What is claimed is:
1. A process for producing diamines which comprises the steps of:
(1) reacting a dialdehyde with ammonia and hydrogen in the presence of an alcohol represented by the following general formula (I)
ROH(I)
wherein R represents methyl group or ethyl group, and a hydrogenation catalyst, to synthesize the corresponding diamine;
(2) separating and recovering said alcohol by distilling the reaction mixture obtained in the step (1);
(3) separating the diamine by purifying the distillation residue obtained in the step (2); and
(4) feeding at least part of said alcohol recovered in the step (2) to the step (1);
said step (1) comprising maintaining the amount of ammonia at a level of at least 200 moles per mole of the primary amine represented by the following general formula (II)
RNH2(II)
wherein R is as defined above that has formed in the step (1) and accumulated in the reaction vessel for step (1).
2. The process according to claim 1, wherein said dialdehyde is a linear aliphatic aldehyde, a branched aliphatic dialdehyde, an alicyclic dialdehyde or an aromatic dialdehyde.
3. The process according to claim 2, wherein said linear aliphatic dialdehyde is butanedial, hexanedial, octanedial, nonanedial, decanedial, undecanedial, dodecanedial, tetradecanedial, hexadecanedial, octadecanedial or eicosanedial; said branched aliphatic dialdehyde is 2-methyloctanedial, 2-methylnonanedial or 2,7-dimethyloctanedial; said alicyclic dialdehyde is 1,3-cyclohexanedicarbaldehyde, 1,4-cyclohexanedicarbaldehyde, 3(4),8(9)-tricyclo5.2.1.0decanedicarbaldehyde or 2(3),5(6)-bicyclo2.2.1heptanedicarbaldehyde;, and said aromatic dialdehyde is terephthalaldehyde or isophthalaldehyde.
4. The process according to claim 1, wherein said dialdehyde is a mixture of a linear aliphatic dialdehyde and a branched aliphatic dialdehyde.
5. The process according to claim 4, wherein said linear aliphatic dialdehyde is 1,9-nonanedial and said branched aliphatic dialdehyde is 2-methyl-1,8-octanedial.
6. The process according to claim 1, wherein the concentration of said dialdehyde is in a range of 5 to 30% by weight based on the total weight of the liquid phase in the reaction vessel.
7. The process according to claim 1, wherein the amount of said alcohol used is in a range of 0.5 to 50 times by weight based on the weight of said dialdehyde.
8. The process according to claim 7, wherein the amount of said alcohol used is in a range of 2 to 10 times by weight based on the weight of said dialdehyde.
9. The process according to claim 1, wherein said hydrogenation catalyst is a Raney catalyst or a supported catalyst comprising a metal having hydrogenation activity on a support.
10. The process according to claim 9, wherein said Raney catalyst is Raney nickel, Raney cobalt or Raney copper, and said supported catalyst is nickel, cobalt, platinum, palladium, rhodium, ruthenium or copper supported on Kieselguhr, silica, alumina, silica-alumina, clay, titania, zirconia, magnesia, calcia, lanthanum oxide, niobium oxide or carbon.
11. The process according to claim 1, wherein the amount of said hydrogenation catalyst is in a range of 0.01 to 30% by weight based on the total weight of the liquid phase in the reaction vessel.
12. The process according to claim 11, wherein the amount of said hydrogenation catalyst is in a range of 0.1 to 10% by weight based on the total weight of the liquid phase in the reaction vessel.
13. The process according to claim 1, wherein the amount of ammonia is in a range of 2 to 300 moles per mole of said dialdehyde.
14. The process according to claim 13, wherein the amount of ammonia is in a range of 5 to 100 moles per mole of said dialdehyde.
15. The process according to claim 14, wherein the amount of ammonia is in a range of 5 to 50 moles per mole of said dialdehyde.
