Algae Biorefinery – Material and energy use of algae

Algae offer as much as 30 times greater biomass productivity than terrestrial plants, and are able to fix carbon and convert it into a number of interesting products. The numerous challenges in algae production and use extend across the entire process chain. They include the selection of suitable algal phyla, cultivation (which takes place either in open ponds or in closed systems), extraction of the biomass from the suspension, through to optimal use of the obtained biomass. The basic suitability of aquatic biomass for material use and energy supply has been demonstrated in a large number of studies. Numerous research projects are concerned with identifying the optimal processes to enable its widespread implementation. [... aus der Einleitung

Investigation on the simultaneous removal of COS, CS2 and O2 from coke oven gas by hydrogenation on a Pd/Al2O3 catalyst

The present study deals with the processing of coke oven gas mainly composed of H2, CH4, N2 and CO to provide a feedstock for the synthesis of base chemicals. In this respect, the particular focus of this work is the simultaneous reduction of critical trace components like COS, CS2 and O2 by catalytic reaction with H2. The investigations were performed in synthetic coke oven exhaust using a Pd/Al2O3 catalyst. The results of the hydrogenation tests showed complete conversion of COS, CS2 and O2 at 200 °C and above with selective formation of H2S. However, below 200 °C the conversion of O2 was markedly reduced and CH3SH appeared as a by-product. Mechanistic studies were performed by in situ diffuse reflectance infrared Fourier transform spectroscopy coupled with mass spectrometry. These investigations demonstrated dissociative adsorption of COS on the catalyst at 150 °C resulting in the formation of bridged CO adsorbates and probably elemental sulfur. It is assumed that these species predominate the active Pd surface under reaction conditions. Consequently, the adsorption of O2 and the reaction to H2O is suppressed thus substantiating the decrease in performance at low temperatures. However, increasing the temperature to 200 °C and above leads to desorption of CO and sulfur compounds restoring the efficiency of the catalyst.TU Berlin, Open-Access-Mittel - 202

Influence of single- and double-flame spray pyrolysis on the structure of MnOₓ/γ-Al₂O₃ and FeOₓ/γ-Al₂O₃ catalysts and their behaviour in CO removal under lean exhaust gas conditions

MnOx/Al2O3 and FeOx/Al2O3 samples were prepared by two-nozzle flame spray pyrolysis to minimize the formation of composite phases. For this purpose, manganese(ii) naphthenate or iron(ii) naphthenate and aluminium-sec-butylate were sprayed in separate flames and both the structure and the catalytic performance of the materials in CO oxidation were compared to the corresponding single-nozzle flame spray pyrolysis catalysts. Characterization by X-ray diffraction, diffuse reflectance UV-vis spectroscopy and X-ray absorption near-edge structure unravelled that the phases formed in double-flame spray pyrolysis (DFSP) were significantly different from those in single-flame spray pyrolysis; highly dispersed separate entities of manganese/iron oxide and alumina were identified in this case. Despite a slightly lower BET surface area the DFSP prepared samples performed generally better in catalytic CO oxidation than those derived from one single flame. In addition, the manganese-based catalysts were more effective for CO conversion than the corresponding iron-based samples, even at low concentrations

A Review of Photocatalysts Prepared by Sol-Gel Method for VOCs Removal

The sol-gel process is a wet-chemical technique (chemical solution deposition), which has been widely used in the fields of materials science, ceramic engineering, and especially in the preparation of photocatalysts. Volatile organic compounds (VOCs) are prevalent components of indoor air pollution. Among the approaches to remove VOCs from indoor air, photocatalytic oxidation (PCO) is regarded as a promising method. This paper is a review of the status of research on the sol-gel method for photocatalyst preparation and for the PCO purification of VOCs. The review and discussion will focus on the preparation and coating of various photocatalysts, operational parameters, and will provide an overview of general PCO models described in the literature

Analysis of hydrogenation products of biocrude obtained from hydrothermally liquefied algal biomass by comprehensive gas chromatography mass spectrometry (GC×GC-MS)

