Study on Modification and Sulfur-Resistance Characteristics of Dolomite Catalysts over Wash Oil Catalytic Cracking

Abstract

The 0.5% Ni/1% Fe−dolomite catalyst and 1% Fe−dolomite catalyst were used to explore the wash oil catalytic cracking process on a fixedbed reactor. The experimental results were evaluated by yield distributions of gas, liquid, and solid phases; gas composition distributions; and component varieties of cracked oil. Catalysts were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TG), and an automatic sulfur analyzer. Cracked oil was analyzed by gas chromatography−mass spectrometry (GC−MS). XRD analyses revealed that fresh 0.5% Ni/1% Fe−dolomite catalyst had Ni−Fe and NiO crystal phases, while the used catalyst had CaS and NiS phases when there were sulfur-containing compounds with simple structures in the wash oil. TG results showed that H 2 S contributed to the heavy aromatics adsorption on catalyst, and aggravated carbon deposition. GC−MS showed that cracked oil become lighter as a result of acenaphthene cracking into alkanes, biphenylene, and pyrolysis gas. In addition, catalytic cracking of sulfur-containing compounds did not affect the contents of other liquid components.

Catalytic Cracking of Biomass-Derived Hydrocarbon Tars or Model Compounds To Form Biobased Benzene, Toluene, and Xylene Isomer Mixtures

“…Many research groups have extensively studied dolomites because of its highly effective tar conversion. ,− Corella et al showed that tar content at the gasifier outlet was approximately 40% lower using dolomite compared to natural olivine. Moreover, dolomite was 1.4 times more active than olivine in biomass gasification with air but at the same time dolomite generates 4–6 times more particulates as well as more NH 3 in the product compared to olivine.…”

“…Boot-Handford and co-authors observed that calcined dolomite was slightly more effective in biomass-derived tar cracking than calcined limestone, converting 98 wt% of the tar at 900 °C. Recently, Yu and co-workers compared 0.5% Ni–1% Fe–dolomite and 1% Fe–dolomite catalyst for the wash-oil catalytic cracking process in a fixed-bed reactor. It was found that 0.5% Ni–1% Fe–dolomite sample exhibited better catalytic activity in the decomposition of aromatic hydrocarbon than 1% Fe-dolomite catalyst sample.…”

“…21 The diagram in Figure 3 shows that the biomass tar is diverse and complicated, containing more than 10 000 various organic compounds, such as oxygen-containing hydrocarbons, aromatic compounds, sulfur-containing hydrocarbons, and polynuclear aromatic hydrocarbons (PAHs), where is the latter are environmental hazards with carcinogenic character. 10,20,22,23 The formation of tar during gasification processes can cause serious issues for the gasifier and the operation of downstream processes facilities, such as blocking of pipes, cracking of pipes in the filter pores, forming coke and plugging the pipes, condensing on the surface of filters, pumps, and heat exchangers, corroding the surface of the pipes, and consequently reducing the gasification efficiency. 10,20,22,24 There are several methods to remove tar from the syngas such as physical treatment, thermal cracking, plasma-assisted cracking, and catalytic cracking.…”

Cracking of Scrap Tires Pyrolysis Oil in a Fluidized Bed Reactor under Catalytic Cracking Unit Conditions. Effects of Operating Conditions

“…Although desulfurization is not the main goal of the catalytic cracking, during the process, at least half of the sulfur contained in the FCC regular feedstock turns into hydrogen sulfide (H 2 S), and the sulfur compounds that remain in the liquid products are lighter than the starting ones and can be easily removed in a subsequent hydroprocessing stage. 55 The sulfur distribution among the products depends mainly on the kind of feedstock, catalyst, conversion, and operating conditions, in particular, the contact time. 56 Even in the usual feedstocks of the FCC unit, the investigated STPO contains 11 600 ppm of sulfur in the form of organic compounds (Table 1), such as mercaptans, sulfides, and, the most common ones in our feed, benzothiazoles and dibenzothiophenes.…”

Catalytic Upgrading of Coal Pyrolysis Gaseous Tar over Hierarchical Y-Type Zeolites Synthesized Using a Microwave Hydrothermal Method

“…This not only causes waste of resources, but also leads to environmental pollution . The catalytic cracking of gaseous tar before its condensation is an important way to convert it into high value-added products. − Y-type zeolites are solid acid catalysts with three-dimensional porous structure and adjustable acidity, and shows good catalytic effect for the upgrading of coal tar. − Majka et al used different catalysts to catalyze the hydrocracking of coal tar and found that Y-type zeolites showed better catalytic performance. Yan et al used two different zeolites to upgrade the coal pyrolysis gaseous tar, and found that ultra-stable Y-type zeolites could considerably improve the yield of light aromatics, whereas Al/SBA-15 has little effect on the conversion of gaseous tar.…”