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A detailed kinetic model of Fischer–Tropsch synthesis (FTS) product formation, including secondary methane formation and 1-olefin hydrogenation, has been developed. Methane formation in FTS over the cobalt-based catalyst is well known to be higher-than-expected compared to other n-paraffin products under typical reaction conditions. A novel model proposes secondary methane formation on a different type of active site, which is not active in forming C2+ products, to explain this anomalous methane behavior. In addition, a model of secondary 1-olefin hydrogenation has also been developed. Secondary 1-olefin hydrogenation is related to secondary methane formation with both reactions happening on the same type of active sites. The model parameters were estimated from experimental data obtained with Co/Re/γ-Al2O3 catalyst in a slurry-phase stirred tank reactor over a range of conditions (T = 478, 493, and 503 K, P = 1.5 and 2.5 MPa, H2/CO feed ratio = 1.4 and 2.1, and XCO = 16–62%). The proposed model including secondary methane formation and 1-olefin hydrogenation is shown to provide an improved quantitative and qualitative prediction of experimentally observed behavior compared to the detailed model with only primary reactions.

This work aims at investigating the effect of the type of metal (Pt, Pd, Rh, Ru, Cu, Ni, Co) on the performance of ZrO2-supported catalysts for the hydrodeoxygenation of phenol in the gas phase at 573 K and 1 atm. Two different reaction pathways take place depending on the type of the metal. For Pt/ZrO2 and Pd/ZrO2 catalysts, phenol is mainly tautomerized, followed by hydrogenation of the C=C bond of the tautomer intermediate formed, producing cyclohexanone and cyclohexanol. By contrast, the direct dehydroxylation of phenol followed by hydrogenolysis might also occur over more oxophilic metals such as Rh, Ru, Co, and Ni. In addition to the metals, the oxophilic sites of this support represented by Zr4+ and Zr3+ cations near the perimeter of the metal particles also increased the selectivity to deoxygenated products. All catalysts were significantly deactivated mainly owing to the growth of metal particle size and the decrease in the density of oxophilic sites.

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 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 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.