Responsive Joomla Templates by BlueHost Coupon

Reaktionssystem Nickelkarbonyl-Nickel-Kohlenmonoxid

Category: Physikalische Chemie Published: Saturday, 10 May 2014 Written by Daniel

Ni + 4CO = Ni(CO)und Ni(CO)4 = Ni + 4CO

These reactions are a nearly ideal subject to study problems of physical chemistry. Here we should like to mention but few topics.

 

The first concerns the general philosophy for kinetics and mechanism of reversible chemical reactions. It is known that consequences of steps in a reversible process coincide for both directions of the process. It should be right also for our particular case near the equilibrium state. The phenomenon becomes, however, the more complicated the farther from the equilibrium the direct and the opposite reactions proceed : reaction steps arise, that do not coincide for synthesis of nickel tetracarbonyl and for its decomposition. This would be worth to be investigated by modern methods and technics.

 

A pair considerations more. The two following aspects are to be distinguished for the direct reaction. On the one hand, a consequence of stoichiometric steps exists. To be more precise, there are two (or more?) routes of the reaction, the first having the stoichiometric number equal 4. In the presence of ca. >0.1% mol. of Ni(CO)4 in the gas phase the second route becomes to be important, which has the stoichiometric number of 2.

 

One could speculate as to these routes e.g. as follows:

 

 

I stoichiometric number

 

(1) CO  (CO)ads 4

 

(2) (CO)ads + Ni = NiCO 4

 

(3) 2NiCO = Ni(CO)+ Ni 1

 

(4) Ni(CO)2 + NiCO = Ni(CO)+ Ni 1

 

(5) Ni(CO)+ NiCO = Ni(CO)4 + Ni 1

 

II

 

(6) Ni(CO)4 + Ni = Ni2(CO)4 1

 

(7) Ni2(CO)4 + CO = Ni2(CO)5 1

 

(8) Ni2(CO)5 +CO = 2Ni(CO)1

 

(9) Ni(CO)3 + CO = Ni(CO)2

 

 

 

The most striking feature of the reaction kinetics is a sharp maximum of the rate on plots "rate vs. Ni(CO)4 content in the gas phase". The maximum is probably due to abrupt drop from the one stationary state of reaction to the other.

 

On the other hand, the reaction includes the phenomenon of ?surface reconstruction? what makes an implication to be studied.

 

 

 

Turning to the inverse reaction, that is to the decomposition of nickel carbonyl we meet a classic example of ?chemical crystallisation?.

 

It was shown that the reaction (when in free space) proceeds via intermediate clusters Nig(CO)n

 

Identification of the most stable of them would be an interesting contribution to the "Cluster Science".

 

 

Reaktionssystem Nickelkarbonyl-Nickel-Kohlenmonoxid

Ni + 4CO = Ni(CO)und Ni(CO)4 = Ni + 4CO

als ein Modellobjekt für physikalisch-chemischen Forschungen

 

 

 

Methodische Vorteile des Objekts:

1. Ein weiter Bereich von Bedingungen, unter denen die Reaktionen verlaufen

können: 0-250oC, 0,001-300 bar;

 

2. Praktisches Nichtvorhandensein von Nebenreaktionen;

3. Keine Komplikationen aufgrund von Bildung anderer Phasen;

4. Gute Möglichkeiten, Geschwindigkeiten zu messen ab 10-13 Mol/cm2.sec.

 

Interessante Richtungen und Probleme sind wie folgt

 

.I. Thermodynamik

 

1. Chemisches Gleichgewicht und seine Abhängigkeit von dem Grad der Dispersion der Festphase, aber auch von dem Zustand der Oberfläche.

Insbesondere Messungen der Bedingungen, bei welchen es möglich ist, die Reaktion umzukehren, gestatten die Zunahme der Energie der aktiven Orte über den stabilen Zustand der festen Phase hinaus zu bestimmen [S.: Kipnis, Mikhailova: Thermodynamik der Synthese des Nickelkarbonyls, J. Appl. Chemistry USSR, 1972, 45, Nr.7, p. 1450-1456]

 

2. Chemische und Phasegleichgewichte im Bereich der Kondensationsfähigkeit von

Nickelkarbonyl.

Insbesondere Minimum der Löslichkeit des Nickelkarbonyls im komprimierten CO ist im Abhängigkeit von Druck beobachtet [S.: ebd. und J. Phys. Chem. USSR, 1966, 40, Nr. 6, p. 1383-1384]. Auch Rückkondensationseffekte sind wahrscheinlich.

