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Catalysis/ Sorption > RuboLab Catalysis Research Series
Instruments of the RuboCAT series stand out due to their compact design and functionality, which can be customized according to specific requirements. The main features are including:
High-precision mass flow Controllers
Four thermal mass flow controllers are working within a flow range between 2 and 100 mln/min. Other flow rates are available on request.
High-pressure measurements of up to 1 MPa
The instrument is equipped with a back-pressure regulator, providing the opportunity to generate dynamic gas atmospheres of up to 1 MPa.
Humidity control included
The standard version already contains a saturator which can generate humidified gas flows. By adjusting flow rate and temperature, different levels of relative humidity can be achieved.
Highly accurate vapour dosing (option)
In addition, the instrument can be equipped with a highly accurate vapour dosing system using a HPLC pump in combination with an evaporator cell. Any condensable fluids are removed before the pressure regulator by means of an integrated cooling trap.
Wide temperature range
The reactor is temperature controlled within a range between 25 and 1100°C using heating rates of up to 25°C/min.
Pre-heated reactor inlet
Especially in high-pressure regions, the gas flow can lead to an inhomogeneous temperature distribution within the reactor. For compensation, the gas flow is preheated electrically before reaching the reactor.
Integrated TCD sensor
The standard version is already equipped with a thermal conductivity sensor being used for analysis of the dry gas composition.
Integration of mass spectrometer (option)
Additionally, the instrument can be paired with a mass spectrometer, ensuring even higher precision for analysis of the fluid composition. This optional mass spectrometer also makes the analysis of vapour fractions possible.
Exemplary Measurements, Applications
Temperature-programmed reduction (TPR)
TPR is used to investigate the reducibility or thermal behavior of catalysts as a function of temperature. Usually H2 is used as reductant. The figure shows the TPR data measured for a nickel oxide sample (NiO), according to:
Temperature-programmed desorption (TPD)
The binding energy of the adsorbate phase can be determined by means of a TPD measurement. A material previously loaded with adsorbate is heated under defined conditions, which leads to desorption of the previously adsorbed molecules. The desorption is detected by downstream analytics (TCD or MS).
Breakthrough curve (BTC)
The measurement of breakthrough curves is a commonly used method for the evaluation of adsorption capacity and corresponding kinetics: A gas mixture (e.g. CO2-N2) flows through an adsorber filled with the sorbent. First, the preferred adsorbing component will be adhered by the material. After saturation, the component breaks through and is detected by suitable gas analysis.
Sorption Measurement
What does the term “sorption” stand for?
Sorption is a collective term for adsorptive and absorptive processes. Adsorption describes the attachment of molecules of a fluid phase onto the surface of a solid or liquid. In the course of absorption, there is an additional diffusion of fluid molecules into the stationary phase. The reversal process of both sorption processes is the desorption, describing the removal of previously sorbed molecules and the return into the fluid phase. The corresponding nomenclature will be explained by the example of adsorption in the figure on the left side. According to this, the molecules to be adsorbed are called adsorptives. The solid on which the molecules are adsorbed is called adsorbent. In addition, the term adsorbate stands for already adsorbed molecules. In case of an adsorption of different fluid molecules, it is called a coadsorption.
How are sorption processes used on industrial scale?
Corresponding sorption processes are used for example, in pressure swing adsorption plants for the treatment of biogas. In general, the adsorption capacity of sorbents increases with increasing pressure within the sorptive gas phase. This property is used in a PSA plants for biogas purification, i.e. for the separation of CO2 and CH4. In this process, an adsorber filled with a carbon molecular sieve or zeolite, is flown through with biogas under increased gas pressure. Such sorbent materials exhibit a defined pore size distribution. Due to the different molecular diameters of the individual gas components, smaller gas molecules, such as those of carbon dioxide, are being increasingly adsorbed. In this way, a methane-rich product stream is generated. After achieving maximum capacity of sorbent material, the adsorber can be regenerated under reducing gas pressure. A batch operation of up to 6 adsorbers enables a constant generation of pure biomethane.
How can sorption processes be measured?
Knowledge of sorption behavior of used sorbent materials is of great importance for the design of such PSA systems. For this reason, the accurate measurement of sorption capacity is of particular interest. This is often described by means of sorption isotherms. For performing of such sorption measurements, Rubolab offers various instruments of the RuboSORP product line. The Magnetic Suspension Balance is currently the most accurate measurement method for sorption measurement on smallest sample masses and within extreme measuring conditions. Volumetric measurement instruments of the RuboSORP MPA series are the perfect instrument for performing screenings, i.e. the time-saving characterization of several sample materials. Using of RuboSORP BTC / PSA series measuring instruments is suitable for a realistic study of dynamic adsorption processes.
Magnetic Suspension Balance
Accurately determining the mass of lightweight samples is very important in many fields of research. In order to accomplish this, high-resolution analytical balances are an integral piece of equipment. Additionally, many technically relevant processes occur under technically demanding conditions such as high pressure, extreme temperatures, and aggressive or toxic atmospheres. Commercially available analytical balances cannot be used under these conditions. Therefore, the technology of the Magnetic Suspension Balance has been developed. RuboSORP´s Magnetic Suspension Balance technology offers the unique possibility of high-quality analysis under even the most extreme metrological conditions.
