Theoretical and kinetic study of the H-atom abstraction reactions by H atom from alkyl cyclohexanes.

Reaction kinetics of hydrogen atom abstraction from six alkyl cyclohexanes, methyl cyclohexane (MCH), ethyl cyclohexane (ECH), n-propyl cyclohexane (nPCH), iso-propyl cyclohexane (iPCH), sec-butyl cyclohexane (sBCH) and iso-butyl cyclohexane (iBCH), by the H atom are systematically studied in this work. The M06-2X method combined with the 6-311++G(d,p) basis set is used to perform geometry optimization, frequency analysis and zero-point energy calculations for all species. The intrinsic reaction coordinate (IRC) calculations are performed to confirm the transition states connecting the reactants and products correctly. One-dimensional hindered rotors are used to treat the low frequency torsional models with potentials scanned at the M06-2X/6-31G level of theory. Electronic single-point energy calculations for all reactants, transition states, and products are performed at the QCISD(T)/CBS level of theory. High-pressure limiting rate constants of 39 reaction channels are obtained using conventional transition state theory with asymmetric Eckart tunneling corrections in the temperature range 298.15-2000 K. Reaction rate rules for H-atom abstraction by the H atom from alkyl cyclohexanes on primary, secondary and tertiary carbon sites on both the side chain and ring are provided. The obtained rate constants are given by the Arrhenius expression in the temperature range 500-2000 K, which can be used for the combustion kinetics model development for alkyl cyclohexanes.

Synergistic effects of the bimetallic Ni-Fe systems and their application in the reductive amination of polyether polyols.

We report the synthesis of xNi-yFe/γ-Al2O3 catalysts which were applied to the reductive amination of polypropylene glycol (PPG) for the preparation of polyether amine (PEA). The catalysts were characterized by N2-sorption, X-ray diffraction, H2-temperature programmed reduction, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy to reveal the synergistic effect of the bimetallic Ni-Fe-loaded catalysts. It was found that in the reductive amination of PPG to PEA, the conversion and product selectivity of the reaction were closely related to the types of active centers of the catalyst. In particular, the surface Ni0 content increased by adding Fe as a promoter, with a maximum Ni0 content on the 15Ni-7.5Fe/Al2O3 catalyst, which also led to the highest conversion rate (>99%). In addition, no deactivation was observed after three cycles of reaction carried out by the catalyst.

Boosting the catalytic performance of Al2O3-supported Pd catalysts by introducing CeO2 promoters.

Maintaining the stability of noble metals is the key to the long-term stability of supported catalysts. In response to the instability of noble metal species at high temperatures, we developed a synergistic strategy of dual oxide supports. By designing and constructing ceria components with small sizes, we have achieved unity in the ability of catalytic materials to supply oxygen and stabilize metal species. In this study, we prepared Al2O3-CeO2-Pd (AlCePd) catalysts containing trace amounts of Ce through the hydrolysis of cerium acetate, which achieved 100% CO conversion at 160 °C. More importantly, the activity remained at its initial 100% in the long-term durability testing, demonstrating the high stability of AlCePd. In contrast, the CO conversion of the CeO2-Pd (CePd) catalyst decreased from 100% to 54% within 3 h. Through comprehensive studies, we found that this excellent catalytic performance stems from the stabilizing effect of an alumina support and the possible reverse oxygen spillover effect of small-sized ceria components, where small-sized ceria components provide active oxygen for independent Pd species, making it possible for the CO adsorbed on Pd to react with this oxygen species.

A 6-week, phase IIb, randomized, double-blind, placebo-controlled trial of Anyu Peibo capsules for the treatment of major depressive disorder in adults.

