Konstantins Dubencovs

Selective Oxidation of Glycerol to Glyceraldehyde over Novel Monometallic Platinum Catalysts

Several novel monometallic platinum catalysts supported on metal oxides (Al2O3, Y2O3, γ-Al2O3, Lu2O3, ZrO2-Y2O3 TiO2, SiO2, γ-AlO(OH)) and activated carbon (C) were synthesized by extractive-pyrolytic method and tested in glycerol oxidation processes without base addition to obtain glyceraldehyde. It was found that Pt catalyst activity is strongly influenced by support nature, oxygen partial pressure and Pt loading. Pt/Al2O3 and Pt/SiO2 catalysts exhibited the highest activity but selectivity to glyceraldehyde significantly decreased when glycerol conversion increased.

Production of glycolic acid from glycerol using novel fine-disperse platinum catalysts

Using extractive-pyrolytic method fine-disperse Pt containing composites were synthesized and tested in catalytic glycerol oxidation. Catalyst activity and selectivity to glycolic acid was determined oxidizing glycerol in mild conditions. It was concluded that only iron containing platinum catalysts were selective to glycolic acid. Selectivity to glycolic acid reached 53-60% with glycerol conversion 12-56%.

Novel fine-disperse bimetallic Pt-Pd/Al2O3 catalysts for glycerol oxidation with molecular oxygen

Using extractive-pyrolytic method several Pt-Pd bimetallic catalysts supported on plasma-processed alumina nanopowder were synthesized. Pt-Pd loading and glycerol oxidation process parameter influence on catalyst activity and selectivity was determined oxidizing glycerol in mild conditions. Novel bimetallic catalysts in neutral water solutions were practically inactive (glycerol conversion was only 3%) whereas in alkaline solutions they were active and selective to glyceric acid. Using 1.2%Pt-1.2%Pd/Al2O3 catalyst glyceric acid was obtained with 65% selectivity (glycerol conversion was 96%). It was shown that novel fine-disperse bimetallic Pt-Pd/Al2O3 catalysts were more active compared to analogous monometallic Pt/Al2O3 and Pd/Al2O3 catalysts.

Model-based optimization and pO2 control of fed-batch Escherichia coli and Saccharomyces cerevisiae cultivation processes

A model‐based approach for optimization and cascade control of dissolved oxygen partial pressure (pO2) and maximization of biomass in fed‐batch cultivations is presented. The procedure is based on the off‐line model‐based optimization of the optimal feeding rate profiles and the subsequent automatic pO2 control using a proposed cascade control technique. During the model‐based optimization of the process, feeding rate profiles are optimized with respect to the imposed technological constraints (initial and maximal cultivation volume, cultivation time, feeding rate range, maximal oxygen transfer rate and pO2 level). The cascade pO2 control is implemented using activation of cascades for agitation, oxygen enrichment, and correction of the preoptimized feeding rate profiles. The proposed approach is investigated in two typical fed‐batch processes with Escherichia coli and Saccharomyces cerevisiae. The obtained results show that it was possible to achieve sufficiently high biomass levels with respect to the given technological constraints and to improve controllability of the investigated processes.

Au Supported on the TiO2-nanofibers as Novel Catalysts for Glycerol Oxidation

Composites of Au supported on the TiO2-nanofibers (Au/NF-TiO2) were synthesized and tested in glycerol oxidation processes. TiO2-nanofibers were prepared by a microwave-assisted hydrothermal synthesis method. Chemical deposition method was used for nanofibers modification with Au nanoparticles. Oxidation of aqueous glycerol solutions by molecular oxygen in the presence of Au/NF-TiO2 nanocomposites was performed. It was found that Au/NF-TiO2 composites are catalytically active in alkaline glycerol water solutions. The main product of glycerol catalytic oxidation was glyceric acid, by-products were – tartronic, lactic, glycolic, oxalic, acetic and formic acid. It was shown that Au/NF-TiO2 catalysts’ activity and selectivity depend on Au weight loading, glycerol/Au molar ratio, oxygen pressure and NaOH initial concentration. The best result was achieved using the 0.5 wt%Au/NF-TiO2 catalyst: selectivity by glyceric acid was 76% with glycerol conversion 100%.