Fuels produced from microalgae are a promising alternative for fuels from fossil resources. Algae biomass may be transformed by hydrothermal liquefaction (HTL) into biocrudes, which need upgrading by hydrotreatment to meet transportation fuel requirements. In this study, analyses of HTL biocrude catalytically hydrogenated in a batch reactor at temperatures between 360 and 400 °C and residence times between 2.5 and 10.2 h are presented. Selected samples were investigated by comprehensive gas chromatography mass spectrometry (GC×GC) using flame ionization (FID) or mass spectrometry (MS). The main components of the samples before and after the hydrogenation are hydrocarbons of different unsaturation including alkanes, alkenes, monocyclic and bicyclic hydrocarbons and monocyclic aromatic hydrocarbons. Also, small amounts of polyaromatic hydrocarbons are formed. The most frequent class of heteroatomic compounds are nitrogen and oxygen containing compounds. Oxygen containing compounds are primarily of phenolic nature, whilst nitrogen containing compounds show aromatic amine (alkylated aniline and isomers) and pyrrolic structures (alkylated indoles and carbazoles and isomers). Upon proceeding hydrogenation, an increasing content of lower molecular weight hydrocarbons is observed. The analyses allow to track the decrease of heteroatomic compounds and reveal the structure of refractory compounds. Ultimately, the results allow to identify optimum parameters for the hydrogenation of HTL biocrudes from algae, which correspond to a maximum yield of hydrocarbons and acceptable levels of heteroatomic compounds

LOHC-bound hydrogen for catalytic NOx reduction from O2-rich exhaust gas

The present study demonstrates a novel method for the NOx reduction by H2 in lean exhaust gases using H2 released from a Liquid Organic Hydrogen Carrier (LOHC). The concept implies the simultaneous H2 production and H2-deNOx reaction, which both take place on the same catalyst. In a first approach, the catalyst was suspended in the LOHC, while the exhaust flowed through the slurry. The experiments performed with a O2-rich model exhaust and perhydro dibenzyltoluene as LOHC as well as Pd/C, Pt/C and Pt/Al2O3 catalysts evidenced the feasibility of this transfer hydrogenation. As a result, the Pd/C catalyst revealed best H2-deNOx performance providing NOx conversions up to ??% and N2 selectivities of ??°C above 200°C. The characterization of the catalysts by temperature-programmed desorption of CO suggested that the superiority of the Pd/C sample is associated with its pronounced number of active Pd sites. Furthermore, the investigations also showed some LOHC degradation releasing CO, CO2 and hydrocarbons. However, additional experiments excluded significant participation of the formed CO in the H2-deNOx reaction at 210°C and above

Fe based core–shell model catalysts for the reaction of CO2 with H2

Abstract Fe@SiO2 core–shell model catalysts were investigated for the conversion of CO2 and H2 into CH4, CO and H2O. For evaluation of the effect of core size on the catalytic activity, samples with Fe particle sizes of 4, 6 and 8 nm were prepared. Fresh and spent catalysts were thoroughly characterized by X-ray diffraction, 57Fe Mössbauer spectroscopy, transmission electron microscopy, temperature programmed hydrogenation and X-ray photoelectron spectroscopy. As a result, the yield of the major product CO as well as CH4 was increased with Fe core size. Additionally, growing Fe cores led to stronger carburization and higher amount of reactive carbide entities, which drive the CH4 formation. Finally, formation of inactive bulk carbon deposition is strongly suppressed for the core–shell catalysts in comparison to bulk iron oxide catalysts used for CO2 hydrogenation

Algae Biorefinery – Material and energy use of algae

Algae offer as much as 30 times greater biomass productivity than terrestrial plants, and are able to fix carbon and convert it into a number of interesting products. The numerous challenges in algae production and use extend across the entire process chain. They include the selection of suitable algal phyla, cultivation (which takes place either in open ponds or in closed systems), extraction of the biomass from the suspension, through to optimal use of the obtained biomass. The basic suitability of aquatic biomass for material use and energy supply has been demonstrated in a large number of studies. Numerous research projects are concerned with identifying the optimal processes to enable its widespread implementation. [... aus der Einleitung