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1.
Heliyon ; 9(10): e20172, 2023 Oct.
Article in English | MEDLINE | ID: mdl-37810844

ABSTRACT

Colorectal cancer attacks the colon or rectum, with increasing morbidity and mortality globally. The RNA modification 6-methyladenine (m6A) is related to RNA modifications, playing a critical role in colorectal cancer. We aimed to identify prognostic signatures for colorectal cancer using risk prediction algorithms, and to validate these signatures using independent datasets and clinical samples. In this study, 175 cases in GSE17536 were assigned into two clusters using consistent clustering and PCA analysis. A multivariate Cox risk regression model revealed that among 21 m6A RNA methylation regulators, RBM15B, FTO, IGF2BP2, ZCCHC4, and KIAA1429 were remarkably associated with colorectal cancer patients' overall survival (OS); however, Kaplan-Meier (KM) survival assessment showed no significant association between these five regulators and colorectal cancer patients' prognosis. A 5-m6A RNA methylation regulator signature was established using LASSO algorithm. Risk scores of cases in GSE17536, GSE17537 and GSE75500 were calculated, and lower risk scores were associated with better DSS/OS. receiver operating characteristic (ROC) curve and the nomogram revealed the satisfactory predictive efficiency of the risk score model. The risk score could distinguish cases in Cluster1 and Cluster2 and normal and tumor tissues based on GSE37182. The prognostic variables for colorectal cancer patients were assessed using both univariate and multivariate Cox's proportional hazard regression models, which revealed that the stage and risk score were significant risk factors. In this study, a comprehensive set of integrative bioinformatics analyses was conducted to investigate the prognostic and diagnostic potential of a panel of 5 m6A RNA methylated regulators in colorectal cancer patients. The conducted studies included the use of several statistical methods, such as the LASSO regression model, KM survival evaluation, ROC curve, and univariate and multivariate Cox's proportional hazard regression analyses. The findings from these analyses collectively established the prognostic marker, highlighting its significance in predicting patient outcomes and diagnosing colorectal cancer.

2.
World J Gastrointest Surg ; 15(6): 1159-1168, 2023 Jun 27.
Article in English | MEDLINE | ID: mdl-37405094

ABSTRACT

BACKGROUND: The case of Crohn's disease involving the duodenum is rare, and its surgical management requires a thorough understanding. AIM: To investigate the surgical management of duodenal Crohn's disease. METHODS: We systematically reviewed patients diagnosed with duodenal Crohn's disease who underwent surgery in the Department of Geriatrics Surgery of the Second Xiangya Hospital of Central South University from January 1, 2004, to August 31, 2022. The general information, surgical procedures, prognosis, and other information of these patients were collected and summarized. RESULTS: A total of 16 patients were diagnosed with duodenal Crohn's disease, where 6 cases had primary duodenal Crohn's disease, and 10 had secondary duodenal Crohn's disease. Among patients with primary disease, 5 underwent duodenal bypass and gastrojejunostomy, and 1 received pancreaticoduodenectomy. Among those with a secondary disease, 6 underwent closure of duodenal defect and colectomy, 3 received duodenal lesion exclusion and right hemicolectomy, and 1 underwent duodenal lesion exclusion and double-lumen ileostomy. CONCLUSION: Crohn's disease involving the duodenum is a rare condition. Different surgical management should be applied for patients with Crohn's disease presenting with different clinical manifestations.