 

3. Thermodynamische Eigenschaften er kleinsten metallischen Teilchen und Clusters der Formel Nig(CO)n.

Insbesondere ist eine Konkurrenz zwischen Ni-Ni- und Ni-CO-Bindungen zu beobachten. Z.B gilt folgende Gleichung für den Sonderfall Nin(CO)n :

QNi-CO (KJ) = 182 - 88Un/nL

wo Q Ni-CO die durchschnittliche Energie der Ni-CO-Bindungen, L ? die Atomsublimationswärme des festen Nickels und Un die Bildungsenergie des Clusters Nin aus freien Atomen bezeichnen.

II. Kinetik

 

[S.: Kipnis, Kremnev, Mikhailova, Zur Kinetik der Nickelkarbonylsynthese, Proc. Inst. Gipronikel, Leningrad, 1966, Nr. 30, S. 50-56; Kipnis, Mikhailova, Ravdel, Kinetik der Nickelkarbonylsynthese unter Druck, Kinetics and Catalysis, 1967, 8, Nr. 4, S. 803-807;

Kipnis, Mikhailova, Erscheinungen der Autokatalyse in der Reaktion der Nickelkarbonylsynthese, ebd. 1970, 11, Nr. 3, S. 799-800; Kipnis, Kul'kova, Mikhailova, Das Mechanismus der Reaktion der Nickelkarbonylsynthese bei niedrigen Konzentrationen des Produkts in der Gasphase, ebd., 1976, 17, Nr. 2, S. 472-476; Kipnis, Mikhailova, Pomerantseva, Rümschin, Kinetik und Mechanismus der thermischen Zersetzung des Nickelkarbonyls in freiem Raum, J. Appl. Chem. USSR, 1980, 53, Nr. 6, p. 1439-1440]

1. Übergänge zwischen Einwegs- und Zweiwegsstufenmechanismen für die Reaktion der Nickelkarbonylsynthese.

2. Nichtstationäre Erscheinungen sowohl von Relaxations- als auch von spontaner Natur, Induktionsperiode, Schwankungen der Reaktionsgeschwindigkeit und sprungweise Übergänge von einem stationären Zustand zu anderen einschließend.

3. Beziehungen zwischen Stufenmechanismen direkter und umgekehrter Reaktionen in Verbindung mit der Prinzip der mikroskopischen Reversibilität.

4. Stöchiometrische und nichstöchiometrische Stufen bei Reaktionsmechanismen und die Reaktionskinetik.

 

III. Reaktionsfähigkeit fester Oberflächen

 

1. Reaktioneller Umbau der Oberfläche (in der Kombination mit I.1).

2. Veränderungen der Reaktionsfähigkeit durch Dopieren der Oberfläche

3. Veränderungen der Reaktionsfähigkeit durch Legierung des Nickels mit Metallen und Nichtmetallen

Insbesondere Effekte beobachtet sind, die durch Auffüllung der d-Zone des Nickels erzeugt sind; außerdem der innere magnetochemische Effekt, hier: Sprungweise Veränderungen der Reaktionsfähigkeit beim Übergang durch den Curie-Punkt.

4. Einflüsse auf die Reaktionsfähigkeit des Nickels bei der Nickelcarbonylsynthese mit

physikalischen Wirkkräften (mechano- und tribochemische Wirkungen, elektrische und magnetische Felder, Bestrahlungen).

 

IV. Chemische Phasenbildung

 

1. Mechanismen der Keimbildung bei Zerlegung des Nickelkarbonyls; Massenspektrometrie.

2. Entstehung und Koagulation der Kondensationsaerosole, Effekte der gerichteten Koagulation einschließend.

3. Heterogene Keim- und Schichtbildung.

4. Effekte der chemischen Abhängigkeit von der Dimension.

 

V. Physikalische Chemie der Cluster

 

1. Cluster als Übergangszustände und/oder -stoffe in chemischen Reaktionen, insbesondere bei chemischer Phasenbildung.

2. Bildung der Oberflächencluster als ein Modell des Reaktionsumbaus der Oberfläche von Festkörpern.

 

Kurz und gut: Es gibt hier alles Mögliches. Die interessanteste Aufgabe wäre, eine ausführliche Beschreibung des Verlaufes beider Reaktionen zu schaffen, wo einerseits die Stufensequenzen der Reaktionen festgestellt würden; anderseits aber die Veränderungen der Oberfläche, d.h. die reaktionelle Rekonstruktion der Oberfläche bzw. die Phasenbildung beachtet und beschrieben würden. (S. auch den Text in Englisch am Anfang ).

Eine Tabelle der meistens unveröffentlichten Ergebnisse, die diesen kinetischen Alptraum widerspiegeln, ist hier beigelegt.

