Login In
1987 Volume 3 Issue 3
1987, 3(03): 225-226
doi: 10.3866/PKU.WHXB19870301
Abstract:
Based on the principle of flow method, a new method for measuring VLE data without analytical determination of composition is presented. By equal volume exchanging of the y region or the x region inside the VLE determination appara- tus, the boiling point or the dew point is determined while the steady state is reached.
Based on the principle of flow method, a new method for measuring VLE data without analytical determination of composition is presented. By equal volume exchanging of the y region or the x region inside the VLE determination appara- tus, the boiling point or the dew point is determined while the steady state is reached.
1987, 3(03): 227-228
doi: 10.3866/PKU.WHXB19870302
Abstract:
Based on the error equation of ebulliometry~[1]
ε≡x_0-x/x=(k-1)/1+r(r+a) (1)
three type of newly developed ebulliometers, which can be used at r=0 state, are presented. Those ebulliometers were tested by different methods for the measure- ment of infinite activity coefficient γ~∞.
Based on the error equation of ebulliometry~[1]
ε≡x_0-x/x=(k-1)/1+r(r+a) (1)
three type of newly developed ebulliometers, which can be used at r=0 state, are presented. Those ebulliometers were tested by different methods for the measure- ment of infinite activity coefficient γ~∞.
1987, 3(03): 229-236
doi: 10.3866/PKU.WHXB19870303
Abstract:
The NH(A ~3Π)→X ~3∑~-)) fluorescence spectrum, of 331-343 nm, wavelength region was recorded when NH_3 was irradiated by the 193 nm ArF laser beam(Fig.1). The ratio of the intensity I_f of Q(0, 0) to that of Q(1, 1) suggests that 5% of population of NH(A ~3Π) is in the first vibrational state (v′=1). For the ro- tational lines of the P branch, a diagram of In I_f/(2N′+1) vs. Be N′(N′+1) is plotted in Fig.2, in which I_f corresponds to the relative intensities of the ro- tational lines of the P branch and N′ is the rotational quantum number of NH(A ~3Π, v′=0). NH(A ~3Π) is highly rotationally excited in the firt 12 levels with a Boltzmann temperature of T_R=7700 K.
A single-exponential decay of the NH(A ~3Π→X ~3Σ~-) emission was found and a lifetime of (470±40) ns was obtained. The Sterm-Volmer plots are shown in Fig.3. The quenching rate coefficients of NH(A ~3Π) by various gases were measured from the slopes as: k_(H_2)=(4.8±0.5)×10~(-11) cm~3 molec~(-1) s~(-1), k_(NO)=(7.3±1.0)×10~(-11) cm~3 molec~(-1) s~(-1), k_(CH_4)=(6.6±1.5)×10~(-11) cm~3 molec~(-1) s~(-1), and k_(O_2)=(2.9±0.2)×10~(-11) cm~3 molec~(-1) s~(-1). The quenching rate coeffecient of Ar gas is of order of 10~(-13) cm~3 molec~(-1) s~(-1).
The first 193 nm photon is absorbed by NH_3(X ~1A_1′) and makes it to NH_3(Ã). The predissociation of NH_3(Ã ~1A_2″) is very rapid. The nascent NH_2(Ã ~1A_2″) can further absorb a second 193 nm photon to the NH_3(B ~2B_2) state. The bond angle changes tremendously from 141.4° to 50° for a above process. The fragment NH(A ~3Π) species then possesses a high rotational excitation population which agrees the experimental temperature of T_R=7700 K.
The NH(A ~3Π)→X ~3∑~-)) fluorescence spectrum, of 331-343 nm, wavelength region was recorded when NH_3 was irradiated by the 193 nm ArF laser beam(Fig.1). The ratio of the intensity I_f of Q(0, 0) to that of Q(1, 1) suggests that 5% of population of NH(A ~3Π) is in the first vibrational state (v′=1). For the ro- tational lines of the P branch, a diagram of In I_f/(2N′+1) vs. Be N′(N′+1) is plotted in Fig.2, in which I_f corresponds to the relative intensities of the ro- tational lines of the P branch and N′ is the rotational quantum number of NH(A ~3Π, v′=0). NH(A ~3Π) is highly rotationally excited in the firt 12 levels with a Boltzmann temperature of T_R=7700 K.
