Preparation Of Copper-based Hydrotalcite-like Compounds And Its Performance For Catalytic Synthesis Of γ-valerolactone

Hydrotalcite-like compounds are a variety of layered materials which are consist of thepositively charged metal hydroxide layers and interlayer anions, its structure is similarwith brucite （Mg （OH）₂）. Hydrotalcite-like compounds are made up of octahedron and havethe common edge to the form-layered compounds between layers together with hydrogenbonding. The combined metal oxide which comes from hydrotalcit calcinedprecursor has a small and well-distributed size, a larger surface area and a betterstability property, Which could be widely used in oxidation-reduction reaction. In thisexperment, Cu-Mg-Al hydrotalcite-like compounds （LDHs） have been prepared in whichhydrotalcite was used as precursor, then this Cu-Mg-Al hydrotalcite-like compounds is burnedin a muffle furnace at a certain temper-ature for a period of time to obtain thecorresponding mixed metal oxides. The resulted compound metal oxide throughhydrogenation can be transformed into the catalyst for the reaction of catalytic hydroge-nation of γ-valerolactone.In order to prepare a series of Cu-Mg-Al hydrotalcite-like compounds, Na₂CO₃/NaOH as precipitants were used and constant pH coprecipitation method was applied.Moreover, H₂-TPR, XRD, FT-IR, SEM, TG-DTG and activity evaluation methods wereemployed to detect the catalytic characteristics of hydrotalcite-like compounds.when the influence of M²⁺/M³⁺molar ratio, pH value, aging time, agingtemperature and Cu content etc was taken into consideration. From the experiment, it wasfound that these factors can significantly affect the crystal nucleation of hydrotalcite, growthand the crystal morphology generation. These results indicated that the suitable conditions ofpreparing hydrotalcite-like compounds by coprecipitation method were that the pH was about9-10, the molar ratio of M²⁺/M³⁺was about2-4, the molar ratio of Cu/Mg was about1-2, thereaction time was8h, the reaction temperature was65°C.When hydrotalcite-like compounds were used as precursors, throuth high temperaturecalcination in a muffle furnace in hydrogenation can result in the correspondinghydrogenation catalyst, the resulted could be used in the catalytic hydrogenation of levulinateto prepare γ-valerolactone. Considering the influence of the calcination temperature andhydrogen reduction temperature, and some other factors, the suitable conditions were asfollow: calcination temperature500°C, calcination time4h, the hydrogenation temperature350°C.When Cu-Mg-Al hydrotalcite-like compounds were exerted as catalysts, effects of various factors are included to detect in the hydrogenation of γ-valerolactone from levulinicacid, the suitabled conditions were as follow: at a temperature of140°C, the amount ofcatalyst was40%（relative to the mass fraction of levulinic acid）, hydrogen pressure of3.0MPa, the reaction time of150min and speed of500rpm.When active carbon was used as a carrier to preparation Ru/C catalyst, this Ru/C wasapplied as heterogeneous catalyst hydrogenation of methyl levulinate, the fresh and reusedcatalysts were characterized by TEM and XRD, the reaction pathway for the hydrogenation ofmethyl levulinate was proposed when the protic solvent was employed. Effects of variousfactors such as reaction temperature, reaction time, dosage of catalyst and solvent werediscussed. The suitable conditions of preparation of γ-valerolactone by hydrogenation ofmethyl levulinate were as follows: temperature190°C, reaction time150min, dosage ofcatalyst20.0%（based on the mass fraction of methyl levulinate）, pressure at3.0MPa, andabsolute methanol was used as the solvent. In the experiment, the selectivity ofγ-valerolactone was92.2%, and the productivity of γ-valerolactone was92.2%. Compared itsresults with that produced from the ruthenium carbon catalytic, the results showed thatCu-Mg-Al hydrotalcite derivatives with better catalytic performance in the stabilityandrecylingefficiency than that of Ru/C catalyst.