3.
Cancers (Basel) ; 14(20)2022 Oct 17.
Article in English | MEDLINE | ID: mdl-36291863

ABSTRACT

M2 tumor-associated macrophages (TAMs) have been a well-established promoter of oral squamous cell carcinoma (OSCC) progression. However, the mechanisms of M2 TAMs promoting OSCC metastasis have not been elucidated clearly. This study illustrated the regulatory mechanisms in which M2 TAMs enhance OSCC malignancy in a novel point of view. In this study, mass spectrometry was utilized to analyze the proteins expression profile of M2 type monocyte-derived macrophages (MDMs-M2), whose results revealed the high expression of G3BP1 in M2 macrophages. RNA sequencing analyzed the genome-wide changes upon G3BP1 knockdown in MDMs-M2 and identified that CCL13 was the most significantly downregulated inflammatory cytokines in MDMs-M2. Co-immunoprecipitation and qualitative mass spectrometry were used to identify the proteins that directly interacted with endogenous G3BP1 in MDMs-M2. Elevated stress granule (SG) formation in stressed M2 TAMs enhanced the expression of CCL13, which promoted OSCC metastasis both in vitro and in vivo. For mechanisms, we demonstrated SG formation improved DDX3Y/hnRNPF-mediated CCL13 mRNA stability, thus enhancing CCL13 expression and promoting OSCC metastasis. Collectively, our findings demonstrated for the first time the roles of CCL13 in improving OSCC metastasis and illustrated the molecular mechanisms of CCL13 expression regulated by SG, indicating that the SG-CCL13 axis can be the potential targets for TAM-navigated tumor therapy.

4.
Complement Ther Med ; 70: 102854, 2022 Nov.
Article in English | MEDLINE | ID: mdl-35842070

ABSTRACT

BACKGROUND: A pilot randomized controlled trial (RCT) was conducted in mainland China to examine the feasibility, acceptability, and preliminary effects of parent-administered pediatric tuina on attention deficit hyperactivity disorder (ADHD) symptoms in preschool children. An embedded process evaluation was performed to explore barriers and facilitators in the implementation, identify additional questions, and refine the study design for a future fully powered study. METHODS: The process evaluation comprises the following parts: (a) self-reported questionnaires on parents (n = 43), traditional Chinese medicine (TCM) practitioners (n = 2), outcome assessor (n = 1), and research assistant (n = 1); (b) parent logbook on parent-administered pediatric tuina (n = 32); and (c) focus group interview sessions (n = 15). Accomplishment of the self-report questionnaires was voluntary for all participants and compulsory for research personnel and TCM practitioners. The parent logbook on the intervention was filled out by all participants in the intervention group. Participants of focus group interviews were selected via purposive sampling, and data were analyzed with template analysis. Qualitative findings were summarized in tables, while the mean was calculated to reflect the quantitative findings. RESULTS: Perceived benefits, acceptability of parents and children, and professional support from the research team facilitated the implementation of the intervention. Meanwhile, the TCM pattern identification using online mode may limit the accuracy and lead to parents doubting the precision of the TCM pattern. This limitation was regarded as a major barrier. Parents perceived improvements in terms of children's appetite, sleep quality, and parent-child relationship. Participants were generally satisfied with the settings of parent-administered pediatric tuina and showed satisfactory adherence to the implementation. CONCLUSIONS: Implementation of parent-administered pediatric tuina intervention is feasible and acceptable. The intervention can be refined by improving the TCM pattern identification procedure and adjusting outcome settings in a fully powered study in the future.


Subject(s)
Attention Deficit Disorder with Hyperactivity , Child , Child, Preschool , Focus Groups , Humans , Parents , Pilot Projects , Surveys and Questionnaires
5.
Mol Immunol ; 146: 57-68, 2022 06.
Article in English | MEDLINE | ID: mdl-35447415

