Mingzhou Li

20 nm gamma-alumina can be used as a catalyst support because it has a large specific surface area.

Professor Yuri Mirgorod, thank you very much for your answer. It helped me a lot.

Depends on the size of Your reactor, mainly the diameter. If You use 20 mm particles the reactor should be at least 200 mm ID. And the catalyst bed should be some 1000 mm high. Not the best dimensions for a test reactor.

I should use smaller particles in order to have better contact between reactants and catalysts, the smaller particles the bigger is the contact area.

Take a look at these qualities of gAl2O3 from Sasol.

https://sasoldcproducts.blob.core.windows.net/documents/Product%20Brochures/ZA_Inorganics_PURALOX%20CATALOX%20Overview.pdf

Henrik Romar Respected Prof．Henrik Romar，

Thank you very much for your response and the information provided. I have a question regarding the Sasol document on alumina that you sent: Why is the particle size smaller than the pore radius? I look forward to your reply.

Particle size is given in µm and pore radius in nm.

1 µm = 1000 nm so pores are much smaller than the particles.

Henrik Romar Dear Prof．Henrik Romar,

I have a question that has troubled me for a long time, and I hope to get your answer.

In wet impregnation, the catalyst support and the precursor solution have an excess amount of water. I have read about three methods in the literature: 1. Dry at 80°C while stirring until completely dried, then place in a drying oven. 2. Dry at 80°C while stirring until a slurry state is reached, then place in a drying oven. 3. After impregnation and stirring, use a rotary evaporator until the solvent is removed and it is dry. Scrape off the substance adhering to the inside of the flask, then place it in a drying oven. I used the third method, and I am not sure if this approach results in uniform distribution of the metal. Additionally, I am concerned that the third method may cause the precursor salts to adhere to the inner walls without being loaded onto the carrier, and thus might be scraped off together with it. Although I personally believe that the first two methods also result in uneven distribution and also have metal salts that are not loaded onto the carrier.

One more method, dissolve the metal precursor in a volume equal to total pore volume of the support. Add the solution dropvise to the support and let it equilibrate over night. Slowly remove the water using an evaporator for 12 hours. Do a final drying at 80C for another 12 hours.

The evaporator step is critical in order to keep the metals inside the pores and just removal the water. Too fast removal will create something like eggshell catalysts.