DOCSLIB.ORG

(12) Patent Application Publication (10) Pub. No.: US 2006/0142607 A1 Ryu Et Al

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
(12) Patent Application Publication (10) Pub. No.: US 2006/0142607 A1 Ryu Et Al US 2006O142607A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2006/0142607 A1 Ryu et al. (43) Pub. Date: Jun. 29, 2006 (54) PROCESS FOR MAKING DIALKYL Publication Classification CARBONATES (51) Int. Cl. (75) Inventors: J. Yong Ryu, League City, TX (US); CD7C 69/96 (2006.01) Abraham P. Gelbein, Falls Church, VA (52) U.S. Cl. .............................................................. 558/277 (US) Correspondence Address: (57) ABSTRACT Kenneth H. Johnson A process for the production of dialkyl carbonates from the P.O. Box 630708 reaction of alcohol, for example C-C alcohols, with urea is Houston, TX 77263 (US) disclosed wherein the water and ammonium carbamates (73) Assignee: CATALYTIC DISTILLATION TECH- impurities in the feed are removed in a prereactor. The water NOLOGES is reacted with urea in the feed to produce ammonium carbamate which is decomposed along with the ammonium carbamates originally in the feed to ammonia and carbon (21) Appl. No.: 11/358,671 dioxide. In addition some of the urea is reacted with the (22) Filed: Feb. 21, 2006 alcohol in the first reactor to produce alkyl carbamate which is a precursor to dialkyl carbonate. Dialkyl carbonates are Related U.S. Application Data produced in the second reaction Zone. The undesired by product N-alkyl alkyl carbamates are continuously distilled (63) Continuation of application No. 10/821,225, filed on off from the second reaction Zone along with ammonia, Apr. 8, 2004. alcohol and dialkyl carbonates under the steady state reactor operation. N-alkyl alkyl carbamates can be converted to (60) Provisional application No. 60/558,838, filed on Apr. heterocyclic compounds in a third reaction Zone to remove 2, 2004. as Solids from the system. Patent Application Publication Jun. 29, 2006 Sheet 1 of 5 US 2006/0142607 A1 Separation Unit 2. S 29 Ammonium Carbamate (7/(7. 7 Organic waste Patent Application Publication Jun. 29, 2006 Sheet 2 of 5 US 2006/0142607 A1 MeOH DMC Patent Application Publication Jun. 29, 2006 Sheet 3 of 5 US 2006/0142607 A1 Annonium Carbamate Ether 128 2. Patent Application Publication Jun. 29, 2006 Sheet 4 of 5 US 2006/0142607 A1 223 MEC Separation Unit DEC DMC 224 776 / Patent Application Publication Jun. 29, 2006 Sheet 5 of 5 US 2006/0142607 A1 AG US 2006/0142607 A1 Jun. 29, 2006 PROCESS FOR MAKING DALKYL CARBONATES process. In the first step cyclic carbonates are produced by reacting epoxides with carbon dioxide as disclosed in U.S. BACKGROUND OF THE INVENTION Pat. Nos. 4,786,741; 4,851,555 and 4,400,559. In the second 0001) 1. Field of the Invention step dimethyl carbonate is produced along with glycol by exchange reaction of cyclic carbonates with methanol. See 0002 The present invention relates to a process for the for example Y. Okada, etal “Dimethyl Carbonate Production production of dialkyl carbonates, particularly C-C dialkyl for Fuel Additives', ACS, Div. Fuel Chem., Preprint, 41(3), carbonates wherein the reaction occurs simultaneously with 868, 1996, and John F. Knifton, et al., “Ethylene Glycol separation of the reactants and the carbonate products. More Dimethyl Carbonate Cogeneration”, Journal of Molecular particularly the invention relates to a process wherein alco Chemistry, vol. 67, pp. 389-399, 1991. While the process has hol is reacted with urea and/or alkyl carbamate in the its advantages, the reaction rate of epoxides with carbon presence of a complex compound catalyst. More particularly dioxide is slow and requires high pressure. In addition, the the invention relates to a process wherein feed stream exchange reaction of the cyclic carbonate with methanol is impurities are removed to produce stable catalyst perfor limited by equilibrium and methanol and dimethyl carbonate mance, improved reaction rates and trouble free downstream operation of equipment. form an azeotrope making separation difficult. 