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Generic models for the mean carbon number n̄, H/C ratio β and chain growth probability α, as a function of C5+ selectivity for Fischer–Tropsch reactions, have been developed based on gas analysis data and product mass. These models allow predicting the parameters when detailed compositions of oil and wax are unavailable. Meanwhile, the distribution of individual 2–5 methyl paraffins of iron and cobalt catalysts containing K, Zr and Pt promoters or poisoned by COS and HBr were studied. The chain-length-dependent formation of methyl paraffins was demonstrated on both iron and cobalt catalysts. The fraction of the methyl paraffins produced on an active iron catalyst (15–22%) was 5–7 times higher than that of a cobalt catalyst (1–3%). Ethylidene (CH2CH–M) was proposed as one possible iso-chain growth monomer, based on the higher fraction of 3-methyl product. The effects of the promoters and the poisons on the formation of iso-paraffins and 1-olefin were complicated. K (Fe), Zr and S (Co) improved the formation of 1-olefins and suppressed the formation of iso-paraffins, partly due to the electronic effect (back-donation) of the promoters. Pt inhibited the formation of both 1-olefins and iso-paraffins on a cobalt catalyst. Adding HBr was found to promote the formation of iso-paraffins on an iron catalyst.

Deuterium tracer studies coupled with kinetic approach were developed to accurately determine the kinetic isotopic effects (KIE) for the CO hydrogenation and the formations of CO2, CH4 and light hydrocarbons (C2-C4) over iron, cobalt and ruthenium catalysts. Pronounced inverse kinetic isotope effects (IKIE) (kco,H/kco,D = 0.64–0.66) over the Fe and Co catalysts and a moderate IKIE (kco,H/kco,D = ∼0.8) on the Ru catalysts for the CO hydrogenation were obtained under typical FTS conditions. The IKIE was also found in CH4 formation, but the Co and Ru catalysts showed stronger IKIE than the Fe catalysts (kCH4/kCD4 = 0.6 vs 0.87). Regardless of catalyst type, only a minor normal KIE for the CO2 formation was obtained (kCO2, H/kCO2, D ˜ 1.1). The IKIE was found on various light 1-olefins and n-paraffin hydrocarbons as well. All the IKIEs can be explained by thermodynamic and kinetic isotope effects. The results suggested that deuterium was involved in quasi-equilibrated and hydrogenation steps that determined KIE. However, the Fe, Co and Ru catalysts showed different deuterium isotopic effect for the hydrocarbon selectivity. Deuterium promoted chain growth, thus lowered CH4 and light hydrocarbons selectivities and enhanced C5+ selectivity on both the Fe and Co catalysts; while it enhanced the hydrogenation rate to the low hydrocarbons and suppressed the formation of heavier hydrocarbons on the Ru catalysts. Deuterium isotopic effect on the formation of 1-olefins, n-paraffins and 2-olefins in C10-C18 range (in liquid phase) was also studied in detail. Deuterium was found to enhance 1-olefins formation, but suppressed or only slightly changed n-paraffins formation over the Fe and Co catalysts. However, deuterium led to greater amount of n-paraffins and less 1-olefins on the Ru catalysts. The results suggested that the IKIE originated from different hybridization changes of carbon in C–H (sp1->sp2 and/or sp2->sp3) on the Fe, Co and Ru catalysts, which implied different reaction pathways on the Fe, Co and Ru catalysts.

SUMMARY: Like other poultry species, Pekin ducks may develop gait abnormalities due to increased muscle growth relative to the skeletal system. Previous studies have shown that Pekin leg bones grow exponentially in terms of mineral deposition during the first 2 wk of life. Therefore, we hypothesized that a slight food restriction (FR) during that time would reduce muscle mass development sufficiently to allow the skeletal system to more fully develop. Our primary goal was to determine if FR could occur without increasing the time to market weight. To obtain this goal, ducks were provided either 65% (FR65) or 85% (FR85) of the control ducks daily feed intake. Food restricted ducks had lower (P < 0.05) body weights than controls at days 7 and 14. After day 14, when all ducks were fed ad libitum (ad libitum), food restricted ducks ate significantly (P < 0.01) more feed per day than control ducks and subsequently gained body weight at an increased rate. By day 35 there were no significant differences in body weight between FR85 and controls, however both FR groups showed reduced (P < 0.05) breast mass compared to controls. Qualitative assessment of gait also suggested that FR ducks had more uniform leg conformation and gait then did the control ducks and did not show any biological signs of reduced welfare. These data suggest that a slight FR is possible without adding time to market and this paradigm might reduce the occurrence of lameness in growing ducks.

By some accounts, ducks were domesticated between 400 and 10,000 yr ago and have been a growing portion of the poultry industry for decades. Ducks specifically, and waterfowl in general, have unique health, housing, nutrition and welfare concerns compared to their galliform counterparts. Although there have been many research publications in regards to health, nutrition, behavior, and welfare of ducks there have been very few reviews to provide an overview of these numerous studies, and only one text has attempted to review all aspects of the duck industry, from breeders to meat ducks. This review covers incubation, hatching, housing, welfare, nutrition, and euthanasia and highlights the needs for additional research at all levels of duck production. The purpose of this review is to provide guidelines to raise and house ducks for research as specifically related to industry practices.