A single-exponential decay of the NH(A ~3Π→X ~3Σ~-) emission was found and a lifetime of (470±40) ns was obtained. The Sterm-Volmer plots are shown in Fig.3. The quenching rate coefficients of NH(A ~3Π) by various gases were measured from the slopes as: k_(H_2)=(4.8±0.5)×10~(-11) cm~3 molec~(-1) s~(-1), k_(NO)=(7.3±1.0)×10~(-11) cm~3 molec~(-1) s~(-1), k_(CH_4)=(6.6±1.5)×10~(-11) cm~3 molec~(-1) s~(-1), and k_(O_2)=(2.9±0.2)×10~(-11) cm~3 molec~(-1) s~(-1). The quenching rate coeffecient of Ar gas is of order of 10~(-13) cm~3 molec~(-1) s~(-1).
The first 193 nm photon is absorbed by NH_3(X ~1A_1′) and makes it to NH_3(Ã). The predissociation of NH_3(Ã ~1A_2″) is very rapid. The nascent NH_2(Ã ~1A_2″) can further absorb a second 193 nm photon to the NH_3(B ~2B_2) state. The bond angle changes tremendously from 141.4° to 50° for a above process. The fragment NH(A ~3Π) species then possesses a high rotational excitation population which agrees the experimental temperature of T_R=7700 K.
1987, 3(03): 237-241
doi: 10.3866/PKU.WHXB19870304
Abstract:
The surface composition of antimony-iron mixed oxide catalysts has been foundto be dependent upon heat treatment, the surface becoming progressively enriched in antimony at elevated temperature. Surface segregation of antimony has been in-vestigated by X-ray photoelectron spectroscopy (XPS) and values of segregation heat have been obtained. When the ratio of Sb to Fe in the bulk is 0.44, theirratio on surface is approximately 2. It is supposed that surface formation in Sb-Fe mixed oxide catalysts is FeSb_2O_6. The value 0.44 is the critical concentration of Sb segregation to form FeSb_2O_6. Below this critical value and so segregation of the FeSb_2O_6 phase is not observed.
The surface composition of antimony-iron mixed oxide catalysts has been foundto be dependent upon heat treatment, the surface becoming progressively enriched in antimony at elevated temperature. Surface segregation of antimony has been in-vestigated by X-ray photoelectron spectroscopy (XPS) and values of segregation heat have been obtained. When the ratio of Sb to Fe in the bulk is 0.44, theirratio on surface is approximately 2. It is supposed that surface formation in Sb-Fe mixed oxide catalysts is FeSb_2O_6. The value 0.44 is the critical concentration of Sb segregation to form FeSb_2O_6. Below this critical value and so segregation of the FeSb_2O_6 phase is not observed.
1987, 3(03): 242-247
doi: 10.3866/PKU.WHXB19870305
Abstract:
The groups, OH, CH_2, CH_3, C—O—C etc. in fat coal from Feng-Feng in He-Bei province has been examined. The disappearance kinetics of these groups were also determined by IR method. The results showed that the disappearance reactions for these groups followed first-order reaction.The rate constants and corresponding activation energies to each reaction are:
---------------------------------------------------------------------
v/cm~(-1) group 10~2 k/s~(-1) E_a/kJ mol~(-1)
----------------------------
500 ℃ 550 ℃ 600 ℃
---------------------------------------------------------------------
3690 OH 2.92 9.05 9.26 68.1
2920 CH 5.16 9.47 12.8 53.5
1600 Aromatic 1.85 2.03 6.22 71.9
C=C
1035 Asymmetric 2.05 4.21 8.31 81.1
Ar—O—C
1010 Symmetric 1.85 4.17 7.92 85.3
Ar—O—C
-----------------------------------------------------------------------
The groups, OH, CH_2, CH_3, C—O—C etc. in fat coal from Feng-Feng in He-Bei province has been examined. The disappearance kinetics of these groups were also determined by IR method. The results showed that the disappearance reactions for these groups followed first-order reaction.The rate constants and corresponding activation energies to each reaction are:
---------------------------------------------------------------------
v/cm~(-1) group 10~2 k/s~(-1) E_a/kJ mol~(-1)
----------------------------
500 ℃ 550 ℃ 600 ℃
---------------------------------------------------------------------
3690 OH 2.92 9.05 9.26 68.1
2920 CH 5.16 9.47 12.8 53.5
1600 Aromatic 1.85 2.03 6.22 71.9
C=C
1035 Asymmetric 2.05 4.21 8.31 81.1
Ar—O—C
1010 Symmetric 1.85 4.17 7.92 85.3
Ar—O—C
-----------------------------------------------------------------------
1987, 3(03): 248-251
doi: 10.3866/PKU.WHXB19870306
Abstract:
Iodine monofluoride is a potential visible lasing medium due to its ease of emission on IF(B→X) transition in 450-750 nm with favorable Franck-Condon factors. Nevertheless, the production of IF(B~3Π_0~+)) by a chemically-pumped pro- cess involving energy transfer has scarcely been investigated~[1-4].
