GHSV space velocity

Both catalyst space velocity and bed geometry play a role. The gas hourly space velocity (GHSV) is used to relate the volumetric flow rate to the catalyst volume. GHSV has units of inverse hour and is defined as the volume flow rate per catalyst volume. 

The size of the catalyst bed depends mainly on the degree of VOC reduction requited (14). VOC destmction efficiencies up to 95% can usually be attained using reasonable space velocities (14). However, the low GHSVs, and subsequently high catalyst volumes requited to achieve extremely high (eg, 99%) conversions, can sometimes make catalytic oxidation uneconomical. Conventional bed geometries may be found in the Hterature (14). 

GHSV (gas hourly space velocity) = (volumes of feed as gas at STP/h)/(vohime of reactor or its content of catalyst) = SCFH gas feed/fF. 

ALLreviations reactors Latch (B), continuous stirred tank (CST), fixed Led of catalyst (FB), fluidized Led of catalyst (FL), furnace (Furn.), multituLular (MT), semicontinuous stirred tank (SCST), tower (TO), tuLular (TU). Phases liquid (L), gas (G), Loth (LG). Space velocities (hourly) gas (GHSV), liquid (LHSV), weight ( VHSV). Not available, NA. To convert atm to kPa, multiply Ly 101.3. 

If using GHSV = 10,000 h" , the feed is, F = V GHSV = 20 (104) cm or 200 liters/h. Therefore, the 12.600 normal liters in the cylinder will be enough for 60 hours of operation. During these 60 hours, effects of temperature and conversion (by changing space velocity) can be studied at the one, given gas composition in the cylinder. 

Another commonly used term is the gas hourly space velocity (GHSV), which is defined as... 

The reactions were carried out in the steady state flow mode as described previously [11]. Differential kinetics were determined from plots of conversion vs. W/F. Three catalysts CoZSM-5, HZSM-5 and NaZSM-5 (Si/AI = 11) were studied in this work. The catalyst preparation and the standard pretreatment used prior to reaction have been described previously [11]. It involved dehydration in flowing dried 0 as the temperature was raised slowly to 500°C. The feed comprised CH4 (0.28%), NO (0.21 %) or NOj (0.21 %). and/or Oj (2.6%) in He. The flow rate was 75 ml/min and the gas hour space velocity (GHSV) was varied between 4,500 and 250,000 h by changing the weight of catalyst samples. 

The catalytic tests [temperature = 543-703 K liquid hourly space velocity (LHSV) = 2,0 h gas hotuly space velocity (GHSV) (if not differently reported) = 510 h PYC/formaldehyde acetal =1 1 moEmol were carried out in... 

However, the detailed description of the FT product distribution together with the reactant conversion is a very important task for the industrial practice, being an essential prerequisite for the industrialization of the process. In this work, a detailed kinetic model developed for the FTS over a cobalt-based catalyst is presented that represents an evolution of the model published previously by some of us.10 Such a model has been obtained on the basis of experimental data collected in a fixed bed microreactor under conditions relevant to industrial operations (temperature, 210-235°C pressure, 8-25 bar H2/CO feed molar ratio, 1.8-2.7 gas hourly space velocity, (GHSV) 2,000-7,000 cm3 (STP)/h/gcatalyst), and it is able to predict at the same time both the CO and H2 conversions and the hydrocarbon distribution up to a carbon number of 49. The model does not presently include the formation of alcohols and C02, whose selectivity is very low in the FTS on cobalt-based catalysts. 

Other authors have studied the effect of the gas space velocity, and their results are in agreement with those reported in this work concerning the effect of space velocity on CO conversion.13 15 In contrast, it is difficult to make a comparison between literature and our GHSV effects on product distribution. As reported by van der Laan and Beenackers,14 in fact, the effect of the space velocity on product distribution is complex and often controversial, so that... 

Consequently, in the early 1990s, interest in the direct processes decreased markedly, and the emphasis in research on CH4 conversion returned to the indirect processes giving synthesis gas (13). In 1990, Ashcroft et al. (13) reported some effective noble metal catalysts for the reaction about 90% conversion of methane and more than 90% selectivity to CO and H2 were achieved with a lanthanide ruthenium oxide catalyst (L2Ru207, where L = Pr, Eu, Gd, Dy, Yb or Lu) at a temperature of about 1048 K, atmospheric pressure, and a GHSV of 4 X 104 mL (mL catalyst)-1 h-1. This space velocity is much higher than that employed by Prettre et al. (3). Schmidt et al. (14-16) and Choudhary et al. (17) used even higher space velocities (with reactor residence times close to 10-3 s). 

With regard to the operating conditions, catalytic activity tests were carried out at fixed 02 CH4 and H20 CH4 feed ratios of 0.56 and 0.49, respectively, while the space velocity was varied from GHSV = 45 000-90 000 h. ... 

A direct comparison of Al203-supported Pt, Pd, and Ru suggests that Ru is the most active metal for diesel reforming, at least on this support. Berry et al studied diesel reforming at a temperature range of 750 to 850°C and GHSVs of 25,000 to 200,000 h Activity increased in the order Pd < Pt < Ru. Complete conversion of diesel was obtained at 850°C and space velocity of 50,000 h from the ATR of diesel over a y-alumina supported Ru catalyst. 

The most common unit of <2rel is bed volumes per hour (BV/li). Space velocity is also used in catalytic reactors, especially in three-phase fixed-beds, and is referred to as liquid hourly space velocity (LHS V) for the liquid phase, and gas hourly space velocity (GHSV) for gas phase. As mentioned above, space-time and space velocity are measured under the entrance conditions. However, for space velocity, other conditions are frequently used (Fogler, 1999). For example, the LHSV is measured at 60 to 75 °F, and GHSV at standard temperature and pressure. 

Catalytic Combustion Properties of M-substituted Hexaaluminates - Most of the catalytic studies performed over hexaaluminate materials deal with the combustion of CH4 as the main component of natural gas, i.e., the typical fuel of gas turbines. Arai and co-workers were the first to investigate the CH4 combustion activity of BaMAlnOjg with M=Cr, Mn, Fe, Co, Ni prepared via the alkoxide route.5 Activity tests were performed over powder catalysts using a conventional quartz microreactor fed with a diluted CH4-air mixture (1% CH4) at high-space velocity (GHSV=48000 h 1). The results are summarized in Table 3 in terms of T10% (i.e., the temperature required to achieve 10% conversion). 

Space velocities (hourly) gas (GHSV), liquid (LHSV), weight (WHSV). 

To focus only on the binary compositions, the catalysts were evaluated under the following experimental conditions feed 40% propylene and 10% oxygen temperature, 250 °C and 20 000 h-1 of GHSV (gas hourly space velocity). Three different catalyst preparation procedures were used [40] ... 

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