Flexible operation of modular electrochemical CO2 reduction processes

Electrochemical CO2 reduction (eCO2R) is an emerging technology that is capable of producing various organic chemicals from CO2, but its high electricity cost is a big economic obstacle. One solution to reduce the cumulative electricity cost is demand side management, i.e., to adjust the power load based on time-variant electricity prices. However, varying the power load of CO2-electrolyzers often leads to changes in Faraday efficiency towards target components and thereby influences the product composition. Such deviations from the target product composition may be undesired for downstream processes. We tackle this challenge by proposing a flexible operating scheme for a modular eCO2R process. We formulate the economically optimal operation of an eCO2R process with multiple electrolyzer stacks as a parallel-machine scheduling problem. Adjusting the power load of each sub-process properly, we can save electricity costs while the desired product composition is met at any time. We apply an algorithm based on wavelet transform to solve the resulting large-scale nonlinear scheduling problem in tractable time. We solve each optimization problem with a deterministic global optimization software MAiNGO. We examine flexible operation of a modular eCO2R process for syngas production. The case studies show that the modular structure enables savings in the cumulative electricity cost of the eCO2R process via flexible operation while deviations in the syngas composition could be reduced. Also, the maximum ramping speed of the entire process is found to be a key parameter that strongly influences the cost saving.

Biofuel production over Fischer-Tropsch synthesis: effect of Fe-Co/meso-HZSM-5 catalyst weight on product composition and process conversion

Fischer-Tropsch Synthesis (FTS) using Fe-Co/meso-HZSM-5 catalyst has been investigated. The impregnated iron and cobalt on HZSM-5 could be used as bifunction catalyst which combined polimerizing synthesis gas and long hydrocarbon cracking for making biofuel (saturated C5–C25 hydrocarbons as gasoline, kerosene and diesel oil). The study emphasized the effect of catalyst weight on product composition and process conversion. The HZSM-5, had been converted from ammonium ZSM-5 through calcination, and then desilicated with NaOH solution. The Co(NO3)2.6H2O and Fe(NO3)3.9H2O were used as precursor for incipient wetness impregnation (IWI) on amorphous meso-HZSM-5. The catalyst consisted of 10 % Fe and 90 % Co by weight, called 10Fe-90Co/meso-HZSM-5. All catalysts were reduced in situ in the continuous reactor with flowing hydrogen at 25 mL/min, 1 bar, 400 °C for 10 hours. The catalyst performance was observed in the same continuous fixed bed reactor at 25 mL/min synthesis gas (30 % CO, 60 % H2, 10 % N2), 250 °C, 20 bar for 96 hours. Various catalyst weight (1, 1.2, 1.4, 1.6 gram) were applied in FTS. The desilicated HZSM-5 properties (BET analysis) were 6.1–29.9 nm mesoporous diameter, 0.3496 cc/g average mesoporous volume, 526.035 cc/g pore surface area, and the EDX analysis gave 22.1059 Si/Al ratio and 16.11 % loading (by weight) on meso-HZSM-5. The reduced catalyst showed the XRD spectra of Fe (66°), Fe-Co alloy (44.50°) and Co3O4 (36.80°). The reaction using 1 gram of 10Fe-90Co/meso-HZSM-5 catalyst produced the largest composition and conversion. The 1 gram catalyst gave the largest normal selectivity of gasoline (19.15 %) and kerosene (55.18 %). While the largest normal diesel oil selectivity (24.17 %) was obtained from 1.4 gram of catalyst. The CO conversion per gram of catalyst showed similar value (CO conversion of 26–28 %) for all catalyst weight

The Second Hyper-Zagreb Coindex of Chemical Graphs and Some Applications

The second hyper-Zagreb coindex is an efficient topological index that enables us to describe a molecule from its molecular graph. In this current study, we shall evaluate the second hyper-Zagreb coindex of some chemical graphs. In this study, we compute the value of the second hyper-Zagreb coindex of some chemical graph structures such as sildenafil, aspirin, and nicotine. We also present explicit formulas of the second hyper-Zagreb coindex of any graph that results from some interesting graphical operations such as tensor product, Cartesian product, composition, and strong product, and apply them on a q-multiwalled nanotorus.

Thermochemical Recycling of Oily Sludge by Catalytic Pyrolysis: A Review

The main methods of treating oily sludge at home and abroad and the current research status of oily sludge pyrolysis technology are briefly described, and four commonly used catalysts are introduced: metals, metal compounds, molecular sieves, metal-supported molecular sieves, and biomass catalysts for oily sludge. The influence of pyrolysis, the pyrolysis mechanism, and the product composition of oily sludge with the addition of different catalysts are also discussed. Finally, the development direction of preparing new catalysts and the mixed use of multiple catalysts is proposed as a theory to provide for the efficient and reasonable utilization of oily sludge.