Tek-Tips is the largest IT community on the Internet today!

Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!

Register Log in
  • Congratulations TugboatEng on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Biodiesel Physical and Chemical Reaction 1

Status
Not open for further replies.
ddkm

ddkm

Chemical
Joined
Nov 9, 2005
Messages
94
Location
MY
Recently, there is a trend towards more usage of biodiesel as alternative fuels in place of (or as a mixture to) the traditional petroleum diesels. With petroleum diesel, the reaction going on in the engine is some form of "burning" under high pressure (compression) and temperature. This burning creates gases which expand and provide the power stroke required to move the vehicle/engine.

What about biodiesel? As far as I know, biodiesel is very simply a form of methyl ester (or fatty acid methyl esters). When used in the diesel engine, what is happening on a molecular level? Chemically and physically, what change is the ester going through/.

---engineering your life---
 
Sort by date Sort by votes
In first approximation any combustible liquid or solid
can be used as fuel in an IC engine

1.) if it can be finelly dsitributed so it burns fast enough
2.) if the products of combustion can be easily removed
3.) if it doesn't cause too much corrosion or erosion

The rest is engineering and economics

Plesae read FAQ240-1032
My WEB: <
 
Upvote 0 Downvote
25362, thanks for the links. But I had already checked Wiki earlier and they don't mention about how the biodiesel itself is being reacted/converted to produce the power. They focus more on the manufacture of biodiesel. And the other link you provided only talks about the experiments and emissions/performance etc.

I'm looking more at what happens at a molecular level when you put the biodiesel into a diesel car/engine (not during manufacture, I already know that part). Physically and chemically, what happens to the biodiesel methyl ester?

---engineering your life---
 
Upvote 0 Downvote
ddkm - biodiesel just burns in the diesel engine. Are you wondering why it is better than petroleum diesel. The answer lies in what happens to the carbon outside of the engine (the carbon cycle). I hope this helps the discussion.

HAZOP at
 
Upvote 0 Downvote
owg, in a way, I'm also wondering why the biodiesel can burn better. What are the similar chemical structures between biodiesel and its petroleum cousin?

Also, could you elaborate more what happens to the carbon outside of the engine? Thanks.

---engineering your life---
 
Upvote 0 Downvote

Apparently the oxygen in the ester molecule faciltates combustion.
 
Upvote 0 Downvote
Petroleum diesel ignites more slowly (see first link of 25362's above) and burns less completely due to the presence of polycyclic aromatic hydrocarbons (PAHs) [co-joined benzene rings]. These are complex structures requiring complex, stepwise bond breaking during combustion.

Many of the emissions in diesel smoke (aldehydes, benzene and VOCs) are the result of incomplete combustion of PAHs. The lower molecular weight compounds initially present in the fuel actually burn rather cleanly.
"Technical Report No. 1: Toxic Emissions from Diesel Vehicles in Australia"

There are already EPA restrictions on aromatic content of diesel fuel in California & Texas (maybe nationwide, soon?) and overseas. As sulfur content is mostly attached to the PAHs, the new EPA restriction on sulfur content in diesel (15 ppm) effective Oct. 15, 2006 (already in California), I believe will also lower the PAH content. Although PAHs have a high energy content due to higher C-to-H ratio than say alkanes, energy is wasted if combustion is incomplete.

"Lower Sulphur Diesel - What Does This Mean?"

"Effects of Fuels with a Low Aromatic Content on Diesel Engine Exhaust Emissions" [abstract only w/o subscription]
It mentions that "Oxygenated fuels showed lower smoke and NOx emissions."
 
Upvote 0 Downvote
We are trying to epoxidize a biodiesel or methyl ester from soybean oil in order to get a sort of plasticizer to be ued for PVC compounding.Any experience and/or comments?
 
Upvote 0 Downvote
No reply as yet on my question on Epoxidized methyl esters(biodiesel)Am trying to contact someone who had done some work on this.Is it possible?
 
Upvote 0 Downvote
Suggest starting a new thread -- this one deals with combustion reactions of biodiesel.
Good luck.
 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

ReemaK
  • Locked
  • Question Question
h2s scrubbing from a mixture of h2s and nh3
Replies
10
Views
2K
ReemaK
ReemaK
processendbd
  • Locked
  • Question Question
Le Chatelier Principle And Lhhw Reaction Kinetics Related?
Replies
1
Views
766
Latexman
Latexman
shvet
  • Locked
  • Question Question
Process and reactors scaling
Replies
3
Views
1K
pierreick
pierreick
Phani Y
  • Locked
  • Question Question
Reaction Enthalpy for CO2 and MDEA
Replies
0
Views
192
Phani Y
Phani Y
Sawsan311
  • Locked
  • Question Question
Operating Fixed Speed and Variable Speed pumps in Parallel
Replies
7
Views
768
LittleInch
LittleInch

Part and Inventory Search

Sponsor

Back
Top