Iranian Journal of Chemical Engineering (IJChE)

Abstract The rapid growth in global demand for clean and sustainable energy has intensified the need for efficient hydrogen (H2) production technologies. Thermochemical recycling of plastic waste has emerged as a promising approach, offering both environmental benefits and the generation of high-purity, low-carbon H2. This study evaluates the technical and economic feasibility of H2 production from diverse plastic waste streams using Aspen HYSYS and the Aspen Economic Analyzer. The process integrates polymer pyrolysis, chlorine removal, and steam reforming. Feedstocks (200×10³ t/y) include polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyethylene terephthalate (PET), and mixed industrial and municipal waste from packaging (PKG), medical (MED), automotive (AUT), municipal solid waste (MSW), construction (CON), and textile (TEX) sectors. H2 production yield strongly depends on the feedstock composition, ranging from 0.14 to 0.31 t H₂/t feed. PET with the lowest H/C ratio, exhibits the lowest yield, whereas PE and PP achieve the highest yields, albeit with incomplete carbon-to-CO conversion. Oxygenated polymers, such as PET, generate the highest CO2 emissions (~1.4 t/t feed). Economic analysis indicates that PE and MED are the most cost-effective feedstocks, with gross margins of 62 and 66% and annual net profits of 232×10⁶ and 223×10⁶ USD, respectively.

Abstract Nowadays, increasing demand for sustainable energy sources has led to a growing interest in using biomass as a renewable feedstock for producing hydrogen and methanol. The main objectives of this study involve simulation and economic analysis and evaluation of synthesis gas, hydrogen, and methanol production processes from various biomass sources using Aspen HYSYS software. Three lignocellulosic sources were waste wood biomass (WWB), thin hardwood chips biomass (THWCB), and almond shells biomass (ASB). In the first part of the simulation, the unrefined synthesis gas was produced through a multi-stage biomass gasification process. The outcomes reveal that the yield and composition of synthesis gas were increased by raising the steam-to-biomass ratio (SBR). Subsequently, an integrated model for hydrogen production from various biomass sources was examined through gasification in the presence of steam and oxygen through a water-gas shift (WGS) reaction and the separation and purification of the produced hydrogen using a pressure swing adsorption (PSA) unit. Finally, the hydrogen produced in the previous step was fed to the methanol synthesis unit. The results of the simulation of the gasification process of various lignocellulosic biomasses showed that the use of WWB, THWCB, and ASB can yield annual hydrogen production of 261,000, 349,344, and 361,656 kg, respectively. Consequently, the economic analyses indicated that hydrogen and methanol production from biomass is associated with significant efficiency and profitability. Furthermore, the comparison of synthesis gases' heating values derived from three biomasses revealed that the highest heating values were generated from ASB, THWCB, and WWB, respectively.

Abstract In the present work, the effect of synthesis method (simultaneous impregnation and coprecipitation) and copper to nickel active phases loading were investigated in Ni-Cu-Al catalysts. The water/ethanol molar ratio of 6 and gas hourly space velocity (GHSV) of 20000 hr^-1 were used in all the experiments. The catalysts were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) techniques. The catalytic activity results revealed that 13Ni-6Cu/γ-Al₂O₃ impregnated catalyst was more active than co-precipitated one (13NiO-6CuO-81Al₂O₃) in the same amount of compositions of active metals and Al₂O₃, but by increasing the active phases (Cu and Ni) loading in co-precipitated catalysts (24NiO-31CuO-45Al₂O₃, 31NiO-24CuO-45Al₂O₃, 40NiO-15CuO-45 Al₂O₃ and 47NiO-8CuO-45Al₂O₃), they achieved a better performance than 13NiO-6CuO-81Al₂O₃ catalyst. The 40NiO-15CuO-45Al₂O₃ catalyst showed 99% ethanol conversion, as well as 303 hydrogen yield and 4% CO selectivity at 470^oC. SEM images revealed agglomerated particles for the samples with high Al₂O₃ content and with increasing the active phase content in the catalyst the particle sizes decreased. The 40NiO-15CuO-45Al₂O₃ showed smallest particle size among the catalysts.

Abstract Catalytic naphtha reforming is one of the most important processes in which, low quality naphtha is converted into high octane motor gasoline. In this study, a mathematical model was developed and was used for investigation the effect of temperature, pressure, hydrogen to hydrocarbon ratio on the octane number, the yield of product and the undesirable phenomena of coke deposition in a semiregenerative catalytic reforming unit. The result of the model was compared to the plant data to verify the model accuracy. Then, the model was used to find the optimal condition for the maximum value of octane number and yield of product and the minimum value of coke deposition. The optimum condition of the process is estimated using genetic algorithm optimization method as an efficient optimization method. In the optimal condition, the octane number and the yield of the product are improved 0.3% and 1.23% respectively, and the coke deposition is reduced 2.1 %.

Abstract The main focus of this study is improvement of the steam-methane reforming (SMR) process by in-situ CO2 removal to produce high hydrogen content synthesis gas. Sorption-enhanced (SE) concept is applied to improve process performance. In the proposed structure, the solid phase CO2 adsorbents and pre-reformed gas stream are introduced to a gas-flowing solids-fixed bed reactor (GFSFBR). One dimensional mathematical model is developed to evaluate the effect of adsorbents on the efficiency of SMR at steady-state condition. To prove the accuracy of the considered model, simulation results are compared against available industrial plant data. Modeling results represent that application of SE method in SMR enhances syngas production and reduces CO2 content. The reported data indicate that by overcoming thermodynamic limitations and controlling coke formation, CH4 conversion and H2 yield improve about 23% and 29%, respectively. For more investigation, sensitivity analyses of some related parameters of the pre-reformed gas are performed to predict optimum conditions. Finally, the proposed GFSFBR for the SMR process leads to higher hydrogen production and H2/CO ratio. As the last part, non-dominated sorting genetic algorithm-II is applied to perform multi-objective optimization of the SE-SMR.

Abstract Effect of copper content, calcination temperature and activation method on the activity and selectivity of copper-silica aerogel catalysts for hydrogen production from methanol steam reforming was investigated. Results showed the copper content had the highest impact and the activation condition had the lowest impact on the catalyst performance. It was found that Cu-SiO 2 aerogel was a promising catalyst for methanol steam reforming. The only parameter which influences the CO selectivity was copper content. Using the best prepared catalyst, no CO formation was detected in the common condition of reaction. In the used range of feed flow rates, methanol conversion was increased 1.5-2.26 times by increasing the copper content from 7.7 to 13.3wt%. Characteristics/performance relationship showed that the samples in which copper species exist as CuO clusters had the best performance to increase the hydrogen production rate and decrease the CO formation. Formation of CuO clusters was increased by increasing the copper loading and calcination temperature. It was found that due to the reducibility behaviour of copper-silica aerogels the activation method of catalysts had almost no effect on the catalytic performance