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Chemicals from Paraffin Hydrocarbons
Published in James G. Speight, Handbook of Petrochemical Processes, 2019
The technical production of urea is based on the reaction of ammonia with carbon dioxide. The reaction occurs in two steps: ammonium carbamate is formed first, followed by a decomposition step of the carbamate to urea and water. The first reaction is exothermic and the equilibrium is favored at lower temperatures and higher pressures. Higher operating pressures are also desirable for the separation absorption step that results in a higher carbamate solution concentration. A higher ammonia ratio than stoichiometric is used to compensate for the ammonia that dissolves in the melt. The reactor temperature ranges between 170°C and 220°C (340°F–395°F) at a pressure of about 3,000 psi. The second reaction represents the decomposition of the carbamate. The reaction conditions are 200°C (390°F) and 450 psi: 2NH3+CO2→H2NCOONH4H2NCOONH4→H2NCONH2+H2O
2 for Fuels and Chemicals
Published in Prasenjit Mondal, Ajay K. Dalai, Sustainable Utilization of Natural Resources, 2017
The annual world production of urea is 175 (megaton) (Heffer and Prud’homme 2009). About 90% of this urea production is used as fertilizer owing to high nitrogen content (46%), and the remainder is used as an intermediate to produce polymers such as polyurethane (Chih-Hung and Chung-Sung 2014). There are about 330 urea plants worldwide; 54% of these plants are located in South East Asia (Ricci 2003). Urea is an organic compound with a chemical structure consisting of two NH2 groups connected via carbonyl group [C=O]. Urea is formed via a two-step reaction between two moles of ammonia and one mole of CO2 at 185°C–190°C and 152–223 bar. In the first step, ammonia and CO2 react, forming ammonium carbamates [H2NCOO– NH4+], which dehydrate, thus producing one mole of urea [H2NCONH2] (Ricci 2003).
Natural and Process Compressors
Published in Leslie R. Rudnick, Synthetics, Mineral Oils, and Bio-Based Lubricants, 2020
A related process often accompanying the production of ammonia is urea which is made from ammonia and CO2. The ammonia and CO2 are fed into the reactor at high pressure and temperature, and the urea is formed in a two-step reaction, first producing ammonium carbamate and then urea. The urea contains unreacted NH3 and CO2 and ammonium carbamate. As the pressure is reduced and heat applied, the ammonium carbamate decomposes to NH3 and CO2 which are then recycled. The urea solution is then concentrated and granulated for use as fertilizer and chemical feedstock.
Urea addition during hydrolysis for increased ethanol yield from white sweet potato: a promising strategy
Published in Biofuels, 2023
Muhamad Maulana Azimatun Nur, Chisya Ayu Puspitaweni, Maya Puspitasari, Faizah Hadi, Sri Wahyu Murni, Wibiana Wulan Nandari, Tutik Muji Setyoningrum
In contrast to the previous study where sweet potato was hydrolyzed at 100 °C, this study performed pretreatment at 80 °C, leading to lower temperatures and increased energy efficiency during ethanol production. The use of urea during hydrolysis of sweet potato for ethanol production can potentially bring several economic benefits. Urea is an inexpensive nitrogen source. While using commercial enzyme in the hydrolysis process can reduce the cost of ethanol production since the cost of the enzyme is higher. Furthermore, the addition of urea can increase the ethanol yield, which can lead to higher profits for the ethanol producer. Scaling up the process for industrial applications could be feasible, as urea is a widely available worldwide. Despite these promising findings, additional research is needed to determine the optimal conditions for urea addition, including dosage and timing during the hydrolysis or fermentation process. Overall, this study’s results offer a promising avenue for improving ethanol production from white sweet potato while also reducing energy costs.
Carbon capture and utilization technologies: a literature review and recent advances
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2019
Francisco M. Baena-Moreno, Mónica Rodríguez-Galán, Fernando Vega, Bernabé Alonso-Fariñas, Luis F. Vilches Arenas, Benito Navarrete
In this section, the manufacturing of urea from CO2 will be looked into. The synthesis of urea is currently the main consumer of CO2 in organic synthesis. Urea, (CO(NH2)2), is the most widely produced nitrogen fertilizer and is commonly marketed. It is produced at industrial level via the reaction of ammonia with CO2, a two-stage process where ammonia and CO2 react to form ammonium carbamate, which is then dehydrated producing urea. This industrial method is based on the Bosch-Meiser urea process, developed in 1922. This reaction is exothermic and the process requires operating conditions between 150°C and 250°C with pressures of 5–25 MPa (Wang, Xin, and Li 2017; Xiang et al. 2012).
Carbon-dioxide capture, storage and conversion techniques in different sectors – a case study
Published in International Journal of Coal Preparation and Utilization, 2023
Another application for this captured CO2 is in the production of urea, the world’s most widely produced nitrogen fertilizer. Urea is a fertilizer, feed supplement, and a raw material for polymers and pharmaceuticals. A colorless crystalline material melts at 132.7°C (271°F) and decomposes prior to boiling. It is manufactured industrially by reacting ammonia with CO2. Ammonia and CO2 react to make ammonium carbamate, which is subsequently dehydrated to form urea.