Hydrogenation and dehydrogenation on Pd- and Pt- catalysts are encountered in many industrial hydrocarbon processes. The present work considers the development of catalysts and their kinetic modeling along a general and rigorous approach. The first part deals with the kinetics of selective hydrogenation, more particularly of the C3 cut of a thermal cracking unit for olefins production. The kinetics of the gas phase selective hydrogenation of methyl-acetylene (MA) and propadiene (PD) over a Pd/γ-alumina catalyst were investigated in a fixed bed tubular reactor at temperatures 60 - 80 oC and a pressure of 20 bara. Hougen-Watson type kinetic equations were derived. The formation of higher oligomers slowly deactivated the catalyst. The effect of the deactivating agent on the rates of the main reactions as well as on the deactivating agent formation itself was expressed in terms of a deactivation function multiplying the corresponding rates at zero deactivation. Then, the kinetic model was plugged into the reactor model to simulate an industrial adiabatic reactor. In the second part the production of hydrogen from hydrocarbons was investigated. In both cyclohexane and decalin dehydrogenations, conversions higher than 98% could be obtained over Pt/γ-alumina catalyst at temperature of 320 and 340 oC, respectively, with no apparent deactivation for 30 h and with co-feed of H2 in the feed. Except for H2 and trace amounts of side cracking products, less than 0.01%, benzene was the only dehydrogenated product in cyclohexane dehydrogenation. In the case of decalin dehydrogenation, partially dehydrogenated product, tetralin, was also formed with selectivity lower than 5%, depending on operating conditions. A rigorous Hougen-Watson type kinetic model was derived, which accounted for both the dehydrogenation of cis- and trans- decalin in the feed and also the isomerization of the two isomers. Jet A is the logic fuel in the battlefields. The dehydrogenation of Jet A can produce H2 for military fuel cell application. Although the H2 production is lower than that of steam/autothermal reforming, it eliminates the needs of high temperature and product separation operation.

The hydrogenation of aromatic sulfonyl chloride to produce aromatic thiol is an important industrial reaction. The aromatic thiol is a critical intermediate in the production of many pharmaceuticals as well as several agrochemicals. Density Functional Theory (DFT), a quantum mechanical method, was used to investigate the new aromatic thiol production technology at the molecular level in aspects including reaction species adsorption and transition state determination. Plant design methods and economic analysis were performed to determine the economic feasibility of the new technology in the current specialty chemicals market. The quantum mechanical calculations showed that the molecules adsorbed to three simulated (100) Pd catalyst surfaces will preferentially move to configurations that are favorable for reaction progression. The calculations also show that the proposed reaction sequence by DuPont is the most feasible option despite the investigation into an alternative sequence that arose from molecular observations during calculations. Predicted activation energies (Ea) were in the range of 6.88 ? 38.1 kcal/mol which is comparable to the 14.58 kcal/mol determined experimentally by DuPont, and the differences between experimental and simulated values are easily explained. Plant design calculations show that a semi-batch reactor plant can easily produce 2MM lb of thiol/year, giving the owner of the plant an immediate 18% market share in the worldwide market of benzenethiol. Economic analysis shows that a grassroots plant construction is not currently an economically feasible option for corporate investment unless a source of cheap, skilled labor can be found in addition to a means of a 25% discount on certain raw material feed stocks. However, if both of these requirements can be fulfilled then new plant construction will have a payback time of 3.71 years based on the price of benzenethiol in the summer of 2007, $2.27/lb thiol.

This work presents a modeling and control study of a reactive distillation column used for hydrogenation of benzene. A steady state and a dynamic model have been developed to investigate control structures for the column. The most important aspects of this control problem are that the purity of the product streams regarding benzene need to be met. At the same time as little toluene as possible should be converted. The former is a constraint imposed by EPA regulations while the latter is tied to process economics due to the high octane number of toluene. It is required to satisfy both of these objectives even under the influence of disturbances, as the feed composition changes on a regular basis. The dynamic model is used for developing transfer function models of two potential control structures. Pairing of inputs and outputs is performed based upon the Relative Gain Array (RGA) and PI controllers were designed for each control structure. The controller performance was then compared in simulation studies. From our results, control structure 2 performed better than control structure 1. The main advantage of CS2 over CS1 is noticed in the simulation of feed composition disturbance rejection, where CS2 returns all variables back to steady state within 3 hrs while it take CS1 more than 20 hrs to return the temperature variables back to steady state.

