Selective Synthesis Of Ethylene Glycol Monoethyl Ether Over MgAl(Fe) Mixed Oxide Catalysts

Ethylene glycol monoethyl ether (EGME), as a kind of nonionic surfactants, is widely used in washing, paints, leather, etc. It is synthesized via the ethoxylation of alcohols and ethylene oxide (EO). Traditionally, EGME is synthesized in intermittent tank reactor and the reaction is catalyzed by strong alkaline catalysts, such as NaOH, KOH or NaOCH3. In this homogeneous ethoxylation, the distributions of oxyethylene units in the ethoxylated product mixture are much broader due to the primary product can’t be out of system. And it also poses engineering problems (eg. separation, recycling, and corrosion). So, much attention has been focused on the synthesis of the oxyethylation with narrower molecular weight distribution using various solid catalysts.In this work, the hydrotalcites as precursors were synthesized and used to prepare the catalyst of mixed metal oxides (MMOs) for oxyethylation reaction of ethanol with EO in a fixed bed reactor. The structural and pysico-chemical properties of the catalysts were characterized by XRD, FT-IR, TGA, SEM and CO2-TPD. The influences of hydrotalcite types, synthesis conditions, calcination temperature, Mg/Al ratio and the loading amount of Fe ion on the catalytic performance were investigated. And the catalytic stability of the best catalyst was investigated. The main results are shown as follows:(1) Three types of hydrotalcite of Mg/Al, Zn/Al and Cu/Cr were synthesized and were used to prepare the MMOs catalysts. Among them, Mg/Al hydrotalcite possesses a best purity and crystallinity and the MMOs prepared at500℃for4h shows the best catalytic activity, with EO conversion of62.2%and EGME selectivity of91.7%.(2) Synthesis conditions of the hydrotalcite precursor greatly influence the structure and properties of MMOs, especially the pH of the solution in the aging process. In additions, the calcination temperature of hydrotalcite has an effect on the catalytic activity. The higher the calcination temperature, the higher catalytic activity was. The appropriate pH value and calcination temperature are11and500℃, respectively.(3) The Mg/Al ratio and Fe loading in hydrotalcite precursor influence the surface basicity and catalytic performance of MMOs. The amounts of strong basic sites are conducive to increase the activity of MMOs catalyst, especially the conversion of EO.(4) The best catalytic results were obtained over the catalyst of Mg/Al/Fe=10/5/0.76 prepared at500℃for4h, with EO conversion of81.5%for38h. Carbon deposition maybe lead to the deactivation and roasting recovery method can reproduce the hydrotalcite. Moreover, the crystallinity of hydrotalcite and stability of the MMOs catalyst could full recovery after regenerated. The catalyst can be reused, so it has a very good application prospect.