NiO and CoOx Promoted Pt Catalysts for Glycerol Oxidation

Two kinds of Pt/CeO2 catalysts supplemented with NiO or CoOx additives were synthesized by extractive-pyrolytic method and tested in glycerol oxidation processes. It was found that only NiO additive promotes Pt/CeO2 catalysts activity and selectivity to glyceric acid. NiO promoted Pt catalysts activity depends on NiO composites’ calcination temperature, oxygen partial pressure, initial NaOH concentration, as well as temperature. Glycerol conversion increases along with increased oxygen partial pressure from1 to 6 atm and along with decreased glycerol/Pt molar ratio from 5000 to 300. It was found that presence of base is significant in the glycerol oxidation processes over NiO promoted Pt/CeO2 catalysts, and optional NaOH initial concentration is 0.6 mol/L. The best yield of glyceric acid (68%) was reached in the presence of 4.8wt%Pt/5wt%NiO/CeO2 (300 °C) catalyst, when temperature was elevated up to 70 °C.

Model Predictive Feeding Rate Control in Conventional and Single-use Lab-scale Bioreactors: A Study on Practical Application

A developed solution for fed-batch process modeling and model predictive control (MPC), facilitating good manufacturing practice (GMP) based on process elaboration, control, and validation, is presented in the paper. The step-by-step evolution of the socalled “golden batch” optimal biomass growth profile and its control during the process is demonstrated. The case study of an advanced fed-batch control was performed on the recombinant E. coli BL21 lab-scale (5.4 L) biomass production process using the conventional stirred tank glass reactor. Additionally, a test experiment for control reproducibility and applicability assessment of the proposed approach was carried out in a single-use stirred tank reactor (5.7 L). Four sequentially performed experiments are demonstrated as an example for desirable feeding profile evolution for E. coli BL21 biomass production in a glucose-limited fed-batch process. Under different initial biomass and glucose conditions, as well as for different reference feeding profiles selected in the explorative experiments, good tracking quality of preset reference trajectories by the MPC system has been demonstrated. Estimated and experimentally measured biomass mean deviations from the preset reference value at the end of the processes were 4.6 and 3.8 %, respectively. Biomass concentration of 93.6 g L –1 (at 24 h) was reached in the most productive run. Better process controllability and safer process run, in terms of avoiding culture overfeeding but still maintaining a sufficiently high growth rate, was suggested for the process with biomass yield of 79.8 g L –1 (at 24 h). Practical recommen

Production of mono- and bimetallic nanoparticles of noble metals by pyrolysis of organic extracts on silicon dioxide

In the present work the influence of the tri-n-octylammonium (Oct3NH+) salt anion (PtCl62-, PdCl42-, AuCl4−) nature on the phase composition and mean size of crystallites of the extract pyrolysis products on the SiO2 nanopowder has been studied. The XRD phase analysis of the composites (metal loading 2.4 wt.%) made under the same conditions, at the pyrolysis of Pt- and Au-containing extracts has shown the formation of nanoparticles of Pt (dPt = 15 nm) and Au (dAu = 33 nm), respectively. The end-product of the pyrolysis of the Pd-containing extract has an admixture phase of PdO along with the main metal phase (dPd = 21 nm). At the preparation of bimetallic particles (Pt-Pd, Pt-Au, Pd-Au) on the SiO2 nanopowder it has been found that the nanoparticles of the PtPd alloy, Pt and Au or Pd and Au nanoparticles are the products of the thermal decomposition of two-component mixtures of extracts. The investigation of catalytic properties of the produced composites in the reaction of glycerol oxidation by molecular oxygen in alkaline aqueous solutions has shown that all bimetallic composites exhibit catalytic activity in contrast to monometallic ones.