Study on the Pyrolysis Behaviors of Urea-Formaldehyde Resin and Rice Straw Mixed Pellets

In order to study the effect of biomass on the pyrolysis characteristics of urea-formaldehyde resin, the thermogravimetric experiments were carried out respectively using urea-formaldehyde resin (UF), rice straw (RS), and their mixed pellets with different proportions. The pyrolysis kinetics analysis was conducted. The results showed that the pyrolysis process of UF resin and mixed pellets could be divided into three stages: the drying and dehydration of the material, the rapid decomposition of volatile matter, and residue decomposition. The reaction order of UF resin and mixed pellets was discussed using the Coats–Redfern method, the activation energy of UF resin was 54.27 kJ/mol, and this value decreased with the addition of rice straw. As the mass ratio of UF resin to rice straw was 3:1, the activation energy achieved the lowest value, which means that the addition of rice straw was beneficial to the pyrolysis process of UF. In the process of pellet preparation, the falling strength and compressive strength of UF resin pellets can be improved by adding an appropriate proportion of rice straw. In this test, the yield of pyrolytic carbon reached the highest value of 23.93%, as the mass ratio of UF resin to rice straw was 3:2. When the mass ratio was 4:1, the highest liquid product yield of 43.21% was achieved.

Scale Effect on Producing Gaseous and Liquid Chemical Fuels via CO2 Reduction

Producing chemical fuels from sunlight is a sustainable way to utilize solar energy and reduce carbon emissions. Within the current photovoltaic-electrolysis or photoelectrochemical-based solar fuel generation system, electrochemical CO2 reduction is the key step. Although there has been important progress in developing new materials and devices, scaling up electrochemical CO2 reduction is essential to promote the industrial application of this technology. In this work, we use Ag and In as the representative electrocatalyst for producing gas and liquid products in both small and big electrochemical cells. We find that gas production is blocked more easily than liquid products when scaling up the electrochemical cell. Simulation results show that the generated gas product, CO, forms bubbles on the surface of the electrocatalyst, thus blocking the transport of CO2, while there is no such trouble for producing the liquid product such as formate. This work provides methods for studying the mass transfer of CO, and it is also an important reference for scaling up solar fuel generation devices that are constructed based on electrochemical CO2 reduction.

A comprehensive study of the high temperature pyrolysis of sewage sludge: kinetics, energy analysis and products formation

<p>This study evaluates the pyrolysis of sewage sludge until 960 °C using heating rates between 3 K/min and 12 K/min in a macro TG/EGA. Mass and energy balances and kinetic parameters are determined. Thermal decomposition is divided into a low temperature zone (until 550 °C to 590 °C), for decomposition of organic matter, and a high temperature zone, for decomposition of inorganic matter and secondary reactions of the residual organic matter. In dry basis at 570 °C solid, liquid and gaseous products amount to 69.2 wt.-%, 29.2 wt.-% and 1.6 wt.-%, respectively. An increment in the final temperature to 960 °C causes a successive decrease of the solid residue to 56.9 wt.-%. The solid product contains more than 80 wt.-% mineral matter with high amounts of valuable elements, such as Ca and P. An energy requirement of 2.18 MJ/kg of dry sewage sludge is calculated for the pyrolysis until 570 °C. At this temperature, 58.5 % of the energy entering the process is concentrated in the liquid product and 40.0 % in the solid. A suitable set of kinetic parameters is determined through a formal independent parallel reactions model with six-pseudo components, using a combination of isoconversional and fitting methods.</p>

Recent Progress in the Steam Reforming of Bio-Oil for Hydrogen Production: A Review of Operating Parameters, Catalytic Systems and Technological Innovations