The effect of alkali promoter (K, Rb and Cs) on the performance of precipitated iron-based catalysts was investigated for carbon dioxide (CO2) hydrogenation. Characterization by temperature-programmed reduction with CO, Mossbauer spectroscopy, and transmission electron microscopy were used to study the effect of alkali promoter interactions on the carburization and phase transformation behavior of the catalysts. Under similar reaction conditions, cesium (Cs) and rubidium (Rb) promoted catalysts exhibited the highest initial CO2 conversions to higher hydrocarbons. CO2 conversions then decreased to reach steady state conversions around 170 h on stream. At steady state conversion, all three catalysts exhibited similar CO2 conversions and selectivities. For comparison, a lower loaded Cs (1.5 Cs) promoted iron-based catalyst was prepared. It exhibited slightly lower initial conversion than the higher loaded Cs catalyst, but remained very stable. Among all the catalysts at steady state conversion, the 1.5 Cs promoted catalyst exhibited the highest stability. Results indicate a synergistic effect brought on by these promoters that, if balanced, could potentially yield superior CO2 hydrogenation catalysts.

Iron carbide was prepared by the carburization of iron oxalate doped with various alkali metals in flowing CO at 400 °C. The addition of alkali metal (Li, Na, K, Rb or Cs) to iron oxalate was found to decrease the bulk iron carbides formation. However, the amount of carbon deposited on Fe as inferred from temperature programmed hydrogenation and high-resolution transmission electron microscopic studies show an increasing trend with the increase of the basicity of alkali added. The CO2 and H2 conversions of all alkali doped iron catalysts were initially higher but they declined over time irrespective of alkali. The benefits of addition of alkali to iron without any structural and reduction promoters, such as copper, is found to lower the selectivity for methane, higher olefins and oxygenates formation for CO2 hydrogenation.

The explanation for CH4 selectivity for iron based Fischer-Tropsch catalysts in the low conversion region (i.e.

As a follow-up to a previous alkali chloride poisoning study, the effect of up to 100 ppm KCl on the Fischer-Tropsch synthesis (FTS) performance of representative iron (Fe-Si-Cu doped with Rb as the alkali) and cobalt (Pt-Co/Al 2 O 3 ) catalysts was studied at 270 °C and 230 °C, respectively, by co-feeding KCl in a water/ethylene glycol (EG) solution. The used catalysts were characterized by XANES at the K and Cl K-edges; furthermore, ICP was used to analyze residual K and Cl ions possibly remaining in the FTS products. KCl was found to be a weak poison for the iron and cobalt catalysts. The addition of 20–100 ppm KCl deactivated the catalysts to only a low to moderate extent. For the cobalt catalyst, less than 25 ppm KCl was found to give negligible deactivation. The added KCl and EG-H 2 O solvent was found to slightly modify the selectivity for both catalysts, such that KCl slightly promoted light hydrocarbon formation as well as olefins and slightly suppressed C 5+ and 2-olefin formation, while the EG-H 2 O solvent was found to have a different effect on the C 1 C 4 and C 5+ selectivities. It appears that K and Cl played opposite roles in modifying hydrocarbon selectivities. The ICP results suggested 48–98% K and Cl ions were adsorbed by the iron catalyst. XANES results confirmed the presence of K and Cl ions on the used iron and cobalt catalysts and showed a structure with characteristics that were similar to bulk KCl. Two possible mechanisms, including site blocking by K and Cl ions and electronic modification impacting CO/H 2 adsorption, were proposed to explain the deactivating effect of KCl on the iron and cobalt catalysts.

The purpose of this investigation was to examine the effect of sulfur impurity on 1%Pt/KL-zeolite catalyst by co-feeding 500 ppbv hydrogen sulfide (H2S) during hexane aromatization under industrially relevant conditions using a plug flow reactor. Product selectivity and hexane conversion were measured with time-on-stream and compared to a clean run carried out under otherwise identical conditions. Sulfur addition to the feed accelerated the rate of deactivation as observed by rapid declines in both hexane conversion and benzene selectivity; hexene selectivity, the product of the less structurally sensitive dehydrogenation reaction, increased significantly. After 20 h, which was enough time to observe sufficient deactivation, the reaction was stopped. For the purpose of catalyst characterization, after cooling to 150 °C, the catalyst was preserved in Polywax 725 to prevent catalyst oxidation. XANES analysis at the potassium K-edge suggests that the local environment for potassium was not significantly altered by sulfur addition, while sulfur K-edge results indicate that sulfur bound to platinum to form platinum sulfide (PtS, not PtS2). Platinum sulfide is likely responsible for accelerating Pt growth, as observed in DRIFTS of adsorbed CO and HR-TEM/STEM micrographs.

Ga- and In-modified ceria (Ce 0.8 Ga 0.2 O 2 , Ce 0.8 In 0.2 O 2 ) materials were used as supports for cobalt-catalyzed Fischer-Tropsch synthesis (FTS). The addition of Ga to ceria was found to improve CO conversion for cobalt-catalyzed FTS, while the addition of In tended to decrease it. A similar trend was observed with the Ag-promoted cobalt/ceria catalysts. Doping of ceria with Ga or In decreased methane and increased the selectivity to olefins and alcohols for Ag-promoted cobalt/ceria. The sum of the products of olefins and alcohols for various catalysts exhibited a decreasing trend as follows: Ag-Co/Ce-Ga > Ag-Co/Ce-In > Ag-Co/Ce. Results of H 2 -TPR-XANES showed that adding of Ga or In to ceria increases the fraction of Ce 3+ in the surface shell for both unpromoted and Ag-promoted catalysts in the range of temperature typical of catalyst activation. This partially reduced ceria plays an important role in controlling the product selectivity of cobalt-catalyzed FT synthesis.

