Monsanto (BP) Acetic Acid & Related Processes (original) (raw)
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A stable, novel catalyst improves hydrogen production in a membrane reactor
Applied Catalysis A: General, 2005
The membrane reactors employed for the dry reforming reaction were based on different membrane types. This reaction taken as a source of H 2 , was performed in the present work using a wellknown catalyst, Rh/La 2 O 3 , together with a novel one, Rh/La 2 O 3 -SiO 2 , in a hydrogen-permeable membrane reactor. The catalysts were characterized by DRX, TPR, FTIR, LRS, H 2 and CO chemisorption. The effect of the operation variables upon the performance of the membrane reactor was also studied. The novel Rh(0.6%)/La 2 O 3 (27%)-SiO 2 catalyst proved to be the best formulation. Operating at 823 K, both methane and CO 2 conversions were 40% higher than the equilibrium values, producing 0.5 mol H 2 /mol CH 4 . This catalyst, tested at W/F three times lower than the Rh(0.6%)/La 2 O 3 , showed a similar performance. In all cases, the activity of the Rh catalysts remained constant after 100 hours on stream at 823 K. The presence of tiny amounts of graphite only detectable through LRS did not endanger membrane stability. The incorporation of the promoter (La 2 O 3 ) to the silica support induced a parallel increase in the metal dispersion (CO adsorption). The concentration of surface Rh atoms slightly increased with lanthanum addition. The better performance of Rh(0.6%)/La 2 O 3 (27%)-SiO 2 was related to the high dispersion and reaction rate of this formulation.
Hydrogen production in membrane reactors using Rh catalysts on binary supports
Catalysis Today, 2008
The binary supports employed in this work were prepared by different methods. The Ti(7%)-MgO and the Ti(13%)-SiO 2 were obtained using the grafting technique. The La(27%)-SiO 2 was obtained through the incipient wetness impregnation with La(NO 3) 3 of Aerosil 300, previously calcined at 1173 K. The Rh was incorporated to these supports by wet impregnation. The catalysts were first evaluated for the CH 4 + CO 2 reaction in a fixed-bed reactor. They were found to be active and stable as to justify their use in the membrane reactor, which was operated at 823 K achieving methane conversions up to twice as much as the equilibrium values. In all cases, the activity of the Rh solids remained constant after 120 h on stream with very little formation of carbonaceous residues only detected through LRS. The catalysts were characterized through either hydrogen or carbon monoxide chemisorption, TPR, XRD, LRS and XPS. The Rh(0.6)/La-SiO 2 catalyst showed a high metal dispersion that remained constant after use and the highest capacity to restore the CH 4 + CO 2 equilibrium when H 2 was permeated out of the reaction section. The Rh(0.8)/Ti-MgO showed the highest Rh/oxide interaction associated with the lowest capacity to restore the reaction equilibrium. The Rh(0.8)/Ti-SiO 2 exhibited an intermediate activity due in part to the partial segregation of the TiO 2 upon calcinations and the subsequent appearance of small Rh8 crystallites in the used catalysts.
Studies in Surface Science and Catalysis, 2010
It was demonstrated, that the main positive role of citric acid during the hydrotreating catalysts preparation is consist in the formation of bimetallic complex Co 2 [Mo 4 (C 6 H 5 O 7 ) 2 O 11 ]•nH 2 O, that is a good precursor for selective formation of catalyst active phase, so called Co-Mo-S phase type II. The preparation method for this bimetallic complex using different precursor is described. The catalysts prepared by the complex deposition onto alumina support were studied during the different stages of the catalyst genesis. Applicability of these catalysts for ultra low sulfur diesel production was shown.
Ceria-Based Solid Catalysts for Organic Chemistry
Daniel Duprez obtained his Ph.D. from Nancy Polytechnicum (France). After a two-year stay at the Elf Research Center at Solaize (near Lyon, France), he joined the Laboratoire de Catalyse en Chimie Organique de Poitiers (France) in 1978. He developed several projects on the use of isotopic exchange for measuring oxygen and hydrogen mobilities on supported metal catalysts, with applications in H 2 production from biomass resources, H 2 purification, oxidation, and DeNOx reactions and water purification processes (CWAO). Rareearth oxides are frequently used in these catalytic applications, either alone or as "active" supports of metals. Scheme 1. Transformation of 4-methyl-2-pentanol on ceria-based catalysts. Scheme 2. Dehydration of 1,3-diols into allylic alcohols. 656 www.chemsuschem.org Scheme 3. Transformation of 1,4-butanediol over pure CeO 2. Scheme 24. Biginelli-type reaction. Scheme 25. Homocoupling reaction of phenylboronic acid. Scheme 22. Synthesis of benzimidazole. Scheme 23. Mannich-type reaction.
