Furfural refining

Stripping column 2 Dewatering column Figure 3.59 Flow diagram for furfural refining... 

In the manufacture of base oils, one of the refining operations is to extract with the aid of an appropriate solvent (furfural most often) the most aromatic fractions and the polar components. When free of solvent, the extracted aromatic fraction can eventually be refined, particularly to remove color or to thicken it, or still further, to fractionate it. The term, aromatic extract is used in every case. 

The principal direct appHcation of furfural is as a selective solvent. It is used for separating saturated from unsaturated compounds in petroleum refining, for the extractive distillation of butadiene and other hydrocarbons in the manufacture of synthetic mbber and for the production of... 

Lube oil solvent refining includes a collection of subprocesses improving the quality of lubricating oil stock. The raffinate or refined lube oils obtain improved viscosity, color, oxidation resistance, and temperature characteristics. A particular solvent is selected to obtain the desired quality raffinate. The solvents include furfural, phenol, sulfm dioxide, and propane. 

Uses. Solvent refining of lubricating oils, resins, and other organic materials as insecticide, fungicide, germicide an intermediate for tetrahydrofuran, furfural alcohol, phenolic and furan polymers... 

Furfural is used for making other derivatives of 5-membered rings, as a solvent In refining of lubricating oils, and to form copolymer resins with phenol... 

Time will show if there is need for desulfurization of high speed Diesel fuels. There is no doubt that many companies are actively studying desulfurization processes so as to be in a position to make the best choice. Of those for which published information is available for full scale operation, the most attractive seemed to be sulfur dioxide and furfural extraction, the latter having merit because it has successfully handled high sulfur catalytically cracked recycle stocks. The previously mentioned extraction process using anhydrous hydrogen fluoride also seems attractive because of the low treatment and high yield of refined product, but, until the results of commercial operation are fully known its merits cannot be established. 

Propane deasphalting is used extensively in the production of lubricating oils from residual stocks, and is almost always applied prior to selective solvent refining, where a single extraction solvent such as phenol or furfural is used. 

Furfural Process. A patent involving furfural for solvent extraction of lubricating oils was issued to Eichwald of the Royal Dutch Shell Co. in 1925 (10). The first commercial application of the furfural process was at the Lawrenceville, 111., refinery of the Indian Refining Co. in December 1933. 

Numerous process selection studies have led the author to the conclusion that for phenol, furfural, and Duosol processes, correlations of yield versus viscosity index (or any other measure of degree of refinement) will be identical. 

Solvent extraction has become the most widely used method of refining lubricating oils. Selective solvents which extract the less desirable constituents include phenol, furfural, dichloroethyl ether, mixtures of cresylic acid and propane, and liquid sulfur dioxide. Liquid propane precipitates asphaltic constituents and wax and retains the more desirable oil components in solution. Dewaxing may also be accomplished by other solvents such as mixtures of benzene and methyl ethyl ketone. 

Furfural is obtained commercially by mealing pentosan-rich ugricullural residues (corncobs, oat hulls, cottonseed hulls, hagasse. rice hulls) with a dilute acid and removing the furfural by steam distillation. Major industrial uses of furfuraldehyde include (1) the production of t urnns and tetrahydrofurans where the compound is an intermediate (2) Ihc solvent refining of petroleum and rosin products (3) the solvent binding of bonded phenolic products and (4) the extractive distillation of butadiene from other C4 hydrocarbons. 

Solvent extraction has found application for many years in the coal tar industry. Extraction of phenols from coal-tar distillates by washing with caustic soda solution can be considered such a process. In the isomer separation, a process for separation of m- and p-crcsol by dissociation extraction has been reported. Work is in progress in several parts of the world to use solvent extraction for the direct manufacture of chemicals from coal. Crude tall oil is a byproduct of pulp mills. It is refined by solvent extraction using propane or furfural. 

Pentoses contained in hemicellulose are used to produce furfural, a useful industrial chemical, used as a solvent for resins and waxes and in petrochemical refining. It is also used as a feedstock for a range of aromatic substances (it has an almond odour) including preservatives, disinfectants and herbicides. Furfural can be converted to furfuryl alcohol and used to make resins for composite applications with fibreglass and other fibres. These are of interest in the aircraft component and automotive brake sectors. Furfural is commercially derived from acid hydrolysis of waste agricultural by-products, such as sugarcane bagasse, com cobs and cereal brans. Around 450 000 tonnes is produced by this method per year. 

Most furfural is produced from corncobs and oat and rice hulls, primarily by the Quaker Oats Company. The product is used in the chemical industry as a solvent and in wood rosin refining. A large amount of furfural is treated further to give furfuryl alcohol. The furfuryl alcohol is added to urea-formaldehyde resins in applications for adhesives and foundry core binders. 

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