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2004 Volume 20 Issue 7
2004, 20(07): 673-675
doi: 10.3866/PKU.WHXB20040701
Abstract:
A simple method was used to synthesize the iodinated multi hydroxylated SWNTs (SWNTols) by the reaction of SWNTols with NaI in the presence of strong oxidant N-chloro-p-toluenesulfonamide. The formation of the C－I covalent bond was verified by comparing the electron binding energies of iodine of I-SWNTols and the reference materials, which were measured with the synchrotron radiation X-ray photoemission spectroscopy (SRXPS) as well as the conventional X-ray photoelectron spectroscopy (XPS). This result will be useful in applications of SWNTs in the biomedical and pharmaceutical sciences.
A simple method was used to synthesize the iodinated multi hydroxylated SWNTs (SWNTols) by the reaction of SWNTols with NaI in the presence of strong oxidant N-chloro-p-toluenesulfonamide. The formation of the C－I covalent bond was verified by comparing the electron binding energies of iodine of I-SWNTols and the reference materials, which were measured with the synchrotron radiation X-ray photoemission spectroscopy (SRXPS) as well as the conventional X-ray photoelectron spectroscopy (XPS). This result will be useful in applications of SWNTs in the biomedical and pharmaceutical sciences.
2004, 20(07): 676-679
doi: 10.3866/PKU.WHXB20040702
Abstract:
Analysis of protein-protein interface is crucial to understand protein interactions and to develop drugs targeting protein complexes. PP_SITE is a method developed by the author's group to deduce hydrogen bond and hydrophobic properties for protein-protein interface. We have used PP_SITE to perform statistical analysis on protein-protein interfaces. A two-chain non-redundant interface dataset from PDB was constructed and used in the study. According to the hydrophobicity and hydrogen bond characteristics, criteria were selected to differentiate protein interfaces into distinct groups. The size of interface, the proportion of hydrophobic and hydrophilic property and the extent of concentration in hydrophobicity were found to be important for interface classification.
Analysis of protein-protein interface is crucial to understand protein interactions and to develop drugs targeting protein complexes. PP_SITE is a method developed by the author's group to deduce hydrogen bond and hydrophobic properties for protein-protein interface. We have used PP_SITE to perform statistical analysis on protein-protein interfaces. A two-chain non-redundant interface dataset from PDB was constructed and used in the study. According to the hydrophobicity and hydrogen bond characteristics, criteria were selected to differentiate protein interfaces into distinct groups. The size of interface, the proportion of hydrophobic and hydrophilic property and the extent of concentration in hydrophobicity were found to be important for interface classification.
2004, 20(07): 684-689
doi: 10.3866/PKU.WHXB20040704
Abstract:
The 4A,13X and LSX zeolites were ion exchanged with Li＋ repeatedly in water solution, then the adsorption isotherms and breakthrough curves of these zeolites were measured at 25 ℃.The data demonstrate that 4A,13X and LSX highly ion-exchanged with Li＋ have higher adsorption capacity and better adsorption selectivity for N2 over Ar. It is clear that the highly Li＋ exchanged zeolites are od adsorbents for separation of N2 and Ar. From breakthrough curves we know that the zeolites near completely exchanged with Li＋ have a suitable pressure for the adsorption separation of N2 and Ar. In the pressure range we studied, the best pressure is about 0.6 MPa. Comparing with the data from the breakthrough curves of the three highly Li＋ exchanged zeolites we conclude that highly Li＋ exchanged LSX has better properties for the separation of N2 and Ar than the other two zeolites.
The 4A,13X and LSX zeolites were ion exchanged with Li＋ repeatedly in water solution, then the adsorption isotherms and breakthrough curves of these zeolites were measured at 25 ℃.The data demonstrate that 4A,13X and LSX highly ion-exchanged with Li＋ have higher adsorption capacity and better adsorption selectivity for N2 over Ar. It is clear that the highly Li＋ exchanged zeolites are od adsorbents for separation of N2 and Ar. From breakthrough curves we know that the zeolites near completely exchanged with Li＋ have a suitable pressure for the adsorption separation of N2 and Ar. In the pressure range we studied, the best pressure is about 0.6 MPa. Comparing with the data from the breakthrough curves of the three highly Li＋ exchanged zeolites we conclude that highly Li＋ exchanged LSX has better properties for the separation of N2 and Ar than the other two zeolites.
2004, 20(07): 690-695
doi: 10.3866/PKU.WHXB20040705
Abstract:
The effect of polymer chain on the formation of surfactant micelles and the variation of polymer configurational properties are simulated. Results show that polymer chain helps the formation of surfactant micelles if the strength of the interaction between the polymer chain and surfactant exceeds a critical value, which decreases with the increase of the chain length. The value CAC/CMC, ratio of the critical aggregation concentration (CAC) to the critical micelle concentration (CMC), decreases with the increase of the chain length and the interaction strength between the polymer chain and surfactant. There is only dynamic adsorption between the chain and surfactant when surfactant concentration X< CAC; after CAC, however, the size of the surfactant micelle increases and the static adsorption between polymer chain and micelles brings about. The mean-square end-to-end distance 〈R2〉 and mean asphericity 〈A〉are almost constants at very small X, but they drop steeply when X reaches CAC, and finally they increase when the micelles are large enough. Simulation results show that the polymer chain always wraps outside of the surfactant micelles, which supports the experimental model of polymer chain wrapping micelles.
