Vapour-Phase Selective O-Methylation of Catechol with Methanol over Metal Phosphate Catalysts

Abstract

Guaiacol (2-methoxyphenol), an important fine chemical intermediate, is conventionally synthesized by liquid-phase processes with expensive, corrosive and toxic methylating agents such as dimethyl sulphate and dimethyl iodide. Recently, vapour-phase alkylation of catechol (1, 2-dihydroxybenzene) with methanol for the synthesis of guaiacol in the presence of heterogeneous catalysts has received more attention, as the route is economical and environmentally friendly. However, most of the investigated catalysts exhibited unsatisfactory catalytic performance for industrial applications. In this study, five metal phosphates M-P-O (M = La, Ce, Mg, Al, Zn) catalysts were synthesized and tested in the selective O-methylation of catechol with methanol. Among these catalysts, cerium phosphate (CP) showed the highest catalytic activity and guaiacol yield. Lanthanum phosphate (LP) was the second most active, which was still obviously better than magnesium phosphate (MP) and aluminium phosphate (ALP). Zinc phosphate (ZP) was not active in the reaction. Relevant samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), N2 adsorption-desorption, temperature programmed desorption of NH3 or CO2 (NH3-TPD, CO2-TPD). The suitable acid-base properties contribute to the superior catalytic performance of CP. Long-term stability and regeneration tests were also studied.

Hollow Structured Transition Metal Phosphates and Their Applications

“…However, the selectivity of guaiacol was less after the regeneration of cerium phosphate than initially. Moreover, the catalytic activity of transitional metal phosphate catalyst can also be studied by the acidity of the catalyst [107] . Iron doped manganese phosphate(Fe−Mn : P) synthesized through the hydrothermal method was used as a heterogeneous electrocatalyst for electrocatalytic oxygen evolution reaction (OER) (Figure 7).…”

“…Moreover, the catalytic activity of transitional metal phosphate catalyst can also be studied by the acidity of the catalyst. [107] Iron doped manganese phosphate(FeÀ Mn : P) synthesized through the hydrothermal method was used as a heterogeneous electrocatalyst for electrocatalytic oxygen evolution reaction (OER) (Figure 7). The efficiency was compared with nickel foam, IrO 2 (commercially available), and manganese phosphate in an alkaline solution.…”

One-Pot Synthesis of Al-P-O Catalysts and Their Catalytic Properties for O-Methylation of Catechol and Methanol

“…It has been widely believed that solid acid-base catalysts were active catalysts for O-methylation of catechol and methanol. Lots of solid acidbase catalysts, such as supported catalysts [13,17,21], molecular sieve-based catalysts [22], phosphate catalysts [16,[23][24][25][26][27], Mg-Al hydrotalcites catalysts [18], and oxide or mixed oxide catalysts [14,[28][29][30] exhibit catalytic performance for vapour-phase selective Omethylation of catechol and methanol. Among various solid acid-base catalysts, phosphate catalysts, especially aluminophosphates, have been widely used for vapour-phase selective O-methylation of catechol and methanol because of their high activity and low cost.…”

High Catalytic Performance and Sustainability of Zr Modified Aluminophosphate for Vapor-Phase Selective O-Methylation of Catechol with Methanol

“…Several heterogeneous catalysts have been reported to be active in vapor-phase Omethylation of catechol and methanol, including pure and doped metal oxides [6][7][8], supported tungsten compound [9] and metal phosphates [10][11][12][13][14][15][16], etc. Amorphous aluminophosphates, which possess both acid and base sites, are considered effective catalysts for vapor-phase O-methylation of catechol with methanol [12][13][14][15][16].…”

“…Several heterogeneous catalysts have been reported to be active in vapor-phase Omethylation of catechol and methanol, including pure and doped metal oxides [6][7][8], supported tungsten compound [9] and metal phosphates [10][11][12][13][14][15][16], etc. Amorphous aluminophosphates, which possess both acid and base sites, are considered effective catalysts for vapor-phase O-methylation of catechol with methanol [12][13][14][15][16]. The physicochemical properties of aluminophosphate have been reported to depend on modifying catalyst with various metals, optimizing catalyst compositions, and improving catalyst preparation routes [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30].…”