0009. It has been known that dialkyl carbonates can be 0003 2. Related Art prepared by reacting primary aliphatic alcohols such as 0004 Dialkyl carbonates are important commercial com methanol with urea (1) in the presence of various heteroge pounds, the most important of which is dimethyl carbonate neous and homogeneous catalysts Such as dibutyltin (DMC). Dimethyl carbonate is used as a methylating and dimethoxide, tetraphenyltin, etc. See for example P. Ball et carbonylating agent and as a raw material for making al, “Synthesis of Carbonates and Polycarbonates by Reac polycarbonates. It can also be used as a solvent to replace tion of Urea with Hydroxy Compounds’. C1 Mol. Chem., halogenated solvents such as chlorobenzene. Although the vol. 1, pp. 95-108, 1984. Ammonia is a coproduct and it may current price of both dimethyl carbonate and diethyl car be recycled to urea (2) as in the following reaction sequence. bonate is prohibitively expensive to use as fuel additive, both could be used as an oxygenate in reformulated gasoline and an octane component. Dimethyl carbonate has a much (1) higher oxygen content (53%) than MTBE (methyl tertiary butyl ether) or TAME (tertiary amyl methyl ether), and hence not nearly as much is needed to have the same effect. 2ROH + H2N-C-NH2 <=> RO-C-OR + 2 NH It has a RON of 130 and is less volatile than either MTBE alcohol le:8 dialkyl carbonate or TAME. It has a pleasant odor and, unlike ethers, is more (2) readily biodegradable. O 0005. In older commercial processes dimethyl carbonate 2NH + CO2 <===> HN-C-NH + HO was produced from methanol and phosgene. Because of the extreme toxicity and cost of phosgene, there have been efforts to develop better, non-phosgene based processes. 0010 Carbamates are produced at a lower temperature 0006. In one new commercial process, dimethyl carbon followed by production of dialkyl carbonates at higher ate is produced from methanol, carbon monoxide, molecular temperature with ammonia being produced in both steps. oxygen and cuprous chloride via oxidative carbonylation in a two-step slurry process. Such a process is disclosed in EP 0460735A2. The major shortcomings of the process are the O O low production rate, high cost for the separation of products and reactants, formation of by-products, high recycle in-l-Nil, + ROH <====> Ro--Nil, + NH requirements and the need for corrosion resistant reactors alkyl carbonate and process lines. O O 0007 Another new process is disclosed in EP 0742 198 Ro--Nil, + ROH <===> Ro--or + NH A2 and EP 0 505 374 B1 wherein dimethyl carbonate is produced through formation of methyl nitrite instead of the dialkyl carbonate cupric methoxychloride noted above. The by-products are nitrogen oxides, carbon dioxide, methylformate, etc. Dim 0011. As noted the above two reactions are reversible ethyl carbonate in the product stream from the reactor is under reaction conditions. The order of catalytic activity of separated by Solvent extractive distillation using dimethyl organotin compounds is RSn-RSnX-RSnX, wherein oxalate as the solvent to break the azeotropic mixture. X=C1, RO, RCOO, RCOS. A maximum reaction rate and Although the chemistry looks simple and the production rate minimum formation of by-products are reported for dialkyl is improved, the process is very complicated because of the tin (IV) compounds. For most catalysts (Lewis acids), higher separation of a number of the materials, balancing materials catalyst activity is claimed if the reaction is carried out in the in various flow sections of the process, complicated process presence of an appropriate cocatalyst (Lewis base). For control and dealing with methyl nitrite, a hazardous chemi example, the preferred cocatalyst for organic tin (IV) cata cal. lysts such as dibutyltin dimethoxide, dibutyltin oxide, etc. 0008. In another commercial process dimethyl carbonate are triphenylphosphine and 4-dimethylaminopyridine. How is produced from methanol and carbon