Zeolite structure can profoundly promote the activity of supported platinum. In addition, catalytic performances of Pt/ZSM-12 catalysts vary dramatically with platinum deposition procedure, namely ion exchange (IE) and impregnation procedure (IMP). Supported platinum prepared by IMP is more active than the Pt prepared by IE. The MCP/MCH ratio in benzene hydrogenation as an indication of bifunctional catalysis is significantly higher for IE Pt than IMP Pt. IE preparing platinum is located inside ZSM-12 pore and IMP preparing platinum is deposited on the external surface of ZSM-12. After steam treatment, it is found that Pt-atom perfectly migrates from internal channel to external surface and agglomerates into larger particle size for Pt(IE,0.100%,c) and Pt(IMP,0.123,a) catalysts. In contrast to the results of pure benzene hydrogenation at lower temperature (210¢J/240¢J), they are found that if all prepared various Pt/ZSM-12 catalysts were above the inversion temperature (Ti) then the benzene hydrogenation conversion over Pt(IE,0.100%,c) sample is higher than over Pt(IMP,0.123%,a) sample owing to latter provides less Pt-H+ active sites, as well as Pt(IMP,0.123%,a) sample is the most effective catalyst for toluene disproportionation and transalkylation with 1,2,4-trimethylbenzene. Owing to transformation generally is performed at higher temperature, such as above 400¢J, their operation temperatures are indeed above the inversion temperature (Ti) for all Pt/ZSM-12 catalysts. In situ comparing their benzene hydrogenation in transformation, including disproportionation and transalkylation, is suitable and valuable for understanding and determinating the characteristics of Pt/ZSM-12 zeolite catalysts. Relative conversion of benzene hydrogenation in transformation is the probe of characterizing the Pt-location onto ZSM-12 zeolite.

Dynamic models of a reactive distillation column have been developed and implemented in this work. A model describing the steady state behavior of the system has been built in a first step. The results from this steady state model have been compared to data provided from an industrial collaborator and the reconciled model formed the basis for the development of a dynamic model. Four controlled and four manipulated variables have been determined in a subsequent step and step tests for the manipulated variables were simulated. The data generated by the step responses was used for fitting transfer functions between the manipulated and the controlled variables. RGA analysis was performed to find the optimal pairing for controller design. Feedback controllers of PID type were designed between the paired variables found from RGA and the controllers were implemented on the column model. Both servo and regulatory problems have been considered and tested.

