Excellent Low-temperature Performance Research Articles

Promoting metal oxides–zeolite electron interaction on MnCeOx/HY catalyst for boosting nitrogen oxides reduction

The MnOx-CeO2 metal oxides are considered as promising alternative catalysts for selective catalytic reduction with NH3 (NH3-SCR) to remove NOx due to its excellent low temperature performance. However, their strong oxidative ability can lead to NH3 over-oxidation, narrowing the active temperature range and reducing N2 selectivity. Moreover, their weak surface acidity hampers medium to high-temperature activity and alkali metal resistance. Hence, in this study, MnCeOx metal oxides were coupled with HY zeolite to create MnCeOx/HY, demonstrating excellent NH3-SCR performance. The high dispersion of metal oxides on the zeolite surface and their close integration promoted strong electron interaction, effectively reducing oxygen vacancies and surface adsorbed oxygen concentrations. Consequently, the oxidative ability of active metal oxides was appropriately weakened, suppressing undesirable side reactions. MnCeOx/HY also notably suppressed NO adsorption and nitrate formation, promoting the catalytic reaction solely through the E-R mechanism and enhancing N2 selectivity. The abundant strong acid sites on the zeolite surface facilitates NH3 adsorption at moderate to high temperatures, notably expanding the active temperature window. Furthermore, the acid sites of HY zeolite serve as sacrificial sites, preferentially reacting with alkali metals, thus exhibiting excellent resistance to alkali metal poisoning on MnCeOx/HY. Combining with the DFT results, the structure-activity relationships in this study also reveal the importance of the effective synergy between acid sites and redox sites for optimal catalytic performance, offering valuable insights into the development of highly active and alkali-resistant denitrification catalysts.

Unveiling the mechanistic insights into the potassium resistance of 3.5 W-V-1 %K NH3-SCR catalysts: The dual functionality of V-O-W structure as acid and redox sites

The poisoning effect of alkali metals over Vanadium-based catalysts still faced a significant challenge in the selective catalytic reduction of NOx with NH3 (NH3-SCR). In order to improve the alkali (mainly potassium resistance) resistance of the Vanadium-based catalysts, WO3 was introduced into the vanadium oxide catalysts. The obtained 3.5WO3-V2O5(3.5 W-V) catalyst exhibited the excellent low-temperature NH3-SCR performance owing to the formation of V-O-W structures. Noteworthily, when 1 wt% K was introduced into the 3.5 W-V catalyst, vanadium oxide (V-O, V=O) species preferentially bonded to alkali metal K as an acidic sacrifice site, prompting more active V-O-W species to remain. Thus, the 3.5 W-V catalyst also possessed excellent alkali resistance. The NH3-TPD results showed that the 3.5 W-V-1 %K catalyst had a considerable acid site to ensure the adsorption capacity of NH3, while the XPS results showed that the 3.5 W-V-1 %K catalyst had excellent redox performance to ensure the activation capacity of the reactant NH3. Moreover, in-situ DRIFTS transient experiments revealed that the 3.5 W-V and 3.5 W-V-1 %K catalysts were more capable of adsorbing and activating NH3 species to rapidly react with gaseous NO, obeying the Eley-Rideal (E-R) pathway in NH3-SCR reaction. This work provides new insights into poisoning resistant of vanadium-based catalysts.

Co-enhancement of toughness and strength of room-temperature curing epoxy adhesive derived from hydroxyl-terminated polybutadiene based polyurethane resin

