phenol is attributed to the consumption of excess hydroxyl radicals by CMK-3. The effect of temperature,reaction time,volume of H2O2,and amount of catalyst on the catalytic performance of the prepared catalyst were investigated. Under optimized conditions,the catalyst showed excellent catalytic performance for the hydroxylation of benzene to phenol and 18% benzene conversion was achieved with 92% selectivity for phenol and with a TOF value of 8.7 h-1. The stability of catalyst was investigated by determining its activity after the fourth run and it was found to have decreased to 80% of the fresh catalyst's activity.

可见光下改性的纳米孔二氧化硅(LUS-1)光催化苯直接羟基化合成苯酚(英文)

Fe-g-C3N4-LUS-1 was prepared by the thermal decomposition of dicyandiamide inside the pores of LUS-1 under an inert atmosphere.It was used as a photocatalyst for the hydroxylation of benzene to phenol in sunlight.The catalysts were characterized by Fourier transform infrared spectroscopy,N2 adsorption-desorption,X-ray diffraction,and scanning electron microscopy.In Fe-g-C3N4-LUS-1,a single layer of graphitic carbon nitride(g-C3N4) was formed on the surface of LUS-1.The photocatalytic activity of the iron containing g-C3N4 based catalysts was investigated,and the catalytic activity was remarkably enhanced when the reaction condition was changed from dark to sunlight.The best result was obtained with 20%Fe-g-C3N4-LUS-1 in sunlight.

Sonication method synergism with rare earth based nanocatalyst:preparation of NiFe_(2–x)Eu_xO_4 nanostructures and its catalytic applications for the synthesis of benzimidazoles,benzoxazoles,and benzothiazoles under ultrasonic irradiation

A simple and practical ultrasonically synthetic strategy for the preparation of rare-earth based catalyst, nanostructured NiFe2-xEuxO4 was developed. The structtre of NiFe2-xEuxO4 was characterized by various analyses such as X-ray diffraction （XRD）, scanning electron microscopy （SEM） and fourier transform infrared spectroscopy （FT-IR）. The catalytic performance of NiFe2-xEuxO4 was evaluated for the synthesis of benzimidazoles, benzoxazoles and benzothiazoles under ultrasonic irradiation. All reactions were completed in short times and all products were obtained in good to excellent yields in presence of the rare-earth based catalyst. Besides, NiFe2-xEuxO4 could be recovered for 6 times without noticeably decreasing the catalytic activity.

Molecular-level Engineering of S-scheme Heterojunction:the Site-specific Role for Directional Charge Transfer

The promising S-scheme heterojunction photocatalysts are considered as a novel frontier due to their superiority in various solar-driven energy-related applications.Recently,a novel atom-specific tailoring strategy has been introduced on the construction of S-scheme het-erojunction for promoting the electronic transferability.The S-scheme heterojunction is regulated by integrating high-crystalline carbon nitride with Co-doped CeO_(2).Specifically,this atom-specific regulation of S-scheme heterojunction boosts directional electron-driving effect towards functionalized Co sites,benefit-ing for effective photogenerated charge carrier transferability.Moreover,a series of tracking characterizations show that Co-embedded modification promotes CO_(2)photoreduction into hydrogenation steps,resulting in high performance towards CO_(2)-to-CH_(4)photoreduction,which provides new opportunities for the development of multifunctional cooperation in heterogeneous photocatalysis.

Ionic Conductivity in Gelatin-Based Hybrid Solid Electrolytes:The Non-trivial Role of Nanoclay

In this study, the ionic conductivity behavior in hybrid gelatin-based transparent electrolytes including various types of nanoclays with different size, shape and surface properties was characterized. The effects of nanoclay type and nanoclay concentration as well as different experimental conditions, e.g., pH, temperature and crosslinking were also investigated. In general, the impedance spectroscopy results suggested a non- trivial role for nanoclay. Regardless of the nanoclay type, the ionic conductivity slightly increased first and then decreased by increasing the nanoclay concentration. Furthermore, among sodium montmorillonite （Na＋MMT）, lithium montmorillonite （Li＋MMT）, laponite and hydrotalcite, the hybrid electrolytes prepared by Li＋MMT showed higher ionic conductivity. The results also showed that the chemical crosslinking along with sample preparation at optimum pH, where the gelatin chains might be efficiently adsorbed on exfoliated, negatively charged clay nanosheets, plays an important role. In comparison with the ionic conductivity of the neat sample at room temperature （～10-7 S cm-1）, a ten-fold increase was observed for the crosslinked sample containing 2 wt% of Li^＋MMT prepared at optimum pH 3.5. The conductivity behavior as a function of temperature revealed the obedience with the VogeI-Fulcher-Tammann （VFT） model for all samples, suggesting the important role of segmental motions in the ionic conductivity. Finally, a qualitative explanation was presented for the mechanism of the ionic conduction in gelatin-nanoclay hybrid electrolytes.