Trickle Bed Reactor System Research Articles

Continuous flow upgrading of lignin pyrolysis oils to drop-in bio-hydrocarbon fuels over noble metal catalysts

Although there are many studies on the noble metal-based catalysts for the hydrodeoxygenation (HDO) of lignin model compounds such as phenols, HDO studies on lignin biomass pyrolysis oil are relatively scarce. Owing to its complex composition (i.e., a mixture of phenolic monomers and oligomers), the activity and stability of the catalysts for the HDO of pyrolysis oil are significantly different from those for the model compounds. In this study, the catalytic performances of typical HDO catalysts, that is, Ru, Pd, Ru-Re supported on carbon, and the effects of process parameters such as solvent, temperature, and space velocity were investigated for the real lignin pyrolysis oils in a continuous-flow trickle bed reactor system for the first time. We demonstrated that proper tuning of catalyst composition and process parameters allows for producing the deoxygenated hydrocarbon mixtures which can be used for gasoline, jet fuel, and diesel fuels. Specifically, activated carbon promoted the HDO of lignin oil more effectively than acidic supports like HZSM-5 and TiO2 due to the weak adsorption of phenolic molecules. Among the different metals, Ru-Re supported on carbon exhibited the highest deoxygenation activity due to the synergy of the two metals. Tetrahydrofuran was the best solvent for lignin oil processing due to its high solubility and inertness to other side reactions (e.g., excess alkylation with ethanol solvent). The use of low space velocity of 0.2 h−1 and intermediate temperature of 350 °C resulted in the highest yield of the upgrade oil (∼25 wt%) simultaneously with the high level of deoxygenation (O/C < 0.04), mainly consisting of branched cycloalkanes. The causes of the catalyst deactivation and regeneration process are also discussed to provide practical significance.

Aqueous phase reforming of birch and pine hemicellulose hydrolysates

The current work focuses on studying the aqueous phase reforming (APR) of pine and birch hydrolysate obtained from waste wood by using organic acids available from biorefineries. Processing of representative synthetic mixtures was utilized in the work in order to support data interpretation related to the influence of different chemical compound and processing parameters on the APR of the actual hydrolysates. It was shown, that hydrogenation of the hydrolysates prior to APR was not feasible in the presence of formic acid, which ruled out one potential processing route. However, it was successfully demonstrated that birch and pine hydrolysates could be directly processed obtaining close to full conversion. The best results were obtained with tailored bimetallic Pd-Pt/sibunit catalyst in a trickle bed reactor system in the temperature range 175 °C–225 °C.

Methane production from syngas using a trickle-bed reactor setup

Syngas from gasification of waste biomass is a mixture of carbon monoxide (CO), carbon dioxide (CO2), and hydrogen (H2), which can be utilized for the synthesis of biofuels such as methane (CH4). The aim of the study research work was to demonstrate how syngas could be methanated and upgraded to natural gas quality (biomethane) in a fed-batch trickle-bed reactor system using either manure – (AD-M) or sludge-based (AD-WW) inoculum as microbial basis. The methanated syngas had a high concentration of CO2 and did not fulfil the criteria for natural gas quality biomethane. Further upgrading of syngas to biomethane could be achieved simultaneously in the same reactors by addition of exogenous H2, resulting in CH4 concentrations up to 91.0 ± 3.5% (AD-WW) and 95.3 ± 1.0% (AD-M). Microbial analysis indicated that the communities differed between AD-M and AD-WW demonstrating functional redundancy among the microbial communities of different inocula.

Nonlinear mixed-effects models for kinetic parameter estimation with batch reactor data

Traditional fixed-effects models based on nonlinear least squares or Bayesian methods of rate parameter estimation for batch reactor longitudinal data are problematic because such methods assume statistical independence between all measurements across multiple batches. For multiple longitudinal experiments, which yield time series data, such assumptions of independence are clearly inappropriate. Therefore, we investigate the application of nonlinear mixed-effects models for batch reactor experiments. Investigators in other fields use nonlinear mixed-effects models extensively to estimate accurate and nonbiased parameters for data sets with multiple correlated measurements. Such models may be superior for modeling batch reactor longitudinal experiments. Using single response data from a batch recycle trickle bed reactor system for the hydrogenation of acetophenone to 1-phenylethanol over a copper catalyst, we show less correlated parameters as well as improved lag plots and run sequence plots from a mixed-effects model relative to a fixed-effects Bayesian model.

