Steam reforming of polystyrene at a low temperature for high H2/CO gas with bimetallic Ni-Fe/ZrO2 catalyst

Recent Advances in Catalytic Pyrolysis of Municipal Plastic Waste for the Production of Hydrocarbon Fuels

Currently, the resources of fossil fuels, such as crude oil, natural gas, and coal, are depleting day by day due to increasing energy demands. Nowadays, plastic items have witnessed a substantial surge in manufacturing due to their wide range of applications and low cost. Therefore, the amount of plastic waste is increasing rapidly. Hence, the proper management of plastic wastes for sustainable technologies is the need of the hour. Chemical recycling technologies based on pyrolysis are emerging as the best waste management approaches due to their robustness and better economics. However, research on converting plastic waste into fuels and other value-added goods has yet to be undertaken, and more R&D is required to make waste-plastic-based fuels economically viable. In this review article, the current status of the plastic waste pyrolysis process is discussed in detail. Process-controlling parameters such as temperature, pressure, residence time, reactor type, and catalyst dose are also investigated in this review paper. In addition, the application of reaction products is also described in brief. For example, plasto-oil obtained by catalytic pyrolysis may be utilized in various sectors, e.g., transportation, industrial boilers, and power generation. On the other hand, byproducts, such as solid residue (plasto-char), could be used as a road construction material or to make activated carbon or graphenes, while the non-condensable gases have a good potential to be utilized as heating/energy source.

Progress on Catalyst Development for the Steam Reforming of Biomass and Waste Plastics Pyrolysis Volatiles: A Review

In recent decades, the production of H₂ from biomass, waste plastics, and their mixtures has attracted increasing attention in the literature in order to overcome the environmental problems associated with global warming and CO₂ emissions caused by conventional H₂ production processes. In this regard, the strategy based on pyrolysis and in-line catalytic reforming allows for obtaining high H₂ production from a wide variety of feedstocks. In addition, it provides several advantages compared to other thermochemical routes such as steam gasification, making it suitable for its further industrial implementation. This review analyzes the fundamental aspects involving the process of pyrolysis-reforming of biomass and waste plastics. However, the optimum design of transition metal based reforming catalysts is the bottleneck in the development of the process and final H₂ production. Accordingly, this review focuses especially on the influence the catalytic materials (support, promoters, and active phase), synthesis methods, and pyrolysis-reforming conditions have on the process performance. The results reported in the literature for the steam reforming of the volatiles derived from biomass, plastic wastes, and biomass/plastics mixtures on different metal based catalysts have been compared and analyzed in terms of H₂ production.

Recent Progress in Low-Cost Catalysts for Pyrolysis of Plastic Waste to Fuels

The catalytic and thermal decomposition of plastic waste to fuels over low-cost catalysts like zeolite, clay, and bimetallic material is highlighted. In this paper, several relevant studies are examined, specifically the effects of each type of catalyst used on the characteristics and product distribution of the produced products. The type of catalyst plays an important role in the decomposition of plastic waste and the characteristics of the oil yields and quality. In addition, the quality and yield of the oil products depend on several factors such as (i) the operating temperature, (ii) the ratio of plastic waste and catalyst, and (iii) the type of reactor. The development of low-cost catalysts is revisited for designing better and effective materials for plastic solid waste (PSW) conversion to oil/bio-oil products.

Effect of different ash/organics and C/H/O ratios on characteristics and reaction mechanisms of sludge microwave pyrolysis to generate bio-fuels

To study the effects of different ash/organics and C/H/O ratios on bio-fuel characteristics and energy efficiency, four kinds of sludge with different properties were used for microwave pyrolysis (800 °C). Moreover, the microwave pyrolysis reaction mechanisms of different sludge were also explored. The results showed that high-ash sludge could accelerate the frequency of polar molecule rotation in the microwave field due to the presence of oxides with dielectric properties in ash, thereby achieving faster heating rates and higher temperatures. However, compared with high-organic sludge, high-ash sludge exhibited lower bio-gas yield and higher bio-char yield. As the H/C ratio increased from 0.127 to 0.148, the bio-gas yield increased from 15.41% to 40.01%, and the content of H₂ in bio-gas and aliphatics in bio-oil increased to 36.69 vol% and 26.54 wt%, respectively. When the O/C ratio was reduced to 1.31, the content of CO and oxygenated compound in bio-oil increased to 31.25 vol% and 40.04 wt%, which lowered the quality of the bio-oil. Those consequences also determined that a mixture of sludge with different ash/organic ratios could be pyrolyzed to obtain high-quality bio-fuels and high energy efficiency. Differences in C/H/O ratios in the mixed sludge greatly affected the microwave pyrolysis heating process, which affected the pyrolysis reactions and the quality of the bio-fuels. Therefore, this study provides a theoretical basis to elevate the quality of bio-fuels and reduce microwave pyrolysis costs.

Catalytic Steam Reforming of Bio-Oil-Derived Acetic Acid over CeO2-ZnO Supported Ni Nanoparticle Catalysts

The steam reforming of bio-oil-derived acetic acid over the developed Ni/CeO₂-ZnO nanoparticle catalysts for hydrogen production was studied. The correlations of CeO₂ to ZnO mass ratio (CZMR) and nickel loading with the properties and performances of Ni/CeO₂-ZnO catalysts were explored. The H₂, CO, and potential H₂ yields followed a Gaussian normal distribution with increasing the CZMR. An exponential function equation was established to correlate the H₂, CO, and potential H₂ yields with Ni loading. As the CZMR increased from 0 to 1/3, the H₂ yield increased from 57.8 to 69.4%, with a growth rate of 20.1%. Further, on increasing the CZMR from 1/3 to 3, the H₂ yield decreased by 37.6%. The CO yield showed a similar trend for the H₂ yield on increasing the CZMR, which first increased to a peak value, then started to decrease rapidly and finally stabilized. The yield of H₂ increased significantly from 20.6 to 73.5%, with the increase of nickel loading from 0 to 15%. Further, on increasing the nickel loading from 15 to 25%, the H₂ yield increased by only 5.8%. With the CZMR of 1/3 and the nickel loading of 15%, the selectivities of H₂ and CO were as high as 91.6 and 42.3%, respectively.