Halogenated hydrophobic organic compounds (HHOCs) such as 1,2,4,5-tetrachlorobenzene (TeCB) present a threat to both human health and the environment. The common occurrence and recalcitrant nature of HHOCs as soil contaminants necessitate an effective soil remediation method. Wee and Cunningham (2008, 2011, 2013) proposed a clean-up technology called Remedial Extraction and Catalytic Hydrodehalogenation (REACH), which pairs solvent extraction of HHOC contaminants from soil with catalytic hydrodehalogenation to destroy contaminants. Wee and Cunningham (2008, 2011, 2013) utilized a palladium (Pd) catalyst to hydrodehalogenate TeCB to benzene. However, benzene is still a toxic contaminant. Prior research has demonstrated that Pd-catalyzed hydrodehalogenation (HDH) can be paired with Rh-catalyzed hydrogenation to transform TeCB to cyclohexane, which is a less toxic end product (Osborn 2011; Ticknor 2012). However, there remains a need to quantify the effects of different operating conditions on the catalytic reaction rates upon which the technology relies. It was hypothesized that (1) an increased ratio of water to ethanol in water/ethanol solvents would increase the reaction rates of both Pd-catalyzed HDH and Rh-catalyzed hydrogenation, and (2) catalytic reaction rates would be constant above a hydrogen pressure threshold, but would decrease with decreasing hydrogen pressure beneath the threshold. Thus, the objective of this thesis was to contribute to the development of optimal operating parameters for the REACH technology by quantifying the effects of solvent composition and hydrogen pressure on the catalytic conversion of TeCB to cyclohexane in water/ethanol solvents in a batch reactor. Complete conversion of TeCB to cyclohexane was achieved at all experimental conditions tested. The data were consistent with an apparent first-order kinetics model where Pd-catalyzed HDH and Rh-catalyzed hydrogenation occur in series. The effects of three water/ethanol solvent compositions (33:67, 50:50, 67:33) were investigated at 50 psi hydrogen pressure. HDH rate coefficients increased monotonically with an increasing fraction of water in the solvent. When the water fraction in the solvent was increased from 50% to 67%, a larger HDH rate coefficient increase was observed than when the water fraction was increased from 33% to 50%. In both cases, the observed increases were statistically significant at a 95% confidence level. For hydrogenation, rate coefficients at 33% and 50% water were approximately equal. The hydrogenation rate coefficient at 67% water was much greater than the rate coefficients at 50% and 33% water, but the increase was not statistically significant at a 95% confidence level. The observed time for complete conversion of TeCB to cyclohexane decreased with an increasing fraction of water in the solvent, from 12-18 hours with a 33% water solvent to 8-12 hours with a 50% water solvent, and to 1-1.5 hours with a 67% water solvent. The effects of three hydrogen pressures (50 psi, 30 psi, 10 psi) were investigated with a 50:50 water/ethanol solvent. HDH rate coefficients increased monotonically with decreasing hydrogen pressure, though the trend was not statistically significant at a 95% confidence level until the pressure was decreased from 30 psi to 10 psi. This trend can be attributed to the displacement of TeCB by hydrogen on the catalyst surface at higher hydrogen pressures. For hydrogenation, the data suggest that rate coefficients are independent of hydrogen pressure in the pressure range of 10-50 psi, since no statistically significant hydrogen pressure effect was observed. Complete conversion of TeCB to cyclohexane was achieved at hydrogen pressures as low as 5 psi. These findings suggest that a greater fraction of water in the solvent should be utilized in the REACH system when feasible to maximize catalytic reaction rates. These findings also suggest that the REACH system could be operated at hydrogen pressures as low as 5 psi, which would further improve the safety of the technology.

Carbon-carbon bond forming reactions are vital to the synthesis of natural products and pharmaceuticals. In 2003, the 200 best selling prescription drugs reported in Med Ad News are all organic compounds. Synthesizing these compounds involves many carbon-carbon bond forming processes, which are not trivial and typically generate large amounts of waste byproducts. Thus, development of an atom economical and environmentally benign carbon-carbon bond forming methodology is highly desirable. Hydrogenation is one of the most powerful catalytic reactions and has been utilized extensively in industry. Although carbon-carbon bond forming reactions under hydrogenation conditions, such as, alkene hydroformylation and the Fischer-Tropsch reaction are known, they are limited to the coupling of unsaturated hydrocarbons to carbon monoxide. Recently, a breakthrough was made by the Krische group, who demonstrated that catalytic hydrogenative C-C bond forming reactions can be extended to the coupling partners other than carbon monoxide. This discovery has led to the development of a new class of carbon-carbon bond forming reactions. Herein, an overview of transition metal-catalyzed reductive couplings of [pi]-unsaturated systems employing various external reductants is summarized in Chapter 1. Chapters 2-4 describe a series of rhodium- and iridium-catalyzed asymmetric hydrogenative couplings of various alkynes to a wide range of imines and carbonyl compounds. These byproduct-free transformations provide a variety of optically enriched allylic amines and allylic alcohols, which are found in numerous natural products, and are used as versatile precursors for the synthesis of many biologically active compounds. Transfer hydrogenation represents another important class of reactions in organic chemistry. This process employs hydrogen sources other than gaseous dihydrogen, such as isopropanol. The Krische group succeeded in developing a new family of transfer hydrogenative carbon-carbon bond formation reactions. Chapter 5 presents two novel ruthenium- and iridium-catalyzed transfer hydrogenative carbonyl allylation reactions. The catalytic system employing iridium complexes enables highly enantioselective carbonyl allylation from both the alcohol and aldehyde oxidation level. These systems define a departure from the use of preformed organometallic reagents in carbonyl additions that transcends the boundaries of oxidation level. / text