ABSTRACT

Inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), is characterized by chronic inflammation of the lower gastrointestinal tract with unknown etiology. In our previous study, NOD-like receptor 3 (NLRP3) inflammasome activation requiring the interaction of NLRP3 with NIMA Related Kinase 7 (NEK7) had been reported to regulate MODE-K cell pyroptosis and dextran sulfate sodium (DSS)-induced murine colitis. In the present study, miR-200c was closely related to IBD using weighted gene correlation network analysis (WGCNA). MicroRNA-200c (miR-200c) expression was down-regulated in IBD samples and negatively correlated with NLRP3. In MODE-K cells, miR-200c overexpression inhibited cellular inflammation; under adenosine triphosphate (ATP) and lipopolysaccharides (LPS) co-stimulation, miR-200c overexpression attenuated ATP and LPS-induced cell pyroptosis. In the DSS-induced IBD mice model, miR-200c overexpression alleviated DSS-induced IBD symptoms and improved physiological and biochemical indexes. Through direct targeting, miR-200c inhibited NEK7 expression. In MODE-K cells, NEK7 overexpression promoted cellular inflammation and ATP and LPS-induced cell pyroptosis; when co-transduced into MODE-K cells, NEK7 overexpression partially attenuated miR-200c agomir effects on cellular inflammation and ATP and LPS-induced cell pyroptosis. In conclusion, miR-200c, through targeting NEK7, could decrease cellular inflammation levels and NLRP3 inflammasome-related MODE-K cell pyroptosis in vitro and improve DSS-induced murine IBD symptoms in vivo.


Subject(s)
Inflammatory Bowel Diseases , MicroRNAs , NIMA-Related Kinases , NLR Family, Pyrin Domain-Containing 3 Protein , Adenosine Triphosphate , Animals , Inflammasomes/metabolism , Inflammation/genetics , Lipopolysaccharides/pharmacology , Mice , MicroRNAs/genetics , NIMA-Related Kinases/genetics , NIMA-Related Kinases/metabolism , NLR Family, Pyrin Domain-Containing 3 Protein/genetics , NLR Family, Pyrin Domain-Containing 3 Protein/metabolism , Pyroptosis
6.
J Oral Maxillofac Surg ; 80(7): 1284-1293, 2022 07.
Article in English | MEDLINE | ID: mdl-35395224

ABSTRACT

PURPOSE: Endoscopic-assisted surgery of parotid gland tumor is challenging due to the complex anatomic structures. This study compared an innovative endoscopic-assisted operation called the two-lines-four-regions method to a traditional endoscopic-assisted surgery in the treatment of parotid gland tumors. METHODS: In this retrospective cohort study, patients were assigned to the traditional endoscopic group (Trad-En group) and the two-lines-four-regions endoscopic group (Tlfr-En group) according to whether two-lines-four-regions concept was used before the surgery. The primary outcomes are operation time (minutes) and postoperative complications present or absent. Other outcomes including intraoperative blood loss (milliliter), whether to increase auxiliary incision (yes/no), postoperative drainage (milliliter), and retention time (day) are the secondary outcomes. χ2 analysis or Fisher exact test was used to compare the statistical differences of those variables in 2 groups, and a P value of less than .05 was considered to indicate statistical significance. RESULTS: A total of 121 patients with parotid gland tumors underwent endoscopic-assisted surgery; 59 patients were assigned to the Trad-En group, and 62 patients were assigned to the Tlfr-En group. The mean operation times (65.24 ± 14.82 min), blood loss (9.85 ± 3.38 mL), and the amount of drainage (10.52 ± 3.17 mL) in the Tlfr-En group were shorter than the values in the Trad-En group (75.75 ± 14.16 min, 10.52 ± 3.17 mL, and 16.54 ± 3.21 mL, respectively; P < .05). The median follow-up time was 34 months (range 4 to 70 months). No tumor recurrence was found in all patients. CONCLUSIONS: This study demonstrated that the new concept of two-lines-four-regions of parotid gland makes the endoscopic-assisted surgery of parotid gland tumors more simplified, efficient, and minimally invasive.