Incorporation of flexible chains into epoxy adhesives facilitates toughening but usually poses an opposite effect on strengthening. Herein, by combining hydroxyl-terminated polybutadiene (HTPB) with polyether diol as soft chains, epoxy-terminated polyurethane (EHTPU) is synthesized, a strategy balancing strengthening and toughening is developed. The use of polyolefin soft chains substantially contributes to sea-island phase separation for maintaining low glass transition temperature (Tg) and high strength and toughness simultaneously. Specifically, the modified epoxy adhesive has seen a significant increase in shear strength to 19.75 MPa, tensile strength to 48.25 MPa and fracture toughness to 3.63 MPa·m1/2, with increment of 914 %, 268 %, and 149 %, respectively, compared to neat epoxy. Moreover, even under low temperatures of -45 °C, the modified epoxy resin can still maintain a high shear strength, demonstrating excellent low-temperature adhesion performance. At the same time, the incorporation of EHTPU does not significantly affect the overall thermal stability of the epoxy resin, meeting the requirements for stability in practical applications. It is worth mentioning that the adhesive exhibit excellent bonding performance under different environments and substrates, indicating that this composite material has broad application prospects in various industrial fields. These findings provide valuable insights into optimizing the performance of epoxy resins by controlling the introduction of specific modifiers and offer new ideas and methods for the development of room temperature curing epoxy resin adhesives.

Electrolyte Design for NMC811||SiOx-Gr Lithium-Ion Batteries with Excellent Low-Temperature and High-Rate Performance

The use of high-nickel NMC811 cathode and SiOx-Gr anode can greatly improve the overall energy densities of lithium-ion batteries. However, the unfavorable solid electrolyte interphase (SEI) layer generated from the decomposition of EC-based electrolytes lead to the poor cycling stability of NMC811||SiOx-Gr cells. Here we report an electrolyte design of 1.5 M LiPF6 dissolved in FEC/MA/BN 2:2:6 by volume, which can form thin, robust, and homogeneous SEI layer to greatly improve the charge transfer at the electrode-electrolyte interface. Importantly, the designed electrolyte shows an outstanding low temperature performance that it can deliver a capacity of 123.3 mAh g–1 after 50 cycles at −20 °C with a current density of 0.5 C, overwhelming the standard EC-based electrolyte (1.2 M LiPF6 EC/EMC 3:7 by volume) with a capacity of 35.7 mAh g–1. The electrolyte also has a superior rate performance that it achieves a capacity of 122.5 mAh g−1 at a high current density of 10 C. Moreover, the LTE electrolyte holds the great potential of extreme fast-charging ability because of the large part of CC contribution in the CCCV charging model at high charging current densities.

Revealing the Molecular Interaction between CTL Base Oil and Additives and Its Application in the Development of Gasoline Engine Oil

In order to improve fuel economy to meet the standard for passenger car oil, a new formulation with good viscosity–temperature performance for gasoline engine oil is required. In this study, coal-to-liquid (CTL) base oil, with a high viscosity index and good low-temperature performance, was selected as the base oil to develop the gasoline engine oil. A systematic study on the molecular interaction between the CTL base oil and the viscosity index improver (VII), including three kinds of hydrogenated styrene diene copolymers (HSD-type) and four kinds of ethylene propylene copolymers (OCP-type), was conducted. It was found that in general, in CTL base oil, the HSD-type VII exhibited a much higher viscosity index, a significantly lower shear stability index, a higher thickening ability, and a lower cold-cranking simulator (CCS) viscosity than that of OCP-type VII. Moreover, when comparing CTL base oil with mineral oil 150N, the combination of CTL base oil and the VII displayed a lower CCS viscosity than that of mineral oil, suggesting it had better low-temperature performance and was able to quickly form a protective oil film on the surface, which was beneficial for the cold start. The functional group distribution state of the VII in base oil was analyzed using synchrotron radiation micro-infrared microscope (SR Micro-IR) technology, which revealed that HSD-1 had a better molecular interaction with CTL6 than 150N because of the better uniformity of the C=C group distribution. Based on this, a SP 0W-20 gasoline engine oil was developed by the combination of CTL base oil and the HSD-1 viscosity index improver, together with an additive package, a polymethacrylate pour point depressant, and a non-silicone defoamer, which showed excellent low-temperature performance, thermal oxidation stability, and detergency performance compared to the reference oil.

In Situ Encapsulation of SnS2/MoS2 Heterojunctions by Amphiphilic Graphene for High-Energy and Ultrastable Lithium-Ion Anodes.

