The direct partial oxidation of methane to methanol promises an energy‐efficient and environmental‐friendly utilization of natural gas. Unfortunately, current technologies confront a grand challenge in catalysis, particularly in the context of distributed sources. Research has been focused on the design of homogenous and heterogenous catalysts to improve the activation of methane under thermal and electrochemical conditions. However, the intrinsic relationship between thermal and electrochemical systems has not been exploited yet. This review intends to bridge the studies of thermal and electrochemical catalysts, in both homogenous and heterogenous systems, for methane activation from a mechanistic point of view. It is expected to provide a framework to rationalize the design of electrocatalysts beyond the state of art. First, methane activation systems reported previously are reviewed and classified into two basic mechanisms: dehydrogenation and deprotonation. Based on the mechanism types, activity and selectivity descriptors are defined to understand the performance of current catalysts and guide the design of future catalysts. Moreover, methods to enhance the activity and selectivity are discussed to emphasize the unique advantage of electrocatalysis in overcoming the limitations of traditional thermal catalysis. Finally, immense opportunities and challenges for catalyst design are discussed by unifying thermal and electrochemical catalysis.

One of the ways by which grease is evaluated is by using a four‐ball wear test using ASTM D2266. However, actual applications may require bearings to be subjected to spectrum loading conditions. This study focuses on using ball milling to mitigate the wear from sharp edges in the MoS2 particles. Two different blends of greases were formulated using MoS2 in the as‐received state (unmilled) and milled MoS2; they were tested under spectrum loading conditions where the load and frequency of the tests were treated as variables. It was found that ball milling of the MoS2 significantly reduces the wear under spectrum loading condition both for ramp‐up and ramp‐down conditions. It was also shown that shortening the time step for both the ramp‐up and ramp‐down cycles resulted in larger wear for unmilled MoS2 particles in comparison with milled MoS2 particles in grease. The milling process did not play a significant role when frequency of the test was either ramped up or down. Copyright © 2015 John Wiley & Sons, Ltd.

Two different greases formulated using MoS2 and a combination of ZDDP and functionalized PTFE (F-PTFE) were examined under spectrum loading conditions where loads, frequency, and duration of the steps were treated as variables. Combination of ZDDP and F-PTFE were synergistic resulting in a significant reduction in the wear and friction under spectrum loading condition. Decreasing the time step during the ramp up and ramp down cycles resulted in larger wear for the grease containing MoS2 particles in comparison to ZDDP/F-PTFE in grease. The tribofilm formed on the surface was analyzed using various characterization techniques like SEM, EDS, and Stereo Optical Microscopy. Tribofilms from MoS2 additives had extensive amounts of abrasive and adhesive wear and showed the formation of MoS2 on the surface on the other hand the tribofilms from ZDDP/F-PTFE had smaller amounts of severe wear and exhibited patchy tribofilms of Zn-phosphates as well as sulfides of Zn and Fe.

Atmospheric water capture (AWC) has tremendous potential to address the global shortage of clean drinking water. The Ni 2 Cl 2 (BTDD) metal−organic framework (MOF) has shown optimal water sorption performance under low relative humidity conditions, but its potentially high production costs, stemming in part from its lengthy multiday synthesis, has hindered widespread implementation. As with most traditional MOF syntheses, the original synthesis of Ni 2 Cl 2 (BTDD) involves batch reactors that have intrinsic inefficiencies impacting productivity during scale-up. We report a continuous manufacturing process for Ni 2 Cl 2 (BTDD) that can achieve higher yields, reduced solvent use, and drastically faster crystallization times in comparison to the batch process. Optimization of the synthesis space in the flow reactor as a function of residence time, temperature, and solvent volume yields 50% and 40% reductions in methanol and hydrochloric acid consumption by volume, respectively, with a simultaneous 3-fold increase in productivity (defined in units of kg MOF m −3 day −1 ). A computational fluid dynamics (CFD) model was developed to quantitate productivity enhancements in the flow reactor based on improved heat-transfer rates, larger surface-area to volume ratios, and effective residence times. This work adds critical facets to the growing body of research suggesting that the synthesis of MOFs in flow reactors offers unique opportunities to reduce production costs.

Effects of diesel soot composition and accumulated vehicle mileage on soot oxidation characteristics were examined. Four soot samples were extracted from the crankcase oils of diesel engines that had accumulated different mileages. Carbon black was used as a comparative example. Soot structure was studied in situ using X-ray diffraction as it was oxidized to temperatures as high as 700 °C. The soot from older engines exhibited a higher increase in lattice spacing (d 002) with an increase in temperature that resulted in soot samples being at lower temperatures, thereby reducing the oxidation resistance. Composition of the residues after oxidation was studied using X-ray diffraction, energy-dispersive spectroscopy, and X-ray absorption near-edge structure. Oxidation residue of the soot samples is made up of decomposed lubricant additives compounds and debris from wear and tribofilms. XRD phase analysis showed that crystalline compounds in soot are CaSO4, CaZn2­(PO4)2, Ca3­(PO4)2, Zn3­(PO4)2, and ZnO. The turbostratic structure of all the soots irrespective of engine age is similar prior to oxidation; however, the embedded crystalline and amorphous species in the soot change with accumulated mileage. Surface area of the soot measured using BET was found to be inversely proportional to the weight of residue.

The continous flow reactor can synthesize MOF-808—an industrially relevant MOF—in 5 minutes compared to 48 hours in Batch, while maintaining crystallinity and porosity of the final product.

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A fundamental understanding of the crystallization pathways for metal− organic frameworks (MOFs) allows for exploring the untapped combinatorial space of the organic and inorganic building units, creating possibilities to synthesize highly crystalline frameworks with desired physicochemical properties. In this work, we employ a continuous flow reactor to elucidate the kinetics of crystallization for the Zr-based MOF-808 using time-resolved powder X-ray diffraction measurements. Specifically, we fit the crystallization curves obtained experimentally using the Gualtieri model to determine the rate constants for nucleation (k N ) and growth (k G ) for different linker concentrations and temperatures. Higher linker concentrations reduce the competitive coordination of the formate ligand (growth modulator) with the secondary building unit, resulting in higher nucleation and growth rates. The activation energies obtained from Arrhenius plots for nucleation (E a (N)) and growth (E a (G)) are 64.7 ± 4 and 59.2 ± 5 kJ mol −1 , respectively. At constant residence time, temperature, and composition, higher flow velocities increase the advective transport of precursor species to nucleation sites in the slugs resulting in increased crystal growth rates and thus higher average crystal sizes. Variation in the total flow rate from 0.334 to 1.067 mL/min increased the average crystal sizes from ∼105 ± 22 to ∼180 ± 19 nm, with other parameters held constant. We demonstrate that performing crystallization in the flow reactor provides a unique opportunity to tailor MOF crystal sizes. By strictly controlling the temperature, residence time, and mixing parameters, our results showcase the advantages of flow systems for performing rigorous crystallization and structural evolution studies that can be applied for the synthesis of other MOFs with tailored physicochemical properties.