We have succeeded in producing NF(b~1∑~+)) species directly in the F-F_2-NH_3 system via a supersonic regime. It is of interest to extend our studies to ob- tain IF(B~3Π_0~+) by energy transfer between NF(b~1∑~+) and ground state IF, in the hope of developing a visible chemical laser.
As in reference[5], the experimental arrangement cosists essentially of a remodeled supersonic c_w HF chemical laser, a 0.3 M polychromator and an optical multichannel analyzer. F_2, D_2 and CF_3I are burned in a combustor to produce F atoms and IF molecules. The supersonic stream of F+F_2_IF flowing out of the nozzle bank is then mixed with a subsonic stream of NH_3 in a 30 cm long reaction zone.
The IF(B→X) emission was observed from the OMA recordings in the range of 450 to 750 nm with 33 band heads as shown in Fig.2.
Fig.3 shows the distribution of NH_2~*, NH~*, NF(b) and IF(B) emissions along X.
The production of IF(B) may include the following steps:
F+NH_3→NH_2~*+HF(v≤2) (1)
F+NH_2~*→NH~*+HF(v≤4) (2)
F_2+NH~*→NF(a)+HF (3)
NH(a)+HF(v)→NF(b)+HF (4)
NH~++IF(X)→NH(X)+IF(B) (5)
NF(b)+IF(X)→NF(X)+IF(B) (6)
The initial rise in IF(B), as shown in Fig.3, is consistent with[5]. The continued rise in IF(B) is probably due to excitation by NF(b) which rises more steeply than NH~* decays with distance. Unless IF(B) is excited by another species it cannot decrease while NF(b) increases unless IF(X) is being chemically removed.
Iodine monofluoride is a potential visible lasing medium due to its ease of emission on IF(B→X) transition in 450-750 nm with favorable Franck-Condon factors. Nevertheless, the production of IF(B~3Π_0~+)) by a chemically-pumped pro- cess involving energy transfer has scarcely been investigated~[1-4].
We have succeeded in producing NF(b~1∑~+)) species directly in the F-F_2-NH_3 system via a supersonic regime. It is of interest to extend our studies to ob- tain IF(B~3Π_0~+) by energy transfer between NF(b~1∑~+) and ground state IF, in the hope of developing a visible chemical laser.
As in reference[5], the experimental arrangement cosists essentially of a remodeled supersonic c_w HF chemical laser, a 0.3 M polychromator and an optical multichannel analyzer. F_2, D_2 and CF_3I are burned in a combustor to produce F atoms and IF molecules. The supersonic stream of F+F_2_IF flowing out of the nozzle bank is then mixed with a subsonic stream of NH_3 in a 30 cm long reaction zone.
The IF(B→X) emission was observed from the OMA recordings in the range of 450 to 750 nm with 33 band heads as shown in Fig.2.
Fig.3 shows the distribution of NH_2~*, NH~*, NF(b) and IF(B) emissions along X.
The production of IF(B) may include the following steps:
F+NH_3→NH_2~*+HF(v≤2) (1)
F+NH_2~*→NH~*+HF(v≤4) (2)
F_2+NH~*→NF(a)+HF (3)
NH(a)+HF(v)→NF(b)+HF (4)
NH~++IF(X)→NH(X)+IF(B) (5)
NF(b)+IF(X)→NF(X)+IF(B) (6)
The initial rise in IF(B), as shown in Fig.3, is consistent with[5]. The continued rise in IF(B) is probably due to excitation by NF(b) which rises more steeply than NH~* decays with distance. Unless IF(B) is excited by another species it cannot decrease while NF(b) increases unless IF(X) is being chemically removed.
1987, 3(03): 252-257
doi: 10.3866/PKU.WHXB19870307
Abstract:
In this paper, high temperature calorimeter which is France SETARAM has been modified and introduced, Differential heats of adsorption for gas/solid system over the temperature range from ambient temperature to 800 K could be carried out in this apparatus, In the experimental procedure the amount of adsorption for gas or vapour could be measured by a light-spot microbarometer. The conversion factors for the apparatus have been determined through a electric-heating me- thod instead of standard materials which are usually used in temperature program process. By using this apparatus the heat of adsorption for pyrodine on H-Y zeolite at different temperatures have been measured.
