• Energy Research

AbstractMicrowave (MW)‐assisted catalytic pyrolysis represents a promising method for transforming petroleum‐based plastic waste into valuable chemicals, offering a pathway towards more sustainable circular economy. In this study, catalytic pyrolysis of low‐density polyethylene (LDPE) was conducted under MW irradiation. The influence of various catalyst types (HZSM‐5, Ga/ZSM‐5, Ga/Ni/ZSM‐5, Ga/Co/ZSM‐5, and Ga/Cu/ZSM‐5) on product yield and distribution was examined. The results revealed that the Ga/ZSM‐5 catalyst yielded the maximum liquid oil, approximately 41%. Ga/Ni/ZSM‐5 performed excellently in the production of long‐chain olefins, constituting about 27% of the liquid fraction. However, Ga/Co/ZSM‐5 led to the production of heavy pyrolysis oil containing nearly 25% long‐chain paraffins, rendering it unsuitable for producing high‐value chemicals. Conversely, the Ga/Cu/ZSM‐5 catalyst yielded an aromatic‐rich pyrolysis oil, with benzene derivatives constituting approximately 90% of the liquid oil fraction, thus proving to be a suitable catalyst for the intended application. The liquid product distribution was compared with a petroleum assay by SimDist, and this suggested that utilizing the HZSM‐5 catalyst could yield an 86.4% naphtha fraction. The study also revealed that the Ga/Cu/ZSM‐5 catalyst generated the largest amounts of hydrogen and syngas, as determined by a MicroGC analysis of the gas products. This catalyst also exhibited the maximum coke deposition (1.35%) postreaction, which was attributed to its high aromatic hydrocarbon content in the pyrolysis oil and maximal hydrogen release. A comparison of fresh and spent catalyst properties was conducted to gain insights into catalyst activity and to correlate the effects of metal doping on product distribution. These findings underscore the potential of MW‐assisted catalytic pyrolysis, particularly with the Ga/Cu/ZSM‐5 catalyst, for the efficient conversion of plastic waste into valuable chemicals, thereby contributing to sustainable resource utilization and environmental conservation.

Abstract The elevated energy demands from past decades has created the energy gaps which can mainly be fulfilled through the consumption of natural fossil fuels but at the expense of increased greenhouse gas emissions. Therefore, the need of clean and sustainable options to meet energy gaps have increased significantly. Gasification and steam methane reforming are the efficient technologies which resourcefully produce the syngas and hydrogen from coal and natural gas, respectively. The syngas and hydrogen can be further utilized to generate power or other Fischer Tropsch chemicals. In this study, two process models are developed and technically compared to analyze the production capacity of syngas and hydrogen. First model is developed based on conventional entrained flow gasification process which is validated with data provided by DOE followed by its integration with the reforming process that leads to the second model. The integrated gasification and reforming process model is developed to maximize the hydrogen production while reducing the overall carbon dioxide emissions. Furthermore, the integrated model eradicates the possibility of reformer’s catalyst deactivation due to significant amount of H2S present in the coal derived syngas. It has been seen from results that updated model offers 37% increase in H2/CO ratio, 10% increase in cold gas efficiency (CGE), 25% increase in overall H2 production, and 13% reduction in CO2 emission per unit amount of hydrogen production compared to base case model. Furthermore, economic analysis indicated 8% reduction in cost for case 2 while presenting 7% enhanced hydrogen contents.

Abstract We report a strategy for production of 5-nonanone which is a bio-based platform chemical that can be produced in large quantity from a variety of lignocellulosic biomass sources. In this strategy, the cellulose and hemicellulose fractions of lignocellulosic biomass are catalytically converted to γ -valerolactone (GVL) using the biomass derived GVL as a solvent. To generate the integrated strategy, we develop separation subsystems to achieve high purity of product. Importantly, GVL can be upgraded to 5-nonanone with high yield in a single reactor using a dual catalyst bed of Pd/Nb2O5 plus ceria-zirconia. We design a heat exchanger network to satisfy the total energy requirements of the integrated process via combusting lignin fraction of biomass. Economic feasibility of the process is investigated using discounted cash flow analysis.

The present work discusses the development and application of a machine-learning-based model to predict the enthalpy of combustion of various oxygenated fuels of interest. A detailed dataset containing 207 pure compounds and 38 surrogate fuels has been prepared, representing various chemical classes, namely paraffins, olefins, naphthenes, aromatics, alcohols, ethers, ketones, and aldehydes. The dataset was subsequently used for constructing an artificial neural network (ANN) model with 14 input layers, 26 hidden layers, and 1 output layer for predicting the enthalpy of combustion for various oxygenated fuels. The ANN model was trained using the collected dataset, validated, and finally tested to verify its accuracy in predicting the enthalpy of combustion. The results for various oxygenated fuels are discussed, especially in terms of the influence of different functional groups in shaping the enthalpy of combustion values. In predicting the enthalpy of combustion, 96.3% accuracy was achieved using the ANN model. The developed model can be successfully employed to predict the enthalpies of neat compounds and mixtures as the obtained percentage error of 4.2 is within the vicinity of experimental uncertainty.