Lithium-ion batteries with transition metal sulfides (TMSs) anodes promise a high capacity, abundant resources, and environmental friendliness, yet they suffer from fast degradation and low Coulombic efficiency. Here, a heterostructured bimetallic TMS anode is fabricated by in situ encapsulating SnS2/MoS2 nanoparticles within an amphiphilic hollow double-graphene sheet (DGS). The hierarchically porous DGS consists of inner hydrophilic graphene and outer hydrophobic graphene, which can accelerate electron/ion migration and strongly hold the integrity of alloy microparticles during expansion and/or shrinkage. Moreover, catalytic Mo converted from lithiated MoS2 can promote the reaction kinetics and suppress heterointerface passivation by forming a building-in-electric field, thereby enhancing the reversible conversion of Sn to SnS2. Consequently, the SnS2/MoS2/DGS anode with high gravimetric and high volumetric capacities achieves 200 cycles with a high initial Coulombic efficiency of >90%, as well as excellent low-temperature performance. When the commercial Li(Ni0.8Co0.1Mn0.1)O2 (NCM811) cathode is paired with the prelithiated SnS2/MoS2/DGS anode, the full cells deliver high gravimetric and volumetric energy densities of 577Wh kg-1 and 853Wh L-1, respectively. This work highlights the significance of integrating spatial confinement and atomic heterointerface engineering to solve the shortcomings of conversion-/alloying typed TMS-based anodes to construct outstanding high-energy LIBs.

Correlation analysis of evaluation methods and indicators for low-temperature performance of epoxy asphalt

Selecting an epoxy asphalt (EA) material with excellent low-temperature performance is a challenging task due to that the traditional test methods and indicators for thermoplastic asphalt may not be appropriate for thermosetting EA, and the binders’ low-temperature performance does not always match that of mixtures. The primary purpose of this study is to determine the appropriate low-temperature evaluation methods and indexes of EA materials and the correlation between the low-temperature performance of EA binder and EA mixture (EAM). First, the low-temperature performance of four EA binders was analyzed using tensile, bending beam rheometer (BBR), and dynamic mechanical analysis (DMA) tests. Then, the low-temperature cracking resistance of the EAMs was evaluated through beam bending and semi-circular bend (SCB) tests. Finally, Pearson correlation analysis was performed separately on the low-temperature indicators of EA binders and EAMs. Moreover, the Grey correlation analysis was employed to determine the correlation between the low-temperature properties of the two. The results showed that the correlation between fracture elongation (ε) and other test indicators was not significant. The multiple indicators of the BBR, such as viscoelastic parameters, viscous deformation ratio (JR), along with the glass transition temperature (Tg) of the DMA, showed consistent evaluation results for the low-temperature performance of the four EA binders. However, the correlation of these indicators with the cracking resistance of the EAM was notably different. The flexural strain energy density of the beam bending test and SCB fracture energies demonstrated excellent correlation. The grey correlation analysis results of these two indicators as reference series were highly similar. Specifically, the novel JR in this study and the Tg exhibited a better correlation with the low-temperature cracking resistance of EAM. These two indicators were preferentially recommended for the evaluation of the low-temperature performance of EA and the prediction of the low-temperature cracking resistance of EAM.

Vitrified Metal-Organic Framework Composite Electrolyte Enabling Dendrite-Free and Long-Lifespan Solid-State Lithium Metal Batteries.

Solid-state lithium metal batteries (LMBs) are still plagued with low ionic conductivity and inferior interfacial contact, which hinder their practical implementation. Herein, a quasi-solid-state composite electrolyte, poly(1,3-dioxolane) (PDOL)/glassy ZIF-62 (PGZ) with fast ion transport and intimate interface contact, is fabricated via in situ polymerization. The in situ polymerization of DOL in an electrolyte matrix not only improves the exterior interface between electrolyte/electrode but also optimizes the inner interfaces among glassy particles, rendering PGZ as an uninterrupted ionic conductor. Moreover, PGZ inherits the superior ionic conductivity and the robust dendrite prohibition of glassy MOFs originating from their grain-boundary-free nature, isotropy, and abundant groups containing N species. As expected, our proposed PGZ exhibits a prominent ionic conductivity of 6.3 × 10-4 S cm-1 at 20 °C. Li|PGZ|LiFePO4 delivers an outstanding rate performance (103 mAh g-1 at 4C) and a stable cycling capacity (118 mAh g-1 at 1C over 1000 cycles). PGZ also presents excellent low-temperature cycling performance with 75 mAh g-1 for 480 cycles at -20 °C and excellent flame retardance. Even at a high loading of 12.1 mg cm-2, it can still discharge at 140 mAh g-1 for 100 cycles. Hence, PGZ prepared via in situ polymerization holds enormous prospects as a solid-state electrolyte for high-performance and safe LMBs.