In previous work, Na-doping of Pt/YSZ was found to facilitate the low temperature water gas shift reaction (LT-WGS), and the promoting effect was ascribed to an electronic weakening of the C H bond of the formate species, a proposed intermediate in the catalytic cycle. Formate has also been implicated as an intermediate in steam-assisted formic acid decomposition (SAFAD) and methanol steam reforming (MSR) pathways. In the current contribution, Na-doping was also found to significantly accelerate the SAFAD reaction. The high activity of Pt/YSZ for SAFAD, as well as the promoting effect of Na, are in stark contrast to the view that formates are too stable, precluding them as intermediates for LT-WGS. With MSR, a remarkable promoting effect of Na doping was observed in the selectivity to CO 2 (>90% for Na-doped relative to 22% for undoped at 300 °C); however, at the doping levels used in the current work, the activity was lower for the Na doped catalyst and further optimization is needed to improve MSR conversion.

XANES K-edge spectra of potassium promoter in precipitated Fe catalysts were acquired following activation by carburization in CO and as a function of time on-stream during the course of a Fischer–Tropsch synthesis run for a 100Fe:2K catalyst by withdrawing catalysts, sealed in wax product, for analysis. CO-activated and end-of-run spectra of the catalyst were also obtained for a 100Fe:5K catalyst. Peaks representing electronic transitions and multiple scattering were observed and resembled reference spectra for potassium carbonate or potassium formate. The shift in the multiple scattering peak to higher energy was consistent with sintering of potassium promoter during the course of the reaction test. The catalyst, however, retained its carbidic state, as demonstrated by XANES and EXAFS spectra at the iron K-edge, suggesting that sintering of potassium did not adversely affect the carburization rate, which is important for preventing iron carbides from oxidizing. The method serves a starting point for developing better understanding of the chemical state and changes in structure occurring with alkali promoter.

The influences of nitric acid treatment on a carbon nanotube (CNT) support and the preparation method, incipient wetness impregnation (IWI) versus chemical vapor deposition (CVD), on catalytic performance during Fischer–Tropsch (FT) synthesis were examined using a slurry phase reactor. Acid treated CNT (ACNT) supported Ru catalysts exhibited higher activities compared to Ru supported on untreated CNTs (UCNTs). The acid-treated CVD catalyst had higher initial CO conversion (smaller average Ru particle size) but sintered more due to a greater tendency for Ru to be deposited exterior to CNT channels relative to IWI. After the initial decline and leveling off period, the ACNT IWI catalyst had the highest steady activity among the catalysts tested. The ACNT IWI catalyst also displayed greater oxygenate selectivity (∼17%) compared to ACNT CVD (∼12%) and UCNT IWI (∼10%) catalysts at similar conversions. Acid treatment created adsorption sites on the CNT surface that anchor Ru precursors and promote CO insertion ...

Conversion of bio-oil from flash pyrolysis of biomass is a way to produce useful renewable feedstocks for the chemicals industry. Dehydration of pentanediol (1,5- and 2,4-pentanediol) was investigated over CeO2, CeO2-Ga2O3, and CeO2-In2O3 catalysts at 250–350 °C. Adding Ga or In (20 mol%) improved the conversion of pentanediol over CeO2, but adversely affected selectivity. In the base case, 1,5-pentanediol was converted on CeO2 to 4-penten-1-ol and 1-pentanol, desired linear alcohols, together with unwanted cyclopentanol and cyclopentanone byproducts. Adding gallium or indium to ceria increased the selectivity towards undesired cyclized products like tetrahydropyran and tetrahydropyran-2-one due to increased acidity. In the base case, 2,4-pentanediol converted on CeO2 to unsaturated alcohol (e. g., 3-penten-2-ol > 74 % selectivity), but adding Ga or In promoted acid-catalyzed cracking. Tuning the acid-base characteristics of ceria significantly alters the product distribution.

The effect of cobalt substitution with nickel was investigated for the Fischer&ndash, Tropsch synthesis reaction. Catalysts having different Ni/Co ratios were prepared by aqueous incipient wetness co-impregnation, characterized, and tested using a continuously stirred tank reactor (CSTR) for more than 200 h. The addition of nickel did not significantly modify the morphological properties measured. XRD, STEM, and TPR-XANES results showed intimate contact between nickel and cobalt, strongly suggesting the formation of a Co-Ni solid oxide solution in each case. Moreover, TPR-XANES indicated that nickel addition improves the cobalt reducibility. This may be due to H2 dissociation and spillover, but is more likely the results of a chemical effect of intimate contact between Co and Ni resulting in Co-Ni alloying after activation. FTS testing revealed a lower initial activity when nickel was added. However, CO conversion continuously increased with time on-stream until a steady-state value (34%&ndash, 37% depending on Ni/Co ratio) was achieved, which was very close to the value observed for undoped Co/Al2O3. This trend suggests nickel can stabilize cobalt nanoparticles even at a lower weight percentage of Co. Currently, the cobalt price is 2.13 times the price of nickel. Thus, comparing the activity/price, the catalyst with a Ni/Co ratio of 25/75 has better performance than the unpromoted catalyst. Finally, nickel-promoted catalysts exhibited slightly higher initial selectivity for light hydrocarbons, but this difference typically diminished with time on-stream, once leveling off in conversion was achieved, the C5+ selectivities were similar (&asymp, 80%) for Ni/Co ratios up to 10/90, and only slightly lower (&asymp, 77%) at Ni/Co of 25/75.

Cobalt and iron have long history of importance in the field of catalysis that continues to this day [...]

