On-line GC analysis

On-line GC analysis (Shimadzu GC 14A) was used to measure product selectivity and methane conversion. Details on the analysis procedure used for batch and continuous-flow operation are given elsewhere [12]. The molecular sieve trap was found to trap practically all ethylene, COj and HjO produced a significant, and controllable via the adsorbent mass, percentage of ethane and practically no methane, oxygen or CO, for temperatures 50-70 C. The trap was heated to -300°C in order to release all trapped products into the recirculating gas phase (in the case of batch operation), or in a slow He stream (in the case of continuous flow operation). 

For the n-Cq reforming and n-C[2 isomerization reactions the catalysts were run in a fixed bed micro reactor equipped with on-line GC analysis. The catalyst, together with a quartz powder diluent, was added to a 6 inch reactor bed. A thermocouple was inserted into the center of the bed. The catalysts were calcined at 350-500°C immediately prior to use and reduced in H2 at 350-500°C for 1 hour. n-Heptane or dodecane (Fluka, puriss grade) were introduced via a liquid feed pump. The mns were made at 100-175 psi with a H2/n-heptane (or n-Ci2) feed ratio of 7 and a weight hourly space velocity of 6-11. 

The catalytic test of propane ODH reaction was performed in the 350-600°C range in a quartz fixed bed flow reactor with on line GC analysis. The free volume of the reactor after the catalyst bed was filled with quartz particles to minimize the homogeneous reactions. All the testing set was placed in a thermostat with heated lines to the gas chromatographs at about 100°C to prevent water condensation. The feed gas composition was C3H8/02/N2 = 20/10/70 vol.% at total gas flow 50 cm3 min-1. Catalyst fractions of 0.2-0.315 mm particle size and of 80 mg weight were loaded into the reactor. Before the reaction, the catalyst samples in the reactor were kept under airflow at 600°C for lh. 

The reactor effluent was analyzed by on-line GC-analysis prior to condensation. Each reactor line was equipped with a HP 5890 GC with flame ionization detector (FID), interfaced with a PC for data handling and storage. The method of analysis, based on HP s PONA analysis, included all important hydrocarbons up to C,. Heavier components than this were only present in trace amounts, and were not analyzed. Research octane numbers (RON) were calculated from GC-analysis based on an adapted version of the method presented by Anderson et al. (5). The hydrogen yield was calculated from GC-analysis as the hydrogen balance over the reactor. 

The catalytic tests were performed in a fixed bed apparatus feeding n-heptane, at P=50 bar and H2/HC molar ratio equal to 18, at 75 catalytic performance of each catalyst was evaluated on the basis of n-heptane conversion, branched C isomers selectivity and their distribution into Mono-branched, Di-branched and Tri-branched compounds. 

Merck research grade H2S (5% vol.), alcohol (2,5 helium as a carrier gas and on line GC analysis. 

The experiments were performed in the Tapered Element Oscillating Microbalance (TEOM) reactor (7,8), in which carbon formation and deactivation could be measured simultaneously by coupling with on-line GC analysis. The dry reforming of methane was studied on an industrial Ni (11 wt%)/(Ca0)a-Al203 catalyst at temperatures of 500 °C and 650 °C, total pressures of 0.1 MPa and 0.5 MPa and a CO2/CH4 ratio of 1. The BET surface area of the catalyst was 5.5 m /g, and the Ni surface area 0.33 m /g. The detailed experimental procedures were similar to that reported previously (7). 

The problem with GC as an analysis tool for the evolved component is that it takes much more time to separate the evolved components than to analyse their mass in the MS. If the sample is heated by a linear thermal programme (as is the case in thermal analysis), then many interesting kinetic phenomena may occur during separation of components in the GC. This makes on-line GC analysis of the evolved components difficult. The evolved components could be trapped at moments of interest [116], thus overcoming the sampling rate problem. However, this is not the best solution. With the introduction of computer control and some modification of the conventional GC apparatus, the speed of GC analysis makes on-line evolved gas analysis possible. 

Conventional IRMS requires relatively large sample volumes in a purified gaseous form. Recently, an on-line GC-IRMS system has been developed which combines the high purification effect of GC with the utmost precision of IRMS. Sometimes this system may not be Sufficient to determine characteristic minor components from complex matrices, and therefore MDGC-IRMS systems have been developed for the analysis of complex plant extracts and flavour components (25-27). 

The catalyst testing was carried out in a gas phase downflow stainless steel tubular reactor with on-line gas analysis using a Model 5890 Hewlett-Packard gas chromatograph (GC) equipped with heated in-line automated Valeo sampling valves and a CP-sD 5 or CP-sil 13 capillary WCOT colunm. GC/MS analyses of condensable products, especially with respect to O-isotopic distribution, was also carried out using a CP-sil 13 capillary column. For analysis of chiral compounds, a Chirasil-CD capillary fused silica column was employed. 

In chromatography-FTIR applications, in most instances, IR spectroscopy alone cannot provide unequivocal mixture-component identification. For this reason, chromatography-FTIR results are often combined with retention indices or mass-spectral analysis to improve structure assignments. In GC-FTIR instrumentation the capillary column terminates directly at the light-pipe entrance, and the flow is returned to the GC oven to allow in-line detection by FID or MS. Recently, a multihyphenated system consisting of a GC, combined with a cryostatic interfaced FT1R spectrometer and FID detector, and a mass spectrometer, has been described [197]. Obviously, GC-FTIR-MS is a versatile complex mixture analysis technique that can provide unequivocal and unambiguous compound identification [198,199]. Actually, on-line GC-IR, with... 

Noncondensable gases leaving the condensation vessels were depressurized (by means of an electronic back-pressure, Brooks Instrument model 5866), totalized (by means of an on-line flow gas meter, Ritter model TG05-5), and periodically analyzed with an on-line GC (Hewlett-Packard model 6890) equipped with three columns and two detectors for the analysis of Cj-C10 hydrocarbons (A1203 plot capillary column connected to a flame ionization detector), H2, CH4,... 

Naphthas with different initial and final boiling points were compared by pilot reactor testing. The pilot reactor unit consisted of isothermal, once-through reactors with on-line GCs for full product analysis and octane number determination. Octane numbers, reformate yields and composition as well as gas yields were measured as a function of reaction temperature at 16 bar reaction pressure and a molar Hj/HC ratio of 4.3. Catalyst deactivation was studied over two weeks periods at high severity conditions, i.e. 102.4 RON and a Hj/HC ratio of 2.2. Test results, with emphasis on the yields of benzene and other aromatics, reformate and hydrogen yields as well as catalyst deactivation, are presented. 

The catalysts were pelletised, crushed and sieved the fraction with a diameter between 0.7 and 1.0 mm was collected. Reactions were performed downflow at atmospheric pressure with 1.00 g of material, stored under ambient in a borosilicate glass tube (i.d. 7 mm) heated by a fluidised bed oven. The catalysts were pretreated with ammonia/nitro-gen at 400°C to accomplish the reduction of Cu to Cu [8,9]. The reaction feed gas (33.4 ml/min) contained 16.5 vol% water or ammonia and 0.84 vol% chlorobenzene the WHSV (20°C) was 0.078 h (gp Q /gj,3 ). In experiments with other chloroaromatics, equal substrate vapour pressures and nucleophile/substrate ratios were used. Quantitative analysis was performed by on-line GC, product identification by mass spectrometry. 

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