Dispersibility of CNTs in polar solvents can be increased by modifying them with polar functional groups (-OH, -COOH) through oxidation. 

Boiling point of tetradecane is ~ 250C, while for Ethanol it is ~78C. If you do mix tetradecane and ethanol, I think you could simply vaporise the ethanol by heating to ~80C though I am not sure of the effect this would have on the suspension of CNTs.

http://iopscience.iop.org/article/10.1088/0957-0233/18/12/005/meta

Use GUM ARABIC as a dispersing agent.

To make CNTs hydrophilic, oxidation is a good idea just as said in the first comment. Dispersion of the tubes also depends on their length. It is easier for shorter tubes. Wrapping the CNTs with Polyethylene glycol (PEG) will make them water soluble. There is a lot of literature about this.

Thank you guys for help. Anuj, I will check info on that gun arabic. Never seen any paper on this.

Hi Mihir, thanks for the paper. functionalized cnt would be a good choice. I will check what are commercially available. 

Thanks Carola, I found the peg funcationalized cnt. I will check to decide is best for me.

any form of carbon is insoluble in all solvents, it can only be dispersed - please note the difference.

You may try to disperse them in small amount of solvents similar to DMF then add tetradecane in larger amount.

here is the paper on GA used in dispersion of CNTs in aqueous solutions.

http://pubs.acs.org/doi/abs/10.1021/nl010065f 

It depends on what kind of application of Carbon Nanotubes you are looking for. And what kind of CNTs you are interested in, is that MWCNT or SWNT? does it matter if you have a mix of m-SWNT and sc-SWNTs or no you want to use pure sc-SWNT instead ... all of these gives you different approaches. 

functionalization of CNTs alters their optoelectronic properties that is important thing to recognize. Instead, non-covalent functionalization of CNTs is safe approach to use to disperse them in proper solvent. 

In this case, water as you said, you can use FMN molecules to disperse them CNTs in water, we have introduced this method in our group since 2008 (Plz see the link below). Tetradecane is hydrophobic similar to pristine CNTs, so I am positive there would be good interaction btw dispersed CNT by FMN in water with it, and as you said you can later on remove water by freeze-drying or air-drying (you dont want to apply heat to evaporate, can affect badly dispersion of CNTs) to get rid of water.

source:

"Selection of carbon nanotubes with specific chiralities using helical assemblies of flavin mononucleotide" Nature Nanotechnology, 2008.

http://www.nature.com/nnano/journal/v3/n6/full/nnano.2008.148.html

if you have difficulty to get it let me know. Good luck.

freeze-drying is of course a milder approach, but likely has also negative impact on dispersibility. Would expect that concentrating instead of full solvent removal and stepwise change of solvent composition can circumvent this.