Sustainable development in chemical engineering offers technical, industrially relevant solutions to environmental and economic issues. This work focuses on three specific issues; improving solvent selection and reducing costly experimentation, improving catalyst recovery while reducing reaction time, and producing commercial viable biofuels by cost effective pretreatments and valuable side product extractions. Novel solvent systems are a sustainable solution because they provide the ability to replace costly solvents with cheap, benign, and recyclable systems. Specifically, this work investigated the use of one novel solvent system, Gas Expanded Liquids (GXL).When a solvent is exposed to a gas in which it is miscible at modest pressures and temperatures, the liquid solvent becomes expanded, providing a unique tunable and reversible solvent with properties that can be much different then that of the solvent itself. If you apply this gas to a mixture of two liquids of a solid dissolved in a liquid phase, it can often provide a miscibility switch, aiding in separation, crystallization, and recovery of products or catalysts. In this work several different applications for organic solvents expanded with carbon dioxide were studied including miscibility switches for catalyst recycle, pretreatment of biomass for improved bio-ethanol production, and extraction of valuable chemicals from lignin waste in the pulp and paper industry. Solid solubility models to improve solvent selection and predict unique solvent mixtures during crystallization were also studied. The results reported here show promise for the use of GXL novel solvent systems and solid solubility models in many sustainable applications.

Attaching soft long side chain on conjugated polymers will form liguid cystal structure. Our research is to synthesis the polypyrrole with alkyl chains on nitrogen site and carbon site and observe the effects. We observe the phase transition by X-ray and DSC. But it is hrad to observe because of its absorbing light. Between observing, we just can find the liguid crystal transition on the polypyrrole with octadecane alkyl side chain on nitrogen site. Besides, we can find the 2.8Å and 3.2Å peaks By shearing and solvent casting. Such a phenomenon is common in conjugated polymers. But it is hard to explain. Besides, substituted on different sites will bring different results. Substituted on nitrogen site will lead to bigger d-sapcing than substituted on carbon site. This is because of the difference on co-planity. By the correlation function, we can realize that longer side chain, bigger fluctuation, but better layer structures.

No description available.

In this research,we observed PAMA(poly(n-alkyl methacrylate)) and PAA(poly(n-alkyl acrylate)¡^side chain crystalline.We find side chain is longer and crystalize more easily,melting point is higher.In the result of DSC thermograms,the length of side chain is 6 carbons,we can't find any thermal transition.But the length of side chain is 12¡B18 carbons,we only found Tm.In PLM observation,we only get side chain crystalline's picture,and can't see any liquid crystalline yet. Although in X-ray's illustrative can find layer structure's diffraction peak,but i think this evidence can't prove the system that is liquid crystalline.It just can be said that the layed structure was formed by side chain crystallization.

No description available.

<p> Self-consistent field theory (SCFT) is a well established theoretical framework for describing the thermodynamics of block copolymer melts and blends. Combined with numerical methods, the SCFT can give useful and accurate predictions regarding the phase behavior of polymer blends. </p> <p> We have applied SCFT to study the phase behavior of blends composed of diblock copolymers (AB) and homopolymers (C). Two cases are studied in detail. In the first case the homopolymers have a repulsive interaction to the diblock copolymers. We found an interesting feature in the phase diagram that there exists a bump of the phase boundary line when A is the majority-component. In the second case, the homopolymers have an attractive interaction to one of the blocks of the diblock copolymers. A closed-loop of microphase separation region forms for strong interactions. For both cases, we have investigated the effects of homopolymer concentration, homopolymer chain length, and monomer-monomer interactions, on the phase behavior of the system. </p> <p> We also investigated micelle formation in polymer blends. Diblock copolymers (AB) blended with homopolymers (A) can self-assemble into lamellar, cylindrical and spherical micelles. The critical micelle concentrations for different geometries are determined using self-consistent field theory. The effect of varying copolymer block asymmetry, homopolymer molecular weight and monomer-monomer interactions on micelle morphology are examined. \\Then the blends are confined between two flat surfaces, the shape of the micelles may differ from that of the bulk micelles. We study the shape variation of a. spherical micelle under confinement and its dependence on the film thickness and surface selectivity. </p> / Thesis / Doctor of Philosophy (PhD)

