To explore options for simple, safe, and compact chemical reactors that preserve wanted metastable initial products from sequential unwanted reactions, academic and industrial researchers have tried to repurpose reciprocating piston equipment or an “engine-like” design to be used as a chemical reactor. Piston reactors offer the benefit of achieving very high temperature and pressure conditions at very short and defined residence times. Such conditions offer promise for enhanced performance for several chemical conversions. This paper provides a review of the published literature and patents in the field of piston reactors to provide an overview of the current state-of-the-art. The review covers multiple aspects of piston reactors and their applications, reactor design options and their operation, catalyst and ignition placement, tested reactions, experimental setups as well as modeling and simulation. Several research gaps are highlighted as a motivation for future research in the field. To help interested readers into the topic, basic concepts and fundamentals of piston reactors are provided.

We explored the practical advantages and limitations of applying a UiO-66-based metal–organic framework (MOF) catalyst in a flow microreactor demonstrated by the catalytic hydrolysis of ethyl paraoxon, an organophosphorus chemical agent. The influences of the following factors on the reaction yield were investigated: a) catalyst properties such as crystal size (14, 200, and 540 nm), functionality (NH₂ group), and particle size, and b) process conditions: temperature (20, 40, and 60 °C), space times, and concentration of the substrate. In addition, long-term catalyst stability was tested with an 18 h continuous run. We found that tableting and sieving is a viable method to obtain MOF particles of a suitable size to be successfully screened under flow conditions in a microreactor. This method was used successfully to study the effects of crystal size, functionality, temperature, reagent concentration, and residence time. Catalyst particles with a sieved fraction between 125 and 250 µm were found to be optimal. A smaller sieved fraction size showed a major limitation due to the very high pressure drop. The low apparent activation energy indicated that internal mass transfer may exist. A dedicated separate study is required to assess the impact of pore diffusion and site accessibility.

Microreactor is a very attractive laboratory device for screening conditions and solvents in an efficient, safe and fast manner. Most reported work on microreactors for CO₂ capturing deals with absorption and mass transfer performance with a limited number of studies on solvent regeneration. For the first time, foaming, which is a major operational challenge of CO₂ capturing is being studied in combination with absorption and desorption in a capillary microreactor setup. To demonstrate the setup capabilities, three known amine-based solvents (MEA, MDEA, and AMP) were selected for the screening and evaluation studies. MEA had the highest CO₂ absorption efficiency while MDEA had the lowest one. CO₂ absorption efficiency increased with temperature, liquid flow rate, and amine concentration as per the literature. During the absorption work, the Taylor flow regime was maintained at the reactor inlet. CO₂ desorption of loaded amine solutions was investigated at different concentrations and temperatures up to 85°C. MDEA solution had the highest desorption efficiency, followed by AMP and the least desorption efficiency was that of MEA. Foaming experimental results showed that MEA had a larger foaming region compared to AMP. However, more foaming happened with AMP at higher gas and liquid flow rates. A plug flow mathematical reactor model was developed to simulate the MEA-CO₂ system. The model captured well the performance and trends of the studied system, however the absolute prediction deviated due to uncertainties in the used physical properties and mass transfer correlation. Selecting a solvent for chemical absorption depends on many more factors than these three studied parameters. Still, microreactor proves a valuable tool to generate experimental results under different conditions, with the least amount of consumables (less than 1 L solvents were used), in a fast manner, combined with a knowledge insight because of the uniqueness of the Taylor flow regime.

Metal‐Organic Frameworks (MOFs) represent a highly promising class of materials with diverse applications, particularly as catalytic materials. However, their synthesis typically yields powders available only at laboratory‐scale quantities, usually in the gram range or less. This study addresses the challenge of testing limited amounts of MOF catalysts for demanding applications, such as multiphase gas‐liquid‐solid reactions in flow, utilizing a packed‐bed microreactor. Specifically, we investigate the performance of a nanoparticle (NP) ‐immobilized Pd@UiO‐66 MOF catalyst in the selective semi‐hydrogenation of phenylacetylene to styrene, serving as a model reaction. Maintaining the Taylor flow regime upstream of the catalyst bed was crucial to ensure reproducible and reliable experimental results. We conducted 88 experiments at varying liquid flow rates, temperatures ranging from 15 to 45 °C, and relative pressures spanning 0.28 to 8 bar. Styrene selectivity within the range of 80–92.3 % was achieved at phenylacetylene conversions below 20 %. Notably, the optimal condition for styrene selectivity (70 %) was attained at 98.9 % phenylacetylene conversion under the lowest H ₂ pressure and highest temperature, demonstrating the significance of low H ₂ concentration for achieving optimal styrene selectivity. Remarkably, the catalyst exhibited stable activity and selectivity over a 20 h testing period, indicating its robust performance under prolonged reaction conditions. This study demonstrates the potential of the proposed catalyst testing system as a rapid and efficient approach for early‐stage exploration studies, particularly when limited quantities of catalyst, typically in the gram scale or less, are available.

To effectively evaluate the feasibility of plastic waste via chemical routes such as pyrolysis, decision-makers need comprehensive economic and environmental assessments based on reliable sustainability metrics, which are derived from navigating complex interactions across multiple scales. Despite the extensive research in this field, a significant gap remains in linking these scales through a common working framework. This work presents a methodology, with steps and checklists that bridge laboratory experimental results to high-level decision-making, demonstrated using plastic waste pyrolysis to fuels. From the experimental laboratory data, a 4-lumped kinetic model was incorporated in 1D pseudo-homogeneous plug flow reactor model to predict the reactor performance. The reactor performance was examined by varying residence time, heat transfer coefficient, and wall temperature, focusing on their impact on product. The conditions that gave the lowest reactor energy consumption and maximum plastic throughput were selected for further analysis. Two process flow sheets were constructed around this case: one using gas products for heat supply and another producing LPG (C2–C3) with liquid products. The results from the developed processes are benchmarked against five systems from the literature using multicriteria analysis on annual cost, product sales, profit, and circularity. The study showed that using gas to supply heat in pyrolysis maximized circularity (DOCI = 0.6) due to resource efficiency, whereas selling LPG (C2–C3) along with the liquid products yields the highest profit 2.2 MM USD/y. Overall, the variability in results highlights the potential of this one common framework methodology toward making decision more visible right from laboratory investigation, addressing the lack of methodological integration across the scales including modeling gaps, and identifying the most sustainable option for plastic waste conversion. Graphical Abstract