The effect of polymer chain on the formation of surfactant micelles and the variation of polymer configurational properties are simulated. Results show that polymer chain helps the formation of surfactant micelles if the strength of the interaction between the polymer chain and surfactant exceeds a critical value, which decreases with the increase of the chain length. The value CAC/CMC, ratio of the critical aggregation concentration (CAC) to the critical micelle concentration (CMC), decreases with the increase of the chain length and the interaction strength between the polymer chain and surfactant. There is only dynamic adsorption between the chain and surfactant when surfactant concentration X< CAC; after CAC, however, the size of the surfactant micelle increases and the static adsorption between polymer chain and micelles brings about. The mean-square end-to-end distance 〈R2〉 and mean asphericity 〈A〉are almost constants at very small X, but they drop steeply when X reaches CAC, and finally they increase when the micelles are large enough. Simulation results show that the polymer chain always wraps outside of the surfactant micelles, which supports the experimental model of polymer chain wrapping micelles.
2004, 20(07): 696-700
doi: 10.3866/PKU.WHXB20040706
Abstract:
The sorption of dichlorobenzene isomers in AlPO4-5 over the temperature range of 303～675 K was simulated by Monte Carlo method with Cerius2 developed by MSI. The isotherms and the average potential energy of dichlorobenzene isomers in the framework were obtained. It was observed that the sorption capacity for o-dichlorobenzene was higher than that for p-dichlorobenzene at low temperature, which could be well interpreted on the basis of the packing fashion of sorbates in the channel of molecular sieves; by contrast, the adsorption capacity of p-dichlorobenzene was higher than that of o-dichlorobenzene at high temperature. Moreover, the average potential energy of dichlorobenzene decreased with the loading, and that of o-dichlorobenzene showed a sharp decrease at higher loadings.
The sorption of dichlorobenzene isomers in AlPO4-5 over the temperature range of 303～675 K was simulated by Monte Carlo method with Cerius2 developed by MSI. The isotherms and the average potential energy of dichlorobenzene isomers in the framework were obtained. It was observed that the sorption capacity for o-dichlorobenzene was higher than that for p-dichlorobenzene at low temperature, which could be well interpreted on the basis of the packing fashion of sorbates in the channel of molecular sieves; by contrast, the adsorption capacity of p-dichlorobenzene was higher than that of o-dichlorobenzene at high temperature. Moreover, the average potential energy of dichlorobenzene decreased with the loading, and that of o-dichlorobenzene showed a sharp decrease at higher loadings.
2004, 20(07): 701-706
doi: 10.3866/PKU.WHXB20040707
Abstract:
In order to investigate the effects of the crystals on glass transition and enthalpy relaxation behaviors, differential scanning calorimetry (DSC) and cryomicroscopy technique were used to study ethylene glycol (EG) and its aqueous solution (50％EG, mass fraction) with different crystallinity. Isothermal crystallization method was used in devitrification region to get different crystal fractions after samples quenched below the glass transition temperature (Tg).The DSC thermograms upon heating showed that EG had a single glass transition while 50％EG had two (amorphous phaseⅠ and the warmer one, phase Ⅱ)with different crystal fractions. Tg of phaseⅠ was equal to while phase Ⅱ was 6 ℃ higher than Tg of 50％EG in purely amorphous phase. It is believed that the lower transition represents the glass transition of bulk amorphous phase of EG aqueous solution glass state, while the second one is related to inclusions, whose mobility is restricted by ice crystals. Cryomicroscopy experiments indicated that EG crystal had regular shape while ice crystal in 50％EG aqueous solution glass matrix had no clear surface. It can be concluded that contact area between crystal and amorphous phase in EG is larger than that in 50％EG, which is helpful to explain double glass-like transitions. Isothermal annealing experiments at temperatures lower than Tg were also conducted on these amorphous samples in DSC, and KWW（Kohlrausch-Williams-Watts）decay function was used to analyze DSC enthalpy relaxation data. The results showed that both the two amorphous phases presented in 50％EG experience enthalpy relaxation, and the relaxation process of phase Ⅰ is faster than that of phase Ⅱ at the same value of (Tg－Ta).
