载体Al/Si比对Cu-ZnO-ZrO2催化剂上CO2加氢合成甲醇的影响

用直接合成法制备了不同铝硅物质的量比Al-SBA-15(β)(β=n(Al)/n(Si)=0,0.02,0.03,0.05)介孔分子筛,并采用浸渍法制备了金属负载量m=35%的CZZ/Al-SBA-15(β)负载型介孔催化剂,考察了Al/Si比对负载催化剂结构和性能的影响。采用N_2吸附-脱附、X射线衍射(XRD)、H_2程序升温还原(H_2-TPR)、CO_2吸附(CO_2-TPD)、NH3吸附(NH3-TPD)和透射电子显微镜(TEM)等手段对样品进行了表征,在固定床反应器上评价了其CO_2加氢合成甲醇的催化性能。实验结果表明,CZZ/Al-SBA-15(β)具有介孔结构,Al的引入不但增加了载体表面酸性位点,同时还提高了催化剂表面铜分散度(DCu%)和铜比表面积(SCu)以及促进了Cu~+-O-Zn活性位的形成,从而大大提高了催化剂的活性。其中CZZ/Al-SBA-15(0.03)催化剂的甲醇选择性达到26%,与不掺铝的CZZ/Al-SBA-15(0)催化剂相比,甲醇选择性提高了11%,但随着掺Al量的继续增加,酸性太强,CO_2吸附能力下降,活性反而降低。     

纳米孔硅铝层柱蒙脱石复合材料的制备和性能研究

以蒙脱石为原料、十六烷基三甲基溴化铵和十二烷胺为结构导向剂,直接利用正硅酸乙酯和异丙醇铝混合物为层柱前驱体,合成了新型纳米孔径硅铝层柱蒙脱石复合材料。运用XRD、TG、FT-IR和N₂等温吸附-脱附等技术表征复合材料。结果表明:合成材料具有大通道(层间距为3.45 nm)、孔径较大且分布窄(平均孔径为2.0 nm)、高比表面积(S_BET=502.0 m2/g)和高热稳定性(大于750 ℃)。和硅层柱多孔粘土复合材料相比,铝的掺入对孔结构和热稳定性影响较小,但明显提高了酸性和酸强度。      

偏高岭土水热合成高硅SAPO-5分子筛及其表征

以具有一定活性的偏高岭土兼作铝源与硅源,正磷酸作磷源,三乙醇胺和十六烷基三甲基溴化铵为复合模板剂,采用分段晶化的方法水热合成了高硅磷酸硅铝分子筛(SAPO-5). 利用X射线衍射分析（XRD）、红外光谱分析（FTIR）、扫描电镜(SEM)、²⁹Si, ²⁷Al MAS-NMR (固态核磁共振)、X光电能谱(XPS),吸附氨的程序升温脱附（NH₃-TPD）等手段对产物进行了表征. 研究结果表明:采用十六烷基三甲基溴化铵复合三乙醇胺作模板剂,可以促进SAPO-5晶体产物的形成,其产物形貌为尺寸大约20μm×5μm×5μm的规则柱状晶体. IR、MAS NMR及XPS分析表明,反应后结构中的Si、Al的配位环境发生了较大的变化,形成了较多Al(OP)₄及Si(AlO)₄两种四配位结构,其Si/Al为0.56. 产物分子筛中的总酸量为0.578mmol/g,中强酸与弱酸比例为0.684.     

Cation selectivity of natural and synthetic ionophores probed with laser-induced liquid beam mass spectrometry

The novel laser desorption method laser-induced liquid beam ionization/desorption (LILBID) is applied to the mass spectrometric examination of selective ion binding by natural and synthetic ionophores in methanol solutions. The ions are desorbed from a liquid jet with an IR laser pulse and then extracted perpendicularly into a reflectron time-of-flight (RE-TOF) analyzer. LILBID studies on the natural ion carriers valinomycin and monensin A are presented, as well as those on the synthetic crown ethers 18-crown-6, diaza-18-crown-6, and benzo-15-crown-5. No fragment ions are detected, and the measured ion selectivity is in good qualitative agreement with published stability constants of the complexes. The observed specific recognition of silver ions by diaza-18-crown-6 can be rationalized by the principle of hard and soft acids and bases, which predicts stable complexes when the polarizabilities of Lewis acid and base are similar. Weak, noncovalent interactions like those in the sandwich complex between two benzo-15-crown-5 molecules with one potassium ion are detected with LILBID. Their preservation during the process of ion desorption depends on the laser intensity. A comparison with spectra obtained by using electrospray ionization (ESI) and matrix assisted laser desorption/ionization (MALDI) shows that LILBID can potentially become a sensitive tool for the screening of weak but specific molecular interactions.     