Background: Almost one-third of patients with major depressive disorder (MDD) do not respond to conventional antidepressants, and new treatments for MDD are urgently needed. Objectives: This phase IIb clinical trial was designed to evaluate the efficacy and safety of Anyu Peibo capsules in the treatment of adults with MDD. Design: A multicenter, randomized, double-blind, placebo-controlled, parallel-group, fixed-dose study. Methods: A total of 172 patients with MDD from nine study centers were randomized (1:1) to receive placebo (n = 86) or oral Anyu Peibo capsules (0.8 g) twice per day (n = 86) for 6 weeks. The primary endpoint was the change in the Montgomery Åsberg Depression Rating Scale (MADRS) total score from baseline to week 6, analyzed using an analysis of covariance (ANCOVA) approach with the baseline MADRS score, center effect and center by group interaction as the covariates. Other efficacy endpoints and variables included clinical response and remission rates according to the MADRS and the 17-item Hamilton Depression Rating Scale (HAMD-17) scores, the change in the HAMD-17, Clinical Global Impression - Severity scale and Clinical Global Impression - Improvement scale scores and the reduction in the Hamilton Anxiety Scale from baseline to week 6. Results: The mean baseline MADRS total scores were 29.20 and 29.72 in the Anyu Peibo (n = 82) and placebo groups (n = 81), respectively. The least squares mean change in the MADRS score from baseline to week 6 was 16.59 points in the Anyu Peibo group and 14.51 points in the placebo group. Although there were greater reductions in the MADRS score from baseline to week 6 in the Anyu Peibo capsule group compared to the placebo group, the difference did not reach statistical significance (least-squares mean difference, 2.07 points; 95% confidence interval, -0.27 to 4.41; p = 0.0819). The results of sensitivity analyses by ANCOVA with the last observation carried forward method for missing data indicated that the administration of Anyu Peibo capsules may lead to a significant reduction in depressive symptoms compared to the placebo (least-squares mean difference: 3.29 points; 95% confidence interval: 0.64-5.93; p = 0.0152). Furthermore, Anyu Peibo capsules showed significant benefits over placebo when the change in the HAMD-17 score from baseline to week 6 was evaluated as the secondary analysis (t = 2.01; 95% confidence interval, 0.03-4.23; p = 0.0464). Conclusion: Anyu Peibo capsules may have an effective and safe antidepressant effect, which warrants further research.

Effect of lubricating base oil on the oxidation behavior of diesel exhaust soot.

In this study, the oxidation behaviors of soot particles from diesel engine when using neat diesel fuel (DF) and lubricating base oil-blended fuel (BBF) were investigated. The changes in the average particle size and nanostructure parameters during soot oxidation process were analyzed. Exhaust particulate matter (PM) samples were collected from a four-stroke, four-cylinder and turbo0charged diesel engine operated under 1200 rpm and 200 Nm. DF and BBF Soot samples with different oxidation weight losses of 20 %, 40 %, and 60 % were obtained by thermogravimetric isothermal oxidation experiments at 600 °C, and the particle size and nanostructure parameters (fringe length, La; fringe tortuosity, Tf) were characterized using high-resolution transmission electron microscopy (HRTEM). Results show that the DF soot particles exhibited an oxidation mode that was initially dominated by surface oxidation and gradually deviated to internal oxidation. Combustion of the base oil increased the soot internal oxidation tendency. HRTEM results showed that as the soot oxidation progressed, the primary particles showed a shell-core, onion-like and hollow structure gradually. The La of the primary particles gradually increased, and the Tf gradually decreased, indicating that the soot layer crystallites were rearranged during the oxidation process, which resulted in a disordered nanostructure that transitioned to a more graphitized nanostructure.

Effect of metallic lubricant additives on morphology, nanostructure, graphitization degree and oxidation reactivity of diesel particles.