Subject(s)
Parotid Gland , Parotid Neoplasms , Endoscopy/methods , Humans , Neoplasm Recurrence, Local/surgery , Parotid Gland/surgery , Parotid Neoplasms/surgery , Retrospective Studies , Treatment Outcome
7.
Cell Death Discov ; 8(1): 62, 2022 Feb 14.
Article in English | MEDLINE | ID: mdl-35165276

ABSTRACT

The inflammatory bowel diseases (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), are chronic inflammatory disorders of the intestine. Dysregulated cytokine secretion and signal transduction mechanisms via intestinal epithelial cells are involved in IBD pathogenesis, in which the transcription factor NF-κB plays a critical role. In this study, METTL3, which plays a key role in inflammation regulation, has been recognized significantly up-regulated in IBD samples, DSS-induced IBD mice, and LPS-treated MODE-K cells. Within LPS-treated MODE-K cells, METTL3 knockdown promoted cell viability, inhibited cell apoptosis, decreased apoptotic caspase3/9 cleavage, and decreased the levels of proinflammatory cytokines (IL-1ß, TNF-α, IL-6, and IL-18) and inflammatory enzymes (COX-2 and iNOS). Under the same conditions, METTL3 knockdown inhibited, whereas METTL3 overexpression promoted p65 phosphorylation in MODE-K cells; NF-κB inhibitor JSH-23 partially abolished the promotive effects of METTL3 overexpression upon p65 phosphorylation. Consistently, the effects of METTL3 overexpression upon LPS-stimulated MODE-K cells were partially abolished by JSH-23. Lastly, METTL3 knockdown in DSS-induced IBD mice significantly ameliorated DSS-induced IBD and inhibited DSS-induced p65 phosphorylation. In conclusion, METTL3 overexpression aggravates LPS-induced cellular inflammation in mouse intestinal epithelial cells and DSS-induced IBD in mice. The NF-κB signaling might be involved, and the regulatory mechanism remains to be investigated in our future study.

8.
Biosci Trends ; 15(3): 171-179, 2021 Jul 06.
Article in English | MEDLINE | ID: mdl-34121045

ABSTRACT

The incidence of inflammatory bowel disease (IBD) with a poor prognosis is increasing, and a single field is not capable of fully diagnosing and comprehensively treating IBD. The purpose of the current study was to explore the role of a multidisciplinary team (MDT) in the diagnosis and treatment of IBD. Subjects were 55 patients with IBD who underwent surgery at this hospital before the establishment of a MDT (before June 2016) and 276 patients who were discussed by a MDT; 72 of the latter patients underwent surgery. The preoperative rate of diagnosis, preoperative basic nutritional status, frequency of emergency surgery, and surgical complications in the two groups were compared to determine whether the MDT significantly affected the diagnosis and treatment of IBD and to explore trends in the types of patients with IBD and treatment decision-making since the establishment of MDT. Results revealed that the MDT significantly improved preoperative diagnostic accuracy for patients with IBD who underwent surgery (p < 0.005), and the frequency of elective surgery decreased significantly (p < 0.005). There were significant differences in the rate of clinical recurrence (p < 0.005) and the rate of additional surgery (p < 0.01) between the two groups, with higher rates in the control group. In terms of preoperative nutritional status, the proportion of decreased serum albumin and hemoglobin in the experimental group was significantly lower than that in the control group (p < 0.05). MDT plays a positive role in accurate preoperative diagnosis, improvement of preoperative preparations, and a reduction in postoperative adverse events for patients with IBD undergoing surgery.


Subject(s)
Elective Surgical Procedures/adverse effects , Inflammatory Bowel Diseases/therapy , Patient Care Team , Postoperative Complications/epidemiology , Adolescent , Adult , Elective Surgical Procedures/methods , Female , Humans , Incidence , Inflammatory Bowel Diseases/diagnosis , Inflammatory Bowel Diseases/epidemiology , Male , Postoperative Complications/etiology , Postoperative Complications/prevention & control , Retrospective Studies , Young Adult
9.
Cell Death Dis ; 10(12): 906, 2019 12 02.
Article in English | MEDLINE | ID: mdl-31787755

