Peculiar behavior of MWW materials in aldol condensation of furfural and acetone

Abstract

MWW family of different structural types (MCM-22, MCM-49, MCM-56 and MCM-36) was used as catalysts for aldol condensation of furfural and acetone studied in a batch reactor at 100 °C, autogenous pressure and a reaction time of 0-4 h. To establish a relation between physico-chemical and catalytic properties of microporous materials, the samples were characterized by XRD, SEM, N2 adsorption, FTIR and TGA. It was found that the acidic solids possessed appreciable activity in the reaction and resulted in the formation of products of aldehyde-ketone interaction. Surprisingly, MCM-22 and MCM-49, i.e. three-dimensional materials containing internal supercages, exhibited higher activity than two MCM-36 catalysts with two-dimensional character having larger accessible external surface area due to expansion of the interlayer space by swelling and pillaring treatments. Moreover, all MWW family catalysts gave higher conversion than the large-pore zeolite BEA. Nevertheless, furfural conversion decreased rapidly for all the studied materials due to coke formation. Unexpectedly, the deactivation was found to be more severe for MCM-36 catalysts than for MCM-22 and MCM-49, which was attributed to the reaction taking place also in supercages that are protected by 10-ring channels from severe coking. In contrast the cups located on the external surface were coked rapidly.

Furfural: a renewable and versatile platform molecule for the synthesis of chemicals and fuels

“…306 Other authors have explored other catalysts including N-substituted Na-Y; 316 Co-Al spinels; 317,318 mixed oxides such as Mg-Al, [319][320][321] Ca-Zr, 322 WO 3 -ZrO 2 , 323 other MgO-ZrO 2 species, 322,[324][325][326][327] supported Mg-Zr oxides on graphite 328 or MgO/Na-Y, 329 dolomites 330 , chitosan, 331 and zeolites. 332,333 For prospective industrial applications of these catalysts, it is of paramount importance to address the stability of the solids in the reaction medium along with the activity. Most of the studies compiled in Table 8 refer to the deposition of heavy species as the main cause of deactivation.…”

From 3D to 2D zeolite catalytic materials

“…Owing to their enhanced external surface areas compared to conventional zeolites, two-dimensional zeolites are considered more appropriate catalysts for aldol condensation reactions involving bulky compounds, as they occur in primary pyrolysis vapours from biomass. Kikhtyanin et al 380 explored a variety of layered zeolites belonging to the MWW family in aldol condensation of furfural and acetone. A batch reactor operating at 100 1C under autogenous pressure was employed and their activity was compared with that of Beta zeolites.…”

Layer like porous materials with hierarchical structure

“…Rodrigues et al 299 and Kikhtyanin et al 300 studied the formation of coke in the comparative studies of MCM-22, pillared MCM-36 and delaminated ITQ-2. In both studies it was found that the hierarchization of the structure prevented excessive coke formation and the catalyst life-time was substantially increased.…”