In this paper, high temperature calorimeter which is France SETARAM has been modified and introduced, Differential heats of adsorption for gas/solid system over the temperature range from ambient temperature to 800 K could be carried out in this apparatus, In the experimental procedure the amount of adsorption for gas or vapour could be measured by a light-spot microbarometer. The conversion factors for the apparatus have been determined through a electric-heating me- thod instead of standard materials which are usually used in temperature program process. By using this apparatus the heat of adsorption for pyrodine on H-Y zeolite at different temperatures have been measured.
1987, 3(03): 258-264
doi: 10.3866/PKU.WHXB19870308
Abstract:
In 1970, W. L. Masterton and T. P. Lee applied the scaled particle theory to nonpolar solute system, and drived an applicable formula of salting-out con- stant. This work has tried to apply the scaled particle theory to polar solute system, and drived a formula of salting-out constant for polar nonelectrolyte.
The k_s values of CH_3COOH, n-CH_3CH_2COOH, n-CH_3(CH_2)_2COOH, n-CH_3(CH_2)_4-COOH, and n-CH_3(CH_2)_5COOH in four small ion aqueous salt solutions were calcu- lated. The modified formula gave the results in better agreement with the experiment than the original formula.
In 1970, W. L. Masterton and T. P. Lee applied the scaled particle theory to nonpolar solute system, and drived an applicable formula of salting-out con- stant. This work has tried to apply the scaled particle theory to polar solute system, and drived a formula of salting-out constant for polar nonelectrolyte.
The k_s values of CH_3COOH, n-CH_3CH_2COOH, n-CH_3(CH_2)_2COOH, n-CH_3(CH_2)_4-COOH, and n-CH_3(CH_2)_5COOH in four small ion aqueous salt solutions were calcu- lated. The modified formula gave the results in better agreement with the experiment than the original formula.
1987, 3(03): 265-271
doi: 10.3866/PKU.WHXB19870309
Abstract:
The maximum coordination number of complex of molybdenum (Ⅵ) with L- Asparagine has been determined by polarimetry. The complexes with 1:1 form in the systems of Molybdenum (Ⅵ)-L-Asparagine and Molybdenum(Ⅵ)-L- Aspartic acid were demonstrated by pH potentiometric studies. The thermodynmic parameters ΔHø、ΔGø、ΔS~ø of these coordination reactions have been reported and discussed in this paper.
1987, 3(03): 272-277
doi: 10.3866/PKU.WHXB19870310
Abstract:
In this paper the pK values of both commonly commercial UV-absorbers-2-hydroxy-4-methoxy-benzophenone (UV-9) and 2,4-dihydroxy-benzophenone (UV-0) at ground and excited states have been determined.
The unusual relation curve between absorption intensity and pH value for UV-0 was explained reasonablely.
The energy-loss mechanism of UV-absorbers described above has been discussed by means of the pK values which were obtained in this work.
In this paper the pK values of both commonly commercial UV-absorbers-2-hydroxy-4-methoxy-benzophenone (UV-9) and 2,4-dihydroxy-benzophenone (UV-0) at ground and excited states have been determined.
The unusual relation curve between absorption intensity and pH value for UV-0 was explained reasonablely.
The energy-loss mechanism of UV-absorbers described above has been discussed by means of the pK values which were obtained in this work.
1987, 3(03): 278-285
doi: 10.3866/PKU.WHXB19870311
Abstract:
The kinetics of aerobic oxidation of ascorbic acid(H_2A) catalyzed by Cu(Ⅱ) and its polyamine chelates, of which chelate number vary from 2 to 5, was stu- died,The chelating agents used were ethylenediamine(en), diethylenetriamine(dien), triethylenetetramine(trien) and tetraethylenepentamine(tetren). The pH value was maintained constant by an automatic titrator without using buffer.
The results showed that Cu(Ⅱ) could form a complex with ascorbate, however they did not react directly. Cu(Ⅱ) and Cu(Ⅱ)(en) did not react directly. Cu(Ⅱ) and Cu(Ⅱ)(en) did not change their valence during the catalytic processes. The kinetic determination showed that Cu(Ⅱ)(dien), Cu(Ⅱ)(trien), Cu(Ⅱ)(tetren) and Cu(Ⅱ)(en)_2, of which chelate number are larger than 2 were catalytically inactive. For Cu(Ⅱ)(en) catalyzed reaction, the rate was first order with respect to Cu(Ⅱ)(en) and conformed to the Michaelis-Menten equation with respect to ascorbate. For free Cu(Ⅱ) catalyzed reaction, the rate was first order with respect to both Cu(Ⅱ) and ascorbate.
