Thermal argon detector

The Separation of a Mixture of Hydrocarbons Monitored by the Thermal Argon Detector and the FID... 

It is seen that the performance of the two detectors is very similar. The thermal argon detector is not, presently, commercially available. However, its high sensitivity, freedom from radioactivity and electron producing ancillaries make it a very simple detector to fabricate and... 

The Simple or Macro Argon Detector Sensor The Micro Argon Detector The Triode Detector The Thermal Argon Detector The Helium Detector The Pulsed Helium Discharge Detector The Electron Capture Detector The Pulsed Discharge Electron Capture Detector References Chapter 7... 

The gas chromatograph (GC) is a Hewlett-Packard 5890 GC with a thermal conductivity detector. A 5A mole sieve column is used with argon carrier gas this gives peaks going in the same direction for both hydrogen and nitrogen. 

The purpose of the carrier is to transport the sample through the column to the detector. The selection of the proper carrier gas is very important because it affects both column and detector performance. Unfortunately, the carrier gas that gives the optimum column performance is not always ideal for the particular detector. The detector that is employed usually dictates the carrier to be used. For instance, an electron capture detector operating in the pulsed mode requires an argon-methane mixture a thermal conductivity detector works best with hydrogen or helium. The most common carrier gases are listed in Table 6.1. 

Temperature programmed reduction (TPR) was performed using an equipment described in detail elsewhere [12]. Approximately 100 mg of catalyst was loaded in the quartz reactor tube and was heated at a rate of 0.167 K/s in a flow of 0,5 cm3(STP)/s of 66% hydrogen in argon. Hydrogen consumption was detected with a thermal conductivity detector (TCD). In order to prevent preliminary reduction of the catalyst, samples containing palladium were cooled to about 223 K during the time required to stabilize the detector. 

The development of the ionization detectors by Lovelock that evolved from the original argon detector culminated in the invention of the electron capture detector [2]. However, the electron capture detector operates on a different principle from that of the argon detector. A low energy 3-ray source is used in the sensor to produce electrons and ions. The first source to be used was tritium absorbed into a silver foil but, due to its relative instability at high temperatures, this was quickly replaced by the far more thermally stable Ni source. 

In TPD/TPR experiments, a mixture of H2/Ar (25%/75% v/v) was introduced at 30 ml/min lo reduce mg of calcined catalyst sample in a fixed bed reactor, while heating from 303 to 973K at 10 K/min. The effluent stream was monitored for hydrogen with a thermal conductivity detector after removal of moisture in a ice-acetone trap. After each TPR experiment, the catalyst was cooled in Ar from 973K to room temperature, and hydrogen adsorption was performed at room temperature for 1 hour. Argon was then used... 

Product analysis was carried out using a Hewlett-Packard 5890II gas chromatograph, fitted with both a thermal conductivity detector, and a methanator/flame ionisation detector. Separation of the products was achieved using a 3m Porapak Q packed column, with argon carrier gas. Reference data and pure component injections were used to identify the major peaks, and response factors for the products and reactants were determined and taken into account in the calculation of the conversion and product distribution. In all cases stoichiometric gas mixtures were used and carbon balances were better than 97%. Conversions and yields were calculated as follows ... 

The type of detector to be employed determines the nature of the carrier gas which may be used. Argon is used with the argon ionization detector. Helium is used with flame-ionization, thermal conductivity, thermionic emission, and cross-section detectors. Hydrogen may be used in thermal conductivity detectors to give maximum sensitivity. Probably the commonest and cheapest carrier gas is nitrogen, which can be used with flame-ionization, electron capture, thermal conductivity, and cross-section detectors. Argon-methane mixtures may be used with electron capture detectors. 

Adsorption isotherms of cyclopentane vapours were measured at 20°c. Temperature programmed reduction profiles were measured by the continuous flow technique with a thermal conductivity detector. Simultaneous TG, DTG and DTA were carried out in an argon atmosphere at the heating rate of 10 K.min Catalytic measurements were performed in a continuous flow integral fixed bed reactor under 0.1 MPa at 200°C. The inlet C0/H ratios ranged from 0.5 to 2.0, the space velocity was... 

Thermal conductivity detectors have been discussed in detail by Ingraham (107), who also described their application to thermodynamic and kinetic measurements. In this same book. Lodding (4) describes the gas density detector as well as several ionization detectors, such as the argon ionization detector, the electron capture detector, and others. Flame ionization detectors have been described in detail by Brody and Chaney (108) and Johnson (109). The latter also discusses other types of detectors. Malone and McFad-den (110) described many different types of special identification detectors, such as those listed in Table 8.3. Numerous texts on gas chromatography describe a wide variety of detectors, many of them useful in EGD and EGA. 

Hydrogen production rates were measured using a Varian Model 3700 gas chromatograph (Walnut Creek, CA) equipped with a molecular sieve 5A column and a thermal conductivity detector. Argon was used as the carrier gas. 

A Perkin-Elmer Auto-system gas chromatograph (GC), which houses a 30-m, 0.53-mm (ID) fused silica capillary column (Carboxen 1010 Plot, Supelco), was used to analyze the gaseous samples from the liquefaction process. Temperature programmed step heating was performed as follows 40°C for 1.7 min, increase by 40°C/min imtil 220°C, and leave at 220°C for 1.8 min. Argon was the carrier gas at a flow rate of 20 ml/min. Two detectors were used for gas analysis a flame ionization detector (FID) for carbon-bearing species and a thermal conductivity detector (TCD) for H2. Uncertainties in reported concentrations are estimated to be within 5% [8]. 

Gas Analysis. Product gas volumes were measured by a calibrated wet test meter. Gas compositions were determined with a Beckman model GC-5 dual column, dual thermal conductivity detector (TCD) chromatograph. One detector used a helium carrier with a Porapak Q column, and the other used an argon carrier with a molecular sieve column. Data reduction was aided by an Auto Lab System IV digital integrator equipped with a calculation module. 

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