In order to investigate the effects of the crystals on glass transition and enthalpy relaxation behaviors, differential scanning calorimetry (DSC) and cryomicroscopy technique were used to study ethylene glycol (EG) and its aqueous solution (50％EG, mass fraction) with different crystallinity. Isothermal crystallization method was used in devitrification region to get different crystal fractions after samples quenched below the glass transition temperature (Tg).The DSC thermograms upon heating showed that EG had a single glass transition while 50％EG had two (amorphous phaseⅠ and the warmer one, phase Ⅱ)with different crystal fractions. Tg of phaseⅠ was equal to while phase Ⅱ was 6 ℃ higher than Tg of 50％EG in purely amorphous phase. It is believed that the lower transition represents the glass transition of bulk amorphous phase of EG aqueous solution glass state, while the second one is related to inclusions, whose mobility is restricted by ice crystals. Cryomicroscopy experiments indicated that EG crystal had regular shape while ice crystal in 50％EG aqueous solution glass matrix had no clear surface. It can be concluded that contact area between crystal and amorphous phase in EG is larger than that in 50％EG, which is helpful to explain double glass-like transitions. Isothermal annealing experiments at temperatures lower than Tg were also conducted on these amorphous samples in DSC, and KWW（Kohlrausch-Williams-Watts）decay function was used to analyze DSC enthalpy relaxation data. The results showed that both the two amorphous phases presented in 50％EG experience enthalpy relaxation, and the relaxation process of phase Ⅰ is faster than that of phase Ⅱ at the same value of (Tg－Ta).
2004, 20(07): 707-711
doi: 10.3866/PKU.WHXB20040708
Abstract:
Three lithium titanium composite oxides were prepared from different TiO2, and the electrochemical performance of the composite oxides was tested. The results proved that, Li4Ti5O12 prepared from nanocrystalline titanium dioxide showed a od lithiation performance. The reversible capacity of the material was more than 95 mA•h•g－1, the charge-discharge efficiency was almost 100％ and the cyclic performance was od. When the lithium intercalation≥85％ or the lithium extraction≥90％, its charge potential or discharge potential would change quickly. This Li4Ti5O12 is od candidate material of negative electrode for lithium-ion battery.
Three lithium titanium composite oxides were prepared from different TiO2, and the electrochemical performance of the composite oxides was tested. The results proved that, Li4Ti5O12 prepared from nanocrystalline titanium dioxide showed a od lithiation performance. The reversible capacity of the material was more than 95 mA•h•g－1, the charge-discharge efficiency was almost 100％ and the cyclic performance was od. When the lithium intercalation≥85％ or the lithium extraction≥90％, its charge potential or discharge potential would change quickly. This Li4Ti5O12 is od candidate material of negative electrode for lithium-ion battery.
2004, 20(07): 712-716
doi: 10.3866/PKU.WHXB20040709
Abstract:
The Pb-based complex perovskite relaxor ferroelectrics (RFE) of Pb(Mg1/3Nb2/3)O3(PMN) and Pb(Zn1/3Nb2/3)O3(PZN) ceramics were prepared by conventional methods. The dynamics on microdomain-macrodomain transition of relaxor ferroelectrics was investigated by using amended local freezing glass-model. The dynamics on microdomain growth was also studied. The result shows that microdomain-macrodomain transition is a quantum transition process, while its driving forces are mainly heating force and energy force. The stability of the microdomain-macrodomain transition in RFE is judged by both the activating energy and state parameter. The stability of the microdomain growth was judged by the K value of stability.
The Pb-based complex perovskite relaxor ferroelectrics (RFE) of Pb(Mg1/3Nb2/3)O3(PMN) and Pb(Zn1/3Nb2/3)O3(PZN) ceramics were prepared by conventional methods. The dynamics on microdomain-macrodomain transition of relaxor ferroelectrics was investigated by using amended local freezing glass-model. The dynamics on microdomain growth was also studied. The result shows that microdomain-macrodomain transition is a quantum transition process, while its driving forces are mainly heating force and energy force. The stability of the microdomain-macrodomain transition in RFE is judged by both the activating energy and state parameter. The stability of the microdomain growth was judged by the K value of stability.
2004, 20(07): 717-721
doi: 10.3866/PKU.WHXB20040710
Abstract:
The hydrothermal precipitation in the Al2(SO4)3-CO(NH2)2-H2O system under the conditions of [Al3＋]=0.2 mol•L－1,[CO(NH2)2]:[Al3＋]=2:1 and 2 h at different temperatures has been studied. Very light boehmite powders in the form of porous agglomeration of several micron size covered with needle clusters are obtained at above 140 ℃.The reaction solution and the products are characterized by ICP-AES, XRD, FT-IR, SEM, BET and particle size distribution. The precipitation of aluminum hydroxide gel or amorphous powder is almost completed at 140 ℃. With the reaction temperature raised to 180 ℃, crystallinity of the products, whose tap density varies among 117.2～158.2 kg•m－3,becomes more perfect and the specific surface area increases from 75.3 m2•g－1 to 88.3 m2•g－1 as well. However, the average diameter decreases moderately. The γ-Al2O3 powders formed by calcination of aforementioned boehmites at 550 ℃ for 2 h have the same shape and higher specific surface area compared with their corresponding precursors.