A mechanism via a ternary complex, Cu(Ⅱ)HAO_2, was proposed. It was suggested that Cu(Ⅱ) and Cu(Ⅱ)(en) under the same initial step in the catalytic processes.
The kinetics of aerobic oxidation of ascorbic acid(H_2A) catalyzed by Cu(Ⅱ) and its polyamine chelates, of which chelate number vary from 2 to 5, was stu- died,The chelating agents used were ethylenediamine(en), diethylenetriamine(dien), triethylenetetramine(trien) and tetraethylenepentamine(tetren). The pH value was maintained constant by an automatic titrator without using buffer.
The results showed that Cu(Ⅱ) could form a complex with ascorbate, however they did not react directly. Cu(Ⅱ) and Cu(Ⅱ)(en) did not react directly. Cu(Ⅱ) and Cu(Ⅱ)(en) did not change their valence during the catalytic processes. The kinetic determination showed that Cu(Ⅱ)(dien), Cu(Ⅱ)(trien), Cu(Ⅱ)(tetren) and Cu(Ⅱ)(en)_2, of which chelate number are larger than 2 were catalytically inactive. For Cu(Ⅱ)(en) catalyzed reaction, the rate was first order with respect to Cu(Ⅱ)(en) and conformed to the Michaelis-Menten equation with respect to ascorbate. For free Cu(Ⅱ) catalyzed reaction, the rate was first order with respect to both Cu(Ⅱ) and ascorbate.
A mechanism via a ternary complex, Cu(Ⅱ)HAO_2, was proposed. It was suggested that Cu(Ⅱ) and Cu(Ⅱ)(en) under the same initial step in the catalytic processes.
1987, 3(03): 286-291
doi: 10.3866/PKU.WHXB19870312
Abstract:
The electroreduction of low concentration iodate in H_2SO_4 was studied on the platinum electrode. The intermediate I_2 and the final product I~-, which are form- ed during the electroreduction of iodate, are detected by using the rotating ring-disk electrode. The kinetic parameters were measured. The mechanism of eletroreduction of iodate are proposed here.
The electroreduction of low concentration iodate in H_2SO_4 was studied on the platinum electrode. The intermediate I_2 and the final product I~-, which are form- ed during the electroreduction of iodate, are detected by using the rotating ring-disk electrode. The kinetic parameters were measured. The mechanism of eletroreduction of iodate are proposed here.
1987, 3(03): 292-297
doi: 10.3866/PKU.WHXB19870313
Abstract:
The monodispersive octchedral AgBr (0.8 μm) emulsion was prepared by the double-jet method. After doping I~- (1×10~(-3)-4×10~(-2)mol I~-/mol AgBr) on the sur- face of AgBr, the dielectric absorption peak of samples shifted gradually to hi- gher frequencies. When doped I~- content is lower than 1×10~(-2)mol/mol AgBr, the absorption peaks are dispersive. When doped I~- content is≥1×10~-mol/mol AgBr, the absorption peaks are sharper and do not shift markedly to higher frequencies any longer. In the sample with 1×10~(-2) mol I~-/mol AgBr, the strongest X-ray diffraction peak (002) of AgI has been observed. In the sample with 4×10~(-2) moo I~-/mol AgBr, three strongest peaks (100), (002), (110) of the β-AgI have been obsrved. The results of X-ray analysis show that these AgI are chiefly epitaxial on the surface of AgBr by substitution. On the average, 1 mol% I~- can substitute about five layers Br~- ions on (111) surface of AgBr (0.8 μm).
From the above experimental results, it may be considered that the thickness of the surface layer which influence on the interfacial polarization is about 0.2 nm. In this thickness range, if I~- distribution is heterogeneous, the dielectric absorption peak of sample will be getting dispersive.
The monodispersive octchedral AgBr (0.8 μm) emulsion was prepared by the double-jet method. After doping I~- (1×10~(-3)-4×10~(-2)mol I~-/mol AgBr) on the sur- face of AgBr, the dielectric absorption peak of samples shifted gradually to hi- gher frequencies. When doped I~- content is lower than 1×10~(-2)mol/mol AgBr, the absorption peaks are dispersive. When doped I~- content is≥1×10~-mol/mol AgBr, the absorption peaks are sharper and do not shift markedly to higher frequencies any longer. In the sample with 1×10~(-2) mol I~-/mol AgBr, the strongest X-ray diffraction peak (002) of AgI has been observed. In the sample with 4×10~(-2) moo I~-/mol AgBr, three strongest peaks (100), (002), (110) of the β-AgI have been obsrved. The results of X-ray analysis show that these AgI are chiefly epitaxial on the surface of AgBr by substitution. On the average, 1 mol% I~- can substitute about five layers Br~- ions on (111) surface of AgBr (0.8 μm).