Preparation and Properties of Epoxy Adhesives with Fast Curing at Room Temperature and Low-Temperature Resistance.

Developing a highly efficient multifunctional epoxy adhesive is still an enormous challenge, which can rapidly cure at room temperature and has excellent low-temperature resistance performance and is crucial for the epoxy adhesive and electrical sealing fields during severe cold seasons. Herein, diglycidyl phthalate (DP) was synthesized with phthalic anhydride (PA) and epichlorohydrin (ECH) to enhance the curing rate and low-temperature resistance of bisphenol A diglycidyl ether (DGEBA) adhesive. The modified DP/DGEBA adhesives were systematically analyzed by gel time, mechanical properties, and aging resistance (time, temperature, and dry/wet treatment). The results showed that DP with highly active ester groups significantly accelerates the curing speed of DP/DGEBA. DP's rigid aromatic ring-benzene ring and flexible group-ester group gave the adhesive better low-temperature resistance. When the addition of DP was 10 wt % (based on the mass of DGEBA), the gel time of DP/DGEBA epoxy adhesives was reduced by 58 min compared to unmodified DGEBA epoxy adhesive, and after aging at low temperature (-20 °C) for 7 days, the tensile shear strengths of polyvinyl chloride (PVC) and aluminum plate increased by 76.2 and 80.6%, respectively. The results of non-isothermal curing kinetics and dynamic mechanical analysis suggested that when the amount of DP was 10 wt %, the reaction activation energy of DP/DGEBA epoxy adhesive decreased by 4.0%, and the cross-linking density increased by 8.9%. Moreover, the toughness of the modified adhesive was also improved. This study opens up a feasible way for the development of a low temperature-resistant epoxy adhesive cured rapidly at room temperature in practical application.

Preoxidation and Prilling Combined with Doping Strategy to Build High-Performance Recycling Spent LiFePO4 Materials.

Direct regeneration has gained much attention in LiFePO4 battery recycling due to its simplicity, ecofriendliness, and cost savings. However, the excess carbon residues from binder decomposition, conductive carbon, and coated carbon in spent LiFePO4 impair electrochemical performance of direct regenerated LiFePO4. Herein, we report a preoxidation and prilling collaborative doping strategy to restore spent LiFePO4 by direct regeneration. The excess carbon is effectively removed by preoxidation. At the same time, prilling not only reduces the size of the primary particles and shortens the diffusion distance of Li+ but also improves the tap density of the regenerated materials. Besides, the Li+ transmission of the regenerated LiFePO4 is further improved by Ti4+ doping. Compared with commercial LiFePO4, it has excellent low-temperature performance. The collaborative strategy provides a new insight into regenerating high-performance spent LiFePO4.

Significantly enhanced low-temperature activity and SO2/H2O tolerance of Mn–Ce-Ox/TiO2 catalyst prepared by a facile citric acid assisted impregnation method

