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Ammonia Synthesis
Published in Martyn V. Twigg, Catalyst Handbook, 2018
The cyanamide route to ammonia is shown in equations (1), (2) and (3). Calcium carbide (CaC2), obtained by fusion of lime and carbon, reacts at 1000°C with nitrogen to form calcium cyanamide (CaCN2). Hydrolysis of the cyanamide yields ammonia, with simultaneous precipitation of calcium carbonate. The first plant was commissioned in Italy in 1906, and other plants using the process were built in Germany and the USA. Somewhat surprisingly, in Germany production by the cyanamide route had reached 140 000 tonnes per year by 1915. However, the process was inefficient in its use of energy, and required 230 GJ tonne−1of nitrogen, but such was the need for explosives that this extreme cost was apparently justified.
Mesoporous graphitic carbon nitride for adsorptive desulfurization in an isooctane solution
Published in Journal of Sulfur Chemistry, 2022
Xianli Huang, Yueyue Zhang, Yue Lai, Yang Li
With continuing advances in materials science, an increasing number of new functional materials have been applied for the adsorption process, e.g. graphitic carbon nitride (g-C3N4) [18,19]. To date, g-C3N4 has drawn much scientific attention due to its environment-friendly superiority. Usually, g-C3N4 is widely used as a metal-free photocatalyst in the field of hydrogen evolution, water splitting or pollutant destruction and so on [20,21]. The pyrolysis of precursors rich in carbon and nitrogen, such as dicyandiamide [22,23], cyanamide [24–26], thiourea [27,28], urea [29,30] and melamine [31] is utilized extensively. However, the low specific surface area is a big hurdle. Due to the graphitic layered structure, the surface area of g-C3N4 prepared by direct polycondensation of C-, N- and H-containing precursors is normally low (ca. 10m2/g) [32]. Different methods have been applied to overcome this disadvantage, like the formation of nano-architectures [33]. We have attempted to synthesize mesoporous g-C3N4 with large surface areas and accidentally found its outstanding porous structures have good adsorption ability towards sulfur compounds during an adsorptive desulfurization process [34].
Synergistic influence of SiC and C3N4 reinforcements on the characteristics of ZrB2-based composites
Published in Journal of Asian Ceramic Societies, 2021
Zohre Ahmadi, Mohammad Zakeri, Mohammad Farvizi, Aziz Habibi-Yangjeh, Soheila Asadzadeh-Khaneghah, Mehdi Shahedi Asl
Graphitic carbon nitride (g-C3N4), as a member of polymeric semiconductor materials, has received tremendous attention due to its excellent properties such as nontoxicity, thermal/chemical stability, cheap, and simple preparation methods [44–47]. The combination of these unrivaled characteristics of this semiconductor makes it a suitable material for using in various applications like photoreactivity, carbon dioxide reduction, photocurrent, solar energy, and fuel cells [48–52]. Graphitic C3N4 powder was easily synthesized via one-step calcination of inexpensive organic precursors like thiourea, melamine, urea, and cyanamide having “earth-abundant” elements [53–55]. In our previous research, the role of g-C3N4 additive on the mechanical features and sinterability of ZrB2-based materials was studied for the first time. Introduction of C3N4 in ZrB2 ceramics not only led to the finer microstructure and improved densification via the in-situ formation of ZrC and BN, but also resulted in enhanced mechanical properties when only 5 wt% C3N4 has been added to ZrB2 [56].
Solid-phase synthesis of sulfur containing heterocycles
Published in Journal of Sulfur Chemistry, 2018
The carbon disulfide, cyanamide, and potassium hydroxide were reacted in aqueous EtOH for the preparation of Merrifield resin (Scheme 22). Solid-supported cyanocarbonimidodithioate was formed with a good loading capacity in the presence of dimethylformamide solvent. One-pot three-component reaction of Merrifield resin with cyanamide and carbon disulfide displayed a lower loading capacity of about 40% in comparison to stepwise pathway. Thorpe–Ziegler cyclization provided thiazole resin on treating resin with ethyl 2-bromoacetate or 2-bromoacetophenone and triethylamine at 80°C. Sulfone resin was obtained when the sulfonyl resin was oxidized with m-CPBA. The nucleophilic addition of various amines liberated the desired thiazoles from resin. Other substituent groups were attached onto 4-aminothiazole by acylation with acid chloride and the urea formation with isocyanate of the intermediate resin. The reaction with isocyanate and acylation with acid chloride furnished thiazolo resin under microwave (MW) irradiation. Similarly, as above sulfanyl resin was treated with m-CPBA to give sulfonyl resin and then 2,4,5-trisubstituted thiazoles were synthesized on treating sulfonyl resin with appropriate amines [19,30,53].