dioxide in a two-step ever, thermal decomposition of intermediate alkyl carbam US 2006/0142607 A1 Jun. 29, 2006 ates and urea to isocyanic acid (HNCO) or isocyanuric acid catalyst containing alkyoxy groups, for example, the meth ((HNCO)) and alcohol or ammonia (a coproduct of urea oxy groups on the organotin complex compound molecules decomposition) is also facilitated by the organotin com are highly reactive with water molecules resulting in pounds such as dibutyltin dimethoxide or dibutyltin oxide hydrolysis of the bond between the tin atom and oxygen employed in the synthesis of dialkyl carbamates. WO atom of methoxy group. Ammonium carbamate causes 95/17369 discloses a process for producing dialkyl carbon problems for controlling the backpressure in the dialkyl ate Such as dimethyl carbonate in two steps from alcohols carbonate producing reactor and plugging the cooling sys and urea, utilizing the chemistry and catalysts published by tem (condenser) of the product vapor stream from the P. Ball et al. In the first step, alcohol is reacted with urea to dialkyl reactor, because of the deposition of ammonium produce an alkyl carbamate. In the second step, dialkyl carbamate. carbonate is produced by reacting further the alkyl carbam ate with alcohol at temperatures higher than the first step. SUMMARY OF THE INVENTION The reactions are carried out by employing an autoclave reactor. However, when methanol is reacted with methyl 0017 Briefly the present invention is an improved pro carbamate or urea, N-alkyl by-products such as N-methyl cess for production of dialkyl carbonate comprising the steps methyl carbamate (N-MMC) and N-alkyl urea are also of: produced according to the following reactions: 0018 (a) feeding a stream containing urea, alcohol, water and ammonium carbamate to a first reaction Zone: O 0019 (b) concurrently in said first reaction Zone, CHO-C-NH + (CHO)2CO ===> 0020 (i) reacting water with urea to form ammonium O carbamate, CH-O-C-NH-CH + CHOH+CO 0021 (ii) decomposing the ammonium carbamate in O the feed and the ammonium carbamate from the reac tion of water with urea into ammonia and carbon CH-O-C-NH-CH + dioxide, and CHOH <====> (CH3)2CO + CH3NH2 0022 (c) removing ammonia, carbon dioxide and said alcohol from said first reaction Zone as a first overheads: 0012.
Load more

Recommended publications
  • Synthesis of 2-Substituted Benzimidazole-5-Carbamates As 1109 Potential Antifilarial Agents Siya Ram, Dean S
    Jul-Aug 1986 Synthesis of 2-Substituted Benzimidazole-5-carbamates as 1109 Potential Antifilarial Agents Siya Ram, Dean S. Wise and Leroy B. Townsend* Department of Medicinal Chemistry, College of Pharmacy, and Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1065 Received August 26, 1985 A number of 2,5-disubstituted benzimidazoles have been prepared from 2-benzyl-5-nitrobenzimidazole (5) and 2-p-fluorobenzyl-5-nitrobenzimidazole(6), and evaluated as potential antifilarial agents. None of the compounds prepared in this study have demonstrated any significant antifilarial activity. J. Heterocyclic Chem.. 23, 1109 (1986). A large group of benzimidazole derivatives are highly effective as an anthelmintics [ 11. Among these, meben- dazole (la, methyl 5-benzoylbenzimidazole-2-carbamate) and flubendazole (lb, methyl 5-p-fluorobenzoylbenzimida- 5. x-H zole-Z-carbamate) have demonstrated a broad-spectrum of 6, X-F activity against helminth diseases including filarial infec- 4.. XZH tions [2-51. In our continuing studies to develop new an- b. X=F tifilarial agents [6-81, we have found that two of the metabolites of mebendazole, methyl 5-(c~-hydroxylbenzyl)- 0 I benzimidazole-2-carbamate (lc), and, methyl 5-benzyl- benzimidazole-2-carbamate (la)possess antifilarial activi- ty very similar to that of the parent drug la [9]. Recently, a 9.X:H. R:CH, 10, X= F . R -CH, series of benzothiazoles, typified by structure 2, were 11, X=H. R-C,H, I 7, XzH I c:o taco, I CH,OH OR / reported to possess both micro- and macrofilarial activity against B. pahangi [lo].
