Preparation, Properties And Applications Of Isostearic Acid

Isostearic acid is used as a chemical raw material widely, with the characteristics of low melting point, strong antioxidant capacity. And the market demand is super. Nowdays, isostearic acid in industry mainly obtained from by-products of dimer acid, which is complicated, difficult to purify and low yield. So it is hard to meet domestic demand. Besides, the research of isostearic acid at home and abroad had mainly focused on the selection and preparation of catalysts. The better effect is acquired in zeolite-catalyzed isomerization of high pure oleic acid to branched-chain isomers. But high standard raw material and lower selectivity made it difficult to realize industrialization. In this paper, isostearic acids was prepared by isomerization and hydrogenation of industrial oleic acid and H-Ferrierite zeolite is used as the catalyst of isomerization. The study involved the synthesis and isolation of isostearic acid, the process optimization of tri-isostearin’s preparation, the reuse and regeneration of H-Ferrierite zeolite and the acid value, viscosity, refrative etc. of isostearic acid and three esters.Isostearic acids was prepared by isomerization and then hydrogenation of industrial oleic acid with acidified ferrierite zeolite as isomerization catalyst. The conversion of oleic acid and yield of isostearic acids as standard, base additive kinds and its amount, co-solvent kinds and its amount, catalyst amount, reaction time and temperature were investigated by single factor experiments and with yield of isostearic as response values, key affecting factor were optimized by response surface methodology. The results showed that the optimal isomerization conditions were obtained as follows: TPP amount 8 wt% of catalytic, water addition 3.3 wt% of oleic acid, catalytic amount 5.3 wt% of oleic acid, reaction time 6.8 h, reaction temperature 273.5 ℃; the yield of isostearic acids reached 81.92% under the optimal condions.Crude isosteatic acid was separated into monomer acid and oligomer by reducing pressure distillation. The components in the monomer acid were determined by GC and identified by GC-MS. And oligomer was indentified by MS. The results demonstrated that Crude isosteatic acid mainly contains the decarboxylation of saturated fatty acid, palmitic acid, isostearic acid, stearic acid, hydroxystearate, γ-stearolactone and dimer acidThe influences of catalystic amount, hydrogen pressure, temperature, time and stirring speed on the hydrogenation reaction of iso-oleic acid were investigated by using Ni/C as catalyst. The result revealed that the iodine value of isostearic acid could be dropped to 3.18 g I2/(100g) when the reaction was carried out at 1 wt% catalyst dosage(with respect to iso-oleic acid), hydrogen pressure of 4 MPa and a temperature of 220 ℃ after 4 h.The recycled and regeneration of zeolite were discussed. The structure and performance of regenerated catalyst were characterized by Fourier transform infrared spectroscopy(FTIR), Scanning electron microscope(SEM), X-ray diffraction(XRD) and Thermogravimetric analyzer(TGA). the outcome showed that the reused catalysts were ineffective. The acidity and activity of catalyst was reduced with the increase of recycling frequency. The zeolite catalyst was recyclable and reused up to 10 times. Ferrierite own strong acid-proof and thermal-proof, multiple acidification could not damage the structure of the catalyst. With the increase of catalyst regeneration frequency, the number of organics which were adsorpted on the surface of catalyst increased, the activity of catalyst decreased. but the activity of catalyst could be recovered when the organics on the surface of catalyst were removed by calcining.Low temperature crystallization was used to extract isostearic acid from crud isostearic acid, and the effects of solvent and its amount, crystallization temperature and time on The separation of isostearic acid were investigated, and isostearic acid was further purified by using vacuum distillation. Isostearic acid was further identified by FTIR, TGA, and Nuclear magnetic resonance hydrogen spectrum(1H NMR), and isostearic acid value, iodine value, saponification value, viscosity and other physical properties were determined. the isostearic acid yield of 90.42% and isostearic acid content of 88.74% were obtained under the optimal condition(hexane as solvent, solvent radio 2.3:1,-9.5 ℃ for 11.4 h). The purity of isostearic acid could reach 96.48% under the vacuum distillation. The acid value of purified product was 196.53, Iodine value was 4.24, Saponification value was 198.72, Viscosity index was 306, Refractive index was 1.448, and Pour point was 0 ℃.The acidic catalyst H-MMT was prepared at the optimum conditions and used to produce tri-isostearin. The effects of acid / methanol molar ratio, catalyst dosage, reaction time and temperature were also investigated. The esterification rate was over 95% under the conditions of acid / methanol molar ratio 5~5.5:1, catalyst dosage 1%(based on the isostearic acid mass), reaction time 6~7 h and reaction temperature 180℃. The thermal stability、pour point and viscosity-temperature of trimethylolpropane which prepared in this paper achieve the ideal standard. And experiments revealed that tri-isostearin had high thermal stability and its decomposition temperature is 320℃, and viscosity is 143. The Acid value of purified product was 2.46 mgKOH/g, Hydroxyl value was 14.34, Saponification value was 178.72 mgKOH/g, Refractive index was 1.468(25 ℃) and Pour point was-20 ℃.