ABSTRACT

Inflammatory bowel disease (IBD) is one of the most common diseases in the gastrointestinal tract related to aberrant inflammation. Pyroptosis, which is characterized by inflammasome formation, the activation of caspase-1, and the separation of the N- and C-terminals of GSDMD, might be related to IBD pathogenesis. NEK7 is an important component of the NLRP3 inflammasome in macrophages. We attempted to investigate the mechanism of NEK7 interacting with NLRP3 to modulate the pyroptosis in IBD. NEK7 mRNA and protein expression and pyroptosis-associated factors, including Caspase-1 (p45, p20), NLRP3, and GSDMD, were upregulated in IBD tissues. NEK7 knockdown abolish ATP + LPS-induced pyroptosis in vitro and improved DSS-induced chronic colitis in vivo. NEK7 interacted with NLRP3, as revealed by Co-IP and GST pull-down assays, to exert its effects. Moreover, short-term LPS treatment alone induced no significant changes in NEK7 protein level. TLR4/NF-κB signaling in MODE-K cells could be activated by LPS treatment. LPS-induced NEK7 upregulation could be significantly reversed by JSH-23, an inhibitor of p65. Furthermore, LUC and ChIP assays revealed that RELA might activate the transcription of NEK7 via targeting its promoter region. LPS-induced TLR4/NF-κB activation causes an increase in NEK7 expression by RELA binding NEK7 promoter region. In conclusion, NEK7 interacts with NLRP3 to modulate NLRP3 inflammasome activation, therefore modulating the pyroptosis in MODE-K cells and DSS-induced chronic colitis in mice. We provide a novel mechanism of NEK7-NLRP3 interaction affecting IBD via pyroptosis.


Subject(s)
Inflammatory Bowel Diseases/metabolism , Inflammatory Bowel Diseases/pathology , NF-kappa B/metabolism , NIMA-Related Kinases/metabolism , NLR Family, Pyrin Domain-Containing 3 Protein/metabolism , Pyroptosis , Signal Transduction , Animals , Cell Line , Dextran Sulfate , Disease Models, Animal , Epithelial Cells/metabolism , Epithelial Cells/ultrastructure , Female , HEK293 Cells , Humans , Inflammatory Bowel Diseases/genetics , Lipopolysaccharides/pharmacology , Mice, Inbred C57BL , Models, Biological , NIMA-Related Kinases/genetics , Protein Binding/drug effects , Pyroptosis/drug effects , RNA, Messenger/genetics , RNA, Messenger/metabolism , Signal Transduction/drug effects , Toll-Like Receptor 4/metabolism , Transcription, Genetic/drug effects
10.
J Am Chem Soc ; 140(44): 14799-14806, 2018 Nov 07.
Article in English | MEDLINE | ID: mdl-30351925

ABSTRACT

Early 3d transition metals are not focal catalytic candidates for many chemical processes because they have strong affinities to O, N, C, or H, etc., which would hinder the conversion of those species to products. Metallic Mn, as a representative, undergoes nitridation under ammonia synthesis conditions forming bulk phase nitride and unfortunately exhibits negligible catalytic activity. Here we show that alkali or alkaline earth metal hydrides (i.e., LiH, NaH, KH, CaH2 and BaH2, AHs for short) promotes the catalytic activity of Mn nitride by orders of magnitude. The sequence of promotion is BaH2 > LiH > KH > CaH2 > NaH, which is different from the order observed in conventional oxide or hydroxide promoters. AHs, featured by bearing negatively charged hydrogen atoms, have chemical potentials in removing N from Mn nitride and thus lead to significant enhancement of N2 activation and subsequent conversion to NH3. Detailed investigations on Mn-LiH catalytic system disclosed that the active phase and kinetic behavior depend strongly on reaction conditions. Based on the understanding of the synergy between AHs and Mn nitride, a strategy in the design and development of early transition metals as effective catalysts for ammonia synthesis and other chemical processes is proposed.