From the above experimental results, it may be considered that the thickness of the surface layer which influence on the interfacial polarization is about 0.2 nm. In this thickness range, if I~- distribution is heterogeneous, the dielectric absorption peak of sample will be getting dispersive.
1987, 3(03): 298-305
doi: 10.3866/PKU.WHXB19870314
Abstract:
During the investigation of the relative orientation between donor and acceptor in weak CT-complexes, it has been noticed that the electrostatic action between molecules should be considered much more. Based on the analysis of thin crystal structures, a “head-to-head” geometrically matching model has been proposed. From the analysis of the energy of action between donor and acceptor using this model and the measurement of the equilibrium constants, it has been found that when homolo us donors act with sameacceptor, because of the geometrical match effect, the stability of the ground state of the complex does not change monotoneously with the asending serial number of donor wheras the stabilities at the ends of the given donor series are smaller and the largest stability presents in middle.
In IR spectra, a similar trends of relative intensity of some adsorption peaks been observed.
During the investigation of the relative orientation between donor and acceptor in weak CT-complexes, it has been noticed that the electrostatic action between molecules should be considered much more. Based on the analysis of thin crystal structures, a “head-to-head” geometrically matching model has been proposed. From the analysis of the energy of action between donor and acceptor using this model and the measurement of the equilibrium constants, it has been found that when homolo us donors act with sameacceptor, because of the geometrical match effect, the stability of the ground state of the complex does not change monotoneously with the asending serial number of donor wheras the stabilities at the ends of the given donor series are smaller and the largest stability presents in middle.
In IR spectra, a similar trends of relative intensity of some adsorption peaks been observed.
1987, 3(03): 306-312
doi: 10.3866/PKU.WHXB19870315
Abstract:
CNDO calculations for decomposition of formaldehyde on Ni(110) surface are carried out. The adsorption models of formaldehyde on Ni(110) surface have been proposed(Fig.3). The total energies of the various models were minimized by cha- nging the Ni-O distance(Fig.6), the equilibrium distances and the adsorotion ener- gies at the equilibrium distances have been obtained(table 2). The relative sta- bilities of the various models are as follows:
fourfold hollow site bridge site lying adsorption top site
The point group symmery that is pressrved during the decompoiton has been analysed. According to the concept of conservation of orbital symmetry, the decomposition of formaldehyde is thermally forbidden (Fig.4). the d orbital of Ni makes the thermal reaction symmetry allowed. In this way, we illustrated the catalystic effect of nickel.
From the data of binding energies, atomic net charge and Mulliken bond order (table 3), it can be concluded that lying adsorption may be as the intermediate tate which is more favourable for the decompoition of formaldehyde than other adsorption models.
CNDO calculations for decomposition of formaldehyde on Ni(110) surface are carried out. The adsorption models of formaldehyde on Ni(110) surface have been proposed(Fig.3). The total energies of the various models were minimized by cha- nging the Ni-O distance(Fig.6), the equilibrium distances and the adsorotion ener- gies at the equilibrium distances have been obtained(table 2). The relative sta- bilities of the various models are as follows:
fourfold hollow site bridge site lying adsorption top site
The point group symmery that is pressrved during the decompoiton has been analysed. According to the concept of conservation of orbital symmetry, the decomposition of formaldehyde is thermally forbidden (Fig.4). the d orbital of Ni makes the thermal reaction symmetry allowed. In this way, we illustrated the catalystic effect of nickel.
From the data of binding energies, atomic net charge and Mulliken bond order (table 3), it can be concluded that lying adsorption may be as the intermediate tate which is more favourable for the decompoition of formaldehyde than other adsorption models.
1987, 3(03): 313-320
doi: 10.3866/PKU.WHXB19870316
Abstract:
A consulting table method (CTM) of determining E_d according to T_m and h_m is presented. A relationship, which is the basis of this method, between h_m, T_m and E_d in TPD spectrum of first order desorption kinetics is deduced as follows:
h_m/S_m=(k_0/b)exp(- E_d/RT_m)
where h_m, S_m, k_0, b, E_d, R and T_m are peak height, peak area of T≥T_m, pre- exponential factor, heating rate, activation energy of desorption, standard gas cons- tant and peak temperature, respectively. It has been proved that the number of independent variable in the above five variables is 2. The h_m value has a dimension of K~(-1) and may be evaluated by the following equation:
h_m=W_(ABCD)/W_0(T_D-T_A)
where W_(ABCD) is the weight of the paper corresponding to the rectangle ABCD (see Fig.1), W_o is that under the spectrum T_LPT_H, T_D and T_A are the temperatures at D and A, respectively.