Nearly a century ago, Fischer and Tropsch discovered a means of synthesizing organic compounds ranging from C1 to C70 by reacting carbon monoxide and hydrogen on a catalyst. Fischer&ndash, Tropsch synthesis (FTS) is now known as a pseudo-polymerization process taking a mixture of CO as H2 (also known as syngas) to produce a vast array of hydrocarbons, along with various small amounts of oxygenated materials. Despite the decades spent studying this process, it is still considered a black-box reaction with a mechanism that is still under debate. This investigation sought to improve our understanding by taking data from a series of experimental Fischer&ndash, Tropsch synthesis runs to build a computational model. The experimental runs were completed in an isothermal continuous stirred-tank reactor, allowing for comparison across a series of completed catalyst tests. Similar catalytic recipes were chosen so that conditional comparisons of pressure, temperature, SV, and CO/H2 could be made. Further, results from the output of the reactor that included the deviations in product selectivity, especially that of methane and CO2, were considered. Cobalt was chosen for these exams for its industrial relevance and respectfully clean process as it does not intrinsically undergo the water&ndash, gas shift (WGS). The primary focus of this manuscript was to compare runs using cobalt-based catalysts that varied in two oxide catalyst supports. The results were obtained by creating two differential equations, one for H2 and one for CO, in terms of products or groups of products. These were analyzed using sensitivity analysis (SA) to determine the products or groups that impact the model the most. The results revealed a significant difference in sensitivity between the two catalyst&ndash, support combinations. When the model equations for H2 and CO were split, the results indicated that the CO equation was significantly more sensitive to CO2 production than the H2 equation.

In a previous study, we demonstrated that a 15% feed restriction (FR) during the first 2 wk after hatch could improve gait in Pekin meat ducks, but did result in reduced breast mass. We hypothesized that feed restriction after day 5 following muscle satellite cell development would allow the full growth of the breast meat. To accomplish this goal, 300 1-day-old ducklings (Maple Leaf Farms Inc.) were randomly allocated to 1 of the 3 groups (n = 4 pens, 25 ducks per pen): (1) Control group fed to ad libitum; (2) 85% daily feed intake from days 1 to 14 (FR 85% 1–14); 85% daily feed intake from days 5 to 14 (FR 85% 5–14). All ducks were vaccinated with inactivated Salmonella enteritidis on day 14 and boosted on day 26. The FR 85% 5–14 did show similar production standards to controls, and improved gait characteristics (P < 0.05). To determine if the partial feed restriction would have an impact on intestinal epithelial tight junction integrity, we treated ducks on days 7, 14, 21, 28, and 35 with 8.32 mg/kg FITC-d in water per os and blood samples were obtained via the tibial vein 1 h later. Serum samples were analyzed for presence and quantification of FITC-d. Feed restriction elicited a significant increase in FITC-d permeability at all points of evaluation. Anti-S. enteritidis specific IgY responses were assessed by ELISA from serum collected at 14 D, 28 D, and 35 D. Although all ducks showed an increase humoral immune response to the S. enteritidis, both feed restricted groups showed reduced IgY production compared to ad lib controls. Our data suggest that although the FR 5–14 feed restriction paradigm may reduce gait abnormalities without affecting production rates, some challenges exist due to increased gut leakiness or decreased acquired immune activity. Future studies will look at altering the feed restriction milieu to ameliorate these challenges.

Many factors affect the comfort of automotive seats including pressure distribution, vibration, temperature, and backrest inclination. However, one aspect of seating that has not been well studied is leg splay; splay is a rotation at the hips which causes the knees to move outward. The work presented here identified the ranges of "comfortable" splay in different styles of seats and related changes in seating pressure due to leg splay. Sixteen midsized male participants were tested in six seats: a flat control, three mid-sized sedan, a sports car, and a pickup truck. Participants sat with two leg conditions: 1) shoulder width apart and 2) rotating their legs to splay to a self-identified, comfortable position. For each test, the participant placed his left leg on a foot support and right leg on a depressible pedal to mimic a driving position. In each posture, leg angle and seat pan pressures were collected. Of the seats tested, the flat wooden seat had the highest possible splay (24.5°). The three sedan seats had similar splay angles (16.1-18.5°). The lowest splay values were in the sports car seat (8.96°) and truck seat (7.46°). This reduction in splay was attributed to the more aggressive bolsters in the sports car and a higher seat design position in the pickup truck seat. Following participant splay the pressures in the seat bolsters increased while the pressure in the left thigh and left buttocks regions decreased. By determining the comfortable ranges of splay and how pressure distribution is affected, seat designers and automobile manufacturers can use these data when evaluating seat designs and occupant positioning.

The hydrogenation of carbon dioxide over K-promoted FeCo bimetallic catalysts prepared by sequential oxalate decomposition and carburization of FeCo with CO was studied in a fixed-bed reactor at 240 °C and 1.2 MPa. The initial CO2 conversion was found to be dependent on K loading, whereas both unpromoted and K-promoted FeCo catalysts (except 90Fe10Co3.0K) exhibited similar levels of CO2 conversion after a few hours of time on stream. A decarburization study on freshly activated and used FeCo suggests that potassium increases the stability of iron carbides and graphitic carbon under a reducing atmosphere. Also, K addition tends to decrease the hydrogenation function of FeCo bimetallic catalysts and, thus, controls product selectivity. Under similar CO2 conversions, potassium enhanced acetic acid formation while suppressing ethanol production, which indicates that a common intermediate might be responsible for the changes observed with C2 oxygenates.

Vapor-phase catalytic dehydration of 2-octanol was investigated over CeO2-CaO mixed oxides at 300°C and atmospheric pressure. Ca doping to a molar composition of 75Ce25Ca increased the activity for 2-octanol dehydration, while further increases in Ca content detrimentally affected conversion. Catalyst surface area and pore volume increased with increasing Ca content in CeO2-CaO mixed oxides. Hydrogen TPR profiles indicate that the partially reduced state of surface ceria (i.e., Ce3+), which increases with increasing Ca loading, might play an important role in promoting activity. This is analogous to our earlier work [Appl. Catal. A: Gen. 394(2011) 105-116] on low temperature water-gas shift, where a promoting effect of Ca-doping was observed with ceria supported Pt catalysts. In that case, TPR, TPR-XANES, and DRIFTS measurements indicated that Ca enhanced both O-mobility and reducibility of ceria by weakening the Ce-O bond.