11.
Chemistry ; 24(6): 1342-1347, 2018 Jan 26.
Article in English | MEDLINE | ID: mdl-29024174

ABSTRACT

Complex hydrides have played important roles in energy storage area. Here a complex hydride made of Li2 NH and LiBH4 was synthesized, which has a structure tentatively indexed using an orthorhombic cell with a space group of Pna21 and lattice parameters of a=10.121, b=6.997, and c=11.457 Å. The Li2 NH-LiBH4 sample (in a molar ratio of 1:1) shows excellent hydrogenation kinetics, starting to absorb H2 at 310 K, which is more than 100 K lower than that of pristine Li2 NH. Furthermore, the Li+ ion conductivity of the Li2 NH-LiBH4 sample is about 1.0×10-5  S cm-1 at room temperature, and is higher than that of either Li2 NH or LiBH4 at 373 K. Those unique properties of the Li2 NH-LiBH4 complex render it a promising candidate for hydrogen storage and Li ion conduction.

12.
Angew Chem Int Ed Engl ; 56(30): 8716-8720, 2017 07 17.
Article in English | MEDLINE | ID: mdl-28556376

ABSTRACT

Lithium hydride (LiH) has a strong effect on iron leading to an approximately 3 orders of magnitude increase in catalytic ammonia synthesis. The existence of lithium-iron ternary hydride species at the surface/interface of the catalyst were identified and characterized for the first time by gas-phase optical spectroscopy coupled with mass spectrometry and quantum chemical calculations. The ternary hydride species may serve as centers that readily activate and hydrogenate dinitrogen, forming Fe-(NH2 )-Li and LiNH2 moieties-possibly through a redox reaction of dinitrogen and hydridic hydrogen (LiH) that is mediated by iron-showing distinct differences from ammonia formation mediated by conventional iron or ruthenium-based catalysts. Hydrogen-associated activation and conversion of dinitrogen are discussed.

13.
Chem Sci ; 8(1): 781-788, 2017 Jan 01.
Article in English | MEDLINE | ID: mdl-28451227

ABSTRACT

Development of non-noble metal catalysts with similar activity and stability to noble metals is of significant importance in the conversion and utilization of clean energy. The catalytic hydrolysis of ammonia borane (AB) to produce 3 equiv. of H2, as an example of where noble metal catalysts significantly outperform their non-noble peers, serves as an excellent test site for the design and optimization of non-noble metal catalysts. Our kinetic isotopic effect measurements reveal, for the first time, that the kinetic key step of the hydrolysis is the activation of H2O. Deducibly, a transition metal with an optimal electronic structure that bonds H2O and -OH in intermediate strengths would favor the hydrolysis of AB. By employing a covalent triazine framework (CTF), a newly developed porous material capable of donating electrons through the lone pairs on N, the electron densities of nano-sized Co and Ni supported on CTF are markedly increased, as well as their catalytic activities. Specifically, Co/CTF exhibits a total turnover frequency of 42.3 molH2 molCo-1 min-1 at room temperature, which is superior to all peer non-noble metal catalysts ever reported and even comparable to some noble metal catalysts.

