HAL Id: cea-02339603
Submitted on 30 Oct 2019
HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.
Besides its utilization as a preservative and antibacterial agent in the agriculture industry, formicacid (FA) is at the crossroads of novel sustainable energy strategies. With a high energy density of 2104 Wh . L –1 , FA is indeed
investigated as a potential energy vector as a fuel in electrochemical fuel cells. Additionally, FA is an attractive hydrogen carrier because of its relatively high hydrogen content (4.4 wt%) and “hydrogen batteries” have been proposed, which rely on the reversible hydrogenation of CO 2 and dehydrogenation of formicacid, in basic
H NMR of the crude reaction mixture.
While MeOLi and MeONa were found inactive at 19 °C, these catalysts decompose MF toCOandmethanol at 30 °C and a longer reaction time was required in the presence of the lithium derivative (8 vs 3 h) (Entries 2, 3 and 5 in Table 1). The rubidium salt MeORb exhibited a catalytic activity close to MeOK (Entry 9 in Table 1). As alkali cations have been shown to influence the performances of catalytic systems by coordination to oxygen-rich substrates, the coordination sphere of the potassium cation in MeOK was modulated by the addition of exogenous chelating ligands. Addition of 5.0 mol% of the 18–C–6 crown ether or the 2,2,2-cryptand had no impact on the catalytic performances of MeOK, suggesting an innocent role of K + . The difference in
reduction of carbon dioxide (CO 2 ) into carbon-based fuels,
combining higher graviometric and volumetric energy densities.
This can be accomplished either directly through the generation of formicacid, methanoland higher hydrocarbons, or indirectly via the formation of carbon monoxide, which can be used as a feedstock chemical for the synthesis of alkanes through the Fischer-Tropsch process. Moreover, CO 2 reduction presents the
3 ) 3 Cl] [2.347 and 2.318(1) Å]; 76 the Cu−P bond length is also similar to those measured in 5 and 5’ .
Catalytic hydroboration of CO 2 with 3 , 3’ , 4, 4’, 5 and 5’
Having in hand a series of first row transition metal complexes, namely 3 , 3’ , 4, 4’, 5 and 5’ , their catalytic properties were explored in the field of CO 2 transformation. CO 2 conversion is currently dominated by non-redox processes that enable the functionalization of CO 2 to carbonates, carbamates and urethanes. 35,36, 77-7835, 79,80 Recent progresses have enabled the coupling of CO 2 and epoxides to either cyclic or polymeric carbonates, with a high regio- and stereoselectivity and using earth abundant metal catalysts. 81-86 These methods are progressively turning into efficient technologies and some of them are currently under pilot development. 80, 87 In contrast to functionalization strategies, the reduction of CO 2 offers an access to more energetic C 1 products such as formicacid, carbon monoxide or methanol, with carbon atoms at the +II and –II oxidation states. 36, 77-78,64a,68,88 So far, the electro-reduction of CO
generated by electroreduction of CO 2 and it is commonly employed to generate hydrides in transition
metal chemistry. 3,5 We have recently investigated the reductive properties of silylformates
(R 3 SiOCHO), readily formed from siloxanes andformicacid: using tailored organometallic
complexes, silylformates can act as surrogates of hydrosilanes and promote the reduction of carbonyl groups by transfer hydrosilylation. The utilization of silylformates and borylformates will be presented in the reductionand functionalization of C=O and O-H bonds from the perspective of catalysis, mechanisms and main group element synthetic chemistry. 4,6-8
turn, be utilized for the reduction of 4a. In contrast, conversion of 6 to the hemiaminal complex 14 (ESI†) requires an activation energy of 17.2 kcal mol 1 and it is irreversible, yielding the methylamine product 3a, with an overall energy balance of 30.4 kcal mol 1 . This mechanism is thus in agreement with the experimental results pointing to a convergent reduction of 4a via both transfer hydrogenation from HCOOH and hydro- genation. Importantly, this mechanism also shows that the disproportionation of HCOOH tomethanol is less favored than the reduction of 4a as it requires an activation energy of 20.8 kcal mol 1 for an exergonicity of 26.1 kcal mol 1 . Never- theless, methanol formation is unproductive in the methylation of 2a because the energy barrier required to regenerate 6 from formaldehyde exceeds 24.8 kcal mol 1 (Fig. S5, ESI†). Finally, it Table 2 Ruthenium-catalyzed methylation of substituted amines with
commodity chemicals such as formaldehyde, acetic acid or light olefins via the methanol-to-olefins (MTO) process. Nevertheless, the current methanol production methods is negatively impacted by the use of fossil resources. The production of CH 3 OH would therefore strongly benefit from the advent of more sustainable processes like the six-
electron reduction of CO 2 by hydrogenation, for example. An alternative strategy has recently emerged to generate
will be discussed and exemplified with novel catalytic processes to convert CO 2 to formamides, N-heterocycles, methylamines andmethanol,
using hydroboranes, hydrosilanes or formicacid as reductants. These new catalytic reactions rely on the use of simple organocatalysts or Zn, Fe and Ru organometallic complexes. The mechanisms at play in these transformations will be presented, based on DFT calculations and isolation of reactive catalytic intermediates. 1-9
give silyl formate 2b in 70 % isolated yield (92 % purity), after separation from the solid by-product Na 2 SO 4 and the dibutyl ether
solvent by distillation.
