Sorbent-enhanced/membrane-assisted steam-methane reforming

Contemporary avenues of the Hydrogen industry: Opportunities and challenges in the eco-friendly approach

Hydrogen (H₂) is a possible energy transporter and feedstock for energy decarbonization, transportation, and chemical sectors while reducing global warming's consequences. The predominant commercial method for producing H₂ today is steam methane reforming (SMR). However, there is still room for development in process intensification, energy optimization, and environmental concerns related to CO₂ emissions. Reactors using metallic membranes (MRs) can handle both problems. Compared to traditional reactors, MRs operates at substantially lower pressures and temperatures. As a result, capital and operational costs may be significantly cheaper than traditional reactors. Furthermore, metallic membranes (MMs), particularly Pd and its alloys, naturally permit only H₂ permeability, enabling the production of a stream with a purity of up to 99.999%. This review describes several methods for H₂ production based on the energy sources utilized. SRM with CO₂ capture and storage (CCUS), pyrolysis of methane, and water electrolysis are all investigated as process technologies. A debate based on a color code was also created to classify the purity of H₂ generation. Although producing H₂ using fossil fuels is presently the least expensive method, green H₂ generation has the potential to become an affordable alternative in the future. From 2030 onward, green H₂ is anticipated to be less costly than blue hydrogen. Green H₂ is more expensive than fossil-based H₂ since it uses more energy. Blue H₂ has several tempting qualities, but the CCUS technology is pricey, and blue H₂ contains carbon. At this time, almost 80-95% of CO₂ can be stored and captured by the CCUS technology. Nanomaterials are becoming more significant in solving problems with H₂ generation and storage. Sustainable nanoparticles, such as photocatalysts and bio-derived particles, have been emphasized for H₂ synthesis. New directions in H₂ synthesis and nanomaterials for H₂ storage have also been discussed. Further, an overview of the H₂ value chain is provided at the end, emphasizing the financial implications and outlook for 2050, i.e., carbon-free H₂ and zero-emission H₂.

Novel Membrane Reactor Concepts for Hydrogen Production from Hydrocarbons: A Review

Membrane reactors are attracting increasing attention for ultrapure hydrogen production from fossil fuel, integrating catalytic reaction and separation processes into one single unit thus can realize the removal of hydrogen or introduction of reactant in situ, which removes the thermodynamic bottleneck and improves hydrogen yield and selectivity. In this review, the state-of-the-art concepts for hydrogen production through membrane reactors are introduced, mainly including fixed bed membrane reactors, fluidized bed membrane reactors, and micro-channel membrane reactors, referring higher hydrocarbons as feedstock, such as ethanol, propane, or heptane; novel heating methods, like solar energy realized through molten salt; new modular designs, including panel and tubular configurations; ultra-compact micro-channel designs; carbon dioxide capture with chemical looping; multifuel processors for liquid and/or solid hydrocarbons; etc. Recent developments and commercialization hurdles for each type of membrane reactor are summarized. Modeling the reactor is fundamental to explore complex hydrodynamics in reactor systems, meaningful to investigate the effects of some important operating factors on reactor performances. Researches for reactor modeling are also discussed. Reaction kinetics for hydrocarbons reforming and reactor hydrodynamics are summarized respectively. Cold model is introduced to investigate physical phenomena in reactors.