The carbon pathways in the dry reforming of methane with carbon dioxide (DRM) towards syngas at 750°C have been investigated for the first time over 5 wt% Ni supported on Ti 4+-doped ceria using various transient and isotopic experiments. The obtained results revealed important information about the effect of Ce 1-x Ti x O 2-δ support chemical composition (x = 0, 0.2 and 0.5) on the transient rates of "carbon" deposition via CH 4 /He (methane decomposition) and CO/He (Boudouard reaction), and on the rate of "carbon" removal via the participation of labile active oxygen of support under DRM reaction conditions. The alternative path of CO 2 activation on the oxygen vacant sites of support was also probed by transient isothermal reduction (use of hydrogen) at 750°C followed by transient CO 2 /He reaction. Quantification of the amount (mg C g −1 cat) of inactive "carbon" accumulated as a function of time on stream in DRM and support chemical composition as well as of the origin of it (CH 4 vs CO 2 activation route), was made after conducting temperature-programmed oxidation (TPO) experiments coupled with the use of 13 CO 2. It was illustrated that 5 wt% Ni (d Ni ∼ 20 nm) supported on Ce 0.8 Ti 0.2 O 2-δ solid solution improves the H 2-yield and H 2 /CO product gas ratio compared to 5 wt% Ni/CeO 2 of similar Ni mean particle size but remarkably caused a drastic reduction in the rate of "carbon" deposition. After 12 h of DRM (20% CH 4 , CH 4 /CO 2 = 1), Ni/Ce 0.8 Ti 0.2 O 2-δ accumulates ∼ 270 times less "carbon" the origin of which was the CH 4 activation and not the CO disproportionation route. The 5 wt% Ni/Ce 0.8 Ti 0.2 O 2 catalyst developed presented high CH 4 and CO 2 conversions (75% and 82%), a H 2-yiled of 64% and an H 2 /CO product gas ratio of 1.3 after 100 h of DRM at 750°C (40%CH 4 /40%CO 2 /He; GHSV = 30,000 h −1) with a relatively low amount (73 mg "C" g cat −1 or 7.3 wt%) of inactive "carbon", which is considered to the best of our knowledge, as one of the lowest values reported in the literature for monometallic Ni supported catalysts under the examined DRM reaction conditions. [13-15], with the former route to also provide active "carbon" towards CO gas product formation, while the latter route provides inactive "carbon" [16,17]. It is also to be noted that the carbon formed by
Investigation of the oxygen storage process on ceria- and ceria�zirconia-supported catalysts
Catalysis Today, 2002
A total of 10 noble metal (Rh, Pt, Pd, Ru and Ir) catalysts, either supported on CeO 2 or Ce 0.63 Zr 0.37 O 2 , were prepared. Catalysts were fully characterized using XRD, N 2 adsorption at −196 • C, TEM and H 2 chemisorption. Oxygen storage processes were carefully investigated. The influence of temperature was checked and a key role of oxygen diffusion was further demonstrated. A review of the reactions involved in the CO transient oxidation reaction is finally proposed. (C. Descorme).