The effects of co-fed ammonia in synthesis gas on the activity and product selectivities of a typical cobalt catalyst (0.5% Pt–25% Co/Al2O3) were investigated during the Fischer–Tropsch synthesis using a continuously stirred tank reactor (CSTR). The product selectivities were compared at a similar CO conversion level for various concentrations (10–1000 ppmv) of ammonia, as well as clean (un-poisoned) conditions. The addition of 10–1000 ppmv ammonia (concentration of ammonia with respect to the syngas feed) significantly decreased activity; the percentage of deactivation was similar (∼40%) for the various concentrations of ammonia used. At similar CO conversions, the addition of ammonia caused an increase in olefin selectivity and the corresponding paraffin and alcohol selectivities were decreased compared to the ammonia free synthesis conditions. Olefin selectivity increased with increasing concentration of ammonia, and the paraffin and alcohol selectivities were decreased with increasing ammonia concentration. At similar CO conversions, ammonia addition exhibited a positive effect on hydrocarbon selectivity (i.e., lower light gas products and higher C5+) and also light gas product selectivities (C1–C4) were decreased and C5+ selectivity increased with increasing concentration of ammonia compared to ammonia free conditions.

Fischer-Tropsch synthesis was conducted in a small channel compact heat exchange reactor that was constructed of aluminum. While limited to lower temperature-pressure regions of the Fischer-Tropsch synthesis, the reactor could be operated in an isothermal mode with nearly a constant temperature along the length of the channel. The results obtained with the compact heat exchange reactor were similar to those obtained in the isothermal continuous stirred tank reactor, with respect to both activity and selectivity. Following a planned or unplanned shutdown, the reactor could be restarted to produce essentially the same catalytic activity and selectivity as before the shutdown.

The effect of phosphorus addition on silica-supported cobalt catalyst was investigated for Fischer-Tropsch synthesis (FTS). As shown by STEM images and chemisorption, the addition of phosphorus to cobalt of up to 1 wt% increased the dispersion of cobalt. Further addition of phosphorus (e.g., 3 and 5 wt.%), as demonstrated by TPR, pulse reoxidation, and XANES, significantly hindered the reduction of cobalt oxides. The cobalt FTS catalysts containing 0.5 and 1.0 wt% P exhibited greater stability in comparison with undoped and 3.0 wt% P containing cobalt catalysts. Analysis of XANES spectra at the P and Co K-edges, along with DRIFTS results of H 2 -activated cobalt catalysts, suggest that cobalt particles interact with PO 4 3− ions, indicating a role played by P in anchoring Co particles to the support, thus hindering the cobalt sintering rate. The initial selectivity to methane was slightly higher for 0.5%P-20%Co/SiO 2 and 1.0%P-20%Co/SiO 2 catalysts compared to the undoped catalyst, but at longer times differences were small. At higher loadings of P (3 wt.%), FT activity and selectivity were adversely and irreversibly affected.

The effect of co-fed hydrogen chloride (HCl) in syngas on the performance of iron and cobalt-based Fischer–Tropsch (FT) catalysts was investigated in our earlier studies (Ma et al. in ACS Catal 5:3124–3136, 2015; Davis et al., DOE final report, 2011; Gnanamani et al. in Catal Lett 144:1127–1133, 2014). For an iron catalyst, lower HCl concentrations (

The effect of solvent on the hydrogen-deuterium isotopic homomolecular exchange rate over a 26.4% Ni/Al2O3 catalyst was investigated using a plug flow reactor at room temperature (23 °C) and at atmospheric pressure. In this study, two different molecular weight solvents were tested: n-pentane ( M W ¯ (average molecular weight) = 72), and n-hexadecane ( M W ¯ = 226). At dry (without addition of solvent) and n-pentane solvent addition conditions, similar amounts of H2 and D2 are consumed and the concentration of the HD produced is two times the consumption of H2 or D2. Thus, these conditions exhibited around 100% exchange with the formation of H2:HD:D2 having a 1:2:1 ratio. With n-hexadecane solvent, the initial exchange rate was approximately 45%, but the exchange rate decreased with time and reached a steady state rate after 60 min on-stream. The lower exchange rate of the n-hexadecane solvent might be due to the limited mobility of reactant molecules in the liquid-filled pores of the catalyst. The exchange rate of the catalyst is decreased with increasing molecular weight and density of the solvent. An isotopic partitioning preference was not observed for the nickel catalyst under various co-fed solvents, and similar findings were observed in our previous work (Catalysis Letters 143 (2013) 1368–1373).

The effect of 1.0 ppm H2S in the syngas feed on initial activity and selectivity of a 0.5%Pt–25%Co/Al2O3 catalyst was studied by comparing the catalyst performance under H2S and sulfur free conditions. The reaction tests were performed using a 1-L slurry phase reactor for 141–212 h under constant reaction conditions: 220 °C, 2.0 MPa, H2/CO = 2.0 and 6.0 Nl/g-cat/h. In the H2S poisoning test, an H2S in N2 gas mixture was added to the syngas feed (1.0 ppm) after running the Fischer–Tropsch synthesis (FTS) reaction for ca. 6.0 h; as such, the impact of H2S on the initial deactivation of the cobalt catalyst (unsteady state) was successfully assessed. The used catalysts were characterized by XANES to investigate if Co–S surface species were formed during the deactivation. The initial deactivation under 1.0 ppm H2S condition was significantly higher (by 2.0–2.4 times) than that under clean conditions. CH4 selectivity increased substantially and C5+ selectivity decreased greatly with time regardless of whether H2S was added or not; however, the addition of H2S accelerated the changes in the hydrocarbon selectivities, which were likely caused by the sharp deactivation of the catalyst in the presence of H2S. After co-feeding the sulfur for 141 h, a comparison was made at similar conversions by adjusting space velocity; the sulfur pretreated cobalt catalysts favored heavier hydrocarbons (C5+) formation and suppressed lower hydrocarbon formation. The addition of H2S to the feed increased CO2 selectivity and the secondary reaction of 1-olefins. The XANES results revealed that surface species involving Co–S bonding formed on the cobalt catalyst after exposure to H2S during FTS. This was likely the primary reason for the abnormal selectivity trends observed during and after the deactivation of the catalyst by sulfur. This study points out a possible approach to increase the selectivity to heavy hydrocarbons by properly sulfiding the cobalt catalyst prior to the FTS reaction.