Lysozyme adsorption onto mesoporous materials: effect of pore geometry and stability of adsorbents

In this paper, adsorption of lysozyme onto two kinds of mesoporous adsorbents (KIT-5 and AISBA-15) has been investigated and the results on the effects of pore geometry and stability of the adsorbents are also discussed. The KIT-5 mesoporous silica materials possess cage-type pore geometry while the AISBA-15 adsorbent has mesopores of cylindrical type with rather large diameter (9.7 nm). Adsorption of lysozyme onto AISBA-15 aluminosilicate obeys a Langmuir isotherm, resulting in pore occupation of 25 to 30%. In contrast, the KIT-5 adsorbents showed very small adsorption capacities for the lysozyme adsorption, typically falling in 6 to 13% of pore occupation. The cage-type KIT-5 adsorbents have narrow channel (4 to 6 nm) where penetration of the lysozyme (3 x 3 x 4.5 nm) might be restricted. The KIT-5 adsorbent tends to collapse after long-time immersion in water, as indicated by XRD patterns, while the AISBA-15 adsorbent retains its regular structure even after immersion in basic water for 4 days. These facts confirm superiority of the AISBA-15 as an adsorbent as compared with the KIT-5 mesoporous silicates. This research strikingly demonstrates the selection of mesoporous materials is crucial to achieve efficient immobilization of biomaterials in aqueous environment.     

Effect of ultraviolet illumination and ambient gases on the photoluminescence and electrical properties of nanoporous silicon layer for organic vapor sensor

The purpose of this research, the nanoporous silicon layer were fabricated and investigated the physical properties such as photoluminescence and the electrical properties in order to develop organic vapor sensor by using nanoporous silicon. The Changes in the photoluminescence intensity of nanoporous silicon samples are studied during ultraviolet illumination in various ambient gases such as nitrogen, oxigen and vacuum. In this paper, the nanoporous silicon layer was used as organic vapor adsorption and sensing element. The advantage of this device are simple process compatible in silicon technology and usable in room temperature. The structure of this device consists of nanoporous silicon layer which is formed by anodization of silicon wafer in hydrofluoric acid solution and aluminum electrode which deposited on the top of nanoporous silicon layer by evaporator. The nanoporous silicon sensors were placed in a gas chamber with various organic vapor such as ethanol, methanol and isopropyl alcohol. From studying on electrical characteristics of this device, it is found that the nanoporous silicon layer can detect the different organic vapor. Therefore, the nanoporous silicon is important material for organic vapor sensor and it can develop to other applications about gas sensors in the future.     

AAO模板受热失重及发光机理的研究

为了深入理解草酸溶液中制备的阳极氧化铝(AAO)模板受热失重以及草酸根对模板发光性能的影响,利用程序升温脱附与质谱联用(TPD-MS)、热重分析(TGA)、差热分析(DTA)以及光致发光(PL)等技术对AAO模板进行了系统研究.热失重分析结果表明,当温度低于402.2℃时,发生H2O、CO以及CO2分子的脱附以及掺杂草酸的分解,其中H2O的脱附为失重的主要原因;在402.2~866.7℃范围内,主要是草酸盐分解放出CO和CO2引起失重,CO为主要产物;碳酸盐以及残余的草酸盐的剧烈分解发生在866.7~1022.9℃范围内,主要放出CO2,并且引起大量失重.由热重结果及脱附产物中CO的摩尔比得到草酸根残余量随处理温度的变化趋势.最后,对模板PL强度、草酸根含量以及氧空位缺陷(F+)浓度三者随处理温度的变化趋势进行了关联,对AAO模板发光的原因进行了分析.     

