Research On Epoxidation And Hydroxylation Of Rubber Seed Oil And Its Application

With the development of the whole society, demands for the petroleum-based non-renewable resources increase day by day. In order to relieve the shortage of energy and meet environmental concerns, researchers have gradually paid more attentions to the chemical utilization of renewable resources. Vegetable oil, as an important renewable resource, has been used in many fields. A variety of chemical products prepared from vegetable oil had emerged into the market, although most of them were prepared from edible oils such as soybean oil (SBO), rapeseed oil, which had problems that fighting for food with human and fighting for fields with grain. Rubber seed oil (RSO) which obtained from rubber seed is one of the important vegetable oil. The utilization of rubber seed oil can avoid the above problems because it is inedible and by-product of rubber tree. At present, vegetable oil-based chemicals can be obtained by epoxidation for epoxy products and hydroxylation for polyols. However, some strong corrosion inorganic acids, such as sulfuric acid, were generally used as catalyst in the epoxidation process of vegetable oils. And these catalysts not only eroded equipment and pollute the environment, but also were difficult to be separated completely from products, which made the product post-treatment technology complex. In this paper, by using RSO as the raw material, a novel mesoporous molecular sieve Ti-MCM-41 was used as catalyst in the epoxidation process of RSO for production of epoxidized RSO (ERSO). And rubber seed oil based polyol (RSO-polyol) were prepared from the ERSO by hydroxylation method. All the processes could meet the demands for green, environment friendly.(1) The properties of RSO were tested and characterized by GC-MS (Gas Chromatography-Mass Spectrometry), FTIR (Fourier Translation Infrared Spectrum),*H MR(Nuclear Magnetic Resonance Spectrometry),13C NMR, DSC (Differential Scanning Calorimetry), TG (Thermogravimetric Analysis), etc. The fatty acid compositions and content of RSO had been compared with SBO. It was found that the fatty acid compositions of RSO with unsaturated fatty acid of 86.09% were similar to SBO. And the theoretical epoxy value of RSO could be up to 7.98%, which meant that the RSO could be a good raw material for preparing ERSO and RSO-polyol.(2) The mesoporous molecular sieve Ti-MCM-41 was prepared by dipping method. The optimum preparation conditions for the Ti-MCM-41 catalyst were obtained from epoxidation of oleic acid methyl ester. And the recyclability and regenerability of the catalyst were also tested. Results showed that the Ti-MCM-41 catalyst had a good catalytic performance in the epoxidation after thrice recycle and regeneration, which the epoxy value of epoxided oleic acid methyl ester was still more than 5%. FTIR、X-Ray Diffraction (XRD), N2Adsorption-Desorption Isotherms (BET) and Energy Dispersive X-Ray (EDAX) were employed to characterize Ti-MCM-41 catalyst. Results showed that with the increasing of the loading amount of Ti, the long-range order of MCM-41 was destroyed, while the specific surface area and pore volume were decreased, pore size was almost unchanged. Moreover, results of Transmission Electron Microscopy (TEM) analysis showed that the Ti-MCM-41 catalyst exhibited regular arrangements of the six party structure and parallel distribution with one-dimension. The pore and the skeleton was the alternate structure.(3) Epoxidation of RSO was carried out using the above green and heterogeneous Ti-MCM-41 as catalyst and the optimal conditions were obtained. It was found that with the increase of reaction time, reaction temperature and amount of catalyst, the epoxy value of ERSO increased firstly, then decreased. The optimal conditions for preparation of ERSO were reaction time of 5h, reaction temperature of 70℃, tert butyl hydrogen peroxide/RSO mole ratio of 4：1, titanium/RSO mole ratio of 0.05:1. Under this optimal conditions, ERSO could be obtained with the iodine value of 11.7g/100g, the epoxy value of 5.6%, average molecular weight of 929.93 g/mol, the conversion of double bond of 90%, and the relative epoxidation conversion of 80.9%. Compare with epoxidized soybean oil (ESBO) according to HG/T 4386-2012 industry standards, ERSO had the similar properties, while the epoxy value of ERSO was slightly lower and the iodine value was slightly higher. The GC-MS, FTIR and NMR analysis results of ERSO showed that epoxy group was formed after epoxidation reaction and its content in ERSO was around 70.39%. But it was also found that there still remained a small number of double bond and hydroxyl compounds in the ERSO. The DSC analysis results showed that the ERSO had a good low-temperature-resistance, which was better than RSO. The TG analysis results showed that there were two stages during the pyrolysis of ERSO, and the total weight loss could be up to 99.58%. However, the thermal stability of ERSO was lower than that of RSO.