Mesoporous Molecular Sieves Catalyzed Reaction Of Fatty Alcohol Ethoxylate

Ethoxylates are obtained by the addition of ethylene oxide to hydrophobic substrates having a labile hydrogen atom. The reaction is traditionally carried out in the presence of alkaline catalysts NaOH. Broad-range-distributed products are obtained, which contain significant amounts of homologues having very short and / or very long polyoxyethylene chains and of which the properties are far away from those having the optimized length of the hydrophilic chain. In recent years, a number of papers have shown that synthetic anionic clays and hydrotalcite, containing Mg and Al composite oxides, are efficient and selective catalysts for some base-catalyzed organic reactions, particularly the ethoxylation of fatty alcohols with a narrow distribution of molecular weight of the ethoxylated oligomers . In this paper, many kinds of mesoporous materials were synthesized and expected to allow the higher catalytic activity for oxyethylation of fatty alcohol and the more narrowed chain distribution of polyoxyethlene.1. The synthesis of mesoporous molecular sievesMesoporous MCM-41 molecular sieves containing aluminum and lanthanum ions(Al-La-MCM-41) with Si/(A1+La) ratio equal to 30 and only aluminum ions or only lanthanum with Si/Al or Si/La ratio equal to 10, 20 or 30, respectively, were synthesized under hydrothermal conditions using cetyltrimethylammonium bromide(CTAB)surfactants as template and ethyl silicate(TEOS) as silica source in ethylenediamine. Pure silica mesoporous molecular sieves MCM-41 and those containing aluminum (Al-MCM-41) or lanthanum (La-MCM-41) with si/Al(si/La) ratio equal to 30 and 80, respectively ,were synthesized under hydrothermal conditions using cetylpyridinium chloride(CPCl) surfactants and nonylphenolpolyoxyethylene ether(TX-100) as composite templates and ethyl silicate(TEOS) as silica source in chlorhydric acid.Mesoporous iron oxide with a hexagonal structure was synthesized using iron nitrate as the reagent and sodium dodecyl sulfate (SDS) as template in the presence of ethylenediamine. Cobalt oxide/dodecyl sulfate mesoporous material was synthesized by hydrothermal method with SDS as template and ethylenediamine as alkali medium. Mesoporous Al-Mg composite oxide with a hexagonal structure was synthesized using aluminium nitrate and magnesium nitrate as the reagents and sodium dodecyl sulfate (SDS) as template in the presence of ethylenediamine.2. The characterization of mesoporous molecular sievesThe mesoporous materials, La-Al-MCM-41, Al-MCM-41, La-MCM-41, mesoporous iron oxide ,Cobalt oxide/dodecyl sulfate mesoporous composite and mesoporous Al-Mg composite oxide were characterized using several techniques, e.g. powder X-ray diffraction (XRD), nitrogen adsorption-desorption measurements , Fourier transform-infra red spectroscopy (FT-IR) , and transmission electron microscopy (TEM)and NH₃ adsorption-desorption (NH₃-TPD). XRD and BET studies indicated that the calcined La-Al-MCM-41, Al-MCM-41, La-MCM-41 had the standard MCM-41 structure and ordered pore structure and highly specific surfacearea. The average pore diameter is about 2.6nm.Calcined mesoporous iron oxide had the standard hexagonal framework structure and 5.4 nm average pore diameter.The effects of different pH, contents of the surfactant and the reaction temperature on the crystalline structure of the cobalt oxide/dodecyl sulfate mesoporous material were investigated. The experimental results indicated that when Co:SDS:H2NCH2CH2NH2:H20(mol ratio) =1: 0. 8^l. 1:1. 2—2. 4:200, the material had the ordered cubic pore structure.XRD, nitrogen adsorption-desorption and TEM studies indicate that the mesoporous Al-Mg composite oxide has hexagonal framework structure and average pore diameter of 2.6nm. The specific surface area of mesoporous Al-Mg composite oxide is 280³00m2.g"' (BET). 3. The catalysis perfoumance for oxyethylation of fatty alcoholThe all samples were used in the ethyloxylation as catalysts .The results show that Al-MCM-41 has higher catalytic activity than La-MCM-41 microporous molecular sieves. Catalytic Performances of Al-MCM-41 Mesoporou molecular Sieve in oxyethylation of fatty alcohol were experimental investigated. The results showed Al-MCM-41 exhibited highly catalytic activity for oxyethylation of octanol and ethoxylates with narrow molecular distributed were formed. Increasing in the reaction temperature, initial pressure and amount of the Al-MCM-41 catalyst increased the reaction rate of ethylene oxide (EO) for oxyethylation of octanol. The distribution selectivity coefficient of octanol polyoxyethylene ether was 20 as the average degree of oxyethylation of EO was 5.5. The reaction rate constant of octanol and ethylene oxide is 0.035 min"1 under the reaction temperature 130 °C.The reaction rate constant of octanol and ethylene oxide is 0.035 min"1 under the reaction temperature 155 °C, reaction pressure of 0.55MPa and 5% mesoporous iron oxide. Narrow-range distributed ethoxylates were formed in the presence of mesoporous iron oxide catalyst based on its reaction pathway and stereospecific catalysis. The distribution selectivity coefficient of octanol polyoxyethylene ether was 21 while average degree of oxyethylation was equal to 6.5.The catalysis rate of the cobalt oxide/dodecyl sulfate mesoporous material is rapidly reduced with the oxyethylation of octanol although a short induction period. This attribute to the collapse of the mesoporous pore structure in reaction process. The distribution selectivity coefficient of octanol polyoxyethylene ether was 6.6 while average degree of oxyethylation was equal to 3.2³.4.Mesoporous Al-Mg composite oxide exhibits higher catalytic activity than Mg-Al hydrotalcite for oxyethylation of fatty alcohol. The reaction rate constant of octanol and ethylene oxide is 0.056 min"1 under the reaction temperature 170 °C, reaction pressure of 0.6MPa and 5% mesoporous Al-Mg composite oxide. Narrow-range distributed ethoxylates are formed in the presence of mesoporous Al-Mg composite oxide catalyst. The distribution selectivity coefficient (Cs) is 24 and 16.7, respectively,using mesoporous Al-Mg composite oxide and Mg-Alhydrotalcite as catalyst for oxyethylation of octanol when average adduct degree of ethoxylates is 6.4.