This study has been dedicated towards the conversion of plastics to methanol and hydrogen. The base design (case 1) represents the conventional design for producing syngas via steam gasification of waste plastics followed by CO2 and H₂S removal. The syngas then processed in the methanol synthesis reactor to produce methanol, whereas, the remaining unconverted gases are processed in water gas shift reactors to produce hydrogen. On the other hand, an alternative design (case 2) has been also developed with an aim to increase the H2 and methanol production, which integrates the plastic gasification and the methane reforming units to utilize the high energy stream from gasification unit to heat up the feed stream of reforming unit. Both the cases have been techno-economically compared to evaluate the process feasibility. The comparative analysis revealed that case 2 outperforms the case 1 in terms of both process efficiency and economics.

Abstract Since decades, one of the major troublesome environmental issue to the society is Polystyrene waste. Thermal conversion method can be used to transform the plastic waste into useful energy source. In this study, liquefaction technique using ethanol as a solvent was used to produce liquid fuel from polystyrene. The experiments were performed at different temperatures (290–370 °C), ethanol to polystyrene ratios (0.25:1–4:1) and reaction times (15–75 min) in an autoclave batch reactor. After characterization, quantitative and qualitative evaluation of liquid products; results showed that at temperature of 350 °C, ethanol to polystyrene ratio of 0.5:1 and reaction time of 60 min, highest liquid yield of 84.7 wt% was achieved. The viscosity, density, pH, calorific value and flash point of the oil product at this condition was 0.36 cP, 0.88 g/mL, 6.86, 40.91 MJ/kg and 55 °C respectively. Through GC–MS analysis, it was found that the oil product was mostly composed of aromatics, alkenes and alkyls; which made the liquid oil suitable to be used as fuel. In addition, comparative study was conducted by replacing ethanol with water as solvent under same conditions. Based on results, study proved ethanol to be better solvent than water which is commonly used in liquefaction process. Lastly, the liquid fuel produced is suitable to be used as alternative energy source for conventional fossil fuels.

The torrefaction of lignocellulose biomass was conducted to produce biochar with properties compatible with coal. Two lignocellulose biomasses, pearl millet (PM) and walnut shell (WS), were torrefied at different process temperatures (230-300 °C), residence times (30-90 min), and different compositional biomass blends to improve the characteristics of the biochar product. The resulting biochar product exhibited favorable changes in their properties. The pure biomasses and their blends obtained a high biochar yield (41-91%). The gross calorific value (GCV) ranged from 22 to 27 MJ/kg, showing an increase of 22-59% compared to the raw biomass. The torrefaction temperature had the most notable effect on the biochar quantity and quality. The biochar samples obtained from the torrefaction of different blends showed a higher GCV and other physicochemical characteristics than the pure biomasses. Scanning electron microscopy showed that these products might also be used for other applications.

Abstract Liquefaction of poly-isoprene based rubber (PIR) was performed using ethanol as a solvent for the production of liquid fuel and chemicals. An autoclave batch reactor was used to perform the ethanolysis of PIR at different temperature ranges (250–375 °C), with different ethanol to PIR ratio (0.5:1 to 4:1), and at different reaction times (15–75mins). The experimental results showed that a maximum yield of 86 wt % was achieved at temperature of 325 °C, ethanol to PIR ratio 1/1, and reaction time of 30 min. This liquid oil yield is about 14% higher than the yield obtained from the pyrolysis of PIR at 500 °C and about 10% higher than the yield obtained from hydrothermal liquefaction of PIR at 375 °C. Moreover, the utilization of ethanol in the process was also incorporated and product yields were redefined. Furthermore, ethanol contributed to enhance the quality of liquid-oil, particularly in term of viscosity, acidity, and energy density. Furthermore, the FTIR analysis showed methyl and methylene were most dominating functional groups found in the liquid product and GCMS analysis identified that they were presented by alkenes, aromatics, and alkyls.

Abstract An increase in energy demand in the recent decades have created energy shortages that can be fulfilled by the use of fossil fuels. Gasification and reforming techniques are effective methods for producing syngas and hydrogen from natural gas and coal. The two process models have been developed in this study, in which syngas and hydrogen is produced from coal and natural gas. The case 1 relies on the entrained flow gasification unit which is validated by literature data, and then integrated with the reforming process reforming to generate the case 2. The integrated gasifier and reforming model was created to increase H2 output while lowering the total carbon footprints. In case of 2nd model, the hydrogen to carbon monoxide ratio (HCR) is 1.20 which is almost 88% higher than the baseline. Due to the higher HCR in case 2, the overall production of H2 is 55% higher than the case 2. Moreover, the efficiency of case 2 is 18.5% higher which reduces the carbon emissions by 69.6% per unit of hydrogen production compared to case 1.Furthermore, the investment per ton of hydrogen production and hydrogen selling prices in Case 2 is 28.9% lower compared to the case 1 design.