The present review focuses on the production of renewable hydrogen through the catalytic steam reforming of bio-oil, the liquid product of the fast pyrolysis of biomass. Although in theory the process is capable of producing high yields of hydrogen, in practice, certain technological issues require radical improvements before its commercialization. Herein, we illustrate the fundamental knowledge behind the technology of the steam reforming of bio-oil and critically discuss the major factors influencing the reforming process such as the feedstock composition, the reactor design, the reaction temperature and pressure, the steam to carbon ratio and the hour space velocity. We also emphasize the latest research for the best suited reforming catalysts among the specific groups of noble metal, transition metal, bimetallic and perovskite type catalysts. The effect of the catalyst preparation method and the technological obstacle of catalytic deactivation due to coke deposition, metal sintering, metal oxidation and sulfur poisoning are addressed. Finally, various novel modified steam reforming techniques which are under development are discussed, such as the in-line two-stage pyrolysis and steam reforming, the sorption enhanced steam reforming (SESR) and the chemical looping steam reforming (CLSR). Moreover, we argue that while the majority of research studies examine hydrogen generation using different model compounds, much work must be done to optimally treat the raw or aqueous bio-oil mixtures for efficient practical use. Moreover, further research is also required on the reaction mechanisms and kinetics of the process, as these have not yet been fully understood.

Transforming Plastic Waste into Porous Carbon for Capturing Carbon Dioxide: A Review

Plastic waste generation has increased dramatically every day. Indiscriminate disposal of plastic wastes can lead to several negative impacts on the environment, such as a significant increase in greenhouse gas emissions and water pollution. Therefore, it is wise to think of other alternatives to reduce plastic wastes without affecting the environment, including converting them into valuable products using effective methods such as pyrolysis. Products from the pyrolysis process encompassing of liquid, gas, and solid residues (char) can be turned into beneficial products, as the liquid product can be used as a commercial fuel and char can function as an excellent adsorbent. The char produced from plastic wastes could be modified to enhance carbon dioxide (CO2) adsorption performance. Therefore, this review attempts to compile relevant knowledge on the potential of adsorbents derived from waste plastic to capture CO2. This review was performed in accordance with PRISMA guidelines. The plastic-waste-derived activated carbon, as an adsorbent, could provide a promising method to solve the two environmental issues (CO2 emission and solid management) simultaneously. In addition, the future perspective on char derived from waste plastics is highlighted.

Synthesis, Characterizations and Catalysis of Sulfated Silica and Nickel Modified Silica Catalysts for Diethyl Ether (DEE) Production from Ethanol towards Renewable Energy Applications

Sulfated silica (SO4/SiO2) and nickel impregnated sulfated silica (Ni-SO4/SiO2) catalysts have been successfully carried out for the conversion of ethanol into diethyl ether (DEE) as a biofuel. The aims of this research were to study the effects of acidity on the SO4/SiO2 and Ni-SO4/SiO2 catalysts in the conversion of ethanol into diethyl ether. This study focuses on the increases in activity and selectivity of SiO2 with the impregnation of sulfate and Ni metal, which had good activity and acidity and were less expensive. The SO4/SiO2 catalysts were prepared using TEOS (Tetraethyl Orthosilicate) as a precursor and sulfuric acid with various concentrations (1, 2, 3, 4 M). The results showed that SO4/SiO2 acid catalyst treated with 2 M H2SO4 and calcined at 400 °C (SS-2-400) was the catalyst with highest total acidity (2.87 g/mmol), while the impregnation of Ni metal showed the highest acidity value at 3%/Ni-SS-2 catalyst (4.89 g/mmol). The SS-2-400 and 3%/Ni-SS-2 catalysts were selected and applied in the ethanol dehydration process into diethyl ether at temperatures 175, 200, and 225 °C. The activity and selectivity of SS-2-400 and 3%/Ni-SS-2 catalysts shown the conversion of ethanol reached up to 9.54% with good selectivity towards diethyl ether liquid product formation.

