This study reports on the unique water vapor adsorption properties of biomass-derived starch particles (SPs). SPs offer an alternative desiccant for air-to-air energy exchangers in heating, ventilation, and air conditioning systems because of their remarkable adsorption–desorption performance. SP 15 has a particle diameter ( d p ) of 15 μm with a surface area (SA) of 2.89 m 2 /g and a pore width ( P w ) of 80 Å. Microporous starch particles (SP 15 ) were compared with high amylose starch (HAS 15 ; SA = 0.56 m 2 /g, d p = 15 μm, P w = 46 Å) and silica gel (SG 13 ; SA = 478 m 2 /g, d p = 13 μm, P w = 62 Å). Transient water vapor tests were performed using a customized small-scale energy exchanger coated with SP 15 , HAS 15 , and SG 13 . The water swelling (%) for SP 15 was ca. 2 orders of magnitude greater with markedly higher (ca. three- and six-fold) water vapor uptake compared to HAS 15 and SG 13 , respectively. At similar desiccant coating levels on the energy exchanger, the latent effectiveness of the SP 15 system was much improved (4–31%) over the HAS 15 and SG 13 systems at controlled operating conditions. SP 15 is a unique desiccant material with high affinity for water vapor and superior adsorption properties where ca. 98% regeneration was achieved under mild conditions. Therefore, SPs display unique adsorption–desorption properties, herein referred to as the “Goldilocks effect”. This contribution reports on the utility of SPs as promising desiccant coatings in air-to-air energy exchangers for ventilation systems or as advanced materials for potential water/energy harvesting applications.
The sorption of water vapor on high amylose starch was investigated as an alternative desiccant for air-to-air energy exchangers used in ventilation units. Sorption performance of micron-sized mesoporous high amylose starch (HAS15, d p = 15 μm, P w = 46 Å) and two mesoporous silica gel samples (SG13, d p = 13 μm, P w = 62 Å; P w = 62 Å; SG55, d p = 55 μm, P w = 77 Å) were studied and compared. Transient water vapor sorption tests were performed using small-scale energy exchangers coated with HAS15 and silica gel. Although N2 gas adsorption tests showed lower sorption capacity for HAS15 compared to the silica gel samples, higher sorption rates and uptake capacity were shown for HAS15 when measured by water vapor transient sorption results. In addition, the latent effectiveness, an indicator of moisture recovery efficiency for exchangers, was calculated for each exchanger. With the same amount of desiccant coated on the energy exchanger channels, the latent effectiveness of the HAS-coated material was 2%–13% greater than that of the silica gel materials, depending on the operating conditions.
Cellulose (CE) was cross-linked with epichlorohydrin (EPI) at variable compositions, and the fractionation properties were investigated in binary water−ethanol (W−E) solutions, including the pure solvent systems. The relative uptake of each solvent was measured using quantitative 1 H nuclear magnetic resonance (qNMR) spectroscopy. This study highlights the utility of qNMR as a rapid screening method for estimation of solvent selective fractionation in binary mixtures. The uptake properties of CE−EPI cross-linked polymers with ethanol and water were well-described using the Sips isotherm model. Modeling shows that the monolayer surface coverage (Q m ) of ethanol and water onto the polymer materials covers a range (1.13−2.44 g/g) of values with heterogeneous adsorption behavior, in agreement with the Sips exponential fitting parameter (n s ≠ 1). The CE−EPI adsorbents display unique fractionation with water and ethanol from binary solutions, as evidenced by the relative selectivity (R selectivity ) value in binary W−E solvent systems. The R selectivity [Q m (W)/Q m (E)] values at saturative conditions varied (from 1.10 to 2.03) and further illustrate that CE materials display molecular selective solvent fractionation in binary W−E solutions. This study provides a greater molecular level understanding for the adsorptive uptake properties of CE that are relevant to developing CE-based adsorbent technology for the fractionation of biofuels and related chemical separations.
Oxidation is a chemical reaction that occurs in lubricants upon exposure to an oxidizing agent such as oxygen and can be catalyzed by copper and iron. Antioxidants are a group of chemicals that can be used in the formulation of lubricants to stop or reduce the rate of oxidation. Based on the mechanism of action, antioxidants are categorized as primary antioxidants (radical scavengers), secondary antioxidants (Peroxide decomposers), and metal deactivators (complex-forming or chelating agents). Selection of the antioxidants in a formulation is a critical decision that depends on the base oil, application and other ingredients in the formulations. Presence of some other ingredients in the product with antagonistic behavior may suppress the role of antioxidants; however, optimal application of antioxidants with synergistic behavior would increase the stabilization impact of the ingredients on the base oil.
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