The hydrothermal precipitation in the Al2(SO4)3-CO(NH2)2-H2O system under the conditions of [Al3＋]=0.2 mol•L－1,[CO(NH2)2]:[Al3＋]=2:1 and 2 h at different temperatures has been studied. Very light boehmite powders in the form of porous agglomeration of several micron size covered with needle clusters are obtained at above 140 ℃.The reaction solution and the products are characterized by ICP-AES, XRD, FT-IR, SEM, BET and particle size distribution. The precipitation of aluminum hydroxide gel or amorphous powder is almost completed at 140 ℃. With the reaction temperature raised to 180 ℃, crystallinity of the products, whose tap density varies among 117.2～158.2 kg•m－3,becomes more perfect and the specific surface area increases from 75.3 m2•g－1 to 88.3 m2•g－1 as well. However, the average diameter decreases moderately. The γ-Al2O3 powders formed by calcination of aforementioned boehmites at 550 ℃ for 2 h have the same shape and higher specific surface area compared with their corresponding precursors.
2004, 20(07): 722-726
doi: 10.3866/PKU.WHXB20040711
Abstract:
Rare-earth oxides Ln2O3(Ln=La, Ce) ultrafine nano suspensions in pure water were prepared by a high energy ball-milling technique. The effects of ball milling time and rotating speed on the stability of suspensions and particles structure were investigated. Increasing the ball-milling time and rotating speed is in favor of improving the stability of suspensions. The size, distribution and surface charge characteristics of particle in suspensions maybe the important factors for stability of suspensions. These suspensions have excellent stability, high concentration, high surface tension and low viscosity.
Rare-earth oxides Ln2O3(Ln=La, Ce) ultrafine nano suspensions in pure water were prepared by a high energy ball-milling technique. The effects of ball milling time and rotating speed on the stability of suspensions and particles structure were investigated. Increasing the ball-milling time and rotating speed is in favor of improving the stability of suspensions. The size, distribution and surface charge characteristics of particle in suspensions maybe the important factors for stability of suspensions. These suspensions have excellent stability, high concentration, high surface tension and low viscosity.
2004, 20(07): 727-730
doi: 10.3866/PKU.WHXB20040712
Abstract:
The states of Cu3/2PMo12O40,which was used as a modifier for Raney nickel and Raney cobalt, were investigated by XPS technique. It was found that valence states of Cu2＋ and Mo6＋ were greatly changed, i.e. Cu2＋ was reduced to Cu0 while Mo6＋ was partially reduced to Mo5＋ and Mo4+.These changes were due to the presence of active hydrogen adsorbed onto the surface of Raney nickel and Raney cobalt catalysts. Raney nickel contained less low oxidation state Mo than Raney cobalt, which was probably due to the different activity of adsorbed hydrogen species on the Raney nickel surface and Raney cobalt surface. The presence of Cu was beneficial to the hydrogenation of carbonyl. The existence of Mo improved the adsorption and activation of carbonyl. In another word, the presence of Cu and Mo complemented each other in the hydrogenation of carbonyl.
The states of Cu3/2PMo12O40,which was used as a modifier for Raney nickel and Raney cobalt, were investigated by XPS technique. It was found that valence states of Cu2＋ and Mo6＋ were greatly changed, i.e. Cu2＋ was reduced to Cu0 while Mo6＋ was partially reduced to Mo5＋ and Mo4+.These changes were due to the presence of active hydrogen adsorbed onto the surface of Raney nickel and Raney cobalt catalysts. Raney nickel contained less low oxidation state Mo than Raney cobalt, which was probably due to the different activity of adsorbed hydrogen species on the Raney nickel surface and Raney cobalt surface. The presence of Cu was beneficial to the hydrogenation of carbonyl. The existence of Mo improved the adsorption and activation of carbonyl. In another word, the presence of Cu and Mo complemented each other in the hydrogenation of carbonyl.
2004, 20(07): 731-734
doi: 10.3866/PKU.WHXB20040713
Abstract:
Nano-structured Onion-like Fullerenes(NSOFs) were synthesized by DC arc-discharge. Soots in different regions of oven were characterized and analyzed by SEM and HRTEM. Comparing to HOPG, Raman shift appears in NSOFs. The results indicate that NSOFs from cathode area have higher degree of crystallization. In addition, blue shift, E2g mode hardening 7 cm－1, may be due to its quantum dimension effect and uneven diameter distrbution.
Nano-structured Onion-like Fullerenes(NSOFs) were synthesized by DC arc-discharge. Soots in different regions of oven were characterized and analyzed by SEM and HRTEM. Comparing to HOPG, Raman shift appears in NSOFs. The results indicate that NSOFs from cathode area have higher degree of crystallization. In addition, blue shift, E2g mode hardening 7 cm－1, may be due to its quantum dimension effect and uneven diameter distrbution.
