HANOI UNIVERSITY OF MINING AND GEOLOGY
ADVANCED PROGRAM IN CHEMICAL ENGINEERING
ADECH04 – FINAL
Problem 1 : Suggest routes that might be suitable for the large- scale manufacture of
𝐶
𝐻
2
𝑂𝐶𝐻𝐶
𝐻
2
𝐶
𝐻
3 from 1-butene (1,2-epoxy butane epoxide )
𝐶
𝐻
2=𝐶𝐶
𝐻
3
𝐶𝑁 from isobutene (Methacrylonitrile)
The production of methacrylonitrile via isobutylene ammoxidation, using similar procedures as described for propylene is not in high demand as feedstock for MTBE production. Methacrylonitrile can be used as an alternative route to methacrylic acid and methylmethacrylate via hydrolysis to methacrylanide, which can then be esterified to methylmethacrylate or hydrolyzed to methacrylic acid.

Problem 2 :
Acetic acid is produced by the carbonylation of methanol :
𝐶
𝐻
3
𝑂𝐻+𝐶𝑂→𝐶
𝐻
3
𝐶𝑂𝑂𝐻
The process uses a catalyst system containing rhodium and isodine
𝑂
2
𝐼
2 , and operates at 150°𝐶 to 200°C and 30-40 atm. Methanol is completely converted, and the yield of acetic acid is about 99% based on methanol.
Suggest a block diagram for the process of acetic acid production from natural gas ( use steam reforming )
Consumption of methanol in 2014 was about 3.35 million tones. Manufacture of acetic acid consumes about 10% methanol. Estimate what proportion of acetic acid was made from methanol, given that total acetic acid production was about 1.3 million tones.
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We utilize a partial oxidation reactor (10) to which is fed a natural gas stream (11) and an oxygen stream (12). The reaction product (13) is passed through a waste heat boiler (14) to recover excess heat of reaction. If necessary, some water may be removed from the reaction product. The product stream 15 then continues to the water and methanol separator 16. Water is recovered via line 26 and the methanol is fed to the carbonylation reactor via line 27.
The carbonylation reactor 17 where the carbonylation of methanol and carbon monoxide takes place in the presence of a catalyst. Additional methanol from an external source is fed into the reactor via inlet line 18. Excess methane and carbon dioxide are recycled to the partial oxidation reactor 10 via recycle line 19. This recycle stream passes through a scrubber 25 for removing carbon dioxide so that the concentration of carbon dioxide in the flow system of the invention is controlled within an acceptable level. The reaction product from the carbonylation reactor 20 is fed to an acetic acid recovery system 21. Methanol present in the recovery system is recycled via line 22 to the carbonylation reactor 17 and product acetic acid 23 is recovered from the recovery system 21.

Problem 3 : Interpretation of flow diagram of terephthalic acid manufacture by p-xylene oxidation. (fig.5.14)
The feed passes to the oxidation reactor at which oxidation occurs. Most of TPA precipitates, because of its low solubility in the solvent. This yields a three phase system; solid TPA crystals; solvent with some dissolved TPA; and vapor consisting of nitrogen, acetic acid, water, and a small amount of oxygen. The over head vapors from the reactor are condensed in heat exchangers, and the condensate is refluxed to the reactor.
Steam, which is generated by condensation, used as heating source in other parts of the process. Oxygen depleted gas from the condensers is scrubbed to remove most uncondensed vapors.
Oxidation reactor operates at 175 - 225 ⁰C and 1500 - 3000 kPa, at residence time about 2.5 hours. Reactor is lined with titanium to withstand the highly corrosive bromine and acetic acid. The pressure of hydrogenation reactor is held above the vapor pressure of water to maintain a liquid phase.
The effluent stream from the reactor contains TPA as slurry. This slurry passes through a surge vessel that operates at a lower pressure than the reactor. More TPA crystallizes and the cooled slurry is then ready to be processed at close to atmospheric conditions. The slurry is fed to a centrifugation unit at which most of water removed from the product.
After centrifugation, one stream is fed to the recovery unit and the other to a rotary drier. Preheated air is sent to the drier to remove the moisture present in the final product. TPA crystals are obtained from the drier by 99% purity, then conveyed to storage, from which they are in turn fed to the purification step.
Water formed and some undesirable by-products must be removed from acetic acid solvent. Mother liquor from the centrifuge is purified in a solvent recovery tower to purify acetic acid. The purified acetic acid from the top of the tower is recycled to the reactor and combined with fresh acetic acid and the bottom product can be processed for catalyst recovery and regeneration. Vents from the oxidation process, are sent to a gas scrubbing tower then to water removal tower to remove the water formed as the overhead stream which sent to waste water treatment.
The slurry formed contains at least 15 wt% TPA and the rest are impurities accessible to the purification reaction. The solution flows