Hydrodeoxygenation of Pyrolysis Oils

AbstractThe hydrodeoxygenation (HDO) of bio‐oil derived from white oak wood using non‐sulfided catalysts was studied in a two zone continuous flow trickle bed reactor system. The major organic components of the pyrolysis oil were pyrolytic lignin (large phenolic polymers), xylose, levoglucosan, organic acids (primarily acetic acid), and hydroxyacetaldehyde. The first zone was a low temperature zone (130 °C) that contained a Ru/C catalyst. In this zone, carbonyl groups were hydrogenated, producing propylene glycol (from hydroxyacetone), ethylene glycol (from hydroxyacetaldehyde), and sorbitol (from levoglucosan). A more severe hydrotreatment was performed in a second zone containing a bifunctional Pt/ZrP catalyst at a temperature between 300 and 400 °C. In the two‐stage HDO, an organic phase was produced that consisted of a distribution of hydrocarbons that were primarily cyclic alkanes (naphthenes) ranging from C7 to C24. The organic phase carbon yield decreased with increasing reaction temperature in the second zone. Catalyst deactivation and reactor plugging by coking occurred under all reaction conditions after 55–72 h time on stream (TOS). After ≈55 h TOS, more than 25 % of the carbon in the original bio‐oil was accumulated as coke, with increasing amounts for higher temperatures in the second zone. Hydrotreatment gave rise to &gt;C5 hydrocarbon (gasoline and distillate‐range fuel) overall yields between ≈30 and 47 carbon % for all experiments compared to the 79.5 % theoretical yield calculated for the bio‐oil feedstock. Coke formation and undesired cracking to C1–C4 hydrocarbon gases were the main causes of lower fuel carbon yields.

Hydrotreating of low temperature coal tar to produce clean liquid fuels

Clean liquid oil was obtained from low temperature coal tar (LCT) via hydrotreating in trickle-bed reactor (TBR) system filled with commercial catalysts. The effects of hydrogen pressure (10–16MPa), reactor temperature (350–410°C) and liquid hourly space velocity (LHSV) (0.25–1h−1) on hydrotreating performance were investigated while hydrogen to oil volume ratio was maintained constant at 1600LN/L in all cases. The degree of sulfur removal was greater than nitrogen removal with increasing temperature, pressure and contact time over the commercial catalyst. The TBR system was capable of removing nitrogen and sulfur from 1.14 and 0.34wt % in the feed to 63μgg−1 and 8μgg−1, respectively in the products. Gasoline (<180°C) and diesel (180–360°C) fraction were separated from the oil products and analyzed. The gasoline fraction produced from LCT by hydrotreating comply with gasoline specifications for distillation range, sulfur content, induction period and gum presence. But it did not meet the specifications for RON (Research Octane Number) specifications. Diesel fraction produced from LCT meet all quality tests as fuels which could be directly used as motor fuels without upgrading. The results indicated that the raw LCT could be considerably upgraded through catalytic hydrotreating and high-quality fuels were obtained.

Mathematical modeling of a three-phase trickle bed reactor

The transient behavior in a three-phase trickle bed reactor system (N2/H2O-KCl/activated carbon, 298 K, 1.01 bar) was evaluated using a dynamic tracer method. The system operated with liquid and gas phases flowing downward with constant gas flow Q G = 2.50 x 10-6 m³ s-1 and the liquid phase flow (Q L) varying in the range from 4.25x10-6 m³ s-1 to 0.50x10-6 m³ s-1. The evolution of the KCl concentration in the aqueous liquid phase was measured at the outlet of the reactor in response to the concentration increase at reactor inlet. A mathematical model was formulated and the solutions of the equations fitted to the measured tracer concentrations. The order of magnitude of the axial dispersion, liquid-solid mass transfer and partial wetting efficiency coefficients were estimated based on a numerical optimization procedure where the initial values of these coefficients, obtained by empirical correlations, were modified by comparing experimental and calculated tracer concentrations. The final optimized values of the coefficients were calculated by the minimization of a quadratic objective function. Three correlations were proposed to estimate the parameters values under the conditions employed. By comparing experimental and predicted tracer concentration step evolutions under different operating conditions the model was validated.

Design, scale up and safe piloting of thymol hydrogenation and menthol racemisation

The hydrogenation of thymol and the racemisation of a menthol mixture were investigated as part of the development of novel continuous process for the production of l-menthol. The key innovation in this l-menthol process is enzymatic enantioselective resolution of l-menthol from 8 menthol isomers mixture. This continuous biocatalytic step has significant impact on process economy. The productivity of the enzyme (mass of l-mentylacetate produced/mass enzyme) is a key performance measurement of this process. The demonstration of the required enzyme productivity was therefore a key objective of the process piloting. The effect of possible side products and impurities on the process also needed to be tested and therefore five cycles of piloting were performed using approximately 500 kg of feed into resolution in each cycle. The required quantities of the racemic menthol mixture were obtained by thymol hydrogenation in pilot plant trickle-bed reactor. Both hydrogenation and racemisation were developed as batch processes at laboratory scale and tested at bench scale in a continuous trickle-bed reactor system and scaled up to a pilot scale trickle-bed reactor. A bench scale trickle-bed reactor was designed, constructed and extensively used in the optimisation of the hydrogenation of thymol to racemic menthol. The process was successfully operated for more than 660 h in a bench scale reactor and subsequently scaled up to a pilot scale trickle-bed reactor. The pilot scale experiments were used to verify process scale-up and generate material for menthol resolution and downstream processing. Both the bench and pilot scale reactors were operated as adiabatic systems and the operation was found to be safe and reliable. Safety problems leading to formation of undesirable hot spots were experienced as consequence of insufficient catalyst wetting, high thymol concentration in the feed (above 40 wt.%) and because of possible equipment, operation and power failure.

