Philips-type catalyst

Linear high-density polyethylene (HDPE) is mainly manufactured by using traditional Ziegler-Natta and metal oxide Philips-type initiators in suspension polymerization [173]. More expensive metallocene catalysts are also used but accoimted for less than 5% of the total HDPE production in 2002 [172]. About 14 billion pounds of high density polyethylene was produced in the United States in 2001. 

Catalyst structure was characterized by XRD (Philips PW 1050 Cusa) SEM (JEOL, ISM 35) DRS (SPM-2 monochromator VEB Zeiss, Jena) with a reflection cell of the R-45/0 type XPS (Surface Science SSX-100, small spot). Low temperature nitrogen adsorption (Micromeritics, ASAP 2000) was performed for textural properties investigation. 

A tubular stainless steel reactor (I.D. 104 mm) heated by an electrical oven at atmospheric pressure is used for the oxidation of toluene [Fig. 1]. The toluene is dosed with an HPLC pump (LKB2150) to an evaporator at 320 °C and then mixed to the O2 and N2 flows which are controlled with mass flow controllers (Bronkhorst High-Tech B. V ). Nitrogen is used as diluent. The catalyst fixed-bed preceded by quartz beads is maintained between quartz wool. The temperature of the fixed-bed is measured with a K-type thermocouple (Philips AG). The outlet gases are cooled in three consecutive condensers. The liquid products are collected and analysed by gas chromatography with a flame ionisation detector for quantification (Perkin-Elmer Autosystem gas chromatograph, capillary column Supelco SPB-1, 30 m x 0.53 mm I.D. X 0.50 jum film thickness) and with an electron ionisation detector for identification (Hewlett-Packard, G1800A, GCD System, capillary column HP-5, 30 m x 0.25 mm I.D. x 0.25 fm film thickness). The experiments are carried out at a conversion less than 5 per cent. 

Equation 2.87 can be used to represent the CLD of polyolefins made with the combination of two or more metallocenes very well [35, 38]. This is a reasonably easy case, since the individual metallocenes can be tested separately to obtain the values of Flory s T parameter. For multiple-site catalysts, such as heterogeneous Ziegler-Natta and Philips catalysts, the procedure for obtaining r values for each site type is more elaborate and involves the deconvolution of the MWD into several Flory s distributions. This subject will not be covered in this chapter the reader is directed to references 39 and 40 at the end of the chapter for more information on this subject. Suffice to say that MWD deconvolution involves the use of a non-linear least-squares optimization routine to... 

The reactor, plates as well as the housing, is constructed of stainless steel. Each plate contains 34 rectangular channels of 300 pm width, 240 pm depth and 20 mm length. It contains S reaction plates (coated with catalyst) and 5 thermostatisation plates glued together. The deposited catalyst mass is 75 mg, the measured reactor volume, Vr, is about 0.5 cm. For the experiments described here, the reactor block is heated from the outside by an electrical tape. As the enthalpy of the model reaction is small and low reactant concentrations are applied, a homogeneous temperature distribution is obtained. The temperature inside the reactor is measured using a K-type thermocouple (Philips AG, Dietikon, Switzerland) introduced into the outlet tube. 

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