The numerical values which show relationships between h_m, T_m and E_d are tabulated in table 1. In this table, the peak temperatures range from 200 K to 1100 K with interval of 10 K and the activation energy of desorpton range from 20 kJ mol~(-1) to 220 kJ mol~(-1) with interval of 20 kJ mol~(-1). The calculation tolerance of the T_m values in the table are generally within ±0.1 K which only causes a slight error in the h_m value. The relative error of interpolation between two points possessing ΔE_d=20 kJ mol~(-1) or ΔT_m=10 K is within 1%. From table 1 and by using interpolation, it is very easy to evaluate the E_d values from a pair of h_m and T_m values which represents the total information of a spectrum.
Considering that the CTM utilizes the whole information of a TPD spectrum and determines E_d without assuming k_0 value, it has advantages that E_d and k_0 may be determined by only one run of TPD experiment, the data treatment may be simple accomplished without any more computer calculation, and the reliability of results is as high as that obtained by the spectrogram superposition method (SSM)~[2].
A consulting table method (CTM) of determining E_d according to T_m and h_m is presented. A relationship, which is the basis of this method, between h_m, T_m and E_d in TPD spectrum of first order desorption kinetics is deduced as follows:
h_m/S_m=(k_0/b)exp(- E_d/RT_m)
where h_m, S_m, k_0, b, E_d, R and T_m are peak height, peak area of T≥T_m, pre- exponential factor, heating rate, activation energy of desorption, standard gas cons- tant and peak temperature, respectively. It has been proved that the number of independent variable in the above five variables is 2. The h_m value has a dimension of K~(-1) and may be evaluated by the following equation:
h_m=W_(ABCD)/W_0(T_D-T_A)
where W_(ABCD) is the weight of the paper corresponding to the rectangle ABCD (see Fig.1), W_o is that under the spectrum T_LPT_H, T_D and T_A are the temperatures at D and A, respectively.
The numerical values which show relationships between h_m, T_m and E_d are tabulated in table 1. In this table, the peak temperatures range from 200 K to 1100 K with interval of 10 K and the activation energy of desorpton range from 20 kJ mol~(-1) to 220 kJ mol~(-1) with interval of 20 kJ mol~(-1). The calculation tolerance of the T_m values in the table are generally within ±0.1 K which only causes a slight error in the h_m value. The relative error of interpolation between two points possessing ΔE_d=20 kJ mol~(-1) or ΔT_m=10 K is within 1%. From table 1 and by using interpolation, it is very easy to evaluate the E_d values from a pair of h_m and T_m values which represents the total information of a spectrum.
Considering that the CTM utilizes the whole information of a TPD spectrum and determines E_d without assuming k_0 value, it has advantages that E_d and k_0 may be determined by only one run of TPD experiment, the data treatment may be simple accomplished without any more computer calculation, and the reliability of results is as high as that obtained by the spectrogram superposition method (SSM)~[2].
1987, 3(03): 321-325
doi: 10.3866/PKU.WHXB19870317
Abstract:
The standardless simultaneous equation method with regression analysis of multi specimens in quantitative phase determination of XRD was applied for sur- face dispersion studies on V_2O_5-TiO_2 system. The dispersive characteristics of vana- dium oxide in V_2O_5-TiO_2 mixtures and in V_2O_5/TiO_2 catalysts prepared from oxyvanadium oxalate after roasting were compared in this paper.
The standardless simultaneous equation method with regression analysis of multi specimens in quantitative phase determination of XRD was applied for sur- face dispersion studies on V_2O_5-TiO_2 system. The dispersive characteristics of vana- dium oxide in V_2O_5-TiO_2 mixtures and in V_2O_5/TiO_2 catalysts prepared from oxyvanadium oxalate after roasting were compared in this paper.
1987, 3(03): 326-329
doi: 10.3866/PKU.WHXB19870318
Abstract:
The activity coefficients of benzene and n-hexane in solutions of LiCl, NaBr and NH_4Br in methanol were measured at 298.15±0.06 K. Thecomposition of binary mixture of benzene-methanol and n-hexane-methanol was constant at each experi- mental run. Benzene or n-hexane content in equilibrium gas phase was expressed by gas chromatography and the value of activity coefficient of the component was determined by the ratio of heights of chromatographic peaks. Experimental results show that the salting out effect of benzene in methanol is smaller than that of n-hexane and the salting in factor of n-hexane by lithium ion is smaller than that of benzene, thus the mechanism of salt modified solvent was discussed preliminarily.