    [Show full text]
  • A Novel Nonphosgene Process for the Synthesis of Methyl Nphenyl
    Chinese Journal of Chemistry, 2004.22.782-786 Article A Novel Non-phosgene Process for the Synthesis of Methyl N-Phenyl Carbamate from Methanol and Phenylurea: Effect of Solvent and Catalyst WANG, Xin-Kuia(3/l&S) YAN, Shi-Run'vb(/q@%d) CAO, Yong*(g!F!) FAN, Kang-Nian'pb(3i5@+) HE,He-Yongb(W@B!) KANG, Mao-Qing"(fiit$W) PENG, Shao-Yia(G9B) a Institute of Coal Chemistty Chinese Academy of Sciences, Taiyuan, Shami 030001, China b Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Deparfment of Chemistv, Fudan University, Shanghai 200433. China A novel environmentally benign process for the synthesis of methyl N-phenyl carbamate (Mpc) from methanol and phenylurea was studied. Effect of solvent and catalyst on the reaction behavior was investigated. The IR spectra of methanol and phenylurea dissolved in different solvents were also recorded. Compared with use of methanol as both a reactant and a solvent, phenylurea conversion and selectivity to Mpc increased by using toluene, benzene or anisole as a solvent, while phenylurea conversion decreased slightly by using n-octane as a solvent. The phenylurea conversion declined nearly 50% when dimethyl sulfoxide (DMSO) was used as a reaction media, and MPC selec- tivity decreased as well. The catalytic reaction tests showed that a basic catalyst enhanced the selectivity to Mpc while an acidic catalyst promoted the formation of methyl carbamate and aniline. Moderate degree of basicity showed the best catalyhc performance in the cases studied. Keywords methyl N-phenyl carbamate synthesis, phenylurea, phosgene-free, solvent effect, acid-base catalyst Introduction tion of methanol from DMC azeotrope, and DMC is relatively expensive.
    [Show full text]
  • Environmental-Friendly Synthesis of Alkyl Carbamates from Urea and Alcohols with Silica Gel Supported Catalysts
    catalysts Article Environmental-Friendly Synthesis of Alkyl Carbamates from Urea and Alcohols with Silica Gel Supported Catalysts Yubo Ma 1,2 , Lei Wang 1,3,*, Xiaodong Yang 4,* and Ronghui Zhang 5 1 School of Chemical Engineering, Chongqing Chemical Industry Vocational College, Chongqing 401220, China; [email protected] 2 Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China 3 Department of Chemistry and Chemical Engineering, Xinjiang University, Urumqi 830011, China 4 Institute of Resources and Environment Science, Xinjiang University, Urumqi 830011, China 5 Guangdong Key Laboratory of Intelligent Transportation System, School of Engineering, Sun Yat-sen University, Guangzhou 510275, China; [email protected] * Correspondence: [email protected] (L.W.); [email protected] (X.Y.) Received: 7 October 2018; Accepted: 19 November 2018; Published: 23 November 2018 Abstract: TiO2/SiO2, Cr2O3-NiO/SiO2, and TiO2-Cr2O3/SiO2 were prepared by the impregnation method for alkyl carbamate synthesis using urea as the carbonyl source. Up to 97.5% methyl carbamate yield, 97% ethyl carbamate yield, and 96% butyl carbamate yield could be achieved, respectively. The catalysts were characterized by ICP-AES, BET, XRD, XPS, NH3-TPD, and EPMA. Catalytic activity investigation revealed that TiO2/SiO2, Cr2O3-NiO/SiO2, and TiO2-Cr2O3/SiO2 were effective catalysts for methyl carbamate (MC), ethyl carbamate (EC), and butyl carbamate (BC), respectively. The recycling tests suggested that these silica gel supported catalyst system is active, stable, and reusable. A total of 96–97% alkyl carbamate (methyl, ethyl, and butyl) could be obtained in a 2 L autoclave, and these data suggested that our catalyst system is relatively easy to scale up.