2004, 20(07): 735-739
doi: 10.3866/PKU.WHXB20040714
Abstract:
The adsorption behavior and photooxidation kinetics of OH－ at TiO2 thin film electrodes in solution of alcohols have been studied by electrochemical measurements. The results show that the adsorption model of OH－ on TiO2 surface corresponds to the Langmuir isotherm and under high enough applied bias potential the photooxidation kinetics can be described by Langmuir-Hinshelwood expression. Hydroxide ions are regarded to be the reactant with photogenerated holes and adsorbed water could not be captured by the holes and, consequently, the photocurrent is proportional to the density of OH－ adsorbed on TiO2 surface under the condition of high enough light intensity. In solution with high content of alcohols, the recombining reaction between radical and photogenerating electron can hardly occur, where the rate-limiting step is the formation of photo-driven OH• radical.
The adsorption behavior and photooxidation kinetics of OH－ at TiO2 thin film electrodes in solution of alcohols have been studied by electrochemical measurements. The results show that the adsorption model of OH－ on TiO2 surface corresponds to the Langmuir isotherm and under high enough applied bias potential the photooxidation kinetics can be described by Langmuir-Hinshelwood expression. Hydroxide ions are regarded to be the reactant with photogenerated holes and adsorbed water could not be captured by the holes and, consequently, the photocurrent is proportional to the density of OH－ adsorbed on TiO2 surface under the condition of high enough light intensity. In solution with high content of alcohols, the recombining reaction between radical and photogenerating electron can hardly occur, where the rate-limiting step is the formation of photo-driven OH• radical.
2004, 20(07): 740-744
doi: 10.3866/PKU.WHXB20040715
Abstract:
The electrochemical activities of Ti based IrO2 active coating electrodes in Na2SO4 aqueous solutions containing methanol, formic acid and formaldehyde, respectively, were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS).The activity was quantitatively characterized by the double-layer capacitance,Cdl. The results showed that in comporison with that in H2SO4 electrolyte the electrode activity in Na2SO4 solution with the same concentration declines dramatically. The active surface area of the electrodes was also found to decrease in the presence of these small organic moleculars. It was found that the electrooxidation of organic compounds can take place in a wide potential region, but with a slow reaction rate. The organic oxidation is facilitated by the oxygen evolution on this type of electrode.
The electrochemical activities of Ti based IrO2 active coating electrodes in Na2SO4 aqueous solutions containing methanol, formic acid and formaldehyde, respectively, were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS).The activity was quantitatively characterized by the double-layer capacitance,Cdl. The results showed that in comporison with that in H2SO4 electrolyte the electrode activity in Na2SO4 solution with the same concentration declines dramatically. The active surface area of the electrodes was also found to decrease in the presence of these small organic moleculars. It was found that the electrooxidation of organic compounds can take place in a wide potential region, but with a slow reaction rate. The organic oxidation is facilitated by the oxygen evolution on this type of electrode.
Investigation of VPO Catalyst Transforming Gaseous Cyclohexane into Maleic Anhydride and Acetic Acid
2004, 20(07): 745-748
doi: 10.3866/PKU.WHXB20040716
Abstract:
In order to investigate the new reaction concerning the transformation of gas-cyclohexane into maleic anhydride and acetic acid, various solid VPO catalysts were prepared by different preparation methods. The main crystalline phase of the catalysts and the average oxidation value of vanadium in the catalysts were determined respectively by XRD、FT-IR and chemical titration. Experiment results revealed that the main crystalline phase, crystallization，activation ambience, and V4＋/ V5＋ ratio in the catalysts affected catalytic activity and selectivity. The catalysts whose main crystalline phase is (VO)2P2O7 possessed high crystallinity and feasible V4＋/ V5＋ ratio. (VO)2P2O7 calcinated in reaction ambience occupied higher selectivity.
In order to investigate the new reaction concerning the transformation of gas-cyclohexane into maleic anhydride and acetic acid, various solid VPO catalysts were prepared by different preparation methods. The main crystalline phase of the catalysts and the average oxidation value of vanadium in the catalysts were determined respectively by XRD、FT-IR and chemical titration. Experiment results revealed that the main crystalline phase, crystallization，activation ambience, and V4＋/ V5＋ ratio in the catalysts affected catalytic activity and selectivity. The catalysts whose main crystalline phase is (VO)2P2O7 possessed high crystallinity and feasible V4＋/ V5＋ ratio. (VO)2P2O7 calcinated in reaction ambience occupied higher selectivity.
2004, 20(07): 749-754
doi: 10.3866/PKU.WHXB20040717
Abstract:
Titanium tartrate complex has been successfully grafted onto hexa nal mesoporous silicas (HMS) or encapsulated into microporous NaY zeolite by means of chemically bonding or “ship in bottle” methods. The UV-Vis diffuse reflection spectra confirmed that two kinds of heterogeneous catalysts had very similar Ti sites. The FT-IR confirmed that Ti tartrate could be bound to the surface hydroxyls of HMS, leading to the appearance of a weak band at 960 cm－1 and a ligand's carbonyl band at 1 736～1 744 cm－1 in their spectra; and only a ligand's carbonyl band was observed in the IR spectra of fresh and recycling Ti tartrate encapsulated NaY samples, indicating that Ti tartrate complex could be steadily encapsulated into the super cages of NaY zeolite. In catalyzing the epoxidation of cinnamyl alcohol with tetrabutyl hydroperoxide(TBHP) as an oxidant, the Ti tartrate grafted HMS showed a higher catalytic activity than the Ti tartrate encapsulated NaY, this is mainly due to the former has a higher Ti loading than the latter. As for as their selectivity for the epoxides,the latter (near 100％) was by far better than the former (about 80％),this is perhaps due to the Na＋ located in the super cages and the particular microporous structure of NaY can efficiently restrain the by-reaction such as opening, addition and polymerization of the epoxides.
