Methane dry reforming over nickel perovsikite catalysts

In recent years dry reforming of methane (DRM) has received considerable attention as a promising alternative to steam reforming for synthesis gas (H2 and CO) production. This process could be industrially advantageous, yielding a syngas with a H2/CO ratio close to 1, suitable for Fischer-Tropsch synthesis to liquid hydrocarbons and for production of valuable oxygenated chemicals. The major drawback of the process is the endothermicity of the reaction that implies the use of a suitable catalyst to work at relatively low temperatures (923-1,023 K). Higher temperatures would make the process unaffordable for an industrial development and would increase the risk of undesirable side reactions, such as coke formation, that are the main causes of catalyst deactivation. In this work the activity of nickel perovskite catalysts were studied and the results were compared with rhodium perovskite. It is well known that rhodium is very active and stable for dry reforming but its high cost makes its utilization limited. The Ni, due to its low cost, is a promising substitute even if it is more susceptible to coking. The perovskite structure allows a high dispersion of the metal into the catalyst increasing the catalytic activity. In this work the Ni perovskite was obtained with two methods (auto-combustion and modified citrate methods). The results pointed out that the Ni perovskite obtained with the auto-combustion method is a promising route for the use of Ni in this process. The experimental tests show that with Ni catalyst very good activity can be achieved from temperature of 973 K

Biocrude production by hydrothermal liquefaction of olive residue

Hydrothermal liquefaction (HTL) converts biomass into a crude bio-oil by thermally and hydrolytically decomposing the biomacromolecules into smaller compounds. The crude bio-oil, or biocrude, is an energy dense product that can potentially be used as a substitute for petroleum crudes. Liquefaction also produces gases, solids, and water-soluble compounds that can be converted to obtain valuable chemical species or can be used as energy vectors. The process is usually performed in water at 250°C-370°C and under pressures of 4-22 MPa: depending on the adopted pressure and temperature the process can be carried out in sub-critical or super-critical conditions. In the conditions reached in hydrothermal reactors, water changes its properties and acts as a catalyst for the biomass decomposition reactions. One of the main advantages of this process is that the energy expensive biomass-drying step, required in all the thermochemical processes, is not necessary, allowing the use of biomass with high moisture content such as microalgae or olive residue and grape mark. In this work, the feasibility of a hydrothermal process conducted under sub-critical conditions to obtain a bio-oil from the residue of olive oil production is investigated. The experimental tests were performed at 320°C and about 13 MPa, using a biomass to water weight ratio of 1:5. The influence of two different catalysts on the bio-oil yield and quality was investigated: CaO and a zeolite (faujasite-Na). CaO allows the increase of bio-oil yields, while the selected zeolite enhances the deoxygenation reactions, thus improving the bio-oil quality in terms of heating value

Use of low-cost materials for tar abatement process

In the present work char, olivine and mayenite were used as bed materials to study ability to remove tar produced in biomass thermal processing. The tar gases formed from the pyrolysis reactions of the olive pomace biomass were forced to pass through the bed material. Nitrogen was used as carrier gas. The temperature of the bed was set at 660 °C and no oxidizing agent was added during the tests. The char was produced from the pyrolysis of olive pomace biomass. Olivine was used without any pre-treatment. Mayenite was synthesized in laboratory using CaCO3 and Al2O3 as precursors. Among the tested materials, mayenite showed the best tar removal capacity and stability, with a total tar removal of about 60% after 60 min time on stream, while in the case of char and olivine the attained value was 15%. The measured average nitrogen-free gas flow value in the tests carried out with mayenite was 0.84 NL min-1, whereas in the case of char and olivine the obtained average gas flow values were 0.65 and 0.55 NL min-1, respectively. Accordingly, the higher average hydrogen amount was measured in the tests using mayenite as bed material (36%)

Improved photocatalytic properties of doped titanium-based nanometric oxides

Photocatalysis is considered one of the most promising technologies for applications in the environmental field especially in the abatement of water-soluble organic pollutants. In this field, titanium dioxide nanoparticles have drawn much attention recently; however, the use of this oxide presents some limitation since it allows to obtain high photoresponse and degradation efficiency only under UV light irradiation, that represents the 3 to 4% of the solar radiation, so preventing its environmental large-scale applications under diffuse daylight. In this work the photocatalytic efficiencyoftitanium-based oxides systems containing alkaline earth metals such as barium and strontium, prepared by a simple sol-gel method was investigated, evaluating the degradation of methylene blue as model compound under UV and visible light irradiation. The results were compared with those obtained with Degussa P25 titanium dioxide. The achieved degradation percentage of methylene blue are very promising showing that under visible light irradiation it is possible to obtain a maximum dye removal percentage ~ 50 % higher than that obtained with the Degussa P25

Hydrothermal liquefaction of biomass. Influence of temperature and biomass composition on the bio-oil production

Hydrothermal liquefaction is a promising process for the production of high quality bio-oil from biomass. Aim of this study is to investigate the effect of temperature and biomass composition on the yield and quality of bio-oils produced from three different biomass such as natural hay, oak wood and walnut shell. The hydrothermal liquefaction of cellulose was also investigated. The experimental tests, conducted in water sub-critical conditions, were carried out in a microreactor in a temperature range of 240–320 °C with a reaction time of 30 min. All the products of the process were analyzed and characterized by elemental analysis and GC–MS. It was observed an increase of the bio-oil yields with the lignin content of biomass, being the maximum bio-oil yield obtained for walnut shell and the minimum one for cellulose. This trend is representative of the obtained bio-oils composition, where the phenolic compounds are the major constituents, while the other identified compounds were mainly alcohols, ketones and aldehyde

