GREEN CHEMISTRY
Figure 3 - Reaction & work-up processes using THF & MTHP
a
600 ,....., 500
C\I
0 I C\I 400
Q. Q.
300 200
> 100 0
b
�
0..
c
�
I-
d
0
100 % 98 % 96 % 94 % 92 % go %
0
Test conditions
- Under air at 25 ° C , without stabiliser - POV is measured by lodometry method
�MTHP
5 10 15 20 25 30 -THF Days
0 20 40 60 80 100 Time / hr
100.0 %
T
II'"
99.8 % 99.6 % 99-4 % 99.2 %
Test conditions - 20 % HCI / Solvent = 1 : 1 ( wt .) at 50 ° C
�MTHP
Test conditions - 20 % NaOH / Solvent = 1:1 ( wt .) at 50 ° C
�MTHP
-2MTHF
99.0 % -THF 0 20 40 60 80 100
100 %
- *
60 % �
Q) .µ
Time / hr
Test conditions 80 % - 1.6M n-Buli / hexane 30ml + solvent 30ml
- 50 ° C
ea |
|
...... ea
::,
|
40 % |
"O |
20 % |
rJJ |
|
Q) c::: |
0 % |
0.0 |
0.5 |
1.0 |
1.5 |
2.0 |
|
|
time / h |
|
|
-MTHP -THF -2MTHF
Figure 4 – Stability to oxidation ( a ), acid ( b ) & base ( c ) & residual rate of n-BuLi of MTHP & other solvents process to obtain 1 tonne of product by a reaction and work-up process using THF and MTHP .
In the case of THF , heating is required to concentrate the reaction mixture and 10.1 kg of CO 2 is emitted per tonne of product . Then , water and ethyl acetate , the extracting solvent , are added for extraction , and the ethyl acetate is concentrated . This process also requires heating , which emits a further 9.6 kg of CO 2 per tonne of product , bringing the total to 19.7 .
With MTHP , it is not necessary to concentrate the reaction mixture ; the extraction is completed by simply adding water . Only the concentration of MTHP requires heating so the process using MTHP only emits 9.4 kg of CO 2
/ tonne of product , reducing CO 2 emissions by almost half compared to processes using THF . In addition , the MTHP process reduces wastewater load and facilitates the recycling of the solvent at a high recovery rate . In the process using THF , a considerable amount of THF and ethyl acetate elutes into the water layer during extraction , causing an increase in wastewater load . There is also a problem with recyclability due to large losses in extraction . By contrast , MTHP has a low solubility in water , which reduces the wastewater load , and it can be recycled with a high recovery rate .
THF is not recoverable because it is miscible with water . 2-methyl THF ( 2MTHF ) is recoverable , but its high solubility in water ( 14 wt %) results in a lower recovery rate . MTHP has a recovery rate of 99 % after separation . Even if dehydration is performed to a moisture content of 50 ppm , the recovery rate is 93 %.
We believe that MTHP can play a significant role in making various chemical processes greener because of its excellent stability and versatility . Its stability is compared to that of common ether solvents shown in Figure 4 .
Ether solvents often have problems with peroxide formation due to oxidation . MTHP has high oxidation stability and is resistant to peroxide
31