The activity coefficients of benzene and n-hexane in solutions of LiCl, NaBr and NH_4Br in methanol were measured at 298.15±0.06 K. Thecomposition of binary mixture of benzene-methanol and n-hexane-methanol was constant at each experi- mental run. Benzene or n-hexane content in equilibrium gas phase was expressed by gas chromatography and the value of activity coefficient of the component was determined by the ratio of heights of chromatographic peaks. Experimental results show that the salting out effect of benzene in methanol is smaller than that of n-hexane and the salting in factor of n-hexane by lithium ion is smaller than that of benzene, thus the mechanism of salt modified solvent was discussed preliminarily.
1987, 3(03): 330-333
doi: 10.3866/PKU.WHXB19870319
Abstract:
CdS deposited polycarbonate membranes were made by a very simple way: separation of a Lucite cell into two compartments by two pieces of Teflon sheets which were tightly inserted into the slot of the cell. The membrane was placed between holes of the Teflon sheets. The cadmium nitrate aqueous solution were poured into one compartment, and sodium sulfide aqueous solution to the other chamber, were introduced simultaneously. The CdS precipitates formed in situ blocked the tiny holes of the membrane. On illumination, about 150 mV photovoltage (V_(op)) and 0.5 μAcm~(-2) photocurrent (I_(sc)) could be produced, one side of the membrane acted as photoanode and the other side photocathode. By means of coprecipitating CdS and FeS (the ratio of FeS to CdS in the mixture wasabout 1 : 1000) onto the membrane, the maximum V_(op) and I_(sc) of the membrane could reach 500 mV and 3.0 μAcm~(-2), respectively. CdS_xSe_(1-x) mixture deposited membrane has also been tested and found to have both the advantages ofhigh photovoltage (over 400 mV) and od stability after modification. The essential aspect of the system, modelled after the photosynthetic thylakoid membrane, contains an asymmetrical, ultrathin semiconductor polycrystallites membrane separating two aqueous solutions.
-----------------------------
* To whom all correspondence should should be addressed.
CdS deposited polycarbonate membranes were made by a very simple way: separation of a Lucite cell into two compartments by two pieces of Teflon sheets which were tightly inserted into the slot of the cell. The membrane was placed between holes of the Teflon sheets. The cadmium nitrate aqueous solution were poured into one compartment, and sodium sulfide aqueous solution to the other chamber, were introduced simultaneously. The CdS precipitates formed in situ blocked the tiny holes of the membrane. On illumination, about 150 mV photovoltage (V_(op)) and 0.5 μAcm~(-2) photocurrent (I_(sc)) could be produced, one side of the membrane acted as photoanode and the other side photocathode. By means of coprecipitating CdS and FeS (the ratio of FeS to CdS in the mixture wasabout 1 : 1000) onto the membrane, the maximum V_(op) and I_(sc) of the membrane could reach 500 mV and 3.0 μAcm~(-2), respectively. CdS_xSe_(1-x) mixture deposited membrane has also been tested and found to have both the advantages ofhigh photovoltage (over 400 mV) and od stability after modification. The essential aspect of the system, modelled after the photosynthetic thylakoid membrane, contains an asymmetrical, ultrathin semiconductor polycrystallites membrane separating two aqueous solutions.
-----------------------------
* To whom all correspondence should should be addressed.
1987, 3(03): 334-336
doi: 10.3866/PKU.WHXB19870320
Abstract:
Formation mechanism of TmI_2 in Tm-HgI_2 system was studied by DTA and X-ray powder diffraction technique. Experimental and calculated results showed that formation of TmI_2 (in Tm-HgI_2 system) Could be devided in three steps; (1)At 260-280 ℃, TmI_3 appears. (2) At 280-330 ℃, some TmI_2 forms, (3) The further reaction of TmI_3 with Tm forms TmI_2 at 500-600 ℃.
The conditions for the preparation of TmI_2 were discussed as well.
Formation mechanism of TmI_2 in Tm-HgI_2 system was studied by DTA and X-ray powder diffraction technique. Experimental and calculated results showed that formation of TmI_2 (in Tm-HgI_2 system) Could be devided in three steps; (1)At 260-280 ℃, TmI_3 appears. (2) At 280-330 ℃, some TmI_2 forms, (3) The further reaction of TmI_3 with Tm forms TmI_2 at 500-600 ℃.
The conditions for the preparation of TmI_2 were discussed as well.
