Towards process intensification : remediation of fouling in continuous microscale synthesis of phosphated TiO2

The use of continuous flow microreactors offers an interesting approach among the process intensification tools available. Fouling in a microreactor during synthesis of industrially relevant nanoparticles was investigated. In order to achieve this, microscale synthesis of phosphated TiO2 nanoparticles from titanium(IV) isopropoxide (TTIP) and titanium(IV) butoxide (TBUT) was employed. A continuous three step process, consisting of hydrolysis of the respective alkoxide, phosphate modification and precipitation was developed. The resulting catalyst was characterized by means of nitrogen adsorption, dynamic light scattering and SEM/EDX. It was observed that TTIP resulted in massive fouling, while a stable process was possible with TBUT. This was related to the nucleation time of the particles. The particle size directly after the critical hydrolysis step was investigated. The particles formed with TTIP as a precursor (3.4 nm) were larger than those obtained from TBUT (2.4 nm). Diffusion based reactant concentration gradients within the multilamellar micromixer were calculated, and the corresponding Damköhler numbers for mixing were estimated to be 2.6∙10^-3 for TBUT and 3.5∙10^-2 for TTIP respectively. These numbers highlight the influence of incomplete mixing on fouling for TTIP as a precursor. Thus, our work demonstrates the necessity to consider the reaction kinetics during process intensification by miniaturization

Preparation of highly active phosphated TiO2 catalysts via continuous sol–gel synthesis in a microreactor

Microreactors, featuring μm-sized tubes, offer greater flexibility and precise control of chemical processes compared to conventional large-scale reactors, due to their elevated surface-to-volume ratio and modular construction. However, their application in catalyst production has been largely neglected. Herein, we present the development of a microreactor process for the one-step sol–gel preparation of phosphated TiO2 – a catalyst which has been recently demonstrated to be an eco-friendly material for the selective synthesis of the platform chemical 5-hydroxymethylfurfural (5-HMF) from bio-derived glucose. In order to establish catalyst preparation–property–performance relationships, 18 samples were prepared according to a D-optimal experimental plan with a central point. The key properties of these samples (porosity, crystallite size, mole bulk fraction of P) were correlated, using quadratic and interaction models, with the catalytic performance (conversion, selectivity, reaction rate) of 5-HMF synthesis as a test reaction. The optimal calculated catalyst features were set as target parameters to optimise catalyst synthesis applying quadratic correlation functions. An optimal catalyst was obtained, validating the models employed, with a yield of almost 100% and a space–time yield of ca. 3 orders of magnitude higher than that of a conventional batch process. The high yield could be mainly attributed to the optimal hydrolysis ratio and temperature. Controlling the TiO2 crystallite size and surface acidity in conjunction with fine-tuning of the porous properties in the microreactor led to increased glucose conversion, surface based formation rates of 5-HMF, and selectivity towards 5-HMF of the optimal catalyst in relation to the batch-prepared material

Jets and energy flow in photon-proton collisions at HERA

Properties of the hadronic final state in photoproduction events with large transverse energy are studied at the electron-proton collider HERA. Distributions of the transverse energy, jets and underlying event energy are compared to \overline{p}p data and QCD calculations. The comparisons show that the \gamma p events can be consistently described by QCD models including -- in addition to the primary hard scattering process -- interactions between the two beam remnants. The differential jet cross sections d\sigma/dE_T^{jet} and d\sigma/d\eta^{jet} are measured

Разработка интерактивной моделирующей системы технологии низкотемпературной сепарации газа

We present a study of J ψ meson production in collisions of 26.7 GeV electrons with 820 GeV protons, performed with the H1-detector at the HERA collider at DESY. The J ψ mesons are detected via their leptonic decays both to electrons and muons. Requiring exactly two particles in the detector, a cross section of σ(ep → J ψ X) = (8.8±2.0±2.2) nb is determined for 30 GeV ≤ W γp ≤ 180 GeV and Q 2 ≲ 4 GeV 2 . Using the flux of quasi-real photons with Q 2 ≲ 4 GeV 2 , a total production cross section of σ ( γp → J / ψX ) = (56±13±14) nb is derived at an average W γp =90 GeV. The distribution of the squared momentum transfer t from the proton to the J ψ can be fitted using an exponential exp(− b ∥ t ∥) below a ∥ t ∥ of 0.75 GeV 2 yielding a slope parameter of b = (4.7±1.9) GeV −2

New miniature stirred-tank bioreactors for parallel study of enzymatic biomass hydrolysis

Many factors strongly influence the enzymatic hydrolysis of biomass to fermentable sugars (feedstock composition, pretreatment, enzymes and enzyme loading). In order to optimize the reaction conditions for the hydrolysis of biomass, an accurate high-throughput bioprocess development tool is mandatory, which enables a parallelization and an easy scale-up. New S-shaped impellers were developed for magnetically inductive driven stirred-tank bioreactors at a 10 mL-scale. An efficient and reproducible homogenization was shown at 20% w/w solids loading of microcrystalline cellulose and at, 4-10% with wheat straw in 48 parallel operated stirred-tank bioreactors. The scale-up was successfully validated for the enzymatic hydrolysis of wheat straw suspensions and microcrystalline cellulose mixtures by application of a cellulase complex at a milliliter- and liter-scale. As an example, the parallel stirred-tank bioreactor system was applied for the evaluation of enzymatic batch hydrolyses of plant materials with varying pretreatments