【Question】Hydrogenation reaction – issues with hydrogen circulation!
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This post was last edited by ztt06 on 2009-10-24 at 16:07. Hello everyone, I have a question. I’m not involved in oil refining; I work in organic synthesis, using autoclaves for hydrogenation reactions, and methanol is used as the solvent in these reactions. Drawing on the catalytic hydrogenation process, the current concept is as follows: 1. Add a hydrogen circulation pump to draw out the hydrogen gas from the upper part of the hydrogenation reactor, and then return it into the reactor through the gas distribution pipes at the bottom of the reactor. 2. The purpose of this cycle is to increase the gas-liquid contact area for the hydrogen reaction and shorten the reaction time. This process encounters several issues: 1. Since methanol is used as the solvent, the gas in the upper space of the reactor is actually a mixture of hydrogen and methanol vapor. Does this mixture need to be separated before it can be fed into the hydrogen compressor, or can it be fed in directly? 2. The high-pressure reactor used for the reaction has only a few cubic meters in volume, and the space at the top of the reactor is also only 2–3 cubic meters. Is there a hydrogen circulation pump with such a low pumping capacity? Please give me your guidance!
1. Separation is necessary to prevent liquid from reaching the inlet of the circulation pump; cooling is also required to protect the compressor； 2. I don’t know what the high pressure is Is there a reciprocating pump for pressurization? ； 3. Is the temperature during the reaction high, and does the cold hydrogen circulation have an impact on the reaction? ； 4. What is the hydrogen concentration? New hydrogen replenishment facilities are required ； 5. Is there a suitable compressor? Please have a professional in equipment give an answer; I’m not sure
First of all, thank you so much! I have a few more questions: 1. What method is used to separate hydrogen gas from methanol gas? Is it complicated? 2. The pressure is about 1 MPa, I guess. 3. At a temperature of 60~80 degrees Celsius, the cold hydrogen cycle has no effect on the reaction. 4. In the reaction system, there are only two gases: methanol gas and hydrogen gas. Total pressure is 1 MPa.
Hydrogen and methanol-water are first cooled to condense most of the methanol, followed by gas-liquid separation. It also ensures that hydrogen enters the hydrogen circulator at an appropriate temperature; the temperature of the hydrogen rises further after passing through the circulator, and cooling may be required if necessary. The hydrogenation reaction is essentially an exothermic reaction, so it does not have any impact on the reaction.
I would like to ask: At 1 MPa and 60–80 degrees Celsius, is methanol a gas?
1. Separating methanol from hydrogen by condensing methanol vapor not only prevents methanol-water mixtures from reaching the compressor and causing damage, but also improves the purity of hydrogen in the circulating hydrogen. It is worth noting that you also need to consider replenishing new hydrogen. 2. Small-output reciprocating compressors are not available on the market currently. It is recommended to use a centrifugal type.
4# dongzhuli1999 Thank you to the two people who replied above:） Hehe! Thank you! Methanol at 1 MPa and over 60 degrees should also be in vapor form, right? Or has it actually turned into a liquid?
The volume equivalent is relatively small; adding a filler section is sufficient, and there’s no need to use a dedicated condenser. The circulating compressor can be diaphragm-type; for fresh hydrogen, I assume you’re using cylinders, so there shouldn’t be any problem
It’s not that difficult to fulfill the original poster’s wish; as the people above have explained clearly, the quantity is just too small
This post was last edited by yyszyj on 2021-3-30 08:23. In my opinion, such a reaction should not be designed to involve hydrogen circulation; if it is a reactor, increasing the speed of the stirrer will suffice to enhance gas-liquid contact, and using circulation is neither energy-efficient nor environmentally friendly.
It is recommended to use a micro fixed-bed reactor