A simple kinetic model based on the zeolite acid strength, the number of Brønsted acid sites, and the catalyst efficiency was developed for the cracking of n-hexane. A series of HY zeolites with a mesopore volume from 0.04 to 0.32 cm3/g was synthesized and characterized by various physical-chemical methods and tested for n-hexane cracking. The generation of mesoporosity influenced several other important parameters, such as acidity and extra-framework aluminum. Zero-length column diffusion measurements for mesitylene showed a large decrease in the characteristic diffusion time upon the introduction of mesoporosity, which changed only slightly with a further increase in mesoporosity. Similar n-hexane physisorption enthalpies were measured for all samples. The highest initial activity for n-hexane cracking per catalyst volume was observed for the sample with an intermediate mesopore volume of 0.15 cm3/g. The three mesoporous H-USY zeolites showed the same value of the intrinsic rate constant and the same activation energy. The difference in initial activity of the mesoporous zeolites was caused by the difference in the number of Brønsted acid sites. The increase in initial activity for the mesoporous zeolites compared to a microporous zeolite was caused by an increase in the acid strength.
A new route is presented as a stepwise upgrading process from black liquor issued from the kraft process to hybrid gasoline: (i) hydrothermal liquefaction (HTL) to produce biocrude, (ii) removal of alkaline metal salts, (iii) hydrodeoxygenation (HDO) for oxygen removal and decrease of molar weight, and finally (iv) coprocessing with vacuum gas oil (VGO) by catalytic cracking to produce gasoline as a secondgeneration transportation biofuel. A high degree of deoxygenation was found to be quite beneficial to the further cracking of the refined crude oil into gasoline fractions. Thus, for this coprocessing step, it was found that, by limiting the percentage of added pretreated biocrude to about 10 wt %, high naphtha yields (45% compared to 48% for pure VGO cracking) were maintained, and without a significant change in the coke yield. This result is promising since naphtha, the gasoline-rich fraction, is the main target product in FCC. More research is needed in the detailed characterization of the coprocessing products and in checking the quality and compatibility of the hybrid fuel with gasoline standards. Further optimization in the HTL and HDO steps can likely be achieved, possibly allowing coprocessing of larger quantities of HDO biocrude than 10 wt %.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.