NOVELTY - Increasing hydrogen purity in hydrogen-containing streams associated with a petrochemical processes involves subjecting hydrogen-containing stream to rapid cycle pressure swing adsorption unit containing several adsorbent beds and having a total cycle time of less than 30 seconds and a pressure drop within each adsorbent bed of greater than 5 inches of water per foot of bed length.    USE - For increasing hydrogen purity in hydrogen-containing streams associated with petrochemical processes e.g. xylene isomerization, ethylbenzene hydroisomerization to xylenes, toluene disproportionation, selective toluene disproportionation, and toluene, benzene and 9C+ transalkylation processes (claimed).    ADVANTAGE - The use of rapid cycle pressure swing adsorption (RCPSA) unit, containing several adsorbent beds and having a total cycle time of less than 30 seconds (preferably less than 15 seconds, especially less than 5 seconds, particularly less than 2 seconds) and a pressure drop within each adsorbent bed of greater than 5 (preferably greater than 10, especially greater than 20) inches of water per foot of bed length, increases the concentration of hydrogen in the hydroprocessing units, and the efficient use of hydrogen resulting in higher product yields. In contrast with conventional pressure swing adsorption (PSA), the flow and pressure variations required for the RCPSA sorption/desorption cycle changes in a number of separate increments on the order of seconds per cycle, which smoothes out the pressure and flow rate pulsations encountered by the compression and valving machinery. The footprint, investment, and the amount of active adsorbent required for RCPSA is significantly lower than that for a conventional PSA unit processing an equivalent amount of gas. The structured adsorbents has a high mass transfer rate since the gas flow is through the channels formed by the structured sheets of the adsorbent which offers a significant improvement in mass transfer as compared to a traditional packed fixed bed arrangement as utilized in conventional PSA. These extraordinarily high mass transfer rate ratios allows RCPSA to produce high purity hydrogen at a high recovery rate with only a fraction of the equipment size, adsorbent volume, and cost of conventional PSA. The structured adsorbent also results in significantly greater pressure drops to be achieved through the adsorbent than conventional PSA without the detrimental effects associated with particulate bed technology. These higher adsorbent bed unit length pressure drops allows RCPSA adsorbent beds to be significantly more compact, shorter, and efficient than conventional PSA. The high unit length pressure drops allows high vapor velocities to be achieved across the structured adsorbent beds. This results in a greater mass contact rate between the process fluids and the adsorbent materials in a unit of time than can be achieved by conventional PSA. This result in shorter bed lengths, higher gas phase transfer rates and improved hydrogen recovery. In hydroprocessing, the increased hydrogen (H2) purity translates to higher H2 partial pressures in the hydroprocessing reactor(s). This both increases the reaction kinetics and decreases the rate of catalyst deactivation. The benefits of higher H2 partial pressures can be exploited in a variety of ways, such as operating at lower reactor temperature, which reduces energy costs, decreases catalyst deactivation, and extends catalyst life; increasing unit feed rate; processing more sour (higher sulfur) feedstocks; processing higher concentrations of cracked feedstocks; improving product color, particularly near end of run; and debottlenecking existing compressors and/or treat gas circuits. The increasing H2 recovery reduces the demand for purchased, manufactured, or other sources of H2 within the refinery; increases hydroprocessing feed rates at constant (existing) makeup gas demands; improves hydrogen purity in hydroprocessing for increased heteroatom removal efficiencies; and removes a portion of the H2 from refinery fuel gas which is detrimental to the fuel gas due to hydrogen's low BTU value which can present combustion capacity limitations and difficulties for some furnace burners.