1,3,5-tri-tert-butylbenzene (TTBB) is solid at ambient conditions, and has substantial solubility in liquid and supercritical carbon dioxide. We present the phase behavior of TTBB-CO2 binary system at temperatures between 298 and 328 K and at pressures up to 20 MPa. Phase diagrams showing the liquid-vapor, solid-liquid and solid-vapor equilibrium envelopes are constructed by pressure-volume-temperature measurements in a variable-volume sapphire cell. TTBB is highly soluble in CO2 over a wide range of compositions. Single-phase states are achieved at moderate pressures, even with very high TTBB concentrations. For example, at 328 K, a binary system containing TTBB at a concentration of 95% by weight forms a single-phase above 2.04 MPa. TTBB exhibits a significant melting-point depression in the presence Of CO2, 45 K at 3.11 MPa, where the normal melting point of 343 K is reduced to 298 K. With its high solubility in carbon dioxide, TTBB has potential uses as a binder or template in materials forming processes using dense carbon dioxide. (C) 2007 Elsevier B.V. All rights reserved.