This thesis is an experimental investigation of phase behavior, crystallization, gelation and phase separation kinetics of polymer solutions in dense fluids at high pressures. The miscibility and dynamics of phase separation were investigated in solutions of atactic polystyrene with low polydispersity (Mw = 129,200; PDI = 1.02) in acetone. Controlled pressure quench experiments were conducted at different polymer concentrations to determine both the binodal and the spinodal envelops using time- and angle resolved light scattering techniques. At each concentration, a series of rapid pressure quenches with different penetration depths in a range from 0.1 MPa to 3 MPa were imposed and the time evolution of the angular distribution of the scattered light intensities was monitored. The solution with 11.4 wt % polymer concentration underwent phase separation by spinodal decomposition mechanism for both shallow and deep quenches. Below this critical polymer concentration, phase separation was found to proceed by nucleation and growth mechanism for shallow quenches, but by spinodal decomposition for deeper quenches. Gelation and crystallization processes and the influence of pressure and the fluid [Cho et al. 1993]composition were investigated in solutions of poly(4-methyl-1-pentene) [P4MP1] in n-pentane + CO₂ and in solutions of syndiotactic polystyrene [sPS] in toluene + CO₂, and also in acetophenone + CO₂ fluid mixtures over a pressure range up to 55 MPa and carbon dioxide levels up to 50 wt %. In pure pentane, P4MP1 undergoes crystallization and leads to Form III polymorph at low pressures, but to Form II at high pressures. In n-pentane + CO₂ mixture fluids, the polymorphic state changes from a mixture of Forms III and II to Form II and eventually to Form I with increasing CO₂ content. High level of carbon dioxide (≥40 wt %) in the solution was found to lead to gelation instead of crystallization. No liquid-liquid phase boundaries could be observed in any of the P4MP1 solutions. In contrast to P4MP1 in n-pentane, syndiotactic polystyrene was found to undergo gelation in toluene or acetophenone forming a polymer-solvent compound with the δ crystal form. Also in contrast to P4MP1 systems, addition of carbon dioxide to sPS solutions alters the process from that of gelation to crystallization leading to the β crystal form. In solutions with high CO₂ level, in addition to the gelation or crystallization boundaries, a liquid-liquid phase separation boundary was also observed. The phase separation path followed was found to influence the eventual morphology and the crystal state of the polymer. In sPS solutions in toluene + CO₂, if the sol-gel boundary were crossed first by cooling the solution at a fixed pressure, the resulting morphology was found to be fibrillar and the polymer displayed the δ crystal form. If instead, the liquid—liquid phase boundary were crossed first by reducing pressure at a fixed temperature, the polymer-rich phase leads to a stacked-lamellar morphology with the β crystal form while the polymer-lean phase leads to a mixed morphology with lamellar layers connected by fibrils with the polymer displaying δ + β crystal forms. In solutions in acetophenone + carbon dioxide, when the gelation boundary is crossed first, the resulting structure is the δ form as in the toluene + CO₂ case. At comparable CO₂ levels, when the L-L phase boundary is crossed first, in the acetophenone system, polymer-rich phase was found to generate a mixture of δ + β forms while only the δ form was found in the polymer-lean phase, in contrast to the observations in the toluene + CO₂ systems. Based on crystallographic, spectral and microscopic data, a thermodynamic framework was developed which provides a mechanistic account for the formation of the different polymorphs. / Ph. D.

The depletion of oil reserves and higher oil prices has made chemical enhanced oil recovery (EOR) methods more attractive in recent years. Because of geological heterogeneity, unfavorable mobility ratio, and capillary forces, conventional oil recovery (including water flooding) leaves behind much oil in reservoir, often as much as 70% OOIP (original oil in place). Surfactant/polymer flooding targets these bypassed oil left after waterflood by reducing water mobility and oil/water interfacial tension. The complexity and uncertainty of reservoir characterization make the design and implementation of a robust and effective surfactant/polymer flooding to be quite challenging. Accurate numerical simulation prior to the field surfactant/polymer flooding is essential for a successful design and implementation of surfactant/polymer flooding. A recently developed unified polymer viscosity model was implemented into our existing polymer module within our in-house reservoir simulator, the Implicit Parallel Accurate Reservoir Simulator (IPARS). The new viscosity model is capable of simulating not only the Newtonian and shear-thinning rheology of polymer solution but also the shear-thickening behavior, which may occur near the wellbore with high injection rates when high molecular weight Partially Hydrolyzed Acrylamide (HPAM) polymers are injected. We have added a full capability of surfactant/polymer flooding to TRCHEM module of IPARS using a simplified but mechanistic and user-friendly approach for modeling surfactant/water/oil phase behavior. The features of surfactant module include: 1) surfactant component transport in porous media; 2) surfactant adsorption on the rock; 3) surfactant/oil/water phase behavior transitioned with salinity of Type II(-), Type III, and Type II(+) phase behaviors; 4) compositional microemulsion phase viscosity correlation and 5) relative permeabilities based on the trapping number. With the parallel capability of IPARS, commercial scale simulation of surfactant/polymer flooding becomes practical and affordable. Several numerical examples are presented in this dissertation. The results of surfactant/polymer flood are verified by comparing with the results obtained from UTCHEM, a three-dimensional chemical flood simulator developed at the University of Texas at Austin. The parallel capability and scalability are also demonstrated. / text

