# How to convert isopropanol to acetone and hydrogen

From Wikipedia:

Isopropyl alcohol can be oxidized to acetone, which is the corresponding ketone. This can be achieved using oxidizing agents such as chromic acid, or by dehydrogenation of isopropyl alcohol over a heated copper catalyst: $$\ce{C3H8O -> C3H6O + H2}$$

However, how exactly do I do this? Is it possible to do this by simply mixing isopropanol with an oxidizer (e.g. sodium chlorate)? Also, if the copper catalyst is actually required, what temperature is needed to drive the reaction? Neither the Wikipedia article nor the cited source provide much information on this. I want acetone as opposed to isopropanol, as a fuel, because its flash point is lower and it is much easier to ignite.

This is just an experiment, and if this method of producing acetone is impractical, I will just make/obtain it in other ways.

• The method is impractical except on an industrial scale. Not sure how hot the copper would be but I'd guess several hundreds degrees C at least. "Pure" isopropyl alcohol would be "blown" over the hot copper so there is a huge fire and explosion hazard with this. Such a process would require careful engineering to maintain control. Definitely not something to try in your basement. – MaxW Apr 22 '16 at 7:06
• @MaxW What about the method with the oxidiser? – sadljkfhalskdjfh Apr 22 '16 at 9:00
• Both acetone and isopropanol are readily available and cheap chemicals. Making your own is a terrible way to obtain them. If you want acetone, just buy it. – matt_black Apr 22 '16 at 10:24

There are several ways to convert isopropanol to acetone.

1. Use of $\ce{Cr2O3}$ as catalyst[1]

The conversion of isopropyl alcohol to acetone has been studied over $\ce{Cr2O3}$ powder at 473 K in a flowing microcatalytic reactor. Appreciable steady-state catalytic activity was achieved only when oxygen was present in the reactant gas flow. The effect of mild pretreatment of $\ce{Cr2O3}$ in $\ce{O2–N2}$ at 473 K on the initial activity, and the observed dependence of the process on $\ce{O2}$ pressure has been related to the oxidation–reduction cycle of the surface chromium species. $\ce{Cr^{(3+n)+}}$ on the surface of $\ce{Cr2O3}$ have been considered to be the active species, where n= 1–3.

2 . Catalytic dehydrogenation of isopropanol

a) Source 1.

Catalytic dehydrogenation of isopropanol can be chosen as an alternative synthetic route when high-purity acetone is required, such as in biomedical applications. Turton et.al. mentions that a single pass conversion of 85-92% with respect to isopropanol, with reactor conditions of 2 bar and 350° C, is generally achieved. A molten salt stream will be used a heat source for the endothermic reaction:

$$\ce{(CH3)2CHOH -> (CH3)3CO + H2}$$

The acetone produced in the reactor passes into a phase separator and then into a separation system that includes one stripping and two distillation columns. A recycle stream takes a mixture of unreacted isopropyl alcohol and water, with a trace amount of acetone, back into a mixer that feeds the reaction system. Using the catalyst which will be employed throughout this analysis, the reaction is first order with respect to the concentration of isopropanol and has an Arrhenius dependence on temperature with E=72.38 MJ/kmol and k=351,000 cubic m gas/cubic m reactor sec.

b) Source 2

At the beginning of the process, feed including i-propyl alcohol and water, and recycle stream are mixed in feed drum. From here, this mixture is send to vaporizer to changestream’s phase as vapour. After vaporizer, mixture is heated to reaction temperature in theheater. Reactor used is a tubular flow reactor. Acetone, hydrogen gas (H2) are produced andwater and i-propyl-alcohol are discharged. The mixture with acetone, hydrogen, water, i- propyl-alcohol are sent to cooler and then to condenser. After condenser the mixture is sent toflash unit. Hydrogen, acetone, i-propyl-alcohol and water are obtained as top product. This top product is sent to scrubber to remove hydrogen. The bottom product of flash unit which isformed by acetone, water, i-propyl-alcohol are mixed with the bottom product of scrubber before acetone column. In acetone column, acetone is obtained from top product with 99 wt%. i-propyl alcohol and water and also 0.1% of acetone is sent to i-propyl-alcohol column from bottom product. The top product of this column is sent to feed drum and bottom product is thrown away as waste water.

1. Using chromic acid [2]

Oxidation at 25' to 40' is accordingly specified, requiring the mixture to be chilled in ice after each addition of oxidant. In 1926 the writer worked out a student experiment which involves the same reaction, the oxidation being effected by gradual addition of chromic acid solution to the boiling solution of isopropyl alcohol in water. The reaction is carried out in a flask surmounted by a short fractionating column, through which the acetone is distilled during and after the oxidation. The crude acetone (collected below 65'), and several subsequent fractions, are redistilled through the column, permitting the easy isolation of a high yield (70% to 80% or more) of acetone boiling 57' to 60' and over 99% pure, and also the isolation of any unchanged isopropyl alcohol (76' to 82').

References:

1. Ilyas, M.; Shah, S.; Nigar, R.; Khan, H. Conversion of isopropyl alcohol to acetone catalysed by Cr2O3 at 473 K: role of molecular oxygen. Faraday Trans. 1994, 90 (16), 2413. DOI: 10.1039/FT9949002413.
2. Wagner, E. C. Oxidation of isopropyl alcohol to acetone. A student experiment. J. Chem. Educ. 1934, 11 (5), 309. DOI: 10.1021/ed011p309.

You can consider transfer hydrogenation using isopropanol as a hydrogen source. Many years ago I wanted to make a coordination polymer from trans-1,2-diphenylphospinoethylene and nickel chloride. I put the reagents together in a autoclave and heated it. I allowed the thing to cool slowly and I got some nice orange crystals.

These turned out to be the dppe complex of nickel with two chlorides on the nickel. What happened was that the alkene in the diphosphine was hydrogenated by hydrogen formed from the isopropanol being converted partly into acetone.