14.
Chem Asian J ; 12(14): 1758-1764, 2017 Jul 18.
Article in English | MEDLINE | ID: mdl-28421668

ABSTRACT

The hydrogen desorption pathways and storage properties of 2 Mg(NH2 )2 -3 LiH-xLiBH4 samples (x=0, 1, 2, and 4) were investigated systematically by a combination of pressure composition isotherm (PCI), differential scanning calorimetric (DSC), and volumetric release methods. Experimental results showed that the desorption peak temperatures of 2 Mg(NH2 )2 -3 LiH-xLiBH4 samples were approximately 10-15 °C lower than that of 2 Mg(NH2 )2 -3 LiH. The 2 Mg(NH2 )2 -3 LiH-4 LiBH4 composite in particular began to release hydrogen at 90 °C, thereby exhibiting superior dehydrogenation performance. All of the LiBH4 -doped samples could be fully dehydrogenated and re-hydrogenated at a temperature of 143 °C. The high hydrogen pressure region (above 50 bar) of PCI curves for the LiBH4 -doped samples rose as the amount of LiBH4 increased. LiBH4 changed the desorption pathway of the 2 Mg(NH2 )2 -3 LiH sample under a hydrogen pressure of 50 bar, thereby resulting in the formation of MgNH and molten [LiNH2 -2 LiBH4 ]. That is different from the dehydrogenation pathway of 2 Mg(NH2 )2 -3 LiH sample without LiBH4 , which formed Li2 Mg2 N3 H3 and LiNH2 , as reported previously. In addition, the results of DSC analyses showed that the doped samples exhibited two independent endothermic events, which might be related to two different desorption pathways.

15.
Chem Asian J ; 12(4): 470-475, 2017 Feb 16.
Article in English | MEDLINE | ID: mdl-28070940

ABSTRACT

Significant progress has been made on the synthesis and application of mesoporous γ-alumina. To date, little attention has been paid to the synthesis of microporous crystalline alumina. Here, fabrication of microporous crystalline γ-alumina using a microporous covalent triazine framework (CTF-1) as a template is described. Microporous crystalline γ-alumina with a micro-meso binary pore system was replicated by infiltration of aluminum nitrate into the micropores of the CTF-1 template through a NH3 /water-vapor-induced internal hydrolysis method, followed by thermal treatment, and subsequent removal of the CTF-1 template with a 30 % H2 O2 aqueous solution. The obtained crystalline γ-alumina material exhibits a large surface area (349 m2 g-1 ) with micropore distribution centered at about 1.27 nm. Ru supported on microporous γ-Al2 O3 can be employed as catalyst for hydrolytic dehydrogenation of ammonia borane, and it exhibits high catalytic activity and good durability. This finding provides a new benchmark for preparing well-defined crystalline microporous alumina materials by a template method, which can be applied in a wide range of fields.

16.
Nat Chem ; 9(1): 64-70, 2017 01.
Article in English | MEDLINE | ID: mdl-27995914

ABSTRACT

Ammonia synthesis under mild conditions is a goal that has been long sought after. Previous investigations have shown that adsorption and transition-state energies of intermediates in this process on transition metals (TMs) scale with each other. This prevents the independent optimization of these energies that would result in the ideal catalyst: one that activates reactants well, but binds intermediates relatively weakly. Here we demonstrate that these scaling relations can be broken by intervening in the TM-mediated catalysis with a second catalytic site, LiH. The negatively charged hydrogen atoms of LiH act as strong reducing agents, which remove activated nitrogen atoms from the TM or its nitride (TMN), and as an immediate source of hydrogen, which binds nitrogen atoms to form LiNH2. LiNH2 further splits H2 heterolytically to give off NH3 and regenerate LiH. This synergy between TM (or TMN) and LiH creates a favourable pathway that allows both early and late 3d TM-LiH composites to exhibit unprecedented lower-temperature catalytic activities.

17.
Phys Chem Chem Phys ; 18(36): 25257-25264, 2016 Sep 14.
Article in English | MEDLINE | ID: mdl-27722371

ABSTRACT

Sodium amide, NaNH2, has recently been shown to be a useful catalyst to decompose NH3 into H2 and N2, however, sodium hydroxide is omnipresent and commercially available NaNH2 usually contains impurities of NaOH (<2%). The thermal decomposition of NaNH2 and NaNH2-NaOH composites is systematically investigated and discussed. NaNH2 is partially dissolved in NaOH at T > 100 °C, forming a non-stoichiometric solid solution of Na(OH)1-x(NH2)x (0 < x < ∼0.30), which crystallizes in an orthorhombic unit cell with the space group P212121 determined by synchrotron powder X-ray diffraction. The composite xNaNH2-(1 - x)NaOH (∼0.70 < x < 0.72) shows a lowered melting point, ∼160 °C, compared to 200 and 318 °C for neat NaNH2 and NaOH, respectively. We report that 0.36 mol of NH3 per mol of NaNH2 is released below 400 °C during heating in an argon atmosphere, initiated at its melting point, T = 200 °C, possibly due to the formation of the mixed sodium amide imide solid solution. Furthermore, NaOH reacts with NaNH2 at elevated temperatures and provides the release of additional NH3.