(4) Polyunsaturated fatty acids (PUFA) from RSO were obtained by using the method of urea complex fractionation. The optimum conditions for preparing the epoxy polyunsaturated fatty acids (EPUFA) were studied by using sulfuric acid as the catalyst and hydrogen peroxide as the oxygen source. The results showed that the epoxy value of EPUFA increased firstly and then decreased with the increase of hydrogen peroxide dosage, glacial acetic acid dosage, reaction time and reaction temperature. The optimum conditions for preparing EPUFA were: PUFA/hydrogen peroxide mass ratio of 1:2.5, PUFA/glacial acetic acid mass ratio of 1:0.9, the reaction time of 3h and reaction temperature of 65℃. Under this optimum conditions, the EPUFA could be obtained with the iodine value of 5.32 g/100g, acid value of 197.5 mgKOH/g, epoxy value of 8.28%. Even though the epoxy value of EPUFA was lower than the theoretical one. The FTIR analysis of PUFA showed that the epoxy groups were formed during the epoxidation of PUFA using sulfuric acid as the catalyst. But ring-opening reaction was happened at the same time. Due to the low yield of the polyunsaturated fatty acids with 38%-45%, EPUFA could not be used as the raw material for the preparation of polyols. So the ERSO catalyzed by Ti-MCM-41 was used to prepare RSO-polyol.(5) The hydroxylation reaction of ERSO was studied using fluorine boric acid as catalyst, methanol and isopropanol as the hydroxyl reagent. The optimum conditions for preparing RSO-polyol were obtained. The results showed that the hydroxyl value of RSO-polyol increased firstly then decreased with the reaction time, reaction temperature, the total amount of alcohols, the amount of catalyst, the mass ratio of methanol and isopropanol. The optimum preparation conditions were as follows:the reaction time of 30min, the reaction temperature of 70, the mass ratio of ERSO and the total amount of alcohols of 1:4, the mass ratio of fluorine boric acid/ERSO of 1:100, and the mass ratio of methanol/isopropanol was 1:3. Under the optimum conditions, the RSO-polyol could be obtained with acid value of 2.75 mgKOH/g, hydroxyl value of 348.2 mgKOH/g, average molecular weight of 991.82g/mol, moisture content of 0.093%, and the viscosity of 5634 mPa-s. FTIR and NMR analysis results showed that the epoxy group in ERSO had a ring-opening reaction to form hydroxyl compound. The DSC analysis showed that the low-temperature-resistance of RSO-polyol was better than that of RSO and ERSO. The TG analysis showed that there were three stages during the pyrolysis of RSO-polyol, and the total weight loss could be up to 81.32%. And the thermal stability of RSO-polyol was lower than that of RSO and ERSO.(6) The influences of RSO-polyol substitution amount on the properties of polyurethane (PU) foams were studied. The results showed that when the substitution amounts of RSO-polyol was less 20%, the apparent density and compressive strength of RSO-based PU (RSO-PU) foams could meet the requirements of Chinese national standard Ⅱ for rigid PU foams in applications of refrigerators and freezers. The FTIR analysis results showed that RSO-PU foams were prepared successfully with the substitution of glycerol by RSO-polyol. The TG analysis results showed that there are four stages during the pyrolysis of RSO-PU foams. The thermal stability of RSO-PU foams had been improved with the increasing of RSO-polyol substitution amounts. The SEM analysis results showed that when the substitution amounts of RSO-polyol were low, foaming was the main effect factor that made the foams with evenly, regular, meticulous structure, and excellent mechanical properties. With the increasing of the substitution amounts of RSO-polyol, plasticizing was the main effect factor that made the foams with big and non-homogeneous structure, and mechanical properties of the foams were decreased.The above results demonstrated that the mesoporous molecular sieves Ti-MCM-41 catalyst could be used in the epoxidation reaction of RSO to prepare ERSO which could further be use in the synthesis of RSO-polyol. Moreover, RSO-polyol was applied to prepare PU foams which had favorable mechanical and physical properties, and higher thermal stability. It could be achieved the aim of chemical products from renewable rubber seed oil resources to take the replace of petroleum chemical products.