Catalytic Hydrogenation of Corn Stalk to Ethylene Glycol and 1,2-Propylene Glycol

Abstract

The use of whole lignocellulosic biomass as the feedstock for cellulose conversion is of great significance for largescale, low-cost biomass conversion to biofuel and other useful chemicals. We recently achieved the direct conversion of cellulose (pure microcrystalline cellulose) into ethylene glycol at high yields over tungsten carbide catalysts. Here, corn stalk, an agricultural residue available in large quantities, was used as a lignocellulosic feedstock for conversion over nickel-promoted tungsten carbide catalysts under hydrothermal conditions and a hydrogen atmosphere. Nine different pretreatment methods were employed to convert the raw corn stalk to cellulosic feedstock with different chemical components and structures before the catalytic reaction. We found that corn stalks pretreated with 1,4-butanediol, NaOH, H 2 O 2 , and ammonia produced much higher yields of ethylene glycol (EG) and 1,2-propylene glycol (1,2-PG) compared to raw corn stalks, whereas pretreatments with ethanol solution, hot water, hot limewater, and supercritical CO 2 just slightly improved the EG and 1,2-PG yields and corn stalk conversion. The hemicellulose in the corn stalk can be effectively converted to EG and 1,2-PG without hindering the cellulose conversion. In contrast, the lignin was resistant to degradation in the reaction and also inhibited EG and 1,2-PG production. The crystallinity of cellulose did not appear to have notable influence on the EG and 1,2-PG production. In view of the environmental benignity and low cost, pretreatment with ammonia and/or diluted H 2 O 2 solution might be a practical method for corn stalk conversion, after which the derived cellulosic feedstock is readily converted into EG and 1,2-PG at an overall yield of 48% in the reaction.

Mechanism and Kinetic Analysis of the Hydrogenolysis of Cellulose to Polyols

“…The cost of catalysts was greatly reduced due to the convenience in the preparation and the better reusability of catalysts without decay in the performance [28,115]. The feedstock involved microcrystalline cellulose and raw biomass, in detail including corn stover [22], birch wood [24], miscanthus [119], concentrated glucose [116,120], and Jerusalem artichoke [121]. The product distributions were tuned between EG, erythritol, and hexitols by varying the ratio of tungsten and hydrogenation metals [88].…”

Temperature-controlled phase-transfer catalysis for ethylene glycol production from cellulose

“…On the other hand, it guarantees easy separation and recovery of tungsten acid. Taking into account that raw biomass, if properly pretreated, 10 can be well converted into EG with such a tungsten-based catalyst, it can be expected that the combination of tungsten acid and Ru/AC will constitute a promising candidate for the future commercialization of the one-pot conversion of biomass to EG due to its high efficiency, low cost, and exceptional reusability.…”

Remarkable effect of extremely dilute H2SO4 on the cellulose conversion to ethylene glycol

“…Among others, the one-pot conversion of cellulose to ethylene glycol (EG) has been paid considerable attention as this unique transformation leads to a high yield of EG (up to 75 wt%) which is commercially attractive. Since the first report of this reaction in 2008 [5], Zhang and coworkers have made systematic studies on the catalysts development [6][7][8], optimization of pretreatment and reaction conditions [9,10], reaction kinetics [11,12], and mechanism understanding [13,14]. For example, following the development of Nipromoted tungsten carbide, they further explored three-dimensional carbon supported tungsten carbide catalyst which afforded EG yield as high as 73% even without the promotion of Ni [6,7].…”