Two different Mn–Ce-Ox/TiO2 catalysts were prepared by ordinary impregnation (denoted as MCT) and citric acid assisted impregnation (denoted as MCT-CA) methods, respectively. Excellent NOx removal is achieved over MCT-CA for selective catalytic reduction with NH3 (NH3-SCR), and 100% NOx conversion is obtained at 125 °C under weight hour space velocity (WHSV) of 80000 mL/(gcat·h). Particularly, 100% NOx is converted on MCT-CA in the presence of 10 vol% H2O at 175 °C. As H2O and SO2 coexist in the reaction system for 9 h, NOx conversion can still be maintained >90%, much higher than that (22%) of MCT. A series of characterization results indicates that MCT-CA exhibits a larger BET specific surface area, pore volume, and pore size, which enhances the dispersion of Mn and Ce oxides and promotes the rapid adsorption of reactants and desorption of products. Additionally, MCT-CA possesses more Mn4+, Ce3+, chemisorbed oxygen species, and stronger reducibility, facilitating the conversion of NO to NO2. Specially, the amount of active NH3 species and active nitrate species on MCT-CA is much more than that over MCT. The combined effect of the aforementioned factors devotes to the excellent low-temperature SCR performance and tolerance to H2O/SO2 over MCT-CA.

Specific roles of lattice oxygen and asymmetric interface Cu-[Ox]-Ce structure-relating chemisorbed oxygen over CuO/CeO2 on the catalysis of benzene combustion

Copper-ceria catalysts exhibit high prospects in the catalysis of VOCs combustion, during which lattice oxygen and chemisorbed oxygen species play indispensable roles. However, understanding their specific operating mechanisms still remains a challenge. Shaped CeO2 and CuO/CeO2 counterparts were synthesized for benzene catalytic combustion. Pure CeO2, especially for nanorod-CeO2, possessed high low-temperature activity (LTA) due to numerous active lattice oxygen following the initial step of Mars-van Krevelen mechanism. Conversely, the impaired LTA (15–40 °C upshift at 15 % conversion) but improved high-temperature activity (HTA) were obtained by varying surface local environment upon CuO loading. 5 wt% CuO/nanoparticle-CeO2 exhibited the highest mobile chemisorbed oxygen relating to the strong oxygen transfer capacity of asymmetric interface Cu-[Ox]-Ce structures affected by ceria crystal planes and sizes was verified by density functional theory calculations and experiments, despite the strong CuO-CeO2 synergistic effects. This study provides a promising direction for engineering benzene degradation catalysts with excellent low-temperature performance.

Trehalose in Trace Quantities as a Multifunctional Electrolyte Additive for Highly Reversible Zinc Metal Anodes.

The unsatisfactory performance of Zn metal anodes significantly impedes the commercial application of aqueous zinc-ion batteries (AZIBs). Herein, we introduce a trace amount of a multifunctional trehalose additive to enhance the stability and reversibility of Zn metal anodes. The trehalose additive exhibits a stronger Zn2+ ion affinity due to abundant lone-pair electrons, disrupting hydrogen bonds in H2O, regulating solvation structures, and tuning the Zn-electrolyte interface. Consequently, the Zn metal anode demonstrates a remarkable Coulombic efficiency of 99.80% and a cycle stability exceeding 4500 h at 1 mA cm-2. Even under stringent conditions of 10 mA cm-2, the Zn metal anode maintains a cumulative capacity of 2500 mA h cm-2 without a short circuit. Furthermore, Zn//Zn symmetric batteries exhibit excellent low-temperature cycle performance (over 400 h at -10 °C). As a proof of concept, assembled Zn//NH4V4O10 and Zn//MnO2 pouch cells demonstrate an improved electrochemical performance. This work presents an electrolyte additive strategy for achieving stable zinc anode operation in AZIBs.

Overview and Prospects of Sodium Battery Development in the Context of Accelerated Penetration of Electrification

Electrification is an essential way to promote the green transformation of energy. Sodium power has attracted wide attention at home and abroad due to its abundant reserves, excellent low-temperature performance, and great safety. This paper firstly overviews the current development status of sodium batteries, analyzes the comparative advantages of sodium batteries over lithium batteries, and evaluates the future comprehensive positioning of sodium batteries. Secondly, the characteristics and progress of the current stage of technology routes of positive and negative electrode materials for sodium batteries are elaborated, and development suggestions are put forward. Finally, the application prospect and economy of sodium batteries are thoroughly analyzed, and the future market space of sodium batteries is preliminarily predicted.