The two-step protocol depicted in Scheme 6a affords an efficient recycling procedure for the conversion of the siloxane by- product to the starting trimethylsilyl formate 2b. The net reaction balance involves the utilization of sodium formate and sulphuric acidto obtain methanoland sodium sulfate in 77 % yield in nonane (44 % isolated yield), while 77 % of the silicon compounds can be recycled (45 % isolated yield) (Scheme 6b). This methanol yield outperforms most of the state-of-the-art FA disproportionation protocols and compares well to the recent report of Himeda, Laurenczy et al., who obtained 75 % MeOH yield in D 2 O, using stoichiometric quantities of H 2 SO 4 .  The
The COware® two-chamber system consisting of a CO- producing chamber connected to a CO-consuming chamber, developed by the group of Skrydstrup et. al., seems to be fitting to our strategy.  In this technique, CO precursors such as 9- methylfluorene-9-carbonyl chloride or methyldiphenyl- silacarboxylic acid were used to produce CO, which was efficiently utilized in amino-, alkoxy-, and thio-carbonylation, carbonylative α-arylation, Suzuki−Miyaura, Heck, Sonogashira, and C−H activation. 
Using CO2 as a carbon source to synthesize useful chemicals is of great interest. 1,2 It is an abundant and inexpensive feedstock whose removal from industrial emissions is highly desirable to mitigate the greenhouse effect. One example of CO 2 conversion to a useful liquid hydrocarbon is hydrogenation of CO 2 toformicacid (HCOOH). Formicacid is an important chemical used in making animal feeds, in tanning and dyeing leather and textile, and as a food preservative. Currently, formicacid synthesis is mainly performed through a two-step process: (1) the carbonylation of methanolto methyl formate (HCOOCH3) using high-pressures of toxic CO as the feedstock, and (2) the hydrolysis of HCOOCH3 toformicacidandmethanol. Producing formicacid by direct hydrogenation of CO 2 is a promising alternate route in terms of economy, ecology, and safety. Thus a detailed microscopic understanding on the reaction mechanism for CO 2 hydrogenation is of great importance.
Over the last years, our group has developed novel catalytic reactions for the conversion of CO 2 to
formamides, N-heterocycles, methylamines andmethanol, using hydroboranes, hydrosilanes or formicacid as reductants. 2-9 In parallel, we have developed an unprecedented strategy to isolate
simple aromatics, in a pure form, from natural lignin in 15 different wood species. 9-10 These new
values for the Northern Hemisphere.
