Solid Na Ag NaCl MgO ?? ??? ??

1
???????
2
???????
????????????????,????????,??????????????,?????
????
Solid Na Ag NaCl MgO ?? ???
?? ?/(mJ m-2) 200 800 190 1200
25.4 33.1 2400
3
??????????????????? ?,???????????
?????????????????? ?????,??????????
?????
??????????????????? ??????
4
2. Basic concepts (1) adsorbent(???) and
adsorbate (???)
???????????????,???????,????????????
???????????????????
??????????,????????????????????????
5
(2) adsorption equilibrium
At equilibrium ra rd ra rate of
adsorption rd rate of desorption
(3) Amount adsorbed (???)
(1)?????????????????
??????????(STP)
(2)??????????????????
6
(4) Adsorption curves
???????????????,???????,???????????????,?
????????,?????????????,??
(a)T??,q f (p),???????
(b)p??,q f (T),???????
(c)q??,p f (T),???????
7
(a) ????????
?????????????????????????????????????????????
???????????5???(??p/ps????,ps???????????????,
p???????)
8
????????
(?)?2.5nm???????????????????????78K?N2????????????
???????????
9
(No Transcript)
10
????????
(?)???S??????????????,??????????????1?,???????????
11
????????
(?)???????????????????????????????,?352K?,Br2?????
???
12
????????
(?)????????????????????????????,???????????323K?,?
?????????????????
13
????????
(?)????????,??????????373K?,?????????????????
14
(b) ?????
(c) ?????
V1 V2 V3
V
p1 p2 p3
p
T
T
15
3. Adsorption isothermal equations
(1) Langmuir equation (1916)
Basic assumptions
(a) Adsorption is monolayer.
(b) The surface of solid is uniform.
(c) There is not interacting force among
the molecules adsorbed.
16
Considered adsorption as a reaction
ka , kd ????????(??)???????
????
p ???????? ??????(fraction of the surface
covered) 1- ? ?????(fraction of the surface
vacancy)
????
17
Langmuir isothermal adsorption equation
?
a ka/kd ????(adsorption coefficient)
(??????)
18
Discussion (a) isotherm at low pressure ,
apltlt1,?ap, V?p at high pressure, apgtgt1, ?1, V
Vmax Vmax saturated amount of adsorption
(???????????????????)
Vm?????????????????Am,???????????S????A?
19
(b) ???????
?p/V?p??,??Vmax ?a.
20
?Ha ?????(adsorption heat at constant
pressure)
?Halt 0
In general
T? , a?, G?
21
p
T
22
(d) Other situations
?????????????????????
???????
?Langmuir??????????
23
Langmuir?????
?????? ?A?B?????????,A?B?????????????
24
Langmuir?????
??????qA,qB???
?i????????Langmuir?????
25
Langmuir?????
Langmuir????????
1.??????????,??????
2.????????,?????????????
3.????? ???,Langmuir?????????
26
?????????
???????????????
(1)??????????????
?????????????
(2)???????????????
????????????
(3)?????
????
27
?????????
??,??????????
??,?????????????????????????
28
????(Elovich)??
29
????(Elovich)??
??????
????????(Elovich)??
30
?????
??????,
??
31
??????
???????,??????????????????????????, ???????????
32
Freundlich?????
33
Freundlich?????
Freundlich????????????
Freundlich?????q ??????Langmuir?????
34
(4)BET(Brunauer-Emmett-Teller) equation
(1938)
Basic assumption
(a) Adsorption is multilayer
(b) Surface is uniform and there is
not interacting force among the
molecules adsorbed.
(c) adsorption heat above the first layer are the
same and equal to the condensed heat of gas.
35
BET??(????????)
Vm saturated amount of monolayer
adsorption c constant dependent on adsorption
heat pv saturated vapor pressure of adsorbat
liquid at adsorption temperature
36
BET??
??????,?????????
37
BET??
????????,????????,???????0.050.35???
????,????????????
????,????????,??????
38
BET??
??????????,????????,?????????,??????n?,?BE
T??????????
?n 1,???????,??????? Langmuir???
?n 8,(p/ps)8?0,?????????????????????????0.3
50.60??????
39
4. ????????? Physical adsorption and chemical
adsorption
????????????
???? ????
??? ???? ???? ???
??(???) ?? ??? ????
???? ??? ???,???
?? ??? ????????? ???? ???? ??,
??. ??????
??????
?????????????,??????,???????????,?????????????????
???????????????????,??????-????????????????
40
??????(H2?Ni?)
H2(g) H2(??) 2H(??)
Ed ????? Ea ??????? ?aH ????? ?rH
????(??)? DHH H2????
41
???
??????
??????????????????????????????????,??????
?????????????,????
??????
???????,??????????????
????????????????????,?Glt0,????????????????
?,???, ?Slt0,?H?GT?S, ?Hlt0?
42
??????
?????
?????,???????????????????,?Q??????????????
???????????????????????????
?????
?????????????q?,???????dq?????dQ,?????????
q????????