Role of optimization parameters in the production of nanoporous carbon from mandarin shells by microwave-assisted chemical activation and utilization as dye adsorbent

In this study, mandarin (Citrus reticulata) shells (MS) were used as a new precursor material for preparation of nanoporous carbon by chemical activation method with H₃PO₄ in the presence of microwave radiation. The obtained nanoporous carbon (MNC) was characterized using nitrogen adsorption-desorption isotherms, scanning electron microscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy and Boehm titration analysis. When using impregnation ratio of 2.0 at 500?°C for 1?h, specific surface area of prepared MNC reached the maximum value, which is 1021?m²/g. Pore properties of MNC were strongly influenced by impregnation ratio, activation temperature and activation time. For industrial and environmental applications, MNC was tested towards the removal of basic blue 9 (BB9) and acid yellow 36 (AY36) dyes in aqueous media and compared with other carbon adsorbents. The high sorption capacities were 294?mg/g for BB9 and 417?mg/g for AY36. The results indicate that MNC could be regard as a valuable adsorbent to treatment dye pollutants.     

Synthesis and characterization of nanosized micro-mesoporous Zr–SiO2 via Ionic liquid templating

A series of micro-mesoporous Zr–SiO₂ composites with nanoscale domains were prepared by using ionic liquid (IL) as a template at 373 K in only 3 h with one-step. The synthesized Zr–SiO₂ materials were characterized by N₂ adsorption–desorption, scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, diffuse reflectance UV–Vis spectroscopy, thermogravimetric analysis and temperature program desorption technologies. The results show that the synthesized composite materials possess nanoparticle with a mean diameter of about 100 nm and a large surface area more than 1000 m²/g, and the hierarchically porous structure is preserved after removing template by calcination at high temperature and treating in boiling water for 72 h. The heteroatom of zirconium has been successfully incorporated into the structure framework and/or has been highly dispersed on the surface of materials. The prepared materials contain moderate to strong acid sites and the surface acid site concentration is 0.18–0.42 sites/nm². The amount of strong acid sites increases with a decrease of Si/Zr ratio, which leads to increased temperature for removing IL templates.     

Acidity and acid strength distribution of the crystalline microporous MAPO-36 molecular sieve

n situ i.r. acidity measurements of MAPO-36 show the presence of Brönsted and Lewis acid sites. The temperature-programmed desorption spectra of pyridine, obtained by the mass spectrometric technique, over MAPO-36, AIPO₄-5, and SAPO-5 reveal the presence of the two types of acid sites. At a comparable concentration of the substituted element (Si or Mg) in the aluminophosphates of types 5 and 36, the concentration of Brönsted acid sites is significantly higher in MAPO-36. The results of temperature-programmed desorption and stepwise thermal desorption of pyridine (using g.c. techniques) indicates that MAPO-36, SAPO-5, and AIPO₄-5 respectively) above 673 K indicate the substitution of Mg²⁺ for some of the Al³⁺ in the aluminophosphate framework of type 36.     

Selective formation of ethyltoluene by alkylation of toluene with ethanol over modified HZSM-5 zeolites

The selective formation of para-ethyltoluene using toluene and ethanol was studied using unmodified as well as modified shape-selective HZSM-5 catalysts. The reaction was carried out in a fixed-bed reactor in the temperature range 573–723 K and atmospheric pressure. The effect of reaction temperature, steaming temperature, and toluene-to-ethanol mole ratio on the conversion, activity, and selectivity were studied over unmodified and modified HZSM-5 zeolites. The parent zeolite HZSM-5 was modified by inorganic additives such as phosphorus, magnesium, and boron using ion-exchange and impregnation techniques.The experimental data were analyzed and reaction models were proposed based on the Langmuir-Hinshelwood-Hougen-Watson approach (LHHW) and the Eley-Rideal mechanism. The modification of HZSM-5 resulted in an increase of activation energy from a value of 61.78 kJ/mol (unmodified HZSM-5) to 97.03 kJ/mol (Mg-HZSM-5). The increase in apparent activation energy of the modified catalyst is attributed to the lower acid strength and not to the decreased number of acid sites responsible for the alkylation reaction.     

Characterization and acidic properties of Al-SBA-3 mesoporous material

SBA-3 mesostructured silica containing framework aluminum is reported here. This material was successfully synthesized using sodium aluminate via post synthesis method. The structural properties of this novel material were studied by X-ray diffraction and FTIR. The Al insertion was determined by ²⁷Al-NMR and the acidity was monitored by infrared spectroscopy of Pyridine adsorption/desorption. The ²⁷Al NMR results indicate that Al has been effectively incorporated into the framework of SBA-3 material by post-synthesis method. The bridging hydroxyl (Si₃O-Al-OH) acid sites are observed after the adsorption of basic probe molecules, such as pyridine; this fact strongly supports the presence of Bronsted acid sites. The alumination of Si-SBA-3 produces stronger Brønsted acidity than the conventional mesoporous aluminosilicates.     

