Jianjian Wang

Efficient catalytic conversion of fructose into hydroxymethylfurfural by a novel carbon-based solid acid

A novel carbon-based solid acid, which was prepared by a facile and eco-friendly approach from glucose and p-toluenesulfonic acid (TsOH), was used to catalyze fructose dehydration into 5-hydroxymethylfurfural (HMF) for the first time and exhibits excellent catalytic performance. As high as 91.2% yield of HMF was achieved in dimethyl sulfoxide (DMSO) at 130 °C after only 1.5 h. Besides, this catalyst also displayed a good reusability.

Direct conversion of carbohydrates to 5-hydroxymethylfurfural using Sn-Mont catalyst

5-Hydroxymethylfurfural (HMF) is a very important intermediate in the fine chemical industry. This study aims to investigate the direct conversion of glucose or glucose-based carbohydrates, such as sucrose, cellobiose, inulin, starch and cellulose, to HMF by using a Sn-Mont catalyst. With the use of this catalyst, a HMF yield of 53.5% was achieved from glucose in a mono-phase medium of tetrahydrofuran (THF)/dimethylsulfoxide (DMSO) at 160 °C for 3 h. The success of one-step conversion of glucose to HMF is attributed to the Sn-Mont catalyst containing two types of acid sites, Lewis acid and Bronsted acid sites. The former one plays a crucial role in the isomerization of glucose to fructose and the latter one is active in the dehydration of generated fructose to HMF. Furthermore, Sn-Mont catalyst also demonstrated excellent activity in the conversion of disaccharides and polysaccharides and as high as 39.1% HMF was directly obtained from cellulose in a THF/H2O–NaCl bi-phasic system.

Mesoporous niobium phosphate: an excellent solid acid for the dehydration of fructose to 5-hydroxymethylfurfural in water

By using cetyltrimethylammonium bromide (CTAB) as the template, a series of mesoporous niobium phosphates were synthesized at different pH values in an aqueous solution. Techniques such as small-angle X-ray diffraction, transmission electron microscopy (TEM) and N2 sorption technique were employed to characterize the mesoporous structures of thus-synthesized materials, EDAX to detect the composition, FTIR and solid state 31P MAS NMR to investigate the framework information, while their acidic properties were analyzed using NH3-TPD and pyridine-FTIR. Samples prepared at neutral to acidic conditions exhibited high surface area (213–297 m2 g−1), narrow pore size distribution (3–4 nm) and a great number of strong Lewis and Bronsted acid sites. These materials exhibited excellent activity in the dehydration of fructose to 5-hydroxymethylfurfural (HMF) in water. The maximum HMF yield reached 45% under 130 °C with a reaction time of 0.5 h and the yield slightly decreased to 32% after five cycles and the five-cycled catalyst can be almost regenerated by calcination at 500 °C with the yield of 40%. The excellent catalytic activity obtained in the aqueous phase can be attributed to its high acid site density and the tolerance to water.

High-yield production of levulinic acid from cellulose and its upgrading to γ-valerolactone

Direct catalytic conversion of cellulose to levulinic acid (LA) by niobium-based solid acids and further upgrading to γ-valerolactone (GVL) on a Ru/C catalyst were realized through sequential reactions in a reactor. Firstly, using aluminium-modified mesoporous niobium phosphate as a catalyst, cellulose can be directly converted to LA with as high as 52.9% yield in aqueous solution, even in the presence of the Ru/C catalyst. To the best of our knowledge, this is the best result over a heterogeneous catalyst so far. It was found that the type of acid (Lewis and Bronsted acids) and acid strength had an influence on the yield of LA; the doping of aluminium can enhance the strong Lewis and Bronsted acids, especially the strong Lewis acid, thus resulting in the increase of LA yield from cellulose as well as from glucose and HMF. Such an enhancement by a Lewis acid on LA yield from HMF was further confirmed by adding lanthanum trifluoroacetate [(TfO)3La], a strong Lewis acid, in the catalytic system (HCl, (TfO)3H, niobium phosphate), indicating that a suitable ratio of Lewis/Bronsted acid is important for higher selectivity to LA from HMF, as well as from cellulose. Then, after replacing N2 with H2, the generated LA in the reaction mixture can be directly converted to γ-valerolactone through hydrogenation over the Ru/C catalyst without further separation of LA.

Recent advances in the catalytic production of glucose from lignocellulosic biomass

Recently, research on the catalytic production of glucose, the first platform chemical in biorefinery, has become attractive in catalysis studies and the chemical/fuel industry owing to its broad applications. It opens up a new route for achieving sustainable chemical production and energy supply. From this viewpoint, this contribution attempts to overview the recent advances in the catalytic routes for the synthesis of glucose from lignocellulosic biomass over various homogeneous and heterogeneous catalysts.

Efficient catalytic conversion of lignocellulosic biomass into renewable liquid biofuels via furan derivatives

Efficient production and sequential utilization of furan derivatives will provide a promising approach towards achieving renewable liquid biofuels from biomass. This study aims to investigate the simultaneous production of furfural and 5-(hydroxymethyl)furfural (HMF) from biomass and further upgrade them into biofuels. Firstly, furfural and HMF are obtained together with high yields from a mixture of C5 (xylose) and C6 (glucose) sugars, or from lignocellulosic biomass, such as birch, cornstalk, pine, bagasse, and poplar in a tetrahydrofuran (THF)/H2O–NaCl biphasic system under mild conditions. The co-existence of C5/C6 sugars or impurities in lignocellulosic biomass has little influence on the simultaneous production of furfural and HMF. Then, the generated furfural and HMF in the upper organic phase are directly used as substrates without extra separation and purification processes, and efficiently upgraded to 2-methylfuran (MF) and 2,5-dimethylfuran (DMF), both of which are considered as promising renewable liquid biofuels with high-energy content. Hence, the seamless integration of lignocellulosic biomass into renewable liquid biofuels will accelerate our society moving towards a renewable transportation economy by utilizing cheap feedstocks, mild reaction conditions, and cost saving in separation and purification.

Production of methyl levulinate from cellulose: selectivity and mechanism study

The alcoholysis of cellulose into methyl levulinate (ML) in methanol media was investigated in the presence of several kinds of acid catalyst. One of the synthesized solid niobium-based phosphate catalysts was found to be highly efficient for the generation of ML, reaching an ML yield as high as 56%, higher than the LA yield (52%) in aqueous solution with the same reaction conditions as those used in our previous study (Green Chem., 2014, 16, 3846–3853). More interestingly, in water, very strong Lewis acid promoted the formation of LA; but in methanol, Bronsted acid enhanced the formation of ML. In-depth investigation showed that the mechanism and type of intermediates of cellulose alcoholysis in methanol were different from those in water and a high Bronsted/Lewis acid ratio (known as B/L acid ratio) of solid catalysts is needed to prevent the generation of by-products, namely, methyl lactate and 1,1,2-trimethoxyethane. This new-proposed reaction mechanism affected by the B/L acid ratio was very helpful for the design of efficient catalysts.