Can a capacitor be used to regulate voltage?

No. You will just damage the capacitor, and it will fail in some way, depending on the value of R and construction of capacitor. Perhaps go up in smoke, perhaps just leak fluids, perhaps it may handle the 24 volts and do nothing, at least for a while.

Note that the voltage a capacitor can handle (at least for a while) is usually well over the voltage specification.

.

This arrangement will not do what you intend.

The voltage rating on a capacitor does not mean that the capacitor will maintain that voltage across its plates, if an RC series combination is subjected to a higher voltage. Such a voltage rating on the capacitor means that it is recommended that you do not charge the capacitor to any voltage higher than the stated value if you do not want the capacitor's materials to fail.

When predicting circuit behavior with capacitors operated safely, it is important that you pay attention to the value of capacitance instead. This is marked in uF, nF, or pF on the side, and in a code of numbers decoded similar to the method of resistance color codes. F stands for Farads, and u, n, and p are prefixes for micro, nano, and pico respectively.

If you construct this circuit with an ideal load, and an ideal capacitor (which will not fail), you will have the exponential response of the charging of the capacitor transient. Once steady state is achieved and the capacitor is fully charged, you will have an output of 24 volts. In reality, a real load will make it less, because its resistance in combination of the resistor's resistance will make a resistive voltage divider.

Voltage is meant to be regulated with diodes or zener diodes. All that regulate means is to ensure a value of voltage will not exceed a certain value. If it attempts, the other devices in series will accept the excess voltage drop. Only diodes exhibit this behavior, and possibly other complex transistor circuits. Capacitors, resistors and inductors do not.

Regulate Voltage

A capacitor is not capable of regulation. However, a capacitor can be used to step down voltage (but not DC).