A convenient method for measuring gas-liquid volumetric mass transfer coefficient in micro reactors

The research on gas-liquid multiphase reactions using micro reactors is becoming increasingly widespread, given their excellent mass transfer performance. Establishing an accurate and reliable method to measure the gas-liquid mass transfer performance of micro reactors is crucial for evaluating and optimizing the design of micro reactor structure. In this paper, the physical absorption method of aqueous solution-CO_(2) and the chemical absorption method of sodium carbonate solution-CO_(2) were proposed. By analyzing the chemical reaction equilibrium during the absorption process, the relationship between the mass transfer of CO_(2) and the solubility of hydroxide ions in the solution was established, and the total gas-liquid mass transfer coefficient was immediately obtained by measuring the p H value. The corresponding testing platform and process have been established based on the characteristics of the proposed method to ensure fast and accurate measurement. In addition, the chemical absorption method takes into account temperature factors that were not previously considered. The volumetric mass transfer coefficient measured by these two methods is in the same range as those measured by other methods using the same microchannel structure in previous literature. The methods have the advantages of low equipment cost, faster measurement speed, and simpler procedures, which can facilitate its wide application to the evaluation of the mass transfer performance and hence can guide the structure optimization of microchannel reactors.

Precision Synthesis of a Long-Chain Silane Coupling Agent Using Micro Flow Reactors and Its Application in Dentistry

In dentistry, a wide range of materials is available for restorative treatment;a typical product of such restorative materials mainly consists of radically polymerizable monomer(s) and inorganic filler(s) (for added physical strength), as well as a surface modifier (e.g. silane coupling agent) for improved affinity between monomer and filler. It is favorable to use an optimal surface modifier depending on the respective restorative materials. However, commercially available surface modifiers, which are synthesized by the ton, are not always suited for what is required for properties of the many different dental restorative materials. As a potential solution to such a problem, we focused on the latest technology, “micro flow reactors” that enabled an on-demand low-volume synthesis of many types of surface modifiers. Using micro reaction fields of such flow reactors, we synthesized a novel long-chain silane coupling agent. Compared to the control system synthesized using a conventional reaction flask, the novel system enabled significant reduction in reaction time without inducing any major side reactions. A dental composite resin that was treated with the novel coupling agent exhibited higher toughness, suggesting that such a silane coupling agent was an effective surface modifier.

Dimensional Analysis and Similarity Method Driving Self-similar Solutions of the First and Second Kind Inducing Energy

Nearly all scientists,at conjunction with simplifying a differential equation,have probably used dimensional analysis.Dimensional analysis(also called the Factor-Label Method or the Unit Factor Method)is an approach to the problem that uses the fact that one can multiply any number or expression without changing its value.This is a useful technique.However,the reader should take care to understand that chemistry is not simply a mathematics problem.In every physical problem,the result must match the real world.In physics and science,dimensional analysis is a tool to find or check relations among physical quantities by using their dimensions.The dimension of a physical quantity is the combination of the fundamental physical dimensions(usually mass,length,time,electric charge,and temperature)which describe it;for example,speed has the dimension length/time,and may be measured in meters per second,miles per hour,or other units.Dimensional analysis is necessary because a physical law must be independent of the units used to measure the physical variables in order to be general for all cases.One of the most derivation elements from dimensional analysis is scaling and consequently arriving at similarity methods that branch out to two different groups namely self-similarity as the first one,and second kind that through them one can solve the most complex none-linear ODEs(Ordinary Differential Equations)and PDEs(Partial Differential Equations)as well.These equations can be solved either in Eulearian or Lagrangian coordinate systems with their associated BCs(Boundary Conditions)or ICs(Initial Conditions).Exemplary ODEs and PDEs in the form of none-linear can be seen in strong explosives or implosives scenario,where the results can easily be converted to induction of energy in a control forms for a peaceful purpose(i.e.,fission or fusion reactions).

The green fuel from carbon waste： optimization and product selectivity model studies

Increase in greenhouse gases, has made scientists to substitute alternative fuels for fossil fuels. Nowadays, converting biomass into liquid by Fischer-Tropsch synthesis is a major concern for alternative fuels （gasoline, diesel etc.）. Selectivity of Fischer-Tropsch hydrocarbon product （green fuel） is an important issue. In this study, the experimental data has been obtained from three factors; temperature, H2/CO ratio and pressure in the fixed bed micro reactor. T = 543-618 （K）, P = 3-10 （bar）, H2/CO = 1-2 and space velocity = 4500 （l/h） were the reactor conditions. The results of product modeling for methane （CH4）, ethane （C2H6）, ethylene （C2H4） and CO conversion with experimental data were compared. The effective parameters and the interaction between them were investigated in the model. H2/CO ratio and pressure and interaction between pressure and H2/CO in ethane selectivity model and CO conversion and interaction between temperature and H2/CO ratio in methane selectivity model and ethylene gave the best results. To determine the optimal conditions for light hydrocarbons, ANOVA and RSM were employed. Finally, products optimization was done and results were concluded.

Fluidization of micro-interconnected fluidized beds for chemical looping

The micro-interconnected fluidized bed(MIFB)was designed to improve the evaluation condition of oxygen carrier,which is difficult to perform in a lab-scale interconnected fluidized bed because of the large demand for bed inventory.The reduction of bed inventory in the MIFB was mainly achieved by the appropriate miniaturization of the reactor size,in which the wall effect and operating flexibility should be taken into consideration.With hematite serving as the oxygen carrier,stable and flexible fluidization could be realized with 342.9 g of bed inventory.Internal perforated plates were arranged in the middle of the reactor to improve gas-solid distribution,which also could restrain the slugging formation and increase the particle residence time by 28.9%.A different fluidization phenomenon was observed in this two-stage reactor in which the particle fluidization was reconstructed in the upper chamber.Throughout 48 h of cold operation,the hematite oxygen carrier attrition rate was evaluated as 0.151 wt.%/h corresponding to 660 h lifetime,where 12.5%of particle attrition was contributed by internal perforated plates.An excellent fitting performance was found between the pressure difference in the risers and the upward particle flow,but the correction factor should be adjusted according to the fluidization flow.

Chemical Interpretation on the Multi-Stage Oxidation of Diethyl Ether

Multi-stage ignition and/or double NTC(negative temperature coefficient)behavior resulted from the low-temperature oxidation of ether compounds are still not clearly explained.We have investigated the oxidation mechanism of a stoichiometric DEE(diethyl ether)/air mixture by using a micro flow reactor with a controlled temperature profile to see the detail of low-temperature weak flame structure.The simulation was also performed to understand the chemical kinetics mechanism of observed weak flame structure.Chemiluminescence measurement showed separated weak flame in the temperature range of 600 K-800 K.The simulation also qualitatively reproduced this separated weak flame,and showed four peak of heat release.From the reaction flow analysis,it was found that(1)O-O bond scission reaction of keto-hydroperoxide produced by DEE,(2)O-O bond scission reaction of CH3O2H,CH3CO3H,and C2H5O2H,(3)O-O bond scission reaction of H2O2,and(4)H+O2=O+OH are key chain branching reactions to explain the multi-stage oxidation.