Carbon-Carbon Bond Forming Reactions Over Metal Oxide Catalysts

Abstract

Alcohol coupling, also known as the Guerbet reaction, is a potentially important process to increase the value of short chain alcohols. Metal oxides, metal phosphates and supported transition metals like copper are some examples of heterogeneous catalysts for the reaction.However, the wide variety of catalyst compositions, reaction conditions, and reactor configurations used to study the reaction complicates a direct comparison of various catalysts.Herein, rates over different catalysts will be compared. One existing gap in the current literature is a thorough comparison of the surface acid and base properties of catalysts employed in the Guerbet coupling of alcohols. In this work, various bifunctional materials were synthesized, characterized, and used in Guerbet alcohol coupling and other probe reactions of acid and base catalysts.One well-studied reaction catalyzed by acids and bases is transesterification. Two series of Mg:Zr mixed oxides, prepared by either co-precipitation or sol-gel synthesis, were characterized and evaluated in the base-catalyzed transesterification of tributyrin with methanol.A co-precipitated Mg-rich mixed oxide catalyst with Mg:Zr 11:1 was approximately 300% more active than MgO on a surface area basis, whereas pure ZrO 2 was inactive for the reaction. To explore the nature of the activity enhancement, samples were characterized by X-ray diffraction, N 2 adsorption, CO 2 adsorption microcalorimetry and DRIFTS of adsorbed CO 2 and CH 3 OH.Although the sol-gel synthesis method provided better atomic-level mixing of Mg and Zr, the resulting catalysts were not as effective as mixed oxides prepared by co-precipitation. The most active mixed oxide (Mg:Zr 11:1) exhibited a high initial heat of CO 2 adsorption and modified modes of methanol adsorption compared to MgO. However, the CO 2 adsorption capacity did not correlate to catalyst activity.

The Production of Isophorone

“…The conversion, selectivity, and yield for the catalysts mentioned in Section 5.2 are summarized in Table 3. In addition to the 47 literature results presented in this review, many other studies have been conducted [243][244][245][246][247][248][249][250][251][252][253][254][255][256][257][258][259] and many other patents have been published [260][261][262][263][264][265][266][267][268][269].…”