Gold and gold-based bimetallic catalysts for acetylene hydrochlorination were prepared with HAuCl.sub.4 * 4H.sub.2O and BiCl.sub.3 as precursors and γ-Al.sub.2O.sub.3 as the support. Their catalytic ...performances for acetylene hydrochlorination were tested in a fixed-bed reactor under the fixed reaction conditions of temperature 150°C, C.sub.2H.sub.2 hourly space velocity 120 h.sup.-1, feed volume ratio V (HCl)/ V (C.sub.2H.sub.2) = 1.05. Then they were analyzed by the characterization methods of BET, XRD, SEM, TG, TPR and XPS. The results showed that the Au/γ-Al.sub.2O.sub.3 catalyst exhibited a high activity with only 0.1 wt% Au loading but it deactivated easily for both coke deposition and valance change. With the addition of Bi, it inhibited the reduction of Au.sup.3+ to Au.sup.0 in both the preparation and the reaction process. Besides, the coke deposition was apparently weakened. The best catalytic performance was obtained over 0.1 Au5Bi/γ-Al.sub.2O.sub.3 catalyst with an acetylene conversion of 96% and a selectivity to VCM of more than 99% (Au loading, only 0.1 wt%) for running more than 10 h.
In the present work, the laminar premixed acetyleneahydrogenaair and ethanolahydrogenaair flames were investigated numerically. Laminar flame speeds, the adiabatic flame temperatures were obtained ...utilizing CHEMKIN PREMIX and EQUI codes, respectively. Sensitivity analysis was performed and flame structure was analyzed. The results show that for acetyleneahydrogenaair flames, combustion is promoted by H and O radicals. The highest flame speed (247 cm/s) was obtained in mixture with 95% H2a5% C2H2 at I> = 1.0. The region between 0.95 < XH2 < 1.0 was referred to as the acetylene-accelerating hydrogen combustion since the flame speed increases with increase the acetylene fraction in the mixture. Further increase in the acetylene fraction decreases the H radicals in the flame front. In ethanolahydrogenaair mixtures, the mixture reactivity is determined by H, OH and O radicals. For XH2 < 0.6, the flame speed in this regime increases linearly with increasing the hydrogen fraction. For XH2 > 0.8, the hydrogen chemistry control the combustion and ethanol addition inhibits the reactivity and reduces linearly the laminar flame speed. For 0.6 < XH2 < 0.8, the laminar flame speed increases exponentially with the increase of hydrogen fraction.
An ideal adsorbent for separation requires optimizing both storage capacity and selectivity, but maximizing both or achieving a desired balance remain challenging. Herein, a de‐linker strategy is ...proposed to address this issue for metal–organic frameworks (MOFs). Broadly speaking, the de‐linker idea targets a class of materials that may be viewed as being intermediate between zeolites and MOFs. Its feasibility is shown here by a series of ultra‐microporous MOFs (SNNU‐98‐M, M=Mn, Co, Ni, Zn). SNNU‐98 exhibit high volumetric C2H2 uptake capacity under low and ambient pressures (175.3 cm3 cm−3 @ 0.1 bar, 222.9 cm3 cm−3 @ 1 bar, 298 K), as well as extraordinary selectivity (2405.7 for C2H2/C2H4, 22.7 for C2H2/CO2). Remarkably, SNNU‐98‐Mn can efficiently separate C2H2 from C2H2/CO2 and C2H2/C2H4 mixtures with a benchmark C2H2/C2H4 (1/99) breakthrough time of 2325 min g−1, and produce 99.9999 % C2H4 with a productivity up to 64.6 mmol g−1, surpassing values of reported MOF adsorbents.
Benchmark acetylene adsorbents come to existence via novel cluster‐cluster‐type metal–organic frameworks designed by a de‐linker strategy and are capable of reaching the highest acetylene storage capacity, top‐level IAST selectivity, benchmark breakthrough interval time, and extraordinary productivity for C2H2/C2H4 and C2H2/CO2 mixtures.
Dinitrogen (N.sub.2) fixation associated with moss-dwelling bacteria (diazotrophs) is a N source in boreal forests. In feather moss-dominated understories of Fennoscandia, N.sub.2 fixation rates ...increase with forest age due to N limitation. Whether this is applicable across different boreal ecosystems and successional pathways is not fully understood. In eastern Canada, increasing Sphagnum dominance starting about 100 years post-fire (paludification), is prevalent. Our main objectives were to determine how potential moss-associated N.sub.2 fixation and relative contributions of Sphagnum and other mosses vary with time since fire and to explore the mechanisms driving observed patterns. Sampling was conducted in eight black spruce forests (Picea mariana; 64-724 years post-fire) in northwestern Quebec, Canada, along an established post-fire successional gradient. Potential N.sub.2 fixation was measured with the acetylene reduction method in seven common moss species (Pleurozium schreberi, Hylocomium splendens, Dicranum polysetum, Sphagnum capillifolium, Sphagnum angustifolium, Sphagnum russowii, and Sphagnum magellanicum). N.sub.2 fixation rates by moss communities were low and seemed to increase with stand age, but large variability was found between sites and species. The mechanisms underlying N.sub.2 fixation rates were related to a switch in moss communities from feather moss to a Sphagnum dominance, which had the highest individual acetylene reduction rates, and to an increasing frequency of N.sub.2-fixing samples in old forests. This study provided one of the first records of moss-associated N.sub.2 fixation in eastern Canada and offers insights into how regional and cross-continental differences in moss community composition determine N cycling in boreal forests.
