Sabaithip Tungkamani

Conversion enhancement of tubular fixed-bed reactor for Fischer-Tropsch synthesis using static mixer

Abstract Recently, Fischer-Tropsch synthesis (FTS) has become an interesting technology because of its potential role in producing biofuels via Biomass-to-Liquids (BTL) processes. In Fischer-Tropsch (FT) section, biomass-derived syngas, mainly composed of a mixture of carbon monoxide (CO) and hydrogen (H 2 ), is converted into various forms of hydrocarbon products over a catalyst at specified temperature and pressure. Fixed-bed reactors are typically used for these processes as conventional FT reactors. The fixed-bed or packed-bed type reactor has its drawbacks, which are heat transfer limitation, i.e. a hot spot problem involved highly exothermic characteristics of FT reaction, and mass transfer limitation due to the condensation of liquid hydrocarbon products occurred on catalyst surface. This work is initiated to develop a new chemical reactor design in which a better distribution of gaseous reactants and hydrocarbon products could be achieved, and led to higher throughput and conversion. The main goal of the research is the enhancement of a fixed-bed reactor, focusing on the application of Kenics™ static mixer insertion in the tubular packed-bed reactor. Two FTS experiments were carried out using two reactors i.e., with and without static mixer insertion within catalytic beds. The modeled syngas used was a mixed gas composed of H 2 /CO in 2: 1 molar ratio that was fed at the rate of 30 mL(STP)-min– 1 (GHSV ≈ 136 mL. g ca −1 .h −1 ) into the fixed Ru supported aluminum catalyst bed of weight 13.3 g. The reaction was carried out at 180 °C and atmospheric pressure continuously for 36 h for both experiments. Both transient and steady-state conversions (in terms of time on stream) were reported. The results revealed that the steady-state CO conversion for the case using the static mixer was approximately 3.5 times higher than that of the case without static mixer. In both cases, the values of chain growth probability of hydrocarbon products (α) for Fischer-Tropsch synthesis were 0.92 and 0.89 for the case with and without static mixer, respectively.

The Effect of Preparation Method on Ni/Ce/Al Catalyst for High Temperature Water-Gas Shift Reaction

High temperature water gas shift (HT-WGS) is an important catalytic process connected with reforming process in hydrogen production. Ni/CeO2-Al2O3 (or Al2O3) catalysts were studied in this work on the effect of catalyst preparation method toward the physicochemical properties and the HT-WGS activity. Ni/CeO2-Al2O3 were prepared by sol-gel and impregnation methods whereas Ni/Al2O3 was prepared by impregnation method. The catalyst samples were characterized by XRD, H2-TPR and H2-TPD techniques. The catalytic activities of HT-WGS catalysts was demonstrated at 550°C, GHSV of 2x105 mLh-1gcat-1and steam-to-CO ratio of 3. Nickel was detected as a nickel aluminate phase in the calcined catalyst. Ni strongly interacted with support in the calcined catalyst prepared by sol-gel method. The strong metal-support interaction can be resisted by preparing catalyst via impregnation and CeO2 can promote the H2O dissociation in HT-WGS mechanism. The highest metal dispersion, largest metal surface area and greatest HT-WGS activity were consequently achieved by Ni/CeO2-Al2O3 prepared from impregnation method.

Investigation of Coke Formation in Dry Methane Reforming over Nickel-based Monolithic Catalysts

Coking accumulations via dry methane reforming (DMR) over 10NAM monolithic catalyst and pelletized catalyst was investigated. 10NAM catalyst was synthesized and coated on a wall of monolithic reactor. Pelletized catalyst of 10NAM was also prepared for the comparison. Consequently, catalyst was characterized by BET, and . The catalytic reaction was undergone at under atmospheric pressure and to reactant ratio of 1:2. The coking formation over spent catalyst was then carried out in the hydrogen flow using temperature programmed technique (TPH). According to the results, DMR over 10NAM monolithic catalyst exhibits a minimized coking formation comparing to the use of pelletized catalyst. This could be attributed to a prominent heat transfer efficiency of the monolithic catalyst.

Polymeric Material Application for The Production of Ceramic Foam Catalyst

Ceramic foams are prepared as positive images corresponding to a plastic foam structure which exhibits high porosities (85–90%). This structure makes the ceramic foams attractive as a catalyst in a dry reforming process, because it could reduce a high pressure drop problem. This problem causes low mass and heat transfers in the process. Furthermore, the reactants would shortly contact to catalyst surface, thus low conversion could occur. Therefore, this research addressed the preparation of dry reforming catalysts using a sol-gel catalyst preparation via a polymeric sponge method. The specific objectives of this work are to investigate the effects of polymer foam structure (such as porosity, pore sizes, and cell characteristics) on a catalyst performance and to observe the influences of catalyst preparation parameters to yield a replica of the original structure of polymeric foam. To accomplish these objectives industrial waste foams, polyurethane (PU) and polyvinyl alcohol (PVA) foams, were used as a polymeric template. Results indicated that the porosity of the polyurethane and polyvinyl alcohol foams were about 99% and 97%. Their average cell sizes were approximate 200 and 50 micrometres, respectively. The cell characteristics of polymer foams exhibited the character of a high permeability material that can be able to dip with ceramic slurry, which was synthesized with various viscosities, during a catalyst preparation step. Next, morphology of ceramic foams was explored using scanning electron microscopy (SEM), and catalyst properties, such as; temperature profile of catalyst reduction, metal dispersion, and surface area, were also characterized by H2TPR and H2-TPD techniques, and BET, respectively. From the results, it was found that metal-particle dispersion was relatively high about 5.89%, whereas the surface area of ceramic foam catalysts was 64.52 m 2 /g. Finally, the catalytic behaviour toward hydrogen production through the dry reforming of methane using a fixed-bed reactor was evaluated under certain operating conditions. The approaches from this research provide a direction for further improvement of marketable environmental friendly catalyst production.

