FurfuralSince 1922, Furfural has been and still is the primary building block of furan chemistry.
Furfural (fûr’fərəl) or furfuraldehyde (fûr’fərăl’dəhīd) is an industrial chemical derived from a variety of lignocellulosic biomass such as forest residues or agricultural by-products, i.e. its origin is non-food or non-coal/oil based.
Furfural is the primary building block of furan chemistry, which offers alternatives for the many chemicals, polymers and plastics currently made from oil, coal or gas .
Furfural (“FF”) is an intermediate chemical used in the refining of lubricant oils and rosins. It is also used as herbicides, fungicides, soil fumigants, and as a building block in the production of Lycra® (PolyTHF).
Furfural, as well as its derivative furfuryl alcohol (“FA”), can be used either by itself or together with phenol, acetone, or urea to make resins. Such resins are used in the manufacture of casting moulds, fiberglass, some aircraft components, and automotive brake linings.
Besides the conversion into FA, FF is used as an extractive solvent, motor car fuel, wax recovery, lubricant, adhesive.
By-products are used for flavours:
Since 2003, new applications for the use of furfural have been developed in the bio-fuels, wood treatment, bio-plastics and agricultural sectors. These uses are further descried on the furfural markets pages.
Furfural was first isolated in 1832 by the German chemist Johann Wolfgang Döbereiner, 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.
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).
|Pentosan + n.Water||——————————->
Acid (Catalyst), 100°C
|Pentose – (3 x Water)||——————————->
Acid (Catalyst), >175°C
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
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 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)
t is the time (minute)
CH 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.
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.
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.
|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.
Exothermic. This value is for methanol.
|Insoluble in water|
Dr. Karl Zeitsch emphasized that furfural is a unique chemical and used these anomalies as the foundation for his SupraYield® patents.
While many of the physical properties of furfural are important in the detailed design of industrial plants, there are a few unusual properties which have a major impact on the design principles. Since its inception, DalinYebo has dedicated its time and resources in order to research and understand those properties and how they impact on the design of new processes or how old processes could be optimised.
 The DalinYebo Team of J. Buzzard, B. McKeon and P. Steiner, together with Professor D. Arnold (University if KwaZulu Natal) was awarded the South African Institute of Chemical Engineering (SAIChE) Gold medal in 2004 for the development of the novel SupraYield® technology.
 Referenced by Dr. K.J. Zeitsch (3 Jun 1928 – 12 Sep 2001; BSc. Eng (Chem), Doctorate in Technical Chemistry; Author of technical papers; Inventor; Holder of many patents.) in “The Chemistry and Technology of Furfural and its many By-products”, Elsevier, 2000.
Furfural and its many By-products
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