Titanium tartrate complex has been successfully grafted onto hexa nal mesoporous silicas (HMS) or encapsulated into microporous NaY zeolite by means of chemically bonding or “ship in bottle” methods. The UV-Vis diffuse reflection spectra confirmed that two kinds of heterogeneous catalysts had very similar Ti sites. The FT-IR confirmed that Ti tartrate could be bound to the surface hydroxyls of HMS, leading to the appearance of a weak band at 960 cm－1 and a ligand's carbonyl band at 1 736～1 744 cm－1 in their spectra; and only a ligand's carbonyl band was observed in the IR spectra of fresh and recycling Ti tartrate encapsulated NaY samples, indicating that Ti tartrate complex could be steadily encapsulated into the super cages of NaY zeolite. In catalyzing the epoxidation of cinnamyl alcohol with tetrabutyl hydroperoxide(TBHP) as an oxidant, the Ti tartrate grafted HMS showed a higher catalytic activity than the Ti tartrate encapsulated NaY, this is mainly due to the former has a higher Ti loading than the latter. As for as their selectivity for the epoxides,the latter (near 100％) was by far better than the former (about 80％),this is perhaps due to the Na＋ located in the super cages and the particular microporous structure of NaY can efficiently restrain the by-reaction such as opening, addition and polymerization of the epoxides.
2004, 20(07): 755-758
doi: 10.3866/PKU.WHXB20040718
Abstract:
The production of hydrogen by anaerobic photocatalytic reforming degradation of aqueous monoethanolamine (ethanolamine, shortened form in the following text)solution has been investigated using a Pt/TiO2 catalyst. The effect of many factors such as ethanolamine concentration, catalyst surface chemical state, and pH of systems on the photocatalytic production of hydrogen have been studied in detail. The catalyst and the products were characterized using HNMR, XRD and XPS techniques; the possible reaction mechanism was discussed. The hydrogen production was achieved simultaneously with the photocatalytic reforming degradation of aqueous ethanolamine solution. It was showed that the aim of both producing hydrogen and photocatalytic reforming degradation of aqueous organic pollutant could be achieved using a Pt/TiO2 catalyst. The Pt particles were identified as existed in Pt0 state on the TiO2. The pH and the ethanolamine concentration affect the hydrogen production rate significantly. At the same time, it was found that the optimum concentration of ethanolamine, pH value and Pt loading is 0.05 mol•L－1, 4～10 and 0.5％～1.0％ respectively. And the amino substituted carbonyl compounds was the main intermediates.
The production of hydrogen by anaerobic photocatalytic reforming degradation of aqueous monoethanolamine (ethanolamine, shortened form in the following text)solution has been investigated using a Pt/TiO2 catalyst. The effect of many factors such as ethanolamine concentration, catalyst surface chemical state, and pH of systems on the photocatalytic production of hydrogen have been studied in detail. The catalyst and the products were characterized using HNMR, XRD and XPS techniques; the possible reaction mechanism was discussed. The hydrogen production was achieved simultaneously with the photocatalytic reforming degradation of aqueous ethanolamine solution. It was showed that the aim of both producing hydrogen and photocatalytic reforming degradation of aqueous organic pollutant could be achieved using a Pt/TiO2 catalyst. The Pt particles were identified as existed in Pt0 state on the TiO2. The pH and the ethanolamine concentration affect the hydrogen production rate significantly. At the same time, it was found that the optimum concentration of ethanolamine, pH value and Pt loading is 0.05 mol•L－1, 4～10 and 0.5％～1.0％ respectively. And the amino substituted carbonyl compounds was the main intermediates.
2004, 20(07): 759-762
doi: 10.3866/PKU.WHXB20040719
Abstract:
In this thesis, the coupling interactions of the salt-water oscillator and liquid membrane oscillator have been investigated in order to increase the potentials and create a reversible chemical oscillator. The results indicate that:(1) the increase of the potentials may be attributed to the resonance of the coupling; (2) a reversible oscillator was formed by the coupling of the salt-water oscillator and liquid membrane oscillator. And a possible mechanism for the coupling and reversible oscillation was presented: a coordination compound was produced in the diffusion process, which dissolves in the oil phase but not in the water phase. Furthermore, when electrified, the coordination compound dissociates and the reversible oscillation takes place. So the application of the salt-water oscillator, especially in the second battery, may be extended.