Employing a scanning tunneling microscopy based beak junction technique and mechanically controlled break junction experiments, we investigated tolane (diphenylacetylene)-type single molecular ...junctions having four different anchoring groups (SH, pyridyl (PY), NH2, and CN) at a solid/liquid interface. The combination of current–distance and current–voltage measurements and their quantitative statistical analysis revealed the following sequence for junction formation probability and stability: PY > SH > NH2 > CN. For all single molecular junctions investigated, we observed the evolution through multiple junction configurations, with a particularly well-defined binding geometry for PY. The comparison of density functional theory type model calculations and molecular dynamics simulations with the experimental results revealed structure and mechanistic details of the evolution of the different types of (single) molecular junctions upon stretching quantitatively.
Effects of acetylene on a bimetallic AuaCu/C catalyst for the hydrochlorination of acetylene were investigated. The deactivation of catalyst was observed after acetylene treatment. This result could ...be ascribed to the reduction of active species and carbon deposition on the surface of the catalyst. DFT calculations indicated that multi-adsorption of acetylene could take place on the surface of catalyst leading to active species loss. Monte Carlo simulations show that excess hydrogen chloride could be favorable to minimize the negative effects of acetylene by timely converting the adsorbed acetylene into vinyl chloride.
An isothiocyanate-functionalized tetraphenylethene is synthesized and used as a fluorescent bioprobe for mitochondrion imaging with high specificity and photostability. The covalent conjugation of ...the bioprobe to mitochondrial proteins endows it with high resistance to microenvironmental changes, enabling it for real-time monitoring of mitophagy.
The available processes for removing acetylene impurities from crude ethylene are tremendously energy‐intensive. Herein, we demonstrate a novel aqueous Zn–C2H2 battery, which not only switches ...energy‐consuming acetylene removal to electricity generation, but also reduces acetylene to ethylene through a unique discharge mechanism: C2H2+Zn+H2O→C2H4+ZnO. Under a pure acetylene stream, this Zn–C2H2 battery exhibits an open circuit potential of 1.14 V and a peak power density of 2.2 mW cm−2, which exceed those of reported Zn–CO2 batteries. Even for simulated crude ethylene, the Zn–C2H2 battery manifests an acetylene conversion of 99.97 % and continuously produces polymer‐grade ethylene with only ≈3 ppm acetylene during a long‐term discharge operation. Such a functional battery is universally appliable for reducing other alkynes and generating electricity. Therefore, this work provides an effective strategy for green ethylene purification and the design of functional batteries.
A novel aqueous Zn–C2H2 battery is reported, which not only switches energy‐consuming acetylene removal to electricity generation, but also reduces acetylene to ethylene through a unique discharge mechanism: C2H2+Zn+H2O→C2H4+ZnO. The Zn–C2H2 battery under a pure acetylene stream manifests an open‐circuit potential of 1.14 V and a peak power density of 2.2 mW cm−2. For crude ethylene, the Zn–C2H2 battery produces polymer‐grade ethylene.
A study of polymer synthesis from acetylenic monomers is presented. Advances in the creation of new catalysts have allowed such reactions, resulting in acetylene polymers that may revolutionize ...polymer chemistry.
Bioinspired complexes employing the ligands 6‐tert‐butylpyridazine‐3‐thione (SPn) and pyridine‐2‐thione (SPy) were synthesized and fully characterized to mimic the tungstoenzyme acetylene hydratase ...(AH). The complexes W(CO)(C2H2)(CHCH‐SPy)(SPy) (4) and W(CO)(C2H2)(CHCH‐SPn)(SPn) (5) were formed by intramolecular nucleophilic attack of the nitrogen donors of the ligand on the coordinated C2H2 molecule. Labelling experiments using C2D2 with the SPy system revealed the insertion reaction proceeding via a bis‐acetylene intermediate. The starting complex W(CO)(C2H2)(SPy)2 (6) for these studies was accessed by the new acetylene precursor mixture W(CO)(C2H2)n(MeCN)3−nBr2 (n=1 and 2; 7). All complexes represent rare examples in the field of W−C2H2 chemistry with 4 and 5 being the first of their kind. In the ongoing debate on the enzymatic mechanism, the findings support activation of acetylene by the tungsten center.
C2H2 under attack! Bioinspired model complexes for acetylene hydratase demonstrate that nucleophilic attack on a W−C2H2 adduct is feasible. With the insertion of the enzyme's substrate acetylene into the W−N bond of the biomimetic ligand, data, which support the still disputed mechanism involving a W‐η2‐C2H2 intermediate, is provided (see scheme).
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