Mechanism and Kinetic Analysis of the Hydrogenolysis of Cellulose to Polyols

Abstract

The catalytic hydrogenolysis of cellulose to polyols represents an attractive process for biomass conversion to value-added products with a high atom economy. In the past decade, extensive studies have been conducted and promptly accumulated a rich knowledge in this field. In this chapter, we focus on the review of reaction mechanisms and kinetics after a brief description of the catalyst development for this process. In view of the different polyol products, the present review is mainly composed of two parts: cellulose conversion to sugar alcohols and cellulose hydrogenolysis to ethylene glycol and 1,2-propylene glycol. The reaction mechanisms are discussed and summarized to obtain general rules in terms of the specific performance of various catalysts. The reaction kinetics of cellulose hydrogenolysis are analyzed on the basis of the kinetics of the individual reaction steps and their correlations in the whole route covering in detail the reactions of cellulose hydrolysis, sugar hydrogenation, retro-aldol condensation, and sugar condensations. Finally, the prospective for the reaction mechanism and kinetics study of cellulose hydrogenolysis is presented.

Magnetically Recoverable Bifunctional Catalysts for the Conversion of Cellulose to 1,2-Propylene Glycol

“…As the WO x loading was increased from 5 to 25%, the conversion rate of cellulose showed a slow upward trend from 89.92 to 93.40%. The main reason for the above results was that the hydrolysis of cellulose into glucose was mainly based on H + that high-temperature water or H 2 produced through the hydrogen spillover effect on the surface of metallic Ru sites at 493 K. Meanwhile, WO x providing Lewis acidic sites was also able to enhance cellulose conversion. − This result is consistent with a literature report . When the WO x loading was less than 20%, the 1,2-PG selectivity increased with the rise of WO x loading, reaching a maximum of 30.8% when the WO x loading was 20%.…”

Selectivity Control for Cellulose to Diols: Dancing on Eggs

“…55,56 Since cellulose hydrolysis is the first and also the ratedetermining step, this Lewis acidity leads to an enhancement in cellulose conversion. 14 Second, the transition-metal species remains active in acidic reaction medium; therefore, additional acids could be introduced to the reaction system to improve the rate of cellulose conversion without deterioration in the EG selectivity. For example, when cellulose conversion was conducted using tungstenic catalysts in combination with a small amount of sulfuric acid, the reaction efficiency was enhanced notably.…”

“…In comparison to base catalysts, transition-metal catalysts have notable advantages in cellulose conversion, in view of the following aspects. First, many of the transition-metal catalysts could partially hydrolyze to form hydroxides during the reaction, providing Lewis acidity for cellulose hydrolysis. , Since cellulose hydrolysis is the first and also the rate-determining step, this Lewis acidity leads to an enhancement in cellulose conversion . Second, the transition-metal species remains active in acidic reaction medium; therefore, additional acids could be introduced to the reaction system to improve the rate of cellulose conversion without deterioration in the EG selectivity.…”

“…The EG yield unprecedentedly reached 61% over an optimal nickel–tungsten carbide catalyst. This process was later named DLEG, representing direct lignocellulose to ethylene glycol . In the following years, extensive studies were conducted by many groups worldwide to explore new catalysts, deeply understand the reaction mechanism, tune the reaction selectivity, model and identify the reaction kinetics, and exploit a variety of feasible feedstocks. − Significant progress has been made from the aspects of both fundamental scientific interest and practical industrial applications.…”

Synergistic Effect of Ni/W/Cu on MgAl2O4 for One-Pot Hydrogenolysis of Cellulose to Ethylene Glycol at a Low H2 Pressure

“…Thus, a multifunctional catalyst that contains an acid site for cellulose hydrolysis, active sites to promote the retro-aldol condensation, and active sites to promote hydrogenation is most attractive and efficient. 7 Numerous multifunctional catalyst systems have been exploited for the one-pot conversion of cellulose to EG. W-based materials are efficient catalysts for retro-aldol condensation.…”