Brief introduction
Hydro-phthalic anhydrides -- tetra-hydrophthalic anhydride, hexa-hydrophthalic anhydride, methyl tetrahydrophthalic anhydride (MTHPA), and methyl hexahydrophthalic anhydride (MHHPA) -- are used by the electronic information industry and are important intermediates for the pharmaceutical, pesticide, resin, and national defense industries. They have low toxicity and low volatility and are mainly used for curing agents of epoxy resin.
Process
The synthesis of MTHPA from maleic anhydride and pentadiene is a typical Diels-Alder condensation reaction, i.e. the unsaturated maleic anhydride with olefinic bonds is a dienophile. It takes a 1,4 addition reaction with pentadiene, a catenary diene with conjugated diene, to generate a cyclohexene ring - hydroaromatic compound. The production flow goes as followings: with polymerization inhibitors, maleic anhydride reacts with pentadiene to generate MTHPA; after a preliminary separation of MTHPA, isomerization catalyst is added to continue the reaction to generate liquid MTHPA; after rectification, the colorless, transparent liquid MTHPA presults. MHHPA is the product of the hydrogenation of MTHPAT and follows a similar process.
Product quality
Quality indicators of MTHPA
|
Item |
Indicator |
|
Appearance |
Colorless, transparent liquid |
|
Chroma (Pt-Co scale) |
<200 |
|
Specific gravity (25℃) |
1.21±0.04 |
|
Viscosity cp (25℃) |
50~70 |
|
Melting point ℃ |
≤-15 |
|
Acid value mgKOH/g |
660~670 |
|
Anhydride content % |
≥41 |
|
Heating loss % |
<1 |
|
Free acid % |
<1 |
Quality indicators of MHHPA
|
Item |
Indicator |
|
Appearance |
Colorless, transparent liquid |
|
Specific gravity (25℃) |
1.16±0.04 |
|
Viscosity cp (25℃) |
50~60 |
|
Melting point ℃ |
≤-15 |
|
Acid value mgKOH/g |
≥660 |
|
Iodine value |
<2 |
|
HHPA content % |
≥99% |
|
Free acid % |
≤0.5 |
Technical indicators
|
Item |
Specification |
Unit |
Consumption quota |
|
Maleic anhydride |
Industrial grade |
t |
0.7 |
|
C5 fraction |
Industrial grade |
t |
0.5 |
|
Catalyst |
Industrial grade |
kg |
4 |
|
Cooling water |
|
t |
50 |
|
Electricity |
220V/380V |
kWh |
800 |
|
Steam |
0.8MPa |
t |
2.5 |
Waste treatment
The process is highly selective with few byproducts. Only a small amount of organic liquid waste is discharged from the rectification tower and it can be incinerated.