Reservoir pressure and solution gas can significantly alter the microemulsion phase behavior and the design of a surfactant-polymer flood. This dissertation shows how to predict changes in microemulsion phase behavior from dead oil at atmospheric pressure to live crude at reservoir pressure. Our method requires obtaining only a few glass pipette measurements of microemulsion phase behavior at atmospheric pressure. The key finding is that at reservoir pressure the optimum solubilization ratio and the logarithm of optimal salinity behave linearly with equivalent alkane carbon number (EACN). These trends are predicted from the experimental data at atmospheric pressure based on density calculations of pure components using the Peng-Robinson equation-of-state (PREOS). We show that predictions of the optimum conditions for live oil are in good agreement with the few experimental measurements that are available in the literature. We also present new measurements at atmospheric pressure to verify the established trends. The experiments show that while pressure induces a phase transition from upper microemulsion (Winsor Type II+) to lower microemulsion (Winsor Type II-), solution gas does the opposite. An increase in pressure decreases the optimum solubilization ratio and shifts the optimum salinity to a larger value. Adding methane to dead oil at constant pressure does the reverse. Thus, these effects are coupled and both must be taken into account. We show using a numerical simulator that these changes in the optimum conditions can impact oil recovery if not accounted for in the SP design. / text

This Thesis presents the results of phase behavior calculations and simulation of asphaltene precipitation, flocculation, and deposition in five Middle-Eastern wells from different fields, based on a reliable experimental data provided for this purpose. The asphaltene precipitation, flocculation, and deposition have been simulated throughout the primary (pressure depletion), secondary (Waterflooding) and tertiary recovery (CO₂ injection) stages. Asphaltene precipitation becomes a serious problem especially when it causes plugging of the formation, wellbore, or production facilities, which will significantly affect the productivity and final recovery of the area. To help preventing asphaltene precipitation a bottomhole pressure higher than the asphaltene onset pressure (AOP) has been applied. Also, water and CO₂ injection has provided enough support for pressure maintenance, which helps in preventing asphaltene. Several scenarios were tested to investigate and identify the cases with lowest asphaltene precipitation and higher recovery. It has been considered obligatory to have a representative numerical simulation model that can predict the phase behavior of asphaltene precipitation, flocculation, and deposition accurately. The first part of this thesis includes a comprehensive literature review of asphaltene precipitation flocculation, and deposition that include asphaltene structure, models and prevention techniques. The second part of the thesis includes a detailed study of modeling asphaltene precipitation phase behavior utilizing experimental and real field data obtained from five Middle-Eastern wells from different fields. Experimental data include measurements of asphaltene onset pressure (AOP), saturation pressure, and PVT data. Asphaltene precipitation was modeled by using WinProp (a phase behavior utility from CMG) which uses Nghiem solid model. Saturation pressures, PVT, and AOP data were used to match Peng-Robinson EOS and the precipitation model was matched by the experimental data of AOP. The third part of the thesis includes a one-dimensional simulation comparison study of asphaltene precipitation between three different compositional simulators; UTCOMP, ECLIPSE and CMG/GEM. The last part of the thesis includes a full field scale study based on a heterogeneous three-dimensional cartesian single-well model. The objective of this study was to assess the effect of asphaltene precipitation, flocculation, and deposition in the well productivity and the economic impacts related to it. Different production practices were applied to define the most appropriate and efficient production strategy. This study includes a discussion and comparison of production rates with and without asphaltene precipitation, flocculation, and deposition and a comparison of asphaltene precipitation, flocculation, and deposition at different times using different bottomhole and production rate constraints. Several cases (i.e., WAG cycles, completion, target layers of injection, etc.) will be tested to come up with the optimum completion and operating strategy in the presences asphaltene. Despite the work devoted to understanding this subject, asphaltene still represents a challenging and unresolved problem. This thesis will help bridge the gap of this limited understanding in the field of asphaltene. / text