Experimental Methods for the Evaluation of the Efficiency of an Innovative Sulfur-Dissolving Product in HP-HT Conditions

During production from sour gas reservoirs, precipitation of elemental sulfur can take place in production tubing, resulting in plugging of the well and stop of production. Injection in tubing of products devoted to dissolving sulfur can be an efficient solution for plug removal and production restoring. Traditionally, organic solvents (like toluene) are employed for solid sulfur dissolution. In the present work, experimental investigations have been performed on a particular innovative liquid product designed as active phase for wellbore injection or near wellbore applications. The analyses about the behavior of the considered product were conducted at HP-HT conditions. For this purpose, PVT laboratory equipment was employed, being able to reproduce the conditions of interest for the formation of elemental sulfur plug in well. An important preliminary optimization phase on the experimental setup was necessary to assure the correct management of studied liquid substance and solid sulfur. Integration of main outcomes with other kind of analyses allowed to depict a complete representation of the behavior: microscopy analysis of the liquid phase and high-resolution tomography of solid sulfur before and after the interaction were employed. A key point of the experimental characterization is the reproduction of significant involved phenomena. A preliminary effort was necessary for reproducing the realistic crystal form expected during the precipitation of solid sulfur in well. The dissolution efficiency of the liquid product is evaluated by observing its physical interaction with sulfur in a HP-HT cell. Particular attention was paid to correctly handling employed substances at the considered pressure and temperature conditions. A detailed description of the optimized equipment used in laboratory is provided. Several dissolution tests have been conducted at different temperature and pressure conditions, aiming to observe the dependence of the dissolution efficiency on the thermodynamic parameters. A visual qualitative analysis was performed on both the liquid product and the solid plug, before and after the interaction in cell. This allowed to deepen the comprehension of the dynamics of sulfur dissolution, which takes place not only from the top face of the plug, but also from preferential paths (fractures) present inside the plug itself. The presence of sulfur crystals dispersed in the liquid product after sampling from the cell is also evident at the end of the tests. The studied novel sulfur-dissolving liquid active phase is a candidate for remedial job injection at well in case of plugging due to solid elemental sulfur precipitation. The analyses here presented allowed to characterize the dissolution potential of this product. An optimized workflow was designed, including different kind of experimental disciplines.

CO2 Liquefaction Close to the Triple Point Pressure

For vessel-based transport of liquid CO2 in carbon capture and storage chains, transport at 8 bar(a) enable significant cost reductions compared to transport at higher pressures for most transport distances and volumes. Transport at even lower pressures could further reduce the costs. There are, however, concerns related to dry ice formation and potential clogging in parts of the chain that could lead to operational issues when operating close to the triple point pressure of CO2. In this paper, results from an experimental campaign to de-risk and gain operational experience from the low-pressure CO2 liquefaction process are described. Six experiments using pure CO2 or CO2/N2 mixtures are presented. In four of the experiments, the liquid product pressure was continuously lowered until dry ice was detected and eventually clogged the system. In the final two experiments, the liquefaction process was run in steady-state at low liquefaction pressures for five hours to ensure that there is no undetected dry ice in the process that could lead to accumulation and operational issues over time. These experiments demonstrate that pure CO2 can be safely liquefied at 5.8 bar(a) and a CO2/N2 mixture can be liquefied at 6.5 bar(a) without issues related to dry ice formation.

Effectively Synthesizing SO4/TiO2 Catalyst and Its Performance for Converting Ethanol into Diethyl Ether (DEE)

This SO4/TiO2 catalyst as a heterogeneous acidic catalyst was synthesized in various concentrations of H2SO4. The activity and selectivity of the SO4/TiO2 catalyst on the dehydration reaction of ethanol to diethyl ether were studied as well. The SO4/TiO2 was prepared from TiO2 powder by wet impregnation method with a various aqueous solution of H2SO4 (1; 2; 3 M H2SO4) and calcination temperature (400, 500, and 600 °C) to obtain a catalyst with optimum acidity. The catalysts were characterized using FTIR, XRD, SEM-EDX, SAA, TGA/DSC, and acidity test gravimetrically with ammonia. The liquid product of DEE was analyzed by gas chromatography (GC) to analyze the selectivity of the catalyst. The catalyst TS-3-400 had the highest activity and selectivity in the dehydration reaction of ethanol to diethyl ether at a temperature of 225 °C, with a conversion of 51.83% and a DEE selectivity of 1.72%.