Pacific Northwest National Laboratory

About: Pacific Northwest National Laboratory is a facility organization based out in Richland, Washington, United States. It is known for research contribution in the topics: Catalysis & Aerosol. The organization has 11581 authors who have published 27934 publications receiving 1120489 citations. The organization is also known as: PNL & PNNL.

Ethylenediamine-modified SBA-15 as Regenerable CO2 Sorbent

Abstract: The CO2 adsorption properties of an ethylenediamine-modified mesoporous silica, EDA-SBA-15, have been examined. Adsorption isotherms were collected by TGA measurements, and the breakthrough time and adsorption capacity were measured using a fixed-bed flow system. The EDA-SBA-15 sorbent adsorbs around 20 mg/g of CO2 from 15% CO2 in N2 at 25 °C and 1 atm total pressure. In pure CO2 at 1 atm, its adsorption capacity is 86 mg/g at 22 °C. The EDA-SBA-15 sorbent is fully regenerable by thermal swings during cyclic adsorption/desorption. Desorption of CO2 occurs at 110 °C on EDA-SBA-15 and the sorbent is stable in air up to 200 °C. The CO2 uptake by EDA-SBA-15 is not influenced by humidity. The adsorption capacity data are compared with those of previously reported amine-modified silica sorbents.

Sintering-Resistant Single-Site Nickel Catalyst Supported by Metal–Organic Framework

Abstract: Developing supported single-site catalysts is an important goal in heterogeneous catalysis since the well-defined active sites afford opportunities for detailed mechanistic studies, thereby facilitating the design of improved catalysts. We present herein a method for installing Ni ions uniformly and precisely on the node of a Zr-based metal–organic framework (MOF), NU-1000, in high density and large quantity (denoted as Ni-AIM) using atomic layer deposition (ALD) in a MOF (AIM). Ni-AIM is demonstrated to be an efficient gas-phase hydrogenation catalyst upon activation. The structure of the active sites in Ni-AIM is proposed, revealing its single-site nature. More importantly, due to the organic linker used to construct the MOF support, the Ni ions stay isolated throughout the hydrogenation catalysis, in accord with its long-term stability. A quantum chemical characterization of the catalyst and the catalytic process complements the experimental results. With validation of computational modeling protocols,...

Breakup of Temperature Inversions in Deep Mountain Valleys: Part I. Observations.

Abstract: The breakup of temperature inversions in the deep mountain valleys of western Colorado has been studied by means of tethered balloon observations of wind and temperature structure on clear weather days in different seasons. Vertical potential temperature structure profiles evolve following one of three patterns. Two of the patterns are special cases of the third pattern, in which inversions are destroyed by two continuous processes-upward growth of a convective boundary layer (CBL) into the base of the valley inversion, and descent of the inversion top. The three idealized patterns are described and 21 case studies of inversion breakup following the patterns are summarized. Inversion breakup begins at sunrise and is generally completed in 3½–5 h, unless the valley is snow covered or the ground is wet. Warming of the inversion layer is consistent with subsidence heating. An hypothesis is offered to explain the observations, stressing the role of the sensible heat flux in causing the CBL to grow an...

Mitigating Voltage Fade in Cathode Materials by Improving the Atomic Level Uniformity of Elemental Distribution

Abstract: Lithium- and manganese-rich (LMR) layered-structure materials are very promising cathodes for high energy density lithium-ion batteries. However, their voltage fading mechanism and its relationships with fundamental structural changes are far from being well understood. Here we report for the first time the mitigation of voltage and energy fade of LMR cathodes by improving the atomic level spatial uniformity of the chemical species. The results reveal that LMR cathodes (Li[Li0.2Ni0.2M0.6]O2) prepared by coprecipitation and sol–gel methods, which are dominated by a LiMO2 type R3m structure, show significant nonuniform Ni distribution at particle surfaces. In contrast, the LMR cathode prepared by a hydrothermal assisted method is dominated by a Li2MO3 type C2/m structure with minimal Ni-rich surfaces. The samples with uniform atomic level spatial distribution demonstrate much better capacity retention and much smaller voltage fade as compared to those with significant nonuniform Ni distribution. The fundam...