Reaction Route Selection for Cellulose Hydrogenolysis into C2/C3 Glycols by ZnO-Modified Ni-W/\u03b2-zeolite Catalysts

Minyan Gu,Long Yang,Bo-Yu Peng,Yalei Zhang,Wenjie Dong,Zheng Shen,Wei Zhang,Ling Kong

doi:10.1038/s41598-019-48103-6

Abstract

A β-zeolite-supported nickel and tungsten catalyst (Ni-W/β) was employed to generate C2/C3 glycols (ethylene and propylene glycols) in a satisfactory yield from cellulose. After optimizing the acidity of the support, the Ni-W synergy and the co-catalyst, the yield of C2/C3 glycols reached 70.1% (C %), with propylene glycol accounting for 51.1% of the product. This performance was attributed to the effective control of the major reaction steps, namely, hydrolysis, isomerization, retro-aldol condensation and hydrogenation, by the tailored Ni-W-ZnO/β catalyst. The characterization and reaction results indicated that the cellulose hydrolysis step was promoted by the appropriate acidic sites of the β-zeolite, and the reaction routes to C2/C3 glycols were influenced by the mass loading of Ni-W through the synergy of nickel and tungsten oxide, in which Ni is effective in the hydrogenation while W facilitates bond cleavage via a retro-aldol condensation (C6 to C2/C3). Moreover, with the leaching of metal during four cycles of reuse, the catalytic performance was also influenced by the synergy of Ni and W. In addition, the isomerization of glucose to fructose was promoted by ZnO and afforded a high yield of propylene glycol.

Highlights

With diminishing fossil resources and increasing environmental concerns worldwide, searching for alternative fuels has attracted great interest in recent years
The cellulose conversions obtained with SnOx-modified Pt/Al2O3 and Ni/Al2O3 catalysts remained below 23% (C%), which was attributed to the fact that these catalysts cannot facilitate cellulose hydrolysis
To promote the selective transformation of cellulose into C2/C3 glycols and increase the proportion of C3 glycol in the glycol products, we attempted to control the synergy of the retro-aldol condensation, hydrogenation and isomerization reactions

Summary

Introduction

With diminishing fossil resources and increasing environmental concerns worldwide, searching for alternative fuels has attracted great interest in recent years. They[22] introduced WOx into a Cu/Al2O3 catalyst and achieved a PG carbon yield of 38.1%, which was attributed to the glucose-fructose isomerization and retro-aldol condensation steps. To balance the hydrolysis, retro-aldol condensation and hydrogenation and to realize the selective conversion of cellulose into C2/C3 glycols, three aspects will be investigated and discussed: 1) a tailored catalyst will be designed and synthesized, including support selection, support structure modification, control of the Ni-W synergy and co-catalyst screening; 2) the effect of the above factors on the reaction route and the overall mechanism will be studied via a series of catalytic reactions and analyses; 3) the reuse performance and the relationship between Ni-W leaching and product distribution during reuse will be utilized to verify the effect of Ni-W on reaction route selection

Methods

Results

Conclusion