Sequential impregnation and calcination were used to fill the pores of a commercial alumina support with alumina. In this manner, two different pore-modified alumina supports were synthesized. To account for the diminished pore size, cobalt loadings were lowered as appropriate to ensure a similar cobalt size range (e.g., clusters 14–18 nm in diameter) and comparable extents of reduction. This was confirmed by measurements from TPR, hydrogen chemisorption/pulse reoxidation, and EXAFS/XANES spectroscopies. Catalysts were tested using a slurry phase CSTR reactor at commercially relevant FTS conditions. Selectivities were compared at both high and low levels of conversion for the catalyst series. Decreasing the pore length, as measured by PSD data, appears to lessen the adverse effect that the higher relative diffusional rate of hydrogen versus carbon monoxide has on the H2/CO surface fugacity ratio on the catalyst surface. That is, moving the cobalt particles closer to the pore mouth may prevent the H2/CO ratio from being augmented at the surface of cobalt particles due to diffusion or other factors, and inhibits excessive chain termination that would lead to higher light product selectivities. Pore filling thus results in a catalyst that is similar to an egg-shell catalyst. With increased pore filling by alumina, C1 C4 light gas selectivities decreased, in a systematic way, by as much as 33% (relative basis), and the C5+ selectivity improved by as much as 10.3% (relative basis) in comparison with the 22.4%Co/Al2O3 (IWI) reference catalyst. This greater effectiveness offers an opportunity for more environmentally benign chemical processing.

This review is divided into three main sections. The first section of this overview examines in detail recent techno-economic analyses on the utilization of biomass as a source of syngas for Fischer-Tropsch synthesis (FTS). FTS is a highly localized industry, and depends on the sources of syngas available, the products desired, and the demand for co- production of electricity. Where coal or natural gas coexist in the region where biomass is available, economics may favor producing or blending syngas from multiple resources, making biomass-to-liquids a highly complex scenario. Land use management is essential for sustainable biomass production, if used as the carbon source for FTS. The second section discusses FTS mechanisms, reactions and catalysts. Supposing the catalyst surface energy favors CO hydrogenation to FTS products, the sweet spot of FTS, selectivity will depend on the degree of back- donation from the metal. The degree of electron back-donation from the catalyst surface to both adsorbed CO and vinylic intermediates in part controls the FT synthesis product distribution. When the back-donation is sufficient, chain growth favors longer chained linear hydrocarbons (paraffins, alpha olefins, linear alcohols) suitable for upgrading to diesel, jet fuels, lubricants, and waxes. When back-donation is less significant, monomethyl branched hydrocarbons, internal olefins, and oxygenates (esters, acids and ketones) are elevated. Lastly, active supports are discussed for increasing the termination rate to oxygenates and olefins, as are hybrid catalysts that simultaneously carry out FTS and upgrading, often through secondary reactions. The last section provides an overview of the commercial scale reactor designs including the fixed bed, fluidized bed, and slurry bubble column reactor currently used in the FTS process. Economically, FTS is favored at larger scales; however, new compact reactor designs are coming into play aimed at monetizing highly localized (e.g. biomass) and stranded resources (e.g. natural gas). These types of reactors, involving microchannel and heat exchanger designs, must be highly efficient at managing heat, cost-effective, and mobile in order to exploit non-traditional sources of syngas.

The bulk of the products that were synthesized from Fischer&ndash, Tropsch synthesis (FTS) is a wide range (C1&ndash, C70+) of hydrocarbons, primarily straight-chained paraffins. Additional hydrocarbon products, which can also be a majority, are linear olefins, specifically: 1-olefin, trans-2-olefin, and cis-2-olefin. Minor hydrocarbon products can include isomerized hydrocarbons, predominantly methyl-branched paraffin, cyclic hydrocarbons mainly derived from high-temperature FTS and internal olefins. Combined, these products provide 80&ndash, 95% of the total products (excluding CO2) generated from syngas. A vast number of different oxygenated species, such as aldehydes, ketones, acids, and alcohols, are also embedded in this product range. These materials can be used to probe the FTS mechanism or to produce alternative chemicals. The purpose of this article is to compare the product selectivity over several FTS catalysts. Discussions center on typical product selectivity of commonly used catalysts, as well as some uncommon formulations that display selectivity anomalies. Reaction tests were conducted while using an isothermal continuously stirred tank reactor. Carbon mole percentages of CO that are converted to specific materials for Co, Fe, and Ru catalysts vary, but they depend on support type (especially with cobalt and ruthenium) and promoters (especially with iron). All three active metals produced linear alcohols as the major oxygenated product. In addition, only iron produced significant selectivities to acids, aldehydes, and ketones. Iron catalysts consistently produced the most isomerized products of the catalysts that were tested. Not only does product selectivity provide a fingerprint of the catalyst formulation, but it also points to a viable proposed mechanistic route.

