Andreas Bösmann

1-n-Butyl-3-methylimidazolium ([bmim]) octylsulfate—an even ‘greener’ ionic liquid

Ionic liquids are considered as green solvents mainly due to their lack of vapour pressure. In fact, environmental and safety problems arising through the volatility of organic solvents can be avoided by the use of these innovative liquids. However, typical ionic liquids consist of halogen containing anions (such as [AlCl4]−, [PF6]−, [BF4]−, [CF3SO3]− or [(CF3SO2)2N]−) which in some regard limit their ‘greenness’. The presence of halogen atoms may cause serious concerns if the hydrolysis stability of the anion is poor (e.g. for [AlCl4]− and [PF6]−) or if a thermal treatment of spent ionic liquids is desired. In both cases additional effort is needed to avoid the liberation of toxic and corrosive HF or HCl into the environment. In this context, we present here the synthesis and application of 1-n-butyl-3-methylimidazolium ([bmim]) [n-C8H17OSO3] which represents a halogen-free and relatively hydrolysis-stable ionic liquid. Moreover, the technical availability and the well documented toxicology of the octylsulfate anion make this ionic liquid a highly interesting candidate for industrial application.

Deep desulfurization of diesel fuel by extraction with ionic liquids

A new approach for the deep desulfurization of diesel fuels by extraction with ionic liquids is described.

Oxidative Depolymerization of Lignin in Ionic Liquids

Beech lignin was oxidatively cleaved in ionic liquids to give phenols, unsaturated propylaromatics, and aromatic aldehydes. A multiparallel batch reactor system was used to screen different ionic liquids and metal catalysts. Mn(NO(3))(2) in 1-ethyl-3-methylimidazolium trifluoromethanesulfonate [EMIM][CF(3)SO(3)] proved to be the most effective reaction system. A larger scale batch reaction with this system in a 300 mL autoclave (11 g lignin starting material) resulted in a maximum conversion of 66.3 % (24 h at 100 degrees C, 84x10(5) Pa air). By adjusting the reaction conditions and catalyst loading, the selectivity of the process could be shifted from syringaldehyde as the predominant product to 2,6-dimethoxy-1,4-benzoquinone (DMBQ). Surprisingly, the latter could be isolated as a pure substance in 11.5 wt % overall yield by a simple extraction/crystallization process.

Selective catalytic conversion of biobased carbohydrates to formic acid using molecular oxygen

A new and straightforward method to transform carbohydrate-based biomass to formic acid (FA) by oxidation with molecular oxygen in aqueous solution using a Keggin-type H5PV2Mo10O40 polyoxometalate as catalyst is presented. Several water-soluble carbohydrates were fully and selectively converted to formic acid and CO2 under very mild conditions. It is worth noting, even complex biomass mixtures, such as poplar wood sawdust, were transformed to formic acid, giving 19 wt% yield (11% based on the carbon atoms in the feedstock) under non-optimized conditions.

Evaluation of industrially applied heat-transfer fluids as liquid organic hydrogen carrier systems.

Liquid organic hydrogen carrier (LOHC) systems offer a very attractive method for the decentralized storage of renewable excess energy. In this contribution, industrially well-established heat-transfer oils (typically sold under trade names, e.g., Marlotherm) are proposed as a new class of LOHC systems. It is demonstrated that the liquid mixture of isomeric dibenzyltoluenes (m.p. -39 to -34 °C, b.p. 390 °C) can be readily hydrogenated to the corresponding mixture of perhydrogenated analogues by binding 6.2 wt% of H2. The liquid H2 -rich form can be stored and transported similarly to diesel fuel. It readily undergoes catalytic dehydrogenation at temperatures above 260 °C, which proves its applicability as a reversible H2 carrier. The presented LOHC systems are further characterized by their excellent technical availability at comparably low prices, full registration of the H2 -lean forms, and excellent thermal stabilities.

Selective oxidation of complex, water-insoluble biomass to formic acid using additives as reaction accelerators

The oxidation of complex, water-insoluble biomass to formic acid is reported using a Keggin-type polyoxometalate (H5PV2Mo10O40) as the homogeneous catalyst, oxygen as the oxidant, water as the solvent and p-toluenesulfonic acid as the best additive. The reaction proceeds at 90 °C and 30 bar O2 and transforms feedstock like wood, waste paper, or even cyanobacteria to formic acid and CO2 as the sole products. The reaction obtains up to 53% yield in formic acid for xylan as the feedstock within 24 h. Besides the role of the additive as a reaction promoter, the formic acid isolation and the recycling of catalyst and additive are demonstrated.

Catalytic production of hydrogen from glucose and other carbohydrates under exceptionally mild reaction conditions

A catalytic reaction system for the production of hydrogen from sugars and even water-insoluble biomass like cellulose is presented. The reaction system is based on an ionic liquid that has the role to dissolve the carbohydrate feedstock and a ruthenium catalyst. As hydrogen dissolves in this media at very low level, hydrogen consuming side reactions have been hindered, leading to a gaseous product mixture consisting mainly of hydrogen and carbon dioxide. Investigations with isotopic labelling suggest a reaction sequence in which glucose first thermally decomposes to formic acid followed by Ru-catalyzed decomposition of the latter to hydrogen and CO2.

Environmental and health impact assessment of Liquid Organic Hydrogen Carrier (LOHC) systems – challenges and preliminary results

Liquid Organic Hydrogen Carrier (LOHC) systems offer a very attractive way to store and transport hydrogen, a technical feature that is highly desirable to link unsteady energy production from renewables with the vision of a sustainable, CO2-free, hydrogen-based energy system. LOHCs can be charged and discharged with considerable amounts of hydrogen in cyclic, catalytic hydrogenation and dehydrogenation processes. As their physico-chemical properties are very similar to diesel, todays infrastructure for liquid fuels can be used for their handling thus greatly facilitating the step-wise transition from todays fossil system to a CO2 emission free energy supply for both, stationary and mobile applications. However, for a broader application of these liquids it is mandatory to study in addition to their technical performance also their potential impact on the environment and human health. This paper presents the first account on the toxicological profile of some potential LOHC structures. Moreover, it documents the importance of an early integration of hazard assessment in technology development and reveals for the specific case of LOHC structures the need for additional research in order to overcome some challenges in the hazard assessment for these liquids.

Spectroscopic and electrochemical characterization of heteropoly acids for their optimized application in selective biomass oxidation to formic acid

Different Keggin-type polyoxometalates have been synthesized and characterized in order to identify optimized homogeneous catalysts for the selective oxidation of biomass to formic acid (FA) using oxygen as an oxidant and p-toluenesulfonic acid as an additive. Applying the optimized polyoxometalate catalyst system H8[PV5Mo7O40] (HPA-5), a total FA-yield (with respect to carbon in the biogenic feedstock) of 60% for glucose within 8 h reaction time and 28% for cellulose within 24 h reaction time could be achieved. The transformation is characterized by its mild reaction temperature, its excellent selectivity to FA in the liquid product phase and its applicability to a very wide range of biogenic raw materials including non-edible biopolymers and complex biogenic mixtures.

Enhanced Activity and Selectivity in Catalytic Methanol Steam Reforming by Basic Alkali Metal Salt Coatings

Steam reforming is the method of choice if hydrogen has to be produced from methanol in high yields.[1] Under ideal conditions, the reaction converts methanol and water into carbon dioxide and three moles of hydrogen in a moderately endothermic transformation, as shown in Equation (1).