18.
Chem Asian J ; 11(12): 1849-55, 2016 Jun 21.
Article in English | MEDLINE | ID: mdl-27124013

ABSTRACT

The synthesis of two-dimensional (2D) polymer nanosheets with a well-defined microporous structure remains challenging in materials science. Here, a new kind of 2D microporous carbonaceous polymer nanosheets was synthesized through polymerization of a very low concentration of 1,4-dicyanobenzene in molten zinc chloride at 400-500 °C. This type of nanosheets has a thickness in the range of 3-20 nm, well-defined microporosity, a high surface area (∼537 m(2) g(-1) ), and a large micropore volume (∼0.45 cm(3) g(-1) ). The microporous carbonaceous polymer nanosheets exhibit superior CO2 sorption capability (8.14 wt % at 298 K and 1 bar) and a relatively high CO2 selectivity toward N2 (25.6). Starting from different aromatic nitrile monomers, a variety of 2D carbonaceous polymer nanosheets can be obtained showing a certain universality of the ionothermal method reported herein.

19.
Chemistry ; 22(23): 7727-9, 2016 06 01.
Article in English | MEDLINE | ID: mdl-27017580

ABSTRACT

Ammonium aminodiboranate ([NH4 ][BH3 NH2 BH3 ]) is a long-sought isomer of diammoniate of diborane ([NH3 BH2 NH3 ][BH4 ]) and ammonia borane (NH3 BH3 ) dimer. Our results show that [NH4 ][BH3 NH2 BH3 ] is stable in tetrahydrofuran at -18 °C and decomposes rapidly to NH3 BH2 NH2 BH3 and H2 at elevated temperatures. The decomposition pathway is dictated by the dihydrogen bonding between H(δ+) on NH4 (+) and H(δ-) on BH3 , as confirmed by theoretical calculations. This is in contrast to the interconversion between [NH3 BH2 NH3 ][BH4 ] and (NH3 BH3 )2 , although all three have dihydrogen bonds and the same stoichiometry.

20.
ChemSusChem ; 9(4): 364-9, 2016 Feb 19.
Article in English | MEDLINE | ID: mdl-26914173

ABSTRACT

Ammonia has high gravimetric and volumetric hydrogen densities and is, therefore, considered a promising carrier for the production of COx -free molecular H2 for forthcoming energy systems. Alkaline earth metals are generally regarded as structural promoters of catalysts and employed in numerous catalytic processes. Here, we report that calcium imide (CaNH) has a strong synergistic effect on Mn6 N5 in catalyzing the decomposition of NH3 , leading to a ca. 40 % drop in apparent activation energy. At 773 K, the H2 formation rate over a Mn6 N5 -11CaNH composite catalyst is about an order of magnitude higher than that of Mn6 N5 and comparable to the highly active Ni/SBA-15 and Ru/Al2 O3 catalysts. Analysis by means of temperature-programmed decomposition (TPD), X-ray diffraction (XRD), and X-ray absorption near edge spectroscopy (XANES) reveal that CaNH participates in the catalysis via forming a [Ca6 MnN5 ]-like intermediate, thus altering the reaction pathway and energetics. A two-step catalytic cycle, accounting for the synergy between CaNH and Mn6 N5 , is proposed.


Subject(s)
Ammonia/chemistry , Calcium Compounds/chemistry , Manganese Compounds/chemistry , Catalysis , Hydrogen/chemistry , X-Ray Absorption Spectroscopy , X-Ray Diffraction
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