    [Show full text]
  • Ethyl Carbamate 1. Exposure Data
    ETHYL CARBAMATE There appears to be no general consensus on a common trivial name for this sub- stance: ethyl carbamate and urethane (or urethan) are both commonly used; however, a preference for ethyl carbamate was noted in the more recent literature. The name urethane is also sometimes applied to high-molecular-weight polyurethanes used as foams, elastomers and coatings. Such products are not made from and do not generate the chemical ethyl carbamate on decomposition. Due to this possible confusion, the term ethyl carbamate has been used in this monograph. 1. exposure Data 1.1 Chemical and physical data 1.1.1. synonyms CAS Registry No.:.51–79–6 synonyms: Carbamic acid ethyl ester; ethylurethan; ethyl urethan; ethyl urethane; urethan; urethane 1.1.2. Chemical.formula.and.relative.molecular.mass NH2COOC2H5 Relative molecular mass: 89.1 1.1.3. Chemical.and.physical.properties.of.the.pure.substance From Budavari (2000) (a) Description: Colourless, almost odourless, columnar crystals or white granular powder; the pH of an aqueous solution is neutral (b) Boiling-point: 182–184.°C (c) Melting-point: 48–50.°C (d) solubility: Dissolves in water (1 g/0.5 mL), ethanol (1 g/0.8 mL), chloroform (1 g/0.9 mL), ether (1 g/1.5 mL), glycerol (1 g/2.5 mL) and olive oil (1 g/32 mL) (e).Volatility: Sublimes readily at 103°C at 54 mm Hg; volatile at room temperature –1281– 1282 IARC MONOGRAPHS VOLUME 96 1.1.4. Technical.products.and.impurities Trade names for ethyl carbamate include Leucothane, Leucethane and Pracarbamine.
    [Show full text]
  • Highly Selective Phosgene-Free Carbamoylation of Aniline By
    Article pubs.acs.org/OPRD Highly Selective Phosgene-Free Carbamoylation of Aniline by Dimethyl Carbonate under Continuous-Flow Conditions Sandra Grego, Fabio Arico,̀ and Pietro Tundo* Department of Environmental Sciences, Informatics and Statistics, Ca’ Foscari University of Venice, Dorsoduro 2137, 30123 Venezia, Italia ABSTRACT: Over the last 20 years organic carbamates have found numerous applications in pesticides, fungicides, herbicides, dyes, pharmaceuticals, cosmetics, and as protecting groups and intermediates for polyurethane synthesis. Recently, in order to avoid phosgene-based synthesis of carbamates, many environmentally benign and alternative pathways have been investigated. However, few examples of carbamoylation of aniline in continuous-flow apparatus have been reported. In this work, we report a high-yielding, dimethyl carbonate (DMC)-mediated carbamoylation of aniline in a fixed-bed continuously fed reactor employing basic zinc carbonate as catalyst. Several variables of the system have been investigated (i.e. molar ratio of reagents , flow rate, and reaction temperature) to optimize the operating conditions of the system. 1. INTRODUCTION Recently, several examples of carbamoylation of aniline,9 4,4′-methylenedibenzenamine10 (for the synthesis of methylene Organic carbamates are industrially relevant compounds which, 11 over the last 20 years, have found numerous applications in diphenyl diisocyanate, MDI) and 2,4-diaminotoluene (for the pesticides, fungicides, herbicides, dyes, pharmaceuticals, cos- synthesis of toluene diisocyanate TDI) have been reported by 1 DMC chemistry in the presence of either homogeneous or metics, and as protecting groups. Carbamates can also be ffi readily converted into isocyanates for polyurethane synthesis supported catalysts. An example is the e cient carbamoylation via thermodecomposition.2 of 2,4-diaminotoluene (DAT) by gold-catalyzed phosgene-free Industrially, these compounds are synthesised predominantly synthesis.