Low-pollution asphalt: Road performance, emission reduction efficacy, and modification mechanism

To further improve the emission reduction efficiency and enhance the road performance of emission reduction modified asphalt. A low-pollution asphalt (TBD-A) was prepared with tourmaline, biochar, and diatomite (TBD). A testing and evaluation method for the emission reduction efficacy of TBD-A has been proposed. The road performance of TBD-A was evaluated based on DSR, MSCR, BBR, and LAS. The evolution law of the emission reduction effect of TBD-A was clarified. Based on DSC, FTIR, and TG, the improvement mechanism of the road performance and emission reduction mechanism of TBD-A were revealed. The results show that the high-temperature performance, creep recovery ability, and fatigue life of TBD-A increase with TBD content rising. The low-temperature performance of TBD-A is superior to that of asphalt slurry. Controlling the TBD content and temperature can ensure the excellent low-temperature performance of TBD-A. The emission reduction efficacy of TBD-A increases as temperature and adsorption time rise. The comprehensive emission reduction rate of TBD-rubber-powder asphalt is the highest, reaching 64% at 190 °C. TBD and asphalt are physically blended. TBD increases asphalt's glass transition temperature while decreasing the thermal decomposition rate. The temperature stability and sensitivity of asphalt have been improved. Asphalt harmful substances are adsorbed by the multi-level pore structure of TBD, as well as are reduced and degraded by the spontaneous polarization effect.

Boosting Low-Temperature CO2 Hydrogenation over Ni-based Catalysts by Tuning Strong Metal-Support Interactions.

Rational design of low-cost and efficient transition-metal catalysts for low-temperature CO2 activation is significant and poses great challenges. Herein, a strategy via regulating the local electron density of active sites is developed to boost CO2 methanation that normally requires >350 °C for commercial Ni catalysts. An optimal Ni/ZrO2 catalyst affords an excellent low-temperature performance hitherto, with a CO2 conversion of 84.0 %, CH4 selectivity of 98.6 % even at 230 °C and GHSV of 12,000 mL g-1 h-1 for 106 h, reflecting one of the best CO2 methanation performance to date on Ni-based catalysts. Combined a series of in situ spectroscopic characterization studies reveal that re-constructing monoclinic-ZrO2 supported Ni species with abundant oxygen vacancies can facilitate CO2 activation, owing to the enhanced local electron density of Ni induced by the strong metal-support interactions. These findings might be of great aid for construction of robust catalysts with an enhanced performance for CO2 emission abatement and beyond.

Highly concentrated solvation structure for reversible high-voltage lithium-ion battery at low temperature

The commercial electrolytes exhibit subpar performance under low temperature and high voltage, severely limiting the application of lithium-ion batteries (LIBs) for extreme temperature and high energy density. As a groundbreaking advancement, the regulation of Li+ solvation structure was adopted and highly concentrated in this work, obtaining an improved electrolyte with excellent low-temperature and high-voltage performance. The electrolyte exhibited outstanding oxidation potential of 5.25 V and high ionic conductivity, maintaining transparency liquid even at −60 °C. Notably, the NCM811||Li cell exhibited high initial capacity (71.41 % of that at room temperature) at −40 °C 0.2C, with almost no capacity decay after 50 cycles. Impressively, the as-assembled NCM811||Graphite pouch battery (2.5 Ah) showed an initial capacity of 2.07 Ah at 0.1C under −30 °C, with an excellent capacity retention ratio of 84.53 % after 50 cycles. This work points out a promising approach for the practical application of high-voltage LIBs at low temperature.