16. The process according to claim 1, wherein the reaction temperature is in a range of 40 to 200 C.
17. The process according to claim 16, wherein the reaction temperature is in a range of 100 to 180 C.
18. The process according to claim 1, wherein the reaction pressure is 0.1 to 20 MPa in terms of hydrogen partial pressure.
19. The process according to claim 18, wherein the reaction pressure is 0.5 to 15 MPa in terms of hydrogen partial pressure.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of operating a base station to wirelessly transmit voice or streaming communications and data communications to a plurality of user terminals on a carrier, the method comprising:
repeatedly and sequentially wirelessly transmitting time division multiplexed superframes to the plurality of user terminals on the carrier, wherein each time division multiplexed superframe comprises a plurality of frames, wherein at least one of the frames carries voice communications, and wherein at least one of the frames carries data communications;
for each frame carrying voice communications, transmitting a plurality of voice packets contained in the frame;
wherein each voice packet includes voice bits for a respective user; and
wherein each voice packet includes a preamble having a user identifier and an indication of the length of the voice packet.
2. The method of claim 1, wherein at least one Walsh function is employed to identify the user and to indicate the length of a voice packet.
3. The method of claim 2, wherein a single Walsh function both identifies the respective user and indicates the length of the voice packet.
4. The method of claim 2, wherein:
a first unique Walsh function of the preamble identifies the user; and
a second unique Walsh function of the preamble indicates the length of voice packet.
5. The method of claim 4, wherein:
the first unique Walsh function is modulated on the carrier during a first time period of the preamble; and
the second unique Walsh function is modulated on the carrier during a second time period of the preamble.
6. The method of claim 5, wherein both the first unique Walsh function and the second unique Walsh function are modulated on an in-phase portion of the carrier.
7. The method of claim 3, wherein:
the first unique Walsh function is modulated on an in-phase portion of the carrier; and
the second unique Walsh function is modulated on the quadrature-phase portion of the carrier.
8. The method of claim 7, wherein the first unique Walsh function and the second unique Walsh function are concurrently modulated on the carrier.
9. The method of claim 1, wherein at least one voice packet also includes a pointer to a subsequent voice packet.
10. The method of claim 9, wherein at least one Walsh function is employed to identify the user and to indicate the length of a voice packet.
11. A superframe embodied on a carrier that carries voice or streaming communications and data communications intended for a plurality of user terminals, the superframe comprising:
a plurality of frames, wherein at least one of the frames carries voice communications, and wherein at least one of the frames carries data communications;
for each frame carrying voice communications, a plurality of voice packets contained in the frame;
wherein each voice packet includes voice bits for a respective user; and
wherein each voice packet includes a preamble having a user identifier and an indication of the length of the voice packet.
12. The superframe of claim 11, wherein at least one Walsh function is employed to identify the user and to indicate the length of a voice packet.
13. The superframe of claim 12, wherein a single Walsh function both identifies the respective user and indicates the length of the voice packet.
14. The superframe of claim 12, wherein:
a first unique Walsh function of the preamble identifies the user; and
a second unique Walsh function of the preamble indicates the length of voice packet.
15. The superframe of claim 14, wherein:
the first unique Walsh function is modulated on the carrier during a first time period of the preamble; and
the second unique Walsh function is modulated on the carrier during a second time period of the preamble.
16. The superframe of claim 15, wherein both the first unique Walsh function and the second unique Walsh function are modulated on an in-phase portion of the carrier.
17. The superframe of claim 14, wherein:
the first unique Walsh function is modulated on an in-phase portion of the carrier; and
the second unique Walsh function is modulated on the quadrature-phase portion of the carrier.
18. The superframe of claim 17, wherein the first unique Walsh function and the second unique Walsh function are concurrently modulated on the carrier.
19. The method of claim 11, wherein at least one voice packet also includes a pointer to a subsequent voice packet.
20. The method of claim 19, wherein at least one Walsh function is employed to identify the user and to indicate the length of a voice packet.