Quantitative cradle-to-gate environmental impacts for ethylene production from naphtha (petroleum crude), ethane (natural gas) and ethanol (corn-based) are predicted using GaBi Ò software. A comparison reveals that the majority of the predicted environmental impacts for these feedstocks fall within the same order of magnitude. Soil and water pollution associated with corn-based ethylene are however much higher. The main causative factor for greenhouse gas emissions, acidification and air pollution is the burning of fossil-based fuel for agricultural operations, production of fertilizers and pesticides needed for cultivation (in the case of ethanol), ocean-based transportation (for naphtha) and the chemical processing steps (for all feedstocks). An assessment of the environmental impacts of different energy sources (coal, natural gas and fuel oil) reveals almost similar carbon footprints for all the fossil fuels used to produce a given quantity of energy. For most of the environmental impact categories, the GaBi Ò software reliably predicts the qualitative trends. The predicted emissions agree well with the actual emissions data reported by a coal-based power plant (Lawrence Energy Center, Lawrence, KS) and a natural gas-based power plant (Astoria Generating Station, Queens, NY) to the United States Environmental Protection Agency. The analysis shows that for ethylene production, fuel burning at the power plant to produce energy is by far the dominant source (78-93 % depending on the fuel source) of adverse environmental impacts.

Significant ethylene epoxidation activity was observed over Nb-and W-incorporated KIT-6 materials with aqueous hydrogen peroxide (H 2 O 2 ) as the oxidant and methanol as solvent under mild operating conditions (35°C and 50 bar) where CO 2 formation is avoided. The Nb-KIT-6 materials generally show greater epoxidation activity compared to the W-KIT-6 materials. Further, the ethylene oxide (EO) productivity observed with these materials [30-800 mg EO h −1 (g metal)] is of the same order of magnitude as that of the conventional silver (Ag)-based gas phase ethylene epoxidation process. Our results reveal that the framework-incorporated metal species, rather than the extra-framework metal oxide species, are mainly responsible for the observed epoxidation activity. However, the tetrahedrally coordinated framework metal species also introduce Lewis acidity that promotes their solvolysis (which in turn results in their gradual leaching) as well as H 2 O 2 decomposition. These results and mechanistic insights provide rational guidance for developing catalysts with improved leaching resistance and minimal H 2 O 2 decomposition.

An ethylene epoxidation process concept that employs methyltrioxorhenium (MTO) as catalyst and H 2 O 2 as oxidant and selectively produces EO (with no CO 2 as byproduct) has been demonstrated recently by researchers at the University of Kansas Center for Environmentally Beneficial Catalysis (CEBC). On the basis of a plant-scale simulation of the CEBC process using Aspen HYSYS, preliminary economic and environmental assessments of the process are performed, both of which are benchmarked against the conventional silver-catalyzed ethylene epoxidation process. The capital costs for both processes lie within prediction uncertainty. The EO production cost for the conventional process is estimated to be 58 ¢/lb EO.The CEBC process has the potential to be competitive with the conventional process if the MTO catalyst remains active, selective and stable for at least one year at a leaching rate of approximately 0.11 lb MTO/h (or 0.7 ppm Re in the reactor effluent). While CO 2 emissions as byproduct are eliminated in the CEBC process, comparative cradle-to-gate life cycle assessments (LCA) reveal that the quantitative overall environmental impacts on air quality, water quality, and greenhouse gas emissions are similar for both processes and lie within the uncertainties of such predictions. The LCA results point to sources outside the EO production plants as the major contributors to potential environmental impacts: natural gas-based energy required for raw material production (ethylene in both processes and hydrogen peroxide in the CEBC process) and to the significant requirements of coal-based electrical power for compressing large volumes of recycled ethylene and diluent gases in the conventional process. H 2 O 2 production via a highly selective direct synthesis route and effective H 2 O 2 utilization/recycle (without decomposing it) will further reduce the environmental footprint of the CEBC-EO process.

in Wiley Online Library (wileyonlinelibrary.com).Recently a homogeneous liquid-phase ethylene oxide (EO) process with nearly total EO selectivity, catalyzed by methyltrioxorhenium with H 2 O 2 as an oxidant, was reported. Fundamental mass transfer and kinetic studies of this reaction are reported in the present work. Volumetric expansion studies revealed that the liquid reaction phase (methanol þ H 2 O 2 / H 2 O) is expanded by up to 12% by compressed ethylene in the 20-40 C range and up to 50 bars. This represents an increase in ethylene solubility by approximately one-order of magnitude, attributed to the unique exploitation of nearcritical ethylene (P c ¼ 50.76 bar; T c ¼ 9.5 C). Interphase mass-transfer coefficients for ethylene dissolution into the liquid phase were obtained experimentally. Operating at conditions that enhanced the ethylene solubility and eliminated interphase mass-transfer limitations maximized the EO productivity (1.61-4.97 g EO/h/g cat), rendering it comparable to the conventional process. Intrinsic kinetic parameters, estimated from fixed-time semibatch reactor studies, disclosed the moderate activation energy (57 AE 2 kJ/mol). (a) Ethanol þ methanol binary system; (b) (ethylene þ methanol þ 50 wt % H 2 O 2 /H 2 O) ternary system. Initial composition of liquid phase ¼ 0.748 mol methanol þ 0.134 mol H 2 O 2 þ 0.253 mol H 2 O. Initial volume of liquid phase ¼ 15 mL. The size of the plotted data points represents the experimental uncertainty. Ethylene P ¼ 50 bars; T ¼ 40 C; MTO amount ¼ 0.361 mmol; methanol ¼ 0.748 mol; H 2 O 2 ¼ 0.116 mol; H 2 O ¼ 0.220 mol; acetonitrile ¼ 0.0191 mol; pyridine N-oxide ¼ 2.19 mmol; batch time ¼ 5 h; agitation speed (Ä : 1,200 rpm, h: 400 rpm).