1,721,166 research outputs found
The chemistry of N-CO2 bonds: synthesis of carbamic acids and their derivatives, isocyanates, and ureas
No full textThe chapter provides an updated account of the research activity concerning the utilization of carbon dioxide in the synthesis of carbamates, isocyanates, and ureas
Mechanistic Studies on the Role of Carbon Dioxide in the Synthesis of Methylcarbamates from Amines and Dialkylcarbonates in the Presence of CO2
No full textN-alkylmethylcarbamates have been synthesized from amines and dimethylcarbonate (DMC) in the presence of carbon dioxide. The catatylic rote of CO2 in the overall process has been investigated and elucidated
Sintesi di carbammati da ammine e carbonati organici via attivazione del diossido di carbonio
No full textCarbammati organici RNHC(O)OR' dove R e R',che possono essere uguali o diversi, rappresentano residui alchilici, alchilici sostituiti, cicloalchilici, cicloalchilici sostituiti, sono stati preparati per reazione di ammine RNH2 e carbonati organici (R'O)2C=O in presenza di diossido di carbonio, via attivazione dell'eterocumulene
Mixed anhydrides: key intermediates in carbamates forming processes of industrial interest
No full textAlkali-metal-assisted Transfer of Carbamate Group from Phosphocarbamates to Alkyl Halides: a New Easy Way to Alkali-metal Carbamates and to Carbamate Esters
No full textPhosphocarbamates P(O2CNR2)x(NR2)3 –x(R = alkyl; x= 1 or 2), easily obtainable by insertion of CO2 in the P–N bond of the corresponding aminophosphines P(NR2)3, have been used as a source of carbamate groups in the reaction with alkyl halides, R′X, to afford carbamate esters. The reaction is mediated by alkali-metal halides, MY, and requires the presence of a suitable macrocyclic polyether (L). The overall reaction occurs in two steps: the carbamic group is first transferred to the alkali-metal cation to give a carbamate salt [ML][O2CNR2] which then reacts with the alkyl halide affording R2NC(O)OR′. The yield and selectivity to the carbamate ester are remarkably influenced by the nature of MY. The influence of the nature of the alkali-metal salt in the overall process and the role of the macrocyclic ligand in modifying the reactivity of the R2NCO2– anion in alkali-metal carbamates are discussed
Merging the Green-H2 production with Carbon Recycling for stepping towards the Carbon Cyclic Economy
Full text linkHydrogen Economy and Cyclic Economy are advocated, together with the use of perennial (solar, wind, hydro, geo-power, SWHG) and renewable (biomass) energy sources, for defossilizing anthropic activities and mitigating climate change. Each option has intrinsic limits that prevent a stand-alone success in reaching the target. Humans have recycled goods (metals, water, paper, and now plastics) to a different extent since very long time. Recycling carbon (which is already performed at the industrial level in the form of CO2 utilization and with recycling paper and plastics) is a key point for the future. The conversion of CO2 into chemicals and materials is carried out since the late 1800s (Solvay process) and is today performed at scale of 230 Mt/y. It is time to implement on a scale of several Gt/y the conversion of CO2 into energy products, possibly mimicking Nature which does not use hydrogen. In the short term, a few conditions must be met to make operative on a large scale the production of fuels from recycled-C, namely the availability of low-cost: i. abundant, pure concentrated streams of CO2, ii. non-fossil primary energy sources, and iii. non-fossil-hydrogen. The large-scale production of hydrogen by Methane Steam Reforming with CO2 capture (Blue-H2) seems to be a realistic and sustainable solution. Green-H2 could in principle be produced on a large scale through the electrolysis of water powered by perennial primary sources, but hurdles such as the availability of materials for the construction of long-living, robust electrochemical cells (membranes, electrodes) must be abated for a substantial scale-up with respect to existing capacity. The actual political situation makes difficult to rely on external supplies. Supposed that cheap hydrogen will be available, its direct use in energy production can be confronted with the indirect use that implies the hydrogenation of CO2 into fuels (E-fuels), an almost ready technology. The two strategies have both pros and cons and can be integrated. E-Fuels can also represent an option for storing the energy of intermittent sources. In the medium-long term, the direct co-processing of CO2 and water via co-electrolysis may avoid the production/transport/ use of hydrogen. In the long term, coprocessing of CO2 and H2O to fuels via photochemical or photoelectrochemical processes can become a strategic technology
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