.. is made e.g. from corncobs, oat hulls and wheat bran and sugar cane bagasse. The name furfural comes from the Latin word furfur, meaning bran. Furfural is a viscous, colorless liquid that has a pleasant aromatic odor; upon exposure to air it turns dark brown or black. It boils at 162°C; it is soluble in ethanol and ether and somewhat soluble in water. It is one of the strongest solvents and has a flash point of 60°C. It’s risk profile is similar to dieseline/kerosene and is not dangerous to handle.

Ecoral™ is the DalinYebo label for furfural that is made in an environmental responsible manner, e.g. by using (award-winning[1]) technology developed and/or implemented by our subsidiary International Furan Technologies (Pty) Ltd (www.ift.co.za).

Furfural was first isolated in 1832 by the German chemist Johann Wolfgang Döbereiner[2], who formed a very small quantity of it as a by-product of formic acid synthesis. At the time, formic acid was formed by the distillation of dead ants, and Döbereiner’s ant bodies probably contained some plant matter.

Other milestones:
  In 1840, the Scottish chemist John Stenhouse found that the same chemical could be produced by distilling a wide variety of crop materials, including corn, oats, bran, and sawdust, with aqueous sulphuric acid, and he determined that this chemical had an empirical formula of C₄H₃OCHO.
 In 1845, English Chemist G. Fownes proposed the name “furfurol” (furfur – bran; oleum – oil). Later the suffix “ol” was changed to “al” because of the aldehyde function.
 In 1901, the German chemist Carl Harries deduced furfural’s structure.
  In 1922, the Quaker Oates factory at Cedar Rapids (Iowa, USA) started a small commercial furfural production of ±2.5 tons per day.
 From 1934 onwards, the industrial scale furfural production was established.
 In 1944 US Government built the Memphis ( Tennessee) plant to support war effort. Today, the Memphis facility no longer produces furfural, but is the home of the world’s largest furfural-based specialty and fine chemicals business (PennAkem, LLC).

Furfural is formed from pentosan[3], a five-carbon cellulose, which occurs prolifically in natural woody products such as oat hulls, corncobs, bagasse, wood chips and other vegetable waste. The reactions are simple. The acidified feedstock is heated, at 100°C the pentosan is hydrolyzed to pentose[4] (xylose) a soluble sugar which is dissolved in the water located within the feedstock particle.

Pentosan + n.Water

——————————-> Acid (Catalyst), 100°C

Pentose – (3 x Water)

——————————-> Acid (Catalyst), >175°C

Furfural

The stoichiometry of these two steps can be illustrated as follows:

(1) Hydrolysis of pentosan to pentose

Pentosan	+	n x Water	—>	n x Pentose
(C5H8O4)n	+	n x H2O	—>	n x C5H10O5
n x 132.114 kg	+	n x 18.016 kg	—>	n x 150.130 kg

(2) Dehydration of pentose to furfural

Pentose	–	3 x Water	—>	Furfural
C5H10O5	–	3 x H2O	—>	C5H4O2
150.130 kg	–	54.048 kg	—>	96.082 kg

(3) The overall reaction can therefore be summarized as

Pentosan	–	2 x Water	—>	Furfural
132.114 kg	–	36.032 kg	—>	96.082 kg

From this last step it is clear that the theoretical yield of furfural from pentosan in mass terms is

Given perfect conditions, 100 kg of pentosan would be converted to 72.73 kg of furfural. The actual yield of an industrial plant is often reported relative to this ideal yield. For example a plant with a yield of 60 % would produce

Reaction Kinetics

Under the conditions used in industrial processes the hydrolysis reaction from pentosan to pentose is extremely rapid and in practical terms for bagasse has little effect on the overall reaction rate. The dehydration of pentose to furfural was studied by Root et al[5] using pure pentose in sealed glass ampoules. Under these ideal conditions the rate of disappearance of xylose was found to be

where

[XY] is the xylose concentration (mole/liter)

 Figure 1 – The effect of acid concentration and temperature on xylose disappearance

t is the time (minute)

C_H is the initial hydrogen ion concentration (mole/liter)

T is the absolute temperature (Kelvin)

While this ideal situation does not fully describe the situation in an industrial reactor, it can be seen that the reaction rate is increased by increasing the acid concentration and by increasing the temperature. These effects are summarized in the graph below.

 

Loss Reactions

As soon as the furfural is formed, it is subject to loss reactions. There are two principal routes to losses. These are the resinification of furfural, where it reacts with itself to form polymers, and condensation reactions where furfural reacts with intermediates in the xylose to furfural reaction. There are two very important considerations with respect to these loss reactions. The first is that while they are accelerated by higher temperatures, the effect on their rates is significantly less than for the xylose to furfural reaction. The net effect of this is that if the reaction can be performed at a higher temperature the yield of furfural is improved. The second consideration is that the loss reactions can only occur in the liquid phase, so a general principle in increasing the furfural yield is to remove the furfural from the liquid phase as early as possible.

Characteristics/Properties

Furfural has unique physical and thermodynamic properties. They are presented in the table below and are compared against ethanol, a solvent which is rich in oxygen but does not incorporate the furan ring and benzene with no oxygen but a ring. The differences are self-evident. – Also refer to MSDS.

Properties	Furfural	Ethanol	Benzene
Formula	C4H3OCHO	CH3CH2OH	C6H6
Molecular weight	96	46	78
Density. (g/ml)	1.16	0.789	0.879
Oxygen content. %	33	35	0
Boiling Point. °C	161.7	78.3	80
Boiling point of azeotrope. °C	97.85	78	69.25
Freezing point °C	-36.5	-117.3	+5.5
Auto-ignition temperature, °C	392	422	498
Flash point. °C	60	12.7	-11
Solubility in water (g/100 ml water)	8.3	∞	0.082
Partial heat of solution in water. (cal/mole)	+2938 Highly endothermic	-1300 Exothermic. This value is for methanol.	Insoluble in water