Current Opinion in Chemical Engineering最新文献

The oil and gas (O&G) industry has expanded significantly and brought to the surface large volumes of saline water called produced water (PW), which comprises of underground formation water, injection water, and chemical additives used during extraction and production. PW is traditionally managed via injection wells, evaporation/seepage pits, or recycling for on-site operations. There is increasing interest in PW treatment and reuse outside O&G fields due to freshwater scarcity and concerns about seismic events linked to deep-well injection. Adopting treated PW for reuse outside the O&G sector needs to address the challenges of complex water chemistry, limited toxicity data, and knowledge gaps for appropriate regulatory responses, including risk assessment frameworks on human health and the environment, socio-technical–economic assessments of treatment and reuse applications, and long-term demonstrations and monitoring of fit-for-purpose reuse. This opinion paper proposes a holistic, state-of-the-science pathway for PW treatment, management, and fit-for-purpose reuse outside O&G fields.

The societal concerns about the widespread occurrence of toxic per- and polyfluoroalkyl substances (PFAS) in different compartments of the environment have been increasing. Many remediation techniques are being investigated to lower PFAS levels in the aquatic environment. Among these various methods, ultraviolet-assisted advanced reduction processes (UV-ARPs) that use highly reducing hydrated electrons (e_aq^–) to convert PFAS into nonfluorinated small organics and fluoride (F^–) ions have received significant attention in recent years. This mini-review provides a mechanistic understanding of the degradation of PFAS using UV coupled with reductants — sulfite and iodide (i.e. UV-sulfite and UV-iodide systems). The potential advantages and difficulties of scaling up UV-ARP technology for real-time PFAS degradation are discussed. Emphasis is laid on the effectivity of UV-ARP under anoxic conditions in water. Yet, in the presence of dissolved oxygen and dissolved organic matter (DOM), PFAS degradation efficacy decreases mainly due to the rapid reactions of O₂ with reductive species (e.g. hydrated electron (e_aq^–) and atomic hydrogen (H^•)) and UV absorption by DOM. This review aims to draw the researcher's attention to pretreatment to remove DOM and anoxic conditions needed to realize the effectiveness of UV-ARPs in degrading PFAS in complex environmental water samples.

Electro-driven separation processes offer several potential advantages over pressure-driven separation processes such as reverse osmosis for water reuse and desalination, including energy savings for low-salinity waters, cation or anion selectivity, and versatility for fit-for-purpose treatment. In this perspective, we review technologies for electro-driven separation processes and evaluate their prospect for marginalized water sources and fit-for-purpose water treatment, which include improving freshwater sustainability, protecting environmental flows, and improving recycling of industrial process streams and municipal wastewater reuse. We discuss critical aspects related to application, implementation, and techno-economic evaluation of electro-driven separation technologies. Electro-driven processes provide viable options to enhance a circular water economy by reducing salinity and selectively separating contaminants while recovering valuable products with increased environmental sustainability.

To the achievement of carbon neutrality and sustainable chemical industries, optimization and reformation of energy (heat) management for catalyst design and catalysis process developments play a key role. This review examines the underlying mechanism of fundamental solid-based catalysis, for example, structure of active sites, chemical kinetics, and molecular transport, affected by temperature. In situ/operando multiscale thermometry aimed to the temperature-monitoring of local active sites, catalyst body, or reactor is overviewed. Toward precise heat supply for active sites, the examples of state-of-the-art heating techniques for solid catalysts are analyzed in detail. Through recent examples, we illustrate that innovative heating techniques combined with online spatiotemporal-resolved thermometry may initiate transformative industrial catalytic processes.

Chemical looping combustion (CLC) is under development for fuel combustion, an art of technology in terms of less energy penalty for CO₂ removal. In addition to the oxygen carrier (OC) development, the autothermal operation is another key for the success of CLC, which is mainly determined by a difference of heat of combustion per mole O₂ between the fuel and oxygen carrier (dQ_Fuel-OC). Ideally, the developed OC should have dQ_Fuel-OC > 0, that is, the coupling of OC-fuel needs to be evaluated at the beginning to check the feasibility of autothermal operation.