In this thesis, the coupling interactions of the salt-water oscillator and liquid membrane oscillator have been investigated in order to increase the potentials and create a reversible chemical oscillator. The results indicate that:(1) the increase of the potentials may be attributed to the resonance of the coupling; (2) a reversible oscillator was formed by the coupling of the salt-water oscillator and liquid membrane oscillator. And a possible mechanism for the coupling and reversible oscillation was presented: a coordination compound was produced in the diffusion process, which dissolves in the oil phase but not in the water phase. Furthermore, when electrified, the coordination compound dissociates and the reversible oscillation takes place. So the application of the salt-water oscillator, especially in the second battery, may be extended.
2004, 20(07): 763-766
doi: 10.3866/PKU.WHXB20040720
Abstract:
The viscosity behaviors of cationic gemini surfactants were investigated and the behaviors were found to be closely related to spacer groups and alkyl chains of the gemini surfactants. For gemini surfactants with shorter spacer group, i.e. s = 2, 3 or 4,their solutions exhibit striking viscosity behaviors. However, there is a time effect on viscosity for solutions of some gemini surfactants with s = 4. But for gemini surfactants with spacer group s = 6, the solutions have almost the same viscosity as that of solvent even at high concentration. The viscosity increases with the increasing of alkyl carbon number at the same surfactant concentration. For some surfactants with spacer group s =2 or 3, the viscosities of solutions under a maximum as a function of temperature. The mixtures of gemini surfactants and sodium salicylate (NaSal) also exhibit a great viscosification
The viscosity behaviors of cationic gemini surfactants were investigated and the behaviors were found to be closely related to spacer groups and alkyl chains of the gemini surfactants. For gemini surfactants with shorter spacer group, i.e. s = 2, 3 or 4,their solutions exhibit striking viscosity behaviors. However, there is a time effect on viscosity for solutions of some gemini surfactants with s = 4. But for gemini surfactants with spacer group s = 6, the solutions have almost the same viscosity as that of solvent even at high concentration. The viscosity increases with the increasing of alkyl carbon number at the same surfactant concentration. For some surfactants with spacer group s =2 or 3, the viscosities of solutions under a maximum as a function of temperature. The mixtures of gemini surfactants and sodium salicylate (NaSal) also exhibit a great viscosification
2004, 20(07): 767-771
doi: 10.3866/PKU.WHXB20040721
Abstract:
The ternary solid complex, Tb(Et2dtc)3(phen),has been synthesized with sodium diethyldithiocarbamate(NaEt2dtc), 1,10-phenanthroline(o-phen•H2O) and low hydrated terbium chloride in absolute ethanol. IR spectrum of the complex showed that the Tb3＋ coordinated with six sulfur atoms of three NaEt2dtc and two nitrogen atoms of phen. The enthalpies change of liquid-phase reaction of formation,ΔrHmθ(l),was determined as(－21.819±0.055) kJ•mol－1 at 298.15 K by a microcalorimeter, the enthalpies change of the solid-phase reaction of formation,ΔrHmθ(s), was calculated as(128.476±0.675) kJ•mol－1 on the basis of a thermochemical cycle. The thermodynamic of reaction of formation was studied by changing the temperature of liquid-phase reaction. The constant-volume combustion energy of the complex,ΔcU, was determined as(－17646.95±8.64) kJ•mol－1 by a precise rotating-bomb calorimeter at 298.15 K. Its standard enthalpies of combustion,ΔcHmθ, and standard enthalpies of formation,ΔfHmθ, were calculated as(－17666.16±8.64) kJ•mol－1 and (－1084.04±9.49) kJ•mol－1, respectively.
The ternary solid complex, Tb(Et2dtc)3(phen),has been synthesized with sodium diethyldithiocarbamate(NaEt2dtc), 1,10-phenanthroline(o-phen•H2O) and low hydrated terbium chloride in absolute ethanol. IR spectrum of the complex showed that the Tb3＋ coordinated with six sulfur atoms of three NaEt2dtc and two nitrogen atoms of phen. The enthalpies change of liquid-phase reaction of formation,ΔrHmθ(l),was determined as(－21.819±0.055) kJ•mol－1 at 298.15 K by a microcalorimeter, the enthalpies change of the solid-phase reaction of formation,ΔrHmθ(s), was calculated as(128.476±0.675) kJ•mol－1 on the basis of a thermochemical cycle. The thermodynamic of reaction of formation was studied by changing the temperature of liquid-phase reaction. The constant-volume combustion energy of the complex,ΔcU, was determined as(－17646.95±8.64) kJ•mol－1 by a precise rotating-bomb calorimeter at 298.15 K. Its standard enthalpies of combustion,ΔcHmθ, and standard enthalpies of formation,ΔfHmθ, were calculated as(－17666.16±8.64) kJ•mol－1 and (－1084.04±9.49) kJ•mol－1, respectively.
