What is maleic anhydride BDO?
Maleic anhydride process BDO, as the name suggests, is a process to prepare BDO from maleic anhydride. The raw material maleic anhydride can be oxidized from benzene or butane. Due to environmental pollution, the domestic phenyl-maleic anhydride plant has been suspended for a long time or modified to produce maleic anhydride by butane oxidation. At present, 80% of the global maleic anhydride production is using fixed-bed butane process, which has the characteristics of easy availability of raw materials, low pollution and high product yield.
Maleic anhydride method can be divided into direct hydrogenation method and indirect hydrogenation method according to the different steps of maleic anhydride hydrogenation, and indirect hydrogenation method can be divided into gas phase hydrogenation method and liquid phase hydrogenation method according to the material form during hydrogenation.
Direct and indirect hydrogenation
Direct hydrogenation process
Direct hydrogenation of maleic anhydride was first developed by Mitsubishi Petrochemical and Mitsubishi Chemical in the 1960s. The process can simultaneously produce THF (tetrahydrofuran), GBL (Y-butyl lactone) and BDO series products in different proportions. The corresponding composition of the products is also different with different reaction conditions.
Esterification hydrogenation process
Indirect esterification hydrogenation process was first developed by Davy Company in UK, so it is also called Davy process. Hydrogenation reaction can be carried out in the gas phase or liquid phase, using copper catalyst, the main reaction conditions are much milder than the direct hydrogenation process of maleic anhydride.
As the hydrogenation of maleic anhydride is a strong exothermic reaction, the direct hydrogenation reaction conditions are harsh, the control difficulty is high, there is no industrial operation device at present, the operation device is used in the indirect method.
Gas phase and liquid phase hydrogenation
The chemical reaction equations of the two are consistent, and the difference lies in whether the hydrogenation unit dimethyl maleate reacts in the gas phase or in the liquid phase.
The gas phase hydrogenation maleic anhydride method represented by British Davy is to gasify all the materials into gas phase and then react with hydrogen (also gas phase) during hydrogenation reaction to finally produce BDO and a small amount of THF (a small amount of GBL can also be produced by side according to needs).
The liquid phase hydrogenation maleic anhydride method represented by Conser in Italy does not require gasification step, but directly reacts liquid phase materials with hydrogen (gas phase) to produce BDO. Therefore, this method can also be called mixed phase hydrogenation maleic anhydride method.
At present, the process of most technology companies is gas phase hydrogenation.
Consumption and emission
In the BDO process line of n-butane maleic anhydride method, the main consumption of n-butane 1.15t and hydrogen 1200 m3 for the production of tons of BDO is roughly. The main raw materials of this method are n-butane and hydrogen. The price of n-butane is 5,000 yuan /t, and the raw material cost of BDO production is about 10,500 yuan /t. If we purchase maleic anhydride to produce BDO, the current market price of maleic anhydride is about 12,000 yuan /t, and a ton of BDO consumes about 1.12t maleic anhydride, so the production cost of BDO is relatively high.
Therefore, almost all the newly built maleic anhydride BDO projects in recent years have chosen n-butane as raw material to make maleic anhydride by themselves. N-butane maleic anhydride process, if it can be combined with the existing petrochemical cracking unit, using the byproduct of n-butane cracking unit to produce maleic anhydride to produce BDO, will greatly reduce the production cost of BDO, plus n-butane maleic anhydride process has high product quality, low project investment, less pollutant emissions, mature technology and other advantages, will be more competitive in the market.
Process route advantage
The main source of n-butane, one of the raw materials of BDO by maleic anhydride process, is the by-product of the separation of C4 fractions from petroleum cracking in large refining and chemical plants. Second, oil field gas and wet natural gas, LPG (liquefied petroleum gas) importers, domestic maleic anhydride process BDO enterprises mainly distributed in coastal areas, can rely on petroleum refining enterprises or ports to obtain raw material n-butane.
In our "much gas (natural gas)" area, there are few BDO units, and natural gas contains about 1% n-butane. N-butane can be obtained by fractional condensation at the same time of natural gas liquefaction (that is, the separation of butane at the same time of natural gas deethane), and it does not affect the continued use of natural gas. It is suitable for the new enterprises in the northwest region with natural gas source. In the future, it has a large growth space and can realize the green and low-carbon development of BDO industry in Northwest China.
In conclusion, the process route of n-butane maleic anhydride BDO has obvious cost advantages, mature technology, less pollution, and great development potential.
