This study investigated the transfer of oxygen and hydrogen species from steam to product during the catalytic cracking of heavy oil with iron oxide-based catalysts containing zirconia and alumina. Light oil and carbon dioxide were produced in the catalytic oxidative cracking of petroleum residual oil in the presence of steam. The alkene/alkane ratio of light aliphatic hydrocarbons decreased and carbon dioxide yield increased with higher flow rate ratio of steam to feedstock. The steam catalytic cracking of dodecylbenzene as a model compound of heavy oil showed lower alkene/alkane ratio and generation of a small amount of oxygen-containing compounds. The oxygen species derived from steam reacted with heavy oil and were transferred to carbon dioxide and a small amount of oxygen-containing compounds, producing hydrogen species from the steam. The hydrogen species were transferred to light hydrocarbons, thus suppressing alkene generation. The alkene/alkane ratio decreased with higher supporting zirconia content in the catalyst because zirconia promotes hydrogen generation from steam.
Ethanol produced from lignocellulosic biomass (bioethanol) is a promising alternative fuel to gasoline. Production of bioethanol from lignocellulose requires various steps, including pretreatment, enzymatic hydrolysis and fermentation. However, many fermentation inhibitors, including furfural and 5-hydroxymethyl furfural, are generated during the hydrothermal pretreatment of lignocellulose. Recent studies have identified techniques for removing fermentation inhibitors from lignocellulosic hydrolysate. The present study focused on the effect of low-concentration furfural on ethanol production by Saccharomyces cerevisiae. Specifically, gene expression of furfural-inducible genes was analyzed using a S. cerevisiae DNA microarray. The expression of most sulfur amino acid biosynthesis genes increased in response to furfural. To determine whether furfural induces the depletion of sulfur-containing amino acids, the effect of the addition of methionine on yeast growth was investigated. However, exogenous addition of methionine did not compensate for the inhibitory effect. The findings of this study show that furfural affects amino acid synthesis, even at low concentrations, and may be important in the development of high-efficiency processes for large-scale bioethanol production from lignocellulosic biomass.
Production of new hydrocarbon biodiesel, which can be synthesized from various vegetable oils by catalytic decarboxylation, was investigated with a fixed bed rector. The diesel fraction oils of C-10-C-20 aliphatic hydrocarbons as the major products were obtained smoothly with the reactor using waste cooking oil, jatropha oil, dark oil, and palm oil. Higher yields of C-21 + compounds, compared to the case of the agitating reactor, show that heavier products could flow out from the catalyst bed before decomposition to the lighter hydrocarbons. An MgO/SiO2 catalyst was found to be more effective than an active carbon-supported catalyst. In particular, cracked oil with a lower acid value (AV) was obtained with the former catalyst. Influence of reaction temperature and the feed rate of the reactant was examined to find that optimal conditions are 450 degrees C and LHSV = 0.3 h(-1). Although catalyst activity was maintained for about 24 h at LHSV = 0.3 h(-1), deactivation by carbon deposition, especially for an increase in AV, was observed thereafter However, the activity could be regenerated by a simple calcination with air.
Efficient cold-start process of hydrogen production by oxidative reforming (OR) of hydrocarbon was developed using Rh catalyst supported on carriers with redox properties. In this process, the heat generated by re-oxidation of reduced catalyst rapidly heats the catalyst from ambient temperature to the catalytic auto-ignition temperature of the OR. OR was triggered at ambient temperature over Rh/CeO2 after reduction at 873 K, but not over Rh catalysts supported on Pr6O11 and Tb4O7, oxides of rare earth elements with redox characters like cerium. Over the latter catalysts, reduction of the carrier occurred at lower temperatures than over CeO2, but the reduced oxides were not re-oxidized at ambient temperature. Our results emphasized that re-oxidation as well as reduction of the catalyst are the key characteristics of the carrier for triggering OR at ambient temperature. With the use of Rh/Ce0.5Zr0.5O2 with excellent redox properties at low temperature, triggering OR of hydrocarbons at ambient temperature was achieved even under non-adiabatic conditions, where heat losses occur, over the catalyst after reduction at 373 K and after in-situ reduction by hydrogen formed during the OR. This new catalytic process is expected to be useful for the development of self-sufficient reforming processes for a new generation of fuel cells.
Desulfurization of heavy oil using steam was examined by catalytic cracking of atmospheric residual oil (AR) with iron oxide-based catalyst. The yield of hydrogen sulfide increased with higher ratio of steam to feedstock, whereas hydrogen sulfide was little produced in AR cracking without steam. Sulfur concentration of oil decreased to half that of feedstock, and some sulfur compounds were deposited on the catalyst. Oxidative cracking of heavy oil using oxygen species derived from steam produced hydrogen species from steam, so part of the hydrogen species reacted with heavy sulfur compounds on the catalyst to produce hydrogen sulfide, light sulfur compounds, and hydrocarbons. Some oxygen species could be transferred to sulfur dioxide. Therefore, hydrogenation and oxidation by the hydrogen and oxygen species derived from steam can cause desulfurization of AR. Cyclic sulfur compounds containing a thiophene ring in heavy oil are less reactive than acyclic sulfur compounds, so the reactivity of cyclic sulfur compounds was examined by catalytic cracking of dibenzothiophene. Dibenzothiophene was decomposed with the catalyst to produce carbon dioxide and hydrogen sulfide. Therefore, both acyclic and cyclic sulfur compounds can be decomposed with the catalyst and steam.
