Biomass is an important feedstock for the renewable production of fuels, chemicals, and energy. As of 2005, over 3% of the total energy consumption in the United States was supplied by biomass, and it recently surpassed hydroelectric energy as the largest domestic source of renewable energy. Similarly, the European Union received 66.1% of its renewable energy from biomass, which thus surpassed the total combined contribution from hydropower, wind power, geothermal energy, and solar power. In addition to energy, the production of chemicals from biomass is also essential; indeed, the only renewable source of liquid transportation fuels is currently obtained from biomass.

The Catalytic Valorization of Lignin for the Production of Renewable Chemicals

and Fuels Changzhi Li,† Xiaochen Zhao,† Aiqin Wang,† George W. Huber,†,‡ and Tao Zhang*,† †State Key Laborotary of Catalysis, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China ‡Department of Chemical and Biological Engineering, University of WisconsinMadison, Madison, Wisconsin 53706, United States

Catalytic Transformation of Lignin for the Production of Chemicals and Fuels

Note: Times Cited: 875 Reference EPFL-ARTICLE-206025doi:10.1021/cr0501846View record in Web of Science URL: ://WOS:000249839900009 Record created on 2015-03-03, modified on 2017-05-12

Complex Hydrides for Hydrogen Storage

As the oil reserves are depleting the need of an alternative fuel source is becoming increasingly apparent. One prospective method for producing fuels in the future is conversion of biomass into bio-oil and then upgrading the bio-oil over a catalyst, this method is the focus of this review article. Bio-oil production can be facilitated through flash pyrolysis, which has been identified as one of the most feasible routes. The bio-oil has a high oxygen content and therefore low stability over time and a low heating value. Upgrading is desirable to remove the oxygen and in this way make it resemble crude oil. Two general routes for bio-oil upgrading have been considered: hydrodeoxygenation (HDO) and zeolite cracking. HDO is a high pressure operation where hydrogen is used to exclude oxygen from the bio-oil, giving a high grade oil product equivalent to crude oil. Catalysts for the reaction are traditional hydrodesulphurization (HDS) catalysts, such as Co–MoS2/Al2O3, or metal catalysts, as for example Pd/C. However, catalyst lifetimes of much more than 200 h have not been achieved with any current catalyst due to carbon deposition. Zeolite cracking is an alternative path, where zeolites, e.g. HZSM-5, are used as catalysts for the deoxygenation reaction. In these systems hydrogen is not a requirement, so operation is performed at atmospheric pressure. However, extensive carbon deposition results in very short catalyst lifetimes. Furthermore a general restriction in the hydrogen content of the bio-oil results in a low H/C ratio of the oil product as no additional hydrogen is supplied. Overall, oil from zeolite cracking is of a low grade, with heating values approximately 25% lower than that of crude oil. Of the two mentioned routes, HDO appears to have the best potential, as zeolite cracking cannot produce fuels of acceptable grade for the current infrastructure. HDO is evaluated as being a path to fuels in a grade and at a price equivalent to present fossil fuels, but several tasks still have to be addressed within this process. Catalyst development, understanding of the carbon forming mechanisms, understanding of the kinetics, elucidation of sulphur as a source of deactivation, evaluation of the requirement for high pressure, and sustainable sources for hydrogen are all areas which have to be elucidated before commercialisation of the process.

A review of catalytic upgrading of bio-oil to engine fuels

Lignin, a major component of lignocellulose, is the largest source of aromatic building blocks on the planet and harbors great potential to serve as starting material for the production of biobased products. Despite the initial challenges associated with the robust and irregular structure of lignin, the valorization of this intriguing aromatic biopolymer has come a long way: recently, many creative strategies emerged that deliver defined products via catalytic or biocatalytic depolymerization in good yields. The purpose of this review is to provide insight into these novel approaches and the potential application of such emerging new structures for the synthesis of biobased polymers or pharmacologically active molecules. Existing strategies for functionalization or defunctionalization of lignin-based compounds are also summarized. Following the whole value chain from raw lignocellulose through depolymerization to application whenever possible, specific lignin-based compounds emerge that could be in the fu...

Bright Side of Lignin Depolymerization: Toward New Platform Chemicals

Catalytic hydrotreatment or hydrodeoxygenation (HDO) has been researched extensively with the crude bio-oil and its model compounds over conventional sulfided Ni(Mo), Co(Mo) catalysts and supported noble metal catalysts. These types of catalysts showed themselves unsuitable for the target HDO process, which resulted in an urgent need to search for a new catalytic system meeting such requirements as low cost, stability against coke formation and leaching of active components due to adverse effect of the acidic medium (bio-oil). In the present work a series of Ni-based catalysts with different stabilizing components has been tested in the hydrodeoxygenation (HDO) of guaiacol (2-methoxyphenol), bio-oil model compound. The process has been carried out in an autoclave at 320 °C and 17 MPa H2. The main products were cyclohexane, 1-methylcyclohexane-1,2-diol, and cyclohexanone. The reaction scheme of guaiacol conversion explaining the formation of main products has been suggested. The catalyst activity was found to rise with an increase in the active component loading and depend on the catalyst preparation method. The most active catalysts in HDO of guaiacol were Ni-based catalysts prepared by a sol–gel method and stabilized with SiO2 and ZrO2. According to TPR, XRD, XPS, and HRTEM, the high activity of these catalysts correlates with the high nickel loading and the high specific area of active component provided by the formation of nickel oxide–silicate species. The effect of temperature on the product distribution and catalyst activity in the target process (HDO) has been investigated as well. The catalysts were shown to be very promising systems for the production of hydrocarbon fuels by the catalytic upgrading of bio-oil.