The advantages and developments of CLC have been well-reviewed by Henderson and recently by Lyngfelt, Abuelgasim et al., Abdalla et al., and Adánez-Rubio et al., as well as by a handbook. In this communication, the feasibility of autothermal operation of CLC is systematically analyzed. The selection of OC to couple with fuel, capacity of OC, impact of OC support materials, circulation rate of OC (mass and heat), heat-up of feeds, impact of aeration gas, reaction kinetics, and operation of CLC are discussed, aimed at providing some insights and approaches in the development of OC, which is, in any situation, fuel-determined. More attention is needed so that the CLC process can be operated in an autothermal mode and scaled up commercially in the future for CO₂ removal.

The ever-increasing global demand for energy and functional materials, coupled with the growing threat of global warming, necessitates the development of new technologies for the large-scale production of green energy carriers and materials. ThermoCatalytic Decomposition (TCD) of methane is an environmentally and economically favorable approach to produce hydrogen and valuable carbon nanomaterials simultaneously, without direct greenhouse gas emissions. The chemical kinetics of TCD can be captured by considering the maximum reaction rate and deactivation factor. However, additional studies are required to obtain a deeper understanding of the deactivation mechanisms that limit catalyst performance over time. Moreover, the development of sustainable catalysts that align with the desired application of the carbon product is essential. In order to advance the development of TCD reactors and processes, further research is urgently needed. The challenges that need to be addressed include the impact of catalyst particle growth on the reaction and reactor performance. Fluidized bed reactors (FBRs) are considered the most viable units for TCD, but require comprehensive experimental and modeling studies to assess and overcome the design and operational challenges. Numerical modeling is crucial for designing, optimizing, and evaluating TCD reactors and processes. Coupled Computational Fluid Dynamics–Discrete Element Method models with intraparticle models such as MultiGrain Model, can provide a more representation view of the complex multiscale phenomena of TCD in FBRs, enabling researchers and engineers to explore effectively different reactor concepts and designs.

Combustion of fossil fuel mostly derived originally from plant matter provides more than 80% of the energy that maintains the modern standard of living and accounts for nearly all of carbon dioxide (CO₂) emissions that now significantly exceed the amount of CO₂ required for plant life. Development of alternative non-fossil energy resources that at least keep up with the overall increase in energy demand can stop the continued increase in atmospheric CO₂ concentration, thereby reaching the often-cited goal for net-zero greenhouse gas emissions without the need to stop fossil fuel combustion. However, increasing combustion of fossil fuel partly satisfies increasing energy demand and maintains fossil fuel dominance in the energy supply. Geologic sequestration of CO₂ from stationary point source capture could mitigate nearly half of combustion emissions. As well, sequestering CO₂ acquired through direct air capture of atmospheric CO₂ could balance emissions from moving sources primarily related to transportation.

Per- and polyfluoroalkyl substances (PFAS) are persistent anthropogenic chemicals ubiquitously detected in aqueous environments. Ion exchange (IX) process is one viable technology that has exhibited promising potentials for effective removal of PFAS. IX resins offer the ability to be regenerated and reused but leave a PFAS-laden concentrate that must be treated before environmental discharge. Advanced oxidation/reduction processes such as photo- and electrochemical processes can degrade a wide range of PFAS structures, where their standalone and coupled deployment as well as integration with IX process are reviewed herein. This review identifies superior IX resin structures and novel photomediators/catalysts and electrode materials that propose prospective research lines in PFAS remediation. The knowledge obtained from this review is beneficial from both theoretical and practical perspectives for realizing sustainable remediation of PFAS.

Per- and polyfluoroalkyl substances (PFAS) are highly recalcitrant environmental contaminants that pose a serious threat to living species. As such, many chemical degradation techniques have been proposed and investigated for the efficient destruction of PFAS. A complete and efficient mineralization of high-profile and chemically diverse PFAS contaminants remains an elusive challenge facing society. The underlying reaction mechanisms for PFAS degradation approaches typically involve defluorination, cleavage of the polar head group, or thermal unimolecular reaction. These initial reaction mechanisms and subsequent reaction channels of intermediates will be discussed for various degradation strategies. This contribution aims to highlight recent efforts elucidating PFAS chemical degradation mechanisms to facilitate the advancement of PFAS destruction methods.