Patent GB-799263-A (GB)
Title: Rapid directed interesterification of glycerides
IPC: C11C3/10
Filed: 1955-07-08
Abstract: A continuous or semi-continuous process for the low-temperature catalytic interesterification of mixtures of triglycerides which differ in their melting points, comprises (a) rapidly chilling a vigorously agitated flowing stream of the mixture, the time of chilling being no more than 1 minute, so that a cloud of extremely minute crystals forms in the agitated mixture; (b) effecting directed catalytic rearrangement in the rapidly chilled triglyceride mixture after the extraction of heat from the mixture has been discontinued; and (c) interrupting the interesterification <PICT:0799263/III/1> <PICT:0799263/III/2> process by inactivating the catalyst before the interesterification has gone to equilibrium.  The continuous process is illustrated by Fig. 1, in which melted lard is fed from storage tank 1 through heater 2, where its temperature is raised to about 330 DEG  F., to vacuum flash drier 3, in which the moisture content is reduced below 0.01 per cent.  The dried lard is then transferred by pump 4 to heat exchanger 5 in which the temperature is reduced to about 100 DEG  F.; thence it passes through pipe 6 to the catalyst dispersion mixer 9 (valve 7 being open and valve 40 closed) into which a dispersion of catalyst is fed from catalyst storage tank 8. The lard-catalyst dispersion is held for several minutes in tank 10 to allow time for the activation of the catalyst and is then drawn through line 11 by pump 13 (valve 12 being open and valve 43 closed) and passed through the scraped-wall freezer 14, which reduces its temperature to 70 DEG  F. so rapidly that there is an initial supercooling, quickly followed by the formation of a heavy cloud of minute solid fat crystals throughout the flowing mass.  The chilled mixture than passes slowly through one or more of the crystallizers 17a, 17b, 17c, each of which has mechanical stirring means and in which the bulk of the interesterification occurs.  The temperature of the mixture gradually rises, but the reaction is brought to an end before equilibrium is reached, by means of an aqueous catalyst deactivating agent, or an aqueous solution of phosphoric acid or monosodium orthophosphate, e.g. water introduced via 19 into mixer 20.  The mixture is quickly passed through heater 22 to melt the solid, and then through the degasifier 23 into surge tank 24. The mixture is then centrifuged in 25 and the "foots" run off, the processed lard passing to storage tank 27.  If desired, the catalyst may be preactivated before it is added to the lard, in which case the lard is rapidly chilled in 14 before the catalyst is added, valves 7 and 12 being closed, and valves 40 and 43 being open.  Also, the rapid chilling may be accomplished in more than one step, either by providing two or more freezers 14 in series, or by recycling a portion of the mixture leaving the freezer.  The semi-continuous process is illustrated by Fig. 4.  Lard from tank 301 and catalyst from tank 302 are passed successively into vessels 303a, 303b to form a dispersion.  The dispersion is drawn alternately from vessels 303a, 303b, and passed continuously through freezer 314 into one of a battery of independent batch crystallizers 317a, 317b, 317c whence, after a suitable reaction time, the batch is withdrawn, deactivated and separated as before. Suitable catalysts for use in the interestification process are sodium methoxide dissolved in methanol or suspended in xylene, or sodium tert.-butoxide suspended in xylene. If desired, the triglyceride mixture may be "prerandomized" while wholly in a liquid condition before chilling.  The deactivation of the catalyst is generally so arranged that the interesterification is ended when a quarter to a half of the saturated radicals are combined as trisaturates.  If desired the resulting product may be hydrogenated.  Although primarily directed towards the manufacture of shortening from lard, the process may be applied to vegetable, animal and marine oils and fats, or to blends with partially or fully hydrogenated oils.  Specifications 574,807, 590,737, 590,916, 604,136, 616,190, 632,089, 648,995, 653,521, 680,703, [both in Group I], and 799,264 and U.S.A.  Specification 1,783,864 are referred to.