Ni-based sol–gel catalysts as promising systems for crude bio-oil upgrading: Guaiacol hydrodeoxygenation study

Development of new catalytic systems for upgraded bio-fuels production from bio-crude-oil and biodiesel

The activity and selectivity of model NiCu–SiO 2 catalysts with the high metal loading (90%) and various Ni content was studied in anisole hydrotreatment at 280 °C and a hydrogen pressure of 6 MPa in a batch reactor. To obtain the alloys with the homogeneous phase composition, the catalysts were prepared by simultaneous decomposition of metal salts with the subsequent stabilization with 10 wt% SiO 2 . The composition of the Ni y Cu 1− y alloy surface was estimated from the combination of XPS and XRD data. On the basis of obtained kinetic data, a reaction scheme of anisole conversion was proposed. The scheme includes two parallel routes, one of which leads to C ar O bond cleavage with the formation of benzene, which is then converted to cyclohexane (HDO route), while the second route leads to hydrogenation of the aromatic ring of anisole with the formation of methoxycyclohexane and cyclohexanol (HYD route). The experimental dependence of anisole conversion was described by the first-order kinetics with respect to the reagents. The effect of the surface composition of the active phase Ni y Cu 1− y on the specific catalytic activity was examined. According to the proposed reaction scheme, the dependence of the first-order rate constants for both routes on the nickel content in the active component of the catalysts was determined. The selectivities of both reaction routes of anisole conversion (HDO and HYD) were found to be independent of the Ni content except for the nickel-rich and copper-rich sides. The specific catalytic activity in the HDO route rises with an increase in the nickel content in the whole range of Ni loading.

Anisole hydrodeoxygenation over Ni–Cu bimetallic catalysts: The effect of Ni/Cu ratio on selectivity

The effect of molybdenum on activity of Ni-based catalysts in the hydrodeoxygenation of fatty acid esters was studied. Catalysts Ni-Cu/Al 2 O 3 , Ni-Mo/Al 2 O 3 , Cu-Mo/Al 2 O 3 , Mo/Al 2 O 3 , and Ni-Cu-Mo/Al 2 O 3 with different ratios Ni/Mo were prepared and tested in the hydrodeoxygenation of methyl palmitate and ethyl caprate at 300 °С, 1 MPa. It was found that an increase in the Mo content (from 0.0% to 6.9%) in the Ni-Cu-Mo/Al 2 O 3 catalysts leads to an increase in the yield of normal alkanes. The catalysts were characterized by X-ray photoelectron spectroscopy (XPS), temperature programmed reduction and X-ray diffraction techniques. The XPS data showed that the increase in the conversion of fatty acid esters is related to changes in the ratio between different oxidation states of molybdenum (Mo 0 , Mo 4+ , and Mo 6+ ) on the surface of the Ni-Cu-Mo/Al 2 O 3 catalysts.

Influence of Mo on catalytic activity of Ni-based catalysts in hydrodeoxygenation of esters

The catalytic properties of Co 3 O 4 in NaBH 4 and NH 3 BH 3 hydrolysis have been studied. Experiments were carried out at 20–40 °C using 0.12 M hydride solution. According to magnetic susceptibility measurements, FTIR, XRD, and TEM studies, Co 3 O 4 is reduced to the ferromagnetic catalytically active Co 2 B phase under the action of the NaBH 4 hydrolysis reaction medium. A correlation was found between the content of the cobalt boride phase formed in situ and catalyst activity. The reduction of Co 3 O 4 in NH 3 BH 3 proceeds at slower rate than in NaBH 4 . The addition to a solution of NH 3 BH 3 of even a small amount of NaBH 4 increases considerably the reduction rate of Co 3 O 4 . Using a Co 3 O 4 -based precursor instead of the widely used CoCl 2 leads to the formation of a stable catalytically active phase of cobalt boride.

Olga A. Bulavchenko

Papers

Ni-based sol–gel catalysts as promising systems for crude bio-oil upgrading: Guaiacol hydrodeoxygenation study

Development of new catalytic systems for upgraded bio-fuels production from bio-crude-oil and biodiesel

Anisole hydrodeoxygenation over Ni–Cu bimetallic catalysts: The effect of Ni/Cu ratio on selectivity

Influence of Mo on catalytic activity of Ni-based catalysts in hydrodeoxygenation of esters

Cobalt oxide catalyst for hydrolysis of sodium borohydride and ammonia borane