Synthesis and sintering of ZrO2-CeO2 powder by use of polymeric precursor based on Pechini process

Nanocrystalline ZrO₂-12 mol % CeO₂powders were synthesized using a polymeric precursor method based on the Pechini process. X-ray diffraction (XRD) patterns showed that the method was effective to synthesize tetragonal zirconia single-phase. The mean crystallite size attained ranges from 6 to 15 nm. The BET surface areas were relatively high reaching 97 m²/g. Studies by nitrogen adsorption/desorption on powders, dilatometry of the compacts, and transmission electron microscopy (TEM) of the powders, were also developed to verify the particles agglomeration state. Both citric acid : ethylene glycol ratio and calcination temperature affected the powder morphology, which influenced the sinterability and microstructure of the sintered material, as showed by scanning electron microscopy (SEM).     

Positional isomerization of butene-2 over nanoporous MCM-48 catalysts

Positional isomerization of butene-2 to butene-1 was investigated over nanoporous MCM-48 catalysts. The effects of the method and the amount of aluminum incorporation into MCM-48 on the catalyst characteristics were studied, with respect to the butene-2 isomerization reaction. Incorporation of aluminum into MCM-48 using a post-synthetic grafting method (P) or direct sol-gel method (D) increases the total acid amount due to the increase in the Lewis acidity level. From the results of butene-2 isomerization, the yield of butene-1 was increased although the selectivity of butene-1 was decreased due to an increase of byproducts such as i-butene, cracked fraction, and C5+ hydrocarbons. This trend is nearly identical over both catalyst preparation methods; the effect of Al incorporation method on the butene-1 yield and the selectivity appeared negligible. The maximum yield of butene-1 was 27.1 wt% by feeding pure butene-2 in the reaction condition as follows: a temperature of 450 degrees C, atmospheric pressure, and with the WHSV at 70 h(-1).     

Thermodynamic Analysis of the Gasification of Municipal Solid Waste

This work aims to understand the gasification performance of municipal solid waste (MSW) by means of thermodynamic analysis. Thermodynamic analysis is based on the assumption that the gasification reactions take place at the thermodynamic equilibrium condition, without regard to the reactor and process characteristics. First, model components of MSW including food, green wastes, paper, textiles, rubber, chlorine-free plastic, and polyvinyl chloride were chosen as the feedstock of a steam gasification process, with the steam temperature ranging from 973 K to 2273 K and the steam-to-MSW ratio (STMR) ranging from 1 to 5. It was found that the effect of the STMR on the gasification performance was almost the same as that of the steam temperature. All the differences among the seven types of MSW were caused by the variation of their compositions. Next, the gasification of actual MSW was analyzed using this thermodynamic equilibrium model. It was possible to count the inorganic components of actual MSW as silicon dioxide or aluminum oxide for the purpose of simplification, due to the fact that the inorganic components mainly affected the reactor temperature. A detailed comparison was made of the composition of the gaseous products obtained using steam, hydrogen, and air gasifying agents to provide basic knowledge regarding the appropriate choice of gasifying agent in MSW treatment upon demand.     

SO24-／ZrMCM-48和H-ZrMCM-48的制备与催化性能

以正硅酸乙酯为硅源、硫酸锆为锆源、十六烷基三甲基溴化铵为模板剂,在氟化物存在的条件下,120℃下水热法合成ZrMCM-48介孔分子筛．分别用H2S04和NH4NO3对ZrMCM48进行修饰,得到酸性的SO24-／ZrMCM-48和H-zrMCM48介孔分子筛．通过x射线衍射仪（XRD）、NH3-TPD、N2吸附-脱附、透射电子显微镜（TEM）等方法对所得样品进行表征,并通过苯酚与叔丁醇的烷基化反应考察其催化性能．结果表明：ZrMCM-48、SO24-／ZrMCM-48和H-ZrMCM48都具有MCM48典型的立方介孔结构．经H2SO4和NH4NO3修饰后得到的样品的介孔有序性下降,ZrMCM48的弱酸中心较多,强酸中心相对缺乏;样品H-ZrMCM-48和SO24-／ZrMCM-48,除具有弱酸中心外,还有一定量的强酸中心,并且SO24-／ZrMCM-48比H-ZrMCM-48的强酸中心多．在相同的实验条件下,SO24-／ZrMCM-48催化剂的催化活性明显高于H-zrMCM48和zrMCM48,反应温度为140℃时,苯酚转化率高达91．6％．对于SO24-／ZrMCM-48催化剂,在低温时有利于选择性制备2,4-DTBP,高温时有利于选择性制备4-TBP．     