    [Show full text]
  • An Improved Method for Determination of Ethyl Carbamate in Korean Traditional Rice Wine I-S Woo1,I-Hkim1, U-J Yun1, S-K Chung1, I-K Rhee2, S-W Choi3 and H-D Park1
    Journal of Industrial Microbiology & Biotechnology (2001) 26, 363 – 368 D 2001 Nature Publishing Group 1367-5435/01 $17.00 www.nature.com/jim An improved method for determination of ethyl carbamate in Korean traditional rice wine I-S Woo1,I-HKim1, U-J Yun1, S-K Chung1, I-K Rhee2, S-W Choi3 and H-D Park1 1Department of Food Science and Technology, Kyungpook National University, 1370 Sankyuk, Taegu 702-701, Korea; 2Department of Agricultural Chemistry, Kyungpook National University, 1370 Sankyuk, Taegu 702-701, Korea; 3Department of Food Science and Nutrition, Catholic University of Daegu, Hayang, Kyungpook 712-702, Korea An improved extraction method for ethyl carbamate, a genotoxic and carcinogenic compound found in various fermented foods and beverages, was investigated for its determination in the two most typical Korean traditional rice wines, takju and yakju. When the rice wines were extracted twice with chloroform at 308C for 60 min, the recovery of ethyl carbamate was less than 16%. When they were saturated with NaCl before extraction, the recovery of ethyl carbamate increased to 24.4% in takju and 67.2% in yakju. Adjustment of pH to 9.0 after NaCl saturation in takju resulted in a dramatic increase of recovery to 81.2%, but not in yakju. When the contents of ethyl carbamate and its precursor, urea, in various Korean traditional rice wines were determined, there was no correlation between the two contents. This is due to the fact that storage time is more important than urea content in the formation of ethyl carbamate in rice wine. In addition, its storage at high temperature resulted in a dramatic increase in ethyl carbamate content according to the prolonged storage time, suggesting that storage time and temperature play a key role in the formation of ethyl carbamate in Korean traditional rice wine.
    [Show full text]
  • Synthesis of Dimethyl Carbonate from Urea and Methanol M
    Reducing the Carbon Footprint of Fuels and Petrochemicals DGMK Conference October 8 – 10, 2012, Berlin, Germany Synthesis of Dimethyl Carbonate from Urea and Methanol M. Polyakov*, V.N. Kalevaru*, K. Müller**, W. Arlt**, J. Strautmann***, D. Kruse***, A. Martin* *Leibniz Institute for Catalysis at University of Rostock, Germany, **Friedrich-Alexander- University Erlangen-Nuremberg, Germany, ***Creavis Technologies and Innovation, Evonik Industries AG, Marl, Germany This project is funded by the German state of North Rhine-Westphalia (Ministry for innovation, science and research) and co-financed by the EU (European Regional Development Fund) as well as by Evonik Industries AG. Abstract Alcoholation of urea with methanol to produce dimethyl carbonate (DMC) is an interesting approach from both the ecological and economical points of view because the urea synthesis usually occurs by the direct use of carbon dioxide. Literature survey reveals that metal oxide catalysts for instance MgO, ZnO, etc. or polyphosphoric acids are mostly used as catalysts for this reaction. In this contribution, we describe the application of ZnO, MgO, CaO, TiO2, ZrO2 or Al2O3 catalysts for the above mentioned reaction. The catalytic activity of different metal oxides towards DMC synthesis was checked and additionally a comparison of achieved conversions with that of predictions made by thermodynamic calculations was also carried out. The achieved conversions are in good agreement with those of calculated ones. The test results reveal that the reaction pressure and temperature have a strong influence on the formation of DMC. Higher reaction pressure improved the yield of DMC. Among different catalysts investigated, ZnO displayed the best performance. The conversion of urea in most cases is close to 100 % and methyl carbamate MC is the major product of the reaction.
