Influence of Brönsted Acid Sites on Activated Carbon-Based Catalyst for Acetylene Dimerization

Activated carbon (AC) has been widely used as a support material with both tunable acidity and abundant functional groups for solid acid catalysts in various chemical processes such as acetylene dimerization. A facile, mild acid modification method that directly activates AC to generate rich defects and oxygen functional group surface structures with Brönsted acid sites and an enhanced conductivity is presented here. Impressively, the catalyst with optimized Brönsted acid sites and an enhanced dispersion of active components exhibited a superior acetylene dimerization catalytic activity. Moreover, theoretical calculations indicated that an increase in hydrogen concentration could inhibit the formation of coke. This research offered a feasible potential way to devise and construct a carbon-based solid acid catalyst with an excellent catalytic performance

Deactivation Mechanism and Regeneration of the CuCl/Activated Carbon Catalyst for Gas–Solid Acetylene Dimerization

Acetylene dimerization is necessary to the coal chemical industry for producing monovinylacetylene, while the deactivation mechanism and regeneration of catalysts have not been studied in detail, which is crucial to the design of high-efficiency catalysts for acetylene dimerization. Herein, the deactivation mechanism and regeneration methods of CuCl/activated carbon catalysts in gas–solid acetylene dimerization were studied in detail. The catalysts with different reaction times were analyzed by temperature-programmed desorption of ammonia (NH3-TPD), Fourier transform infrared (FT-IR), thermogravimetry (TG), pyridine-FTIR, and X-ray photoelectron spectroscopy (XPS) analyses. NH3-TPD results demonstrated that as the time went on, the strong acid in the samples was enhanced, while the weak acid was weakened. Similarly, pyridine-FTIR results indicated that both Brönsted and Lewis acids in the samples were decreased. TG and XPS results showed that the reasons for deactivation for acetylene dimerization in the gas–solid reaction were significantly affected by coke deposition and the change of Cu valence. The more the content of Cu+, the higher the acetylene conversion rate, implying that Cu+ may be the active center of the acetylene dimerization reaction. Thus, removing carbon deposition through calcining and increasing the content of Cu+ was an effective way of regenerating the catalyst. This work strengthened the understanding of the deactivation behavior and provides a practicable regeneration method for the catalyst in gas–solid acetylene dimerization

Adhesion enhancement for nickel layer deposited on carbon fiber reinforced polymer (CFRP) composites by pretreatment processes for lightning strike

Carbon fiber-reinforced polymer (CFRP) is an engineering composites with excellent performance. The adhesion strength of nickel layer on CFRP composite was enhanced by pretreatment processes, including sandblasting and activation. The surface roughness, wettability, phase and microstructure of the CRFP and the layer were determined by surface profile-meter, goniometer, X-ray diffraction and scanning electronic microscopy, respectively. The adhesion force of nickel layer on CFRP composite was estimated by 3 M tape and pull-out test. The results showed that electroless nickel layer was composed of crystalline phase with small grain size, which belonged to medium-phosphorus deposits. The sandblasting improved the surface roughness and wettability of CFRP surface and rendered hydrophobic surface hydrophilic. The surface roughness of CFRP composites after sandblasting was enhanced by about 60.2%, at the same time the adhesion strength of the layer metalized CFRP composites after sandblasting was improved by 131%. After 3 M tape test, the adhesion state of nickel-CFRP composites with and without sandblasting could be qualitatively classified as grade 5B and 1B, respectively. The good adhesion of nickel layer on CFRP composite was generated from the increase in the surface roughness of CFRP composites after sandblasting and chemical activation, resulting in hydrogen bonds and covalent bonds. The lightning strike test showed that electroless nickel layer did not provide sufficient protection for the sandblasted CFRP composite when subjected to an big impulse current of up to 40 kA current peak and 8–20 μs duration due to the high electrical resistivity.</p

Construction of Cu(DMF)₂Cl Active Sites for Gas–Solid Acetylene Dimerization: Effects of DMF Ligand and Catalytic Mechanism

Dimerization of acetylene to monovinylacetylene (MVA) is a vital process for producing chloroprene rubber in the industry and is highly attractive and challenging. To study the influence of ligands on the catalytic performance of the Cu-based catalyst and the catalytic mechanism in the gas–solid acetylene dimerization reaction, the Cu-based catalyst modified with N,N-dimethylformamide (DMF) ligands was prepared via an incipient wetness method, which increased the average MVA yield by 50% compared to Cu/AC catalysts. X-ray photoelectron spectroscopy, X-ray absorption fine structure spectroscopy, hydrogen temperature-programmed reduction, and transmission electron microscopy results revealed that the Cu-15DMF/AC catalyst formed a Cu–O coordination structure during the process of preparation, which thus changed the electronic environment, enhanced the reducibility of Cu­(II) species, and improved the dispersion of active metals. Furthermore, the gas–solid acetylene dimerization reaction in the catalytic mechanism of Cu/AC and Cu-DMF/AC catalysts was comprehensively elucidated through the DFT calculation. It is demonstrated that the rate-determining step for the Cu/AC catalyst was Cu­(II) reduction with Cl dissociation (Ts1), whereas the Cu-DMF/AC catalyst was acetylene addition (Ts2). The coordination of DMF and Cu species reduced the energy barrier of the dimerization of acetylene to form MVA and raised the energy barrier of the side reaction. This study provides valuable insights into designing efficient and reusable Cu-based catalysts for gas–solid acetylene dimerization

Additional file 7 of Genome-wide identification and function analysis of HMAD gene family in cotton (Gossypium spp.)

Additional file 7 : Table S4. Primers of qRT-PCR used in this study

The correlation between time to amplification and amount of target DNA.

<p>The plot reported the fluorescence in millivolts (mV) on the Y-axis and time in minutes on the X-axis. 1, 100 ng/μL; 2, 10 ng/μL; 3, 1 ng/μL; 4, 100 pg/μL; 5, 10 pg/μL; 6, 1 pg/μL; PC, positive control; NC, negative control.</p

Sensitivity and Specificity of the RealAmp assay compared to VITEK 2 system and PCR assay.

*<p>: The species of <i>Acinetobacter</i> determined by 16S rRNA gene sequencing.</p><p>VITEK 2 system: a fluorescence-based automated identification system.</p><p>RealAmp: real-time loop-mediated isothermal amplification.</p><p>PCR: polymerase chain reaction.</p

Additional file 8 of Genome-wide identification and function analysis of HMAD gene family in cotton (Gossypium spp.)

Additional file 8 : Table S5. The information of transcriptome data of HMAD genes between control and treatment with 300 mM Na2SO4

Additional file 5 of Genome-wide identification and function analysis of HMAD gene family in cotton (Gossypium spp.)

Additional file 5 : Table S2. Analysis of high-expression gene with cis-elements