Olive oil residue gasification and syngas integrated clean up system

Gasification is one of the most promising technologies to convert low quality fuels into more valuable ones. The main problem in the use of biomass in gasification processes is the high amount of tar released in the pyrolysis step. It is thus necessary to recover the tar and to transform it in lighter combustible gas species such as CH4, CO and H2 by means of catalytic processes. In this work the gasification of olive husk is performed in order to produce a high quality syngas, composed mainly of carbon monoxide and hydrogen, using an innovative laboratory scale plant composed of a unique reactor divided into three sections. The first section is dedicated to the pyrolysis, the second to the gasification of char produced during pyrolysis and the third to the catalytic reforming of tar. In the reformer two catalysts were tested: a CeO2 promoted bimetallic Ni-Co catalyst and a Ni catalyst, both supported on γ-Al2O3. This plant design allows one to minimize the heat dispersion enhancing the energy efficiency of the unit

Rh, Ru and Pt ternary perovskites type oxides BaZr(1-x)MexO3 for methane dry reforming

In recent years dry reforming of methane has received considerable attention as a promising alternative to steam reforming for synthesis gas (H2 and CO) production, yielding a syngas with a H2/CO ratio close to 1 and thus suitable for many chemical processes. The major drawback of the process is the endothermicity of the reaction that implies the use of a suitable catalyst to work at relatively low temperatures (923–1023 K). In this work methane dry reforming over three ternary perovskite type oxides BaZr(1-x)MexO3 using Rh, Ru and Pt as metal was studied at atmospheric pressure and in a temperature range 850–1150 K. Experimental tests at different temperatures were performed in order to analyze and compare the performances of the catalysts and to carry out a detailed kinetic study. Furthermore, long duration tests were conducted to evaluate the possible deactivation of the perovskites. Rhodium-perovskite catalyst shows the highest activity for dry methane reforming while the Pt one the lowest. No deactivation of the catalysts was observed meaning that the perovskite structure is very stable and allows to minimize the carbon deposition that is the main responsible of catalyst deactivation in this process

Carbon dioxide reforming of tar during biomass gasification

The energy demand increase and the necessity to contain CO2 emissions lead to a growing interest on renewable and CO2 free energy sources. Gasification has been identified as a key technology to enhance the environmental tolerability of low quality fuels such as biomass. The principal problem related with the use of biomass in gasification processes is the high quantity of tar released during the pyrolysis step of this fuel. Tar can account up to 50% of the total volatiles and contains a great part of the biomass energy. For this reason it is necessary to recover the tar and to transform it in combustible lighter gas species such as methane, carbon monoxide and hydrogen by means of catalytic processes. Another important issue is to lower the carbon dioxide content of the produced gas in order to increase its calorific value. The dry reforming represents an interesting solution. In this work the dry reforming of tar in a two stages bench scale reactor is proposed. In the proposed dry reforming process the tar reacts with the carbon dioxide released during the biomass pyrolysis to form carbon monoxide and hydrogen. It is thus possible to recover the tar energy converting it into CO and H2 and to lower the syngas dilution using the CO2 as a reagent. The dry reforming is a catalytic process and one of the major issues is the deactivation of the catalysts due to carbon deposition. The solution of this problem is very important in the case of tar dry reforming because of its high C/H ratio, which intensifies this phenomenon. Nickel has been extensively studied for the dry reforming but it is known that it suffers from carbon deposition. In this work Ce-promoted bimetallic Ni-Co catalysts with two different supports were tested. Copyright © 2014,AIDIC Servizi S.r.l

Methane dry reforming on Ru perovskites, AZrRuO 3 : Influence of preparation method and substitution of A cation with alkaline earth metals

Dry reforming could become an effective route to mitigate CO 2 emission. The process required high temperatures due to its endothermicity and its accompanied by coke formation; therefore, the development of suitable catalysts is fundamental. In this work, ternary perovskites type oxides, AZrRuO 3 , were synthetized and used in the methane dry reforming. The influences of the preparation method, modified citrate and autocombustion method, and of substitution of the A cation within alkaline earth metals (Ba, Sr and Ca) on the texture, physiochemical characteristics, activity and stability of the catalysts were evaluated. Tests were conducted in a fixed bed bench scale reactor in a temperature range of 600-750 °C. Catalysts synthetized by autocombustion method showed higher reducibility and major surface area and thus better performance in the methane dry reforming. Between them, SrZrRUO 3 gave the best results in terms of conversion and stability during long duration tests (66 h). Furthermore, these catalysts showed very good resistance to thermal stresses as demonstrated by XRD analysis performed on used catalysts

Pyrolysis wastewater treatment by adsorption on biochars produced by poplar biomass

yrolysis is a widely studied thermochemical process, however the disposal of the produced byproducts is an unexplored field. In particular, the acqueous phase, characterized by a high organic load (TOC), must be necessarily treated. Aims of this work is to study the potentiality of biochar as adsorbent material for the treatment of this wastewater. For this aim, pyrolysis wastewater and biochar produced in the same plant were used. Two biochars produced at different temperatures (550 and 750 °C) and an activated biochar produced by chemical activation with NaOH of the raw biomass were tested. The study shows that higher temperature in the biochar production leads to higher sorption capacity of the organic compounds due to an increase of the surface area. The activation process further increases the surface area of the biochar that becomes similar to that of a commercial activated carbon while the sorption capacity exceeds that of commercial activated carbon of 2.5 times