Industrial catalyst processes, such as the Fischer-Tropsch (FT) process, produce a vast array of products from syngas (H2 /CO), such as jet fuel, gasoline, diesel, synthetic rubbers, monomers for plastics industries, and other oil/wax materials for specific purposes such as cosmetics. Multitudes of publications since the discovery of the FT process in 1925 have been composed, attempting to elucidate the mechanism. Many of these publications attempt to investigate the mechanism of FT by the utilization of specific deuterium experimentation through the switching of the syngas from H2 /CO to D2 /CO. Results from this switching indicated that hydrogen was involved in the rate-limited step; the overall process conversion produced an inverse kinetic isotope effect. To confirm that results were not hindered by the physical switch of the hydrogen isotopes, further experimentation was performed using equal molar of each isotope competitively (equal molar H2 /D2 )/CO. Complications arose from this competitive work as it generated fully exchanged products, i.e. all partially deuterated hydrocarbons that could not be separated by chromatography. These compounds could no longer be separated by the chromatography and required a further separation by mass. The overall scope for this work was to determine if a range of partially deuterated paraffin compounds, generated by FT, can be analyzed using an EI-MSD without interinstrumental H/D exchange. Results indicate that no real exchange occurs in the EI MSD for a carbon range from about C6 to C16 . Even though the materials cannot be separated chromatographically, they can be further separated and analyzed to determine the overall H/D content for these specific chain lengths.

The sulfur limit, the relationship between the sulfur added and the surface Fe atoms lost (Fe/S), and mechanism of sulfur poisoning were studied using an iron Fischer–Tropsch synthesis (FTS) catalyst (100 Fe/5.1 Si/2.0Cu/3.0K). The FTS reaction was carried out at 230–270 °C, 1.3 MPa, H2/CO = 0.67–0.77 and 30–70% CO conversion using a 1-L slurry phase reactor. The used Fe catalysts were characterized by XRD, Mossbauer spectroscopy and XANES spectroscopy to understand the deactivation mechanism of the Fe based catalyst after adding up to 1 ppm H2S in the feed. Co-feeding of 0.1 ppm H2S in syngas for 70 h caused a very small change in the activity of the Fe catalyst, but increasing the H2S level to 0.2 ppm or above resulted in measurable deactivation of the Fe catalyst over a similar time period. The limit of sulfur level in the syngas feed (sensitivity) was determined to be 50 ppb. The added sulfur improved the selectivities of the secondary reactions of olefins and the WGS reaction even though the rates for these declined. The addition of H2S decreased CH4 selectivity and increased C5+ selectivities of the Fe catalyst. The Fe/S ratio, which can be used to define the poisoning ability of sulfur for the iron catalyst, was quantified based on the deactivation data obtained. The Fe/S ratio strongly depended on temperature and decreased remarkably with increasing temperature. At 270 °C one sulfur atom was found to eliminate ∼6 surface Fe atoms, and the ratio increased to 7.2 at 260 °C and increased further to 13.5 at 230 °C. The Fe/S relationship with increasing temperature is in good agreement with sulfur sorption theory. The changes in FTS and WGS rates of the Fe catalyst by sulfur were also studied. The decreases in rates of the two reactions were nearly the same. The results of XRD and Mossbauer spectroscopy indicated that the online addition of sulfur did not greatly alter the distributions of iron carbide and magnetite. Both data sets consistently suggest an adsorption mechanism, in line with the results of reaction testing. XANES results at the S K-edge further confirmed sulfur adsorption, and some sulfide and sulfate species, likely confined to the surface zone, were detected. In this study, the sulfur tolerances of the precipitated Fe and a supported Co catalyst were compared at an identical temperature (i.e., 230 °C), and similar M/S ratios (13.5–15.0) were obtained.

The effect of solvent on the hydrogen-deuterium isotopic homomolecular exchange over a traditional Fischer-Tropsch cobalt catalyst (25 % Co/Al2O3) was investigated using a plug flow reactor at two different reaction temperatures (room temperature (26 °C) and –20 °C) and at atmospheric pressure. In this study, three different solvents were tested, including n-pentane, n-hexadecane, and C-30 oil. The consumption of H2 and D2 is the same, and the concentration of the HD produced is twice the consumption of H2 or D2 at dry (without solvent) conditions. At room temperature and at –20 °C, conditions without solvent exhibited 100 mol% exchange with the formation of H2:HD:D2 having a 1:2:1 ratio. For n-pentane solvent, the exchange rates were ∼97 and ∼80 mol% at 26 and −20 °C, respectively. For the n-hexadecane and C30 oil solvents, the initial exchange rate was ∼50 mol%, with the exchange rate decreasing over time. The lower exchange rate with the n-hexadecane and C30 oil solvents, and also n-pentane at –20 °C, is likely due primarily to the limited mobility of reactant molecules in the liquid-filled pores of the catalyst. Blocking or covering of the pores of the catalyst depends on the molecular mass and density of the solvent. No isotopic partitioning preference was observed at two different temperatures and various solvents for the active cobalt catalyst.

Silver addition, in low amounts (0.0054 or 0.013 %), to a 1 %Pt/KL catalysts prepared by a sequential CVD procedure using acetylacetonates resulted in improved benzene selectivity at similar conversion levels compared to the undoped 1 %Pt/KL CVD catalyst. Both hydrogenolysis and aromatization require an ensemble of atoms to constitute the active site, but hydrogenolysis is more structure sensitive. Silver, which is a relatively inert metal catalyst, blocks a fraction of Pt surface sites, lowering the overall n-hexane rate. When added in low levels, silver disrupts to a greater degree the Pt ensembles responsible for hydrogenolysis relative to those required for aromatization. This was confirmed by DRIFTS of adsorbed CO measurements, which showed that higher wavenumber bands attributed to larger Pt ensembles were suppressed to a greater extent relative to lower wavenumber bands (i.e., arising from smaller ensembles).

