Book Description

In attempts to address the threats of climate change, countries are making efforts to mitigate their emissions of greenhouse gases like carbon dioxide (CO2). The transition from economies driven by energy and chemicals derived from fossil fuel feedstocks to cleaner alternative fuels and technologies are met with great challenges. In the field of fuel and chemical production specifically, the transformation of carbon monoxide (CO) and CO2, produced through alternative technologies, to value added chemical products require catalysts that are active, selective, and stable. Current research efforts have focused on heavy characterization of catalysts in attempts of establishing a structure-activity correlation to help design and engineer the catalyst of the future. This thesis will focus on the design and characterization of two supported transition metal phosphide (TMP) catalysts, molybdenum phosphide (MoP) and ruthenium phosphide (RuP), and a bimetallic nickel iron (NiFe) catalyst. The first TMP, MoP, was specifically designed and optimized for the higher alcohol synthesis (HAS) reaction from synthesis gas (syngas) (CO/H2). Higher alcohols are defined as an alcohol group containing two or more carbon atoms., like ethanol. Through a systematic design approach, the optimal amount of potassium (K) promoter, P and Mo was determined and synthesized on three different supports: amorphous silica (SiO2), ordered silica (SBA-15), and mesoporous carbon (C). The different combinations led to contrasting catalytic performance with respect the HAS activity. The second TMP, RuP, was designed and optimized for the methanol synthesis (MS) reaction. Ru catalysts are known as Fischer-Tropsch synthesis (FTS) catalysts as they selectively produce hydrocarbons. This study was able to change the intrinsic catalytic nature of Ru through addition of P. Catalytic results showed that the presence of P transformed the Ru FTS catalyst to a MS catalyst. The NiFe catalyst was tested for the ethane dehydrogenation reaction, in which the essential feedstock chemical ethylene is produced. This catalyst was tested for direct ethane dehydrogenation, in which only ethane is fed to the reactor along with H2 to mitigate coking, and oxidative ethane dehydrogenation, where CO2 is fed to promote the reacting and mitigate coking. The catalysts were also synthesized on two different supports, SiO2 and C, to quantify support effects. The overall goal of these studies was to determine the influence that addition of promoters, like K, phosphides, and secondary metals have on catalytic properties and how we might use that to design catalysts with improved activity, selectivity, and stability.