 

[a] Kinetics of nickel carbonyl synthesis under pressure (A. Ya. Kipnis, N. F. Mikhailova, A.A. Ravdel) Kinetics and Catalysis (Moscow), 1967, v. 8, No. 4, p. 803-807;

[b] Autocatalytic effects in nickel carbonyl synthesis (A. Ya. Kipnis, N. F. Mikhailova) -

Ibidem, 1970, v. 11, No. 3, p. 799-800;

[c] Mechanism of the reaction of nickel carbonyl synthesis at low concentrations of the product in the gas phase

(A. Ya. Kipnis, N. V. Kul'kova, N. F. Mikhailova) - Ibidem, 1976, v. 17, No. 2, p. 472-476;

[d] Thermodynamics of nickel carbonyl sythesis (A. Ya. Kipnis, N. F. Mikhailova) ?

J. Appl. Chem. USSR, 1972, v. 45, No. 7, p. 1450-1456.

[e] Applied kinetics of heterogeneous decomposition of nickel carbonyl (I. N. Kalitovich, A. Ya. Kipnis, N. F.

Mikhailova, D. N. Taganov) Ibidem, 1974, v.47, No. 1, p. 43-48.

 


 

No.     t, oC    Pco, atm            Pcarbonyl, atm                 rate, 10-6 mole/cm2.min

1          60        10.3                 0.077                           0.0552

2          80        10.3                 0.077                           0.0884

3          80        10.3                 0.055                           0.173

4          80        14.95               0.10                            0.773

5          125      10.3                 0.077                          0.678

6          100      10.3                 0.055                          0.410

7          100      10.3                 0.050                          0.332

8          100      10.2                 0.15                            0.521

9          100      10.1                 0.19                            0.363

10        100      10.1                 0.21                            0.300

11        100      10.1                 0.23                            0.360

12        100      10.0                 0.30                            0.189

13        100      9.9                   0.47                            0.156

14        100      15.0                 0.070                          0.710

15        100      14.9                 0.110                          0.60

16        100      14.9                 0.110                          0.617

17        100      14.9                 0.16                            0.789

18        100      14.9                 0.16                            1.01

19        100      14.9                 0.16                            1.04

20        100      14.8                 0.16                            1.01

21        100      14.8                 0.24                            0.284

22        100      14.8                 0.30                            0.268

23        100      19.7                 0.027                          0.852

24        100      19.7                 0.027                          0.742

25        100      29.1                 0.0155                        2.38

26*      100      48                    0.0102                        3.69

27*      100      48                    0.010                          3.98

28        100      94                    0.20                            5.84

29        100      94                    0.20                            6.08

30        100      235                  0.50                            12.8

31        100      235                  0.50                            12.2

..........................................................................................

32*      100      187                  3.34                            29.5

33*      100      185                  4.64                            4.26

34*      100      185                  4.82                            0.78

..........................................................................................

35*      100      187                  2.80                             19.7

36*      100      186                  3.88                            5.25

37*      100      186                  4.12                            2.60

..........................................................................................

38*      100      184                  3.56                            16.7

39*      100      182                  4.05                            2.91

40*      100      185                  5.35                            3.90

..........................................................................................

41        150      10.3                 0.055                          0.790

42        150      10.3                 0.055                          0.836

43        150      10.3                 0.051                          0.662

44        150      10.2                 0.13                            1.766

45        150      10.2                 0.16                            0.994

46        150      10.2                 0.18                            1.215

47        150      10.1                 0.19                            0.915

48        150      10.0                 0.32                            0.536

49        150      10.0                 0.33                            0.568

50        150      9.9                   0.44                            0.489

51        150      12.1                 0.091                          1.545

52        150      15.0                 0.075                          2.40

53        150      14.9                 0.11                            2.25

54        150      14.9                 0.12                            1.15

55        150      14.8                 0.27                            0.915

56        150      14.1                 0.96                            0.63

57        150      19.7                 0.10                            2.58

58        150      29.0                 0.16                            4.83

59        150      47.9                 0.10                            9.14

...........................................................................................

60*      150      44.5                 0.47                            45.0

61*      150      44.3                 0.71                            30.5

62*      150      44.0                 0.98                            5.26

63*      150      44.0                 1.20                            29.0     [sic!]

.............................................................................................

64*      150      48.0                 0.24                            3.64    

65*      150      47.3                 0.71                            10.44

66*      150      47.2                 0.79                            11.78

67*      150      47.1                 0.85                            7.17

68*      150      45.7                 2.27                            4.12

69*      150      45.7                 2.34                            4.19

70*      150      45.6                 2.41                            2.70

............................................................................................

71        150      93.8                 0.20                            11.7

72        150      93.8                 0.20                            12.4

73        150      93.7                 0.25                            17.6

74        150      93.7                 0.25                            17.0                         

75        150      93.7                 0.25                            16.0

............................................................................................

76*      150      94.6                 0.38                            13.2

77*      150      94.6                 0.44                            14.9

78*      150      94.4                 0.57                            43.0

.........................................................................................

79*      150      93.7                 0.27                            14.2

80*      150      93.5                 0.50                            14.4

81*      150      89.4                 4.6                              7.60

..........................................................................................