A series of Co–Fe bimetallic catalysts was prepared, characterized, and studied for the hydrogenation of carbon dioxide. The catalyst precursors were prepared via an oxalate coprecipitation method. Monometallic (Co or Fe) and bimetallic (Co–Fe) oxalate precursors were decomposed under a N2 flow at 400 °C and further pretreated under a CO flow at 250 °C. The catalysts (before decomposition of the oxalates or after activation) were characterized by BET, TGA-MS, X-ray diffraction, CO-TPR, SEM, HR-TEM, and Mossbauer spectroscopy techniques. The hydrogenation reaction of CO2 was performed using Co–Fe bimetallic catalysts pretreated in situ in a fixed-bed catalytic microreactor operating in the temperature range of 200–270 °C and a pressure of 0.92 MPa. With increasing Fe fraction, the selectivity to C2–C4 for Co–Fe catalyst increased under all operating conditions. The alcohol selectivity was found to increase with increasing iron content of the Co–Fe catalyst up to 50%, but then it dropped with further additi...

The effect of Cu, Mn and Zn addition on cobalt ferrite was investigated for Fischer–Tropsch synthesis (FTS). Oxalate co-precipitation followed by decomposition under inert conditions was used to obtain various metal containing cobalt ferrites (Co0.7M0.3Fe2O4). The carburization of cobalt ferrite in flowing CO at 270 °C and 175 psig yielded iron carbides (χ-Fe5C2 and e′-Fe2.2C) along with a bimetallic FeCo alloy. The extent of carburization was compared among Cu, Mn, and Zn doped catalysts with undoped cobalt ferrites under similar conditions. XRD and Mossbauer spectroscopy analysis of the freshly carburized samples followed by passivation revealed that carburization of cobalt ferrite did not change appreciably with addition of Cu or Mn. On the other hand, Zn was found to retard the carburization of cobalt ferrite. Analysis of the used FT catalysts suggests that Cu is less efficient over Mn and Zn in stabilizing the iron carbides (i.e., active form of iron) during FT synthesis. The FT activity remains more or less the same for the undoped, Cu and Zn containing cobalt ferrites at higher temperatures. The CO conversion of Co0.7Mn0.3Fe2.0 catalyst was much lower than the other catalysts tested. Addition of Zn or Mn to cobalt ferrite was found to promote alcohol formation, particularly at higher reaction temperatures. The water–gas shift activity of the catalysts was found to decrease in the following order, Co1.0Fe2.0 > Co0.7Mn0.3Fe2.0 > Co0.7Zn0.3Fe2.0 > Co0.7Cu0.3Fe2.0.

The presence of hydroxyl or keto functional group affects both activity and selectivity for dehydrocyclization of C6 hydrocarbon over Pt/(Na)–Al2O3 catalyst. Under similar reaction conditions, n-hexane produces benzene as the primary product (>40 %), whereas dehydration is a major reaction pathway for 2-hexanol and yields mainly hexenes (>70 %). However, 2-hexanone was found to be involved in a variety of reactions over Pt/(Na)–Al2O3 catalyst and produces lower hydrocarbons (C2–C5), 5-dodecanone, 2- and 5-nonanones, and 2-acetyl-3-propyl-2-cyclohexen-1-one. The presence of hydroxyl (–OH) or keto group (=C=O) at the C-2 position alters the interaction of C6 hydrocarbon with the catalyst surface which eventually controls the overall product selectivity.

Fischer–Tropsch (FT) synthesis continues to receive widespread attention. Even after 90 years of investigation, the mechanistic route has yet to be fully defined. FT, as a polymerization process, uses CO and H2 as the reactants to produce a broad spectrum of hydrocarbons. Since the conception of the FT synthesis, several different isotopic routes have been employed for mechanistic studies. Various isotopes, such as 13C, 14C, 18O, and 2H, have been utilized through different types of experiments to shed light on the active site(s), the rate-limiting step, and the catalytic pathways. Direct evidence in the FT mechanism has been uncovered by utilizing experiments such as H2/D2 switching trials, as these experiments attempt to shed light on the rate-limiting step of CO hydrogenation. However, before hydrogen participates in the mechanism of CO hydrogenation, it may first dissociatively adsorb on the catalyst surface. The aim of this work is to ascertain to what extent H and D partition on the surface. This is accomplished by passing an equimolar H/D gas mixture over the activated FT catalyst, followed by a TPD method to determine if the active carbide surface displays a partitioning preference toward one of the isotopes. If a preference is observed, then the interpretation of kinetic isotopic effect (KIE) data ascertained in the CO hydrogenation switching experiments could potentially be affected. However, only a very slight isotopic preference toward deuterium was observed, and it is deemed not significant enough to affect an interpretation of the KIE based on H/D switching.

Tracer studies were performed on cobalt and iron Fischer–Tropsch catalysts using a synthesis gas containing a 20:80 mixture of 13C18O and 12C16O. The objective of the work was to investigate the antecedents of the C–O bonds in alcohols and CO2 formed during Fischer–Tropsch (FT) synthesis. It was found that chain growth proceeded by a CO insertion mechanism over both cobalt and iron catalysts. Over the cobalt catalyst, the dominant pathway for methanol synthesis involved a partial hydrogenation of CO as well as CO2 by a reaction pathway separate from the Fischer–Tropsch pathway. Over the iron catalyst, the majority of the methanol was formed by partial hydrogenation of only CO through the FT reaction pathway. Iron is active for water gas shift conversion, which produced CO2. Oxygen exchange reactions of CO2 were likely over both catalysts and complicated the interpretation of the results.