2004, 20(07): 772-775
doi: 10.3866/PKU.WHXB20040722
Abstract:
In the H2O2-Na2S2O3 reaction system both the pH value and [H2O2]0/[Na2S2O3]0 are important factors for stability of different intermediates. In this paper, the influences of the two factors on the composition and stability of the products were investigated. The results show that sulfur(0) is the main productat pH< 3, while tetrathionate is stable only in the pH range between 3 and 6. The concentration of sulfate will increase when pH and [H2O2]0/[Na2S2O3]0 are getting high. In neutral and week base solutions, the concentration of S(IV) species shows a peak value.
In the H2O2-Na2S2O3 reaction system both the pH value and [H2O2]0/[Na2S2O3]0 are important factors for stability of different intermediates. In this paper, the influences of the two factors on the composition and stability of the products were investigated. The results show that sulfur(0) is the main productat pH< 3, while tetrathionate is stable only in the pH range between 3 and 6. The concentration of sulfate will increase when pH and [H2O2]0/[Na2S2O3]0 are getting high. In neutral and week base solutions, the concentration of S(IV) species shows a peak value.
2004, 20(07): 776-779
doi: 10.3866/PKU.WHXB20040723
Abstract:
The mechanisms responsible for synergism between alkyl benzene sulfonate and methyl oleate in surfactant/brine/model oil and surfactant/alkali/model oil systems were studied. The results show that different mechanisms exist in above two systems. To the former,methyl oleate mainly influences the partition of surfactants in oil phase and aqueous phase by changing EACN value of oil phase. To the latter, the role of methyl oleate in influencing the partition of surfactant in oil phase and aqueous phase competes with its adsorption role at the interface. In this experimental condition, the result of competition between above two roles is different for surfactant with different structure.
The mechanisms responsible for synergism between alkyl benzene sulfonate and methyl oleate in surfactant/brine/model oil and surfactant/alkali/model oil systems were studied. The results show that different mechanisms exist in above two systems. To the former,methyl oleate mainly influences the partition of surfactants in oil phase and aqueous phase by changing EACN value of oil phase. To the latter, the role of methyl oleate in influencing the partition of surfactant in oil phase and aqueous phase competes with its adsorption role at the interface. In this experimental condition, the result of competition between above two roles is different for surfactant with different structure.
2004, 20(07): 780-784
doi: 10.3866/PKU.WHXB20040724
Abstract:
A series of Ni-SiO2 aerogel and xerogel catalysts were prepared by sol-gel supercritical drying (SCD) and general drying methods using tetraethylorthosilicate (TEOS) as a precursor of silica and nickel nitrate as starting material of nickel. Water or alcohol was used as solvent. Based on the experimental results of nitrogen adsorption-desorption, XRD, temperature-programmed reduction (TPR), IR, temperature-programmed desorption of hydrogen (H2-TPD) and activity evaluation, the physical and chemical properties and catalytic performance of the catalysts for hydrogenation of m-dinitrobenzene to m-phenylenediamine were investigated. Both the Ni-SiO2 aerogel catalysts had high specific surface areas, but their catalytic activity and selectivity were low due to their small active surface areas caused by sintering of nickel crystallite. For the Ni-SiO2 xerogel catalyst that used alcohol as solvent, well-dispersed nickel particles were formed, but the strong interaction between nickel and the support made the catalyst difficult to be reduced, thus resulting in lower degree of the utilization of metal. However, the xerogel catalyst that made use of water solution exhibited the highest catalytic activity and selectivity for m-phenylenediamine attributed to its higher surface area of active nickel, over which the conversion of m-dinitrobenzene and the yield of m-phenylenediamine were up to 92.6％ and 88.4％, respectively, under the conditions of 2.6 MPa and 373 K after reaction for 1 h.
A series of Ni-SiO2 aerogel and xerogel catalysts were prepared by sol-gel supercritical drying (SCD) and general drying methods using tetraethylorthosilicate (TEOS) as a precursor of silica and nickel nitrate as starting material of nickel. Water or alcohol was used as solvent. Based on the experimental results of nitrogen adsorption-desorption, XRD, temperature-programmed reduction (TPR), IR, temperature-programmed desorption of hydrogen (H2-TPD) and activity evaluation, the physical and chemical properties and catalytic performance of the catalysts for hydrogenation of m-dinitrobenzene to m-phenylenediamine were investigated. Both the Ni-SiO2 aerogel catalysts had high specific surface areas, but their catalytic activity and selectivity were low due to their small active surface areas caused by sintering of nickel crystallite. For the Ni-SiO2 xerogel catalyst that used alcohol as solvent, well-dispersed nickel particles were formed, but the strong interaction between nickel and the support made the catalyst difficult to be reduced, thus resulting in lower degree of the utilization of metal. However, the xerogel catalyst that made use of water solution exhibited the highest catalytic activity and selectivity for m-phenylenediamine attributed to its higher surface area of active nickel, over which the conversion of m-dinitrobenzene and the yield of m-phenylenediamine were up to 92.6％ and 88.4％, respectively, under the conditions of 2.6 MPa and 373 K after reaction for 1 h.
