The review focuses on the application of supercritical fluids as antisolvents in the pharmaceutical field and demonstrates the supercritical antisolvent method in the use of drug encapsulation. The main factors for choosing the solvent and biodegradable polymer to produce fine particles to ensure effective drug delivery are emphasized and the effect of polymer structure on drug encapsulation is illustrated. The review also demonstrates the drug release mechanism and polymeric controlled release system, and discusses the effects of the various conditions in the process, such as pressure, temperature, concentration, chemical compositions (organic solvents, drug, and biodegradable polymer), nozzle geometry, CO 2 flow rate, and the liquid phase flow rate on particle size and its distribution.

Kinetics of transesterification of palm-based methyl esters (POME) with trimethylolpropane (TMP) to polyol esters was investigated. A kinetic model of reaction was obtained by assuming a series of irreversible elementary reactions at various temperatures. The reaction rate constants were determined under limited conditions. The optimal ratios for k 2 /k 1 and k 3 /k 1 were 0.70-0.80 and 0.21-0.25, respectively. Both palm oil methyl esters (PPOME) and palm-kernel oil methyl esters (PKOME) were reacted with TMP by using sodium methoxide as catalyst. The POME-to-TMP molar ratio and catalyst weight percentage were held constant at 10:1 and 0.4%, respectively. The effects of temperature (70-110°C) and raw materials (PKOME and PPOME) were investigated and found to have a significant impact on the reaction kinetics. When using a large excess of POME and continual withdrawal of methanol via vacuum, the reaction reached completion in less than 20 min at 80°C. After removal of unreacted POME, the final product contained approximately 98 wt% triesters.

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A reliable, simultaneous analysis of palm oil polyol esters using capillary column GC is described. The polyol esters were esterified from palm oil methyl esters (POME) and palm kernel oil methyl esters (PKOME) with trimethylolpropane [2-ethyl-2-(hydroxymethyl)-1,3-propanediol; TMP] to produce the biodegradable base oil for lubricant production. Analysis was performed using a high-temperature capillary column, SGE HT5 operated at a temperature gradient of 6°C/min starting from 80 to 340°C. Before injection, the sample was derivatized with N,Obis(trimethylsilyl)trifluoroacetamide in ethyl acetate at 40°C for at least 10 min. This procedure provides a complete separation of reaction products: TMP, methyl esters, monoesters (ME), diesters (DE), and triesters (TE). As expected, the ME from palm kernel oil was resolved into five major peaks, DE into seven peaks, and TE into 10 peaks. Since no standard was available for this sample, the identities of the peaks were established by a secondary standard that was derived from pure methyl esters. This GC method has made possible the simultaneous determination of reaction product compositions in order to assess the extent of reaction.

Palm oil based trimethylolpropane (TMP) esters are potential biodegradable base stocks for environmentally friendly lubricants. To improve the low-temperature properties of palm oil based TMP esters, which are well below the requirements set by the lubricants' manufacturers, the high oleic content palm oil based TMP ester with a pour point between −10 and −32 °C was synthesized. The synthesis of palm oil polyol esters was performed by transesterification of fractionated palm oil methyl esters with TMP using sodium methoxide as a catalyst. Nearly complete conversion to palm TMP triesters (98% w/w) was obtained. The palm oil methyl esters were fractionated at 150−180 °C and 0.1 mbar prior to the synthesis to reduce the saturated fatty acid content. The fractionation and reaction took place using the same experimental setup. The effects of composition on pour points, viscosity, and viscosity index of the high oleic content palm oil based TMP esters were also evaluated. The concentration of C16:0 methyl ester in the starting material should be below 10% w/w to ensure that the pour points of high oleic content palm oil based TMP esters are below −30 °C. In addition, the reaction conversion to triester must also be maintained above 90% w/w to produce TMP esters with excellent pour points. Operating temperature had a negligible effect on the reaction yield so long as the temperature was kept above 120 °C. There were small variations in the viscosities and viscosity index values of high oleic content palm oil based TMP, in the region of 50 cSt and 199, respectively.