This paper investigates the impact of metallic lubricant additives on the morphology, nanostructure, graphitization degree, and oxidation reactivity of diesel exhaust particles. The experiments were conducted on a turbocharged heavy-duty diesel engine. Four typical lubricant oil additives, including Ca-based, Zn-based, Mo-based and ashless additives, were mixed into diesel at 0.5% and 1.0% by mass. Analytical characterization equipment used in this study includes a high resolution transmission electron microscopy (HRTEM), a Raman spectroscopy, and a Thermogravimetric analyzer (TGA). Results showed that the lubricant additives significantly changed the soot properties. Diesel fuels blended with ashless and Zn-based additives led to a more disordered nanostructure of diesel particles, thereby improving their oxidation reactivity. When Ca and Mo additives participated in combustion, the oxidation mass loss curve of soot particles shifted to a higher temperature range due to the combined effect of the physical and chemical characteristics of soot particles and the catalytic oxidation of metallic ash. Although Ca, Mo, and other metals in lubricant additives could promote the soot oxidation, the changes in the physicochemical properties of soot particles (including increased fringe length, reduced fringe tortuosity, and higher graphitization degree) rendered it more difficult to oxidize.

[Development of bio-jet fuel production technology: a review].

Due to the large amount of greenhouse gas emissions and the high dependence on fossil fuels, the sustainable development of aviation industry has attracted worldwide attention. Bio-jet fuel is considered to be a promising alternative to traditional aviation fuel. This article summarizes the representative technological route, development status, opportunities and challenges faced by the development of bio-jet fuel industry. So far, several bio-jet fuel production technologies have been certified by the American Society for Testing and Materials (ASTM). Hydroprocessed esters and fatty acids is currently the most mature process that can be fully commercialized. Considering economic characteristics and technology maturity, Fischer-Tropsch is promising in near term.

Ni nanocatalysts supported on MIL-53(Al) for DCPD hydrogenation.

Metal organic frameworks (MOFs) with many unique advantages have drawn wide attention in the field of catalysis. However, the poor structural stability of MOFs limits its application. Heat treatment for MOFs can enhance its electrical conductivity and structural stability, which helps to improve the catalytic performance. Ni nanoparticles supported on MIL-53(Al) were synthesized through different heat treatment temperature. Catalysts with uniform distribution of active nickel and rich mesoporous structure were obtained by adjusting the heat treatment temperature to 500 °C. The results show this catalyst has the best hydrogenation activity and stability. Under the reaction conditions of 60 °C and 2 h, the conversion rate of DCPD is 100%, and the selectivity of endo-THDCPD is higher than 95%. After five cycles, the catalyst also show excellent stability and high activity, the conversion rate of DCPD is still 100%.

Highly Efficient Hydroisomerization of Endo-Tetrahydrodicyclopentadiene to Exo-Tetrahydrodicyclopentadiene over Pt/HY.

The fast deactivation caused by serious formation of coke is a major challenge in catalytic isomerization of endo-tetrahydrodicyclopentadiene (endo-THDCPD) into exo-tetrahydrodicyclopentadiene (exo-THDCPD) over the HY zeolite. In order to suppress the coke formation for the isomerization process, the conventional HY zeolite was modified with Pt at 0.3 wt %. Then, the hydroisomerization of endo-THDCPD into exo-THDCPD was evaluated over a fixed-bed reactor. The catalytic stability of Pt/HY was greatly enhanced in comparison to that of the HY zeolite. The Pt/HY catalyst provided 97% endo-THDCPD conversion and 96% selectivity for exo-THDCPD without deactivation after 100 h. Moreover, the formation mechanism of coke on the HY zeolite during the isomerization process was proposed based on the results of the coke analysis. It was indicated that the coke was generated from the oligomerization and condensation of olefin species, which originated from the ß-scission reaction or hydride transfer reaction of intermediates. The lower coke formation over Pt/HY was attributed to the lower amount of coke precursors, which could be hydrogenated by activated H2 over Pt sites. Therefore, Pt on Pt/HY and H2 were two crucial factors in efficiently enhancing the catalytic stability of the HY zeolite for this isomerization reaction.

Ferrocene-based conjugated microporous polymer and its multiwalled carbon nanotube composite for direct photocatalytic benzene hydroxylation to phenol.

