Direct conversion of synthesis gas to aromatic hydrocarbons: Variation of product distribution with time‐on‐stream

Abstract

The synthesis of hydrocarbons from syngas was studied over a zirconia-based cobalt-nickel catalyst (FT catalyst) alone as well as mixed with zeolite HZSM-5 at 101.3 kPa in a 12.7 mm i.d. down flow reactor. The product distribution was recorded as a function of time-on-stream for several days of continuous operation under fixed operating conditions of 250°C and Hz/CO = I . For the FT t HZSM-5 system, a dramatic variation in the product distribution takes place during the first 24 h of operation. A comparison of time-on-stream results obtained using FT catalyst alone and mixed with HZSM-5 suggests that the reactions leading to the build-up of overall product distribution are slower over HZSM-5 compared to those taking place over R catalyst. These diffcrcnces have been attributed to the different nature of reactions taking place over the two components of the mixed catalyst system. Analyses of the coke on the deactivated catalysts are also reported.

Recent Advances in Direct Synthesis of Value‐Added Aromatic Chemicals from Syngas by Cascade Reactions over Bifunctional Catalysts

“…Addition of small quantities (0.4−3 wt%) of Mg, Zr, La, and Th oxides into the Co/HZSM‐5 were also not helpful to improve the aromatic selectivity because they decreased the amount of the Brönsted acid sites . In parallel, Bruce et al and Varma et al monitored independently the variations of product distribution of FTS catalyst (Co–Ni–ZrO 2 ), which was significantly changed by HZSM‐5 addition through suppressing the aliphatic hydrocarbon selectivity, although the aromatic selectivity was in comparable range (≈20–29 wt%), the CO conversion was very low with the values of 9–11% (entries 4 and 5) as compared to the Co/HZSM‐5 (entries 1 and 2, Table 2 ). The bifunctional Co–Ni–ZrO 2 /HZSM‐5 catalyst displayed wide aromatic monomer distributions with the main products of toluene (19.9 wt%), xylenes and ethyl benzene (36.1 wt%) besides other alkyl benzenes (33.7 wt%) .…”

“…In parallel, Bruce et al and Varma et al monitored independently the variations of product distribution of FTS catalyst (Co–Ni–ZrO 2 ), which was significantly changed by HZSM‐5 addition through suppressing the aliphatic hydrocarbon selectivity, although the aromatic selectivity was in comparable range (≈20–29 wt%), the CO conversion was very low with the values of 9–11% (entries 4 and 5) as compared to the Co/HZSM‐5 (entries 1 and 2, Table 2 ). The bifunctional Co–Ni–ZrO 2 /HZSM‐5 catalyst displayed wide aromatic monomer distributions with the main products of toluene (19.9 wt%), xylenes and ethyl benzene (36.1 wt%) besides other alkyl benzenes (33.7 wt%) . In comparison with the Co‐based catalysts, Fe or other methanol synthesis catalysts are more favored for the production of aromatic monomers from syngas, although both catalysts have their own advantages and disadvantages.…”

Lignin Recovery and Lignin-Based Products

“…83,85 Therefore, the future production of large-volume products such as benzene, toluene, and xylene (BTX) should preferentially be done by further development of catalyst systems able to convert syngas into specific aromatic hydrocarbons. 89,90 Here, black liquor gasification as well as gasification using green biomass are renewable alternatives to the use of coal.…”

Hydrogenation of carbon dioxide by hybrid catalysts, direct synthesis of aromatics from carbon dioxide and hydrogen

“…Carbon monoxide is first hydrogenated on the hydrogenation catalyst and then the products are further converted on the zeolite to form aromatics. With the combination of a medium pore HZSM-5 zeolite and various kinds of Fischer Tropsch (Caesar et al, 1979;Shamsi et al, 1984;Bruce et al, 1984;Varma et al, 1985Varma et al, , 1986Varma et al, , 1987 or methanol synthesis catalysts (Chang et al, 1979;Thomson and Wolf, 1988), aromatics can be directly synthesized from carbon monoxide and hydrogen with the selectivity as high as 90% (Chang et al, 1979). For carbon dioxide, Fujimoto and Shikada (1987) has combined a copper-zinc methanol *To whom correspondence should be addressed.…”