*Article* **Selective Conversion of Glucose to 5-Hydroxymethylfurfural by Using L-Type Zeolites with Di** ff**erent Morphologies**

### **María José Ginés-Molina 1,**†**, Nur Hidayahni Ahmad 2,**†**, Sandra Mérida-Morales 1,**†**, Cristina García-Sancho 1, Svetlana Mintova 3, Ng Eng-Poh 2,\* and Pedro Maireles-Torres 1,\***



Received: 25 November 2019; Accepted: 13 December 2019; Published: 16 December 2019

**Abstract:** In the present work, the morphology of L-type zeolite (LTL topology) has been modified in order to evaluate the influence of several protonated-form LTL-zeolites with di fferent morphologies on their stability and catalytic performance in the conversion of glucose into 5-hydroxymethylfurfural (5-HMF). Physico-chemical characterization of the LTL-based catalysts has revealed that the three types of morphologies (needle, short rod and cylinder) are active, providing complete glucose conversion and high 5-HMF yield values. The addition of CaCl2 had a positive influence on the catalytic performance. It was found that morphology influences the textural and acid properties of LTL-zeolites, and hence their catalytic performance. The best catalytic results have been obtained with the NEEDLE-LTL, showing nanoparticles with a length of 4.46 μm and a width of 0.63 μm, which attains a 5-HMF yield of 63%, at 175 ◦C after 90 min of reaction, and a glucose conversion of 88%. The reusability study has revealed a progressive decrease in 5-HMF yield after each catalytic cycle. Di fferent regeneration methods have been essayed without recovering the initial catalytic activity. The presence of organic molecules in micropores has been demonstrated by TG analysis, which are di fficult to remove even after a regeneration process at 550 ◦C.

**Keywords:** biomass; glucose; 5-hydroxymethylfurfural; LTL-zeolites; heterogeneous catalysis