Carbon-carbon bond forming reactions are fundamental transformations for constructing structurally complex organic building blocks, especially in the realm of natural products synthesis. Classical protocols for forming a C-C bond typically require the use of stoichiometrically preformed organometallic reagents, constituting a major drawback for organic synthesis on process scale. Since the emergence of transition metal catalysis in hydrogenation and hydrogenative C-C coupling reactions, atom and step economy have become important considerations in the development of sustainable methods. In the Krische laboratory, our goal is to utilize abundant, renewable feedstocks, so that the reactions can proceed in an efficient and atom-economical manner. Our research focuses on developing new C-C bond forming protocols that transcend the use of stoichiometric, preformed organometallic reagents, in which [pi]-unsaturates can be employed as surrogates to discrete premetallated reagents. Under transition metal catalyzed transfer hydrogenation conditions, alcohols can engage in C-C coupling, avoiding unnecessary redox manipulations prior to carbonyl addition. Stereoselective variants of these reactions are also under extensive investigation to effect stereo-induction by way of chiral motifs found in ligands and counterions. The research presented in this dissertation represents the development of a new class of C-C bond forming transformations useful for constructing synthetic challenging molecules. Development of transfer hydrogenative C-C bond forming reactions in the form of carbonyl additions such as carbonyl allylation, carbonyl propargylation, carbonyl vinylation etc. are discussed in detail. Additionally, these methods avoid the use of stoichiometric chiral allenylmetal, propargylmetal or vinylmetal reagents, respectively, accessing diastereo- and enantioenriched products of carbonyl additions in the absence of stoichiometric organometallic byproducts. By exploiting the atom-economical transfer hydrogenative carbonyl addition protocols using ruthenium and iridium, preparations of important structural motifs that are abundant in natural products, such as allylic alcohols, homoallylic alcohols and homopropargylic alcohols, become more feasible and accessible. / text

Ansamycin natural products have historically been a rich source of new drugs for the treatment of bacterial infections and cancer. The C17-benzene ansamycins in particular have shown excellent preclinical results as potential anti-fungal and anti-cancer medicines. However, their thorough clinical evaluation has been hampered by the absence of a concise synthetic strategy. In order to address this issue, recently developed hydrogenative carbon-carbon bond forming methods were applied toward a short total synthesis of C17-benzene ansamycins. This class of natural products provides a challenging testing ground for these methods while facilitating the further development of compounds which may be used as treatments for life threatening diseases. In the first synthetic approach to the C17-benzene ansamycins key bond formations include direct iridium catalyzed carbonyl crotylation from the alcohol oxidation level followed by chelation-controlled dienylation to form the stereotriad, which is attached to the arene via Suzuki cross-coupling. The diene-containing carboxylic acid is prepared using rhodium catalyzed acetylene-aldehyde reductive C-C coupling mediated by gaseous hydrogen. Finally, ring-closing metathesis delivers the cytotrienin core. The second approach toward triene-containing C17-benzene ansamycins resulted in the syntheses of trienomycins A and F, which were prepared in 16 steps (longest linear sequence) and 28 total steps. The C11-C13 stereotriad was generated via enantioselective ruthenium-catalyzed alcohol CH syn crotylation followed by chelation-controlled carbonyl dienylation. Finally, diene-diene ring closing metathesis to form the macrocycle. The present approach is 14 steps shorter (LLS) than the prior syntheses of trienomycins A and F, and eight steps shorter than any prior synthesis of a triene-containing C17-benzene ansamycin. / text

A central tenant of organic synthesis is the construction of carbon-carbon bonds. One of the traditional methods for carrying out such transformations is that of carbonyl addition. Unfortunately, traditional carbonyl addition chemistry suffers various drawbacks: preactivation, moisture sensitivity, and the generation of stoichiometric organometallic waste. The research presented in this dissertation focuses on the development of methods that make use of nucleophile-electrophile pairs generated in situ via transfer hydrogenation, which allow the formation of carbonyl or imine addition products from the alcohol or amine oxidation level; streamlining the construction of complex molecules from simple, readily available starting materials. Additionally, studies toward the total synthesis of the fibrinogen receptor inhibitor tetrafibricin, utilizing the methods developed in catalytic carbon-carbon bond formation through the addition, transfer or removal of hydrogen, are presented. / text