Effects of vanadium supported on ZrO 2 and sulfolane on the synthesis of phenol by hydroxylation of benzene with oxygen
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Catalysis Letters Vol. 102, Nos. 3–4, August 2005 (Ó 2005) DOI: 10.1007/s10562-005-5846-6
Effects of vanadium supported on ZrO2 and sulfolane on the synthesis of phenol by hydroxylation of benzene with oxygen and acetic acid on palladium catalyst Kazuhisa Murata*, Ryu Yanyong, and Megumu Inaba Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology, AIST Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8565 Japan
Received 22 February 2005; accepted 18 March 2005
The catalyst system consisting of Pd, transition metal-modified ZrO2 and acetic acid was found to catalyze the hydroxylation of benzene with molecular oxygen without hydrogen and phenol was formed. Of transition metals employed, only vanadium additive was found to be effective for improving the rate of phenol formation as well as the selectivity, while any other transition metals such as iron, molybdenym, tungsten and yttrium were not promotive. Support effects on vanadium were in the order: V/ZrO2> V/ Al2O3> V/SiO2. The highest rate of phenol formation was obtained at 0.5wt%V/ZrO2 catalyst. Phenol selectivity was dramatically improved by the addition of sulfolane, while benzene conversion and STY of phenol formation decreased. It is assumed that Pd(II) and Pd(IV) intermediates derived from acetic acid, oxygen and palladium acetate could play an important role in hydroxylation of benzene. KEY WORDS: hydroxylation; benzene; phenol; Vanadium-modified Palladium; Acetic acid-Sulfolane solvent.
1. Introduction Phenol is one of the most important intermediates of the chemical industry and mainly produced by the cumene process, which coproduced acetone in 1:1 molar ratio with respect to phenol [1]. Thus, the cost of phenol is directly concerned with the effective usage of acetone. New processes to produce phenol without acetone and with high selectivity have been explored [2, 3]. In these processes, reducing agents such as H2, CO are important for activation of oxygen. The use of oxygen and hydrogen gave phenol on Cu–Pd/SiO2 catalyst [2], over palladium-containing titanium silicates [4], and over Pt/ Pd-contg. acid resins [5]. Jintoku et al. [3] reported a homogeneous catalyst composed of palladium acetate and phenanthroline in the presence of oxygen and carbon monoxide at 180 °C. Pd(II)-heteropoly acid redox system has been reported in the presence of O2– H2O–AcOH, in which the oxidation of benzene with Pd(II) occurred to form oxidation products and Pd(0), accompanied by reoxidation into Pd(II) by reaction with heteropoly acids [6]. In this case, the role of AcOH is not clear. In a previous paper [7], we reported direct epoxidation of propylene with oxygen and MeOH with Pd(0) and porous oxide, where MeOH is sacrificial reductant. Miyake et al. have reported vanadium effect on the reaction with oxygen/hydrogen on platinum catalyst [8]. Furthermore, Balducci et al. have reported that sulfolane solvent is effective for improving phenol selectivity * To whom correspondence should be addressed.
on oxidation of benzene
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