    [Show full text]
  • Hybrid Computational Toxicology Models for Regulatory Risk Assessment Prachi Pradeep Marquette University
    Marquette University e-Publications@Marquette Dissertations (2009 -) Dissertations, Theses, and Professional Projects Hybrid Computational Toxicology Models for Regulatory Risk Assessment Prachi Pradeep Marquette University Recommended Citation Pradeep, Prachi, "Hybrid Computational Toxicology Models for Regulatory Risk Assessment" (2015). Dissertations (2009 -). Paper 503. http://epublications.marquette.edu/dissertations_mu/503 HYBRID COMPUTATIONAL TOXICOLOGY MODELS FOR REGULATORY RISK ASSESSMENT by PRACHI PRADEEP A Dissertation submitted to the Faculty of the Graduate School, Marquette University, in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Milwaukee, Wisconsin May 2015 ABSTRACT HYBRID COMPUTATIONAL TOXICOLOGY MODELS FOR REGULATORY RISK ASSESSMENT Prachi Pradeep Marquette University, 2015 Computational toxicology is the development of quantitative structure activity relationship (QSAR) models that relate a quantitative measure of chemical structure to a biological effect. In silico QSAR tools are widely accepted as a faster alternative to time-consuming clinical and animal testing methods for regulatory risk assessment of xenobiotics used in consumer products. However, different QSAR tools often make contrasting predictions for a new xenobiotic and may also vary in their predictive ability for different class of xenobiotics. This makes their use challenging, especially in regulatory applications, where transparency and interpretation of predictions play a crucial role in the development of safety
    [Show full text]
  • Synthesis of Dimethyl Carbonate from Urea and Methanol Catalyzed by the Metallic Compounds at Atmospheric Pressure
    http://www.paper.edu.cn Catalysis Communications 7 (2006) 472–477 www.elsevier.com/locate/catcom Synthesis of dimethyl carbonate from urea and methanol catalyzed by the metallic compounds at atmospheric pressure Bolun Yang *, Dongpeng Wang, Hongye Lin, Jianjun Sun, Xiaoping Wang Chemical Engineering Department, Xi’an Jiaotong University, Shaanxi, Xi’an 710049, PR China Received 7 October 2005; received in revised form 12 January 2006; accepted 13 January 2006 Available online 9 March 2006 Abstract A novel route was proposed for producing dimethyl carbonate (DMC) at atmospheric pressure from urea and methanol catalyzed by the metallic compounds with a high boiling point electron donor compounds (polyethylene glycol dimethyl ether) (PGDE) as solvent. The effects of various operation conditions, such as methanol/urea initial molar ratio, catalyst concentration, urea/PGDE initial mass ratio, flow rate of circulating, reaction temperature, stirring speed and reaction time on DMC yield were investigated, respectively. Experimental results indicate that the using of PGDE as solvent enable this synthesis reaction to reach the requisite temperature and restrain the decomposition of urea and MC; removing the products, DMC and ammonia effectively from the reaction system in time is important to improve the yield of DMC. The DMC yield of 28.8% can be obtained in the optimal reaction conditions. This new pro- cess shows some advantages such as easily operating, effectively removing NH3 from the reaction system and lower cost. Ó 2006 Published by Elsevier B.V. Keywords: Dimethyl carbonate; Metallic compound; Urea; Methanol; Atmospheric pressure 1. Introduction cal [1–3]. Nowadays, DMC has become the new basic mate- rial of organic synthesis field.
    [Show full text]
  • Dimethyl Carbonate: a Modern Green Reagent and Solvent
    Russian Chemical Reviews 79 (6) 479 ± 489 (2010) # 2010 Russian Academy of Sciences and Turpion Ltd DOI 10.1070/RC2010v079n06ABEH004113 Dimethyl carbonate: a modern green reagent and solvent F AricoÁ , P Tundo Contents I. Introduction 479 II. Production of dimethyl carbonate 479 III. Reactivity of dimethyl carbonate 480 IV. Conclusions 487 Abstract. The published data on dimethyl carbonate as a other carboxylating or alkylating agents (phosgene and non-toxic reagent and solvent in organic synthesis are methyl halides, respectively). Dimethyl carbonate does not generalized and discussed. The methods for dimethyl produce inorganic salts. In fact, the leaving group, methyl carbonate production and its use as a methylating and carbonate, decomposes giving only methanol and CO2 as methoxycarbonylating agent are considered. Special atten- by-products. Dimethyl carbonate is classified as a flam- tion is paid to the eco-friendly processes that meet the mable liquid, smells like methanol and does not have `Green chemistry' requirements. The bibliography includes irritating or mutagenic effects by either contact or inhala- 104 references.references. tion. Therefore, it can be handled safely without the special precautions required for the poisonous and mutagenic I. Introduction methyl halides and DMS, and extremely toxic phosgene. Besides, DMC is widely studied also for its many potential Green chemistry, as one of the primary methods of pollu- applications.6, 7 In fact, recent research indicate DMC as an tion prevention, is a fairly recent phenomenon. `Green' oxygenated fuel additive of gasoline or diesel oil to replace organic syntheses must include some of the following tert-butyl methyl ether.8 Dimethyl carbonate can reduce the requirements: avoid waste, be atom efficient, avoid the use surface tension of diesel boiling range fuels leading to an and production of toxic and dangerous chemicals, avoid improved (diesel) fuel with better deinjection delivery and auxiliary substances (e.g., solvents), use renewable materi- spray.