Experimental and Modeling Study of Kinetics and Selectivity in the Oxidation of a Poly(.alpha.-olefin) Lubricant

A major means of lubricant oil degradation is by oxidation in the presence of metal surfaces that can have catalytic activity. An experimental and modeling study has been carried out on the oxidation kinetics and selectivity of a typical poly(α-olefin) (PAO) lubricant in the presence of both inert (glass) and active (brass, steel) surfaces in the temperature range 170-240°C. Inhibition of the reaction by zinc dialkyl dithiophosphate (ZDP) has been investigated. A batch recycling trickle-bed reactor system has been developed which provides reliable data on intrinsic chemical kinetics. Reaction rates are a strong function of temperature, with products appearing in the order of water, carbon dioxide, aldehydes, ketones, acids, and alcohols in both gas and liquid phases. Significant changes in viscosity and molecular weight were observed for T>200°C. A four-lump (PAO, carbonyl-containing compounds in the liquid phase, gaseous products, and deposits) kinetic model has been developed that gives good agreement with experimental results, including oxidation rate promotion by metals and inhibition by ZDP

Mass-transfer and kinetic aspects in continuous bioreactors usingRhodospirillum rubrum

In designing bioreactors for the conversion of sparingly soluble gases, both mass transfer and kinetic effects must be considered.Rhodospirillum rubrum, an anaerobic photosynthetic bacterium capable of carrying out the water gas shift reaction, is an ideal organism for studying the relative importance of mass-transfer and kinetics since the cell concentration in continuous reactors employingR. rubrum may be regulated by the quantity of light supplied to the bacterium. This article addresses the performance ofR. rubrum in continuous stirred-tank and trickle-bed reactors, with particular attention given to the importance of mass-transfer and reaction kinetics in modeling reactor performance. Estimates of mass-transfer coefficients are made for a trickle-bed reactor system based upon reactor performance equations and experimental observations.

A MATHEMATICAL MODEL FOR THE CATALYST DEACTIVATION IN A COMMERCIAL RESIDUE HYDRODESULFURIZATION REACTOR SYSTEM

A mathematical model that describes catalyst deactivation in a commercial Residue Hydrodesulfurization (RDS) system is proposed. In this model, coking, metal deposition and the decrease of effective diffusivities are all considered, so that it can predict the dynamics of catalyst activity during a long run of an RDS system. The RDS system under consideration here is a complex trickle bed reactor system with four adiabatic reactors in series, between which the oil is quenched by hydrogen to prevent the catalysts in the next reactor from being damaged by high temperature. This article shows that by incorporating a catalyst deactivation model into the overall reactor system model, the predicted catalyst aging curve assumes the “S” shape, characteristic of real RDS system. The model prediction are compared with data from an operating refinery and the agreement is pleasing. KEYWORDS Residue Hydrodesulfurization(RDS) Apparent activity Catalyst deactivation curve Pore radius.

Kinetic studies of upgrading pine pyrolytic oil by hydrotreatment

Pyrolytic oil, produced by the Tech-Air Corporation from Southern Pine sawdust and bark, was hydrotreated in a trickle bed reactor system. Changes in product composition as a function of reaction temperature, hydrogen pressure, space velocity and catalyst type were determined quantitatively by size exclusion chromatography - gas chromatography (SEC-GC) analyses and elemental analyses. The catalysts used in the reactions were Pt/Al 2O 3/SiO 3, and sulfided CoMo/γ-Al 2O 3, Ni-W/γ-Al 2O 3 and Ni-Mo/γ-Al 2O 3. The reaction temperatures ranged from 623 K to 673 K, and the reaction pressures varied from 5,272 kPa (750 psig) to 10,433 kPa (1,500 psig). Weighthourly space velocity was changed from 0.5 to 3.0 h −1. Two models, one for overall oxygen removal and the other for the compositional changes in hydrotreated oil, were developed. Oxygen removal was not a function of space velocity and was modeled by an empirical function of temperature and pressure. A pseudo first order reaction network was used to relate the kinetics of a five “lump” model.