[ 34 ] We do suggest, however, that in light of the differ-
ences between background sites, and particularly the appar- ent seasonality of the differences between sites, care should be taken in selection of the appropriate background site for a particular experiment. Any remaining biases must be cor- rected for in the bias term b. Low-altitude coastal sites or midcontinent sites far from pollution sources could also be used as background. It is, however, difficult to identify sites of these types which are not influenced by local sources. Conditional sampling only when meteorological conditions indicate air from a clean air sector could alleviate this problem. When CO 2ff at multiple surface locations is being
In this work, we combine results of four different techniques to obtain complementary views on the HS sorptive fractionation on α-Al 2 O 3 carrying aluminol sites: UV-visible absorption (UV-Vis), total organic
carbon analysis (TOC), C(1s) near edge X-ray fine structure spectroscopy (NEXAFS) and time-resolved luminescence spectroscopy (TRLS). UV-visible absorption spectra of HS are supposed to give little structural information about the functionality due to the lack of detailed and characteristic bands (36). Its use for determining HS concentration remaining in solution after sorption is unreliable (20). However, a decomposition of UV-Vis spectra to monitor the properties of NOM has been proposed (37). Considering that HS contains ‘building block molecules’ that differ by their substituents (31, 32), one can see HS, in a first approximation, as a distribution of chromophores (38). TOC analysis is the most appropriate to determine accurately the concentration of humic substances (20). Specific UV-Vis Absorbance (SUVA=A 254 nm /TOC), is a useful approach for probing aromaticity of humic samples (39). Synchrotron-
Industries) capped with two 20 µm sintered stainless steel disks to prevent mechanical entrainment. The liquid CO 2 was pumped at 1 mL/min and 25 MPa using a high pressure
pump (PU-2080-CO 2 plus, Jasco, standard uncertainty on the CO 2 flow rate, ± 3.3·10 −5 cm 3 /s)
and circulated in a heat exchanger attached to a stove (FED 115, Binder) enclosing the whole device. The solubilized portion of the amidophosphonate compound was transported in the SC-CO 2 to a back-pressure regulator (Tescom, 26-1700 series), before being gathered
there have been few reports of the chemiresistive response of CNTs to carboxylic acids. Specifically, vertically aligned CNT arrays have a chemicapacitive response toformicacid. 28 Chemical-vapor-deposition-grown graphene becomes more conductive upon exposure to acetic acid vapor. 29 A single- CNT field effect transistor (FET) responds to propanoic acid vapors upon functionalization with guanine-rich single- stranded DNA. 30 However, these device architectures require greater manufacturing and operating complexity than chemiresistors based on solution-processed networks of CNTs. Networks of covalently-modified CNTs have been reported to increase in resistance, non-selectively, on expo- sure to acetic acid or other volatile organics via a swelling mechanism. 31,32 Studies on CNT-based vapor sensors discrim- inating between formicand other carboxylic acids are lack- ing.
Received: 16 February 2005 – Published in Atmos. Chem. Phys. Discuss.: 31 May 2005 Revised: 30 September 2005 – Accepted: 12 October 2005 – Published: 24 October 2005
Abstract. A novel atmospheric methanol measurement technique, employing selective gas-phase catalytic conver- sion of methanolto formaldehyde followed by detection of the formaldehyde product, has been developed and tested. The effects of temperature, gas flow rate, gas composi- tion, reactor-bed length, and reactor-bed composition on the methanol conversion efficiency of a molybdenum-rich, iron- molybdate catalyst [Mo-Fe-O] were studied. Best results were achieved using a 1:4 mixture (w/w) of the catalyst in quartz sand. Optimal methanolto formaldehyde conversion (>95% efficiency) occurred at a catalyst housing tempera- ture of 345 ◦ C and an estimated sample-air/catalyst contact time of <0.2 seconds. Potential interferences arising from conversion of methane and a number of common volatile organic compounds (VOC) to formaldehyde were found to be negligible under most atmospheric conditions and cata- lyst housing temperatures. Using the new technique, atmo- spheric measurements of methanol were made at the Univer- sity of Bremen campus from 1 to 15 July 2004. Methanol mixing ratios ranged from 1 to 5 ppb with distinct maxima at night. Formaldehyde mixing ratios, obtained in conjunction with methanol by periodically bypassing the catalytic con- verter, ranged from 0.2 to 1.6 ppb with maxima during mid- day. These results suggest that selective, catalytic methanolto formaldehyde conversion, coupled with existing formalde- hyde measurement instrumentation, is an inexpensive and ef- fective means for monitoring atmospheric methanol.
Brayton cycle working at temperature lower than 600 °C. It has been observed that, in industrial CO 2 grade, that is to say
containing an amount of impurity (O 2 + H 2 O) usually > 10 ppm, common 9-12Cr steel grades such as T91, T122 or VM12
suffer from fast growing oxide scale coupled to strong carburization whatever the working CO 2 pressure . A corrosion
mechanism explaining these coupled oxidation-carburization phenomena has been proposed [1-4]. Recent studies have shown, however, that these same common 9-12 Cr steel grades could form protective Cr rich oxide scale without any carburization of the substrate in research CO 2 grade containing, in that case, very low amount of impurity (usually < 10