Catalytic Deoxygenation of Stearic Acid in a Continuous Reactor over a Mesoporous Carbon-Supported Pd Catalyst (original) (raw)
Related papers
Synthesis of Biodiesel via Deoxygenation of Stearic Acid over Supported Pd/C Catalyst
Catalysis Letters, 2008
High catalytic activity was achieved in the deoxygenation of stearic acid in dodecane in a temperature range of 270–300 °C under 17 bar helium over palladium on nanocomposite carbon Sibunit. Besides n-heptadecane, which was obtained previously in this reaction with palladium on activated carbon, n-pentadecane was also formed in significant amounts.
Deoxygenation of palmitic and stearic acid over supported Pd catalysts: Effect of metal dispersion
Applied Catalysis A-general, 2009
Catalytic deoxygenation of palmitic and stearic acids mixture was studied over four synthesized Pd catalysts supported on synthetic carbon (Sibunit) in a semibatch reactor and dodecane as a solvent at 260-300 8C. The catalysts were prepared by precipitation deposition method using Pd chlorides as metal precursors. All catalysts contained 1 wt.% Pd, however, the metal dispersion was systematically varied. An optimum metal dispersion giving the highest reaction rate was observed. The main liquid phase products were n-heptadecane and n-pentadecane, which were formed in parallel. In addition to the particle size effect the impact of mass transfer was elucidated and a detail discussion on temperature programmed desorption of CO from the fresh and spent samples was provided.
It has been found that catalytic deoxygenation of triglycerides is a viable pathway for obtaining renewable liquid fuels to contribute to meet the global energy demand. In this study, SBA-15 mesoporous silica was synthesized in a pure form and modified with mesitylene (TMB) as a swelling molecule (SBA15-TMB). Catalysts with 0.5, 1.5 and 3.0 wt% Pd were synthesized and tested by deoxygenation of stearic acid (SA), obtaining initial conversions of 68-98% that decreased to 36-73% after 6 h time-on-stream. The most abundant product was n-heptadecane, with a selectivity of ~ 90%. The most active catalyst evaluated with SA was 3.0 wt% Pd over unmodified SBA-15 (30Pd/SBA-15). Subsequently, fresh and regenerated 30Pd/SBA-15 catalysts were tested with waste cooking oil (WCO) feed, obtaining conversions of 74 and 72%, respectively, but the fresh catalyst allowed a better oxygen removal (91%. Additionally, commercial Pd(10wt %)/C catalyst was evaluated, obtaining results comparable to those for the regenerated 30Pd/SBA-15 catalyst. The main WCO reaction product for all catalysts was a diesel fraction (C 12-C 21), and the quality of the products was not very different, following the order: Pd(10wt %)/C > 3.0Pd/ SBA-15-regenerated > 3.0Pd/SBA-15-fresh. The results obtained indicate that shynthetized catalysts of this study are promising for obtaining renewable diesel from low-cost feeds while using low hydrogen consumption.
Applied Catalysis A: General, 2015
Supported Pd nanocatalysts were prepared by deposition of Pd nanoparticles (NPs) onto spherical mesoporous carbon beads (MB) functionalized by thermal or acidic treatement. The Pd NPs were synthesized by decomposition of [Pd 2 (dba) 3 ] (dba: dibenzylideneacetone) under dihydrogen either directly on the carbon supports without stabilizer leading to naked Pd NPs (Pd/MB series) or in solution in the presence of a stabilizer (polymer (PVP series) or triphenylphosphine (TPP series)) to obtain stable colloidal solutions that were further used to impregnate the carbon materials to have carbon-deposited Pd NPs. The NPs deposited on carbon displayed a Pd loading from 0.5 to 14.8 wt.% and were characterized by different techniques (nitrogen physisorption at 77 K, H 2-chemissorption and TPD, XRD, XPS and HRTEM). Their catalytic performance in deoxygenation of oleic acid was evaluated in batch and flow reaction conditions. Flow conditions led to superior results compared to batch. No aromatic compounds were detected as side products, but in the case of the Pd/MB series, octadecanol and octadecane were significantly formed suggesting the involvement of a deoxygenation mechanism in which the hydrocarbons were produced via both decarbonylation/decarboxylation and dehydration steps. Further experiments carried out in H 2 /N 2 mixture or in pure N 2 highlighted the key role of hydrogen. For a N 2 /H 2 of 2.5:1 the dehydration route was crossing out and even no traces of octadecanol nor octadecane were detected. Then, complete removal of H 2 produced heptadecene in a high excess compared to heptadecane (almost 7-1) thus suggesting the decarbonylation/decarboxylation steps as the main route. ICP-OES measurements indicated no leaching of palladium and simple washing of catalysts with mesitylene allowed recycling without any change in conversion or product distribution.