长程有序纳米孔氧化铝模板的制备与研究

以硫酸和草酸溶液为电解液,采用二次阳极氧化法制备出高度长程有序的纳米孔氧化铝(AAO)模板,并结合扫描电子显微镜(SEM)对其微观结构及形貌进行了观察和表征.通过研究不同的氧化电压和电解液浓度对AAO模板纳米孔形貌(孔径、孔间距、面密度和长程有序性)的影响,得到了最佳的氧化电压和电解液浓度.     

Inorganic replication of human hair and in situ synthesis of gold nanoparticles

The structure of hair was replicated via a solgel process using human hair as a template. When using silicate and tetraethoxysilane (TEOS) as the precursor, the cell structure of the hair cuticle was not well replicated. When using Ti(OnBu)₄ as the precursor, however, titania microtubes were obtained, with nanopores in their walls and nanoporous platelets on their outer surfaces, which were derived from cuticle cells on the hair surfaces. The nanopores in the microtubes acted as an effective nanoreactor for in situ synthesis of Au nanoparticles. The microchannels, nanopores and noble metal nanoparticles may provide a unique combination that would be attractive in applications such as catalysis, adsorption, and separation.     

15N/14N position-specific isotopic analyses of polynitrogenous amino acids

15N/14N isotope ratios are widely used to study processes and systems involving amino acids. Nitrogen isotope fractionation in biological processes occurs primarily at sites of bond-breaking and formation; the finest discrimination for "isotopic fingerprinting" and studies of isotopic fluxes is thus obtained at the position-specific level. While there are numerous reports of natural intramolecular carbon isotope variability, there are no literature reports of 15N/14N position-specific isotopic analysis (N-PSIA) of biologically relevant molecules. We report a methodology for high-precision N-PSIA of four polynitrogenous alpha-amino acids (asparagine, glutamine, lysine, histidine) and the first survey of natural intramolecular 15N/14N in these biomolecules. Selective liberation of N-atoms from multiple commercial standards of each parent amino acid was achieved by an appropriate enzymatic reaction or by acid hydrolysis. 15N/14N measurements were performed on N-ethoxycarbonyl ethyl ester derivatives of the parent amino acids and their analogues by gas chromatography combustion isotope ratio mass spectrometry, and the average precision for replicate injections was found to be SD(delta15N) = 0.3%. Position-specific delta15N values of the parent amino acid were directly observed or indirectly calculated using mass balance. The average precision obtained for directly measured positions was SD(delta15N) = 0.2-0.4%. The average precision for indirectly obtained positions was SD(delta15N) = 0.6-1.3% as a result of propagation of errors. Enrichment in the side chain-N with respect to the peptide-N was observed in nearly all of the amino acid sources, most notably in asparagine (average delta delta(side-peptide) = + 11%), which may be indicative of its method of production. In some cases, it was possible to distinguish commercial sources by N-PSIA that could not be distinguished at the compound-specific level.     

Influence of carboxyl group formation on ammonia adsorption of NiO-templated nanoporous carbon surfaces

The scope of this work was to control the surface functional groups of nanoporous carbons (NPs) by oxidizing agents (nitric acid and hydrogen peroxide) treatments and to investigate the relation between carboxyl group and ammonia removal efficiency. The NPs were directly prepared from a cation exchange resin by the carbonization of a mixture with Ni acetate at 900 °C. N₂/-196 °C adsorption, Boehm's titrations, and X-ray photoelectron spectroscopy (XPS) analyzes were employed to confirm the physicochemical properties of NPs. The ammonia removal efficiency was confirmed by temperature programmed desorption (TPD) technique. In the result, the oxygen content of NPs increased after various treatments and the highest content of carboxyl group formation appeared at a 2:3 volume ratio of HNO₃/H₂O₂. It was also found that the oxidation treatment led to an increase in ammonia removal efficiency of NPs, mainly due to an increase of acid oxygen functional groups (such as carboxyl) on NPs surfaces.