82*      150      94.0                 0.010                          1.35

83*      150      95.0                 0.040                          5.18

84*      150      93.9                 0.090                          2.48

85*      150      93.9                 0.110                          9.87

86*      150      93.9                 0.130                          9.09

87*      150      93.8                 0.19                            30.6

..........................................................................................

88        150      235                  0.50                            28.7

.........................................................................................

89*      150      238                  4.80                            298

90*      150      237                  6.44                            92.5

91*      150      236                  6.80                            29.1

92*      150      236                  6.97                            27.0

..........................................................................................

93*      150      229                  6.10                            474

94*      150      229                  6.7                              41.2

..........................................................................................

95*      175      94                    0.158                          3.41

96*      175      93.4                 0.57                            12.5

97*      175      93                    0.91                            11.8

..........................................................................................

98*      175      93                    1.14                            14.0

99*      175      92.6                 1.37                            18.7

100*    175      92.3                 1.64                            30.5

101*    175      90                    3.82                            11.1

102*    175      90                    3.90                            33.0

103*    175      90                    4.0                              19.3

104*    175      90                    4.03                            2.75      

...........................................................................................

105      200      15                    0.11                            0.60

106      200      15                    0.10                            0.30

107      200      19.6                 0.105                          3.83

108      200      19.6                 0.10                            2.60

109      200      23.4                 0.135                          7.57

110      200      23.4                 0.135                          7.81

111      200      28.8                 0.34                            7.81

112      200      28.8                 0.34                            8.05

113      200      35.3                 0.29                             15.7

114      200      35.3                 0.29                            13.6

115      200      47.8                 0.11                            25.1

116      200      47.8                 0.11                            24.6

..........................................................................................

117*    200      44.8                 0.17                            8.6

118*    200      44.6                 0.43                            54.5

119*    200      44.1                 0.90                            12.6

120*    200      43.8                 1.16                            5.75

..........................................................................................

121*    200      44.7                 0.31                            11.2

122*    200      44.4                 0.60                            35.2

123*    200      43.8                 1.19                            4.25

124*    200      43.7                 1.30                            21.3     sic!

..........................................................................................

125*    200      44.8                 0.20                            30.1

126*    200      44.5                 0.47                            19.3

127*    200      44.1                 0.90                            10.7

128*    200      43.8                 1.24                            19.6     sic!

..........................................................................................

129*    200      46.7                 1.20                            7.60

130*    200      46.6                 1.36                            8.97

131*    200      46.4                 1.48                            4.90

.........................................................................................

132*    200      94.3                 0.66                            37.7

133*    200      93.5                 1.47                            36.2

134*    200      93.0                 1.98                            15.0

135*    200      92.7                 2.34                            34.0        

..........................................................................................

136*    200      93.2                 1.76                            35.9

137*    200      91.3                 3.74                            12.4

138*    200      90.8                 4.17                            19.6

139*    200      90.3                 4.68                            43.4     sic!

.........................................................................................

140*    200      93.5                 1.47                            23.4

141*    200      92.1                 2.87                            11.7

142*    200      91.8                 3.18                            5.7

143*    200      91.3                 3.69                            50.2     sic!

.........................................................................................

144*    200      93.4                 1.56                            54.0

145*    200      91.8                 3.17                            18.0

146*    200      91.6                 3.37                            24.9

147*    200      91.3                 3.69                            49.6     sic!

.........................................................................................

148*    200      94.1                 0.83                            96.4

149*    200      94.0                 0.96                            66.7

150*    200      93.4                 1.50                            50.4

151*    200      93.1                 1.87                            30.6

152*    200      92.6                 2.36                            36.7

..........................................................................................

153*    200      91.1                 3.80                            12.9

154*    200      90.9                 4.06                            12.5

155*    200      90.6                 4.30                            6.82

156*    200      90.3                 4.61                            14.5

157*    200      90.1                 4.85                            5.25

.........................................................................................

158      200      94.8                 0.20                            37.4

159      200      141                  0.30                            64.7

..........................................................................................

160*    200      238                  0.075                          5.33

161*    200      238                  0.225                          9.5

162*    200      237.4               0.55                            36.6

163*    200      237                  1.0                              31.9

.........................................................................................

164*    200      234                  1.0                              39.7

165*    200      232                  2.5                              216

166*    200      228                  6.8                              106.5

 

 

* Data marked with an asterisk are not published. These measurements were conducted in stirred reactors (3000 rotations per minute) so that compressed gas was flowed through nickel shavings (99.99%Ni) without temperature and concentrations gradients. The nickel sample stayed the same within a set of measurements at the temperature and pressure given, but at different nickel carbonyl concentrations. These sets are separated by empty lines.

 

 

Hits: 1341