Selective deoxygenation of stearic acid via an anhydride pathway
RSC Advances, 2012
Pd/γ-Al 2 O 3 (4.5 wt% Pd) was obtained from BASF. Room temperature XRD measurements were carried out using a Bruker-AXS D2 Phaser powder X-ray diffractometer, in Bragg-Brentano mode, equipped with a Lynxeye detector. The radiation used is Cobalt Kα 1,2, l = 1.79026 Å, operated at 30 kV, 10 mÅ. The system is theta-theta coupled with a goniometer radius of 217.5 mm. The XRD diffractogram of the catalyst can be found in figure S2. Nitrogen physisorption was performed at 77 K using a Micromeritics Tristar 3000 V, 6.04 Å. The obtained data were used to calculate the BET surface area. Prior to the physisorption measurements, the samples were dried at 473 K for about 14 h under nitrogen flow. Micropore volumes and external surface areas were determined using t-plot analysis and are shown in
Chemical Engineering Communications, 2019
The calcination temperature (Cal-Temp) plays a vital role in the performance of supported metal catalysts. In this work, the alumina supported Ni, NiMo, Co, and CoMo catalysts were prepared at different Cal-Temp. The catalysts were characterized by various techniques to identify the catalytically active different surface species to correlate their role in the hydrodeoxygenation of stearic acid. With increasing Cal-Temp, the metal dispersion was increased for Ni, NiMo, and CoMo catalyst (up to 973 K) and decreased for Co catalyst. With increasing Cal-Temp, the catalytic activity was thus increased for Ni and NiMo catalyst and decreased for Co catalyst. The activity of CoMo catalyst was, however, enhanced with rising Cal-Temp up to 973 K and declined slightly after that. The optimum Cal-Temp for Ni, NiMo, Co, and CoMo catalyst was found to be 1023 K, 973 K, 773 K, and 973 K. The reaction followed the decarbonylation route over active metallic centers (Ni and Co) and the HDO route over oxophilic M 2þ ÁMoO 2 (M ¼ Ni/Co) and reducible cobalt oxide species. The C 17 alkane was thus the principal product over Ni catalyst, whereas C 18 alkane was the primary product over CoMo and NiMo catalyst. In contrast, both C 17 and C 18 alkanes were significant over Co catalyst.
Studies on Nickel-based Bimetallic Catalysts for the Hydrodeoxygenation of Stearic Acid
IOP conference series, 2020
Fatty acids, which are contained in vegetable oils, can be converted into alkanes through the hydrodeoxygenation (HDO) reaction, as an alternative fuel. In this study, the HDO of stearic acid was carried out in the presence of nickel-based bimetallic catalysts supported on Silica-Alumina (SiAl) in an autoclave batch reactor using decane as a solvent. Various metals, including Fe, Cu, and Co, were added into Ni catalysts using conventional wet impregnation method. Among others, additional Cu on Ni/SiAl increased the performance of the catalyst for the reaction.
Fuel, 2019
Selective production of octadecane through the hydrodeoxygenation of oleic acid in hexane containing pressurized CO 2 , a green reaction media, using a mesocellular foam (MCF) supported Fe-Pd-Ni/MCF catalyst was demonstrated in this study. In addition to hexane containing pressurized CO 2 playing a key role in directing the hydrotreatment of oleic acid towards hydrodeoxygenation over decarboxylation/decarbonylation, the use of MCF as the support helped achieve higher selectivity for octadecane, the major hydrodeoxygenation product while at the same time completely negating heptadecane, the decarboxylation/decarbonylation product. Negligible diffusion resistance aided by the 3-dimensional cage like structure and large pore opening of MCF, plus a better dispersion of the catalyst were identified as major reasons for enhancement of octadecane yield. An octadecane yield of 93% at 4 h was achieved through an optimization of temperature to 278°C and a H 2 pressure to 40 bars, while the CO 2 pressure was kept constant at 20 bars. The activation energy for the hydrodeoxygenation of stearic acid to octadecane was observed to be a 43.6% reduction over the existing literature. An increased spillover of H 2 onto the surface of Fe nanoparticles, triggered by an increased sticking capability of H 2 on Pd-Ni alloy patches formed on the top Fe nanoparticles, was proposed as the major reason for this acceleration. The proposed catalyst could not only avoid production of undesired decarbonized product heptadecane but also reduce energy requirement to achieve higher yield over reported data due to the lowering of temperature and time, indicating its superiority.
This study reports the hydrodeoxygenation (HDO) of stearic acid (SA) into paraffinic biofuel with synthesized palladium-oxalate zeolite supported catalyst (PdOx/Zeol). The PdOx/Zeol was synthesized via the functionalization of dihydrogen tetrachloropalladate (II) with aqueous oxalic acid (OxA) to form the polynuclear palladium(II) oxalate (PdOx), which was supported on zeolite. The SEM and XRD characterization results showed that the zeolite support is highly crystalline but loss some degree of crystallinity in the PdOx/Zeol sample after PdOx incorporation. The activity of the PdOx/Zeol tested on the HDO of SA showed that temperature, pressure, gas flow rate, and PdOx/Zeol loading have significant effects on the HDO process, and their best observed conditions were 360 °C, 20 bar, 100 mL/min, and 25 mg, respectively to achieve 92% biofuel production from 35 g SA. The biofuel product distribution showed 71% n-C18H38, 18% iso-C18H38, and 3% C17H36. The presence of iso-C18H38, which is an excellent biofuel value-added-component due to its low freezing point, was ascribed to the functionalization of Pd with OxA, which increases PdOx/Zeol acidity. The results showed that PdOx/Zeol is a prospective catalyst toward further research and commercialization of HDO process of SA.