Measurement Technology
Magnetic Suspension Balance technology allows high resolution mass determination under extreme conditions. An industrial microbalance is located outside the cell. Thanks to contactless magnetic suspension coupling, mass changes within the pressurized cell can be determined. When perfroming a measurement, the sample whose mass change is being measured is attached to a permanent magnet. The actual position is detected and controlled via a high-performance PID controller. In order to establish a free levitation position for permanent magnet and measurement object, voltage is applied to a electromagnet outside of the measurement cell. This allows the sample mass to be measured contact free under extreme conditions. Load decoupling allows the object weight being measured to be subtracted for taring or calibrating the measurement signal. In this case, only the permanent magnet remains in levitation position (zero-point position). When measuring point is selected, the measurement object is lifted, corresponding weight is detected by the microbalance. The measurement objects can be a crucible, containing sample material, for example being used to measure adsorption isotherms or catalytic reactions. In addition, the measurement object could also be sinker with calibrated volume for high accurate density measurement of the sinker surrounding fluid. The RuboSORP Magnetic Suspension Balance is an advanced technology for measuring the mass of two measurement objects at the same time.
Available Versions
The unique technology ensures measurements within a pressure range of up to 700 bar and a maximum temperature of 400°C. The measurement cell and all components in fluid contact are resistant to aggressive and toxic atmospheres. Due to this, a variety of different fluids can be used, e.g. inertgas, aggressive and toxic gases, supercritical fluids, flammable and explodable gases, gas mixtures and vapor.
Highlights
Simultaneous Measurement of two Samples
The Magnetic Suspension Balance can simultaneously measure two different sample materials or sinker (Dual sample version).
Forced Flow Through Measurement Conditions
The Magnetic Suspension Balance can be equipped with a forced flow though sample crucible which improves interaction between sample and surrounding fluid atmosphere.
Most Advanced Magnetic Suspension Balance Technology
The Balance is equipped with unique features, e.g. a self-optimizing Magnetic Suspension Balance controller as well as a failsafe high speed ethernet interface.
Integrated Calculation of Measurement Uncertainty
The software which will be used for controlling RuboSORP Magnetic Suspension Balance contains an integrated calculation of measurement uncertainy according to GUM guidelines (Guide to the expression of uncertainties in measurement). This allows a more holistic view of data and best level of scientific work.
Applications
Chlorine Gas Adsorption
The figure shows the experimental results of adsorption measurement using highly toxic chlorine gas. This data was collected simultaneously on two materials within a pressure range of up to 3.5 bar at 10°C. For this purpose, the Magnetic Suspension Balance has been equipped with two sample crucibles to measure both samples at the same time (dual sample measurement).
Adsorption of Biogas on Zeolite
With increasing usage of biogas as energy source, the corresponding purification treatment of its gas components has become increasingly more important. The figure shows the pure gas isotherms of CO2, CH4, N2 and H2 measured on zeolite, which is an industrially used sorbent for biogas purification. In combination with an appropriate dosing unit, the Magnetic Suspension Balance can also be used to measure the corresponding gas mixture adsorption.
Fluid Density Measurement
Sinkers with a known volume can be used instead of sample crucibles for high accurate determination of fluid phase density, even in supercritical atmospheres. The figure shows density data of CO2 measured in sub-critical and supercritical state. By using a sinker and sample crucible as measurement objects a combined measurement of adsorption and fluid density can be obtained.
Breakthrough Curve Systems
The technical use of sorption processes has increased in importance during the last decades. The applications are widely diversified, ranging from biogas processing to medical technology or gas storage. The characterization of correspondent sorbent materials often occurs by means of gravimetric or volumetric methods. In addition, the detection of breakthrough curves within an adsorber column can be used to determine sorption capacity, heat of adsorption and corresponding kinetic.
With instruments of RuboSORP BTC/PSA series, Rubolab offers tailor-made solutions for measuring breakthrough curves within adsorber columns. Each instrument is equipped with a gas dosing unit for gas mixture generation. The pressurized gas mixture will be flown through an adsorber, filled with sorbent material. Gas handling occurs by means of thermal mass flow controllers, sorptive gas pressure will be controlled by using pressure controlling valve. The standard version of our instrument can be used for measurement within a pressure range of up to 7 bar (higher pressure on request).
The figure on the left shows a breakthrough curve of CO2-N2-mixture, measured with the RuboSORP BTC/PSA. Thanks to intuitive and easy-to-use software, such measurements are performed fully automated. In Addition, the software also calculates corresponding measuerment results (e.g. adsorption isotherms).
An instrument equipped with one adsorber column can be used for the measurement of breakthrough curves.
In addition, two or more adsorbers can be integrated for studying complex pressure swing adsorption processes (PSA).
References:
S. Nandi et.al., A single-ligand ultra-microporous MOF for precombustion CO2 capture and hydrogen purification, Sci.Adv.2015;1 (2015)
S.Nandi et al., Exceptionally stable Bakelite-type polymers for efficient pre-combustion CO2 capture and H2 purification,J. Mater. Chem. A, 2017,5, 8431-8439
RuboSORP Magnetic Suspension Balance in Combination with Rubolab Gas Dosing Units
In combination with our Gas Dosing Units, the RuboSORP Magnetic Suspension Balance can be used as fully automated measurement instrument. Rubolab´s gas dosing units are often designed according to the customer´s specifications. The standard versions can be devided into two general groups: the GDU DYNAMIC and GDU STATIC series. GDU DYNAMIC series units are used to generate dynamic atmospheres within connected Magnetic Suspension Balance. These systems contain several types of thermal mass flow controllers to generate pure gas flows and defined gas mixtures. Depending on the existing fluid flows, the system pressure will be controlled using a front pressure controlling valve. In contrast, systems of GDU STATIC series generate statically pressurized atmospheres within the Magnetic Suspension Balance using pulsed width controlled dosing valves.