Distillation: processes – separatory – Plural distillations performed on same material
Patent
1991-11-19
1994-10-11
Manoharan, Virginia
Distillation: processes, separatory
Plural distillations performed on same material
159 471, 159DIG10, 203 99, 556187, 556190, B01D 300
Patent
active
053544331
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for producing a flow of triisobutylaluminum from liquid triisobutylaluminum containing isobutene.
Such a method is known from U.S. Pat. No. 2,847,320. TIBA (triisobutylaluminum) is used for depositing an aluminum layer on a substrate by chemical means. For this purpose, the TIBA should be present in a gaseous state. TIBA is delivered as a liquid product and consequently has to be evaporated. In this process, isobutene inter alinea is released as an undesirable by-product. In the method and apparatus according to U.S. Pat. No. 2,847,320, it is necessary to use relatively high grade TIBA to keep the quantity of isobutylene as low as possible. Using TIBA having laboratory grade means that the costs for depositing an aluminum layer will increase.
The invention aims to overcome this drawback and to provide a method making it possible to use industrial grade TIBA.
The introduction of a preheating step of the TIBA before supplying to the evaporator and removing the isobutene released, results in a TIBA product of higher quality which can be used to deposit aluminum on a substrate. Because of the preheating step industrial grade TIBA can be used.
Preferably, the preheating is carried out at 30.degree.-40.degree. C. and the evaporation at 40.degree.-60.degree. C.
According to a further advantageous embodiment, the proportioned vapor flow containing essentially TIBA is fed to a reactor and the discharge therefrom is combined with the vapor containing isobutene described above. By combining the two vapor flows, it is possible to provide a single removal system. Such a removal system is of importance, because, if the reactor employs reduced pressure, the outlet for used TIBA may take place via the pump connection. It is undesirable that TIBA reaches said pump because the pump may be damaged thereby. In order to avoid this, the TIBA (or isobutene respectively) has to be removed before reaching the pump. This can be done by cooling the exhaust gases. This may be carried out in at least two steps. In this case, essentially all the TIBA is removed in the first step and essentially the isobutene in the second, colder step.
BRIEF DESCRIPTION OF THE DRAWING
The sole figure is a schematic block diagram of the process of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Here a substrate schematically indicated by 1 has to be treated in a reactor generally indicated by 2 in a manner such that an aluminum layer is deposited thereon. The reactor 2 may be a reactor such as is described, for example, in NL-A-8,900,544. For this purpose, the apparatus according to the invention comprises a source 3 of TIBA connected via a pipe 4 to a vessel 5. The pipe 4 incorporates a filter 6 and a proportioning pump 7. Connected to pipe 4 is a flushing pipe 8 for, for example, N.sub.2. After being passed through the wall of vessel 5, pipe 4 opens into chamber 9. The said chamber 9 has a terraced bottom 10 in the center of which an overflow 11 is fitted whose end 12 opens into a cavity 13 in the center of a plate evaporator indicated as a whole by 14. Both the plate evaporator 14 and container 15 in which chamber 9 is provided are provided with heating means 16 and 17, respectively. A thermally insulating material may possibly be provided between container 15 and plate evaporator 14. Container 15 is provided with an outlet pipe 18 which is connected to outlet pipe 19 of vessel 2. An adjustable shut-off valve 20 is fitted in outlet pipe 19. Outlet pipe 19 opens, on the other hand, into cooling vessel 21. This vessel is supplied via pipes 22, 23 with a coolant from cooling apparatus 25. A cooling plate 26 is fitted in cooling vessel 21 and an outlet 27 is embodied near the bottom. An outlet 28 projecting to some extent above the bottom of the vessel is connected to freezing vessel 30. Fitted in the latter are cooling plates 31 which are cooled with liquid nitrogen supplied from source 43 via pipe 42. Connected to freezing vessel 30 is an outlet 45 which is connected to pump system 32 which opens into remo
REFERENCES:
patent: 2847320 (1958-08-01), Bulloff
patent: 4923717 (1990-05-01), Gladfelter et al.
patent: 4924936 (1990-05-01), McKown
patent: 5144053 (1992-09-01), Allen et al.
Granneman Ernst H. A.
Kwakman Laurens F. T.
Piekaar Hans W.
Sluijk Boudewijn G.
ASM International N.V.
Manoharan Virginia
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