Sciencemadness Discussion Board

Molybdenum Disulfide

bereal511 - 27-7-2006 at 15:56

I'm debating on whether or not I should buy a few ounces of molybdenum disulfide because I'm not 100% sure if I can use it in the catalytic reaction I want to use it for. It's quite possible that the experimental application I want to use it for is way beyond my current abilities (catalytic conversion of carbon monoxide and hydrogen gas into alcohols).

I'd hate to waste my money on the stuff, so I was wondering if there was any other use for molybdenum disulfide (powdered form) besides its industrial catalytic use and lubrication capabilities.

not_important - 27-7-2006 at 16:17

You do know that the CO + H2 reactions run at 250 to 350 C and 15 to 100 atmospheres?

Molybdenum is used for some pigments, although not as the disulfide. Roasting the disulfide in air converts it to the oxide, which can be used to make molybdates. The major use for the disulfide as such is as ou said - lubrication and catalysts.

bereal511 - 27-7-2006 at 18:08

Yes, I do.

I'm still trying to figure out a way to do the pressurization, but that's just all part of the fun...

[Edited on 28-7-2006 by bereal511]

ethan_c - 28-7-2006 at 10:58

Quote:
Originally posted by bereal511
I'd hate to waste my money on the stuff, so I was wondering if there was any other use for molybdenum disulfide (powdered form) besides its industrial catalytic use and lubrication capabilities.


Even for a broke high school kid like me, MoS<sub>2</sub> is not expensive at all. I think you can get it for ~$4 an ounce or something on eBay, and it ain't much more at any auto shop.

Roasting

chloric1 - 9-9-2006 at 07:11

I am roasting it right now. I am using Mapp gas and I have the flame pretty high. My "Inorganic preparations" book says not heat the iron dish of MoS2 more than a dull red heat. Unfortunately I do not have a low form iron dish as I am using a cast iron pipe cap as a crucible. I use orange heat and I put a hole in the middle of my mixture to maximize surface contact with oxygen. When hot the Molybdenum trioxide is hornet yellow but lightens to a vanilla color at room temperature.

Curious thing is that you must periodically stir the mixture or considerable portion will fuse to the iron!! Now I now I am not so much melting the MoO3 or MoO2 but I believe the remaining sulfide is actually attacking the iron:o I attribute this to insufficient oxygen supply at the buttom so now I stir every 5 or 10 minutes.

bereal511 - 9-9-2006 at 08:43

I'm curious, what will you be using the molybdenum oxides that you have formed for?

chloric1 - 9-9-2006 at 09:00

Well at first I will make ammonium molybdate to help purify my product as it is very crude. I have read about complex blue and violet oxides and this fascinates me. This could be an avenue to coloring of metals. I want create enough inventory to research various effects under various reaction conditions.

Magpie - 27-10-2008 at 14:36

I have some molybdenite ore and would like to use it to make ammonium molybdate. I have not found a detailed procedure for this, just bits and pieces. Here's what I think would work:

1. Crush and ball mill the ore to <100 microns.
2. Roast at 600-700C to convert the MoS2 to MoO3.
3. React the roasted product with aqueous ammonia.
4. Filter off the slilica/gangue, saving the filtrate.
5. Evaporate the filtrate, allowing crystals of ammonium molydate to form.

Has anyone tried this? Please comment on my proposed procedure, offer suggestions and improvements, etc.

chemkid - 27-10-2008 at 16:41

ethan_c Could you elaborate on your comment about auto shops and molybdenum?

chloric1 - 27-10-2008 at 18:02

Quote:
Originally posted by Magpie
I have some molybdenite ore and would like to use it to make ammonium molybdate. I have not found a detailed procedure for this, just bits and pieces. Here's what I think would work:

1. Crush and ball mill the ore to <100 microns.
2. Roast at 600-700C to convert the MoS2 to MoO3.
3. React the roasted product with aqueous ammonia.
4. Filter off the slilica/gangue, saving the filtrate.
5. Evaporate the filtrate, allowing crystals of ammonium molydate to form.

Has anyone tried this? Please comment on my proposed procedure, offer suggestions and improvements, etc.


@magpie- See my post above the e-book that I got the idea for roasting molybdenite with, said not to exceed a dull red heat. I heated alot hotter and the disulfide fuses to the dish. An electric furnace would be ideal but a controlled flame would be better. I am reading a book about ion-exchangers and they talk briefly about analyzing molybdenite ore when it is low portions. Dissolve MoS2 in 3% NaOCL and heat to 45 Celsium for 30 minutes. The equation is as follows: 7NaOCl +MoS2>> S2O3 + MoO4- + 7 NaCl. So you will need ALOT of bleach but good news it only needs to be 3% so you can water it down. Next you run through an alkaline exchange resin and elute with 3M NaOH to get stronger solution of Mo. This can be preicipitates with H2SO4 or CaCl2.

Magpie - 28-10-2008 at 10:02

@chloric1:

I have an electric muffle furnace, and knives.com suggests that a dull red heat is ~650C. So I will try that.

I don't have any ion exchange resins. I see them on ebay but they seem too expensive, at least for this project.

What is this book on "inorganic preparations" that you are referring to?

chloric1 - 28-10-2008 at 17:27

Magpie-

the book I was refering to was this:

Ion exchangers; properties and applications. Edited by Andree Fe Coers.
by Dorfner, Konrad.
Ann Arbor, Mich.] Ann Arbor Science [1972]

A good read. It is introductory level and it opens up all the possibilities with ion exchangers.

By the way, for a little over $7, 500 grams of strongly acid cation exchanger is available on ebay here is the link to the item.

You should be able to use 6% bleach to cut volumes down and oxidize the thiosulfate with chlorine. Still will require significant 'boiling down" but you can add sulfuric acid to precipitate MoO3

[Edited on 10/28/2008 by chloric1]

Magpie - 28-10-2008 at 18:15

Thanks chloric1 for the reference and link. I'm just not ready to enter the world of ion echange just yet.

I did find a source of small iron vessels: Lodge cast ironware. They make a few mini-utensils that seem just right for my muffle furnace. I bought their tiny 3.5" frying pan today for $4. I burned off their pre-seasoning crap by subjecting the pan to 650C for a couple hours. It looks a lot better now:

iron pan.jpg - 52kB