One-pot conversion of furfural to useful bio-products in the presence of a Sn,Al-containing zeolite beta catalyst prepared via post-synthesis routes

Abstract

Aiming at the valorisation of furfural (Fur) via sustainable routes based on process intensification and heterogeneous catalysis, the one-pot conversion of this renewable platform chemical to useful bio-products, namely furfuryl alkyl ethers (FEs), levulinate esters (LEs), levulinic acid (LA), angelica lactones (AnLs) and -valerolactone (GVL), was investigated using a single heterogeneous catalyst, in 2-butanol, at 120 ºC. Various chemical 2 reactions are involved in this process, which requires catalysts with active sites for acid and reduction chemistry. For this purpose, it was explored for the first time the catalytic potentialities of modified versions of zeolite beta containing Al and Sn sites prepared from commercially available nanocrystaline zeolite beta via post-synthesis partial dealumination followed by solid-state ion-exchange. The post-synthesis conditions influenced considerably the catalytic performances of these types of materials. The best-performing catalyst was (Sn) SSIE -beta1 with Si/(Al+Sn)=19 (Sn/Al=27.6), which led to total yield of bio-products of 83% at 86% Fur conversion, and exhibited steady catalytic performance for six consecutive runs. A systematic catalytic study using the prepared catalysts with different bio-products as substrates, together with the molecular level and microstructural characterisation of the materials, helped understand the effects of different material properties on the specific reaction pathways in the overall system. These studies led to mechanistic insights into the reaction network of Fur to the bio-products in alcohol media, upon which a kinetic model was developed for the first time. The superior performance of (Sn) SSIE -beta1 in various steps was related to the dealumination degree, dispersion and amount of Sn-sites, and acid properties.

Integrated reduction and acid-catalysed conversion of furfural in alcohol medium using Zr,Al-containing ordered micro/mesoporous silicates

“…The SEM images of (Zr) SSIE -beta and (ZrAl) SSIE -beta showed aggregates of small pseudospherical shaped crystallites (Figure 2), similar to that reported for the synthetic precursor materials H-beta and deAl-beta [46]. The elemental mappings showed fairly homogeneous metal dispersions; no particles of bulk zirconia or alumina were observed, which is consistent with the PXRD studies.…”

“…On the other hand, the PXRD patterns for (Zr) SSIE -beta and (ZrAl) SSIE -beta are similar to those reported for deAl-beta and H-beta, indicating that the crystalline structure was preserved during the modification treatments [46]. Bulk ZrO 2 exhibited characteristic reflections of the crystalline monoclinic phase (ICDD PDF4 + 2013 reference code no.…”

“…The Zr-and Al-containing beta materials were prepared from nanocrystalline NH 4 -beta, following similar protocols to those described in the literature [46,78], which involved (i) calcination of NH 4 -beta (550 ºC, 10 h) to give H-beta, (ii) partial dealumination of H-beta with HNO 3 (13 M aq., 100 ºC) to give deAl-beta (possessing a framework with vacant tetrahedral sites), (iii) solid-state ion-exchange (SSIE) to introduce the desired metal centers into the framework, and (iv) final calcination at 550 ºC in an air flow (20 mL min -1 ) for 3 h.…”

“…HNO 3 ) samples were the same as those reported in ref. [46] The material deAl-beta was subjected to SSIE for Zr, or Zr plus Al giving (Zr) SSIE -beta and (ZrAl) SSIE -beta, respectively. For (Zr) SSIE -beta, a solid mixture of zirconium(IV) acetylacetonate and deAl-beta (0.844 mmol Zr per gram of deAlbeta) was ground in an agate pestle and mortar at room temperature.…”

“…The micro reactors were modelled as perfectly stirred batch reactors, similar to that desacribed previously by our group [46]. The mass balance equations are given by:…”