Excellent low-temperature dehydrogenation performance and reversibility of 0.55LiBH4-0.45Mg(BH4)2 composite catalyzed by few-layer Ti2C

The 0.55LiBH4-0.45Mg(BH4)2 (LMBH) eutectic composite is promising for solid-state hydrogen storage, as it exhibits a high hydrogen capacity and a very low initial dehydrogenation temperature. However, its main hydrogen release steps still require higher temperatures. In the present study, few-layer Ti2C has been synthesized and utilized as catalysts in the LMBH. Compositing LMBH with varying amounts of Ti2C (10, 20, 30, and 40 wt%) results in low initial dehydrogenation temperatures (164–110 °C), fast desorption rates and high hydrogen capacities (7.5–10.5 wt%) at a low temperature of 260 °C. The LMBH-30Ti2C composite yields 6.5 wt% H2 even at as low as 200 °C. Additionally, the LMBH-30Ti2C composite could reversibly store 3.5 wt% H2 during the second to fourth dehydrogenation cycles without degradation. The outstanding hydrogen storage performance could be attributed to decomposition driven by reactions between high-valence Ti ions and LMBH, the in-situ formation of the active metal Ti catalyst, and the prevention of aggregation in the Ti2C-doped LMBH.

Petroleum-like fuels with substantially enriched branched iso-paraffins and benzenes via boehmite-assisted pyrolysis of oil shale

Oil shale (OS) is a potential alternative to substitute/supplement traditional fossil fuels, where catalyst-assisted OS pyrolysis has become a subject of general concern. While great progresses have been realized in this field, the pursuit of high-performance catalysts for a niche OS utilization still remains a formidable challenge, because most of the catalysts face various problems, including, high cost, unsatisfactory performances, etc. Based on a two-stage flash pyrolysis, we herein report our efforts about this issue by using boehmite, a low-cost industrially relevant material of an easy availability, as catalyst. We show that boehmite could arouse 17.0 % decreases in activation energy of OS pyrolysis. When the pyrolysis is executed at the 1st stage (450 °C), the content of hydrocarbons and short-chain aliphatic hydrocarbons (≤C13), which are desired for petroleum-like fuels (PLFs), increases evidently by 56.73 % and 158.5 %, respectively, while that of heteroatomic compounds and long-chain aliphatic hydrocarbons (≥C20), which are undesired for PLFs, decreases distinctly by 60.09 % and 41.6 %, respectively, indicating an evident improvement in the quality of the pyrolysates. Fascinatingly, the content of branched iso-paraffins, especially, monomethyl-, dimethyl- and trimethyl-branched paraffins, which are either efficient octane number boosters, important tectons for functional surfactants, or significant component for high-quality fuels of excellent low-temperature performances, increases substantially by ca. 180.2 % from ca. 16.02 % to 44.89 %. For the 2nd stage at 585 °C, besides a distinctly improved quality of the pyrolysates, the content of benzene, toluene, xylene and trimethylbenzene, which are value-added chemicals broadly employed in numerous industrial fields of paramount importance, is enriched distinctly by 94 %, 65.2 %, 13 %, and 19 %, respectively. We find that the concentration of the Brönsted acid sites (BASs) of the employed boehmite, which contain 94 % medium and strong BASs, is substantially lower than that of Lewis acid sites (LASs), which contain merely 54.91 % medium and strong LASs, such that the competitive-collaborative actions of BASs and LASs confer boehmite with outstanding catalytic reactivity.

Tribology and Rheology of Polypropylene Grease with MoS2 and ZDDP Additives at Low Temperatures

Polypropylene (PP) grease is a type of lubricating grease with excellent low-temperature performance. The wear and friction performance of steel/steel couples lubricated with PP grease containing molybdenum disulfide (MoS2), zinc dialkyldithophosphate (ZDDP) and MoS2/ZDDP as additives at low temperatures was investigated using an Optimol SRV reciprocating tester. Compared with MoS2 or ZDDP as single additives, the combination of MoS2 and ZDDP resulted in outstanding tribological properties, especially for higher-load, longer-duration and low-temperature working conditions. The analysis of the wear surface indicated that MoS2 not only adhered to the steel surfaces to form a solid film, but also combined with ZDDP to form a tribofilm. The active components of the additives reached the metal surfaces effectively, indicating that the polymer system did not interfere with the function of the additives. The rheological experiment results also showed that PP grease with additives can maintain stable viscoelasticity, viscosity recovery rates and ductility at low temperatures.