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The melting of an ABS resin was simulated using a three-dimensional finite element simulation of the two-phase flow in the compression section of a single-screw extruder. Screw freezing experiments were also conducted to compare the numerical predictions with the corresponding experimental data. Numerical simulations as well as experiments exhibited the Maddock melting mechanism and numerical predictions were in good agreement with the corresponding experimental data. The sensitivity of the melting profile to various material properties and processing conditions was numerically analyzed. With a constant flow rate enforced at the entrance of the screw channel, the screw and barrel temperature were found to have a minor effect on the melting profile. However, these parameters were found to have a significant effect on the predicted pressure profile along the screw channel. When the zero-traction boundary condition was imposed at the entrance of the screw channel, a change in the screw or barrel temperature affected the flow rate in the screw channel, which resulted in a significant change in the solid fraction at the same cross-section.

Operating conditions for both the first step and the second step of the two-step process greatly affect alkylate quality and yields; statistical analyses indicate preferred conditions. With n-butenes as olefins, alkylates with research octane number (RON) values in the 99-100.5 range can be produced at operating conditions that are unacceptable in a one-step process. The isoparaffins in the alkylates are produced by three chemical mechanisms, and the relative importance of each differs with the RON of the alkylate.

Conjunct polymers, which are byproducts formed during the alkylation of isobutane with C3-C5 olefins, dilute the acid catalyst used so that it eventually loses effectiveness. For alkylations involving both n-butenes and sulfuric acid, decomposition of sec-butyl sulfates produces conjunct polymers, liquid hydrocarbons rich in heavy isoparaffins and olefins, sulfur dioxide, and water. During alkylation the polymers are present as conjunct polymer sulfates that contain sulfone, sulfonic acid, or sulfonic acid ester groups. NMR and IR spectroscopies were used to elucidate the structure of the conjunct

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