The Effect of K Promoter on Ni-Co (Bimetallic) Catalyst for Dry Methane Reforming

10 wt% (Ni-Co) catalysts with different Ni and Co content : 10%Ni, 9%Ni1%Co, 7%Ni3%Co, 5%Ni5%Co, 3%Ni7%Co, and 10%Co; were prepared using sol-gel method followed by incipient wetness impregnation method. To investigate the catalytic activity including the stability, dry methane reforming were demonstrated over the pelletized catalysts at under atmospheric pressure in a feedstock for 360 min. The results showed that bimetallic catalysts with the Co content equal to or greater than 3% were more stable than monometallic catalysts (10%Ni and 10%Co). The temperature programmed hydrogenation interpreted that the additional of Co into Ni catalyst improved the carbon resistance from methane cracking. Promoted this type of bimetallic catalyst using 1wt% K (trimetallic catalyst) prevented the carbon formation on the catalyst. The temperature programmed desorption of indicated that this trimetallic catalyst has a greater number of strong basic sites. Moreover, the appearance of K lowered the number of weak basic sites and decreased the conversion of methane by 12 %.

Effect of Reaction Conditions on the Catalytic Performance of Ruthenium Supported Alumina Catalyst for Fischer-Tropsch Synthesis

A Ru/ɤ-Al2O3 catalyst was prepared using by sol-gel technique in order to study its conversion and selectivity in the Fischer-Tropsch Synthesis (FTS). The effects of reaction conditions on the performance of a catalyst were carried out in a fixed bed reactor. The variation of the steady-state experiments were investigated under reaction temperature of 160-220˚C, inlet H2/CO molar feed ratio of 1/1-3/1, which both atmospheric pressure and gas space hour velocity of 1061 hr− 1 were restricted. The influence of changing factors on CO conversion and on the selectivity of the formation of different hydrocarbon products in the reaction conditions was performed and compared to assess optimum operating conditions. In terms of FTS results, the increase of reaction temperatures led to increase of CO conversion and light hydrocarbon, while higher H2/CO ratio has strongly influenced to increase the selectivity to higher molecular weight hydrocarbons and chain growth probability (α). Moreover, our catalyst was also markedly found to maintain selectivity to diesel faction for a wide range of H2/CO molar feed ratios from BTL application.

Syngas Production via Carbon Dioxide Reforming of Methane in a Wall-Coated Monolith Reactor

The production of syngas via carbon dioxide reforming or dry methane reforming (DMR) was studied in the present study. To reduce pressure drop and improve the performance, the reaction was carried out over a 10%Ni/Al2O3-MgO catalyst in a wall-coated monolith reactor at about 600 °C, atmospheric pressure. The monolith reactor comprised of 37 circular flow channels of 3-mm-diameter. The reactant gases i.e. CH4 and CO2 at stoichiometric molar ratio of 1:2 was fed into the reactor at the volumetric flow rate of 450, 600 and 750 mL/min corresponding to various gas space velocities (GSV) i.e. 0.57, 0.76, and 0.96 s-1, respectively. Under 24-hr continuous operations, the stability of system could be sustained and the deactivation by carbon deposition was not observed. The experimental results did show that the conversion of methane depended upon the GSV i.e. the %CH4 conversion were 50, 45 and 40% for the GSV of 0.57, 0.76, and 0.96 s-1, respectively. In addition, the %H2 yield, %H2 selectivity, %CO yield, %CO selectivity also depended on the feeding rate and so affected the performance of the wall-coated monolith reactor as a reformer.

Investigations of Hydrodynamics and Heat Transfers in a Modified Reactor Using Fluid Mixers

The performance of a packed-bed reactor typically used in Gas-to-Liquid (GTL) or Biomass-to-Liquid (BTL) technologies in producing liquid fuels was affected by unfavorable high pressure drop, flow and temperature maldistributions which in turn could cause severe catalyst deactivation, and result in inefficient reaction etc. A certain types of fluid mixers such as KenicsTM or Mixing & Stirring type static mixers had been suggested to improve the performance of this type of reactor. In order to design a proper modified reactor by mean of an installation of such mixing structures for the pilot plant in liquid fuel production via Fischer-Tropsch Synthesis (FTS) conducted at the RCC research center, this study had to characterize the hydrodynamics and heat transfers within a packed-bed modified by KenicsTM and Mixing & Stirring type static mixers. During the FTS, the syngas i.e. CO and H2 was fed through the bed of catalyst causing the temperature rise due to an exothermic enthalpy, and the flow and temperature distributions of mixed gas within the catalyst bed were influenced. The improved velocity and temperature distributions and heat transfers were exhibited by using such mixers e.g. rather uniform distributions and higher heat transfer coefficient. Thus, the better performance of the reactor could be expected.