Ferrocene is used as a catalytically active site and building block to construct a new conjugated microporous polymer (CMP), named Fc-POP. A corresponding carbon nanotube composite (CNTs@Fc-POP) with tubular structure was obtained through the π-π interaction between multi-walled carbon nanotubes (MWCNTs) and reactive molecules. This innovative modification method of carbon nanotubes provides a way to construct functionalized carbon materials. The two materials can achieve high conversion and selectivity of benzene hydroxylation to phenol under light irradiation using hydrogen peroxide (H2O2) as an oxidant. Due to the synergistic effect between the carbon nanotubes and the ferrocene group, the incorporation of MWCNTs can improve the yield of phenol significantly. This work explores a new photocatalystic system and expands the related photocatalytic application of CNTs.

Recycling Strategy and Repression Elimination for Lignocellulosic-Based Farnesene Production with an Engineered Escherichia coli.

Farnesene is an important chemical platform for many industrial products, such as biofuels and polymers. We performed high-efficiency utilization of corncobs for ß-farnesene production by separate hydrolysis and fermentation with an optimized Escherichia coli strain. First, we developed a recycling strategy for both corncob pretreatment and cellulose hydrolysis, which saved great amounts of pretreatment reagents and presented a 96.83% cellulose conversion rate into glucose. However, the corncob hydrolysate strongly repressed cell growth and ß-farnesene production, being caused by high-concentrated citrate. Through expressing a heterologous ATP citrate lyase and screening for a suitable expression host, an optimized strain was constructed that produced ß-farnesene at 4.06 g/L after 48 h in a 5 L fermenter, representing an approximately 2.3-fold increase over the initial strain. Therefore, the proposed strategy about the recycling process and repression elimination was successful and suitable for the production of lignocellulosic-based ß-farnesene, which can be further studied to scale up for industrialization.

Utilization of biodiesel by-product as substrate for high-production of ß-farnesene via relatively balanced mevalonate pathway in Escherichia coli.

Farnesene has been identified as suitable jet fuel substitutes and metabolic engineering for microbial production of farnesene is an alternative and attractive route. In this study, due to accumulation of toxic intermediate isopentenyl pyrophosphate (IPP), an engineered Escherichia coli strain harboring heterologous mevalonate pathway produced only 4.11mg/L ß-farnesene. Through higher-level expression of isopentenyl diphosphate isomerase and farnesyl diphosphate synthase to minimize the accumulated IPP, another engineered strain with relatively balanced mevalonate pathway was constructed and had the highest production of ß-farnesene to date (8.74g/L) by Escherichia coli in a lab bioreactor. Furthermore, this is the first report on utilization of biodiesel by-product (simple purification) as substrate for high-production of ß-farnesene by the engineered strain optimized and ß-farnesene concentration reached 2.83g/L in a lab bioreactor. Therefore, the engineered strain optimized could be used as a platform host for high-production of other terpenoids using biodiesel by-product as substrate.

Aging and age-related diseases--from endocrine therapy to target therapy.

Aging represents an important health issue not only for the individual, but also for society in general. Burdens associated with aging are expanding as longevity increases. This has led to an enhanced focus on issues related to aging and age-related diseases. Until recently, anti-aging endocrine-therapy has been largely limited to hormone-replacement therapy (HRT) that is associated with multiple side effects, including an increased risk of cancer. This has greatly limited the application of HRT in anti-aging therapy. Recently, the focus of anti-aging research has expanded from endocrine signaling pathways to effects on regulatory gene networks. In this regard, the GHRH-GH-IGF-1/Insulin, TOR-S6K1,NAD(+)-Sirtuin, P53, Klotho and APOE pathways have been linked to processes associated with age-related diseases, including cancer, cardiovascular disease, diabetes, osteoporosis, and neurodegenerative diseases, all of which directly influence health in aging, and represent key targets in anti-aging therapy.