Combined Steam Reforming of Methane and Formic Acid To Produce Syngas with an Adjustable H2:CO Ratio

Syngas is an important intermediate in the chemical process industry. It is used for the production of hydrocarbons, acetic acid, oxo-alcohols, and other chemicals. Depending on the target product and stoichiometry of the reaction, an optimum (molar) ratio between hydrogen and carbon monoxide (H2:CO) in the syngas is required. Different technologies are available to control the H2:CO molar ratio in the syngas. The combination of steam reforming of methane (SRM) and the water-gas shift (WGS) reaction is the most established approach for syngas production. In this work, to adjust the H2:CO ratio, we have considered formic acid (FA) as a source for both hydrogen and carbon monoxide. Using thermochemical equilibrium calculations, we show that the syngas composition can be controlled by cofeeding formic acid into the SRM process. The H2:CO molar ratio can be adjusted to a value between one and three by adjusting the concentration of FA in the reaction feed. At steam reforming conditions, typically above 900 K, FA can decompose to water and carbon monoxide and/or to hydrogen and carbon dioxide. Our results show that cofeeding FA into the SRM process can adjust the H2:CO molar ratio in a single step. This can potentially be an alternative to the WGS process.Engineering Thermodynamic

Cellulose assisted combustion synthesis of porous Cu-Ni nanopowders

Porous nanopowders of Cu-Ni were synthesized using cellulose fibres as impregnation media at ambient pressure using combustion based techniques. The synthesized nanopowders were characterized using XRD, BET, SEM, TEM etc. The phase development during the synthesis process was evaluated by performing TGA/DTA experiments. The effect of the amount of precursor on the microstructure and porosity of the nanomaterials was investigated and compared with Cu-Ni synthesized using the Solution Combustion Synthesis (SCS) method. The syntheses of nanopowders proceed via ignition in the reaction media containing metal precursors which is followed by high temperature cellulose combustion. Total pore volume and average pore diameter in case of cellulose assisted synthesized samples were found to be greater as compared to SCS samples.Scopu

Online monitoring of the solvent and absorbed acid gas concentration in a CO2 capture process using monoethanolamine

A method has been developed for online liquid analysis of the amine and absorbed CO2 concentrations in a postcombustion capture process using monoethanolamine (MEA) as a solvent. Online monitoring of the dynamic behavior of these parameters is important in process control and is currently achieved only using Fourier transform infrared spectroscopy. The developed method is based on cheap and easy measurable quantities. Inverse least-squares models were built at two temperature levels, based on a set of 29 calibration samples with different MEA and CO2 concentrations. Density, conductivity, refractive index, and sonic speed measurements were used as input data. The developed model has been validated during continuous operation of a CO2 capture pilot miniplant. Concentrations of MEA and CO2 in the liquid phase were predicted with an accuracy of 0.53 and 0.31 wt %, with MEA and CO2 concentrations ranging from 19.5 to 27.7 wt % and from 1.51 to 5.74 wt %, respectively. Process dynamics, like step changes in the CO2 flue gas concentration, were covered accurately, as well. The model showed good robustness to changes in temperature. Combining density, conductivity, refractive index, and sonic speed measurements with a multivariate chemometric method allows the real-time and accurate monitoring of the acid gas and MEA concentrations in CO2 absorption processes.Scopu

Solar hydrogen production via thermochemical iron oxide-iron sulfate water splitting cycle

This paper reports the thermodynamic analysis of solar H2 production via two-step thermochemical iron oxide–iron sulfate (IO–IS) water splitting cycle. The first step belongs to the exothermic oxidation of FeO via SO2 and H2O producing FeSO4 and H2 and second step corresponds to the endothermic reduction of FeSO4 into FeO, SO2, and O2. The products, FeO and SO2 can be recycled to step 1 and hence, reutilized for the production of H2 via water splitting reaction. Thermodynamic equilibrium compositions and variations in enthalpy, entropy and Gibbs free energy of the thermal reduction and water splitting reactions were computed as a function of reaction temperatures. Furthermore, the effect of molar flow rate of inert Ar (n˙Ar) on thermal reduction temperature (TR) and equilibrium compositions during the thermal reduction of FeSO4 was also examined. Second law thermodynamic analysis was performed to determine the cycle efficiency (ηcycle) and solar to fuel energy conversion efficiency (ηsolar−to−fuel) attainable with and without heat recuperation for varying n˙Ar (0–30 mol/s) and TR (1280–1510 K). Results obtained indicate ηcycle = 39.56% and ηsolar−to−fuel = 47.74% (without heat recuperation) and ηcycle = 51.77% and ηsolar−to−fuel = 62.43% (by applying 50% heat recuperation) at TR = 1510 K.The authors gratefully acknowledge the financial support provided by the Qatar University internal grant QUUG-CENG-CHE-13/14-4 .Scopu

Electrochemical Reduction of CO₂to Oxalic Acid: Experiments, Process Modeling, and Economics

We performed H-cell and flow cell experiments to study the electrochemical reduction of CO2 to oxalic acid (OA) on a lead (Pb) cathode in various nonaqueous solvents. The effects of anolyte, catholyte, supporting electrolyte, temperature, water content, and cathode potential on the Faraday efficiency (FE), current density (CD), and product concentration were investigated. We show that a high FE for OA can be achieved (up to 90%) at a cathode potential of -2.5 V vs Ag/AgCl but at relatively low CDs (10-20 mA/cm2). The FE of OA decreases significantly with increasing water content of the catholyte, which causes byproduct formation (e.g., formate, glycolic acid, and glyoxylic acid). A process design and techno-economic evaluation of the electrochemical conversion of CO2 to OA is presented. The results show that the electrochemical route for OA production can compete with the fossil-fuel based route for the base case scenario (CD of 100 mA/cm2, OA FE of 80%, cell voltage of 4 V, electrolyzer CAPEX of $20000/m2, electricity price of$30/MWh, and OA price of $1000/ton). A sensitivity analysis shows that the market price of OA has a huge influence on the economics. A market price of at least$700/ton is required to have a positive net present value and a payback time of less than 10 years. The performance and economics of the process can be further improved by increasing the CD and FE of OA by using gas diffusion electrodes and eliminating water from the cathode, lowering the cell voltage by increasing the conductivity of the electrolyte solutions, and developing better OA separation methods. Engineering ThermodynamicsLarge Scale Energy Storag