Applied Catalysis B: Environmental
The effects of Ce 1-x Pr x O 2-␦ support composition (x = 0.0-0.8) and reaction temperature (550-750 • C) on the catalytic activity and selectivity and important features of the mechanism of the dry reforming of methane (DRM) over supported Ni (5 wt%) were investigated. Of particular interest were the effects on the concentration of active and inactive carbon formed, the relative contribution of CH 4 and CO 2 activation routes towards carbon formation and the structure and morphology of the inactive carbon which was formed. For these carbon characterization studies, steady-state isotopic transient kinetic analysis (13 CO 2-SSITKA), temperature-programmed oxidation (TPO) following 13 CO 2 / 12 CH 4 /He dry reforming, thermal gravimetric analysis coupled with TPO (TGA-TPO), scanning electron miscroscopy (SEM-EDX) and transmission electron microscopy with atomic resolution (HRTEM) and powder X-ray diffraction (XRD) were employed. The relative amount of inactive carbon formed via the CH 4 and CO 2 activation routes was found to strongly depend on reaction temperature and Pr-dopant support composition. At 550 • C, the contribution of the CO 2 activation route to the inactive carbon formation (besides that of the CH 4 activation route) was 65.7 and 60.1%, respectively, for Ni supported on CeO 2 and Ce 0.2 Pr 0.8 O 2 carriers, whereas at 750 • C the respective values were 54.0 and 50.9%. Filamentous carbon and thin layers of graphitic carbon were identified as the main morphologies of inactive carbon. The surface coverage of active carbon that truly participates in the formation of CO was found to depend on support composition and reaction temperature (Â C = 0.03-0.15 at 550 • C and 0.07-3.4 at 750 • C). A pool of inactive reversibly adsorbed CO 2 was measured (Â = 1.5-4.1) for the first time, which was dependent on support composition and reaction T. The introduction of 20 atom-% Pr in the ceria lattice caused a significant reduction in the rate of inactive carbon formation with marginal decrease in catalyst's activity and stability after 25 h on stream. Further introduction of Pr-dopant (80 atom-%) caused drastic reduction in the deposited carbon after 25 h on the reaction stream at 750 • C (0.07 wt% C) but with appreciable decrease in CH 4-and CO 2-conversions and H 2 /CO gas-product ratio (a drop by a factor of 1.85, 1.45 and 1.47, respectively). The latter decrease in catalyst's performance is correlated with the increase in the pool of inactive adsorbed CO 2 in the form of carbonate-like species.
Exchange and oxidation of C16O on 18O-predosed Rh-Al2O3 and Rh-CeO2 catalysts
Catalysis Today, 1996
Exchange and oxidation of C 160 were investigated at 450°C on 180-predosed Rh and Pt catalysts supported on A1203, CeO 2 and CeO2-AI203. In all cases, a rapid exchange of CI60 with the surface can be observed. CO oxidation leads to C 160 2, C 260180 and C 180 2. Significant formation of C 16Oi.28 is due to the relatively high 260 coverage in reaction resulting from the C160 exchange and from an exchange between O surface species and 260 internal atoms. Hydrogen is also formed via a water-gas shift reaction (CO + surface OH) in higher proportion on CeO2-containing catalysts than on A1203. Chlorine inhibits all the reactions (exchange, oxidation and WGS) and particularly the internal exchange.
Industrial & Engineering Chemistry Research, 1987
exp(-25943/RT) s-l. The high apparent activation energies common in chemical reactions confirm the assumption of a kinetic regime in this gas-liquid reaction under our experimental conditions. The complete solubility of the reagents and products in the solvent was assured. The high yield and selectivity for this reaction, e.g., 98% at 158 OC, make its application possible for industrial use. The low solubility of reagents and products is nevertheless a problem that must be treated. Solubility data in this system and with other solvents as well as kinetic data in the presence of the solid phase must be obtained. Mechanism Approximation Several authon have suggested mechanisms for this type of oxidation; in every case they look complex and not strictly decided. Koshitani et al. (1982) gave a mechanism through anthrone formation that resulted in impure product. No intermediate acetal is obtained in this system (acetic acid solvent), so it cannot be extrapolated to our experiments. Brossard et al. (1977) obtained the acetal with possible evolution, but no detailed steps for the reaction were given. Rindone and Scolastico (1971) in reactions with cerium catalyst suggested the existence of a carbonium ion that could be easily attacked by the solvent. Thus, from these contributions and on the basis of the kinetic results obtained, for the dependence of reagents and catalyst, we propose a possible mechanism (Scheme 1). Mechanism. This is based on two steps (reactions 1 and 2) to form 9-anthryl radical by Cu2+ catalyst attack (Wilk et al., 1966; Andrulis et al., 1966), as has been shown in some of these types of reactions. Then by typical propagation reactions 3-7 (Koshitani et al., 1982; Lyons, 1977), a 9-anthronyl radical is produced, where Cu(I), Cu(II), and AN are involved. Step 5' might be viewed as a resonance hybrid. On the basis of other works (Gill, 1970), we thought that 9-anthronyl radical might react with Cu(II) to give an 9-anthronyl cation (eq 8). This compound could react with the solvent (eq 9) to obtain the intermediate product I. The solvent has then an important role in the mechanism, as it is obtained. Finally the intermediate gives rise to anthraquinone by means of a hydrolysis equation. This mechanism can be used according to a mechanistic approach and the steady-state principle, for the intermediate production rate, considering reaction 10 as irreversible, This equation agrees with experimental data; there is no dependence on O2 concentration, first order on Cu2+ and AN in the first reaction, but zero order in the second reaction. Registry No. I, 64420-66-2; C a r 2 , 7789-45-9; HO(CH2)20H,