    [Show full text]
  • Some Nitrobenzenes and Other Industrial Chemicals (IARC
    SOME NITROBENZENES AND OTHER INDUSTRIAL CHEMICALS SOME NITROBENZENES AND OTHER INDUSTRIAL CHEMICALS SOME NITROBENZENES AND OTHER INDUSTRIAL CHEMICALS VOLUME 123 IARC MONOGRAPHS ON THE EVALUATION OF CARCINOGENIC RISKS TO HUMANS SOME NITROBENZENES AND OTHER INDUSTRIAL CHEMICALS VOLUME 123 This publication represents the views and expert opinions of an IARC Working Group on the Evaluation of Carcinogenic Risks to Humans, which met in Lyon, 9–16 October 2018 LYON, FRANCE - 2020 IARC MONOGRAPHS ON THE EVALUATION OF CARCINOGENIC RISKS TO HUMANS IARC MONOGRAPHS In 1969, the International Agency for Research on Cancer (IARC) initiated a programme on the evaluation of the carcinogenic risk of chemicals to humans involving the production of critically evaluated monographs on individual chemicals. The programme was subsequently expanded to include evaluations of carcinogenic risks associated with exposures to complex mixtures, lifestyle factors and biological and physical agents, as well as those in specific occupations. The objective of the programme is to elaborate and publish in the form of monographs critical reviews of data on carcinogenicity for agents to which humans are known to be exposed and on specific exposure situations; to evaluate these data in terms of human risk with the help of international working groups of experts in carcinogenesis and related fields; and to indicate where additional research efforts are needed. The lists of IARC evaluations are regularly updated and are available on the Internet athttp:// monographs.iarc.fr/.
    [Show full text]
  • ||||III USOO5534649A United States Patent (19) 11 Patent Number: 5,534,649 Cho Et Al
    ||||III USOO5534649A United States Patent (19) 11 Patent Number: 5,534,649 Cho et al. 45 Date of Patent: Jul. 9, 1996 (54) PROCESS FOR PREPARING DIALKYL 59-3463 1/1984 Japan. CARBONATES 2212456 8/1990 Japan. 4270249 9/1992 Japan. 75 Inventors: Tsurahide Cho, Tokyo; Takaaki Tamura, Kawasaki, Toshitsura Cho, OTHER PUBLICATIONS ty Kazumi Suzuki, Kawasaki, all English Language Abstract of Japanese Patent No. p 4-270249 (A)(1992). 73) Assignees: Tama Chemicals Co., Ltd., Tokyo, English Language Abstract of Japanese Patent No. 59-3463 Japan; Moses Lake Industries, Inc., (1984). Moses Lake, Wash. English Language Abstract of Japanese Patent No. 54-41820 (1979). 21 Appl. No.: 365,846 English Language Abstract of Japanese Patent No. 22 Filed: Dec. 29, 1994 2-212456 (A)(1990). 30 Foreign Application Priority Data Primary Examiner-Johann Richter Assistant Examiner-Michael G. Ambrose Oct. 21, 1994 (JP) Japan .................................... 6-2571.75 Attorney, Agent, or Firm-Birch, Stewart, Kolasch & Birch (51) Int. Cl. ..................... CO7C 68/OO (52) U.S. Cl. .............................................................. 558/277 57 ABSTRACT (58) Field of Search ............................................... 558/277 This invention relates to a process for preparing dialkyl 56) References Cited carbonates by the reaction of one kind or a mixture of two or more kinds selected from urea, methyl carbamate and U.S. PATENT DOCUMENTS ethyl carbamate with methanol and/or ethanol in the pres 2,834,799 5/1958 Sowa ....................................... is ence of a catalyst under pressure at 100° to 250° C. and the 4,327,035 4/1982 Heitz et al. ............................. 558/277 process does not use poisonous phosgene or carbon mon 4,331,610 , 5/1982 Heitz et al.
    [Show full text]