Conversion of Polyethylene into Transportation Fuels by the Combination of Thermal Cracking and Catalytic Hydroreforming over Ni-Supported Hierarchical Beta Zeolite

Abstract

The oil obtained from the thermal cracking of low-density polyethylene (LDPE) is formed mainly by linear hydrocarbons with a high quantity of olefins, which hinders the possible application of this product in the formulation of transportation fuels. However, hydroreforming of this oil using bifunctional catalysts with high accessibility to the active sites would allow for the properties of the gasoline and diesel fractions to be significantly upgraded. This is the case of the catalyst employed here because it consists of hierarchical Beta zeolite (with a bimodal micro-mesoporosity) and containing 7 wt % Ni. The presence of nickel in the catalyst increased the share of gasolines with regard to the h-Beta support. The effect of the main variables involved in the hydroreforming process has been investigated and optimized, showing that the extent of hydrocracking is favored when increasing the temperature, the pressure, and the catalyst/feed ratio, leading to enhanced gasoline yields at the expense of heavy (C 19 −C 40 ) and especially light (C 13 −C 18 ) diesel fractions because of the faster diffusion of the latter. Ni/h-Beta proved to be an especially adequate catalyst for obtaining gasolines; therefore, a maximum in the selectivity toward gasoline (up to 68.7%) was found in the hydroreforming at 40 bar of hydrogen pressure. On the other hand, the values of the bromine index indicated that 80−100% of the olefins present in the raw oil were hydrogenated depending upon the reaction conditions. In addition, the Ni/h-Beta catalyst showed high activity for aromatization and, especially, hydroisomerization reactions. Thus, a 53% share of isoparaffins in the gasolines was obtained at long reaction times. The gasoline and diesel fractions obtained showed a high research octane number (RON) (>80) and cetane indexes above specifications (>70), respectively, which is indicative of their high quality as transportation fuels.

Production of aromatic compounds from catalytic fast pyrolysis of Jatropha residues using metal/HZSM-5 prepared by ion-exchange and impregnation methods

“…The addition of metal improved the formation of benzene, toluene, and napthalenes. The aromatic compounds produced during catalytic run were in the range of gasoline (C 5 eC 12 ) [46]. Therefore, these aromatics could improve heating value in bio-oil.…”

Thermally stable phosphorus and nickel modified ZSM-5 zeolites for catalytic co-pyrolysis of biomass and plastics

“…39,52 To get more information on the acidity changes, pyridine adsorption was conducted to quantify the Brönsted and Lewis acid sties on the zeolites. 39,40,52 3.2. In contrast, the Lewis acid sites on the zeolites increased signicantly aer P and especially Ni impregnation (see Table 1).…”

Hydroreforming of the oils from LDPE thermal cracking over Ni–Ru and Ru supported over hierarchical Beta zeolite

“…and it has been found that Ni/hierarchical Beta zeolite (Ni/h-Beta) provides a high selectivity to the desired products, gasoline and automotive diesel (55% and 27%, respectively) [14]. These results were ascribed to the bimodal microporous/mesoporous pore structure of the hierarchical Beta zeolite, which allows a better accessibility of the reagents toward the acid sites as well as an improved dispersion of the nickel active phase.…”